Water purification from cationic organic dyes using kaolin-based ceramic materials

The development of effective sorbents based on cheap natural raw materials for water purification from synthetic organic dyes is an important environmental problem. It is known that layered silicates are distinguished by mechanical strength, thermal and chemical resistance, high dispersion, ion exchange, availability and low cost. However, the main disadvantage of natural clays is their insufficiently high sorption capacity with respect to organic toxicants. Therefore, to increase it, the surface of clay minerals is modified by various physical and chemical methods. The object of study is kaolin from the Glukhovets deposit (Ukraine), the main rock-forming mineral of which is kaolinite. After its thermal modification followed by acid activation with chloride acid, sorbents with sufficiently high structural-sorption properties and increased sorption capacity with respect to the synthetic organic dye, methylene blue, are obtained. The influence of the conditions for the synthesis of ceramic materials on the physicochemical features of the dye removal from the aqueous medium is studied. The dependence of the values of methylene blue sorption by silicate sorbents on the temperature of kaolin treatment and the concentration of chloride acid, which was used for its acid activation, is studied. It has been established that the specific surface of the obtained samples is significantly affected by both the kaolin treatment temperature and the concentration of perchloric acid. Thus, under certain experimental conditions, sorption materials were obtained with a specific surface area of 140 m2/g, which significantly exceeds that for the original kaolin, which is 9 m2/g. A significant increase in the sorption capacity of acid-activated samples compared to the original clay and heat-treated forms was established. The value of the maximum sorption of methylene blue for acid-activated samples exceeds that for natural kaolin by almost 2 times and reaches 16 mg/g.