Optimization of nickel biosorption by chemically modified brown macroalgae (Pelvetia canaliculata)

In the present work, various forms of algae Pelvetia canaliculata were prepared by different chemical modifications, in order to get the best form of algae for the maximum uptake of nickel. Potentiometric titration revealed that the carboxyl groups were more abundant (3.9 mmol/g) as compared to hydroxyl groups (2.0 mmol/g) on the biosorbent surface. Fourier transform infrared (FTIR) analysis of algae was done to identify the role of different functional groups present on algae surface during nickel biosorption. The protonated algae showed least sorption of nickel suggesting that after acid treatment, some of the binding sites were destroyed. Among the various forms of prepared algae, Na-algae prepared directly from raw algae (without protonation) showed highest uptake of nickel. The release of sodium ions during the uptake of nickel ions has shown that the current biosorption mechanism involves ion-exchange being a stoichiometrical ratio of 2:1 between sodium and nickel ions.

► Biosorption of Ni(II) on various chemically modified brown algae was investigated.
► Na-algae prepared from raw algae showed the highest uptake of Ni(II).
► Biosorption involved ion-exchange between Na and Ni ions with stoichiometry 2:1.
► Parameter for total binding strength (ξ) was found to be, Ni > Mg > Ca > K > Na.