Separation Of Particles Research Articles

Investigating the impact of pillar shape on flexible erythrocyte separation through deterministic lateral displacement

The deterministic lateral displacement (DLD) method has gradually moved beyond the separation of spherical rigid particles and has been successfully applied to the field of biological cells, especially to the separation of disc-shaped flexible erythrocytes. Different shapes of micropillars in the DLD device significantly affect the sorting performance of erythrocytes. We investigated the effect of the flow field in the gap of micropillars of different shapes (circular, triangular, I-shaped) on the behavior of erythrocyte tumbling motion. The simulation results showed that in the I-shaped pillar DLD device, compared with the circular and triangular pillars, the erythrocytes exhibited a stable and continuous flipping motion during the movement along the array offset direction, which enabled the effective separation size to be maintained at a high level. In addition, the formula for calculating the critical diameter of the I-shaped pillar DLD array for separating erythrocytes was obtained by fitting, which provides strong support for a more efficient design of the I-shaped pillar DLD device dedicated to erythrocyte sorting.

Separation of fine particles and liquid using a physical trapping method via a stepped structure

Separation of fine particles and liquid using a physical trapping method via a stepped structure

Simulation study on rotor speed of combined rotary separator in coal pneumatic conveying

The separator is a key component of coal pneumatic conveying systems, which plays an important role in improving particle collection efficiency and reducing dust pollution. In this paper, a combined rotary separator was designed. Based on the traditional cyclone separator, the rotor blades were installed and matched with the guide vanes to increase the material separation and collection performance. The influence of rotor speed on the characteristics of the separator was studied by computational fluid dynamics simulation, and the flow field velocity and pressure distribution and the particle trajectory and separation degree were obtained. The results showed that the flow field tangential velocity plays a dominant role in the separation process and is approximately symmetrically distributed with the rotor axis as the center. The velocity of the flow field in the inner rotor is approximately positively correlated with the rotor speed, and the tangential velocity gradually decreases with the increase in the flow field height. The static pressure of the flow field is approximately axisymmetric along the rotor axis, and there is a pressure gradient from the outer separation cone to the rotor axis. The particles in the separator show a separation phenomenon based on the different sizes, and the change trend of the separation degree under different rotor speeds is similar. When the rotor speed is 160 rpm, the particles maintain the highest integrity. The rotor speed of 320 rpm has a protective effect on coarse particles above 1000 µm.

An air-fluidized magnetic separator and its separation performance for steel slag

In order to address the issue of magnetic agglomeration leading to poor magnetic separation efficiency and low activity enhancement, resulting in limited utilization of steel slag fine powder material, this study proposes a novel dry magnetic separator with air fluidization as the feeding method. The new separator incorporates adjustable magnetic field strength based on the material’s magnetic properties, enabling individual particle separation through a magnetic mesh while simultaneously enhancing mechanical and ultrasonic composite vibration. In addition, it enhances competitiveness by incorporating negative pressure suction. Primary magnetic separation tests on a steel slag fine powder material demonstrate that the air fluidized dry magnetic separator effectively separates inert minerals from active minerals in the steel slag powder. The iron grade in the magnetic products reaches 21.81%, which is 6.88% higher than that of the original steel slag, while the iron grade in non-magnetic products decreases to 11.93%, representing a 3% reduction compared to the original steel slag composition. Further sweeping and selection processes are expected to further improve these results, ultimately achieving effective utilization of steel slag.

Low-cost, manual centrifuge for separation of particles from water

Water separation is a critical process with far-reaching implications for the environment, public health, and various industries. Traditional water filtration methods are often limited to commercial use, posing challenges for individuals lacking access to clean water, or the equipment to separate particles suspended in water. In this study, we developed a spinning device for water separation through centrifugal and rotation force. Our goal was to create a device that could provide a low-cost alternative for removing contaminants from water. During the testing, we found that the device had a theoretical efficiency of 67% and longer separation times consistently produced significantly lower absorbance values in the visible range, indicating more effective particle removal. A computational model was also used to simulate the movement of particles under the influence of rotational forces, and showed that the smallest particle in this experiment (microplastics) can be theoretically moved by the rotational forces. This study underscores the promise of a manually powered spinning toy as an innovative and efficient tool for water separation and contaminant removal, holding the potential to address global water quality challenges.

Results and Perspectives of Timepix Detectors in Space—From Radiation Monitoring in Low Earth Orbit to Astroparticle Physics

In space application, hybrid pixel detectors of the Timepix family have been considered mainly for the measurement of radiation levels and dosimetry in low earth orbits. Using the example of the Space Application of Timepix Radiation Monitor (SATRAM), we demonstrate the unique capabilities of Timepix-based miniaturized radiation detectors for particle separation. We present the incident proton energy spectrum in the geographic location of SAA obtained by using Bayesian unfolding of the stopping power spectrum measured with a single-layer Timepix. We assess the measurement stability and the resiliency of the detector to the space environment, thereby demonstrating that even though degradation is observed, data quality has not been affected significantly over more than 10 years. Based on the SATRAM heritage and the capabilities of the latest-generation Timepix series chips, we discuss their applicability for use in a compact magnetic spectrometer for a deep space mission or in the Jupiter radiation belts, as well as their capability for use as single-layer X- and γ-ray polarimeters. The latter was supported by the measurement of the polarization of scattered radiation in a laboratory experiment, where a modulation of 80% was found.

Occupation-Dependent Particle Separation in One-Dimensional Non-Hermitian Lattices.

We unveil an exotic phenomenon arising from the intricate interplay between non-Hermiticity and many-body physics, namely, an occupation-dependent particle separation for hardcore bosons in a one-dimensional lattice driven by unidirectional non-Hermitian pumping. Taking hardcore bosons as an example, we find that a pair of particles occupying the same unit cell exhibit an opposite non-Hermitian pumping direction to that of unpaired ones occupying different unit cells. By turning on an intracell interaction, many-body eigenstates split in their real energies, forming separable clusters in the complex energy plane with either left-, right-, or bipolar-types of non-Hermitian skin effect (NHSE). The dependency of skin accumulating directions on particle occupation is further justified with local sublattice correlation and entanglement entropy of many-body eigenstates. Dynamically, this occupation-dependent NHSE manifests as uni- or bidirectional pumping for many-body initial states, allowing for spatially separating paired and unpaired particles. Our results unveil the possibility of designing and exploring novel non-Hermitian phases originated from particle nonconservation in subsystems (e.g., orbitals, sublattices, or spin species) and their spatial configurations.

Microplastic separation and enrichment in microchannels under derivative electric field gradient by bipolar electrode reactions

The decomposed plastic products in the natural environment evolve into tiny plastic particles with characteristics such as small size, lightweight, and difficulty in removal, resulting in a significant pollution issue in aquatic environments. Significant progress has been made in microplastic separation technology benefiting from microfluidic chips in recent years. Based on the mechanisms of microfluidic control technology, this study investigates the enrichment and separation mechanisms of polystyrene particles in an unbuffered solution. The Faraday reaction caused by the bipolar electrodes changes the electric field gradient and improves the separation efficiency. We also propose an evaluation scheme to measure the separation efficiency. Finite element simulations are conducted to parametrically analyze the influence of applied voltages, channel geometry, and size of electrodes on plastic particle separation. The numerical cases indicate that the electrode-installed microfluidic channels separate microplastic particles effectively and precisely. The electrodes play an important role in local electric field distribution and trigger violent chemical reactions. By optimizing the microchannel structure, applied voltages, and separation channel angle, an optimal solution for separating microplastic particles can be found. This study could supply some references to control microplastic pollution in the future.

Particulate filtration by cryogenic condensation using a high efficiency Stairmand cyclone separator

This paper describes the synergy of a high-efficiency Stairmand cyclonic separator and the phenomenon of condensation generated by the low temperatures of the mixture of liquid nitrogen and ethanol, to increase the separation efficiency on particles with diameters of 1 μm, 45 μm, 75 μm, 150 μm and 250 μm. The cyclone separator adds the phenomenon of condensation, generating a film of liquid water on its internal walls. The film of liquid water causes a loss of kinetic energy in the particles, reducing their speed and becoming stuck. Al2O3 particles and pozzolana rock particles are used to perform the particle separation experimental tests. A computational fluid dynamics analysis using the second order RSM model is incorporated to describe the fluid dynamic behavior of the particles within the separator cyclone. The results in computational fluid dynamics show the agglomeration of larger diameter particles near the internal walls. Using condensation as a phase change generated by cryogenic mixing results in an overall particle separation efficiency of 76.00 %, standing for an increment of 70.14 % in comparison to a conventional high-efficiency Stairmand separator cyclone.Technological innovation: Particles, filtration, separation, condensation, cryogenic.

Seasonal charge distributions of submicron atmospheric particles in Yokohama, Japan

Charge distribution measurements are required to understand the spatiotemporal distribution of the number concentrations of submicron atmospheric particles that affect radiative forcing and particle deposition in human airways. The number concentrations of non-charged and charged particles within the 0.3–0.5 μm diameter (D) range were measured at Keio University in Yokohama, Japan, from June 2022 to January 2023 by combining a parallel-pate particle separator and optical particle counters to investigate critical parameters controlling the charging state of submicron atmospheric particles. The measurement uncertainties in the average charge number per particle (pave) and the standard deviation (1σ), derived from the charge distribution of the submicron particles, were within 15%. The monthly median values of 1σ increased in summer and decreased in winter and correlated with the water vapor amount and wind speed. The 1σ values in summer and winter, derived from the seasonally averaged charge distributions of particles, were close to those from the theoretically calculated charge distribution of particles within 0.387–0.5 μm D range and with D = 0.3 μm, respectively, suggesting that the observed particle charge distributions approached the stationary charge distribution for the effective D. In summer, the frequent transport of water molecules and ions from the Pacific Ocean causes efficient collisions between multiple ions and submicron particles with a larger effective D, which may expand the charge distribution of particles. The polarity ratio, the concentration of positively charged particles relative to that of negatively charged particles, was almost unity, indicating the well-balanced charge polarity of the submicron atmospheric particles. The polarity ratio and pave changed significantly during lightning events, indicating that the atmospheric particle charge balance broke. Our findings show that the charge distribution of submicron atmospheric particles can be partly controlled by meteorological parameters (e.g., absolute humidity) and the microphysical properties of the particles.

Evaluation of Fe-Ni Composite Oxygen Carrier in Coal Chemical Looping Gasification

Although coal chemical looping gasification (CCLG) is a promising technology for the efficient utilization of coal, limited studies concerned about the industrial application of oxygen carrier in CCLG system owing to its performance requirements including high reactivity with solid fuel, high carbon conversion, and good mechanical property. To meet the requirements of oxygen carriers in CCLG system, novel Fe-Ni composite oxygen carrier (OC) samples were successfully prepared. The performances of these OCs were evaluated in a fixed bed reactor, where they were reduced by solid fuel and then fully oxidized by air. Both fixed bed tests and thermodynamic analysis showed that the prepare OCs exhibited high reactivity with coal and syngas selectivity, making them suitable for the CCLG process. Specifically, when the loading amount of NiO was 20 wt%, the Fe-Ni composite OCs achieved the highest carbon conversion (93.03%) and synthesis gas selectivity (73.29%). Additionally, the thermogravimetric data revealed that the Curie temperature of the OCs was higher than 550°C, making them suitable for magnetic separation of the OC particles and carbon residue in the CCLG system.

On-chip label-free sorting and enrichment of microplastic particles by using deterministic lateral displacement

A novel deterministic lateral displacement (DLD) method employing a pressure-driven flow for the continuous size-based separation of microplastic particles is presented in this paper. To induce the DLD effect, arrays of triangular posts were designed to enhance the sorting resolution and reduce the particles clogging. For the particles with a diameter larger than the critical diameter (Dc) in the DLD device, they move in bump mode with collision to microposts. While, the particles flow in zigzag mode if their sizes are below the Dc value. The DLD microfluidic chip enables simplified fabrication process and shows property of label-free and high throughput. Numerical studies were conducted to discuss the Dc values in the microchannel with horizontally symmetrical and asymmetrical posts, where Dc was found smaller in the asymmetric horizontal flow, enabling higher separation sensitivity and resolution. Experiments were conducted to demonstrate the separation of 10 μm and 15 μm polystyrene microplastic particles, and different types of polystyrene and polyethylene microplastic particles by adjusting the flow rates. In order to achieve successful separation, the flow rates between the sheath flow and the sample solution were well matched. In this way, the proposed DLD microfluidic chip with horizontally asymmetrical triangular posts shows property of label-free, high throughput, capability to analyze microplastic particle selectively and sensitively, possibility of sorting nanoplastic particles.

Effect of fluidized bed shapes on gas-solid fluidization characters and flow regime transition

The technology of gas-solid dense-phase fluidized bed separation is applied in the separation of fine particles in minerals due to its stable and reliable characteristics. The experiment collected time-domain distribution signals of pressure drop from fluidized beds with different shapes, systematically analyzed the spatiotemporal distribution characteristics of bed density, and studied the effects of bed shape and fluidization number N on the fluidization and flow transition of the bed layer. The results indicate significant differences in Umf among fluidized beds with different shapes, and the tapered bed requires the highest energy for fluidization. When N=1.3, the cylindrical bed layer is the most stable, maintaining an average density of 1.8 g/cm3, with a density fluctuation variance of 0.02 g/cm3. Additionally, when N<1.0, almost no bubbles inside the bed layer. With an increase in gas velocity, the time-domain distribution of pressure drop signals shows different degrees of fluctuation. When N=1.1, Conspicuous non-uniform particle flow is evident in the tapered bed, with a bubble main frequency of 8 Hz, an amplitude of 27.1, and the highest pressure drop energy signal, indicating that the tapered bed enters the bubbling state prematurely. Finally, fine coal separation experiments were conducted, and the results showed that the minimum E value for the cylindrical bed is 0.08 g/cm3, while the maximum E value for the tapered bed is 0.17 g/cm3.

Rapid separation of MOFs particles with the aid of PVDF hollow fiber membrane

Metal-organic frameworks (MOFs) have been widely investigated due to their fascinating structures and properties. However, the time-cost synthetic process and the difficult separation from liquid phase hinder their practical application. In this study, a self-made automatic apparatus containing commercial poly(vinylidene fluoride) (PVDF) hollow fiber membranes was used to separate MOFs from large-volume suspension. Taking MIL-88A(Fe) synthesized with industrial-grade chemicals as an example, the investment cost, operation cost, human cost, time duration during separation process, and unit cost price of MIL-88A(Fe) were significantly reduced by 62%, 82%, 100%, 90%, and 36%, respectively, compared to those of centrifugation. More importantly, MIL-88A(Fe) powders that were separated and purified by the apparatus were easy to be removed from membrane surface by slight vibration, which displayed good morphology, crystallinity, as well as high degradation efficiency toward organic contaminants via photo-Fenton reaction. Meanwhile, the membrane can be reused instantly without any rinse. More encouragingly, this method is applicable to other MOFs’ separation, like ZIF-8 and ZIF-67. This study further confirmed the potential and prospective of high-throughput production and facile separation of MOFs for practical applications.

Nanocellulose-based membranes with pH- and temperature-responsive pore size for selective separation

Smart gating membranes have drawn much attention due to the controllable pore structure. Herein, a smart gating membrane with dual responsiveness was prepared from bacteria cellulose (BC) grafted with pH- and temperature-responsive polymers. By external stimulation, the average pore size of the membrane can be controlled from 33.75 nm to 144.81 nm, and the pure water flux can be regulated from 342 to 2118 L·m−2·h−1 with remarkable variation in the pH range of 1–11 and temperature range of 20–60 °C. The adjustability of pore size is able to achieve the gradient selective separation of particles and polymers with different sizes. In addition, owing to the underwater superoleophobicity and the nanoscale pore structure, the membrane separation efficiencies of emulsified oils are higher than 99 %. Moreover, the controllable pore size endows the membrane with good self-cleaning performance. This nanocellulose-based smart gating membrane has potential applications in the fields of controllable permeation, selective separation, fluid transport, and drug/chemical controlled release systems.

Investigation into Detection Efficiency Deviations in Aviation Soot and Calibration Particles Based on Condensation Particle Counting

Aviation soot constitutes a significant threat to human well-being, underscoring the critical importance of accurate measurements. The condensation particle counter (CPC) is the primary instrument for quantifying aviation soot, with detection efficiency being a crucial parameter. The properties of small particles and the symmetry of their growth pathways are closely related to the detection efficiency of the CPC. In laboratory environments, sodium chloride is conventionally utilized to calibrate the CPC’s detection efficiency. However, aviation soot exhibits distinctive morphological characteristics compared to the calibration particles, leading to detection efficiencies obtained from calibration particles that may not be applicable to aviation soot. To address this issue, a quantitative study was performed to explore the detection efficiency deviations between aviation soot and calibration particles. The experiment initially utilized a differential mobility analyzer to size select the two types of polydisperse particles into monodisperse particles. Subsequently, measurements of the separated particles were performed using the TSI Corporation’s aerosol electrometer and a rigorously validated CPC (BH-CPC). These allowed for determining the detection efficiency deviation in the BH-CPC for the two types of particles at different particle sizes. Furthermore, the influence of the operating temperature of the BH-CPC on this detection efficiency deviation was investigated. The experimental results indicate a significant detection efficiency deviation between aviation soot and sodium chloride. In the range of 10–40 nm, the absolute detection efficiency deviation can reach a maximum of 0.15, and the relative deviation can reach a maximum of 0.75. And this detection efficiency deviation can be reduced by establishing a relevant relationship between the detection efficiency of the operating temperature and the calibration temperature. Compared to the saturated segment calibration temperature of 50 °C, the aviation soot detection efficiency is closer to the sodium chloride detection efficiency at the calibration temperature of 50 °C when the saturated segment operates at a temperature of 45 °C. These studies provide crucial theoretical guidance for enhancing the precision of aviation soot emission detection and establish a foundation for future research in monitoring and controlling soot emissions within the aviation sector.

ПРОГНОЗИРОВАНИЕ ИЗНОСОСТОЙКОСТИ ПАР ТРЕНИЯ СКОЛЬЖЕНИЯ

The necessity to predict optimal wear resistance of sliding couplers at the design stage is grounded. A tribological analysis of the wear of sliding couplers is carried out during the entire period of operation in various modes corresponding to the following stages: start-up, steady-state wear and shutdown. The existing approaches to solving contact problems in the interaction of solids, taking into account physico-mechanical processes in the surface layers of couplers during their wear, are analyzed. A wear model is proposed based on the destruction of the contacting surfaces of a coupler with the separation of particles, which size varies depending on the load characteristics, physico-mechanical and structural parameters, thermal properties, quality of the lubricant, etc. The results of testing prototypes for wear resistance and numerical implementation of the proposed model for predicting the wear resistance of a sliding coupler with similar characteristics are presented. It is found out that the proposed wear model makes it possible to predict (calculate) the wear resistance of a sliding coupler in a certain range by changing the initial data, thereby eliminating the need for rather laborious tests of couplers for wear under the influence of various factors.

Dielectrophoretic Particle Chromatography: From Batch Processing to Semi-Continuous High-Throughput Separation

The development of highly selective separation processes is a focus of current research. In 2016, the German Science Foundation funded a priority program SPP 2045 “MehrDimPart—highly specific multidimensional fractionation of fine particles with technical relevance” that aims to develop new or enhance existing approaches for the separation of nano- and micrometer-sized particles. Dielectrophoretic separators achieve highly selective separations of (bio-)particles in microfluidic devices or can handle large quantities when non-selective separation is sufficient. Recently, separator designs were developed that aim to combine a high throughput and high selectivity. Here, we summarize the development from a microfluidic fast chromatographic separation via frequency modulated dielectrophoretic particle chromatography (DPC) toward a macrofluidic high throughput separation. Further, we provide a starting point for future work by providing new experimental data demonstrating for the first time the trapping of 200 nm polystyrene particles in a dielectrophoretic high-throughput separator that uses printed circuit boards as alternatives for expensive electrode arrays.

Enhancing particle focusing: a comparative experimental study of modified square wave and square wave microchannels in lift and Dean vortex regimes

Serpentine microchannels are known for their effective particle focusing through Dean flow-induced rotational effects, which are used in compact designs for size-dependent focusing in medical diagnostics. This study explores square serpentine microchannels, a geometry that has recently gained prominence in inertial microfluidics, and presents a modification of square wave microchannels for improved particle separation and focusing. The proposed modification incorporates an additional U-shaped unit to convert the square wave microchannel into a non-axisymmetric structure, which enhances the Dean flow and consequently increases the Dean drag force. Extensive experiments were conducted covering a wide range of Reynolds numbers and particle sizes (2.45 µm to 12 µm). The particle concentration capability and streak position dynamics of the two structures were compared in detail. The results indicate that the modified square-wave microchannel exhibits efficient particle separation in the lower part of the Dean vortex-dominated regime. With increasing Reynolds number, the particles are successively focused into two streaks in the lift force-dominated regime and into a single streak in the Dean vortex-dominated regime, in this modified square wave geometry. These streaks have a low standard deviation around a mean value. In the Dean vortex-dominated regime, the location of the particle stream is highly dependent on the particle size, which allows good particle separation. Particle focusing occurs at lower Reynolds numbers in both the lift-dominated and lift/Dean drag-dominated regions than in the square wave microchannel. The innovative serpentine channel is particularly useful for the Dean drag-dominated regime and introduces a unique asymmetry that affects the particle focusing dynamics. The proposed device offers significant advantages in terms of efficiency, parallelization, footprint, and throughput over existing geometries.

Motility-induced phase separation of soft active Brownian particles

Motility-induced phase separation (MIPS) is the hallmark of non-equilibrium phase transition in active matter. Here, by means of Brownian dynamics simulations, we determine the phase behavior and the critical point for phase separation induced by motility of a two-dimensional system of soft active Brownian particles, whose interaction is modeled by the generalized purely repulsive Weeks–Chandler–Andersen potential. We refer to this model as soft active Brownian particles. We determine and analyze the influence of particle softness on the MIPS and show that the liquid–gas coexistence region is wider, the softer the interparticle interactions becomes. Moreover, the critical value of the self-propulsion velocity at which diluted and dense phases start to coexist also increases; as a consequence, the softer the particle interaction is, the bigger self-propulsion velocities are needed in order to observe a MIPS.