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As an alternative to bisphenol A, bisphenol S (BPS) is considered an emerging concern. In this study, the degradation of BPS by persulfate (PS), ultraviolet (UV), and UV/PS was comprehensively examined in ultra-pure and saline waters. UV/PS effectively degraded BPS, and the observed first-order rate constant, kobs, increased from 0.021 to 0.382 min−1 with an increasing PS concentration from 100 to 1000 μΜ. The addition of humic acid (HA) inhibited the degradation of BPS, and 1/kobs was directly proportional to the concentration of HA. In salty water containing 540 mM Cl− or 0.8 mM Br−, UV/PS possessed a higher degradation ability for BPS: the corresponding kobs values were 1.45 and 1.66 times that of the control sample, respectively. Eighteen degradation products, including β-scission, sulfate addition, quinone type, ring-opening, and cross-coupling, were identified using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Two possible pathways were proposed: (i) the initial step was considered to be an electron transfer reaction from BPS to SO4•−, leading to the formation of a phenyl radical cation R1, and then phenol radical R4, 4-hydroxybenzenesulfonate cation R5, phenoxyl radical R3, resonant-type carbon-centered radical R2, and their secondary products; (ii) another pathway was the sulfate addition and hydroxylation. These primary reaction sites were further verified by theoretical calculation. This study highlights the effectiveness of UV/PS as a promising strategy for the remediation of BPS and other endocrine-disrupting chemicals in ultra-pure and saline waters (540 mM NaCl or/and 0.8 mM NaBr).

HOCl and UV activated HOCl (UV/HOCl) have been applied for water disinfection and abatement of organic contaminants. However, the production of toxic byproducts in the HOCl and UV/HOCl treatment should be scrutinized. This contribution comparatively investigated the elimination of 4-nitrophenol and the generation of chlorinated byproducts in HOCl and UV/HOCl treatment processes. 61.4% of 4-nitrophenol was removed by UV/HOCl in 5 min with HOCl dose of 60 μM, significantly higher than that by UV (3.3%) or HOCl alone (32.0%). Radical quenching test showed that HO• and Cl• played important roles in UV/HOCl process. 2-Chloro-4-nitrophenol and 2,6-dichloro-4-nitrophenol were generated consecutively in HOCl process; but their formation was less in the UV/HOCl process. Trichloronitromethane (TCNM) was only found in the UV/HOCl process, and its production increased with increasing HOCl dosage. Besides chlorinated products hydroxylated and dinitrated products were also identified in the UV/HOCl process. Transformation pathways involving electrophilic substitution, hydroxylation, and nitration were proposed for 4-nitrophenol transformation in the UV/HOCl process. Wastewater matrix could significantly promote the transformation of 4-nitrophenol to 2-chloro-4-nitrophenol in UV/HOCl process. Results of this study are helpful to advance the understanding of the transformation of nitrophenolic compounds and assess the formation potential of chlorinated byproducts in HOCl and UV/HOCl disinfection processes.

Purpose The purpose of this paper is to introduce cyclic electrochemical impedance spectroscopy (EIS) method to understand the corrosion evolution behavior of structural materials in secondary circuit water environments of pressurized water reactor (PWR) system. Design/methodology/approach The cyclic EIS has been used to understand the corrosion evolution of 304 stainless steel (SS) in simulated secondary circuit water environment. Scanning electron microscopy and X-ray photoelectron spectroscopy have been used to characterize the microstructure and corrosion morphology of 304 SS sample. Findings Cyclic EIS measurement is applicable in gaining information on the corrosion evolution of 304 SS in high-temperature and high-pressure (HTHP) water environments. Based on analyses of the cyclic EIS data, it is considered that the measured EIS response of 304 SS sample under HTHP water environment mainly comes from the compact inner part of the newly formed oxide layer, which gradually inhibits the progress of electrochemical reactions at the oxide layer/substrate interface. Originality/value The cyclic EIS has been introduced into HTHP water environment, and its reliability has been evaluated. It may find a wide application in corrosion studies of materials under HTHP water environments, which is critical for a safe operation in nuclear power plants and beneficial for the development of corrosion-resistant materials in PWR system.

Nitroaromatic compounds are environmental contaminants that are classically attributed to an anthropogenic origin. On the contrary, we hypothesized that nitrophenolic compounds could be formed by reaction of natural organic matter and nitrite ( NO 2 - ) in sunlit waters. We exposed water samples containing natural organic matter and nitrite to natural sunlight and artificial ultraviolet irradiation. Results show the formation 6.6 nM of 4-nitrophenol and 33.6 nM of 3-nitro-4-hydroxybenzoic acid after 28 h under natural sunlight with 0.3 mM of nitrite. This formation was accelerated with ultraviolet light or with increasing nitrite levels. This formation is explained by the reaction of nitrogen dioxide radical ( NO 2 ∙ ), generated by nitrite photolysis, with phenolic moieties in natural organic matter macromolecules via H-abstraction, generating phenoxyl radicals which couple with another nitrogen dioxide radical to generate nitrophenolic compounds. Overall, the natural contribution of nitrophenolic compounds has been probably overlooked in the environment.

Purpose The purpose of this paper is to optimize a suitable electrochemical method in evaluating the corrosion rate of structural materials of 20# carbon steel, P280GH carbon steel, 17-4PH stainless steel, 304 stainless steel and Alloy 690TT in high-temperature and high-pressure (HTHP) water of pressurized water reactor secondary circuit system. Design/methodology/approach Weight-loss method has been used to obtain the corrosion rate value of each structural material in simulated HTHP water. Besides, linear polarization method and weak polarization curve-based three-point method and four-point method have been compared in obtaining a sound corrosion rate value from the potentiodynamic polarization curve. Scanning electron microscopy (SEM) and atomic force microscope have been used to characterize the microstructure and corrosion morphology of each structural material. Findings Although there is deviation in gaining the corrosion rate value compared to weight-loss test, the weak polarization curve-based four-point method has been found to be a suitable electrochemical method in gaining corrosion rate value of structural materials in HTHP waters. Originality/value This paper proposes a suitable and reliable electrochemical method in gaining the corrosion rate value of structural materials in HTHP waters. The proposed weak polarization curve-based four-point method provides a timesaving and high-efficient way in corrosion rate evaluation of secondary circuit structural materials and thus has a potential application in nuclear power plants.

Salbutamol (SAL) has been widely used as medicine both in treating asthma and in animal primary production; an increasing number of reports have detected SAL in natural waters. The photolysis kinetic and pathway of SAL in aquatic system were studied, as well as the effect of several natural water constituents, such as nitrate, dissolved oxygen (DO) and ferric ions. According to our research, the direct photolysis of SAL followed pseudo-first-order reaction kinetics. Alkaline condition could promote the degradation of SAL; the increase of solution pH would simultaneously increase the fraction of the deprotonated forms of SAL (including the deprotonated and zwitterionic species), which were easier to be excited, and result in the bathochromic shift of the UV-Vis spectrum and, finally, accelerate the degradation rate of SAL. The presence of nitrate could enhance the removal rate of SAL via generation hydroxyl radical (·OH) under irradiation. In addition, the absence of oxygen in the reaction solution could decrease the photolysis. Moreover, Fe(III) was able to chelate with SAL to form an octahedral complex, which was photochemically reactive. The octahedral complex could generate ·OH to oxidize SAL itself in turn. The pathways of SAL photolysis were also investigated by means of the solid phase extraction (SPE)-LC-MS method. The major pathways of SAL photodegradation included oxidation and side-chain cleavage.

The objective of this research was to compare the transformation of Br − and formation of brominated byproducts in UV/persulfate (PS) and UV/H 2 O 2 processes. It was revealed that Br − was efficiently transformed to free bromine which reacted with humic acid (HA) or dihydroxybenzoic acid resulting in the formation of brominated byproducts such as bromoacetic acids (BAAs) in UV/PS system. In contrast, no free bromine and brominated byproducts could be detected in UV/H 2 O 2 system, although the oxidization of Br − was evident. We presumed that the oxidation of Br − by hydroxyl radicals led to the formation of bromine radicals. However, the bromine radical species could be immediately reduced back to Br − by H 2 O 2 before coupling to each other to form free bromine, which explains the undetection of free bromine and BAAs in UV/H 2 O 2 . In addition to free bromine, we found that the phenolic functionalities in HA molecules, which served as the principal reactive sites for free chlorine attack, could be in situ generated when HA was exposed to free radicals. This study demonstrates that UV/H 2 O 2 is more suitable than UV/PS for the treatment of environmental matrices containing Br − . Graphical abstract Graphical abstract

The presence of estrogens in livestock excrement has raised concerns about their potential negative influence on animals and the overall food cycle. This is the first investigation to simultaneously remove estrogens, including estriol (E3), bisphenol A (BPA), diethylstilbestrol (DES), estradiol (E2), and ethinyl estradiol (EE2), from cow manure using a Fenton oxidation technique. Based on the residual concentrations and removal efficiency of estrogens, the Fenton oxidation reaction conditions were optimized as follows: a H2O2 dosage of 2.56 mmol/g, a Fe(II) to H2O2 molar ratio of 0.125 M/M, a solid to water mass ratio of 2 g/mL, an initial pH of 3, and a reaction time of 24 h. Under these conditions, the simultaneous removal efficiencies of E3, BPA, DES, E2, and EE2, with initial concentrations in cow manure of 97.40, 96.54, 100.22, 95.01, and 72.49 mg/kg, were 84.9%, 99.5%, 99.1%, 97.8%, and 84.5%, respectively. We clarified the possible Fenton oxidation reaction mechanisms that governed the degradation of estrogens. We concluded that Fenton oxidation technique could be effective for efficient removal of estrogens in livestock excrement. Results are of great importance for cow manure reuse in agricultural management, and can be used to reduce the threat of environmental estrogens to human health and ecological safety.

Sulfaquinoxaline (SQX) is a coccidiostatic drug widely used in poultry and swine production and has been frequently detected in various environmental compartments such as surface water, groundwater, soils, and sediments. In the present study, degradation of SQX by ferrous ion-activated peroxymonosulfate oxidation process (Fe(II)/PMS), a promising in situ chemical oxidation (ISCO) technique, was systematically investigated. Experimental results showed that Fe(II)/PMS process appeared to be more efficient for SQX removal relative to Fe(II)/persulfate process (Fe(II)/PS). An optimal Fe(II):PMS molar ratio of 1:1 was found to be necessary for efficient removal of SQX. Increasing the solution pH hampered the degradation of SQX, and no enhancement in SQX degradation was observed when chelating agents S,S′ -ethylenediamine- N,N′ -disuccinic acid (EDDS) and citrate were present. The presence of Suwannee River fulvic acid (SRFA), as a representative of aquatic natural organic matter (NOM), could inhibit the degradation of SQX. SQX was more susceptible to Fe(II)/PMS oxidation in comparison to its substructural analog 2-amino-quinoxaline (2-AQ) and other sulfonamides, i.e., sulfapyridine (SPD) and sulfadiazine (SDZ). Transformation products of SQX were enriched by solid-phase extraction (SPE) and identified by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). On the basis of the TPs identified, detailed reaction pathways for SQX degradation including sulfonamide bond cleavage, SO 2 extrusion, and aniline moiety oxidation were proposed. Our contribution may provide some useful information for better understanding the kinetics and mechanisms of SQX degradation by sulfate radical-based advanced oxidation processes (SR-AOPs).

Sulfate radical (\\[{\\text{SO}}_{4}^{ \\cdot - }\\])-based advanced oxidation processes (SR-AOPs) are promising in situ chemical oxidation technologies that received increasing interest recently. The application of SR-AOPs for decontamination may, however, generate unexpected toxic by-products. This contribution reports that \\[{\\text{SO}}_{4}^{ \\cdot - }\\] can incorporate nitrite (NO2−) nitrogen into chlorophenols, resulting in the formation of chloronitrophenols which pose greater environmental concerns. Nitrogen dioxide radical (\\[{\\text{NO}}_{2}^{ \\cdot }\\]) and phenoxy radical are important precursors responsible for the formation of chloronitrophenols. High concentrations of NO2− inhibited the transformation of chlorophenol but promoted the formation of chloronitrophenol. This study underscores a need for caution in the application of SR-AOPs in the presence of NO2−, because chloronitrophenols can be more genotoxic and mutagenic than chlorophenols.