Oxidation of 1,3-diphenylguanidine (DPG) by goethite activated persulfate: Mechanisms, products identification and reaction sites prediction

Jinbin Lai; Ting Tang; Xiaodong Du; Rui Wang; Jiahao Liang; Dehao Song; Zhi Dang; Guining Lu

doi:10.1016/j.envres.2023.116308

Oxidation of 1,3-diphenylguanidine (DPG) by goethite activated persulfate: Mechanisms, products identification and reaction sites prediction

Environ Res. 2023 Sep 1:232:116308. doi: 10.1016/j.envres.2023.116308. Epub 2023 Jun 7.

Authors

Jinbin Lai¹, Ting Tang², Xiaodong Du¹, Rui Wang³, Jiahao Liang¹, Dehao Song¹, Zhi Dang⁴, Guining Lu⁵

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
² School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, 510006, China. Electronic address: tangt@scut.edu.cn.
³ South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China.
⁴ School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, South China University of Technology, Guangzhou, 510006, China.
⁵ School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, 510006, China. Electronic address: gnlu@foxmail.com.

PMID: 37290617
DOI: 10.1016/j.envres.2023.116308

Abstract

As emerging pollutants continue to be discovered, studies on the degradation behavior of emerging pollutants have proliferated, but few studies have focused on the reactivity of the new pollutants themselves. The work investigated the oxidation of a representative roadway runoff-derived organic contaminant, 1,3-diphenylguanidine (DPG) by goethite activated persulfate (PS). DPG exhibited the highest degradation rate (k_d = 0.42 h^-1) with present of PS and goethite at pH 5.0, then started to decrease with increasing pH. Chloride ion inhibited DPG degradation by scavenging HO·. Both HO· and SO₄^-· were generated in goethite activated PS system. Competitive kinetic experiments and flash photolysis experiments were conducted to investigate free radical reaction rate. The second-order reaction rate constants for DPG reacting with HO· and SO₄^-· were quantified (k_{DPG + HO·,}k_{DPG + SO4}-_·), which both reached above 10⁹ M^-1 s^-1. Chemical structures of five products were identified, four of them were previously detected in DPG photodegradation, bromination and chlorination processes. By density functional theory (DFT) calculations, ortho- and para- C were more easily attacked by both HO· and SO₄^-·. Abstraction of H on N by HO· and SO₄^-· were the favorable pathways, and the product TP-210 might be generated by cyclization of DPG radical from abstraction of H on N (3). The results of this study help us to better understand the reactivity of DPG with SO₄^-· and HO·.

Keywords: DFT; DPG; Persulfate; Reactivity; Roadway runoff; Second-order reaction rate.

MeSH terms

Iron Compounds*
Kinetics
Oxidation-Reduction
Sulfates / chemistry
Water Pollutants, Chemical* / analysis

Substances

goethite
diphenylguanidine
Water Pollutants, Chemical
Iron Compounds
Sulfates