Ceramic capillary membrane has received much attention due to its relatively high pack density and favorable mechanical strength.However

it is difficult to prepare capillary membrane on its thin support by a dip-coating method.In this study

alumina microfiltration membranes were prepared on the inner surface of alumina capillary support(outer diameter 4 mm

inner diameter 2.5 mm)by a dip-coating method.Scanning electron microscopy(SEM)observation

gas bubble pressure(GBP)method and membrane permeation test were carried out to evaluate membrane performance.Two major effects in preparation of crack-free membrane

capillary filtration and film-coating

upon the thin support were studied.The as-prepared crack-free membrane presents a narrow pore size distribution

a mean pore size of about 0.6μm and a high pure water flux of 86000 L·m

-2

·h

-1

·MPa.It is proved that the membrane thickness should be sufficiently large to overcome the defects of support surface

but it is only one of the prerequisites for the formation of crack-free membrane.Furthermore

it is demonstrated that the capillary filtration effect is greatly restricted for thin capillary support with the dip-coating method and the film-coating effect plays a crucial role in the formation of crack-free membrane.