Ionothermal Carbonization of Sugarcane Bagasse in 1-Alkyl-3-methylimidazolium Ionic Liquids: Insights into the Role of the Chloroferrate Anion.

We report the ionothermal carbonization (ITC) of lignocellulosic biomass in imidazolium tetrachloroferrate ionic liquids (ILs) as an advantageous approach for the preparation of nanostructured carbonaceous materials, namely, ionochars. In a previous study, we investigated the role of the imidazolium cation and demonstrated the possibility of controlling both the textural and morphological properties of ionochars by cation engineering. Although essential for providing intermediate Lewis acidity and relatively high thermal stability, the role of the chloroferrate anion is still open to debate. Herein, we investigated the ITC of sugarcane bagasse and its main component, cellulose, in 1-alkyl-3-methylimidazolium ILs with different chloroferrate anions. We identified anionic speciation and its impact on the properties of the IL by Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The obtained ionochars were characterized by gas physisorption, electron microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and 13C solid-state CP-MAS NMR spectroscopy. We show that the anionic species have a predominant impact on the textural and morphological properties of the ionochars.

α-Aminobisphosphonate Copolymers Based on Poly(ε-caprolactone)s and Poly(ethylene glycol): A New Opportunity for Actinide Complexation.

Original α-aminobisphosphonate-based copolymers were synthesized and successfully used for actinide complexation. For this purpose, poly(α-chloro-ε-caprolactone-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(α-chloro-ε-caprolactone-co-ε-caprolactone) copolymers were first prepared by ring-opening copolymerization of ε-caprolactone (εCL) and α-chloro-ε-caprolactone using poly(ethylene glycol) (PEG) as a macro-initiator and tin(II) octanoate as a catalyst. The chloride functions were then converted to azide moieties by chemical modification, and finally α-aminobisphosphonate alkyne ligand (TzBP) was grafted using click chemistry, to afford well-defined poly(αTzBPεCL-co-εCL)-b-PEG-b-poly(αTzBPεCL-co-εCL) copolymers. Three copolymers, showing different α-aminobisphosphonate group ratios, were prepared (7, 18, and 38%), namely, CP8, CP9, and CP10, respectively. They were characterized by 1H and 31P NMR and size exclusion chromatography. Sorption properties of these copolymers were evaluated by isothermal titration calorimetry (ITC) with neodymium [Nd(III)] and cerium [Ce(III)] cations, used as surrogates of actinides, especially uranium and plutonium, respectively. ITC enabled the determination of the full thermodynamic profile and the calculation of the complete set of thermodynamic parameter (ΔH, TΔS, and ΔG), with the Ka constant and the n stoichiometry. The results showed that the number of cations sorbed by the functional copolymers logically increased with the number of bisphosphonate functions borne by the macromolecular chain, independently of the complexed cation. Additionally, CP9 and CP10 copolymers showed higher sorption capacities [21.4 and 34.0 mg·g-1 for Nd(III) and 9.6 and 14.3 mg·g-1 for Ce(III), respectively] than most of the systems previously described in the literature. CP9 also showed a highest binding constant (7000 M-1). These copolymers, based on non-toxic and biocompatible poly(ε-caprolactone) and PEG, are of great interest for external body decontamination of actinides as they combine high number of complexing groups, thus leading to great decontamination efficiency, and limited diffusion through the skin due to their high-molecular weight, thus avoiding additional possible internal contamination.

Guest-Assisted Proton Conduction in the Sulfonic Mesoporous MIL-101 MOF.

Post-synthesis modification of MIL-101(Cr)-NO2 was explored in order to decorate the organic backbone by propyl-sulfonic groups, with the aim to incorporate mobile and acidic protons for solid-state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10-3  S cm-1 . Propitiously, the impregnation of the material by strong acidic molecules (H2 SO4 ) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10-1  S cm-1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.

Microwave-assisted hydrothermal synthesis of manganate nanoflowers for selective retention of strontium.

An alternative microwave-assisted hydrothermal route for the preparation of manganate nanoflowers under basic conditions has been proposed in view of potential uses in selective retention of strontium from multicomponent aqueous streams. Based on the combination of such characterization techniques as Scanning and Transmission Electronic Microscopy, X-ray photoelectron spectroscopy, and X-ray Diffraction, as well as taking advantage of the computer-aided structure simulation, homogeneous nanoflower morphology possessing a layered structure and K+ compensating cations was evidenced as corresponding to the KMn4O8 chemical formula. The nanoflower sample was subsequently tested for the selective adsorption of strontium and cesium by measuring the individual adsorption isotherms from single-solute and multicomponent aqueous solutions. The material appeared selective towards strontium against cesium even in multicomponent solutions provided that the concentration of calcium remained low. This difference in the retention selectivity was rationalized based on the Density Functional Theory (DFT) calculations of the energy of adsorption and direct calorimetry measurements of the enthalpy of displacement for the individual cations.

Interactions between Oppositely Charged Polyelectrolytes by Isothermal Titration Calorimetry: Effect of Ionic Strength and Charge Density.

In this study, binding of linear poly(l-lysine) to a series of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate copolymers was examined by isothermal titration calorimetry (ITC). Binding constant and stoichiometry were systematically determined at different ionic strengths and for different polyanion charge densities varying between 15% and 100%. The range of investigated ionic strengths was carefully adjusted according to the polyanion charge densities to get measurable binding constants (i.e., formation binding constant typically comprised between 104 and 106 M-1) by isothermal titration calorimetry (ITC). The number of released counterions during the polyelectrolyte complex formation was determined from the log-log dependence of the binding constant according to the ionic strength and was compared to the total number of condensed counterions estimated from the Manning theory. Experimental results obtained by ITC are in very good agreement with those previously obtained by frontal analysis continuous capillary electrophoresis (FACCE) and can be used to model and predict the binding parameters at any ionic strength or any polyanion charge density. Thermodynamic parameters of the complexation between the oppositely charged polyelectrolytes confirm that the complex formation was entropically driven together with a favorable (but minor) enthalpic contribution. For the first time, specificities, advantages/disadvantages of ITC, and FACCE techniques for studying polyelectrolyte complexations are compared and discussed, using the same experimental conditions.

Ionosilicas as efficient sorbents for anionic contaminants: Radiolytic stability and ion capacity.

Ammonium based hybrid ionosilicas were prepared from tetrasilylated ammonium precursors. The formed material exhibited high specific surface area together with mesoporosity. Our results indicate that ionosilicas display high exchange capacity for iodide. They were submitted to 10MeV electron irradiation at a total dose of 1.7MGy. Irradiation was shown not to alter the properties of ionosilica: the morphological, textural and surface properties of the material are hardly modified. The sorption properties (sorption capacity and cumulative displacement enthalpy) are similar before and after electron irradiation. This high radiolytical stability confirms that these innovative materials have therefore high potential as anion traps for future applications in decontamination processes or long term storage of radioactive waste.