Mechanical Filtration Research Articles

Moisture‐Resistant Nanofiber Membrane Loaded with Copper‐Manganese‐Tin Oxides for Dust and CO Filtration in High Humidity Environments

AbstractThis study presents a novel protective membrane, (0.8MnCuSnOx‐NaCl)@M, designed for high‐efficiency filtration of dust particles and carbon monoxide (CO) gas offers superior moisture resistance, air permeability, and catalytic functionality in high‐humidity underground settings. The membrane, incorporating tin oxide‐doped CuMnOx into polyvinylidene fluoride (PVDF) fibers with sodium chloride (NaCl), achieves 99.99% air filtration efficiency, 323.68 mm s−1 air permeability, and 92.5% CO catalytic filtration efficiency. Concurrently, the membrane exhibited exceptional hydrophobicity, characterized by a substantial water contact angle of 116.7°, negligible water staining, and a high hydrostatic pressure rating of 2035 Pa, suitable for humid environments. Furthermore, the water absorption profile of the membrane featured a diminished hydroxyl vibrational band, accompanied by a sustained CO conversion efficiency, attesting to its resistance to moisture‐induced deterioration. Computational fluid dynamics (CFD) simulations further clarify the membrane's filtration mechanism, indicating its potential for selective CO and particle filtration. This study provides a reliable idea for the development of moisture‐resistant fiber membranes with high efficiency for filtration of dust and CO. and underscores the synergy of experimental and theoretical approaches.

Design and testing of an innovative electro-dynamic filter for gas turbine intake systems

Abstract Gas turbines require filtered air to preserve the efficiency and the life of the system. Different degradation processes can occur depending on the size and composition of the contaminants. The compressor’s performance can be negatively impacted by fouling and erosion, which alter the shape and roughness of the blades. To limit the effects of the aforementioned phenomena, multistage filtration systems are commonly installed to reduce the contamination at the gas turbine inlet. Traditionally, particle separation is performed through mechanical filtration, which means that the particles are trapped inside cartridges of porous materials. This typology of filter guarantees a high filtration efficiency but on the other hand, generates remarkable pressure drop increasing over time. Inertial filters instead separate contaminants from the flow by utilizing the effect of inertial force acting on solid particles. In recent years, electrostatic filters have become widespread. The fibers of the filters are charged with an electrostatic field before installation and this charge is capable of separating and attracting metallic particles from the airflow. However, the electrostatic field’s effect diminishes with the exposure time with this type of filter. This work presents an innovative electro-dynamic filtration system for gas turbine application. The geometry and electrical features of the devices are designed to keep low-pressure drop and high capturing efficiency over time. To achieve these goals, a numerical campaign is performed using an in-house OpenFOAM solver, which takes into account the effect of the electrostatic force of the Lagrangian phase. After the definition of the optimal geometry, experimental tests are performed to validate the numerical results. Finally, a comprehensive laboratory-scale campaign is carried out to evaluate filtration efficiency under various environmental conditions, including different types of contaminants, concentrations, and exposure times.

Dietary superdosing of phytase positively affects growth, mineral utilization and amino acid availability of channel catfish (Ictalurus punctatus)

The present study investigated the effects of supplementing high levels (superdosing) of dietary phytase on growth performance, mineral utilization and digestibility of amino acids in different regions of the gastrointestinal (GI) tract of fingerling channel catfish. The negative control (NC) diet was formulated with primarily soybean meal as a protein feedstuff which contributed 0.61 % total phosphorus (P) but was deficient in available P at 0.11 % of diet. Five other diets were formulated either with supplemental monocalcium phosphate at 1 % of diet in the positive control (PC), or supplemented with Quantum Blue phytase (AB Vista, Plantation, Florida) at 1000, 2000, 4000, or 8000 phytase units (FTU)/kg of diet. Groups of 20 catfish were each stocked into 24 aquaria operated as a closed, recirculating system with biological and mechanical filtration. All dietary treatments were assigned randomly to quadruplicate aquaria and initially fed at 6 % of total body weight per day. Feed quantities were adjusted weekly after weighing all fish in each aquarium as a group, and feeding levels were maintained close to apparent satiation throughout the 8-week feeding trial. Phytase supplementation significantly (P < 0.05) increased various responses of channel catfish including weight gain, feed efficiency, and protein retention compared to catfish fed the NC diet, resulting in values that were similar to catfish fed the PC diet. Moreover, catfish fed the phytase-supplemented diets had higher bone ash, calcium (Ca), magnesium (Mg), P, manganese (Mn), and zinc (Zn), as well as retention of Ca, Mg, P, iron (Fe), Mn, and Zn in whole-body tissues. Additionally, apparent availability of P from the posterior intestinal region increased with dietary phytase supplementation, with reduced excretion of nitrogen, Ca, Mg, P, copper (Cu), Mn, and Zn observed in comparison to fish fed the NC diet. Apparent digestibility coefficients for many of the indispensable and dispensable amino acids were increased by phytase supplementation, except for histidine, methionine, threonine, and taurine. This improvement in amino acid availability occurred only in the posterior region of the gastrointestinal tract. Channel catfish fed the diet containing 4000 FTU/kg diet had the highest postprandial plasma phosphorus level most of the time, except at 24 h after feeding. Based on these various responses, the optimal dietary phytase dosage was determined to average 5492 FTU/kg diet.

A Novel Piezoelectric Nonwoven Fabric for Recoverable High-Efficiency Filters.

Serious haze pollution, mainly caused by fine and ultrafine particulate matters (PMs) and aerosols, poses a significant threat to the public health, especially when the aerodynamic diameter is less than 2.5 μm. Electrostatic capture techniques, such as polymer electret filters and kinetic plasma processes, are widely used instead of mechanical filtration with high removal efficiency and low wind resistance (pressure drop). However, the inability to recharge, coupled with the generation of ozone byproducts, makes it challenging to meet the requirements for both recoverability and highly efficient filtration. Here, we propose an electrostatic filter as an alternative to conventional polymer electrets, aiming to achieve an ultrahigh removal efficiency, long-term performance stability, and reusability. Piezoelectric LiNbO3 (LN) particles are integrated into the polypropylene (PP) matrix through the melt-blown strategy to fabricate the LN/PP nonwoven fabric. Benefiting from the employment of piezoelectric LN particles, the LN/PP nonwovens exhibit an ultrahigh removal efficiency of 99.9% for PM0.3 to PM10. The airflow facilitates the sustained regeneration of piezoelectric charges on the surface of LN/PP nonwovens, thereby maintaining a removal efficiency of approximately 95% for continuous filtration over 11 days. Even after eight cycles of washing, the removal efficiency of the LN/PP nonwovens remains at nearly 90%, demonstrating the excellent reusability. Our proposed strategy offers an ingenious combination of high-efficiency and recoverability for filters, holding great promise for reducing plastic pollution.

Study on the performance of electrostatic agglomeration enhances magnetic filter material for filtering fugitive particles in the iron and steel industry

In this work, a new method is proposed to utilize a magnetic filter material to suppress the escape of fugitive particles in the iron and steel industry. The magnetic filter material was prepared using the impregnation method, exhibiting superior demagnetization resistance. The magnetic field effect generated by magnetic filter material was combined with the diffusion, interception, and inertial effects of traditional filtration mechanisms to enhance the removal of fugitive particles. The magnetic polyimide filter material improves the filtration efficiency of particles with a diameter less than 2.0 μm by approximately 20% compared with polyimide filter materials. In addition, the filtration performance was further enhanced through electrostatic agglomeration. When the positive electrode voltage is +18 kV, and the negative electrode voltage is −16 kV, after the bipolar pre-charging treatment of fugitive particles with a diameter of 0.1–1.0 μm, the magnetic polyimide filter material can achieve a filtration efficiency of more than 90%, the magnetic polyimide (P84), magnetic polyphenylene sulfide (PPS), and magnetic fiberglass filter materials all achieve a filtration efficiency of over 94% with a diameter of 0.5–1.0 μm. This study lays the foundation for the proposal new dust removal methods for the iron and steel industry.

Multi-steps microfiltration of micelles from fermentation of Streptomyces tsukubaensis and its impact on proteins retention and tacrolimus yield

This study reports the application of microfiltration Streptomyces tsukubaensis micelles from fermentation broths, for tacrolimus recovery, investigating the use of a new multi-step microfiltration approach. Equal volumes of acetone were added to the fermented broth, and the resultant mixture was processed through multi-step microfiltration at 26 °C in a pressurized chamber, with operational pressures of 1 bar and 2 bar, using membranes with pore sizes of 0.22 μm and 3.0 μm. The permeate was recirculated, configuring ten steps of operation using the same membrane. The analysis of micelles microfiltration focused on the influence of multi-step processes on permeate flow and time steps, allowing exploration of pore blocking models. The cake filtration mechanism was identified as predominant for global filtration. The study achieved a 97 % micelles rejection rate in ten steps with a 3.0 μm pore membrane at 1 bar. Protein retention was also studied, showing a final retention rate of 60 %, with 40 % of proteins in the final permeate. This multi-step filtration process acts as microfiltration for micelles and ultrafiltration for proteins, improving tacrolimus purity. However, the tacrolimus yield was reduced by 9 %, attributed to increased tacrolimus adsorption on the gel/cake layer surface rather than steric factors.

Dynamic behavior and mechanistic analysis in filtration of dilute particulate suspensions through nanofibrous membrane

Nanofibrous membranes have garnered significant interest in membrane filtration due to their high porosity, small pore sizes, and complex interconnected pore structures. Although many studies focus on size exclusion in surface filtration, the filtration behavior and mechanisms for particles smaller than the pore size have been relatively underexplored. In this study, membrane filtration using nanofibrous membranes was employed to elucidate the filtration behavior and mechanisms for polystyrene latex suspensions with particles smaller than the pore size. The results indicated that reducing fiber diameter decreases the pore size and enhances particle rejection, with particle retention occurring within the intricate three-dimensional nanofiber pore network. In contrast, the effect of the membrane’s basis weight was less significant compared to fiber diameter. This observation can be attributed to the concept of effective thickness; once this thickness is exceeded, particles are prevented from penetrating deeper into the membrane. The filtration model was analyzed using Hermans-Bredée blockage filtration theory and cake filtration theory, considering the mass of trapped particles within the membranes. The model characterizes the filtration process as initially following standard blocking, progressing to cake filtration once a sufficient number of pores become clogged.

Energy-Efficient and Accelerated Resource Allocation in O-RAN Slicing Using Deep Reinforcement Learning and Transfer Learning

Abstract Next Generation Wireless Networks (NGWNs) have two main components: Network Slicing and Open Radio Access Networks (O-RAN). NS is needed to handle various Quality of Services (QoS). O-RAN adopts an open environment for network vendors and Mobile Network Operators (MNOs). In recent years, Deep Reinforcement Learning (DRL) approaches have been proposed to solve some key issues in NGWNs. The primary obstacles preventing the DRL deployment are being slowly converged and unstable. Additionally, these algorithms have enormous carbon emissions that negatively impact climate change. This paper tackles the dynamic allocation problem of O-RAN radio resources for better QoS, faster convergence, stability, lower energy and power consumption, and reduced carbon emissions. Firstly, we develop an agent with a newly designed latency-based reward function and a top-k filtration mechanism for actions. Then, we propose a policy Transfer Learning approach to accelerate agent convergence. We compared our model to another two models.

Open-cell ceramic foam filters for melt filtration: Processing, characterization, improvement and application

Open-cell ceramic foams are widely used as filters for the purification of molten metals due to their high permeability and high efficiency for capturing non-metallic inclusions. With the consideration of manufacture and filtration behaviour, most filters are produced by replica methods. The intrinsic multiscale porous structure requires the ceramic foams to have sufficient strength. As a consequence, different processing approaches, material compositions and characterizations are investigated. Meanwhile, to further enhance the filtration performance, the functionalization of ceramic foam filters is often conducted with surface coating. This review summarizes the processing and characteristics of ceramic foam filters (CFFs), the nature and formation of non-metallic inclusions (NMIs), the filtration mechanism and applications of CFFs. The characterization of mechanical and filtration performance, as well as the corresponding strengthening and functionalization methods are also presented.

A brief history and future directions of dielectrophoretic filtration: A review.

Dielectrophoresis (DEP) is an electrokinetic effect first studied in the early 20th century. Since then, DEP has gained significant interest in research, owing to its ability to solve particle separation problems in various industries. Dielectrophoretic filtration (DEP filtration) is a separation method using DEP to filter a wide range of microparticles, from bacterial cells to catalytic particles. DEP filtration can selectively separate particles based on size or dielectric properties, recover trapped particles and avoid common problems associated with mechanical filtration based on pore size (e.g. pressure drops and regular filter replacements). This review describes the simple beginnings of DEP filtration and how our understanding and applications for DEP filtration have progressed over time. A brief section of DEP theory as well as a note on the general outlook for DEP filtration in the future is presented. DEP filtration offers an exciting opportunity to selectively separate diverse particle mixtures. To achieve such a feat, technical challenges such as Joule Heating and low throughputs must be addressed.

Prediction and analysis of dominant factors influencing moisture content during vacuum screening based on machine learning

The study of the dominant factors influencing moisture content is essential for investigating vacuum filtration mechanisms. In view of the present situation where there is insufficient experimental data and the dominant factors influencing the moisture content of a filter cake have not been identified, in this study a vacuum filtration apparatus was designed and constructed. Quartz sand particles were used as the filtration material. 300 datasets of moisture contents of a filter cake were obtained under different experimental conditions. Multiple Linear Regression, artificial neural network, decision tree, random forest, and extreme gradient boosting were used to establish a prediction model for moisture content during vacuum screening. By comprehensively analyzing the feature importance rankings and the effects of positive and negative correlations, the dominant factors influencing the moisture content of the filter cake during vacuum screening were the particle ratio, screen mesh, and airflow rate. This finding not only provides a scientific basis for the optimization of vacuum screening technology but also points the way for improving screening efficiency in practical applications. It is of significant importance for deepening the understanding of the vacuum screening mechanism and promoting its extensive application.

Parabens, bisphenols, and triclosan in coral polyps, algae, and sediments from sanya, China: Occurrence, profiles, and environmental implications

Parabens, bisphenols (BPs), and triclosan (TCS) are common environmental phenols widely applied in industrial products, pharmaceuticals, and personal care products. They are endocrine disruptors and pervade the natural environment, causing significant detrimental impacts on ecosystems, including marine habitats. Therefore, in this study, 40 samples comprising coral polyps, algae, and sediments were collected from Sanya, Hainan Province, China, in which the presence and compositional profiles of parabens, BPs, and TCS were examined to identify their fate in the oceans. The results unveiled the ubiquitous occurrence of at least one paraben or bisphenol in all samples, with TCS detected in over 80% of cases. Notably, coral samples contained the most contaminants (median concentration: 9.42 ng/g dry weight-dw), followed by sediment samples (5.95 ng/g dw) and algal samples (3.58 ng/g dw). Attributed to their broadest application, methylparaben (MeP) and propylparaben (PrP) emerged as the primary paraben constituents. MeP displayed the highest median concentration in coral samples (4.42 ng/g dw), probably related to its high-water solubility and the filtration mechanism employed by the coral polyps during seawater intake. Intriguingly, bisphenol P (BPP) superseded bisphenol A (BPA) as the dominant bisphenol, especially in the algal samples, probably owing to the lipophilic character of BPP and the enhanced biodegradability of BPA within aquatic environments. The highest concentration of TCS (3.44 ng/g dw) was found in the sediment samples, associated with its long half-life in the sediments. Furthermore, the correlation between multiple parabens and TCS implies their co-use to augment antimicrobial efficacy. Future research should prioritize the examination of these phenols in diverse marine environmental media. Corresponding toxicological experiments should be conducted to visualize their transport dynamics, degradation byproducts, and toxicity to marine biota to gain insights into the risks they pose to the marine ecosystem.

Effectiveness of the recirculation air cleaner in real conditions at variation of the air flow and PM2.5 content

Technical data on the effectiveness of air purifiers are usually obtained in laboratory conditions in special aerosol stands with test chambers or boxes of a small volume, while in real conditions the purifiers are used in rooms with a volume of at least 40-60 m3 with a permanent presence of people (distribution respiratory diseases emitted with breathing) and entry of PM2.5..PM10 particles into the room from working equipment (printers, chargers, power tools, etc.). There are already enough scientific materials on this matter, which prove that the actual efficiency of air purifiers in real conditions is much lower than the data given by the manufacturers. Therefore, there is a need to determine the optimal performance of the air purifier in real conditions in order to achieve the WHO recommended levels of safe indoor pollution with a maximum time interval of 1 hour, besides, taking into account that the air outside has a higher level of pollution with particles of PM 2.5. In this study, we strive to obtain a PM 2.5 value of 5 μg/m3 with a PM2.5 level in the air outside of 16.7 μg/m3. The calculated value of CADR for light pollution should be at least half of the power of the air purifier for the projected cleaning duration of no more than 1 hour. A smaller value of CADR leads to further accumulation of pollutants, which reduces the work of the cleaner. In this study, the value of CADR was at L=100 m3/hour the value of CADR= 59 m3/hour with the efficiency of filter inserts in 73% and natural sedimentation of particles in 25%, and at L=310 m3/hour the value of CADR= 59 m3/hour at efficiency of filter inserts in 94% and natural sedimentation of particles in 18%. The process of natural deposition and the amount of external pollution do not allow to clean the air without the use of mechanical filtration for any of the pollutants specified in the study.

Ionic-liquid/Carbowax 20 M functionalized capsule phase microextraction platform for the extraction of phosphodiesterase-5 inhibitors from human serum and urine prior to their determination by LC–MS

Capsule phase microextraction (CPME) is an efficient bioanalytical technique that streamlines the sample preparation by integrating the filtration and stirring mechanism directly into the device. A novel composite sorbent designed to be selective towards the target analytes consisting of mixed-mode sorbent chemistry synthesized by sol–gel technology is found promising and superior to the conventional C18 sorbents. Herein we describe the encapsulation of an ionic liquid (IL)/Carbowax 20M-functionalized sol–gel sorbent (sol–gel IL/Carbowax 20 M) in the lumen of porous polypropylene tubes for the capsule phase microextraction of three phosphodiesterase-5 inhibitors namely avanafil, sildenafil, and tadalafil in human serum and urine samples. The CPME device was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The experimental parameters of CPME procedure (e.g. sample pH and ionic strength, extraction time, stirring rate, elution solvent and volume) were carefully optimized to achieve the highest possible extraction efficiency for the analytes. Method validation was conducted in terms of precision, linearity, accuracy, matrix effect, lower limits of quantification, and limits of detection (LOD). The method linearity was investigated in the range of 50–1000 ng mL−1 for all analytes while the precision was less than 11.8 % in all cases. For all analytes, the LOD values were 17 ng mL−1. The IL/CW 20M-functionalized microextraction capsules could be reused at least 25 times both for urine and serum samples. The green character and the applicability of the proposed method were evaluated using the ComplexGAPI and BAGI indexes. The optimized CPME protocol exhibited reduced consumption of organic solvent and generation of waste, cost-effectiveness, and simplicity. Finally, the proposed method was successfully applied to the analysis of sildenafil in human urine after administration of drug-containing formulation.

Single-use chromatographic clarification to eliminate endonuclease treatment in production of recombinant adeno-associated viral vectors

In current manufacturing processes for recombinant adeno-associated viral vectors (rAAV), endonuclease treatment is used prior to depth filtration to break down host cell DNA that is released from cells post-lysis. Without this treatment, traditional depth filters exhibit negligible clearance of host cell DNA, a key process-related impurity. In this work, we evaluate single-use chromatographic clarification using Harvest RCTM filters (3 M) to process rAAV8 and rAAV9 HEK293 cell culture lysate with and without endonuclease pretreatment. We demonstrate endonuclease-free clarification for both serotypes with yield >90 % and up to 3 log reduction of host cell DNA, from >104 ng/mL to <50 ng/mL, matching or exceeding the filtrate quality in traditional depth filtration with 100 U/mL of endonuclease added during lysis. The addition of 100 mM of salt in the harvest buffer is also shown to improve filtration throughput, prevent filter clogging, and limit rAVV binding to the filter device. Finally, a mechanistic cake-fiber fouling model is shown to be a good representation of the Harvest RCTM filtration mechanism. The endonuclease-free clarification approach enables cost savings of USD 100,000 per 500 L batch, equivalent to the cost of cGMP-grade endonuclease at this scale. The benefits of endonuclease-free clarification further include easier raw material sourcing as well as eliminating the need for a residual endonuclease assay in rAAV manufacturing processes.

Enhanced sludge dewatering using a novel synergistic iron/peroxymonosulfate-polyacrylamide method

In the sludge dewatering process, a formidable challenge arises due to the robust interactions between extracellular polymeric substances (EPS) and bound water. This study introduces a novel, synergistic conditioning method that combines iron (Fe2+)/peroxymonosulfate (PMS) and polyacrylamide (PAM) to significantly enhance sludge dewatering efficiency. The application of the Fe2+/PMS-PAM conditioning method led to a substantial reduction in specific filtration resistance (SFR) by 82.75% and capillary suction time (CST) by 80.44%, marking a considerable improvement in dewatering performance. Comprehensive analyses revealed that pre-oxidation with Fe2+/PMS in the Fe2+/PMS-PAM process effectively degraded EPS, facilitating the release of bound water. Subsequently, PAM enhanced the flocculation of fine sludge particles resulting from the advanced oxidation processes (AOPs). Furthermore, analysis based on the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory demonstrated shifts in interaction energies, highlighting the breakdown of energy barriers within the sludge and a transition in surface characteristics from hydrophilic (3.79 mJ m−2) to hydrophobic (−61.86 mJ m−2). This shift promoted the spontaneous aggregation of sludge particles. The innovative use of the Flory-Huggins theory provided insights into the sludge filtration mechanism from a chemical potential perspective, linking these changes to SFR. The introduction of Fe2+/PMS-PAM conditioning disrupted the uniformity of the EPS-formed gel layer, significantly reducing the chemical potential difference between the permeate and the water in the gel layer, leading to a lower SFR and enhanced dewatering performance. This thermodynamic approach significantly enhances our understanding of sludge dewatering and conditioning. These findings represent a paradigm shift, offering innovative strategies for sludge treatment and expanding our comprehension of dewatering and conditioning techniques.

Re-Circulatory Aquaculture Systems: A Pathway to Sustainable Fish Farming

Recirculating Aquaculture Systems (RAS) represent a transformative approach to sustainable fish farming that offers a viable solution to meet the growing global demand for seafood while minimizing environmental impact. These closed-loop systems recirculate and reuse water, reducing water consumption by up to 99% compared to traditional aquaculture methods. RAS also mitigate the risk of disease transmission, escapement, and pollution by isolating farmed fish from natural populations and the surrounding environment. Technologically advanced RAS employ mechanical filtration, biological filtration, and disinfection processes to maintain optimal water quality for fish growth. This high level of control allows for the farming of a wide range of species, including predatory finfish, in locations far from coastal areas. Furthermore, the integration of aquaponics in RAS enables the production of high-quality vegetables and herbs using the nutrient-rich wastewater, creating a sustainable closed-loop system. Despite the higher initial investment required, RAS have demonstrated consistent profitability and the potential for significant returns. By promoting "in-sourcing" and creating local jobs, RAS can contribute to the economic development of communities while reducing the carbon footprint associated with international seafood trade. As the aquaculture industry continues to evolve, RAS are poised to play a crucial role in ensuring the long-term sustainability of fish farming. By combining technological advancements with environmental stewardship, RAS offer a promising pathway towards meeting the world's growing demand for seafood while preserving the health of our aquatic ecosystems.

Negative Voltage Electrospinning for the Production of Highly Efficient PVDF Filters

AbstractIn recent years, the demand for filter media has increased dramatically, driven by the need to manufacture personal protective equipment and for various applications in the industrial and civil sectors. Nanofiber‐based membranes are proposed as potential alternatives to commercial filtration devices. This study presents the design and implementation of an innovative pre‐industrial electrospinning setup, combining a negatively charged spinneret and a positively charged counter‐electrode, capable of producing polyvinylidene fluoride (PVDF) nanofibers with an average diameter of 410 nm and electrostatic surface potential values 3.7 times higher compared to a conventional electrospinning process, eliminating the need for further post‐treatment. These properties are essential for improving mechanical and electrostatic filtration of small particles, including infectious droplets. The surface potential of the membranes is also long‐lasting, as evidenced by tests one year after manufacture. As a case‐study, these filters are used to manufacture surgical masks, reporting excellent performance in terms of bacterial filtration efficiency (BFE) up to 99.9%, and breathability (29.8±4.5 Pa cm−2) when compared to commercially available meltblown polypropylene (PP) face masks, and also complied with the stringent European standard (EN14683:2019) for type‐II surgical masks. Furthermore, the pre‐industrial setup allows for increased production capacity of up to 42 000 m2 per year, suitable for large‐scale production.

Bio‐inspired hierarchical bamboo‐based air filters for efficient removal of particulate matter and toxic gases

AbstractAir pollution is caused by the perilous accumulation of particulate matter (PM) and harmful gas molecules of different sizes. There is an urgent need to develop highly efficient air filtration systems capable of removing particles with a wide size distribution. However, the efficiency of current air filters is compromised by controlling their hierarchical pore size. Inspired by the graded filtration mechanisms in the human respiratory system, microporous ZIF‐67 is in situ synthesized on a 3D interconnected network of bamboo cellulose fibers (BCFs) to fabricate a multiscale porous filter with a comprehensive pore size distribution. The macropores between the BCFs, mesopores formed by the BCF microfibers, and micropores within the ZIF‐67 synergistically facilitate the removal of particulates of different sizes. The filtration capabilities of PM2.5 and PM0.3 could reach 99.3% and 98.6%, respectively, whereas the adsorption of formaldehyde is 88.7% within 30 min. In addition, the filter exhibits excellent antibacterial properties (99.9%), biodegradability (80.1% degradation after 14 days), thermal stability, and skin‐friendly properties (0 irritation). This study may inspire the research of using natural features of renewable resources to design high‐performance air‐filtration materials for various applications.

Multifactorial evaluation of an ultra-fast process for electrospinning of recycled expanded polystyrene to manufacture high-efficiency membranes for nanoparticle air filtration

The increased production of polystyrene waste has led to the need to find efficient ways to dispose of it. One possibility is the use of solid waste to produce filter media by the electrospinning technique. The aim of this work was to develop an ultra-fast electrospinning process applied to recycled polystyrene, with statistical evaluation of the influence of polymeric solution parameters (polymer concentration and percentage of DL-limonene) and process variables (flow rate, voltage, and type of support) on nanoparticle collection efficiency, air permeability, and fiber diameter. An extensive characterization of the materials and evaluation of the morphology of the fibers was also carried out. It was found that recycled expanded polystyrene could be used in electrospinning to produce polymeric membranes. The optimized condition that resulted in the highest nanoparticle collection efficiency was a polymer concentration of 13.5%, percentage of DL-limonene of 50%, voltage of 25 kV, and flow rate of 1.2 mL/h, resulting in values of 99.97 ± 0.01%, 2.6 ± 0.5 × 10−13 m2, 0.19 Pa-1, and 708 ± 176 nm for the collection efficiency of nanoparticles in the range from 6.38 to 232.9 nm, permeability, quality factor, and mean fiber diameter, respectively. All the parameters were found to influence collection efficiency and fiber diameter. The use of DL-limonene, a natural solvent, provided benefits including increased collection efficiency and decreased fiber size. In addition, the electrostatic filtration mechanism was evaluated using the presence of a copper grid as a support for the nanofibers. The findings demonstrated that an electrospinning time of only 5 min was sufficient to obtain filters with high collection efficiencies and low pressure drops, opening perspectives for the application of polystyrene waste in the development of materials with excellent characteristics for application in the area of atmospheric pollution mitigation.