Synthesis Of Mixed Matrix Membranes Research Articles

Tailoring the separation performance of a carbon nanotube-based mixed matrix membrane decorated with metal–organic framework

Synthesis of mixed matrix membranes (MMM) using carbon nanotubes (CNTs) has shown great prospects for achieving excellent selective separation because of its special structure. Nevertheless, the preparation of highly selective MMM faces challenges, which is attributed to the obstacles encountered by CNTs dispersion in polymer matrix and elimination of interface defects. A novel CNT-based composite decorated with metal–organic framework (MOF) was synthesized and applied to the preparation of MMM. MOF was post modified, and then carboxyl groups were inserted on the outer surface of CNTs. The synthetic MMM (Cu-MOF-en@MWCNT) not only has selective adsorption on dyes, but also has selective photodegradation on dyes. The method of using CNTs to wrap the outside of MOF has great potential in dye separation. The performance of MMM was further improved by decorating MOF on the filler to improve the selectivity to the designated dye.

Effect of ionic liquid inclusion and amino–functionalized SAPO-34 on the performance of mixed matrix membranes for CO2/CH4 separation

Surface voids and filler agglomeration affect the membrane’s structure and gas separation which limits the use of mixed matrix membranes (MMM) for carbon dioxide (CO2) separation in industry. Therefore, synthesis of MMM with ionic liquid and modified inorganic fillers had improved performance and morphologies. In this regards the filler surface (SAPO-34) was modified by introducing organic amino cation, namely ethylenediamine (EDA) and hexylamine (HA). Four (04) mixed matrix membranes were synthesized by the incorporation of un-modified and modified filler along with ionic liquid (IL) in polyethersulfone (PES) matrix. The effects of IL addition and filler functionalization on morphology, thermal and mechanical stability were investigated; while pure gas permeation test using carbon dioxide (CO2) and methane (CH4) was carried out at 4 bar pressure to analyze the membrane gas transport properties. Characterization showed that surface voids and hard agglomerations disappeared by the addition of modified SAPO-34 and ionic liquid [emim][Tf2N]. Moreover, membranes were thermally and mechanically stable after the addition of IL and modified SAPO-34. Synergetic effect of IL and modified filler exhibited excellent CO2/CH4 selectivity (37.23) for PES + IL + modified SAPO-34 + HA MMM.

A Drying‐Free, Water‐Based Process for Fabricating Mixed‐Matrix Membranes with Outstanding Pervaporation Performance

AbstractDespite much progress in the development of mixed matrix membranes (MMMs) for many advanced applications, the synthesis of MMMs without particle agglomeration or phase separation at high nanofiller loadings is still challenging. In this work, we synthesized nanoporous zeolitic imidazole framework (ZIF‐8) nanoparticles with a particle size of 60 nm and a pore size of 0.34 nm in water and directly added them into an aqueous solution of the organic polymer poly(vinyl alcohol) (PVA) without an intermediate drying process. This approach led to a high‐quality PVA/ZIF‐8 MMM with enhanced performance in ethanol dehydration by pervaporation. The permeability of this MMM is three times higher than that of pristine PVA, and the separation factor is nearly nine times larger than that of pristine PVA. The significantly improved separation performance was attributed to the increase in the fractional free volume in the membranes.

Crystallization in THF: the possibility of one-pot synthesis of mixed matrix membranes containing MOF MIL-68(Al)

A new methodology has been developed consisting of the use of the same solvent (tetrahydrofuran, THF) for both nanosized MOF MIL-68(Al) crystallization and polysulfone (PSF) mixed matrix membrane (MMM) casting, using this MOF as filler. The usual solvent for MIL-68 is dimethylformamide. However, the synthesis of this MOF has been studied here in THF (a solvent almost never used for MOFs) which makes possible the one-pot processability of both MOF and PSF, without the stages of crystal separation and drying from the mother liquor. The 8 wt% MIL-68(Al)@PSF MMMs were superior to the pure PSF membrane in the separation of both H2/CH4 and CO2/CH4 mixtures.

Synthesis of MEL type zeolite with different kinds of morphology for the recovery of 1-butanol from aqueous solution

Size, shape and morphology of zeolite crystallites play an important role in the synthesis of mixed matrix membranes having good membrane productivity, selectivity and stability. In the present work emphasis is placed on the use of hydrothermally synthesized high silica MEL type zeolite with hydrophobic character for the preparation of mixed matrix membranes. The morphological study shows that the sizes for crystals of MEL3 and MEL5 are at the nano scale while for hexagonal crystals of MEL4 and spherical crystals of MEL6 ranges in micro scale (20–35μm). The prime objective of this study is to develop new zeolite for the preparation of mixed matrix membrane, so before the use of these materials for the same purpose, adsorption potentials of these zeolite materials for 1-butanol were also investigated. Thereafter adsorption data was fitted to the Langmuir and Freundlich adsorption models. The later model achieved best fit with the experimental data. The high negative value of Gibbs free energy change (∆Go) indicates the feasible and spontaneous adsorption of 1-butanol on MEL6 zeolite. Negative values of heat of adsorption (∆Ho) and entropy change (∆So) indicate exothermic adsorption process with low degree of randomness.

Membrane-based technologies for biogas separations

Over the past two decades, membrane processes have gained a lot of attention for the separation of gases. They have been found to be very suitable for wide scale applications owing to their reasonable cost, good selectivity and easily engineered modules. This critical review primarily focuses on the various aspects of membrane processes related to the separation of biogas, more in specific CO(2) and H(2)S removal from CH(4) and H(2) streams. Considering the limitations of inorganic materials for membranes, the present review will only focus on work done with polymeric materials. An overview on the performance of commercial membranes and lab-made membranes highlighting the problems associated with their applications will be given first. The development studies carried out to enhance the performance of membranes for gas separation will be discussed in the subsequent section. This review has been broadly divided into three sections (i) performance of commercial polymeric membranes (ii) performance of lab-made polymeric membranes and (iii) performance of mixed matrix membranes (MMMs) for gas separations. It will include structural modifications at polymer level, polymer blending, as well as synthesis of mixed matrix membranes, for which addition of silane-coupling agents and selection of suitable fillers will receive special attention. Apart from an overview of the different membrane materials, the study will also highlight the effects of different operating conditions that eventually decide the performance and longevity of membrane applications in gas separations. The discussion will be largely restricted to the studies carried out on polyimide (PI), cellulose acetate (CA), polysulfone (PSf) and polydimethyl siloxane (PDMS) membranes, as these membrane materials have been most widely used for commercial applications. Finally, the most important strategies that would ensure new commercial applications will be discussed (156 references).