EDTA Therapy for Vascular Disease

Chelation Natural Miracle For Protecting Your Heart

Chelation therapy has been conclusively shown to be up to 82 Percent Effective at dissolving the plaque that blocks arteries! In the ebook Chelation Natural Miracle For Protecting Your Heart you'll discover: The frustrating reason many doctors are ignoring Edta chelationor even openly rejecting it. The deadly heart surgeries even the American Heart Association admits are unnecessary. The hidden signs and symptoms of heart attacks and strokes? Are you in danger right now?. The average number of years stripped away by heart and vessel disease. Can you get them back?. The newest set of risk factors for heart disease (they'll likely surprise you!). Shady government practices that protect Big Pharma and keep Edta chelation out of the public eye. How the Roman Empire could have been savedif only they'd known about Edta chelation. Why Edta chelation is guaranteed to be safeeven in extremely high doses. (It puts aspirin to shame!). The shocking truth about plaque in young childrenand how to keep your little ones safer. Why dentists, artists and welders need Edta chelationand whether your workplace is dangerous too. The differences between IV and oral chelationand which kind of Edta is right for you. Other forms of chelationand how these little-known treatments can dramatically boost your health.

Chelation Natural Miracle For Protecting Your Heart Summary

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Photodegradation of [FeIIIEDTA

As discussed in Section 6.3 some EDTA complexes are light-sensitive for instance, Fe(III)EDTA can undergo total photolysis in a sunny day within several hours. Others are only slightly affected (e.g., Mn(II)EDTA , Co(III)EDTA ), while others are not affected by light at all. The ability of Fe(III)EDTA to undergo a photoredox reaction is very fortunate because as stated above EDTA is a refractory compound and thus the natural pho-tolytic pathway provides a means for its destruction. In the following qualitative experiment, an Fe(III)EDTA complex will be exposed to light (either natural or artificial) and decomposed to produce Fe(II), which then reacts with iron hexacyanate (III) yielding a highly colored solution of another complex (see Ibanez, 2000).

Box 64 Ion interactions ion pairing ligands and chelation

EDTA EDTA-metal complex Fig. 2 Chelation between a metal ion (M+) and ethylenediaminetetra-acetic acid (EDTA), a well-known laboratory ligand. Note that the six coordination bonds (white) are made between dissociated -O- groups and lone pairs of electrons (denoted by double dots) on the N atoms of the EDTA. Similar coordination bonds are made in fulvic acid chelates. Ligands and chelation

Economic Costs of EDTA Application under Field Conditions

The limitations for the use of EDTA under field conditions are furthermore economic ones. An example The application of 1 mmol Na2EDTA (molar mass 372.24 g mol-1) to one square meter of agricultural soil (300 kg of soil m 2 arable layer depth 25 cm bulk density 1.2 g cm 3) would consume about 112 g of EDTA. This would result in a need of more than 1.1 tonnes of EDTA per ha for applying the low doses of 1 mmol EDTA kg 1. The German trading company Omikron offers 25 kg bags of Disodium EDTA Dihydrate with a purity of over 98.0 for 298 Euro including taxes (March 2010). Therefore, applying 1 mmol EDTA kg-1 would result in costs for the chemical of more than 13.300 Euro per ha. Considering the fact that a higher dose of EDTA would be needed and that for several years the costs of enhanced phytoextraction would increase dramatically making it not feasible for economic reasons. However, if a large amount of chelating agents is ordered for large-scale remediation activities a reduced price...

Chelation

In plants, the synthesis of thiol-containing, cation-chelating compounds, such as glutathione (GSH), phytochelatins, and metallothioneins, is a frequent response to heavy metals transported into the symplast (Cobbett and Goldsbrough 2002). Other compounds such as amino acids, organic acids, and phenols have also been identified as heavy metal chelators (Rauser 1999). Chelating agents are found to limit the circulation of toxicants within the plant organism, forming stable complexes with metal ions (Prasad 1995). For example, in Pistia stratiotes and Eichhornia crassipes exposed to Cd, glutathione levels remarkably increased. In a species more responsive to Cd exposure - P. stratiotes - this increase in glutathione concentration correlated with abundant phytochelatin synthesis both in roots and in leaves (Sanita di Toppi et al. 2007). Also, Cd2+ exposure in the mosses Fontinalis antipyretica and F. dalecarlica increased the glutathione pool. Analytical electron microscopy provided...

Metal Chelation

Regarding the deleterious effects of heavy metals on the living organisms, it is considered that mainly the osmotically free forms of the metal ions are genuinely toxic, as they are prone to bind nonspecifically to biomolecules or to interfere with the essential metals' metabolism. To avoid the growth impairments caused by the potentially toxic heavy metals, hyperaccummulating plants must possess biochemical defense mechanisms. Plants developed a number of strategies to resist this toxicity, including active efflux, sequestration, and binding of heavy metals inside the cells by strong ligands. The primary antidote against the osmotically free ions may be the presence of chelating agents that form easily nontoxic complexes. Thus, an essential component of tolerance is the buffering of free metal ions in the cytoplasm via chelation with high-affinity ligands. The response of plants is complex with considerable variation between species. Several detoxification strategies are known to...

Heavy Metal Tolerance Mechanisms in Plants

Heavy metals such as Cu and Zn are essential for normal plant growth, although elevated concentrations of both essential and nonessential metals can result in growth inhibition and toxicity symptoms. Some plant species, however, have evolved tolerant races that can survive and thrive on such metalliferous soils, presumably by adapting mechanisms that may also be involved in the general homeostasis of, and constitutive tolerance to, essential metal ions as found in all plants. Plants have a range of potential mechanisms at the cellular level that might be involved in the detoxification and thus tolerance to heavy metal stress. The strategies for avoiding heavy metal buildup are diverse. Extracellularly they include roles for mycorrhizas and for cell wall and extracellular exudates. Tolerance could also involve the plasma membrane, either by reducing the uptake of heavy metals or by stimulating the efflux pumping of metals that have entered the cytosol. Within the protoplast a variety...

Extracellular Avoidance of Metal Buildup 1511 Mycorrhizas

Fig. 1.3 Summary of potential cellular mechanisms available for metal detoxification and tolerance in higher plants. 1. Restriction of metal movement to roots by mycorrhizas. 2. Binding to cell wall and root exudates. 3. Reduced influx across plasma membrane. 4. Active efflux into apoplast. 5. Chelation in cytosol by various ligands. 6. Repair and protection of plasma membrane under stress condition. 7. Transport of PC-Cd complex into the vacuole. 8. Transport and accumulation of metals in vacuole (modified from Marschner 1995) In relation to the role of ectomycorrhizas in metal tolerance by the host plant, most mechanisms that have been proposed involve various exclusion processes that restrict metal movement to the host roots. These have been extensively reviewed and assessed (Jentschke and Godbold 2000) and include absorption of metals by the hyphal sheath, reduced access to the apoplast due to the hydrophobicity of the fungal sheath, chelation by fungal exudates, and adsorption...

Heavy Metal Tolerance

The entrance through leaves is little and is related to the leaf morphology e.g., downy leaves absorb the heavy metals better from atmosphere. The uptake rate depends on the pH of soil solution, organic matter content and concentrations of other ions in the soil. At higher pH value, the solubility of many metal salts in soil solution declines due to the formation of less soluble compounds, as a result their biological availability in the soil decreases. Adding synthetic chelating agents, such as EGTA and EDTA to the soil polluted with heavy metals enhances the uptake and this characteristic can be used for cleansing the soils polluted with heavy metals. In addition to this other ions present in the soil solution considerably affect the uptake of heavy metals by various plant tissues. There is no particular mechanism known, probably other ions present in the soil solution interact and compete with each other thus leading to less biological availability of metal ions and reduction in...

Assessing the Mobility of Metals in Solid Wastes and Contaminated Soils

For revealing the free and several of the stable chelated forms of metals present in soils and reflect the metal availability in both the short-term and relatively long-term, one can use single extraction with ethylenediamine tetraacetic acid (EDTA). Besides its relevance for assessing the rapid mobility in barren surface of mining areas, the EDTA-extractable fraction has been found to give the best correlation with the amounts of metals taken up by plants (Ure 1996 Lo and Yang 1999), so is a useful tool also for designing the bioremediation of the contaminated sites.

Phytoremediation Prospects

In the first point, when chelants were used to increase soil soluble metal levels as to help their uptake in plants, the chelant bound metal (e.g., Pb) might be less toxic than free metal, and hence might induce less stress on plants (Andra et al., 2009) and on the environment (Shibata et al., 2007). Whereas, the metal-solubilising effect of chelant e.g., EDTA, was shorter-lived in the less contaminated and more highly calcareous soil (Walker et al., 2003). Even if toxic availability is decreased by adding amendments, it is still in the soil and keeping potential hazards (Kirkham, 2006). Furthermore, chelants addition technique might create

Bioavailability of Heavy Metals

The bioavailability of metals in soils is considered in terms of a series of single-extraction methods, including the use of ethylenediaminetetraacetic acid (EDTA), acetic acid, diethylenetriaminepentaacetic acid (DTPA), ammonium nitrate, calcium chloride, and sodium nitrate

Analytical Chemical Procedures

Specific extractants and sequential fractionation are also widely used procedures to estimate metal or nutrient availability to plants (see, e.g., Houba et al. 1996). Several extractants can be considered, like diethylene triamine penta acetate (DTPA), ethylene diamine tetra acetic acid (EDTA), acetic acid, HNO3, HCl, or other mineral acids (Allen 2002). Each reagent might be considered specific for extracting a certain fraction of metals. As an example, EDTA and DTPA are often used as extractants of exchangeable and organically bound trace metals and also to dissolve metal precipitates. These procedures can also be considered as chelating extractions, showing a correlation between water and total digestion extractions. Another technique also used for the identification of the solid phase associated with metals is an x-ray absorption fine structure methodology (EXAFS) (Manceau et al. 2003).

Type B ternary surface complex

According to Ref. 46, ternary adsorption complexes should be statistically less stable than binary adsorption complexes, as the static Jahn-Tellcr deformation of a metal cation's coordination shell resulting from ligand complexation allows fewer available positions for metal binding than the uncomplexed species. However, examples exist where ternary surface complexes, usually involving organic ligands such as EDTA 47 or humic or fulvic acids 48-50 , form strongly adsorbed species that limit the subsequent desorption from the surface that would have been more likely to occur in the absence of the ligands. As demonstrated in Fig. 9 and Eq. (3-5), inner- and outer-sphere adsorption complexes are typically envisioned as mononuclear species, i.e. as single metal atoms adsorbing to a surface.

Mechanism of Chemical or Physical Remediation

Dotted bonds to Pb are coordinate chelators such as ethylenediamine-tetraacetic acid (EDTA), both the solubility and bioavailability of heavy metals are improved. A chelating reagent's molecule can form several coordinative bonds to a certain metal atom, increasing its concentration in soil aqueous phase and mobility (Baker et al. 2000) (Fig. 4.1). Considering some metal ions strongly bonds to the soil phase and are less bioavailable, powerful chelating reagents are employed such as Na salt of EDTA. However, such approach needs not only expensive chemical reagent and machines but also many technicians. Worse, excessively usage of chemical chelates has been proven to pollute the ground water and negatively affect soil quality, for many necessary ions are also chelated unselectively. For example, elements Fe and Ca are usually lost after the spray of EDTA, because their concentration in the soil is much higher than those target heavy metals such as Pb and...

Mechanism of Animal Remediation

Animal here mainly refers to earthworm, because it is one of the most important soil organisms and plays an indispensable role in improving soil quality (Sriprang et al. 2002, 2003 Kashiwa et al. 2001 Fox et al. 1982). By their feeding, burrowing, excreting, and metabolic redox material, both soil texture and nutrition content are improved. Chemical groups such as -COOH and -CO are generated and exuded, which acidify soil and activate heavy metals. Several kinds of gel material are also excreted which facilitate complexion and chelation of metal ions. However, because of the relatively small amount and specific surface area compared with microbes, such improvement is neither notable nor stable. According to Yang et al. (Baker et al. 2000), after Eisenia foetida earthworm was inoculated, pH of a cock manure decreased by 0.7-0.9. However, if the inoculation occurred in an acidic red 2. Nature chelators As we know, chelators such as EDTA can bind to heavy metal ions and render them...

Mechanism of Microremediation 4241 Metal Binding Mechanism

A big disadvantage of microremediation is that absorbed heavy metals would still stay in the soil, so symbiotic mechanism would be more effective by combining both microremediation and phytoremediation. Due to the symbiotic microbes' large amount and specific surface area, binding reagents such as MTs, PCs, and organic acid will be excreted more by symbiotic systems than by sole plants. Thus soil will be improved with better acidification, which ultimately leads to better solubility, mobility, and bioavailability of heavy metals. After heavy metal particles are activated, the subsequent process can be divided into two ways. One is that metal ions are accumulated by plants root, transported in the xylem and detoxified through chelation, vacuolar compartmentalization, and volatilization, just as normal phytoremediation does. The other way is heavy metals will be accumulated in rhizosphere and nodules. Rhizosphere bacteria's essential role in achieving optimum rates of selenium...

Literature References

C. Topete-Pastor, J. Garcia-Pintor, E. Metal Complexes and the Environment Microscale Experiments with Iron-EDTA Chelates, Chetn. Educ. 2000,5, 226-230. Lockhart, H. B., Jr. Blakeley, R. V. Aerobic Photodegradation of Fe(III)-(Ethylenedinitrilo)tetraacetate (Ferric EDTA). Implications for Natural Waters, Environ. Sci. Technol. 1975,12, 1035-1038. McArdell, C. S. Stone, A. T. Tian, J. Reaction of EDTA and Related Aminocarboxylate Chelating Agents with CoIUOOH (Heterogenite) and MnmOOH (Mangan-ite), Environ. Sci. Technol. 1998, 32, 2923-2930. Xue, Y. Traina, S. J. Oxidation Kinetics of Co (II)-EDTA in Aqueous and Semi-Aqueous Goethite Suspensions, Environ. Sci. Technol. 1996, 30, 1975 1981.

Measuring Bioavailability

Bioavailability tests need to consider two distinct aspects a physical, chemically driven solubilization process and a physiologically driven uptake process Soil characteristics and plant characteristics determine bioavailability From a chemical point of view, it is possible to determine the amount of pollutant in the soil solution and or the amount that can be most easily released from the solid phase (e .g., metals retained with electrostatic bonds) . For this purpose we can use either direct sampling of the solution present in the pore system or make use of bland extractants, such as water or alkaline saline solutions that have the specific characteristic of not modifying the soil particle surfaces . Alternatively, more energetic extracting agents can be used, such as complexing agents (EDTA, DTPA), whose action, however, is more aggressive than that of a plant

Adsorption as a Key Step for Dechlorination

Studies on the reductive dechlorination on ZVI surfaces are mostly performed in systems containing only chlorinated compounds and iron in the aqueous phase. Processes actually occurring in reactive iron barriers, however, could be much more complex due to the presence of other chemical constituents in the system. The ambient constitutes may include anthropogenic contaminants that are co-disposed with chlorinated compounds and natural occurring constituents in soils and groundwater (e.g., natural organic matter, HC03 , HS ). These chemicals may compete with chlorinated solvents for the adsorption sites on ZVI and thus inhibit the reductive dechlorination, or facilitate the iron corrosion and thus enhance the rate of dechlorination. For example, the reduction rate of carbon tetrachloride is decreased by both redox active ligands (catechol and ascorbate) and non-redox active ligands (EDTA and acetate) (Johnson et al., 1998). Various

Molecular Mechanisms of Metal Homeostasis and Tolerance

An example is the aluminum (Al) tolerance mechanism in wheat, which avoids the Al uptake by the exudation of OAs and further formation of Al-OA complexes (Delhaize et al., 1993 Kochian et al., 2004). The exudation of OAs has been studied in roots of P. tremula exposed to HMs by (Qin et al., 2007). They showed that Cu induced root exudation of oxalate, malate and formate, while Zn induced root exudation of formate. These OAs could be associated to an exclusion mechanism decreasing the HM uptake by the ion chelation at the rhizosphere. Plants have evolved a suite of cytoplasmatic mechanisms that control and respond to the toxicity of both essential and nonessential HMs. In this way, there are two basic strategies for decreasing the toxicity of metals chelation or efflux from the cytosol, either into the apoplast or by intracellular sequestration through specific ligands for HMs. Two of the best characterized HM binding ligands in plant cells are the phytochelatins (PCs) and...

Chemically Assisted HM Accumulation by Legume Microbe

A frequently observed negative effect of symbiotrophic microorganisms on the content of HMs in legumes should be taken into account for application of these plants in phytoremediation. On the one hand this phenomenon may play beneficial role to grazing animals when legumes are utilised in phytostabilization and revegetation technologies. On the other hand, this restricts accumulation of HMs in harvested plant parts and output of pollutants from soil resulting in decreased phytoextraction efficiency. It should be mentioned that microorganisms possess several mechanisms of metal mobilization and may increase availability of HMs in the rhizosphere resulting in enhanced metal uptake by plants (Gadd, 1990 Wenzel, 2009). Therefore, selection of microorganisms associated with legumes and harbouring traits for increasing HM availability and or stimulating metal uptake and transport systems in plants may be a promising approach for improved phytoextraction. Low metal availability in the...

Extracellular Chelators

The most common and effective way to accumulate iron is the production of siderophores. These low-molecular weight compounds possess a high affinity and selectivity for iron (Hider and Kong 2010 Rajkumar et al. 2010), but also can bind other metals (Dimkpa et al. 2009a). In contrast to gram-negative bacteria, less information on iron chelation and transport is available for gram-positives (Hider and Kong 2010). It could be shown that it is common in streptomycetes to produce different siderophores at the same time, which may provide an advantage in competition with other microorganisms in soil (Chater et al. 2010). Actinomycetes isolated from medicinal plant rhizosphere soils mainly, with 89 , belonged to the genus Streptomy-ces, a high number of which were able to produce siderophores (Khamna et al. 2009).

Biomarkers of chromate exposure

The biomarkers available to assess chromate exposure and effect represents useful types of biomarkers. In fact, since a portion of the Cr bound to DNA can be eliminated by exposing the DNA to EDTA,8 one can address whether the adducts detected were Cr-DNA adducts. There are few adducts that display this unique chemical property of EDTA reversibility, and therefore it is a useful way to identify DNA adducts that contain Cr.

Oxidative state of Cr and toxicity

This uptake-reduction binding process leads to a significant accumulation of Cr inside the cell (up to several hundred-fold) over extracellular concentrations.8a Tight binding of Cr(III) by intracellular macromolecules also results in long-term retention of significant amounts of Cr(III). The high stability of Cr(III) complexes with biological ligands is illustrated by the observation that the administration of a strong chelator EDTA did not lead to an increased excretion of Cr from control or highly exposed human sub-jects.1011 Ascorbate and low-molecular weight thiols such as glutathione and cysteine are believed to be the major intracellular reducers of Cr(VI).12-14

Soil Factors 11231 pH

Tejada et al. (2008) found that increasing Ni levels reduced soil enzyme activities, and that soil amendment with organic wastes (crushed cotton gin compost, poultry manure) reduced the toxicity of nickel to soil enzyme activities (urease, BBA-protease, alkaline phosphatase, b-glucosidase and arylsulfatase). Organic amendments enhance soil enzyme activity for the following reasons (1) intra- and extracellular enzymes stimulate microbial activity in the added materials, (2) carboxyl, phenolic, alcohol, and carbonyl functional groups in the humic substances react with toxic ions, forming metal-humate complexes (metal chelation) and stabilizing them (Nannipieri 1994 Dick 1997 Pascual et al. 1998). Tejada et al. (2008) summarized the following results from different studies. Carboxyl groups play an important role stabilizing toxic ions in the humic acids (McKnight et al. 2001). Although fulvic acids contain more carboxyl groups than humic acids (Stevenson 1994), studies show that metal...

Green Chemistry Materials and Function

These green chemistry initiatives have received a substantial boost by the U.S. government's sponsorship of an annual Presidential awards ceremony for the best examples of green chemistry applications. Over the past several years, this awards program has recognized Bayer's environmentally friendly synthesis of biodegradable chelating agents, PPG Industry's use of yttrium as a substitute for lead in cationic electrocoatings, and Rohm and Hass's design of an environmentally safe marine antifouling coating to replace tributyltin oxides. For other examples see the Internet site www.epa.gov greenchemistry.

Role of Phytochelatins PCs in Metal Tolerance

The key to understanding accumulation is identification and characterization of corresponding ligands. One recurrent mechanism for heavy metal detoxification is chelation by ligand. A number of chelation ligands such as PCs, glutathione (GSH) and metallothionines (MTs) ligands have now been recognized in plants.

Competition between aqueous and solid phases

Estuaries receive industrial wastewaters containing Ni ethylenediaminetetraacetate (NiEDTA2-), which is supposed to be that strongly complexed Ni species. To further identify this ligand, its source and fate, Bedsworth and Sedlak (1999) performed simultaneous measurements of NiEDTA2- by high-performance liquid chromatography (HPLC) and cathodic stripping voltametry in combination with a chelating resin column in water samples from the San Francisco Bay. Wastewater analysis indicated that NiEDTA2- accounts indeed for the strongly complexed Ni in waste effluents. Equilibrium speciation calculations suggested, what we already know from other study areas, that even other metals, like Cu(II), Zn(II), and Pb(II), are similarly discharged as EDTA complexes from wastewater treatment systems (compare for more details previous AF-MFG technical reports on this particular issue). Also seasonal variations have been observed in Ni speciation due to the discharge of stable NiEDTA2-complexes from...

Mechanisms to Prevent Cells from Heavy Metal Toxicity

Extracellular and intracellular mechanisms are involved in heavy metal tolerance for fungi. Mostly such mechanisms have not explicitly been studied in mycorrhizal fungi, but it appears likely that data from non-mycorrhizal basidiomycetes (or ascomycetes) can be translated to ECM since they use the same mechanisms (Fig. 10.2). Extracellular chelation by excreted ligands, such as citrate and oxalate, as well as cell-wall binding or an enhanced efflux reduce the amount of heavy metals in the cell. Intracellular chelation by metallothioneins phytochelatins or Fig. 10.2 Potentially involved elements of heavy metal stress response in ectomycorrhiza (1) extracellular modification of metal ions (M) by excreted enzymes (E), (2) extracellular chelation by excreted ligands (L) like low molecular weight organic acids, which may reduce extracellular pH, (3) cell wall binding, (4) reduced influx across plasma membrane, (5) enhanced efflux, (6) intracellular chelation by metallothioneins (MT) or...

Resistance or Tolerance to Metals in Plants

Excretion of complexed compounds that reduce the availability of the metal in the soil or water exclusion of the metal through selective absorption of elements retention of the metal in roots, preventing its translocation to the aerial part chelation or sequestration of heavy metals by ligands, compartmentalization, biotransformation and mechanisms of cellular repair development of enzymes tolerant to the metal. Chelation of metallic ions by specific ligands of high affinity diminishes the concentration of free ions in the solution. The main ligands associated to metals found in plant tissue include amino acids, oligo and polypeptides (glutathione, phytochelatins, metallothioneins) (Patra et al., 2004), macrocyclical agents (porphyrins, cobalamines, chlorophylls), polysaccharides and glycosides (ramnogalacturonana), nucleobases, oligo-

Sedimentwater systems

Sequential chemical extraction of trace metals from sediments is intended - in each specific step - to release metals associated with a specific sediment phase (for more details see section 5.4.4 below). As reactions between solute metals and particle surfaces are heterogeneous (i.e. adsorption, electron and proton transfers), the extraction efficiency is more kinetically controlled and strongly depends on the availability of specific surface areas and the type of reactive sites (i.e. high- and low-energy sites). In general, results of the chemical extraction depend on (i) the extraction time, (ii) the liquid solid ratio, and (iii) effects based on the pH and buffer carbonate status of the sample (Reuther, 1999). Faced with the selection of a chemical extraction procedure, a great variety of options have been described, covering various leaching tests, single-step extraction, using different types of buffer solutions, chelating agents or weak acids, and multistep sequential extraction.

Chemical extraction and mobility

Also the fact that still a multitude of various digestion solutions of varying strength is used to assess the degree of total metal contamination, is contributing to handle current speciation data based on chemical extractants with great care. Sutherland et al. (2001) recently tried to test the capability of different extractants in identifying significant contaminant levels in road sediments. In their study, they included a total four-acid digestion scheme, a microwave-assisted digestion with conc. HNO3 (USEPA 3051), 0.5 M cold HCl, and 0.05M EDTA (pH 7). The authors summarized that the weak extractants they used (i. e. HCl and EDTA) were most successful to indicate the degree of anthropogenic metal contamination, why they recommend to use these agents more widely.

Laboratory Report Sheetexperiment

Amount of EDTA added _mg Condensed formula of the EDTA used _ Color of the Fe(II)EDTA complex _ Color of the Fe(II)(NO)(EDTA) complex _ d) Regeneration of the Fe(II)EDTA If the VIS absorption spectra of the solutions of Fe(II), Fe(II)EDTA , and Fe(II)(NO)(EDTA) were taken, insert here a copy and interpret qualitatively the differences observed. If the spectrum after reduction was taken, also insert it here and compare with the others.

Postlaboratory Problems And Questions

Removal of insoluble NO from a flue-gas stream can be accomplished by scrubbing with a solution containing Fe(II)EDTA (as in the present experiment). The unavoidable presence of 02 produces the oxidation of Fe(II)EDTA to Fe(III)EDTA, which is unreactive toward NO and thus renders the process useless. Consequently, the reduction of Fe(III)EDTA is a key step toward the success of the global process. To this end, bisulfite can be used as a reducing agent as follows (L symbolizes the EDTA ligand)

Some Applications of Complexing

From the general coordination properties discussed for Ca(II), we can predict that a satisfactory complexing agent for replacement of phosphate in detergents would have to be a chelating agent, since only then would adequate stability of the complex be likely. Oxygen should be the chief donor atom, since only this donor atom is hard enough to interact strongly with Ca(II) while at the same time being part of a more elaborate molecule. There are also requirements of nontoxicity, biodegradability, and low cost. An example of a very effective chelating agent for calcium is ethylenediaminetetraacetic acid, EDTA

Los Alamos National Laboratory Uranium Heap Leaching Technology Abstract

According to the vendor, another possible application of the technology is to support remedial treatments using surfactants, mild acids or bases, or special chelating agents. Heap leaching can be used with ex situ bioremediation techniques, where biological agents actively convert or degrade toxic substances. Contaminated soil can be placed in a heap and nutrients, oxygen, and other bioreactor stimulants can be added to increase the efficiency of the biological process.

Chemical extraction and plant uptake

In a recent review, Schramel et al. (2000) examined several single and sequential extraction schemes developed to assess Cu mobility and bioavailability in contaminated agricultural soils. They found that both EDTA and acetic acid are widely used as extractants for plant-available Cu species, while deionized water, NH4NO3 and CaCl2 extract more electrostatically weakly bound metals representing mobile phases in the soil. By means of own experiments, no vertical Cu translocation was found in hopfields, although Cu was highly plant-available. 1 M NH4NO3 is now used as the standard method of assessing metal bioavailability for regulatory purposes in the Federal State of Baden-W rttemberg, Germany (DIN 1995). pH, and was the reason why only minor effects on the free and exchangeable Cu and Ni pool (BaCl2 + EDTA-extractable) were observed. Measurements of CE of copper were made by Zhang et al. (2001) on 29 different soils covering a wide range of concentrations both as EDTA-extractable Cu...

Microbial Biosorption for Arsenic Remediation

Adsorption, ion exchange, coordination, complexation, chelation and precipitation. It may help to transfer soluble arsenic into solid phases, thus helping to remove it from groundwater or immobilize it in soils and sediments. It also can be used potentially for the drinking water treatment process (Wang and Zhao 2009).

Chemical Immobilization Plot Experiment

However, the concentrations of DTPA-extractable Pb dropped from 16.3 to 7.6 mg kg-1 due to the increase in pH and the immobilization processes. It is well known that Pb mobility is reduced by adding organic matter to the soil, due to the formation of chelating agents from humic acids. Therefore, organic wastes can be successfully used in mining areas to reduce metal toxicity to plants (Bradshaw 2000 Tordoff et al. 2000).

Bioremediation Options for Metal Contaminated Sites

Composting Composting is a technique that involves combining contaminated soil with non hazardous organic amendments such as manure or agricultural wastes. The presence of these organic materials supports the development of a rich microbial population and elevated temperature characteristic of composting. Composting in prepared beds holds a number of possibilities for bioremediation of metals degrading organic chelating agents, altering pH, redox potential and production of surfactants.

Hyperaccumulation as a Primary Tool for Heavy Metal Bioremediation

Ni2+ H+ antiport V-ATPase at the tonoplast that can drive vacuolar accumulation of Ni through a secondary active transport mechanism Slow vacuolar (SV) channel activity Cd, Ni, Zn Metal chelation phenolics Organic acid chelation Suppression of endogenous arsenate reduction in roots may serve to enhance root-to-shoot translocation of As Chelation by phytochelatins Enhanced root-to-shoot translocation Glutathione, rather than phytochelatins involved in Zn and Pb transport Metal chelation with organic ligands

Fractionation Methods TIE and EDA

To enable identification of the (groups or classes of) chemicals responsible for tox-icity of the sample, a TIE approach can be followed. The TIE approach was first developed for the characterization of effluent toxicity (USEPA 1991 Norberg-King et al. 1992 Durhan et al. 1993 Mount and Norberg-King 1993). The first line in the TIE approach is to determine toxicity of the effluent sample using bioassays. The second line includes identification of priority pollutants by chemical analysis and determination of their toxicity either by additional testing or by collecting literature data. The final step is to try to explain the toxicity of the effluent sample from the knowledge on the toxicity of the priority pollutants. The second line usually requires a more sophisticated approach, including, for instance, fractionation schemes and associated chemical techniques to unravel the identity of the toxicants in the complex mixture. Often a stepwise selective removal of certain fractions is...

Genetic and chemical validation 41 AtKAPAS from transgenic E coli

Total RNA isolated from leaf tissues of A. thaliana was used for preparation of poly(A)+mRNA. Double-stranded cDNA was constructed from 5 g of poly(A)+mRNA with the Time Saver cDNA synthesis kit (Pharmacia, Piscataway, NJ, USA), using Oligo(dT)18 as a primer. By performing PCR (polymerase chain reaction) with the two primers, the full-length AtKAPAS cDNA was amplified and isolated from A. thaliana cDNA library prepared. The primers encompassing the full-length cDNA of AtKAPAS, KAPAFB GATAAA-3') and KAPARH were synthesized to include EcoRI and Xhol restriction site, respectively. Primers of KAPAFB and KAPARH were used in a PCR reaction to amplify the AtKAPAS-encoding region. The resulting PCR fragment was digested with EcoRI and XhoI, and cloned into MBP (maltose binding protein) fusion vector (Bioprogen Co., Ltd., Korea) to generate construct pEMBPek-KAPAS (Fig. 2). E. coli BL21-Gold(DE) (Stratagene, USA) was transformed with expression vector pEMBPek-KAPAS and than cultured in LB...

Chelant Assisted Phytoextraction of Metals

A wide range of synthetic chelants have been tested for chelant-induced phytoextraction. Aminopolycarboxylate chelants (APCs) are the most commonly used chelants. Ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), acid (HEDTA), nitrilotriacetic acid (NTA), Ethylenediamine-N,N'-disuccinic acid (EDDS), methylglycinediacetic acid (MGDA), glutamic acid diacetic acid (GLDA) are examples of typically used APCs for metal phytoextraction. In particular, EDTA is the most widely used APC owing to its ability to form strong water-soluble chelant complexes with most toxic metals 18, 61, 62 . The efficiency of the phytoextraction process depends in large part on how the chelant is applied to the contaminated soil. The chelant is applied to the soil matrix either in a single dose after the optimum growth of the accumulator crop, or in small multiple doses gradually during the growth cycle 63 . Phytoextraction efficiency is reportedly improved by the combined...

Eco Environmental Consequences

Free-form of chelants, particularly APCs, exhibit poor photo-, chemo- and biodegradability in the environment 61, 70, 76-80 and, in most cases, metal complexation raises the threshold values for toxic effects of metals 72, 81, 82 . Metal-complexes with varying reactivity may form depending on the metals and speciation of chelating agents which is an important factor to determine their eco-environmental fate 76, 83 . Chelant materials are non-toxic to many forms of life in terms of acute toxicity while chronic toxicity effects are unknown 84, 85 . EDTA, which is widely used among the chelants, have low toxicity profile for human health as concluded from the extensive evaluation of different legislative bodies 86 . However, excretion of metals and cell membrane permeability in mammals is affected at extreme ingestion of EDTA 87, 88 .

Restoration Techniques Used in Poland Versus Spontaneous Succession

The research on heavy metal uptake by plants growing on zinc industrial wastes collected from Trzebionka was carried out using 15 cultivars of Zea mays (Jurkiewicz et al. 2004) and P. lanceolata. In the first case, the aims were to check whether (1) mycorrhizal colonization influences heavy metal uptake by maize, (2) there is a variability in uptake between plant cultivars, and (3) mycor-rhiza development has any effect when EDTA - (a chelating agent known to mobilize heavy metals in soil) - is used. In this experiment, Glomus intraradices was chosen as a fungal symbiont. Analysis of mycorrhizal parameters indicated differences among the varieties, but between different treatments of the same variety, results were generally statistically insignificant. Although the EDTA treatment strongly decreased the activity of the fungal alkaline phosphatase (indicator of fungal viability), the treatment did not totally eliminate the arbuscular mycorrhizal fungi (AMF) from the soil. Modification...

Phytoextraction of Cadmium Contaminated Soils

Over 420 plant species of hyperaccumulator from all over the world were discovered according to Baker et al. (2000), but many of them have a low growth rate and very low biomass. The application of chelating agents and genetic engineering were the two strategies to be developed to increase the uptake of HM by plants. The synthesized chelating agents, such as EDTA (ethylenedinitrilo tetraacetic acid), DTPA (diethylenetrinitrilo pentaacetic acid), HEDTA (hydroxyl- ethylenediamine triacetic acid), CDTA acid), EGTA (ethylenebis (oxyethylenetrinitrilo) tetraacetic acid), and EDDS (S,S-ethylenediamine disuccinic acid) were applied to HM-contaminated soil to increase their mobility and bioavailability and thus the amount of HMs were accumulated in the upper parts of plants (Huang and Cunningham, 1996 Huang et al., 1997 Blaylock et al., 1997 Ebbs and Kochian, 1998 Wu et al., 1999 Lai and Chen, 2004 2005 Luo et al., 2006 Tandy et al., 2006). However, synthetic chelating agents at high...

Methods of Determination of Heavy Metal Forms Single Chemical Extraction

Another group of procedures determining the so-called available forms that have been added to biosolids include the use of dilute acids such as acetic or hydrochloric acid and or in combination with chelates, for example, ethylenediaminetetraacetic acid (EDTA) Berrow and Webber (1972), using 0 42 M acetic acid, extracted greater than 95 of the total Zn The heavy metals Cu and Ni also exhibited a similar high solubility in 0 095 M acetic acid, because 50 to 75 of the total was extracted (Jenkins and Cooper, 1964) Stover et al . (1976), using 0.5 M HCl, extracted 60 to 73 of the metals Cd, Ni, and Zn and 18 to 24 of Cu and Pb In general, anaerobic incubation reduced the percentage of extractable heavy metals

Sequential Chemical extraction

Substances that are believed to extract metals from specific fractions of bio-solids Emmerich et al (1982b), working with anaerobically digested sludge, applied the same sequential extraction that they applied to soils, using solutions of 0.5 M KNO3 (exchangeable forms), water (adsorbed forms), 0.5 M NaOH (organically bound forms), 0.05 M Na2-EDTA (carbonate-bound forms), and 4 . 0 M HNO3 at 70 to 80 C (residual forms, bound in clay lattice structure) They made it clear that the quantities extracted by the procedure they followed did not consist of specific forms of metals, but of chemically similar forms that are extracted by particular extractants This study showed that the exchangeable fraction was found to be 11 ), whereas the remaining metals comprised an insignificant percentage (

Discharge of Potentially Toxic Metals

Addition of EDTA to the soil considerably increases the water-soluble concentrations of potentially toxic metals. Several authors have already stated that the low biodegradability of EDTA does not make it suitable for large-scale field applications (e.g., Kos and Lestan, 2004 Tandy et al., 2004). Neugschwandtner et al. (2008) reported in a field experiment a 326-fold increase of the water-soluble Pb concentration in the upper soil layer (0-5 cm) 58 d following the application of 9 mmol EDTA kg 1 soil. Water-soluble Pb was still 4.3-fold higher in the depth of 45-50 cm compared to the variant un-treated with EDTA. Only a small percentage of that mobilized water-soluble fraction can be taken up by the plants. Meers et al. (2005) reported in a comparison between four different crops that a maximum of 1.1 of Pb mobilized by EDTA could be recovered in the plant shoots. The rest of the metal-chelant complexes remains in the soil and is subjected to degradation processes and leaching....

CoMobilization of Macro and Micronutrients

A high co-mobilization of macronutrients (Ca, K, Mg) and micronutrients (Fe, Mn) by EDTA that caused competition to target potentially toxic metals during the phytoextraction process was reported by Neugschwandtner et al. (2009) in a field experiment (pH of Na2EDTA-solution 4.6). An increase of water-soluble nutrient concentrations of 12-times (Fe), 101-times (Mn), 3.7-times (Ca), 1.6-times (Mg), and 1.2-times (K), respectively, in the upper soil layer (0-5 cm) following 40 d after the application of 9 mmol EDTA kg 1 was observed. In a depth of 25-30 cm, total water-soluble Fe and Ca were still increased 1.7-fold whereas total water-soluble fractions of all other nutrients were in the same range in the control and the EDTA treatments. Especially Fe is an important competitor to target metals for chelating agents due to its high concentration in soils and its relatively high complex formation stability constant. Mobilization of macro- and micronutrients is caused by formation of...

Proteomic Studies in Response to Heavy Metal Toxicity

Protein-metabolite interaction analysis is an efficient way to demonstrate heavy metal sequestration and the interaction of metals with proteins and metabolites. Pull-down assays using various affinity columns, such as glutathione (GSH)-sepharose beads, could be a useful technique for determining the response of GSH-binding proteins (Smith et al. 2004). While GSH itself is a metal-binding metabolite, it is also a key precursor of the well-known metal-binding metabolite phytochelatin. Using this technique coupled with MS analyses, several Cu-and Cd-responsive glutathione-S-transferases (GSTs) have been identified in Arabidopsis (Smith et al. 2004 Roth et al. 2006). Immobilized metal-affinity chromatography (IMAC) is another technique for directly isolating metal-binding proteins. To obtain a better understanding of Cu transport, chelation, and sequestration, Kung et al. (2006) screened a total of 35 unique Cu-interacting proteins in Arabidopsis roots using Cu-IMAC. Thus, the...

Heavy Metal Detoxification and Tolerance in Higher Plants

Potential cellular mechanisms for metal detoxification and tolerance in higher plants are summarized as (1) restriction of metal movement to roots by mycorrhizas, (2) binding to cell wall and root exudates, (3) reduced influx across plasma membrane, (4) active efflux into apoplast, (5) chelation in cytosol by various ligands, (6) repair and protection of plasma membrane under stress conditions, and (7) transport of and accumulation of metals in vacuole (Hall 2002).

Factors Affecting Uptake and Transport

Phytosiderophores are chelators that facilitate uptake of various metals in grasses. They are biosynthesized from nicotianamine that chelate metals and may facilitate their transport (Taiz and Zeiger 2002). Chelation in roots can affect phytoremediation efficiency as it may facilitate root sequestration, translocation, and or tolerance. Root sequestration may be desirable for phytostabilization (less exposure to wildlife), whereas export to xylem is desirable for phytoextraction. Bioavailability of various toxic substances including cyanide can be enhanced by using chelators that are released by plants and bacteria. Chelators such as siderophores, organic acids, and phenolics can release various metal cations from soil particles. This usually increases availability of the toxic substances for

Practicalities In The Use Of Polyelectrolytes

A summary of the toxicity of polymers to freshwater organisms indicates that fish are more sensitive to cationic polymers, but algae are sensitive to anionic polymers because of the chelation of nutrient metal cations 114 . This effect can be offset by the addition of Ca++. The presence of humic substances or clays can markedly reduce the bioavailabilty and hence toxicity of the polymers, and this must be taken into account in any risk assessment of environmental damage resulting from the presence of polymer in surface waters.

The Determination Of Hardness In A Water Sample

The method described below relies on the competitive complexation of divalent metal ions by ethylenediaminetetraacetic acid (EDTA) or an indicator. The chemical structure for the disodium salt of EDTA is in Figure 13.1. Note the lone pairs of electrons on the two nitrogens. These, combined with the dissociated car-boxyl groups, enable formation of a one-to-one hexadentate complex (one cation bonded to six sites on one EDTA molecule) with each divalent ion in solution. Although the complexation constant (describing the location of the complexation equilibrium) is a function of pH, virtually all common divalent ions will be com-plexed at pH values greater than 10, the pH used in this titration experiment and in most hardness tests. Thus, the value for hardness calculated from the experimental results includes all divalent ions in a water sample. Three indicators are commonly used in the EDTA titration Eriochrome Black T (Erio T), Calcon, and Calmagite. The use of Eriochrome Black T...

Phytoremediation of Toxins

Phytoremediation of contaminated soils can be achieved through various processes. These include phytoextraction, phytoimmobilization or phytostabiliza-tion, phytotransformation, phytodegradation, phytostimulation, phytovolatilization and rhizofiltration (Schwitzguebel 2000 Cummings 2009). Of these strategies, phytoextraction or phytoaccumulation consists of natural or induced (enhancement through use of chelating agents) potential of plants, algae and lichens to uptake and remove pollutants from soil, water environment by accumulating them into harvestable biomass. This method is traditionally used for the removal of heavy metals and salts from the contaminated soils. Phytostabilization is stabilization of the toxic pollutants over a long-term. Some plants have natural ability to immobilize pollutants by providing a region around the roots where these pollutants can be precipitated and stabilized. Unlike phytoextraction, phytostabilization involves sequestering of toxins into the...

Uptake and Transport of Cyanide By Plants

Phytoremediation, may provide opportunity to remediate cyanide and iron cyanide contamination, provided that these compounds can be transported and assimilated by plants after passive or active uptake. Translocation from root to shoot requires a membrane transport step from root symplast into xylem apoplast. The impermeable suberin layer in the cell wall of the root endodermis (Casparian strip) prevents toxic substances from flowing straight from the soil solution or root apoplast into the root xylem (Taiz and Zeiger 2002). Organic pollutants pass the membrane between root symplast and xylem apoplast via simple diffusion. When pollutants are sequestered in tissues, they are often bound by chelators or form conjugates. Chelators that are involved in metal sequestration include the tripeptide GSH (y - glu-cys-gly) and its oligomers, the phytochelatins (PCs) (Pickering et al. 2000). After chelation, an ABC-type transporter can actively transport the metal-chelate complex to the vacuole,...

Biosorption of Heavy Metals

Heavy Metal Biosorptionthrough Biomass

Figure 10.1 presents some of the biosorbents that have been recently tested and analysed for their metal ions removal capacity. Research on biosorption is revealing that it is sometimes a complex phenomenon where the metallic species could be deposited in the solid biosorbent through various sorption processes, such as ion exchange, complexation, chelation, microprecipitation and oxidation reduction. The sections to follow highlight the pollution and toxicity characteristics of some selected heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and summarize in a representative manner the various biosorbents that have been studied for their removal from synthetic and or natural contaminated aqueous media.

Plants as Biosorbents 1281 Vascular Plants

(Mukherjee and Kumar 2005), with different arsenic ions concentrations. The second phase was up to 96 and 12 h (Table 12.3). The adsorption of metal ions onto a plant surface was conducted in a relatively short-time, while the uptake of metal ions took a long-time and was more complex (Veglio and Beolchini 1997 Hoffman et al. 2004 Mukherjee and Kumar 2005). Pandey et al. (2009) reported chelation of As(III) with the -OH groups for fresh different parts of the biomass of Momordica charantia.

Conclusion Of The Plant Adaptation

Plants and their associated microbes can remediate cyanide via cyanide uptake, transport, degradation and assimilation in plants. Experiments using free cyanide have shown that many terrestrial and aquatic plants including willow, sorghum, cassava and water hyacinth can remove cyanide from the growing medium. Cyanide uptake in plants can be associated with a very complex physiological mechanism which includes transport and assimilation of cyanide within the plants for catering plant's nitrogen needs. Phytoremediation offers a cost-effective and environment-friendly alternative or complementary technology for conventional remediation methods. Although phytoremediation can work effectively, the underlying biological processes are still largely unknown in many cases. Some important processes that require further study are plant-microbe interactions, detailed cyanide transport, chelation and degradation mechanisms in plants. Collection of this information would be useful in developing...

Phytoremediation with Genetically Modified Legumes and Symbiotrophic Microorganisms

It is assumed that for successful phytoremediation technologies, plants having high metal tolerance, metal uptake potential, biomass production and growth rate are required. However, no natural metalliferous and hyperaccumulating species neither agricultural crops possess sufficient level of all these characteristics. One promising method of attack and overcome these shortcomings is the creation of genetically modified plants via transgenic techniques and mutagenesis. A number of genetically modified plants were generated in order to modify their tolerance to and accumulation of HMs, and the related reports were repeatedly reviewed (Kramer and Chardonnens, 2001 Pilon-Smith and Pilon, 2002 Vassilev et al., 2004 Zhang et al., 2006 Goel et al., 2009). Different approaches in genetic manipulations with plants such as transferring or mutagenising the genes responsible for HM tolerance, uptake, cellular and long-distance transport, binding and chelation, as well as transformation and...

Mechanisms of Silver Nanoparticle Formation

Chelating Agents and Silver Uptake Silver ions may exist as simple hydrated ions in solution or may form complexes with a variety of complexing agents. EDTA is one of the more widely used chelating agents for a variety of metal ions and has been used in an attempt to increase the accumulation of silver in plants (Harris and Bali, 2008). However, although the quantitative results were not disclosed, it was noted that EDTA resulted in a lower uptake of silver than with uncomplexed silver.

Pathways of Heavy Metal Access

Klipp Vningar

In order to assess bioavailability of individual metals for certain plant species, chemical extraction techniques are used most commonly. In general, the readily soluble plus the weakly adsorbed (i.e. exchangeable) metal fraction is considered to be bioavailable. Organisms such as worms can also be used to assess bioavailability. The main categories used as extrac-tants are dilute acids such as HC1 or H2S04, and chelating agents such as EDTA and DTPA. The method most widely used is described in Ref. 6. This method and variations of it include in general the selection of chemical reagents from the least to the most aggressive in sequential fashion and from the least to the greatest extremes in temperature and stirring. The various fractions can be described as follows water soluble (metal exists in soil solution either in free ionic or complexed form), exchangeable (metal is sorbed by electrostatic attraction to negatively charged exchange sites), sorbed (adsorption onto specific...

Phytoremediation A Potential Tool of Bioremediation

Sebertia Acuminate

(EDTA, EGTA etc.) Higher bioaccumulation factors were found for Cd in V. baoshanensis and for Zn in S. alfredii and these resulted in greater extractions of Cd and Zn, respectively. The extraction ability of R. crispus to remove Cd and Zn was considerable, due to its higher biomass. Addition of EDTA enhanced the accumulation of Pb in shoots of V. baoshanensis, S. alfredii, Rumex K-1, and R. Crispus The basic strategies of phytoextraction are (a) development of chelate-assisted phytoextraction, which can be called induced phytoextraction and (b) long-term continuous phytoextraction. If metal availability is not adequate for sufficient plant uptake, chelates or acidifying agents may be added to the soil to release them 65, 168-169 . Several chelating agents, such as EDTA (ethylene diamine tetra acetic acid), EGTA (ethylene glycol-O,O'-bis- 2-amino-ethyl -N,N, N',N',-tetra acetic acid), EDDHA (ethylenediamine di o-hyroxyphenylacetic acid), EDDS (ethylene diamine disuccinate) and citric...

Transport of Zn Across Membranes 741 Diversity of Zn Transporters

Recently, a zinc-induced facilitator 1 (ZIF1) has been reported to influence the detoxification and accumulation of Zn in Arabidopsis thaliana and to be different from the known Zn transporters, which transport free Zn cation (Haydon and Cobbett 2007). Carboxylic organic acids are effective ligands for chelation of Zn in plant cells. Therefore, ZIF1 is thought to transport low-molecular-mass Zn-ligands, such as organic acids, and or Zn-ligand complexes into the vacuoles.

Methods Of Determination

EDTA Titrimetric Method This method involves the use of solutions of ethylenediaminetetraacetic acid (EDTA) or its sodium salt as the titrating agent. These compounds, usually represented by EDTA, are chelating agents and form extremely stable complex ions with Ca2+, Mg2*, and other divalent ions causing hardness, as shown in the equation M2+ + EDTA - M EDTA compla (19.2) The successful use of EDTA for determining hardness depends upon having an indicator present to show when EDTA is present in excess, or when all the ions causing hardness have been complexed. During the titration with EDTA, all free hardness ions are complexed according to Eq. (19.2). Finally, the EDTA disrupts the wine red (M Eriochrome Black T) complex because it is capable of forming a more stable complex with the hardness ions. This action frees the Eriochrome Black T indicator, and the wine red color changes to a distinct blue color, heralding the end of the titration. Although the EDTA method is subject to...

Mechanism of Phytoremediation

As a common chelant, ethylenediaminetetraacetic acid (EDTA) was added to the soil and promoted metal bioavailability and then plants' accumulation. After EDTA addition, lead concentration was logically increased in jack beans (Canavalia ensiformis) (Gabos, 2009), in cabbage shoots (Shen et al., 2002), and in root and shoot tissues of vetiver grass (Vetiveria zizanioides) (Andra et al., 2009), with an increase up to 15-24 folds higher than control. Appropriate level of EDTA application can increase cadmium accumulation in rainbow pink (Dianthus chinensis) (Lai and Chen, 2005), and in stems and leaves of Solanum nigrum (Sun et al., 2009). Some heavy metal uptake was enhanced by 117 in root, 62 in stem, 86 in leaves of Jatropha curcas when EDTA was applied at 0.3 g kg (Jamil et al., 2009). Other chelants can also be assistants for metals' bioavailability and thus uptake by plants. This could be certified in quantities of examples. Organic manure increased copper bioavailability and...

Polymetallic Contamination

The content of antioxidants, such as thiols, ascorbate, and glutathione, was decreased by Cd treatment, but Zn supplementation restored its level by enhancing the activity of enzymes of the ascorbate-glutathione cycle. This phenomenon has not been observed under only Zn treatment (Aravind and Prasad 2005c). In plants subjected to Cd stress and supplemented with zinc, a higher antioxidative status resulted in a significantly lower level of reactive oxygen species, such as superoxide anion-radical, hydroxyl radical, and H2O2. Also, in these plants, protein and DNA damages were remarkably lower compared to Cd-only treated material (Aravind et al. 2009). The heavy metal stress-induced formation of glutathione was significantly increased by Zn supplementation unlike the organic acids-mediated chelation mechanism, which seemed to be insensitive to Zn (Aravind and Prasad 2005d).

Induced Phytoextraction or Chelate Assisted Phytoextraction

Oligopeptide ligands, such as phytochelatins (PCs) and metallothioneins (MTs), are induced by the presence of or interact with heavy metals found in plant cells (Cobbett 2000). These peptides bind with the heavy metal, forming stable complexes, and thus neutralize them and minimize the toxicity of the metal ion 68 . Phytochelatins (PCs) are synthesized from glutathione, and have the structure Gly-(g-Glu-Cys)n, where n 2-11. Around a hundred phytochelating ligands have been reported in plant species exposed to heavy metals (Rauser 1999). MTs are small, gene-encoded, Cys-rich polypeptides. PCs are functionally the same as MTs (Grill et al. 1987). Chelating agents such as ethylenediaminetetraacetic acid (EDTA) have been isolated from plants that are involved in the uptake of heavy metals and their detoxification. The addition of chelators to a Pb-contaminated soil (total soil Pb 2,500 mg kg-1) increased shoot Pb concentrations of Zea mays (corn) and Pisun sativum (pea) from less than 500...

CoPrecipitation Synthesis

The stabilization capping of iron oxides, magnetite, and maghemite has been the main application of dextran in chemistry of oxide materials (Laurent et al. 2008) , dextran coatings being considered as an eco-alternative to the polyethylene glycol (Weissleder et al. 1989, 1990 Stark et al. 1988) Along with its biocompatibility (Berry et al. 2003 Laurent et al. 2004 Gamarra et al. 2005), the polysaccharide and its derivatives have a high affinity (polar interactions, complexation chelation and hydrogen bonds) for iron oxide surfaces (Tartaj et al. 2006). Dextran-coated colloidal magnetic iron oxides are used in magnetic resonance imaging (Stark et al. 1988 Josephson et al. 1991) cell labeling and tracking (Arbab et al. 2004 Bulte 2006 Frank et al. 2003) and cell sorting (Radbruch et al. 1994 Ito et al. 2005). Most of the dextran coating procedures are performed in situ (Palmacci et al. 1995 Molday and MacKenzie 1982) but post-synthesis methods are also used, namely the grafting of the...

So3h Is Uv Active Or

The sensitizers can be regenerated if the produced radical cation of the dye obtains an electron from the electron donor (organic pollutants). The dye-sensitized TiO2 can be considered as photocatalysts, which can degrade other organic pollutants under visible irradiation without the dyes being destroyed. Hodak et al. (1996) have reported the degradation of phenols, thiophenols, 4-chlorophenols, hydroquinones, and salicylic acid by a phthalocyanine dye (hydroxyalumi-numtricarboxymonoamide phthalocyanine) sensitization of the TiO2 semiconductor particles, while EDTA, oxalic acid, and benzoquinone did not show any changes after irradiation. They proposed that the radical cation of the phthalocyanine produced by the electron injection of the dye into the conduction band of the TiO2 is the species responsible for the oxidation of the substrates (Hodak et al. 1996). Investigation of the photocatalytic activity of polycrystalline TiO2 samples sensitized by Cu(II)- or metal-free porphyrin...

Biosorption A Green Remediation

Some types of biomass are waste byproducts of large-scale industrial fermentations while other metal-binding biomass types can be readily harvested from the oceans. Some biosorbents can bind and collect a wide range of heavy metals and organic molecules like dyes and pesticides with no specific priority, whereas others are specific for certain types of metals. When choosing the biomass for metal biosorption experiments, its origin is a major factor to be considered. In general terms, biomass can come from industrial wastes which should be obtained free of charge, organisms that can be obtained easily in large amounts in nature (e.g. bacteria, yeast, algae) or fast-growing organisms that are specifically cultivated or propagated for biosorption purposes (crab shells, seaweeds). Research on biosorption is revealing that it is sometimes a complex phenomenon where the pollutant species could be deposited in the solid biosorbent through various sorption processes, such as ion exchange,...

Soil Hydrolase Enzymes To Assess Soil Contamination

Enzymes Soil

The first mechanism is possible for intracellular enzymes, via mechanisms that prevent metals from passing through cell membranes. Protective mechanisms for extracellular enzymes appear less likely since metal ions are smaller than most enzyme substrates. However, extracellular enzymes can be protected if the site of inhibition is remote from the enzyme's active site and is inaccessible to the metal ion. The second mechanism is a certainty. Heavy metals interact very strongly with soil inorganic and organic constituents through adsorption, chelation, and precipitation reactions that render them much less available. Effectively, most of the metal is ''locked-up,'' and only the small amount in soluble form at the site of enzyme activity (intracellular or extracellular) is able to interact with the enzymes. Lahdesmaki and Piispanen (71), using fractionation techniques, found a very much greater inhibitory effect of Zn and Cu salts on protease, cellulase, and amylase

Heavy Metal Sequestration

Apart from vacuolar sequestration, plants possess additional morphological features that are also involved in heavy metal sequestration and detoxification. Several reports have confirmed the involvement of glandular trichomes and epidermal structures (hydropotes) in the chelation, sequestration, and detoxification of the metals.

Putting It All Together Where Chemistry Enters Into The Modeling Effort

Edta Contamination Chemistry

Ethyenediaminetetraacetic acid (EDTA) is a widely used chemical in industry and is very good at complexing metal ions. We can use EDTA as a com-plexing agent for mercury, which lowers the mercury's toxicity but at the same time increases its mobility by keeping it in solution. Draw a speciation diagram for a closed system (Case II) of 10ppm Hg as a function of EDTA concentration. Use a log EDTA concentration range from 5 to -35. Hg2 + + EDTA2+ fi HgEDTA K 3.16 x 1023 Hg2+ + EDTA- fi HgEDTA + Pj 1.00 x 1027

Sources Used in Nuclear Medicine

51 Cr-EDTA aEDTA, ethylenediaminetetraacetic acid 99mTc-arcitumomab, radiolabeled monoclonal antibody DMSA, dimercaptosuccinic acid DTPA, diethylenetriaminepentaacetic acid MAA, macroaggregated albumin MAG3, mercaptoacetylglycylglycine nofetumomab merpentan, radiolabeled monoclonal antibody sestamibi, 2-methoxyisobutyl isonitrile (Figure 14-9) 99mTc sulfur colloid, Tc2S7 capromab pendetide and imicromab pentetate, radiolabeled indium monoclonal antibodies.

Alkaline Earth Metals Beryllium Magnesium Calcium Strontium and Barium

Magnesium and calcium ions are extremely common in natural water systems, with calcium carbonate (limestone) and dolomite CaMg(CO3)2 being two widespread natural sources. Solubility in water is influenced by pH and CO2 content. The two ions are responsible for the hardness of water, which manifests itself by precipitation with soaps, the calcium carbonate deposits that form when water is heated (boiler scale), and so on. For many purposes (washing, waters for certain heat exchange processes), the precipitates formed by calcium and magnesium ions are obnoxious, and the ions must be held in solution by chelation or removed by ion exchange processes or precipitation in a way that prevents the formation of harmful products. Both magnesium and calcium are essential elements needed in significant amounts by living organisms. Except in the context of the problems just noted, they are not harmful either in solution or as particulate material. Chemically, magnesium behaves similarly to calcium...

Differences of Phytextraction Efficiency under Model and under Field Conditions

A further limitation is the possible biomass yield decrease after EDTA application and the generally too low target metal uptake rates of the plants. Huang et al. (1997) calculated that phytoextraction of Pb can only be feasible if systems can be developed in which more than 1 of Pb in the soil is accumulated in the shoots and more than 20 tonnes of biomass is produced per hectare and year. In our experiment the addition of 9 mmol EDTA kg 1 resulted in a maximum Pb uptake of 0.30 (pot experiment) and 0.0049 (field experiment), respectively, of the total element content in the soil in the first experimental year. Dry harvestable biomass production of Zea mays was decreased from 9.4 0.4 to 2.1 0.2 t ha-1. All these values are far lower than those stated by Huang et al. (1997).

Characteristics of Plants Used for Phytoremediation of Heavy Metals

Plants respond to negative effects of exposition to toxic levels of HMs developing different homeostatic mechanisms to maintain essential metallic ions in suitable concentrations within different cell compartments and minimize the damage caused by non-essential metallic ions. In this way, a regulated network of transport, chelation, traffic and compartmentation control the absorption, distribution and detoxification of the metallic ions (Clemens et al., 2002). The way in which is regulated determinate the ability of plants for restricting uptake and or root to shoot transport, and sequestrating and compartmenting metals in organs and or organelles.

Remediation of Heavy Metals From Soils

A plant that grows fast produces rapidly a large quantity of biomass, and is able to tolerate and accumulate greater concentrations of heavy metals in shoots is an ideal plant for phytoextraction. Most of the commonly known heavy metal accumulators belong to the Brassicaceae family (Kumar et al. 1995). Although hyperaccumulator plants have exceptionally high metal accumulating capacity, most of these have a slow growth rate and often produce limited amounts of biomass when the concentration of available metal in the contaminated soil is very high. An alternative is to use species with a lower metal accumulating capacity but higher growth rates, such as Indian mustard (Brassica juncea) another alternative is to provide them with an associated plant growth-promoting rhizobacteria, which also is considered an important component of phytoremediation technology (Wenzel et al. 1999 Glick 2003). Obviously, the rhizosphere contains a large microbial population with high metabolic activity...

Uptake And Translocation Of Inorganic Pollutants

In soils metal ions are usually strongly bound to soil particles. To improve the bioavailability of metal micronutrients trees have evolved several strategies 6 , e.g. producing and secreting metal-chelating chemicals which, by chelation, mobilize iron, copper and zinc, as well as exuding protons in order to change the pH of the soil in the root zone, thereby solubilising the soil-bound metal ions 13 . The physiological and biochemical mechanisms that explain differences in metal mobility in trees are not well understood 8 . Since in trees metals are transported through the xylem their mobility towards the shoots may be strongly retarded by the high cation exchange capacity of the xylem cell walls. As a result, anionic metal-chelate complexes are more efficiently transported in the transpiration stream. Thus, in the practice of dendroremediation, uptake and accumulation of metals in aerial tissues of plants can be enhanced through the application synthetic and or natural chelating...

Effects of Earthworms on Heavy Metal Availability in the Soil

Dissolved organic carbon (DOC) in the soil solution may considerably affect metal adsorption and uptake through two possible mechanisms (1) the adsorption of organic anions, increasing the negatively charged colloidal surface area, thus causing an increase in metal adsorption (Parfitt and Russell 1977 Barrow 1985), and (2) competition between the colloidal surfaces and DOC, which decreases metal adsorption to soil. Zhu and Alva (1993) showed that there is a positive relationship between the dissolved organic carbon in the soil solution and Zn solubility and uptake based on an increase in Zn chelation. Similarly, Dudley et al. (1986) noted that increasing the DOC in the soil solution also increased Cu uptake. DOC can form complexes with various metals, and these complexes are more soluble and readily taken up than free metal ions (Norvell 1972 Prasad et al. 1976). However, this enhancing effect of DOC on the uptake of metals can be restricted by adsorption to soil minerals. This is...

Trace Element Biogeochemistry in the Rhizosphere

Complexation and Chelation of Trace Elements in Rhizosphere 151 Complexation and Chelation of Trace Elements in Rhizosphere Growth of T. caerulescens for 90 days resulted in Cd depletion of NaNO3-, DTPA- and EDTA-extractable pools which was most apparent in the acidic soil sequential extraction showed that most Cd extracted by the plants from the acidic soil originated from the fraction assigned as organic Cd pool in the calcareous soil, only a small amount of Cd was removed by T. caerulescens, mostly from the fraction assigned as carbonate pool Leaching of TEs from the rhizosphere after mobilization by root exu-dates to deeper soil layers has attracted some attention in recent research Seuntjens, Nowack, and Schulin (2004) performed a modeling study on Cu uptake into roots and Cu leaching in the presence of EDTA and oxalate EDTA was found to stabilize Cu at pH 6 due to the formation of Cu-EDTA surface complexes on goethite. At pH 7.5, increased leaching of Cu below the rootzone was...

Dielectric spectroscopy

The concentration of hemoglobin is 100 mg mL in 0.25 M Tris buffer (pH 8), and that of DNA is 500 mg mL, in 10 mM Tris and 1 mM EDTA (pH 8) buffer. E. coli aresuspended in 85 0.1 M CaCl2 15 glycerol. For our measurements, we employed molded microfluidic channels and simpler enclosed wells. Results are consistent (within a scaling factor for the fluid -CPW overlap length) for sample volumes ranging from 3 pL to 2 0 mL. For the following discussions, we present data from capped 10 mL wells.

Interactions of Fungi with Heavy Metals in the Soil Environment

Fungi are able to restrict the entry of toxic metal species into cells by (1) extracellular metal sequestration - binding the metal to siderophores or other fungi-derived metabolites (2) binding it to the cell wall and wall-associated components, and (3) reducing its uptake by intracellular chelation or sequestration. The above defense mechanisms act simultaneously the mycorrhizal fungus Paxillus involutus is able to produce oxalate that binds some extracellular metals. The heavy metals that are not bound come into contact with mycelium and are localized in or near the cell wall, in the vacuoles, and in the cytoplasm. For Cd, its distribution among the three biomass components listed above was 50 , 20 , and 30 , respectively (Blaudez et al. 2000). Similar detoxification systems may act both intra- and extra-cellularly in the case of nickel immobilized by Aspergillus niger, Ni oxalate crystals have been documented in the extracellular fraction as well as in the cell wall and cytoplasm...

Mobilization and Immobilization of Heavy Metals

Malic acid excretion by saprotrophic and mycorrhizal fungi. Ectomycorrhizal fungi can form micropores (3-10 mm) in weatherable minerals, and hyphal tips are able to excrete micro- to millimolar concentrations of these organic acids (Jongmans et al. 1997). Heavy metals can be mobilized during this process as well as during fungal weathering of limestone, sandstone, marble or other minerals (Gadd 2007). The ability to solubilize metals from metal oxides is frequently present among soil micromycetes (e.g., Aspergillus and Penicillium spp.). One-third of 56 soil isolates were able to solubilize either ZnO, Zn3(PO4)2, or Co3(PO4)2, and five strains solubilized all of the compounds (Sayer et al. 1995). In addition, pyromorphite (Pb5(PO4)3Cl) can be solubilized by several organic acid-producing fungi (Sayer et al. 1999). While acidification seems to be the most frequent mechanism of metal solubilization, there are also other mechanisms that involve metal chelation, such as MnO and Zn...

Microbial Transformation of Arsenic

Depending on the physical-chemical conditions of the environment, some arsenic compounds can be easily solubilized in water and taken up by microorganisms, resulting in high levels of bioavailability. Microorganisms have developed various strategies to counteract arsenic toxicity firstly, active extrusion of arsenic secondly, intracellular chelation (in eukaryotes) by various metal-binding peptides including glutathione (GSH), phytochelatins (PCs), and metallothioneins (MTs) thirdly, arsenic transformation to various organic forms which could be potentially less toxic (Fig. 12.3). Understanding the molecular and genetic level of arsenic metabolism will be, therefore, an important knowledge base for developing efficient and selective arsenic bioremediation approaches, which has so far been considered as a cost-effective and environmental friendly way for heavy metal removal.

Remediation Techniques

Soil remediation is one of the permanent alternatives to remove metal contaminants from soils. The remediation of metal-contaminated soils involves physical, chemical, and biological techniques. Physical techniques are based on approaches generally applied in mining and the mineral processing industry to extract the desired metal-bearing particles from mineral ores (Dermont et al. 2008). These approaches involve mechanical screening, hydrodynamic classification, gravity concentration, froth flotation, magnetic separation, electrostatic separation, and attrition scrubbing (Dermont et al. 2008). Chemical techniques are based on application of leaching solutions containing chemical reagents to enhance the solubility of metals and to transfer the metals from the soils into extractant solution. Depending on the metal type, degree of contamination, and soil characteristics different chemical reagent including acids, salts and high-concentration chloride solutions, chelating agents,...

Of toxic agents

The lead cost-benefit analysis succeeded over that of asbestos because there was a valuable biological marker indicative of low-level lead exposure no such marker exists for asbestos. One of the key driving forces in the control of lead has been the ability to relate relatively low levels of exposure to adverse population endpoints, such as a lowering of IQ. At the relatively low blood lead levels due solely to leaded gasoline, it is not possible to point to a specific individual and state with certainty that their IQ has been affected. However, the power provided by coupling population-based research to a valid measure of exposure has permitted the recognition of subtle IQ effects occurring at relatively low blood lead levels.18 Studies showing such effects were responsible for the Centers for Disease Control (CDC) decreasing the blood lead level for which corrective action was required. The economic costs associated with such action, including just repeating the assay or prescribing...

Soil Washing

This technique involves the use of acids (HCI and HNO3), chelators (EDTA, Nitriloacetic acid, DTPA, etc.), and other anionic surfactant (biosurfactant) (Neilson et al. 2003) to solubilize the polluting metals. It may take the form of in situ treatment, which involves soil flushing with pumps (Neilson et al. 2003), or ex situ treatment, which involves washing an excavated portion of the contaminated site with these agents followed by the return of clean soil residue to the site (Lone et al. 2008). This method is generally expensive and it is fraught with lots of side effects (Lone et al. 2008).

Phytochelatins

Chelation of metals in the cytosol by high-affinity ligands is potentially a very important mechanism of heavy metal detoxification and tolerance. Potential ligands include amino acids and organic acids, and two classes of peptides, the phytochelatins and the metallothioneins (Rauser 1999 Clemens 2001). The phytochelatins have been the most widely studied in plants, particularly in relation to Cd tolerance (Cobbett 2000 Goldsbrough 2000).

Fractionation

Because alkali extractions can dissolve silica, contaminating the humic fractions, and dissolve protoplasmic and structural components from organic tissues, milder extractants (e.g., Na4P2O7 and EDTA, dilute acid mixtures with HF, and organic solvents) can also be employed however, they will also reduce the amount of soil organic matter extracted 25 . In addition, gel permeation chromatography, ultrafiltration membranes, adsorption on hydrophobic resins (XAD, non-ionic methylmethacrylate polymer), adsorption on ion exchange resins, charcoal and Al2O3, and centrifugation are also used for SPHS fractionation 45 .

Organic Acids

Organic acids as amino acids and carboxylic acids are suggestive potential ligands for chelation, owing to the capacity of metal ions to react with S, N, and O (Clemens Ectomycorrhizal symbionts associated with plant roots play specific role in modulating metal stress in plants (Schutzendubel and Polle 2002). Mycorrhiza usually adopt the principle of metal exclusion like absorption of metal by fungal hyphae, non-accessibility to apoplast, and chelation, thereby restricting the movement of metals into the roots. Ectomycorrhizal fungi Pisolothus tincotrius (Tam 1995) and Paxillus involutus (Blaudez et al. 2000) have been shown to tolerate Cd and play a role in Cd-metal amelioration.

Partners

It is known that many of the AMF are well adapted to environments characterized by high concentrations of HMs and survive for long periods in polluted soils, but negative effects of HMs on root colonization and mycorrhizal structures in roots were also described (Leyval et al., 1997 Leyval and Joner 2001, Ouziad et al., 2005 Giasson et al., 2008 Andrade et al., 2004). These micro-symbionts developed a number of mechanisms of HM tolerance such as (1) extracellular or intracellular metal sequestration and precipitation with organic acids and other ligands, polyphoshates and metallothioneins (2) metal biosorption by protein glomalin (3) metal binding to cell walls and intracellular metal chelation (4) reduced uptake or increased efflux of HMs by fungal cells. However there are also observations showing significant inhibition of mycorrhizal root colonization by the presence of HMs in soil. Since AMF are obligate symbionts, their HM tolerance depends on the host plant (plant metabolism and...

Biomineralization

In addition to chelation, the induction of mineral formation can lead to metal depletion in the direct surroundings of a bacterial cell. Biomineralization is the process in which microorganisms aid the growth of crystals by providing either a crystallization initiator or anions for mineralization. Both of these approaches to biomin-eralization depend on the presence of cells, and the latter depends on the presence of actively growing, living cells. One well-studied example of biomineral formation is provided by the intracellular magnetite-containing bodies formed by magnetot-actic bacteria (Bauerlein 2003). An extracellular biomineralization process appears to be more conducive to metal resistance. The formation of hydrozincite in zinc-rich mine effluents has been described (De Giudici et al. 2007). There, the precipitates formed with bacterial inocula were the dominant species of zinc in the AMD waters. This biomineralization would also allow growth under high nickel stress. Indeed,...

In surface waters

The development of highly sensitive and element-specific detectors, like electrothermal vaporization atomic absorption and inductively coupled plasma atomic emission, mass spectroscopic instrumentation, and of electrochemical methods, like ASV, and hence the tremendous lowering of the analytical detection limit (down to ppt levels) for total concentrations of almost all metals, has concomitantly supported developments to further improve the selectivity and reproducibility of chemical and instrumental separation methods (like exchange resin, dialysis membrane, competitive chelation or chromatographic techniques) to identify and quantify particular metal species in complex natural waters (see Reuther 1999 and Allen 2002). As a first approach the distribution of metal compounds in aqueous phases can be defined according to their size as dissolved ( 1 nm), colloidal (1 nm - 0.2 m) and particulate metals ( 0.2 m). Resulting partitioning or distribution coefficients (kd) provide an estimate...

Blepharis Aspera

Understanding chelation mechanism is an important aspect in developing plants as agents of phytoremediation for contaminated sites. Recent advances have been made by Mmatli et al to study aspects of chelation in Blepharis Aspera as plausible mechanism for detoxification using LC-SPE-NMR 27 . In these studies reverse phase HPLC with UV detection was used to isolate compounds of the plant extracts. SPE column packed with porous graphite carbon was employed to enable multiple trappings of the target compound and hence improve NMR sensitivity. The major compounds were identified by NMR as phenyl propanoids verbascoside and isoverbascoside and these were present in 0.7 w w and 0.2 w w dry weight respectively 27 . The potential of these compounds verbascoside and isoverbascoside to complex with metals (Cu2+, Ni2+ and Fe2+) was further investigated using ES-MS and UV-Vis spectrometer. Through the significant shift in absorbances the UV-Vis spectroscopy results confirmed complexation of...

Phytoremediation

Induced phytoextraction consists of two basic processes that involve metal release to the soil solution combined with metal transport, via xylem, to the aerial part of the plant that will be harvested (Salt et al., 1998). This type of phytoextraction is more advanced and currently commercially implemented (Nascimento and Xing, 2006). A good example of this sort of phytoremediation is that reported for Pb in soil in which EDTA was applied (Salt et al., 1998). However, the main limitation for the use of synthetic chelants in the field, especially EDTA, is its low biodegradation. This results in maintenance of high contents of soluble metals in the soil for long periods, which increases the lixiviation risks (Meers et al., 2004).

Aspartic Acid

Aspartic acid can be produced chemically by amination of fumaric acid with ammonia however, these are asymmetric and hinder the further development of the process. Using biotransformation, aspartic acid can be produced from oxaloa-cetate (Krebs cycle) via fermentative or enzymatic conversion. Aspartic acid is used to make chelating agents and sweeteners and can be reduced to produce amino analogs of carboxylic acids. The dehydration reaction can be improved by employing solid catalysts (replacing liquid catalysts). The resulting aspartic anhydride can be used as a chemical intermediate. Through esterification, polyaspartic acid (PAA) and polyaspartates can be synthesized but controlling the molecular weight is a challenge. These polymers have several uses and can be used as alternatives to polyacrylic acid and polycarboxylates.