Immobilized chitosan-montmorillonite composite adsorbent and its photocatalytic regeneration for the removal of methyl orange

In this study, chitosan and clay-montmorillonite (CS-MT) composite was prepared and immobilized on glass plates for the removal of methyl orange (MO) dye from aqueous solution. The immobilized CS-MT was characterized using scanning electron microscopy-energy dispersive X-ray (SEM–EDX), Fourier transform infrared (FTIR), pore structural analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The addition of MT into the CS matrix produced a heterogeneous surface and slightly increased the surface area of the composite film. The adsorption study revealed that the pseudo-second-order kinetic and Langmuir isotherm models could well describe the adsorption of MO dye onto the immobilized CS-MT. After saturation, the spent CS-MT was regenerated via the TiO2 photocatalytic oxidation under UV–Vis irradiation. During the regeneration, the spent CS-MT underwent two concurrent processes: desorption of MO dye and photocatalytic oxidation of desorbed dye by the TiO2 photocatalyst. The photocatalytic regeneration of the spent immobilized CS-MT was highly effective in ultra-pure water at pH 11, as it mineralized up to 86% of the desorbed MO within 20 h of regeneration time.