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Let’s commemorate the 100th anniversary of “pervaporation” by committing ourselves to position it as it deserves. Dear editor, this Submission is a letter to the Editor, and thus, a abstract does not apply.Therefore, this section will be used as a space for my comment or suggestion because it is needed for the next step. When we submit a letter to the editor, the abstract section maybe should not be available. Thus, we do not have problem during the Submission. I hope this section will be managed in the future for letter to the editor.Let’s commemorate the 100th anniversary of “pervaporation” by committing ourselves to position it as it deserves.
Encapsulation, invented in 1953 by B.K. Green & L. Schleicher employed in the laboratories of the National Cash Register Company, Dayton, USA, is defned as a technology of packaging solids, liquids, or gaseous materials in miniature, sealed capsules that can release their contents at controlled rates under specifc conditions. Encapsulation involves the incorporation of food ingredients, enzymes, cells, or other materials in small capsules. Microcapsules offer food processors a means to protect sensitive food components, ensure against nutritional loss, utilize otherwise sensitive ingredients, incorporate unusual or time-release mechanisms into the formulation, mask or preserve flavors and aromas, and transform liquids into easily handled solid ingredients. Various techniques are employed to form microcapsules, including: spray drying, extrusion coating, fluidized-bed coating, coacervation, layer-by-layer, and interfacial polymerization method. Recent developments in each of these techniques are discussed in this review, comprehensively.
Chitosan (CS) and alginate (Alg) are complementary in their membrane performance, but the combination of them is normally difcult to use due to their different solubilities. Layer-by-Layer deposition appears to be an effective method for improving the separation efciency of a composite membrane. In this work, the polyelectrolyte multilayer composite membranes (PEMCMs) were fabricated by depositing CS and Alg solutions alternatively onto a hydrolyzed porous poly(acrylonitrile) (PAN) substrate under a reduced pressure, as evidenced by Attenuated total reflectance Fourier transform infrared spectroscopy, contact angle and zeta potential measurement. Pervaporation results showed that the water selectivity increased while the flux decreased with the growth of CS/Alg-based polyelectrolyte layer. It was interesting that the sorption process dominated the pervaporation process when the numbers of polyelectrolyte layers were less than 7. However, the diffusion effect was more profound than the sorption effect as more than 8 polyelectrolyte layers were deposited on the PAN substrate. In particular, the prepared CS/Alg PEMCMs exhibited highly improved water selectivities towards alcohol/water mixtures, and a good compromise between flux and separation factor was observed when compared to other polyelectrolyte-based membranes. For separating 90% IPA/water mixtures at 60 ºC, the (CS/Alg)4 composite membrane displayed a separation factor of 4491 and a flux of 596 g/m2.h, respectively. These results indicate that the fabricated CS/Alg composite membranes are excellent waterpermselective ones for alcohol dehydration.
Integrally-skinned asymmetric Polyetherimide/Poly (vinyl alcohol) (PEI/PVA) hollow fber membranes for pervaporation dehydration were fabricated by non-solvent induced phase inversion. PVA inside the PEI matrix could be crosslinked to provide membrane performance stability during long term operation. The effects of different PEI/PVA blend ratio, external coagulant type and flow rate, and crosslinking conditions on the membrane structure and the separation performance were investigated. Generally, hollow fbers using PEI/PVA blend are less selective than those of neat PEI, probably due to the defects evolved between PEI and PVA. The influence of coagulant type on membrane pervaporation performance was specifc to dope formulation; when using n-butanol as external coagulant, the higher the coagulant flow rate, the better the membrane separation performance. PVA crosslinking by maleic acid (MA) enhanced the membrane performance, obviously. PEI/PVA Hollow fbers formed using n-butanol as external coagulant obtained a separation factor of 28 after crosslinking, much better than 4.4 with the original one. The crosslinked membrane exhibited higher stability than the neat PEI membrane. The separation factor of the latter degraded by more than half after around 200 h operation. Finally, this work has provided a new approach for fabricating crosslinkable asymmetric membrane suitable for pervaporation dehydratio.
In this study, polyphenylsulfone (PPSU) hollow fiber membrane was fabricated via a wet spinning method with the addition of ethylene glycol (EG) in the range of 0-10 wt% as the additive. The EG was added to improve the membrane pore formation and interconnectivity for better membrane contactor performance in extracting and removing the free fatty acid (FFA) from crude palm oil (CPO). Four different hollow fiber membranes consisted of 14PPSU-0EG, 14PPSU-2EG, 14PPSU-6EG and 14PPSU-10EG were characterized for their morphologies, wettability and pore sizes. From the characterization, it was proven that the presence of EG has promoted the formation of more uniform interconnected finger-like structure with double-layer membrane morphology. In membrane contactor performance testing, sodium hydroxide (NaOH) was used as liquid extractant due to the high affinity of free fatty acid (FFA) towards NaOH. Unfortunately, the new developed PPSU hollow fiber membrane with the presence of EG has significantly (P<0.05) reduced the membrane contactor performance from 16.54% FFA removal using 14PPSU-0EG to less than 5% FFA removal in the treated CPO permeate after 3 hours operation. It may be due to a significant (P<0.05) reduction in membrane hydrophobicity which reduced the oil wettability and interfacial contact between CPO and NaOH at the membrane interface. Nevertheless, no soap formation was detected in the permeate collection.
In this work, different kinetic patterns (homographic, exponential-linear and exponential) of hydraulic resistance in ultrafltration process of a colloidal system have been investigated. Exponential kinetic model, as the best approach, was employed for description of dynamic hydraulic resistance of skim milk ultrafltration at different feed flow rates (FR) (10, 30 and 46 L/min), transmembrane pressures (TMP) (0.3, 0.6 and 1 atm), temperatures (30, 40 and 50°C), pH levels (5.6, 6, 6.6, 6.9 and 7.6) and NaCl concentrations (0, 0.03, 0.06 and 0.12 %w/w). Results indicated that the initial resistance (R0), steady-state resistance (R∞), resistance increment rate (k) and resistance increment extent (RE) increased with TMP and ionic strength increasing and FR decreasing. The most sensitive factor for prediction of RT (total hydraulic resistance), R0 and R∞ was the NaCl concentration. Also, the highest sensitive factors for RE and k were temperature (0.77) and TMP (0.60), respectively.
Recovery of sugars from cane molasses (i.e. the by-product of sugar industries) is of great interest to industry and academia. The prerequisite for refning cane molasses is removal of pigments and suspended solids present in the molasses. In this work, the utilization of membrane separation for clarifcation and decoloration of cane molasses has been examined. Three operation modes (dilution-concentration, dilution-concentration-diafltration, and dilution-diafltration-concentration) were employed for color removal with a tight 2 kDa ultrafltration (UF) membrane. Results showed that the operation modes with diafltration could result in higher sugar recovery than dilution-concentration mode, though the latter had the higher permeate flux. Then, in order to further improve the permeate flux of the 2 kDa UF, fve pretreatments were carried out to remove suspended solids and large pigments. It was found that the pretreatment with ceramic membrane fltration was better than centrifuge and precipitation, particularly in terms of permeate flux for the tight UF membrane. Although the permeate flux for the tight UF after a UF pretreatment equipped with a 150 kDa UF membrane was higher than that with a 50 kDa UF membrane, the permeate flux during the pretreatment was the highest for the 50 kDa UF. The obtained decolorized syrup can be further purifed by nanofltration for the separation of sucrose and reducing sugars. Thus, refnement of cane molasses with membrane technology provides an alternative to conventional refnement methods and shows promising prospects of industrial application.
The great demand of beverages, both alcohol-free and with low alcohol content, is a great challenge for the production of beverages with controlled alcohol content through the use of sustainable enological practices. The present work addresses this challenge with the processing of grape must by reverse osmosis (RO) for must reconstitution with different sugar contents prior to the alcoholic fermentation. The original must came from grapes grown in Quinta do Quinto, in Santarém, collected after destemming and mechanic crushing, and preserved in a refrigerated chamber at -1.6 °C until processing by RO. The RO processing was carried out in Escola Superior Agrária de Santarém, with a pilot plant equipped with RO spiral wound modules, M38RO, from Alfa Laval, Denmark. The total membrane permeation area is 15 m2. The work pressure was 55 bar. The original must had 23.7 oBrix, a density of 1108 g.L-1, 15.2% (v/v) of probable alcohol, and a conductivity of 2.01 mS.cm-1. The must reconstitution was carried out, by mixing the concentrated grape must with the vegetal water produced by RO (permeate) to obtain beverages with a nominal alcohol content of 5%, 7%, 10% and 13% (v/v). The fermentation average temperature was between 18.2 and 19.7 °C, and the fnal density rounded about 993 g.cm-3. The beverages were analysed by different parameters, including total polyphenols, total anthocyanins, colour intensity and hue, the coordinates CIELab, alcohol content, total acidity, volatile acidity, pH, free SO2 and total SO2. The attributes of the beverage, corresponding to the visual appearance, aroma and taste senses, as well as the overall judgment were evaluated by the tasters. The proposed method can produce beverages with controlled low alcohol content. The decrease of the alcohol content led to lower content of polyphenols compounds which influenced the sensory evaluatio.
Poly(ether ether ketone) with cardo group-based (PEEK-WC) membranes, in hollow fber (HF) confguration, were prepared via the dry-wet spinning technique through the phase inversion process and used to clarify kiwifruit juice. The depectinised juice was processed according to a batch concentration confguration in selected operating conditions (transmembrane pressure, 1.6 bar; feed flowrate 70 L/h; temperature, 25±2 °C) up to a volume reduction factor (VRF) of 1.8. The quality of clarifed juice was analysed in terms of total antioxidant activity (TAA), content of ascorbic, malic, succinic and citric acid, total polyphenols, suspended solids and total soluble solids (TSS). The prepared membranes allowed to remove suspended solids producing a clear juice with a content of organic acids, vitamin C and polyphenols comparable to that of the fresh juice. Accordingly, the TAA of the fresh juice was well preserved in the clarifed juice.