INFLUENCE OF ACID MODIFICATION ON HYDROPHOBIC/HYDROPHILIC PROPERTIES OF CLINOPTILOLITE

Abstract

Zeolites are natural microporous minerals of the hydrated aluminosilicate group of alkali and alkaline earth metals with a framework crystal structure. The open frame-hollow structure of zeolites with a rigidly fixed size of entrances to cavities and channels determines the specific adsorption, ion-exchange and molecular-sieve properties of zeolites. Therefore, zeolites are widely used for purification of natural waters and industrial effluents, air, soils, biological samples, concentration, separation and separation of heavy, alkaline and alkaline earth metals, and also for separation and adsorption of gases as catalysts. An important parameter of zeolites is the atomic ratio of the main elements of the Si/Al crystalline framework, which determines such properties of the mineral as the maximum ion-exchange capacity and selectivity to a certain ion, thermal, hydrothermal and radiation stability, surface characteristics and molecular sieve features, catalytic activity and other. Clinoptilolite is one of the most common natural minerals of zeolite. Zeolites are modified by physical or chemical methods to increase sorption capacity, selectivity to specific ions, and change surface properties. The acid/alkaline modification of clinoptilolite has been shown to control its hydrophobic/hydrophilic properties. As a result of acid treatment, Al is removed from the crystalline structure, resulting in an increasing in the specific surface area of the samples, a reduction in the width of the pores, and a reduction in the adsorption of water vapor. It has been shown that acid treatment leads to an increase in the hydrophobic properties of clinoptylolite as a result of a decrease in the number of Si-O-Al polar bonds.

Keywords

• clinoptilolite
• adsorption
• acid/base modification