Estudio de Recuperacion de Iones Cobre de Aguas Mineras utilizando Membranas Lfquidas Emulsificadas MLE

El presente trabajo muestra los resultados del estudio de implementation ydesarrollo del proceso de membranas lfquidas emulsificadas MLE para la recuperacion de Cu2 + . Se utilizo LIX-860 (un salicilaldoxima) como extractante "carrier"para el cobre y SPAN-80 (un emulsificante) para estabilizar la membrana lfquida,el stripping fue una solution de acido sulfurico y la alimentation una solution delg/lt de Cu2 + que fue una simulation de los residuos lfquidos producidos por lasempresas mineras. Se realizo un estudio de efectos medios con todos los factoresque influyen sobre la estabilidad de la membrana y la recuperacion del cobre. Losresultados mostraron que una velocidad de agitation de 2000 rpm permite formaremulsiones sumamente pequenas y muy estables, tambien se encontro que la concentracion del extractante LIX-860, el tiempo y la velocidad de agitation durantela extraction son los factores que controlan el proceso MLE. Finalmente, este estudio permitio estimar las condiciones optimas del proceso y ademas, se encontro quetecnicamente es factible aplicar este proceso de recuperacion a los residuos lfquidosvertidos por las empresas mineras de Chile lograndose recuperaciones sumamentesignificativas

Pebax/Polyethlylene glycol blend thin film composite membranes for CO2 separation: Performance with mixed gases

The paper describes the performance of Pebax©/Polyethylene glycol (PEG) blend thin film composite membranes for CO2 separation from gas mixtures containing H2, N2 and CH4. Membranes were tested at different conditionstemperature andpressure dependence of gas flux and selectivity were explored. The temperature dependence was correlated with the Arrhenius equation to determinethe activation energy of single gas permeation. Single and mixed gas permeation was measured for different pressures at 293K up to 20 bar. Improvedpermeabilities and CO2/H2 selectivities were obtained in the newly developed composite membranes

PEG modified poly(amide-b-ethylene oxide) membranes for CO2 separation

In the present work, membranes from commercially available Pebaxr MH 1657 and its blends with low molecular weight poly(ethylene glycol) PEG were prepared by using a simple binary solvent (ethanol/water). Dense film membranes show excellent compatibility with PEG system up to 50 wt.% of content. Gas transport properties have been determined for four gases (H2, N2, CH4, CO2) and the obtained permeabilities were correlated with polymer properties and morphology of the membranes. The permeability of CO2 in Pebaxr/PEG membrane (50 wt.% of PEG) was increased two fold regarding to the pristine Pebaxr. Although CO2/N2 and CO2/CH4 selectivity remained constant, an enhancement of CO2/H2 selectivity was observed. These results were attributed to the presence of EO units which increases CO2 permeability, and to a probable increase of fractional free-volume. Furthermore, for free-volume discussion and permeability of gases, additive and Maxwell models were used

Amphiphilic Poly(vinyl alcohol) Membranes Leaving Out Chemical Cross-Linkers: Design, Synthesis, and Function of Tailor-Made Poly(vinyl alcohol)-b-poly(styrene) Copolymers

Tailor-made poly(vinyl alcohol)-b-poly(styrene) copolymers (PVA-b-PS) for separation membranes are synthesized by the combination of reversible-deactivation radical polymerization techniques. The special features of these di-block copolymers are the high molecular weight (>70 kDa), the high PVA content (>80 wt%), and the good film-forming property. They are soluble only in hot dimethyl sulfoxide, but by the “solvent-switch” technique, they self-assemble in aqueous media to form micelles. When the self-assembled micelles are cast on a porous substrate, thin-film membranes with higher water permeance than that of PVA homopolymer are obtained. Thus, by using these tailor-made PVA-b-PS copolymers, it is demonstrated that chemical cross-linkers and acid catalysts can no longer be needed to produce PVA membranes, since the PS nanodomains within the PVA matrix act as cross-linking points. Lastly, subsequent thermal annealing of the thin film enhances the membrane selectivity due to the improved microphase separation

Propylene/1-hexene copolymer as a tailor-made poly(propylene) for membrane preparation via the thermally induced phase separation (TIPS) process

Poly[propylene-co-(1-hexene)], one example of a "tailor-made poly(propylene)", was synthesized using an iso-specific metallocene catalyst in order to study the influence of copolymer composition on the pore size of isotactic poly(propylene) (iPP) membranes prepared by the TIPS process. The structure of the copolymers and their properties in solution were analyzed and discussed in relation to the polymer-diluent phase diagram, the droplet growth kinetics during the TIPS process, the viscosity of the system and the final pore size of the membranes. The crystallization curve in the phase diagram was found to shift significantly as comonomer content increased and thus the droplet growth period was drastically increased. The resulting increase of the characteristic pore size in the membranes demonstrated that it is possible to use tailor-made poly(propylene)s to control the pore size in porous membranes prepared via the TIPS process (under otherwise constant conditions)

Synthesis and characterization of tailor-made N-vinylpyrrolidone copolymers and their blend membranes with polyvinyl alcohol for bioethanol dehydration by pervaporation

Tailor-made poly( N -vinylpyrrolidone- co -(2-[dimethylamino]ethyl methacrylate)) P(NVP- co -DMAEMA) and poly( N -vinylpyrrolidone- co - N -vinylimidazole) P(NVP- co -PNVIm) with defined monomer molar ratio are synthesized via free radical polymerization. The random copolymers are fully characterized and then blended with polyvinyl alcohol (PVA) to investigate their chemical and thermal properties as membrane materials. Composite membranes are further prepared from the PVA/copolymer blends on a porous support, which are evaluated in terms of separation performance for the dehydration of ethanol by pervaporation. The membranes prepared from the blends exhibit up to four times higher water permeances than pristine PVA membrane, albeit the selectivity is slightly lower. Nevertheless, the membranes from blends with a ratio of 95:5 (PVA/copolymer) show improved selectivity and higher permeance values compared to the commercial PERVAP TM 4155-80, especially the blends composed by the copolymers of coPDMAEMA60 and coPDMAEMA20. The membrane prepared from the blend containing the homopolymer coPDMAEMA100 exhibits the highest water/ethanol selectivity and shows stable separation performance throughout the whole long-term stability test. Thus, this study demonstrated that by synthesizing tailored copolymers (rather using the commercial ones) and blending with PVA, the separation performance of membranes can be significantly improved and tuned for specific dehydration processes