Synthesis of Clinoptilolite Zeolite and Investigation the Influence of Various Factors on the Crystallization Process in Natural System Obsidian-Halloysite

Abstract

The crystallization process of a practically important zeolite of clinoptilolite has been studied, which can be used as an adsorbent, catalyst. The influence of various factors on the speed and selectivity of synthesis using natural minerals obsidian and halloysite of Nakhchivan has been investigated. The starting material was a natural mineral of Nakhchivan—volcanic glass obsidian from the peak of Gapydzhik of Ordubad district and halloysite of Pirigel deposits. The influence of temperature of 100–250°C, the mass ratio of the initial components of halloysite (H) and obsidian (O) H : O equal to 1 : 1, 1 : 2, 1 : 3, 2 : 1 and 3 : 1, a concentration of a thermal solution of NaOH of 10–30%, the duration of the process is in the range of 10–50 h and the “aging” process on the crystallization of clinoptilolite were studied. It has been established that the optimal conditions for the synthesis of clinoptilolite with 100% crystallinity and phase purity is as follows: temperature 150 ± 2°C, concentration of thermal solution of NaOH of 15–20%, quantitative ratio of the initial components of halloysite (H) and obsidian (O) H : O, equal to 1 : 2, processing time—20 h. The synthesis of zeolite of clinoptilolite using natural minerals from the Nakhchivan Autonomous Republic was carried out in the presence of tetramethylammonium hydroxide (TMAOH). The effect of temperature, concentration of thermal alkali solution, ratio of initial components, process time, duration of “aging” on crystallization of clinoptilolite was studied. It has been shown that violation of optimal synthesis conditions leads to a decrease in the selectivity of the process and the formation of other zeolites (phillipsite, gismondine), aluminosilicates (anortithe, albite) or mixtures thereof, as well as quartz and cristobalite. The “aging” process was studied in the duration range from 1 to 3 days. It has been established that an increase in the duration of “aging” leads to an increase in the linear rate of crystallization of clinoptilolite zeolite.