183 research outputs found

    Hybrid hollow silica nanospheres for separation chemistry Influence of synthesis parameters

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    International audienceNowadays, separation of chemical elements is an important stake for many applications. Although liquid-liquid extraction represents the most applied method at industrial scale, it involves many economic and environmental constraints related to the use of large quantities of solvents. There is therefore a growing interest for alternatives as solid-liquid separation and flotation processes which however, require re-designing the actual industrial installations and present limited performances, in terms of extraction capacity and selectivity.This project proposes to evaluate a new approach allowing to maintain the existing separation installations, by replacing the organic phases of liquid-liquid extraction processes, with a porous liquid. Porous liquids were discovered in 2014 by the Oak Ridge Corporation. They are solid materials made up with hollow nanoparticles of silica, that present the particularity to become liquid when grafted with ionic functions. To date, these materials have only been tested for gas separation. Being at the exact junction between liquid-liquid and solid-liquid extraction processes, porous liquids would allow exploiting the advantages of the two processes. Therefore, we propose to form new porous liquids based on various synthesis methods and to test them for extraction at both solid and liquid state. Various synthesis parameters were investigated to control and understand the morphology of the nanospheres as well as their effect on their future extraction properties. Size, shape and homogeneity of the particles could be changed and controlled. To complete this understanding, a Small Angle X-ray Scattering (SAXS) analysis (Fig.1) was done completed by Transmission Electron Microscop

    Tailored structuring of functionalized silsesquioxanes in a one-step approach

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    International audienceThe silica hybrid materials prepared from tailor-made precursors with different headgroups in several experimental conditions (acid or base catalysis in water or THF) were studied in order to identify the structure directing mechanisms

    Permeability of porous liquids

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    International audienc

    Leaching of rare earth elements (REEs) and impurities from phosphogypsum: A preliminary insight for further recovery of critical raw materials

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    International audiencePhosphogypsum is a pollutant waste generated by the fertilizer industry. Managing this pollutant is challenging due to the large volumes generated worldwide. A promising route is the valorization of phosphogypsum to recover rare earth elements. However, optimized recovery schemes are needed to create a cost-effective and environmentally friendly process. This paper studies the extraction efficiency of rare earth elements from phosphogypsum and the release of impurities during leaching in a variety of solutions and different working conditions. The best leaching performance was obtained using a 3 M nitric acid (above 80%) solution that achieved a dissolution rate of 63% of the gypsum originally present. In contrast, using 0.5 M sulfuric acid extracted between 46% and 58% of the rare earth elements contained in phosphogypsum, dissolving less than 6% of the gypsum. This higher dissolution of gypsum led to a higher release of impurities by nitric acid. Increasing reaction times from 2 h to 8 h yielded an improvement of leaching efficiency of around 8% for both leaching solutions, while also promoting an increase of 6% in the release of impurities. Adding DTPA resulted in poor leaching performance (from 13% to 22%). Pretreating phosphogypsum with water can remove a significant fraction of the impurities without scavenging rare earth elements. Mineralogical and chemical evidence suggests unreacted phosphate and fluoride are the most probable minerals hosting rare earth element minerals in phos-phogypsum. The results of this study could contribute to optimizing recovery methods to extract rare earth elements from phosphogypsum worldwide, thus helping achieve the goals of the circular economy

    New Hybrid TiO2 Nano-structured Materials for Lanthanides Separation

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    International audienceNew nano-structured hybrid EDTA- or DTPA/TiO2 materials were synthesized and were applied to the selective lanthanum(III)/gadolinium(III) separation in aqueous solutions

    The Pictet-Spengler reaction: an efficient diastereoselective access to new funtionnalized tetrahydroisoquinolines

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