Introduction

Presently, due to the accumulation of waste materials, environmental problems are getting acute worldwide. The conditions for waste materials storage and disposal frequently do not meet current health requirements and cause pollution of the surface and ground water, soils, and air. There is clearly an awareness of how serious the situation is becoming, with respect to the protection of our natural resources, and the necessity for dealing with environmental problems.

In the last decade, several commercial waste recovery projects have been implemented for waste conversion into secondary gaseous, liquid, or solid products. The interest for developing and using those processes is increasing due to economic and environmental reasons. Within this context, the conversion of natural organic wastes into environmentally-friendly porous materials is a technological alternative to their disposal.

Low-cost adsorbents for air/water purification have recently been reviewed by Pollard et al. [1]. Activated carbons from coconut husk, grain husk, domestic wastes, and tires have been used for phenols removal [2]. Several low-cost activated materials from rice husk [3], coconut [4, 5], bituminous coal [6], sphagnum moss peat [7], sawdust [8], and industrial solid wastes [9] have been reported as adsorbents for heavy metals removal. Activated carbons from soybean hull, sugarcane bagasse, peanut shell, and rice straw were found to be suitable for air purification from toxic gases [10].

Recently, a novel approach to the wastes recovery via their co-processing has been proposed. The existence of synergistic effects between the blend components during their conversion into solid products is still an open issue. Some authors have observed the absence of synergistic effects [11-16], whereas evidence of their presence has been reported for co-gasification [17-19] and co-pyrolysis [20].

We have observed a synergistic effect during the co-activation of comingled wastes [21]. The adsorption capacity of the activated carbons produced was found to be higher than those of commercial Norit and Merck activated carbons for Cr (III) removal [21]. Therefore, there is a strong interest in developing innovative processes, for producing secondary environmental friendly adsorbent materials from co-mingled wastes, and to optimize their properties in order to selectively remove heavy metals from waste water.

The main purpose of this study is to produce an activated carbon from co-mingled waste, and to use it as an adsorbent to remove 3-d transition metals, such as Cu (II), Co (II), Ni (II), Fe (II), and Mn (II), from real waste-water solutions.

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