Filtration Flux Research Articles

Modeling Soil Moisture Redistribution and Infiltration Dynamics in Urban Drainage Systems

Hydrological modeling has become a common approach for the design of stormwater management strategies which, at the same time, increasingly rely on permeable and decentralized systems to mitigate the impacts of urbanization. In most applications, little attention is however paid to the temporal variability of infiltration fluxes resulting from soil moisture redistribution between rain events. In this study, a conceptual infiltration-redistribution model is introduced to investigate the importance of the description of infiltration fluxes for the modeling of sustainable urban drainage systems (SUDS). Model verification against numerical solution of Richards equation is first conducted. Performance indicators simulated with the model for a large range of infiltration scenarios are later compared to those obtained with simpler approaches, commonly used in urban hydrology. The model is shown to replicate at a low computational cost numerical solutions of Richards equation. Regarding SUDS modeling, results indicate that a correct description of the temporal variability of infiltration fluxes (1) may be needed for some configurations to assess long-term volume-reduction efficiencies and (2) is more generally required when examining frequency-based performance indicators.

Production and purification of fructo-oligosaccharides using an enzyme membrane bioreactor and subsequent fermentation with probiotic Bacillus coagulans

Fructo-oligosaccharides (FOS) are low-calorie sweeteners that can be synthesized by the transfructosylation of sucrose using enzymes known as fructosyltransferases. However, enzymatic conversion is inhibited by the accumulation of glucose as a byproduct, which limits the conversion rate and yield. We therefore developed a semi-continuous production process in an enzyme membrane bioreactor (EMBR) system followed by fermentation with the probiotic bacterium Bacillus coagulans. Filtration experiments were conducted in total recycle mode to evaluate membrane fouling using the resistance-in-series model. We found that fouling was predominantly caused by the accumulation of proteins at the membrane surface, which accounted for 29.6–95.5% of the total filtration resistance depending on the conditions. Using these data, we were able to achieve a stable filtration flux that fulfilled the requirements of the EMBR system by regulating the filtration parameters. The average concentration of total FOS in the products of EMBR reached 270 g·L−1, which was 4.6% higher than the batch process. Subsequently, the crude FOS preparation was treated by fed-batch fermentation with B. coagulans. The monosaccharides in the reaction mix (glucose and fructose) were completely removed, increasing the concentration of FOS to 195.9 g·L−1 and the purity to 96.6%.

A new Correlation for Predicting the Filtration Flux Development in a Membrane Tube

In the present study, the mass transfer characteristics in a tubular membrane are analysed. Based on the available experimental data, a new reliable correlation is elaborated to predict the mass transfer as the term of the permeate flux inside membrane tubes. Analysing of available results shows that the filtration time (tF), and the concentration of suspensions (C) are directly affecting the permeate flux (Pf). Therefore, the present analytical study was conducted to propose a new correlation. This correlation is compared with other experimental data; a very satisfactory agreement has been achieved.

Nanofiltration of solutions containing organic and inorganic salts: Relationship between feed and permeate proportions

Nanofiltration can be considered for the purification of valuable products obtained by fermentation, like organic acids. In this work, nanofiltration experiments are carried out with synthetic solutions of different compositions containing acetate (Ac), propionate (Pr), and butyrate (Bu), as well as inorganic salts (NaCl). Although the retention of charged solutes can be significantly modified according to the composition of the solution, it is observed that there is a filtration flux above which the solutes proportions in the permeate remain constant. These proportions do not depend on the total concentration but only on the solutes proportions in the feed. Finally, individual solute transfer is found to vary linearly with the total solute flux. Similar trends are observed with two NF membranes despite their different properties.

Quantifying water use and groundwater recharge under flood irrigation in an arid oasis of northwestern China

Accurate knowledge of evapotranspiration (ET) and irrigation return flow is critical for the sustainable management of water resources in arid inland river basins. Flood irrigation with large amounts of groundwater and resulting return flow may be not suitable for cropland with long cultivation history. In the midstream of the Heihe River Basin of northwestern China, flood-irrigated cropland with rotation of spring wheat and spring maize from 2005 to 2014 was selected as study area. Deep percolation fluxes below the 1.5 m, 3.0 m and 5.0 m layers were determined based on soil water balance, for which, soil evaporation, transpiration and soil water content (SWC) dynamics during the growing seasons were calibrated and validated by the HYDRUS-1D simulation. Mean annual soil evaporation and transpiration were 64.11 mm and 352.36 mm for spring wheat and 84.03 mm and 447.43 mm for spring maize, respectively. Large amounts of water discharged within the first few days after irrigation from the second to the last irrigation events. Deep percolation below the 1.5 m soil were 841.87 mm and 973.73 mm, occupying 67.10 % and 68.00 % of applied water during the growing seasons of spring wheat and spring maize, respectively. About 108.86 mm and 70.72 mm water percolated from the 0–1.5 m soil were stored in the 1.5–3.0 m layer, respectively. Groundwater recharge (the amount of deep percolation below 5.0 m) amounted to 734.03 mm and 1002.10 mm, occupying 58.86 % and 70.20 % of applied irrigation during the growing seasons of spring wheat and spring maize, respectively. Mean water productivity were 4.24 kg ha−1 mm−1 for spring wheat and 5.86 kg ha−1 mm−1 for spring maize. The impact of decreasing irrigation amount on deep percolation was assessed by assuming 80 % (80 % I), 60 % (60 % I), 50 % (50 % I) and 40 % (40 % I) of current irrigation quota (I) of each event throughout the growing seasons from 2005 to 2014. Even the 40 % I treatment would satisfy water demand of spring wheat and spring maize, and deep percolation would decrease remarkably. The percentage of percolated water from the 0–1.5 m soil to irrigation would decrease on average by 8.31 %, 22.43 %, 33.88 % and 49.78 % under the treatments of 80 % I, 60 % I, 50 % I and 40 % I, respectively. Groundwater recharge would occupy 48.90 %, 34.20 %, 24.45 % and 21.79 % of irrigated water for spring wheat and 62.32 %, 50.21 %, 42.68 % and 40.44 % of irrigated water for spring maize, respectively. The 50 % I treatment would improve water productivity by at least 2.52 kg ha-1 mm-1 for spring wheat and 5.26 kg ha-1 mm-1 for spring maize. The hypothesized irrigation schedule with current frequency and 50 % quota of each event is promising to improve crop water utilization and protect groundwater resources. Optimized irrigation strategy for irrigated agriculture in the midstream will aid the comprehensive management of water resources at a watershed scale in the arid inland river basins.

P1114HA-130 HEMOPERFUSION CARTRIDGE IN THE TREATMENT OF CAST NEPHROPATHY IN A 58-YEAR-OLD MALE WITH MULTIPLE MYELOMA: A CASE REPORT

Abstract Background and Aims Multiple myeloma is a plasma cell neoplasm that results in the production of monoclonal immunoglobulin. Renal failure is a common complication of multiple myeloma, occurring in approximately one-half of patients on initial presentation and is associated with increased mortality. Cast nephropathy in particular, is considered to be one of the major mechanisms of renal failure in multiple myeloma, and is characterized by precipitation of free light chains in the distal nephron, leading to intratubular obstruction, inflammation and fibrosis. Recent studies have demonstrated the use of extracorporeal methods such as plasmapheresis and high-cutoff membrane dialysis as an adjunctive therapy to chemotherapy in the management of cast nephropathy, however currently there are no existing guidelines in the use of extracorporeal therapies in the management of complications of multiple myeloma. Hemoperfusion is an extracorporeal treatment technique which utilizes adsorption in the removal of specific toxins. The HA 130 cartridge in particular has a resin pore size distribution of 500Da- 40 KDa and is able to remove molecules at 5-30kDa. In this case report we describe the use of HA 130 hemoperfusion cartridge in the treatment of cast nephropathy in Multiple Myeloma. Method A 58-year-old male, diabetic, non-hypertensive came in for 5-day history of generalized body weakness, associated with myalgia, lumbar pain and undocumented fever, with 1-day history of loose stools and vomiting. Upon admission blood tests done revealed anemia with a hemoglobin of 7.8g/dl, creatinine of 9.97mg/dL and potassium of 5.5mmol/L. He was diagnosed with acute renal failure and underwent hemodialysis on the second hospital day. On workup he had lytic bone lesions in the spine, pelvis and cranium on CT scan and x-ray. Serum Protein Electrophoresis (SPEP) and Serum Free Light Chain (sFLC) tests showed a monoclonal gammopathy. Serum beta 2 microglobulin was elevated at 12,618ng/ml. Free kappa and lambda light chains were also elevated at 19,250mg/L and 25.7mg/L, respectively. Bone marrow biopsy was done, with findings of markedly hypercellular marrow with 80% plasma cells confirming the diagnosis of Multiple Myeloma. Combined hemodialysis with hemoperfusion were done using HA 130 filter and hi flux dialyzer for 2.5 hours then hemodialysis for three times a week. Patient was also started on chemotherapy using Bortezomib with Dexamethasone for 2 cycles. Results Patient had a total of 14 sessions of combined hemoperfusion with hemodialysis. On repeat free kappa light chains decreased to 212.5mg/L. Patient was maintained on hemodialysis three times a week and was discharged after 55 hospital days. Outpatient hemodialysis was continued three times a week, and after 2 weeks, patient showed signs of renal recovery with a repeat creatinine of 2.1mg/dL. Four weeks after discharge, patient was independent of hemodialysis with a repeat creatinine of 1.3mg/dL. Conclusion This report highlights the use of hemoperfusion using HA 130 cartridge in combination with chemotherapy using Bortezomib in reducing free light chain levels in a 58-year-old male that developed renal failure secondary to cast nephropathy. Patient was able to achieve reduction in free light chain levels, improvement in renal function and eventually independence from hemodialysis four weeks after the last hemoperfusion treatment. Further studies using a randomized control trial on the use of hemoperfusion in directly reducing serum free light chain levels is recommended. The value of hemoperfusion on the rate of independence from hemodialysis, as well as survival rates among patients with renal failure secondary to multiple myeloma may also be worth investigating using larger studies.

Pilot studies on the river water treatment using coagulation-UF membrane filtration and direct UF membrane filtration

The pilot tests of UF membrane filtration for river surface water were carried out with coagulation as a pre-treatment (test 1) and without coagulation (test 2). Both UF membrane filtrate water of the test 1 and the test 2 met drinking water quality standard in Vietnam. Additionally, the TMP and the filtration flow rate were kept stably during test periods without changes in operation conditions although the river water turbidity was varied due to heavy rain. It was indicated that the water treatment system can be simple by skipping coagulation and/or sedimentation as pre-treatments. The filtration flux of the test 1 and the test 2 were 138 L/m2 h and 93 L/m2 h, respectively. The flux was higher than the reported reference value indicating that the module number of modules required for the water treatment plant can be reduced by using the FG module. The test data of the test 2 was theoretically analysed by the equations based on Darcy’s low. The estimated TMP correlated highly with measured value (R2=0.71). The optimized parameters were used for the simulation of the operation. The simulation results indicated that the TMP before backwashing is increased around 35 kPa when the river water turbidity increased up to 500 NTU. It was indicated that the CIP interval should take into account the TMP increasing by turbidity variation.

Electrospun nanofibrous polyvinylidene fluoride‐co‐hexafluoropropylene membranes for oil–water separation

AbstractEffective separation of oil from water is of significant importance globally for various applications such as wastewater treatment, oil spill cleanup, and oil purification. Among the numerous approaches for oil removal, membrane separation is considered one of the most promising approaches due to its selectivity and ease of operation. Electrospinning is a promising technique for producing polymeric membranes with tunable structures with interconnected pores, large surface area, and high porosity. In this study, hydrophobic poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) nanofibrous membranes were electrospun and used for this purpose. The effects of various parameters (e.g., polymer concentration, applied voltage, tip to collector distance, and feed rate) were investigated to find the optimum electrospinning conditions. Further, the electrospun membranes were characterized according to average fiber diameter, morphology, average pore size, and wettability to identify the combinations most likely to succeed in oil–water filtration. The physical–chemical properties of the membranes (i.e., thickness, areal density, porosity, average pore size, water/oil contact angle, hydrostatic pressure head, and oil filtration flux) were studied based on standard test methods. The separation efficiency of eight electrospun membranes with various pore sizes and average fiber diameters were tested for diesel/water mixtures. A linear relation was found between the initial oil flux and the average pore size of the membranes. The maximum oil filtration flux of about 224 L/m2/h, achieving over 75% oil recovery in 10 min, was obtained for the electrospun membrane with the average pore size of 4.5 μm. The membranes were successfully used for eight consecutive oil–water separation cycles without noticeable loss of flux.

Underoil Superhydrophilic Metal Felt Fabricated by Modifying Ultrathin Fumed Silica Coatings for the Separation of Water-in-Oil Emulsions.

Although various superhydrophobic/superoleophilic porous materials have been developed and successfully applied to separate water-in-oil emulsions through the size-sieving mechanism, the separation performance is restricted by their nanoscale pore size severely. In this study, the wettability of underoil water on fumed silica was experimentally observed, and the underlying mechanism was investigated by carrying out theoretical analysis and molecular dynamic (MD) simulations. Further, we present a novel, facile, and an inexpensive technique to fabricate an underoil superhydrophilic metal felt with microscale pores for the separation of water-in-oil emulsions using SiO2 nanoparticles (NPs) as building blocks. The as-prepared underoil superhydrophilic coating is closed-packed and ultrathin (the thickness is approximately hundreds of nanometers), as well as capable of being coated on a metal felt with complex structures without blocking its pores. The as-prepared metal felt could adsorb water droplets directly from oil, which endowed it with the ability to separate both surfactant-free and surfactant-stabilized water-in-oil emulsions with high separation efficiency up to 99.7% even though its pore size is larger than that of the emulsified droplet. The filtration flux for the separation of span 80-stabilized emulsion is up to ∼4000 L·m-2·h-1. Its separation performance is better than most of the other traditional membranes and superwettable materials used for the separation of water-in-oil emulsions. Moreover, the as-prepared metal felt retained outstanding separation performance even after 30 cycles of use, which demonstrated its excellent reusability and durability. Additionally, the distinctive wettability of underoil superhydrophilicity endued coated metal felt with superior antifouling properties toward crude oil. Overall, this study not only provides a new perspective on separating water-in-oil emulsions but also gives a universal approach to develop unique wettability surfaces.

Optimization of Air Backwash Frequency during the Ultrafiltration of Seawater.

The main objective of this paper is to study the effect of new air backwash on dead-end ultrafiltration of seawater with a pilot at semi-industrial scale (20 m3/day). To control membrane fouling, two different backwashes were used to clean the membrane: classical backwash (CB) and new air backwash (AB) that consists of injecting air into the membrane module before a classical backwash. To evaluate the efficiency of AB and CB, a resistance in series model was used to calculate each resistance: membrane (Rm), reversible (Rrev) and irreversible (Rirr). The variation of the seawater quality was considered by integrating the turbidity variation versus time. The results indicate clearly that AB was more performant than CB and frequency of AB/CB cycles was important to control membrane fouling. In this study, frequencies of 1/5 and 1/3 appear more efficient than 1/7 and 1/9. In addition, the operation conditions (flux and time of filtration) had an important role in maintaining membrane performance—whatever the variation of the seawater quality.

Dead-end and crossflow ultrafiltration process modelling: Application on chemical mechanical polishing wastewaters

Dynamic simulation of ultrafiltration process is applied to the treatment of chemical mechanical polishing wastewater from microelectronic industry. The ultrafiltration of nanoparticles (NPs) contained in chemical mechanical polishing wastewater is modelled by using different mathematical equations, which are derived from the literature and optimized to the effluent and filtration modes (dead-end or crossflow). A series of ultrafiltration experiments at laboratory scale are carried out by using chemical mechanical polishing wastewater to optimize and validate the models. Complete dead-end and crossflow ultrafiltration models are developed to simulate the treatment performances of chemical mechanical polishing wastewater under dynamic full-scale and different operating conditions, thus including filtration and washing steps. Simulations show that the dead-end mode is not suitable for chemical mechanical polishing wastewater concentration higher than 100mgNPsL−1 due to the too fast fouling time and to the high frequency of washing step. The high concentration of chemical mechanical polishing P wastewater (2600mgNPsL−1) forces industries to use crossflow ultrafiltration to have a profitable process by controlling parameters such as the filtration/backwashing number of cycles, the needed filtering surface and the filtration flux.

Fluidized bed membrane bioreactor achieves high sulfate reduction and filtration performances at moderate temperatures

The study explored the potential of an up-flow sulfate reducing fluidized-bed membrane bioreactor (SR-FMBR) for biogenic sulfide generation at room temperature together with evaluation of filtration and fouling characteristics developed under various operational conditions. The SR-FMBR was tested at different COD/sulfate (mg/mg) ratios for a total of 127 days, initially at 35 °C and then at 23 °C. SR-FMBR was able to achieve COD oxidation and sulfate reduction efficiencies up to 98%, and allowed for biogenic sulfide generation up to 600 mg/L (97% of theoretical value) at room temperature. Alkalinity was generated as a result of sulfate reduction and averaged around 1900 mgCaCO3/L in the permeate. Hence, starting the bioreactor operation at 35 °C and then decreasing it to 23 °C did not adversely affect the process performance. High filtration fluxes up to 9.3 L/m2/h (LMH) could be maintained at employed hydraulic retention times between 24 h and 6 h. Observing relatively high filtration performance was due to keeping a high fraction of biomass attached to the carrier material, which decreased the cake formation potential on the membrane surface compared to conventional MBR operation. The SR-FMBR performance may further be tested for heavy metal removal under sulfidogenic conditions for acid mine drainage treatment.

Transport and Water Age Dynamics in Soils: A Comparative Study of Spatially Integrated and Spatially Explicit Models

AbstractWe address transport by transit times (i.e., the age of water parcels leaving a storage as discharge, deep loss, or evapotranspiration) in subvertical soil systems, key to our understanding of water quality in catchments and streams. While the use of field and lysimeter observations to constrain and validate modeling approaches is generally accepted, different views exist on the relative ranges of applicability of spatially integrated or spatially explicit approaches. This study specifically illustrates how one class of spatially integrated models of transport, based on StorAge Selection (SAS) functions, fares with respect to spatially explicit hydrologic models in a case where detailed tracer data from experimental lysimeters exist and for which both approaches are viable. Data from two lysimeters experiments that differ in atmospheric conditions, size of the installation, tracer type, soil texture, and vegetation are used to contrast results from two transport models: tran‐SAS (space implicit) and HYDRUS‐1D (space explicit). Results suggest that although the two lysimeters are characterized by different transit time distributions, their underlying transport mechanisms are similar and represented well by both models. The comparison between the two models results in robust estimates of the transport timescales and clearly shows that percolation fluxes at the bottom of a lysimeter tend to drain the relatively old components of the soil storage. We conclude that the convergence of the approaches in a geomorphologically simple and data‐rich problem supports extensive uses of the spatially integrated approach in cases where the scale of the problem, or subgrid parameterization needs, may limit the applicability of detailed modeling approaches.

Preparation of underwater superoleophobic membranes via TiO2 electrostatic self-assembly for separation of stratified oil/water mixtures and emulsions

Huge discharge of oily wastewater has seriously threatened the ecosystem and human's health. Superhydrophilic/underwater superoleophobic porous materials have engaged considerable attentions in the application for separation of oil/water mixtures. However, there still exist several challenges in the existing material designs for oil/water separation that need to be addressed, such as terrible stability, high production cost and complex fabrication procedure. Herein, a series of all-inorganic superhydrophilic and underwater superoleophobic filtration materials were designed and fabricated by coating TiO2 via a facile and universal technique of self-assembly, as well as successfully applied for the separation of both stratified oil/water mixtures and emulsions. The as-prepared TiO2 nanoparticle coating is extremely dense, ultrathin and widely applicable for various two-dimensional (2D) and three-dimensional (3D) substrates such as stainless-steel mesh (SSM), metal felt and glass fibrous (GF) membrane. The coating can even be coated on the ultrafine fibers with diameter reaching to hundreds of nanometers. The TiO2 coated SSM with large pores (~35 μm diameter) could efficiently separate the stratified oil/water mixtures with the flux up to 54000 L⋅m−2⋅h−1. Moreover, the TiO2 coated GF membrane with small pores (~5 μm diameter) can separate diverse surfactant-free and surfactant-stabilized emulsions with separation efficiency higher than 98%. More importantly, excellent filtration flux up to ~4000 L⋅m−2⋅h−1 was realized under solely gravity, which is one to two orders of magnitude larger than the flux of traditional filtration membranes, as well as more superior than most of the reported superwettable membranes. Furthermore, the as-prepared GF membrane displays outstanding high-temperature resistance and reusability for long-term application of oil/water separation.

Determination of ultrafiltration resistance using series resistance model in inulin purification from red fruit (Pandanus conoideus L.) pedicel extract

The crude inulin extracted from red fruit pedicels using hydrodynamic cavitation contained inulin and other impurities such as reducing sugars and proteins. Membrane technology is an alternative technology for separating inulin from its impurity. This study aimed to purify the inulin extract and to evaluate the membrane resistance using a series of Membrane Titania (5 × 103 Da pore diameter) with 1–2.6 bar pressure variation on ultrafiltration. The steady-state on the inulin crude filtration at 0 scales and 1 bar occurred at the 25th minutes with a flux value 3.06 L m−2 h−1. The optimum pressure for the transmembrane was at 2.2 bar with permeate flux of 7.75 L m−2 h−1. The amount of flux in the membrane filtration was determined by the resistance of internal membrane, fouling, and polarization.

Application of porous TiAl intermetallic compound in purification of industrial TiCl4 liquid in Ti metallurgy

Industrial TiCl4 liquid, which is a key intermediate in Ti metallurgy, is hard to be purified by traditional porous metals or ceramics due to its characteristics of easy hydrolysis, toxicity and corrosivity. In this work, porous TiAl intermetallic filter tubes were fabricated through a reactive synthesis process, and their filtration properties in industrial TiCl4 liquid were investigated. The cyclic corrosion kinetics of porous TiAl in TiCl4 follows a parabolic rate law, in which the corrosion rate constant is 4.8%, 0.06% and 0.04% of that of porous Ti, Ni and 316L stainless steel, respectively. After the cyclic corrosion of 408 h, the maximum aperture reduction rate of porous TiAl is 3.9%, which is far lower than that of porous Ti, Ni and 316L, indicating good pore structure stability. Porous TiAl filter tubes exhibit clean filtration performance in the solid-liquid separation of raw TiCl4 suspension with stable filtrate solid content of 0.1 wt% and high filtration flux of 8.17 m3 · m−2 · h−1 at the maximum aperture of 17.0 μm. The filtration equation and the filter medium resistance of porous TiAl are determined.

Biosynthesis based membrane filtration coupled with iron nanoparticles reduction process in removal of dyes

In this work, filtration of membrane and reduction of iron nanoparticles (FeNPs) was coupled to remove dyes with different molecular weight. The FeNPs–Calcium alginate (CaAlg) composite membrane was biosynthesized using green tea. The FeNPs–CaAlg composite membrane was characterized by series of instruments. The results indicate that the FeNPs-CaAlg membrane has an excellent performance in filtrating dyes, nearly the same filtration flux with purified water and almost no flux reduction with filtration time. The FeNPs-CaAlg membrane exhibits different rejection performance for dyes with different molecular weight. The mechanism was discussed and it can be concluded that, for dyes with small molecular weight like crystal violet, besides the influence of the change in the effective channel size made by the load of FeNPs, the intensive reducibility of FeNPs also has great effect on the rejection rate.

Optimizing Flux Capacity of Dead-end Filtration Membranes by Controlling Flow with Pulse Width Modulated Periodic Backflush

Standard dead-end sample filtration is used to improve sample purity, but is limited as particle build-up fouls the filter, leading to reduced recovery. The fouling layer can be periodically cleared with backflush algorithms applied through a customized fluidic actuator using variable duty cycles, significantly improving particulate recovery percentage. We show a Pulse Width Modulation (PWM) process can periodically backflush the filter membrane to repeatedly interrupt cake formation and reintegrate the fouling layer into the sample, improving net permeate flux per unit volume of sample by partially restoring filter flux capacity. PWM flow for 2.19 um (targeted) and 7.32 um (untargeted) polystyrene microbeads produced 18-fold higher permeate concentration, higher recovery up to 68.5%, and an 8-fold enrichment increase, compared to a uniform flow. As the duty cycle approaches 50%, the recovery percentage monotonically increases after a critical threshold. Further, we developed and validated a mathematical model to determine that fast, small-volume backflush pulses near 50% duty cycle yield higher recovery by decreasing fouling associated with the cake layer. Optimized PWM flow was then used to purify custom particles for immune activation, achieving 3-fold higher recovery percentage and providing a new route to improve purification yields for diagnostic and cellular applications.

Ethanol-induced one-step fabrication of superhydrophobic-superoleophilic poly(vinylidene fluoride) membrane for efficient oil/water emulsions separation

Surfactant-stabilized emulsions, a main type of hazardous oil/water mixtures have been afflicting human beings for decades. In this work, a highly porous PVDF/PDMS blend membranes with superhydrophobic-superoleophilic property was successfully prepared through ethanol-induced phase inversion. This facile, low cost and effective one-step membrane-forming method endowed the membrane with a superwetting micro-nano hierarchical surface and an interconnected porous internal structure. The optimal membrane exhibited a water contact angle of 164 ± 1.9° and an oil contact angle of 0°. With high porosity and superior selective wettability, the PVDF/PDMS blend membranes can separate multifarious surfactant-stabilized nanoscale emulsions quickly. The optimal membrane shows a filtration flux of 855 ± 45 L m−2 h-1 (the separation efficiency exceeds 99.81 %) when driven by gravity merely. In addition, PVDF/PDMS blend membranes have an excellent reusability in separating the surfactant-stabilized water-in-oil emulsions. These results clearly demonstrate that this membrane-forming method may provide a new reliable pathway for membrane fabrication for oil/water emulsion separation.

Steroid hormone micropollutant removal from water with activated carbon fiber-ultrafiltration composite membranes

Short activated carbon fibers (ACF) with high surface area were fabricated via carbonization in N2 and activation in CO2 at high temperatures, with cellulose fibers as the raw materials. The obtained ACF were subsequently deposited into the support layer of a polyethersulfone (PES) ultrafiltration membrane by a facile filtration process to obtain the sandwich structured ACF-PES composite membrane. The hormone (17β-estradiol, E2) adsorption kinetics and isotherm of ACF in static conditions, as well as E2 removal by filtration with the ACF-PES composite membrane were investigated. In static conditions, ACF rapidly and efficiently adsorbs E2 evidenced by a high removal of >97 %. The fitting of second order kinetics and linear (Henry) adsorption isotherm models indicated the availability of easily accessible adsorption sites. Besides, such efficient E2 adsorption was contributed by many interactions between E2 and ACF, namely hydrophobic interactions, hydrogen bonding and π-π stacking. The incorporation of ACF in a PES membrane resulted in a minor loss of filtration flux compared with the control membrane, but significantly improved E2 removal through adsorption pathway. With only 1.0 mg ACF incorporated (loading 2.0 g/m2), the composite membrane could reject 76 % of E2 from a 100 ng/L solution at a flux of 450 L/m2∙h, demonstrating that ACF-PES can overcome the permeability-selectivity trade-off of traditional UF membranes.