Membrane Molecular Weight Cut Research Articles

Relationship between the Hansen solubility parameter and changes in membrane mass-transfer channels: A quantitative model

The relationship between swelling, the difference (Δδ) in theoretical Hansen solubility parameters (HSP) between the two substances, and the change of membrane mass-transfer channel has been controversial. In this work, a completely new parameter, Swell-Cavity Ratio (SCR), defined as the ratio of membrane molecular weight cut off (MWCO), was introduced to characterize the changes in mass transfer channels before and after membrane swelling. Models of the relationship between Δδ and SCR were successfully constructed for nanoporous glassy (SCR = 0.19 × Δδ0.40) and rubbery (SCR = 17.7 × Δδ-0.93) membranes, using the swelling as a bridge. Based on this contradiction in models, we speculate that SCR variation is strongly related to the separation mechanism of the membranes. The theoretical model accurately calculates the influence of the solvent on the membrane mass transfer channel, allowing for the selection of the best membrane material and pretreatment process to maximize treatment efficiency.

High-flux robust PSf-b-PEG nanofiltration membrane for the precise separation of dyes and salts

We report a novel high-flux nanofiltration (NF) membrane for the precise separation of dyes and salts, which was fabricated using polysulfone-block-polyethylene glycol (PSf-b-PEG) block copolymer through the non-solvent induced phase separation (NIPS) method. The PSf-b-PEG membrane exhibited a very dense sponge-like porous structure with rich interconnected pores, contributing to its superior mechanical strength of 22.4 ± 0.9 MPa. The pore size of PSf-b-PEG membrane was mostly distributed around 1.3 nm in diameter with the mean effective pore size of 3.8 nm in diameter, while the membrane molecular weight cut off (MWCO) towards dyes was about 655 Da. The PSf-b-PEG membrane exhibited a very high water permeance of 49.3 ± 0.9 L m−2 h−1 bar−1 and a precise separation of salts and dyes with high above 98% Congo Red dye rejection and nearly 100% Na2SO4 passage, succeeding the separation performances of current NF membranes used for the separation of dyes and salts. Long-term NF tests prove the highly stable and outstanding separation performances of PSf-b-PEG membrane with the top dense skin layer as the effective selective layer. Our work suggests that the PSf-b-PEG membrane has a great potential to be further optimized and used for practical applications.

Prediction of long term filtration by coupled gel layer and pore transport model for salt removal using mixed matrix hollow fiber ultrafiltration membrane

Characterization and performance of lanthanum cobalt oxide nanoparticle doped hollow fiber ultrafiltration membrane are reported in this paper. Nanoparticles (1 wt%) having zeta potential −30 mV at pH 7 imparted high surface charge (surface potential ~19 mV) to the hollow fibers. At this composition, the membrane became more hydrophilic with contact angle reduced to 520 from 570 corresponding to without nanoparticles. Permeability of hollow fiber with 1 wt% nanoparticles increased by 40% compared to that without nanoparticle. At this composition, the membrane molecular weight cut off was 4000 Da (with average pore diameter 34 nm) belonging to ultrafiltration range. Rejection of sodium chloride was 47% in 1000 mg/l synthetic solution at transmembrane pressure drop 69 kPa and cross flow rate 20 l/h. Performance of developed hollow fiber membrane was also tested using actual seawater with a rejection of 40% total dissolved solids at 138 kPa at 20 l/h with 15 l/m2h permeate flux. A combined gel polarization and pore flow model was used to quantify the long term flux decline and salt concentration in the permeate as function of time.

Removal of fluoride and natural organic matter from natural tropical brackish waters by nanofiltration/reverse osmosis with varying water chemistry

In the context of decentralised brackish water treatment in development applications, the influence of water quality on membrane separation was investigated with real waters. High ionic strength (low net driving pressure) on fluoride (F) retention by nanofiltration (NF) and reverse osmosis (RO) was investigated over a wide pH range (2–12). Further, the influence of pH on the permeation of natural organic matter (NOM) fractions, in particular low molecular weight (LMW) neutrals, was elucidated. Natural and semi-natural waters from Tanzania with similar F concentrations of about 50 mg L−1 but varying NOM and inorganic carbon (IC) concentration were filtered with an NF and RO, namely NF270 and BW30.F retention by NF270 for the feed water with highest ionic strength and IC concentration was lower and attributed to charge screening. This parameter further reduced at high pH due to co-ions (F− and CO32−) interactions and combined (synergistic) effect of high salt concentration and pH on F. High NOM resulted in higher membrane zeta potential in comparison with low NOM natural water. However, there was no significant difference in F retention due to the fact that F retention enhancement was annulled by deposit formation on the membrane. The fraction of NOM found in NF/RO permeates was dominated by LMW neutrals. This was attributed to their size and uncharged nature, while their higher concentration at low pH remains unexplained. More humic substances (HS) of higher molecularity and aromaticity permeated the NF270 when compared with BW30, which can be explained with the different membrane molecular weight cut off (MWCO).The study highlights the complexity of treating tropical natural waters with elevated F and NOM concentrations. In order to develop appropriate membrane systems that will achieve optimal F and NOM removal, the influence of water quality parameters such as pH, NOM content, ionic strength and IC concentration requires understanding. Seasonal variation of water quality as well as operational fluctuations, which occur in particular when such treatment processes are operated with renewable energy, will require such challenges to be addressed. Further, given the high permeability of low molecular weight (LMW) organics significant permeate side fouling may be expected.

Active pectin fragments of high in vitro antiproliferation activities toward human colon adenocarcinoma cells: Rhamnogalacturonan II

This study was to identify active pectin fragments of high in vitro anti-proliferation activities against human colon adenocarcinoma Caco-2 cells, using various pectin fragment preparations dominant with rhamnogalacturonan I (RG-I), rhamnogalacturonan II (RG-II), and galacturonic acid oligomers (GAOS). The samples were prepared from citrus high and low methoxy pectins (HPE and LPE) by endo-α-D-(1,4)-polygalacturonase action coupling with a green process as ultrafiltration (membrane molecular weight cut off > 10k, 1k-10k, and < 1k, giving fragment preparations I, II, and III, respectively). It is indicated that, in the fragment preparations HPE-I, II, and III, the molecular fractions HPE-F1 (RG-I), HPE-F2 (RG-II), and HPE-F3 (GAOS) showed an averaged Mw = 26.7k, 3.4k, and 0.3k, respectively, notably higher than their LPE counterparts. All fragment preparations exhibited concentration-dependent, inhibition effects on Caco-2 cells, where HPE-II (RG-II-domain) revealed an interesting inhibition effect, significantly higher than those did HPE-I (RG-I domain) and HPE-III (GAOS). The HPE-F2 (RG-II) was elucidated and found of IR = 88% at 1.0 mg/mL and half-inhibition concentration (IC50) = 0.12 mg/mL, doubling the effect of HPE-F1 (RG-I) (IR = 45% at 1.0 mg/mL). Conclusively, citrus RG-II fragment showed a promisingly high anti-Caco-2 activity, significantly higher than did RG-I and GAOS, possibly attributed to its special branched structure and low molecular size.

Application of UF-RDM (Ultafiltration Rotating Disk Membrane) module for separation and concentration of leaf protein from alfalfa juice: Optimization of operation conditions

Ultrafiltration Dynamic Rotating Module (UF-DRDM) was an effective alternative method to concentrate leaf protein from alfalfa juice. The effects of operation parameters (membrane, rotating speed, temperature and TMP) on filtration behavior were investigated using full recycling tests and concentration tests. Large membrane molecular weight cut off (MWCO), rotating speed, temperature and TMP improved filtration behavior and productivity. Furthermore, high rotating speed produced high shear rate on membrane surface, enhancing separation performance and membrane cleaning efficiency. But, large MWCO, high temperature and high TMP caused terrible separation performance and high irreversible fouling. Then, series of concentration tests were studied. Large MWCO, high rotating speed, high temperature and great TMP could improve filtration behavior of concentration tests. Finally, concentration tests repeated five times were conducted at optimized operation conditions (2000 rpm, 6 bar, 55 °C and US100P) for checking efficiency, stability and sustainability as well its potential application value. These results from laboratory-scale tests show favorable prospects in the alfalfa juice concentration by UF-DRDM.

AKTIVITAS ANTIBAKTERI DAN ANTIOKSIDAN HIDROLISAT HASIL HIDROLISIS PROTEIN SUSU KAMBING DENGAN EKSTRAK KASAR BROMELIN

Goat milk is highly nutritious foodstuffs that beneficial for improving health. The milk contains bioactive peptides which produced by hydrolysis process. The aim of this study was to evaluate antibacterial and antioxidant activities of hydrolisate produced from hydrolysis of goat milk protein by crude bromelain extract. Hydrolysis of goat milk protein was conducted using crude bromelain (0.1 U/mL) at pH 6, 50°C for 60 min. Hydrolysate was fractionated by using membrane molecular weight cut off 10 kDa. hydrolysate before and after fractionation were assayed for antibacterial and antioxidant activities. Toxicity of the Hydrolysate was determined by hemolysis assay. The result showed that the hydrolysate before and after fractionation inhibited growth of E. coli, S. Typhimurium and L. monocytogenes. Hydrolysate after fractionation has higher antibacterial activity indicated that fractionation was able to improve antibacterial activities of the hydrolysate fraction. The hydrolysate showed scavenging activity to ABTS and DPPH radicals. Fraction 10 kDa not only showed absence of hemolysis but also they were able to reduce autolysis of red blood cells. The result showed that hydrolysate from goat milk hydrolyzed by bromelain were able to be antibacterial and antioxidant.

Hybrid ozonation–ultrafiltration: The formation of bromate in waters containing natural organic matter

The effect of pH, inlet ozone injection rate, initial bromide concentration, membrane coating, hydroxyl radical scavenger, and membrane molecular weight cut off (MWCO) on the formation of bromate in a hybrid membrane filtration–ozonation reactor treating water containing bromide and natural organic matter (NOM) was studied. Variations in the TOC, UV254, SUVA (specific UV absorbance), color and turbidity of water as a function of these parameters were investigated. Bromate formation increased with increasing inlet gaseous ozone injection rate, and initial bromide concentration. The extent of bromate formation decreased with decreasing pH, with increasing TOC concentration, and in the presence of tertiary butyl alcohol (t-BuOH), an OH radical scavenger. The bromate concentrations that were observed with the Mn oxide coated membrane were less than that formed with the TiO2 membrane. An increase in the bromate concentration was observed with decreasing MWCO of the filtration membrane. Consistent with earlier work, experimental results indicated that ozonation can be used to mitigate membrane fouling. If dissolved ozone is present in the system, continuous operation of the hybrid ozonation–membrane filtration system at a permeate flux comparable to the clean water permeate flux can be achieved. An empirical model was developed using multiple linear regression method to estimate bromate formation in the system as a function of bromide concentration, dissolved organic carbon (DOC) concentration, inlet ozone injection rate, pH, and reaction time. Good correlation was achieved between the model predictions and the experimental data. According to the model, bromate formation was favored as bromide concentration, ozone injection rate, and pH increased. However, an increase in DOC concentration reduced bromate formation.

Effects of hypochlorous acid exposure on the rejection of salt, polyethylene glycols, boron and arsenic(V) by nanofiltration and reverse osmosis membranes

The separation layer of polyamide-based (PA) thin film composite (TFC) membranes can be modified by active chlorine species. The PA-TFC membranes, NF90, BW30 and NF270, were exposed to different concentrations of sodium hypochlorite (NaOCl) at pH 5 for 24 h. Elemental composition obtained from X-ray Photoelectron Spectroscopy (XPS) showed that the chlorine content in the PA layer increased with the chlorine concentrations. Treatment of membranes with 10 ppm Cl increased the membrane hydrophilicity. By contrast, when treated with 1000 ppm Cl or more, the membranes became less hydrophilic. Water permeability values for all 3 membrane types declined with increased chlorine concentrations. Filtration of polyethylene glycols (PEGs) with molecular weights of 200, 400 and 600 Daltons (Da) was performed to investigate the influence of chlorine treatment on membrane molecular weight cut off (MWCO) and rejection by size exclusion. Treatment with 10 and 100 ppm Cl lowered the MWCO while treatment with higher concentrations increased the MWCO. All chlorinated membranes experienced higher NaCl rejection compared to virgin ones. The performance of NF90 was tested with respect to the rejection of inorganic contaminants including boron (H3BO3) and arsenic (H2AsO4−). The boron rejection results paralleled PEG rejection whereas those for arsenic followed NaCl rejection patterns. The changes in membrane performance due to chlorine treatment were explained in terms of competing mechanisms: membrane tightening, bond cleavage by N-chlorination and chlorination promoted polyamide hydrolysis.

Membrane molecular weight cut off impacts immunological safety of a novel bioartificial liver system

Objective To investigate the influence of membrane molecular weight cut off in our bioartificial liver(BAL)system.Methods Beagle dogs were used for a model of acute liver failure through D-galactosamine administration.The acute liver failure Beagles were divided into two groups by the membrane molecular weight cut off.Group A was treated with BAL containing 200 kDa retention rating membrane.Group B was treated with BAL containing 1200 kDa retention rating membrane.Each group underwent two six-hour BAL treatments that were performed on day 1 and day 21.BAL medium were examined and levels of IgG,IgM,and complement hemolytic unit of 50％(CH50)antibodies were measured in all Beagles and.Results BAL treatment was associated with a significant decline in levels of CH50.1200 kDa group experienced a significant increase in levels of IgG and IgM after two BAL treatments.Significant levels of canine proteins were detected in BAL medium from 1200 kDa group.Conclusions Xenogeneic immune response in the BAL system was influenced by membrane molecular weight cut off. Key words: Bioartificial liver; Membrane molecular weight cut off; Porcine hepatocyte; Bone marrow mesenchymal stem cells

An experimental study on the effects of membrane molecular weight cut off on a novel bioartificial liver system

Objective To study the effects of membrane molecular weight cut off on a novel bioartificial liver(BAL) system.Methods Healthy beagles underwent 6-hour treatment with a BAL containing membrane with 200 kDa retention rating or 1200 kDa retention rating.The functional changes and cell viability were characterized.Results Hepatocyte performance levels such as albumin secretion,urea synthesis and viability were significantly higher in the 200 kDa retention rating group when compared with the 1200 kDa retention rating group (P＜0.05).Significant levels of canine proteins were detected in the BAL medium from the 1200 kDa retention rating group.Fluorescence microscopy further verified that heavy deposition of canine IgG,IgM and complement (C3) on co-culture cells were obtained after BAL treatment in the 1200 kDa retention rating group.Conclusions Small membrane molecular weight cut off of BAL could reduce the transfer of xenoreactive antibodies into the BAL medium and improved the performance of the BAL. Key words: Bioartificial liver; Membrane molecular weight cut off; Hepatocytes

Bromate formation in a hybrid ozonation-ceramic membrane filtration system

The effect of pH, ozone mass injection rate, initial bromide concentration, and membrane molecular weight cut off (MWCO) on bromate formation in a hybrid membrane filtration–ozonation reactor was studied. Decreasing the pH, significantly reduced bromate formation. Bromate formation increased with increasing gaseous ozone mass injection rate, due to increase in dissolved ozone concentrations. Greater initial bromide concentrations resulted in higher bromate concentrations. An increase in the bromate concentration was observed by reducing MWCO, which resulted in a concomitant increase in the retention time in the system. A model to estimate the rate of bromate formation was developed. Good correlation between the model simulation and the experimental data was achieved.

Influence of particle size and operating parameters on virus ultrafiltration efficiency

In water treatment, virus removal using ultrafiltration is a major step towards better water quality. In this paper, we study virus filtration efficiency using surrogate virus particles and via statistical surface-response approach. We focus on the effect of particle size (20–100 nm range) as a key factor along with the effects of transmembrane pressure (20–60 kPa range) and feed flowrate (0.3–1.0 L/F;min range) on the filtration virus removal efficiency (LRV). The particle size is shown to impart a great deal of influence on surrogate particle removal. The effect of particle-to-pore-size ratio is reported for comparison of membrane molecular weight cut off (MWCO) performance. It was shown experimentally and through the developed empirical regression model that transmembrane pressure plays a major role in controlling the filtration efficiency along with flowrate. In the studied experimental range, higher LRV values are obtained at lower transmembrane pressure (20 kPa) and at higher feed flowrate (1 L/F;min). Further the effect on LRV of the interaction between transmembrane pressure and particle size seems to be more significant than that of the interaction of flowrate with particle size.

The Study of Dynamic Milk Ultrafiltration Performance Influenced by Membrane Molecular Weight Cut off

The effect of membrane molecular weight cut off (MWCO) at three levels (10, 20 & 50 kD) on dynamic behavior of permeate flux (JP), hydraulic resistances (total hydraulic resistance, RT; reversible fouling resistance, Rrf; irreversible fouling resistance, Rif and membrane hydraulic resistance, Rm) and milk solutes rejection (protein, RP; fat, RF; lactose, RL; minerals, RM and total solids, RTS) are studied for the ultrafiltration of milk. Experiments are carried out using the pilot plant UF membrane system equipped with a spiral wound module and a polysulfone amide membrane. A three-stage strategy based on a resistance-in-series model (boundary layer- adsorption) was used to determine the different hydraulic resistances. The results showed that the JP decreases greatly with increasing the process time, but the JP values obtained for 20 kD were considerably higher than 10 kD & 50 kD during the whole process. RT increased during operation at all levels of MWCO, but the hydraulic resistance values for 50 kD were significantly greater than 10 & 20 kD. Results for milk solutes rejection showed that the RP and RF are almost constant with process time at the corresponding MWCO, whereas the RL, RM and RTS significantly increased.

Detailed investigation of effects of operating parameters of ultrafiltration using laboratory-scale ultrafiltration unit

Cross flow ultrafiltration is a pressure driven membrane process in which the fluid to be filtered flows parallel to the membrane surface. The formation of filter cake can be reduced by scouring force of the flow, thus better permeate rate is obtained. Laboratory-scale ultrafiltration experiments with Polyvinyl Alcohol (PVA) solution of known molecular weight was carried out to study the membrane filter performances with respect to operating parameters. These operating parameters included, membrane molecular weight cut off size, molecular weight of PVA, influent concentration, cross flow velocity and applied pressure. It was discovered that clogging in the membrane occurs quite slowly during first 30 minutes, and quasi-steady state was noticed normally after 50 minutes of filtration time. In this study, steady state flux data were used to develop semi-empirical and empirical correlations which are useful in the optimum design of ultrafiltration.