Mechanism of SCN- ions affecting the adsorption of Au(CN)2 - ions on anion exchange resin.

The cyanide leaching process for gold ore is a mainstream gold extraction method due to its high gold leaching efficiency and strong ore adaptability. The resin-in-pulp process is an important cyanidation-based gold recovery technique, which employs weakly basic anion exchange resins with high selectivity and large adsorption capacity as adsorbents, offering the significant advantage of high adsorption efficiency. However, in practical production, repeated resin recycling accumulates SCN- in pulp from residual thiocyanate desorption released during each reuse, significantly reducing Au(CN)2 - adsorption efficiency. To address this issue, this study focuses on the macroporous weakly basic anion exchange resin D301 used in a gold mine in Chifeng, Inner Mongolia, China. Through single-factor tests and comparative experiments, the influence of SCN- ions on the adsorption of Au(CN)2 - by the resin was investigated. Experimental results indicate that under conditions where SCN- ions are present, increasing the experimental temperature or initial solution pH reduces the adsorption efficiency of Au(CN)2 -, whereas increasing the resin dosage effectively enhances adsorption. Microscopic characterization further elucidates the mechanism by which SCN- affects the adsorption process. SEM-EDS analysis reveals that SCN- diminishes the resin's adsorption capacity for Au(CN)2 -. FTIR spectra show the simultaneous presence of characteristic peaks for Au(CN)2 - (C≡N) and SCN- (S-C≡N) on the resin surface, confirming their coexistence. XPS results further verify the existence of characteristic peaks for Au and S elements, indicating that while gold is adsorbed in the form of Au(CN)2 -, the resin also adsorbs SCN- from the solution. In summary, SCN- and Au(CN)2 - exhibit a competitive adsorption mechanism on D301 resin, which is the primary cause of the decreased adsorption efficiency of Au(CN)2 -. It is recommended that when the concentration of SCN- in the pulp accumulates to a high level during the resin-in-pulp gold extraction process, it should be removed by oxidation, thereby enabling efficient adsorption of Au(CN)2 - by the resin. This study provides both theoretical and experimental foundations for addressing SCN- interference and optimizing resin-based gold extraction processes.