Journal of South China University of Technology(Natural Science Edition) ›› 2022, Vol. 50 ›› Issue (8): 102-108.doi: 10.12141/j.issn.1000-565X.210345

Special Issue: 2022年环境科学与技术

• Environmental Science & Technology • Previous Articles     Next Articles

Effect Factors and Generation Pathway of Iodoacetic Acid from Tryptophan During UV Irradiation Combined with Chlorine Disinfection

YANG Yulong FEI Weicheng JI Jingxuan ZHANG Kejia   

  1. College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,Zhejiang,China
  • Received:2021-05-26 Online:2022-08-25 Published:2021-08-31
  • Contact: 张可佳(1983-),女,博士,副教授,博士后研究人员,主要从事饮用水处理技术研究。 E-mail:zhangkj@zju.edu.cn
  • About author:杨玉龙(1973-),男,博士,副教授,主要从事市政工程安全研究。E-mail:yulongy@zju. edu. cn
  • Supported by:
    the National Science and Technology Major Project(2017ZX07201004);the National Natural Science Foundation of China(51978602)

Abstract:

Amino acid is a common nitrogenous compound in water. Iodine disinfection by-products could be produced in the process of tryptophan chlorination disinfection in present of I-. To investigate the generation and mechanism of iodoacetic acid from amino acid during the use of UV and chlorine for disinfection, this paper selected a typical iodoacetic acid, namely, tryptophan, and developed a generation kinetic model. In the investigation, first, the influences of different factors including UV irradiation time, chlorine dosage, pH value, Br- content, and I- content on the generation of iodoacetic acid were explored, and the generation pathway of iodoacetic acid was further analyzed. The results show that the generation process of iodoacetic acid fits the pseudo first-order reaction kinetic model, with a generation rate constant k of 0.17 h-1. UV irradiation time, chlorine dosage, pH value, Br- content, and I- content all exert big influence on the generation process of iodoacetic acid. UV irradiation time promotes the generation of iodoacetic acid, and the yield of iodoacetic acid increases with the increase of UV irradiation time. When the pH value is in the range of 6 ~ 8, the yield of iodoacetic acid increases with the pH value. The generation of iodoacetic acid exhibits a firstly increase and then decrease trend with the increase in chlorine. When the ration of the concentrations of tryptophan and chlorine dosage is 1∶2, the production of IAA reaches the highest (15.30 μg/L). The paper also established an equation describing the relationship among Br- content, I- content and iodoacetic acid yield. It is found that Br- has a negative correlation to the generation of iodoacetic acid, while I- content has a greater positive one. In addition, four products including butanoic acid anhydride and isovaleric anhydride were detected using LC-MS-MS and GC-MS. It is speculated that the generation path of iodoacetic acid is that C12H17NO3 is firstly produced from tryptophan through the action of UV photohydrolysis and hydroxyl radicals, and then isovaleric acid and butyrate acid are generated sequentially under the oxidation of HOCl and HOI, and finally iodoacetic acid is generated.

Key words: tryptophan, UV-light, disinfection by-products, iodoacetic acid, generation pathway

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