Shenzhen Key Laboratory of Organic Pollution Prevention and Control, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Shenzhen, 518055, China.
Shenzhen Key Laboratory of Organic Pollution Prevention and Control, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Shenzhen, 518055, China.
Chemosphere. 2017 Oct;184:1003-1011. doi: 10.1016/j.chemosphere.2017.06.078. Epub 2017 Jun 20.
In order to achieve better removal and analyses of three dissolved inorganic nitrogen (DIN) species via ultraviolet-activated hydrogen peroxide (UV/HO) process, this study systematically investigated the rates of photo-oxidations of ammonia/ammonium (NH/NH) and nitrite (NO) as well as the photo-reduction of nitrate (NO) at varying pH and HO conditions. The results showed that the mass balances of nitrogen were maintained along irradiation despite of interconversions of DIN species, suggesting that no nitrogen gas (N) or other nitrogen-containing compound was formed. NH was more reactive than NH with hydroxyl radical (OH), and by a stepwise HO addition method NH/NH can be completely converted to NO; NO underwent rapid oxidation to form NO when HO was present, suggesting that it is an intermediate compound linking NH/NH and NO; but once HO was depleted, NO can be gradually photo-reduced back to NO at high pH conditions. Other than HO, the transformation kinetics of DINs were all dependent on pH, but to varying aspects and extents: the NH photo-oxidation favored a pH of 10.3, which fell within the pK values of NH (9.24) and HO (11.6); the NO photo-reduction increased with increasing pH provided that it exceeds the pK of peroxynitrous acid (6.8); while the NO photo-oxidation remained stable unless the pH neared the pK of HO (11.6). The study thereby demonstrates a picture of the evolutions of DIN species together during UV/HO irradiation process, and for the first time presents a method to achieve complete conversion of NH to NO with UV/HO process.
为了通过紫外线激活过氧化氢（UV/HO）工艺更好地去除和分析三种溶解无机氮（DIN）物种，本研究系统研究了在不同 pH 和 HO 条件下氨/铵（NH/NH）和亚硝酸盐（NO）的光氧化速率以及硝酸盐（NO）的光还原速率。结果表明，尽管 DIN 物种相互转化，但氮的质量平衡在照射过程中得以维持，这表明没有氮气（N）或其他含氮化合物形成。NH 比 NH 与羟基自由基（OH）更具反应性，并且通过逐步 HO 添加方法可以将 NH/NH 完全转化为 NO；当存在 HO 时，NO 迅速氧化形成 NO，表明它是连接 NH/NH 和 NO 的中间化合物；但一旦 HO 耗尽，NO 可以在高 pH 条件下逐渐光还原回 NO。除 HO 外，DINs 的转化动力学均依赖于 pH，但在不同方面和程度上有所不同：NH 的光氧化有利于 pH 为 10.3，这处于 NH（9.24）和 HO（11.6）的 pK 值范围内；NO 的光还原随着 pH 的增加而增加，前提是它超过过氧亚硝酸（6.8）的 pK；而 NO 的光氧化除非 pH 接近 HO 的 pK（11.6），否则保持稳定。因此，该研究展示了在 UV/HO 辐照过程中 DIN 物种一起演变的情况，并首次提出了一种通过 UV/HO 工艺将 NH 完全转化为 NO 的方法。
