Systematic choice of crosslinker and filler for pervaporation membrane: A case study with dehydration of isopropyl alcohol–water mixtures by polyvinyl alcohol membranes (original) (raw)
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Pervaporation dehydration of ethanol-water mixture using crosslinked poly(vinyl alcohol) membranes
Science and Technology Development Journal
Crosslinked poly(vinyl alcohol) (PVA) composite membranes were synthesized by casting selective crosslinked PVA films on the polyacrylonitrile (PAN) porous substrates. The PVA films were prepared by in-situ crosslinking technique using four different crosslinking agents, such as glutaraldehyde, fumaric acid, maleic acid and malic acid. The separation performance in terms of permeation flux and separation factor of prepared membranes were evaluated for pervaporation dehydration of ethanol/water mixture of 80/20 wt% at 60 oC. The prepared membranes were also characterized by FTIR, SEM, swelling and sessile drop contact angle measurements. It was found that the chemical structure of the PVA membrane was changed via crosslinking reaction. The physicochemical properties (hydrophilicity and swelling degree) and separation performance of the prepared membranes were affected by the chemical structures of the crosslinking agents. Furthermore, there was a trade-off between permeation flux and...
Journal of Industrial and Engineering Chemistry, 2020
Conventional distillation failed to separate a ternary azeotropic mixture of ECH, IPA and water (50/30/ 20 w/w, %) exist in the epoxy resin manufacturing process. Thus, we prepared a PVA-tetraethyl orthosilicate organic-inorganic hybrid membrane and modified the membrane by layer-by-layer deposition of a PVAm/silicotungstic acid polyelectrolyte for the pervaporation (PV) dehydration of ECH/ IPA/water mixtures. In PV experiments at 30 C, the flux decreased from 0.14 to 0.05 kg m À2 h À1 and separation factor increased from and 2099 to 13,320 with TEOS addition in the PVA membrane was observed. And for the layer by layer deposition on PVA-TEOS (4) membranes flux increased and separation factor decreased from 0.14 to 0.28 kg m À2 h À1 and 2099 to 416 with the number of layer of deposition were observed respectively. On varying the feed water content from 20 to 10 wt. %, the pervaporation flux at 30 C decreased from 0.22 to 0.0066 kg m À2 h À1 and the separation factor increased from 1061 to 9094 was observed. By applying the Arrhenius equation, permeation activation energies of ECH and IPA (97.42 and 111.96 kJ mol-1, respectively) are higher than that of water (40.88 kJ mol À1) were reported for the layer by layer membrane.
Desalination, 2002
The performance of commercially available polymeric and microporous silica membranes (both supplied by Sulzer Chemtech GmbH) was investigated with respect to the dehydration ofbinary mixtures of isopropyl alcohol (IPA)/water. The range of concentrations investigated (C Wo < 20 wt.%) was selected according to existing industrial needs. Fluxes and selectivities were monitored as dehydration proceeded, and the performance ofboth membranes has been compared. In addition, the effect of temperature on these parameters was investigated. Over this range, both water and IPA fluxes generally decreased with water concentration. The effect of temperature was investigated in the 70 to 105°C range, covering the pervaporation and vapour permeation operating conditions. Increasing the operating temperature resulted, as expected, in larger water fluxes for both polymeric and silica membranes. For the range of conditions investigated, water fluxes through the SMS membrane were found to be up to three times larger than those ofthe polymeric PERVAP 25 10 membrane. However, IPA fluxes through the SMS membrane were also observed to be higher than those through a PERVAP 25 10 membrane, resulting in a substantial decrease in separation performance.
Journal of Membrane Science, 1997
Crosslinked dense poly(vinyl alcohol) (PVA) membranes with different degrees of hydrolysis were prepared and used in sorption and pervaporation of isopropanol (IPA)/water mixtures. Partial flux of water permeation was increased with the water content in the liquid mixture, but the partial flux of IPA due to the coupling effect of sorption and permeation, had a maximum value. The degree of PVA hydrolysis and the feed temperature influenced the permeation flux and water selectivity due to crystallinity and the number of polar side groups in PVA. Thus the partial flux of water and IPA was inversely proportional to the degree of PVA hydrolysis and the selectivity of PVA for water was proportional to the hydrolysis level of PVA.
Journal of Membrane Science, 1996
Poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by a solution method for the pervaporation separation of acetic acid-water mixtures. In the solution method, dry PVA films were crosslinked by immersion for 2 days at 40°C in reaction solutions which contained different contents of GA, acetone and a catalyst, HC1. In order to fabricate the crosslinked PVA membranes which were stable in aqueous solutions, acetone was used as reaction medium in stead of aqueous inorganic salt solutions which have been commonly used in reaction solution for PVA crosslinking reaction. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of GA was characterized by IR spectroscopy. Swelling measurements were carried out in both water and acetic acid to investigate the swelling behavior of the membranes. The swelling behaviour of a membrane fabricated at different GA content in a reaction solution was dependent on crosslinking density and chemical functional groups created as a result of the reaction between PVA and GA, such as the acetal group, ether linkage and unreacted pendent aldehydes in PVA. The pervaporation separation of acetic acid-water mixtures was performed over a range of 70-90 wt% acetic acid in the feed at temperatures varying from 35 to 50°C to examine the separation performances of the PVA membranes. Permeation behaviour through the membranes was analyzed by using pervaporation activation energies which had been calculated from the Arrhenius plots of permeation rates.
Separation of isopropyl alcohol–water mixtures by pervaporation using crosslink IPN membranes
Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH to produce a full interpenetrating network (IPN) membrane termed as PVAH. Accordingly, three such full crosslink IPNs, i.e. PVAHI, PVAHII and PVAHIII containing varied weight ratio of PVOH and copolymer along with crosslink PVOH (which has not been modified by copolymerization) have been synthesized and used for pervaporative separation of isopropanol (IPA)–water mixtures. Permeability and water selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, PVAHIII were found to show highest flux but lower selectivity while PVAHI membrane showed optimum performance in terms of both flux and selectiv-ity.
Journal of Applied Polymer Science, 2004
Hybnd membranes were prepared using poly(vmyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by conden sation The obtained membranes were characterized by Founer transform infrared spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry The remarkable decrease m degree of swelling was observed with increasing TEOS content in membranes and is at tributed to the formation of hydrogen and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water-acetic acid mixtures was mvestigated in terms of feed concentration and the content of TEOS used as crosslinkmg agent The membrane can taming 1 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of3 33 x 10"2 kg/m2 h at 30 °C for 10 mass% of water in the feed Except for membrane M-l, the observed values of water flux are close to the values of total flux in the mvestigated composition range, signifying that the developed membranes are highly water selective From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated The resulting activation energy values, obtained for water permeation being lower than those of acetic acid permeation values, suggest that the membranes have higher separation efficiency The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-l, signifying that coupled-transport is minimal as due to higher selective nature of membranes Further, the activation energy values for permeation of water and diffusion of water are almost equivalent, suggesting that both diflusion and permeation contribute almost equally to the pervaporation process The negative heat of sorption values (A Hs) for water m all the membranes suggests the Langmuir's mode of sorption