Wolfgang Ostwald Prize 1993 awarded to Wolfgang Helfrich

Wolfgang Helfrich, Berlin, received the Wolfgang Ostwald Prize of the KolloidGesellschaft for his fundamental work on complex fluids and colloids, in particular for his contributions to the cooperative behavior of liquid crystals and membrane systems. W. Helfrich is a real pioneer in these interdisciplinary research fields. On the one hand, he made novel experimental discoveries, on the other hand, he developed basic theoretical concepts which turned out to be crucial for research...

Xray microscopy studies of aqueous colloidal systems

The aggregation of hematite particles with a diameter of nominal 80 nm by CaCl2 was investigated. 150 mg freeze dried hematite was suspended in 10 ml bidistilled water by ultrasonic treatment. To 1 ml aliquots different amounts of a 1 CaCl2 2 H20 solution were added. In Fig. 3 primary hematite particles suspended by ultrasonic treatment in bidistilled water are shown. As can be seen, the primary particles are completely dispersed. The addition of CaCl2 leads to an aggregation of the particles....

Fiberoptic flocculation sensor FOFS

Flocculation Sensor

The measuring device is made up of three integrated units an arrangement for mixing in the flocculation aid and a region for floe formation, a fiber-optic sensor fitted in an enveloped-flow cell, detector electronics connected to a computer for combined data analysis and control of dosing. The principle of the experimental arrangement of the FOFS is shown schematically in Fig. 2. The medium to be flocculated is turbulently mixed with the solution of the flocculation aid in a mixing chamber,...

Results and discussion

Silica, silicate surfaces and cationic surfactants Precipitated silica, silica gel and quartz adsorbents with pH-dependent surface charge sites The adsorption of cationic surfactants from aqueous solutions on solid surfaces with dissociable surface sites depends greatly on the pH of the medium. On the one hand, it is determined by the pH-dependent surface charge state of the adsorbent. The point of zero charge (p.z.c.) of silica surfaces is usually at low pH, most frequently below 4 34 , From...

Bentonites adsorbents of toxic substances

Lagaly Institute of Inorganic Chemistry University of Kiel Olshausenstrafie 40 24098 Kiel, FRG Abstract The use of bentonites as adsorbents results from the reactivity of montmorillonite which is the main mineral in this clay-like material. Montmorillonite, a 2 1 clay mineral, impresses by a diversity of reactions in the interlayer space and at the external surfaces, which are the cause of strong adsorption of heavy metal ions and organic compounds. Bentonite adsorbents are used as...

Environmental specimen bank of the Federal Republic of Germany Significance of surfactants

Klumpp M. J. Schwuger Institute of Applied Physical Chemistry, Research Centre J lich (KFA), P.O. Box 1913, 52425 J lich, FRG Abstract Environmental contaminants in water, soil, and air, as well as changes in their concentration with respect to space and time may be quite effectively detected by the analysis of appropriate indicators (biomatrices from different levels of the food chain, sediments, sludges, dusts) which accumulate these chemicals by several...

Pathways of vesiculation

Wolfgang Helfrich Fachbereich Physik, Freie Universit t Berlin, Arnimallee 14, 14195 Berlin, FRG Abstract Possible ways of producing bilayer vesicles are reviewed from the theoretical point of view. The emphasis is on vesiculation driven by a negative bending energy of spherical vesicles, called spontaneous vesiculation. A new model is presented to explain the existence of onions, i.e. concentric spheres of equidistant membranes. Key words vesicles onion-like membrane structures bending...

The swelling of clay

When the clay in a soil absorbs water, it swells into the neighboring pores and reduces their radii. According to Poiseuille's law, the rate of fluid flow through a circular pore is proportional to the fourth power of the radius of the pore. Consequently, the swelling of clay in a soil reduces the permeability of the soil to water and, thereby, the convective transport of toxic substances dissolved in the water. It is clear, therefore, that clay swelling and environmental pollution are related....

Screening method for assessing the effectiveness of flocculation aids for waste water treatment

In waste water treatment, flocculation (coagulation) of the solid particles present in the water or sludge is induced by polymeric flocculants. Voluminous, stable floes are formed, which speeds up the process of sedimentation and makes dewatering of the sludge possible. Depending on the nature of the water or sludge, it is necessary to select polymeric flocculants which have optimal properties with respect to effectiveness and economics. The fiber-optic flocculation sensor has the particular...

Substances

The following commercially available fillers were used Kaolin Spex IF, calcium carbonates of the type Hydrocarb 90 OG (powder and slurry). The specific surface area of the fillers used for adsorption was determined by the BET method (Sorptomatik 1800, Carlo Erba Strumentazione, Italy). It was 7.5 nr g for kaolin and 10.3 m2 g for Hydrocarb 90 OG. Fibers Sulfate-bleach-ed cellulose from soft wood was used for the adsorption experiments. The cellulose fibers were disintegrated and left to swell...

I

Fig. 11 29Si-NMR spectra of sodium silicate solution Na Si 2 at 20 C, obtained from different sources, a) From waterglass solution Na Si 0.6 b) From amorphous silica 33 smaller and the growth of precursor to a critical size is slower, so many building blocks have time to reorient and become precursory. In that way, more nuclei are formed and, consequently, smaller crytals are obtained. However, although aging temperature causes significant effects, it is too slow to be of practical use. For a...

Of coagulating reagents with the sol

Coagulation has been analyzed so far as the result of two major reaction steps, the destabilization of the colloids and the transport and adherence of the destabilized dispersed solids to form permanent aggregates. And this model suffices to explain all observations as long as coagulation is studied in a laboratory context, i.e., small-volume batch reactions. As soon as coagulation is explored in a technical context, under conditions of continuous flow and in larger reactor vessels, then the...

Conclusion

Smectite clay adsorbents (bentonites) offer a broad scale of applications and bind different kinds of compounds (Table 3). Percolation experiments are now widely used to test the adsorption behavior of absorbents for practical purposes. An enormous pool of data is produced. However, the data must be used very cautiously as they are often obtained under less defined conditions and far from equilibrium. The interaction of organic materials with smectites often change the particle-particle...

Steinkopff Prize 1993 recipient Duan Vudelic

Dusan Vucelic was born July 17, 1938 in Belgrade, where he completed a Master of Science degree at the Faculty of Physical Chemistry of Belgrade University in 1964. In 1970, he received his doctorate in Physical Chemistry, his thesis being NMR Relaxation of Molecules at Interphases, a field with only a few publications at that time. Subsequently, he became assistant professor of solid state physical chemistry at Belgrade University. Since 1981, Dusan Vucelic has held a full...

Bentonites as adsorbents

Bentonite adsorbents are or may be used as organically modified bentonite and Crude bentonite and sodium bentonite (soda activated bentonite) bind heavy metal ions by cation exchange. Usually, the preference is (see also 70 ) Cu2+ > Pb2+ > Zn2+ > Cd2+ > Mn2+ . The separation factor as or selectivity coefficient Ks depend not only on the layer charge, but change with proceeding exchange, too 62 64 , The separation factor (bars concentration at the surface) for a mixture of Cu2+ and Mn2+...

Of the BASF waste water treatment plant

Diagram Flocculation Water Treatment

The individual steps of mechanical and biological waste water treatment in the BASF plant (Ludwigshafen, FRG) 17, 18 are shown in Fig. 10. After neutralization of the 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Fig. 9 Flocculation of municipal sewage sludge with Sedipur products (Kl, K2) Fig. 10 Flow diagram of the BASF waste water treatment plant 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Fig. 9 Flocculation of municipal sewage sludge with Sedipur products (Kl, K2) Fig. 10 Flow diagram of the...

Materials and methods

The following solids were used as adsorbents Silicagel R (Reanal, Hungary, analytical grade), silica powder (precipitated from commercial sodium silicate solution by alcohol and then dried and sieved. The Na+ content at the surface of the precipitated silica was 3.07 mmol per 100 g solid powder, determined poten-tiometrically.), silicates Sepiolite (Spain), Zeolite 13X (Linde, FRG), kaolinite (Zettlitz, FRG), illite (Fuz rrad-v ny, Hungary), montmorillonite (Mad, Hungary), and vermiculite...

Predicting synergism in binary mixtures of surfactants

Surfactant Research Institute, Brooklyn College, City University of New York, Brooklyn, New York 11210, USA Abstract Chemicals in the environment continue to cause concern. One method of decreasing the environmental impact of surfactants is to design new molecules that are more efficient and effective in their interfacial activity. New types of surfactants with two hydrophilic and two or three hydrophobic groups in the molecule, called gemini surfactants, exhibit these characteristics. When...

Polyhydroxoaluminum smectites

One way to prepare pillared smectites and probably the simplest method for scaling up to industrial production is introducing polyhydroxoaluminum cations by cation exchange. These cations are formed when NaOH is added to aluminum salt solutions in amounts NaOH Al3 lt 3 typical 1 2.5 100 105 , Usually, the polyhydroxoaluminum smectites are heated to 300 400 C to dehydrate them into polyoxoaluminum smectites. As adsorbents they may also be used in the uncalcinated form. Zielke and Pinnavaia 106...

Clay mineralorganic interactions

The layer structure of 2 1 clay minerals provides different types of surfaces and different sites for the interaction with organic compounds Fig. 1 the external surfaces with distinct differences between the basal plane and edge surfaces and internal surfaces. The organic molecules can interact with the exchangeable interlayer cations, the cations or anions residing at the edges, the silanol and aluminol groups on the edges, and the silox-ane oxygen atoms of the layers. The oxygen atoms of the...

Experimental results

Preparation and properties of the magnetite particles The magnetite Fe304 particles were prepared in the water carrier by coprecipitation of concentrated iron II and iron III salt solutions with ammonium hydroxide. The particles have the following physical properties Medium particle core diamter 10 1 nm Specific area BET-method 130 m2 g Saturation polarization about 400 mT, No hysteresis in the magnetization curve. Magnetite sols ferrofluids have been well known for about 30 years. Our...