es9b05389_si_001.pdf (3.15 MB)

Synchronous Reduction–Oxidation Process for Efficient Removal of Trichloroacetic Acid: H* Initiates Dechlorination and ·OH Is Responsible for Removal Efficiency

Download (3.15 MB)
journal contribution
posted on 06.12.2019 by Jun Zhang, Qinghua Ji, Huachun Lan, Gong Zhang, Huijuan Liu, Jiuhui Qu
Degradation of chlorinated disinfection by-products using the electroreduction process has been considered as a promising approach for advanced water treatment, while the removal efficiency is restricted by a high barrier for dechlorination of intermediates only by reductive atomic hydrogen (H*) and excessive cost required for reducing atmosphere. In this paper, we predict that the dechlorination efficiency for trichloroacetic acid (TCA), a typical chlorinated disinfection by-product, can be accelerated via a synchronous reduction–oxidation process, where the dechlorination barrier can be lowered by the oxidation reactions toward the critical intermediates using hydroxyl radicals (·OH). Based on scientific findings, we constructed a synchronous reduction–oxidation platform using a Pd-loaded Cu/Cu2O/CuO array as the core component. According to the combined results of theoretical and experimental analyses, we found that the high dispersion of nano-sized Pd on a photocathode was beneficial for the production of a high concentration of H* at low overpotential, a perquisite for initiating the dechlorination reaction. Simultaneously, excess H* has the potential to convert O2 to H2O2 in ambient conditions (air condition), and H2O2 can be further activated by a Cu-containing substrate to ·OH for attacking the critical intermediates. In this system, ∼89.1% of TCA was completely dechlorinated and ∼26.8% mineralization was achieved in 60 min, which was in contrast to the value of ∼65.7% and mineralization efficiency of only ∼1.7% achieved through the reduction process (Ar condition).