The efficiency of Congo red (CR) removal by low-pressure ultraviolet photolysis of nitrate (UV/NO₃⁻) process was investigated in this study. Results showed that CR degradation through direct UV (254 nm) photolysis could be ignored, but CR was obviously removed in UV/NO₃⁻ process. Moreover, the contributions of UV, NO₂ and OH to the degradation of CR were explored to be roughly 0.63%, 17.46% and 81.90%, respectively. In addition, the observed pseudo-first-order rate constants for the degradation of CR (k_obs) were assessed by the effects of different water matrices and operation conditions, including NO₃⁻ dosage, CR concentration, solution pH, chloride ion (Cl⁻), natural organic matter (NOM) and carbonate/bicarbonate (CO₃²⁻/HCO₃⁻). The k_obs was increased by nearly 12.9 times with the addition of NO₃⁻ dosage from 1 mM to 200 mM due to the generation of more active components (e.g., OH and NO₂). Higher doses of CR reduced the k_obs, which could be attributed to the filter effects of CR on UV irradiation. Although the photolysis of NO₃⁻ could be expedited under acidic conditions, the k_obs was decelerated because of the protonation of CR (pKa = 4.1, 25 °C). While in alkaline conditions, the k_obs was also reduced as the decrease in redox potential of OH. The presence of Cl⁻ (0–7 mM) exhibited no scavenging effect on the k_obs, which suggested the secondary radicals (i.e., chlorine radicals (e.g., Cl, Cl₂⁻)) could oxidize CR effectively. NOM restricted the degradation of CR significantly, resulting from the filter effects of NOM (ε = 0.11 LmgC⁻¹cm⁻¹) on UV and the effects of radical scavenging. The k_obs was improved obviously with the participation of CO₃²⁻/HCO₃⁻ (0–7 mM), ascribing to the oxidation of carbonate radical (CO₃⁻) and the increased steady state concentration of NO₂. The degradation of CR in UV/NO₃⁻ process has the potential for practical applications in real water. Furthermore, eight intermediates were proposed by Liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hydroxylation, nitrification and other aromatic products in the reaction of CR with OH and/or NO₂ were readily produced by H-abstraction, addition reaction and electron transfer.

刚果红效率通过低压（CR）去除硝酸盐的紫外光解（UV / NO ₃ ^- ）处理在本研究中调查。结果表明，通过直接UV CR降解（254纳米）光解可以忽略不计，但在CR UV / NO明显除去₃ ^-过程。此外，UV，NO ₂和OH对CR降解的贡献分别约为0.63％，17.46％和81.90％。此外，通过不同水基质和操作条件（包括NO _3-）的影响，评估了_观察到的CR降解的拟一级反应速率常数（k _obs）^。剂量，CR浓度，溶液的pH值，氯离子（CL ^- ），天然有机物质（NOM）和碳酸盐/碳酸氢盐（CO ₃ ^{2- /} HCO ₃ ^- ）。所述ķ _OBS通过加入NO的增加近12.9倍₃ ^-剂量从1 mM到200mM的由于多种活性成分（例如，产生OH和NO ₂）。较高剂量的CR可降低k _obs，这可能归因于CR对紫外线辐射的滤光效果。虽然NO的光解₃ ^-可以酸性条件下，下加快ķ _OBS由于CR的质子传递而使d减速（pKa = 4.1，25°C）。在碱性条件下，随着OH氧化还原电位的降低，k _obs也降低。氯的存在^-（0-7毫米）显示出在没有清除作用ķ _OBS，这表明辅助基团（即，氯自由基（例如Cl ，氯₂ ^- ））可有效地氧化CR。NOM显着限制了CR的降解，这归因于NOM对UV的过滤作用（ε  = 0.11 L mgC ^-1 cm ^-1）和自由基清除的作用。该ķ _OBS用CO的参与明显提高₃ ^2- / HCO ₃ ^-（0-7毫米），归咎于到的碳酸根（CO氧化₃ ^- ）和增加的稳态浓度NO ₂。CR的在UV / NO的降解₃ ^-过程具有用于实时水实际应用中的潜力。此外，通过液相色谱-串联质谱法（LC-MS / MS）提出了八种中间体。CR与OH和/或NO ₂的反应中的羟基化，硝化和其他芳族产物很容易通过氢吸收，加成反应和电子转移而产生。