Silver adsorption from gold leaching cyanide wastewater by a green functionalized magnetic graphene oxide Nano-adsorbent

Abstract

A nanoadsorbent made of magnetic graphene oxide that was functionalized by glutathione (GSH/Fe3O4@GO NPs) was synthetized. Various characterization methods were employed to clarify the adsorbent's morphology and structure. The results confirmed the formation of nanosheets of graphene oxide with the homogenous coating of Fe3O4 nanoparticles and well conjugated glutathione (GSH) on its surface. This adsorbent was utilized to adsorb silver ion from synthetic AgCN solutions at pH = 10.5. A central composite design (CCD) was used to investigate the impact of silver and cyanide concentration. The significance of the concentration of cyanide and its interaction with silver concentration was confirmed. When the concentrations of silver and cyanide were 128 mg/L and 528 mg/L, respectively, the maximum adsorption capacity achieved was 586 mg/g. The successful fitting of the Freundlich isotherm explains the multilayer adsorption on the heterogeneous surface of the adsorbent. This adsorbent also showed significant efficiency in silver adsorption from a real cyanide wastewater sample as was predicted by the statistical model. The silver adsorption capacity of 123 mg/g were obtained from a gold cyanide leaching process wastewater (24.8 mg/L). The GSH/Fe3O4@GO NPs were found to be an effective adsorbent for extracting and separating silver ions from cyanide solutions.