Bactericidal adsorbents obtained by ion exchange modification of natural phillipsite

Abstract

Zeolite adsorbents and ion exchangers reducing the concentrations of contaminants in aqueous medium, containing bioactive metals and endowed with bactericidal properties are promising for application in environmental protection practice and medicine. Phillipsite has a high ion exchange capacity and can be used to produce such materials. Silver-, copper-, and zinc-containing micro-mesoporous zeolite materials have been prepared on the basis of natural phillipsite from the Shukhuti field, Western Georgia (Saqartvelo), using ionexchange reactions between grinded and washed by dilute hydrogen chloride solution zeolite 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 analysis and sorption data (nitrogen adsorption-desorption isotherms at 77 K and water vapour sorption at room temperature), powder X-ray diffraction patterns, Fourier transform infra-red spectra, and scanning electron microscope images. Obtained materials keep the crystal structure and general sorption and ion-exchange properties of phillipsite, they contain up to 230 mg/g of silver, 66 mg/g of copper, and 86 mg/g of zinc, which is several times higher than the content of bioactive metals in the cationexchange forms of clinoptilolite and synthetic zeolites obtained by ion exchange in the liquid phase described in the literature. Prepared silver-, copper-, and zinc-containing phillipsites show bactericidal and bacteriostatic activity towards Escherichia coli regardless of whether the number of released ions of the bioactive metal reaches the minimum inhibitory concentration in solution. The procedure of dry ion-exchange synthesis leads to an increase in the dispersion of the material, but does not affect the developed mesoporous system of phillipsite and the total pore volume averaging 0.285 cm 3 /g. The compliance of proposed method for preparation of silver-, copper-, and zinccontaining forms of phillipsite with high environmental standards is confirmed by its low Sheldon's factor E in comparison with the similar green chemistry metrics of conventional methods of the ion exchange in solutions.

Application of Georgian Natural Analcime for Production of Ion Exchangers

“…As expected, the highest indicators are characteristic of synthetic zeolite, the achieved content of bioactive metals is several times higher than indicated in [11,12] (0.27, 0.27, and 0.28 mmol/g for Ag, Cu, and Zn, respectively). Of course, the specific content of bioactive metals in analcime is lower, but it is comparable to the content in recently obtained phillipsites (230, 66, and 86 mg/g of Ag, Cu, Zn, respevtively [13]) and is higher than that shown for clinoptilolites of various origins [14][15][16].…”

“…Ion exchange reactions do not change the crystal structure of the zeolite, this is confirmed by the powder X-ray diffraction patterns of the modified samples: characteristic peaks of the ANA structure (2Θ = 15.8, 26.0, and 30.5 o ) remain in XRD patterns, only their intensities change; XRD pattern of the LTA structure [10] remains unchanged. No notable changes were observed in the IR spectra of the modified samples as compared with the vibration bands of starting zeolitic material, only the intensity of the broad band at 3200 -3700 cm -1 corresponding to the asymmetric stretching of OH group is increased due to the larger number of water molecules in the samples containing silver, copper, and zinc.…”