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Processing spodumene for lithium is challenging as it requires a high temperature transformation of the natural α-monoclinic form to β-tetragonal form, usually followed by acid baking and digestion. This three-step extraction process requires significant heat energy, acid, process complexity and residence time, leading to both operating and capital costs. An approach which helps to eliminate this challenge will therefore be a milestone in processing spodumene. This study, thus, investigates a direct chlorination of α-spodumene using calcium chloride followed by water leaching of the residue to recover lithium, which reduces the energy requirement and number of unit operations. HSC Chemistry software was used to simulate the process using both phases (α and β) of the mineral up to 1100 °C prior to experimental investigation. The α-form was the only polymorph identified in residues after leaching, suggesting that the extraction is directly from the α-phase. However, an initial formation of a metastable β-form followed by a fast synthesis of lithium chloride from it is also suspected. Under optimal conditions of calcium chloride/spodumene molar ratio of 2.0, and 1000 °C treatment for 60 minutes, almost 90 percent lithium chloride was extracted and 85 percent was recovered to the leach solution with the remainder exiting with the off-gas. An apparent activation energy of about 122 ± 6 kJ mol

Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 microns and the degree of liberation of major minerals was found to be more than 90%. The thermal behavior of spodumene and the concentration of its polymorphs were studied by heat treatments in the range of 900 to 1050 °C. All three polymorphs of the mineral (α, γ and β) were identified. Full transformation of the α-phase was achieved at 975 °C and 1000 °C after 240 and 60 min treatments, respectively. SEM images of thermally treated concentrate revealed fracturing of spodumene grains, producing minor cracks initially which became more prominent with increasing temperature. Material disintegration, melting and agglomeration with gangue minerals were also observed at higher temperatures. The metastable γ-phase achieved a peak concentration of 23% after 120 min at 975 °C. We suggest 1050 °C to be the threshold temperature for the process where even a short residence time causes appreciable transformation, however, 1000 °C may be the ideal temperature for processing the concentrate due to the degree of material disintegration and α-phase transformation observed. The application of a first-order kinetic model yields kinetic parameters which fit the experimental data well. The resultant apparent activation energies of 655 and 731 kJ mol−1 obtained for α- and γ-decay, respectively, confirm the strong temperature dependence for the spodumene polymorph transformations.

International audience; Leaching reactions in hydrochloric acid of several cathodic materials used in lithium-ion batteries were investigated between 25 °C and 82 °C. The dissolution rate increased as follows: NMC811 (LiNi0.8Mn0.1Co0.1O2) > NMC622 (LiNi0.6Mn0.2Co0.2O2) >> NMC532 (LiNi0.5Mn0.3Co0.2O2) > NMC111 (LiNi1/3Mn1/3Co1/3O2). The dissolution of lithium is faster than that for nickel, cobalt and manganese. Data analysis demonstrated that NMC dissolution is always a two-step process. In the first step, NMC was transformed very quickly into a new lithium-defficient phase. This phase was subsequently dissolved during a second-rate limiting step. No significant impact of the solid/liquid ratio on the leaching kinetics was observed as far as the solid-liquid ratio remained below the stochiometric composition. Finally, a shrinking core model and a first-order rate law were used to investigate the leaching kinetics of the second rate-limiting step, which is the main step involved during NMC digestion in hydrochloric acid.

Titanium chemistry in aqueous acidic media has been extensively investigated over the last decades. Hydrolyzed species such as Ti(OH)

Lithium-ion battery is the technology of choice in the development of electric vehicles. This technology is now mature although there are still many challenges to increase their energy density while ensuring an irreproachable safety of use. For this goal, it is necessary to develop new cathodic materials that can be cycled at higher voltages and electrolytes compatible with these materials. But the challenge does not only concern the production of efficient batteries for the electrochemical storage of energy since lithium-ion battery technology relies on the use of critical and/or strategic value resources. It is therefore crucial to include Lithium-ion batteries development in a circular economy approach very early. In particular, optimized recycling and reuse of battery components must both minimize their impact on the environment and limit geopolitical issues related to tensions on the mineral resources necessary for lithium-ion battery production. Although recycling will never replace mining, it reduces resource dependence by ensuring the presence of exploitable resources in the territory, which is particularly important for countries like France where exploited or exploitable resources are limited. This conference addresses the development of a new hydrometallurgical process combining leaching of cathodic material from spent lithium-ion battery in acidic chloride media and solvent extraction process. Most of recycling processes reported in the literature rely on the sulphate route and a few studies investigate the potentialities of the chloride route despite many advantages and the possibility to develop new chemistry, which could get easier the metal separation. The leaching mechanisms and the solvent extraction equilibria will be presented in this conference. Based on the comprehension of the physicochemistry of leaching and solvent extraction, the present study will introduce a new hydrometallurgical process for the production of cobalt, nickel, manganese and lithium from spent cathodic materials.

This paper concerns the development of an environment-friendly hydrometallurgical flowsheet dedicated to the recovery of zinc and nickel from a waste residue collected from an Iranian zinc plant. In particular, valuable metals from Ni-Cd cake waste generated at this plant were recovered by a simple hydrometallurgical process using minimum acid for leaching, and solvent extraction step was designed such that addition of sodium hydroxide was not required and the effluent generated is safe to dispose off. The waste was leached with a mixture of hydrochloric acid and sulfuric acid in the presence of hydrogen peroxide in order to achieve a good selectivity towards iron and calcium. Afterwards, cementation was performed at pH 5 in order to remove cadmium. Liquid&ndash, liquid extraction was then implemented to produce high-purity solutions of zinc and nickel. Zinc-nickel separation was obtained at pH 2 by using a mixture of bis-(2-ehtyl-hexyl)-phosphoric acid (HDEHP) and tris-2-ethylhexyl amine (TEHA) diluted in an aliphatic kerosene. TEHA did not directly participate but helped in the extraction of zinc by scavenging the protons released by HDEHP. Therefore, no alkaline solution was necessary for maintaining the equilibrium pH during liquid&ndash, liquid extraction. Finally, this flowsheet allowed to recover more than 95% of zinc and nickel from the residue with more than 99% purity.

International audience; Twenty-two new bifunctional sulfones containing ester, ether and carbonate moieties have been synthesized in the present work. Their physicochemical properties (dynamic viscosity, ionic conductivity in the presence of lithium bis-trifluoromethanesulfonimidate (LiTFSI), boiling and melting points) and their anodic stability have been investigated. Major drawbacks for the use of these sulfones in Lithium Batteries (LiBs) are their high viscosities and high melting points. Nevertheless, these solvents exhibit high anodic stability at platinum, glassy carbon and NMC (LiNi1/3Mn1/3Co1/3) electrodes and their ionic conductivities in the presence of LiTFSI remain high enough to envisage their use in LiBs despite their high viscosities. In particular, 3-methoxytetrahydrothiophene 1,1-dioxide (MESL) is the most interesting one among the 22 synthesized sulfones, because MESL exhibits an oxidation potential at a NMC cathode in the presence of LiTFSI of 4.9 V vs. Li/Li + , an ionic conductivity equal to 1 mS.cm-1 , and a low melting point as well as a high boiling point.

A novel ionic liquid-in-water microemulsion (IL101/TX100/water) was developed for sustainable extraction and separation of precious metals (i.e., Au, Pd, and Pt) in acidic chloride media. Five-step protocol is composed of (i) mixing the feed solution containing precious metals with the ionic liquid based microemulsion; (ii) heating for phase splitting; (iii) phase separation; (iv) stripping; (v) regeneration. The aqueous microemulsion combines green properties of ionic liquid and advantages of microemulsion, and thus affords significant environmental benefits. Phase behaviour and structure of the microemulsion were determined by measuring the conductivity. Effect of various parameters was investigated for the complete extraction and selective recovery of highly pure precious metals (> 99.9% w/w). Based on anion exchange mechanism and micellar structure of the aqueous microemulsion phase, the extraction of Au(III), Pt(IV) and Pd(II) from chloride media characterized by 31P NMR spectroscopies was proposed as{(([P66614]+)m([A]n −)q(Cl−)m-nq)(TX-100)p} where [A]n − refers to the anionic metal species to be extracted, p denotes the average aggregation number of the TX-100 micelles, m the average number of [P66614]+ Cl− molecules in each (TX-100)p micelle and q the average number of [A]n − species extracted per micelle. Two-step stripping strategy was successfully adapted to treat the loaded ionic liquid-surfactant-rich (ILSR) phases with low aggressive media for the selective recovery of Au(III) with Na2S2O3 and Pd(II) and Pt(IV) with thiourea/HCl. The possible recirculation of regenerated ILSR phase without loss of performance was examined within five extraction-stripping cycles. Finally, a flow-sheet towards “zero-waste” concept was proposed for the complete extraction and selective recovery of individual precious metals using environmentally friendly aqueous microemulsion.

International audience; The liquid-liquid extraction of cobalt(II) from an acidic chloride solution by using bis-(2ethylhexyl) phosphoric acid (D2EHPA) diluted in kerosene has been modelled by means of a combination of physicochemical and engineering approaches. This model is able to calculate the performance of solvent extraction flowsheets (residual fraction at the outlet of the flowsheet and concentration factor between the feed solution and eluate) as a function of pH, leach solution flowrate, solvent flowrate and stripping solution flowrate. The influence of these parameters and mixer-settlers arrangements on the performance of eleven flowsheets is discussed.

Solvent extraction is a mature technology that is used in many industrial applications for the extraction and/or purification of metals contained in aqueous solutions. Such a technology could be advantageously utilized to produce high-grade salts of lithium, cobalt, nickel, and manganese from mine or lithium-ion battery recycling. However, nickel–cobalt–manganese separation is not easy by means of commercial extractants. Such a separation could be achieved providing that process operation would be always optimized. Modelling tools could help achieve this goal. This paper presents the development of a global model implementing a physicochemical model and an engineering model, which can predict the influence of pH, flowrates, and mixers-settlers arrangement on the performances of liquid–liquid extraction.

The small world of lithium is booming due to the emergence of electric vehicles. The development of sustainable and economic processes to recover lithium from primary and secondary resources is essential to face up the expected global demand of lithium. Electrodialysis seems to be an interesting alternative among the different technologies available to produce lithium from brines, ores and spent lithium-ion batteries via hydrometallurgical route. However, electrodialysis is presently mainly used at industrial scale in water treatment. This paper gives an overview of recent advances in the development of electrodialysis technology, which could be an asset for the next generations of processes involved in lithium production.

International audience; Oxalate-based aqueous media represent one of the rare options for solubilizing macroscopic amount of niobium (Nb) and tantalum (Ta) without using toxic fluoride-based mixtures. Recent progress in the hydrometallurgy of Nb and Ta also highlighted the potential of oxalate-nitrate media for the separation of Nb and Ta. Nonetheless, the resulting purified aqueous solutions, containing Nb or Ta in HNO3-H2C2O4 mixtures, need to be further processed in order to yield Nb and Ta solid products that can be commercialized. Furthermore, oxalic acid is relatively expensive in the frame of the hydrometallurgy of Nb and its recycling is necessary. In this study, the precipitation of Nb and Ta, as well as their usual minor impurities (Ti and Fe), from oxalic-nitric acid solutions has been investigated for the first time. Neutralization of Nb-HNO3-H2C2O4 mixtures to pH 7-8 by concentrated NaOH or NH4OH was found to be effective at decomposing the oxalate complexes ([NbO(C2O4)3] 3-and [NbO(C2O4)2(H2O)]-) and precipitating Nb in the form of Nb2O5·nH2O while leaving the Page 2/27 oxalate ions in solution. Taking advantage of the solubility difference between nitrate and oxalate salts, the subsequent concentration of the filtrates yields to the recovery of the oxalates as Na2C2O4 or (NH4)2C2O4·H2O and a concentrated solution of sodium or ammonium nitrate. The developed method exhibits high precipitation yields (>99.9%) for Nb and Ta and high recovery yields (>99%) for the nitrates and oxalates. The process was optimized at the laboratory scale (~50 mL) and then validated on industrial Nb and Ta solutions (~225 L) with successful production of purified Nb2O5·nH2O and Ta2O5·nH2O, recovery of the oxalates in the form of Na2C2O4 or (NH4)2C2O4·H2O and a concentration solution of nitrates. Taking together, the proposed precipitation method and the fluoride-free liquid-liquid Nb-Ta separation recently reported pave the way for more suitable hydrometallurgical processes for Nb and Ta.

This paper investigates the reactions involved when LiNi

International audience; We report the building, validation and release of QSPR (Quantitative Structure Property Relationship) models aiming to guide the design of new solvents for the next generation of Li-ion batteries. The dataset compiled from the literature included oxidation potentials (E ox), specific ionic conductivities (k), melting points (T m) and boiling points (T b) for 103 electrolytes. Each of the resulting consensus models assembled 9-19 individual Support Vector Machine models built on different sets of ISIDA fragment descriptors. [1] They were implemented in the ISIDA/Predictor software. Developed models were used to screen a virtual library of 9965 esters and sulfones. The most promising compounds prioritized according to theoretically estimated properties were synthesized and experimentally tested. Despite the tremendous success in the development of new materials for positive electrodes of Lithium-ion batteries, so far little attention was paid to the design of suitable electrolytes. In principle, new electrodes support high voltage, but their application is limited by the poor electrolyte stability to oxidation in high-voltage lithium-ion batteries. Besides, security issues have to be managed due to possible exothermic reactions between the positive electrode and electrolytes, especially at high-voltage. In particular, classical electrolytes such as ethylene carbonate (EC)-dimethyl carbonate (DMC) + lithium hexafluorophos-phate (LiPF 6) can hardly be used at voltage greater than 4.2 V. Higher voltage may lead to dramatic decrease of the cycle ability of the battery and may increase the risk of explosion, fire and release of toxic substances. [2] Thus, increase of flash point, thermal stability and anodic stability of the solvent while minimizing electrolyte viscosity and maximizing ionic conductivity are important goals of electrolyte optimization. In this work, a QSPR approach has been used to guide the design of a new generation of electrolytic solvents. Particular attention was paid to molecules belonging to two different chemotypes: sulfones and esters/ethers. Although, esters and ethers were largely investigated in the literature, their physicochemical and electrochemical properties still need to be optimized for their use in electrolyte for Lithium-ion batteries. Sulfones remain liquid within a large range of temperature, their thermal behavior is very interesting as they are generally non-flammable and have very high flash points (for instance, the flash point of dimethylsulfone is 145°C whereas dimethyl carbonate and a mixture of ethylene carbonate:dimethylcarbonate (1 : 1) exhibit flash points equal to 16 and 25°C, respectively [3]). In this work, 4 key properties [3-4] were considered: ionic conductivities (k) and oxidation potentials (E ox) of lithium-based electrolytes as well as melting points (T m) and boiling points (T b) of dipolar aprotic organic solvents usually considered for Lithium-ion batteries. The electrolyte should have advantageous transport properties in order to reduce the ohmic-drop caused by the internal resistance of the battery cell (high ionic conductivity). The electrolyte must be in liquid state for a large range of temperatures (ideally between À 40°C and 120°C, considering an operating range between À 30°C and 60°C). Simultaneously, the electro-chemical window should be as wide as possible. Currently, oxidation potential of electrolytes reaches about 4-4.2 V at active cathode materials. At high voltage a massive electro-lyte oxidation may occur, leading to a steep increase of the current density with rapid loss of battery cycling performance. Thus, it is highly desirable to design new solvents exhibiting high oxidation potential in the presence of lithium salts. At a first stage, a dataset of 103 dipolar aprotic organic solvents was collected from the literature. This included 155 oxidation potential values measured at 5 mV/s in sulfone or ester solvents in the presence of 1 M LiPF 6 or Lithium bis [a] G.

The production of high purity niobium (Nb) or tantalum (Ta) compounds still relies on processes that require highly acidic conditions and concentrated HF or NH4F solutions. Recent progress in the chemistry of group V elements, along with the evolution of the environmental concerns, call for the development of more sustainable industrial processes for these strategic elements. In sharp contrast with the historical fluoride approach chosen by the Nb and Ta refining industry, there has been a recent surge in the literature concerning the chemistry of these elements in diluted alkaline or oxalate media. We here propose an innovative liquid-liquid extraction process that is amenable to separate Nb and Ta from alkaline feed solutions, can be operated at low acidity and that does not require any fluoride-based chemical. The developed strategy is as follows: first, Nb and Ta are co-extracted from their alkaline solution (pH 12) using a quaternary ammonium salt (Aliquat® 336) dissolved in an organic diluent; then, Nb is selectively back-extracted in a mixture of diluted nitric and oxalic acids; and finally, Ta is stripped in a diluted nitric media. The process also affords purifying Nb from Ti, Fe and Na. Following an optimization at laboratory scale, the full process has been validated during continuous running tests (160 h at 1.4 L h−1) using industrial Nb-Ta caustic solutions coming from the development of the so-called Maboumine process. The developed process works at room temperature, low acidity ([H+] 20 wt% Ta) even when starting from a diluted feed (39 ppm Ta). The proposed strategy paves the way for new Nb and Ta hydrometallurgical processes operating under mild chemical environments and represents a concrete alternative to the current fluoride-intensive industrial methods.

International audience; As one of the most valuable components in waste electrical and electronic equipment (WEEE), the recovery of spent printed circuit boards (PCBs) is economically and strategically relevant. However, their composition drastically changes depending on location, year and the type of appliance in which they were used. For the development of new treatment processes, representative sampling of spent PCBs from large samples is necessary and their raw material compositions should be accurately determined. This study aimed at characterizing spent PCBs by implementing milling, sampling and leaching with an adequate reagent. Sampling was performed on 526 kg of spent PCBs, to obtain different samples milled at 750 µm in order to achieve metal accessibility. These samples were leached by aqua regia and metal contents in the leach solutions were determined. Metal analyses in 40 grams-samples of spent PCBs showed limited composition variation for most metals towards the different samples. Furthermore, a good accordance was found with other studies reported in the literature.

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.

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.

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.

The recovery of Nb(V) and Ta(V) from alkaline solutions was investigated using calcium-bearing reagents (CaCl2(aq), Ca(CH3COO)+(aq), Ca(NTA)−(aq), Ca(EDTA)2−(aq), CaCO3(s) and Ca(OH)2(s)) at 25°C. It was found that hexaniobate and hexatantalate ions (HxNb6O19x−8 and HxTa6O19x−8; 0≤x≤3) can be quantitatively precipitated with calcium chloride, calcium acetate or calcium hydroxide when the ratio (Ca/M)initial is at least 0.4mol/mol (M=Nb, Ta). Precipitation yields higher than 95% are obtained for solutions that contain, as low as, 3∗10−4mol/L of Nb and 1∗10−4mol/L of Ta. Moreover, the proposed precipitation method can be operated in a wide pH range and consumes two times less reactant than the classical way for recovering Nb and Ta which consists of neutralizing their alkaline solutions with a mineral acid. The amorphous calcium niobate concentrate was characterized by elemental analysis (ICP-OES), thermogravimetric analysis (TGA-MS) and Raman spectroscopy and the solid phase K3Ca2.2(H0.6Nb6O19)·nH2O was identified under specific conditions.

Phosphoric acid solutions with 0 < [H3PO4] < 8 mol · L−1 and 0 < U(VI) < 2 mol · L−1 are studied by Infra Red (IR) spectroscopy and modelized using an equation of state adapted for electrolytes. Modeling of H3PO4 solutions without uranium, based on a data set combining literature data and original IR measurement, shows that the dimer H5P2O8− has to be considered for H3PO4 apparent concentration higher than 1 mol · L−1. When uranium(VI) is present and in the considered concentration range, the results of the data treatment are consistent with the existence of three complexes: UO2(H2PO4)+, UO2(H2PO4)2, and UO2(H3PO4)(H2PO4)2, the last two ones being largely predominant.

© 2016 Elsevier B.V. Tantalum (Ta) and niobium (Nb) are two strategic metals essential to several key sectors, like the aerospace, gas and oil, nuclear and electronic industries, but their separation is really difficult due to their almost identical chemical properties. Whereas they are currently produced by hydrometallurgical processes using fluoride-based solutions, efforts are being made to develop cleaner processes by replacing the fluoride media by alkaline ones. However, methods to analyze Nb and Ta simultaneously in alkaline samples are lacking. In this work, we developed a capillary zone electrophoresis (CE) method able to separate and quantify Nb and Ta directly in alkaline media. This method takes advantage of the hexaniobate and hexatantalate ions which are naturally formed at pH > 9 and absorb in the UV domain. First, the detection conditions, the background electrolyte (BGE) pH, the nature of the BGE co-ion and the internal standard (IS) were optimized by a systematic approach. As the BGE counter-ion nature modified the speciation of both ions, sodium- and lithium-based BGE were tested. For each alkaline cation, the BGE ionic strength and separation temperature were optimized using experimental designs. Since changes in the migration order of IS, Nb and Ta were observed within the experimental domain, the resolution was not a monotonic function of ionic strength and separation temperature. This forced us to develop an original data treatment for the prediction of the optimum separation conditions. Depending on the consideration of either peak widths or peak symmetries, with or without additional robustness constraints, four optima were predicted for each tested alkaline cation. The eight predicted optima were tested experimentally and the best experimental optimum was selected considering analysis time, resolution and robustness. The best separation was obtained at 31.0 °C and in a BGE containing 10 mM LiOH and 35 mM LiCH3COO.The separation voltage was finally optimized, resulting in the separation of Nb, Ta, and IS in less than 2.5 min, which is three times faster than any CE method ever reported for the separation of Nb and Ta (acidic media included). Some figures of merit of the method were determined such as linearity ranges and limits of quantitation. Finally, the method was successfully applied to the analysis of a real industrial sample.

International audience; Many studies are now focusing on bioleaching methods to recover metals from WEEE. The efficiency of this process is highly dependent on microorganisms but also on the solid-liquid-gas mass transfer, which is controlled by the reactor design. In this study, bioleaching of comminuted spent printed circuit boards (PCBs) was performed in a stirred tank reactor operated in batch mode and in a double-stage continuous bioreactor. The metal dissolution kinetics were compared. The first stage of the continuous bioreactor was a bubble column in which a BRGM-KCC acidophilic consortium comprising Leptospirillum ferriphilum and Sulfobacillus benefaciens was used to oxidise Fe(II) into Fe(III). The resulting liquor was used to leach out metals contained in PCBs in the second stage of the bioreactor with mechanical stirring. The use of two distinct stages allowed the bacteria to adapt gradually to the PCBs and reach high dissolution yields, i.e. 96% Cu, 73% Ni, 85% Zn and 93% Co when 1% (w/v) PCB scraps were added into the bioleaching reactor, with a hydraulic residence time of 48 hours. By using the double-stage bioreactor, the concentration of PCB scraps could be increased up to 1.8% (w/v) without reducing bioleaching performance. Biomass concentration in the second stage and adaptation of the microorganisms to the toxicity of the metals were sufficient for only the second stage to be used. Under these conditions, the dissolution kinetics were stable, even when iron was provided only by the comminuted PCBs.

International audience; Ferric iron is a low-cost oxidant frequently used in hydrometallurgy and is particularly suitable to leach various metals from printed circuit boards (PCBs). This paper presents the use of the BRGM-KCC acidophilic consortium to generate ferric iron solution in a bubble column run in continuous mode. The influence of influent ferrous iron concentration, ranging from 1 to 9 g L −1 on the bio-oxidation rate was studied in the presence of a solid support. The impacts of the quantity of solid support, the hydraulic residence time (HRT), the culture medium and the type of support were established. Stable performance was achieved over an extended period with a Fe 2+ oxidation rate of 1400 mg L −1 h −1. Cryogenic scanning electron microscopy was used to observe the attachment of cells on the solid support in different operating conditions and showed that the clogging of the solid support with jarosite precipitates influenced its colonization by the microorganisms and the stability of the bioprocess. The operating conditions, and especially the influent ferrous iron concentration and nutritive medium composition , also influenced the structure and the abundance of the microbial community.

International audience; Sulfinates, basic forms of sulfinic acids, constitute key intermediates in organic synthesis for their stability. Given the limited commercial availability of the aliphatic derivatives and the several drawbacks regarding their synthesis, the preparation of alkyl sulfinates remains a challenge. Within the frame of the development of approaches for the conception of aliphatic sulfinates, we describe herein a three-step synthesis of aliphatic sulfinates. This cost-effective method involves the use of 2-mercaptobenzothiazole under mild conditions and exhibits good yields (up to 78% over three steps). This approach provides an access to a wide range of functionalized sulfinates. A good tolerance with respect to diverse functional groups (alkene, alkyne, ether, acetal) was also noted.

The γ-irradiation of a biphasic system composed of tri

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.

An effective solvent extraction-based method has been developed to recover individual platinum group metals (PGMs) (i.e. Pd, Pt and Rh) with high purity from acidic chloride media using phosphonium-based ionic liquid Cyphos IL 101 ([P66614]+Cl−) diluted in xylene used as a model of industrial diluents such as SOLVESSO 150. The system showed the selective co-extraction of Pd(II) and Pt(IV) from a feed solution containing 100 mg L−1 Pt(IV), 55 mg L−1 Pd(II), and 25 mg L−1 Rh(III) in HCl via an anion exchange mechanism, leaving Rh(III) in the raffinate. A McCabe–Thiele diagram demonstrated the quantitative extraction of Pd(II) and Pt(IV) with 0.6 g L−1 [P66614]+Cl− with two counter-current stages at an organic/aqueous (O/A) phase volume ratio of 3/2 at 298 K. The stoichiometry of complexes formed in the organic phases was determined using Job's method and further characterized by 1H, 13C, 31P NMR and UV-vis spectroscopy. More importantly, a two-step stripping strategy was successfully adapted to treat the loaded organic phases with low aggressive media NaSCN and thiourea/HCl for the selective recovery of Pt(IV) and Pd(II), respectively, with high purity >99.9% (w). Three counter-current stages are required for the quantitative stripping of Pt(IV) with 0.1 mol L−1 NaSCN at an O/A ratio of 3, whereas the total stripping of Pd(II) with 0.01 mol L−1 acidic thiourea requires only one stage at an O/A ratio of 5. A series of extraction-stripping processes of up to 5 cycles indicated a possible recirculation of regenerated solvent without loss of performance. Simulated experiments in continuous modes suggest that phosphonium-based ionic liquid such as Cyphos IL 101 can be advantageously used as extractant to recover individually Pd, Pt and Rh from acidic chloride feed solutions as those encountered in the PGM's recycling industry.