陶瓷膜和有机膜超滤处理荔枝汁和膜垢分析及荔枝汁品质研究

应用陶瓷膜和有机膜对荔枝汁进行澄清实验,并进行采用总循环模式(TRM)研究跨膜压力(TMP)和循环流量(Qf)对膜通量(Qp)的影响,确定其各自的最优水平;采用批处理模式(TBM)研究这两个参数最优水平的组合工艺。澄清工艺中：无机陶瓷膜效果优于有机聚醚砜膜,最佳工艺条件为陶瓷膜组件、TMP 0.3MPa、Qf 40L/min。研究在TBM下,膜垢的形成原因,对微分方程--＝k(J－Jlim)J2－n进行拟合,拟合R2为无机膜0.8812和0.8478;有机膜为0.9048,并分析膜垢的形成的模式：有机膜的膜垢主要是层垢(n＝0),无机膜的膜垢形成主要是层垢和部分并在膜垢的综合情况(n＝0,n＝1)。并研究TBM模式下,总糖、总果胶、总蛋白、抗氧化活性等影响果汁品质的物质的动态过程,结果表明：在P＜0.05,无机膜在品质的保持比如总糖、抗氧化活性、总酚的截留滤等方面强于有机膜,其余的品质无显著差异。     

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...     

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...     

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.     

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.     

REVERSE OSMOSIS CONCENTRATION of GREEN TEA JUICE

The reverse osmosis concentration of green tea juice was attempted by using membranes prepared from different polymeric materials. the pore sizes of the membranes were also changed in order to investigate the effect of the pore size on the membrane performance. Special attention was focused on the removal of caffeine from the tea juice while retaining other components such as polyphenols and amino acids. Since severe membrane fouling was observed while tea juice was treated at high concentrations, an attempt was made to describe the membrane fouling by a modified gel model that includes the effect of the interaction between the membrane and the tea juice components.     

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。     

Rotating Disk-Assisted Cross-Flow Ultrafiltration of Sugar Beet Juice

Rotating disk module (RDM)-assisted cross-flow ultrafiltration of sugar beet juice, obtained by cold pulsed electric field-assisted pressing, was studied in full recycling and concentration modes. Results of trans-membrane pressure (TMP) stepping tests with 10- and 50-kDa membranes showed that filtration flux increased with rotation speed and TMP until 1000 rpm and 4 bar. A slight variation of filtration purity was observed for a rotation speed range of 0–2500 rpm. A TMP increase resulted in purity reduction due to the formation of thicker fouling layer. A full recycling test study with a 10-kDa membrane confirmed the influence of TMP and rotation speed on filtration flux. A rotation speed of 1000 rpm and a TMP of 4 bar were selected for sugar beet juice purification, by concentrating juice from 13 to 1 L. The results of concentration mode tests revealed that, with a 10-kDa membrane, the filtrate purity could reach 95.6 ± 0.5 %, which was comparable to the purity of sugar beet juice purified by conventional liming-carbonation method. The flux decline in cross-flow filtration was still important, justifying more effective anti-fouling technologies investigation.     

Chicory juice clarification by membrane filtration using rotating disk module

Clarification is the first step of inulin production from chicory juice, and membrane filtration as an alternative can greatly simplify this process, increase juice yield, improve product quality, and reduce the cost and waste volume. In this study, a rotating disk module (RDM) was used to investigate the clarification of chicory juice by four micro- and ultrafiltration membranes. Compared with dead end filtration, the RDM had a much higher permeate flux and product quality. High rotating speeds produced high permeate fluxes and reduced flux decline, because of the strong back transport of foulant from fouling layer to feed solution. At high rotating speeds of 1500–2000 rpm, the permeate flux increased with membrane pore size and transmembrane pressure (TMP), while at low rotating speeds (<1000 rpm), permeate flux was independent of membrane type and TMP due to a thick deposited fouling layer as a dominant filtration resistance, while carbohydrate transmission decreased at higher TMP because of denser cake layer as an additional selective membrane. The highest carbohydrate transmission (∼98%) and desirable permeate turbidity (2.4 NTU) was obtained at a TMP of 75 kPa and a rotating speed of 2000 rpm for FSM0.45PP membrane. With the RDM, the Volume Reduction Ratio (VRR) could reach 10 with a high permeate flux (106 L m⁻² h⁻¹) in the concentration test, and permeate was still rich in carbohydrate and well clarified. Chemical cleaning with 0.5% P3-ultrasil 10 detergent solution was able to recover 90% water flux of fouled membrane.     

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.     

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。     

超声作用对葡萄汁膜过滤工艺的影响

将超声波技术应用于葡萄汁的超滤膜过滤过程,研究了超滤膜孔径、跨膜压力、超声功率、超声频率等因素对超滤膜通量的影响,结果表明:采用200目滤布的板框过滤使后续的超滤过滤有较大的膜通量.超声波作用下,适宜的葡萄汁超滤膜工艺参数为:跨膜压力0.25 MPa、膜滤温度50℃、超声功率200W和频率40kHz.同无超声波作用相比...     

Fouling Behavior of Polyphenols during Model Juice Ultrafiltration: Effect of Membrane Properties

Fruit juice is a complex mixture, in which polyphenols are active compounds for human health. In this paper, the effects of membrane properties, such as materials and molecular weight cutoff (MWCO), on fouling behavior of four typical polyphenols in model fruit juice ultrafiltration process were investigated. Zeta potential, contact angle, SEM image, and fouling resistances were determined. Static adsorption and rejection content of polyphenols on membranes were measured. Quantitative structure-activity relationship (QSAR) model has been developed to demonstrate the relationships between rejection and molecular parameters. Results showed that materials, MWCOs, hydrophobic properties, electrical parameters, and molecular parameters are critical factors. Membranes which were hydrophobic and positively charged have higher permeate flux and lower fouling resistance. Polyphenols were adsorbed by membranes as irreversible fouling and also had an important contribution in cake layer fouling. Retention of polyphenols on polyethersulfon 5-kDa membrane was the largest, while that on PVDF 50-kDa membrane was the least. According to QSAR analysis, rejections of polyphenols were higher when the molecules have smaller dipole moment, larger connectivity index ³X_p^v, and smaller ⁴X_pc^v.     

Combinatorial optimality of membrane morphology and feedstock during microfiltration of bottle gourd juice

The combinatorial optimality of membrane morphology and process parameters during dead end microfiltration of bottle gourd juice have been addressed in this article. Saw dust and kaolin based low cost ceramic membranes with varied morphology have been chosen to evaluate upon their microfiltration performance. For the chosen membranes, fresh, paper filtered and centrifuged juice samples were considered along with transmembrane pressure differential as process parameters. Combinatorial optimality was based on flux decline trends, fitness of fouling models, irreversible and reversible fouling data, irreversible permeation resistance and nutritional analysis of the permeate samples. An interesting feature of the article had been with respect to feed constitution playing a critical role in influencing the optimal choice of membrane morphology and transmembrane pressure differentials. Among all cases, paper filtered bottle gourd juice, 0.75 μm membrane and 137.9 kPa transmembrane pressure were found to be the best choice in terms of minimal irreversible fouling, lowest protein content, good clarity, good polyphenol and antioxidant activity in the permeate and appropriate flux.     

不同预处理方式对柠檬果汁超滤澄清效果和膜污染情况的影响

利用超声辅助果胶酶法和超滤技术相结合对柠檬果汁进行澄清。以柠檬汁的透光率、果胶含量为指标,讨论不同预处理方式对柠檬果汁超滤澄清效果和膜污染情况的影响。结果表明,采用切割分子量为50 kDa的聚丙烯腈(PAN)超滤膜澄清果汁,不同预处理方式对超滤膜的稳定通量大小的影响规律是酶+超声处理>酶处理>未经酶+超声处理,其稳定通量分别为30、33.5和13 L·m-2·h-1左右。较优的操作压力可确定为0.1 MPa,此时柠檬汁的果胶含量为0.5%,透光率约99.6%,处理效果较好。超声辅助果胶酶法澄清果汁,有利于提高果汁的透光率,并且在后续膜处理过程中,对于提高超滤膜的通量和缓解膜污染都有显著的效果。     

Understanding Nanofiltration Fouling of Phenolic Compounds in Model Juice Solution with Two Membranes

Understanding membrane fouling mechanisms of key nutrition indicators in fruit juices during nanofiltration (NF) are important for quality control of products and manufacture processes. This study evaluated the effects of operating and molecular parameters of six phenolic compounds on fouling resistances during NF with two membranes. Results showed that fouling resistances and mechanisms were significantly different among the six representative phenolic compounds as a result of different molecular parameters such as acidity coefficient, molecular refractive index, octanol-water partition coefficient, and lipo-hydro partition coefficient. Operating time, solution concentration, and transmembrane pressure can also significantly affect the membrane fouling during nanofiltration of gallic acid solution. The images obtained by field emission scanning electron microscopy and atomic force microscopy on new, fouled, and cleaned membranes showed the fouling mechanisms intuitively. For phenolic compounds, a cake/gel layer as a reversible fouling was the main fouling resistance, and the adsorption was a significant role in the irreversible fouling resistance.     

The effect of ultrasound waves on the efficiency of membrane clarification of pomegranate juice

Pomegranate juice has a turbid appearance, which poses difficulties in its concentration process. Membrane clarification can be used to clarify pomegranate juice; however, membrane fouling reduces the permeate flux, limiting its effectiveness. Ultrasound at 30 kHz was used to reduce membrane fouling. Results were compared with the data obtained for membrane clarification without ultrasonic treatment at the same temperature. Results showed that permeate flux increased with ultrasonic treatment. Evaluation of different membrane fouling characteristics showed that the total membrane resistance fell due to the reduction in irreversible fouling and cake resistance. However, ultrasound did not affect the thick caking produced in membrane processing at low feed‐flow rates. Evaluation of the physicochemical properties of pomegranate juice showed that ultrasound can decrease antioxidant activity due to the reduction in total anthocyanin content. Also, total soluble solid content and acidity of pomegranate juice changed with ultrasonic treatment.     

Ultrafiltration fouling of amylose solution: Behavior, characterization and mechanism

Applications of ultrafiltration membrane often deal with feed streams containing amylose starch. This paper describes a detailed investigation of amylose fouling during ultrafiltration. Commercial membranes made of polysulfone and fluoro polymer were used. Both adsorptive and ultrafiltration fouling were investigated. Experiments using different membrane characteristics, feed concentrations and trans-membrane pressures were carried out. The resulting fouling was characterized by water flux and contact angle measurements and was visualized by scanning electron microscopy (SEM). The results suggest that solute adsorption has occurred as noticed by significant water flux reductions as well as changes in membrane characteristics. Further, both reversible and irreversible fouling have occurred during ultrafiltration with irreversible fouling was more dominant. Apparently, cake layer formation initiated by either adsorption due to hydrophobic–hydrophobic interactions or pore blocking is the dominant fouling mechanism. However, pore narrowing instead of pore blocking was also observed for the membrane having large and relative uniform pore structure or for the ultrafiltration using low trans-membrane pressure or low solute concentration. Membrane autopsy using SEM confirmed the formation of solute layer on the membrane surface.     

Modeling flux behavior for membrane filtration of apple juice

The flux behavior of ceramic membranes with different pore sizes (0.2, 0.1 and 0.02 μm) was examined during dead-end membrane filtration of depectinized control (CTJ) and ascorbic acid treated (AAJ) apple juices. A new model based on an expanded exponential relationship was developed. The model represented the flux with precision over the entire filtration process for both juice types and all membrane pore sizes. Two parameters, A and B, provided a measure of the rate of flux decline. The same approach was used to model the permeate flux of CTJ for various 0.2 μm pore size polymeric membrane materials operated in a dead-end mode, and for tubular ultrafiltration membranes of different pore sizes (9, 20 and 100 kDa) operated in crossflow mode.     

ANALYSIS OF THE FOULING MECHANISM IN MICROFILTRATION OF ORANGE JUICE

The purpose of this work is theoretical and experimental evaluation of fouling effects on flux performance in clarification of freshly squeezed orange juice by cross-flow microfiltration. To identify optimum operating conditions to minimize fouling effects, juice was microfiltered on a laboratory scale plant varying axial velocity and transmembrane pressure difference. The observed flux decay was modeled using a modified form of the differential equation used to describe classical dead-end filtration processes. The mechanism of fouling during cross-flow microfiltration was identified by estimation of the model parameters according to a nonlinear regression optimization procedure. Analysis of the results revealed that the separation process is controlled by a cake filtration fouling mechanism as the juice is fed at relatively low velocity (i.e., Re = 5000) and the system is operated at low transmembrane pressure difference. In these operating conditions the permeate flux decays within the first 20–30 min to gradually achieve a limit value. At higher Reynolds number (Re = 15,000), an increase in applied transmembrane pressure (i.e., from 0.3 to 1 bar) allows the limit permeate flux to increase by a factor of about 4. In these conditions the filtration process is controlled by a complete pore blocking fouling mechanism, and the permeate flux becomes approximately invariant with respect to time, and a negligible decay may be observed. Evaluation of specific energy consumption involved in the filtration process is reported.