A new silicon-aluminum-zirconium ternary oxide (SiO2/Al2O3/ZrO2) was prepared by the sol-gel method followed by one-step washing with absolute ethanol or two-step washing with absolute ethanol followed by ultra-pure water. Both ternary oxides presented high surface area (over 340 m2 g-1). The binding energy values for Zr3d and Al2p levels showed the insertion of Zr and Al atoms in silica matrix, confirming the dispersion surface of these elements as shown by scanning electron microscope (SEM) and energy dispersive X-ray fluorescence spectroscopy (EDXRF) data. A weight loss around 40 wt.% was found for both samples submitted to thermogravimetric analysis (TGA). Crystallographic data showed the presence of monoclinic and tetragonal ZrO2 phases in different proportions according to the calcination temperature. Regarding the acid-base properties, temperature-programmed desorption of CO2 (CO2-TPD) profiles suggested that washing with water reduced the overall basicity of the samples and removed the strongest basic sites. However, according to temperature-programmed desorption of NH3 (NH3-TPD) profiles, washing significantly increased the amount of weak acid sites, in agreement with pyridine adsorption data. Brønsted acid sites (BAS) are ever dominant but washing with ethanol followed by water reduced the number of Lewis acid sites (LAS).

This work details the chemical characterization of four NiMo/Al2O3 hydroprocessing generation catalysts (1979-1986, 1993-1998, 2003-2008 and 2008-2011) employed to perform hydrodesulfurization (HDS) of diesel fractions in the same hydrotreater of a Brazilian refinery. The basic differences are the quality of the feedstocks and the HDS experimental conditions. Samples were characterized by X-ray fluorescence, X-ray diffraction, 13C CP-MAS NMR, elemental analysis, loss of volatiles, specific surface area and average pore volume. The amount and variety of foreign elements deposited on the catalyst increased in the most recent generations due to the higher amounts of impurities in the processed feedstocks. Coke became more aromatic and loss of textural properties was more prominent in these samples as expected from the more drastic HDS conditions and the quality of the crude diesel. On the other hand, loss of volatiles was lower due to the low carbon content, partial oxidation of sulfur to sulfate species and oxidation of some elements deposited on the catalyst. Coke tended to ignite as it became more aromatic. For this reason, leaching of decoked samples from the most recent generations by sulfuric acid presented very low yields due to the formation of refractory oxides that are insoluble in the leachant.

This work describes a three-step pre-treatment route for processing spent commercial NiMo/Al2O3 catalysts. Extraction of soluble coke with n-hexane and/or leaching of foulant elements with oxalic acid were performed before burning insoluble coke under air. Oxidized catalysts were leached with 9 mol L-1 sulfuric acid. Iron was the only foulant element partially leached by oxalic acid. The amount of insoluble matter in sulfuric acid was drastically reduced when iron and/or soluble coke were previously removed. Losses of active phase metals (Ni, Mo) during leaching with oxalic acid were compensated by the increase of their recovery in the sulfuric acid leachate.

This work shows routes to recover some elements from their laboratory wastes and broken apparatus (thermometers and densimeters). Most elements chosen present a chemical behavior in aqueous solution which is not currently studied in the ordinary experimental classes. The routes were based on the previous knowledge of the qualitative composition of the wastes treated. Wastes containing chromium were the most difficult to treat. The elements were recovered in good yields and can be reused in new experiments. This work was a very good experience in chemistry for students and shows the need of managing wastes for a better environment.

The anode and the internal paste of spent Zn-C and alkaline batteries were leached with 2 mol L-1 H2SO4 at 80 ºC for 2 h. Solid/liquid ratio was 1/10 (g mL-1). The leachate was treated with Na2S in order to precipitate Hg, Cd and Pb. Zn was quantitatively isolated at pH 1,5-2 by adding Na2S. Mn can be precipitated at pH close to 7. Na2S may be replaced by oxalic acid. Zn precipitated at pH around 0, whereas Mn was quantitatively recovered at pH > 4. Acidity control is a critical parameter. Na2SO4 and carbon are the end products.

This work presents hydrometallurgical routes for recovering valuable elements from spent button cells, based on leaching of internal components with sulfuric acid (Li/MnO2 and Zn-air) or nitric acid (Ag-Zn), at 90 ºC for 2h. Slow evaporation of the leachate crystallized MnSO4.H2O, whereas lithium was partially recovered as LiF. Mercury present in Zn-air and Ag-Zn samples was precipitated as HgS. Silver was recovered as AgCl before mercury precipitation. Zinc and iron were precipitated as hydroxides. The amount of iron varied according to the intensity of the corrosion of the external cell case. Final wastes are neutral and colorless sodium sulfate/nitrate solutions.