Influence Of Membrane Pore Size Research Articles

Effect of pore size and temperature on the behaviour of alpha-lactalbumin and the A and B genetic variants of beta-lactoglobulin during protein fractionation microfiltration

The aim of this study was to investigate the influence of membrane pore size and filtration temperature on six individual milk protein fractions (αS-CN, β- CN, κ-CN, α-LA, β-LG A, β-LG A) during the protein fractionation microfiltration process. Pasteurised skimmed milk was microfiltrated using two different pore sizes of spiral-wound membranes, with pore sizes of 0.2 μm and 0.5 μm, at temperatures of 15 °C and 45 °C respectively. The microfiltration process was carried out with a final volume reduction of 66% and a diafiltration volume of 120% (300 L) of the original feed (250 L). It was observed that neither the pore size nor the filtration temperature significantly (p<0.05) affected the permeation of the α-LA fraction. However, the permeation of the β-LG A and β-LG B fractions can be influenced by membrane pore size and filtration temperature, and the behaviour of the three whey protein fractions, A and B genetic variants of the β-LG and α-LA fractions differs significantly during the microfiltration process. The results of this study could form the basis for the development of new, unique tailor-made milk protein ingredients.

Influence of membrane pore-size on the recovery of endogenous viruses from wastewater using an adsorption-extraction method

The ongoing COVID-19 pandemic has emphasized the significance of wastewater surveillance in monitoring and tracking the spread of infectious diseases, including SARS-CoV-2. The wastewater surveillance approach detects genetic fragments from viruses in wastewater, which could provide an early warning of outbreaks in communities. In this study, we determined the concentrations of four types of endogenous viruses, including non-enveloped DNA (crAssphage and human adenovirus 40/41), non-enveloped RNA (enterovirus), and enveloped RNA (SARS-CoV-2) viruses, from wastewater samples using the adsorption-extraction (AE) method with electronegative HA membranes of different pore sizes (0.22, 0.45, and 0.80 µm). Our findings showed that the membrane with a pore size of 0.80 µm performed comparably to the membrane with a pore size of 0.45 µm for virus detection/quantitation (repeated measurement one-way ANOVA; p > 0.05). We also determined the recovery efficiencies of indigenous crAssphage and pepper mild mottle virus, which showed recovery efficiencies ranging from 50% to 94% and from 20% to 62%, respectively. Our results suggest that the use of larger pore size membranes may be beneficial for processing larger sample volumes, particularly for environmental waters containing low concentrations of viruses. This study offers valuable insights into the application of the AE method for virus recovery from wastewater, which is essential for monitoring and tracking infectious diseases in communities.

A modified premix method for the emulsification of spearmint essential oil (Mentha spicata) by ceramic membranes

A versatile and innovative membrane emulsification system that utilizes a modified premix method was investigated for preparing oil/water emulsions from spearmint essential oil. The modified method (forced-air premix, FAP) is based on flowing air in parallel to the surface of the ceramic membrane at the permeate side, and it was compared to a traditional premix method (conventional premix, CVP) in which pressure was applied only to the feed stream. The influence of membrane pore size, transmembrane pressure, and airflow velocity on the oil emulsion properties was evaluated. In the FAP method, the air stream forces the early shearing and detachment of oil droplets right after the premix permeates the membrane. The results showed that the increase in the operating pressure resulted in the reduction of droplet size and span values for all membranes and methods evaluated. The higher surfactant concentration and presence of forced airflow influenced the reduction of the droplet size and dispersion of emulsions in the FAP method. Stable emulsions were obtained which 28 days of storage.

Purification of polyphenols from apple skins by membrane electro-filtration

Dead-end electro-filtration of polyphenols extracted from apple skin was studied. The influence of membrane pore size (dm = 3.02–50 nm), transmembrane pressure (ΔP = 1–6 bar) and direct current (DC) electric field (U = 5–15 V) on the purification efficiency was investigated. The sieving ratios R of selected membrane UH030 (dm = 4.35 nm) towards the polyphenols, proteins, total solutes, and colour intensity increased with increase of transmembrane pressure. It was demonstrated that utilization of this membrane for the DC electro-filtration allowed more effective rejection of proteins at the anode part of the filter. Such effects can be attributed to the large size of protein molecules and their positive charge. Obtained data evidenced the possibility of selective purification of polyphenols by membrane electro-filtration.

Impact of MWCO and Dopamine/Polyethyleneimine Concentrations on Surface Properties and Filtration Performance of Modified Membranes.

The mussel-inspired method has been investigated to modify commercial ultrafiltration membranes to induce antifouling characteristics. Such features are essential to improve the feasibility of using membrane processes in protein recovery from waste streams, wastewater treatment, and reuse. However, some issues still need to be clarified, such as the influence of membrane pore size and the polymer concentration used in modifying the solution. The aim of the present work is to study a one-step deposition of dopamine (DA) and polyethyleneimine (PEI) on ultrafiltration membrane surfaces. The effects of different membrane molecular weight cut-offs (MWCO, 20, 30, and 50 kDa) and DA/PEI concentrations on membrane performance were assessed by surface characterization (FTIR, AFM, zeta potential, contact angle, protein adsorption) and permeation of protein solution. Results indicate that larger MWCO membranes (50 kDa) are most benefited by modification using DA and PEI. Moreover, PEI is primarily responsible for improving membrane performance in protein solution filtration. The membrane modified with 0.5:4.0 mg mL−1 (DA: PEI) presented a better performance in protein solution filtration, with only 15% of permeate flux drop after 2 h of filtration. The modified membrane can thus be potentially applied to the recovery of proteins from waste streams.

Impact of Membrane Pore Size on the Clarification Performance of Grape Marc Extract by Microfiltration.

The influence of membrane pore size on the permeate flux, fouling mechanism, and rejection of soluble and suspended solids, as well as of phenolics and anthocyanins, in the clarification of grape marc extract by microfiltration (MF) was studied. MF was operated by using three monotubular ceramic membranes with a pore size of 0.14, 0.2, and 0.8 µm, respectively, according to a batch concentration configuration in selected operating conditions (2.25 bar as operating pressure, 4.93 L/min as feed flow rate, and 25 °C as operating temperature). No significant differences in the permeate flux values were appreciated despite the difference in pore size. The mathematical analyses of the flux behavior revealed that intermediate pore blocking is the predominant mechanism for 0.14 and 0.2 µm membranes, whereas complete pore blocking prevails for the 0.8 µm membrane. Differences in the fouling mechanism were associated with differences in the total phenols rejection: the highest rejection was observed for the 0.8 µm membrane followed by 0.2 and 0.14 µm membranes. All selected membranes showed low rejection of sugars, with values lower than 10%, and no retention towards anthocyanins. All the clarified extracts showed a turbidity lower than 4.87 NTU. Based on the experimental results, the 0.14 µm membrane appeared as the best option for the clarification of grape marc extract.

Investigations of the effect of pore size of ceramic membranes on the pilot-scale removal of oil from oil-water emulsion

Oil-water emulsions are one of the most serious pollutants because of the large quantities produced by various industries, such as the petrochemical, oil and gas industries. One of the major methods to remove oil from wastewater is filtration using ceramic tubular microfiltration membranes. However, such membranes are vulnerable to fouling, which causes operational impairment. The aims of this work are to study the influence of membrane pore size on permeate flux and oil removal efficiency at different operating parameters and the reduction in fouling when used in combination with hybrid Coagulation/sand filter-MF pre-treatment process. The droplet size of the oil-water emulsion has an interaction with the pore size of the ceramic membrane. Therefore, each pore size may be optimal, depending upon the concentration of oil in the emulsion, and hence droplet size. Steady-state flux and oil removal efficiency were found to b highest for hybrid coagulation/sand filter –MF due to a reduction of membrane fouling by reducing the oil concentration in the inlet emulsion to the ceramic membrane.

Influence of pore size and membrane surface properties on arsenic removal by nanofiltration membranes

Nanofiltration (NF) has a great potential in removing arsenate from contaminated water. The performance including arsenate rejection, water permeability and resistance to fouling could however differ substantially among NF membranes. This study was conducted to investigate the influence of membrane pore size and surface properties on these aspects of membrane performance. Four fullyaromatic NF membranes with different physicochemical properties were adopted for this study. The results showed that surface charge, hydrophobicity, roughness and pore size could affect water permeability and/or arsenate rejection considerably. A more negative surface charge was desirable to enhance arsenate rejection rates. NF90 and a non-commercialized membrane (M#1) demonstrated the best performance in terms of arsenate rejection and water permeability. The M#1 membrane showed less membrane fouling than NF90 when used for filtration of real arsenic-containing groundwater. This was mainly due to its distinct chemical composition and surface properties. A severe membrane fouling could lead to a substantial reduction of arsenic rejection. The M#1 membrane showed the best performance, which indicated that membrane modification could indeed enhance the overall membrane performance for water treatment.

(Invited) Liquid/Elastomer Composite Membrane with Dynamically Controllable Gas/Liquid Transport

The development of membrane science and technology is central to fields ranging from waste water treatment, petrochemical industry, to biomedical science. The dynamic controllable multiphase transport and separation under a steady-state applied pressure have great benefits for membrane science, but remain elusive. Besides, the membrane fouling problem remains challenging. Here we will introduce the dynamic controllable gas/liquid separation mechanism of liquid/elastomer composite membranes under constant pressure and its adaptable antifouling property, by solid/liquid/liquid interfacial design, pressure monitoring, and theoretical modelling. This study includes the design of liquid/elastomer composite membrane, the establishment of antifouling configuration, the influence of membrane pore size, deformation manner, and deformation magnitude on the substance transport, and thus the development of gas/liquid separation prototype device with good antifouling stability. We believe that this study will bring new opportunities for many real word applications, such as gas-involved chemical reactions, multiphase flow, multiphase separation, multiphase microreactors, bioinspired microfluidics, fuel cells, and materials synthesis and fabrication. This study will have far-reaching implications for the development of multiphase transport and separation.

Influence of Membrane Properties on Pineapple Wine Clarification and Fouling Behavior

The experiment was carried out to investigate the influence of membrane pore size and hydrophobicity on the quality of clarified pineapple wine and fouling characteristics, using stirred cell dead–end microfiltration. The test membranes were mixed cellulose acetate (MCE, pore size 0.45 and 0.22 μm), modified polyvinylidene fluoride (MPVDF, 0.22 μm) and polyethersulfone (PESF, 0.22 μm). It was found that all types of membrane successfully clarified the pineapple wine. The membrane pore size and hydrophobicity played an importance role in membrane fouling, both reversible and irreversible. Regarding the permeate flux and fouling, 0.45 μm MCE was the most suitable for pineapple wine clarification. However, intensive organoleptic test with pilot scale would be needed.

Clarification of Apple Juice Using Polymeric Ultrafiltration Membranes: a Comparative Evaluation of Membrane Fouling and Juice Quality

The aim of this study was to evaluate the performance of three different commercial polymeric ultrafiltration (UF) membranes during clarification of raw apple juice, comparatively. The influence of membrane pore size, roughness, and hydrophobicity on flux profile and fouling was investigated. The initial flux was simultaneously decreased at the beginning of the process, and quite steady flux was obtained in the membranes with rougher surface and more hydrophobic nature. As the pore size and hydrophobicity increased, the reversible fouling became the major resistance, while cake formation was more prominent for the membranes with narrower pore size. The overall quality results revealed that the main quality characteristics of the raw juice can be better retained by using the membranes that have higher resistance to fouling.

Effects of pore size and dissolved organic matters on diffusion of arsenate in aqueous solution

Presented here is the influence of membrane pore size and dissolved organic matters on the diffusion coefficient (D) of aqueous arsenate, investigated by the diffusion cell method for the first time. The pH-dependent diffusion coefficient of arsenate was determined and compared with values from previous studies; the coefficient was found to decrease with increasing pH, showing the validity of our novel diffusion cell method. The D value increased dramatically as a function of membrane pore size at small pore sizes, and then increased slowly at pore sizes larger than 2.0μm. Using the ExpAssoc model, the maximum D value was determined to be 11.2565×10−6cm2/sec. The presence of dissolved organic matters led to a dramatic increase of the D of arsenate, which could be attributed to electrostatic effects and ionic effects of salts. These results improve the understanding of the diffusion behavior of arsenate, especially the important role of various environmental parameters in the study and prediction of the migration of arsenate in aquatic water systems.

A simple approach to predict the stability of phospholipid vesicles to nebulization without performing aerosolization studies

Membrane extrusion was investigated for predicting the stability of soya phosphatidylcholine liposomes and surfactosomes (Tween 80-enriched liposomes) to nebulization. Formulations were prepared with or without cholesterol, and salbutamol sulfate (SBS) or beclometasone dipropionate (BDP) were incorporated as model hydrophilic or hydrophobic drugs respectively. Formulations were extruded through 5, 2, 1 and 0.4μm polycarbonate membrane filters to study the influence of membrane pore size on drug retention by the vesicles. Surfactosomes were found to be very leaky to SBS, such that even without extrusion greater than 50% of the originally entrapped drug was lost; these losses were minimized by the inclusion of cholesterol. The smaller the membrane pore size, the greater the leakage of SBS; hence only around 10% were retained in cholesterol-free surfactosomes extruded through 0.4μm filters. To study the influence of vesicle size on SBS retained entrapment, an excessive extrusion protocol was proposed (51 extrusion cycles through 1μm filters) to compare the stability of freshly prepared vesicles (i.e. unextruded; median size approx. 4.5–6.5μm) with those previously extruded through 1μm pores. Cholesterol was essential for minimizing losses from liposomes, whilst for surfactosomes size reduction prior to extrusion was the only way to minimize SBS losses which reached up to 93.40% of the originally entrapped drug when no cholesterol was included. When extrusion was applied to BDP-loaded vesicles, greater proportions of the drug were retained in the vesicles compared to SBS. Even with extrusion through 0.4μm, BDP retention was around 50–60% with little effect of formulation. Excessive extrusion showed BDP retention using small liposomes (1μm) to be as high as 71–87%, compared to 50–66% for freshly prepared vesicles. The findings, based on extrusion, were compared to studies of vesicle stability to nebulization, published by a range of investigators. It was concluded that extrusion is a valid method for predicting the stability of liposomes to nebulization.

Produced water treatment: Application of Air Gap Membrane Distillation

Air Gap Membrane Distillation (AGMD) has been implemented to treat produced water. The permeate fluxes, rejection factor and energy consumption for three different membranes, TF200, TF450 and TF1000, with pore sizes of 0.2, 0.45 and 1μm, respectively, are measured at different operating parameters. The influence of membrane pore size is investigated for the produced water. Also, the effect of feed flow rate, coolant temperature and feed temperature on permeate flux is studied. The flux increases as the feed temperature and flow rate increase, and declines as the coolant temperatures increase. Moreover, the energy consumption was measured at different pore size and was found to be independent of membrane pore size.

Treatment of saline solutions using Air Gap Membrane Distillation: Experimental study

Air Gap Membrane Distillation (AGMD) has been implemented for four different salts. The permeate fluxes of sodium chloride (NaCl), magnesium chloride (MgCl2), sodium carbonate (Na2CO3), and sodium sulphate (Na2SO4) are measured at different feed concentrations and different operating parameters using Polytetrafluoroethylene (TF200) membrane. The influence of membrane pore size is investigated for the different salts. Also, the effect of feed concentration, feed temperature, coolant temperature and feed flow rate on permeate flux is studied. The flux declines as the concentration of salt and coolant temperatures increase, and increases as the feed temperature and flow rate increase. Moreover, the energy consumption was measured at different salt concentrations for the different membrane pore size and was found to be independent of membrane pore size, and salt type.

Microfiltration of distillery stillage: Influence of membrane pore size

Stillage is one of the most polluted waste products of the food industry. Beside large volume, the stillage contains high amount of suspended solids, high values of chemical oxygen demand and biological oxygen demand, so it should not be discharged in the nature before previous purification. In this work, three ceramic membranes for microfiltration with different pore sizes were tested for stillage purification in order to find the most suitable membrane for the filtration process. Ceramic membranes with a nominal pore size of 200 nm, 450 nm and 800 nm were used for filtration. The influence of pore size on permeate flux and removal efficiency was investigated. A membrane with the pore size of 200 nm showed the best filtration performance so it was chosen for the microfiltration process.

Separation of dispersed substances and galactoglucomannan in thermomechanical pulp process water by microfiltration

Several valuable substances are released from wood during the production of thermomechanical pulp. These substances can be isolated and purified for use as value-added chemicals. The hemicellulose galactoglucomannan (GGM) has attracted a great deal of interest because of its possible applications as an oxygen barrier film in packaging materials, as a hydrogel in biomedical products and as an emulsion stabilizer in food and feed. In order to exploit GGM in pulp mill process water, it must be recovered at a high concentration and high purity. The first step in the purification process is the separation of GGM and dispersed substances. In this work, the influence of membrane pore size, cross-flow velocity and backpulsing on membrane performance during the microfiltration of thermomechanical pulp process water was investigated. The flux of 0.4 and 0.8 μm membranes was lower than the flux of a 0.2 μm membrane, and it was not possible to recover the pure water flux of the 0.4 and 0.8 μm membranes. Increased cross-flow velocity and backpulsing had a positive effect on the flux, but only a minor influence on the retention. The mean molecular mass of GGM in the process water was 9 kg/mol. The retention was therefore expected to be <10%. However, the retention of GGM was >50%, irrespective of the operating conditions.

Treatment of molasses wastewater in a membrane bioreactor: Influence of membrane pore size

Due to high chemical oxygen demand (COD) and its low biodegradability, molasses wastewater is usually classified as a high-strength industrial wastewater. The possibility and efficiency of a membrane bioreactor (MBR), containing lab-made membrane modules, in treating molasses containing wastewater was studied. The research was conducted in two phases, namely a first period of fed-batch operation followed by a second with continuous MBR operation. The results showed that more than 80, 90 and 30%, respectively, of the COD, total nitrogen (TN) and color were removed. There was a clear influence of the membrane pore size on trans-membrane pressure (TMP) build-up. Scanning electron microscopy and Fourier transformed infrared (FT-IR) analyses revealed no significant differences in organic constituents between the membrane cake layer and the activated sludge.

Influence of membrane properties on fouling in submerged membrane bioreactors

Polymeric flat-sheet membranes with different properties were used in filtration experiments with activated sludge from a pilot-scale MBR to investigate the influence of membrane pore size, surface porosity, pore morphology, and hydrophobicity on membrane fouling. An improved flux-step method was used to measure both the critical flux and critical flux for irreversibility. Long term experiments were performed to evaluate if influences of membrane properties on short term could be translated to long term fouling behavior. The results showed that a hydrophilic asymmetric membrane with an interconnected pore structure, a nominal pore size of 0.3 μm, and large surface porosity of 27%, provided the best membrane performance with respect to critical flux and critical flux for irreversibility. The dominant fouling mechanism in long term filtration experiments was gel layer formation, which for this membrane was the least severe, and therefore extended the sustainable time.

Preparation and assessment of fluorous supported liquid membranes based on porous alumina

Fluorous media have gained a foothold in the synthetic and analytical communities. There is a need for membranes or films that have good selectivity for transport of molecules with fluorous tags. We show here that supported liquid membranes (SLMs) based on modified porous alumina have the desired properties. Hydrophobic alumina membranes were prepared by surface modification with perfluoroalkanoic acids. The initial contact angles of modified alumina membranes exceed 130°. FTIR shows the loss of –OH stretching modes and the gain of carboxylate carbonyl stretch as well as C–F stretching modes indicative of the surface modification. SEM shows no gross changes in the membrane morphology resulting from the modification. The resulting modified membranes readily imbibe and hold fluorous solvents forming SLMs. Cinnamyl alcohol ( 1) and its ester with 2H,2H,3H,3H-perfluorononanoic acid (HOOC–(CH 2) 2–(CF 2) 5CF 3) ( 2c) were employed as solutes in transport experiments with the membranes. Transport selectivity (ratio of permeabilities of 2c to 1) was used as a measure of effectiveness in the optimization of modification conditions. Conditions for the surface modification leading to maximum selectivity for transport of 2c over 1 by the resulting SLM were to reflux membranes in 3 mM Krytox 157FSH/HFE 7100 solution for 3 h. Finally, the influence of membrane pore size on transport rate and selectivity was investigated for cinnamyl alcohol and its esters with fluorous carboxylic acids HOOC–(CH 2) 2–(CF 2) n−1 CF 3, n = 2, 4, 6, 8. The transport rate for the smallest pore size (20 nm) and largest solute ( n = 8) is anomalously high. This may be due to solute being transported in the modification layer as well as solvent.