Luísa A. Neves

Proton NMR Relaxometry Study of Nafion Membranes Modified with Ionic Liquid Cations

Proton nuclear magnetic resonance (NMR) relaxometry was used to study the ionic mobility and levels of confinement within Nafion membranes modified by incorporation of selected ionic liquid (IL) cations. These studies were performed aiming at understanding the effect of using different types of ionic liquid cations, and their degree of incorporation, in the values of the spin-lattice relaxation times (T(1)) obtained at different values of frequency and thus detect the influence of confinement level on the ions mobility. The frequency dependence of the proton spin-lattice relaxation rate, R(1) = 1/T(1), for the modified Nafion/IL cation membranes was compared with that obtained for an unmodified Nafion membrane, allowing for distinguishing different contributions of the motions of the molecules depending on the frequency tested. The experimental R(1) results were analyzed in terms of models that consider the sum of the most effective relaxation contributions, to estimate the translational self-diffusion coefficient of the moving molecular species in the modified membranes. The stability of these membranes with temperature in terms of the spin-lattice relaxation was compared with results obtained by thermogravimetric analysis.

Supported ionic liquid membranes for removal of dioxins from high-temperature vapor streams.

Dioxins and dioxin-like chemicals are predominantly produced by thermal processes such as incineration and combustion at concentrations in the range of 10-100 ng of I-TEQ/kg (I-TEQ = international toxic equivalents). In this work, a new approach for the removal of dioxins from high-temperature vapor streams using facilitated supported ionic liquid membranes (SILMs) is proposed. The use of ceramic membranes containing specific ionic liquids, with extremely low volatility, for dioxin removal from incineration sources is proposed owing to their stability at very high temperatures. Supported liquid membranes were prepared by successfully immobilizing the ionic liquids tri-C(8)-C(10)-alkylmethylammonium dicyanamide ([Aliquat][DCA]) and 1-n-octyl-3-methylimidazolium dicyanamide ([Omim][DCA]) inside the porous structure of ceramic membranes. The porous inorganic membranes tested were made of titanium oxide (TiO(2)), with a nominal pore size of 30 nm, and aluminum oxide (Al(2)O(3)), with a nominal pore size of 100 nm. The ionic liquids were characterized, and the membrane performance was assessed for the removal of dioxins. Different materials (membrane pore size, type of ionic liquid, and dioxin) and different operating conditions (temperature and flow rate) were tested to evaluate the efficiency of SILMs for dioxin removal. All membranes prepared were stable at temperatures up to 200 °C. Experiments with model incineration gas were also carried out, and the results obtained validate the potential of using ceramic membranes with immobilized ionic liquids for the removal of dioxins from high-temperature vapor sources.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes.

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S.

Supported Ionic Liquid Membranes and Ion-Jelly® Membranes with [BMIM][DCA]: Comparison of Its Performance for CO2 Separation.

In this work, a supported ionic liquid membrane (SILM) was prepared by impregnating a PVDF membrane with 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) ionic liquid. This membrane was tested for its permeability to pure gases (CO2, N2 and O2) and ideal selectivities were calculated. The SILM performance was also compared to that of Ion-Jelly® membranes, a new type of gelled membranes developed recently. It was found that the PVDF membrane presents permeabilities for pure gases similar or lower to those presented by the Ion-Jelly® membranes, but with increased ideal selectivities. This membrane presents also the highest ideal selectivity (73) for the separation of CO2 from N2 when compared with SILMs using the same PVDF support but with different ionic liquids.

Recovering bioethanol from olive bagasse fermentation by nanofiltration

Abstract The aim of this manuscript was the study of the recovery of bioethanol produced by the fermentation of the lignocellulosic biomass (olive bagasse) by nanofiltration. In terms of downstream processing, the nanofiltration permeate stream was expected to be comprised mostly of water and ethanol, and as such, ethanol may be further recovered by conventional distillation. Different nanofiltration membranes (NF90 and NF270) were tested for their efficiency in the separation of bioethanol. Model aqueous solutions of ethanol and sugars, and real liquors were processed by nanofiltration focusing on flux and rejection performance. The results shown that the more complex medium of a real liquor interacts with the membrane and lower the rejection to target solutes. Generally, both membranes tested were suitable for separating and recovering ethanol from a fermentation medium. The diafiltration mathematical model developed in this work shown to be capable of describing experimental results, which may be consi...

Impact on CO2/N2 and CO2/CH4 Separation Performance Using Cu-BTC with Supported Ionic Liquids-Based Mixed Matrix Membranes

The efficient separation of gases has industrial, economic, and environmental importance. Here, we report the improvement in gas separation performance of a polyimide-based matrix (Matrimid®5218) filled with a Cu-based metal organic framework [MOF, Cu3(BTC)2] with two different ionic liquids (ILs) confined within the pores. The chosen ILs are commonly used in gas solubilization, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]), and the incorporation of the [EMIM][BF4]@Cu-BTC and [EMIM][OTf]@Cu-BTC composites in Matrimid®5218 proved to be an efficient strategy to improve the permeability and selectivity toward CO2/N2 and CO2/CH4 mixtures.

Demonstration of the adhesive properties of the medium-chain-length polyhydroxyalkanoate produced by Pseudomonas chlororaphis subsp. aurantiaca from glycerol

Pseudomonas chlororaphis subsp. aurantiaca (DSM 19603) was grown on crude glycerol from biodiesel production to produce a medium-chain-length polyhydroxyalkanoate (mcl-PHA), composed of 3-hydroxydodecanoate (43 ± 1.8 mol%), 3-hydroxydecanoate (29 ± 3.1 mol%), 3-hydroxytetradecanoate (12 ± 0.4 mol%), 3-hydroxyoctanoate (10 ± 1.5 mol%) and 3-hydroxyhexanoate (6 ± 0.3 mol%). The biopolymer had an average molecular weight of 1.1 × 105 Da, with a polydispersity index of 1.5, and was semi-crystalline, as shown by its crystallinity index of 37 ± 0.2%. It had low melting (44 °C) and glass transition (-48 °C) temperatures, and was thermally stable up to 285 °C. The biopolymer films were elastic and translucid, were hydrophobic and presented relatively high permeability to oxygen and carbon dioxide. The films demonstrated to have good adhesion properties towards porcine skin and human skin. The tension (61.1 ± 20.6 kPa) and shear (12.7 ± 2.14 kPa) bond strength of the mcl-PHA for porcine skin suggest its potential as a biomaterial for the development of novel natural adhesives for wound closure or wound dressings.