Biosorption of Cd and Pb ions from aqueous solutions by biomass of the green microalga, Scenedesmus quadricauda

In this study, the dry biomass of green microalgae Scenedesmus quadricauda was used as a biosorbent to remove Cd and Pb from aqueous solutions. The effect of contact time, solution pH, the initial metal concentration, and biosorbent dose on the removal efficiency of metals from synthetic solutions was investigated. The metal adsorption was relatively fast, and the equilibrium times for both metals were between 30 and 60 min, with the maximum biosorption of Cd and Pb being 66 and 82 %, respectively, at pH 5. Biosorption of Cd and Pb by the biomass followed a pseudo-second-order kinetic model. The biosorption of the metals was better fitted by Langmuir models rather than that by Freundlich. Based on the Langmuir model, the maximum biosorption capacity of S. quadricauda dry biomass for Cd and Pb was predicted to be 135.1 and 333.3 mg g(-1), respectively, at pH 5, corresponding to the obtained experimental values. Desorption of both metals was reached up to 90 % using 0.5 M HNO3; however, the capacity of algal biomass was decreased after the first adsorption-desorption cycle. The removal efficiency of Cd and Pb from industrial wastewater was 65 and 69 %, respectively.