Changes in physicochemical and sorption properties of bleaching clay during heat treatment

The work investigated changes in the physicochemical and colloidal sorption properties of heat-treated bleaching clay after its use in the process of refining vegetable oil. As a comparison, we used bleaching clay heat-treated at different temperatures. Colloidal sorption properties were studied by adsorption of methylene blue dye from aqueous solutions. It has been shown that the adsorption of methylene blue occurs more efficiently with clay fired at a temperature of 350°C. Adsorption in the saturation region for clay heat-treated at 350°C was 0.28 mmol/g or 89.6 mg/g, and for clay fired at 250°C – 0.24 mmol/g or 76/8 mg/g. When the firing temperature increases above 500°C, the adsorption properties of the bleaching clay waste decrease, probably due to the combustion of the carbon layer. Using the example of spent bleaching clay from the Alekseevsky oil extraction plant, it was revealed that during the heat treatment of the material, various types of water (free, interpacket, chemically bound) are removed, which leads to a change in colloidal sorption properties such as particle surface relief, specific surface area, sorption capacity ζ-potential.