Changes in the Physicochemical and Sorption Properties of Bleaching Clay in the Course of Thermal Treatment

The work is devoted to studying changes in the physicochemical and colloid–sorption properties of bleaching clay thermotreated after its use in the process of refining vegetable oil. Bleaching clay thermotreated at different temperatures has been used for comparison. The colloid–sorption properties have been studied by measuring adsorption of methylene blue dye from aqueous solutions. It has been shown that clay annealed at 350°C adsorbs methylene blue most efficiently. In the saturation region, the adsorption by clay thermotreated at 350°C has amounted to 0.28 mmol/g or 89.6 mg/g, while the adsorption by clay annealed at 250°C has appeared to be 0.24 mmol/g or 76.8 mg/g. When the annealing temperature is elevated above 500°C, the adsorption properties of the bleaching clay waste decrease, probably, due to the combustion of the carbon layer. Using bleaching clay waste from the Alekseevsky oil extraction plant as an example, it has been revealed that, during the thermal treatment of the material, various types of water (free, interpackage, and chemically bound one) are removed, thus leading to changes in the colloid–sorption properties, such as particle surface relief, specific surface area, sorption capacity, and ζ potential.