Search

• Electrolysis, permanganate, and O3 showed a satisfactory synergistic effect for various organics degradation. • Reactive manganese species (RMnS) and · OH were the dominant reactive species in E-PM-O3 process. • 1 mg L − 1 gaseous ozone dramatically promoted generating both RMnS and · OH with even lower energy consumption. • In situ formed MnO2 played a critical role for generating both RMnS and · OH. • · OH generated by O3 catalysis transfer colloid MnO2 to free mn (Ⅴ) and mn (Ⅵ) in the E-PM-O3 process. A novel water treatment process combining electrolysis, permanganate and ozone was tested in the laboratory. The combination showed synergistic effects in degrading various organic contaminants (like diclofenac, sulfamethoxazole, carbamazepine, etc.). A small amount of O 3 (1 mg L −1, 60 mL min−1) significantly improved the oxidation and mineralization ability of an electro-permanganate process by generating more reactive manganese species and hydroxyl radicals. The combination required less energy consumption than comparable processes. Mechanism experiments showed that the · OH involved was mainly generated by cathode reduction, homogeneous manganese catalysis, and heterogeneous manganese catalysis of O 3 decomposition. Reactive Mn species were generated by electro-reduction, · OH oxidation or/and O 3 activation. In situ generated Mn (Ⅳ) s plays a vital role in generating · OH and reactive Mn species. · OH generated by O 3 catalysis could transfer colloid Mn (Ⅳ) s to free Mn (Ⅴ) aq and Mn (Ⅵ) aq. And both the · OH and RMnS played the dominant role for DCF removal. Increasing permanganate dosage, O 3 concentration, the current density, C l − , or humic acid, and decreasing the pH all enhanced the degradation of diclofenac, but the presence of PO 4 3 − or HCO 3 − inhibited it. Supplementing electrolysis with permanganate and O 3 might be a practical, sustainable, and economical technology for treating refractory organics in natural waters. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Electrolysis and permanganate (PM) oxidation are two commonly used technologies for water treatment. However, they are often handicapped by their slow reaction rates. To improve the removal efficiency of refractory contaminants, we combined electrolysis with PM using an activated carbon fiber (ACF) as cathode (E-ACF-PM) for the first time to treat diclofenac (DCF) in aqueous solution. Up to 90% DCF was removed in 5 min by E-ACF-PM process. In comparison, only 3.95 and 27.35% of DCF was removed by individual electrolysis and PM oxidation at the same time, respectively. Acidic condition was more conducive to DCF removal. Surprisingly, soluble Mn(III) (aq) formed on the surface of ACF was demonstrated as the principal oxidizing agent in E-ACF-PM process. Further studies showed that all three components (electrolysis + ACF + PM) were necessary to facilitate the heterogeneous generation of reactive Mn(III) (aq). Moreover, SEM images and XPS spectra of ACF before and after treatment revealed that the morphologies and elemental compositions of reacted ACF were nearly unchanged during the E-ACF-PM process. ACF can be remained active and utilized to the rapid degradation of DCF in E-ACF-PM process even after reused for 20 times. Therefore, the E-ACF-PM process may provide a novel and effective alternative on the generation of reactive Mn(III) (aq) in situ for water treatment by green electrochemical reactions. Image 1 • A novel synergistic technology coupling electrolysis and permanganate (PM) was developed. • DCF can be rapidly removed in E-ACF-PM process from raw water. • Mn(III) formed on the ACF cathode played a key role in DCF degradation. • All three components (electrolysis + ACF + PM) were necessary to facilitate the heterogeneous generation of reactive Mn(III). • The recycled ACF for 20 times in E-ACF-PM process still had a satisfactory efficiency. [ABSTRACT FROM AUTHOR]