New insight into alkaline earth metal oxide-activated solid peroxydisulfate for mechanochemical destruction of UV328

Alkaline-earth metal oxide (AEMO)-based defect engineering shows promise for activating solid-phase peroxydisulfate (PDS) in mechanochemical treatment of hazardous organic wastes, yet the interfacial mechanism and dominant reactive species remain ambiguous. Using UV328 as a target waste, we demonstrate that AEMOs catalytically enhance PDS activation with kinetics improvements following the periodic trend: SrO (16.4-fold) > CaO (9.2-fold) > MgO (3.5-fold); however, SrO + PDS suffers a ∼30 min incubation period due to the unfavorable mechanical properties of SrO, compromising overall performance. Multi-probe and radical-capture tests confirm sulfate radicals as the dominant species, with yields matching the periodic trend. Theoretical calculations identify in situ oxygen vacancy (V_O) formation as the key interfacial step, with the surface energy difference between defective and pristine surfaces (denoted as Δγ) emerging as an interfacial kinetic descriptor. Mechanochemically-induced V_O promotes electron release from AEMOs and subsequent reductive activation of amorphous PDS. Adequate AEMO loadings greatly improve waste mineralization, with PDS stoichiometrically transformed into sulfate phases. Notably, CaO + PDS offers the highest mineralization (83.8% for UV328 and ∼80% for three antibiotics) with the lowest cost and life-cycle environmental footprint among three systems. This work provides fresh insights into solid PDS activation through defect engineering, advancing solid‑phase advanced oxidation for hazardous organic waste treatment.