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

Reactive oxygen species, especially hydroxyl radicals (center dot 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 center dot OH during the interactions between iron-containing clay minerals and environmentally prevalent organic acids in dark environments. The results demonstrated that the accumulative center dot 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 center dot OH were generated from the reduction of Na-nontronite-2 (Na-NAu-2) compared with other day minerals in the presence of ascorbic acid (M) at 144 h. X-ray photoelectron spectroscopy ()CPS) and Fourier-transform infrared spectroscopy (MR) analyses indicated that Fe(III) was reduced to Fe(II) by AA during center dot OH formation. Meanwhile, chemical probe tests coupled with quenching experiments confirmed the generation of H2O2 and superoxide radical (O-2 center dot(-)), which participated in the formation of center dot OH. The produced center dot OH/O-2 center dot(-) 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 center dot 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. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Reactive oxygen species, particularly hydroxyl radicals (•OH), play a significant role in the transformation of contaminants and can be generated through interactions between iron-containing clay minerals and environmentally prevalent organic acids. The produced •OH/O-2•(-) species are effective in transforming various organic pollutants, providing valuable insights for the development of new methods for removing contaminants from water and soil environments.