Effect of coating on the environmental applications of zero valent iron nanoparticles: the lindane case.

Commercial stabilized slurry of zero-valent iron nanoparticles (nZVI) as well as laboratory-synthesized polymer-stabilized NZVI nanoparticles were used for lindane (γ-hexachlorocyclohexane) degradation studies in aqueous solution. In the present study, polymer-stabilized iron nanoparticles were stabilized using polyethylene glycol (PEG, Mn ~400 and ~950-1050) and polytetrahydrofuran (PTHF, Mn ~650). To study the effectiveness of the different nanoparticles, a quantitative monitorization of lindane degradation by using solid-phase extraction (SPE) and a qualitative measurement of generated volatile by-products by headspace-solid phase microextraction (HS-SPME) followed by GC/MS were carried out. The obtained data were compared and contrasted with the results obtained in previous work. Results showed that the nanoparticles studied in this work possess superior dechlorination performance compared with previous observations. The freshly prepared Fe(0)-PEG400, Fe(0)-PEG1050 and Fe(0)-PTHF exhibited high reactivity during the dechlorination process of lindane in a very short time. The results obtained with the synthesized nanoparticles were similar to those obtained with commercial nanoparticles. However, in all cases reactivity decreased at reaction's late stage. Degradation of lindane by the studied nanoparticles removed 99.9% of the lindane initial concentration after 72h, except for Fe(0)-PTHF nanoparticles, for which the reaction stopped after 5min. In all cases, the reaction followed a second order kinetics. Finally, comparing the results from this study with our previous work, where different nature polymers were considered (Fe(0)-CMC, Fe(0)-PAA and Fe(0)-PAP), more gradual degradation profile of lindane was observed for Fe(0)-PAA and Fe(0)-CMC. It should be noted that in the present case, the reaction of lindane was speeded up with commercial and Fe(0)-PEG nanoparticles. Nevertheless, in the later case, the composition of by-products was affected by the presence of partially degraded intermediates. Taking into account the current technologies, the high removal rates obtained and the acceptable degradation times required, the proposed technology is suitable for its aimed purpose.

Relevance study of bare and coated zero valent iron nanoparticles for lindane degradation from its by-product monitorization.

Zero-valent iron nanoparticles (NZVI) as well as polymer-stabilized nanoparticles were synthesized and used for lindane (γ-hexachlorocyclohexane) degradation in aqueous solution. To study the effectiveness of the different coated nanoparticles, simple and rapid analytical methods have been developed to measure and to detect lindane and its by-products. For the monitorization of lindane degradation solid-phase extraction (SPE) was used, while volatile by-products formation measurement was carried out by headspace-solid phase microextraction (HS-SPME) followed by GC/MS. The SPE-GC/MS method provides low detection limits (0.2 µg L(-1)), high recovery (above 95%) and it is a valuable tool for kinetic studies of the degradation process for each polymer used, while HS-SPME-GC/MS has proved to be an effective tool for the extraction and evaluation of volatile degradation by-products.

Lesiones diafragmáticas traumáticas / Traumatic diaprhagmatic injuries

Se registran todos los casos de lesiones diafragmáticas, tanto en traumatismos abiertos y cerrados, ingresados en nuestro centro universitario entre agosto de 1987 y agosto de 1999. Se analizan 30 casos, 25 hombres (83,4 por ciento), y 5 mujeres (16,6 por ciento). La edad fluctúa entre 8 y 65 años, con una edad promedio de 29 años. El 67 por ciento de los casos corresponde a traumatismos penetrantes torácicos bajos, 30 por ciento cerrados y un 3 por ciento a iatrogenias. De todos ellos el compromiso del hemitórax izquierdo se presentó en 90 por ciento y sólo en el 10 por ciento de los casos se comprometió el hemitórax derecho. Los elementos diagnósticos fueron radiografía de tórax, tránsito o edema baritada, TAC de tórax, neumoperitoneo diagnóstico, y en 3 casos el diagnóstico se efectuó por videotoracoscopía. El 63 por ciento de los pacientes se operó precozmente, antes de 36 horas, siendo la laparotomía la vía de acceso de elección en los casos agudos. La mortalidad global fue de 3,4 por ciento