Comparative Experimental and Computational Studies of Hydroxyl and Sulfate Radical-Mediated Degradation of Simple and Complex Organic Substrates

• Published in: Environmental science & technology Vol. 56; no. 12; pp. 8819 - 8832
• Main Authors: Chen, Yufan, Vu, Huong Chi, Miller, Christopher J., Garg, Shikha, Pan, Dai, Waite, T. David
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.06.2022
• Subjects: Biodegradability; Biodegradation; Chlorine; Chlorine compounds; Computer applications; Contaminants; Filtration; formates; homolytic cleavage; Hydrogen peroxide; Iron; Mineralization; Municipal wastewater; Nanofiltration; Nanotechnology; Organic carbon; Organic contaminants; Oxidation; Scavenging; Substrates; Sulfates; Total organic carbon; Treatment and Resource Recovery; Wastewater treatment; Wastewater treatment plants; effluent organic matter; Fenton; degradation mechanism; radicals; persulfate; concentrate
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.2c00686

Persulfate (PS)-based advanced oxidation processes (AOPs) have been promoted as alternatives to H2O2-based AOPs. To gauge the potential of this technology, the PS/Fe­(II) and Fenton (H2O2/Fe­(II)) processes were comparatively evaluated using formate as a simple target compound and nanofiltration concentrate from a municipal wastewater treatment plant as a complex suite of contaminants with the aid of kinetic modeling. In terms of the short-term rate and extent of mineralization of formate and the nanofiltration concentrate, PS/Fe­(II) is less effective due to slow Fe­(II)/Fe­(III) cycling attributable to the scavenging of superoxide by PS. However, in the concentrate treatment, PS/Fe­(II) provided a sustained removal of total organic carbon (TOC), with ∼81% removed after 7 days with SO4 •– consistently produced via homolysis of the long-life PS. In comparison, H2O2/Fe­(II) exhibited limited TOC removal over ∼57% after 10 h due to the futile consumption of H2O2 by HO•. PS/Fe­(II) also offers better performance at transforming humic-like moieties to more biodegradable compounds as a result of chlorine radicals formed by the reaction of SO4 •– with the matrix constituents present in the concentrate. The application of PS/Fe­(II) is, however, subject to the limitations of slow oxidation of organic contaminants, release of sulfate, and formation of chlorinated byproducts.