Biosorption of Cadmium from Aqueous Solution by Free and Immobilized Dry Biomass of Chlorella vulgaris

Biosorption by algae is an effective process for the removal of heavy metals from the aqueous solutions. The present work deals with the biosorption of Cd(II) by Chlorella vulgaris in a batch system. The biosorption efficiency of Cd(II) removal was studied at different pH (3-8), initial metal concentrations (20-100ppm), agitation time (5-120min.), agitation speed (50-250rpm), and biomass dosage (0.01-0.1g/50ml of metal solution). The optimum conditions for maximum biosorption capacity for C. vulgaris were at pH 6, initial Cd(II) concentration 75mg/l, biomass dosage 0.08g/50ml metal solution, temperature 25 degrees C, agitation speed 250rpm, and agitation time 30min. The cadmium removal efficiency of the raw and pretreated algal biomass was studied under the optimum conditions. The results showed that pretreatment with acetic acid gave 99.346% as compared with raw biomass. Different algal weights (0.2, 0.15, 0.1, 0.05, and 0.025g) were immobilized with 10ml of 4% calcium alginate. The results showed that the highest cadmium biosorption efficiency was 76.448% for 0.025g as compared with the control. The biosorption mechanisms were examined by Fourier-transform infrared analysis and scanning electron microscopy for raw and pretreated algal biomasses before and after cadmium biosorption. It was found that hydroxyl, amide with hydrogen bond, and carbonyl stretching in carboxyl groups played an important role in biosorption. Article HighlightsRemoval of heavy metals in aqueous solutionsBiosorption of Cd(II) by Chlorella vulgaris in a batch systemImmobilization of Chlorella vulgaris increased the biosorption capacityCulture conditions and environmental conditions affected biosorption capacity