Transport of organic acids through polybenzimidazole based membranes by ‘Chemodialysis’ (original) (raw)
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Dual-mode transport of inorganic acids through polybenzimidazole (PBI) membrane
Journal of Polymer Research, 2012
The diffusion and permeation of sulfuric, perchloric, and phosphoric acids through the polybenzimidazole (PBI) membrane were evaluated by using the timelag method. The results showed that the permeation of these acids in the polymeric film is due to normal Fickian diffusion. Increasing the acidity and concentration of each inorganic acid upstream increased the diffusion coefficients. Permeation results confirmed that the dual-mobility model was applicable. The dual-mobility model constants were found by using a least square program via fitting experimental data to dual-mobility equation. The results have indicated that the partial immobilization of Langmuir sorption coefficient, F, decreases with molecular size of acids. Besides, the diffusion coefficient of acid molecules in Henry's law, D D , increases with increasing acidity of the acids studied. Comparison of permeability coefficients of acids in PBI membrane indicates that permeability increases with acidity. Therefore, diffusion is considered the dominant factor in this transport mechanism.
Polymer, 2009
A series of polybenzimidazoles (PBIs) were prepared from 3,3 0 -diaminobenzidine (DAB) and substituted aromatic dicarboxylic acids. Effects of added polarity, bulk and isomerism in the dicarboxylic acid moiety on the properties of formed aromatic polybenzimidazoles were investigated. Solution polycondensation procedure was optimized for individual case of PBI synthesis in order to obtain inherent viscosity of !1 dL/g. Analysis of physical properties, water uptake, acid doping (H 3 PO 4 and H 2 SO 4 ) and gas permeability was performed. All these PBIs exhibited high thermal stability, good solvent solubility and amorphous nature. The uptake of H 3 PO 4 varied from 9 to 20.1 moles per repeat unit (mol/RU), H 2 SO 4 uptake varied from 3.39 to 3.81 mol/RU, while water uptake varied from 1.8 to 3.6 mol/RU of PBI. The dibromoterephthalic acid and tert-butylisophthalic acid based PBI showed the highest H 3 PO 4 uptake in the series, while tert-butylisophthalic acid based PBI exhibited the highest water uptake. Acid uptake was correlated with swelling of the PBI matrix, while density estimation of H 3 PO 4 -doped PBI by He gas expansion method could be correlated to the physical state of PBI. 5-tert-Butylisophthalic acid and 4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) based PBI exhibited higher H 2 and O 2 permeability than other PBIs. The ideal gas selectivity for O 2 /H 2 was considerably higher for most of the PBIs than conventional gas separation membrane materials. These analyses suggested that some of these PBIs have a potential to be used as a PEM or gas separation membrane material.
Journal of Applied Polymer Science, 2001
The permeation of acetic (AA), propionic (PA), lactic (LA), oxalic (OA), citric (CA), and tartaric (TA) acids through the bipolar ion-exchange membrane Neosepta BP-1 (Tokuyama Corp.) was studied. It was found that the fluxes (J, mol cm Ϫ2 s Ϫ1) and mass-transfer coefficients (k, cm s Ϫ1) increase in the following order: CA Ͻ OA Ͻ LA Ͻ TA Ͻ PA Յ AA. The transport processes in the Neosepta BP-1 membrane are concentration-dependent and can be described phenomenologically using I-Fick's law for diffusion. The permeation phenomena correspond to the solution-diffusion model similarly as to the permeation of carboxylic acids through strongly acidic cationexchange membranes. However, in competitive AA-PA transport experiments, typically for strongly basic membranes, the separation ability of the BP-1 membrane with a preference toward AA was observed. The selectivity coefficients ␣ PA AA calculated as the ratio of the respective mass-transfer coefficients vary in the range from 1.31 Ϯ 0.2 to 2.1 Ϯ 0.6. These values depend on the feed composition and the system arrangement, which means that ␣ PA AA is always higher for the system with the anion-exchange layer is in contact with a feed solution. Rather low fluxes of PA, AA, and other acids, as compared to some monopolar membranes (Neosepta AFN-7, Nafion-120, Flemion), are promising for the application of the bipolar membrane in an electrodialytic separation of carboxylic acids from their aqueous solutions or mixtures.
Journal of Chemical Technology & Biotechnology, 2012
BACKGROUND: Low energy and less expensive membrane based separation of acetic acid-water mixtures would be a better alternative to conventional separation processes. However, suitable acid resistant membranes are still lacking. Thus, the objective of the present study was to develop mixed matrix membrane (MMM) which would allow high flux and water selectivity over a wide range of feed concentrations of acid in water. RESULTS: Three MMMs, namely PANBA0.5, PANBA1.5 and PANBA3 were made by emulsion copolymerization of acrylonitrile (AN) and butyl acrylate (BA) with 5.5 : 1 comonomer ratio and in situ incorporation of 0.5, 1.5 and 3 wt%, sodium montmorilonite (Na-MMT) nanofillers, respectively. For a feed concentration of 99.5 wt% of acid in water the membranes show good permeation flux (2.61, 3.19, 3.97 kg m −2 h −1 µm −1 , for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) and very high separation factors for water (1473, 1370, 1292 for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) at 30 • C. Similarly for a dilute acid-water solution, i.e. for 71.6 wt% acid the membrane showed a very high thickness normalize flux (8.67, 9.44, 11.56 kg m −2 h −1 µm −1 , for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) and good water selectivity (101.7, 95.3, 79 for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) at the same feed temperature. The permeation ratio, permeability, diffusion coefficient and activation energy for permeation of the membranes were also estimated. CONCLUSION: Unlike most of the reported membranes, the present MMMs allowed high flux and selectivity over a wide range of feed concentrations. These membranes may also be effective for separating other similar organic-water mixtures.
Journal of Environmental Chemical Engineering, 2017
A newly fabricated (PI) P84 NF membrane was introduced in this work for overcoming the separation challenges of bio-based succinic acid recovery. PI membranes were fabricated at different polymer concentrations and membrane thicknesses. The inherent properties of the membranes were evaluated using salt rejection, FESEM, a porometer, AFM and the surface zeta potential. The performances of PI membrane for succinic recovery were investigated from a simulated fermentation broth and an actual broth, consisting of succinate, formate, and acetate. The effect of various process conditions of different feed concentrations, pressures, stirring speeds and different concentration ratios of divalent to monovalent ions were investigated. From the results, 20wt% PI membrane was successfully fabricated with average pore size diameter of 0.23nm, and Na2SO4 rejection of 80%. This membrane also exhibited high succinate rejection of 89-96% with a simulated broth, and that the rejection performance improved with increasing pressure and low feed concentration. Meanwhile, the succinate selectivity was improved by 20-51% with the increase in the stirring speed and the ratio of the divalent to monovalent ionic solute concentrations. With the actual broth, 92% succinate rejection was achieved, which was comparable to the rejection performance of the commercial membranes such as NF1 membrane. The membrane also showed excellent chemical stability in the broth based on the consistent FTIR and contact angle before and after the filtration. It can be concluded that the PI P84-based membrane has a great potential in applications for organic acids salts separation and recovery.
Journal of Power Sources, 2009
Phosphoric acid-doped membranes based in poly[2,5-benzimidazole] (ABPBI) were obtained by a new low temperature casting procedure and by the classical high temperature casting from methanesulfonic acid. These membranes, which can be suitable for application in direct methanol proton exchange membrane (PEM) fuel cells, were studied in relation with their phosphoric acid doping level by measuring the free and bonded acid. The water isotherms were also determined for the low and high temperature casted ABPBI membranes. Both, acid and water sorption properties, were compared with those determined in poly [2-2 -(m-fenylene)-5-5 bibenzimidazole] (PBI) membranes. The water sorption of the ABPBI membranes over the range of all water activity is described by the modified BET equation, commonly known as Guggenheim-Anderson-de Boer (GAB) and a two-parameters empirical isotherm. The acid uptake behaviour of the membranes prepared by low and high temperature casting are related with differences in their supramolecular structure.
2003
The electrodialytic separation of a large molecular organic acid using highly water-swollen poly(vinyl alcohol) (PVA)/poly-(styrene sulfonic acid-co-maleic acid) (PSSA-MA) cation-exchange membranes were investigated. The PVA/PSSA-MA membranes exhibited a lower membrane electrical resistance and a higher water-swelling property for large molecular organic ions (i.e., lysine-H + ) compared to the commercial membrane, CMX (Tokuyama, Japan). While the ion-transport number (ITN) of the PVA/PSSA-MA membranes for Na + was higher than 0.95, the ITN for lysine-H + was measured as 0.96-0.98. Further, the energy efficiency in the electrodialysis for separating lysine was improved using the PVA/PSSA-MA membranes. The flux of lysine-H + transported through the PVA/PSSA-MA membrane was measured as 19.8 mol m −2 h −1 while that of the CMX membrane was measured as 16.9 mol m −2 h −1 under the same power consumption (i.e. 4.0 × 10 4 W s).
Experimental Investigation of Pervaporation Membranes for Biobutanol Separation
Journal of Membrane and Separation Technology, 2013
Biotechnological production of chemical building blocks is one important step towards a more sustainable production. Unfortunately, the products to be separated are often highly diluted. Pervaporation has received increasing attention for the separation of small amounts of organic compounds from aqueous solutions, especially in the separation of butanol from water or from fermentation broth. To evaluate the potential of pervaporation for biobutanol recovery a consistent database is required, describing the dependency of permeate fluxes and selectivities on process variables like temperature, permeate pressure as well as feed concentrations and compositions. Therefore, within this work we investigated the separation behaviour of a commercially available polydimethylsiloxane (PDMS) membrane and membranes based on poly(ether block amide) (PEBA) fabricated in our own laboratory. The membranes were tested under varying operating conditions. Fermentation by-products or impurities may affect the pervaporation separation performance. Therefore, in addition, the permeate fluxes and the influence of acetone, ethanol, acetic and butyric acid and 1,3-propanediol have been investigated in detail as well. Several differences in the permeability and selectivity of PDMS and PEBA were observed during the experimental study. Swelling experiments were applied to further analyse the separation behaviour of PDMS and PEBA more in detail. Finally the influence of the observed separation performances on the overall butanol pervaporation process is discussed. It was found that especially well permeating byproducts like acetone can drastically influence the subsequent downstreaming process.