Alexandre Chagnes

Guidelines to design organic electrolytes for lithium-ion batteries: environmental impact, physicochemical and electrochemical properties

Electrolytes for lithium-ion batteries (LiBs) have been put aside for too long because a few new solvents have been designed to match electrolyte specifications. Conversely, significant attention has been paid to synthesize new electrode materials and especially positive electrodes. Particularly, most of the studies dedicated to the investigation of electrolytes for LiBs have been focused on mixing different molecules. Currently, the development of high-voltage materials for LiBs stimulates the synthesis of new solvents and new salts that are more stable against oxidation. Despite the challenges, only a few teams are active in this field in developing a rational approach combining physicochemistry, electrochemistry and modelling from the molecular to the macromolecular levels. After assembling a critical collection of physicochemical and electrochemical data from the literature, this study highlights the main trends between the chemical structure of the organic dipolar aprotic solvents and their physicochemical and electrochemical properties to provide a guide for chemists to design new electrolytes for LiBs. This guide also includes indicators to take into account the environmental impact of solvent production by including a life cycle assessment of eight different solvents.

Effects of structural changes of new organophosphorus cationic exchangers on a solvent extraction of cobalt, nickel and manganese from acidic chloride media

The effects of structural changes of organophosphorus cationic exchangers on metal-distribution curves (extraction efficiency vs. pH) have been investigated for the recovery of cobalt(II), nickel(II) and manganese(II) from acidic chloride solutions. By using alkyl groups with different branching and hydrophobicity and by including oxygen atoms in the hydrophobic chains of the cationic exchangers, it has been shown that the change of the chemical structure in the hydrophobic chains plays an important role in the extraction behaviours and causes more specifically a shift of the extraction curves to higher or lower pH depending on pKa values of extracting agents (evaluated by using QSPR calculations), distribution constants of metal–ligand complexes between organic and aqueous phases and the formation constant of the metal–ligand complexes. Based on the present results, interest in the new cationic exchangers synthesized in the present work for cobalt(II), nickel(II) and manganese(II) separation is also discussed.

Phosphoric acid recovery from concentrated aqueous feeds by a mixture of di-isopropyl ether (DiPE) and tri-n-butylphosphate (TBP): extraction data and modelling

This paper reports experimental data about the extraction of phosphoric acid from concentrated aqueous feeds (3 to 14 M H3PO4) by the mixture of di-isopropyl ether (DiPE) and tri-n-butylphosphate (TBP) at 25 °C: distribution ratios of H3PO4 and water, and change of phase volume ratio during extraction. Then, a simple model based on the extraction isotherms of H3PO4 and water as well as on the mass balance of these two compounds is developed in the case of the mixture of 90% wt DIPE and 10% wt TBP that corresponds to the solvent used at the industrial scale for the production of purified phosphoric acid.

Extraction of Nb(V) by quaternary ammonium-based solvents: toward organic hexaniobate systems

Solvent extraction of Nb(v) from alkaline aqueous media using quaternary ammonium solutions, especially Aliquat® 336 diluted in an aliphatic diluent, was investigated. The hexaniobate ions (HxNb6O19x-8) were extracted into the organic phase with very high yields at room temperature and within a few minutes, affording easy access to organic solutions of hexaniobates. Several parameters were found to influence the extraction of HxNb6O19x-8 including the nature and concentration of alkali cations, confirming subtle effects previously described for polyoxoniobates such as ion-pairing with alkali ions. The extraction of HxNb6O19x-8 with Aliquat® 336 is also influenced if competing anions are present in the aqueous phase (NO3-, Cl-, C2O42-, SO42- and CO32-) and varies with the pH mainly due to the competitive extraction of hydroxide ions at high pH. The co-extraction of sodium ions with HxNb6O19x-8 was observed as well as the co-extraction of water molecules, suggesting a self-association of the extractant. The proposed liquid-liquid extraction generic system paves the way for innovative niobium (and potentially tantalum) hydrometallurgical processes and it may also afford more direct routes for exploring the chemistry of hexaniobates in organic solvents.

Characterization of palladium species after γ-irradiation of a TBP–alkane–Pd(NO3)2 system

The γ-irradiation of a biphasic system composed of tri-n-butylphosphate in tetrapropylene hydrogen (TPH) in contact with palladium(II) nitrate in nitric acid aqueous solution led to the formation of two precipitates. A thorough characterization of these solids was performed by means of various analytical techniques including X-Ray Diffraction (XRD), Thermal Gravimetric Analysis coupled with a Differential Scanning Calorimeter (TGA-DSC), X-ray Photoelectron Spectroscopy (XPS), InfraRed (IR), RAMAN and Nuclear Magnetic Resonance (NMR) Spectroscopy, and ElectroSpray Ionization Mass Spectrometry (ESI-MS). Investigations showed that the two precipitates exhibit quite similar structures. They are composed at least of two compounds: palladium cyanide and palladium species containing ammonium, phosphorous or carbonyl groups. Several mechanisms are proposed to explain the formation of Pd(CN)2.

Liquid-Liquid Extraction of Cobalt(II), Nickel(II) and Manganese(II) from Acidic Chloride Media

The extraction properties of two synthesized cationic exchangers, i.e. bis(1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBoPP) and bis(1,3-diisobutoxypropan-2-yl) phosphoric acid (IPA), have been studied for the liquid-liquid extraction of Co(II), Ni(II) and Mn(II) contained in 1 M HCl. A comparison of the extraction properties of these extractants diluted in kerosene with Cyanex® 272 shows BiDiBoPP and IPA extract advantageously at lower pH than Cyanex® 272 and a better Co(II)-Mn(II) separation is achieved using BiDiBoPP or IPA than with Cyanex® 272.

Semiempirical kinetic modelling of water desalination by electrodialysis processes

ABSTRACT Water desalination was performed by electrodialysis (ED) in batch recirculation mode by means of cationic and anionic membranes containing sulfonate and ammonium groups, respectively. Variations in sodium chloride (NaCl) concentration in dilute compartment versus time during ED experiments were recorded at different voltages, flow rates, and feed concentrations. ED experiments were modelled by means of a semiempirical kinetic model. A good agreement is found between experimental data and the model.

Editors’ Notes on Special Issue 34(3): Research Needs for the Recovery of Uranium and Rare Earths from Phosphoric Acid

World phosphate rock production is expected to increase incrementally from 223 million tons in 2015 to 255 million tons in 2019, and phosphate-processing plants are planned to triple in capacity by 2018 through construction of new facilities as reported by U.S. Geological Survey in their Mineral Commodity Summaries of January 2016. Today, most phosphoric acid production plants are based on the hydrometallurgical route to produce wet phosphoric acid (WPA) instead of the pyrometallurgical route, which is usually less energy efficient. As phosphate rocks contain significant amounts of uranium and rare earths (REs), the increase of the world phosphate rock production paves the way to complementary routes for the production of by-product uranium and REs. Therefore, more and more research aims at developing new hydrometallurgical processes to recover uranium and REs from phosphate rocks. However, several technical barriers must be addressed for developing such processes. Oak Ridge National Laboratory developed the first process for the recovery of uranium(VI) from WPA at the end of 1960s, continuing with further studies and improvements until the 1980s. While REs have never been produced fromWPA at the industrial scale, the Oak Ridge process was operated at the industrial scale in the 1980s and 1990s. At today’s uranium prices, however, this process is not efficient enough to be economically attractive for uranium production. The special issue (3) published earlier in 2016 in Volume 34 of Solvent Extraction and Ion Exchange focuses on recent advances in the recovery of uranium and, to a lesser degree, REs, from WPA. It features six invited papers. The special issue begins with a review paper by Singh et al., which gives an overview of literature reports on the processes for recovery of uranium contained in phosphoric acid by different techniques, with an emphasis on solvent extraction technology. A paper by Reddy and Kumar discusses REs extraction and possible separation and recovery methods from phosphoric acid media. Leaching studies are discussed followed by two extraction techniques: solvent extraction and solid–liquid extraction. Regarding H2SO4 leaching, a major part of the REs accompanies the precipitated gypsum, whereas all REs are soluble when HNO3 or HCl is used as a leaching reagent. Dartiguelongue et al. consider the speciation and thermodynamics of H3PO4 and uranium(VI) in aqueous phosphoric acid solutions, up to 8 mol L, with the aim of modeling the behaviors of uranium(VI) in such a complex medium. Two papers are dedicated to a promising new extractant molecule, namely butyl-1-[N,N-bis (2-ethylhexyl)carbamoyl]nonyl phosphonic acid (DEHCNPB), which exhibits breakthrough properties for the recovery of uranium from WPA. In the paper by Pecheur et al., the DEHCNPB coordination structure toward uranium and its aggregation properties have been fully characterized using experimental and theoretical approaches. Miguirditchian et al. present the experimental work done to develop a full liquid–liquid extraction process based on this new molecule, including tests