Selective Extraction of REEs Thanks to One-Pot Silica Hybrid Materials

International audienceThe importance of rare-earth elements (REEs) in the global economy is rapidly growing, since they are essential to many advanced technologies. Therefore, the development of more performant separation procedures for REEs has become necessary. In the present study, we used silica hybrid materials (SHMs), which were synthesized by an all-in-one approach that allows the direct incorporation of desired functional groups, as sorbent material. Promising results were obtained for the extraction capacities of diglycolamide-functionalized materials. Under the tested conditions, they showed high efficiency (Nd uptake capacity of about 25 mg per g of material) and high selectivity toward REEs from a simulated NdFeB magnet leachate. For these materials, Nd recovery after extraction was achieved with an efficiency of 80% by contacting the loaded material with distilled water at moderate pH (6.5)

Exploring the Aggregation Behavior of Extractant Molecules in Ionic Liquids: A Coupled Polarizable Molecular Dynamics and SAXS Study

International audienceThis study presents a comprehensive investigation of the aggregation behavior of a malonamide extractant molecule (N,N′-dimethyl,N,N′-dioctylhexylethoxymalonamide (DMDOHEMA)) in three different solvents, including two piperidinium- and (trifluoromethylsulfonyl)imide-based ionic liquids (1-ethyl-1-butylpiperidinium bis(trifluoromethylsulfonyl)imide ([EBPip+][NTf2–]) and 1-ethyl-1-octylpiperidinium bis(trifluoromethylsulfonyl)imide ([EOPip+][NTf2–])) and n-dodecane. By combining polarizable molecular dynamics simulations and small-angle X-ray scattering experiments, we extensively investigated the arrangement of supramolecular assemblies of the extractant molecules. Our results showed that the insertion of the alkyl chains of the extractant molecules into the apolar domain of [EOPip+][NTf2–] has a significant impact on the aggregation behavior of the extractant molecules, leading to the formation of smaller aggregates having a higher dispersion compared to other solvents. These findings provide new insights into the physicochemical properties of this type of system and are crucial in designing more effective solvents for rare earth metal extraction

New Carbamoyl Surface-Modified ZrO2 Nanohybrids for Selective Au Extraction from E-Waste

International audienceEfficient and selective extractions of precious and critical metal ions such as Au(III) and Pd(II) were investigated using zirconia nanoparticles surface modified with different organic mono- and di-carbamoyl phosphonic acid ligands. The modification is made on the surface of commercial ZrO2 that is dispersed in aqueous suspension and was achieved by optimizing the Bronsted acid–base reaction in ethanol/H2O solution (1:2), resulting in inorganic–organic systems of ZrO2-Ln (Ln: organic carbamoyl phosphonic acid ligand). The presence, binding, amount, and stability of the organic ligand on the surface of zirconia nanoparticles were confirmed by different characterizations such as TGA, BET, ATR-FTIR, and 31P-NMR. Characterizations showed that all the prepared modified zirconia had a similar specific surface area (50 m2.g−1) and the same amount of ligand on the zirconia surface in a 1:50 molar ratio. ATR-FTIR and 31P-NMR data were used to elucidate the most favorable binding mode. Batch adsorption results showed that (i) ZrO2 surface modified with di-carbamoyl phosphonic acid ligands had the highest adsorption efficiency to extract metals than mono-carbamoyl ligands, and (ii) higher hydrophobicity of the ligand led to better adsorption efficiency. The surface-modified ZrO2 with di-N,N-butyl carbamoyl pentyl phosphonic acid ligand (ZrO2-L6) showed promising stability, efficiency, and reusability in industrial applications for selective gold recovery. In terms of thermodynamic and kinetic adsorption data, ZrO2-L6 fits the Langmuir adsorption model and pseudo-second-order kinetic model for the adsorption of Au(III) with maximum experimental adsorption capacity qmax = 6.4 mg.g−1

A multimodal approach for modeling engagement in conversation

International audienceRecently, engagement has emerged as a key variable explaining the success of conversation. In the perspective of human-machine interaction, an automatic assessment of engagement becomes crucial to better understand the dynamics of an interaction and to design socially-aware robots. This paper presents a predictive model of the level of engagement in conversations. It shows in particular the interest of using a rich multimodal set of features, outperforming the existing models in this domain. In terms of methodology, study is based on two audiovisual corpora of naturalistic face-to-face interactions. These resources have been enriched with various annotations of verbal and nonverbal behaviors, such as smiles, head nods, and feedbacks. In addition, we manually annotated gestures intensity. Based on a review of previous works in psychology and humanmachine interaction, we propose a new definition of the notion of engagement, adequate for the description of this phenomenon both in natural and mediated environments. This definition have been implemented in our annotation scheme. In our work, engagement is studied at the turn level, known to be crucial for the organization of the conversation. Even though there is still a lack of consensus around their precise definition, we have developed a turn detection tool. A multimodal characterization of engagement is performed using a multi-level classification of turns. We claim a set of multimodal cues, involving prosodic, mimo-gestural and morpho-syntactic information, is relevant to characterize the level of engagement of speakers in conversation. Our results significantly outperform the baseline and reach state-of-the-art level (. weighted F-score). The most contributing modalities are identified by testing the performance of a two-layer perceptron when trained on unimodal feature sets and on combinations of two to four modalities. These results support our claim about multimodality: combining features related to the speech fundamental frequency and energy with mimo-gestural features leads to the best performance

Hydrophobic Porous Liquids with Controlled Cavity Size and Physico‐Chemical Properties

International audienceAbstract Developing greener hydrometallurgical processes implies offering alternatives to conventional solvents used for liquid‐liquid extraction (LLE) of metals. In this context, it is proposed to substitute the organic phase by a hydrophobic silica‐based porous liquid (PL). Two different sulfonated hollow silica particles (HSPs) are modified with various polyethoxylated fatty amines (EthAs) forming a canopy that provides both the targeted hydrophobicity and liquefying properties. This study shows that these properties can be tuned by varying the number of ethylene oxide units in the EthA: middle‐range molecular weight EthAs allow obtaining a liquid at room temperature, while too short or too long EthA leads to solid particles. Viscosity is also impacted by the density and size of the silica spheres: less viscous PLs are obtained with small low‐density spheres, while for larger spheres (c.a. 200 nm) the density has a less significant impact on viscosity. According to this approach, hydrophobic PLs are successfully synthesized. When contacted with an aqueous phase, the most hydrophobic PLs obtained allow a subsequent phase separation. Preliminary extraction tests on three rare earth elements have further shown that functionalization of the PL is necessary to observe metal extraction

Hydrophobic Porous Liquids with Controlled Cavity Size and Physico‐Chemical Properties

Abstract Developing greener hydrometallurgical processes implies offering alternatives to conventional solvents used for liquid‐liquid extraction (LLE) of metals. In this context, it is proposed to substitute the organic phase by a hydrophobic silica‐based porous liquid (PL). Two different sulfonated hollow silica particles (HSPs) are modified with various polyethoxylated fatty amines (EthAs) forming a canopy that provides both the targeted hydrophobicity and liquefying properties. This study shows that these properties can be tuned by varying the number of ethylene oxide units in the EthA: middle‐range molecular weight EthAs allow obtaining a liquid at room temperature, while too short or too long EthA leads to solid particles. Viscosity is also impacted by the density and size of the silica spheres: less viscous PLs are obtained with small low‐density spheres, while for larger spheres (c.a. 200 nm) the density has a less significant impact on viscosity. According to this approach, hydrophobic PLs are successfully synthesized. When contacted with an aqueous phase, the most hydrophobic PLs obtained allow a subsequent phase separation. Preliminary extraction tests on three rare earth elements have further shown that functionalization of the PL is necessary to observe metal extraction

Highlighting the selective properties of carbamoylmethylphosphonated hydrosoluble polymers for Gd(III)/Th(IV)/U(VI) separation

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Terephthalaldehyde–Phenolic Resins as a Solid-Phase Extraction System for the Recovery of Rare-Earth Elements

International audienceRare-earth elements (REEs) are involved in most high technology devices and have become critical for many countries. The progress of processes for the extraction and recovery of REEs is therefore essential. Liquid–solid extraction methods are an attractive alternative to the conventional solvent extraction process used for the separation and/or purification of REEs. For this purpose, a solid-phase extraction system was investigated for the extraction and valorization of REEs. Ion-exchange resins were synthesized involving the condensation of terephthalaldehyde with resorcinol under alkaline conditions. The terephthalaldehyde, which is a non-hazardous aromatic dialdehyde, was used as an alternative to formaldehyde that is toxic and traditionally involved to prepare phenolic ion-exchange resins. The resulting formaldehyde-free resole-type phenolic resins were characterized and their ion-exchange capacity was investigated in regard to the extraction of rare-earth elements. We herein present a promising formaldehyde and phenol-free as a potential candidate for solid–liquid extraction REE with a capacity higher than 50 mg/g and the possibility to back-extract the REEs by a striping step using a 2 M HNO3 solution