EFFECT of pH and ENZYMATIC TREATMENT ON MICROFILTRATION and ULTRAFILTRATION of TANGERINE JUICE

Tangerine (Citrus reticulata blanco) juice clarification by crossflow microfiltration and ultrafiltration using polysulphone flat sheet membranes with nominal molecular weight cut off of 25,000, 50,000, 100,000 and 0.1 μm, 0.2 μm pore sizes was studied. the juice was pretreated by polygalacturonase and pH adjustment. the treated juice was clarified with a laboratory scale filtration unit with effective filtration area of 14 cm². Filtration conditions were transmembrane pressure of 93 to 194 kPa, crossflow velocity of 0.96 to 3.5 m/s and 25°C. Membrane performance was evaluated in terms of volume flux and clarity (% transmittance) of the permeate. Pretreatment of the juice by polygalacturonase and adjustment to pH 2 with HCl resulted in a clearer supernatant than enzyme treatment alone. Maximum flux was obtained with the 0.1 μm microfiltration membrane. Flux increased with transmembrane pressure and crossflow velocity. Flux at 194 kPa and 3.5 m/s was 69 L per square meter per hour. Permeate clarity was better at higher transmembrane pressure and lower velocity, due to the effect of the polarized/fouling layer of solute on the membrane surface, which acted as a secondary “dynamic” filter.     

甘蔗混合汁粒径分布及陶瓷微滤膜过滤阻力研究

建立了甘蔗混合汁中颗粒粒径分布测定和分析方法;研究了0．1μm、0．2μm和0．45μm陶瓷微滤膜分析甘蔗混合汁时的阻力分布,探讨了不同膜元件主要阻力形式,确定了阻力分析方法。结果表明：致密性膜的制造精度越高,过滤料液时总阻力相对较小,孔隙率高的膜元件堵塞阻力随膜孔径减小而降低,利于膜通量的恢复和延长使用时间。     

Microfiltration and Ultrafiltration Ceramic Membranes for Apple Juice Clarification

Depectinized control (CTJ) and ascorbic acid treated (AAJ) apple juices were filtered through microfiltration (MF, 0.2 m) and ultrafiltration (UF, 0.02 m) ceramic tubular membranes. Under optimal conditions (8 m/s, 414 kPa and 50°C), the UF membrane resulted in higher steady state flux and less fouling than the MF membrane for both juices. AAJ produced by addition of AA at milling had lower flux for both MF and UF. The chemical, physical and sensory properties of apple juices from MF and UF membranes were similar and changes during storage were comparable.     

Effect of membrane property and operating conditions on phytochemical properties and permeate flux during clarification of pineapple juice

The effects of membrane property on the permeate flux, membrane fouling and quality of clarified pineapple juice were studied. Both microfiltration (membrane pore size of 0.1 and 0.2 μm) and ultrafiltration (membrane molecular weight cut-off (MWCO) of 30 and 100 kDa) membranes were employed. Membrane filtration did not have significant effects on the pH, reducing sugar and acidity of clarified juice whereas the suspended solids and microorganism were completely removed. The 0.2 μm membrane gave the highest permeate flux, total vitamin C content, total phenolic content and antioxidant capacity as well as the highest value of irreversible fouling. Based on these results, the membrane with pore size of 0.2 μm was considered to be the most suitable membrane for the clarification of pineapple juice. The optimum operating conditions for the clarification pineapple juice by membrane filtration was a cross-flow velocity of 3.4 ms⁻¹ and transmembrane pressure (TMP) of 0.7 bar. An average flux of about 37 lm⁻² h⁻¹ was obtained during the microfiltration of pineapple juice under the optimum conditions using batch concentration mode.     

基于红糖生产的蔗汁陶瓷膜过滤工艺技术

采用孔径为8、50 nm及500 nm的陶瓷膜对蔗汁进行过滤澄清生产红糖,解决传统红糖制作利用上浮撇泡方式处理蔗汁清净效果差导致成品糖品质低的问题.对比不同孔径陶瓷膜过滤蔗汁渗透通量大小、清净效果及能耗高低,结合红糖生产工艺需求,得出孔径为50 nm的陶瓷膜最适用于蔗汁过滤澄清生产红糖.在适合的操作条件下,考察孔径为5...     

PROCESSING OF CRUDE PALM OIL WITH CERAMIC MICROFILTRATION MEMBRANE

Membrane separation technology offers a potential application in the processing of crude palm oil. Ceramic membranes with different pore diameters (0.45 and 0.2 micron) were used to conduct the study on micromembrane process. Quality parameters of membrane-processed oils examined included free fatty acid (FFA), carotene, fatty acid composition (FAC), phosphorus and iron contents. The effect of operating parameters such as transmembrane pressure, feed flow and time on permeate flux were evaluated. It was found that 'Ceraflo'ceramic membrane with a pore size of 0.45 micron was only able to reject 14% of phosphorus from the crude oil. Ceramic membrane with pore size of 0.2 micron showed a better phosphorus rejection of 56.8%. The permeate was found to contain 7.13 ppm of phosphorus. The 0.2 micron membrane was also able to remove more than 80% of the iron from crude palm oil. Pore sizes for both membranes were not small enough to remove other components such as FFA, and carotene. Both membranes showed a similar trend in which the permeate flux increased with transmembrane pressure and feed flow until a certain limit where the flux declined with increasing pressure and feed flow. The limits in transmembrane pressures for membrane with pore sizes of 0.45 and 0.2 micron were 1.65 and 1.25 bar, respectively. Whereas the limits in feed flow for 0.45 micron and 0.2 micron membranes were 9.2 and 9.8 L/min     

石榴汁膜除菌工艺研究

以新疆和田酸石榴为原料制作石榴汁,用不同孔径的陶瓷膜对石榴汁进行除菌过滤,对比不同孔径膜的膜通量、除菌效率、成分截留率等参数,确定适于石榴汁膜除菌的膜孔径;并研究了石榴汁陶瓷膜除菌最佳工艺。结果表明,用于石榴汁除菌陶瓷膜的孔径为0.22μm;最佳工艺参数为压力0.20MPa、温度20℃。通过陶瓷膜过滤,可以有效去除石榴汁中的悬浮物和有害微生物,同时保留了其中的营养成分,避免了加热杀菌过程中的褐变、营养成分损失等问题。     

Cross-flow filtration of pectic substances during the enzymatic treatment of mandarin segment membranes

 This study is concerned with the cross-flow filtration of pectic substances, produced by the enzymatic treatment of membranes of mandarin segments, using several filtration membranes with pore sizes of between 0.45 μm and 30 kDa. Pectic substances solubilised in the digestion medium were polymers with an average molecular weight of 90–100 kDa. Pectin was retained by the membrane with a 100-kDa pore size. As a result of the addition of enzymes, pectin was degraded to a mixture of galacturonic acid and galacturonic acid oligomers, which appeared to be distributed between the retentate and the permeate. The final filtration rate of galacturonic acid oligomers was close to 100% when enzymes were present at the filtration membranes. In the absence of enzymes, the filtration rate ranged from 5% to 15%, and the permeation flux tended to decrease. The enzymatic treatment had an important effect on the resistances of the filtration membranes, and also caused a decrease in viscosity. These two factors were responsible for the increase in the permeate flux after the addition of enzymes, where this flux was almost as high as when filtration commenced. Received: 27 October 1997     

Cross-flow filtration of pectic substances during the enzymatic treatment of mandarin segment membranes

 This study is concerned with the cross-flow filtration of pectic substances, produced by the enzymatic treatment of membranes of mandarin segments, using several filtration membranes with pore sizes of between 0.45 μm and 30 kDa. Pectic substances solubilised in the digestion medium were polymers with an average molecular weight of 90–100 kDa. Pectin was retained by the membrane with a 100-kDa pore size. As a result of the addition of enzymes, pectin was degraded to a mixture of galacturonic acid and galacturonic acid oligomers, which appeared to be distributed between the retentate and the permeate. The final filtration rate of galacturonic acid oligomers was close to 100% when enzymes were present at the filtration membranes. In the absence of enzymes, the filtration rate ranged from 5% to 15%, and the permeation flux tended to decrease. The enzymatic treatment had an important effect on the resistances of the filtration membranes, and also caused a decrease in viscosity. These two factors were responsible for the increase in the permeate flux after the addition of enzymes, where this flux was almost as high as when filtration commenced. Received: 27 October 1997     

Process efficiency of casein separation from milk using polymeric spiral-wound microfiltration membranes

Microfiltration is largely used to separate casein micelles from milk serum proteins (SP) to produce a casein-enriched retentate for cheese making and a permeate enriched in native SP. Skim milk microfiltration is typically performed with ceramic membranes and little information is available about the efficiency of spiral-wound (SW) membranes. We determined the effect of SW membrane pore size (0.1 and 0.2 µm) on milk protein separation in total recirculation mode with a transmembrane pressure gradient to evaluate the separation efficiency of milk proteins and energy consumption after repeated concentration and diafiltration (DF). Results obtained in total recirculation mode demonstrated that pore size diameter had no effect on the permeate flux, but a drastic loss of casein was observed in permeate for the 0.2-µm SW membrane. Concentration-DF experiments (concentration factor of 3.0× with 2 sequential DF) were performed with the optimal 0.1-µm SW membrane. We compared these results to previous data we generated with the 0.1-µm graded permeability (GP) membrane. Whereas casein rejection was similar for both membranes, SP rejection was higher for the 0.1-µm SW membrane (rejection coefficient of 0.75 to 0.79 for the 0.1-µm SW membrane versus 0.46 to 0.49 for the GP membrane). The 0.1-µm SW membrane consumed less energy (0.015–0.024 kWh/kg of permeate collected) than the GP membrane (0.077–0.143 kWh/kg of permeate collected). A techno-economic evaluation led us to conclude that the 0.1-µm SW membranes may represent a better option to concentrate casein for cheese milk; however, the GP membrane has greater permeability and its longer lifetime (about 10 yr) potentially makes it an interesting option.     

Effect of membrane clarification on the physicochemical properties of pomegranate juice

Pomegranate juice (PJ) has a turbid appearance which can be clarified by membrane processing. The effect of membrane processing with hydrophilic polyvinylidene fluoride with pore sizes of 0.22 and 0.45 μm and mixed cellulose esters (MCE) with pore sizes of 0.22, 0.1, and 0.025 μm on physicochemical properties of PJ were evaluated. Turbidity, suspended solids, acidity, total soluble solids, total phenolic content and antioxidant activity decreased after passing through the membrane at the same rate for all membranes tested. Total soluble solids content (with mean rejection factor = 20.8%) and antioxidant activity (Efficient concentration 50 was duplicated) had the smallest and the greatest reduction in all membranes, respectively. Also, five important anthocyanins identified by LC/MS decreased after PJ clarification at the same rate for all membranes. Pelargonidin 3‐glucoside had minimum reduction (mean rejection = 7.7%). Ellagic acid also decreased for all membranes. However, MCE 0.025 μm membrane resulted in a greater decrease than did the other membranes (mean rejection = 24.3%).     

Soft purification of lampante olive oil by microfiltration

An efficient membrane-based process for deacidification of lampante olive oil was investigated. The neutralization of the free fatty acids with appropriate soda concentration allows the formation of submicronic particles which are subsequently removed by a microfiltration technique. A total or quasi-complete neutralisation of the acidity is necessary to achieve the complete retention of the soap molecules. Partial neutralization of the acidity leads to a lower membrane separation efficiency. The residual FFA causes permeation of soap molecules across the membrane. When filtered under suitable conditions, lampante olive oils show excellent quality characteristics, i.e., very low residual acidity as well as soap and water contents. The initial fluxes, obtained during crossflow filtration with membrane pore sizes 0.5 and 0.8 μm (147 and 212 l/h m², respectively) after neutralization with 20% NaOH are twice those obtained with 40% NaOH while there is only a slight improvement with the 0.2 μm membrane. The filtered oils show good quality (acidity and residual soaps) in the case of PS 0.2 and 0.5 μm, whereas the 0.8 μm membrane allows some soaps to pass through the membrane. The passage from the laboratory scale (1 kg) to a 50 kg unit shows the practical possibility of scaling up without meeting any particular problems or loss of efficiency.     

Modes of natural organic matter fouling during ultrafiltration

The fouling of ultrafiltration membranes by natural organic matter (NOM), isolated from a potable surface water source, was studied with an emphasis on elucidating fouling modes and the role of aggregates. NOM size was related to membrane pore sizes using parallel membrane fractionation and size exclusion chromatography, such analyses confirmed the predominance of low MW species and identified the presence of aggregates in concentrated NOM solutions. Cake formation was the dominant mode of fouling by the unfiltered feed, which contained aggregates. This was identified by a constant rate of increase in membrane resistance with permeate throughput and was independent of pore size over a 10-1000 kDa molecular weight cutoff (MWCO) range. Prefiltration (to remove aggregates) and dilution (to reduce aggregate concentration) reduced the rate of increase in membrane resistance for the low MWCO membranes but did not change the fouling mode. In contrast, such pretreatment prevented cake formation on the larger MWCO membranes and shifted the mode of fouling to pore blockage. The date lend support for the idea that an initial fouling layer of large aggregates can catalyze the fouling by lower MW species. The fouling layer could be removed from the large MWCO membranes by backwashing, but the lower MWCO membranes exhibited some irreversible fouling, suggesting that low MW species penetrated into the pore structure. A combined pore blockage-cake formation model described the data well and provided insight into how fouling modes evolve during filtration.     

A combined complete pore blocking and cake filtration model during ultrafiltration of polysaccharide in a batch cell

Ultrafiltration experiments of polysaccharide macromolecule have been performed in a batch, stirred as well as unstirred membrane cell using a fully retentive membrane over a wide range of operating conditions. A model based on Hermia’s approach for constant pressure dead-end filtration laws is proposed to analyze the flux decline behavior during ultrafiltration in a batch cell. Two model parameters, namely complete pore blocking coefficient and cake filtration coefficient are obtained by minimizing the error involved between calculated and experimental flux data. These parameters along with known operating conditions, membrane permeability and physical properties of feed enable one to predict the transient permeate flux decline. The effect of various operating conditions, such as feed solute concentration, stirrer speed and transmembrane pressure on the flux decline is studied. Experimental results show that operating conditions have significant effect on the onset of cake formation as well as on the flux decline behavior. Model predicted results are successfully compared with the experimental data.     

Evaluation of the fouling phenomenon in the membrane clarification of black mulberry juice

Mixed cellulose ester (MCE) flat membranes were used to clarify black mulberry juice, the yield of which was limited by fouling. The effects of membrane pore size (0.025, 0.1 and 0.22 μm), transmembrane pressure (0.5, 1, 1.5 and 200 kPa), and cross‐flow velocity (0.1, 0.2, 0.3 and 0.4 m s^?1) on membrane fouling were evaluated; the results showed that fouling increased with increased pore size and pressure, and decreased with increased velocity. Analysis of different resistances showed that both reversible and irreversible fouling resistances have an important role in fouling‐resistance changes. There is no cake resistance in all processes. Microstructure analysis of membrane using scanning electron microscopy confirmed the theory that intermediate blocking was the dominant fouling mechanism in MCE 0.025 μm, and standard blocking was the dominant mechanism in MCE 0.1 and 0.22 μm.     

微滤膜材质对杨梅汁理化品质及抗氧化活性的影响

为了寻找适合杨梅汁澄清处理的微滤膜,选用聚醚砜膜(PES)、尼龙膜(Nylon)、醋酸纤维膜(CA)、聚偏氟乙烯亲水膜(PVDF)、聚四氟乙烯亲水膜(PTFE)和聚丙烯膜(PP)6种材质的微滤膜,研究不同材质滤膜对杨梅汁理化品质的影响.结果表明:6种材质的滤膜均能有效提高杨梅汁的透光率,降低果汁中蛋白质含量;不同材质滤...     

静电纺PA6纳米纤维膜的过滤性能

用98%甲酸溶解聚酰胺6(PA 6)制备质量浓度为13%纺丝液,经静电纺丝获得厚度31～60μm、纤维平均直径217 nm、表面平均孔径为234 nm的纳米纤维非织造膜.由于该纤维膜的断裂强度仅为8.06 MPa,实验以普通聚酯纤维织物为支撑基布,测试了不同样品的过滤性能.结果发现:在气流速度为2.83 L/min时,...     

空气过滤用聚丙烯腈静电纺纤维膜的制备及其性能

为开发用于空气过滤的纳米纤维,采用静电纺丝技术制备了聚丙烯腈(PAN)纳米纤维膜,探讨了其纺丝液质量分数及纺丝电压对所纺纤维微观形貌的影响,同时研究了纤维膜厚度对过滤效率和压降的影响。实验结果表明:PAN纺丝液质量分数为12%,纺丝电压为20 k V时,所得纤维粗细均匀,平均直径为230 nm;当纤维膜厚度由18μm增至35μm时,过滤压降则由121.93 Pa升至591.75 Pa,而过滤效率由81.78%升至99.24%。对过滤性能较好的纤维膜分别进行力学性能和泡压法滤膜孔径测试,测得此纤维膜的弹性模量为223.67 MPa,断裂伸长率为51.96%,拉伸断裂应力为5.93 MPa,拉伸强度为7.77 MPa,拉伸屈服应力为2.79 MPa,平均孔径为2.064 3μm。     

PROCESS INTENSIFICATION OF MEMBRANE SYSTEM FOR CRUDE PALM OIL PRETREATMENT

In the study conventional refining, microfiltration and ultrafiltration processes have been used experimentally to pretreat crude palm oil (CPO) samples with the aim of moving from the usual huge refinery plant to a more process integrated membrane module at ultrascale size that will even perform better than the former. Reduction of phosphorus for the membrane‐permeate of 43.4% was higher than that of bleached oil of 34.4%. When ceramic membranes with pore diameters of 0.45 µm and 0.2 µm were used in microfiltration, it was found that membrane with pore size of 0.45 µm was able to reject 14% of phosphorus, while ceramic membrane with pore size of 0.2 µm showed better phosphorus rejection of 56.8%. Upon applying ceramic membrane with pore sizes of 20 nm and 50 nm, 78.1% and 60% of phosphorus were rejected, respectively. Attributed to the superior performance of the membrane with 20 nm pore size over other membranes and conventional refining method on phosphorus content, a simulation study thus made, showed that the average slurry volume after about 22‐min runs for membrane with pore sizes of 0.45 µm, 0.2 µm, 50 nm and 20 nm, and the average slurry volumes are 0.05, 0.09, 0.13 and 0.18 m ³ , respectively. The percentage decrease between membrane pore size of 0.45 µm and 0.2 µm; 0.45 µm and 50 nm; and 0.45 µm and 20 nm are 73, 49 and 24%, respectively. The ultrafiltration achieved order of process miniaturization of about 10 ² ?10 ³ , which is in accordance with literature. This is a considerable size reduction in the process size, which reflects the magnitude of slurry volume that can be produced within a given time and meets every standard for process intensification through simulated process miniaturization.     

小孔径陶瓷膜澄清甜叶菊提取液的工艺研究

该文研究了小孔径陶瓷膜澄清甜叶菊提取液的效果。通过比较4、5、8、10 nm孔径的陶瓷膜过滤甜叶菊的甜菊糖提取液时的过滤通量、脱色率和收率的区别,确定较优的陶瓷膜孔径;再优化陶瓷膜操作参数。结果表明,5 nm陶瓷膜较优,在40 ℃时,操作压力5 bar,膜面流速4 m/s,浓缩10倍,加30%原液体积水洗滤效果最佳,陶瓷膜平均过滤通量可达102.6 kg/（m2·h）,甜菊糖收率可达99.2%,陶瓷膜过滤结束后先利用质量分数1%~2%的NaOH清洗1 h,再用0.5%~1%硝酸清洗1 h,陶瓷膜水通量恢复率可以达到99%以上,再生效果比较好,可以重复使用。相比絮凝工艺,陶瓷膜脱色率提高了2.6%,甜菊糖收率提高了6.8%,因此膜法工艺可取代传统絮凝工艺实现对甜叶菊提取液的澄清。