Removal of Cd2+ from zinc smelter wastewater using graphene oxide foam cross-linked with epichlorohydrin: comprehensive optimization, isotherms, kinetics, and real water column studies

Abstract

Cd²⁺ poses a significant public health concern. Developing the most efficient and cost-effective compound that can successfully remove Cd²⁺ from polluted water is a massive task. Recent research findings have found that graphene oxide (GO) and its hybrid composite materials have the ability to effectively remove metal ions. Thus, a new foam material, named epichlorohydrin-cross-linked chitosan-GO (EPCSGO), was developed and thoroughly characterized. EPCSGO foam was developed and used to adsorb Cd²⁺ aqueous solutions. Factors including contact time, initial concentration, temperature, and pH were studied to evaluate their impact on EPCSGO's adsorption of Cd²⁺. The maximum capacity of adsorption shown by the fabricated composite was around 146.35 and 206.33 mg g⁻¹ for 0.5 g L⁻¹ for chitosan-GO (CSGO) foam and EPCSGO foam, respectively, and was obtained at pH = 6 and 298 K. Kinetic, isotherm, and thermodynamic analyses indicated that Cd²⁺ adsorption onto EPCSGO involved rate-limiting monolayer kinetics on a homogeneous surface, with endothermic spontaneity at the solid/solution interface. The efficiency of EPCSGO foam for Cd²⁺ removal was assessed using a continuous-mode fixed-bed up-flow column. Experimental data were analyzed using the Thomas, Yoon-Nelson, and Adama-Bohrat column models, with the Thomas model showing the best fit. Furthermore, the potential of EPCSGO for groundwater treatment was examined, with results showing that it effectively reduced Cd²⁺ levels to meet drinking water standards and retain over 90% of its initial efficacy for at least four cycles of reuse.