Analyse Hydrometallurgique et Caracterisation de Miner Secondaires

Abstract

Two copper ores (containing between 1% and 2% of the metal) were analyzed by UV emission spectroscopy, infrared spectroscopy and X-ray diffraction yielding - per se - inconclusive results. The ores were subsequently classified by particle size into three “granular fractions”. Determination of copper, dissolved from each fraction by anaerobic and aerobic digestion with 5% aqueous sulphuric acid, produced illuminating information on the presence of sulfide-and oxide-type copper compounds. Fractionation was further refined by magnetic separations.     

Highly Concentrated Aqueous Dispersions of Graphene Exfoliated by Sodium Taurodeoxycholate: Dispersion Behavior and Potential Application as a Catalyst Support for the Oxygen‐Reduction Reaction

A high‐yielding exfoliation of graphene at high concentrations in aqueous solutions is critical for both fundamental study and future applications. Herein, we demonstrate the formation of stable aqueous dispersions of pristine graphene by using the surfactant sodium taurodeoxycholate under tip sonication at concentrations of up to 7.1 mg mL^?1. TEM showed that about 8 % of the graphene flakes consisted of monolayers and 82 % of the flakes consisted of less than five layers. The dispersions were stable regardless of freezing (?20 °C) or heat treatment (80 °C) for 24 h. The concentration could be significantly improved to about 12 mg mL^?1 by vacuum‐evaporation of the dispersions at ambient temperature. The as‐prepared graphene dispersions were readily cast into conductive films and were also processed to prepare Pt/graphene nanocomposites that were used as highly active electrocatalysts for the oxygen‐reduction reaction.     

Ring-closing metathesis in aqueous micellar medium

Underwater exploration: The ring-closing metathesis of N,N-diallyltosylamine (DATs) and diallyldiethyl malonate has been studied in aqueous micellar medium, at room temperature, in the presence of four different gemini cationic surfactants and various ruthenium catalysts. For the first time, the adsorption mechanisms and the reaction steps involved in this heterogeneous catalytic process were elucidated.     

Morphology-controlled synthesis of poly(oxyethylene)silicone or alkylsilicone surfactants with explicit, atomically defined, branched, hydrophobic tails

Silicone surfactants are widely used in commerce because of the unusual surface activity when compared with fluorocarbon or hydrocarbon surfactants. However, most silicone surfactants are comprised of ill-defined mixtures, which preclude the development of an understanding of structure-surface activity relationships. Herein, we report a synthetic strategy that permits exquisite control over silicone structure by using the B(C(6)F(5))(3)-catalyzed condensation of hydro- and alkoxysilanes. Six different, precise hydrophobes were then mated to hydrophilic poly(oxyethylene)s of three different molecular weights by a metal-free click cyclization to generate a library of explicit silicone surfactants. These compounds were calculated to have a relatively linear value range of the hydrophilic-lipophilic balance, ranging from about 8 to about 15. The solubility of some of the compounds was too low to measure a critical micelle concentration (CMC). The others exhibited a broad range of surface tension values at the CMC that depend both on the length of the hydrophilic tail and, more importantly, the nature of the hydrophobic head group. Subtle distinctions in surfactant-related properties, which can be attributed to the three-dimensional structures, can be seen for compounds with comparable numbers of hydrocarbons and silicon groups.     

阴阳离子表面活性剂体系超低油水界面张力的应用

通过阴阳离子表面活性剂复配,在实际油水体系中获得了超低界面张力.通过在阴离子表面活性剂分子结构中加入乙氧基(EO)链段,以及采用阴阳离子加非离子型表面活性剂的三组分策略,有效解决了混合表面活性剂在水溶液中溶解度问题.进而研究了阳离子表面活性剂结构、非离子表面活性剂结构、三者组分配比、表面活性剂总浓度等因素对油水界面张力的影响,从而在胜利油田多个实际油水体系中获得了较大比例范围和较低浓度区域的油水超低界面张力,部分体系甚至达到了10-4 mN·m-1.由于阴阳离子表面活性剂间强烈的静电吸引作用,相关体系具有很好的抗吸附能力.经过石英砂48 h吸附后,体系仍然具有很好的超低界面张力.     

Inhibited phenol ionization in reverse micelles: confinement effect at the nanometer scale

We found that the absorption spectra of 2-acetylphenol (2-HAP), 4-acetylphenol (4-HAP), and p-nitrophenol (p-NPh) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane reverse micelles (RMs) at various W(0) (W(0) = [H(2)O]/[surfactant]) values studied changed with time if (-)OH ions were present in the RM water pool. There is an evolution of ionized phenol (phenolate) bands to nonionized phenol absorption bands with time and this process is faster at low W(0) values and with phenols with higher bulk water pK(a) values. That is, in bulk water and at the hydroxide anion concentration used, only phenolate species are observed, whereas in AOT RMs at this fixed hydroxide anion concentration, ionized phenols convert into nonionized phenol species over time. Furthermore, we demonstrate that, independent of the (-)OH concentration used to prepare the AOT RMs, the nonionized phenols are the more stable species in the RM media. We explain our results by considering that strong hydrogen-bonding interactions between phenols and the AOT polar head groups result in the existence of only nonionized phenols at the AOT RM interface. The situation is quite different when the phenols are dissolved in cationic benzyl-n-hexadecyldimethylammonium chloride RMs. Therein, only phenolates species are present at the (-)OH concentrations used. The results clearly demonstrate that the classical definition of pH does not apply in a confined environment, such as in the interior of RMs and challenge the general idea that pH can be determined inside RMs.     

Maleic diamide polymerizable surfactants. Applications in emulsion polymerization

A series of new polymerizable non-ionic and ionic surfactants (surfmers) with amides groups on both sides of the C=C double bonds have been prepared upon reaction of maleic isoimide carrying a long alkyl chain (or a benzyl group) with a hydrophilic amine derivative. Their critical micellar concentration (CMC) was measured with a surface tensiometer. They have been engaged in batch emulsion polymerization of styrene, and semi-batch seeded copolymerization of styrene and butyl acrylate, giving stable latexes during the polymerization process, and upon extraction with ethanol, showing a high rate of incorporation at the particle surface. However these surfmers do not confer good steric stabilization properties, which may be expected from the use of non-ionic surfactants. To cite this article: I. Klimenkovs et al., C. R. Chimie 6 (2003).     

New Water‐Soluble Cationic Poly(p‐phenylenevinylene) Derivative: the Interaction with DNA and Selective Fluorescence Enhancement Induced by ssDNA

A new cationic cyano‐substituted poly(p‐phenylenevinylene) (N‐CNPPV) is synthesized by Knoevenagel condensation. The water‐soluble polymer shows different emission spectra in different solvents and displays unique fluorescent behaviors in the mixed solvents of water and THF. The new polymer can form a complex with ssDNA by adopting a more planar conformation, exhibiting red shift of emission wavelength and enhancement of fluorescence intensity. By investigating the fluorescent response of N‐CNPPV to various surfactants, we demonstrate that the hydrophobic interaction and electrostatic interaction result in the selective response of N‐CNPPV to ssDNA. This is the first report on selective fluorescence enhancement of conjugated polyelectrolyte induced by ssDNA.     

Molecular simulations of self-assembly processes of amphiphiles in dilute solutions: the challenge for quantitative modelling

We report on two recent developments in molecular simulations of self-assembly processes of amphiphilic solutions. We focus on the determination of micelle formation of ionic surfactants which exhibit the archetype of self-assembling compounds in solution. The first approach is centred on the challenge in predicting micellisation properties through explicit solvent molecular dynamics simulations. Even with a coarse-grained (CG) approach and the use of highly optimised software packages run on graphics processing unit hardware, it remains in many cases computationally infeasible to directly extract the critical micelle concentration (cmc). However, combined with a recently presented theoretical mean-field model this task becomes resolved. An alternative approach to study self-assembly is through implicit solvent modelling of the surfactants. Here we review some latest results and present new ones regarding capabilities of such a modelling approach in determining the cmc, and the aggregate structures in the dilute regime, that is currently not accessible through explicit solvent simulations, neither through atomistic nor through CG approaches. A special focus is put on surfactant concentration effects and surfactant correlations quantified by scattering intensities that are compared to recently published small-angle X-ray scattering data.     

Cytotoxicity of PMMA-Based Nanoparticles Synthesized Adopting SDS and Tween 80

Summary: in this work the cytotoxicity of PMMA-based nanoparticles against mouse mammary cancer cells (4T1) has been investigated. NPs have been synthesized using either monomer starved semi-batch emulsion polymerization (MSSEP) or standard batch emulsion polymerization (BEP) processes adopting potassium persulfate (KPS) as initiator and two different emulsifiers: sodium dodecyl sulfate (SDS) and Tween 80. The toxicity of NPs produced using SDS has been confirmed in in vitro experiments while it has been found that NPs stabilized with Tween 80 show a good biocompatibility. Moreover, the absence of toxicity of NPs in which the SDS is substituted with Tween 80 adopting ion exchange resins (IER) has been proved. Finally the biocompatibility of the sulfate chain end groups coming from the adopted initiator has been assessed.