Selective recovery mechanism of Au(III) from an aqueous solution by trimethyl phosphate modified poly(glycidyl methacrylate)

A new adsorbing material (PE-PGMA) was prepared by grafting trimethyl phosphate onto poly(glycidyl methacrylate), and it was applied to selectively adsorb gold ions from an aqueous solution. FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), XPS (X-ray photoelectron spectroscopy) and zeta potential analysis were employed to characterize the prepared adsorbent. Three kinetic and isothermic equations were employed to investigate the selective adsorbing mechanism of Au(III) from an aqueous solution. The adsorbent had the highest adsorption rate in the pH range from 2 to 9, thus suggesting that PE-PGMA had a wide acid-base tolerance. The adsorbing equilibrium is attained in 10 min and the maximum adsorption capacity is 601.34 mg/g. The pseudo-second-order and Langmuir models well described the kinetics and isotherms of the adsorption process, respectively. The results certified that the adsorbing process was monolayer sorption and the rate-limiting step was chemical adsorption. After seven cycles of reusability experiments, the adsorbing rate of gold ions decreased from 99.06% to 96.72%, thus proving that the adsorbent has good reusability. Moreover, the adsorbent presented good selectivity for gold ions from the coexisting ions (Cu2+, Ni2+, Co2+, Ge4+ and Pb2+). The chelation interaction between phosphate groups and Au(III) played a significant role in the selective adsorption and higher uptake capacity. Furthermore, the column adsorption and the recovery experiment of gold from laboratory wastewater demonstrated that the PE-PGMA has good potential to recover gold. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.