William Leonardo da Silva

Photocatalytic degradation of nicotine in an aqueous solution using unconventional supported catalysts and commercial ZnO/TiO2 under ultraviolet radiation

Nicotine, a highly toxic alkaloid, has been detected in effluents, surface and groundwater and even bottled mineral water. The present work studied the photocatalytic degradation of nicotine in aqueous solution, under ultraviolet irradiation. The experiments were carried out using commercial (ZnO, TiO2) and non-conventional catalysts, which were prepared from industrial and laboratory waste. Two experimental designs (CCD) were performed for both commercial catalysts, and initial nicotine concentration, catalyst concentration and initial solution pH effects were studied. Then, the synthesized catalysts were tested under the optimal conditions which were found through CCDs. Using commercial catalysts, about 98% of the alkaloid was degraded by ZnO, and 88% by TiO2, in 1h. Among the non-conventional catalysts, the highest photocatalytic degradation (44%) was achieved using the catalyst prepared from a petrochemical industry residue.

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 Spearmans correlations among the photocatalytic activity, the zeta potential (ζp>0.900) and the band gap energy (ζp>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.

Alternative Approaches in Development of Heterogeneous Titania-Based Photocatalyst

Three alternative approaches for the development of heterogeneous photocatalysts are comparatively evaluated, namely (i) the use of molecular imprinting concept for the development of heterogeneous catalysts employing rhodamine B as template and sol– gel as synthesis route; (ii) the impregnation of TiCl4 on mixed nanoand micro-metric silicas, followed by calcination; (iii) the use of industrial and academic chemical residues as source of potential photocatalyst species impregnated on supports. All tests were carried on with rhodamine B as target molecule. For comparative reasons, photocatalytic tests were carried out with commercial titania (P25). The solids were characterized by nitrogen porosimetry, small-angle X-ray scattering (SAXS), zeta potential (ZP), diffuse reflec‐ tance spectroscopy in the ultraviolet region (DRS-UV), diffuse reflectance infrared Fourier transmission spectroscopy (DRIFTS), and Rutherford backscattering spectrometry (RBS). The supported catalysts resulting from silica nanoparticles and residue of the petrochem‐ ical industry achieved higher percentage of the dye degradation under ultraviolet (68.0 and 66.8%, respectively) radiation. The industrial waste reached the highest photocata‐ lytic activity under visible (61%) radiation, while the commercial P25 achieved 82.0and 12.3% for ultraviolet and visible radiation, respectively. The textural and structural characteristics of the supported catalyst prepared with fumed silica and petrochemical waste (SiPe), namely the low-energy bandgap (1.8 eV), large surface area (280 m2 g−1), high pore volume (1.9 cm3 g−1), and high zeta potential value (−36.4 mV), may have been responsible for their high activity.