Biosorption of Zn and Co ions by Evernia prunastri from single and binary metal solutions

Abstract

Dried biomass of lichen Evernia prunastri was studied as biosorbent for zinc and cobalt removal from single and binary ZnCl₂ and CoCl₂ solutions. The solution pH significantly influenced both cobalt and zinc biosorption. Maximum uptake was reached at pH 4–6 and negligible biosorption was observed at pH 2. The experimental data were fitted to the adsorption isotherms. The Langmuir, Redlich-Peterson and Langmuir-Freundlich isotherms were found to represent the measured sorption data well. The maximum sorption capacities onto lichen biomass from single metal solutions calculated by Langmuir equation were 112 μmol g⁻¹ for Zn and 97 μmol g⁻¹ for Co. To evaluate the Zn-Co sorption system, simple curves were replaced by three-dimensional sorption isotherm surfaces. Binary Langmuir type equations were used to fit the experimental data. Results revealed that E. prunastri exhibited preferential uptake of zinc from equimolar binary Zn ²⁺−Co ²⁺ mixtures.

Keywords:

• sorption
• Evernia prunastri
• zinc
• cobalt
• isotherms