Overcoming hydroxyl radical quenching in high-salinity wastewater: Electrostatically shielded porous perovskite boosts adsorption-oxidation of organic contaminants

Free radicals are severely quenched by ubiquitous anions (e.g., Cl⁻) in high-salinity organic wastewater, which severely impedes the application of advanced oxidation processes. To address this, a free radical protection microzone (FRPM) is created on a catalyst through synergistic electrostatic repulsion (between the anionic group and anion) and physical adsorption. Specifically, poly (sodium 4-styrenesulfonate) was used to modify three-dimensionally ordered macroporous perovskite-ceria composite to introduce a surface negative layer, where anions are difficult to enter due to electrostatically repelled by the sulfonic acid group (-SO₃⁻) and avoid free radical quenching. Porous perovskites with large specific surface area and strong adsorption capacity enrich organic pollutants in FRPM through physical adsorption process and remove them by free radicals. The anionic porous perovskite composite (A-3DLFC) can completely remove tetracycline (TC) within 30 min with the k value over 0.1664 min⁻¹ in a variety of high-salinity environments. Quenching experiments and EPR tests showed that surface-bounded hydroxyl radical (·OH) is the main reactive oxygen species. Crucially, density functional theory (DFT) calculations quantitatively substantiate the FRPM mechanism, revealing an exceptionally high energy barrier (+8.19 eV) for the quenching reaction between Cl⁻ and ·OH on the A-3DLFC surface, with the Cl⁻ adsorption process being the primary limiting step (+7.09 eV).