Adsorption of Cd2+ and Ni2+ from Aqueous Single-Metal Solutions on Graphene Oxide-Chitosan-Poly(vinyl alcohol) Hydrogels

The applications of graphene-based adsorbents were limited because of their complicated manufacturing technology and hi cost, thus it is very important to prepare new inexpensive and easily manufactured graphene-based adsorbents. Herein, novel GCP hydrogels with different graphene oxide (GO), chitosan (CS), and poly(vinyl alcohol) (PVA) ratios were facilely prepared through a method of freeze thaw physical cross-linking, which was green and low-cost, and the structural characterization and adsorptive property of the optimum GCP(1:2:4) hydrogel toward Cd2+ and Ni2+ in wastewater was evaluated. It was found that the GCP(1:2:4) hydrogel had good mechanical strength and a special 3D interconnection porous structure. The isotherms of adsorption used the Langmuir model, and the kinetics of adsorption following the pseudo-second order model were confirmed. Moreover, the adsorption property with respect to Cd2+ and Ni2+ in wastewater has been largely effected by the pH and was less influenced by the ionic strength and humic acid, and the GCP(1:2:4) hydrogel possessed excellent adsorptive and recyclable properties. These results demonstrated that the GCP(1:2:4) hydrogel could serve as a desirable adsorbent to get rid of heavy metal ions in sewage.