Lead sorption by living biomass of Chroococcus multicoloratus and Oscillatoria trichoides: kinetics and equilibrium studies

We report here the ability of two freshwater living cyanobacteria, Chroococcus multicoloratus Wood and Oscillatoria trichoides Szafer, to remove lead (Pb²⁺) from aqueous solutions in batch system, wherein the effect of Pb²⁺ on the growth rate of both the cyanobacteria was evaluated. The influence of sorption time, initial pH, initial Pb²⁺ ion concentration, culture density and the biosorption equilibrium kinetics was examined. Biosorption capacity was found to be maximum between a pH of 5 and 5.14, on the second day of exposure and at an initial concentration of 80 and 60 mg L^?1 for C. multicoloratus and O. trichoides, respectively. An initial concentration in the range of 10–120 mg L^?1 significantly decreased the growth and efficiency of Pb²⁺ removal. The maximum sorptive capacity (q _max) obtained from the Langmuir isotherm for C. multicoloratus and O. trichoides was 178.57 and 106.38 mg g^?1, respectively. The pseudo-second-order model was found to correlate well with the experimental data. Metal recovery of 70–77 % was obtained with HCl as a desorbing agent. The results of Fourier transform infrared spectroscopy indicated the participation of hydroxyl, carboxyl and amino groups in the biosorption process. Based on our observations, we suggest that both species appear to be potential viable biosorbents for mildly acidic water contaminated with Pb²⁺.