Cadmium (II) sorption using unmodified and thioglycol acid-modified plantain (<i>Musa paradisiaca</I>) stalk

Abstract

The presence of cadmium in industrial effluents and agricultural runoff has become a significant environmental concern, requiring green methods to reduce cadmium level in the environment, such as sorption using plant and animal wastes. Thioglycolic acid-modified plantain stalk (TGPS) and unmodified plantain stalk (UPS) were tested for their applicability in the sorption of cadmium (II) ions from aqueous systems by batch method. The adsorption process revealed a strong pH and temperature-dependent process with maximum adsorption obtained at 318 K for both the UPS and TGPS and at a pH of 7. The kinetics of both adsorption processes were conformed to the pseudo-second order model with an uptake of 16.95 mg g^-1 and 15.68 mg g^-1 and a rate constant of 0.00761 g mg^-1 min-1 and 0.02407 g mg^-1 min^-1 for TGPS and UPS respectively. The Freundlich adsorption isotherm best fitted the adsorption isotherm for both UPS and TGPS. Studies on the thermodynamic characteristics revealed an endothermic process with ΔH° values of approximately 75 kJmol^-1 and 106 kJmol^-1 for UPS and TGPS, respectively. Negative ΔG values at the studied temperatures suggest that the process was feasible and spontaneous. Also, there was a noticeable increase in the reaction's spontaneity as the temperature increased. The results generally showed that the TGPS exhibited greater sorption efficiency than the UPS as far as cadmium (II) ions were concerned. However, both UPS and TGPS have the efficacy to take up Cd(II) from aqueous solutions.