Disposal of polluted bentonite clays as a means of minimising environmental risk

Abstract

The effective disposal of spent clay sorbents reduce the anthropogenic impact on the environment and to improve recycling technologies for highly dispersed clays. Study aimed to investigate the sorption of organic dye molecules by spent bentonite, previously saturated with chromium (III) ions, with possible subsequent utilisation of the bentonite in pigment compositions. The study was based on a comparative analysis of natural, modified and spent montmorillonite using thermogravimetric analysis, the determination of the colloidal-chemical characteristics of the dispersions, the construction of adsorption isotherms and spectrophotometric monitoring of dye concentrations. Changes in the structure, surface charge, interplanar distance, specific surface area and sorption activity of the samples were analysed. The study established that the saturation of montmorillonite with chromium (III) ions does not lead to a significant deterioration in its properties. This study demonstrated that spent bentonite retains its porous structure, active sorption sites and the ability to effectively adsorb anionic dyes over a wide range of concentrations. The study established that chromium-containing sites can enhance the fixation of dye molecules through complex formation and interaction with the functional groups of the adsorbates. The characteristics of the adsorption of anionic green, blue and black dyes have been analysed, in particular the influence of molecular structure, molecular size and spatial hindrance on adsorption. The study developed an approach for the utilisation of spent bentonite as a secondary mineral base to produce organo-mineral pigment compositions without additional chemical modification. The practical value of these results is determined by their potential application by specialists in environmental safety, wastewater treatment, materials science and pigment coating technologies.