Investigation of the separation of carboxylic acids from aqueous solutions using a pilot scale membrane unit (original) (raw)
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Separation of formic, acetic, and propionic acids from the aqueous stream using membrane solvent extraction has been studied using three different membrane contactors made of polysulfone (PS), polyethersulfone (PES), and polyvinylidene fluoride (PVDF) using two different solvents; including ethyl acetate (EA) and diisopropyl ether (DIPE). The efciency of the membrane and extractants were obtained by partitioning coefcient comparison. The overall mass transfer coefcient was determined by resistance in series model. The results indicated signifcant difference amongst the performance of the membranes for the same system, even though one usually would expect the membrane only to play a role in facilitating high interfacial mass transfer contact area. The observable results of high distribution coefcient were obtained for the propionic acid with the PVDF membrane and EA as an extractant, on the other hand, the formic acid with PVDF and EA as extractants obtained a better mass transfer coefci...
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Synthetic solutions of varying concentrations of carboxylic acids, namely acetic and butyric acids (50 mM, 100 mM) and treated digested agricultural wastewater with a carboxylic acids concentration of 21.08 mM of acetic acid and 15.81 mM of butyric acid were processed with a range of nanofiltration membranes and enrichment schemes to concentrate carboxylic acids. The study was conducted with the scope of platform chemicals recovery from complex effluents, investigating the feasibility of nanofiltration as a method of choice. Membrane filtration is easily scalable into various arrangements, allowing versatility in operation and enrichment treatments, which other recovery practices such as liquid extraction do not allow. Among the five nanofiltration membranes used (NF270, (Dow Chemicals, USA), HL, DL, DK, (Osmonics , USA), LF10 (Nitto Denko, Japan)) the DK, DL and NF270 were identified as the best candidates for carboxylic acids separation and concentration from these complex effluents, both in terms of retention and permeate flux. These membranes achieved retention ratios, up to 75% giving retentates up to 53.94 mM acetate and 28.38 mM butyrate for the agricultural wastewater. Effluents were modified by the addition of alkali and salts (sodium chloride and sodium bicarbonate), and it was found that highest productivity, retention and flux was achieved at pH 7 but at higher pH there was a significant reduction in flux.
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.
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Journal of Applied Membrane Science & Technology, 2020
Reverse osmosis can potentially be used for separation of acetic acid from waste stream. However, the investigation on the separation of this binary mixture utilizing reverse osmosis is scarce. Thus, this study aims to evaluate the feasibility of lab-synthesized and commercially available reverse osmosis membranes to separate low acetic acid concentration from aqueous mixture. A commercially available AG membrane and three laboratory synthesized polysulfone (PSf) membranes were used in this work. Initial test for water permeation using dead end filtration found that 17.5 wt% PSf has the highest water permeability. As the polymer concentration decreases, the membrane porosity increases which decreases the resistance which enables the penetration of the permeant more easily through the membrane matrix resulting in higher water permeation when 17.5wt% PSf was used. Further modification by interfacial polymerization to form a thin polyamide layer on the porous support was seen to have h...
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The separation of acetic acid-water mixtures was carried out using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process, 4-vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft-copolymer by casting method and crosslinked by heat treatment. The effects of feed composition on the separation characteristics were studied and the performances of the separation methods were compared. Permeation rates were found to be high in PV whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1-3.0 kg/m 2 h and separation factors of 2.0-61.0 depending on the composition of the feed mixture and the method.
Behavior of Volatile Compounds in Membrane Distillation: The Case of Carboxylic Acids
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Thanks to its unique features, membrane distillation (MD) has been particularly applied for desalination but also for niches applications with feed solutions containing a mixture of volatile molecules. For such solutions, the complex interplay of the solutes and solvent physicochemical and operating parameters makes it challenging to predict the separation efficiency by MD. There is thus a need for a better understanding of the behavior of volatile compounds in MD as well as the influence of their physicochemical environment. This study aimed at investigating the influence of different operating parameters on rejection efficiency of air-gap MD towards carboxylic acids (formic, acetic and succinic acids). Acid rejection was found to be highly dependent on the carboxylic acid structure. In addition, it increased with the acid concentration, which could be related to the formation of acid dimers in the feed solution. This behavior is opposite to what is classically observed for pressur...
Separation of Succinate from Organic Acid Salts Using Nanofiltration Membranes
CHEMICAL ENGINEERING TRANSACTIONS, 2017
The fermentative production of bio-based succinic acid is often accompanied by organic acid byproducts. In this study, the separation of succinate from organic acid salts (acetate and formate) using pressure-driven nanofiltration (NF) was studied. The performances of three nanofiltration membranes were compared and discussed. The influence of feed ratio on the succinate recovery was not significant given that succinate rejections of greater than 81.9 % were obtained in all cases. A comparison between monovalent rejection and divalent rejection suggests that the separation of multi-salt solution was influenced by the Donnan-steric effects. Taking into account the permeation fluxes and organic acid salt retentions, the NFW membrane manufactured by Synder Filtration was considered the most appropriate membrane for the separation of divalent succinate from other organic acid salts. This study strongly supports the use of NF technology for the downstream recovery of high valuable products.
Separation of organic solutes by membrane pressure-driven processes
Journal of Membrane Science, 1994
The separation of organic solutes by ultrafiltration, nanofiltration and reverse osmosis is evaluated by a steric pore flow model integrated with the boundary layer theory. The modeling of mass transfer at the fluid phase adjacent to the membrane accounts for the effect of fluid dynamics, variation of feed physical properties and mass transfer rates. The membranes were characterized in terms of an average pore radius. The solute fluxes and separations were assumed to be governed by steric and hydrodynamic forces. The permeation experiments were performed with cellulose acetate membranes and dilute aqueous solutions of reference solutes of increasing molecular weight [alcohols, sugars, poly(ethylene glycols) and dextrans]. The flat sheet membranes were prepared in the laboratory with hydraulic permeabilities ranging from 0.65 to 72.2 kg/h m* bar.