Performance of natural and modified smectite: kinetic and thermodynamics involving arsenic (V) adsorption

Abstract

A natural smectite sample has been modified by organofunctionalization process using synthetic route involved the reaction of 2-mercaptopyrimidine with 3-chloropropyltriethoxysilane. The resulting material (S MPY ) was characterized by SEM, FTIR, textural analysis and 29 Si MAS-NMR. The ability of this material to removed As (V) from aqueous solution was followed by series of adsorption isotherms adjusted to the Langmuir equation at room temperature and pH 2.0. The kinetic parameters analyzed by Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k 2 in the 4.9 to 14.0 mmol -1 min -1 range for S MPY . The adsorption process was exothermic (D int H = -4.09 to -5.79 kJ.mol -1 ) accompanied by increase in entropy (D int S = 41.29 to 61.80 JK -1 .mol -1 ) and Gibbs energy (D int G = -22.34 to -24.19 kJmol -1 ). The energetic effect caused by arsenic cation adsorption was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant. Keywords: adsorption, smectite, kinetic, thermodynamic, arsenic. Resumo Uma amostra de esmectita natural foi modificada por processo de organofuncionalização usando rota sintética, envolvendo a reação de 2-mercaptopirimidina com 3-cloropropiltrietoxisilano. O material resultante (S MPY)

ACEME: Direct Aqueous Mineral Carbonation of Dunite Rock

“…We postulate that vicinal silanol group formation has occurred during the carbonation reaction as a result of the amorphous phase reacting with water. A new broad band in 3600-3100 cm −1 region is also observed, and this band has been attributed to the formation of silanol nests [25][26][27][28][29]. Silanol nests are formed through interaction of different silanol groups by extended hydrogen bonding.…”