Rational Design of Hierarchically Porous Interlayer for Highly Permeable and Fouling-Resistant Ceramic Membranes in Water Treatment

Abstract

Ceramic membranes are being increasingly adopted in water and wastewater treatment owing to their performance and long-term benefits. Engineering the microstructure of ceramic membranes for better performance has thus obtained intensive interest. In this work, ceramic membranes with a hierarchically porous interlayer were purposely designed in order to boost the water flux. Titania (TiO2) nanoparticle suspensions with and without polystyrene beads (Ps beads) were coated on the macroporous ceramic support, successively. Followed by co-sintering at 850 ?C, the Ps beads in the interlayer were removed. As a result, a dual-layer membrane structure with the hierarchically porous interlayer being covered by a well-integrated top filtration layer was successfully produced. Efforts were devoted to optimizing the interlayer and the top layer in the level of open porosity and thickness, respectively. A balance between the level of open porosity and structural stability was thus achieved in the interlayer. Significantly, an optimized ceramic membrane with the hierarchically porous interlayer showed a largely increased water flux yet insignificant reduction in particle size retention. The membrane fouling mechanism was revealed to be intermediate pore blocking in the entire filtration process, while that of the conventional ceramic membrane rapidly developed to the cake layer. This suggests that the ceramic membranes with a hierarchically porous interlayer are of high efficiency in water and water treatment benefiting from the enhanced permeate flux and retarded membrane fouling process.