New ceramic membranes from calcinated clay.

The aim of the present work is to obtain porous tubular ceramic membranes f rom natural material. The clay powders were calcinated in air at 900 degree sC for two hours. The resulting powders mixed with certain organic additive s could be extruded to fabricate a porous tubular configuration with highly uniform porous structures. The mean pore diameter, measured by mercury por osimetry, is equal to 9 mum and the porosity is 38% (heat treatment at 1130 degreesC for two hours). Many ceramic membrane manufactures have used this type of large-pore membrane as supports for finer-pore membranes (microfil tration or ultrafiltration). Porous membranes possess very good mechanical strength and negligible flow resistance for the membrane/support, while con taining pores which allow a high degree of permeation.