Enhancement of chromium removal efficiency on adsorption and photocatalytic reduction using a bio-catalyst, titania-impregnated chitosan/xylan hybrid film

• A TiO2-impregnated chitosan/xylan hybrid film was synthesized and applied as a bio-catalyst.
• Adsorption ability of hybrid film relies on the protonated amino group (–NH3+) on its surface.
• Pseudo-first order pattern well described the photocatalytic reduction of Cr(VI).
• High performance in Cr(VI) removal using the hybrid film with kinetics are discussed.

A novel bio-catalyst, titania-impregnated chitosan/xylan hybrid film was prepared by addition of titanium dioxide in the mixture solution of chitosan and xylan in acetic acid. The structure and surface morphology of the obtained catalyst were characterized by X-ray diffraction, and scanning electron microscope. The adsorption and photocatalytic activity of this photocatalyst were evaluated by photocatalytic reduction of chromium(VI) in aqueous solution under ultraviolet irradiation. From the rough surface modification from xylan addition and the chelating ability of chitosan, the enhancement of chromium(VI) removal by adsorption and photocatalysis of this bio-catalyst was pronounced. The photocatalytic reduction rate of chromium(VI) was 0.56 × 10−3 and 0.03 × 10−3 ppm-min for the titania bio-catalyst and titania nanopowder, respectively. The adsorption of chromium(VI) followed the Langmuir adsorption isotherm model. Pseudo-first order model well described the photocatalytic reduction reactions of the bio-catalyst. Significant dependence of chromium(VI) removal on the titania and chitosan loading can be explained in terms of the relationship between kinetics of chromium(VI) photocatalytic reactions and the loading amount of each chemical. According to the Langmuir–Hinshelwood model, the photocatalytic rate constant of surface reaction of chromium(VI) was increased with an increasing of chemical loading (titania and chitosan) in bio-catalyst. Results from this work exhibited that the novel titania-impregnated chitosan/xylan hybrid film can be a potential material for heavy metal removal in photocatalytic process.