Cross-linked chitosan microspheres for efficient and selective gold recovery from gold-bearing leaching solution

Chitosan (CTS), well known for its abundant amine (−NH 2 ) and hydroxyl (-OH) groups have potential application for the adsorption of gold ions. However, its low chemical stability and mechanical strength in acidic solution have barely been explored in gold ions sorption. Herein, cross-linked chitosan microspheres were prepared by pre-crosslinked the amino groups on the chitosan molecular chains with formaldehyde which can efficient and selective gold recovery from gold-bearing leaching solution. The cross-linked chitosan microspheres (CTS-GA) were characterized by FTIR, XPS, SEM and BET, and subsequently applied for gold recovery in an actual gold-bearing mineral leaching solution. The maximum adsorption capacity of CTS-GA for Au(III) can reach 614.08 mg/g (C 0  = 100 mg/L, t  = 24 h, pH = 2). The CTS-GA was analyzed by ZETA, XRD, TEM, and XPS after the adsorption of Au(III). The results reveal the adsorption mechanism of CTS-GA on gold ions. At pH 2, the amino groups on CTS-GA become protonated and generate a positive charge that electrostatically attracts the negatively charged AuCl 4 − . This interaction allows the nitrogen atoms to complexation with the gold ions, forming a complex that enhances adsorption. Additionally, the amino groups of CTS-GA facilitate the reduction of Au(III) to Au(0). Compared with chitosan, the formaldehyde pre-crosslinking strategy effectively retains active amine sites, thereby enhancing adsorption capacity and stability. In exploration of a complex metal ion environmenniulat in an actual gold-bearing mineral leaching solution, it was indicated that the cross-linked chitosan microspheres possess a significant gold recovery efficiency of 96.56 % at gold concentration of 15.97 mg/L. The CTS-GA can selectively recovery gold from gold-bearing leaching solution.