Kinetics and thermodynamics of chromate and phosphate uptake by polypyrrole: batch and column studies

Polypyrrole sorption performance for removal of phosphate and chromate anions from water was evaluated by batch and column studies. The uptake isotherms, kinetics, chromate recycling, and experimental conditions such as temperature, pH, and dosage were optimized. The uptake data fitted Freundlich isotherm model very well, and the removal process was found to be endothermic and spontaneous in nature. The results indicate that the removal of both anions is a physisorption process. The kinetic data were described better by the pseudo second-order kinetic model. The maximum uptake capacities for phosphate and chromate anions were 120 and 26 mg/g respectively. The uptake equilibrium for phosphate and chromate was attained in 120 and 60 min respectively. The solution pH showed insignificant effect on anions removal over a pH range from 2.0 to 10.0. Three well known column uptake models, Thomas, Yoon and Nelson and Yan et al., were used to analyze the experimental data of chromate removal from water by polypyrrole. Thomas model showed better fitting than other models. Polypyrrole was regenerated and reused by using 0.1 M HCl solution. This polymer is a promising sorbent than other materials for phosphate and chromate removal from wastewater.