Efficiency and Mechanism of a Hollow Carbon-Based Single-Atom Iron Catalyst in Activating Periodate for Bisphenol a Degradation

Developing efficient and recyclable periodate (PI)-based advanced oxidation processes (AOPs) for the removal of emerging organic pollutants (EOPs) has attracted considerable attention. However, the structure–activity relationship of single-atom catalyst in PI-AOP systems remains poorly understood. In this study, a hollow carbon-supported single-Fe atom catalyst (HCFe800) was synthesized and applied for PI activation toward bisphenol A (BPA) degradation. Under neutral pH and ambient temperature, HCFe800 enabled complete removal of BPA within 1 min, achieving a degradation rate constant (k) of 5.094 min−1—approximately 3 and 10 times higher than that of Fe-free and solid control catalysts, respectively. After normalization, the apparent degradation rate constant was 1–3 orders of magnitude greater than those of previously reported catalysts. The optimized Fe doping amount and pyrolysis temperature facilitated the formation of atomically dispersed FeN4 sites, which outperformed Fe clusters and iron oxides in catalytic activity. The hollow porous structure further enhanced the exposure of active sites, contributing to the exceptional performance. The HCFe800/PI system remained highly effective across broad pH (3–7) and temperature (5–35 °C) ranges and in the presence of 100-fold concentrations of common inorganic ions. Mechanistic studies revealed that the main reactive species were 1O2, O2•−, and IO3•, with negligible involvement of high-valent Fe species. Eight less-toxic BPA degradation products were identified. Moreover, the system was extendable to various other EOPs and exhibited excellent recyclability via thermal regeneration. This work provided fundamental insights into designing and applying single-atom catalysts for PI-based advanced treatment of EOPs.