Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

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Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Chemistry of persulfates in water and wastewater treatment: A review

BackgroundIncreasing concern over bisphenol A (BPA) as an endocrine-disrupting chemical and its possible effects on human health have prompted the removal of BPA from consumer products, often label...

Bisphenol S and F: A Systematic Review and Comparison of the Hormonal Activity of Bisphenol A Substitutes.

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) × 104 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 for both •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 O3 is proposed to generate SO4•–, while O3•– converts to •OH. A definition of Rct,•OH and Rct,SO4•– (i.e., respective ratios of •OH and SO4•– exposures to O3 exposure) is ...

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

Vibrational and vibronic relaxation and related energy redistribution play an important role in many photoinduced processes of molecules. In the condensed phase, in which collision-induced relaxation is of particular relevance, these phenomena occur on a very rapid time scale between several tens of femtoseconds and 100 ps (1, 2). Spectroscopy with ultrashort laser pulses has been widely applied to elucidate the dynamics and physical mechanisms of intraand intermolecular energy redistribution (3, 4). Indeed, time resolved experiments have provided extensive information not accessible by other experimental techniques. In this article, we present a review on vibrational and vibronic relaxation of large molecules in liquids. Photoinduced redistribution processes of molecules, which consist typically of 20 or more atoms, are considered. We discuss. femtoand picosecond spectroscopy of the intramolecular redistribution and the intermolecular energy transfer from vibrationally hot molecules to their (cold) surrounding. We focus on measurements of vibrational and vibronic lifetimes, as well as on studies of energy redis­ tribution and transport. However, we will not consider dephasing of vibranic or vibrational states, relaxation processes connected to the

VIBRATIONAL AND VIBRONIC RELAlXATION OF LARGE POL-yrATOMIC MOLECULES IN LIQUIDS

The interaction of bisphenol-S (BPS) with serum albumins using steady-state, synchronous, time-resolved, and circular dichroism spectroscopies has been investigated. The binding interactions have also been investigated in the case of bisphenol A (BPA). The fluorescence quenching pathways are different for both of these endocrine disrupting compounds. Steady-state and time-resolved studies reveal static quenching at lower concentrations of BPS and dynamic quenching at higher concentrations. CD results also maintained the concentration dependent variation with a complete distortion of α-helices at 10–5 M BPS. Besides this, addition of sodium dodecyl sulfate (SDS) results in the further unfolding of protein in the case of BPS, whereas time-resolved studies indicated refolding for BPA denatured human serum albumin (HSA). The entire study indicates an irreversible binding of BPS with HSA. Hence, these results reveal the possible involvement of BPS in the physiological pathway raising a health threat as already...

Exploring the interaction of bisphenol-S with serum albumins: a better or worse alternative for bisphenol a?

Atenolol is a β-blocker drug and an identified emerging pollutant. Advanced oxidation processes (AOPs) utilise the reaction of a highly oxidising species (hydroxyl radicals, (•)OH) for the mineralisation of emerging pollutants since conventional treatment methodologies generally fail to degrade these compounds. In the present work, degradation of atenolol was carried out using ultrasound with frequencies ranging from 200 kHz to 1 MHz as a source of hydroxyl radical. The degradation was monitored by HPLC, total organic carbon (TOC) and chemical oxygen demand (COD) reduction and ion chromatography (IC). Nearly 90 % of degradation of atenolol was observed with ultrasound having 350 kHz. Both frequency and power of ultrasound affect the efficiency of degradation. Nearly 100 % degradation was obtained at a pH of 4. Presence of various additives such as sodium dodecyl sulphate, chloride, sulphate, nitrate, phosphate and bicarbonate was found to reduce the efficiency of degradation. Although nearly 100 % degradation of atenolol was observed under various experimental conditions, only about 62 % mineralisation (from TOC and COD measurements) was obtained. Nearly eight intermediate products were identified using high-resolution mass spectrometry (LC-Q-TOF). These products were understood as the results of hydroxyl radical addition to atenolol. The degradation studies were also carried out in river water which also showed a similar degradation profile. A mechanism of degradation and mineralisation is presented.

Sonochemical degradation of a pharmaceutical waste, atenolol, in aqueous medium

Oxidation of substituted triazines by sulfate radical anion (SO) in aqueous medium: a laser flash photolysis and steady state radiolysis study

Ultrafast charge transfer dynamics in 2-aminopurine modified double helical DNA

Reactions of sulphate radical anion (SO·4
-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·4
- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH- leading to the formation of OH adducts.

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P. Manoj

Papers

Exploring the interaction of bisphenol-S with serum albumins: a better or worse alternative for bisphenol a?

Sonochemical degradation of a pharmaceutical waste, atenolol, in aqueous medium

Oxidation of substituted triazines by sulfate radical anion (SO) in aqueous medium: a laser flash photolysis and steady state radiolysis study

Ultrafast charge transfer dynamics in 2-aminopurine modified double helical DNA

Reaction of sulphate radical anion (SO. 4 -) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study