Nitrogen monoxide storage and release properties of local natural zeolite for biological applications

Abstract

In this thesis, nitrogen monoxide (nitric oxide, NO) adsorption, storage and release properties of the local clinoptilolite-rich natural zeolite and its modified forms were investigated. The zeolite particles (75-150 .m, 150-250 .m) were prepared through treatment of the natural zeolite with NaCl and consecutively with aqueous metal (Co2+, Ag+, Cu2+, Fe3+) salt solutions under different conditions. The prepared zeolites were characterized in terms of particle size and morphology, density, mineral and elemental composition, dehydration behavior, porosity, surface area, and infrared spectroscopic characteristics. The total adsorption capacities of the zeolites for NO were calculated from the breakthrough curves obtained at 30 oC on a dynamic adsorption system and found to be in the range of 5.5-8.5 mmol/g. NO was adsorbed in the zeolites reversibly and irreversibly. The total adsorption capacity was mainly contributed from the irreversible adsorption. The irreversible adsorption capacity was related to the type and amount of metal cation in the zeolite. The temperature-programmed desorption (TPD) profiles provided information about the desorption kinetics of the NO species formed on the zeolite surface upon the adsorption. The bands detected in the DRIFTS spectra upon admission of NO were assigned to reversibly and irreversibly adsorbed NO species. The unmodified and iron-sorbed zeolites gained antibacterial activity against E. coli after NO loading. The unmodified zeolite also exhibited antibacterial activity against B. subtilis after NO loading. The NO-loaded unmodified zeolite also exhibited complete bactericidal activity upon contact with both bacteria cells. The unmodified and copper-sorbed zeolites exhibited similar NO release kinetics.