Effect of Thermal Treatment on the Physicochemical Characteristics and Sorption Efficiency of Natural Diatomite and Zeolite

The study presents a comparative analysis of the sorption properties of natural and modified diatomite and zeolite of Kazakhstani origin under dynamic conditions of adsorption of methylene blue (MB). The aim of the study was to experimentally identify the effect of thermal and chemical treatment on the physico-chemical characteristics of minerals and their sorption efficiency. The samples were characterized by BET analysis, Fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and determination of the residual dye concentration after passing the solution through the sorbent layer. It has been shown that moderate heat treatment of diatomite at 400 °C increases its specific surface area from 34.25 to 46.32 m2/g and improves sorption capacity (removal of MB ≈ 53 %), while heating to 700 °C leads to a decrease in porosity and sorption efficiency (≈ 39 %). For zeolite, it was found that the natural sample has limited sorption activity (≈ 58 %), but thermal activation (500 °C) increases the result to ≈ 72 %. The most pronounced effect is observed after acid modification and subsequent calcination: the specific surface area increases to 80.32 m2/g, and the degree of removal of methylene blue reaches about 86%, which is comparable or exceeds the literature data for similar materials. Comparative analysis shows that the sorption activity of diatomite is mainly determined by textural changes during moderate heat treatment, whereas the effectiveness of zeolite increases significantly due to chemical modification and an increase in the number of available ion exchange centers.