Biosorption of Cd2+, Cu2+, Ni2+ and Zn2+ ions from aqueous solutions by pretreated biomass of brown algae

In this paper, marine brown algae Laminaria japonica was chemically modified by crosslinking with epichlorohydrin (EC1 and EC2), or oxidizing by potassium permanganate (PC), or crosslinking with glutaraldehyde (GA), or only washed by distilled water (DW). They were used for equilibrium sorption uptake studies with Cd2+, Cu2+, Ni2+ and Zn2+. The experimental data have been analyzed using Langmuir, Freundlich and Redlich-Peterson isotherms. The results showed that the biosorption equilibrium was well described by both the Langmuir and Redlich-Peterson isotherms. The order of maximum metal uptakes for Cd2+, Cu2+ and Zn2+ was EC1 > EC2 > PC > DW > GA, but the uptakes of Ni2+ are almost the same for these sorbents. Moreover, sorption kinetics has been performed and it was observed that the equilibrium was reached in less than 2 h, which could be described by pseudo-first-order kinetic model. The metal adsorption was strictly pH dependent. The optimum pH values of four metals were in the range of 4.3-6.5 for all sorbents, and the optimum solid/liquid ratio was 3.0 g L−1.