Utilisation of native, heat and acid-treated microalgae Chlamydomonas reinhardtii preparations for biosorption of Cr(VI) ions

The hexavalent chromium biosorption onto native, heat- and acid-treated Chlamydomonas reinhardtii was studied from aqueous solutions. Biosorption equilibrium was established in about 120 min. The surface properties of the microalgae preparations varied with pH, and the maximum absorption of chromium ions on the microalgae preparations was obtained at pH 2.0. The biosorption of chromium ions by the microalgae preparations increased as the initial concentration of chromium ions increased in the medium. The maximum biosorption capacities of the native, heat- and acid-treated algal preparations were 18.2, 25.6 and 21.2 mg Cr(VI) per g of dry biosorbents, respectively. Equilibrium concentration (q(m)) and dissociation constant (K-d) were calculated by fitting the experimental data with the Langmuir isotherms. The chromium adsorption data were analysed using the first- and the second-order kinetic models. The experimental results suggest that the second-order equation is the most appropriate equation to predict the biosorption capacities of all the biosorbents. All the tested algal preparations could be regenerated using 0.1 M NaOH solution, with up to 96% recovery. (c) 2004 Elsevier Ltd. All rights reserved.