Eduardo Rodriguez de San Miguel | Universidad Nacional Autónoma de México (original) (raw)
Papers by Eduardo Rodriguez de San Miguel
Journal of Hazardous Materials, 2014
Chromium(VI) transport through a supported liquid membrane (SLM) system containing the commercial... more 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.
Journal of Chemical Technology & Biotechnology, 2004
Lead(II) and cadmium(II) solvent extraction (SX) with D2EHPA dissolved in heptane and kerosene fr... more Lead(II) and cadmium(II) solvent extraction (SX) with D2EHPA dissolved in heptane and kerosene from aqueous chloride media was studied. Extraction reaction stoichiometries and extraction equilibrium constants were evaluated. Application of a dispersion-free membrane-based extraction and stripping technique with two hollow-fiber contactors under recirculating operation mode allowed a quantitative (>97%) removal of lead from the aqueous solution in the extraction module with a separation factor of 19 and a 62% recovery in the back-extraction module with a separation factor of 6.3 after 7 h under optimum conditions. Mass-transfer coefficients for the system were evaluated. Optimal conditions for transport and separation are reported and compared using SX and the membrane-based technique.
Industrial & Engineering Chemistry Research, 2021
Extraction and recovery of palladium continues to be a technologically and economically challengi... more Extraction and recovery of palladium continues to be a technologically and economically challenging task, particularly in the recycling process of palladium from scrap automotive catalytic converte...
Acta Crystallogr C Cryst Str, 2004
](https://attachments.academia-assets.com/97393417/thumbnails/1.jpg)
](The title compound, [AuBr(C 6 H 11 NS)] n , formed through an Au III 3Au I reduction process, pre... more The title compound, [AuBr(C 6 H 11 NS)] n , formed through an Au III 3Au I reduction process, presents a polymeric structure including Au chains with alternating AuÐAu distances of 3.0898 (8) and 3.1181 (8) A Ê. 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. Comment As an extension of our work on the extractive properties of 3-thiocaprolactam (1-azacycloheptane-2-thione, Hthcl) in liquid±liquid separation processes, we recently directed our efforts toward gold. Au I is classi®ed as a soft acid and is known to coordinate to a variety of soft bases, particularly sulfurcontaining ligands. For instance, thiourea gives a very stable water-soluble Au I complex, viz. [Au{S C(NH 2) 2 } 2 ] + , which is useful in the extraction of gold from ores (Chernyak et al., 1979). Moreover, Au compounds with sulfur-containing ligands are of current interest owing to their fascinating structural chemistry, and due to their wide variety of applications in classical and modern technologies (Schmidbaur, Grohmann, Olmos & Schier, 1999; Schmidbaur, Grohmann & Olmos, 1999) and in medicine (Brown & Smith, 1980; Shaw, 1999). We previously reported the ef®ciency of Hthcl for binding late transition metals with a d 10 electronic con®guration, such as Hg II (Nun Ä ez Gayta  n et al., 1998) and Cd II and Ag I (Berne Á s et al., 1999). We now report the preparation and characterization of the title compound, (I), the ®rst Au I complex including Hthcl as a ligand. The asymmetric unit of (I) contains two Au I ions, two Br À anions and two S-coordinated Hthcl ligands, with all atoms lying on general positions (Fig. 1). The two Au I cations present similar coordination geometries (Table 1). The Br and Hthcl moieties are trans-coordinated [BrÐAuÐS = 172.75 (9) for Au1 and 170.69 (9) for Au2] and a dimeric fragment is formed through an AuÐAu single bond. These [AuBr(Hthcl)] 2 units are joined via an intermolecular AuÁ Á ÁAu interaction [AuÐAu1Á Á ÁAu = 143.595 (18) and AuÐAu2Á Á ÁAu = 148.803 (17) ], forming a one-dimensional inorganic polymer based on an [Au1ÐAu2] I chain running along a 2 1 axis parallel to b (Fig. 2). These chains are densely packed in the metal-organic compounds m414
Membranes, Jan 18, 2011
Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membra... more 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 ...
Talanta, 2001
The ligands 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (L1), 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L... more The ligands 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (L1), 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L2), 4,10-diaza-2,3,11,12-di(4'-tert-butylbenzo)-18-crown-6 (L3) and N,N-di(methylenecarboxyethoxy) 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L4) have been prepared. Partition coefficients and acid dissociation constants for these four diazadibenzocrown ether compounds were determined in water-chloroform. Their effectiveness was assessed in solvent extraction of Pb(2+) from aqueous solutions into toluene. Ligands L3 and L4 provide high selectivity for Pb(2+) over Cd(2+) and Zn(2+) in transport across plasticized cellulose triacetate membranes.
Solvent Extraction and Ion Exchange, 2008
A hollow fiber supported liquid membrane module using one single fiber impregnated with a mixture... more A hollow fiber supported liquid membrane module using one single fiber impregnated with a mixture of 1,10-dibenzyl-1,10-diaza-18-crown-6 and bis(2-ethylhexyl)phosphate dissolved in hexylbenzene was used for passive sampling of ppb levels of Pb(II), Cu(II), Zn(II), Mn(II), ...
Solvent Extraction and Ion Exchange, 1995
The distribution equilibria of In (III) 0.1 mmol/dm3 from HCI concentrated media (2.2-4 mol/dm3) ... more The distribution equilibria of In (III) 0.1 mmol/dm3 from HCI concentrated media (2.2-4 mol/dm3) with the commercial trialkylamine ADOGEN 364 dissolved in kerosene was studied. Due to the association processes that these type of extractants present in the organic phase, a preliminary study was performed by means of a two phase potentiometric titration with the aim of determining the degree
Separation Science and Technology, 2000
TLC-grade silica gel was functionalized with 8-hydroxyquinoline via a catalyzed Mannich amminomet... more TLC-grade silica gel was functionalized with 8-hydroxyquinoline via a catalyzed Mannich amminomethylation reaction. The resulting solid was characterized by FT-IR and used as a sorbent for 0.05–5 mmol·L Cu(II), Cd(II), Zn(II), Pb(II), and Fe(III) from aqueous solutions in the batch mode. Experiments were carried out in both single and multiple cation solutions. The influence of the aqueous media composition on
Journal of Membrane Science, 2005
The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulo... more The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, bis-(2-ethylhexyl)-phosphoric acid (d2ehpa) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (tbep), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5 × 10 −6 mol m −2 s −1 , which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship Pb R 2 2HR and the extraction equilibrium constant value of 6.2 × 10 −4 determined independently by solid-liquid extraction. An activation energy of 11 kJ mol −1 was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was performed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis.
Journal of Membrane Science, 2006
The effects of different components on the performance of a selected polymer inclusion membrane (... more The effects of different components on the performance of a selected polymer inclusion membrane (PIM) system developed for copper transport were assessed by means of different analytical techniques. Copper(II) transport data, thermal analysis, transmission infrared mapping microspectroscopy (TIMM) and AFM were used to characterize chemical and physical behavior of PIMs with different compositions. The prepared membranes, made using cellulose triacetate (CTA) as support, tris(2-n-butoxyethyl) phosphate (TBEP) as plasticizer, together with an additive (ethanol), and LIX ® 84-I, LIX ® 984 or LIX ® 54-100 as carrier, showed increasing copper(II) permeabilities in the order LIX ® 54-100 < LIX ® 984 < LIX ® 84-I. Membrane permeabilities increased up to 2.6-fold in the strip solution side for LIX ® 84-I PIMs cast with ethanol, and Cu(II) accumulation within the membrane was observed to vary with the amount of additive. The modifications of the transport properties of the PIMs were satisfactorily correlated with the distribution profiles of the membrane components (obtained by TIMM), glass transition temperatures, casting method and topographic structure of the films with the aid of a Teas graph implemented for PIM applications. From this graph it was possible to interpret the interactions between the different membrane components in a phenomenological way, thus contributing to improve the understanding of the role played by each one in the development of a more efficient PIM system for copper transport when using LIX ® reagents as carriers.
Journal of Membrane Science, 2008
... permeation. Eduardo Rodríguez de San Miguel a , Corresponding Author Contact Information , E-... more ... permeation. Eduardo Rodríguez de San Miguel a , Corresponding Author Contact Information , E-mail The Corresponding Author , Anel V. Garduño-García a , María E. Núñez-Gaytán b , Julio C. Aguilar a and Josefina de Gyves a. a ...
Journal of Membrane Science, 2009
... PDF (384 K); Export citation; E-mail article; Highlight keywords on: No highlighting Reflect ... more ... PDF (384 K); Export citation; E-mail article; Highlight keywords on: No highlighting Reflect ... proton transport. DNSA has been used before as ion carrier for transport of some radioisotopes [7] and [29] and for Pd(II) extraction [30]. The ...
Journal of Membrane Science, 2009
The synthesis and characterization of new hybrid organic-inorganic membranes (HOIMs) consisting o... more The synthesis and characterization of new hybrid organic-inorganic membranes (HOIMs) consisting of a semi-interpenetrating polymer network, for proton conduction, are described. Silane phases (SPs) were prepared by a sol-gel route and used in the synthesis of the hybrid membranes with cellulose triacetate (CTA) as organic matrix and dinonylnaphthalenesulfonic acid (DNSA) as proton carrier. For the preparation of the SPs dichlorodimethylsilane (DCDMSi) was crosslinked with tetraethoxysilane (TEOS) or phenyltrimethoxysilane (PTMS). FTIR spectroscopy was used to optimize this procedure and solutions 1 H NMR and 29 Si NMR were used to characterize the SPs. The SPs and the sulfonated compound contents were varied with respect to the organic polymer in order to optimize proton conductivity performance of the membrane. The latter property and membrane stability were determined by electrochemical impedance spectroscopy (EIS). Membranes prepared with CTA, DNSA and SP(TEOS), soaked in water for 16 days, showed conductivity values of 0.08-4.14 mS/cm and those prepared with SP(PTMS) of 5.52-23.44 mS/cm. Thermal analyses carried out using DSC and TGA techniques indicate that hybrid membranes are stable up to 175 • C. Results of membrane 29 Si NMR and 13 C NMR, ion-exchange capacity and water uptake are also reported.
Journal of Membrane Science, 2011
Variations in membrane functional (permeabilities in source and receiving phases) and structural ... more Variations in membrane functional (permeabilities in source and receiving phases) and structural (thickness, rubber to glass transition temperature (Tg), electrical resistance, and components’ distribution) properties and transport profiles, promoted by modifications in composition that affect metal ion migration across polymer inclusion membranes (PIMs), were studied and explained through permeation, differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and reflection infrared
Journal of Chemical Technology & Biotechnology, 2009
BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the develop... more BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the development of membrane extraction-based methodologies for its separation. The specific advantages (effective carrier immobilization, easy preparation, versatility, and good mechanical properties) of polymer inclusion membranes (PIMs) make them suitable for this purpose. In this work a novel procedure using PIMs for mercury separation with a commercial available extractant (Cyanex 471X) is described and evaluated through the determination of the efficiency parameters (permeability, selectivity, stability) and membrane characterization. RESULTS: Using a membrane composed of 30% cellulose triacetate (CTA), 60% 2-nitrophenyl octyl ether (NPOE), and 10% w/w Cyanex 471X a 0.1 mmol dm −3 Hg(II) solution prepared in 0.01 mol dm −3 HCl was transported to a 0.05 mol dm −3 NaCl solution at pH 12.3 with permeability values in the feed and strip phases of 0.25 and 0.15 cm min −1 , respectively. A diffusive Fickian-type mechanism was inferred from the results. High separation factors ranging between 2 and 5900, less than 11% of competing metal ions transported, active transport of the metal ion and a successful reuse of the PIM were achieved. CONCLUSION: Optimized PIMs using Cyanex 471X represent an interesting alternative for Hg(II) removal from waters showing high efficiency factors and easy implementation.
Journal of Chemical Technology & Biotechnology, 1996
The coupled transport of In(II1) from concentrated HCl media (2-2-4 rnol dm-3) on a supported liq... more The coupled transport of In(II1) from concentrated HCl media (2-2-4 rnol 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.
Journal of Applied Polymer Science, 2004
Hybnd membranes were prepared using poly(vmyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) v... more Hybnd membranes were prepared using poly(vmyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by conden sation The obtained membranes were characterized by Founer transform infrared spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry The remarkable decrease m degree of swelling was observed with increasing TEOS content in membranes and is at tributed to the formation of hydrogen and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water-acetic acid mixtures was mvestigated in terms of feed concentration and the content of TEOS used as crosslinkmg agent The membrane can taming 1 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of3 33 x 10"2 kg/m2 h at 30 °C for 10 mass% of water in the feed Except for membrane M-l, the observed values of water flux are close to the values of total flux in the mvestigated composition range, signifying that the developed membranes are highly water selective From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated The resulting activation energy values, obtained for water permeation being lower than those of acetic acid permeation values, suggest that the membranes have higher separation efficiency The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-l, signifying that coupled-transport is minimal as due to higher selective nature of membranes Further, the activation energy values for permeation of water and diffusion of water are almost equivalent, suggesting that both diflusion and permeation contribute almost equally to the pervaporation process The negative heat of sorption values (A Hs) for water m all the membranes suggests the Langmuir's mode of sorption
Journal of Analytical Atomic Spectrometry, 2005
Journal of Hazardous Materials, 2014
Chromium(VI) transport through a supported liquid membrane (SLM) system containing the commercial... more 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.
Journal of Chemical Technology & Biotechnology, 2004
Lead(II) and cadmium(II) solvent extraction (SX) with D2EHPA dissolved in heptane and kerosene fr... more Lead(II) and cadmium(II) solvent extraction (SX) with D2EHPA dissolved in heptane and kerosene from aqueous chloride media was studied. Extraction reaction stoichiometries and extraction equilibrium constants were evaluated. Application of a dispersion-free membrane-based extraction and stripping technique with two hollow-fiber contactors under recirculating operation mode allowed a quantitative (>97%) removal of lead from the aqueous solution in the extraction module with a separation factor of 19 and a 62% recovery in the back-extraction module with a separation factor of 6.3 after 7 h under optimum conditions. Mass-transfer coefficients for the system were evaluated. Optimal conditions for transport and separation are reported and compared using SX and the membrane-based technique.
Industrial & Engineering Chemistry Research, 2021
Extraction and recovery of palladium continues to be a technologically and economically challengi... more Extraction and recovery of palladium continues to be a technologically and economically challenging task, particularly in the recycling process of palladium from scrap automotive catalytic converte...
Acta Crystallogr C Cryst Str, 2004
The title compound, [AuBr(C 6 H 11 NS)] n , formed through an Au III 3Au I reduction process, pre... more The title compound, [AuBr(C 6 H 11 NS)] n , formed through an Au III 3Au I reduction process, presents a polymeric structure including Au chains with alternating AuÐAu distances of 3.0898 (8) and 3.1181 (8) A Ê. 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. Comment As an extension of our work on the extractive properties of 3-thiocaprolactam (1-azacycloheptane-2-thione, Hthcl) in liquid±liquid separation processes, we recently directed our efforts toward gold. Au I is classi®ed as a soft acid and is known to coordinate to a variety of soft bases, particularly sulfurcontaining ligands. For instance, thiourea gives a very stable water-soluble Au I complex, viz. [Au{S C(NH 2) 2 } 2 ] + , which is useful in the extraction of gold from ores (Chernyak et al., 1979). Moreover, Au compounds with sulfur-containing ligands are of current interest owing to their fascinating structural chemistry, and due to their wide variety of applications in classical and modern technologies (Schmidbaur, Grohmann, Olmos & Schier, 1999; Schmidbaur, Grohmann & Olmos, 1999) and in medicine (Brown & Smith, 1980; Shaw, 1999). We previously reported the ef®ciency of Hthcl for binding late transition metals with a d 10 electronic con®guration, such as Hg II (Nun Ä ez Gayta  n et al., 1998) and Cd II and Ag I (Berne Á s et al., 1999). We now report the preparation and characterization of the title compound, (I), the ®rst Au I complex including Hthcl as a ligand. The asymmetric unit of (I) contains two Au I ions, two Br À anions and two S-coordinated Hthcl ligands, with all atoms lying on general positions (Fig. 1). The two Au I cations present similar coordination geometries (Table 1). The Br and Hthcl moieties are trans-coordinated [BrÐAuÐS = 172.75 (9) for Au1 and 170.69 (9) for Au2] and a dimeric fragment is formed through an AuÐAu single bond. These [AuBr(Hthcl)] 2 units are joined via an intermolecular AuÁ Á ÁAu interaction [AuÐAu1Á Á ÁAu = 143.595 (18) and AuÐAu2Á Á ÁAu = 148.803 (17) ], forming a one-dimensional inorganic polymer based on an [Au1ÐAu2] I chain running along a 2 1 axis parallel to b (Fig. 2). These chains are densely packed in the metal-organic compounds m414
Membranes, Jan 18, 2011
Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membra... more 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 ...
Talanta, 2001
The ligands 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (L1), 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L... more The ligands 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (L1), 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L2), 4,10-diaza-2,3,11,12-di(4&amp;amp;amp;amp;amp;#39;-tert-butylbenzo)-18-crown-6 (L3) and N,N-di(methylenecarboxyethoxy) 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L4) have been prepared. Partition coefficients and acid dissociation constants for these four diazadibenzocrown ether compounds were determined in water-chloroform. Their effectiveness was assessed in solvent extraction of Pb(2+) from aqueous solutions into toluene. Ligands L3 and L4 provide high selectivity for Pb(2+) over Cd(2+) and Zn(2+) in transport across plasticized cellulose triacetate membranes.
Solvent Extraction and Ion Exchange, 2008
A hollow fiber supported liquid membrane module using one single fiber impregnated with a mixture... more A hollow fiber supported liquid membrane module using one single fiber impregnated with a mixture of 1,10-dibenzyl-1,10-diaza-18-crown-6 and bis(2-ethylhexyl)phosphate dissolved in hexylbenzene was used for passive sampling of ppb levels of Pb(II), Cu(II), Zn(II), Mn(II), ...
Solvent Extraction and Ion Exchange, 1995
The distribution equilibria of In (III) 0.1 mmol/dm3 from HCI concentrated media (2.2-4 mol/dm3) ... more The distribution equilibria of In (III) 0.1 mmol/dm3 from HCI concentrated media (2.2-4 mol/dm3) with the commercial trialkylamine ADOGEN 364 dissolved in kerosene was studied. Due to the association processes that these type of extractants present in the organic phase, a preliminary study was performed by means of a two phase potentiometric titration with the aim of determining the degree
Separation Science and Technology, 2000
TLC-grade silica gel was functionalized with 8-hydroxyquinoline via a catalyzed Mannich amminomet... more TLC-grade silica gel was functionalized with 8-hydroxyquinoline via a catalyzed Mannich amminomethylation reaction. The resulting solid was characterized by FT-IR and used as a sorbent for 0.05–5 mmol·L Cu(II), Cd(II), Zn(II), Pb(II), and Fe(III) from aqueous solutions in the batch mode. Experiments were carried out in both single and multiple cation solutions. The influence of the aqueous media composition on
Journal of Membrane Science, 2005
The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulo... more The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, bis-(2-ethylhexyl)-phosphoric acid (d2ehpa) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (tbep), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5 × 10 −6 mol m −2 s −1 , which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship Pb R 2 2HR and the extraction equilibrium constant value of 6.2 × 10 −4 determined independently by solid-liquid extraction. An activation energy of 11 kJ mol −1 was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was performed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis.
Journal of Membrane Science, 2006
The effects of different components on the performance of a selected polymer inclusion membrane (... more The effects of different components on the performance of a selected polymer inclusion membrane (PIM) system developed for copper transport were assessed by means of different analytical techniques. Copper(II) transport data, thermal analysis, transmission infrared mapping microspectroscopy (TIMM) and AFM were used to characterize chemical and physical behavior of PIMs with different compositions. The prepared membranes, made using cellulose triacetate (CTA) as support, tris(2-n-butoxyethyl) phosphate (TBEP) as plasticizer, together with an additive (ethanol), and LIX ® 84-I, LIX ® 984 or LIX ® 54-100 as carrier, showed increasing copper(II) permeabilities in the order LIX ® 54-100 < LIX ® 984 < LIX ® 84-I. Membrane permeabilities increased up to 2.6-fold in the strip solution side for LIX ® 84-I PIMs cast with ethanol, and Cu(II) accumulation within the membrane was observed to vary with the amount of additive. The modifications of the transport properties of the PIMs were satisfactorily correlated with the distribution profiles of the membrane components (obtained by TIMM), glass transition temperatures, casting method and topographic structure of the films with the aid of a Teas graph implemented for PIM applications. From this graph it was possible to interpret the interactions between the different membrane components in a phenomenological way, thus contributing to improve the understanding of the role played by each one in the development of a more efficient PIM system for copper transport when using LIX ® reagents as carriers.
Journal of Membrane Science, 2008
... permeation. Eduardo Rodríguez de San Miguel a , Corresponding Author Contact Information , E-... more ... permeation. Eduardo Rodríguez de San Miguel a , Corresponding Author Contact Information , E-mail The Corresponding Author , Anel V. Garduño-García a , María E. Núñez-Gaytán b , Julio C. Aguilar a and Josefina de Gyves a. a ...
Journal of Membrane Science, 2009
... PDF (384 K); Export citation; E-mail article; Highlight keywords on: No highlighting Reflect ... more ... PDF (384 K); Export citation; E-mail article; Highlight keywords on: No highlighting Reflect ... proton transport. DNSA has been used before as ion carrier for transport of some radioisotopes [7] and [29] and for Pd(II) extraction [30]. The ...
Journal of Membrane Science, 2009
The synthesis and characterization of new hybrid organic-inorganic membranes (HOIMs) consisting o... more The synthesis and characterization of new hybrid organic-inorganic membranes (HOIMs) consisting of a semi-interpenetrating polymer network, for proton conduction, are described. Silane phases (SPs) were prepared by a sol-gel route and used in the synthesis of the hybrid membranes with cellulose triacetate (CTA) as organic matrix and dinonylnaphthalenesulfonic acid (DNSA) as proton carrier. For the preparation of the SPs dichlorodimethylsilane (DCDMSi) was crosslinked with tetraethoxysilane (TEOS) or phenyltrimethoxysilane (PTMS). FTIR spectroscopy was used to optimize this procedure and solutions 1 H NMR and 29 Si NMR were used to characterize the SPs. The SPs and the sulfonated compound contents were varied with respect to the organic polymer in order to optimize proton conductivity performance of the membrane. The latter property and membrane stability were determined by electrochemical impedance spectroscopy (EIS). Membranes prepared with CTA, DNSA and SP(TEOS), soaked in water for 16 days, showed conductivity values of 0.08-4.14 mS/cm and those prepared with SP(PTMS) of 5.52-23.44 mS/cm. Thermal analyses carried out using DSC and TGA techniques indicate that hybrid membranes are stable up to 175 • C. Results of membrane 29 Si NMR and 13 C NMR, ion-exchange capacity and water uptake are also reported.
Journal of Membrane Science, 2011
Variations in membrane functional (permeabilities in source and receiving phases) and structural ... more Variations in membrane functional (permeabilities in source and receiving phases) and structural (thickness, rubber to glass transition temperature (Tg), electrical resistance, and components’ distribution) properties and transport profiles, promoted by modifications in composition that affect metal ion migration across polymer inclusion membranes (PIMs), were studied and explained through permeation, differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and reflection infrared
Journal of Chemical Technology & Biotechnology, 2009
BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the develop... more BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the development of membrane extraction-based methodologies for its separation. The specific advantages (effective carrier immobilization, easy preparation, versatility, and good mechanical properties) of polymer inclusion membranes (PIMs) make them suitable for this purpose. In this work a novel procedure using PIMs for mercury separation with a commercial available extractant (Cyanex 471X) is described and evaluated through the determination of the efficiency parameters (permeability, selectivity, stability) and membrane characterization. RESULTS: Using a membrane composed of 30% cellulose triacetate (CTA), 60% 2-nitrophenyl octyl ether (NPOE), and 10% w/w Cyanex 471X a 0.1 mmol dm −3 Hg(II) solution prepared in 0.01 mol dm −3 HCl was transported to a 0.05 mol dm −3 NaCl solution at pH 12.3 with permeability values in the feed and strip phases of 0.25 and 0.15 cm min −1 , respectively. A diffusive Fickian-type mechanism was inferred from the results. High separation factors ranging between 2 and 5900, less than 11% of competing metal ions transported, active transport of the metal ion and a successful reuse of the PIM were achieved. CONCLUSION: Optimized PIMs using Cyanex 471X represent an interesting alternative for Hg(II) removal from waters showing high efficiency factors and easy implementation.
Journal of Chemical Technology & Biotechnology, 1996
The coupled transport of In(II1) from concentrated HCl media (2-2-4 rnol dm-3) on a supported liq... more The coupled transport of In(II1) from concentrated HCl media (2-2-4 rnol 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.
Journal of Applied Polymer Science, 2004
Hybnd membranes were prepared using poly(vmyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) v... more Hybnd membranes were prepared using poly(vmyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by conden sation The obtained membranes were characterized by Founer transform infrared spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry The remarkable decrease m degree of swelling was observed with increasing TEOS content in membranes and is at tributed to the formation of hydrogen and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water-acetic acid mixtures was mvestigated in terms of feed concentration and the content of TEOS used as crosslinkmg agent The membrane can taming 1 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of3 33 x 10"2 kg/m2 h at 30 °C for 10 mass% of water in the feed Except for membrane M-l, the observed values of water flux are close to the values of total flux in the mvestigated composition range, signifying that the developed membranes are highly water selective From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated The resulting activation energy values, obtained for water permeation being lower than those of acetic acid permeation values, suggest that the membranes have higher separation efficiency The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-l, signifying that coupled-transport is minimal as due to higher selective nature of membranes Further, the activation energy values for permeation of water and diffusion of water are almost equivalent, suggesting that both diflusion and permeation contribute almost equally to the pervaporation process The negative heat of sorption values (A Hs) for water m all the membranes suggests the Langmuir's mode of sorption
Journal of Analytical Atomic Spectrometry, 2005