The Preparation Of Copper-iron Double Metals Loaded On Magnesium Oxides And The Studu Of Trichloroethylene Catalytic Reductive Dechlorination

Trichloroethylene is the common substance of volatile chlorinated organic pollutants in groundwater,its rapid pollution for groundwater have driven people to seek a economic and effective method for treating it.Metal oxides derived from hydrotalcite-like compounds calcination have high metal dispersion,are widely used for catalyst support,and copper is the common catalyst for hydrodechlorination,this paper,Mg-Fe hydrotalcite-like and copper oxide mixture obtained by co-precipitation method were reduced through hydrogen calcination,obtained Cu-Fe/Mg oxides were used for trichloroethylene degradation.The structure and morphology of the materials were characterized by XRD,SEM,HETEM and XPS,reaction mechanism was deduced according to the dechlorination products and characterization results,at the same time,times of repeated use of dechlorination material was studied.In order to further explore the influence factors of dechlorination,the material with Cu:Mg:Fe=1:2:1 was choosed,the influence of crystallization temperature and calcination temperature on the yields of ethylene and ethane was studied.The following conclusions were obtained by experiment:(1)XRD measurement characterization indicated that,in the precursor,when the n(Mg)=0 and the n(Cu):n(Fe)=3,hydrotalcite-like structure was not observed,copper oxide was the main phase,after introduction of Mg2+,Mg-Fe hydrotalcite-like(Mg6Fe2CO3(OH)16·4H20)layered structures and copper oxide were formed for all precursors.HRTEM measurement characterization indicated that,as for Cu-Fe/Mg oxides derived from calcination reduction of precursors,copper and iron were highly dispersed on the surface of magnesia support,materials with high dechlorination activity were obtained.(2)Alkenes and alkanes were the main dechlorination products,deducing dechlorination reaction is the process of catalyzed hydrogenolysis,the H+ in water produced H2 through the effect of copper-iron battery,then produced[H]through the catalytic effect of copper,reacted with trichloroethylene through catalytic hydrogenolysis,along with physical absorption,the remove of trichloroethylene was performed.(3)Due to the formation of chloride ion during dechlorination reaction,leaded to the poison of active sits,dechlorination materials almost lose activity after four cycles of reaction.(4)When n(Cu):n(Mg):n(Fe)varied from 0.1:2.9:1 to 2:1:1,the dechlorination activity of Cu-Fe/Mg oxides roughly increased first and then decreased,when n(Cu):n(Mg):n(Fe)=1:2:1,the dechlorination activity of material is the highest,the yields of ethylene and ethane first increased from 52.0%to 67.1%,and then decreased to 35.1%;The removal rate of trichloroethylene was 94.8%,94.8%,96.9%,96.9%,95.2%and 97.5%in turn.With the increase of crystallization temperature and calcination temperature,the yields of ethylene and ethane increased first and then decreased.(5)When Cu:Mg:Fe=1:2:1,crystallization temperature of precursors was 80℃,calcination temperature of precursors was 600℃,the dechlorination activity of materials were the best,the maximum yield of ethylene and ethane was 67.1%,the removal rate of trichloroethylene was 96.9%.Due to the metal oxides derived from hydrotalcite-like compounds calcination have good alkaline and metal dispersion,they can be used as support of kinds of catalytic reaction,further will improve reactivity.