Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity

Abstract

In this study, a layer of a pure and dense phase of FAU-type zeolite was synthesized directly on the surface of α-Al2O3 plane macroporous support. Before hydrothermal synthesis, a step of cleaning of the support by an anionic detergent was performed, a roughness surface is created, allowing the anchoring of the zeolite nuclei and then their growth, favoring in this sense the formation of a homogeneous zeolite layer. The obtained membranes were fully characterized using X-ray diffraction analysis (XRD), nitrogen sorption, scanning electron microscopy (SEM), and mercury porosimetry. After 24 h of thermal treatment at 75 °C, a homogeneous zeolite layer composed of bipyramidal crystals of FAU-type zeolite is obtained with a thickness of about 2.5 µm. No obvious defects or cracks can be observed. It was found that the increase in heating temperature could lead to the appearance of an impurity phase, GIS-type zeolite. Then the ideal zeolite membrane was exchanged with Ag+ or Zn2+ cations to studies their antimicrobial properties. Zeolites membranes exchanged with Ag+ showed an agar-diffusive bactericidal activity against gram negative Escherichia coli (E. coli) bacteria. Zn2+ exchanged zeolite membrane presented a bacteriostatic activity that is less diffusive in agar. As expected, non-exchanged zeolite membrane (in its Na+ form) have no effect on bacterial activity. This process is particularly interesting for the synthesis of a good quality FAU-type zeolite membranes with antimicrobial properties.

Preparation of Bactericadal Fillers From Georgian Heulandite-Clinoptilolite and Their Application for Paper Production. Ii. Bactericadal Paper

“…Despite the negative result of the disk diffusion test, all paper samples with metal-containing fillers exhibit antibacterial activity to some extent. A similar situation was described in the study of the antibacterial activity of a synthetic FAUtype zeolite membrane [7]. It was found that membranes exchanged with Ag + showed an agar-diffusive bactericidal activity against E. coli bacteria, but there was no inhibition halo around the initial Na + and Zn 2+ exchanged zeolite membranes.…”

“…for P-CuHCR 2 and P-ZnHCR 2 . The content of zeolite and silver in sample P-AgHCR approximately corresponds to that indicated in [4] for zeolites immobilized on cellulose nanofiber mats, and in [5] for zeolite powders delivering antibacterial performance to cellulosic paper; the silver content is slightly lower, and the zinc content is slightly higher than in a FAU-type zeolite membranes with antimicrobial activity [7].…”

“…However, when evaluating an impact on the colony forming activity (CFA) of a bacterial suspension, a significant decrease in CFA was observed for the bacterial solutions incubated with Zn 2+ exchanged zeolite membrane, suggesting a significant antimicrobial activity for this membrane. The authors of [7] explained this by the fact that "Zn 2+ exchanged zeolite membrane presented a bacteriostatic activity that is less diffusive in agar", and is inferior in activity to Ag + exchanged membrane.…”

A green approach to develop zeolite-thymol antimicrobial composites: analytical characterization and antimicrobial activity evaluation

“…Usually, non-exchanged zeolites (Na-zeolites) did not show antibacterial activity against various bacteria [ 50 , 51 ] even though Na-clinoptinolite resulted active against Helicobacter pylori [ 52 ] as well as commercial zeolite A showed antimicrobial activity against Acinetobacter junii and Saccharomyces cerevisiae in watery medium [ 53 ]. In this respect, ZEO 4A did not show antibacterial activity against different strains ( Table 6 ), even though slightly decreased the viability of S. aureus DSM 799 after 24h of incubation.…”

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

“…They exhibit attractive features that are superior to those of silica, such as their unique pores and their various framework compositions accessible by changing the Si/Al ratio or by substituting silicon atoms with atoms other than aluminum such as germanium or phosphorus. Zeolites also allow incorporating various metal cations in their micropores or external surface by cationic exchange or impregnation, allowing their use in different catalytic applications [ 5 , 6 , 7 , 8 ]. Unfortunately, when used in some catalytic reaction, conventional zeolites with micron-size particles have shown diffusion limitations (high diffusion path length) that can generate a deactivation of acid sites due to the retention of carbonaceous compounds [ 9 , 10 , 11 , 12 ].…”