Particulate Matter Removal Efficiency Research Articles

Biodegradable Facemasks: Biodegradable, Efficient, and Breathable Multi‐Use Face Mask Filter (Adv. Sci. 6/2021)

In article number 2003155, Jeyoung Park, Dongyeop X. Oh, Sung Yeon Hwang, and co‐workers report a biodegradable, moisture‐resistant, highly efficient, and breathable face mask filter based on easy‐to obtain poly(butylene succinate) coated with chitosan nanowhiskers. Integrated microfiber/nanofiber mats present a particulate matter removal efficiency as high as the commercial N95 filter due to a combination of physical sieving and electrostatic adsorption.

Low-Resistance Thiophene-Based Conjugated Microporous Polymer Nanotube Filters for Efficient Particulate Matter Capture and Oil/Water Separation

Air and water pollution poses a serious threat to public health and the sustainable development of the ecological environment. Here, we report the fabrication of new low-resistance nanofilters based on thiophene-based conjugated microporous polymer (T-CMP) nanotubes to remove harmful particulate matter (PM) from air effectively. T-CMP nanotube filters feature inherent superhydrophobicity and hierarchical pores and are prepared by a facile one-pot synthesis. The PM removal efficiency of T-CMP nanotube filters at 90 ± 5% relative humidity exceeds 99.798 ± 0.055% for PM0.3 and 99.998 ± 0.002% for PM2.5, while the lowest pressure drop in the filtration system is only 5 Pa, which is 1-2 orders of magnitude lower than that of traditional fiber-based filters. Benefitting from their excellent porous feature and intrinsic superhydrophobicity, T-CMP nanotube filters also display higher flux during continuous oil-water separation. Based on this superior separation performance, better physicochemical stability, facile manufacturing, and easy scaling-up, such T-CMP nanotube filters might hold great potential for a wide range of applications even under harsh conditions, including PM removal, water treatment, and so on.

Reusable Self-Sterilization Masks Based on Electrothermal Graphene Filters

Surgical mask is recommended by the World Health Organization for personal protection against disease transmission. However, most of the surgical masks on the market are disposable that cannot be self-sterilized for reuse. Thus, when confronting the global public health crisis, a severe shortage of mask resource is inevitable. In this paper, a novel low-cost electrothermal mask with excellent self-sterilization performance and portability is reported to overcome this shortage. First, a flexible, ventilated, and conductive cloth tape is patterned and adhered to the surface of a filter layer made of melt-blown nonwoven fabrics (MNF), which functions as interdigital electrodes. Then, a graphene layer with premier electric and thermal conductivity is coated onto the MNF. Operating under a low voltage of 3 V, the graphene-modified MNF (mod-MNF) can quickly generate large amounts of heat to achieve a high temperature above 80 °C, which can kill the majority of known viruses attached to the filter layer and the mask surface. Finally, the optimized graphene-modified masks based on the mod-MNF filter retain a relatively high particulate matter (PM) removal efficiency and a low-pressure drop. Moreover, the electrothermal masks can maintain almost the same PM removal efficiency over 10 times of electrifying, suggesting its outstanding reusability.

Facile synthesis of porous organic polymers (POPs) membrane via click chemistry for efficient PM2.5 capture

Global environmental problems are facing serious challenges, especially the harm of air pollution to human health. It is meaningful to capture harmful particulate matter (PM) in the air. In this work, we report for the first time the facile synthesis of porous organic polymers (POPs) with macroporous structure, which were synthesized using 1,4-benzenedithiol, 1,4-diethynylbenzene and 1,3-benzenedithiol via click chemistry, for efficient PM capture. PM filtration measurement was simulated by the release of particulate pollutants from cigarette smoke. The test results of porous composite membranes (PCMs) show a high PM removal efficiency for PM2.5 (≥99.80 ± 1.58%) and PM10 (≥99.89 ± 0.89%) in 30 h. The PCMs based on kapok fiber not only has good mechanical properties, but also can be made into membranes of different sizes depending on the size of the substrate. Taking advantage of their simple one-step synthesis via click chemistry with great potentials for scale-up under mild conditions, such PCMs may find useful applications in PM capture.

Development of an Integrated Electrostatic Precipitator and Wet Scrubber System for Controlling Nox and Particulate Matter Emissions From a Semiconductor Manufacturing Process

An integrated electrostatic precipitator (ESP) and wet scrubber system were developed to control nitrogen oxides (NOx) and particulate matter (PM) emissions from a semiconductor manufacturing process. The integrated system consisted of a NO oxidizer, wet scrubber, and ESP. In the NO oxidizer, NO gas was fully oxidized to NO2 by O3 before the flow gas entered the wet scrubber. To control NO2, Na2S was used as a reducing agent, and NaOH was added to suppress H2S in the wet scrubber. The NO2 removal efficiency could be controlled by maintaining an oxidation-reduction potential higher than −330 mV, and H2S was suppressed by keeping the pH higher than 11. To ensure there was no PM peak during the cleaning cycle, dual-type cylindrical collection plates containing a water film were designed. A negative voltage of 15 kV was applied to the collection plate, and the PM removal efficiency was higher than 95%. The experimental particle-removal efficiency was higher than the theoretical value because the ion loading by plasma in the point of use scrubber was greater than the theoretically calculated value. In addition, the PM removal efficiency was maintained at 95% for 60 min through the water film. The integrated ESP and scrubber system were able to control NOx and PM for long periods at a removal efficiency of over 95%.

The PM removal process of wetland plant leaves with different rainfall intensities and duration

Today, particulate-matter (PM) pollution has become one of the most severe air-pollution problems. As the most commonly used method in daily life, phytoremediation can use plant organs (such as leaves) as biological filters for pollutants to repair the atmosphere. At the same time, rainfall can remove PM from plant-leaf surfaces and enable them to adsorb PM again. By simulating natural rainfall, the rainfall characteristics are quantified as rainfall intensity and rainfall duration, and we use the washout-weighing method to obtain the amount of PM removed from the leaf surface. Then, use a scanner to scan the leaves after rain to get their images, and use Image J software to process the images to obtain leaf area. Finally, the amount of PM removed by rain per unit leaf area can be calculated. It will be used to explore the impact of different rainfall intensity and duration on the removal of PM from the leaf surface of wetland plants. The results showed that under three rainfall intensities used in this experiment, the removal of PM from plant-leaf surfaces all increased with an increase in rainfall duration. When the particle size is 10-100-μm, and the rainfall intensity is 30 mm/h, the removal amount of plant particles tested in this experiment is the largest. With increased rainfall duration, the removal of PM from plant-leaf surfaces increased sharply at first, then slowly, and finally tended to be stable. The removal efficiency of PM on the blade surface is most apparent at the early stage of rainfall, and then gradually weakens. Among the four wetland plants tested in this experiment, in the range of 10-100-μm, the number of PM on the leaf surface of Scirpus validus is the largest, and the optimum rainfall intensity is 30 mm/h; in the range of 2.5–10-μm, the number of PM on the leaf surface of Typha orientalis is the largest, and the optimal rainfall intensity is 30 mm/h; in the range of 0.45–2.5-μm, the number of PM on the leaf surface of Iris wilsonii is the largest, and the optimal rainfall intensity is 15 mm/h. Wetland species with high particle accumulation capacity can provide references for vegetation restoration of degraded wetland plants and plant cultivation in constructed wetlands. At the same time, the best rainfall intensity and duration for removing particulate matter on the surface of plant leaves were obtained through experiments, which provided a reference for the design of automatic plant irrigation systems and dust removers in different scenarios.

Performance evaluation and process simulation for synergetic removal of NOx, CO2 and PM using green alkaline solution in a high-gravity rotating packed bed

The high-gravity rotating packed bed (HiGee RPB) developed here can simultaneously remove multiple air pollutants using alkaline solution, thus achieving the flue gas deep purification. The electric-arc-furnace reduction slag (EAFRS) leachate was then used as the alkaline absorbent in HiGee RPB for assessing the removal efficiencies of nitrogen oxide (NOx), carbon dioxide (CO2) and particulate matters (PM) from flue gas. The results indicated the changes to the CO2 capture was enhanced by increasing the initial PH value of the alkaline solution. In contrast, this value has no significant influence on NOx removal. The suitable NOx removal efficiency ranged from 90.9% to 97.09% at the liquid-to-gas (L/G) ratio of 0.01 and high gravity factor of 58.9 to 368. The precipitated calcium carbonate gained from carbonation via HiGee process exhibited similar physical properties to commercial products. In addition, 95.9% of PM removal efficiency was achieved at the L/G ratio and high gravity factor of 0.03 and 235.4, respectively. This treatment furthermore demonstrated a high efficiency for PM collection of over 90% and balanced the energy consumption. Based on the result, an Aspen simulation and a preliminary cost-benefit analysis were carried out to develop a mass-balance model for this system and determine the favorable operating conditions.

Effect of water microdroplet size on the removal of indoor particulate matter

The effective removal of indoor particulate matter (PM) has received considerable attention due to the harmful effects of airborne PM on human health. Although various techniques have been introduced to remove indoor PM, no impeccable method has been established. In this study, we proposed the use of microscale water droplets produced by the ultrasonic module of a commercial household ultrasonic humidifier (UH) for effective PM removal. Water droplet size was regulated using micropinholes. The effect of water microdroplet size on the removal of indoor PM was experimentally investigated. Normalized PM concentration, PM removal efficiency and PM deposition constant were assessed by analyzing the measured temporal variations in PM concentration inside a test chamber. The PM deposition constants measured in this study were compared with those of other previous studies. Deposition events were quantitatively visualized by using a high-speed camera attached with a long-distance microscope. The increase in the deposition rate of surface area and the PM collection ratio were analyzed using digital image processing to examine the interactions between PM particles and water microdroplets with different droplet sizes. As a result, the removal efficiency of PM2.5 particles reaches up to 56.2% when water droplets of d = 2 μm are used. The PM10 removal efficiency is also increased by 73.9% within the initial 30 min. The deposition constant for the smallest water droplets of d = 2 μm is drastically increased. In addition, the increasing rate of the deposition surface area is exponentially increased, as the size of water droplets decreases. The small microscale water droplets generated by a commercial UH attached with a micropinhole are found to be effective for the removal of indoor PM.

Performance Evaluation of Hybrid Air Purification System with Vegetation Soil and Electrostatic Precipitator Filters

This paper describes designing, manufacturing, and evaluating an eco-friendly modular-type air purification system to enhance the removal efficiency of fine particulate matter (PM) in urban public spaces, especially in hotspots. This system consists of artificial soil based-vegetation and electrostatic precipitator (ESP) filters. Unlike the so-called passive removal method, which adsorbs fine PM only by the leaves of plants, the vegetation soil filter based on multi-layered different artificial soils adopts an active removal method in which air purification is performed in the soil itself, bypassing external air by using the air circulation fan in the soil. The ESP filter is designed and evaluated to have a high fine PM removal efficiency, even at high suction velocity, to remove large amounts of outdoor fine PM. Throughout the experimental measurements on the hybrid air purification system with vegetation soil and ESP filters, it is observed that the vegetation soil filter has a 78.5% reduction efficiency for PM2.5 and a 47% for PM10 at the inlet air velocity of 0.15 m/s. The ESP filter also has a 73.1% reduction efficiency for PM2.5 and 87.3% for PM10 at an inlet air velocity of 3 m/s. Based on the performance evaluations of the vegetation soil filter and the ESP filter, it is noted that each individual module will be applied to an air purification tower with vertical expansion and installed in a high concentration area of fine PM in a downtown area to contribute to the fine PM reduction in the community.

Highly Improved Performance of Cotton Air Filters in Particulate Matter Removal by the Incorporation of Metal-Organic Frameworks with Functional Groups Capable of Large Charge Separation.

Currently, air contamination, especially with particulate matters (PMs), is severe in several countries. To increase the efficiency of air filters in PM removal, metal-organic frameworks (MOFs, here, Zr-MOFs, especially with functional groups (FGs) such as -NO2) were coated, after synthesis, onto cotton using covalent bonding for the first time. The removal efficiencies (REs) and quality factors (QFs) of cottons with or without MOFs were in the order: cotton < Zr-MOF/cotton < Zr-MOF-NH2/cotton < Zr-MOF-NH-SO3H/cotton < Zr-MOF-NH3+Cl-/cotton < Zr-MOF-NO2/cotton. This monotonic increase in the PM removal efficiency or QF could be explained with the order of charge separation or developed charges (total, in absolute value: ∼0 to 2.0) on FGs of MOFs. Importantly, Zr-MOF-NO2 coating on cotton showed a very high increase in the performance of cotton in PM removal. QF and RE of Zr-MOF-NO2/cotton were 4.6 times and 6.2 times of the bare cotton, respectively, for PM2.5 removal, even with a very small increase in pressure drop (3 Pa or less) with MOF coating. Based on the research, it can be suggested that coating MOFs on substrates is a promising way to improve the performances of air filters for PM removal, especially when MOFs have FGs that can have large charge separation such as -NO2. This work may pave a way to utilize a functionalized MOF in the effective removal of PMs from air.

Removal of particulate matter from pork belly grilling gas using an orifice wet scrubber

Grilling restaurants are a major contributor to airborne particulate matter (PM) in metropolitan areas. In this study, the removal of PM during the grilling of pork belly using an orifice scrubber, which is a form of gas-induced spray scrubber, was assessed. During grilling, the particle mass concentration was the highest for 1.0 < PM ≤ 2.5 μm (55.5% of total PM emissions), followed by 0.5 < PM ≤ 1.0 (27.1%), PM ≤ 0.5 (10.7%), and PM > 2.5 μm (7.0%). The PM removal efficiency of the orifice scrubber at a gas flow of 4.5 m3 min−1 was > 99.7% for PM ≥ 2.5 μm, 89.4% for 1.0 < PM ≤ 2.5 μm, 62.1% for 0.5 < PM ≤ 1.0, and 36.5% for PM ≤ 0.5 μm. Although further research is necessary to optimize its use, the orifice scrubber offers a user-friendly technology for the control of PM in small grilling restaurants because of its simple design, uncomplicated operation, and satisfactory PM removal performance.

Charged graphene aerogel filter enabled superior particulate matter removal efficiency in harsh environment

Fine particles pose a dangerous threat to our environment and human health. Although a series of air filters have been developed, to achieve high removal efficiency while maintaining a low pressure drop is still a challenging task. Herein, we introduce an additional force into action – the space charge when designing the filter to capture the particulate matters (PMs). The corona discharge drives the PMs toward graphene aerogel filter under the imposed electrostatic force. The prepared filter displays a very high PM removal efficiency and low pressure drop under an extremely high concentration (>10000 μg/m3) of both non-oily particles (>99.9%) and oily particles (>99.6%). In addition, the filter also has the advantages of being active, reusable, and flame-retardant. This charged graphene aerogel filter (CGAF) is very stable and can withstand 10 times washing and 5-min burning.

Field method to evaluate particulate matter removal efficiency of heat recovery ventilation systems for apartment buildings

Field method to evaluate particulate matter removal efficiency of heat recovery ventilation systems for apartment buildings

Efficient removal of indoor particulate matter using water microdroplets generated by a MHz-frequency ultrasonic atomizer

Airborne particulate matter (PM) has emerged as an important global environmental and social issue due to its harmful health effects. Various techniques have been introduced to remove indoor PM. However, an effective and sustainable method has not been established yet because of complex mechanisms and various factors. Here, we propose the use of water microdroplets generated by a MHz-frequency ultrasound, and experimentally examine the effects of the generated microdroplets on PM removal. The PM removal efficiency and PM deposition constant are analyzed by measuring the temporal variation of PM concentration. The measured experimental results are compared with analytical deposition constants. Two collection efficiencies derived in previous studies are employed to substitute a mathematical model used for determining the analytical deposition constants. In addition, the mean diameter and the moving velocity of the microdroplets are experimentally measured via a digital holographic microscopy and particle image velocimetry generated by a MHz-frequency atomizer. The present results demonstrate that water microdroplets generated by the atomizer can be effectively used to remove PM.

Co-removal of CO2 and particulate matter from industrial flue gas by connecting an ammonia scrubber and a granular bed filter

Industry emits huge amount of CO2 and particulate matter (PM) in the form of flue gas. In the context of climate change mitigation and air pollution control, preventing and reducing CO2 and PM from industrial flue gas are of great significance. CO2 and PM are currently removed separately, which puts a burden on environmental investment and land occupancy. In this work, a novel co-removal system is designed for simultaneously and synergistically removing CO2 and PM from industrial flue gas, by connecting an ammonia scrubber (AS) and a granular bed filter (GBF) in series. To validate the concept, an experimental apparatus was built, and the parameters influencing the CO2 and PM removal efficiencies in the AS, GBF and the whole system are investigated. Results show the CO2 and PM removal efficiencies of the co-removal system are 89.46% and 99.76%, respectively, and are higher than that of each single subsystem. In addition, the optimal operating conditions of the co-removal system are determined, including ammonia flow rate, ammonia concentration, filter materials filled in the GBF upper layer, filter materials’ size, and the GBF upper layer height. In addition, the influence and sensitivity of their variations on the system removal efficiency are analysed.

New electrostatic precipitator with dielectric coatings to efficiently and safely remove sub-micro particles in the building environment

The influx of ambient particulate matter (PM) to the indoor environment has threatened human health due to its adverse impacts on respiratory, cardiovascular, and neurological systems. Consequently, PM removal devices with high efficiency and low cost like electrostatic precipitator (ESP) are essential for a healthy and sustainable indoor environment. Traditional two-staged ESP includes particle charging and collection part. In this study, we innovated the collection part by coating the repelling electrodes with dielectric films. Four performance influencing parameters were examined: the voltage difference (Vc) and distance (dc) between the repelling and collecting electrodes, and both the dielectric material and thickness (de). The new ESP achieved its best performance when coated with PET (de =60 μm) at dc =3 mm. The breakdown voltage was promoted from −4 kV (without dielectric film) to −9 kV, and PM removal efficiency was enhanced from 60 % to 92 %. The new ESP had low net ozone production (3–5 ppb), low pressure drop (10–13 Pa), and low energy consumption (18 W/m2), making it an eco-friendly device. Running continuously for one week, the new ESP maintained a single-pass PM removal efficiency of around 90 %, notwithstanding changes in ambient air temperature and relative humidity.

Effective removal of particulate matter from air by using zeolite-coated filters

Zeolites are very effective (much better than MOFs) in removal of particulate matter (PM) from air; NaX/cotton showed 3.6-times the PM removal efficiency of bare cotton with a small increase in the pressure drop of 9 Pa.

A new pin-to-plate corona discharger with clean air protection for particulate matter removal

Abstract High concentration particulate matter (PM) has been a serious environmental problem in China and other developing countries. Electrostatic-based purification technology is a method to remove airborne particles, and can reduce the energy consumption of ventilation fans in buildings because of its low pressure drop. In this study, we developed a new pin-to-plate corona discharger with particle-free external air protection to prevent particles polluting the surface of discharge pins. By using an optical microscope, we observed a certain number of particles deposited on the non-protected (exposed pins) and few particles deposited on the protected pins after they operating for 3 weeks. We experimentally studied the long-term performances of the exposed and protected pins in single-pass PM removal efficiency and ozone production. The results showed that the protected pins produce less ozone and have higher breakdown voltage than the exposed pins. Experimental results indicated that the improved pin-to-plate corona discharger has better long-term performance and is safer than the exposed one. The results of the research can give an understanding of how to improve electrostatic-based purification technologies toward stable discharging for high removal efficiency of particles.

Progress on particulate matter filtration technology: basic concepts, advanced materials, and performances.

The PM (particulate matter)-induced haze problem has caused serious environmental and health concerns. It is still a huge challenge to control PM pollution because of the complex structure, diverse sources and intricate evolution mechanism of the particles. In recent years, there has been increasing efforts to develop advanced strategies for PM treatment. Herein, we wish to provide a systematic summary of recent progress in air filtration. The review covers the definition of PM, the characterization of PM, the mechanism of PM capture, advanced purification materials, and special multifunctional performances. As for characterizing PM particles, removal efficiency, pressure drop, flow rate, quality factor and optical transparency are the basic parameters. For the advanced filters with excellent filtration performance, some special properties such as thermal stability, antibacterial property, flame retardancy, recyclability and special wettability are in great need under certain extreme conditions. Finally, some future prospects for filtration materials, like material choice and structural design, are also discussed.

The Impact of the Morphological Characteristics of Leaves on Particulate Matter Removal Efficiency of Plants

This study was conducted to find out differences in the removal efficiency of particulate matter (PM) depending on the type of plants and the morphological characteristics of leaves. A total of 12 plants were used, with three plants selected for each type of leaves (big leaf, small leaf, compound leaf, needle leaf). We measured the removed amount of PM10 and PM2.5, the structure of the abaxial leaf surface, and the weight of the wax layer of each plant. Plants with the high removal efficiency of PM included Pachira aquatica Aubl., Ardisia crenata, and Dieffenbachia ‘Marianne’, and plants with the low removal efficiency included Nandina domestica Thunb, Schefflera arboricola, and Quercus dentata. The abaxial leaf surface having a high removal efficiency of PM had many large wrinkles, and the abaxial leaf surface having a medium removal efficiency was flat and smooth. On the other hand, there were many fine hairs on the abaxial leaf surface with a low removal efficiency. According to the plant leaf type, the PM10 removal efficiency of plants with needle leaves was about three times higher than that of other plants. In particular, the wax layer of conifers weighed 6–24 times higher than those of other plants. The stomata of conifers were evenly distributed on the adaxial and abaxial leaf surfaces; however, the stomata of Sciadopitys verticillata appeared in the form of papillae unlike general stomata. Therefore, the removal efficiency of PM varied depending on the macro-, and micro-morphological characteristics of plant leaves such as the structure of the abaxial leaf surface, and the weight of the wax layer. Based on this research, selecting plants that are effective in reducing PM in consideration of the plant type and leaf characteristics will improve indoor air quality and decrease exposure of PM to human body. Key words: conifer, leaf surface structure, leaf type, wax layer weight