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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. [ABSTRACT FROM AUTHOR]

Efficient 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. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to evaluate the gadolinium(III) rejection by nanofiltration assisted by complexation with diethylenetriaminepentaacetic acid (DTPA) as chelating agent. The experimental Gd(III) rejections as a function of the pH were compared to species distribution for the Gd(III)–DTPA system calculated using the protonation and thermodynamic stability constants. The Gd(III) rejection varies from 5 to 95% as a function of the pH and follows the Gd(III)/DTPA speciation. However for pH below 1.5 and for high Gd(III) rejection, some differences between the Gd(III)/DTPA speciation and the observed Gd(III) rejection could be noticed. For this reason, the surface charge of organic NF membrane Desal G10 was determined from tangential streaming potential measurements for different pH values (2.0–6.0) in the presence of 0.5mM of Gd(III) nitrate and 0.5mM of DTPA. The isoelectric point (pI) of the Desal G10 membrane was found to be close to 3.4. Thus the rejection of Gd(III) at low pH could be explained by surface force interactions. The influence of the operating parameters on Gd(III) rejection above pI was then studied. For an operational pressure of 3bar, a complex concentration of 0.4mM, a tangential velocity of 145mms−1 and a temperature of 15°C, the differences between the Gd(III)/DTPA speciation and the observed Gd(III) rejection are low and thus Gd(III) rejection with Desal G10 membranes can fit the speciation. [Copyright &y& Elsevier]

This 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 + ][NTf 2 - ]) and 1-ethyl-1-octylpiperidinium bis(trifluoromethylsulfonyl)imide ([EOPip + ][NTf 2 - ])) 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 + ][NTf 2 - ] 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.