Isotherm and thermodynamic studies of the biosorption of Cd(II) from solution by maize leaf

The removal of Cd(II) from dilute solutions using maize (Zea mays) leaf as the biosorbent was studied. The effects of pH, contact time and initial metal ion concentration on the biosorption were monitored. The residual Cd(II) in solution was determined using atomic absorption spectrophotometer. The biosorption was found to be pH-dependent and the optimum pH for the biosorption was pH 3. The biosorption was also time-dependent as maximum biosorption was obtained after 2 h. The Freundlich equation obtained for the biosorption was log = 0.8775 log C-e + 1.095 while the Langmuir equation was (1)/ = 0.0982/C-e - 0.0058. The correlation factors were 0.9943 and 0.9869, respectively. The remo-val efficiency decreases with increase in initial Cd(II) concentration due to reduction in available binding site on the biosorbent for Cd (II). The free energy change for the biosorption at 300 K with an initial Cd(II) concentration of 100 mgL(-1) and pH 3 was -7.17 kJmol(-1). These results indicate that maize leaf has potential for the uptake of Cd(II) from industrial effluents.