Detecting trace dissolved organic nitrogen (DON) in freshwater by converting DON rapidly into nitrate with VUV/H2O2 pretreatment. (November 2022)

• Record Type: Journal Article
• Authors: Li, Boqiang; Yang, Fei; Chen, Baiyang; Li, Juan; Zhu, Lijuan; Li, Wen-Tao
• Is Part Of: Chemosphere. Volume 307:Part 4(2022)
• Publication Date: 2022-11
• Subjects: Dissolved organic nitrogen -- VUV/H2O2 -- Pretreatment -- Nitrate -- Ion chromatography; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.135790
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: 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 H2 O2 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 H2 O2 ), the process converted DON completely into nitrate within just 60 min. Compared to conventional TDN analytical methods, the VUV/H2 O2 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/H2 O2, and IC. Graphical abstract: Image 1 Highlights: VUV and oxidant were combined to convert DON into NOx − . H2 O2 is better than ClO − and S2 O8 2− because it keeps N and is more efficient. The optimal conditions are set at pH 10.3 in water dosed with 500 mg/L of H2 O2 . Compared to VUV, VUV/H2 O2 reduces the operation time greatly from 12 to 1 h. After VUV/H2 O2 pretreatment, it only needs to measure NOx − to quantify DON.