Fabrication, characterization and preliminary testing of all-inorganic ultrafiltration membranes composed entirely of a naturally occurring sepioliteclay mineral

All-inorganic membranes that are composed entirely of sepiolite, a naturall y occurring Mg-silicate clay mineral, have been fabricated. Pinhole-free, s elf-bonded membranes with transecting pores in the large mesopore to macrop ore size range were obtained. Characterization of the thermally treated mem branes by PXRD has revealed that the sepiolite is transformed into sepiolit e anhydride' by heating in air at elevated temperatures. SEM studies have s ubsequently shown that the air dried membranes do not develop cracks or oth er similar flaws even after being subjected to temperatures as high as 750 degreesC for several hours. Calcined sepiolite membranes were tested for th e ultrafiltration of high molecular weight poly(ethylene glycol) and poly(e thylene oxide) molecules in aqueous solution. The MWCO was determined to be close to 300 000 for all of the membranes that were studied in the prelimi nary tests. Significant membrane fouling was observed, which dramatically r educed the permeation flux rate during the ultrafiltration tests. (C) 2001 Elsevier Science B.V. All rights reserved.