| Inorganic ceramic membranes are widely used as filters in environmental science, lifescience and fine chemical, etc. due to their characterization of high percentage of particulates,thermal stable, chemical inert, superior mechanical properties, low energy consumption, longlife cycle, and convenient operation and maintenance. Particularly, in comparison withorganic and metallic membranes, inorganic ceramic membranes are irreplaceable in theapplication of filtering and clarifying techniques under the extreme environment such as hightemperature, strong acid, strong base and strong corrosive. However, the key technology inthe preparation of inorganic ceramic, especially the preparation technology of microfiltrationlayer is necessitated to be improved and optimized.This study focused on the fabrication and improvement of dip-coating suspension for themicrofiltration layer of alumina ceramic membrane. Firstly, this study reviewed thedevelopment and application of inorganic ceramic membranes for microfiltration, comparedthe common methods for the preparation of ceramic membranes, and evaluated the factorswhich control the performances of ceramic membrane. It is found that the solid-state-sinteringmethod and the dip-coating technique are widely used due to the advantages of simple process,low cost and high stability. The stability of dip-coating suspension for the microfiltration layerof alumina ceramic membrane is a key factor in the solid-state-sintering method and thedip-coating technique, because it not only affects the performances of ceramic membrane, butis hard to be controlled due to the influences of too many factors. Therefore, this study hasdone extensive work on controlling and refining the stability of dip-coating suspension for themicrofiltration layer of alumina ceramic membrane. The research results are expected to beused for the establishment of key technologies on the fabrication of high performanceinorganic ceramic membrane for microfiltration in industries.This study used the solid-state-sintering method and the dip-coating technique to preparethe alumina membranes for microfiltration, investigated the factors of controlling the stabilityof dip-coating suspension, and discussed the influences of dip-coating technologies on theperformances of membranes. In the preparation of dip-coating suspension, α-Al2O3powderswere used as solid phase, PVA (polyvinyl alcohol) and CMC (carboxymethyl cellulose) were used as binders,(PAA) polyacrylic acid and dilute nitric acid (HNO3) were used as dispersant.The viscosity and Zeta potential were used to characterize stability of suspension in order tooptimize the mixture design of suspension. In addition, MIP (mercury intrusion) and SEM(scanning electron microscope) were used to investigate the microstructure of ceramicmembrane in order to discuss the filtration performance.In terms of the research results, an optimum mixture design was figured out: the solidphase is employed by the α-Al2O3powders with an average particle size of0.5μm and a solidcontent of5%wt, the binder is employed by the PVA with a content of0.75%wt, thedispersant is employed by the PAA with a content of0.6%wt, and the pH is around at3.15.The apparent viscosity of suspension is9.33×10-3Pa S, and the related sedimentation rate is9.33%, which indicates that the suspension exhibits excellent stability. Further, the viscosityof dip-coating suspension has a significant influence on the integrity of microfiltration layerof ceramic membrane. Based on the above results, the dip-coating suspension can be used asthe microfiltration layer and the intermediate transition of ultrafiltration layer. After dried atroom temperature for24hours, the support body which was coated by above suspension isthen solid-state-sintered to1300℃. Accordingly, the inorganic alumina ceramic membrane formicrofiltration will be prepared. |
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