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Efficient simultaneous degradation and dechlorination of chlorophenylacetonitrile by vacuum ultraviolet-sulfite advanced reduction system
Summary
When water is treated with chlorine to kill germs, it can accidentally create harmful byproducts, including one called 2-CPAN that's found in both tap water and wastewater. Researchers found a new treatment method combining UV light with a sulfite chemical can break down over 98% of this contaminant in tap water and nearly 87% in wastewater within an hour, offering a promising way to make water treatment safer. While still an early-stage lab study, this suggests a practical path toward removing harmful chemical byproducts from the water we drink and use every day.
Disinfection by-products (DBPs) in chlor(am)inated drinking water and wastewater pose risks to human health and ecological safety. Studies on the degradation of the formed DBPs, especially aromatic DBPs, are quite limited. Recently, advanced reduction processes (ARPs), generating highly reactive reductive radicals to break the carbon-halogen bonds, as an emerging technology for refractory organic compound degradation has attracted attention. This study, for the first time, explored the degradation of a representative nitrogenous and aromatic DBP, 2-chlorophenylacetonitrile (2-CPAN), by VUV/UV/sulfite-based ARP system, and investigated the underlying mechanisms and influencing factors. The results demonstrated that VUV/UV/sulfite system achieved over 98.6 % and 86.8 % degradation of 2-CPAN from tap water and wastewater within 60 minutes although inorganic ions existing in real waters slightly inhibited its degradation, highlighting its potential for practical application in real waters. Due to VUV direct photolysis and the generation of more reactive species, VUV/UV/sulfite exhibited superior performance in 2-CPAN degradation (98 %) than UV/sulfite (81 %). Furthermore, VUV/UV/sulfite system maintained a stable degradation efficiency across a wide range of pH (5-11) and sulfite dosages (0.25-5.0 mM), and achieved 90 % degradation even under oxic conditions. Mechanism studies confirmed the presence of hydrated electrons (eaq-), hydroxyl radicals, and hydrogen radicals in VUV/UV/sulfite system, with eaq- identified as the primary contributor to 2-CPAN degradation. Chlorine in 2-CPAN was primarily released as chloride ions, achieving 94 % dehalogenation within 15 minutes. The above findings revealed that VUV/UV/sulfite could be a promising technology for aromatic DBP degradation in real waters.