Removal Of Submicron Particles Research Articles

Wet-resistant, dustproof, and germproof self-powered lignocellulosic triboelectric filters for respiratory protection, monitoring, and diagnosis

The moisture sensitivity and structural defects found in natural cellulose materials limit their ability to serve as substitutes for petroleum-based masks. This study uses a combination of methods, including retaining lignin, embedding silver particles in situ, and using a mixture of coarse and fine fibers to enhance the wet resistance, antibacterial properties, and triboelectric output of lignocellulosic materials. This approach also aimed to balance pressure drop and filtration efficiency. A triboelectric filter (Ag-LCTEF) using a perforated fluorinated ethylene propylene (FEP) film sandwiched between two sheets of Ag-embedded lignocellulose (Ag-LC) was assembled. The resulting Ag-LCTEF enabled self-powered continuous monitoring of breathing signals, boasting impressive submicron particle removal (99.70 %) and antibacterial efficiency (99.18 %), all while maintaining a relatively low-pressure drop of 76 Pa. Notably, the Ag-LCTEF displayed consistent performance and long-term durability even in high humidity conditions of 80 % RH. These remarkable achievements have spurred the suggestion of integrating respiratory protection, monitoring, and diagnostic functions, showcasing its potential for the next generation of wearable electronics. Moreover, naturally safe and biodegradable lignocellulose serves as an environmentally friendly replacement for petroleum-based materials.

Impact of ventilation methods on indoor particle concentrations in a daycare center.

The objective of this study was to quantify the influence of ventilation methods on children's exposure to indoor particles in a daycare center located in an urban area. The ventilation methods applied to the center were monitored for 1 year. It appears that indoor PM10 and PM2.5 concentrations of the center were basically determined by outdoor conditions. The fluctuations in outdoor particle concentration also affected the ventilation behavior during class. The windows and doors of the classroom were frequently closed during both class hours and nights when the outdoor particle concentrations were at high levels. Statistically significant differences in the I/O ratios were found among the ventilation methods. The PM10 I/O ratio with the closed windows was significantly higher (p < 0.01) than that with the open windows, and when the mechanical fans were operated, the I/O ratio dramatically decreased (p < 0.01). The I/O ratio of PM2.5 showed a similar trend to that of PM10 except for the mechanical fan operation. The filters rated lower than MERV 11 appear to be insufficient to remove submicron particles from the mechanically supplied outdoor air when the PM2.5 concentrations are high, such as during the heating period.

Influences of magnetic field on the removal of submicron particles in electrostatic cyclone at different temperatures

Aiming at improving the capture performance of inner vortex electrostatic cyclone (ESC), which is widely used in the field of flue gas purification, magnetic field is introduced to remove submicron particles. The theoretical and physical models of electromagnetic dust removal were established, and the dust-removal efficiency of submicron particles under different temperatures and magnetic fields was numerically simulated by FLUENT. The results show that a rise in temperature leads to a reduction in the grade efficiency of submicron particles of ESC, a decrease in the number of escaped particles at lower temperature, and the differences of the rising amplitude in overall efficiency corresponding to the traditional cyclone, which were 36.7%, 34.8%, 33.8%, and 31.9% at four temperatures. The contribution of temperature to the capture of submicron particles decreases continuously with the increasing temperature, but that of magnetic field progressively increases at this time. The magnetic field environment is conducive to the capture of submicron particles, the removal effect is more obvious with the increase of magnetic flux density, but the ascended ranges of magnetic field and temperature both decrease when it reaches 0.5 T. These results can provide a theoretical basis and a technical reference for the design of ESC.

A nanoscale observation to explain the discrepancy of electron exchange capacities between biochar containing comparable surface redox-active moieties

Biochar, possessing electron exchange capacities (EEC), is generally involved in environmental redox reactions due to the presence of redox-active moieties (RAMs). The phenomenon that chars containing comparable RAMs possess differential EEC revealed that the accessibility of RAMs is important to the redox properties. However, many studies have focused on the type of RAMs, whereas the distribution has been insufficiently investigated. Herein, we achieved nanoscale observation of electroactive moieties on the surface of six chars using a conductive atomic force microscope. For the two specific kinds of chars with submicron particles and opposite current distributions, the submicron particles took up only 1–4‰wt of biochar accounting for approximately 30–50% of electron-donating capacity (EDC), and electron-accepting capacity (EAC) became 87% and 1.40 times as before after removing submicron particles, respectively. Meanwhile, the combined impact of RAMs and surface topography (that uneven distribution of RAMs resulted in outstanding EEC by enhancing accessibility) was clarified. Furthermore, direct evidence of the link between char structure and EEC (that condensed aromatic structures were indispensable to EAC while both heteroatoms and amorphous aromatics contributed to EDC) was established. These findings can aid in understanding the functions of biochar in biotic and abiotic redox processes.Graphical

Efficiently remove submicron particles by a novel foldable electrostatically assisted air coarse filter

Electrostatic assisted air (EAA) coarse filters combine the benefits of electrostatic precipitators and fibrous filters, achieving high filtration efficiency for submicron particulate matters (PM), low pressure drop, and large dust-holding capacity. For application in heating, ventilation, and air conditioning (HVAC) systems, PM removal technology is required to work at high air duct velocity, for example, 1 to 3 m/s. However, both theory and experience have revealed that the pressure drop will increase at large airflow rates. Here, we developed a novel foldable EAA coarse filter by shaping the polarizing electrodes into a zigzag structure and folding the coarse filter between the electrodes. High filtration efficiency for submicron PM (85.0–94.0% for 0.3–0.5 µm PM, 92.0–96.5% for 0.5–1 µm PM) and low pressure drop (5.9–26.4 Pa) at high air duct velocity (1–3 m/s) are achieved by optimizing folding angle (θ) to 45°. We found that θ determines the shape of the PET fold and the nature of electric field, leading to different filtration performances. In order to get the module with better applicability, the optimum θ was determined simultaneously by both filtering velocity and effective polarizing area. The results are expected to facilitate the wide application of EAA coarse filters in HVAC systems for a healthy and energy-saving indoor environment.

Application of Acoustic Agglomeration Technology to Improve the Removal of Submicron Particles from Vehicle Exhaust

The natural processes of interactions between aerosol particles in the ambient air through which they agglomerate is a vast area of chamber research and are inherent to many industries and are often inter-connected with transport engineering. Further improvement of symmetric methods for aerosol particle number and mass concentration reduction made it possible to create various synergic techniques. The study used a 1.9 TDI diesel internal combustion engine, which was supplied with diesel (D100) and second-generation biofuels (NExBTL100) with the EGR exhaust system on and off. Measurements were performed using a Bruel and Kjær “Type 9727” system for measurement of vibrations, a scanning mobility particle sizer (SMPS) and an original agglomeration chamber. The three modes of particle size distributions were observed in the size range from 10 to 470 nm for both D100 and NExBTL100 fuels with and without the use of the EGR system. The application of 21.3 kHz frequency sound with SPL 144.1 dB changed the NExBTL100 generated aerosol particle number concentration but did not sufficiently affect the concentration of D100 emitted particles. The greatest agglomeration effect (21.7 ± 10.0%) was observed in the range of extremely small NExBTL100 derived particles (10–70 nm) when used in combination with an EGR system.

Improving the removal efficiency of fine particulate matters in air pollution control devices: Design and performance of an electrostatic aerosol particle agglomerator

Abstract Removing submicron particles in the size range from 0.1 to 1.0 µm from gas streams is difficult because they cannot be efficiently captured neither through inertial separation nor by diffusion utilized in air pollution control devices. Electrostatic agglomeration is an effective and practical method for improving the removal efficiency of fine particulate matters. For optimizing the performance of electrostatic agglomerators, in addition to the intensity and frequency of an alternating electric field and the particle residence time, an electrostatic aerosol particle agglomerator was designed and established to experimentally evaluate the influence of particle charges on its performance in this study. The results demonstrate that the performance of the electrostatic aerosol agglomerator can be greatly improved in terms of increasing the particle charges from 9 to 19 (e−/particle). Combined with the low frequency of an AC electric field, the agglomeration efficiency can be further enhanced. The highest agglomeration efficiency of 40.2% is achieved in the submicron size range at AC frequency of 45 Hz. Furthermore, the oscillating distance (cm/Hz) is proposed and estimated for correlating the agglomeration efficiency under various testing conditions. It was found that the agglomeration efficiency can be described by a simple power-law equation using this parameter.

Aerosol filtration using hollow-fiber membranes: Effect of permeate velocity and dust amount on separation of submicron TiO2 particles

This work aimed to determine filtration performance of polypropylene hollow-fiber membranes in removing submicron particles from air. Experiments were performed in a chamber simulating dust environment with synthetic submicron-size particles (micronized TiO2). Ahollow-fiber membrane with 300 fibers of a filtration area of 0.43 m2 was tested. By measuring number of particles in chamber (upstream) and on the suction side of the membrane (downstream), the filtration efficiency was determined. Two different weights of synthetic dust (50 and 100 mg) and two permeate velocities (15 and 30 cm/s) were used to compare their influence on particle collection efficiency. Particle counting was carried out using a TSI 3075 condensation particle counter connected to a TSI 3080 scanning mobility particle sizer in 32 particle size channels from 17 to 600 nm. Pressure drop evolution with intense particle loading was recorded and fouling of the membrane was observed after 25, 50 and 90 h of filtration using SEM. The results showed high efficiency, mostly higher than 99.9% with higher pressure drops compared to other materials on HEPA level.

Air filtration performance of symmetric polypropylene hollow-fibre membranes for nanoparticle removal

Abstract This work aimed to determine filtration performance of polypropylene hollow-fibre membranes (HFMs) for removing submicron particles from air. Experiments were performed in a glass chamber supplied with a nanoaerosol particles formed by burning incense sticks. Three types of HFMs varying in packing density, active filtration area and pore-size distribution were tested in an outside-in configuration. By measuring the number of particles upstream and downstream of the HFM, the filtration efficiency was determined. Three permeate velocities (5, 10 and 15 cm/s) were used to compare the velocity effect on filtration efficiency. Particle counting was carried out using a TSI 3075 condensation particle counter connected to a TSI 3080 scanning mobility particle sizer in 48 particle size channels from 18.1 to 100 nm. The results show high efficiency, mostly higher than 99% for particles above 60 nm size. The most penetrating particle sizes (MPPS) were between 35.9 and 40 nm at 5 cm/s with an efficiency of 82–86%. At permeate velocity of 10 and 15 cm/s, MPPS slightly decreased to range of 34.6–40 nm, with efficiency decreasing to 72–84% and 69–83%, respectively. The quality factor of HFMs was within the 2–28 kPa−1 range.

Fouling of microfiltration membranes by flowback and produced waters from the Marcellus shale gas play

There is growing interest in possible options for treatment or reuse of flowback and produced waters from natural gas processing. Here we investigated the fouling characteristics during microfiltration of different flowback and produced waters from hydraulic fracturing sites in the Marcellus shale. All samples caused severe and highly variable fouling, although there was no direct correlation between the fouling rate and total suspended solids, turbidity, or total organic carbon. Furthermore, the fouling of water after prefiltration through a 0.2 μm membrane was also highly variable. Low fouling seen with prefiltered water was mainly due to removal of submicron particles 0.4–0.8 μm during prefiltration. High fouling seen with prefiltered water was mainly caused by a combination of hydrophobic organics and colloidal particles <100 nm in size (quantified by transmission electron microscopy) that passed through the prefiltration membranes. The small colloidal particles were highly stable, likely due to the surfactants and other organics present in the fracking fluids. The colloid concentration was as high as 1011 colloids/ml, which is more than 100 times greater than that in typical seawater. Furthermore, these colloids were only partially removed by MF, causing substantial fouling during a subsequent ultrafiltration. These results clearly show the importance of organics and colloidal material in membrane fouling caused by flowback and produced waters, which is of critical importance in the development of more sustainable treatment strategies in natural gas processing.

Submicron Particle Removal during FPD Oxide TFT Process

In panel manufacturing processes, cleaning process was not considered to be critical thus far. However, as pixel size is becoming smaller nowadays, the number of pixels per unit area is gradually increasing due to the high resolution. Consequently, an influence of submicron sized contaminated particles is increasing, and hence attention needs to be given to cleaning process. For a large area and high resolution panel with a good production yield, a research on an effective cleaning process which can remove the contaminated particles deposited on the Cu, SiO2 and ITO surfaces is required. Generally, physical cleaning processes are used to remove the submicron particles in FPD (Flat Panel Display) process. In this study, we have optimized these cleaning processes to remove the submicron particles from the substrate surface. Here, we achieved a high cleaning efficiency of above 95% in the EIW megasonic cleaning process on all the substrates.

Submicron Particle Removal during FPD Oxide TFT Process

Recently, panel size has become increasingly large reaching the 8th generation (2200mm × 2500mm) and there is a trend that is changing from a-Si TFT (amorphous-Si Thin Film Transistor) to oxide TFT because of a demand for high resolution display and an expansion of OLED (Organic Light Emitting Diodes) industry. In previous panel manufacturing processes, cleaning process was not so important. However, nowadays pixel size is becoming smaller and the number of pixels per unit area is gradually increasing due to the high resolution. Consequently, an influence of submicron sized contaminated particles is increasing, so the importance of cleaning process has increased. In the oxide TFT, to achieve the high resolution, Cu based gate structure having a low resistance characteristic is necessary and in order to prevent a leakage current through the active layer, SiO2 deposition is needed on a gate insulator layer and ITO (Indium Tin Oxide) layer is used as a transparent electrode. For a large area and high resolution panel with a good production yield, a research on an effective cleaning process which can remove the submicron contaminated particles deposited on the Cu, SiO2and ITO surfaces during a TFT manufacturing process, is required. Generally, physical cleaning processes are used to remove the submicron particles in FPD (Flat Panel Display) process. Among them, a research on an eco-friendly physical cleaning processes such as DI water megasonic, mixing-jet, brush and electrolyzed ionized water (EIW) is actively being carried out. In this study, we have optimized these cleaning processes to remove the submicron particles from the substrate surface. The primary objective is to establish an optimal cleaning process by applying above processes for the Cu, SiO2 and ITO substrates. And a mechanism of cleaning process and a theoretical understanding of interaction force such as van der Waals force, zeta potential and electrostatic force between the particle and substrate for the optimization of particle cleaning are studied. In the course of the experiment, the particles (glass and aluminum) which were produced in TFT manufacturing process were intentionally deposited on the Cu, SiO2 and ITO substrate surface. And then, the cleaning test using megasonic (1 MHz and 250 W), mixing-jet (570 lpm CDA and 4 lpm DI water), brush (diamond shape) and EIW (pH 10.2 and -790 mV ORP) processes was conducted. After that, we evaluated the cleaning efficiency by counting the number of particles on the surface before and after the cleaning test using an optical microscope. As a result, we achieved a high cleaning efficiency of above 95% in the electrolyzed ionized water cleaning process by applying the megasonic cleaning on all substrates. Figure 1

Removal of submicron particles from solid surfaces using surfactants

The removal of nano- or submicron particles from solid substrates is of considerable interest in a range of existing industries including cleaning of surfaces inside a spacecraft after evaporation of nanofluids. A method of nanoparticle removal using aqueous surfactant solutions is proposed. The surfactants' cleaning efficiency is investigated for all four combinations of hydrophilic (HL) and hydrophobic (HB) nanoparticles and surfaces, in order to find the most successful cleaning method in each combination. Carbon and silica nanoparticles deposited onto Teflon and glass surfaces were used. Cationic, anionic and non-ionic surfactants with a range of CMCs and HLBs were used in order to identify the best surfactant in each scenario.

Parametric Study for High-Frequency, High-Intensity Ultrasonics in Removal of Sub-Micron Particles

Parametric Study for High-Frequency, High-Intensity Ultrasonics in Removal of Sub-Micron Particles

Use of Pulse-Energized Electrostatic Precipitator to Remove Submicron Particulate Matter in Exhaust Gas

An electrostatic precipitator (ESP) with negative pulse corona discharge for removal of submicron particles in the exhaust gas of thermal equipment such as boilers, burners or internal combustion engines is presented. A wire-cylinder ESP was designed and constructed for experimental testing at laboratory scale. The collection efficiency of submicron particles in the exhaust gas of a diesel burner under various dust loadings and gas velocities was investigated. The results were compared with those obtained from the conventional DC ESP technique. It was found that the pulse peak voltage supply could be set much higher than the sparking limit of the DC energized unit. Thus, the electric field density could be increased, which resulted in a higher collection efficiency. The higher pulse frequency also increased the collection efficiency, especially for submicron particles.

Laser-induced backside wet cleaning technique for glass substrates

The aim of this paper is to study the laser-induced backside wet cleaning techniques for glass substrates. Two kinds of laser cleaning techniques are proposed in this study. The first involves applying an Nd:YAG laser to the backside of the substrate which is submerged in water. A metal plate is placed below the glass substrate. Most of the laser energy will be absorbed by the metal plate. The metal then vaporizes the water and generates a turbulent bubble flow. The bubble flow removes the alumina particles from the surface of the glass substrate. The second involves using a CO2 laser to generate turbulent bubble flow to remove the particles. Both methods were successfully demonstrated for the removal of submicron particles of 0.5 μm in size. The phenomena of bubble generation and diffusion are presented in the paper. Because the laser is applied to the backside of the substrate, the damage due to the laser heat can be significantly reduced. The quality and efficient of the backside processing is better than those of the front side processing. The proposed techniques have great potential to provide an improved solution for glass cleaning.

New Chemical Vapor Delivery Systems for Surface Cleaning

Conventional aqueous wet cleaning methods in semiconductor manufacturing are facing tremendous challenges, with decreasing line widths and high aspects ratio features on the order of a few nanometers. Water and other liquids have surface tensions that frequently prevent complete penetration into nanometer-sized trenches and vias now being fabricated on semiconductor wafers and other substrates. This problem is accentuated by the fact that particle sizes leading to Killer defects are now on the order of 10 nm or less. Nanometer-sized particles can adhere to a surface with a relatively strong force of over a million times its weight. An effective cleaning technique for submicron particle removal will require complete penetration of the device features to surround and dislodge particles, but at the same time not damage the features or etch the surface.

Numerical calculations of submicron particle removal in a spike-plate electrostatic precipitator

A 3D hybrid Finite Element (FE)-Flux Corrected Transport (FCT) numerical algorithm is proposed to evaluate the electrical characteristics of a laboratory scale single stage spikeplate electrostatic precipitator and to predict the collection of submicron particles with diameters in the range of 0.25-1.5 μm. The precipitator consists of two parallel collecting plates with a spiked electrode mounted at the center, parallel to the planes and excited with a high negative dc voltage. The complex interaction between the electric field, fluid dynamics and the particulate flow in this precipitator are taken into account in the simulation. Particles are assumed to be charged by combined field and diffusion charging mechanisms. Motion of submicron particles under electrostatic and aerodynamic forces in turbulent flow is calculated using a Lagrangian-type Discrete Random Walk (DRW) model and User Defined Functions (UDFs) feature of the commercial FLUENT 6.2 software. The electrohydrodynamic secondary flow patterns, particle migration velocity patterns and particle collection efficiencies are examined for three different corona discharge electrode configurations: spikes located only on one side of the electrode with the tips directed either upstream or downstream of the channel, and spikes located on both sides. For a given particle concentration at inlet, the particle deposition rate along the channel and the average charge-to-mass ratios are evaluated for different particle sizes and applied voltages. Finally, the influence of particle concentration on particle collection efficiency for the ESP with spikes on two sides is investigated for -30 kV applied voltage. In selected cases, the numerical results are compared with the existing experimental data.

Removal of submicron particles using a carbon fiber ionizer-assisted medium air filter in a heating, ventilation, and air-conditioning (HVAC) system

Laboratory tests of particle removal were performed with a pair of carbon fiber ionizers installed upstream of a glass fiber air filter. For air flow face velocities of 0.4, 0.6, and 0.8 m/s, the overall particle removal efficiencies of the filter for all submicron particles were 17%, 16%, and 14%, respectively, when the ionizers were not turned on. These values increased to 27%, 23%, and 19%, respectively, when the ionizers were used to generate ions of 6.0 × 10 9 ions/cm 3 in concentration. The carbon fiber ionizers were then installed in front of a glass fiber air filter located in a heating, ventilation, and air-conditioning (HVAC) system. Field tests were performed in a test office room with a total indoor particle concentration of 2.2 × 10 4 particles/cm 3. When the flow rate was 75 cubic meters per hour (CMH), the steady-state values of the total indoor particle concentrations using the glass fiber air filter with and without ionizers decreased to 0.87 × 10 4 particles/cm 3 and 1.15 × 10 4 particles/cm 3, respectively, resulting in a 25% decrease of the ionizer effect. When the operation flow rate was increased to 115 and 150 CMH, the effect of the ionizer decreased to 19% and 17%, respectively. These experimental data match the results calculated using a mass-balance model whose parameters were determined from laboratory tests.

Characteristics of Submicron-sized Aerosol Filtration and Pressure Drop of an Electret Filter Installed in an Air Diffuser in a Residential Apartment Unit

We investigated submicron-sized aerosol filtration and the pressure drop of an electret filter called a “Flimmer filter.” The fibers of the filter are aligned parallel to the direction of the airflow, unlike conventional fibrous filters or conventional electret filters. Lab-scale tests were performed first in a laboratory duct system for submicron particle removal efficiency and pressure drop of the filter. Then, Field tests were conducted in an apartment home using two portable aerosol spectrometers and with a Flimmer filter installed at the terminal of a duct within a mechanical ventilation system. The removal efficiencies at the face velocity of 1.0 m/s for 0.4 μm and 0.6 μm were 52% and 65%, respectively. The removal efficiency for PM1.0 was about 51%. Through an adapted mass balance model, indoor particle concentrations both in number and mass were predicted. The predicted results for the temporal variations of 0.4 and 0.6 μm sized particle, and PM1.0 correlated well with the results obtained from the field tests. When the face velocity was 1.0 m/s, which is the nominal operating condition of the test filter, the pressure drop was 11.5 Pa, which is relatively lower than the pressure drops of other conventional fibrous filters or conventional electret filters having the same filtration efficiency.