The Control Behavior Of Dielectric Barrier Discharge On Typical Emerging Contaminants In The Environment

With the continuous development of chemical industry and the improvement of human requirements on environmental quality standards,various types of emerging contaminants have entered people’s field of vision.Due to the lack of sound laws and corresponding methods to monitor and treatment,environmental problems caused by new pollutants have received extensive attention.Micro-plastics,one of the typical emerging contaminants,have been picked up in recent years in water such as estuaries,lakes,oceans,and natural environments such as soil sediments.Micro-plastics refer to plastic particles with a diameter of less than 5 mm,which have become a research hotpot of emerging contaminants due to their wide distribution,strong durability and adsorption of toxic pollutants.In addition to micro-plastic pollution,tetrabromobisphenol a（TBBPA）,as a commonly used brominated flame retardant in industry,is also one of the common emerging contaminants in the environment.TBBPA has high persistence in the environment and continuously accumulates toxicity.After entering the organism,it will interfere with the normal metabolism of the organism and has certain carcinogenic effect.However,most of the studies on micro-plastics focus on the investigation of micro-plastics pollution,sampling separation technology and physiological toxicity.At the same time,the traditional treatment method of tetrabromobisphenol a has the disadvantages of low efficiency and large energy consumption,so it is necessary to explore a method for the efficient treatment of typical emerging contaminants.Dielectric barrier discharge plasma technology（DBD）,as a kind of advanced oxidation technology,can effectively decompose most pollutants by using a large number of active free radicals and ultraviolet rays generated by discharge,with the advantages of low energy consumption,high efficiency and less pollution.Based on this,a dielectric barrier discharge（DBD）technique was proposed to treat new-type micro-plastics and tetrabromobisphenol a and explore the control effect of this treatment method on typical new-type pollutants.The main conclusions are as follows:（1）A dielectric barrier discharge system was established to treat PVC micro-plastic particles.After DBD treatment,the particle size of PVC micro-plastics significantly decreased,accompanied by the increase of specific surface area,and at the same time,the micro-plastics surface was obviously broken,forming a porous structure.The thermodynamic properties were obviously changed,the thermal stability of micro-plastics after aging was improved,and the glass transition temperature was decreased.A large number of oxidizing active substances generated by DBD can effectively improve the aging degree of PVC micro-plastics,increase the carbonyl index（CI）,increase the number of oxygen-containing functional groups on the surface,change the chemical structure of PVC micro-plastics,make them break the chain of oxidation,and reduce the proportion of Cl elements.In the adsorption experiment,the adsorption TBBPA of PVC micro-plastics conforms to the quasi-first-order adsorption kinetic curve,the isotherm adsorption model belongs to the linear model,and the adsorption capacity of surface treated microplastics for TBBPA is significantly enhanced.（2）Dielectric barrier discharge technology can effectively degrade TBBPA in water environment.To a certain extent,with the increase of discharge voltage and the decrease of initial pollutant concentration,the removal efficiency of TBBPA is significantly improved.The pH of the solution had little effect on the degradation efficiency,and the TOC concentration of the solution decreased obviously after treatment.The active substances that play a major role in the degradation of TBBPA by DBD are·OH and·O₂^-,and ¹O₂ also assists in the degradation,but the effect is relatively small.The decomposition mechanism of the TBBPA product treated with dielectric barrier discharge（DBD）was preliminarily analyzed,and the results showed that DBD treated with tetrabromobisphenol a could degrade the product in two stages,namely cleavage reaction and bromination reaction,which were basically consistent with other degradation mechanisms,proving the feasibility of dielectric barrier discharge（DBD）for TBBPA.When DBD was used to treat the compound contamination system of micro-plastics and tetrabromobisphenol a,the removal efficiency of TBBPA increased with the increase of micro-plastics dosage,which indicated that DBD system could act on the compound contamination system more effectively than treating pollutants alone.