State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology, Shenzhen, 518055, China.
State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology, Shenzhen, 518055, China.
Chemosphere. 2022 Nov;307(Pt 4):135790. doi: 10.1016/j.chemosphere.2022.135790. Epub 2022 Aug 5.
Dissolved organic nitrogen (DON) plays a key role in many biogeochemistry and engineering processes such as forming nitrogenous disinfection byproducts. However, detecting aqueous DON at trace levels is challenging currently because conventional DON conversion methods have very high method detection limits (MDL). In addition, DON is measured indirectly by subtracting dissolved inorganic nitrogen (DIN) from total dissolved nitrogen (TDN), which can propagate analytical errors of each analyte. In order to solve these issues, we isolated DON from DIN with electrodialysis before and herein tested vacuum ultraviolet (VUV) in tandem with several oxidants to convert DON completely into nitrate for subsequent N analysis. Results showed that HO was more suitable than chlorine and persulfate because VUV/chlorine or VUV/persulfate is either inefficient to convert DON or subjected to nonnegligible N loss. To verify the efficiency, we evaluated the effects of typical water and operating variables on the conversions of four model DON compounds and their yields of nitrate. Under optimal conditions (pH 10.3 and 500 mg/L HO), the process converted DON completely into nitrate within just 60 min. Compared to conventional TDN analytical methods, the VUV/HO method features not only better analytical precision but also lower MDL because the formed nitrate can be analyzed at very low MDL by ion chromatography (IC). So, this approach moves one step further to achieve a conceptually new DON analytical method by coupling electrodialysis, VUV/HO, and IC.
溶解有机氮 (DON) 在许多生物地球化学和工程过程中起着关键作用，例如形成含氮消毒副产物。然而，目前检测痕量水中的 DON 具有挑战性，因为传统的 DON 转化方法的方法检测限 (MDL) 非常高。此外，DON 是通过从总溶解氮 (TDN) 中减去溶解无机氮 (DIN) 来间接测量的，这可能会传播每个分析物的分析误差。为了解决这些问题，我们在电渗析之前将 DON 从 DIN 中分离出来，并且在此测试了真空紫外线 (VUV) 与几种氧化剂串联，将 DON 完全转化为硝酸盐，以便随后进行 N 分析。结果表明，HO 比氯和过硫酸盐更适合，因为 VUV/氯或 VUV/过硫酸盐要么对 DON 的转化效率不高，要么会导致不可忽略的 N 损失。为了验证效率，我们评估了四个模型 DON 化合物及其硝酸盐产率的典型水和操作变量对转化的影响。在最佳条件下 (pH 10.3 和 500 mg/L HO)，该过程在短短 60 分钟内将 DON 完全转化为硝酸盐。与传统的 TDN 分析方法相比，VUV/HO 方法不仅具有更好的分析精度，而且具有更低的 MDL，因为形成的硝酸盐可以通过离子色谱 (IC) 在非常低的 MDL 下进行分析。因此，通过电渗析、VUV/HO 和 IC 耦合，该方法在概念上更进一步，实现了一种新的 DON 分析方法。
