Preparation Of Mesoporous Silica Supported Nanoscale Pd/Fe By Double Solvent Method And Study On Degradation Of Trichloroethylene

Reductive dechlorination of chlorinated organic compounds by nanoscale palladium/iron bimetallic compounds can take place at environmental conditions.Chlorinated organics are degraded into non-toxic products or dechlorination,and transformed into organic compounds that are easily utilized by microorganisms in the environment.However,because of the nanoscalemeter effect and the galvanic effect of bimetallic in water,the utilization ratio of Pd/Fe in dechlorination of chlorinated organic compounds was reduced.Therefore,the nanoscale Pd/Fe-mesoporous silica composite was prepared with mesoporous silica as the carrier,which improved the utilization ratio of Pd/Fe in dechlorination of trichloroethylene.The specific surface area,pore size and pore volume of non-expanded mesoporous silica are 653 m2/g?7.82 nm?0.997 m3/g,while this parameter of expanded mesoporous silica reamed by 1,3,5-trimethylbenzene(TMB)are 728 m2/g?22.3 nm?1.68 m3/g.By contrast,the expanded result is obvious.XRD,transmission electron microscopy,nitrogen adsorption desorption and other tests show that nanoscale palladium/iron can be load into the mesoporous silica pores and on the surface by the double solvent method.Mesoporous silica has a certain adsorption effect on trichlorethylene,and as a carrier it can prevent agglomeration of the nanoscale-palladium/iron,increase the specific surface area of nanoscale-palladium/iron,thereby improve the trichlorethylene removal ratio and conversion ratio.Dechlorination of trichlorethylene by nanoscale palladium/iron was by means of hydrogenation.The removal ratio of trichlorethylene of nanoscale palladium/iron-mesoporous silica was higher than that of nanoscale palladium/iron,and the removal ratio of trichlorethylene was 93.2%and 57.4%respectively,the production ratios of ethylene and ethane were 50.7%and 28.9%,respectively,indicating that mesoporous silica is a suitable carrier for nanoscale palladium/iron.The removal and dechlorination ability of trichlorethylene by nanoscale palladium/iron-mesoporous silica increased with the increase of pore volume and dosing,increased at first then decreased with the increase of nanoscale-palladium/iron loading ratio,decreased with the decline of initial concentration of trichlorethylene.After 56 hours of reaction,the removal ratios of trichlorethylene were 61.4%and 93.2%respectively dechlorinated by nanoscale palladium/iron-nonexpanded mesoporous silica and expanded mesoporous silica,and production ratios of ethylene and ethane were 23.0%and 50.7%respectively.The removal ratios of?trichlorethylene were 31.0%?81.5%?93.2%?61.2%?97.6%respectively dechlorinated by nanoscale palladium/iron-nonexpanded mesoporous silica that loading ratio are 2/%?4%?8%?12%?16%,and production ratios of ethylene and ethane were 3.30%?24.9%?50.7%?52.5%?46.3%.The removal ratios of trichlorethylene were 28.8%?57.6%?85.2%respectively dechlorinated by nanoscale palladium/iron-nonexpanded mesoporous silica that dosages were 9,5 g/L,19 g/L,38 g/L respectively,and production ratios of ethylene and ethane were 12.0%?46.4%?61.0%.The removal ratios of trichlorethylene were 94.0%?93.2%?28.8%respectively dechlorinated by nanoscale palladium/iron-nonexpanded mesoporous silica that initial concentrations of trichloroethylene were 5?23.6?and 250 mg/L,and production ratios of ethylene and ethane were 48.8%?50.7%?12.0%.The silica with great pore structure can be used as a carrier to disperse the nanoscale-palladium/iron well and prolong the nanoscale-palladium/iron reactive activity time,suitable for groundwater chlorinated hydrocarbon contamination repair.