Experimental and DFT study on the selective adsorption mechanism of Au(Ⅲ) using amidinothiourea-functionalized UiO-66-NH2

The recovery of precious metals from wastewater not only brings considerable economic benefits, but also reduces environmental pollution. Herein, UiO-66-NH2 was modified by amidinothiourea and used as a adsorbent to selectively recover Au(III) from aqueous solution. The maximum adsorption capacity of the adsorbent for Au(III) was 227.68 mg/g and was higher than that of UiO-66-NH2 (166.23 mg/g) at the optimal pH 3.0 and 298 K. Meanwhile, the adsorbent has excellent selectivity toward Au(III) in wastewater and outstanding reusability after four adsorption-desorption cycles. Significantly, the increase of the adsorption capacity of the adsorbent is mainly attributed to chelation and ion exchange between Au(III) and containing-N/S groups, and the adsorption energy of gold ions on the adsorbent is −35.08 eV based on DFT simulation, indicating that the process is a stable chemisorption and Au(III) can be effectively adsorbed. The results indicate that the adsorbent is effective in the treatment of wastewater containing gold.