Fabrication and characterization of robust zirconia-kaolin hollow fiber membrane: Alkaline dissolution study in ammonia solution

Kaolin has been found to be a more economical alternative in ceramic hollow membrane fabrication compared to alumina, silica, and zirconia despite having similar properties. However, it was discovered that apart from having high mechanical strength and the ability to withstand high operational temperature, the kaolin membrane has the tendency to dissolve in a high alkaline solution. Hence, in this study, zirconia (ZrO2) was imposed to kaolin suspension as co-starting material due to its stable hexagonal properties with kaolin to overcome this drawback. To study the dissolution property of the modified kaolin-based membrane, a phase inversion technique was used to fabricate zirconia-kaolin hollow fiber membrane (ZKHFM) followed by immersion in ammonium hydroxide (NH4OH) as an alkaline solution. Ammonia was aptly chosen for it being considered as one of the pollutants to be removed from wastewater. The mechanism, morphology and properties of the membrane were investigated in terms of sintering temperature, morphology, mechanical strength, pore size and porosity The results showed that ZKHFM with 10 wt% (ZK-10) with sintering temperature of 1,200 °C had the best performance in terms of having high mechanical strength (21MPa), excellent permeation flux (∼1,600 Lm2/h) and lowest dissolution (0.01 g dissolute) at pH 13, indicating the ability of ZKHFM to be used in alkaline solution.