Bactericidal metal-containing zeolites

Abstract

The coronavirus pandemic has increased interest in antibacterial agents containing bioactive metals, for which zeolites are promising carriers. On the other hand, zeolite adsorbents and ion exchangers containing bioactive metals and endowed with bactericidal properties are promising for water treatment and other environmental and medical applications.Silver-, copper-, and zinc-containing microporous materials have been prepared on the base of natural analcime,phillipsite and heulandite from Georgian manifestations using ion-exchange reactions between zeolite microcrystals and a salt of a corresponding transition metal in the solid phase followed by washing with distilled water. Synthesized in such way adsorbent-ion-exchangers are characterized by chemical composition based on the X-ray energy dispersion spectra, powder X-ray diffraction patterns, Fourier transform infra-red spectra and low-temperature adsorption-desorption isotherms of N2. Obtained materials remain the zeolite crystal structure and contain 130–230 mg/g of silver, 65–72 mg/g of copper, and 58–86 mg/g of zinc, as compared with modified samples of synthetic type A zeolite containing up to 380 mg/g of silver, 150 mg/g of copper, and 150 mg/g of zinc. Prepared metal-containing materials show bacteriostatic activity against Gram negative bacterium Escherichia coli, Gram positive bacteria Staphylococcus aureus and Bacillus subtilis, fungal pathogenic yeastCandida albicans, and a fungus Aspergilusniger, and natural zeolites enriched with biometals exhibit a synergistic effect – their mixtures have a higher bacteriostatic activity. It is shown that mixtures of copper and zinc forms have a higher activity than the silver-containing form, which is very important from a practical point of view for replacing expensive silver with cheaper copper and zinc. It has been found that the bacteriostatic activity of metal-containing zeolites is determined not only and not so much by the ions of bioactive metals released into the liquid medium, but an important role ininhibiting the growth of microorganisms plays a type of zeolite matrix. Despite the relatively low ion-exchange capacity, heulandite turned out to be a fairly effective matrix for bioactive metals.