Intercalation of 8-hydroxyquinoline into Na(I)- and Zn(II)-Tunisian montmorillonites: characterization and luminescence properties of elaborated hybrids

The preparations of hybrids based on montmorillonite as inorganic receiver and 8-hydroxyquinoline (8HQ) as organic host have been previously studied via solid-solid reaction at room temperature without studying the effect of physic-chemical parameters on the adsorption processes. In our present work, Na- and Zn-hybrids of 8HQ were elaborated by the extraction of 8HQ by Na(I)- and Zn(II)-montmorillonites from aqueous solution, at different pH and at different initial concentration of 8HQ. The modeling of adsorption isotherms showed that the adsorption of 8HQ follows the Langmuir model at pH 2 and the Freundlich model at pH 6 and 10. The characterization of hybrids showed firstly the swelling properties of montmorillonites and secondly the intercalation of 8HQ in the interlayer space of Na-montmorillonites (Na-Mont) and Zn-montmorillonites (Zn-Mont). The inclusion of 8HQ molecules in the inorganic receiver (clay) is assigned to its complexation with Na+ and Zn2+. The maximum quantities Q(ads) of adsorption of 8HQ occur at pH 2 with Na-Mont and at pH 6 with Zn-Mont. The double Q(ads) of 8HQ adsorbed by Zn-Mont, compared to that of Na-Mont, confirms the formation of complexes [Zn(8HQ)(2)](2+) in the interlayer spaces of Zn-Mont. The thermal analysis demonstrated the stability of both Na- and Zn-hybrids of 8HQ than the free complexes [Na(8HQ)](+) and [Zn(8HQ)(2)](2+). The luminescence properties of resulting hybrids showed the high emission of the hybrid 8HQ/Zn-Mont at pH 6, almost 100 times more intense than 8HQ/Na-Mont.