Preparation Of Alumina Ceramic Filtration Membrane By Spray Coating

Ceramic filtration membranes have attracted wide attention due to their stable chemical properties,high strength,high temperature resistance,corrosion resistance and long service life.Alumina,a commonly used support material for filtration membranes,has high firing cost,high energy consumption,long firing time and low production efficiency because of its high firing temperature.The commonly used membrane preparing method,dip coating,has many problems,such as complicated preparing steps and blockage of support channel.Due to the above reasons,the application of ceramic filtration membranes is still limited.Based on the above situation,the main research work of this research includes two aspects.On the one hand,the sintering temperature of support is reduced by adding firing assistant aids to the aggregate;on the other hand,the filtration membrane is prepared directly on the surface of the support without transition layers by spray coating method,which simplifies the preparation process and improves the permeation of the membrane.In this research,the effect of TiO₂ on the sintering temperature of alumina support was studied.The effects of the additive amount of TiO₂ and the firing temperature on the phase composition,linear shrinkage,open porosity,bending strength,pure water permeance and micro-morphology of the support were analyzed.Experiments show that TiO₂ can help the support produce liquid phase during sintering,reduce sintering temperature and improve bending strength.When the additive amount of TiO₂ is 1.5 wt% and the sintering temperature is 1500?,the bending strength of the support is 41.6 MPa,the open porosity is 39.1%,and the pure water permeance is 9225 Lm^-2h^-1bar^-1.Theoretically,the spray coating method can effectively reduce the infiltration of membrane-forming particles into the support channel.The mechanism of reducing the infiltration of membrane-forming particles into the support channel by spray coating method was studied,by simulating the support channel with capillary glass tube.During the spray coating process,some gas is easily trapped in the support channel,and the continuous liquid column can not be formed,which increases the resistance to capillary adsorption effect and effectively reduces the infiltration of membrane-forming particles into the support.Alumina ceramic micro-filtration membrane was obtained by spraying slurry directly onto the surface of the support without intermediate layer,which simplified the preparation process and increased the water permeance of the membrane.The effects of different sintering conditions on the morphology and pore size distribution of the membrane were studied.The relationship between the thickness and pore size distribution was found.The reliability of the bonding strength between the film and the support was tested,and the rejecting performance of the membrane was characterized.High performance alumina ceramic micro-filtration membranes were prepared by sintering at 1300? and soaking for 2 h.The average pore size was 0.13?m and the pure water permeance is 2893 L m^-2 h^-1 bar^-1.The microfiltration membranes were treated by backwash and pulse backwash.The results showed that there was a high bonding strength between the membrane and the support.After 120 min filtration of graphite ink with an average particle size of 164 nm,the rejection rate of membrane was 98.8%.