Efficient gold (Au)(III) recovery from wastewater using a mercapto-1,3,4-thiodiazole modified Zn-MOF

Efficient recovery of precious metals from secondary resources is of great economic and environmental significance in modern society. Herein, an efficient adsorbent ZIF-8-MTD was designed using 1,3,4-thiadiazole (MTD)-modified zinc-based metal-organic framework (MOF) for efficient recovery of gold (Au)(III) from wastewater. It was found that the ZIF-8-MTD adsorbent has excellent adsorption performance for Au(III), with a maximum adsorption capacity of 1604.53 mg·g−1 at room temperature (15 °C), which is superior to the traditional adsorbent. Particularly, the ZIF-8-MTD adsorbent still maintained a high saturation adsorption capacity of 1088.8 mg·g− 1 at a low Au(III) concentration (10 ppm). The fitting results of adsorption isotherm and kinetic adsorption model indicated that the adsorption process was consistent with Langmuir and pseudo-second-order adsorption models, implying that chemisorption was involved in the adsorption process. Moreover, the results of adsorption selectivity, desorption and adsorption experiments confirmed good adsorption selectivity and recyclability. Combining pH effect experiments, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS) characterizations, we proposed an electrostatic adsorption mechanism in which the coordination interactions between the -SH functional groups in the framework and Au(III) lead them to be adsorbed to the ZIF − 8-MTD surface and partially reduce it to Au(I). More importantly, the outstanding adsorption performance, high selectivity and strong stability make it have great potential for practical application.