Facile and low-cost fabrication of composite hydrogels to improve adsorption of copper ions

Although kaolin has been commonly utilized as a heavy metal adsorbent, its effectiveness is limited when used alone. In this study, an ion permeation method was applied to prepare a variety of sodium alginate/polyvinyl alcohol/kaolin/polyacrylamide (SA/PVA/K/PAM) composite hydrogels. Interactions between various components were studied to elucidate their effects on the water content, copper ion adsorption, and stability of the hydrogels. Scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared microscopy were used to analyze the hydrogel properties. The combination of SA, kaolin, and PAM improved the absorptive capacity of the hydrogel toward Cu2+. Under optimal conditions, the theoretical maximum adsorption capacity was 5.061 mg/g, which was in line with the pseudo-second order model (at pH = 5) for adsorption kinetics. The hydrogel was extremely stable for Cu2+ adsorption under the interference of Na+. Overall, the SA/PVA/K/PAM hydrogel exhibited strong adsorption capacity and stability. Thus, the versatility of the fabricated hydrogel indicates the potential for its use in heavy metal adsorption. This study makes a contribution to the literature by developing a novel and modified hydrogel adsorbent based on an inorganic material (kaolin).