Hollow Fiber Ultrafiltration Research Articles

Improved Protein Removal Performance of PES Hollow-Fiber Ultrafiltration Membrane with Sponge-like Structure.

The research used polyethersulfone (PES) as a membrane material, polyvinylpyrrolidone (PVP) k30 and polyethylene glycol 400 (PEG 400) as water-soluble additives, and dimethylacetamide (DMAc) as a solvent to prepare hollow-fiber ultrafiltration membranes through a nonsolvent-induced phase separation (NIPS) process. The hydrophilic nature of PVP-k30 and PEG caused them to accumulate on the membrane surface during phase separation. The morphology, chemical composition, surface charge, and pore size of the PES membranes were evaluated by SEM, FTIR, zeta potential, and dextran filtration experiments. The paper also investigated how different spinning solution compositions affected membrane morphology and performance. The separation efficiency of membranes with four different morphologies was tested in single-protein and double-protein mixed solutions. The protein separation effectiveness of the membrane was studied through molecular weight cutoff, zeta potential, and static protein adsorption tests. In addition, the operating pressure and pH value were adjusted to improve ultrafiltration process conditions. The PES membrane with an intact sponge-like structure showed the highest separation factor of 11, making it a prime candidate membrane for the separation of bovine serum albumin (BSA) and lysozyme (LYS). The membrane had a minimal static protein adsorption capacity of 48 mg/cm2 and had excellent anti-fouling properties. When pH = 4, the BSA retention rate was 93% and the LYS retention rate was 23%. Furthermore, it exhibited excellent stability over a pH range of 1-13, confirming its suitability for protein separation applications.

Fabrication of hydrophilic PVDF ultrafiltration membranes via thermally induced phase separation coupled with amphiphilic copolymer deposition

In this work, we propose a facile one-step method to fabricate poly(vinylidene fluoride) (PVDF) ultrafiltration hollow fiber membranes through coupled thermally induced phase separation (TIPS) and deposition of amphiphilic copolymer poly(styrene-co-maleic anhydride) (PSMA). A thorough examination of how the addition of PSMA influenced the membrane formation and performance was conducted. The mechanism behind the synergistic effect between TIPS process and deposition of PSMA on the membrane surface was discussed in detail. The difference in the phase separation behavior of PVDF and PSMA during membrane preparation caused the deposition of PSMA forming a hydrophilic layer on the PVDF porous structure without altering the membrane bulk structure. The enrichment of PSMA in membrane outer surface not only improved the hydrophilicity of the membrane, but also effectively reduced the membrane pore size, while maintaining the overall bulk porosity. PSMA deposition resulted in enhanced pure water flux and BSA rejection, effectively overcoming the traditional trade-off between permeability and selectivity. This straightforward approach of blending suitable amphiphilic copolymers into the polymer solution exhibited significant potential for the rapid and large-scale preparation of hydrophilic PVDF-based ultrafiltration membranes in the TIPS process.

Hyperbranched polymer hollow-fiber-composite membranes for pervaporation separation of aromatic/aliphatic hydrocarbon mixtures

The separation of aromatic/aliphatic hydrocarbon mixtures is crucial in the petrochemical industry. Pervaporation is regarded as a promising approach for the separation of aromatic compounds from alkanes. Developing membrane materials with efficient separation performance is still the main task since the membrane should provide chemical stability, high permeation flux and selectivity. In this study, the hyperbranched polymer (HBP) was deposited on the outer surface of a polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membrane by a facile dip-coating method. The dip-coating rate, HBP concentration, and thermal cross-linking temperature were regulated to optimize the membrane structure. The obtained HBP/PVDF hollow fiber composite membrane had a good separation performance for aromatic/aliphatic hydrocarbon mixtures. For the 50%/50% (mass) toluene/n-heptane mixture, the permeation flux of optimized composite membranes could reach 1766 g·m–2·h–1 with the separation factor of 4.1 at 60 °C. Therefore, the HBP/PVDF hollow fiber composite membrane have great application prospects in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures.

Ionic Hyperbranched Poly(amido-amine)-Incorporated Nanofiltration Membranes for High-Efficiency Dye Desalination.

High-efficiency dye desalination is crucial in the textile industry, considering its importance for human health, safe aquatic ecological systems, and resource recovery. In order to solve the problem of effective separation of univalent salt and ionic dye under the condition of high salt, ionic hyperbranched poly(amido-amine) (HBPs) were synthesized based on a simple and scalable one-step polycondensation method and then incorporated into the polyamide (PA) selective layers to construct charged nanochannels through interfacial polymerization (IP) on the surface of a polyvinyl chloride ultrafiltration (PVC-UF) hollow fiber membrane. Both the internal nanopores of HBPs (internal nanochannels) and the interfacial voids between HBPs and the PA matrix (external nanochannels) can be regarded as a fast water molecule transport pathway, while the terminal ionic groups of ionic HBPs endow the nanochannels with charge characteristics for improving ionic dye/salt selectivities. The permeate fluxes and dye/salt selectivities of HBP-TAC/PIP (57.3 L m-2 h-1 and rhodamine B (RB)/NaCl selectivity of 224.0) and HBP-PS/PIP (63.7 L m-2 h-1 and lemon yellow (LY)/NaCl selectivity of 664.0) membranes under 0.4 MPa operation pressure are much higher than PIP-only and HBP-NH2/PIP membranes. At the same time, this project also studied the membrane desalination process in a simulated high-salinity dye/salt mixture system to provide a theoretical basis and technical support for the actual dye desalination process.

Fabrication of hollow fiber membrane microstructures and the investigation of antifouling mechanism for vegetable oil wastewater

In this study, four kinds of hollow fiber ultrafiltration membranes with different hydrophilic chains and surface microstructures were prepared via the “physical blending-surface grafting” method. The influence of surface microstructures for the formation process of the vegetable oil fouling layer on the surface of membranes and antifouling performance were investigated. By characterizing the changes in adhesion force on the surface of membranes and the surface charge of emulsified oil droplets before and after separation, the differences in the flocculation and coalescence processes for emulsified oil droplets on different membrane surfaces were revealed. The synergistic effect of “the flocculation of physical contact by polymer chains, the hydrophilic repulsion of hydration layer and electrostatic neutralization”, led to the formation of large-sized oil droplets on the surface of membranes with weakly charged surface and loose accumulation ultimately, which will in turn weaken the adsorption of pollutants and the irreversible fouling can be delayed. The synergistic antifouling mechanism of “hydrophilic repulsion of the hydration layer-grafting long chains barrier & coalescence” was proposed based on the membrane's antifouling performance, the adhesion and spreading process of pollutants on the membrane surface, as well as the differences of the surface hydration layer microstructure. The membrane modified by grafting PEI and PVA exhibits excellent retention performance (oil rejection rate ∼100 %) and resistance to oil-in-water emulsion fouling (flux recovery rate (FRR) = 99.12 %), weakest adhesion force (9.32 nN) and minimal adhesion mass (1.7 mg) of pollutants on the surface of membrane. This work offers new research insights into the theoretical study and fabrication of hollow fiber ultrafiltration membranes with high oil fouling resistance.

Indirect Evidence that Colloidal Deposition Inside a Hollow Fiber Ultrafiltration Membrane Exacerbated Fouling during Municipal Wastewater Reclamation

Indirect Evidence that Colloidal Deposition Inside a Hollow Fiber Ultrafiltration Membrane Exacerbated Fouling during Municipal Wastewater Reclamation

Effects of multi‐walled carbon nanotubes on structures and properties of heat‐resistant poly(m‐phenylene isophthalamide)‐based hollow fiber ultrafiltration membranes

AbstractThis study is the first attempt to fabricate a heat‐resistant hollow fiber ultrafiltration membrane using poly(m‐phenylene isophthalamide) (PMIA) polymer material, which has rarely been used as conventional polymeric membrane materials. Multi‐walled carbon nanotubes (MWCNTs) are incorporated as reinforcing agents. The PMIA polymer synthesized for this study exhibited an inherent viscosity of 1.6 dL/g, confirming its suitability for membrane fabrication, and successful synthesis was verified through Fourier‐transform infrared analysis. To enhance the dispersibility of MWCNTs during dope solution preparation and their interaction with the PMIA matrix, MWCNTs were acid‐treated and surface characteristics of the acid‐treated MWCNTs were confirmed through x‐ray photoelectron spectroscopy analysis. Scanning electron microscope analysis revealed that the introduction of MWCNTs resulted in thicker PMIA hollow fiber ultrafiltration membranes with symmetrical finger‐like and sponge‐like pore structures. Interestingly, unlike the typical polymer composite systems containing MWCNTs, which often show a dependence on MWCNT content, the mechanical properties of the PMIA/MWCNT membranes in this study seem to exhibit high variability and are not contingent on the MWCNT content. Additionally, filtration performance studies demonstrated that the introduction of MWCNTs substantially increased water permeability, particularly at 1.0 wt% MWCNT content, resulting in a remarkable 130% enhancement compared to pristine PMIA membrane. Simultaneously, even with a small quantity of MWCNTs, the rejection performance of the PMIA/MWCNT membrane witnessed significant improvement due to the reduction in average pore size, effectively overcoming the commonly observed trade‐off phenomenon. In summary, this study clearly showed the effects and changes on the structure and properties of a heat‐resistant PMIA‐based hollow fiber ultrafiltration membranes due to the introduction of MWCNTs.Highlights Heat‐resistant poly(m‐phenylene isophthalamide)‐based hollow fiber ultrafiltration membranes Introduction of multi‐walled carbon nanotubes (MWCNTs) into PMIA membrane as a reinforcing agent Unique structural changes of PMIA membrane originated from the MWCNTs Enhanced tensile strength of PMIA/MWCNT membranes Simultaneous improvement of filtration performance due to MWCNTs

Improved virus concentration methods for wash waters from decontamination of permeable and non-permeable surfaces

Surface decontamination is a method of using wash water to decontaminated surfaces preventing transmission of biological contaminants that can pose potential health risks to responders and the public. However, the risks associated with handling used wash water are largely unknown due to the lack of effective methodology to screen for pathogenic microorganisms present in these samples, especially viral pathogens. This study adapted the dead-end hollow-fiber ultrafiltration (D-HFUF) system to wash waters, including a separate procedure for recovering particle attached viruses. Simulated wash water was created using dechlorinated tap water containing a mild surfactant (0.05 % Tween 80). To determine virus recovery efficiencies, measured amounts of somatic and F+ coliphage were spiked into 2-liter volumes of wash water under the following scenarios: (1) wash water was amended with a measured amount of sterile river sediment with no sediment separation prior to filter concentration; or (2) sediment added to wash water was allowed to settle prior to filter concentrating clarified liquid portions, while precipitated sediment was subjected to viral extraction techniques to recover particle attached virus; and (3) the optimized method was deployed on non-porous and porous surfaces to simulate a decontamination clean-up event. Separation of sediment prior to D-HFUF significantly increased recovery of coliphages, (P = <0.0001) versus filtration of sediment and liquids simultaneously. A tryptic soy broth (TSB) elution solution was significantly more effective (P = ≤0.010) for recovery of both somatic and F+ coliphage, (108 ± 9 % and 92 ± 9 %, respectively), compared to elution buffers containing various surfactants (sodium hexametaphosphate, Tween 80) for recovering particle attached virus. Simulating a biocontaminate clean-up event (using the optimized sediment separation and elution protocol) resulted in coliphage recoveries of 75–96 % (permeable surface) and 71–92 % (non-permeable surface). This procedure can be used to effectively detect viruses in used wash waters aiding in reducing risks to human health during site decontamination.

Microfiltration, ultrafiltration and nanofiltration as a post-treatment of biological treatment process with references to oil field produced water of Moran oilfield of Assam

The selection of an apt technology for the treatment of Oilfield Produced Water (OFPW) depends mainly on the quality of OFPW and methods of pre-and post-treatment processes. The most challenging part of the OFPW treatment process is the removal of Suspended Solid (SS), Oil & Grease (O&G) and dissolved organics. SS and O&G pose an acute problem to the membrane filtration system by fouling the membrane surface which increases operation & maintenance costs and decreases the life of the membrane. Fouling of the membrane surface is mainly attributed to the presence of low molecular weight aromatic compounds and naphthenic acids in the suspended and dissolved organic compounds. Thus, the removal of these suspended and dissolved organic compounds before membrane filtration proffers a challenge to the researchers. In this research, bioremediation process has been applied to remove the organic compounds and the performance and fouling behaviour of hollow fibre Microfiltration (MF), Ultrafiltration (UF) and Nanofiltration (NF) membranes after the bioremediation process has been analyzed in detail. The level of toxicity was determined by comparing the pollutants with the safe discharge limit for disposal into the environment set by Central Pollution Control Board (CPCB), India. The research presents its novelty by using a hydrocarbon-degrading bacteria, Pseudomonas aeruginosa for the Reduction of Organic Loads (ROL) from OFPW of Moran oil field of Upper Assam as a pre-treatment to membrane filtration. The Total Sum Corrected Area (TSCA) method through chromatographic analyses was used for this. The organic loads removal from OFPW by the TSCA method was found to be 67–100%, 100% and 100% after 7, 14 and 21 days of bioremediation respectively. The major parameters in feed OFPW of Moran oil field were found to be pH (7.5–9.3), Total Dissolved Solid (TDS) (1.79–4.75) ppt, O&G (1.78–2.8) ppt, Salinity (2.94–6.98) ppt, Chloride (Cl−) (1.6–3.86) ppt, Bicarbonate (HCO3−) (2.89–4.03) ppt. It was observed that the ranges of pollutants removal by NF was highest such as TDS (26–86%), salinity (81–86%), turbidity (78–94%), hardness (67–75%), O&G (96–99%), Cl− (80–89%) and HCO3− (95–97%).

Dead‐end hollow fiber ultrafiltration capture of environmental DNA for freshwater mussel (Unionidae) species detection with metabarcoding

AbstractInsufficient water sample volumes can be a limiting factor for detecting species with environmental DNA (eDNA) from aquatic habitats. We compared detections of freshwater mussel (Unionidae) communities using large water sample volumes and dead‐end hollow fiber ultrafiltration (D‐HFUF or DEUF) with traditional eDNA filtration methods that use relatively small water sample volumes. Unionid species were detected in approximately 50‐L D‐HFUF eDNA samples with two mitochondrial DNA metabarcoding markers (COI and ND1) and compared to species detection results from eDNA captured from commonly used 1‐L samples filtered with polyethersulfone (PES) filters at three lotic sites in Georgia and Missouri. Of the 431,560 COI and 1,035,472 ND1 reads from all environmental samples of both filter types that passed quality control, 95% (410,755 reads) of COI reads and 85% (883,472 reads) of ND1 reads were assigned to a unionid species. Nineteen different freshwater mussel species were detected across all D‐HFUF samples, and 11 species were detected across all PES samples. Reads assigned to the genus Elliptio could not be resolved beyond the genus level with either marker. From D‐HFUF samples, 15 and 16 mussel species were detected with the COI and ND1 markers, respectively. From PES samples, nine and seven species were detected with the COI and ND1 markers, respectively. More mussel species were detected at each site in D‐HFUF samples than in PES samples regardless of whether results from both markers were combined or evaluated separately. Our results demonstrate the merit of further exploration and optimization of D‐HFUF for capturing eDNA from high‐volume water samples to facilitate detection of unionids and likely other aquatic organisms.

Surface modification of PVDF hollow fiber ultrafiltration membranes for biopharmaceutical products, virus, and bacterial phage removal technology

In this study, radicals were chemically formed at the hydroxyl (-OH) sites on the surface of polyvinylidene fluoride (PVDF) hollow fiber membranes, and anionic-hydrophilic and hydrophobic materials were grafted onto the surface through -OH radical reaction to generate anions (−28, −41 mV). These membranes were then used as biomembranes (BMs) and showed excellent properties. We also studied the effects of chemical surface modification and reduction in pore size (60–130 nm) according to molecular weight. After anionic modification, the electrostatic repulsion between the pore surface and the bacteria prevents adsorption when anionic bacteria pass through the pores. Particles do not pass through the asymmetric pores due to agglomeration, resulting in separation. The hydrophilic membrane had a high initial water flux, but the flux gradually decreased due to fouling. In contrast, the hydrophobic modified membrane had a low initial water flux that eventually stabilized due to excellent fouling resistance. The protein recovery ratio (PRR) was 98.8 % for hydrophilic particles and 99.2 % for hydrophobic molecules, showing a higher PRR than the pristine membrane (96.4 %). An evaluation of removal of the gram-negative bacteria Brevundimonas diminuta (Bd) showed that no bacteria in membrane-purified solutions, confirming 100 % removal efficiencies. The developed membrane can be used in biopharmaceutical production and removal of proteins, retro viruses, and bacteria.

Rechargeable pore-filled composite hollow fiber membranes for water vapor separation

We propose a new method of using high-density polyethylene (HDPE) ultrafiltration hollow fibers, which are inexpensive but difficult to use as a dehumidification membrane. Dehumidification membranes have a wide range of applications and can also offer the benefit of water recovery. Conventional membranes for gas separation consist of a substrate and a thin layer that selectively permeates a desired gas. However, low-cost substrates such as HDPE are limited in their application due to the presence of large pores that prevent defect-free thin layer formation. To address the issue of large pores, we utilized hydrogels made from viscous solutions, that can be stably positioned in large pores. Specifically, we filled the pores of the HDPE substrate with hydrogels consisting of glycerin, polyvinyl alcohol (PVA), and glutaraldehyde (GA). The pore-filled membranes capable of separating water vapor were 40GPGM and 50GPGM, which were filled with 40GPM (40 wt% glycerin/1 wt% PVA/0.5 wt% GA) and 50GPG (50 wt% glycerin/1 wt% PVA/0.5 wt% GA), respectively. Since the pore-filled membranes were filled with viscous hydrogels, they could be washed and recharged. Accordingly, they showed good rechargeability when measuring properties during multiple pore-filling and washing processes. The water vapor permeance/selectivity/water flux of the pore-filled membranes were measured at various temperatures and feed flow rates. The water vapor permeance/selectivity/water flux of 40GPGM and 50GPGM measured at 35 °C and 3.5 L/min were 3400 GPU/110/0.12 kg/m2∙hr and 2398 GPU/469/0.14 kg/m2∙hr, respectively. After continuous operation for 30 days, it was confirmed that the pore-filled membranes had good long-term stability.

Transportation of whey protein-derived peptides using Caco-2 cell model and identification of novel cholesterol-lowering peptides.

The increasing morbidity and mortality of cardiovascular disease have become a major factor in human death. Serum cholesterol is considered to be an important risk factor for inducing coronary heart disease, atherosclerosis and other cardiovascular diseases. To screen intestinal absorbable functional small peptides with cholesterol-lowering activity by enzymatic hydrolysis of whey protein and develop cholesterol-based functional food that may become a substitute for chemically synthesized drugs, providing new ideas for diseases caused by high cholesterol. This study aimed to evaluate the cholesterol-lowering activity of intestinal absorbable whey protein-derived peptides hydrolyzed by alkaline protease, trypsin and chymotrypsin, respectively. The whey protein hydrolysates acquired by enzymatic hydrolysis under optimal conditions were purified by a hollow fiber ultrafiltration membrane with a molecular weight cutoff of 10 kDa. The fractions obtained by Sephadex G-10 gel filtration chromatography were transported through a Caco-2 cell monolayer. The transported peptides were detected in the basolateral aspect of Caco-2 cell monolayers using ultra- performance liquid chromatography-tandem mass spectrometry (UPLC-MS). His-Thr-Ser-Gly-Tyr (HTSGY), Ala-Val-Phe-Lys (AVFK) and Ala-Leu-Pro-Met (ALPM) were unreported peptides with cholesterol-lowering activity. The cholesterol-lowering activities of the three peptides did not change significantly during simulated gastrointestinal digestion. This study not only provides theoretical support for the development of bioactive peptides that can be directly absorbed by the human body, but also provides new treatment ideas for hypercholesterolemia.

Impact of microplastics on organic fouling of hollow fiber membranes

Given the potential hazards of microplastics (MPs), it is desirable to efficiently remove them during wastewater treatment processes. To this end, ultrafiltration (UF) membranes can significantly increase the removal of MPs, however the fouling of such membrane modules can also be impacted by the presence of MPs. Magnetic Resonance Imaging (MRI) was used here to non-invasively quantify the effect of polyethylene (PE) MPs accumulation in a 3D UF hollow fiber (HF) membrane module containing 400 fibers, via direct non-invasive velocity imaging of the flow distribution between individual fibers during module operation. The co-effect of MPs and alginate (a common organic model foulant mimicking extracellular polymeric substances (EPS)) on fouling of the HF module was then explored. Flow was initially equally distributed with fouling causing flow in particular fibers to be significantly reduced. Fouling with MPs resulted in minimal flow distribution disruption and was easily remediated hydraulically, in contrast alginate fouling required chemical cleaning in order to fully restore homogeneous flow distribution between the fibers. The presence of both MPs and alginate resulted in a more heterogeneous disruption of the fibre flow distribution due to fouling and resulted in much more effective hydraulic cleaning of the module.

Temporal and spatial relationships of CrAssphage and enteric viral and bacterial pathogens in wastewater in North Carolina

Enteric disease remains one of the most common concerns for public health, particularly when it results from human exposure to surface and recreational waters contaminated with wastewater. Characterizing the temporal and spatial variation of enteric pathogens prevalent in wastewater is critical to develop approaches to mitigate their distribution in the environment. In this study, we aim to characterize pathogen variability and test the applicability of the human-associated wastewater indicator crAssphage as an indicator of enteric viral and bacterial pathogens. We conducted weekly samplings for 14 months from four wastewater treatment plants in North Carolina, USA. Untreated wastewater samples were processed using hollow fiber ultrafiltration, followed by secondary concentration methods. Adenovirus, norovirus, enterovirus, Salmonella, Shiga toxin 2 (stx2), Campylobacter, and crAssphage were measured by quantitative polymerase chain reaction (qPCR) and reverse transcriptase (rt)-qPCR. Our results revealed significant correlations between crAssphage and human adenovirus, enterovirus, norovirus, Salmonella, and Campylobacter (p<0.01). Pathogens and crAssphage concentrations in untreated wastewater showed distinct seasonal patterns, with peak concentrations of crAssphage and viral pathogens in fall and winter, while bacterial pathogens showed peaked concentrations in either winter (Campylobacter), fall (Salmonella), or summer (stx2). This study enhances the understanding of crAssphage as an alternative molecular indicator for both bacterial and viral pathogens. The findings of this study can also inform microbial modeling efforts for the prediction of the impact of wastewater pathogens on surface waters due to increased flooding events and wastewater overflows associated with climate change.

Comparing Recovery Methods for Wastewater Surveillance of Arthropod-Borne and Enveloped Viruses

The potential public health utility of arthropod-borne virus (arbovirus) wastewater surveillance (WWS) warrants the effort of establishing an effective sample preparation workflow. Here, we investigated different sample clarification, concentration, and extraction methods to determine the best workflow for recovery of spiked arboviral and murine hepatitis virus RNA signals in wastewater. We determined that the sample clarification method with the least loss is filtration through a 0.22 μm filter (9.06 ± 3.68%) when compared with centrifugation. Out of four different concentration methods (centrifugal ultrafiltration, polyethylene glycol precipitation, charged membrane capture and elution, and hollow-fiber ultrafiltration), centrifugal ultrafiltration, specifically using Macrosep Advance column (30 kDa), has the highest mean recovery of 84.76 ± 17.45%. With this method, we can reliably recover seeded arboviruses at concentrations corresponding to 10 infections in 400 to 180,000 people, depending on the shedding rate. As arboviruses are expected to be on the rise due to the expansion of their vectors’ geographic distribution, this research will lay the foundation for managing and reducing the impact of arboviral outbreaks through WWS-informed public health measures.

Reclaiming of Amine CO2 Solvent Using Extraction of Heat Stable Salts in Liquid-Liquid Membrane Contactor

Amine CO2 solvents undergo oxidative degradation with the formation of heat stable salts (HSS). These HSS reduce the sorption capacity of amines and lead to intense corrosion of the equipment. In our work, we propose a membrane-supported liquid-liquid extraction of the HSS from alkanolamines. For this purpose, a hollow fiber membrane contactor was used for the first time. A lab-scale extraction system on the basis of a hollow-fiber liquid-liquid membrane contactor with hollow fiber ultrafiltration polyvinylidenefluoride and polysulfone membranes has been studied. The extraction of the HSS-ions from a 30 wt.% solution of monoethanolamine was carried out using a 0.25-1 M solution of OH-modified methyltrioctylammonium chloride in 1-octanol as an extractant. It has been shown that >90% of HSS ions can be extracted from the alkanolamine solvent within 8 h after extraction. The results obtained confirm the possibility of using membrane extraction with a liquid-liquid membrane contactor for the reclaiming of amine CO2 solvents to increase the general efficiency of carbon dioxide capture.

An autopsy study of hollow fiber and multibore ultrafiltration membranes from a pilot-scale ultra high-recovery filtration system for surface water treatment

The organic fouling characteristics of hollow fiber ultrafiltration (HFUF) and multibore ultrafiltration (MBUF) membranes from long-term ultrafiltration (UF) membrane systems were systemically investigated in this study. The objective was to obtain insights into the fouling behavior of dissolved organic matter (DOM) in a pilot-scale ultra-high-recovery membrane filtration system (p-UHMS) used for surface water treatment. The pilot system consisted of a series of two different UF membranes (1st stage: polyvinylidene fluoride (PVDF) HFUF and 2nd stage: polyethersulfone (PES) MBUF). It was designed to feed the HFUF concentrate to the MBUF membranes to achieve ≥99.5 % total water recovery for surface water treatment, as these advances might enhance the production efficiencies of drinking water. The experimental results confirmed that hydrophobic DOM controlled the formation of HFUF membrane organic fouling, whereas hydrophilic DOM, including polysaccharide-like and protein-like matter, promoted MBUF membrane fouling. These opposing trends were attributed to the hydrophilic characteristics of the MBUF membrane surfaces (contact angle: PVDF = 90–130° and PES ≤ 80°), which reduced the hydrophobic interactions between the UF membrane surfaces and foulants. The performance declines of the MBUF membrane due to fouling layer formation was considerably severer than those of the HFUF membrane, decreasing total permeate water in the p-UHMS. Moreover, the quantity of the desorbed MBUF membrane foulants via 0.1 N NaOH was roughly 7.2 times larger than that of the desorbed HFUF membrane foulants through 0.1 N NaOH, indicating that alkaline-based cleaning agent could much more efficiently recover the performance of the fouled MBUF membranes. Hence, adequate cleaning strategies using alkaline-based agent for the MBUF membrane appeared to be essential for preventing the performance deterioration of the p-UHMS.

Surfactant Treatment for Efficient Gene Detection of Enteric Viruses and Indicators in Surface Water Concentrated by Ultrafiltration.

The hollow fiber ultrafiltration (HFUF)-based microbial concentration method is widely applied for monitoring pathogenic viruses and microbial indicators in environmental water samples. However, the HFUF-based method can co-concentrate substances that interfere with downstream molecular processes-nucleic acid extraction, reverse transcription (RT), and PCR. These inhibitory substances are assumed to be hydrophobic and, therefore, expected to be excluded by a simple surfactant treatment before the silica membrane-based RNA extraction process. In this study, the efficacy and limitations of the sodium deoxycholate (SD) treatment were assessed by quantifying a process control and indigenous viruses using 42 surface water samples concentrated with HFUF. With some exceptions, which tended to be seen in samples with high turbidity (> 4.0 NTU), virus recovery by the ultrafiltration method was sufficiently high (> 10%). RNA extraction-RT-quantitative PCR (RT-qPCR) efficiency of the process control was insufficient (10%) for 30 of the 42 HFUF concentrates without any pretreatments, but it was markedly improved for 21 of the 30 inhibitory concentrates by the SD treatment. Detection rates of indigenous viruses were also improved and no substantial loss of viral RNA was observed. The SD treatment was particularly effective in mitigating RT-qPCR inhibition, although it was not effective in improving RNA extraction efficiency. The methodology is simple and easily applied. These findings indicate that SD treatment can be a good alternative to sample dilution, which is widely applied to mitigate the effect of RT-qPCR inhibition, and can be compatible with other countermeasures.

Influence of additives of amphiphilic block copolymers on the porosity of hollow ultrafiltration membranes based on polyethersulfone

It has been shown that the addition of hydrophilic polyarylatepolyalkylene oxide and polyethersulfone-polyalkylene oxide block copolymers to polyethersulfone can control the porosity of the selective layer of hollow fiber ultrafiltration membranes. The selection of the optimal amount of the additive makes it possible to increase the performance of membranes in the purification of drinking water from microalgae, large mineral particles, bacteria and viruses.