TiO2 supported on Salvinia molesta biochar for heterogeneous photocatalytic degradation of Acid Orange 7 dye

Composites were prepared using Salvinia molesta biochar as a carbonaceous anchor for TiO2, employing two synthesis routes: sol-gel and mechanical mixing. TTiP and TiOSO4 were tested as TiO2 precursors. The composites were characterized using IR spectra, X-ray diffractograms, band gap energies, g Factor of EPR, surface areas, pore sizes and volumes, and scanning electron micrographs of the surfaces. For both synthesis routes, the composites prepared from TTiP showed higher crystallinity, lower band gap, and larger pore size. Due to these characteristics, the samples produced using this precursor presented the best performance in terms of both adsorption (46.5% at 60 min) and photocatalytic efficiency (57.6% at 180 min) under UV irradiation (F15 bulb, GE, 15 W, wavelength range (similar to)380 - 480 nm). The results showed that the impregnation method had a smaller influence on the photocatalytic efficiency of the composites, compared to the effect of the type of TiO2 precursor. However, impregnation by mechanical mixing produced composites that presented higher performance, compared to use of the sol-gel method. This sample presented similar ability to degrade the AO7 in up to six recycles. The (OH)-O-center dot and O-2(center dot-) radicals generated by composite were the main responsible for photodegradation of AO7 and quinone-like structures present in salvinia's biochar, being the major electron acceptors responsible for decreasing the electron/hole recombination.