Selective Removal of Cu2+ Ion in Aqueous Solution by Poly (Acrylic Acid/Acrylamide) Hydrogel

Abstract

Heavy metal pollutants pose a serious threat to the environment and the health of organisms. This study explored the basic characteristics of poly (acrylic acid)/acrylamide (PAAAM) hydrogel, and evaluated its application in heavy metal ions removal from simulated and real electroplating wastewater. The results showed that PAAAM displayed the highest swelling ratio and adsorption capacity of 5% AM. The swelling ratio of 5%-AM-PAAAM reached 30000% in pH 4.0–7.0. The adsorption of Cu 2+ and Ni 2+ reached equilibrium in 60 min, with the maximum adsorption capacities of 159.45 and 107.68 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model and the adsorption isotherm followed the Langmuir model, exhibiting an exothermic adsorption process. In competitive removal process, 5%-AM-PAAAM showed selective adsorption to Cu 2+ than Ni 2+ in aquatic solution. The adsorption mechanism was related to the O-H groups in acrylic acid based on X-ray photoelectron spectroscopy (XPS) detection. In summary, 5%-AM-PAAAM was a specific adsorbent for Cu 2+ in aquatic solution with high Cu 2+ concentration. The swelling ratio and Cu 2+ adsorption of PAAAM decreased with increasing AM ratio. Cu 2+ and Ni 2+ exhibited a lower adsorption capacity at 20 mg/L heavy metal treatment, regardless of single or binary treatments. The maximum adsorption capacities of 5%-AA-PAAAM for Cu 2+ and Ni 2+ were lower than the adsorption capacity of simulated nitrate solution.