Adsorption of Low-Molecular-Weight Amines in Aqueous Solutions to Zeolites: An Approach to Impeding Low-Molecular-Weight Amines from Regenerating N-Nitrosamines.

The combined effects of the porous structure, acidity, and ion-exchange properties of zeolites and the structures of the degradation products of nitrosamines in aqueous solution on adsorption were evaluated. The degradation products of nitrosamines including the aliphatic low-molecular-weight amines methylamine, dimethylamine, ethylamine, and diethylamine and the aromatic amine aniline all exhibited significant adsorption affinities to HZSM-5 zeolites, and aliphatic low-molecular-weight amines exhibited much greater adsorption affinities to HY zeolite than to NaY and HZSM-5 zeolites, but aromatic amines exhibited little adsorption affinity to HY and NaY zeolites. The results of the pH-dependency experiments further indicated that the acidity and polarity of the adsorbates and the acidity of the adsorbents play a combinational role in determining the significance of the adsorption interactions between low-molecular-weight amines in aqueous solution and zeolites. We propose that the acid-base and electrostatic interactions and the shape-selective adsorption properties of HZSM-5 zeolites are all responsible for the adsorption of aliphatic and aromatic low-molecular-weight amines on HZSM-5 zeolites in aqueous solution and that the acid-base and electrostatic interactions and ion-exchange properties of Y-type zeolites all contribute to the adsorption of aliphatic amines on Y-type zeolites in aqueous solution. The findings of the present study might have significant implications for the removal of low-molecular-weight amines from aqueous solutions and the thorough control of N-nitrosamines in water with zeolites. [ABSTRACT FROM AUTHOR]