Study of the antimicrobial and antifouling properties of different oxide surfaces

Abstract

Membrane separation processes find applications in an array of fields as they use far less energy and chemical agents than competing processes. However, a major drawback of membrane technology is that biofilm formation alters membrane performances. Preventing biofilm formation is thus a pivotal challenge for larger-scale development of membrane processes. Here, we studied the comparative antibacterial activities of different inorganic membranes (ceramic and zeolite-coated ceramic with or without copper exchange) using several bacterial strains (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis). In static conditions, alumina plates coated with Cu-exchanged zeolite showed significant bactericidal activity. In dynamic mode (circulation of a contaminated nutrient medium), there was no observable bacterial adhesion at the surface of the Cu-exchanged material. These results confirm the antifouling properties of the Cu-mordenite layer due to both the increased hydrophilicity and antibacterial properties of the active layer.Tests performed with tubular filtration membranes (without copper exchange) showed a significant decline in membrane hydraulic properties during filtration of culture media containing bacteria, whereas copper-exchanged membranes showed no decline in hydraulic permeability. Filtration tests performed with concentrated culture media containing spores of B. subtilis led to a significant decrease in membrane hydraulic permeabilities (but less so with Cu-exchanged membranes). The surfaces showed less effective global antifouling properties during the filtration of a concentrated culture medium due to competition between bacterial growth and the bactericidal effect of copper. Analyses of copper leached in solution show that after a conditioning step, the amount of copper released is negligible.

Application of antimicrobial properties of copper

“…Therefore, scientists have developed copper particles loaded on membranes or filter media to eliminate microbial contamination. [104][105][106][107][108] Although copper is widely used in water treatment, people's physiological health is not adversely affected. After 168 h of experimentally using copper pots to store drinking water, the copper content was still within the permissible limits of the World Health Organization and the EPA.…”

“…Because of improvements in their quality of life, many people do not use groundwater flowing directly from a pipe but do secondary purification through modern water purification facilities. Therefore, scientists have developed copper particles loaded on membranes or filter media to eliminate microbial contamination 104–108 …”

Rational Design and Characterisation of Novel Mono- and Bimetallic Antibacterial Linde Type A Zeolite Materials

“…The negative charges are compensated by cations (usually Na + ), which are bound to the zeolite framework by weak interactions and are, therefore, exchangeable. Ag, Cu, and Zn-exchanged zeolites [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ], as well as zeolite-based composites [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ] and coatings [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ], are well-studied antimicrobial materials (for review, see [ 63 , 64 ]), which have been commercialised. The exchanged-zeolite frameworks release transition metal-ions, by cationic exchanges, and their antimicrobial efficiency are, therefore, related to the salt content of the solution or deposit.…”

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

“…Bacteria tend to form a cohesive biofilm on membrane surfaces, leading to an increase in the hydraulic resistance to permeation flow [7]. Therefore, several studies have developed improved biofouling control strategies for the more sustainable operation of membrane systems, it was demonstrated the potential of silver nanoparticles [7,8,9] and copper nanoparticles [10] as biocides, which can mitigate the membrane biofouling and restrain the flux decline effectively; the membrane systems subsequently showed no decline in hydraulic permeability in the whole membrane. Carbon nanotubes (CNTs) have also emerged as promising filtration and separation materials for water purification, owing to their strong antimicrobial activity, good corrosion stability, large active specific surface area, and excellent sorbent properties [11,12,13,14].…”