Ultrafast decomposition of refractory organics by electric field enhanced permanganate/peroxymonosulfate process

Abstract

A novel water treatment process called electrolysis-enhanced permanganate/peroxymonosulfate (E-PM-PMS) was investigated. The process demonstrated rapid degradation of persistent organic pollutants, such as carbamazepine (CBZ), diclofenac (DCF), and tetracycline (TC). For the degradation of ibuprofen (IBP), the E-PM-PMS process showed the highest mineralization ratio (55.76 %) and the lowest energy consumption (8.930 kWh m⁻³) within 120 min, compared with the PM-PMS (25.93 %, 61.814 kWh m⁻³) and E-PMS (31.07 %, 67.903 kWh m⁻³) processes. Mechanism studies indicated that the introduction of an electric field could promote the Mn(VII)/Mn(VI) cycle to form more permanganate (VI) complexes, resulting in the generation of more active species. Additionally, the MnO₂ produced in large amounts during the reaction could activate PMS to generate active species through the Mn(III)/Mn(IV) cycle, while also being activated by these active species to form Mn(V) and Mn(VI). Both the electric field and PMS reacting with PM led to the formation of various RMnS species (Mn(VI)_aq, Mn(V)_aq, Mn(IV)_s, and Mn(III)_aq). Through radical scavenging, electron paramagnetic resonance (EPR) experiments, it was proved that the degradation of IBP was mainly driven by reactive radicals, which are ${\text{SO}}_{\text{4}}^{\bullet -}$${\text{SO}}_{\text{4}}^{\bullet -}$ (72.24 %) and ^•OH (12.38 %). Twelve intermediate products were detected in total, and four possible degradation pathways for ibuprofen were identified. Within a certain range, increasing PMS concentration, PM dosage, current density, NO₃⁻ concentration, and decreasing the pH improved the efficiency of IBP elimination in the E-PM-PMS process, while Cl⁻, HCO₃⁻, PO₄³⁻, and humic acid hindered it. Overall, the E-PM-PMS process shows promise as an economical, eco-friendly, and efficient water treatment technique