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Adsorption of the gold–thiosulfate complex ion (Au(S2O3)23-) on silver ferrocyanide (AgFC)-impregnated activated carbon in aqueous solution has been studied in order to find an effectual adsorbent for the thiosulfate extracting gold from ores. This study was performed using AgFC-impregnated activated carbon (AC-Ag-R-FC: AC: activated carbon, Ag: silver nitrate, R: heating, FC: potassium ferrocyanide) and an artificial aqueous solution of Au(S2O3)23-. Gold–thiosulfate complex adsorption kinetics and isotherm studies were carried out at pH = 9.0 on modified materials. It has been also found that the adsorption fits the intraparticle diffusion and Freundlich isotherm well. In order to understand the adsorption mechanism, raw and modified materials were characterized by N2 adsorption–desorption measurements at 77 K, scanning electron microscopy and X-ray photoelectron spectroscopy. The maximum adsorption capability of Au(S2O3)23-on AC-Ag-R-FC is 3.55 kgt−1. Clearly, the extraordinary adsorption capacity of AC for Au(S2O3)23- offers a new approach to address challenging gold–thiosulfate complex separation and could promote the future development of thiosulfate leaching gold process. [ABSTRACT FROM AUTHOR]

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(S 2 O 3 ) 2 3- can reach 7.76 mg/g. In order to further examine the recovery of Au(S 2 O 3 ) 2 3- 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(S 2 O 3 ) 2 3- . 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(S 2 O 3 ) 2 3- by Cu/Fe-CLDH. The adsorption isotherm fitting experiment indicates that the adsorption by Cu/Fe-CLDH of Au(S 2 O 3 ) 2 3- conforms to the Langmuir model. During the process of Cu/Fe-CLDH adsorbing Au(S 2 O 3 ) 2 3- , CLDH restored part of the layered structure, and Au(S 2 O 3 ) 2 3- was inserted between the layers as a counteranion. Furthermore, the reduction of Au(S 2 O 3 ) 2 3- by low-valent iron compounds in the adsorbent promoted the process of Cu/Fe-CLDH adsorbing Au(S 2 O 3 ) 2 3- ., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)