Removal of Cadmium (II) Ions from Synthetic Wastewaters by Alginate – Immobilized Penicillium sp Biomass

Abstract

The objective of this investigation was to study the biosorption of Cd (II) from aqueous solution onto Penicillium sp immobilized in calcium alginate and to determine the isotherms and kinetics of the adsorption process. The capacity for Cd (II) biosorption was investigated as a function of pH, adsorbent dose, contact time and initial metal ion concentration. The results showed that the removal efficiency increased with increase in adsorbent dosage and solution pH. For adsorbent dosage, the highest removal efficiency was 93.45% (adsorbent dosage of 200 mg). In terms of pH, the highest removal percentage was 89.75% at pH of 9.0 and Cd (II) ion concentration of 2 mg/L. The experimental data fitted the Freundlich isotherm better than the Langmuir isotherm. Their R2 values were 0.9852 and 0.8053 respectively. The calculated maximum biosorption capacity Qo was 7.12 mg g-1. The values of R2 for the pseudo – first and pseudo – second order kinetics are 0.9007 and 0.9960 respectively. The experimental value of qe, the biosorption capacity at equilibrium, for the pseudo second order model was closer to the theoretical value than that of the pseudo – first order indicating that chemisorption is the probable mechanism of the process.  These results show that the investigated biosorbent is a good low cost adsorbent for the removal of Cd (II) from wastewaters.