Preparation Of High-performance Ultra-thin Flat Ceramic Membrane And Its Application In Oil-water Separation

The rapid development of the social economy has produced a large amount of sewage,if the sewage was not treated,which would inevitably lead to a shortage of water resources.Among many sewage treatment methods,membrane separation method has become a direction of the field of environmental engineering as an efficient physical separation method development.Especially in the recent 10 years,the ultra-thin flat ceramic membrane has emerged in the treatment of oily wastewater due to its many abilities such as low transmembrane pressure and high permeability flux.However,the ultra-thin flat ceramic membrane obtains high permeation flux by the condition of lower transmembrane pressure,which reduces the permeation resistance by reducing the thickness of the support and the membrane layer.The ultra-thin ceramic membrane support(?3 mm)would inevitably lead to higher requirements for the preparation method of the support and film,which becomes pivotal factors affecting the performance of the ultra-thin flat ceramic membrane.In order to obtain ultra-thin ceramic film support by extrusion mold smoothly,through adjustment of the particle gradation of the powder for modifying the mud.Through extrusion mold method,controlled evaporation and optimized sintering to obtain the ultra-thin flat ceramic support with thickness of 1 mm.Through experiment,the best sintering temperature is 1650 ?,the withstand stress is 72.3 N,the porosity is 40 %,and the average pore size is 4.0 ?m.As the result of the thin support thickness,the support couldn't provide sufficient capillary force,resulting in the inability to form a complete and stable wet film.This article first proposes a film formation method using spraying + dip coating method.The spray coating layer prepared by spraying method which disperses the ceramic slurry into droplets by high-pressure air,and the droplets are scattered on the surface of the support to form a layer,which overcomes the capillary of the support that required of the support and the particle size of the slurry powder.So that spraying method could be used to directly prepare a transition layer with a smaller pore size on a support with a larger pore size.However,the surface of the membrane fabricated by spraying method with relatively roughness is not conducive to reduce membrane pollution and ensure penetration stability.The traditional dip coating method is used to prepare the separation membrane layer directly on the sprayed layer,which can control the membrane thickness and surface flatness.The experimental results show that the ultra-thin flat support with the pore size of 4.0 m and the support thickness of 1 mm,the 35 % solids content of 500 nm Al2O3 slurry as the spray coating method slurry,when spraying 11.11 mg/cm~2 on the support to obtain the spray coating layer with the thickness of 30 ?m.The flat dip coating layer fabricated directly on the green spray coating layer,the 35 % solids content of 100 nm Al2O3 slurry as the dip coating method slurry,the optimal dip coating time is 10 s for obtaining the controllable separation layer with the thickness of 20 ?m,the pore size of 50 nm,and the ultrafiltration membrane with the pure water flux of 725.74 L/(m~2·h·bar).The ultra-thin flat ceramic membrane prepared by the optimized process was used to treat oil-water emulsion with the concentration of 1000 mg/L.In the oil-water separation experiment,the membrane separation efficiency was 98.5 %,and the permeation flux was 180 L/(m~2·h·bar).