Study On Degradation Of DDT Based On Advanced Persulfate Oxidation

DDT is an organochlorine pesticide that has been widely used in agriculture,forestry and animal husbandry.It can effectively eliminate pests,which brought huge agricultural benefits to humans and helped humans successfully prevent and treat diseases like malaria and dysentery,saving thousands of lives.However,DDT is stable,difficult to degrade spontaneously in the natural environment,and couldexist for a long time,causing pollution to the ecological environment such as soil,atmosphere,and water.At the same time,DDT is lipophilic,and will be transmitted along with the food chain,which poses a threat to the safety of animals and even humans.Therefore,in recent years,researches on the treatment and degradation of DDT pollution has gradually become a hot issue in the environmental domain.Advanced oxidation processes based on persulfate is a typical advanced oxidation method developed in recent years.It is based on sulfate radical(SO4·-)as the main active material.The sulfate radical has strong oxidizing ability,and can effectively react with various organic pollutants.Therefore,it has been widely used in the study of soil pollution and water pollution.Typycally,the catalyst that can be catalyzed to produce SO4·-is the key to research.In this article,we have also synthesized some transition metal compounds as catalysts,and applied in the persulfate advanced oxidation method to study its performance in degrading organic pollutants DDT.The main research contents are as follows:(1)The CoMn2O4 precursor and Ni(OH)2/CoMn2O4 catalyst were synthesized by hydrothermal method.The micro-morphology and crystal structure of the catalysts were characterized by SEM and XRD.The micro-morphologies of the two samples were both uniform spherical particles.The degradation of DDT by activated PMS with catalysts showed that both samples had good catalytic performance.The catalytic performance of Ni(OH)2/CoMn2O4 was the best,and the degradation rate of DDT was as high as 94.8%.Thedegradationexperiments were carried by using Ni(OH)2/CoMn2O4 as a catalyst.It was found that the higher the concentration of catalyst and PMS,the higher the removal rate of DDT.Free radical capture experiments showed that SO4·-plays a major role in the degradation of DDT.SO4·-are generated by a series of catalytic reactions with PMS and water molecules,where=Co2+ and =Mn2+ act as a Lewis active site in the sample.GC-MS was used to qualitatively analyze the degradation products of DDT.It was found that DDT can generate DDD and DDE by dechlorination and dehydrochlorination,respectively,and then DDD and DDE react with SO4·-to generate DBP,phenol,benzoic acid,etc.and may even be completely mineralized into CO2 and H2O.(2)The CuBi2O4,Ni-CuBi2O4 and Co-CuBi2O4 catalysts were synthesized by hydrothermal method.Their morphology and phases were characterized by XRD and SEM.The results showed that the CuBi2O4 and Ni-CuBi2O4 samples were tetragonal CuBi2O4.However,due to the incorporation of Ni,the diffraction peak intensity decreased.In the Co-CuBi2O4 sample,in addition to the tetragonal CuBi2O4,there are Bi7.53Coo.47O11.92 and Bi2O3 impurities.SEM characterization showed that the synthesized CuBi2O4 and Ni-CuBi2O4 were nanocolumn structures,but the CuBi2O4 nanocolumns are arranged in an orderly manner,forming an air-core circular structure with an inner diameter of 1.8 ?m.However,the Ni-CuBi2O4 nanocolumns showed a disordered distribution,and its EDS spectra showed the presence of characteristic Ni peaks.The morphologies of Co-CuBi2O4 were composed of nanocolumns,a small amount of spherical particles,and irregular bulk structures.The synthesized three samples were used as catalysts to activate PMS to catalyze the degradation of DDT.The study found that the highest DDT degradation rate in the Co-CuBi2O4/PMS system was 87.1%.Using Co-CuBi2O4 as catalystto activate PMS to degrade DDT,it was found that the removal rate and degradation rate constant of DDT increased with the increase of the amount of sample and PMS.Co-CuBi2O4 had the best catalytic activity in the weakly alkaline environment,and the degradation rate of DDT was as high as 94.2%.