Circular recycling concept for silver recovery from photovoltaic cells in Ethaline deep eutectic solvent.

Reducing the number of stages, energy costs and carbon footprint of recycling processes is essential to overcome environmental challenges. The interest in replacing the acids used in traditional hydrometallurgical methods with deep eutectic solvents (DES), which are less toxic and more environmentally friendly, has been growing. The aim of this study is to estimate the potential use of this class of solvents in an ionometallurgical process of leaching and electrodeposition to recover silver as part of the recycling of solar panels, a major challenge of the years to come. In the present work, a circular recycling concept based on an iron redox shuttle was studied to leach and recover silver via electrodeposition. Different DESs were evaluated in combination with a hexahydrated iron(iii) chloride oxidizing agent. Ethaline DES has gained significant interest as it can attain a high silver leaching efficiency of 99.9% on crystallized silicon cell scraps at 75 °C. The promising results led to a comprehensive study of limits of this chemical system, focusing on the relation between the concentration of species (iron and water), the interfacial potential of silver (electrochemical measurements), and surface evolution (X-ray photoelectron spectroscopy analysis). Silver leaching was determined as a mixed control mechanism involving chemical and species diffusion dependence. The concentration of iron(iii) chloride appeared crucial, determining the kinetic of formation of a poorly soluble AgCl layer. Electrodeposition from leachate highlighted the need to use an oxygen-free atmosphere to produce high-quality silver. Finally, leaching at 75 °C and electrodeposition at 50 °C of silver from crystallized silicon cell scraps were demonstrated using Ethaline (1 : 2) + FeCl3·6H2O (0.12 mol L-1) under an argon atmosphere.

Rhodium effects on Pt anode materials in a direct alkaline ethanol fuel cell.

The development of efficient catalysts for ethanol oxidation in alkaline medium requires a synthetic approach that may prevent the surfactant molecules from being adsorbed at the catalytic sites and decreasing the electrochemical performance of the final direct ethanol fuel cell. Toward this goal, the recently reported surfactant-less Bromide Anion Exchange (BAE) method, appears as a promising route to conveniently aim at preparing PtRh alloys dispersed on carbon substrates. The catalysts prepared herein by the BAE method were characterized physicochemically to obtain structural information on the PtRh/C nanomaterials, their morphology (size and shape), and their chemical and surface composition. Electrochemical behavior and properties of these electrodes were then investigated in a half-cell before the implementation of a direct ethanol fuel cell (DEFC) in a home-made anion exchange membrane Teflon cell. The analysis of the electrolytic solution in the anodic compartment by chromatography revealed that acetate was the major reaction product and the carbonate amount increased with the Rh content in the bimetallic composition. With 2.8-3.6 nm particle sizes, the Pt50Rh50/C catalyst exhibited the highest activity towards the ethanol electrooxidation.

Functionalization of phosphocalcic bioceramics for bone repair applications.

This work is devoted to the processing of bone morphogenetic protein (BMP-2) functionalized silicate substituted hydroxyapatite (SiHA) ceramic spheres. The motivation behind it is to develop injectable hydrogel/bioceramic composites for bone reconstruction applications. SiHA microspheres were shaped by spray drying and thoroughly characterized. The silicate substitution was used to provide preferred chemical sites at the ceramic surface for the covalent immobilization of BMP-2. In order to control the density and the release of the immobilized BMP-2, its grafting was performed via ethoxysilanes and polyethylene glycols. A method based on Kaiser's test was used to quantify the free amino groups of grafted organosilanes available at the ceramic surface for BMP-2 immobilization. The SiHA surface modification was investigated by means of X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy and thermogravimetry coupled with mass spectrometry. The BMP-2 bioactivity was assessed, in vitro, by measuring the luciferase expression of a stably transfected C3H10 cell line (C3H10-BRE/Luc cells). The results provided evidence that the BMP-2 grafted onto SiHA spheres remained bioactive.