Adsorption of toxic metal ions from laboratory effluents by agricultural waste

Abstract

The chemistry laboratory effluents usually contains highly toxic organic and inorganic pollutants including metal ions .These hazardous chemical wastes pose serious health problems to living beings. The persistency of toxic metals in environment and their ill health effects are well known. Out of the possible methods to check toxic metal ion pollution, the bio-remediation is of great importance as conventional methods used to remove these toxic metal ions are quite expensive and have certain limitations in terms of efficiency and disposal of secondary waste produced in the process. Adsorption of these metal ions by agricultural waste materials has advantage because of the low cost and high efficiency. Moreover these are environment friendly and there is a possibility of metal ion recovery also. These cellulosic agricultural wastes contain various functional groups like carbonyl, alcohol, acetamido, sulfhydryl etc. which can form chelateswith metal ions and help sequestering of these toxic metals. In the present study rice husk and orange peel have been used for the removal of metal ions from laboratory effluents. Our studies have indicated that the adsorption of metal ions by these bio-sorbents is efficient for the bio-remediation of the laboratory wastewater. Some of these are highly efficient and remove nearly 85% of toxic metal ions. Kinetics of adsorption of metal ions on these materials is also studied. Both Langmuir and Freundlich isotherm models have been studied for mono component adsorption of metal ion by these bio-sorbents. Free energy change for sorption is also calculated. Various physical parameters of laboratory effluent water were compared before and after the adsorption.