Recovery of platinum, tin and indium from spent catalysts in chloride medium using strong basic anion exchange resins

This work describes a route for platinum recovery from spent commercial Pt and PtSnIn/Al₂O₃ catalysts using strong basic mesoporous and macroporous anion exchange resins (Cl⁻ form). The catalysts were leached with aqua regia (75 °C, 20-25 min). Platinum adsorption was influenced by the presence of other metals which form chlorocomplexes (tin, indium) and also base metals (aluminum). However, it was possible to overcome this fact by a sequential desorption procedure. Aluminum was selectively removed from the resins by elution with 3 mol L⁻¹ HCl. Platinum was desorbed passing 1 mol L⁻¹ Na₂S₂O₃ (pH 9). Tin was removed by elution with 0.1 mol L⁻¹ ascorbic acid. Indium was removed using 0.1 mol L⁻¹ EDTA as eluent. Desorption efficiency exceeded 99% for all metals. Metals were recovered in high yields (>98 wt%).     

A Comprehensive Study of Particle Size Distributions with the Use of PostInjection Strategies in DI Diesel Engines

Control strategies such as variations in injection pressure and timing have been used by researchers to reduce in-cylinder exhaust emissions and meet legislation standards. Postinjection has been studied for several years and is now well known as an efficient strategy for reducing soot emission. Diesel gaseous and particle mass emissions have been progressively reduced over the last twenty years as a consequence of increasingly restrictive emission legislation and the application of aftertreatment devices. The main objective of this work is to better understand the effect of postinjection on particle size distribution in diesel exhaust. The approach uses a modern, well-instrumented research engine test cell equipped with a flexible high pressure fuel injection system. The results of this work provide guidelines for developing strategies to reduce particle size distribution in diesel engines. A major improvement in particle size distribution was found in the accumulation mode by using a close postinjection of a small quantity of fuel. For reduction in nucleation mode, a relationship was found with close postinjections of large quantities of fuel.     

Functionalized-radiolabeled hydroxyapatite/tenorite nanoparticles as theranostic agents for osteosarcoma

Hydroxyapatite (HA) nanoparticles (NPs) doped with different radioisotopes for use as theranostic systems play an important role in scientific research nowadays due to their ability to simultaneously act in the treatment and diagnosis of various types of cancers. In this work, we describe the synthesis and characterization of a hydroxyapatite/tenorite nanocomposite functionalized with folic acid, representing a nanotheranostic material with potential for application as an agent in positron emission tomography imaging systems and to act specifically in the treatment and diagnosis of osteosarcoma. ⁶⁴Cu and ³²P were produced by nuclear activation in the TRIGA reactor at CDTN. The obtained samples were characterized by XRD with Rietveld refinement, XAFS, SEM, BET, TGA, FTIR, CHN, ICP-AES, XPS and gamma spectroscopy. We investigated how CuO grows in HA NPs, the stability of the interactions between CuO and HA constituents and the interactions between folic acid and the surface of the HA NPs. The results indicate the formation of a second phase (tenorite) besides hydroxyapatite, and that the interactions between the two phases are stable, resulting in a nanocomposite. Furthermore, the activation of ⁶⁴Cu and ³²P inside the HA matrix, through the exposition to a neutron flux, produces a theranostic material of interest for biological tests.     

New algorithms for power transformer inter-turn fault protection

In the paper new algorithms for detection of internal inter-turn faults in power transformers are described. Such faults are extremely difficult to detect since they induce negligible increase of the currents at the transformer terminals, although the currents flowing at the fault place are very high and dangerous for the transformer to be protected. The algorithms developed are based on the differential equation of the equivalent circuit of the transformer. In one version additional information from a CT installed inside of the triangle of delta side windings is used, which brings very promising results. Theoretical investigations are supported and illustrated with simulation studies performed both with MATLAB and EMTP-ATP programs.     

Synthesis and Characterization of Pyridine Compounds for Amperometric Measurements of Leukocyte Esterase

We introduce a new class of substrates (compounds I – III ) for leukocyte esterase (LE) that react with LE yielding anodic current in direct proportion to LE activity. The kinetic constants K_m and k_cat for the enzymatic reactions were determined by amperometry at a glassy carbon electrode. The binding affinity of I – III for LE was two orders of magnitude better than that of existing optical LE substrates. The specificity constant k_cat/K_m was equal to 2.7, 3.8, and 5.8×10⁵ m ^?1 s^?1 for compounds containing the pyridine ( I ), methoxypyridine ( II ), and (methoxycarbonyl)pyridine ( III ), respectively, thus showing an increase in catalytic efficiency in this order. Compound III had the lowest octanol/water partition coefficient (log p=0.33) along with the highest topological surface area (tPSA=222 Ų) and the best aqueous solubility (4.0 mg mL^?1). The average enzymatic activity of LE released from a single leukocyte was equal to 4.5 nU when measured with compound III .     

Influence of Molybdenum Silicide Additions on High-Temperature Oxidation Resistance of Silicon Nitride Materials

The influence of additions of molybdenum disilicide (MoSi₂) on the microstructure and the mechanical properties of a silicon nitride (Si₃N₄) material, with neodymium oxide (Nd₂O₃) and aluminum nitride (AIN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi₂, were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi₂ additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1400°C were not affected significantly, in comparison to that of monolithic Si₃N₄. The oxidation resistance of the composites, in terms of weight gain, degraded. After 1000 h of oxidation at 1400° and 1450°C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi₂. Nevertheless, after 1000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi₂. An additional layer was formed, caused by processes at the surface of the Si₃N₄ material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si₃N₄ materials. This surface layer, containing Mo₅Si₃ and silicon oxynitride (Si₂ON₂), was the result of reactions between MoSi₂, Si₃N₄, and the oxygen penetrating by diffusion into the material during the hightemperature treatment.