Effect of dimethyl sulfoxide intercalation into kaolinite on etheramine adsorption: experimental and theoretical investigation

Abstract

This study evaluated the effect of dimethyl sulfoxide (DMSO) intercalation in natural kaolinite (KN) on etheramine adsorption. The effects of the parameters pH, initial etheramine concentration and adsorbent mass were investigated using central composite design. Optimal conditions were determined using response surface methodology. Theoretical calculations were performed to optimize the geometries of the kaolinite, DMSO, KDMSO, molecular and protonated etheramine structures, as well as the interaction between etheramine and kaolinite. XRD and FTIR results confirm the intercalation of DMSO into kaolinite, the intercalation process caused a significant increase in the isoelectric point. The results show that the adsorption was more efficient in pH 10 and etheramine concentration of 400 mg L-1 for both adsorbents, and 0.1 g of KN and 0.2 g of KDMSO. The kinetic data most accurately fit the pseudo-second-order model. The fitting of the experimental data to the isotherm models indicated that the Sips is the most appropriate model. The calculation of Eads revealed that mechanism of etheramine removal by KN and KDMSO involve chemisorption. The reusability tests determined that after four uses, the etheramine removal efficiency does not change significantly, enabling the use of kaolinite for wastewater treatment. Theoretical studies have enabled a better understanding of the intercalation process. In addition to increasing the interlayer spacing (2.50–8.01 Å), the introduction of the DMSO molecule modifies the charge distribution in the kaolinite structure, which contributes to the increase in the amount of etheramine adsorbed. The protonated etheramine molecule interacts more effectively with the KDMSO.