Dielectric properties of organofunctionalized kaolinite clay and application in adsorption mercury cation

Abstract

Kaolinite clay samples from Amazon region, Pará state, Brazil, were first intercalated with dimethylsulfoxide (DS) followed by immobilization of (3-aminopropyl)triethoxysilane (APS). The samples were characterized by X-ray diffraction, and zero point charge determination. The chemically modified kaolinite samples showed modification of its physical–chemical properties including: specific area of 25.2–421.5 m 2 g −1 for K 1 and K 1-DS/APS, and 24.7–425.9 m 2 g −1 for K 2 and K 2-DS/APS. New d 0 0 1 values of 1.313 and 1.319 nm for the modified kaolinites K 1-DS/APS and K 2-DS/APS, respectively, were obtained. From electrical property investigations an increase in electric permittivity was observed for real ( ɛ |) and imaginary ( ɛ ||) at low frequencies, which are probably related to the interlayer molecules. The energetic effect caused by mercury cation adsorption was determined through calorimetric titration at the solid–liquid interface and gave net thermal effects that enabled the calculation of the exothermic enthalpic values and the equilibrium constant. From these values negative Gibbs free energy and positive entropy were calculated and this set of thermodynamic data is favorable for mercury/basic center interaction at the solid/liquid interface.