Josefina de Gyves

Cr(VI) transport via a supported ionic liquid membrane containing CYPHOS IL101 as carrier: System analysis and optimization through experimental design strategies

Chromium(VI) transport through a supported liquid membrane (SLM) system containing the commercial ionic liquid CYPHOS IL101 as carrier was studied. A reducing stripping phase was used as a mean to increase recovery and to simultaneously transform Cr(VI) into a less toxic residue for disposal or reuse. General functions which describe the time-depending evolution of the metal fractions in the cell compartments were defined and used in data evaluation. An experimental design strategy, using factorial and central-composite design matrices, was applied to assess the influence of the extractant, NaOH and citrate concentrations in the different phases, while a desirability function scheme allowed the synchronized optimization of depletion and recovery of the analyte. The mechanism for chromium permeation was analyzed and discussed to contribute to the understanding of the transfer process. The influence of metal concentration was evaluated as well. The presence of different interfering ions (Ca(2+), Al(3+), NO3(-), SO4(2-), and Cl(-)) at several Cr(VI): interfering ion ratios was studied through the use of a Plackett and Burman experimental design matrix. Under optimized conditions 90% of recovery was obtained from a feed solution containing 7mgL(-1) of Cr(VI) in 0.01moldm(-3) HCl medium after 5h of pertraction.

An SLM system for the extraction of In(III) from concentrated HCl media using ADOGEN 364 as carrier

The coupled transport of In(III) from concentrated HCl media (2.2-4 mol/dm 3 ) on a supported liquid membrane system using as carrier the commercial trialkylamine ADOGEN 364 dissolved in kerosene was studied. The effect of different parameters such as the stirring rates of feed and strip solutions, carrier concentration, solution volume/membrane area ratio and initial metal concentration on the system are discussed. The experimental results obtained are explained on the basis of a physicochemical model considering diffusion of the metal species in the feed solution, chemical reaction in the membrane surface and diffusion of species through the membrane phase. The values of the mass transfer coefficients in the aqueous and organic phases and the rate constants of the reactions were determined. The influence of the hydrochloric acid concentration on these parameters is established.

Mercury determination in sediments by CVAAS after on line preconcentration by solid phase extraction with a sol-gel sorbent containing CYANEX 471X®

The development of a preconcentration method for the measurement of trace levels of mercury in digested sediments is described. Solid phase extraction (SPE) was used for the preconcentration of mercury coupled on-line by means of a flow injection (FI) system followed by cold vapour atomic absorption spectrometry (CVAAS) detection. The SPE was carried out through a column packed with a sorbent material containing triisobutylphosphine sulfide (CYANEX 471X®) as mercury extractant and prepared by the sol-gel process. The effects of FI variables (argon, eluent, and reductant flow rates, loading and elution times) as well as the eluent concentration on the analytical performance of the method were evaluated. The proposed method was validated under the optimum conditions. The calibration graph was linear from 0.05 µg L−1 to 3.0  µg L−1 of Hg. The detection limit (DL), based on three times the standard deviation of the blank measurement criterion, was 24 ng L−1. The repeatability was 1.5% and 1.8% RSD (n = 10) at concentrations of 0.5 and 1  µg L−1 of Hg, respectively. Method enrichment factors of 16 with a productivity of 30 samples h−1 or 32 with a productivity of 17 samples h−1 were achieved under selected conditions. Certified reference materials, inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapour atomic fluorescence spectrometry (CVAFS), were used to evaluate the accuracy of the proposed method.

Simultaneous Au(III) extraction and in-situ formation of polymeric membrane-supported gold nanoparticles: a sustainable process with application in catalysis

A polymeric membrane-supported catalyst with immobilized gold nanoparticles (AuNPs) was prepared through the extraction and in situ reduction of AuIII salts in a one-step strategy. Polymeric inclusion membranes (PIMs) and polymeric nanoporous membranes (PNMs) were tested as different membrane-support systems. Transport experiments indicated that PIMs composed of cellulose triacetate, 2-nitrophenyloctyl ether, and an aliphatic tertiary amine (Adogen 364 or Alamine 336) were the most efficient supports for AuIII extraction. The simultaneous extraction and reduction processes were proven to be the result of a synergic phenomenon in which all the membrane components were involved. Scanning electron microscopy characterization of cross-sectional samples suggested a distribution of AuNPs throughout the membrane. Transmission electron microscopy characterization of the AuNPs indicated average particle sizes of 36.7 and 2.9 nm for the PIMs and PNMs, respectively. AuNPs supported on PIMs allowed for >95.4 % reduction of a 0.05 mmol L-1 4-nitrophenol aqueous solution with 10 mmol L-1 NaBH4 solution within 25 min.

Evaluation of the measurement of Cu(II) bioavailability in complex aqueous media using a hollow-fiber supported liquid membrane device (HFSLM) and two microalgae species (Pseudokirchneriella subcapitata and Scenedesmus acutus).

The environmental bioavailability of copper was determined using a hollow-fiber supported liquid membrane (HFSLM) device as a chemical surrogate and two microalgae species (Scenedesmus acutus and Pseudokirchneriella subcapitata). Several experimental conditions were studied: pH, the presence of organic matter, inorganic anions, and concomitant cations. The results indicated a strong relationship between the response given by the HFSLM and the microalgae species with free copper concentrations measured by an ion selective electrode (ISE), in accordance with the free-ion activity model (FIAM). A significant positive correlation was evident when comparing the bioavailability results measured by the HFSLM and the S. acutus microalga species, showing that the synthetic device may emulate biological uptake and, consequently, be used as a chemical test for bioavailability measurements using this alga as a biological reference.

Determination of germanium(IV) in sulphide ores by differential pulse polarography in pyrogallol-sulfuric acid media☆

Abstract The evaluation of the polarographic response (dpp) of Ge(IV) in several sulfuric acid media containing pyrogallol allowed to establish optimum conditions for the reduction of this ion. In the media studied, the reduction of Ge(IV) provides a signal that can be used for quantitative analysis. This research led to a method for the determination of Ge(IV) in sulphide ores that involves sepatation of interferences by a liquid-liquid extraction technique. Using a static mercury drop electrode the method yielded a calculated detection limit of 3 × 10−8 M.

Nickel (II) Preconcentration and Speciation Analysis During Transport from Aqueous Solutions Using a Hollow-fiber Permeation Liquid Membrane (HFPLM) Device.

Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membrane (HFSLM) device was studied. A counterflow of protons coupled to complexation with formate provided the driving force of the process, while Kelex 100 was employed as carrier. The influence of variables related to module configuration (acceptor pH and carrier concentration) and to the sample properties (donor pH) on the preconcentration factor, E, was simultaneously studied and optimized using a 3 factor Doehlert matrix response surface methodology. The effect of metal concentration was studied as well. Preconcentration factors as high as 4240 were observed depending on the values of the different variables. The effects of the presence of inorganic anions (NO2−, SO42−, Cl−, NO3−, CO32−, CN−) and dissolved organic matter (DOM) in the form of humic acids were additionally considered in order to carry out a speciation analysis study. Nickel preconcentration was observed to be independent of both effects, except when cyanide was present in the donor phase. A characterization of the transport regime was performed through the analysis of the dependence of E on the temperature. E increases with the increase in temperature according to the equation E(K) = −8617.3 + 30.5T with an activation energy of 56.7 kJ mol−1 suggesting a kinetic-controlled regime. Sample depletion ranged from 12 to 1.2% depending on the volume of the donor phase (100 to 1000 mL, respectively).

catena-Poly­[bromo(ω-thio­capro­lactam-κS)­gold(I)](Au—Au)

The title compound, [AuBr(C 6 H 11 NS)] n , formed through an Au III →Au I reduction process, presents a polymeric structure including Au chains with alternating Au-Au distances of 3.0898 (8) and 3.1181 (8) A. The coordination geometry is best described on the basis of linear [AuBr(C 6 H 11 NS)] molecules, which are associated into a one-dimensional polymer via a common aurophilic interaction.

Synthesis and characterization of hybrid membranes based on sulfonated poly(ether ether ketone) (SPEEK) and polysiloxane

AbstractPolymer electrolyte membrane fuel cells (PEMFC) for hydrogen and methanol have attracted the attention of research groups for many years mainly because they are promising candidates for clean and renewable power sources. The most common commercial product used as PEM is Nafion®. However, certain limitations and high production costs stimulate the research of new materials. In this work, new hybrid proton-conducting membranes for PEMFC based on sulfonated poly(ether ether ketone) and an inorganic–organic polysiloxane phase were obtained with the objective of improving its mechanical, thermal, and chemical resistance properties. The hybrid membranes were prepared by dissolving the base polymer in DMSO and adding different amounts of the polysiloxane phase previously obtained from polydimethylsiloxane and a cross-linking agent (tetraethyl orthosilicate or phenyltrimetoxysilane). Membranes were characterized using infrared spectroscopy and thermal analysis. Macroscopic properties as water uptake, ion-...