Removal of Furfural from Aqueous Solutions by Adsorption Using Organobentonite: Isotherm and Kinetic Studies

Lubricant refineries are facing pollution problems associated with the occasional loss of furfural. This constitutes both an economic loss and an environmental hazard, especially for aquatic organisms. Some studies on the removal of furfural by adsorption onto hydrophobic polymeric resins (XAD-4 and XAD-7), activated carbon and the nanoporous material MCM-48 have been published, but none provides information on the adsorption of furfural onto clays. In the present work, we have studied the efficiency of sodium bentonite modified with the cationic surfactant cethyltrimethylammonium bromide (CTAB) in the adsorption of furfural. The structures of both natural and modified bentonites have been examined using XRD and FT-IR analyses. Adsorption studies were performed in a batch system, with the effects of various experimental parameters such as the contact time, the organobentonite concentration, pH, the initial furfural concentration and the temperature being evaluated. Kinetic results showed that furfural could be removed by CTAB-bentonite after contact for 6 h, with the adsorption process being well described by the pseudo-second-order reaction model. Furfural sorption onto CTAB-bentonite was characterized by a linear isotherm, with the adsorption capacity towards furfural being reduced by increasing temperature. A comparison of furfural adsorption capacities revealed that the capacities decreased in the following order: CTAB-bentonite > XAD-4 > XAD-7.