Kinetic and thermodynamic assessment on isoniazid/montmorillonite adsorption

Abstract The properties of montmorillonite (Mt) as a natural nanocarrier of drugs have been fully reported. Isoniazid (INH), a first-line tuberculostatic drug, was intercalated into this inorganic matrix and the equilibrium and thermodynamic aspects of the adsorption process were evaluated. Adsorption experiments were performed at different times and temperatures in aqueous medium. The overall adsorption process was the result of two simple processes: INH adsorption on the activated sites of Mt. followed by a slight precipitation phase of INH molecules over the adsorbed monolayer. Formation of the nanohybrid was spontaneous, exothermic and exoentropic, obtaining an increase in the thermodynamic stability of the system. The hybrid material (Mt-INH) was successfully prepared with high drug loading. Solid state characterization of the pure materials and the resulting nanohybrid was carried out. Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC), surface charge, X-ray powder diffraction (XRPD) and high resolution transmission electron microscopy (HRTEM) coupled with energy dispersive spectroscopy (XEDS) and elemental X-ray maps served to correctly resolve the structure of the nanohybrid and to assess the nature and degree of the drug-clay interactions.