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.

New Low-Cost Ceramic Microfiltration Membranes for Bacteria Removal

“…They achieved almost total E. coli rejection under UV radiation (and 99.4% rejection under dark conditions, i.e., when the photocatalytic activity of TiO 2 was not activated). Zhu et al also reported a complete removal of both E. coli and S. aureus by a mullite/carbon nanotube composite membrane [ 29 ]. However, the above-mentioned performance all required the addition of nanomaterials, which would undoubtedly increase the overall cost of the membrane.…”

“…The water level above the membrane was kept equal to 13 cm during the entire filtration experiment. The membrane hydraulic permeability (L p ) was determined according to [ 29 ]: where V is the volume of water filtered, A is the membrane surface area, Δt is the sampling time and ΔP is the transmembrane pressure difference.…”

Application of coal fly ash based ceramic membranes in wastewater treatment: A sustainable alternative to commercial materials

“…AlF 3 was observed to influence properties such as phase composition, porosity, bulk density, and aspect ratio of the obtained whiskers. Mullite obtained from CFA was employed together with multiwalled carbon nanotubes (MWCNT) to form a hierarchically structured membrane, the membrane achieved complete retention of E. coli and S. Aureus [ 113 ]. Interestingly, no pore blockage was reported for the material and fouling only occurred due to the bacterial cell deposition of the surface.…”

Materials and Applications for Low-Cost Ceramic Membranes

“…Low-cost membranes prepared from various naturally available or waste materials have also wide application in the water treatment process [15,171]. According to the publications so far, applications of low-cost membranes can be classified as follow: as a support layer for further membrane preparation [66,68,132,172], microfiltration of suspended solid particles [36], oil droplets [32], dye from textile industry [116], bacteria [11,49], humic acid [126], ultrafiltration of uranium and other heavy metals [20,35,66], see Figure 10.…”