Ceramic-Based Composite Membrane with a Porous Network Surface Featuring a Highly Stable Flux for Drinking Water Purification

Abstract

Highly efficient drinking water purification is still an important challenge for membrane techniques where high flux, high rejection, and low fouling are highly emphasized. In the present work, a porous network surface with carbon nanotubes (CNTs) was in situ constructed on hierarchically-structured mullite ceramic membranes. Interestingly, such a composite structure was demonstrated to effectively remove bacteria from drinking water with a highly stable long-term flux. After membrane structure characterizations, separation performance, such as flux and rejection, was assessed by the purification of bacteria-contaminated drinking water. The results confirmed that the mullite-CNT composite membrane claimed a complete removal of two model bacteria (100% rejection of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus)), driven by a trans-membrane pressure of 0.1 MPa, where a surface sieving mechanism was dominant. A highly stable long-term flux for the 24 h filtration process was achieved, which can be attributed to the porous membrane surface with a special randomly-oriented CNTs network structure, featuring very high three-dimensional open porosity, allowing water to rapidly transport. The bacteria were only trapped on the CNTs network surface via surface filtration, without pore plugging, endowing the mullite-CNT membrane with unprecedentedly low fouling propensity to keep high flux with long-term operation time.