Study On Degradation Of Accidental Drinking Water Pollution Of Nitrogen Heterocyclic By Strong Ionization Discharge Technology

In recent years, with the improvement of industrialization level by leaps and bounds, our country has already entered a peak period of major sudden water pollution accidents. The erruption of abrupt drinking water pollution incidents, especially organic pollutions, have led to an extremely serious consequence in people’s daily life and also disturb the stability of the society. Nitrogen heterocyclic compounds are the important chemical materials, widely used in pharmaceutical, coking, pesticides, printing and dyeing, petrochemical and other fields. These compounds have stable structure, good solubility in water, teratogenicity and carcinogenicity, which can cause serious pollution of ecological environment once entering into the water. Therefore, to develop a highly efficient, fast, green technology to treat sudden water pollution caused by nitrogen heterocyclic compounds has great significant in ecological environment protection and safety of drinking water in China.Pyridine and quinoline which are two typical nitrogen heterocyclic compound pollutions in drinking water was treated as the target by a set of integrated water treatment equipment based on strong ionization discharge technology in this paper. The effects of the various affecting factors on the removing ability of nitrogen heterocyclic compounds in drinking water were investigated. And high performance liquid chromatography（HPLC）, liquid mass combination（LC-MS）, ion chromatography（IC） and other testing methods to analyze the intermediate products and the final products. the degradation mechanism of nitrogen heterocyclic compounds and the degradation pathways were discussed.In this paper, the main research results are as follows:（1） Based on dielectric barrier strong ionization discharge, the integration experiment equipment of 1.2 t/h water treatment volumn was used for dringking water tereatment. A variety of active oxygen particles, which could effectively degrade the organic pollutants in the water, were produced in the process of discharge by using O₂ as the ionization medium. The presence and role in the reaction process of the active particles of hydroxyl radical, hydrogen peroxide and ozone were verified. Also, the relationship between the input voltage and active species were examined. With the increase of voltage, ozone concentration increased gradually. This experimental study provides a new train of thought for the emergency treatment of sudden environmental pollution.（2） The influencing factors of voltage, initial concentration, pH value, inorganic ions and inhibitors on pyridine degradation effect were investigated. Under the conditions of various factors, the degradation rules of pyridine were identified by active species. The results showed that the degradation rate of pyridine increased with the improvement of the input voltage, when the water circulation pump flow was 800 L/h and the oxygen flow was 5L/min. With the increase of initial concentration, the degradation rate of pyridine in drinking water reduced gradually; The pH value had a greater influence on the effect on the degradation of pyridine, attained the best effect in neutral conditions, and the degradation rate could reach 94.8%; The inhibitor and inorganic ions in the water of CO₃^2- or HCO₃^- could inhibit the generation of hydroxyl radicals, and the effects of NO3- and Cl- on the degradation rate is not obvious.（3） By HPLC, LC- MS, IC and other analysis methods, the degradation mechanism of pyridine and the paths are shown as the follow: pyridine and active particles would occur electrophilic substitution, dehydrogenation, addition reaction。The intermediate products produced by active species were three hydroxyl pyridine, 2,3-dihydroxy pyridine, fumaric acid, oxalic acid and other small molecule acid. In final, the pyridine had been fully degradated to the CO₂ and H2 O. And the N elements of pyridine formed the NO3- in the process of degradation, eventually. The analysis of dynamics had verified that the strong ionization discharge water treatment system to produce the active particles in the degradation reaction kinetics of pyridine fitted the first-order reaction, the correlation coefficient R2 = 0.9929, and the reaction rate of 20 mg/L pyridine solution with active species was 0.0524 min-1.（4） The effect of impact factors on the degradation effect of quinoline was investigated. Under the conditions of various factors, the degradation rules of quinoline were confirmed by active species. With the increase of the input voltage, the degradation rate of quinoline increased; under neutral conditions, the quinoline had good degradation effect. In alkaline conditions, the degradation effect of quinoline is better than that in acidic conditions;with the increase of initial concentration of quinoline, the quinoline degradation rate decreased gradually; Inorganic ions of Cland NO3- affected less in the process of active particle oxidation of quinoline, while CO₃^2- and HCO₃^- had a greater influence on the degradation of quinoline. After adding 30 mg/L tertiary butyl alcohol, the degradation of quinoline rate decreased from 87.27% to 59.67%, which illustrated that the tertiary butyl alcohol could inhibit the active particles to produce hydroxyl radicals.（5） Based on the oxidation of active material characteristics and the research of pyridine degradation mechanism, the degradation mechanism and way of quinoline were derived: the active species would take the dehydrogenation addition reaction with the quinoline on 5, 8 bit of quinoline molecular to form 5-hydroxyquinoline or 8-hydroxyquinoline. Then, the 5, 8-hydroxyquinoline could be attained. When the benzene ring was broken, the oxalic acid and 2, 3-dimethylpyridine could be generated, respectively. The 2, 3-dimethylpyridine tended to the decarboxylation reaction, which could take off a carboxyl to form picolinic acid or 3-formic acid pyridine. The hydroxyl replaced the existing carboxylic to form hydroxy pyridine, and the hydroxyl groups continued to be oxidized into acyl. When the pyridine ring was broken, the fumaric acid was generated. Finally, the quinoline was oxidized to form macromolecular acid, oxalic acid, formic acid and other small molecule acid, eventually formed the CO₂ and H2 O. When the concentration of quinoline was 20 mg/L, the quinoline oxidation by active species in degradation process conform to the first order reaction dynamics and the reaction rate constant was 0.0287 min-1. The direct oxidation process of ozone and the collaborative oxidation process of ozone and hydroxyl radical both correspond to the first order reaction dynamics.