Photocatalytic Disc-Shaped Composite Systems for Removal of Hazardous Dyes in Aqueous Solutions

Abstract: Rice straw ash (RSA)-based composites, containing titania (TiO2, 50%) or copper phthalocyanine complex (CuPc, 1.0%) or TiO2-CuPc combination, were prepared in disc- shaped forms. Mechano-mixing of TiO2 could develop the mesoporous nature of the composites. TiO2 existed as nanoparticles of average sizes in the range, 16 – 20 nm, homogeneously dispersed on the surface of the ash matrix. Compression of the solids using polymer binder led to only a small decrease in surface parameters, pore dimensions and average size of contained silica nanocrystallites. The composites discs were applied in the adsorption and photo-catalytic degradation (using visible light) of methylene blue (MB) dye, at ambient temperature and neutral pH. The rate of adsorption of MB on the studied composites deceased, according to the second order kinetic model, in the order: RSA-TiO2- CuPc> RSA-TiO2> RSA> RSA-CuPc. TiO2 or TiO2-CuPc combination enhanced the rate of MB adsorption due to development of the composite surface characteristics. The rate of visible-photodegradation of MB, in terms of the first order kinetic model, deceased in the order: RSA ≈ RSA-TiO2> RSA-CuPc> RSA-TiO2-CuPc. TiO2, by generated hydroxyl radicals ( OH) and superoxide radicals