Synthesis and characterization of clays and organoclays for the selective adsorption of N-nitrosamines.

摘要

According to the United States Surgeon General's warning: "Tobacco Smoke Causes Serious Health Problems." In this research, N-nitrosamines were chosen for adsorption studies because they are some of the most potent carcinogenic compounds in tobacco smoke. The main hypothesis of this investigation is that clays can be used to trap N-nitrosamines. Clays were selected because they are naturally charged particles. The clay's natural charge can be the key factor for adsorbing N-nitrosamines. Montmorillonite clays of differing cation exchange capacities were chosen to study the effect of clay's surface charge density on the adsorption of N-nitrosamines. These clays were also modified to enhance the adsorption and selectivity to trap N-nitrosamines. The chemical approach is to characterize and use these clay materials as solid stationary phases for infinite dilution inverse gas chromatography. Clays were characterized by X-ray diffraction, Nitrogen/Carbon elemental analysis, Surface Area and Thermal analysis. Characterization results indicated new "porous and non-porous organoclay" materials.; The binding energies for the adsorption of N-nitrosamines onto these clay adsorbent materials were calculated via a Clausius-Clapeyron relation from the infinite dilution inverse gas chromatography specific retention volume. These binding energies were used to develop, hypothetical mechanisms for the adsorption process. Theoretical calculations for the topography of the clay and molecular dimensions of the N-nitrosamines were used to complement the hypothetical adsorption mechanisms.; Different adsorption trends were discovered and therefore different mechanisms were proposed. The mechanisms for the binding of N-nitrosamines on the clay adsorbent materials were: (1) ion-permanent dipole and additive London dispersive attractive forces (on the surface of sodium homoionic clays), (2) additive London dispersive attractive forces (in the pores of organoclays) and (3) additive London dispersive attractive forces (on the surface of non-porous organoclays). All of these adsorption mechanisms were affected by the clay's surface charge density and by the molecular size of the N-nitrosamines.; This investigation indicates that clays can be used to trap N-nitrosamines; and that the adsorption of N-nitrosamines on certain organoclay adsorbent materials is simultaneously stronger and selective. The results of this research indicate that clays and organoclays are an alternate solution to the adsorption problem of N-nitrosamines.