Optimization of Cu(II), Ni(II), Cd(II) and Pb(II) biosorption by red marine alga Kappaphycus alvarezii

Abstract

The aim of this investigation was to study the potential of red seaweed Kappaphycus alvarezii for the removal of Cu(II), Ni(II), Cd(II) and Pb(II) from aqueous solutions. The mechanism of biosorption was identified as the interaction of positively charged metal ions and negatively charged functional groups on the surface of K. alvarezii through FTIR and SEM analysis. Owing to the above mechanism, the biosorption capacity of red seaweed was significantly affected by solution pH. Biosorption isotherms obtained at pH 4.5 indicated that K. alvarezii provided higher uptake for Pb (0.51 mmol/g), followed by Cd (0.48 mmol/g), Cu (0.47 mmol/g) and Ni (0.38 mmol/g). The reason for varied affinity of a biosorbent towards a particular metal ion was correlated with its atomic weight, ionic radius and electronegativity. Of the different isotherm models (Langmuir, Freundlich, Toth and Sips), the Toth model better predicted experimental isotherm data with high correlation coefficients and low % error values. Kinetic studies indicated that the rate of metal removal by K. alvarezii was high with 90% of the process completed within 45 min. Desorption experiments with different elutants (0.01 M NaOH, 0.1 M NaOH, 0.01 M HCl and 0.1 M HCl) revealed that maximum desorption of all metal ions from metal-loaded K. alvarezii can be achieved with 0.01 M HCl.

Keywords:

• Bioremediation
• Biosorption
• Heavy metals
• Seaweed
• Water treatment

Acknowledgements

This work was financially supported by Ramalingaswami Re-entry Fellowship (Department of Biotechnology, Ministry of India, India) and Fast Track Scheme for Young Scientist (Department of Science and Technology, Ministry of India, India).