Interfacial reaction between organic acids and iron-containing clay minerals: Hydroxyl radical generation and phenolic compounds degradation

Song Zhao; Ze Liu; Ru Zhang; Jinsong Liu; Jinbo Liu; Yunchao Dai; Chi Zhang; Hanzhong Jia

doi:10.1016/j.scitotenv.2021.147025

Interfacial reaction between organic acids and iron-containing clay minerals: Hydroxyl radical generation and phenolic compounds degradation

Sci Total Environ. 2021 Aug 20:783:147025. doi: 10.1016/j.scitotenv.2021.147025. Epub 2021 Apr 18.

Authors

Song Zhao¹, Ze Liu¹, Ru Zhang¹, Jinsong Liu¹, Jinbo Liu¹, Yunchao Dai¹, Chi Zhang¹, Hanzhong Jia²

Affiliations

¹ College of Resources and Environment, Northwest A & F University, Yangling 712100, China.
² College of Resources and Environment, Northwest A & F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China; State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Yangling 712100, China. Electronic address: jiahz@nwafu.edu.cn.

PMID: 34088140
DOI: 10.1016/j.scitotenv.2021.147025

Abstract

Reactive oxygen species, especially hydroxyl radicals (OH), exert a distinguished role in the transformation of contaminants, and their in-situ generation attracts wide attentions in environmental and geochemical areas. The present work explored the potential formation of OH during the interactions between iron-containing clay minerals and environmentally prevalent organic acids in dark environments. The results demonstrated that the accumulative OH concentrations were related to the solution pH, the types of clay minerals, and the nature of organic acid species. At pH 5.5, 1.2- 15.2 times of OH were generated from the reduction of Na-nontronite-2 (Na-NAu-2) compared with other clay minerals in the presence of ascorbic acid (AA) at 144 h. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses indicated that Fe(III) was reduced to Fe(II) by AA during OH formation. Meanwhile, chemical probe tests coupled with quenching experiments confirmed the generation of H₂O₂ and superoxide radical (O₂^-), which participated in the formation of OH. The produced OH/O₂^- can transform 68.4%, 86.4%, and 50.1% of phenol, p-nitrophenol, and 2,4-dichlorophenol within 168 h in AA-Na-NAu-2 suspension, respectively. This work provides valuable insights into OH production in the mutual interaction between organic acids and iron-bearing clays, which is helpful for the development of a new method for removing organic pollutants from contaminated water and soil environments.

Keywords: Ascorbic acid; Degradation; Fe(III)-containing clay minerals; Hydroxyl radical; Phenolic compounds.