Removal of Cadmium Ions from Aqueous Samples by Synechocystis sp.

Abstract

The biosorption of cadmium ions from aqueous solution by dried, immobilized dried and immobilized live Synechocystis sp. was investigated. Sorption of plain Ca-alginate beads, which were used as substrate for immobilization, was also studied for comparison. Removal efficiency of biosorbents was studied as a function of pH (2-8), temperature (20–40°C), initial cadmium ion concentration (50–300 mg/L), and contact time (0–120 min). The maximum biosorption capacities of the dried, immobilized dried, and immobilized live Synechocystis sp. and plain Ca-alginate beads were found as 75.7, 4.9, 4.3, and 3.9 mg/g, respectively at optimum conditions. Biosorption equilibrium was established in about 15 min. Dried biomass of Synechocystis sp. was found to be more suitable and an efficient biosorbent for the removal of cadmium ion from aqueous solution. Both of the isotherm models (Langmuir and Freundlich) were suitable for describing the biosorption of cadmium by the dried biomass of Synechocystis sp. All the tested cyanobacterial forms could be recovered more than 90% and reused in five biosorption–desorption cycles without any considerable loss in the biosorption capacity.