Biosorption of trivalent chromium by free and immobilized blue green algae: Kinetics and equilibrium studies

Abstract

The process of biosorption of trivalent chromium (Cr^{3 +}) by live culture of Spirulina platensis and the sorption potential by the dried biomass, in both free and immobilized states have been investigated for a simulated chrome liquor in the concentration range of 100–4500 ppm. Both live and dried biomass were very good biosorbents as they could remove high amounts of chromium from tannery wastewater. Polyurethane foam and sodium alginate were used as immobilizing agents and their performances compared. Biosorption kinetic data on Cr^{3 +} sorption onto dried biomass were analyzed using pseudo–first-and pseudo–second-order kinetic models in batch column experiments. The second-order equation was more appropriate to predict the rate of biosorption.

Subsequently, the effects of height of packing & diameter of the column, concentration of blue-green algae (BGA) in varying amounts of sodium alginate, chromium concentration were studied. The results fit into both Langmuir & Freundlich isotherm models with very high regression coefficients. Furthermore, equilibrium studies using retan chrome liquor (RCL), with a chromium concentration of 1660 ppm, obtained from a tannery also showed promising results. In general, our studies indicate the efficacy of the algal species in removal of chromium from tannery wastewater.

Keywords:

• Spirulina sp.
• metal biosorption
• immobilization
• packed column
• sorption rate
• adsorption isotherm

Acknowledgments

The authors wish to thank Dr. T. Ramasami, former Director, CLRI, Chennai for his permission to undertake this study and encouragement; Dr. S. Sadulla, Head, CHORD, CLRI, for providing facilities for scale-up studies, Mr. V. K. Rangaswamy, former Head, Glass Blowing Section, CLRI for his expertise in designing the column tubes and valuable suggestions, Ms. A. Yashothai, Project Assistant, CHORD, CLRI for her assistance in chemical analysis, Mr. A. Hariharan, Mr. S. Ashwin, Mr. Sathyendra Tripati, Mr. P. Murari, Ms. N. Archana, Ms. B. Ayshwarya Lakshmi, project students for their help rendered in carrying out this research work.