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

Abstract

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.