Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China.
Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China.
Sci Total Environ. 2022 Jan 20;805:150418. doi: 10.1016/j.scitotenv.2021.150418. Epub 2021 Sep 17.
Carcinogenic N, N-Dimethylnitrosamine (NDMA) has been reported to generate significantly during ozonation of fuel additive unsymmetrical dimethylhydrazine (UDMH), the combined ozone/Peroxy-Monosulfate (O/PMS) technology was tried for reducing its formation in this study. The influence of PMS dosages, ozone concentrations, pH, Br and humic acid (HA) on NDMA formation from UDMH were investigated. In addition, the reduction mechanisms were explored by intermediates identification and Gaussian calculation. The results demonstrated that O/PMS technology was effective on NDMA reduction, reaching an efficiency of 81% with 80 μM PMS. Higher NDMA reduction rates were achieved by O/PMS with increasing pH within the scope of research (from 5 to 9), achieving a maximum of 69.9% at pH 9. The presence of bromide ion facilitated NDMA generation during ozonation, but the reduction efficiency by O/PMS slightly improved from 66.3% to 70.6%. The presence of HA reduced NDMA formation in O/PMS system. The contribution of SO on NDMA reduction accounted for ~64%, which was higher than that of •OH (41.4%); however, its promotion role on conversing UDMH to NDMA was lower than O. Therefore, the technology could reduce NDMA formation effectively. In addition, the results of Gaussian calculation manifested that the N atom in -NH group of UDMH was easily attacked not only by •OH but also by O, so it is the key path that determines final NDMA formation. This study would provide reference for reducing NDMA formation during ozonation of UDMH-containing water matrixes.
已报道致癌性 N，N-二甲基亚硝胺（NDMA）在燃料添加剂不对称二甲肼（UDMH）的臭氧化过程中会大量生成。本研究尝试采用臭氧/过一硫酸盐（O/PMS）联合技术来降低其生成量。考察了过一硫酸盐剂量、臭氧浓度、pH 值、溴离子和腐殖酸（HA）对 UDMH 生成 NDMA 的影响。此外，通过中间体鉴定和高斯计算探讨了还原机制。结果表明，O/PMS 技术对 NDMA 的去除有效，在 80 μM 过一硫酸盐时去除率达到 81%。在研究范围内（pH 值 5-9），随着 pH 值的升高，O/PMS 对 NDMA 的还原率更高，在 pH 值为 9 时达到 69.9%的最大值。溴离子的存在促进了臭氧化过程中 NDMA 的生成，但 O/PMS 的还原效率略有提高，从 66.3%提高到 70.6%。HA 的存在降低了 O/PMS 体系中 NDMA 的生成。SO 对 NDMA 还原的贡献约为 64%，高于•OH（41.4%）；然而，其对 UDMH 向 NDMA 转化的促进作用低于 O。因此，该技术可以有效地降低 NDMA 的生成。此外，高斯计算的结果表明，UDMH 中-NH 基团中的 N 原子不仅容易受到•OH 的攻击，也容易受到 O 的攻击，因此这是决定最终 NDMA 生成的关键途径。本研究将为降低含 UDMH 水基质臭氧化过程中 NDMA 的生成提供参考。
