A review study of biosorption of heavy metals and comparison between different biosorbents

With rapid industrial development,problems related to pollution are becoming severe water pollution is one of the most serious problems because inorganic and organic wastes are discharged to the aquatic environment either in water soluble or insoluble forms. heavy metal ions have lethal effects on all forms of life and these enter the food chain through the disposal of wastes in water channels. from among various metal ions,lead,mercury,cadmium and chromium(vi) are at the top on the toxicity list. due to non-biodegradability,metal ions accumulate and their amounts are increased along the food chain. hence,their toxic effects are more pronounced in the animals at higher trophic levels. various techniques have been employed for the treatment of dye/metal bearing industrial effluents,however those processes are often inefficient and economically unviable. a variety of biological materials have been used as sorbents for the uptake of metal ions from aqueous solutions. the main advantage of biosorption is that it is a cheap process with good metal recovery results and ecofriendly. natural biomasses can be used as biosorbents,either ones that are abundant locally or residual byproducts from industrial plants,mainly agricultural wastes. the biosorption mechanism and important effective factors on batch biosorption process were studied.