Analysis of Highly Efficient Adsorption of Au(S2O3)2 3- by Calcined Cu/Fe Layered Double Hydroxides.

Abstract

One of the main problems affecting the application of gold thiosulfate leaching is the difficulty in recovering gold from the leaching solution. Our previous studies revealed that when using calcined Mg/Al layered double hydroxides (LDHs), the single adsorption capacity of Au(S2O3)23– can reach 7.76 mg/g. In order to further examine the recovery of Au(S2O3)23– by various types of LDHs, the divalent metal and trivalent metal ions in LDHs were altered. Also, thiosulfate anions are introduced between the layers of LDHs to reduce the competitive adsorption of thiosulfate ions in the solution. Results show that the calcined LDHs (CLDH) prepared with Cu/Fe-LDHs are the best at adsorbing Au(S2O3)23–. Compared with Mg/Al-CLDH, the single adsorption capacity reaches 48.6 mg/g. The pseudo-second-order kinetic model is more suitable for describing the adsorption of Au(S2O3)23– by Cu/Fe-CLDH. The adsorption isotherm fitting experiment indicates that the adsorption by Cu/Fe-CLDH of Au(S2O3)23– conforms to the Langmuir model. During the process of Cu/Fe-CLDH adsorbing Au(S2O3)23–, CLDH restored part of the layered structure, and Au(S2O3)23– was inserted between the layers as a counteranion. Furthermore, the reduction of Au(S2O3)23– by low-valent iron compounds in the adsorbent promoted the process of Cu/Fe-CLDH adsorbing Au(S2O3)23–.