Industrial, agricultural and domestic activities of human have affected the environmental system, resulting in drastic problems such as the generation of wastewater containing high levels of pollutants. Although many heavy metals are necessary in small amounts for normal development of the biological cycles, most of them become toxic at high concentrations. Lead, mercury, nickel, zinc, copper and chromium are often detected in appreciable amounts in industrial wastewaters, which originate from mining activities, metal plating, smelting, paint manufacture, pigment manufacture, pesticides, tanneries, printing and photographic industries, etc. 1. Since heavy metals are non-biodegradable and can be accumulated in living tissues causing various diseases and disorders, they must be removed from solution prior to their discharge. To date, various methods including chemical treatment with lime, precipitation, ionexchange, reverse osmosis, electro-dialysis, membrane filtration, solvent extraction and adsorption are often used for the removal and recovery of heavy metals from wastewaters. Among them, adsorption is the most effective and widely used method for the removal of different pollutants 2. Recently, much attention is given to prepare adsorbents from various wastes generated from forestry 3 , fishery 4,5 and by-products of agriculture 6-12. According to hard and soft acids and bases (HSAB) classification system, sulfur can be considered as a soft ligand
