Abstract：
Monochloramine (NH2Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH2Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH2Cl is typically generated from combining sodium hypochlorite and ammonium chloride or sulfate. This study investigated the degradation of four compounds of interest - acetaminophen, caffeine, sucralose and 1,4-dioxane - in UV/NH2Cl at the bench scale to study their reactivity with reactive chlorine species (RCS) and reactive nitrogen species (RNS). With methanol acting as a scavenger of •OH radicals, the performance of UV/NH2Cl was compared to UV/H2O2 and UV/HOCl. In UV/H2O2, dioxane was severely inhibited at 1-2 mg/L H2O2 and comparable at 5 mg/L to UV/NH2Cl. When ammonium sulfate ((NH4)2SO4) was used as the ammonia source over ammonium chloride (NH4Cl), the overall degradation of micropollutants was higher and caffeine was exclusively degraded. At 1-2 mg/L NH2Cl, dioxane degraded by 16.2-17.8% and 2.92-5.29% from (NH4)2SO4 and NH4Cl respectively while caffeine degraded by 7.45-9.61% with NH2Cl ((NH4)2SO4), but not degrade with NH2Cl (NH4Cl). The higher concentration of chloride ions from NH4Cl significantly influenced the speciation of generated radicals and impacted micropollutant degradation. This suggests that the reactivity of more selective RCS (Cl2•-, •ClO, ClOH•-) and RNS (•NH2, •NO, •NO2, etc.) varies with micropollutants of interest. The presence of higher chloride concentration from the ammonia source inhibited the generation of •OH radicals with •OH consumed by RNS to form NO3- (μg/L levels), showing the impact of the choice of ammonia source and the water matrix on UV/NH2Cl performance.
摘要：
将一氯胺(NH2Cl)施加在反渗透(RO)膜的上游用于生物污染控制。残留的NH2Cl可以在下游进行紫外光解，产生AOP发生的反应性物种。在台秤上，NH2Cl通常由次氯酸钠和氯化铵或硫酸盐的组合产生。这项研究调查了四种感兴趣的化合物-对乙酰氨基酚的降解，咖啡因,三氯蔗糖和1,4-二恶烷-在台架规模的UV/NH2Cl中研究其与活性氯物种（RCS）和活性氮物种（RNS）的反应性。用甲醇作为•OH自由基的清除剂，将UV/NH2Cl与UV/H2O2和UV/HOCl的性能进行了比较。在UV/H2O2中，二恶烷在1-2mg/LH2O2时受到严重抑制，在5mg/L时与UV/NH2Cl相当。当使用硫酸铵((NH4)2SO4)作为氨源在氯化铵(NH4Cl)上,微污染物的整体降解较高，咖啡因仅被降解。在1-2毫克/升的NH2Cl，二恶烷分别从（NH4）2SO4和NH4Cl降解16.2-17.8％和2.92-5.29％，而咖啡因用NH2Cl（（NH4）2SO4）降解7.45-9.61％，但不能用NH2Cl(NH4Cl)降解。NH4Cl中氯离子的较高浓度会显着影响所生成自由基的形态并影响微污染物的降解。这表明更具选择性的RCS(Cl2·-，•ClO,ClOH•-)和RNS(•NH2,•NO,•NO2等。)随感兴趣的微污染物而变化。来自氨源的较高氯化物浓度的存在抑制了•OH自由基的产生，•OH被RNS消耗以形成NO3-（μg/L水平），表明氨源和水基质的选择对UV/NH2Cl性能的影响。
