Single-atom Zn anchored on reduced graphene oxide for enhanced peroxymonosulfate activation: Critical role of Zn-O3 coordination structure and catalytic mechanism

In this study, single-atom Zn (SA-Zn) was anchored on reduced graphene oxide (rGO) to form a highly integrated catalyst, denoted as SA-Zn/rGO, designed to enhance the catalytic efficiency in the peroxymonosulfate (PMS) advanced oxidation process. The system efficiently removed 2 mg L- 1 sulfamethoxazole within 3 minutes, demonstrating an impressive observed reaction rate constant of 2.28 min- 1. Furthermore, the SA-Zn/rGO/PMS system displayed robust adaptability across various environmental interferences, including pH levels, inorganic ions, and humic acid. This high catalytic performance was primarily attributed to the dominant nonradical pathway driven by singlet oxygen (1O2). Structural characterization using X-ray absorption near edge structure, extended X-ray absorption fine structure spectroscopy, and density functional theory calculations revealed that Zn-O3 coordination structure plays a pivotal role in enhancing PMS adsorption and promoting the thermodynamic 1O2 formation through the combination of two adjacent oxygenated intermediates (*O). In addition, SA Zn/rGO was integrated into an ultrafiltration membrane to construct a catalytic membrane, which exhibited excellent PMS activation and high stability after 120 minutes of continuous operation. These findings shed light on the catalytic behavior of SA-Zn sites in activating PMS, presenting a promising strategy for wastewater remediation.