Production of Sulfate Radical and Hydroxyl Radical by Reaction of Ozone with Peroxymonosulfate: A Novel Advanced Oxidation Process

Abstract

In this work, simultaneous generation of hydroxyl radical (•OH) and sulfate radical (SO4•−) by the reaction of ozone (O3) with peroxymonosulfate (PMS; HSO5−) has been proposed and experimentally verified. We demonstrate that the reaction between the anion of PMS (i.e.,SO52−) and O3 is primarily responsible for driving O3 consumption with a measured second order rate constant of (2.12 ± 0.03) × 10(4) M(-1) s(-1). The formation of both •OH and SO4•− from the reaction between SO52− and O3 is confirmed by chemical probes (i.e., nitrobenzene for •OH and atrazine forb oth •OH and SO4•−). The yields of •OH and SO4•− are determined to be 0.43 ± 0.1 and 0.45 ± 0.1 per mol of O3 consumption, respectively. An adduct,−O3SOO− + O3 → −O3SO5−, is assumed as the first step, which further decomposes into SO5•− and O3•−. The subsequent reaction of SO5•− with O3is proposed to generate SO4•−, while O3•− converts to •OH. A definition of R(ct,•OH) and R(ct,SO4•−) (i.e., respective ratios of •OH and SO4•− exposures to O3 exposure) is adopted to quantify relative contributions of •OH and SO4•−. Increasing pH leads to increases in both values of R(ct,•OH) and R(ct,SO4•−) but does not significantly affect the ratio of R(ct,SO4•−) to R(ct,•OH) (i.e., R(ct,SO4•−)/R(ct,•OH)), which represents the relative formation of SO4•− to •OH. The presence of bicarbonate appreciably inhibits the degradation of probes and fairly decreases the relative contribution of •OH for their degradation, which may be attributed to the conversion of both •OH and SO4•− to the more selective carbonate radical (CO3•−).Humic acid promotes O3 consumption to generate •OH and thus leads to an increase in the R(ct,•OH) value in the O3/PMS process,w hile humic acid has negligible influence on the R(ct,SO4•−) value. This discrepancy is reasonably explained by the negligible effect of humic acid on SO4•− formation and a lower rate constant for the reaction of humic acid with SO4•− than with •OH. In addition, the efficacy of the O3/PMS process in real water is also confirmed.

Direct fabrication of lamellar self-supporting Co3O4/N/C peroxymonosulfate activation catalysts for effective aniline degradation

“…PMS activation depends on the electron transfer from catalyst to PMS, which destroyed the O 3 -SOAOH bond and formed the sulfate radicals. The abundant free electrons in the sp 2 -hybridized carbon structure can contribute to electron transfer, so that PMS can produce sulfate and hydroxyl radicals [35,85]. The PMS activation mechanisms on Co 3 O 4 /N/C for aniline degradation can be proposed as follows.…”

Accelerated ZnMoO4 photocatalytic degradation of pirimicarb under UV light mediated by peroxymonosulfate

“…The incorporation of various radical species such as hydroxyl and sulfate radicals has been reported to enhance the performance of semiconductors in photocatalytic oxidations. Sulfate free radicals have been demonstrated to exhibit better activity than hydroxyl radicals due to their high reactive potential (2.5–3.1 eV), wide range of pH (2–9) and longer lifetime . Sulfate‐based oxidants such as peroxymonosulfate (PMS; or oxone) and peroxydisulfate are commonly employed to generate sulfate radicals by reaction with transition metal ions (e.g.…”

“…Sulfate free radicals have been demonstrated to exhibit better activity than hydroxyl radicals due to their high reactive potential (2.5-3.1 eV), wide range of pH (2)(3)(4)(5)(6)(7)(8)(9) and longer lifetime. [28][29][30] Sulfate-based oxidants such as peroxymonosulfate (PMS; or oxone) and peroxydisulfate are commonly employed to generate sulfate radicals by reaction with transition metal ions (e.g. cobalt or silver) or via degradation upon UV irradiation, among other methods.…”

Peroxymonosulfate activated by amorphous particulate MnO2 for mineralization of benzene gas: Redox reaction, weighting analysis, and numerical modelling

“…Apart from oxygen radicals (i.e., hydroxyl radicals •OH and superoxide radicals •O 2 -) mostly emerged in the advanced oxidation processes (AOPs), sulfate radicals (SO 4 -• ) with a stronger redox potential of 2.5 ~ 3.1 V have been studied as another major oxide to degrade a wide range of organic compounds in wastewater purification and soil remediation, such as carbonyls, chlorophenols, and polycyclic aromatic hydrocarbons [1][2][3][4][5]. There are two basic persulfate anions to be activated to generate sulfate radicals, one is persulfate (PS), and the other is PMS.…”

“…Electron spin-resonance spectroscopy (ESR, ER200-SRC, Bruker, Germany) was also used for the determination of the production and intensity of free radicals. X-ray photoemission spectroscopy (XPS) was recorded on a Thermo ESCALAB 250 system which all the binding energies were calibrated to the C 1s peak at 284.8 eV of the surface adventitious carbon.Reaction solutions were sampled at predetermined time intervals and excessive HONH3 Cl was then injected into samples to quench the reaction. The residual concentrations of AMO and PMS were determined by UV-vis spectrophotometry (Text S4, a Varian Cary 100 Scan UV-Visible system equipped with a labsphere diffuse reflectance accessory) and iodometric titration, respectively[30].…”