Biomedical subjects

Jean-Claude Bollinger

Publications and source records attributed to Jean-Claude Bollinger.

13 recordsLinked to original sources

PubMed2006

Chromium and nickel mobilization from a contaminated soil using chelants.

The mobilization of chromium and nickel from an industrial soil was investigated using two biodegradable chelants (citric acid and histidine), compared with a persistent one (ethylenediaminetetraacetic acid). Successive metal mobilizations were carried out in batch experiments. The main reactions involved were estimated by modeling the system with MINEQL+. For a single mobilization, citric acid was the most effective for Cr mobilization and EDTA for Ni. Their effectiveness could be explained by their ability to solubilize the mineral matrix and by the competition for the surfaces sites to desorb Cr(VI). Before and after the mobilizations, the distribution of metals was determined by a sequential extraction procedure. Only slight modifications were observed due to the low percentage of solubilized metal. A concentration of 0.05 mol L(-1) (citric acid and EDTA) allows a good compromise between metal mobilization and preservation of the soil mineral integrity.

Biodegradation, Environmental↗

PubMed2006

Flow microcalorimetric study of butyrylcholinesterase kinetics and inhibition.

The enzymatic hydrolysis of butyrylcholine, catalyzed by horse serum butyrylcholinesterase (EC 3.1.1.8), was studied at 37 degrees C in Tris buffer (pH 7.5) by flow microcalorimetry. A convolution procedure, using the Gamma distribution to represent the impulse response of the calorimeter, was developed to analyze the microcalorimetric curves. After correction for buffer protonation, the hydrolysis reaction was found to be slightly endothermic, with Delta H=+9.8 kJ mol(-1). Enzyme kinetics was studied with both the differential and integrated forms of the Michaelis equation with equivalent results: Michaelis constant K(m)=3.3mM, catalytic constant k(cat)=1.7 x 10(3)s(-1), bimolecular rate constant k(s)=5.1 x 10(5)M(-1)s(-1). The reaction product, choline, was found to be a competitive inhibitor with a dissociation constant K(i)=9.1mM. Betaine had a slightly higher affinity for the enzyme, but the inhibition was only partial. This study confirms the usefulness of microcalorimetry for the kinetic study of enzymes and their inhibitors.

Animals↗

PubMed2005

Arsenic removal by adsorption on iron(III) phosphate.

Under natural conditions, arsenic is often associated with iron oxides and iron(III) oxidative capacity towards As(III) is well known. In this study, As(III) and As(V) removal was performed using synthesised iron(III) phosphate, either amorphous or crystalline. This solid can combine (i) As(III) oxidation by iron(III) and (ii) phosphate substitution by As(V) due to their similar properties. Results showed that adsorption capacities were higher towards As(III), leading to Fe2+ and HAsO4(2-) leaching. Solid dissolution and phosphate/arsenate exchange led to the presence of Fe3+ and PO4(3-) in solution, therefore various precipitates involving As(V) can be produced: with Fe2+ as Fe3(AsO4)2.8H2O(s) and with Fe3+ as FeAsO4.2H2O(s). Such formations have been assessed by thermodynamic calculations. This sorbent can be a potential candidate for industrial waste treatment, although the high release of phosphate and iron will exclude its application in drinking water plants.

Adsorption↗

PubMed2005

Sequential heavy metals extraction from polluted solids: influence of sulfate overconcentration.

The effect of sulfate on the chemical partitioning of Cu, Cd, and Pb in solid phases was assessed in this study. Modified BCR sequential extraction, speeded up by focused ultrasound, was systematically applied to various mixtures of typical geochemical solid phases (an artificial goethite spiked with Cu, Cd, and Pb and natural clays), with or without the addition of calcium sulfate. Sulfate was added so that three different concentrations were found in sequential extracts: 0.5, 1, and 1.5 g/L of sulfate. First, the results suggested that the goethite-surface adsorption sites for sulfate are limited. Then, significant changes in Cd and Pb fractionation were observed in the presence of sulfate, whereas Cu remained strongly adsorbed on the solid phases. The main modifications observed in all the studied samples were a decrease in metal amounts in the first three fractions to the profit of an increase in the residual fraction. These results suggested that the adsorption of metals onto the studied solids was enhanced by the presence of sulfate. From these considerations, some hypotheses are advanced to describe the behavior of Cu, Cd, and Pb and their adsorption mechanisms on solid phases in sulfate-rich systems.

Journal Article↗

PubMed2004

Compositional changes in cement-stabilized waste during leach tests--comparison of SEM/EDX data with predictions from geochemical speciation modeling.

Cement-based stabilization/solidification (s/s) is a widely used treatment process for hazardous wastes containing toxic metals. The treated waste consists of a complex mixture of several solid phases produced by cement hydration reactions. Understanding and predicting the effects of leaching on these individual phases is essential for assessing the long-term immobilization of metal contaminants in s/s waste exposed to rain and groundwater. In this paper, particles of crushed Portland cement doped with copper, lead, and zinc nitrates were leached with nitric acid solutions maintained at constant pH in the range pH 4-7. Changes in solid composition at the microscopic scale were measured by scanning electron microscopy and energy dispersive X-ray spectrometry (SEM/EDX). The geochemical equilibrium model SOLTEQ-B, which accounts for the incongruent solubility behavior of calcium silicate hydrate, was used to simulate the compositional changes in the hydration gel for increasing extents of leaching. Measured concentrations of calcium, silicon, and sulfur were successfully predicted at all extents of leaching. Aluminum, lead, and zinc concentrations were also in good agreement with model predictions, except in the remineralization zones that form when metals solubilized in the outer regions of the s/s waste particles diffuse toward the interior and reprecipitate at higher pH. Copper was less accurately modeled at high extents of leaching. Accounting for the incorporation of contaminant metals into the cement hydration gel (in opposition to assuming the presence of individual metal hydroxides) is crucial for successfully predicting contaminant metal concentrations in the hydration gel at low and intermediate extents of leaching.

Journal Article↗

PubMed2004

Dynamic arsenic removal on a MnO2-loaded resin.

Previous batch studies on a polystyrene matrix loaded with manganese dioxide, synthesized from an anionic commercial resin in chloride form, have proven the efficiency of this sorbent in As(V) and As(III) removal. This solid is now tested with column experiments to predict its behavior in a treatment process. An artificial water, with a composition in major ions similar to that of granitic water, often contaminated with arsenic, was prepared. This artificial water was used to simulate arsenic removal processes under near-natural conditions and with a stable composition. Furthermore, the hydride generation AAS analytical method was optimized to measure low arsenic concentrations (1 to 20 microg/L).

Journal Article↗

PubMed2004

As(V) retention and As(III) simultaneous oxidation and removal on a MnO2-loaded polystyrene resin.

Based on KMnO4 oxidative capacity, a polystyrene matrix loaded with manganese dioxide was synthesized from an anionic commercial resin in chloride form. This medium, called R-MnO2, was tested for As(V) retention and for As(III) simultaneous oxidation and removal. Equilibrium was reached in 2 h and isotherms showed that R-MnO2 maximal capacities towards As(III) and As(V) are, respectively, 0.7 and 0.3 mmol/g. Various mechanisms were involved in As(III) retention: oxidation of H3AsO3(0) by MnO2(s) leading to the formation of HAsO4(2)- and Mn2+, fixation of As(V) formed on the resin beads and precipitation of Mn3(AsO4)2 with Mn2+ released. Successive arsenic desorption and retention steps were performed and showed that the quantity desorbed was low compared to the quantity removed during the first stage of the process. A second removal step, carried out under the same conditions as the first one, proved that the matrix second-removal capacity was weak. This solid sorbent, although not reusable, can be considered in field application as arsenic retention is really strong.

Journal Article↗

PubMed2004

Performance of ion-exchanger grafted textiles for industrial water treatment in dynamic reactors.

The performance of a special class of grafted textiles in removing metal cations from industrial wastewaters was examined in continuous reactors. The influence of various parameters on the ion exchange process (reactor geometry, inlet metal ion concentration, solution flow rate, concentration and type of reagent, etc.) was studied over the complete service cycle of the exchanger (saturation, desorption, regeneration, rinsing). Dynamic ion exchange characteristics were determined and compared with those of resins under identical operating conditions. Higher efficiency of fibrous ion exchangers compared to analogous resins, was shown at all stages of the service cycle. Results were expressed as a function of breakthrough capacity, exchanger utilisation efficiency, volume of solution treated, eluted metal concentration. The use of different reactor geometries showed two of the many possible applications of grafted textiles in water treatment processes.

Industrial Waste↗

PubMed2003

Inhibition of human serum arylesterase by metal chlorides.

The inhibition of arylesterase (paraoxonase, EC 3.1.8.1) by metal chlorides was studied with both pooled human serum (A phenotype) and purified enzyme, using phenyl acetate as substrate. Inhibition data were analysed with the Hill equation. Results obtained with whole serum and purified enzyme were very similar. On the basis of the Hill coefficient, n(H), three groups of inhibitors were distinguished: (1) Cu(2+) and Hg(2+) for which n(H)=1, suggesting a single binding site (probably the free cysteine at position 283); these metals were mixed inhibitors, with more affinity for the free enzyme than for the enzyme-substrate complex; (2) Mn(2+), Co(2+), Ni(2+), Zn(2+), and Cd(2+) for which n(H)>1, suggesting several cooperative binding sites; (3) La(3+), for which n(H)<1. Within groups (1) and (2) the inhibiting potency followed the order of the periodic table. For the 3d elements the inhibiting order followed the Irving-Williams series, with the classical exception of Cu(2+). Only Zn(2+) was inhibitory at its physiological concentration.

Carboxylic Ester Hydrolases↗

PubMed2002

Arsenic adsorption onto pillared clays and iron oxides.

Arsenic adsorption was carried out on simple materials such as goethite and amorphous iron hydroxide, and more complex matrices such as clay pillared with titanium(IV), iron(III), and aluminum(III). These matrices were synthesized from a bentonite whose montmorillonitic fraction was pillared according to optimized parameters. These sorbents were characterized by various methods: XRD, FTIR, BET, DTA/TGA, surface acidity, and zetametry. Elimination of arsenite and arsenate as a function of pH was studied. Arsenate elimination was favored at acidic pH, whereas optimal arsenite elimination was obtained at 4<pH<9. For pH values above 10, the pillared clays were damaged and elimination decreased. Equilibrium time and adsorption isotherms were also determined for arsenite and arsenate at each matrix auto-equilibrium pH. Amorphous iron hydroxide had the highest adsorption capacities both towards arsenate and arsenite. Adsorption capacities of goethite and iron- and titanium-pillared clays toward arsenate were similar, but those toward arsenite were different. Desorption experiments from the various matrices were carried out. Iron- and titanium-pillared clays showed a desorption capacity above 95% and around 40% respectively, but no desorption rate could be obtained for iron (hydr)oxides as they were damaged during the process.

Adsorption↗

PubMed2002

Influence of carbonates on the surface charge of a natural solid.

Carbonates are the predominating species in natural chemical processes. Thus, understanding the reactions that occur on their surfaces is very important. The aim of this study was to determine the influence of carbonates on the surface charge of a natural soil sample. First, surface properties of a synthesized calcite were determined using a simplified surface speciation model correlated to potentiometric titrations, and then intrinsic acidity constants and pH(znpc) (pH where protonic surface charge is equal to 0) were studied for solids with different percentages of calcite. A strong influence on surface properties of the solids was evidenced even for small additional quantities of calcite.

Journal Article↗

PubMed2002

Washing powders and the environment: has TAED any influence on the complexing behaviour of phosphonic acids?

Complexation properties of two phosphonic acids: nitrilotris (methylenephosphonic acid) and 1-hydroxyethane-1,1'-diphosphonic acid, with Cu(II) and Ca(II) have been previously determined by pH and ionic selective electrode titrations. These phosphonic acids are commonly added to washing powders as polyphosphate substitutes and are here studied in the presence of another detergent compound: tetraacetylethylenediamine (TAED), a bleaching activator. Product concentrations were chosen in order to correspond to component concentration ratios encountered in washing powders. Potentiometric titrations were carried out to determine the possible TAED interferences; they indicate that TAED and its by-products have no action on phosphonic acid complexing behaviour. Under our experimental conditions, the action of TAED was modelled with acetic acid and ethylenediamine, the final by-products of TAED hydrolysis. If we take into account both phosphonic and acetic acids, speciation diagrams corresponding to representative fresh water systems showed that the acetic acid does not influence cation speciation.

Copper↗

PubMed2002

Inhibition of butyrylcholinesterase by phenothiazine derivatives.

The inhibition of horse serum butyrylcholinesterase (EC 3.1.1.8) by 10 phenothiazine or thioxanthene derivatives was studied with a purified enzyme. Most compounds were mixed inhibitors, but for some of them an apparent competitive inhibition was observed. The competitive inhibition constants (K) were in the range 0.05 to 5 microM. The structures of the inhibitors were modeled by geometry optimization with the AM1 semi-empirical molecular orbital method and octanol/water partition coefficients were estimated with the CLOGP software. Quantitative structure-activity relationships identified lipophilicity, molecular volume, and electronic energies as the main determinants of inhibition. This quantitative model suggested hydrophobic and charge-transfer interactions of the phenothiazine ring with a tryptophan residue at the "anionic" site of the enzyme, and a hydrophobic interaction of the lateral chain with nonpolar amino acids.

Animals↗