Development of nanostructured membranes for environmental applications

Two new methods for the fabrication of porous membranes were studied. Ceramic membranes were obtained from alumoxane and ferroxane nanoparticles casted onto porous support materials. The synthesis of ferroxane nanoparticles was further investigated, in particular the kinetics of the reaction and the structure of the materials obtained by particle size measurements and EXAFS. The ceramics were characterized by nitrogen absorption isotherms, scanning electron microscope, and atomic force microscope. The permeability and molecular weight cut off (MWCO) of the ferroxane derived membranes were measured. These membranes have an average pore size of 24 run and a MWCO of 180,000 Daltons, which corresponds to the ultrafiltration range. The ferroxane nanoparticles were reacted with compounds containing other metallic atoms and mixed metal oxide nanoparticles were obtained. The nanoparticles can be applied to the fabrication of mixed metal oxide ceramics used in catalysis, fuel cells and other applications. The conductivity and surface acidity were determined in order to evaluate these materials as possible proton exchange membranes for fuel cells. The second fabrication method considered in this study is the template-derived process. Deposits of silica nanoparticles of variable morphology were prepared to be used as templates for porous membranes. The variables that control the morphology of the deposits were investigated, in particular those related to the solvent chemistry of the nanoparticle suspensions. The templates were obtained by self-assembly and Langmuir-Blodgett layer-by-layer deposition. By controlling the template deposition process, the self-assembly method was used to create dendritic templates with an asymmetric structure. The Langmuir-Blodgett technique was used to create bilayers of different pore size. Polystyrene membranes were fabricated as replicas of these template structures. The pore structure of the polymeric membranes was studied by scanning electron microscopy

Selective determination of Cr (VI) by on-line solid phase extraction FI-SPE-FAAS using an ion exchanger resin as sorbent: An improvement treatment of the analytical signal

A flow injection (FI) technique based on an on-line solid phase extraction (SPE) coupled with flame atomic absorption spectroscopy (FAAS) to selectively quantify chromium (VI) in the presence of chromium (III) was developed. An anion exchanger was used as solid sorbent and the detection limit found was two order of magnitude lower than that expected quantifying by FAAS. Until now, quantitative determinations in FAAS were carried out by measuring the height of the peaks rather than their area. In our hands, the software was reconfigured and the area under the peaks could be measured. Considering area instead of height, the enhancement factor increases from 6.7 to 360 (approx. 54 times) giving a detection limit of 0.034 μg·L− 1, lower than that obtained using much more expensive instruments such as electrothermal atomic absorption spectrometry (ETAAS) or inductively coupled plasma-atomic emission spectrometry (IPC-AES), greatly enhancing the potential of this methodology for future use in speciation studies. The operation conditions were: pH 3, sample loading 50 mL·min− 1, elution flow rate 7.5 mL·min− 1. The anion exchanger lifetime was over 100 adsorption/desorption cycles. Anions commonly present in natural aqueous systems did not interfere in the chromium retention. The accuracy was validated using a certified reference material (Fluka Analytical, QC3453).Fil: Rossi, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Errea, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: de Cortalezzi, María Marta Fidalgo. University of Missouri; Estados UnidosFil: Stripeikis, Jorge Daniel. Instituto Tecnológico de Buenos Aires; Argentin

Electrostatic interactions in virus removal by ultrafiltration membranes

Ultrafiltration membranes are increasingly used in potabilization to remove viral particles. This removal iscontrolled by electrostatic repulsion, attachment and size exclusion. The effect of electrostatic interaction invirus filtration was investigated. Our work included characterization of bacteriophage PP7 and polyethersulfonemembrane with respect to size and surface charge; the removal of this bacteriophage at laboratory scale byultrafiltration membrane process and the mechanism and limitations were analyzed and discussed under DLVOand XDLVO theories. A partial removal of the bacteriophage was achieved; however, enhanced separation maybe achieved considering that the process is affected by the aqueous matrix. The presence of divalent cationsdiminished the effectiveness of the procedure as opposed to monovalent cations and species with amphotericbehavior such as bicarbonate. DLVO and XDLVO predicted the interactions studied between bacteriophage PP7and polyethersulfone membrane.Fil: Gentile, Guillermina Jose. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; ArgentinaFil: Cruz, Mercedes Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Rajal, Verónica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Fidalgo de Cortalezzi, Maria Marta. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; Argentin