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

Abstract

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 triethylenetetramine (TETA). These microspheres were used to recover a gold(I) thiosulfate complex. Scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller technique, 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.