The modified clay performance in adsorption process of Pb2+ ions from aqueous phase—Thermodynamic study

Smectite clay sample from Acre state, Amazon region, Brazil, was used for pillaring and organofunctionalization process in the present study. The pillaring ions were obtained through chemical reaction of AlCl3·6H2O/NaOH, Ti(OC2H5)4/HCl, Cr3(OH)44+/NaOH and ZrOCl2·8H2O solutions. The resulting materials were organofunctionalized with 3-Aminopropyltriethoxysilane (APS). The adsorption capacity was investigated with Pb2+, ions from aqueous solution in pH 5.0 and controlled temperature 298 ± 0.20 K. The Langmuir, Freundlich and Temkin adsorption isotherms models have been applied to fit the experimental data, linear regression. The energetic effect caused by metal 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.