The Application Of Atmospheric Pressure Dielectric Barrier Discharge Plasma In The Treatment Of Wastewater Discharged From Textile And Dying Mills

Among various methods of industrial wastewater treatments of refractory organics, the low-temperature plasma technology, with a stronger organics degradation and oxidation ability, had become a research hotspot in the field of wastewater treatment technology. Atmospheric pressure dielectric barrier discharge (DBD) plasma possessing advantages, such as, simple operation, rapid degradation rate, low energy consumption, completed purification, no secondary pollution, running under normal temperature and pressure, etc., had great development potential and broad industrial prosperities.The DBD plasma technology was used in the treatment of persistent organic pollutants degradation in this paper. Based on the solution containing polyvinyl alcohol (PVA) and trichromatic acidic dyes as simulated desizing wastewater and printing and dyeing wastewater respectively, we focused on the following research.The amount of reactive ions produced during the process of DBD treatment was determined. We confirmed the existence of hydroxyl radical and that its amount increased linearly with time, indicating that the plasma treatment was a relatively stable process.The optimum conditions of the degradation of polyvinyl alcohol by DBD plasma treatment had been explored. The influence of initial PVA concentration, initial pH value, discharge gap distance, reaction time on the treatment effect of polyvinyl alcohol degradation was systematic studied. Considering the mechanism of Fenton reaction, a small amount of Fe2+was added into the solution as a kind of catalyst to improve the degradation efficiency. The results are shown bellow. With the PVA initial concentration of1000mg/L, the initial pH value of6.2, the discharge gap of10mm, the degradation rate can achieve96.30%after being treated for25minutes, meanwhile COD removal efficiency can achieve24.94%after1hour, which suggested the DBD plasma technology can degrade PVA effectively. Adding Fe2+, polyvinyl alcohol degradation rate increased significantly. The possible degradation mechanism of PVA exposed to DBD plasma had been presented based on the analysis of viscosity, thermogravimetry and FT-IR spectroscopy of PVA samples before and after treatment.The DBD technique was also used for the discoloration and degradation of trichromatic acidic dyes (Acid Yellow117, Acid Red249, Acid Blue80) and their mixture in this study. The influence of reaction time, initial pH value and electrolyte concentration on the efficiency of treatment had been investigated. The decolorization efficiency of monogenetic dye solution and their mixed solution had been discussed. We also performed a kinetics research about decolorization process of these solutions. The results fully showed that the DBD plasma treatment can make the monogenetic dyes degraded effectively, while remarkable efficiency can be also acquired for the mixture solution. Azo group and aromatic conjugated group of the dye molecules were gradually oxygenated and degraded through long time treatment. Decoloration of dye solutions was more effective at acidic conditions than at basic conditions. The presence of sodium sulfate had a different impact on dye decolorization for various dyes. The decoloration process of these three trichromatic acidic dyes obeyed the first-order reaction.