Adsorção de cromo hexavalente por hidróxido de alumínio amorfo em meio aquoso: isotermas e termodinâmica

Abstract

The presence of potentially toxic metals in the environment lethally affects the ecosystem, which means that environmental responsibility actions have being developed in order to minimize the damage caused by those elements. Therefore, this study has been evaluated the removal of hexavalent chromium by amorphous aluminium hydroxide in aqueous media under experimental temperature conditions of 25, 45 and 55 °C, and concentrations of adsorbate ranging from 30 to 300 mg L -1 . The adsorbate has been synthesized by the precipitation method, and characterized by the diffuse reflectance in near infrared (NIR) method, obtaining three significant peaks that described the product. By using partition coefficient (Kp), it was possible to establish the saturation point on the adsorbate active sites. The equilibrium isotherms, based on the determination coefficient (R2 ) indicated the adjustment order: Sips> RedlichPeterson> Koble-Corregan> amorphous aluminium hydroxide Langmuir> Jovanivich> Freundlich. The negative values of (∆G°) and enthalpy (∆H°) indicated that the reaction is spontaneous and the process is exothermic, respectively. The maximum adsorption capacity (qmax) of the amorphous aluminium hydroxide was 77,52 mg g-1 , which proves the removal efficiency in the hexavalent chromium in aqueous media.