Utilisation of agricultural wastes for decontaminating industrial/domestic wastewaters from toxic metals

Abstract

Toxic heavy metal cations can be selectively removed from domestic, mining and industrial waste streams by contact with certain agricultural by-products (e.g. bagasse, bark and onion skin). The metals are sorbed on modified agricultural by-products by ion-exchange or chelation or adsorption. Both equilibrium and column experiments were carried out with solutions of heavy metals (such as Cu 2+, Pb 2+, Cd 2+, Hg 2+) to determine rate, selectivity and capacity of the agricultural substrates for heavy metal cations. The capacity of the substrates for the majority of the metal ions studied is well above 1 mequiv. g −1 of the substrate. The toxic/valuable metal ions can be recovered and the substrates can be repeatedly reused. The data indicate the potential use of these agricultural waste materials as an alternative to the expensive commercial ion-exchange resins, to remove toxic metals from contaminated water to acceptable safety limits.