Potential of agricultural and agroindustrial wastes as adsorbent materials of toxic heavy metals: a review

Most of the population does not have water access with the required quality and quantity, because natural resources are adversely affected by anthropic activities. Agricultural and industrial activities result in the release of a high amount of contaminants into the environment, among these, toxic heavy metals are the ones that are of most concern to the society. These metals (Hg, Pb, Cd and Cr - for example) can be accumulated and bioaccumulated in the trophic chain. When high concentrations of these elements are in the human organism, metabolic, renal and blood dysfunctions, cancers, among others, can occur. Another increasing environmental problem is the high amount of agricultural wastes produced annually. Population growth generates an inelastic demand for food, and the production of these food results in an increasing amount of waste. The use of these wastes to produce adsorbents could add value to these residues. Moreover, the new adsorbents could be used in the decontamination of polluted waters containing toxic metals such as Hg, Pb, Cd, Cr and others. Also, these residues from agriculture could also be used to produce activated carbons, since activated carbons can adsorb more heavy metal than in natura material. Aiming to solve two environmental problems at once (the decontamination of heavy metals from waters and the correct destination of solid agroindustry wastes), this study investigated the capacity and viability of the decontamination of waters by the use of adsorbents produced from agroindustrial biomasses.