Maryse Bacquet

Synthesis and Characterization of Silica Gels Functionalized with Monochlorotriazinyl β-Cyclodextrin and their Sorption Capacities towards Organic Compounds

Different supports, containing a new derivative ofβ-cyclodextrin – monochlorotriazinylβ-cyclodextrin (β-CDMCT) – used forthe reduction of pollutants in waste water, have beenprepared. They are based on silica gel, initially eithercoated with polyethyleneimine (PEI) or grafted with3-aminopropyltrimethoxysilane, functionalized in asecond step with β-CDMCT. In order to obtainsorbents with high β-cyclodextrin content andmaximum accessibility of the β-CD cavity, thefuntionalization was studied while varying experimentalconditions. Thermogravimetry, Raman spectroscopy,specific surface area and pore size distribution were usedfor the characterization of supports. Sorption experimentsshow that these sorbents have sorption capacities towardssome organic pollutants. The mechanism of sorption is bothphysical adsorption in the polymer network (for supportsobtained by coating) and/or the formation of an inclusioncomplex between β-CDMCT and guest molecules.

Poly(ethylenimine) coated onto silica gels: Adsorption capacity toward lead and mercury

A series of poly(ethylenimines) (PEI) coated onto silica gels has been tested for the ability to complex lead and mercury in aqueous solutions. The study of the kinetics of metal uptake revealed that all sorbents exhibit a fast rate of sorption. The saturation capacities of the different systems were evaluated according to the Langmuir equation. The influence of different parameters like pH, textural characteristics of silica, and amount of coated polymer were discussed. Finally, cycles of stripping and sorption for lead metal were investigated in column system to evaluate the long-term stability of the sorption properties. One striking result was that crosslinking PEI onto silica prevents the desorption of PEI and greatly improves the sorption capacity.

The removal of organic pollutants from water using new silica-supported β-cyclodextrin derivatives

Two series of supports obtained with a methacryloyl-β-cyclodextrin derivative grafted or coated onto silica have been tested for their ability to sorb aromatic pollutants in aqueous solutions. The study of the kinetics of pollutant uptake revealed that all supports exhibit a fast rate of sorption. The adsorption isotherms were correlated with the Langmuir and Freundlich models and permit to conclude that the sorption mechanisms depend on the structure and the concentration of the pollutant. Finally, cycles of stripping and sorption were investigated in a column system to evaluate the stability of the sorption properties.

Polysiloxane surface modified with bipyrazolic tripodal receptor for quantitative lead adsorption

A new silica gel compound modified N,N-bis(3,5-dimethylpyrazol-1-ylmethyl) amine (SiN(2)Pz) was synthesized and characterized by elemental analysis, FT-IR, (13)C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area and BJH pore sizes. The new surface exhibits good chemical and thermal stability determined by thermogravimetry curves (TGA). The effect of pH and stirring time on the adsorption of Pb(II) were studied. The process of metal retention was followed by batch method and the optimum pH value for the quantitative adsorption of this toxic metal ion was 7. At this pH value, the new functionalized polysiloxane presents further improvements and shows higher affinity (123mg of Pb(2+)/g of silica) for the effective adsorption of Pb(II) compared to others described sorbents. The extracted amounts of Pb(II) were determined by atomic absorption measurements.

Organically Modified Silica with Pyrazole-3-carbaldehyde as a New Sorbent for Solid-Liquid Extraction of Heavy Metals

A new chelating matrix, SiNP, has been prepared by immobilizing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel modified with 3-aminopropyl-trimethoxysilane. This new chelating material was well characterized by elemental analysis, FT-IR spectroscopy, cross polarization magic angle spinning solid state 13C-NMR, nitrogen adsorption-desorption isotherm, BET surface area, BJH pore size, and scanning electron microscopy (SEM). The new product exhibits good chemical and thermal stability as determined by thermogravimetry curves (TGA). The new prepared material was used as an adsorbent for the solid-phase extraction (SPE) of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions using a batch method, prior to their determination by flame atomic adsorption spectrometry. The adsorption capacity was investigated using kinetics and pH effects. Common coexisting ions did not interfere with separation and determination.

Immobilization of pyrazole compounds on silica gels and their preliminary use in metal ion extraction

A series of acyclic pyrazole derivatives was prepared by condensation reactions. These compounds were covalently immobilized on silica gel through a flexible 3-glycidoxypropyltrimethoxysilane spacer arm. These materials were used as sorbents for the recovery of heavy and alkali metal ions from aqueous solutions. They exhibit good selectivity between heavy metal ions and alkali ions with an affinity especially high towards mercury. The comparison with liquid-liquid extraction shows that the capacity is not affected by the grafting of the pyrazole rings on the surface of silica. In addition, the solid-liquid process is more convenient in terms of facility of use.

New silica gels functionalized with 2-hydroxy-3-methacryloyloxypropyl-β-cyclodextrin using coating or grafting methods

The synthesis of a large range of supports based on silica functionalized by a new derivative of β-cyclodextrin, 2-hydroxy-3-methacryloyloxypropyl-β-cyclodextrin (βCDMAHP monomer), is described. Two methods of reaction were chosen: (1) coating via a radical polymerization of the βCDMAHP monomer (E1 series) and (2) radical grafting after silanization of silica using γ-methacryloyltrimethoxysilane (G1 series). As a preliminary step, a detailed spectroscopic characterization of the βCDMAHP was undertaken. Subsequently, within the two approaches, the experimental conditions were varied in order to investigate the effect on the βCD content in the functionalized supports. The changes in the porosity of the silica were also analysed. Finally, a comparison of the two methods is discussed, bearing in mind that these sorbents are to be used for water decontamination applications.

Polyamines adsorbed onto silica gel: A Raman microprobe analysis

Polyamine [especially poly(ethylenimine) and poly(4-vinylpyridine)] adsorption onto silica gels for chromatography and water-decontamination experiments, using a Raman microprobe, is reviewed. First, the bare silica are characterized. Then, the polyamines and the adsorbed polyamines spectra are compared. We show that polyamine adsorption onto silica occurs with two kinds of polymer populations: chemisorbed (trains due to important interactions between silanol and the nitrogen atom) and physisorbed (multilayers) polymer. The modifications of chemisorbed polymer bands are stronger than are the physisorbed ones.

New HPLC stationary phases based on (methacryloyloxypropyl-β-cyclodextrin-co-N-vinylpyrrolidone) copolymers coated on silica. Preparation and characterisation

New silica based supports for use in HPLC separations have been prepared by the coating of a series of copolymers containing various molar fractions of vinylpyrrolidone (VP) and methacryloyloxypropyl beta cyclodextrin (βW7 MAHP) units on LiChrospher Si100. These chromatographic supports were fully characterised using the following techniques: thermogravimetric analysis, specific area and porous volume measurements, scanning electron micrography, NMR, EDAX and RAMAN spectroscopy. It was demonstrated that the interactions of the copolymer with the silica surface imply the VP units through H-bonding between the amide groups and the silanol functions explaining the increase of the polymer adsorption with the VP residue content. The analysis of the surface area, porous volume and pore size distribution showed that the coating process involved first the largest pores of silica and in a second step the smallest ones. From the 29Si NMR spectroscopy and scanning electron microscopy analysis, it appears that only the supports with high amounts of polymer adsorbed ensured a complete passivation of the silanol groups.

An inorganic–organic hybrid material made of a silica-immobilized Schiff base receptor and its preliminary use in heavy metal removal

A novel and excellent host for heavy metals was synthesized by chemical immobilization of a (E)-4-((pyridin-2-yl-methylene)amino)phenol Schiff base receptor onto silica particles. The new hybrid material (SPSB) was analyzed and evaluated by elemental analysis, FT-IR spectroscopy, solid-state 13C NMR, scanning electron microscopy, BET surface area and BJH analyses. The surface exhibits good thermal stability determined by thermogravimetry and good chemical stability examined in various acidic and buffer solutions (pH 1–7). The coordination ability of SPSB was found to be most efficient in the pH range 6.5–8 for Hg2+, Cd2+, Pb2+ and Zn2+. Alkali coexisting ions did not interfere with separation and determination. The adsorbent can be regenerated at ease without destruction. Heavy metal removal performance (99 mg g−1) was found to be higher compared to previous literature reports.