Development of Stable, Efficient, and Recyclable Amine-Containing Microspheres for Gold(I) Thiosulfate Complex Recovery

It is desirable to develop a highly stable, cost-effective, and recyclable adsorbent to adsorb Au(I) from thiosulfate solutions. In this study, reliable aminated microspheres (PS- TETA) were synthesized via a one-pot method that profited from active chloromethyl group-induced nucleophilic substitution between chloromethylated polystyrene (PS-Cl) and triethylene-tetramine (TETA). These microspheres were used to recover a gold(I) thiosulfate complex. Scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller tech-nique, and X-ray photoelectron spectroscopy were adopted to analyze the surface elements and structure of PS-TETA. Additionally, influencing parameters, such as pH, thiosulfate concentration, and temperature, were investigated. The results indicated that the synthetic process and gold-adsorption behavior of PS-TETA was directly related to the surface chlorine and amine groups. The adsorption process was exothermic and consistent with the Freundlich isotherm model and pseudo-second-order kinetics. Complete adsorption of Au(I) was achieved with a maximum capacity of 23.79 kg t-1. Na2SO3 proved to be an effective desorbent and exhibited a satisfactory adsorption ability of the adsorbent even after five cycles. Anion exchange as a reasonable Au(S2O3)23- adsorption mechanism of PS-TETA is proposed. This study offers a practical method for synthesizing aminated microspheres with excellent properties to recover Au(I) from thiosulfate solutions.