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Highlights: MPUV/chlorine increased the chlorine demand and DBPFP of benzoic acid and nitrobenzene. MPUV/chlorine showed no further activation on active DBP precursors. MPUV/chlorine at pH 6 showed greater impact on precursors' DBPFP than at pH 8. MPUV/chlorine increased the BSF of THMs in the presence of bromine. Linear correlation was observed between changes in precursors' chlorine demand and DBPFP. UV/chlorine advanced oxidation process (AOP), as a potential alternative to UV/H2O2 in water treatment, may pose a potential risk of increased disinfection by-product (DBP) formation and is of great concern. In this paper, seven benzene derivatives, containing two chlorine-inert and five chlorine-active compounds, were selected as typical model DBP precursors, and the effects of medium pressure UV/chlorine (MPUV/chlorine) on their chlorine demand and DBP formation potential (DBPFP) were evaluated. The results showed that MPUV/chlorine could significantly increase the chlorine demand and DBPFP of the two inert precursors. For the four slow but active DBP precursors, MPUV/chlorine may accelerate their short-term DBP formation, whereas it showed an insignificant effect or even reduced their chlorine demand and DBPFP. For the only fast and active DBP precursor, MPUV/chlorine showed an insignificant effect on its short-term DBP formation or DBPFP. The overall effect of MPUV/chlorine was more significant at pH 6 than at pH 8. In the presence of Br−, MPUV/chlorine significantly increased the bromine substitution factors of THMs. In addition, linear fitting results indicated that the UV/chlorine-induced change in overall chlorine demand may be considered as a potential indicator for the prediction of DBPFP alteration. [ABSTRACT FROM AUTHOR]

In this work, the degradation performance of Fe2+/PAA/H2O2 on three typical pollutants (reactive black 5, ANL, and PVA) in textile wastewater was investigated in comparison with Fe2+/H2O2. Therein, Fe2+/PAA/H2O2 had a high removal on RB5 (99%) mainly owing to the contribution of peroxyl radicals and/or Fe(IV). Fe2+/H2O2 showed a relatively high removal on PVA (28%) mainly resulting from ·OH. Fe2+/PAA/H2O2 and Fe2+/H2O2 showed comparative removals on ANL. Additionally, Fe2+/PAA/H2O2 was more sensitive to pH than Fe2+/H2O2. The coexisting anions (20–2000 mg/L) showed inhibition on their removals and followed an order of HCO3− > SO42− > Cl−. Humic acid (5 and 10 mg C/L) posed notable inhibition on their removals following an order of reactive black 5 (RB5) > ANL > PVA. In practical wastewater effluent, PVA removal was dramatically inhibited by 88%. Bioluminescent bacteria test results suggested that the toxicity of Fe2+/PAA/H2O2 treated systems was lower than that of Fe2+/H2O2. RB5 degradation had three possible pathways with the proposed mechanisms of hydroxylation, dehydrogenation, and demethylation. The results may favor the performance evaluation of Fe2+/PAA/H2O2 in the advanced treatment of textile wastewater. [ABSTRACT FROM AUTHOR]

UV/persulfate (UV/PS) has been as an efficient method to remove many organic contaminants in water. However, little is known about the impact of UV/PS pretrement on the formation of disinfection byproducts (DBPs) during chlorination of 2,4-Di-tert-butylphenol (2,4-D). This research evaluated that UV/PS preoxidation of 2,4-D greatly decreased the DBPs generation during following chlorination. In the 2,4-D solution without any treatment system (O system), trichloromethane (TCM) as the only detected DBP increased with the increase of chlorine dosage. While the formation of TCM declined with the increase of PS dosage in the PS and UV/PS preoxidation systems and decreased the estimated toxicity accordingly. And it was found the residual PS in system could combine free chlorine to further oxidize 2,4-D. And intermediate products were analysed by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. In the presence of bromine, the bromodichloromethane augmented first and then slowly decreased while dibromochloromethane and tribromethane increased both in O and UV/PS systems with the increase of [Br − ]. Bromine substitution was decreased by preoxidation of UV/PS. UV/PS could decrease the total-DBPs formation when used in the real water matrix contained 100 μg/L 2,4-D. [ABSTRACT FROM AUTHOR]

The adsorption of bentazon on two types of granular activated carbons (GACs), VRU F36X16 (VRU) and WS-480 (WS) from aqueous solution was evaluated by kinetics, isotherms, and thermodynamic models in this study. The impacts of initial bentazon concentration, temperature, and initial solution pH were also investigated. The equilibrium adsorption capacity (qe) of each GAC was appreciable under the experimental condition, especially VRU. For either GAC, the adsorption process fitted pseudo-second-order equation best and statistics matched two-step intra-particle diffusion model well. Dubinin–Radushkevich model was the most suitable one for bentazon adsorption on VRU, while Redlich and Peterson model best described bentazon adsorption on WS. Both for VRU and WS, the adsorption process was exothermic and belonged to physisorption. Theqeof VRU and WS increased as initial bentazon concentration increased, though the removal rate of bentazon decreased. 25°C was the optimal condition for bentazon adsorption on either GAC, while theqeof both GACs dropped as the temperature increased. Although the increase in pH could hinder bentazon adsorption on GACs significantly, there was a slight change in the adsorption capacities of VRU and WS when initial solution pH was in the range 5–9. [ABSTRACT FROM AUTHOR]

In this study, the degradation performance of 2,4-Di-tert-butylphenol (2,4-D) by the ultraviolet/persulfate (UV/PS) process was evaluated for the first time. To better understand the possible degradation mechanism in the UV/PS advance oxidation process system, a kinetic model involved hydroxyl and sulfate radicals was developed for predicting pseudo-first order rate constants (k o ) and radical contributions. The results showed that the degradation of 2,4-D was promoted by increasing dosages of PS. H 2 PO 4 - almost had no significant impact on the degradation of 2,4-D, whereas the removal of 2,4-D was suppressed when NO 3 - dosage was added up to 50 mM. HCO 3 - , HPO 4 2 - and natural organic matter significantly inhibited the degradation of 2,4-D. The reaction rate constants between SO 4 - and 2,4-D were not affected by pH. However, the degradation was suppressed with the increasing pH due to the increasing HPO 4 2 - from the phosphate buffer in alkaline. The degradation of 2,4-D was promoted by adding Cl − . The proposed degradation pathways were elucidated on the basis of results obtained by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. [ABSTRACT FROM AUTHOR]

UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS) processes as alternative methods for removal of imidacloprid (IMP) were conducted for the first time. The reaction rate constants between IMP and the sulfate or hydroxyl radical were calculated as 2.33 × 10 9 or 2.42 × 10 10 M − 1 s − 1 , respectively. The degradation of IMP was greatly improved by UV/PS and UV/PMS compared with only UV or oxidant. At any given dosage, UV/PS achieved higher IMP removal rate than UV/PMS. The pH range affecting the degradation in the UV/PS and UV/PMS systems were different in the ranges of 6–8 and 9 to 10. SO 4 2 − , F− and NO 3 − had no obvious effect on the degradation in the UV/PS and UV/PMS systems. CO 3 2 − and PO 4 3 − inhibited the degradation of IMP in the UV/PS system, while they enhanced the degradation in the UV/PMS system. Algae organic matters (AOM) were used to consider the impact of the degradation of IMP for the first time. The removal of IMP were restrained by both AOM and natural organic matters. The higher removal rate of IMP demonstrated that both UV/PS and UV/PMS were suitable for treating the water containing IMP, while UV/PS was cost-effective than UV/PMS based on the total cost calculation. Finally, the degradation pathways of IMP were proposed. Image 1 • Imidacloprid (IMP) was degraded by UV/PS and UV/PMS for the first time. • Reaction rate between IMP and Image 3 was calculated as 2.33 × 10 9 M − 1 s − 1 . • Reaction rates between IMP and Image 2 was calculated as 2.42 × 10 10 M − 1 s − 1 . • AOM restrained removal of IMP in the oxidation systems studied for the first time. • UV/PS was more cost-effective than UV/PMS based on the total cost calculation. [ABSTRACT FROM AUTHOR]

In this paper, a compact repetitive nanosecond pulsed power generator based on transmission line transformer (TLT) is developed for non-thermal plasma generation. The high voltage capacitor, the spark gap switch and the input side of the TLT are built into a compact structure to obtain a fast high-power pulse. The properly designed magnetic cores placed around the coaxial cables of the TLT have been chosen to obtain a higher voltage gain. The layout of TLT is optimized to make the generator more compact. Experiment test shows that voltage pulses of 30 kV with rise time of about 25 ns, pulse duration of about 100 ns, pulse repetition rate of 500 pps have been achieved. [ABSTRACT FROM AUTHOR]

The priority pollutant antimony (Sb) exists primarily as Sb(V) and Sb(III) in natural waters, and Sb(III) is generally with greater mobility and toxicity than Sb(V). The bio-reduction of Sb(V) would not become a meaningful Sb-removal process unless the accumulation of produced dissolved Sb(III) could be controlled. Here, we examined the dissimilatory antimonate bio-reduction with or without the coexistence of sulfate using Sb-acclimated biomass. Results demonstrated that 0.8 mM Sb(V) was almost completely bio-reduced within 20 h along with 48.6% Sb(III) recovery. Kinetic parameters q max and K s calculated were 0.54 mg-Sb mg-DW −1 h −1 and 41.96 mg L −1 , respectively. When the concentrations of coexisting sulfate were 0.8 mM, 1.6 mM, and 4 mM, the reduction of 0.8 mM Sb(V) was accomplished within 17, 9, and 5 h, respectively, along with no final Sb(III) recovery. Also, the bio-reduction of sulfate occurred synchronously. The precipitated Sb 2 O 3 and Sb 2 S 3 were characterized by scanning electron microscopy coupled with energy dispersive spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with bacterial compositions of the seed sludge obtained from anaerobic digestion tank in a wastewater treatment plant, new genera of Pseudomonas and Geobacter emerged with large proportions in both Sb-fed and Sb-sulfate-fed sludge, and a small portion of sulfate reduction bacteria emerged only in Sb-sulfate-fed culture. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of MIEX resin as an efficient adsorbent for the removal of clofibric acid (CA) and diclofenac (DCF). The adsorption performance of CA and DCF are investigated by a batch mode in single-component or bi-component adsorption system. Various factors influencing the adsorption of CA and DCF, including initial concentration, contact time, adsorbent dosage, initial solution pH, agitation speed, natural organic matter and coexistent anions are studied. The Langmuir model can well describe CA adsorption in single-component system, while the Freundlich model gives better fitting in bi-component system. The DCF adsorption can be well fitted by the Freundlich model in both systems. Thermodynamic analyses show that the adsorption of CA and DCF is an endothermic (ΔH o > 0), entropy driven (ΔS o > 0) process and more randomness exists in the DCF adsorption process. The values of Gibbs free energy (ΔG o < 0) indicate the adsorption of DCF is spontaneous but nonspontaneous (ΔG o > 0) for CA adsorption. The kinetic data suggest the adsorption of CA and DCF follow the pseudo-first-order model in both systems and the intra-particle is not the unique rate-limiting step. The adsorption process is controlled simultaneously by external mass transfer and surface diffusion according to the surface diffusion modified Biot number (Bi s ) ranging from 1.06 to 26.15. Moreover, the possible removal mechanism for CA and DCF is respectively proposed based on the ion exchange stoichiometry. [ABSTRACT FROM AUTHOR]