Dora Ángela Hoyos

Synthesis and structure of a porous zinc vanadate, Zn3(VO4)2·3H2O

A zinc vanadate with the formula Zn3(VO4)2·3H2O was synthesized by hydrothermal reaction of a gel of composition [(CH3CO2)2Zn·2H2O] : 0.5V2O5: 0.4 [1,3-diaminepropane] : 1.5 NaOH : 114 H2O, held at 170°C for 24 hours. The structure was determined ab initio by means of the EXPO direct methods program and refined with GSAS. The pale yellow solid crystallizes in the hexagonal space group P-6 with a= 6.07877(8), c= 7.1827(2) Å. The structure consists of vanadium tetrahedra bonded to distorted octahedral zinc atoms to create one dimensional columnar passageways for molecules. Though occupied by water in the as synthesized form, the passages could host other small molecules.

Synthesis and structure of the incomplete cuboidal clusters [W3Se4H3(dmpe)3]+, [W3Se4H3−x(OH)x(dmpe)3]+ and [W3Se4(OH)3(dmpe)3]+, and the mechanism of the acid-assisted substitution of the coordinated hydrides

The novel incomplete cuboidal cluster [W3Se4H3(dmpe)3](PF6), [1](PF6), has been prepared by reduction of [W3Se4Br3(dmpe)3](PF6) with LiBH4 in THF solution. The trihydroxo complex [W3Se4(OH)3(dmpe)3](PF6), [2](PF6), was obtained by reacting [W3Se4Br3(dmpe)3](PF6) with NaOH in MeCN-H2O solution. The complexes [1](PF6) and [2](PF6) were converted to their BPh4- salts by treatment with NaBPh4. Recrystallisation of [1](BPh4) in the presence of traces of water affords the mixed dihydride hydroxo complex [W3Se4H2(OH)(dmpe)3](BPh4). The crystal structures of [1](BPh4), [2](BPh4) and [W3Se4H2(OH)(dmpe)3](BPh4) have been resolved. Although the [1]+ trihydride does not react with an excess of halide salts, reaction with HX leads to [W3Se4X3(dmpe)3]+ (X = Cl, Br). The kinetics of this reaction has been studied at 25 degrees C in MeCN-H2O solution (1:1, v/v) and found to occur with two consecutive kinetic steps. The first step is independent of the nature and concentration of the X(-) anion but shows a first order dependence on the concentration of acid (k1 = 12.0 mol(-1) dm(3) s(-1)), whereas the second one is independent of the nature and concentration of both the acid and added salts (k2 = 0.024 s(-1)). In contrast, the reaction of [2]+ with acids occurs in a single step with kobs = 0.63 s(-1)(HCl) and 0.17 s(-1)(HBr). These kinetic results are discussed on the basis of the mechanism previously proposed for the reactions of the analogous [W3S4H3(dmpe)3]+ cluster, with special emphasis on the effects caused by the change of S by Se on the rate constants for the different processes involved.

Structural characterization of a porous zinc vanadate: Zn 3 (VO 4 ) 2 ⋅3H 2 O

A novel porous material of composition Zn 3 (VO 4 ) 2 ⋅3H 2 O was prepared hydrothermally. The solid crystallizes in the hexagonal space group P 6 , with a =6.078 77(8), c =7.1827(2) A, and V =229.857 A 3 .

INVENTARIO DE LOS RESIDUOS SÓLIDOS GENERADOS EN LAS EMPRESAS ANTIOQUEÑAS PERTENECIENTES A LOS PRINCIPALES SECTORES ECONÓMICOS DEL DEPARTAMENTO

Este articulo muestra los resultados de una investigacion sobre la produccion de residuos solidos generados por las empresas Antioquenas. Investigacion que fue desarrollada por la Universidad de San Buenaventura, la Universidad de Medellin y la Universidad de Antioquia dentro del programa Expedicion Antioquia 2013. Para lo cual, se evaluo la produccion de residuos generados en empresas pertenecientes a las actividades economicas; agricultura, ganaderia, caza y silvicultura; Explotacion de minas y canteras; Industrias manufactureras y Construccion. El proposito del estudio fue conocer la tipologia, cantidad e impacto ambiental de los residuos generados en el departamento en los sectores seleccionados, constituyendose en una base para futuras investigaciones, orientadas a determinar el potencial aprovechamiento de los residuos para la elaboracion de nuevos productos. La zona de estudio corresponde al 80,8% de la superficie del departamento de Antioquia, subregiones, Bajo Cauca, Nordeste, Norte, Oriente, Suroeste, Uraba y Valle de Aburra; las cuales concentran las zonas industriales, mineras y agropecuarias mas representativas del departamento, ademas de ser subregiones altamente pobladas con un crecimiento en infraestructura, representado en un sector de construccion fortalecido. La metodologia utilizada fue la construccion de bases de datos de las empresas de los sectores seleccionados para posteriormente obtener informacion de la generacion de residuos solidos por medio de encuestas realizadas por un aplicativo web, personal o telefonicamente.