Polyurethane Filter Research Articles

The Response Surface Optimization of the Performance of Modified Polyurethane Membranes for Phenol Removal

In this study, polyurethane (PU) filter membranes were modified with MIL-53(Al) in order to improve phenol removal efficiency. First, one-way analysis of variance (ANOVA) was used to determine that modifier dosage and temperature were significant influences, and pH had a small effect. Then, Design-Expert 13 software was used to derive higher-order fitting equations based on Box–Behnken design, and the parameters were optimized by a system of partial differential equations. Finally, the optimized parameters were obtained by solving the system of partial differential equations, and the reproducibility of the experiment was confirmed using a t-test. The results showed that the modified filter membranes significantly enhanced phenol removal efficiency by 93.34%, which verifies the accuracy of the model and the reproducibility of the experiment and provides theoretical basis and data support for the promotion of the modified membrane.

A PM2.5 pollution-level adaptive air filtration system based on elastic filters for reducing energy consumption

Exacerbated by human activities and natural events, air pollution poses severe health risks, requiring effective control measures to ensure healthy living environments. Traditional filtration systems that employ high-efficiency particulate air (HEPA) filters are capable of effectively removing particulate matter (PM) in indoor environments. However, these systems often work without considering the fluctuations in air pollution levels, leading to high energy consumption. This study proposed a novel PM2.5 pollution-level adaptive air filtration system that combined elastic thermoplastic polyurethane (TPU) filters and an Internet of Things (IoT) system. The developed system can effectively adjust its filtration performance (i.e., pressure drop and PM2.5 filtration efficiency) in response to real-time air quality conditions by mechanically altering the structures of TPU filters. Furthermore, while operating in varied pollution conditions, the proposed system demonstrated remarkable reductions in pressure drop without notably compromising the pollution control capability. Finally, the energy consumption of the pollution-level adaptive air filtration system was estimated when applied in mechanical ventilation systems in different cities (Hong Kong, Beijing, and Xi’an) with various pollution conditions. The results revealed that, compared to a traditional fixed system, the annual energy consumption could be reduced by up to ∼26.4 % in Hong Kong.

Microplastics and volatile organic compounds released from face masks after disinfection: Layers and materials differences

Effective disinfection methods are critical for ensuring the reusability of masks, yet these methods may inadvertently introduce health concerns associated with microplastics (MPs) and volatile organic compounds (VOCs). This study investigated the impact of ultraviolet germicidal irradiation (UVGI) and sodium hypochlorite (NaClO) bleaching on mask filter layers composed of four distinct materials. Our results revealed that UVGI induced more pronounced damage compared to bleaching, leading to the significant release of both MPs and VOCs. After UVGI treatment at conventional disinfection doses, meltblown (MB) fabrics released MPs reaching 864 ± 182 μg/g (92 ± 19 particles/g). For all filter layers, the quantity of released MPs followed the order: MB > HDPE>PU ≈ NW. These MPs were identified as degraded debris from the mask filter layers. The specific VOCs generated varied depending on the material composition. Non-woven (NW) and MB fabrics, both comprised of polypropylene, predominantly produced various branched aliphatic hydrocarbons and their derivative oxides. The cotton-like fabric, composed of high-density polyethylene, primarily emitted different linear aliphatic hydrocarbons and oxygenates. In contrast, the polyurethane filter layer of reusable masks released aromatic compounds, nitrogenous compounds, and their oxidation products. The formation of VOCs was primarily attributed to bond breakage and oxidative damage to the filter structure resulting from the disinfection process. In summary, as UVGI induced higher yields of MPs and VOCs compared to bleaching, the latter would be a safer option for mask disinfection.

Magnetic hydrophobic cellulose-modified polyurethane filter for efficient oil-water separation in a complex water environment

Magnetic porous materials have been of interest for oil-water separation due to their efficient ease of separation. This work presented a facile approach for preparing a magnetic polyurethane foam (PUF) modified with pretreated cellulose-decafluorobiphenyl (MCF). The prepared materials were characterized using several techniques. They showed high oil-water separation for a variety of oils and chemical solvents. More significantly, the absorbed oil was easily retrieved by squeezing. After several absorbing-squeezing cycles, the modified PUF maintained a high magnetic responsivity, due to the addition of Fe3O4 magnetic nanoparticles, and still exhibited a significant oil absorption capacity. MCF's oil absorption capacity, separation efficiency, oil flux, and reusability were evaluated. The results reveal that the prepared material has a high absorption capacity which varies between 9 and 32 times its own weight, excellent separation efficiency (>97.68 %), and high flux which reaches 48,750 Lm−2h−1 for n-hexane, and high reusability (>50 times) in oil-water separation. The magnetic MCF foam could be reused through a simple squeeze treatment. The oil-water separation performance of MCF is excellent in complex environments including acidic solutions (pH = 2), basic solutions (pH = 12), and simulated seawater. This makes it a very promising material for the aforementioned purposes.

Deposition of CaFe2O4 and LaFeO3 perovskites on polyurethane filter: A new photocatalytic support for flowthrough degradation of tetracycline antibiotic

The immobilization of powder catalysts on substrates has been the subject of increasing interest in the field of photocatalysis. For the first time, highly efficient LaFeO3 and CaFe2O4 perovskites were hydrothermally deposited on polyurethane filters (LFO/PU, CFO/PU). Furthermore, the photo-Fenton catalytic decomposition of tetracycline antibiotic by the new catalyst filters was explored under visible light irradiation. The structural, optical, and morphological characteristics of the photo-active filters were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), UV–visible diffusion spectra (UV–vis DRS), X-Ray fluorescence (XRF), and thermogravimetric/dynamic thermal analyses (TG-DTG). The decomposition studies were conducted in both batch and micro-flow reactor systems. The effects of solution pH, reactive species, and water type on the reaction mechanism were examined. It was found that the photo-Fenton degradation of tetracycline improved when the perovskite proportions on the filter were increased; the removal rates reached 94% and 80% forLFO/PU and CFO/PU, respectively. The high degradation performance obtained in lake (∼71%) and seawater (∼76%) demonstrated the great potential of photo-active catalyst filters, and their excellent stability was confirmed by reusability tests. In the continuous flow system, the photocatalytic filters kept the degradation rate stable at 83% and 44% after 7 h of examination forLFO/PU and CFO/PU, respectively. These results suggest that the as-prepared catalytic filters may be suitable for industrial photocatalytic applications.

Electrically Responsive Coarse Filters Endowed by High-Dielectric-Constant Surface Coatings toward Efficient Removal of Ultrafine Particles and Ozone

Ambient ultrafine particles (UFPs) cause severe health threats, and UFPs can transport in indoor environments through building envelopes. In building HVAC (heating, ventilation, and air conditioning) systems, fibrous filtration has been extensively used to resist particulate matter. However, there is an intrinsic conflict between fibrous filters’ high filtration efficiency and low air resistance. Herein, we designed a dielectric-coated fiber structure and fabricated electrically responsive coarse filters to remove UFPs by utilizing the Coulomb force between the charged particles and the polarized fibers. The electrical responsiveness endowed the filters with an excellent performance for the removal of UFPs. With the synergistic improvement of particle precharging and filter polarization, the UFPs’ removal efficiency of the coated filter increased from ∼0% to the highest of 90.50%, with ultralow ∼13.0 Pa air resistance at 1 m/s face air velocity, which ensured a considerable filtration performance even under large face air velocity. Furthermore, the combination of MnO2 and polyurethane (PU) filters performed with the ability to remove the unwanted ozone generated by particle precharging. The promising features give these filters excellent potential for use in energy-efficient electrostatic air-cleaning devices, thus achieving a healthy and sustainable environment.

Increased Adsorption of Heavy Metal Ions in Multi-Walled Carbon Nanotubes with Improved Dispersion Stability.

In recent years, carbon nanotubes (CNTs) have been intensively studied as an effective adsorbent for the removal of pollutants from wastewater. One of the main problems for its use corresponds to the agglomeration of the CNTs due to the interactions between them, which prevents using their entire surface area. In this study, we test the effect of dispersion of oxidized multi-walled carbon nanotubes (MWCNTs) on the removal of heavy metals from acidic solutions. For this, polyurethane filters were dyed with a well-dispersed oxidized MWCNTs solution using chemical and mechanical dispersion methods. Filters were used in column experiments, and the sorption capacity increased more than six times (600%) compared to experiments with suspended MWCNTs. Further, kinetic experiments showed a faster saturation on MWCNTs in column experiments. These results contribute to a better understanding of the effect of dispersion on the use of CNTs as heavy metal ions adsorbent.

Design and fabrication of nanocomposite-based polyurethane filter for‏ ‏improving municipal waste water quality and removing organic pollutants

Nanotechnology has been used in different industries for years. In this study, polyurethane filter, modified with nano-sized polypyrrole–ZnO was used for wastewater quality improvement. The effect of coating method and influential parameters on polymer morphology was studied by Fourier transform infrared spectroscopy and scanning electron microscopy. The results revealed that the uniformly synthesized polymers are seed like. The size of synthesized nanoparticles was observed to be about 50–120 nm. The effect of the number of iterative filtration and the height of the filter on improving the quality of the waste water was investigated using central composite design. After filtration, spectroscopy method, gas chromatography method, and some other devices such as biochemical oxygen demand meter and salt meter were used to evaluate the quality of the waste water. The results indicated that the filter efficiency in optimizing parameters such as total dissolved solids, biochemical oxygen demand, chemical oxygen demand, color, salinity, hardness, pH, and organic compounds removal is desirable. After data modeling, the optimal thickness of the filter was 3.8 cm and the most appropriate iteration for filtration was eight times obtained using a graphical method. Results showed that the designed filter had an excellent ability to improve wastewater quality and can be used in water and wastewater refining instruments.

Development of antibacterial and antifungal silver-coated polyurethane foams as air filtration units for the prevention of respiratory diseases

The development of silver-coated polyurethane filters as filtration units for the prevention of the respiratory diseases. An innovative silver deposition technology based on the photo-reduction in a silver salt was adopted. The efficacy of the technology in providing a homogeneous distribution of the silver particles was verified by scanning electron microscopy and energy dispersive X-ray spectroscopy. The materials were tested through microbiological procedures used in industry to verify the efficacy of the silver-coated filters on the viability and growth of selected micro-organisms. Direct inoculation test, filtration experiment and shaking tests were performed on microbial human pathogens associated with air filtration units and respiratory disease, namely Legionella pneumophila, Pseudomonas aeruginosa, Aspergillus niger and Aspergillus flavus, by adopting Escherichia coli and Staphylococcus aureus as control organisms. The results provided evidence of the effectiveness of the silver coating in reducing the bioaerosolization of viable human pathogens into environments using recirculated air. Micro-organisms can affect the air quality in indoor environments and can be responsible for infectious, allergic or toxic disturbances on human airways. The development of an adequate bioaerosol control might ameliorate a positive health effect in humans.

Preparation of electrospun polyurethane filter media and their collection mechanisms for ultrafine particles

Electrospinning is a simple and versatile process to produce polymer nanofibers, which are useful for ultrafine particle filtration. In this study, a polyurethane filter with an average fiber diameter of 150–250 nm was prepared through the electrospinning process and its filtration characteristics were investigated. We found that the electrospun fiber diameter was highly dependent on the polyurethane concentration, electric field, and tip-to-collector distance. As the polyurethane concentration, electric field, and tip-to-collector distance under the same electric field increased, the fiber diameter increased. We also found that the produced filter media had a minimum collection efficiency at particles sizes from 80 to 100 nm, which implies an electrostatic attraction between the filter and the test particles. Furthermore, we observed that interception was a predominant collection mechanism at Peclet numbers higher than 10 in nanofiber filtration for ultrafine particles. Implications: A polyurethane nanofiber filter with excellent mechanical properties was prepared, and the effect of operating conditions on fiber morphology was examined. The filter fabricated by an electrospinning process is charged and has high filtration efficiency due to electrostatic force. Therefore, it can be a good alternative to control hazardous ultrafine particles.

A Flexible Multifunctional Sensor Based on Carbon Nanotube/Polyurethane Composite

A sensor was made of a polymer composite composed of electrically-conductive carbon nanotubes embedded in elastic polyurethane. The composite was prepared using a polyurethane filter membrane, enmeshing it, and melding together with carbon nanotubes. Testing has shown that the composite can be elongated as much as 400% during which the electrical resistance is increased 270 times. The composite is also sensitive to compression and to organic solvent vapors. These properties indicate the composite could have applications as a highly-deformable strain and chemical vapors sensing element and also as flexible electromagnetic shielding or protection against lightning. As an example of the use of the composite as a strain sensor, the pressure variation between a shoe and floor during walking and knee flexion during cycling has been monitored.

A highly-deformable composite composed of an entangled network of electrically-conductive carbon-nanotubes embedded in elastic polyurethane

The electrical resistance change of a highly extensible composite consisting of a network of entangled multi-wall carbon nanotubes in a thermoplastic polyurethane elastomer is tested. The composite is prepared by taking a non-woven polyurethane filter membrane, enmeshing it with carbon nanotubes and melding them together. Testing has shown that the material can be elongated as much as 400% during which the resistance is increased more than 270 times. It indicates favorable properties of the composite for its use as a highly-deformation strain sensing element, a strain-electric signal transducer, electromagnetic field shielding and protection against lightning. As an example of its use as a strain sensor, human knee flexion and knee cyclic movement has been monitored. This may be of use in orthopedics and rehabilitation.

Effect of switching gas inlet position on the performance of a polyurethane biofilter under transient loading for the removal of benzene, toluene and xylene mixtures

The performance of a polyurethane (PU) biofilter was evaluated using different operating modes (unidirectional flow (UF) and flow-directional switching (FDS) operations) under transient loading conditions (intermittent and shutdown). Gas mixtures containing benzene, toluene and xylene (BTX) were employed as model gases. Quantitative real-time PCR methods were used for targeting the tmoA gene responsible for BTX degradation and estimating density of the BTX-degraders in the PU filter bed. Although the overall BTX Removal efficiencies at the outlet (50 h−1 of space velocity) were similar between the UF and FDS biofilters, the removability of BTX in the FDS biofilter was higher than that in the UF biofilter until the 3rd sampling position (68 h−1 of space velocity). The BTX removal potentials and tmoA gene copy numbers of the FDS biofilter remained constant, irrespective of the distances from the inlet, but those of the UF biofilter increased with increasing distance from the inlet position. These results indicate that an even distribution of BTX degraders in the FDS filter bed contributed to better BTX removal performance. After a 10 day-shutdown, the performances of the UF and SDF biofilters were rapidly restored within 1 day.

Reduction of ammonia and volatile organic compounds from food waste-composting facilities using a novel anti-clogging biofilter system

The performance of a pilot-scale anti-clogging biofilter system (ABS) was evaluated over a period of 125days for treating ammonia and volatile organic compounds emitted from a full-scale food waste-composting facility. The pilot-scale ABS was designed to intermittently and automatically remove excess biomass using an agitator. When the pressure drop in the polyurethane filter bed was increased to a set point (50mm H2O m−1), due to excess biomass acclimation, the agitator automatically worked by the differential pressure switch, without biofilter shutdown. A high removal efficiency (97–99%) was stably maintained for the 125days after an acclimation period of 1week, even thought the inlet gas concentrations fluctuated from 0.16 to 0.55gm−3. Due the intermittent automatic agitation of the filter bed, the biomass concentration and pressure drop in the biofilter were maintained within the ranges of 1.1–2.0g-DCW gPU−1 and below 50mm H2O m−1, respectively.

Initial clinical experience with distal embolic protection using “Filtrap”, a novel filter device with a self-expandable spiral basket in patients undergoing percutaneous coronary intervention

We developed a new filter-type distal protection guide wire, Filtrap, that uses a polyurethane filter with 1834 100-μm micropores covering the distal half of a spindle-shaped spiral Ni-Ti basket. The basket is 5 mm in diameter, self-expandable, and is mounted at the distal end of the system. This study aimed to assess the usefulness and safety of Filtrap during percutaneous coronary intervention (PCI). Early angiographic and in-hospital outcomes were reviewed in 14 patients, including 9 acute coronary syndrome patients, treated with Filtrap during PCI. All lesions were located in native coronary arteries but one was located in a saphenous vein graft. The Filtrap was successfully delivered and deployed distal to the lesion in 13 of 14 patients (93%). All PCI procedures including stent implantation were successfully completed except for 2 AMI patients, who ended up with Thrombolysis in Myocardial Infarction (TIMI) 2 coronary flow. One of these 2 patients had a distal embolization which occurred after thrombectomy before Filtrap insertion. The mean time of device insertion was 9.4±3.2min. Five patients showed transient no-reflow that was completely restored immediately with removal of the device. Embolic debris was entrapped in 8 (62%) of these cases. All patients were free from in-hospital events except for one patient with a large anterior acute myocardial infarction who received an emergency surgery due to a free wall cardiac rupture. These results suggest that the Filtrap is a practical and safe device for embolic protection during PCI.

Comparative study of predeposit and bedside leucodepletion filters

Background: Removal of leucocytes from cellular blood components is associated with reduction of several transfusion associated adverse reactions. Methods: A total of 400 units of packed red blood cells (RBCs) were subjected to leucodepletion at room temperature and 4°C using different commercially available prestorage and bedside filters (Terumo Penpol Immugard III and Pall Medical BPF-4). Prefiltration and post-filtration parameters were compared to assess the efficacy of prestorage leucodepletion vis-à-vis bedside leucodepletion and the requirement of universal leucodepletion. Result: Mean post-filtration red cell recovery ranged from 88.49-93.49% with all bags showing more than 85% red cell recovery. Mean post-filtration residual leucocyte count ranged from 0.205 x 10 6-0.338 x 10 6/bag with all bags showing more than log 3 leucoreduction. Prestorage leucoreduction achieved by the polyurethane filter was better than that achieved by the polyester filter. Red cell recovery with the bedside filters at room temperature was significantly less than that with prestorage filters at either temperature. Conclusion: This study suggests that prestorage leucoreduction is preferable over bedside leucoreduction and that polyurethane filters are better than polyester filters since leucodepletion achieved with the former is higher. We recommend selective log 3 leucodepletion using polyurethane prestorage filters for patients with specific indications.

Development of a Size-Selective Inlet-Simulating ICRP Lung Deposition Fraction

A size-selective inlet made of polyurethane filter foam was designed and fabricated to simulate a portion of the ICRP respiratory deposition curve. A downstream aerosol measuring device then could be used to generate aerosol concentration data that represented the fraction reaching the respiratory system. This article introduces useful knowledge about porous foam penetration for particle size ranges below those reported in the previous studies. Different porosities of polyurethane foam filters were tested for aerosol penetration. Among the parameters operated in this work were (1) foam porosity (ppi), (2) filter thickness, (3) face velocity, and (4) packing density of the filter foams. Di-octyl phthalate was used as the test agent. A constant output atomizer and an ultrasonic atomizing nozzle were used to generate polydisperse submicrometer–and micrometer-sized particles, respectively. Aerosol concentrations and size distributions upstream and downstream of the filter foams were monitored by using a scanning mobility particle sizer (for particles with diameters smaller than 0.7 µ m) and an aerodynamic particle sizer (for particles larger than 0.7 µ m). The aerosol output was neutralized by a radioactive source. A lognormal-distribution curve with a mode of 0.25 µ m and a GSD of 6.2 was set as the primary target curve simulating the light-work ICRP deposition model. The results showed that the most penetrating size (also referred to as collection minimum) of the filter foams decreased upon increasing the foam porosity, packing density, and face velocity. In this work, the highest foam porosity and packing density we could acquire were 100 ppi and 0.2, respectively. By adjusting the face velocity, the most penetrating size was moved to 0.25 µ m, which happened to be the most penetrating size for ICRP light-work criterion. The whole aerosol penetration curve could further fit to the modified ICRP curve by adjusting the filter thickness. There are numerous ways to match the ICRP definition. This size-selective inlet becomes even more versatile if the auxiliary detector and vacuum system are operated under different flow rates to simulate light-to-heavy workloads.

Effects of extended storage of whole blood before leucocyte depletion on coagulation factors in plasma

The aim of this study was to evaluate the quality of leucocyte-depleted plasma produced from leucocyte-depleted whole blood, stored for different periods of times before filtration through polyurethane filters. Whole blood was collected, from 48 voluntary donors, into quadruple blood bag sets with integrated whole-blood filters, and stored at room temperature for 1, 2, 6, or 18 h before filtration. Five samples were taken: one directly from the donor; one immediately after collection; one before and one after filtration; and one from plasma units before freezing. All samples were analysed for the following parameters: prothrombin time; activated partial thromboplastin time; prothrombin fragments F1+2; fibrinogen; factors VIII, XI and XII; von Willebrand factor antigen; ristocetin cofactor activity; collagen-binding capacity; multimers; and complement C3a-desArg. Different whole-blood storage times before filtration did not have a significant effect on the stability of coagulation factors. The activity of all investigated coagulation factors in plasma was generally above 90 U/dl, even after 18 h of storage of whole blood before filtration. von Willebrand factor multimeric distribution remained stable throughout the process. However, activation of complement did occur during storage. Leucodepleted plasma originating from leucodepleted whole blood maintains a satisfactory level of coagulation factors, even after the storage of whole blood for 18 h at room temperature before filtration.

白血球除去フィルター及び放射線照射が血小板機能に及ぼす影響について

In the present study, we investigated the effects of radiation and leukocyte-reduction filters on platelet function. Platelet aggregation in response to collagen and ADP were measured prior to and after irradiation and filtration, as were the platelet recovery rate and complement factor C3. Four types of leukocyte-reduction filter were used, namely positively-, negatively-, and non-charged filters (all of polyester composition), as well as a polyurethane filter. Radiation itself did not significantly affect either the platelet recovery rate, platelet function, or C3 value. On the other hand, filtration through polyester leukocyte-reduction filters resulted in a significant reduction in the platelet recovery rate, an effect not observed with the polyurethane filter. However, none of the filters caused significant changes in platelet function or in C3 value. We concluded that radiation and filtration do not cause significant changes in platelet function, but polyurethane filters are superior to polyester filters in relation to platelet recovery.

Initial clinical experience with distal protection using the FilterWire in patients undergoing coronary artery and saphenous vein graft percutaneous intervention.

Percutaneous coronary intervention (PCI) of saphenous vein grafts (SVG) and native coronary arteries may be associated with embolization of particulate debris into the distal microcirculation. The FilterWire uses a polyurethane filter bag contained on a radiopaque loop to trap embolic debris during native vessel and SVG intervention. The objectives of this study were to assess the feasibility and safety of the FilterWire during PCI and to examine the size and content of the particulate debris captured during SVG and native vessel intervention. Early angiographic, in-hospital, and 30-day clinical outcomes were reviewed in 35 patients with 36 lesions treated with the FilterWire during PCI. Lesions were located in 22 (61%) native coronary arteries and in 14 (39%) SVGs. Multivessel coronary artery disease was present in 75% of patients. Lesions were complex (ACC/AHA complexity B2 or C) in 81% of cases. The FilterWire was successfully delivered and deployed distal to the site of coronary intervention in 92% of lesions, including 95% of native vessels and 82% of SVG lesions. Embolic debris was entrapped in 82% of these cases. The average particulate debris had a mean major axis of 490 microm (range, 45-3,302 microm) and minor axis of 226 microm (range, 33-1,677 microm). Although reduced flow was common (36.1%) when the FilterWire was in place, there were no sustained episodes of abrupt closure and only one (2.8%) patient developed sustained no-reflow after FilterWire removal. Distal branch vessel embolization was found in four (11.1%) cases. Major adverse cardiac events occurred in 5 (14%) of 35 patients treated with the device, although 2 of these patients were evolving an acute myocardial infarction at the time of the procedure; in patients meeting the prospectively defined inclusion criteria, the major adverse cardiac event was 6%. These results suggest that the FilterWire is a feasible and safe method of collecting particulate debris released during SVG and native vessel coronary intervention. Its benefit over conventional therapy and other distal protection devices is currently under study.