NDMA reduction mechanism of UDMH by O3/PMS technology

• Published in: The Science of the total environment 2022-01, Vol.805, p.150418-150418, Article 150418
• Main Authors: Huang, Yongjun, He, Zixiang, Liao, Xiaobin, Cheng, Yusheng, Qi, Huan
• Format: Article
• Language: English
• Subjects: NDMA; O3/PMS technology; Ozonation; UDMH
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.150418

Carcinogenic N, N-Dimethylnitrosamine (NDMA) has been reported to generate significantly during ozonation of fuel additive unsymmetrical dimethylhydrazine (UDMH), the combined ozone/Peroxy-Monosulfate (O3/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 O3/PMS technology was effective on NDMA reduction, reaching an efficiency of 81% with 80 μM PMS. Higher NDMA reduction rates were achieved by O3/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 O3/PMS slightly improved from 66.3% to 70.6%. The presence of HA reduced NDMA formation in O3/PMS system. The contribution of SO4•− 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 O3. Therefore, the technology could reduce NDMA formation effectively. In addition, the results of Gaussian calculation manifested that the N atom in -NH2 group of UDMH was easily attacked not only by •OH but also by O3, 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. [Display omitted] •The O3/PMS technology could significantly reduce NDMA formation from UDMH during ozonation.•The NDMA reduction efficiency in O3/PMS system lessened at the presence of HA.•The contribution of SO4•− on NDMA reduction was higher than that of •OH, which accounted for ~64%.•The formed SO4•− played roles on conversing UDMH to NDMA, but its promotion role was lower than O3.•N atom in the -NH2 group of UDMH was the key site that promoted the formation of NDMA.