Synthesis of azole-functionalized microspheres and their adsorption properties for gold(I) thiosulfate complex.

Gold is an essential precious metal with exceptional properties. Thus, azole-functionalized microspheres (PS-3-AT) were prepared by grafting 3-amino-1,2,4-triazole (3-AT) into chloromethyl polystyrene beans (PS-Cl) and used as a novel adsorbent for the gold(I)-thiosulfate complex. The effects of initial gold concentration, thiosulfate concentration, temperature, and pH on the Au(SO) adsorption process over PS-3-AT were investigated. In this study, PS-3-AT was considered an effective adsorbent for Au(I) recovery from a thiosulfate solution, demonstrating that PS-3-AT completely adsorbed Au(SO) with an adsorption capacity of 39.8 kg t achieved during multistage adsorption testing. Through adsorption kinetics and isotherm studies, the pseudo-second-order and Freundlich models well describe the adsorption process of PS-3-AT for Au(I), also suggesting the exothermic nature. Furthermore, SEM, FT-IR spectroscopy, BET, and XPS techniques were used to characterize the surface and structural properties of the samples. Notably, a reliable adsorption mechanism was developed that proposed the formation of the -NHCl group during the grafting process and Cl exchange with Au(SO) to achieve Au(I) capture. Moreover, quantum chemistry calculations and the independent gradient model (IGM) were adopted to visualize the interaction between PS-3-AT and Au(SO) at an atomic level. The desorption ratio was 97.9% while 2 M NaCl was used as the desorbent, and regeneration with PS-3-AT was achieved after five cycles. Therefore, the facile synthetic method and adsorption properties of PS-3-AT for the gold(I)-thiosulfate complex are satisfactory, which is valuable for the development of thiosulfate gold leaching technologies.