Nicolas Fatin-Rouge | Université de Poitiers (original) (raw)
Papers by Nicolas Fatin-Rouge
Journal of Environmental Chemical Engineering, 2013
ABSTRACT We studied a chemical treatment in order to reuse aqueous solutions of chelating agents ... more ABSTRACT We studied a chemical treatment in order to reuse aqueous solutions of chelating agents for trace-metals extraction from a contaminated soil. FeS, air-sparging and Ca3(PO4)2 were successively used to precipitate Cu, Ni and Pb from chelates in soil extracts and recover polyaminocarboxylates in their Ca-form. The results of batch experiments showed that the reused extracting solutions kept their high extraction efficiency after 3-runs. Chelant and solution losses were stable on each run and ranged from 10 to 20%. The low solubility and the stability of FeS in mild acidic conditions make it a promising reagent for metal precipitation and chelant recovery in soil-washing.
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](Journal of the Chemical Society, Dalton Transactions, 2002
hexakis(dimethylphosphinoylmethoxy)calix[6]arene (B 6 bL 6) has been synthesised. Temperature dep... more hexakis(dimethylphosphinoylmethoxy)calix[6]arene (B 6 bL 6) has been synthesised. Temperature dependent 1 H and 31 P NMR studies indicate a mixture of conformers with a time-averaged C 6v symmetry at 405 K in dmso-d 6 ; ∆G ≠ values for conformational interconversion processes are equal to 68(1) and 75(2) kJ mol Ϫ1 and reveal a semi-flexible macrocycle with alternate in-out cone conformation, a fact confirmed by molecular mechanics and dynamics calculations. B 6 bL 6 crystallises as a dimer where the two calixarenes are linked through hydrogen bonding and surrounded by water and toluene molecules in the lattice. UV-Vis spectrophotometric titration of B 6 bL 6 with La() in acetonitrile yields stability constants log β 1 = 9.8 and log β 2 = 19.6 for the 1 : 1 and 1 : 2 (Ln : B 6 bL 6) species, respectively. The corresponding complexes with La, Eu, Gd and Tb have been isolated and characterised. Lifetime determinations of the Eu() and Tb() complexes in acetonitrile solution are consistent with no or little interaction of water molecules in the inner coordination sphere. The new ligand sensitises reasonably well the luminescence of the Tb() (Q abs = 4.8%, τ f = 2.1 ms, 1 : 1 complex) and Eu() (Q abs = 2.5%, τ = 2.0 ms, 1 : 2 complex) ions. DALTON FULL PAPER
Arabian Journal of Chemistry, 2017
Polymer assisted ultrafiltration (PAUF) is a relatively new process in water and wastewater treat... more Polymer assisted ultrafiltration (PAUF) is a relatively new process in water and wastewater treatment and the subject of an increasing number of papers in the field of membrane science. Among the commercial polymers used, poly(ethyleneimine) and poly(acrylic acid) are the most popular to complex numerous metal ions. Recently, there is an increasing interest in the use of chitosan, a natural linear polymer, as chelating agent for complexing metals. Chitosan has a high potential in wastewater treatment mainly due to its polyelectrolyte properties at acidic pH. The objectives of this review are to present the PAUF process and to highlight the advantages gained from the use of chitosan in the process of complexation-ultrafiltration. For this, a PAUF-based literature survey has been compiled and is discussed. From these data, chitosan, a biopolymer that is non-toxic to humans and the environment, is found to be effective in removing metal ions and exhibits high selectivity. It might be a promising polyelectrolyte for PAUF purposes.
Water Research, 2006
The removal of divalent metal ions from hard waters or galvanic wastewater by polymerassisted mem... more The removal of divalent metal ions from hard waters or galvanic wastewater by polymerassisted membrane filtration using alginate was investigated. The ability of this natural polymer to form aggregates and gels in presence of metal ions was studied, in order to carry out metal removal by ultra or micro-filtration. Alginate titrations have shown the presence of amine groups in addition to carboxylates onto the polymer backbone. The binding properties of alginate with divalent cations have been studied, showing an increasing affinity for Ca 2+ over Mg 2+ as polymer concentration increases, and the relative affinity Pb 2+ XCu 2+ 4Zn 2+ 4Ni 2+. The softening of hard natural waters was achieved successfully and easily, but needs an optimal alginate concentration $4 Â 10 À2 M. The alginate powder can be directly added to hard waters. Except for Ni 2+ , metal-removal was efficient. Polymer regeneration has shown that Cu 2+-complexes are labiles.
The Journal of Physical Chemistry B, 2006
Small angle neutron scattering (SANS) and fluorescence correlation spectroscopy (FCS) measurement... more Small angle neutron scattering (SANS) and fluorescence correlation spectroscopy (FCS) measurements were carried out on agarose hydrogels to link their microscopic structure to the diffusivity of solutes at different scales. SANS allowed for the determination of the distribution of void volumes within the gels. They were shown to be compatible with a random network of cylindrical fibers as described by the Ogston model. FCS measured solute diffusivity in spaces similar in size to the void volumes, and thus, the results reflected the gel heterogeneity. Solute diffusivity was predicted by modeling the gel as microscopic geometrical cells. Variations in the diffusivity of solutes of different sizes could be predicted from the structural parameters of the gel using theory, taking into account obstruction by cylindrical cells and solute hydrodynamics. Prediction of the FCS autocorrelation functions for solutes from a cell model demonstrated a lack of sensitivity of this technique for multicomponent analysis.
The Journal of Physical Chemistry B, 2003
The nature and density of charged sites in an agarose gel have been studied. Diffusion and partit... more The nature and density of charged sites in an agarose gel have been studied. Diffusion and partition coefficients of various organic and inorganic ions have been measured as a function of ionic strength, µ, and pH to investigate the solute-gel interactions resulting from charge effects and specific complexation. The majority of binding sites in the gel are pyruvate groups, with an intrinsic protonation constant of log K a int) 3.9. We measured the charge density of the gel as a function of added salt and pH and evaluated the Donnan potential. The partition coefficients of cations decrease and those of anions increase with increasing ionic strength because of progressive screening of the anionic sites in the gel, as predicted by the Boltzmann and Poisson-Boltzmann equations. The charges in the gel become completely screened at µ ≈ 10-2. As predicted with the Smoluchowski-Poisson-Boltzmann theory, the diffusion coefficient of cationic species is reduced at low ionic strength. We tested both cylindrical and spherical symmetries of Poisson-Boltzmann cell models to describe these variations and obtained better results with the former. In addition to electrostatic effects, we detected specific interactions between metal ions and the gel, and we determined the intrinsic association constants. General models are presented for the partitioning and diffusion of solutes in the gel, which consider steric, electrostatic, and chemical interactions.
Langmuir, 2007
Fluorescence correlation spectroscopy (FCS) has been used to study the diffusion of nanometric so... more Fluorescence correlation spectroscopy (FCS) has been used to study the diffusion of nanometric solutes in agarose gel, at microscopic and macroscopic scales. Agarose gel was prepared and put in contact with aqueous solution. Several factors were studied: (i) the role of gel relaxation after its preparation, (ii) the specific structure of the interfacial zone and its role on the local diffusion coefficient of solutes, and (iii) the comparison between the local diffusion coefficient and the average diffusion coefficient in the gel. Fluorescent dyes and labeled biomolecules were used to cover a size range of solutes of 1.5 to 15 nm. Their transport through the interface from the solution toward the gel was modeled by the first Fick's law based on either average diffusion coefficients or the knowledge of local diffusion coefficients in the system. Experimental results have shown that, at the liquid/gel interface, a gel layer with a thickness of 120 microm is formed with characteristics significantly different from the bulk gel. In particular, in this layer, the porosity of agarose fiber network is significantly lower than in the bulk gel. The diffusion coefficient of solutes in this layer is consequently decreased for steric reasons. Modeling of solute transport shows that, in the bulk gel, macroscopic diffusion satisfactorily follows the classical Fick's diffusion laws. For the tested solutes, the local diffusion coefficients in the bulk gel, measured at microscopic scale by FCS, were equal, within experimental errors, to the average diffusion coefficients applicable at macroscopic scales (>or=mm). This confirms that anomalous diffusion applies only to solutes with sizes close to the gel pore size and at short time (<or=min) and spatial scales (<or=1 microm).
Journal of the American Chemical Society, 2000
Journal of Membrane Science, 2007
Transport of four metallic salts (CuCl2, ZnCl2, NiCl2 and CaCl2) through a polyamide nanofiltrati... more Transport of four metallic salts (CuCl2, ZnCl2, NiCl2 and CaCl2) through a polyamide nanofiltration (NF) membrane has been investigated experimentally from rejection rate and tangential streaming potential measurements. Rejection rates have been further analyzed by means of the steric, electric and dielectric exclusion (SEDE) homogeneous model with the effective dielectric constant of the solution inside pores as the single adjustable
Journal of Environmental Science and Health, Part A, 2000
Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for th... more Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for their ability to uptake heavy metals from a contaminated soil. Twenty healthy plants of each species were transplanted to plastic pots containing the soil contaminated with elevated concentrations of Cd, Cr, Cu, Ni, Pb, and Zn. The plants were harvested after 45 days. Below-and above-ground tissues (roots and shoots) were analyzed separately to determine metals concentrations. Compared with the control group, the effects of S,S-ethylenediaminedisuccinic acid (S,S-EDDS) on the uptake of Cd, Cr, Cu, Ni, Pb, and Zn by two medicinal plants were also investigated. The initial contaminant concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in soil were 2.34, 30.53, 16.14, 20.99, 35.77, and 102.31 mg/kg, respectively. The results of metal accumulation with EDDS application showed that EDDS was more efficient at solubilizing Cu and Zn than the control group. Translocation of metals from roots to shoots was most pronounced for Cu and Zn. The only metal that did not result in a transfer factor (TF) !0.3 for at least one of the two test species was Pb. The enrichment factor (E) was also low for Pb. The lower TF and E for Pb illustrated the tendency of that metal to remain bound to soil particles and not transfer into plant tissues. These data suggest that these two medicinal species of Amaranthus could be hyperaccumulators of several of these metals, and were particularly effective in accumulating Zn and Cu. Pb and Cd, while accumulated in measurable amounts, did not decrease significantly in the soil, suggesting these species may not be the best choice for plants to be used when bioremediating Pb-or Cd-contaminated areas.
Journal of Electroanalytical Chemistry, 2006
In environmental processes, the contribution of macromolecular or colloidal metal complexes to th... more In environmental processes, the contribution of macromolecular or colloidal metal complexes to the overall diffusion flux of metal may be of major importance. For labile complexes, the computation of such flux is based on the concept of average diffusion coefficient, which has only been checked systematically with small size ligands and in aqueous solution. This concept is checked here, both
Journal of Colloid and Interface Science, 2007
Tangential streaming potential (TSP) measurements have been carried out so as to assess the elect... more Tangential streaming potential (TSP) measurements have been carried out so as to assess the electrokinetic properties of the active layer of organic nanofiltration (NF) membranes. Due to the porous structure of NF membranes, cares must be taken to convert the experimental data into zeta potential. Indeed, an assumption that is implicitly made in Smoluchowski's theory (or in related approaches accounting for the surface conduction phenomenon) is that both streaming and conduction currents involved in the streaming potential process flow through an identical path. Such an assumption does not hold with porous membranes since the conduction current is expected to flow wherever the electric conductivity differs from zero. Consequently, a non-negligible share of the conduction current is likely to flow through the membrane body filled with the electrolyte solution. This phenomenon has been taken into account by carrying out a series of TSP measurements at various channel heights. Experiments have been conducted with various electrolyte solutions. The inferred zeta potentials have been further converted into membrane volume charge densities which have been used to predict the membrane performances in terms of rejection rates. The conventional NF theory, i.e. based on a steric/Donnan exclusion mechanism, has been found to be unable to describe the experimental rejection rates. Using the volume charge density of the membrane as an adjustable parameter, it has been shown that the conventional theory even predicts the opposite sign for the membrane charge. On the other hand, the experimental rejection rates have been well described by including dielectric effects in the exclusion mechanism. In this case, a noticeable lowering of the effective dielectric constant of the electrolyte solution inside pores has been predicted (with respect to the bulk value).
Journal of Alloys and Compounds, 2004
MRI contrast properties of self-aggregated nanoparticles made from Gd III and 1,2,4,5-tetrakis(py... more MRI contrast properties of self-aggregated nanoparticles made from Gd III and 1,2,4,5-tetrakis(pyrazol-1-yl-methyl-3-carboxylate)benzene (L) are investigated. Viscosity of GdL 2 suspensions and size-characteristics of GdL 2 nanoparticles allow an estimate of their large rotational correlation time. Moreover, two to three H 2 O molecules are bound, on average, to Gd III ions, as deduced from 17 O NMR titration of the Dy III analogue. The large relaxivity of the particles, along with the prominent peak in the range 20-60 MHz, are the consequence of these two properties. Longitudinal (r 1) and transverse (r 2) relaxivities are determined as a function of monomer concentration at 20 • C and 20 MHz. The ratio r 1 /r 2 appears to be favorable for MR imaging using T 1-weighted gradient echo sequences. According to preliminary tests conducted under physiological conditions, the GdL 2 nanoparticles have some potential as contrast agent provided their stability can be increased.
Inorganica Chimica Acta, 1999
... program and linked to an IBM PS/2 computer. An automatic burette (Metrohm 6.3013.210, 10 ml, ... more ... program and linked to an IBM PS/2 computer. An automatic burette (Metrohm 6.3013.210, 10 ml, accuracy 0.03 ml), was used along with a Metrohm 6.0238.000 glass electrode. The latter was prepared with the same electrolyte ...
Inorganic Chemistry, 2000
Helvetica Chimica Acta, 2001
ABSTRACT We report in this paper the coordination and kinetic properties of two oligobipyridine s... more ABSTRACT We report in this paper the coordination and kinetic properties of two oligobipyridine strands, which contain three 2,2′-bipyridine subunits separated by oxydimethylene bridges, the 4,4′-bis(CONET2)-substituted L and the 4,4′-bis(CO2Et)-substituted L′. Spectrophotometric measurements allowed the characterization of thermodynamic complexes and kinetic intermediates* which are involved in the self-assembly process of L2Cu3 and LCu3 helicates. The reaction presents positive cooperativity for the binding of two 2,2′-bipyridine strands to the cuprous cations. While reactive kinetic intermediates* present distorted coordination geometries around CuI, the final rearrangement of the tricuprous bistranded helicates allows more closely tetrahedral coordination of each cation and reduces the interactions. Differences in the bulkiness and electronic properties of the L and L′ substituents do not affect significantly the stability of the corresponding helicates, but greatly influence binding rates in the self-assembly process.
European Polymer Journal, 2006
Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experi... more Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experiments were used to investigate the conformational and electrical properties of polyacrylic acids (PAA). On the one hand, titration curves were calculated to get an insight into the role of pH on the degree of ionization and conformation of PAA chains. On the other hand, experimental potentiometric titrations of PAA were also achieved for different PAA molecular weights and compared to the calculated titration curves obtained by Monte Carlo coarse grained simulations. It was found that for a large range at intermediate PAA ionizations, a good correlation is obtained between experimental and simulations data thanks to the prominence of electrostatic interactions in this domain. The effect of ionic concentration and PAA molecular weight on the titration curves was also investigated. In order to get a better understanding of PAA conformational behavior, we also investigated PAA diffusion properties in aqueous solutions as a function of pH and ionic strength by fluorescence correlation spectroscopy (FCS), thanks to its high sensitivity to measure diffusion coefficients of tracer solutes. Good qualitative agreements were observed between experimental diffusivities and polymer properties calculated from MC simulations. It was shown that the high molecular weight PAA chains display more significant changes in diffusivity in agreement with the ionization degrees and conformational changes observed in the simulations.
European Journal of Inorganic Chemistry, 2003
A new polycarboxylate ligand H 5 L has been synthesized by the attachment of five benzoate subuni... more A new polycarboxylate ligand H 5 L has been synthesized by the attachment of five benzoate subunits onto a diethylenetriamine framework. Seven pK a values have been determined by potentiometry, spectrophotometry and NMR spectroscopy as 1.9(2), 2.8(2), 3.87(5), 4.58(6), 4.87(6), 9.19(6) and 11.68(5), the first four corresponding to the carboxylic functions and the last three to amine sites. The interaction between H 5 L and Ln III ions in dilute aqueous solution has been examined by UV/Vis absorption and emission spectrometries, and has been found to result in monometallic complexes that are moderately stable in the pH range 3.7−7.5. Conditional stability constants at pH 5.3 are logK 11 = 5.3(2), 6.6(1), 6.5(1) and 7.2(3) for La, Eu, Tb and Lu, respectively. In the case of Tb III , the stability constants for [Tb(HL)] − and [Tb(H 2 L)] are
Desalination, 2010
The retention of Cu(II)– and Ni(II)–nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic ac... more The retention of Cu(II)– and Ni(II)–nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) complexes in dilute solutions ([M-chelate]=0.5mM) by ultrafiltration in presence of polyethylenimine (PEI) or chitosan 10mM was studied. Metal retentions larger than 98% were observed for PEI in the pH-range of 4–9. The excellent metal retention resulted from the combination of covalent binding and electrostatic interactions. The metal retention
Journal of Environmental Chemical Engineering, 2013
ABSTRACT We studied a chemical treatment in order to reuse aqueous solutions of chelating agents ... more ABSTRACT We studied a chemical treatment in order to reuse aqueous solutions of chelating agents for trace-metals extraction from a contaminated soil. FeS, air-sparging and Ca3(PO4)2 were successively used to precipitate Cu, Ni and Pb from chelates in soil extracts and recover polyaminocarboxylates in their Ca-form. The results of batch experiments showed that the reused extracting solutions kept their high extraction efficiency after 3-runs. Chelant and solution losses were stable on each run and ranged from 10 to 20%. The low solubility and the stability of FeS in mild acidic conditions make it a promising reagent for metal precipitation and chelant recovery in soil-washing.
Journal of the Chemical Society, Dalton Transactions, 2002
hexakis(dimethylphosphinoylmethoxy)calix[6]arene (B 6 bL 6) has been synthesised. Temperature dep... more hexakis(dimethylphosphinoylmethoxy)calix[6]arene (B 6 bL 6) has been synthesised. Temperature dependent 1 H and 31 P NMR studies indicate a mixture of conformers with a time-averaged C 6v symmetry at 405 K in dmso-d 6 ; ∆G ≠ values for conformational interconversion processes are equal to 68(1) and 75(2) kJ mol Ϫ1 and reveal a semi-flexible macrocycle with alternate in-out cone conformation, a fact confirmed by molecular mechanics and dynamics calculations. B 6 bL 6 crystallises as a dimer where the two calixarenes are linked through hydrogen bonding and surrounded by water and toluene molecules in the lattice. UV-Vis spectrophotometric titration of B 6 bL 6 with La() in acetonitrile yields stability constants log β 1 = 9.8 and log β 2 = 19.6 for the 1 : 1 and 1 : 2 (Ln : B 6 bL 6) species, respectively. The corresponding complexes with La, Eu, Gd and Tb have been isolated and characterised. Lifetime determinations of the Eu() and Tb() complexes in acetonitrile solution are consistent with no or little interaction of water molecules in the inner coordination sphere. The new ligand sensitises reasonably well the luminescence of the Tb() (Q abs = 4.8%, τ f = 2.1 ms, 1 : 1 complex) and Eu() (Q abs = 2.5%, τ = 2.0 ms, 1 : 2 complex) ions. DALTON FULL PAPER
Arabian Journal of Chemistry, 2017
Polymer assisted ultrafiltration (PAUF) is a relatively new process in water and wastewater treat... more Polymer assisted ultrafiltration (PAUF) is a relatively new process in water and wastewater treatment and the subject of an increasing number of papers in the field of membrane science. Among the commercial polymers used, poly(ethyleneimine) and poly(acrylic acid) are the most popular to complex numerous metal ions. Recently, there is an increasing interest in the use of chitosan, a natural linear polymer, as chelating agent for complexing metals. Chitosan has a high potential in wastewater treatment mainly due to its polyelectrolyte properties at acidic pH. The objectives of this review are to present the PAUF process and to highlight the advantages gained from the use of chitosan in the process of complexation-ultrafiltration. For this, a PAUF-based literature survey has been compiled and is discussed. From these data, chitosan, a biopolymer that is non-toxic to humans and the environment, is found to be effective in removing metal ions and exhibits high selectivity. It might be a promising polyelectrolyte for PAUF purposes.
Water Research, 2006
The removal of divalent metal ions from hard waters or galvanic wastewater by polymerassisted mem... more The removal of divalent metal ions from hard waters or galvanic wastewater by polymerassisted membrane filtration using alginate was investigated. The ability of this natural polymer to form aggregates and gels in presence of metal ions was studied, in order to carry out metal removal by ultra or micro-filtration. Alginate titrations have shown the presence of amine groups in addition to carboxylates onto the polymer backbone. The binding properties of alginate with divalent cations have been studied, showing an increasing affinity for Ca 2+ over Mg 2+ as polymer concentration increases, and the relative affinity Pb 2+ XCu 2+ 4Zn 2+ 4Ni 2+. The softening of hard natural waters was achieved successfully and easily, but needs an optimal alginate concentration $4 Â 10 À2 M. The alginate powder can be directly added to hard waters. Except for Ni 2+ , metal-removal was efficient. Polymer regeneration has shown that Cu 2+-complexes are labiles.
The Journal of Physical Chemistry B, 2006
Small angle neutron scattering (SANS) and fluorescence correlation spectroscopy (FCS) measurement... more Small angle neutron scattering (SANS) and fluorescence correlation spectroscopy (FCS) measurements were carried out on agarose hydrogels to link their microscopic structure to the diffusivity of solutes at different scales. SANS allowed for the determination of the distribution of void volumes within the gels. They were shown to be compatible with a random network of cylindrical fibers as described by the Ogston model. FCS measured solute diffusivity in spaces similar in size to the void volumes, and thus, the results reflected the gel heterogeneity. Solute diffusivity was predicted by modeling the gel as microscopic geometrical cells. Variations in the diffusivity of solutes of different sizes could be predicted from the structural parameters of the gel using theory, taking into account obstruction by cylindrical cells and solute hydrodynamics. Prediction of the FCS autocorrelation functions for solutes from a cell model demonstrated a lack of sensitivity of this technique for multicomponent analysis.
The Journal of Physical Chemistry B, 2003
The nature and density of charged sites in an agarose gel have been studied. Diffusion and partit... more The nature and density of charged sites in an agarose gel have been studied. Diffusion and partition coefficients of various organic and inorganic ions have been measured as a function of ionic strength, µ, and pH to investigate the solute-gel interactions resulting from charge effects and specific complexation. The majority of binding sites in the gel are pyruvate groups, with an intrinsic protonation constant of log K a int) 3.9. We measured the charge density of the gel as a function of added salt and pH and evaluated the Donnan potential. The partition coefficients of cations decrease and those of anions increase with increasing ionic strength because of progressive screening of the anionic sites in the gel, as predicted by the Boltzmann and Poisson-Boltzmann equations. The charges in the gel become completely screened at µ ≈ 10-2. As predicted with the Smoluchowski-Poisson-Boltzmann theory, the diffusion coefficient of cationic species is reduced at low ionic strength. We tested both cylindrical and spherical symmetries of Poisson-Boltzmann cell models to describe these variations and obtained better results with the former. In addition to electrostatic effects, we detected specific interactions between metal ions and the gel, and we determined the intrinsic association constants. General models are presented for the partitioning and diffusion of solutes in the gel, which consider steric, electrostatic, and chemical interactions.
Langmuir, 2007
Fluorescence correlation spectroscopy (FCS) has been used to study the diffusion of nanometric so... more Fluorescence correlation spectroscopy (FCS) has been used to study the diffusion of nanometric solutes in agarose gel, at microscopic and macroscopic scales. Agarose gel was prepared and put in contact with aqueous solution. Several factors were studied: (i) the role of gel relaxation after its preparation, (ii) the specific structure of the interfacial zone and its role on the local diffusion coefficient of solutes, and (iii) the comparison between the local diffusion coefficient and the average diffusion coefficient in the gel. Fluorescent dyes and labeled biomolecules were used to cover a size range of solutes of 1.5 to 15 nm. Their transport through the interface from the solution toward the gel was modeled by the first Fick's law based on either average diffusion coefficients or the knowledge of local diffusion coefficients in the system. Experimental results have shown that, at the liquid/gel interface, a gel layer with a thickness of 120 microm is formed with characteristics significantly different from the bulk gel. In particular, in this layer, the porosity of agarose fiber network is significantly lower than in the bulk gel. The diffusion coefficient of solutes in this layer is consequently decreased for steric reasons. Modeling of solute transport shows that, in the bulk gel, macroscopic diffusion satisfactorily follows the classical Fick's diffusion laws. For the tested solutes, the local diffusion coefficients in the bulk gel, measured at microscopic scale by FCS, were equal, within experimental errors, to the average diffusion coefficients applicable at macroscopic scales (>or=mm). This confirms that anomalous diffusion applies only to solutes with sizes close to the gel pore size and at short time (<or=min) and spatial scales (<or=1 microm).
Journal of the American Chemical Society, 2000
Journal of Membrane Science, 2007
Transport of four metallic salts (CuCl2, ZnCl2, NiCl2 and CaCl2) through a polyamide nanofiltrati... more Transport of four metallic salts (CuCl2, ZnCl2, NiCl2 and CaCl2) through a polyamide nanofiltration (NF) membrane has been investigated experimentally from rejection rate and tangential streaming potential measurements. Rejection rates have been further analyzed by means of the steric, electric and dielectric exclusion (SEDE) homogeneous model with the effective dielectric constant of the solution inside pores as the single adjustable
Journal of Environmental Science and Health, Part A, 2000
Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for th... more Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for their ability to uptake heavy metals from a contaminated soil. Twenty healthy plants of each species were transplanted to plastic pots containing the soil contaminated with elevated concentrations of Cd, Cr, Cu, Ni, Pb, and Zn. The plants were harvested after 45 days. Below-and above-ground tissues (roots and shoots) were analyzed separately to determine metals concentrations. Compared with the control group, the effects of S,S-ethylenediaminedisuccinic acid (S,S-EDDS) on the uptake of Cd, Cr, Cu, Ni, Pb, and Zn by two medicinal plants were also investigated. The initial contaminant concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in soil were 2.34, 30.53, 16.14, 20.99, 35.77, and 102.31 mg/kg, respectively. The results of metal accumulation with EDDS application showed that EDDS was more efficient at solubilizing Cu and Zn than the control group. Translocation of metals from roots to shoots was most pronounced for Cu and Zn. The only metal that did not result in a transfer factor (TF) !0.3 for at least one of the two test species was Pb. The enrichment factor (E) was also low for Pb. The lower TF and E for Pb illustrated the tendency of that metal to remain bound to soil particles and not transfer into plant tissues. These data suggest that these two medicinal species of Amaranthus could be hyperaccumulators of several of these metals, and were particularly effective in accumulating Zn and Cu. Pb and Cd, while accumulated in measurable amounts, did not decrease significantly in the soil, suggesting these species may not be the best choice for plants to be used when bioremediating Pb-or Cd-contaminated areas.
Journal of Electroanalytical Chemistry, 2006
In environmental processes, the contribution of macromolecular or colloidal metal complexes to th... more In environmental processes, the contribution of macromolecular or colloidal metal complexes to the overall diffusion flux of metal may be of major importance. For labile complexes, the computation of such flux is based on the concept of average diffusion coefficient, which has only been checked systematically with small size ligands and in aqueous solution. This concept is checked here, both
Journal of Colloid and Interface Science, 2007
Tangential streaming potential (TSP) measurements have been carried out so as to assess the elect... more Tangential streaming potential (TSP) measurements have been carried out so as to assess the electrokinetic properties of the active layer of organic nanofiltration (NF) membranes. Due to the porous structure of NF membranes, cares must be taken to convert the experimental data into zeta potential. Indeed, an assumption that is implicitly made in Smoluchowski's theory (or in related approaches accounting for the surface conduction phenomenon) is that both streaming and conduction currents involved in the streaming potential process flow through an identical path. Such an assumption does not hold with porous membranes since the conduction current is expected to flow wherever the electric conductivity differs from zero. Consequently, a non-negligible share of the conduction current is likely to flow through the membrane body filled with the electrolyte solution. This phenomenon has been taken into account by carrying out a series of TSP measurements at various channel heights. Experiments have been conducted with various electrolyte solutions. The inferred zeta potentials have been further converted into membrane volume charge densities which have been used to predict the membrane performances in terms of rejection rates. The conventional NF theory, i.e. based on a steric/Donnan exclusion mechanism, has been found to be unable to describe the experimental rejection rates. Using the volume charge density of the membrane as an adjustable parameter, it has been shown that the conventional theory even predicts the opposite sign for the membrane charge. On the other hand, the experimental rejection rates have been well described by including dielectric effects in the exclusion mechanism. In this case, a noticeable lowering of the effective dielectric constant of the electrolyte solution inside pores has been predicted (with respect to the bulk value).
Journal of Alloys and Compounds, 2004
MRI contrast properties of self-aggregated nanoparticles made from Gd III and 1,2,4,5-tetrakis(py... more MRI contrast properties of self-aggregated nanoparticles made from Gd III and 1,2,4,5-tetrakis(pyrazol-1-yl-methyl-3-carboxylate)benzene (L) are investigated. Viscosity of GdL 2 suspensions and size-characteristics of GdL 2 nanoparticles allow an estimate of their large rotational correlation time. Moreover, two to three H 2 O molecules are bound, on average, to Gd III ions, as deduced from 17 O NMR titration of the Dy III analogue. The large relaxivity of the particles, along with the prominent peak in the range 20-60 MHz, are the consequence of these two properties. Longitudinal (r 1) and transverse (r 2) relaxivities are determined as a function of monomer concentration at 20 • C and 20 MHz. The ratio r 1 /r 2 appears to be favorable for MR imaging using T 1-weighted gradient echo sequences. According to preliminary tests conducted under physiological conditions, the GdL 2 nanoparticles have some potential as contrast agent provided their stability can be increased.
Inorganica Chimica Acta, 1999
... program and linked to an IBM PS/2 computer. An automatic burette (Metrohm 6.3013.210, 10 ml, ... more ... program and linked to an IBM PS/2 computer. An automatic burette (Metrohm 6.3013.210, 10 ml, accuracy 0.03 ml), was used along with a Metrohm 6.0238.000 glass electrode. The latter was prepared with the same electrolyte ...
Inorganic Chemistry, 2000
Helvetica Chimica Acta, 2001
ABSTRACT We report in this paper the coordination and kinetic properties of two oligobipyridine s... more ABSTRACT We report in this paper the coordination and kinetic properties of two oligobipyridine strands, which contain three 2,2′-bipyridine subunits separated by oxydimethylene bridges, the 4,4′-bis(CONET2)-substituted L and the 4,4′-bis(CO2Et)-substituted L′. Spectrophotometric measurements allowed the characterization of thermodynamic complexes and kinetic intermediates* which are involved in the self-assembly process of L2Cu3 and LCu3 helicates. The reaction presents positive cooperativity for the binding of two 2,2′-bipyridine strands to the cuprous cations. While reactive kinetic intermediates* present distorted coordination geometries around CuI, the final rearrangement of the tricuprous bistranded helicates allows more closely tetrahedral coordination of each cation and reduces the interactions. Differences in the bulkiness and electronic properties of the L and L′ substituents do not affect significantly the stability of the corresponding helicates, but greatly influence binding rates in the self-assembly process.
European Polymer Journal, 2006
Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experi... more Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experiments were used to investigate the conformational and electrical properties of polyacrylic acids (PAA). On the one hand, titration curves were calculated to get an insight into the role of pH on the degree of ionization and conformation of PAA chains. On the other hand, experimental potentiometric titrations of PAA were also achieved for different PAA molecular weights and compared to the calculated titration curves obtained by Monte Carlo coarse grained simulations. It was found that for a large range at intermediate PAA ionizations, a good correlation is obtained between experimental and simulations data thanks to the prominence of electrostatic interactions in this domain. The effect of ionic concentration and PAA molecular weight on the titration curves was also investigated. In order to get a better understanding of PAA conformational behavior, we also investigated PAA diffusion properties in aqueous solutions as a function of pH and ionic strength by fluorescence correlation spectroscopy (FCS), thanks to its high sensitivity to measure diffusion coefficients of tracer solutes. Good qualitative agreements were observed between experimental diffusivities and polymer properties calculated from MC simulations. It was shown that the high molecular weight PAA chains display more significant changes in diffusivity in agreement with the ionization degrees and conformational changes observed in the simulations.
European Journal of Inorganic Chemistry, 2003
A new polycarboxylate ligand H 5 L has been synthesized by the attachment of five benzoate subuni... more A new polycarboxylate ligand H 5 L has been synthesized by the attachment of five benzoate subunits onto a diethylenetriamine framework. Seven pK a values have been determined by potentiometry, spectrophotometry and NMR spectroscopy as 1.9(2), 2.8(2), 3.87(5), 4.58(6), 4.87(6), 9.19(6) and 11.68(5), the first four corresponding to the carboxylic functions and the last three to amine sites. The interaction between H 5 L and Ln III ions in dilute aqueous solution has been examined by UV/Vis absorption and emission spectrometries, and has been found to result in monometallic complexes that are moderately stable in the pH range 3.7−7.5. Conditional stability constants at pH 5.3 are logK 11 = 5.3(2), 6.6(1), 6.5(1) and 7.2(3) for La, Eu, Tb and Lu, respectively. In the case of Tb III , the stability constants for [Tb(HL)] − and [Tb(H 2 L)] are
Desalination, 2010
The retention of Cu(II)– and Ni(II)–nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic ac... more The retention of Cu(II)– and Ni(II)–nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) complexes in dilute solutions ([M-chelate]=0.5mM) by ultrafiltration in presence of polyethylenimine (PEI) or chitosan 10mM was studied. Metal retentions larger than 98% were observed for PEI in the pH-range of 4–9. The excellent metal retention resulted from the combination of covalent binding and electrostatic interactions. The metal retention