Variable Temperature Infrared Spectroscopy Studies of Aromatic Acid Adsorbate Effects on Montmorillonite Dehydration

Molecular interactions between benzoic, salicylic, and acetylsalicylic acids and water contained within montmorillonite clay interlayer spaces are characterized by using variable temperature diffuse reflection infrared Fourier transform spectroscopy (VT-DRIFTS). By using sample perturbation and difference spectroscopy, infrared (IR) spectral variations resulting from the removal of interlayer water are used to characterize aromatic acid local environment changes. Difference spectra features representing functional group perturbations are correlated with changes in IR absorptions associated with –O–H and –C = O stretching vibrations. Results suggest that adsorbate carboxylic acid functionalities participate in extensive hydrogen bonding and that the strengths of these interactions are diminished when clays are dehydrated. The nature of these interactions and their temperature-dependent properties are found to depend on adsorbate structure and concentration as well as the clay interlayer cation.

Triazines removal by selective polymeric adsorbent

The objective of the study was to investigate sorption of simazine, atrazine, propazine and terbuthylazine on specific polymeric adsorbent and thereby evaluate the possibility of triazine-based herbicide removal from the aqueous solution. In order to obtain polymer adsorbent for triazines removal, the poly(divinylbenzene) was synthesized in radical polymerization using bead polymerization, and modified with maleic anhydride in Diels–Alder reaction with subsequent base hydrolysis. The porous material containing carboxyl groups was obtained. Experiments have been performed in single and multi-component mixtures of herbicide in the ppm concentration range. Introduction of carboxyl groups into polymer structure resulted in obtaining specific interactions, such as hydrogen bonds between modified poly(divinylbenzene) and triazines, therefore intensification of adsorption was observed. Calculated distribution coefficients of triazines (K = 2600–35 100) testify to their effective removal from aqueous solutions on the studied adsorbent. Selective sorption of triazines is observed and explained in relation to the binding mechanism which involve hydrophobic interactions and hydrogen bonding. The effect of the adsorbate structure on the ability to form specific interactions with the tested adsorbent was investigated. The kinetic of sorption and the parameters of Langmuir and Freundlich isotherms for the studied systems were determined.