Application of supported ionic liquid membranes (SILMs) for biobutanol pervaporation

Innovative strategies for enhancing gas separation: Ionic liquid-coated PES membranes for improved CO2/N2 selectivity and permeance

As a cost-effective advancement in membrane technology, this study investigates the impact of PEG additive and CBT on the structural, stability, and gas permeance properties of PES-coated membranes, utilizing 1-dodecyl-3-methylimidazolium chloride ionic liquid ([DDMI][Cl] IL) as a carrier liquid. BET and FT-IR analyses highlight the significant enhancement in performance through the immobilization of pores with [DDMIM][Cl] IL. The investigation focuses on PES-M5-coated membranes, revealing excellent stability in finger-like pore structures prepared through direct immersion and nitrogen pressure immobilization. PES-M5-coated membranes with [DDMIM][Cl] IL via direct immersion experience lower weight loss than those coated using nitrogen pressure, with critical pressures at 1.4 and 1.25 bar, respectively. The study identifies PES-coated membranes, particularly PES-M25 (20.88 GPU) with macro-void pores and PES-M5 (29 GPU) with finger-like pores, exhibiting the highest CO2 permeance and CO2/N2 selectivity. As a cost-effective advancement in membrane technology, ionic liquids are employed in support membranes to enhance gas separation. Employing pure PES membranes with varying pore structures, created through the NIPS method, the study immobilizes [DDMI][Cl] IL in membrane pores through nitrogen pressure and direct immersion. Results underscore the successful application of porous support materials coated with ionic liquids for continuous CO2 and sulfur compound separation, showcasing competitive permeability and selectivity compared to traditional polymer membranes.

Exploring the potential of highly selective deep eutectic solvents (DES) based membranes for dehydration of butanol via pervaporation

N-butanol has unique physicochemical and combustion properties, similar to gasoline, which makes it an environmentally friendly alternative to conventional fuels. To improve the efficiency, the dehydration of butanol is necessary. This paper aims to investigate the performance of Deep Eutectic Solvents (DESs) based membranes for the dehydration of n-butanol by the pervaporation process. Three DES with different combinations of hydrogen bond donors and acceptors, i.e., DL-menthol: Lauric acid (DES), DL-menthol-Palmitic acid (DES), and [TETA] Cl: Thymol (DES), were used. We hypothesized that (i) incorporation of hydrophobic DES would increase the hydrophobicity of the membranes; (ii) specific functional groups (phenolic group, amine group) in DESs would enhance the butanol-philic character of membranes, and (iii) hydrophobic DESs would increase the butanol separation efficiency and permeability of membranes. FTIR analysis and physicochemical parameters of the resultant liquid mixture validated the DESs' production. The DESs were then filled into the permeable support, resulting in supported liquid membranes (SLMs). An additional layer of polydimethylsiloxane (PDMS) was coated directly on the DES-PSf layer to prevent leaching out of DES. A feed containing a 6 wt % aqueous solution of butanol under varying temperatures was studied. The results showed that among all membranes, [TETA] Cl: Thymol DES-based membrane showed the highest sorption of 36% at room temperature. The introduction of DES in membranes resulted in a remarkable increase in the separation factor while sustaining a reasonable flux. Among all the membranes, the DL-menthol: Lauric acid (DES) based membrane exhibited the highest separation factor of 57 with a total flux of 0.11 kg/m². h. Significantly high butanol-water separation was attributed to the low viscosity and high butanol solubility of the chosen DES, which makes it a suitable substitute to conventional ILs.

Functions of Ionic Liquids in Preparing Membranes for Liquid Separations: A Review

Membranes are widely used for liquid separations such as removing solute components from solvents or liquid/liquid separations. Due to negligible vapor pressure, adjustable physical properties, and thermal stability, the application of ionic liquids (ILs) has been extended to fabricating a myriad of membranes for liquid separations. A comprehensive overview of the recent developments in ILs in fabricating membranes for liquid separations is highlighted in this review article. Four major functions of ILs are discussed in detail, including their usage as (i) raw membrane materials, (ii) physical additives, (iii) chemical modifiers, and (iv) solvents. Meanwhile, the applications of IL assisted membranes are discussed, highlighting the issues, challenges, and future perspectives of these IL assisted membranes in liquid separations.

Development of novel hydrophilic ionic liquid membranes for the recovery of biobutanol through pervaporation

This paper aims to develop novel hydrophilic ionic liquid membranes using pervaporation for the recovery of biobutanol. Multiple polyvinyl alcohol (PVA) membranes based on three commercial ionic liquids with different loading were prepared for various experimental trials. The ionic liquids selected for the study include tributyl (tetradecyl) phosphonium chloride ([TBTDP][Cl]), tetrabutyl phosphonium bromide ([TBP][Br]) and tributyl methyl phosphonium methylsulphate ([TBMP][MS]). The synthesized membranes were characterized and tested in a custom-built pervaporation set-up. All ionic liquid membranes showed better results with total flux of 1.58 kg/m²h, 1.43 kg/m²h, 1.38 kg/m²h at 30% loading of [TBP][Br], [TBMP][MS] and [TBTDP][Cl] respectively. The comparison of ionic liquid membranes revealed that by incorporating [TBMP]MS to PVA matrix resulted in a maximum separation factor of 147 at 30 wt% loading combined with a relatively higher total flux of 1.43 kg/m²h. Density functional theory (DFT) calculations were also carried out to evaluate the experimental observations along with theoretical studies. The improved permeation properties make these phosphonium based ionic liquid a promising additive in PVA matrix for butanol-water separation under varying temperature conditions.

Selective Recovery of n-Butanol from Aqueous Solutions with Functionalized Poly(epoxide ionic liquid)-Based Polyurethane Membranes by Pervaporation

In this study, hydroxyl-terminated polybutadiene-poly(epoxide ionic liquid)-poly(urethane urea) (HTPB-PEIL-PU) membranes, HTPB-PEIL1-PU and HTPB-PEIL2-PU, were prepared by the reaction of functionalized PEIL, poly(1-methylimidazole-3-methyl-ethyloxy)hexafluorophosphate or poly(1-methylimidazole-3-methyl-ethyloxy)bistrifluoromethanesulfonimidate, respectively, with HTPB using 4,4'-diphenylmethane diisocyanate (MDI) as the chain extender. The HTPB-PEIL-PU and HTPB membranes were investigated for the selective recovery of n-butanol from aqueous solutions by pervaporation. PEIL was confirmed to be successfully embedded in the PU membranes by ¹H NMR, Fourier transform infrared, and differential scanning calorimetry measurements. According to our mechanical measurements, the HTPB-PEIL-PU membranes retain the mechanical properties of the original PU membrane. PEIL was shown to enhance the diffusion rate of n-butanol significantly based on swelling behavior tests. The pervaporation flux through the HTPB-PEIL1-PU membrane increased with increasing feed temperature and feed concentration. In contrast, the separation factor of the HTPB-PEIL1-PU membrane increased with increasing feed temperature but decreased with increasing feed concentration. In addition, the HTPB-PEIL2-PU membrane exhibited an optimal separation factor of up to 29.2 at a feed concentration of 3% and a feed temperature of 70 °C, which is superior to that (22.7) through pure HTPB membranes. Furthermore, the HTPB-PEIL1-PU and HTPB-PEIL2-PU membranes show better long-term stability than other supported ionic liquid membranes.

A Bibliometric Analysis of Research on Supported Ionic Liquid Membranes during the 1995-2015 Period: Study of the Main Applications and Trending Topics

A bibliometric analysis based on Scopus database was performed to identify the global research trends related to Supported Ionic Liquid Membranes (SILMs) during the time period from 1995 to 2015. This work tries to improve the understanding of the most relevant research topics and applications. The results from the analysis reveal that only after 2005 the research efforts focused on SILMs became significant, since the references found before that year are scarce. The most important research works on the four main application groups for SILMs defined in this work (carbon dioxide separation, other gas phase separations, pervaporation and liquid phase separations) were summarized in this paper. Carbon dioxide separation appeared as the application that has received by far the most attention according to the research trends during the analysed period. Comments about other significant applications that are gaining attention, such as the employment of SILMs in analytical tasks or their consideration for the production of fuel cells, have been included.