The UV/chlorine process is an emerging advanced oxidation process (AOP) used for the degradation of micropollutants. However, the radical chemistry of this AOP is largely unknown for the degradation of numerous structurally diverse micropollutants in water matrices of varying quality. These issues were addressed by grouping 34 pharmaceuticals and personal care products (PPCPs) according to the radical chemistry of their degradation in the UV/chlorine process at practical PPCP concentrations (1 μg L) and in different water matrices. The contributions of HO and reactive chlorine species (RCS), including Cl, Cl, and ClO, to the degradation of different PPCPs were compound specific. RCS showed considerable reactivity with olefins and benzene derivatives, such as phenols, anilines, and alkyl-/alkoxybenzenes. A good linear relationship was found between the RCS reactivity and negative values of the Hammett ∑σ constant for aromatic PPCPs, indicating that electron-donating groups promote the attack of benzene derivatives by RCS. The contribution of HO, but not necessarily RCS, to PPCP removal decreased with increasing pH. ClO showed high reactivity with some PPCPs, such as carbamazepine, caffeine, and gemfibrozil, with second-order rate constants of 9.2 × 10, 1.03 × 10, and 4.16 × 10 M s, respectively, which contributed to their degradation. Natural organic matter (NOM) induced significant scavenging of ClO and greatly decreased the degradation of PPCPs that was attributable to ClO, with a second-order rate constant of 4.5 × 10 (mg L) s. Alkalinity inhibited the degradation of PPCPs that was primarily attacked by HO and Cl but had negligible effects on the degradation of PPCPs by ClO. This is the first study on the reactivity of RCS, particularly ClO, with structurally diverse PPCPs under simulated drinking water condition.

Advanced oxidation processes (AOPs), such as hydroxyl radical (HO)- and sulfate radical (SO)-mediated oxidation, are alternatives for the attenuation of pharmaceuticals and personal care products (PPCPs) in wastewater effluents. However, the kinetics of these reactions needs to be investigated. In this study, kinetic models for 15 PPCPs were built to predict the degradation of PPCPs in both HO- and SO-mediated oxidation. In the UV/HO process, a simplified kinetic model involving only steady state concentrations of HO and its biomolecular reaction rate constants is suitable for predicting the removal of PPCPs, indicating the dominant role of HO in the removal of PPCPs. In the UV/KSO process, the calculated steady state concentrations of CO and bromine radicals (Br, Br and BrCl) were 600-fold and 1-2 orders of magnitude higher than the concentrations of SO, respectively. The kinetic model, involving both SO and CO as reactive species, was more accurate for predicting the removal of the 9 PPCPs, except for salbutamol and nitroimidazoles. The steric and ionic effects of organic matter toward SO could lead to overestimations of the removal efficiencies of the SO-mediated oxidation of nitroimidazoles in wastewater effluents.

No abstract

No abstract

Formation of the semiconductor/dielectric double-layered films via vertical phase separations from polymer blends is an effective method to fabricate organic thin-film transistors (OTFTs). Here, we introduce a simple one-step processing method for the vertical phase separation of poly­(3-hexylthiophene-2,5-diyl) (P3HT) and poly­(methyl methacrylate) (PMMA) blends in OTFTs and their applications for high-performance nitrogen dioxide (NO2) sensors. Compared to the conventional two-step coated OTFT sensors, one-step processed devices exhibit a great enhancement of the responsivity from 116 to 1481% for 30 ppm NO2 concentration and a limit of detection of ∼0.7 ppb. Studies of the microstructures of the blend films and the electrical properties of the sensors reveal that the devices formed by the one-step vertical phase separation have better capability for the adsorption of NO2 molecules. Moreover, a careful adjustment of the blend ratio between P3HT and PMMA can further improve the performance of the NO2 sensors, ranging from sensitivity to selectivity and to the ability of recovery. This simple one-step processing method demonstrates a potential possibility for developing high-performance, low-cost, and large-area OTFT gas sensors.

Halides and natural organic matter (NOM) are inevitable in aquatic environment and influence the degradation of contaminants in sulfate radical (SO)-based advanced oxidation processes. This study investigated the formation of chlorate in the coexposure of SO, chloride (Cl), bromide (Br) and/or NOM in UV/persulfate (UV/PDS) and cobalt(II)/peroxymonosulfate (Co/PMS) systems. The formation of chlorate increased with increasing Cl concentration in the UV/PDS system, however, in the Co/PMS system, it initially increased and then decreased. The chlorate formation involved the formation of hypochlorous acid/hypochlorite (HOCl/OCl) as an intermediate in both systems. The formation was primarily attributable to SO in the UV/PDS system, whereas Co(III) played a significant role in the oxidation of Cl to HOCl/OCl and SO was important for the oxidation of HOCl/OCl to chlorate in the Co/PMS system. The pseudo-first-order rate constants ( k') of the transformation from Cl to HOCl/OCl were 3.32 × 10 s and 9.23 × 10 s in UV/PDS and Co/PMS, respectively. Meanwhile, k' of HOCl/OCl to chlorate in UV/PDS and Co/PMS were 2.43 × 10 s and 2.70 × 10 s, respectively. Br completely inhibited the chlorate formation in UV/PDS, but inhibited it by 45.2% in Co/PMS. The k' of SO reacting with Br to form hypobromous acid/hypobromite (HOBr/OBr) was calculated to be 378 times higher than that of Cl to HOCl/OCl, but the k' of Co(III) reacting with Br to form HOBr/OBr was comparable to that of Cl to HOCl/OCl. NOM also significantly inhibited the chlorate formation, due to the consumption of SO and reactive chlorine species (RCS, such as Cl·, ClO· and HOCl/OCl). This study demonstrated the formation of chlorate in SO-based AOPs, which should to be considered in their application in water treatment.

No abstract

No abstract