Wang Wen-Long, Bai Qing, Wu Yun-Peng, Ouyang Wan-Yue, Lee Min-Yong, Wu Qian-Yuan
Key Laboratory of Microorganism Application and Risk Control of Shenzhen, Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
Division of Chemical Research, National Institute of Environmental Research, Seogu, Incheon 22689, Republic of Korea.
Environ Sci Technol. 2024 Aug 12. doi: 10.1021/acs.est.4c01934.
Vacuum-UV (185 nm, VUV) is widely applied to polish reverse osmosis permeate (ROP), such as the production of electronics-grade ultrapure water. In this study, the VUV oxidation of acetaldehyde, a common carbonyl in ROP, was found to be influenced by anions even at low concentrations. Interestingly, the influencing extent and mechanism varied depending on the anions. Bicarbonate minimally affected the VUV-photon absorption and OH consumption, but at 5000 μg-C·L, it decreased the degradation of acetaldehyde by 58.7% possibly by scavenging organic radicals or other radical chain reactions. Nitrate strongly competed for VUV-photon absorption and OH scavenging through the formation of nitrite, and at 500 μg-N·L, it decreased the removal rate of acetaldehyde degradation by 71.2% and the mineralization rate of dissolved organic carbon by 53.4%. Chloride competed for VUV-photon absorption and also generated reactive chlorine species, which did not affect acetaldehyde degradation but influenced the formation of organic byproducts. The radical chain reactions or activation of anions under VUV irradiation could compensate for the decrease in oxidation performance and need further investigation. In real ROPs, the VUV oxidation of acetaldehyde remained efficient, but mineralization was hindered due to nitrate and chloride anions. This study deepens the understanding of the photochemistry and feasibility of VUV in water with low concentrations of anions.
真空紫外线（185纳米，VUV）被广泛应用于反渗透渗透液（ROP）的净化，比如电子级超纯水的生产。在本研究中，发现即使在低浓度下，ROP中常见的羰基化合物乙醛的VUV氧化也会受到阴离子的影响。有趣的是，影响程度和机制因阴离子而异。碳酸氢根对VUV光子吸收和羟基消耗的影响最小，但在5000微克碳每升时，它可能通过清除有机自由基或其他自由基链反应使乙醛的降解率降低了58.7%。硝酸根通过形成亚硝酸根强烈竞争VUV光子吸收和羟基清除，在500微克氮每升时，它使乙醛降解的去除率降低了71.2%，溶解有机碳的矿化率降低了53.4%。氯离子竞争VUV光子吸收并产生活性氯物种，这虽不影响乙醛降解，但影响有机副产物的形成。VUV辐照下阴离子的自由基链反应或活化可能会弥补氧化性能的下降，这需要进一步研究。在实际的ROP中，乙醛的VUV氧化仍然有效，但由于硝酸根和氯离子的存在，矿化受到阻碍。本研究加深了对低浓度阴离子水中VUV光化学和可行性的理解。
