Zinc and cadmium biosorption by untreated and calcium-treated Macrocystis pyrifera in a batch system

Zinc and cadmium can be efficiently removed from solutions using the brown algae, Macrocystis pyrifera. Treatment with CaCl2 allowed stabilization of the biosorbent. The maximum biosorption capacities in mono-component systems were 0.91 mmol g−1 and 0.89 mmol g−1 and the Langmuir affinity coefficients were 1.76 L mmol−1 and 1.25 L mmol−1 for Zn(II) and Cd(II), respectively. In two-component systems, Zn(II) and Cd(II) adsorption capacities were reduced by 50% and 40%, respectively and the biosorbent showed a preference for Cd(II) over Zn(II). HNO3 (0.1 M) and EDTA (0.1 M) achieved 90–100% desorption of both ions from the loaded biomass. While HNO3 preserved the biomass structure, EDTA destroyed it completely. Fourier transform infrared spectra identified the contribution of carboxylic, amine and sulfonate groups on Zn(II) and Cd(II) biosorption. These results showed that biosorption using M. pyrifera-treated biomass could be an affordable and simple process for cadmium and zinc removal from wastewaters.