Laurent Duclaux

Application of Ulva lactuca and Systoceira stricta algae-based activated carbons to hazardous cationic dyes removal from industrial effluents

Marine algae Ulva lactuca (ULV-AC) and Systoceira stricta (SYS-AC) based activated carbons were investigated as potential adsorbents for the removal of hazardous cationic dyes. Both algae were surface oxidised by phosphoric acid for 2 and subsequently air activated at 600 °C for 3 h. Dyes adsorption parameters such as solution pH, contact time, carbon dosage, temperature and ionic strength were measured in batch experiments. Adsorption capacities of 400 and 526 mg/g for Malachite green and Safranine O by the SYS-AC and ULV-AC respectively were significantly enhanced by the chemical treatments. Model equations such as Langmuir, Freundlich and Temkin isotherms were used to analyse the adsorption equilibrium data and the best fits to the experimental data were provided by the first two isotherm models. BET, FT-IR, iodine number and methylene blue index determination were also performed to characterize the adsorbents. To describe the adsorption mechanism, kinetic models such as pseudo-second-order and the intra particle diffusion were applied. Thermodynamic analysis of the adsorption processes of both dyes confirms their spontaneity and endothermicity. Increasing solution ionic strength increased significantly the adsorption of Safranine O. This study shows that surface modified algae can be an alternative to the commercially available adsorbents for dyes removal from liquid effluents.

Effect of sonication conditions: solvent, time, temperature and reactor type on the preparation of micron sized vermiculite particles.

The effects of temperature, time, solvent and sonication conditions under air and Argon are described for the preparation of micron and sub-micron sized vermiculite particles in a double-jacketed Rosett-type or cylindrical reactor. The resulting materials were characterized via X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area analysis, chemical analysis (elemental analysis), Thermogravimetry analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5h of sonication, whereas longer times promoted aggregation again. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures according to physical/chemical properties of the used solvent. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction [001]; but structural changes were not observed. Sonication at different conditions also led to surface modifications of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicated clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type.

Synthesis and characterization of SWNT-heavy alkali metal intercalation compounds, effect of host SWNTs materials

Abstract Singlewall carbon nanotubes (SWNTs) produced by electric-arc and laser ablation methods were characterized by X-ray diffraction before and after the reaction with alkali metals (M=K, Rb, and Cs). Reaction with annealed SWNTs gave MC 8 composition at saturation. The alkali metal lattice showed short range order incommensurate with graphene cylinders of SWNTs. X-ray diffractogram simulations have enabled the study of the influence of SWNTs structure on that of intercalation compounds. Chemically-purified bundles, constituted of open SWNTs, can be intercalated inside and between the tubes forming disordered structures. Annealed or pristine bundles were intercalated only between the tubes leading to short or long range ordered structure depending on host crystallinity and alkali metal (K, Rb or Cs). The expansion of the 2D SWNTs lattice after intercalation is comparable to graphite intercalation compounds. Some 2D arrangements of SWNTs and K atoms are proposed and discussed to reproduce XRD results. 13 C NMR and ESR studies of annealed doped SWNTs emphasize the fact that the intercalation compounds of SWNTs are metallic.

Clay/carbon nanocomposites as precursors of electrode materials for lithium-ion batteries and supercapacitors

Abstract Chars prepared by pyrolysis of organic precursors (Indoine Blue, Safranine, Pyrene) in the interlayer space of taeniolite were used as electrode materials in lithium/carbon cells. Due to oxidation of interlayer carbon by the silicate host, they contain a high amount of surface groups, and their essentially mesoporous character is attributed to the space liberated by the elimination of the clay template. A large reversible capacity for lithium insertion, up to 900 mAh/g, was detected for these materials. The chars presented a high capacitance which could reach 85 F/g in KOH electrolyte if they were formed below 850°C. Such a high value relatively to the low BET surface area of the chars is strictly related to the important mesopore volume and to the rich surface functionality.

Reactive milling of graphite with lithium: Application to lithium batteries

Reactive milling of graphite with lithium has been performed in order to develop bonding between carbon and lithium atoms and thus to prepare insertion compounds with C/Li molar ratios lower than 6 (C/Li=6, 4 and 2). A test of these new compounds as anodes of Li batteries has shown higher reversible capacities than graphite (372 mA h/g), weaker hysteresis, and smaller irreversible capacities than milled graphite under the same conditions. This is explained by the formation of a lithiated surface.

Novel carbons from nanocomposites for high lithium storage

Abstract Carbons obtained by the pyrolysis of Taeniolite/Indoine blue and Taeniolite/Safranine nanocomposites were investigated for the lithium storage in Li/carbon cells. A high reversible capacity (900 mA h/g) was found, especially for carbons prepared at 700°C. The mesoporous character due to the oxidation of the interlayer carbon by the neighbour SiO 4 tetrahedra during the pyrolysis is responsible for the important insertion of lithium and for the capacitive properties (90 F/g). The high polarisation between insertion and extraction of lithium is strictly connected with these properties. For comparison, carbons reduced with hydrogen and obtained from the pure precursor (Indoine blue) were investigated to elucidate the role of heteroatoms. Voltammetry experiments proved that insertion of lithium is kinetically limited.

Binary adsorption isotherms of two ionic liquids and ibuprofen on an activated carbon cloth: simulation and interpretations using statistical and COSMO-RS models

The adsorption equilibriums of binary mixtures of the 4-tert-butyl-1-propylpyridinium bromide (referred to IL1) and 4-tert-butyl-1-(2 carboxyethyl) pyridinium bromide (referred to IL2) ionic liquids and ibuprofen (2-(4-(2-methylpropyl) phenyl) propanoic acid: IBP) on activated carbon cloth were investigated. The binary adsorption isotherms of the studied systems (IL1/IL2, IL1/IBP and IL2/IBP) have been studied in different conditions (different temperatures ranging from 286 to 313 K and at various concentration ratios 0.5, 1 and 2). The experimental isotherms have been simulated by some new statistical physics models established from the grand canonical ensemble. According to the most appropriate model, the adsorbed ILs and IBP molecules are assumed to be parallel to the activated cloth surface. An inhibition effect has been observed between the adsorbed molecules. The determination of the monolayer adsorbed uptake at saturation has shown an endothermic adsorption process of IBP and an exothermic one of IL1 and IL2. The estimated energy values demonstrate a physical adsorption whatever the adsorbate species. The microscopic adsorption process was interpreted from the point of view of molecular stereography and interaction energy. Moreover, a conductor-like screening model for real solvents (COSMO-RS) has been applied to calculate three specific interaction energies between the adsorbate molecules and a graphene layer modeling the activated carbon surface, i.e., the electrostatic misfit energy (EMF), the hydrogen-bonding energy (EHB) and the van der Waals energy (EvdW).

Experimental and theoretical studies of adsorption of ibuprofen on raw and two chemically modified activated carbons: new physicochemical interpretations

Knowledge of the ibuprofen (IBP) adsorption isotherms is important to understand and to improve its depollution process. In this work, the double layer model with two energies was applied to simulate the adsorption isotherms of ibuprofen on raw activated and two chemically modified granular activated carbons, obtained experimentally at pH = 7 and at different temperatures (298, 313 and 323 K). The chemically modified samples were obtained by treatment at 700 °C under nitrogen flow and ultrasonic treatment in H2O2 solution of the raw granulated activated carbon. The establishment of the model is based on a statistical physics approach, particularly on the grand canonical ensemble. The double layer model with two energies for each layer was found to be the best model to describe the adsorption process of ibuprofen. Using this model, the different adsorption isotherms of ibuprofen were described sterically and energetically through these parameters. The different parameters were interpreted as a function of temperature. In addition to this, the entropy, free enthalpy and the internal energy governing the adsorption process were calculated and interpreted.

A rosette cooling cell: more effective container for solubilization of single-walled carbon nanotubes under probe-type ultrasonic irradiation.

Probe-type ultrasonication has been employed for surfactant-aided solubilization, or individualization, of single-walled carbon nanotubes (SWNTs). The resulting solution can be used not only for spectroscopic analyses such as absorption, photoluminescence, and circular dichroism, but also for separation by density gradient ultracentrifugation, dielectrophoresis, chromatography, and polymer wrapping. In spite of its importance, the sonochemical processing of SWNTs has not been considered seriously. Herein, we report on a more efficient cooling cell for probe-type ultrasonication. As compared with a conventional cylindrical cell, the concentration of the SWNTs solubilized in water was found to be almost double in a rosette cooling cell after ultracentrifugation. The efficiency of a rosette cell can be attributed to the higher efficiency in circulation and cooling of the SWNT dispersion as well as enhancement of the cavitation process.

Characterization and application of three novel biosorbents “Eucalyptus globulus, Cynara cardunculus, and Prunus cerasefera” to dye removal

Abstract Three biosorbents: Eucalyptus globulus, Cynara cardunculus, and Prunus cerasefera leaves were tested to remove Methylene Blue from aqueous solutions. The three biosorbents were characterized by the determination of the Methylene Blue accessible surface, iodine number, BET specific surface area using nitrogen adsorption at 77 K, morphological analysis by scanning electron microscopy, pHPZC, and FTIR analysis. The Methylene Blue adsorption uptakes of the biosorbents were studied as a function of pH, biosorbent dose, stirring speed, ionic strength, and contact time. Optimal conditions for maximum removal of Methylene Blue were found to be: a pH of 10, an adsorbent dose of 8 g L−1, and a contact time of 2 h for E. globulus and C. cardunculus, and a pH of 6.5, an adsorbent dose of 4 g L−1 and a contact time of 2 h for P. cerasefera. The Langmuir models as determined from batch experiments yielded a maximum capacity of adsorption by biosorbent prepared from E. globulus leaves of 250 mg g−1 against 333 ...