The Effects of Coexisting Copper, Iron, Cobalt, Nickel, and Zinc Ions on Gold Recovery by Enhanced Cementation via Galvanic Interactions between Zero-Valent Aluminum and Activated Carbon in Ammonium Thiosulfate Systems

Abstract

The use of galvanic interactions between zero-valent aluminum (ZVAl) and activated carbon (AC) to recover gold (Au) ions is a promising technique to overcome the challenges due to the poor recovery in ammonium thiosulfate systems, but the applicability to practical Au ore processing remains elusive so far. The present study describes (1) the recovery of Au ions from low Au concentrations, which are typical concentrations used in Au ore processing; and (2) an investigation into the effects of various coexisting base metal ions that can be present in pregnant ore-leached solutions. The results showed that high Au recovery (i.e., over 85%) was obtained even at low Au concentrations under the following conditions: 1:1 of 0.15 g of ZVAl and AC with 10 mL of ammonium thiosulfate solution containing 5 mg/L of Au ions at 25 °C for 1 h in an anoxic atmosphere. Selected coexisting metal ions (i.e., copper, iron, cobalt, nickel, and zinc) were studied to establish their effects on Au recovery, and the results showed that the Au recovery was enhanced (about 90%) when copper ions coexist in the solution with minimal effects from other competing base metal ions.

Investigation of the Bimodal Leaching Response of RAM Chip Gold Fingers in Ammonia Thiosulfate Solution

“…As is well known, Cu and Cu sulfide species can be problematic as cementing agents, causing the deposition of leached Au ions in thiosulfate solutions [30][31][32][33]. In support of this hypothesis, the research by Jeon et al on Au cementation in the solution containing thiosulfate and PCB materials indicates that the dissolved Au thiosulfate complex is preferentially cemented on the surface of Cu [34,35]. In particular, Au cementation on Cu was significantly enhanced when Al coexisted.…”

“…The corresponding concentrations of Cu, NH 3 , and S 2 O 3 were 0.05 M, 1.5 M, and 1 M, respectively. As indicated by the Eh-pH diagram in Figure 11, at current leaching conditions, from pH 9 to 10, there were three possible Cu species across different Eh ranges from 0 to 0.25 V. Under reductive conditions (at a lower Eh range below 0 V), Cu stably exists at Cu 2 S, indicating the formation of Cu 2 S precipitates, which further results in the co-precipitation of Au ions [35]. This may also be suggested by Figure 7b.…”

“…They discovered that Au deposition in ammoniacal thiosulfate solution was enhanced by increasing Cu concentration up to 50 mM. Furthermore, their SEM-EDS results showed that the deposition of Au occurred together with the deposition of Cu [35]. Moreover, in a heterogeneous material like PCBs, the presence of Al tends to stimulate Au deposition on Cu [34].…”

Advances in Selective Flotation and Leaching Process in Metallurgy

“…In this Special Issue, four articles deal with hydrometallurgical processing for Cu, gold (Au), and rare earth metals (REMs) [15][16][17][18]. Chae et al [15] studied hydrochloric acid (HCl) leaching behaviors of Cu and antimony (Sb) in speiss obtained from top submerged lance (TSL) furnace.…”

“…The Cu-catalyzed ammonium thiosulfate leaching is one of the most promising alternatives to cyanidation for extracting gold from ores [17]. A major problem of thiosulfate leaching is its difficulty in recovering gold from the PLS; that is, the conventional Au recovery techniques (e.g., activated carbon (AC) adsorption and cementation using base metals) are inefficient.…”