ABSTRACT
Husk of tur dal (Cajanus cajan) was investigated as a new biosorbent for the removal of Fe (III) and Cr (VI) ions from aqueous solutions. Parameters like agitation time, adsorbent dosage and pH were studied at different initial Fe (III) and Cr (VI) concentrations. The biosorptive capacity of the Tur dal husk was dependent on the pH of the chromium and iron solution, with pH 2 and 2.5 respectively being optimal. The adsorption data fit well with Langmuir and Freundlich isotherm models. The practical limiting adsorption capacity (qmax) calculated from the Langmuir isotherm was 96.05 mg of Cr(VI)/ g of the biosorbent at an initial pH of 2.0 and 66.65 mg/g at pH 2.5. The infrared spectra of the biomass revealed that hydroxyl, carboxyl and amide bonds are involved in the uptake of Cr (VI) and Fe (III) ions. Characterisation of tur dal husk has revealed that it is an excellent material for treating wastewaters containing low concentration of metal ions.