Insight into the synergistic photocatalytic-adsorptive removal of methyl orange dye using TiO2/chitosan based photocatalyst

Abstract

The removal of methyl orange (MO) dye has been studied using TiO₂/chitosan-montmorillonite (TiO₂/Cs-MT) bilayer photocatalyst which also functions as an adsorbent. The dye removal experiments were conducted in the dark and under UV-Vis light irradiation via adsorption and photocatalysis-adsorption processes, respectively. The adsorption modelings were employed on the dark experimental data and compared with the immobilized and suspended Cs-Mt counterparts. It was found that the bilayer photocatalyst closely followed the adsorption properties of immobilized Cs-Mt which obeyed the pseudo-second-order kinetic and film diffusion models. Fluorescent analysis revealed that the charge separation was enhanced in the presence of Cs-Mt as a sub-layer of TiO₂. Under light irradiation, the photocatalytic activity of TiO₂/Cs-MT corresponded to its adsorption counterpart trend and was optimized at pH 6.5 and 20 mg L^-1 of MO dye solution. High removal efficiency and synergism of MO by TiO₂/Cs-MT over TiO₂ single layer were observed throughout the 10 cycles of application due to contribution of adsorption of Cs-Mt sub-layer and photocatalysis by TiO₂ top layer.

Keywords: Chitosan; Methyl orange; TiO(2).