The development of a heterogeneous Fenton-like catalyst, possessing a high degradation efficiency in a wide pH range, is crucial for wastewater treatment. An Fe–Mn–SiO₂ catalyst was designed and prepared by a hydrothermal method. Density functional theory (DFT) calculations demonstrated that the dual reaction centers were produced around the Fe and Mn atoms, due to valence-electron density distribution. The Fe–Mn–SiO₂ catalyst with dual reaction centers was applied for sulfamethazine (SMT) degradation in the Fenton-like process at a pH value of 4.0–8.6. Almost 100% SMT degradation efficiency was achieved under neutral pH at room temperature within 180 min. Moreover, the Fe–Mn–SiO₂/H₂O₂ system showed a high degradation efficiency (60–100%) for removing a wide range of aromatic pollutants, including bisphenol A, phenol, 4-chlorophenol, phenytoin, and ibuprofen. Besides, this process showed strong resistance to interference of inorganic anions (Cl⁻, SO₄ ²⁻, NO₃ ⁻ and HCO₃ ⁻). Electron paramagnetic resonance and radical scavenger experiments confirmed that the generated ¹O₂ and O₂˙⁻/HO₂˙ played an important role in the degradation of organic pollutants. In the Fe–Mn–SiO₂/H₂O₂ system, the electron-rich center around Fe was responsible for the reduction of H₂O₂ to ¹O₂, O₂˙⁻/HO₂˙ and ˙OH radicals, and then the electron-poor center around Mn adsorbed pollutants and transferred electrons to the electron-rich center around Fe via the Fe–O–Mn bridge.

Improving the performance of single-atom catalysts (SACs) is still challenging in Fenton-like reactions for degrading refractory organic pollutants. Here, we designed P and N co-doped Fe SACs to regulate the electronic structure of Fe active sites and enhance the reaction kinetics of peroxymonosulfate (PMS) activation. The obtained heteroatom-doped Fe SACs for the first time exhibited an ultra-low activation energy (ca. 3.7 kJ mol⁻¹) and excellent degradation efficiency for bisphenol A (BPA) in a wide pH range (4.3–9.2). The superior reaction kinetics of the Fe SACs were attributed to enriching the electron density of atomic Fe and then forming dual electron-rich/-deficient sites, which accelerated the electron transformation to generate reactive oxygen species (ROS). In this study the heteroatom-doped Fe SACs with rapid reaction kinetics are achieved, and provides an idea to design SACs with superior performance in heterogeneous Fenton-like reactions.

Fe–N₅ SAC efficiently activates peroxymonosulfate, resulting in remarkable 4-CP degradation efficiency with turnover frequency of 59.8 L (min g)⁻¹, and holds potential application in environmental remediation.

Dual-atom catalysts (DACs) driven by peroxymonosulfate (PMS) activation have demonstrated significant potential for addressing the inherent scaling relationship limitation of reaction intermediates, but in-depth mechanistic insight into synergistic interactions between dual-metal sites remains elusive. The Fe–Mn DAC has been designed with the largest electronegativity difference among Fe-based metal pairs to enhance electron transfer and synergistic interactions. The Fe–Mn DAC exhibits exceptional catalytic performance for bisphenol A (BPA) degradation, achieving a reaction rate constant (k_obs) of 1.36 min⁻¹, and a turnover frequency to PMS concentration ratio of 34.0 L min⁻¹ g⁻², which significantly surpasses the performance of reported state-of-the-art DACs, SACs, and nanocatalysts. The log k_obs value correlated well with the σ⁺ value (R² = 0.80), indicating that the Fe–Mn DAC readily targets pollutants with strong electron-donating abilities. Besides, ¹O₂ plays a key role in the Fe–Mn DAC/PMS system for BPA degradation. Based on density functional theory calculations, Fe and Mn active sites with a large electronegativity difference effectively enhance the synergistic interactions and decouple the activation and stabilization of reaction intermediates to address the inherent scaling relationship limitation. This study provides a robust framework for the rational design of DACs to enable efficient and sustainable water treatment.

This research investigated the establishment of a mathematical model for the ozonation of dimethyl phthalate (DMP) through the analysis of the mass transfer and reactions in a semi-batch bubble column reactor. Negative step tracer experiments were conducted with ozone as a tracer, which indicated that the gas phase is perfectly well mixed at the gas flow rate of 400 mL/min. Based on the results from ozone absorption experiments the mass transfer coefficient of ozone was determined to be 0.0054 s−1. The measured stoichiometry ratio of the direct reaction between ozone and DMP was about 5. The calculated rate constant was 0.87 L/(mol·s) for the direct reaction between ozone and DMP. A mathematical model was established based on the component mass balance in the reaction system involving the direct and indirect reactions and mass transfer between gas and liquid phases enhanced by the chemical reactions. The model can predict the removal of DMP for the early stage of the ozonation process well. At the latter stage, the predicated removals deviated from the measured results mainly due to the consumption of ozone by side reactions.