Application of polymer-sepiolite composites for adsorption of Cu(II) and Ni(II) from aqueous solution: equilibrium and kinetic studies

摘要

In this study, humic acid-immobilized-amine-modified polyacrylamide/sepiolite (Ha-Am-Paa-Sep) and phytic acid-modified polyacrylamide/sepiolite composites (Phy-Paa-Sep) were prepared and characterized for removal of Cu(II) and Ni(II) from aqueous solutions. The effects of contact time, initial concentration of adsorbent and metal ions, pH and temperature on the adsorption process were investigated. The optimum adsorption of metal ions occurred at pH 5 and 25°C. Ion exchange and complexation reactions were the main mechanisms for adsorption of metal ions. Removal of metal ions followed a pseudo-second-order kinetics and equilibrium occurred after 60 min. The conformity of various adsorption models to the equilibrium data was evaluated among which Freundlich isotherm model gave the best fitting result. The highest monolayer adsorption capacity of Cu(II) and Ni(II) ions were 244 and 250 mg·g?1 for Ha-Am-Paa-Sep and 256.4 and 277 mg·g?1 for Phy-Paa-Sep, respectively, at room temperature. Ultimately, desorption experiments were performed and the results showed approximately 95% of adsorbed metal ions were desorbed.