Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium—Thermodynamic of adsorption process

Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298±1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic (ΔintH=−4.15–5.98 kJ mol−1) accompanied by increase in entropy (ΔintS=41.32–62.20 J k−1 mol−1) and Gibbs energy (ΔintG=−22.44−24.56 kJ mol−1). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid–liquid interface in the spontaneous process.