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

AbstractThe 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. Kin...