Biosorption characteristics of Spirulina and Chlorella cells for the accumulation of heavy metals

Abstract

The biosorption of heavy metals by dried Chlorella vulgaris and Spirulina platensis-Spirulina maxima cells was studied under various experimental conditions. The effects of biosorbent dosage, pH, adsorption time, temperature, initial metal concentration on the biosorption were examined. A biosorption process can be divided into two parts: the first part follows zeroorder and the second part pseudo second-order kinetics. Characterization of biosorption equilibrium was evaluated employing the Langmuir and Dubinin- -Radushkevich models using non-linear regression. The optimum pH range was found to be 5.0-6.0 for Pb(II) and 4.0-6.0 for Cu(II) and Cd(II) adsorption. Based on the experimental data, the maximum adsorption capacities for Pb(II), Cd(II) and Cu(II) were 144, 161 and 138 mg g-1 by Chlorella cells and 370, 201 and 165 mg g-1 by Spirulina cells. The corresponding values for activated carbon were 86, 134 and 43 mg g-1, respectively.