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ABSTRACT
The adsorption capacity of four different biochar adsorbents prepared from corn cobs and cassava peels at 350 and 450℃ for the removal of cadmium and lead ions from their aqueous solutions were investigated. The biochars were characterized in terms of physico-chemical properties, functional groups, surface characteristics and thermal behaviour. The effects of adsorption process variables on the adsorption capacity of the biochars for the the removal of cadmium and lead ions were evaluated using the one factor at a time method. The adsorption process variables considered and their range of values are initial metal concentration of 20 to 100 mg/l, biochar dosage of 0.2 to 1.0 g, contact time of 20 to 100 mins, and pH of 2 - 11. The characterization of the biochars revealed that all biochars had similar microporous distribution, thermal behaviour and functional groups, close surface area values and slightly different physicochemical properties. Maximum removal efficiencies of the biochars were achieved using an initial metal concentration of 20 mg/l, biochar dosage of 1.0 g, contact time of 100 mins and pH of 11. It was observed that Pb2+ ion was generally more adsorbed in all the adsorption experiments by the different biochar adsorbents than Cd2+ . The high values of the removal efficiencies obtained showed that all biochars were effective in treating aqueous solutions laden with cadmium and lead ions.
