Ternary oxide silica-alumina-zirconia (SiO2/Al2O3/ZrO2) obtained by the sol-gel process was applied as novel adsorbent of ions in aqueous solution. Batch isotherms were performed using standard CuII, CdII and CaII solutions at variable pH and different concentrations. Adsorption capacity was best at weakly acidic pH. The maximum adsorption capacities were 2.28 mg g−1 for CaII, 9.89 mg g−1 for CdII, and 14.88 mg g−1 for CuII. The adsorption data fitted well to the single and dual-site Langmuir-Freundlich isotherm models. However, since the adsorption is very low in the sites with high energy, the single-site Langmuir-Freundlich provided a good fit as well. Whereas, the site responsible for the most ion adsorption was assigned to the Zr−OH group. A real sample of produced water was also tested. The new adsorbent showed a wide ability to retain many metal ions (alkali-earth, transition, and p-block metals) and even some anions were also caught by the adsorbent. The ternary oxide silica-alumina-zirconia was found to be a promising alternative adsorbent for metal ions in aqueous media.

This paper reports the use of cryolite from the Pitinga Mine (Amazonas state, Brazil) as raw material in hydrogen fluoride production. Samples were initially characterized by chemical and mineralogical analyses. They presented low silica content (< 4 wt.%). After milling, cryolite samples were digested with concentrated sulfuric acid under stirring (200 rpm) and variable temperature, time and liquid to solid ratio conditions. Under the best experimental conditions (140 °C, 3-5 h), 96 wt.% of fluorine was recovered as hydrogen fluoride. The application of a 23 full factorial design showed that temperature and reaction time were relevant parameters during leaching, whereas liquid to solid ratio was not statistically significant.

Foram investigadas as influências do tempo de eletrólise, da área anódica, da densidade de corrente e do tipo de eletrólito na degradação de fenol e de seus subprodutos de oxidação em anodo de Ti/RuO2. Foi observado que na presença de cloreto ocorreu rápida degradação de fenol e de seus subprodutos. Resultados de cromatografia gasosa/espectroscopia de massa (GC/MS) mostraram que a presença de cloreto levou à formação inicial de clorofenóis através do Cl2 e/ou OCl¯ gerados durante a eletrólise. Entretanto, eles posteriormente atuaram na degradação dos clorofenóis. As concentrações limites estabelecidas pelo Órgão Ambiental Brasileiro (CONAMA) para descartes de fenol e clorofenóis foram obtidas após 360 min de eletrólise a uma densidade de corrente fixa de 10 mA cm-2.Voltamogramas cíclicos obtidos antes e após 436 h de eletrólise em condições severas de salinidade (2 mol L-1) e densidade de corrente (800 mA cm-2) mostraram que o eletrodo de Ti/RuO2 não perdeu suas propriedades eletrocatalíticas

The influences of electrolysis time, anodic area, current density and supporting electrolyte on phenol and its byproducts degradation on a Ti/RuO2 anode were investigated. It was observed that phenol and its byproducts were rapidly broken down in the presence of chloride ions. Gas chromatography/mass spectrometry (GC/MS) data have shown that the presence of chloride ions lead to chlorophenols formation, due to reactions with Cl2 and/or OCl¯ generated during electrolysis. However, these intermediate products were also degraded later by the oxidizing agents. The standards established by the CONAMA (Brazilian National Council for the Environment) for phenols and chlorophenols in effluents were achieved after 360 min of electrolysis with a current density of 10 mA cm-2. Cyclic voltammograms obtained with the anodes before and after 436 h of electrolysis under severe salinity conditions (2 mol L-1) and current density (800 mA cm-2) showed that Ti/RuO2 did not lose its electrocatalytic properties. This fact indicates that Ti/RuO2 can be used for the treatment of effluents containing phenols in a chloride environment

Este trabalho descreve a hidrogenação do 2-etil-hexen-2-al em um reator de lama em fase líquida sobre catalisadores Ni/Al2O3 (teor de Ni entre 4,4-17,0% p/p). Resultados de DRX, DRS e TPR mostraram a presença de espécies superficiais de Ni2+ em coordenação octaédrica (óxido de níquel superficial) e tetraédrica (fases do tipo espinélio) nas subcamadas do suporte. Nas amostras com altos teores de Ni, foram observados cristalitos de óxido de níquel, seja em coordenação octaédrica ou tetraédrica. A maior seletividade para a formação do intermediário 2-etil-hexanal foi obtida com o catalisador contendo 7,3% p/p de Ni. A freqüência de reação (TOF) independe da concentração de níquel, sugerindo que esta reação de hidrogenação é insensível à estrutura.

This work describes the hydrogenation of 2-ethyl-hexen-2-al in a slurry bed reactor in liquid phase on Ni/Al2O3 catalysts (4.4-17.0% wt Ni). XRD, DRS and TPR results showed the presence of superficial Ni2+ species in octahedral (surface Ni oxide) and tetrahedral coordination (spinel-type phase) in the subsurface of the support. Nickel oxide crystallites were found in samples with Ni content above 7.3%, either in tetrahedral or octahedral coordination. The highest selectivity for 2-ethyl-hexanal was obtained with the catalysts containing 7.3% wt Ni. The turnover frequency (TOF) was independent on the Ni concentration, suggesting that this hydrogenation reaction is structure insensitive.

This work presents a detailed study of the leaching behavior of deactivated hydrotreating catalysts (CoMo, NiMo/Al2O3) in presence of oxalate and NH4+ ions in various media. The yield of metals recovery may be optimized by adjusting several experimental parameters (time, temperature, etc). Leaching is limited by physical factors (diffusional effects caused by coke) and by the existence of silicate/spinel-like species which are poorly soluble in leaching solutions. Coke may be eliminated by an oxidation step at temperatures between 300-400ºC. Above 400ºC, solubilization of Ni and Co is drastically reduced. 50-90% wt of sulphate species and 15-30% wt of phosphate ions are solubilized during leaching. Silicon (as SiO2) is not solubilized. The best Ni-Co-Mo recoveries are in the 70-90% wt range; Fe recovery may be quantitative, whereas Al leaching may be lower than 5% wt.