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.

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.

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.

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.