Enhancement of biosorption of zinc ions from aqueous solution by immobilized Candida utilis and Candida tropicalis cells

The cells of Candida utilis and Candida tropicalis were immobilized by calcium alginate gel and used for the investigation of biosorption parameters for the removal of zinc ions from aqueous solution. The isotherms, kinetics and thermodynamics of biosorption were studied in batch system under optimum operating conditions. Experimental equilibrium data were analyzed using Langmuir, Freundlich and Dubinin-Raduskhkevich isotherm models by linear and non-linear regression. The functional groups responsible for the biosorption of zinc ions were identified using Fourier transform infrared spectra. Immobilized C. utilis exhibited the highest biosorption capacity of 181.7 mg g−1 at 45 °C for removal of zinc ions from aqueous solution. The kinetics analysis of the experimental data showed that the biosorption process followed the pseudo second order kinetic. Different desorbing agents were investigated for elution of adsorbed zinc ions from the immobilized biomass and regenerated biosorbent was reused without significant loss in its biosorption capacity. Thermodynamic parameters were calculated by using the biosorption equilibrium constant based on Langmuir isotherm.