Empregaram-se nanopartículas de aluminofosfatos amorfos, com diâmetro de 23 a 30 nm, para adsorção de íons chumbo (Pb2+) em soluções aquosas. Os materiais foram preparados por meio de biossíntese usando como modelos biológicos Saccharomyces cerevisiae. Os estudos de adsorção foram feitos empregando-se o método batch, usando 100 mg do sólido nanométrico e 200 µg L-1 de íons chumbo. A determinação quantitativa de Pb2+ foi realizada por meio de espectrometria de absorção atômica com atomização eletrotérmica (EAA-HG). Os valores obtidos para a percentagem de remoção (% EF), capacidade de adsorção qe (µg g-1) e grau de remoção Kd (mL g-1) foram de 40; 90 e 800 em média, respectivamente. Os resultados obtidos demonstraram as potencialidades destes materiais para a adsorção de íons Pb2+ e para a remediação de águas poluídas.

Amorphous aluminophosphates nanoparticles with diameter sizes from 23 to 30 nm were used for the adsorption of lead ions (Pb2+) in aqueous solutions. The materials were biosynthesized using Saccharomyces cerevisiae as a biological template. Adsorption studies were conducted using the batch method, employing 100 mg of the solid and 200 µg L-1 of lead ions. The quantitative determination of Pb2+ was carried out by electrothermal atomic absorption spectrometry (ETAAS). The percentage of removal (EF), adsorption capacity qe (µg g-1) and removal coefficient Kd (mL g-1) averaged 40, 90 and 800, respectively. The results showed the potential of these materials for the adsorption of Pb2+ ions, and that these materials are good candidates for use in the remediation of contaminated water.

Se emplearon nanopartículas de aluminofosfatos amorfos entre 23 a 30 nm de diámetro para la adsorción de iones plomo (Pb2+) en soluciones acuosas. Los materiales fueron sintetizados mediante biosíntesis utilizando como plantillas biológicas las células de levadura Saccharomyces cerevisiae. Los estudios de adsorción se llevaron a cabo empleando el método batch, utilizando 100 mg del sólido nanométrico y 200 µg L-1 de iones plomo. La determinación cuantitativa de Pb+2 fue realizada mediante espectrometría de absorción atómica con atomización electrotérmica (EAA-HG). Los valores obtenidos para el porcentaje de remoción (% EF), capacidad de adsorción qe (µg g-1) y coeficiente de remoción Kd (mL g-1) fueron de 40; 90 y 800 en promedio, respectivamente. Los resultados obtenidos demostraron las potencialidades que presentan estos materiales para la adsorción de iones Pb2+, siendo excelentes candidatos para la remediación de aguas contaminadas.

Activated (AS) and carboxymethylated (CMS0.24) cassava starch derivatives were studied as corrosion inhibitors for carbon steel XC35 in a 200 mgL-1 NaCl solution. They were characterized by back titration and Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical techniques were used to evaluate the inhibitive properties of starches at room temperature and the chemical composition of the protective films was determined by X-Ray Photoelectron Spectroscopy (XPS). Electrochemical measurements revealed that AS acts as mixed inhibitor, whereas CMS0.24 mainly inhibits the anodic reaction. In both cases, the protection increased with the inhibitor concentration; nevertheless, after 24 hours of immersion, the CMS0.24 loses its properties, while AS molecules still maintains them. XPS analyses show that the inhibitive films are composed of an iron oxide/hydroxide mixture in which starch molecules are incorporated. Results were explained taking into consideration the hydrophilicity and the strength of the ionic interaction of the starches with the metal surface.

En el presente trabajo se evaluó el efecto del pretratamiento de activación en catalizadores carburados de NiMo y CoMo soportados sobre γ-Al2O3 para la reacción HDS del tiofeno a presión atmosférica. Se comparó la influencia de la activación bajo corriente de H2 o de CS2/H2 por un lapso de dos horas a 300 ºC. Las pruebas fueron aplicadas a los precursores oxídicos y luego de carburados y a catalizadores comerciales equivalentes en la reacción de HDS de tiofeno a 400 ºC. Los sólidos fueron caracterizados por difracción de rayos-X, espectroscopia de infrarrojo por transformada de Fourier, fisisorción de N2 (método BET) y análisis elemental. La caracterización de los sólidos sugiere la formación de fases mixtas mientras que los resultados de actividad indican que los pretratamientos estudiados ejercen influencias similares sobre la actividad de los carburos metálicos, observándose apenas un ligero aumento en la conversión del tiofeno cuando el sólido es activado con CS2/H2

reaction at atmospheric pressure. Two activation procedures were compared: flow of either CS2/H2 or H2, both of them at 300 ºC for two hours. Both commercial and laboratory synthesized NiMo and CoMo oxidic and carbided catalysts were tested in the tiophene HDS reaction at 400 ºC. All the samples were characterized by means of X-ray diffraction, Fourier-transform infrared spectroscopy, physorption of N2 (BET method) and elemental analysis. Characterization suggest that there are mixed phases in the solids; on the other hand catalysts activity tests indicates that, for carbides the pretreatments studied do not have any major influence over tiophene conversion, although it is observed a slight improvement in the activity when the carbide catalyst are activated by CS2/H2 gas flow

Silver nanoparticles (AgNPs) were prepared by means of the polyol method in the absence of stabilizing polymers. To accomplish this objective, AgNO3 was added to ethylene glycol in the presence of NaOH (1 mol.L-1), the suspension formed was irradiated with a microwave source for 60 seconds at a power of 465 watts. It was found that under these conditions AgNPs of sizes between 4-18 nm are formed. Also the results indicate that part of the ethylene glycol is oxidized to carbonyl compounds that reduce the Ag+. These organic compounds are adsorbed on the surfaces of AgNPs, forming a protective film that prevents their aggregation.