Coupling electrocatalytic hydrodechlorination with UV/Sulfite technology for efficient degradation of chlorinated...

Chlorinated organic compounds (COCs) are toxic, bioaccumulative, and potential carcinogens, posing significant risks to health and ecosystems. Their removal is challenging with conventional methods like biological and advanced oxidation processes (AOPs). Advanced reduction processes (ARPs) have gained attention for their efficiency in degrading persistent contaminants. This study integrates electrocatalytic hydrodechlorination (EHDC) with UV/sulfite systems (UV/sulfite-EHDC) to enhance the degradation and mineralization of COCs, focusing on the kinetics, inhibition mechanisms, and byproducts of 2,4-dichlorobenzoic acid (2,4-DCBA) degradation. Results showed significant degradation enhancement at neutral pH, with principal component analysis indicating pH as the most crucial factor. At pH 7.0, hydrated electrons (e_aq^-) facilitated reduction, while H* predominated at pH 4.0. Above pH 7.0, sulfite radicals (SO3^•-) and eaq- influenced degradation. EPR and quenching studies revealed that reductive species (e_aq^-, SO₃^•-, H*) dominated initially, transitioning to oxidative species (^•OH) at later stages. The UV/sulfite-EHDC system achieved 96 % degradation of 2,4-DCBA without oxygen and 47.2 % with oxygen. It also achieved 98.4 %, 94.6 %, and 63.4 % reductions of 4-chlorophenol (4-CP) in distilled water, tap water, and actual wastewater. Mass spectrometry confirmed C-C bond cleavage in the aromatic ring. This study highlights the UV/sulfite-EHDC system as an effective technology for COC removal from wastewater.