Industrial and agroindustrial wastes: an echotechnological approach to the production of supported photocatalysts

Agroindustrial wastes (rice husk, exhausted bark acacia, and tobacco dust) and foundry sands from the iron foundry industry were employed as a support source for photocatalysts. TiCl₄ was used as the titanium precursor in the preparation of the supported photocatalysts. The solids were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), diffuse reflectance spectroscopy over the ultraviolet range (DRS-UV), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), nitrogen adsorption–desorption at −196 °C and zeta potential (ZP) measurements. The systems were evaluated for the photodegradation of rhodamine B (RhB). Among the tested systems, the highest percentage of dye degradation was reached by the catalyst prepared with foundry sand supports, with values of 65% under ultraviolet and 39% under visible radiation, whereas under the same conditions, the catalyst prepared with rice husk showed the best photocatalytic performance among the samples prepared with agroindustrial wastes with values of 43% under ultraviolet and 38% under visible radiation. Strong Spearman's correlations among the photocatalytic activity, the zeta potential (ζ_p > 0.900) and the band gap energy (ζ_p > 0.895) were observed. Exploratory tests with tap water samples revealed that the system may be sensitive to other analytes present in these environmental samples.