The reactions between peroxymonosulfate (PMS) and quinones were investigated for the first time in this work, where benzoquinone (BQ) was selected as a model quinone. It was demonstrated that BQ could efficiently activate PMS for the degradation of sulfamethoxazole (SMX; a frequently detected antibiotic in the environments), and the degradation rate increased with solution pH from 7 to 10. Interestingly, quenching studies suggested that neither hydroxyl radical (•OH) nor sulfate radical (SO4•-) was produced therein. Instead, the generation of singlet oxygen (1O2) was proved by using two chemical probes (i.e., 2,2,6,6-tetramethyl-4-piperidinol and 9,10-diphenylanthracene) with the appearance of 1O2 indicative products detected by electron paramagnetic resonance spectrometry and liquid chromatography mass spectrometry, respectively. A catalytic mechanism was proposed involving the formation of a dioxirane intermediate between PMS and BQ and the subsequent decomposition of this intermediate into 1O2. Accordingly, a kinetic model was developed, and it well described the experimental observation that the pH-dependent decomposition rate of PMS was first-order with respect to BQ. These findings have important implications for the development of novel nonradical oxidation processes based on PMS, because 1O2 as a moderately reactive electrophile may suffer less interference from background organic matters compared with nonselective •OH and SO4•-.

a b s t r a c tComposting is commonly used for the treatment and resource utilization of sewage sludge, and natural zeolite and nitrification inhibitors can be used for nitrogen conservation during sludge composting, while their impacts on ARGs control are still unclear. Therefore, three lab-scale composting reactors, A (the control), B (natural zeolite addition) and C (nitrification inhibitor addition of 3,4-dimethylpyrazole phosphate, DMPP), were established. The impacts of natural zeolite and DMPP on the levels of ARGs were investigated, as were the roles that heavy metals, mobile genetic elements (MGEs) and the bacterial community play in ARGs evolution. The results showed that total ARGs copies were enriched 2.04 and 1.95 times in reactors A and C, respectively, but were reduced by 1.5% in reactor B due to the reduction of conjugation and co-selection of heavy metals caused by natural zeolite. Although some ARGs (bla CTX-M , bla TEM , ermB, ereA and tetW) were reduced by 0.3e2 logs, others (ermF, sulI, sulII, tetG, tetX, mefA and aac(6 0 )-Ib-cr) increased by 0.3e1.3 logs after sludge composting. Although the contributors for the ARGs profiles in different stages were quite different, the results of a partial redundancy analysis, Mantel test and Procrustes analysis showed that the bacterial community was the main contributor to the changes in ARGs compared to MGEs and heavy metals. Network analysis determined the potential host bacteria for various ARGs and further confirmed our results.

Recent studies have shown that manganese dioxide (MnO2) can significantly accelerate the oxidation kinetics of phenolic compounds such as triclosan and chlorophenols by potassium permanganate (Mn(VII)) in slightly acidic solutions. However, the role of MnO2 (i.e., as an oxidant vs catalyst) is still unclear. In this work, it was demonstrated that Mn(VII) oxidized triclosan (i.e., trichloro-2-phenoxyphenol) and its analogue 2-phenoxyphenol, mainly generating ether bond cleavage products (i.e., 2,4-dichlorophenol and phenol, respectively), while MnO2 reacted with them producing appreciable dimers as well as hydroxylated and quinone-like products. Using these two phenoxyphenols as mechanistic probes, it was interestingly found that MnO2 formed in situ or prepared ex situ greatly accelerated the kinetics but negligibly affected the pathways of their oxidation by Mn(VII) at acidic pH 5. The yields (R) of indicative products 2,4-dichlorophenol and phenol from their respective probes (i.e., molar ratios of product formed to probe lost) under various experimental conditions were quantified. Comparable R values were obtained during the treatment by Mn(VII) in the absence vs presence of MnO2. Meanwhile, it was confirmed that MnO2 could accelerate the kinetics of Mn(VII) oxidation of refractory nitrophenols (i.e., 2-nitrophenol and 4-nitrophenol), which otherwise showed negligible reactivity toward Mn(VII) and MnO2 individually, and the effect of MnO2 was strongly dependent upon its concentration as well as solution pH. These results clearly rule out the role of MnO2 as a mild co-oxidant and suggest a potential catalytic effect on Mn(VII) oxidation of phenolic compounds regardless of their susceptibility to oxidation by MnO2.

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In this work, it was found that the most widely used brominated flame retardant tetrabromobisphenol A (TBrBPA) could be transformed by free chlorine over a wide pH range from 5 to 10 with apparent second-order rate constants from 138 to 3210 M(-1)·s(-1). A total of eight products, including one quinone-like compound (i.e., 2,6-dibromoquinone), two dimers, and several simple halogenated phenols (e.g., 4-(2-hydroxyisopropyl)-2,6-dibromophenol, 2,6-dibromohydroquinone, and 2,4,6-tribromophenol), were detected by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) using a novel precursor ion scan (PIS) approach. A tentative reaction pathway was proposed: chlorine initially oxidized TBrBPA leading to the formation of a phenoxy radical, and then this primary radical and its secondary intermediates (e.g., 2,6-dibromo-4-isopropylphenol carbocation) formed via beta-scission subsequently underwent substitution, dimerization, and oxidation reactions. Humic acid (HA) considerably inhibited the degradation rates of TBrBPA by chlorine even accounting for oxidant consumption. A similar inhibitory effect of HA was also observed in permanganate and ferrate oxidation. This inhibitory effect was possibly attributed to the fact that HA competitively reacted with the phenoxy radical of TBrBPA and reversed it back to parent TBrBPA. This study confirms that chlorine can transform phenolic compounds (e.g., TBrBPA) via electron transfer rather than the well-documented electrophilic substitution, which also have implications on the formation pathway of halo-benzoquinones during chlorine disinfection. These findings can improve the understanding of chlorine chemistry in water and wastewater treatment.

Tunable chirality of helical polymers through external achiral stimuli is highly valuable for fabrication of intelligent chiral materials. Recently, we reported that through dendronization of phenylacetylene (PA) with threefold dendritic oligo­(ethylene glycols) (OEG) via alanine linkage, the corresponding polymers feature water solubility, thermoresponsiveness with cloud points (T cps) around 31.5 °C, and helical structures. In the present study, effects of various anions on the chiral structures and properties of dendronized PA homopolymer (PG1) and copolymers (PG1 m EB n ) from dendronized macromonomer (G1) and the hydrophobic comonomer 4-ethynylbenzaldehyde (EB) were examined. The T cp of PG1 largely increased in the presence of so-called salt-in anions such as PF6 – (47.0 °C) and SCN– (37.7 °C), whereas it slightly decreased with salt-out anions like SO4 2– (29.2 °C) and Cl– (30.8 °C). These results can be correlated with Hofmeister series (HS), and essentially explained in terms of the competitive interactions of the three components, i.e., OEG moiety, water molecule, and the anions. PG1 assumed a right-handed helical conformation at room temperature in the absence and presence of salt-in anions including PF6 – and underwent helix inversion above T cp according to circular dichroism (CD) spectroscopy. On the other hand, in the presence of salt-out anions like SO4 2–, the CD spectral pattern changed above T cp with a red shift, suggesting formation of a different type of helix. Phase transition processes were further clarified by IR spectroscopy. Copolymers PG1 m EB n with different OEG coverages were utilized to confirm the crowding effects of dendritic pendants. When carrying a lower coverage of OEG dendrons, chirality of the copolymer PG1 14 EB 1 became much dependent on anions. We assume that the crowded OEG moieties along the poly­(phenylacetylene) (PPA) backbone provide a molecular envelope, which plays a key role for the differential interactions between polymers and anions below and above the T cps.

Epoxy/polysufone (PSF) composites cured with 4,4'‐diaminodiphenyl sulfone (DDS) and 4,4'‐diaminodiphenyl methane (DDM) were fabricated, and the effect of dual curing reaction of diamines with epoxy on morphology, mechanical, and thermal performance was investigated. DSC results indicated that DDM was more reactive than DDS and the activation energy decreased with the rising of DDM content. Structures with small domain size at the early stage of phase separation were fixed by the fast epoxy‐DDM reaction. When the DDM content was elevated to a high level, large dual structures were changed to fine bicontinuous structures, which was favorable to improve the mechanical property. The mechanical performance of epoxy composites was enhanced and the maximum values were achieved when the DDM/DDS ratio was located at 75/25 (PSF/DDS0.25‐DDM0.75). The flexural and tensile strength relative to epoxy/DDM system were enhanced more than those relative to epoxy/DDS, while the increase in toughness was the opposite. TGA measurement showed that thermal stability of epoxy/PSF composites was improved because of the restricting effect of continuous PSF domains on thermal motion of epoxy. DMA analysis exhibited two relaxation peaks for PSF/DDS0.25‐DDM0.75, which could be attributed to the formation of phase separated morphology and epoxy network with different cross‐link density.

In this work, the epoxy systems modified with polysulfone (PSF) and cellulose nanofiber (CNF) cured at different temperatures are prepared to investigate the effect of CNF on curing reaction, morphology evolution, rheology, thermal, and mechanical performance of composites. The reaction rate is increased and the activation energy is decreased with CNF incorporation, implying an accelerating effect of CNF on the epoxy-amine reaction. The phase separation and gelation of the epoxy/PSF/CNF system start earlier compared with the binary system of epoxy/PSF. While it is displayed by rheology that both the system viscosity and relaxation time are elevated with CNF, presenting an inhibiting effect on phase evolution. Morphologies with smaller domain size are finally freezed by the epoxy gelation. The enhancement of impact performance for the epoxy/PSF/CNF composites is indicated by 40.2% increase in the impact strength, which is attributed to the finer phase-separated morphology, the uniformly distributed CNF within the polymer matrix and the good load transfer between phases. In addition, the thermal stability of composites is improved as the CNFs existed in the phase-separated polymer matrix can restrict the thermal motion of molecules during decomposition process.