Study On Low Cost Preparation Of Alumina Ceramic Membrane By Gelcasting With MMA System And Its Separation Characteristics

Membrane separation technology mainly includes microfiltration,ultrafiltration,nanofiltration and reverse osmosis.Due to its high separation efficiency,convenient operation,low energy consumption,safe working environment,no pollution and many other advantages,membrane separation technology is widely used in the fields of food,medicine,metallurgy,energy chemical,environmental protection,etc.According to different membrane materials,the membranes could be divided into two categories: organic membrane and inorganic membrane.In the inorganic membrane,the ceramic membrane is the main one,which has the advantages of high temperature resistance,acid and alkali resistance,long service life and so on.Therefore,it would have broad prospects for development.At present,the commercial ceramic membrane is generally asymmetric,and the preparation process requires several steps of sintering and coating,not only cumbersome process,and energy-consuming,resulting in high cost of ceramic membrane preparation.Thus,in this paper,two kinds of different forming processes were used to prepare the support and separation layer and the ceramic membrane was obtained for one time.In order to explore the separation ability,the filter performance was tested with the dye-containing wastewater,and finally the organic/inorganic composite membrane was used to improve the removal rate.In order to solve the problem that the sintering temperature of the support was high,the sintering process was studied.Adding composite sintering agent(NaSiO3+TiO2+CaCO3+MgO)into aggregate to lower the sintering temperature of support,the effects of NaSiO3 addition on the properties of the supports were mainly discussed.It was found that the addition of NaSiO3 could obviously promote the sintering of support,but content should be controlled properly.Through orthogonal experiment,the optimal parameter of NaSiO3,pore forming agent content,binder content and holding time were 4%,6%,0.6% and 2h.Based on the optimal conditions,the effect of temperature was mainly discussed,and the best performance of the ceramic membrane was obtained at the lower temperature range of 1400-1450?,indicating it was suitable for used as a carrier of more precise separation layer.The traditional gelcasting process was improved by using MMA as the organic monomer.After the bulk polymerization was carried out,the pre-polymer was mixed with the powder aggregate to form coating slurry,then coating it on the layer support to form a gel layer.Finally,the asymmetric ceramic membrane was obtained by co-sintering.The experimental results showed that when the amount of initiator was 0.1% by water bath heating for 11.5 min at 90? the viscosity of prepolymer was about 350mPa?S,which showed good fluidity.The prepolymer could be mixed with alumina powder as coating slurry.The volume fraction of solid phase became larger with the smaller particle size while the sintering temperature,the smaller the pure water flux,porosity and pore size of ceramic membrane became smaller with the higher sintering temperature.In order to obtain the ceramic membrane with small pore size and uniform distribution,the raw material of average particle size with 4.49 ?m,volume fraction of solid phase with 50% and sintering temperature with 1420? was selected.Through the filtration of two different dye wastewater,it was found that the ceramic membrane prepared by gelcasting with MMA system had better performance than that of traditional grouting,which indicated that the gelcasting with MMA system had a certain application value in the preparation of the top film.In order to strengthen the filtration performance,by chosen low-cost organic film loaded on the ceramic membrane to prepare the organic/inorganic composite membrane.The effects of polyether sulphone concentration,dipping time,dipping temperature and coagulation bath temperature were investigated.The results showed that when the concentration of polyether sulphone and the dipping temperature was higher,the pure water flux of the composite membrane was lower and the removal rate of the direct dye wastewater was higher.Meanwhile,the higher the coagulation bath temperature was,the higher the water flux and the lower the removal rate of direct dye was.Dipping time had little effect.The results showed that when the concentration of polyether sulphone of 15%,the dipping time of 1h,the dipping temperature of 40? and the coagulation bath temperature of 20? were measured the membrane flux obtained 416.8 L?m-2?h-1and the removal rate of dye-contained could reach 94.12%.