Separation Of Large Particles Research Articles

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

Lab-based Martian analogue experiments investigating electric and magnetic fields of dust devils

Dust devils – rotating vortices of lofted particulates formed by convection from solar heating - are a prevalent aspect of Martian weather.Within a dust devil, particles become charged though triboelectrification, and observations of terrestrial dust devils have revealed electric and magnetic fields. Understanding the behaviour of these aeolian events is vital for mission planning and duration, for example, with the Insight lander as a prime example of a mission cut short due to obscuration of solar panels by lofted dust, which is highly likely to be charged. Charged dust devils on Mars strongly imply the existence of electric discharges due to the low breakdown field. The existence of discharges would in turn imply a global electric circuit on the planet – with implications for organic chemical formation and methane losses.This work presents a laboratory-based experimental set up for investigation into both electric and magnetic fields and the feasibility of using Martian analogue dust as alternative to in-situ measurements. In a dust devil, there are two main driving motions – a vertical separation of small and large particles, and the characteristic tight spiralling motion. The experimental set-up splits these components, allowing investigation into each. It is made up of a carefully designed cylindrical tank into which dusts or powders can be dropped to allow triboelectric charging as they fall under gravity. The base of the tank has a Faraday cup for charge measurement and there is also a field mill looking into the tank from the top. The rotational component is achieved using a paddle arrangement for samples placed in the base of the tank. Electric and magnetic fields have successfully been detected from charged dust with this system.

Efficient separation of large particles and giant cancer cells using an isosceles trapezoidal spiral microchannel.

Polyploid giant cancer cells (PGCCs) contribute to the genetic heterogeneity and evolutionary dynamics of tumors. Their size, however, complicates their isolation from mainstream tumor cell populations. Standard techniques like fluorescence-activated cell sorting (FACS) rely on fluorescent labeling, introducing potential challenges in subsequent PGCC analyses. In response, we developed the Isosceles Trapezoidal Spiral Microchannel (ITSμC), a microfluidic device optimizing the Dean drag force (FD) and exploiting uniform vortices for enhanced separation. Numerical simulations highlighted ITSμC's advantage in producing robust FD compared to rectangular and standard trapezoidal channels. Empirical results confirmed its ability to segregate larger polystyrene (PS) particles (avg. diameter: 50 μm) toward the inner wall, while directing smaller ones (avg. diameter: 23 μm) outward. Utilizing ITSμC, we efficiently isolated PGCCs from doxorubicin-resistant triple-negative breast cancer (DOXR-TNBC) and patient-derived cancer (PDC) cells, achieving outstanding purity, yield, and viability rates (all greater than 90%). This precision was accomplished without fluorescent markers, and the versatility of ITSμC suggests its potential in differentiating a wide range of heterogeneous cell populations.

CFD structural design of an intake air louver for low pressure drop and high large particle separation efficiency

Due to the inadequate separation efficiency of current louver used in industrial, commercial, and residential buildings in separating large particle, leading to clogging of subsequent high-efficiency filters and increased fan energy consumption. Therefore, it is essential to increase separation efficiency of large particle for fresh air intake to reduce the burden on the filter. In this study, a novel louver has higher large particle separation efficiency with lower pressure drop was developed based on experiments and computational fluid dynamics (CFD) model. The effect of different structural parameters (number, length and location of dustproof hooks) and inlet air velocity on separation efficiency and pressure drop was evaluated. Results showed that mentioned factors could pose important impacts on pressure drop and separation efficiency. With the increase of inlet air velocity from 2.3 m/s to 2.8 m/s, the separation efficiency of the louver was decreased from 80.3 % to 57.3 %, while the pressure drop of the louver was increased from 11.1 Pa to 13.9 Pa. In addition, when inlet air velocity was 2.8 m/s, compared with the commercial louver, the pressure drop of louver was reduced by 89.5 %, the large particle separation efficiency was increased by 158.6 %.

Study on the performance of downhole axial cyclone with spiral fins for drainage and sand removal

When dewatering and resurrecting natural gas-flooded wells, sand-out problems can pose a serious hazard to downhole tools. At present, the downhole cyclone has more research on the separation of large particles of 60–70 µm, which is a serious hazard, but there is little research on the separation of fine particles of 10 µm. To improve the separation efficiency of downhole fine sand particles, this paper designs a new type of axial cyclone, in which a spiral fin is installed at the axis of the cyclone to improve the strength of the cyclone inner cyclone flow through the spiral fin so that the fine particles involved in the inner cyclone flow are thrown back into the outer cyclone flow area. This paper combines theoretical analysis, experimental study, and numerical simulation to compare and analyze the fluid transport law and internal flow field characteristics in the new cyclone and the basic cyclone, and the results show that the separation efficiency of the new cyclone for 10 µm fine particles is significantly improved and the pressure drop is slightly increased. In this paper, we also optimized the structural parameters such as envelope diameter, pitch, and length of the spiral fins. The separation performance is optimal when the envelope diameter is 10 mm, pitch is 40 mm and length is 240 mm, and the separation efficiency of 10 µm fine particles can reach 65.1%, which is a year-on-year increase of 99.1% compared with the basic separator, and the pressure drop is 0.231 MPa, which is a year-on-year increase of 31.2%.

Selective enrichment of plasma cell-free messenger RNA in cancer-associated extracellular vesicles

Extracellular vesicles (EVs) have been shown as key mediators of extracellular small RNA transport. However, carriers of cell-free messenger RNA (cf-mRNA) in human biofluids and their association with cancer remain poorly understood. Here, we performed a transcriptomic analysis of size-fractionated plasma from lung cancer, liver cancer, multiple myeloma, and healthy donors. Morphology and size distribution analysis showed the successful separation of large and medium particles from other soluble plasma protein fractions. We developed a strategy to purify and sequence ultra-low amounts of cf-mRNA from particle and protein enriched subpopulations with the implementation of RNA spike-ins to control for technical variability and to normalize for intrinsic drastic differences in cf-mRNA amount carried in each plasma fraction. We found that the majority of cf-mRNA was enriched and protected in EVs with remarkable stability in RNase-rich environments. We observed specific enrichment patterns of cancer-associated cf-mRNA in each particle and protein enriched subpopulation. The EV-enriched differentiating genes were associated with specific biological pathways, such as immune systems, liver function, and toxic substance regulation in lung cancer, liver cancer, and multiple myeloma, respectively. Our results suggest that dissecting the complexity of EV subpopulations illuminates their biological significance and offers a promising liquid biopsy approach.

Apparent viscosity of high-density fluidized bed and synergistic effect of density and apparent viscosity on particle separation

ABSTRACT For gas-solid fluidization separation, mineral particles are separated under the joint action of bed density and apparent viscosity. In present study, the apparent viscosity of high-density binary mixture media was investigated by the falling ball method. Moreover, the significant effects of bed density and apparent viscosity on simulated mineral pellets and their interactions were investigated. The apparent viscosity model of high-density gas-solid fluidized beds was modified, and it was found that the Pearson correlation coefficient is 0.86. The results show that the apparent viscosity of high-density gas-solid fluidized bed decreases with increasing fluidization gas velocity. When the fluidization number is higher than 1.3, the apparent viscosity is basically stable in the range of 3.96–5.21 Pa·s. Under low apparent viscosity, when the pellet diameter is 20 mm and the density difference ∆ρ is greater than 0.27 g/cm3, gravity is the dominant factor affecting the settling behavior of the pellet. Under high apparent viscosity, the effect of viscous resistance on the settling behavior of pellets is dominant when the ∆ρ is less than 0.27 g/cm3. Based on the performed analyses, the low-viscosity medium can be selected for the separation of large mineral particles. Furthermore, for high-viscosity medium, the influence of bubbles on particle sedimentation can be effectively alleviated and it can be selected for the separation of small particles.

Yukawa-Friedel-tail pair potentials for warm dense matter applications.

Accurate equationsof state (EOS) and plasma transport properties are essential for numerical simulations of warm dense matter encountered in many high-energy-density situations. Molecular dynamics (MD) is a simulation method that generates EOS and transport data using an externally provided potential to dynamically evolve the particles without further reference to the electrons. To minimize computational cost, pair potentials needed in MD may be obtained from the neutral-pseudoatom (NPA) approach, a form of single-ion density functional theory (DFT), where many-ion effects are included via ion-ion correlation functionals. Standard N-ion DFT-MD provides pair potentials via the force matching technique but at much greater computational cost. Here we propose a simple analytic model for pair potentials with physically meaningful parameters based on a Yukawa form with a thermally damped Friedel tail (YFT) applicable to systems containing free electrons. The YFT model accurately fits NPA pair potentials or the nonparametric force-matched potentials from N-ion DFT-MD, showing excellent agreement for a wide range of conditions. The YFT form provides accurate extrapolations of the NPA or force-matched potentials for small and large particle separations within a physical model. Our method can be adopted to treat plasma mixtures, allowing for large-scale simulations of multispecies warm dense matter.

Nucleation and growth of iron pebbles explains the formation of iron-rich planets akin to Mercury

The pathway to forming the iron-rich planet Mercury remains mysterious. Its core makes up 70% of the planetary mass, which implies a significant enrichment of iron relative to silicates, while its mantle is strongly depleted in oxidised iron. The high core mass fraction is traditionally ascribed to evaporative loss of silicates, for example following a giant impact, but the high abundance of moderately volatile elements in the mantle of Mercury is inconsistent with reaching temperatures significantly above 1000 K during its formation. Here we explore the nucleation of solid particles from a gas of solar composition that cools down in the hot inner regions of the protoplanetary disc. The high surface tension of iron causes iron particles to nucleate homogeneously (i.e. not on a more refractory substrate) under very high supersaturation. The low nucleation rates lead to depositional growth of large iron pebbles on a sparse population of nucleated iron nanoparticles. Silicates in the form of iron-free MgSiO3 nucleate at similar temperatures but obtain smaller sizes because of the much higher number of nucleated particles. This results in a chemical separation of large iron particles from silicate particles with ten times lower Stokes numbers. We propose that such conditions lead to the formation of iron-rich planetesimals by the streaming instability. In this view, Mercury formed by accretion of iron-rich planetesimals with a subsolar abundance of highly reduced silicate material. Our results imply that the iron-rich planets known to orbit the Sun and other stars are not required to have experienced mantle-stripping impacts. Instead, their formation could be a direct consequence of temperature fluctuations in protoplanetary discs and chemical separation of distinct crystal species through the ensuing nucleation process.

Simple Method for the Extraction and Determination of Ti-, Zn-, Ag-, and Au-Containing Nanoparticles in Sediments Using Single-Particle Inductively Coupled Plasma Mass Spectrometry.

The quantitative analysis of nanoparticles (NPs) in the environment is significantly important for the exploration of the occurrence, fate, and toxicological behaviors of NPs and their subsequent environmental risks. Some protocols have been recommended for the separation and extraction of NPs that are potentially dispersed in complex environmental matrixes, e.g. sediments and soils, but they remain limited. However, certain factors that may significantly affect extraction efficiency have not been comprehensively explored. In this study, on the basis of the single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) technique, a simple standardized protocol for separating and analyzing metal-containing NPs in sediment samples was developed. On consideration of the extraction efficiencies of indigenous NPs (Ti- and Zn-NPs) and spiked NPs (Ag- and Au-NPs) in sediments, sedimentation with a settling time of 6 h is recommended for the separation of NPs and large particles, and the optimal sediment to water ratio, ultrasonication power, time, and temperature are 0.4 mg/mL, 285 W, 20 min, and 15-25 °C, respectively. On the basis of the optimized method, the recoveries of spiked Ag and Au-NPs were 71.4% and 81.1%, respectively. The applicability of the optimal protocols was verified, and TOC was proved to be an important factor controlling the separation and extraction of NPs in environmental samples. The separation and extraction of NPs in elevated TOC samples can be improved by increasing the ultrasonication power, time, and temperature.

Continuous Interfacial Centrifugal Separation and Recovery of Silver Nanoparticles

AbstractContinuous‐flow separation and recovery of silver nanoparticles (AgNPs) using an annular centrifugal extractor (ACE) is demonstrated. Separation was achieved at the liquid‐liquid interface based on the balance between centrifugal force and the solubility of the capping agent. A mathematical model is presented to understand the mechanism in greater detail. The separation of poly(vinylpyrrolidone) (PVP)‐coated AgNPs in an ACE using a strong immiscible solvent was performed. The material accumulated at the interface was separated periodically without discontinuing the operation. The method is also suitable for separation of large particles or 1D/2D nanostructures even employing a single annular centrifugal extractor. Stable AgNPs were selected for a detailed antimicrobial activity study.

Confined Space Enables Spontaneous Liquid Separation by Molecular Size: Selective Absorption of Alkanes into a Polyolefin Cast Film

The depletion force has been used to explain phase separation phenomena in colloidal systems. Here, we showed that depletion force can explain not only phase separation of large and small colloidal particles but also preferential absorption of larger molecules from a mixture of large and small molecules in a liquid state. When a polyolefin cast film was immersed in a mixture of long and short normal alkanes, the longer molecules were selectively absorbed into the film. This experimental result was explained from the viewpoint of depletion force. The main finding was the use of confined space to emphasize the separation tendency caused by the force. In general, the increase in entropy may serve as a driving force to mix molecules. However, if sufficiently narrow pores are present, large and small molecules are separated naturally by size as the entropy increases. This finding will lead to size exclusion chromatography of low-mass molecules, similar to gel permeation chromatography of macromolecules. In order to demonstrate the effect of depletion force, we selected and experimented with a system based on a polyolefin isotactic poly(4-methyl-1-pentene) (P4MP1) film and a normal alkane mixture and realized high molecular selectivity. The P4MP1 film we used can be prepared simply by evaporating the solvent from the solution and casting the film. On the basis of the Asakura-Oosawa theory, we concluded that spontaneous and high molecular selectivity is attributed to the depletion force provided by the small sub-nanopores with uniform size in the film.

Interplay between Short- and Long-Ranged Forces Leading to the Formation of Ag Nanoparticle Superlattice.

Nanoparticle (NP) superlattices have attracted increasing attention due to their unique physicochemical properties. However, key questions persist regarding the correlation between short- and long-range driving forces for nanoparticle assembly and resultant capability to predict the transient and final superlattice structure. Here the self-assembly of Ag NPs in aqueous solutions is investigated by employing in situ liquid cell transmission electron microscopy, combined with atomic force microscopy-based force measurements, and theoretical calculations. Despite the NPs exhibiting instantaneous Brownian motion, it is found that the dynamic behavior of NPs is correlated with the van der Waals force, sometimes unexpectedly over relatively large particle separations. After the NPs assemble into clusters, a delicate balance between the hydration and van der Waals forces results in a distinct distribution of particle separation, which is ascribed to layers of hydrated ions adsorbed on the NP surface. The study demonstrates pivotal roles of the complicated correlation between interparticle forces; potentially enabling the control of particle separation, which is critical for tailoring the properties of NP superlattices.

Enhanced and suppressed multiscale dispersion of bidisperse inertial particles due to gravity

Using Direct Numerical Simulations (DNS), we investigate how gravity modifies the multiscale dispersion of bidisperse inertial particles in isotropic turbulence. The DNS has a Taylor Reynolds number $R_\lambda=398$, and we simulate Stokes numbers (based on the Kolmogorov timescale) in the range $St\leq 3$ , and consider Froude numbers $Fr = 0.052$ and $\infty$, corresponding to strong gravity and no gravity, respectively. The degree of bidispersity is quantified by the difference in the Stokes number of the particles $|\Delta St|$. We first consider the mean-square separation of bidisperse particle-pairs and find that without gravity (i.e. $Fr = \infty$), bidispersity leads to an enhancement of the the mean-square separation over a significant range of scales. When $|\Delta St|\geq O(1)$, the relative dispersion is further enhanced by gravity due to the large difference in the settling velocities of the two particles. However, when $|\Delta St|\ll1$, gravity suppresses the relative dispersion as the settling velocity contribution is small, and gravity suppresses the non-local contribution to the particle dynamics. In order to gain further insights, we consider separately the relative dispersion in the vertical (parallel to gravity) and horizontal directions. As expected, the vertical relative dispersion can be strongly enhanced by gravity due to differences in the settling velocities of the two particles. However, a key finding of our study is that gravity can also significantly enhance the horizontal relative dispersion. This non-trivial effect occurs because fast settling particles experience rapid fluctuations in the fluid velocity field along their trajectory, leading to enhanced particle accelerations and relative velocities. For sufficiently large initial particle separations...

Capillary Interaction and Self-Assembly of Tilted Magnetic Ellipsoidal Particles at Liquid Interfaces.

Magnetic ellipsoidal particles adsorbed at a liquid interface provide exciting opportunities for creating switchable functional materials, where self-assembly can be switched on and off using an external field [Davies et al., Adv. Mater., 2014, 26, 6715]. In order to gain a deeper understanding of this novel system in the presence of an external field, we study the capillary interaction and self-assembly of tilted ellipsoids using analytical theory and finite element simulations. We derive an analytical expression for the dipolar capillary interaction between tilted ellipsoids in elliptical polar coordinates, which exhibits a 1/r2 power law dependence in the far field (i.e., large particle separations r) and correctly captures the orientational dependence of the capillary interactions in the near field. Using this dipole potential and finite element simulations, we further analyze the energy landscape of particle clusters consisting of up to eight tilted ellipsoids in contact. For clusters of two particles, we find that the side-to-side configuration is stable, whereas the tip-to-tip configuration is unstable. However, for clusters of more than three particles, we find that circular loops of side-to-side particles become globally stable, whereas linear chains of side-to-side particles become metastable. Furthermore, the energy barrier for the linear-to-loop transition decreases with increasing particle number. Our results explain both thermodynamically and kinetically why tilted ellipsoids assemble side-to-side locally but have a strong tendency to form loops on larger length scales.

Two-point active microrheology in a viscous medium exploiting a motional resonance excited in dual-trap optical tweezers.

Two-point microrheology measurements from widely separated colloidal particles approach the bulk viscosity of the host medium more reliably than corresponding single-point measurements. In addition, active microrheology offers the advantage of enhanced signal to noise over passive techniques. Recently, we reported the observation of a motional resonance induced in a probe particle in dual-trap optical tweezers when the control particle was driven externally [Paul et al., Phys. Rev. E 96, 050102(R) (2017)2470-004510.1103/PhysRevE.96.050102]. We now demonstrate that the amplitude and phase characteristics of the motional resonance can be used as a sensitive tool for active two-point microrheology to measure the viscosity of a viscous fluid. Thus, we measure the viscosity of viscous liquids from both the amplitude and phase response of the resonance, and demonstrate that the zero crossing of the phase response of the probe particle with respect to the external drive is superior compared to the amplitude response in measuring viscosity at large particle separations. We compare our viscosity measurements with those using a commercial rheometer and obtain an agreement ∼1%. The method can be extended to viscoelastic material where the frequency dependence of the resonance may provide further accuracy for active microrheological measurements.

Particle-pair relative velocity measurement in high-Reynolds-number homogeneous and isotropic turbulence using 4-frame particle tracking velocimetry

The radial relative velocity between particles suspended in turbulent flow plays a critical role in droplet collision and growth. We present a simple and accurate approach to RV measurement in isotropic turbulence - planar 4-frame particle tracking velocimetry - using routine PIV hardware. This study demonstrates the feasibility of accurately measuring RV using routine hardware and verifies, for the first time, the path-history and inertial filtering effects on particle-pair RV at large particle separations experimentally.

Reducing the critical particle diameter in (highly) asymmetric sieve-based lateral displacement devices

Deterministic lateral displacement technology was originally developed in the realm of microfluidics, but has potential for larger scale separation as well. In our previous studies, we proposed a sieve-based lateral displacement device inspired on the principle of deterministic lateral displacement. The advantages of this new device is that it gives a lower pressure drop, lower risk of particle accumulation, higher throughput and is simpler to manufacture. However, until now this device has only been investigated for its separation of large particles of around 785 µm diameter. To separate smaller particles, we investigate several design parameters for their influence on the critical particle diameter. In a dimensionless evaluation, device designs with different geometry and dimensions were compared. It was found that sieve-based lateral displacement devices are able to displace particles due to the crucial role of the flow profile, despite of their unusual and asymmetric design. These results demonstrate the possibility to actively steer the velocity profile in order to reduce the critical diameter in deterministic lateral displacement devices, which makes this separation principle more accessible for large-scale, high throughput applications.

Effects of grinding montmorillonite and illite on their modification by dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate

Montmorillonite (Mt) and illite (Ilt) were ground for different times under wet condition and sequentially subjected to organic modification by dioctadecyl dimethyl ammonium chloride (DDAC). The influence of the grinding time on the obtained products in terms of DDAC loading and ClO4− adsorption were evaluated. Multiple techniques were used to characterize the changes in structure and morphology before and after mechanical or organic modification. Compared with Ilt, Mt showed a stronger resistance to mechanical treatment due to its swelling property. Silicon nuclear magnetic resonance (29Si NMR) spectra and X-ray diffraction (XRD) patterns of samples ground for 30min indicate the disintegration of Ilt and exfoliation of Mt, resulting in increase of ClO4− uptake by 147% for OIlt and 13% for OMt. Three stages in the grinding Mt can be proposed, including the separation of large particles into small particles, exfoliation of small particles, and disintegration of exfoliated single layers. In contrast, two stages are involved in the grinding Ilt, which are the destruction/exfoliation of large particles and further disintegration of small exfoliated layers.

Performance Determination of Novel Design Eddy Current Separator for Recycling of Non-Ferrous Metal Particles

Improvements were made in the study for the design of the conventional Eddy Current Separator (ECS) used for separating small sized non-ferrous particles in the waste. These improvements include decreasing the air gap between the material and magnetic drum, making the drum position adjustable and placing the splitter closer to the drum. Thus, small particles were separated with high efficiency. The magnetic drum was removed from inside the ECS conveyor belt system as design change and was placed as a separate unit. Hence, the force generated on the test material increased by about 5.5 times while the air gap between the non-ferrous materials and drum decreased from 3 mm to 1 mm. The non-metal material in the waste is separated before the drum in the novel design. Whereas non-ferrous metal particles are separated by falling into the splitter as a result of the force generated as soon as the particles fall on the drum. Every material that passes through the drum can be recycled as a result of moving the splitter closer to the contact point of the drum. In addition, the drum can also be used for the efficient separation of large particles since its position can be adjusted according to the size of the waste material. The performance of the novel design ECS was verified via analytical approaches, finite element analysis (FEA) and experimental studies.