Degradation mechanism and decomposition of sulfamethoxazole aqueous solution with persulfate activated by dielectric barrier discharge.

The present study focused on the degradation of sulfamethoxazole (SMX) aqueous solution and the toxicity of processing aqueous by the dielectric barrier discharge (DBD) activated persulfate (PS). The effects of input voltage, input frequency, duty cycle, and PS dosage ratio on the SMX degradation efficiency were measured. Based on the results of the Response Surface Methodology (RSM), SMX degradation efficiency reached 83.21% which is 10.54% higher than that without PS, and the kinetic constant was 0.067 min-1 in 30 min when the input voltage at 204 V (input power at 110.6 W), the input frequency at 186 Hz, the duty cycle at 63%, and the PS dosage ratio at 5.1:1. The addition of PS can produce more active particles reached 1.756 mg/L (O3), 0.118 mg/L (H2O2), 0.154 mmol/L (·OH) in 30 min. Furthermore, the DBD plasma system effectively activated an optimal amount of PS, leading to improved removal efficiency of COD, and TOC to 30.21% and 47.21%, respectively. Subsequently, eight primary by-products were pinpointed, alongside the observation of three distinct pathways of transformation. Predictions from the ECOSAR software indicated that most of the degradation intermediates were less toxic than SMX. The biological toxicity experiments elucidated that the treatment with the DBD/PS system effectively reduced the mortality of zebrafish larvae caused by SMX from 100% to 20.13% and improved the hatching rate from 55.69% to 80.86%. In particular, it is important to note that the degradation intermediates exhibit teratogenic effects on zebrafish larvae.

Efficient degradation and mineralization of aniline in aqueous solution by new dielectric barrier discharge non-thermal plasma.

Aniline is a priority pollutant that is unfavorable to the environment and human health due to its carcinogenic and mutagenic nature. The performance of the dielectric barrier discharge reactor was examined based on the aniline degradation efficiency. Different parameters were studied and optimized to treat various wastewater conditions. Role of active species for aniline degradation was investigated by the addition of inhibitors and promoters. The optimum conditions were 20 mg/L initial concentration, 1.8 kV applied voltage, 4 L/min gas flow rate and a pH of 8.82. It was observed that 87% of aniline was degraded in 60 min of dielectric barrier discharge treatment at optimum conditions. UV-Vis spectra showed gradual increase in the treatment efficiency of aniline with the propagation of treatment time. Mineralization of AN was confirmed by TOC measurement and a decrease in pH during the process. To elicit the aniline degradation route, HPLC and LC-MS techniques were used to detect the intermediates and byproducts. It was identified that aniline degraded into different organic byproducts and was dissociated into carbon dioxide and water. Comparison of the current system with existing advanced oxidation processes showed that DBD has a remarkable potential for the elimination of organic pollutants.

Degradation of the nonylphenol aqueous solution by strong ionization discharge: evaluation of degradation mechanism and the water toxicity of zebrafish.

Nonylphenol (NP) is a typical environmental endogenous disrupter with low concentration and high toxicity. This paper describes the mechanism of NP degradation in solution by strong ionization dielectric barrier discharge (SIDBD). Furthermore, the degradation performance of NP by SIDBD was tested by changing the equipment voltage, the initial concentration of NP in aqueous solution, pH, and inorganic ions. Degradation pathways of NP were detected using a high-performance liquid chromatography-mass spectrometer. The biological effects of NP degradation were assessed by detecting indicators of embryonic development in zebrafish (survival rate, fetal movement, heartbeat, the body length, behavior, deformity) and adult fish (sex differentiation, weight, ovarian testes pathological section analysis). The results showed when the input O2 was 5 L/min and the voltage was 3.2 kV, the degradation efficiency of NP can reach 99.0% after 60 min of experiment. Equipment voltage, initial concentration of NP in solution, pH, inorganic ions and other factors can influence the degradation efficiency of NP by DBD. At the higher concentration of NP, the greater influence on embryonic development in zebrafish was noticed. Although the effects of NP on zebrafish sex differentiation were not obvious, it showed significant male weight inhibition and decrease in sperm number.

Butyl Benzyl Phthalate in Urban Sewage by Magnetic-Based Immunoassay: Environmental Levels and Risk Assessment.

A magnetic-based immunoassay (MBI) combined with biotin-streptavidin amplification was proposed for butyl benzyl phthalate (BBP) investigation and risk assessment. The values of LOD (limit of detection, IC10) and IC50 were 0.57 ng/mL and 119.61 ng/mL, with a detection range of 0.57-24,977.71 ng/mL for MBI. The specificity, accuracy and precision are well demonstrated. A total of 36 environmental water samples of urban sewage from Zhenjiang, China, were collected and assessed for BBP contamination. The results show that BBP-positive levels ranged from 2.47 to 89.21 ng/mL, with a positive rate of 77.8%. The health effects of BBP in the urban sewage were within a controllable range, and the ambient severity for health (ASI) was below 1.49. The highest value of AS for ecology (ASII) was 7.43, which indicates a potential harm to ecology. The entropy value of risk quotient was below 100, the highest being 59.47, which poses a low risk to the environment and ecology, indicating that there is a need to strengthen BBP controls. The non-carcinogenic risk of BBP exposure from drinking water was higher for females than that for males, and the non-carcinogenic risk from drinking-water and bathing pathways was negligible. This study could provide an alternative method for detecting BBP and essential information for controlling BBP contamination.

Dielectric barrier discharge plasma coupled with WO3 for bisphenol A degradation.

Based on the difficulty of the refractory organic compounds degradation in water by the traditional wastewater treatment methods, the research relies on the technology of the dielectric barrier discharge plasma (DBDP) and the catalysis of the nano WO3, investigating the bisphenol A (BPA) degradation in the synergistic system of DBDP/WO3. The coupled degradation percentage of the BPA under different amounts of WO3 addition, different initial solution pH and carrier gas were investigated to confirm the catalysis of the WO3 in the DBDP system. It was obtained from the experimental results that the optimal additive amount of the WO3 was 175 mg L-1 and change of the solution pH value and the carrier gas variety could not change the catalysis of the WO3. The BPA degradation percentage could reach 100% after treating 30 min in the DBDP/WO3 system with 0.5 L min-1 O2 as the carrier gas. The WO3 still had a better catalysis after four times usage and the discharge had little effect on the microstructure of the WO3. The existence of the WO3 in the DBDP system could result in the reduction of the O3 concentration and the enhancement of the H2O2 concentration, which improve the catalysis of the WO3 in the DBDP system, while the experiments on the scavengers' addition verified the major role of the OH on the BPA degradation. The catalytic mechanism of the WO3 as well as the BPA degradation pathway was also speculated in the research.

Experimental study of nitrobenzene degradation in water by strong ionization dielectric barrier discharge.

Nitrobenzene (NB) is toxic and carcinogenic aromatic compound widely used in several industries which is ultimately found in their effluents. In this work, dielectric barrier discharge (DBD) reactor was employed for the degradation of nitrobenzene in aqueous solution. Active species like O3 and •OH produced by DBD reactor were mixed with water which degraded the NB. The results indicated that the lower NB concentrations slightly acidic conditions and high voltage ranges showed the optimum efficiencies. Moreover, the impacts of active species inhibitors isopropyl alcohol (IPA), tert-butanol (TBA), inorganic ions for instance sulfates ( S O 4 2 - ), bicarbonates ( H C O 3 - ), nitrates ( N O 3 - ), carbonates ( C O 3 2 - ) and chlorides (Cl-) on the degradation of NB were examined. This analysis showed that the hydroxyl radical was captured by the addition of these inhibitors and resulted in the decrease in efficiencies. Byproducts produced during the degradation of nitrobenzene were assessed by analytical techniques of high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), UV-visible spectroscopy and total organic carbon (TOC) analysis. Main intermediate products were nitrophenols and low molecular weight organic acids including oxalic acid and acetic acid that were eventually mineralized to CO2 and H2O. The dielectric barrier discharge technology was found productive for the degradation of nitroaromatic compounds.

Catalysis of rGO-WO3 nanocomposite for aqueous bisphenol A degradation in dielectric barrier discharge plasma oxidation process.

Due to the multi-catalysis of the WO3 and excellent properties of the graphene (GO), a series of rGO-WO3 nanocomposites were prepared through the hydrothermal synthesis procedure by changing the material ratio, the reaction temperature and the reaction time in this paper, and then added it into a dielectric barrier discharge plasma (DBDP) system for investigating the bisphenol A (BPA)'s degradation and corresponding catalytic mechanism of the rGO-WO3 in the DBDP system. The obtained results show that there was an optimum dosage of the rGO-WO3 (40 mg/L) as well as the preparation conditions (5:1000 mass ratio of the GO and the WO3, 18 h reaction time and 120 °C reaction temperature) for achieving the highest catalytic effect, and the highest degradation rate constant of the BPA was 0.03129 min-1. The determined higher TOC removal, higher COD removal as well as UV-Vis analysis also demonstrated the catalysis of the rGO-WO3. The measurement of the change of the O3 and the H2O2 concentrations in the reaction system with or without the rGO-WO3 and with or without the BPA proved the catalysis of the rGO-WO3 on the ·OH formation, while the combination of the GO had the positive effect for enhancing the catalytic effect. A figure on the catalysis and degradation procedure of the BPA in the DBDP/rGO-WO3 system was provided in the paper.

Synthesis of Fe3O4/C with Cauliflower-Like BiVO4 for Improved Separation Efficiency of Charge Carriers and Photocatalytic Activity.

Fe3O4/C/BiVO4 composite photocatalyst was fabricated successfully by a simple approach using yeast as a carbon source. Fe3O4/C/BiVO4 sample exhibited higher efficiency for photocatalytic degradation of tetracycline (TC) as compared to pure BiVO4 under visible light. In addition, after five recycles of photodegradation of TC, Fe3O4/C/BiVO4 showed a slight loss in photocatalytic activity, which confirmed its stability and long-time reusability. The photocatalytic mechanism was studied by active species trapping experiments, which revealed that the holes (h+) and superoxide radical (˙O-2) played a key role in TC degradation. Moreover, photocatalyst could be easily recycled by an external magnetic field and reused without any loss in photocatalytic activity. This work provides a simple, eco-friendly and exemplary strategy for improving photodegradation activity of BiVO4-based photocatalyst.

Research on the degradation mechanism of pyridine in drinking water by dielectric barrier discharge.

Pyridine, an important chemical raw material, is widely used in industry, for example in textiles, leather, printing, dyeing, etc. In this research, a dielectric barrier discharge (DBD) system was developed to remove pyridine, as a representative type of nitrogen heterocyclic compound in drinking water. First, the influence of the active species inhibitors tertiary butanol alcohol (TBA), HCO3-, and CO32- on the degradation rate of pyridine was investigated to verify the existence of active species produced by the strong ionization discharge in the system. The intermediate and final products generated in the degradation process of pyridine were confirmed and analyzed through a series of analytical techniques, including liquid chromatography-mass spectrometry (LC-MS), high performance liquid chromatography (HPLC), ion chromatography (IC), total organic carbon (TOC) analysis, ultraviolet (UV) spectroscopy, etc. The results showed that the degradation of pyridine was mainly due to the strong oxidizing power of ozone and hydroxyl radical produced by the DBD system. Several intermediate products including 3-hydroxyl pyridine, fumaric acid, 2, 3-dihydroxypyridine, and oxalic acid were detected. Nitrogen was removed from the pyridine molecule to form nitrate. Through analysis of the degradation mechanism of pyridine, the oxidation pathway was deduced. The study provided a theoretical and experimental basis for the application of DBD strong ionization discharge in treatment of nitrogen heterocyclic compounds in drinking water.

Kinetic analysis of acid orange 7 degradation by pulsed discharge plasma combined with activated carbon and the synergistic mechanism exploration.

The synergistic technique of pulsed discharge plasma (PDP) and activated carbon (AC) was built to investigate the kinetics of acid orange 7 (AO7) degradation under different conditions of AC addition, electrode gap, initial pH value of solution, gas variety and gas flow rate. Emission spectra of OH and O, UV-vis absorption spectra of the AO7 solution and TOC removal were measured to illustrate the synergistic mechanism of the PDP and the AC. The obtained results indicated that the kinetic constant of AO7 degradation increased from 0.00947 min(-1) to 0.01419 min(-1) when 4 g AC was added into the PDP system; AO7 degradation was higher in the case of alkaline solution when oxygen was used as the flow gas in the PDP/AC system, 2 L/min oxygen flow was more favorable for the degradation. Results of the relative emission intensities of OH and O indicated the catalytic effect of the AC on the active species formation as well as the important role of the two radicals for the AO7 degradation. There was no new peaks appeared by the UV-vis analysis of the AO7 solution after 60 min treatment. The highest TOC removal in the PDP/AC system was 30.3%, which was achieved under the condition of 4 L/min air flow rate and 3 initial pH value.

Study on Emission Spectrum of OH Radicals in a Combination System of Pulsed Discharge Plasma and Activated Carbon.

Based on the higher oxidation potential of OH radicals (2.8 V), the synergetic effect of pulsed discharge plasma (PDP) and activated carbon (AC) and the advantages of emission spectroscopic detection, such as easy operation, high accuracy and high sensitivity, the relative emission spectra of the OH radicals generated in the PDP/AC system with oxygen flow were measured by the emission spectroscopic detection technique and the spectral intensity of the OH radicals was used to represent the relative amount of the OH radicals formed in the reaction system. The effect of additive amount of the AC, peak pulse voltage and electrode gap on the relative emission spectrum intensities of OH radicals were investigated to illustrate the crucial factors for the OH radicals formation in the PDP/AC system. In addition, the formation of OH radicals in the two liquid phases of distilled water and acid orange 7 (AO7) solution in the sole PDP system and the PDP/AC system were investigated to testify the synergetic mechanism of PDP/AC and the oxidization of OH radicals on the organic compounds in the reaction system. The obtained results showed that the catalytic effect of the AC increased with the increase of the additive amount of the AC in the PDP system, which led to the increase of the relative emission spectral intensities of the formed OH radicals in the synergistic system; higher peak pulse voltage was in favor of the energy input in the discharge system and then enhanced the formation of OH radicals; increase of the electrode gap led to the decrease of energy efficiency in the reaction system and the decrease of the formed OH radicals in the PDP/AC system; the formation of OH radicals in the PDP/AC system was higher than that in the sole PDP system both in the distilled water and in the AO7 solution; the formation of OH radicals in the distilled water was higher than those in the AO7 solution no matter the reaction system was the sole PDP system or the PDP/AC system. The two results indicated that the AC addition was beneficial to the formation of OH radicals in the PDP system and the OH radicals had an important effect on the organic compounds degradation both in the sole PDP system and in the PDP/AC system.

Adsorption of lead(II) by silica/cell composites from aqueous solution: kinetic, equilibrium, and thermodynamics studies.

Silica/cell composites were prepared for the adsorption of lead ions, Pb(II), from aqueous solution in a batch system. The silica/cell composites possessed micropores, high surface area, and abundant functional groups. Adsorption performance was investigated by analyzing the effects of such factors as the initial pH, contact time with different initial concentration, and initial Pb(II) concentration at different temperature. The kinetic data were fitted to pseudo-second-order and intraparticle diffusion kinetic models. The results were better fitted by the pseudo-second-order kinetic model. Intraparticle diffusion increased with an increase of initial concentration and the sorption process was controlled by film diffusion. The Langmuir isotherm model was fitted to the experimental data significantly better than Freundlich and Dubinin-Radushkevich isotherm models. The maximum adsorption capacity was 97.10 mg g(-1), according to the Langmuir isotherm model. Thermodynamics parameters confirmed the spontaneous, endothermic, and entropy-gained nature within the studied temperature range (from 298 to 318 K). The composites could be effectively desorbed by the 2.0 mol L(-1) HNO3 solution and would be a potential adsorbent.

A Study on the Treatment of CO2, SO2, Nox, and Fly Ash by Pulse Activation.

This paper presents a technique for the complete, simultaneous decomposition of CO2, SO2, and NOx, as well as the simultaneous removal of fly ash by ultra-high voltage pulse activation. Ultra-high voltage narrow pulse is used to make the gases in the reactor become active molecules, which are then dissociated into nonpoisonous gas molecules and solid particles under the control of a directional reaction model. By using a sufficient charge and a strong electric field, the fly ash can be removed. It becomes the carrier of C and S, and its efficiency is 99.5%. Owing to the action of catalyst B (using Ni as the mother's body), the activation energy of CO2, SO2, and NOx gases is reduced in great magnitude, and their removal efficiency can reach 75~90% at normal pressure and 180 °C.