Synthesis Of CaWO4 Loaded Electroconductive Fly Ash Geopolymer And Treatment Of Dyeing Wastewater

Fly ash?FA?is the main solid waste discharged from the coal-fired power plant.The long-term accumulation of fly ash not only takes up a large amount of land resources,but also causes serious environmental problem.The high value-added utilization of fly ash has important practical significance for the cleaning production of coal-fired power plant.In this paper,the conductive graphene fly ash geopolymer?GRFAG?was prepared by using FA as raw material,Na₂SiO₃·9H₂O and KOH as the alkaline activators and graphene as the conductive medium.The mechanical properties and electrical performance of GRFAG were investigated.CaWO₄/GRFAG catalysts were synthesized by loading CaWO₄ semiconductor on the support of GRFAG by incipient wetness impregnation method.CaWO₄/GRFAG catalysts were characterized by XRD,FESEM,XPS,N₂ adsorption-desorption and other analysis methods.The photocatalytic degradation of indigo carmine dye performance of CaWO₄/GRFAG catalysts was evaluated by response surface methodology?RSM?.The graphene granulated blast furnace slag based polymer and graphene fly ash geopolymer were synthesised.The mechanical properties of these two polymers with graphene addition were studied.The results showed that when the graphene addition was 0.01wt%,the compressive strength of graphene granulated blast furnace slag based polymer and graphene fly ash geopolymer were 53.3 MPa and 53.4 MPa.With the increase of dosage of graphene,the mechanical properties of polymer presented the change trend of first increase and after decrease.XRD,FESEM results showed that the graphene did not participate in the hydration process of fly ash geopolymer.The addition of graphene can significantly improve the conductive properties of fly ash geopolymer.When the dosage of graphene was 1.0 wt%,the conductivity was 0.27 S/m which was higher than without graphene addition?0.00071 S/m?.N₂ adsorption-desorption results showed that graphene addition increased the specific surface area.The CaWO₄/GRFAG catalysts were synthesised by incipient wetness impregnation that?NH₄?₆W₇O₂₄·6H₂O reacted with CaO at 500?in inert atmosphere.The XRD and FESEM results indicated that the CaWO₄ was loaded on on the surface of the catalyst carrier load.The properties of photocatalytic degradation of indigo carmine dye by GR/FAG were evaluated.The result showed that the electrical conductivity of catalyst was positively correlated with the degradation rate of dye.When the graphene addition was1.0wt%the degradation of dye approach to 90.2%in 90 min,due to the graphene played an important role in electron transmission and impelled the separation of photoelectrons from vacancies which may improve the active of catalyst.The effects of the dosage of catalysts,the loading of active components and the concentration of dye on the degradation rate of the dye were investigated by response surface methodology?RSM?.The optimal experimental condition was 0.07 g of catalyst,5.4wt%of CaWO₄ loading,26.25 mg/L of dye concentration and the indigo carmine dye degradation rate was 95.02%which was extremely close to the predicted value?95.12%?implying that the regression model has great reliability.