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The ionic liquids 1-n-butyl-3-methylimidazolium chloride (C4MImCl), 1-n-butyl-3-methylimidazolium hexafluorophosphate (C4MImPF6), 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C4MImNTf2), 1-n-butyl-2,3-dimethylimidazolium chloride (C4MMImCl) and 1-n-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (C4MMImNTf2) were degraded under UV and visible radiation in the presence of a silica-supported photocatalyst (SiTi), which was derived from a petrochemical residual catalyst slurry rich in titanium and magnesium. These ionic liquid advanced oxidation processes were studied by UV spectroscopy and electrospray ionization mass spectrometry. After 120 min of irradiation, 50.2, 48.7, 45.3, 40.7 and 35.3% of C4MImCl, C4MImPF6, C4MImNTf2, C4MMImCl and C4MMImNTf2 were degraded under UV and 45.4, 43.6, 40.2, 36.8 and 32.7% of C4MImCl, C4MImPF6, C4MImNTf2, C4MMImCl and C4MMImNTf2 were degraded under visible light, respectively. The commercial titania P25 catalyst degraded 66.3 and 50.2% of C4MImCl under UV and visible radiation, respectively. Regarding the stability of photocatalyst SiTi, it was reused five times with only minor loss of catalytic activity. Doping of SiTi with 25 wt% Mg2+/SiO2 resulted in improved degradation values of 64.6% (UV irradiation) and 65.3% (visible irradiation) of C4MImCl. Cytotoxicity assays (MTT reduction and Neutral Red incorporation) on NIH/3T3 cells after 24 h of irradiation of C4MImCl indicated the absence of in vitro cytotoxicity. Altogether, this study opens new opportunities for the management of petrochemical waste, providing access to effective and stable heterogeneous photocatalysts for the degradation of imidazolium ionic liquids.

Mesoporous nanoparticles and mixed-structure silica with existing nanometric and micrometric domains on their surface were prepared using SiCl4. TiCl4 was used as precursor to obtain nano- and mixed heterogeneous supported titania photocatalysts. The systems and, for comparative reasons, commercial (P25) were evaluated for Rhodamine B (RhB) photodegradation in deionized and lake water solution. The structural differences between nano- and mixed photocatalysts were observed and are due to the degree of particles structural organization, according to small-angle X-ray scattering (SAXS) profiles. The structural analysis obtained by fractal dimension (pL) showed that photocatalysts which were organized as mass fractal structures presented higher catalytic activity than the photocatalysts of rough surface fractal or non-fractal. A compressive discussion on surface topology, size, band gap, surface area, surface charge density, and catalysts amount was done to explain the effect of these features on the photocatalysts performance. The distribution of Ti-O-Si species on the support surface was determined by X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). The higher photocatalytic activity for the degradation of RhB dye was achieved by SNCl5Ti sample. This catalyst achieved high efficiency factor, EF = mg of RhB degraded/ mg of catalyst, equal to 0.020 and 0.0132, under UV and Vis radiation, respectively, which is lower catalyst amount than the similar TiO2-SiO2 based systems reported in the literature. These findings broaden the opportunities to degrade other harmful pollutants in wastewater. This work also provides an insight on how structural properties are correlated to the efficiency of titania supported nano/micrometric catalysts.

A series of eleven drugs, namely, atorvastatin calcium, diclofenac sodium, fluoxetine, ketoconazole, ibuprofen, dexamethasone, tioconazole, naphazoline hydrochloride, valsartan, guaifenesin and paracetamol, were comparatively degraded under UV and visible radiation in the presence of a supported photocatalyst generated from the catalyst residue from a Ziegler–Natta catalyst petrochemical plant. The presence of Mg (4.4%) and Ti (2.5%) afforded a catalyst that was active over the UV and visible spectral regions. For comparative reasons, commercial P25 (titania) was also evaluated. Among the tested systems, the highest drug degradation was observed under UV (48.6%) and visible (45.2%) radiation with the synthesized photocatalyst, whereas under the same conditions, the commercial P25 catalyst achieved 66.3% and 50.2% degradation, for UV and visible radiation, respectively. Despite the comparable degradation capability, the proposed photocatalyst could be reused five times without losing catalyst activity.

Industrial galvanic bath residuals, residual silver-containing solutions from photography classes, residual metal-containing solutions from academic analytical chemistry classes, and residual Ziegler–Natta catalyst slurry from a petrochemical plant were employed as sources for photocatalysts. The residues were impregnated on silica, with subsequent calcination. The solids were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Rutherford backscattering spectrometry (RBS), diffuse reflectance spectroscopy in the ultraviolet (DRS-UV), small-angle X-ray scattering (SAXS), nitrogen porosimetry and zeta potential (ZP) measurements. The catalysts contained Zn, Ti, Ag, Cr or Cu. All the systems presented also included carbon in their composition. Metal content ranged from 0.01 to 0.60 wt%. The systems were evaluated by the photodegradation of Rhodamine B (RhB). For comparative reasons, P25 (Degussa) was also employed as a catalyst. The supported catalysts resulting from the residue of the petrochemical industry achieved the highest percentage of the dye degradation in the ultraviolet (67%) and visible (61%) radiation, while the commercial P25 achieved 93% and 14% for ultraviolet and visible radiation, respectively.

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.