Research On Preparation And Catalytic Properties Of Expanded Graphite/Zinc Oxide Nanocomposites

Nowadays, a large number of wastewater discharge has caused seriouspollution of water bodies, among them, phenolic wastewater has great toxicity,and it is difficult to degrade, which has already been paid high attention by thecommunity. Expanded graphite is a kind of carbon material having a porousstructure, possesses many excellent chemical properties, and expanded graphitehas superior adsorptive capability owing to its huge surface area, it is a kind ofnew functional materials in the field of wastewater treatment. The surface ofnano-zinc oxide has more active sites, so it exhibits stronger photocatalyticactivity when compared with ordinary zinc oxide. Combined expanded graphitewith nano-zinc oxide can solve many problems, for instance, the density ofindividual zinc oxide is large, zinc oxide is easy to reunite during photocatalyticreaction and is difficult to recycle after the reaction, thus expanded graphite/zincoxide nanocomposites have high research value and broad application prospects.In this paper, after comparison, expanded graphite prepared by using lowsulfur expandable graphite via microwave expansion was adopted as carrier forsubsequent preparation of the catalyst. Next, expanded graphite/zinc oxidecomposites were prepared by sol method and composites synthesized underdifferent conditions were characterized by XRD, SEM, EDS, specific surfacearea and pore size distribution. Finally, we investigated the properties ofcomposite materials prepared by experiments for photocatalytic degradation ofphenol wastewater.This paper concluded that expanded graphite/zinc oxide composites hadbeen prepared by sol method successfully, impregnation process using expandedgraphite, three-time impregnation and using sol without aging for theimpregnation of expanded graphite could increase the loading amounts of zinc oxide on composites, three-time impregnation would reduce the specific surfacearea of the composites, raising calcination temperature could increase the crystalsize of zinc oxide, zinc oxide was not only distributed in the surface of theexpanded graphite, but also entered its holes and the room between its sheets toload. Although the crystal size of zinc oxide on composites synthesized byprecipitation method was small, zinc oxide would generate serious reunion, thecrystal size of pure zinc oxide prepared by sol-gel method was large, thus thephotocatalytic properties of these two catalysts were poor. Finally, catalyst5obtained via three impregnation processes and catalyst7synthesized by using solwithout aging for the impregnation of expanded graphite had the highestphotocatalytic activity. After UV irradiation of6hours, the degradation rate ofthe two catalysts for phenol wastewater were both55.0%.