Study On Preparation Of Fly Ash Porous Ceramics And Its Absorption Of Cr(Ⅵ)

Fly ash is an industrial solid waste from coal combustion,and its resource utilization is of great importance to improve the ecological environment and promote green and sustainable development.Fly ash can be prepared into porous ceramics for water purification,but the current effect of fly ash porous ceramics for direct treatment of chromium-containing wastewater is less than ideal,and it is necessary to modify them to improve their adsorption properties.Rare earth elements such as lanthanum and cerium have good adsorption properties,but the cost of using rare earth elements alone for water treatment is very high.Therefore,this study uses local fly ash from Baotou as the main raw material and uses rare earth elements to modify fly ash porous ceramics to treat chromiumcontaining wastewater,which has certain theoretical and practical significance to improve the adsorption performance of porous ceramics,reduce economic costs and achieve waste treatment.In this paper,local fly ash from Baotou was used as the main raw material to prepare porous ceramics by adding porogenic agents.The effects of alumina doping,porogenic agent doping,sintering temperature and holding time on the properties of porous ceramics were investigated,and the best formulation and sintering system were selected.The modified porous ceramics were prepared by impregnation with rare-earth solutions,and the effects of pH,adsorption time,initial concentration,dosing amount and temperature on the adsorption performance were investigated,and the adsorption model of the modified porous ceramics on Cr(Ⅵ)was established and the adsorption mechanism was discussed.In addition,the regeneration experiments were carried out on the saturated adsorbed modified porous ceramics to study their cyclic regeneration performance.The results show that the optimum conditions for the preparation of fly ash porous ceramics are: 45% fly ash addition,15% alumina doping,30% porous agent doping,4%starch and calcium carbonate addition,2% montmorillonite addition,sintering temperature of 1200°C and holding time of 30 min.The best adsorption performance of the porous ceramics modified with 0.4 mol/L LaCl3/CeCl3(1:1)solution was achieved with the following optimized adsorption conditions: pH 5.1,adsorption time 24 h,50 g/L dosage,initial concentration of Cr(Ⅵ)in solution 100 mg/L and adsorption temperature 303 K.The adsorption behaviour of the modified porous ceramics for Cr(Ⅵ)was more in line with quasi-secondary kinetics.The adsorption behaviour of the modified porous ceramics was more in line with the quasi-secondary kinetic model,where intraparticle diffusion was not the only rate-limiting step.The adsorption of Cr(Ⅵ)by the modified porous ceramics is a spontaneous and disordered increase of the heat absorption reaction.The adsorption is a combination of pHysical and chemical adsorption and the reaction mechanism is the exchange of ligands with Cr(Ⅵ)by electrostatic gravitation and the active functional group-OH of the modified porous ceramics.After desorption from 0.1 mol/L HCl solution,the porous ceramics showed the best readsorption effect.After four cycles of desorption and readsorption,the readsorption rate could still reach more than 60%.The modified porous ceramics can be used as a recycling adsorption material for the treatment of industrial wastewater.