New polyurethane-anatase titania porous hybrid composite for the degradation of azo-compounds wastes

New TiO₂-based organic–inorganic porous hybrid materials were developed for color degradation and tested in azo-compounds aqueous solution. Porous composite materials, with pore size between 100 and 200 μm and pore volume fraction between 62% and 76%, were synthesized using micro-particles of TiO₂ in anatase phase agglutinated with solvent-free, mono-component polyurethane; the pores were generated by the CO₂ produced during the chemical reaction. The high porosity of the samples improves the contact with the colored solution increasing the photocatalytic effect. The degradation process was well fitted using a first order chemical reaction and the constant rate k determined. The best samples showed k values of 0.091 h⁻¹ and 0.076 h⁻¹ using visible light with a power of 100 mW/cm² and k values of 1.465 h⁻¹ and 1.652 h⁻¹ using UV light with a power of 80 mW/cm²; these values are comparable or better to other reported in literature obtained under similar conditions. Additionally, the use of polyurethane increases the abrasion resistance improving the lifetime of the photocatalytic material. The materials were characterized using X-rays diffraction, SEM and UV–Vis spectroscopy.