Influence of the nature of the solvent on the selectivity of the sorption of α-tocopherol on modified clinoptilolite

Abstract

One of the areas of application of aluminosilicates is the development of carriers of drugs and vitamins with prolonged action. The mechanism of fixing BAS on the surface is influenced by both the properties of the solvent and the hydrophilic-hydrophobic balance of the adsorbent and adsorbate. It is of interest to establish the influence of the polarity of the solvent on the adsorption of a fat-soluble vitamin, in particular α-tocopherol, on a modified clinoptilolite with different degrees of hydrophobicity.

In the work, vitamin E (α-tocopherol) from Sigma (Germany) was used. As a sorbent, frame aluminosilicate clinoptilolite (deposit of the Subpolar Ural Ugra), recommended as an enterosorbent Klimont, was chosen. Adsorption of α-tocopherol was studied on 4 M hydrochloric acid [12] activated and modified with organochlorosilanes (methyldichlorosilane (DMDCA) and trimethylchlorosilane (TMXC)) sorbent [13]. Ethanol, hexane and ethyl acetate were used as solvents. The sorption equilibrium in the system "modified clinoptilolite (fraction 0.02-0.06 mm) - solution of α-tocopherol" was studied at a temperature of 295 ± 2 K under static conditions using the variable concentration method. IR spectra of modified clinoptilolite before and after sorption of α-tocopherol were recorded on a Bruker Equinox 55 spectrometer with Fourier transform in diffuse reflection (DRIFT) mode in the 400-4000 cm-1 frequency range.

The paper presents the results of studying the regularity of sorption of α-tocopherol on acid-activated and methylated alumosilicate framed clinoptilolite. The influence of the polarity of the solvent, the nature of the reaction centers and their availability on the equilibrium adsorption characteristics of α-tocopherol on clinoptilolite is revealed. It has been established that the acid-activated sorbent possesses an increased affinity for α-tocopherol molecules from the ethanol solution. The methylated sorbent is highly selective for α-tocopherol when adsorbed from hexane.

An increase in the selectivity of acid-activated clinoptilolite to vitamin from ethanol was revealed. It has been shown that the adsorption of alpha-tocopherol on clinoptilolite modified with methyl silanes increases with decreasing polarity of the solvent. The mechanism of vitamin fixation on acid-activated and modified TMHC and DMDCA clinoptilolite was established.