Application of carboxymethyl polysaccharides as bio-sorbents for the sequestration of heavy metals in aquatic environments.

The removal of hazardous heavy metals from the environment is imperative in order to have quality of water. Robust and eco-friendly technologies are required for the treatment of domestic, agricultural and industrial effluents. The effective treatment of wastewaters can be done using chemically modified polysaccharides as adsorbents of these toxic heavy metals. A popular method used by researchers to chemically polysaccharide adsorbents is carboxymethylation. Carboxymethyl polysaccharides, generally, have higher adsorption capacities for heavy metals than their unmodified forms. This paper reviews the applications of carboxymethyl polysaccharides as adsorbents of heavy metals in wastewaters. The review places particular emphasis on the use of carboxymethylated cellulose, chitosan and starch for the adsorption of heavy metals in contaminated aqueous environments. The literature reviewed generally showed that these carboxymethyl polysaccharides are good adsorbents of heavy metals. Some modifications, however, are required to enhance the chemical and mechanical strength of these carboxymethyl polysaccharides.