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

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.

In situ formation of surface-functionalized ionic calcium carbonate nanoparticles with liquid-like behaviours and their electrical properties

This paper reports a new route to synthesize calcium carbonate (CaCO₃)-based nanoscale ionic materials (NIMs) via an in situ formation method to form the CaCO₃ nanoparticles with a polysiloxane quaternary ammonium salt (PQAC) corona (PQAC-CaCO₃ nanoparticles), followed by an ionic exchange reaction to fabricate a poly(ethylene glycol)-tailed sulfonate anion (NPEP) canopy. The chemical compositions and structures of the CaCO₃-based NIMs synthesized in this work were confirmed by Fourier-transform infrared spectroscopy and solid-state ¹³C NMR spectroscopy. Transmission electron microscopic observation indicated that the CaCO₃-based NIMs presented a rhombohedral shape with a well-defined core-shell structure, and they also obtained an NPEP canopy with a thickness of 4-6 nm. X-ray powder diffraction investigation confirmed that the CaCO₃ inner core had a calcite crystalline structure, whereas the NPEP canopy was amorphous. The NPEP canopy was found to show a characteristic crystallization-melting behaviour in the presence of the ion bonding with PQAC-CaCO₃ nanoparticles according to the characterization of differential scanning calorimetry. Thermogravimetric analysis indicated that the CaCO₃-based NIMs achieved a high content of NPEP canopy as well as an improvement in thermal stability owing to the ion-bonding effect. Most of all, the CaCO₃-based NIMs demonstrated a liquid-like behaviour above the critical temperature in the absence of solvent. Moreover, the CaCO₃-based NIMs also showed a relatively high electrical conductivity with a temperature dependency due to the ionic conductive effect. This work will provide a more feasible and energy-saving methodology for the preparation of CaCO₃-based NIMs to promote their industrialization and extensive applications.

Synthesis and properties of highly dispersed ionic silica-poly(ethylene oxide) nanohybrids

We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent.