Removal Of Typical Organic Pollutants In Water By Radio Frequency Discharge Plasma Technology Underwater

As the world has industrialized and its population has grown,the problem of water pollution has intensified.Refractory biodegradable organic substances in water has a complex chemical structure and strong stability.Because they are not easily degraded by microorganisms.They accumulate and enrich in the natural environment and cause harm to the animal or human body through the food chain due to the characteristics of refractory.Among them,the dye wastewater,halogen-containing wastewater and antibiotics are several important types of pollution of water pollution.At present,the degradation methods are mainly adsorption method,photocatalytic oxidation technology and biodegradation method.However,These methods have respective shortcomings.Some of the challenges currently faced by adsorption method are:poor dispersibility of adsorbent,small adsorption capacity and even cause secondary pollution.The adsorption method is only a physical transfer which can not remove the degradation of such substances.Photocatalytic oxidation technology is less efficient and requires more energy.Biological method is time-consuming and inefficient.Gamma irradiation is high-cost and needs complex equipment for practical applications.Therefore,it is necessary to find an economic and effective method to deal with refractory organic matter in water.Radio-frequency discharge plasma technology is a kind of low-temperature plasma technology developed in recent years.It has rich electrons,ions,free radicals and excited molecules in the high reactivity reaction process which can achieve the reaction difficult to carry out in conventional conditions.In this paper,the effects of radio frequency plasma on the degradation of typical organic pollutants in water and its mechanism were studied.The effects of initial concentration,initial pH and OH scavenger on the removal of typical organic pollutants were analyzed.Meanwhile,the changes of hydrogen peroxide,intermediate product and its possible reaction mechanism were also studied.This paper mainly includes four chapters.The first part is about the research progress of low temperature plasma technology,analyzing the advantages and disadvantages of various kinds of low temperature plasma water treatment technology,discussing the advantages of radio frequency discharge plasma in water treatment.The experimental platform is introduced.The second part studies the degradation of the typical azo dyes—Weak Acid Brilliant Red B by radio frequency discharge plasma technology in water.The intermediates of the reaction process were detected by UV-Vis spectrophotometer and ion chromatography.The experimental results show that the radio frequency discharge plasma is an efficient technique for removing azo dyes,and the discharge breakdown voltage decreases with the decrease of conductivity.After 60min discharge treatment,the removal rate reached 89%.Brilliant Red B in the solution of acidic conditions,can be more easily degradable.Free radical scavengers have obvious inhibitory effect on the decolorization efficiency of Brilliant Red B,and the inhibitory effect is tertbutanol>methanol.Both the ferrous and trivalent iron salts can promote the removal of Brilliant Red B,and the effect was Fe²⁺>Fe³⁺.The main degradation products are small molecular organic acids.The·OH produced by the discharge plays a major contribution to the decoloration of Brilliant Red B.The third part studies the typical haloacetic acid—monobromoacetic acid degradationinwaterbyradiofrequencydischargeplasmatechnology.Monobromoacetic acid can be effectively degraded.Alkaline solutions and free radical scavengers can increase the removal rate of monobromoacetic acid.Due to the participation of nitrogen in the atmosphere,the pH of the solution varies during the atmosphere and argon atmosphere.The main intermediates are formic acid,acetic acid,oxalic acid,bromate,the final products are inorganics,water and bromide ions.Hydrated electrons may be the main material that is responsible for the degradation of bromoacetic acid,and hydroxyl radicals for mainly oxidized.The fourth part studies the degradation of typical antibiotics—metronidazole by radio frequency discharge plasma technology.The metronidazole concentration was detected by liquid chromatography,and the intermediate product were determined by ion chromatography.The results show that the degradation effect of metronidazole is effective.pH has no significant effect on the removal of metronidazole.The main intermediates in the reaction are formic acid,nitrite ion,oxalic acid,nitric acid and acetic acid,and the final products are inorganic and nitrogen.Hydrogen ions play a major role in the reaction,and hydroxyl radicals for mainly oxidized.