Prediction of 1,4-dioxane decomposition during VUV treatment by model simulation taking into account effects of coexisting inorganic ions

Bioelectrochemical Treatment of 1,4-Dioxane in the Presence of Chlorinated Solvents: Design, Process, and Sustainability Considerations

“…These E EO values are higher than those previously reported for UV-based technologies, which can achieve 1,4-dioxane treatment at single digit kWh·m –3 or in the case of vacuum ultraviolet (VUV) treatment even below − However, commonly occurring inorganic ions and organic co-contaminants including inhibiting chlorinated solvents may increase power consumption, and the addition of oxidants during ozone- or H 2 O 2 -based UV treatment needs to be considered. , The comparatively higher energy consumption for (bio)­electrochemical 1,4-dioxane oxidation in our experiments is at least partly due to the fact that this parameter was not determined in a reactor optimized for mass transfer but at seepage velocities representative of groundwater, where mass transfer solely relied on slow diffusion processes. High-flow pumping in ex situ reactors is expected to increase mass transfer and consequently decrease energy consumption …”

“…In the environment, 1,4-dioxane has shown remarkable recalcitrance to natural biological and chemical attenuation processes, and its removal by traditional water treatment approaches has proven to be a challenge. Generally, strong oxidants are needed to activate the diether ring. − Several studies have demonstrated that advanced oxidation processes (AOPs) such as H 2 O 2 , plasma, UV, peroxymonosulfate, and ozone treatment are effective in generating reactive oxygen species (ROS) to degrade 1,4-dioxane. − Electrochemical oxidation has emerged as a promising technology to remove persistent organic pollutants − because it is cost-competitive with other AOPs and can be implemented for in situ groundwater treatment by using mesh electrodes. , Indirect oxidation through generated ROS such as ·OH and direct electron transfer were shown as the main degradation mechanism of this technology . However, in spite of the effectiveness of the electrochemical oxidation processes, high capital costs and considerable energy consumption have thus far deferred field-scale applications.…”

Insights into the photocatalytic ozonation over Ag2O-ZnO@g-C3N4 composite: Cooperative structure, degradation performance, and synergistic mechanisms

“…S4a, when Cl − ion was added into the process, Cl − ion could react with • OH (k • OH, Cl − = 4.3×10 9 M −1 s −1 ) and the valance band hole to produce less oxidative agent Cl • that would further propagate to form chlorinate byproduct inhibiting the degradation efficiency of OA markedly [54]. Similarly, NO3 − ion was also could act as a • OH scavenger (k • OH, NO3 − = 1.0×10 5 M −1 s −1 ) hindering the photocatalytic ozonation activity rather than removal process [14,55]. In addition, as displayed in Eqs (3-6) [56], other ions including CO3 2− , HCO3 − , PO4 3− , and SO4 2− also may scavenge the radicals like • OH and O2 •− to form other ions in PhOx process, which could decrease the react rate due to comparative adsorption.…”

H2S Removal from Groundwater by Chemical Free Advanced Oxidation Process Using UV-C/VUV Radiation

“…However, considering the radiation requirements, it seems that it would be beneficial to add some pretreatment to reduce interferences from substances present in groundwater (e.g., bicarbonate chloride and sulfate) that compete with the sulfide for the generated ·OH radicals. For groundwater not contaminated by high levels of chloride and nitrates, bicarbonate and carbonate ions are major ·OH scavengers [ 20 ]. Hence, in this case, a simple reduction of pH prior to oxidation (converting these ions to the less reactive H 2 CO 3 ) should improve the process efficiency.…”

“…The direct formation of hydroxyl radicals makes VUV radiation among the most advanced oxidation processes [ 14 ]. In recent years, there is accumulating evidence for the potential of a VUV-based AOP for removal of persistent pollutants both in deionized water (e.g., [ 15 , 16 ]) as well as in more realistic water matrices (e.g., [ 17 , 18 , 19 , 20 , 21 ]). Like all AOP processes, a successful VUV-based AOP needs to minimize the formation of undesired intermediates and overcome interferences from other compounds that may compete for the hydroxyl radicals formed (e.g., carbonate, bicarbonate, chloride, and natural organic matter) or act as inner UV filters (e.g., nitrates and NOM) (e.g., [ 21 , 22 ]).…”