| Ceramic membranes have the.advantages of high temperature resistance,corrosion resistance,microbial corrosion resistance,high strength,large processing capacity,and have been widely applied in the field of separation.Alumina ceramic membrane with high cost performance,widely used in food,medical,chemical and other industries.However,the irregular alumina particles used in the preparation of alumina ceramic membranes are prone to cracks and uneven pore structures on the surface of the ceramic membrane during the sintering process.At the same time,the surface of the membrane is relatively rough,and the retention performance and permeation flux of the ceramic membrane will be affected.In view of the above problems,this paper uses ultrafine spherical alumina prepared by thermal plasma to prepare ceramic ultrafiltration membranes.The ultrafine spherical alumina has the particle size of about 100 nm,the smooth surface and the high zeta potential.Adjusting the sintering temperature and the solid content of the slurry,the immersion time,the concentration of polyvinyl alcohol and the applied voltage regulate the microstructure of the ceramic membrane surface.The membrane with no defects,uniform structure,high permeation flux is prepared by the ultrafine spherical alumina.(1)The ultrafine alumina with dense spherical powders prepared by plasma is characterized,and it is found the alumina has the particle size of about 100 nm and the narrow particle size distribution.The alumina powders have the high zeta potential When the pH value is 7,the zeta potential is 54.06 mV.The stability of alumina slurry is high,and no delamination occurs at room temperature for 14 days.Then,the dense spherical alumina particles are used as raw materials to form a relatively uniform sintered neck by sintering the closely packed spherical particles,and the ceramic membrane with a narrow pore size distribution and no defect on the membrane surface is prepared.The effects of the sintering temperature of the ceramic membrane,the solid content of the alumina slurry,the concentration of polyvinyl alcohol,and the immersion time on the microstructure morphology and performance of the ceramic membrane are studied.The performance of the ceramic membrane is evaluated by filtering the nano-silicon dispersion slurry.The regulation law of the microstructure morphology of the ceramic membrane is obtained.The sintering mechanism of spherical ultrafine alumina ceramic membrane and the filtration blocking model of ceramic membrane to filter nano-silicon dispersion slurry are discussed.Finally,the prepared ceramic membrane is used to treat the cold-rolled emulsified oil wastewater of Handan Iron and Steel Plant.The oil content of the treated permeate was 9.34 mg/L,and the oil content rejection rate reached 98.58%.(2)In view of the filter blocking caused by the lack of flatness on the surface of the ceramic membrane,spherical alumina of the high zeta potential are used to adjust the arrangement of the alumina particles on the surface and cross section of the ceramic membrane after dipping and pulling with the assistant of the electric field.The aluminum particles are rearranged by sliding to prepare the ceramic ultrafiltration membrane with uniform pore structure and smooth membrane surface.The effect of different applied voltages on the morphology and properties of the ceramic membrane is studied.It is found that with the increase of the applied voltage,the sintering degree of the ceramic membrane particles increased and the surface roughness of the ceramic membrane gradually decreased.The performance of the ceramic membrane with different applied voltages is evaluated by filtering the cutting fluid emulsified oil.When the applied voltage was 80 V,the emulsified oil rejection rate reached 97.83%.As the applied voltage increases,the time for the filtered cutting fluid emulsified oil to reach equilibrium increases,and the permeation flux increases.Finally,the membrane fouling process of emulsified oil filtered by ceramic membranes with different surface roughness is studied.The results show that the larger the roughness of the ceramic membrane,the easier the emulsified oil particles adhere to the surface of the ceramic membrane to block the pores,resulting in a decrease in permeation flux. |
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