Particle Concentration Research Articles

Hybrid particle-phase field model and renormalized surface tension in dilute suspensions of nanoparticles

We present a two-phase field model and a hybrid particle-phase field model to simulate dilute colloidal sedimentation and flotation near a liquid-gas interface (or fluid-fluid interface in general). Both models are coupled to the incompressible Stokes equation, which is solved numerically using a combination of sine and regular Fourier transforms to account for the no-slip boundary conditions at the boundaries. The continuum two-phase field model allows us to analytically solve the equilibrium interfacial profile using a perturbative approach, demonstrating excellent agreement with numerical simulations. Notably, we show that strong coupling to particle dynamics can significantly alter the liquid-gas interface, thereby modifying the liquid-gas interfacial tension. In particular, we show that the renormalized surface tension is monotonically decreasing with increasing colloidal particle concentration and decreasing buoyant mass. Published by the American Physical Society 2024

Modeling and Simulation of Sand Particle Trajectories and Erosion in a Transonic Fan Stage

Abstract In desert regions, the high concentrations of dust and sand particles carried by storms are sucked into aircraft engines, leading to severe erosion. This numerical study analyses the movement of sand particles and the erosion process in the front components of a high-bypass turbofan engine (HBTFE). The components include the Pitot intake, spinner, fan, core flow inlet guide vanes (IGVs), and secondary flow outlet guide vanes (OGVs). The study focuses on the engine operating conditions during takeoff from a Saharan airfield. The flow field data is obtained separately, and exported to an in-house particle tracking code based on the Lagrangian approach. The finite element method (FEM) is used to track the particles as they move through the mesh cells and determine the precise impacts and conditions to calculate the local erosion rates and material removal. Obtained results indicate large numbers of sand particles impacting the fan blade at high frequency from the hub up to approximately 80% of the span, due to their deflection by the Pitot intake lip and outer contour. The pressure side (PS) of the fan blade experiences extreme erosion rates, while the highest erosion rates occur at the leading edge (LE) and towards the trailing edge (TE). At the exit of the fan blade, a significant amount of particles pass through the OGVs and typically erode its PS, while fewer particles from the lower sections of the fan pass through the IGVs. These findings reveal the erosion-prone areas that need special coating protection.

Indoor Environmental Quality in Portuguese Office Buildings: Influencing Factors and Impact of an Intervention Study

Office workers spend a considerable part of their day at the workplace, making it vital to ensure proper indoor environmental quality (IEQ) conditions in office buildings. This work aimed to identify significant factors influencing IEQ and assess the effectiveness of an environmental intervention program, which included the introduction of indoor plants, carbon dioxide (CO2) sensors, ventilation, and printer relocation (source control), in six modern office buildings in improving IEQ. Thirty office spaces in Porto, Portugal, were randomly divided into intervention and control groups. Indoor air quality, thermal comfort, illuminance, and noise were monitored before and after a 14-day intervention implementation. Occupancy, natural ventilation, floor type, and cleaning time significantly influenced IEQ levels. Biophilic interventions appeared to decrease volatile organic compound concentrations by 30%. Installing CO2 sensors and optimizing ventilation strategies in an office that mainly relies on natural ventilation effectively improved air renewal and resulted in a 28% decrease in CO2 levels. The implementation of a source control intervention led to a decrease in ultrafine particle and ozone concentrations by 14% and 85%, respectively. However, an unexpected increase in airborne particle levels was detected. Overall, for a sample of offices that presented acceptable IEQ levels, the intervention program had only minor or inconsistent impacts. Offices with declared IEQ problems are prime candidates for further research to fully understand the potential of environmental interventions.

The emission and physicochemical properties of airborne microplastics and nanoplastics generated during the mechanical recycling of plastic via shredding

This study examined the emission and physicochemical properties of microplastics and nanoplastics (MPs/NPs) generated during shredding, which is regularly used in mechanical recycling. Waste and new polyethylene terephthalate, polypropylene, and high-density polyethylene were investigated herein for a total of six categories. The concentration and size distribution of particles were measured using two spectrometer instruments, and morphology and elemental composition of emitted particles were analyzed with microscopy and spectroscopy. This study found that number concentrations in both submicron and micron sizes of respirable particles were 3–2910× higher during periods of shredding than pre-shredding background concentrations. Maximum concentrations of particles within 10–420 nm, across all six categories, ranged from 22,000- to 1,300,000-particles/cm3 during shredding, compared to average background levels of 700 particles/cm3. Maximum concentrations of particles within 0.3 to 10 μm, across all six categories, ranged from 24- to 2000-particles/cm3 during shredding, compared to average background levels of 2 particles/cm3. Waste plastics consistently generated higher emissions than their new counterparts, which is attributed to the labels, adhesives, and increased additives incorporated into the waste plastic. Morphology varied drastically between particles and an elemental composition analysis found that the samples consisted primarily of C and O, representing the polymer material, as well as Na, Mg, Al, Si, Cu, Cl, K, Ca, Ti, Fe, Rb, and Br representing additives, label, and other contaminates. The shredding of plastic has the potential to expose workers to elevated concentrations of airborne MPs/NPs, especially those between 10 and 100 nm.

Boosting Erosion‐Corrosion Resistance: Collaborative Ni–P Electroless Deposition on Poly‐Amino‐Alcohol@Functionalized GO Matrices

AbstractIn recent years, protective coatings have become crucial in graphene‐based chemical studies. This research investigates the anticorrosive properties of coatings created by co‐depositing carbon compounds. Electroless Ni−P‐PAA@F‐GO coatings were applied to stainless steel by adding various amounts of PAA@F‐GO particles to the Ni−P bath. The coated samples were analyzed using X‐ray diffraction and micro‐hardness tests, revealing a peak hardness of 764 HV at 30 mg/L PAA@F‐GO, compared to 521 HV for standard Ni−P coatings. Corrosion performance was evaluated in a 3 % sodium chloride solution, showing that despite a higher corrosion‐erosion rate. Although the coated samples exhibited a corrosion‐erosion rate 4.7 times higher than untreated samples, the mass loss was notably more pronounced in the untreated samples. The study found that adding PAA@F‐GO particles improved corrosion resistance and durability, with optimal results at a specific particle concentration. The enhanced performance is attributed to the increased roughness, impermeability, and hydrophobicity of the functionalized graphene oxide.

Electrodeposition of Ni-WC composite coatings: formation, structure and properties

Currently, electroplating is actively developing, and one of its promising areas is the study of composite electrochemical coatings (CEC). They are of great interest to the industrial sector, especially for mechanical engineering, due to their unique properties. CEC contain microscopic particles as additives that can significantly improve coating properties such as hardness and wear resistance. This is especially important for the manufacturing of high-quality parts of industrial mechanisms. These areas can lead to new advances in the development of better and more durable materials. In this work, composite coatings of nickel-tungsten carbide were obtained by the method of electrodeposition. The deposition was carried out in a sulfuric acid electrolyte with different concentrations of tungsten carbide. Formation of composite coatings was carried out at a concentration of dispersed particles in a sulfate electrolyte of 10 g/L. The coatings have no pores or cracks. Nickel and tungsten carbide phases were detected in the coatings by X-ray phase and micro-X-ray spectral analyses. Inclusions of WC in the nickel matrix lead to an increase in the microhardness of the coating by 10–15 times. Wear resistance was assessed under dry sliding friction with reciprocating motion; a decrease in the volume of worn material by 2–3 times was noted when tungsten carbide was added into the nickel matrix.

Study on Atomization Mechanism of Oil Injection Lubrication for Rolling Bearing Based on Stratified Method

The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using FLUENT computational fluid dynamics software (Ansys 19.2). The complex motion boundary conditions of the rolling elements were addressed through a layered approach. We can obtain more accurate boundary layer flow field changes and statistics of the diameter of oil particles in lubricating oil atomization, which lays the foundation for analyzing the law of influence on lubricating oil atomization. The results show that as the number of boundary layer layers increases, the influence of the boundary layer flow field on the lubricating oil is more obvious. The oil particle size is excessively flat, and the concentration of large particles of oil appears to decrease. As the speed increases, the amount of oil in the cavity decreases, but the oil droplets are also fragmented, which intensifies the atomization and reduces the particle diameter. This reduces the Sauter Mean Diameter (SMD), which is not conducive to the lubrication of the bearing. Under different injection pressures, when the injection pressure is large, it is beneficial to the lubrication of the bearing.

Associations Between High-Density Lipoprotein Cholesterol Efflux and Brain Grey Matter Volume.

Objective: High-density lipoprotein cholesterol efflux function may prevent brain amyloid beta deposition and neurodegeneration. However, the relevance of this finding has not been established in the diverse middle-aged population. Methods: We examined 1826 adults (47% Black adults) who participated in the Dallas Heart Study to determine associations between high-density lipoprotein (HDL) measures and brain structure and function. White matter hyperintensities (WMH) and whole-brain grey matter volume (GMV) were measured using brain MRI, and the Montreal Cognitive Assessment (MoCA) was used to measure neurocognitive function. HDL cholesterol efflux capacity (HDL-CEC) was assessed using fluorescence-labeled cholesterol efflux from J774 macrophages, and HDL particle size measures were assessed using nuclear magnetic resonance (NMR) spectroscopy (LipoScience). Multivariable linear regressions were performed to elucidate associations between HDL-CEC and brain and cognitive phenotypes after adjustment for traditional risk factors such as age, smoking status, time spent in daily physical activity, and education level. Results: Higher HDL-CEC and small HDL particle (HDL-P) concentration were positively associated with higher GMV normalized to total cranial volume (TCV) (GMV/TCV) after adjustment for relevant risk factors (β = 0.078 [95% CI: 0.029, 0.126], p = 0.002, and β = 0.063 [95% CI: 0.014, 0.111], p = 0.012, respectively). Conversely, there were no associations between HDL measures and WMH or MoCA (all p > 0.05). Associations of HDL-CEC and small HDL-P with GMV/TCV were not modified by ApoE-ε4 status or race/ethnicity. Interpretation: Higher HDL cholesterol efflux and higher plasma concentration of small HDL-P were associated with higher GMV/TCV. Additional studies are needed to explore the potential neuroprotective functions of HDL.

Semi-Lagrangian simulation of particle laden flows using an SPH framework

Particle–laden flows occur in many natural and industrial systems and simulating them can be particularly challenging. The coupling of smoothed particle hydrodynamics (SPH) with the discrete element method (DEM) can effectively simulate particle-laden multiphase fluid dynamical systems, due to the shared Lagrangian nature of both methods. However, this approach has some inherent shortcomings, including a prohibitively small time step when dealing with small particles. An alternative approach is to use an Eulerian-Eulerian reference frame, usually using finite element or finite volume discretisations. In this approach, momentum and continuity equations are solved for each discrete phase as well as the continuous phase, and particles are modelled by means of concentration and velocity fields. This approach can suffer from strong numerical diffusion in the advection of the concentrations when absolute velocities of the phases are high, whilst their relative velocities are small. This numerical diffusion can obscure important aspects of the behaviour as it can smooth out details, especially in the particle concentration fields. In order to mitigate the shortcomings of these existing techniques, we present a new SPH-based semi-Lagrangian framework for solving the momentum and continuity equations for all phases in particle-laden flows. In this framework, the discrete and continuous phases move relative to a reference frame that moves at a momentum-averaged velocity. By focusing on velocities relative to the reference frame our method substantially reduces numerical diffusion compared to traditional Eulerian-Eulerian approaches, at a lower computational cost compared to Lagrangian-Lagrangian approaches. The simulation approach is validated by means of comparisons to both computational and experimental results for a number of relevant systems including particle-liquid separation in an inclined channel, particle sedimentation in a liquid, and gas-particle fluidised beds. This new method is shown to compare very favourably in terms of both the accuracy of the results and the computational cost required to achieve them.

Acoustic enrichment of sperm for in vitro fertilization.

Assisted reproductive technology (ART) has emerged as a crucial method in modern medicine for tackling infertility. However, the success of fertilization depends on the quality and quantity of sperm, often necessitating invasive surgical intervention, which presents challenges for non-invasive in vitro fertilization. Acoustic microfluidics technology has found widespread application across various biological contexts. In this paper, we propose to introduce a novel approach using asymmetric acoustic streaming generated by a single interdigital transducer (IDT) to enhance sperm concentration and improve fertilization in vitro, particularly in cases of moderate oligozoospermia. The concentration of particles increased approximately 6-fold in the central region after acoustic enrichment. Moreover, sperm motility was significantly improved without additional DNA fragmentation, and all the oocytes remained viable after 5 min of acoustic enrichment. Notably, acoustic enrichment accelerated fertilization and embryo development, leading to a higher fertilization rate and faster cleavage speed. Specifically, within 36 hours, the multiple-cell embryo ratio was significantly increased compared to the control group. This finding further validates the feasibility and non-invasiveness of acoustic enrichment for sperm fertilization in vitro. This work provides a promising tool for in vitro fertilization, holding significant implications for assisted reproduction.

Intelligent neuron based interpretation of carreau trihybrid nanofluid model with streamline analysis: Configuration of distinct geometries

This current attempt develops a more efficient predictive model that can accurately simulate the behavior of Carreau trihybrid nanofluids in non-trivial configurations. This study interprets thermal behavior of Carreau trihybrid nanofluid model with streamline analysis considering the two geometries wedge and cone. Three nanoparticles are involved in base fluid (water) with physical effects of non-uniform heat sink source and nonlinear thermal radiation are assumed for heat transport and Lorentz forces are considered for velocity inspection. Furthermore, this study employs intelligent neural networks to interpret data for streamline and thermal transport analysis, focusing on the specific cases of wedge and cone geometries. Initial data fetched through bvp4c and further, obtained data trained through supervised neural scheme, Levenberg marquardt neural network (LM-NN) is applied and required predictions are made. Higher “Gc” indicates stronger solutal buoyancy forces, which promote upward fluid movement, thereby increasing the velocity gradient. With increasing (M), the velocity profile decreases. Fluid exhibits enhancing the velocity gradient with higher (n). Higher particle concentration enhances the fluid's viscosity and resistance.

Cu-doped calcium phosphate supraparticles for bone tissue regeneration.

Calcium phosphate (CaP) minerals have shown great promise as bone replacement materials due to their similarity to the mineral phase of natural bone. In addition to biocompatibility and osseointegration, the prevention of infection is crucial, especially due to the high concern of antibiotic resistance. In this context, a controlled drug release as well as biodegradation are important features which depend on the porosity of CaP. An increase in porosity can be achieved by using nanoparticles (NPs), which can be processed to supraparticles, combining the properties of nano- and micromaterials. In this study, Cu-doped CaP supraparticles were prepared to improve the bone substitute properties while providing antibacterial effects. In this context, a modified sol-gel process was used for the synthesis of CaP NPs, where a Ca/P molar ratio of 1.10 resulted in the formation of crystalline β-tricalcium phosphate (β-TCP) after calcination at 1000 °C. In the next step, CaP NPs with Cu2+ (0.5-15.0 wt%) were processed into supraparticles by a spray drying method. Cu release experiments of the different Cu-doped CaP supraparticles demonstrated a long-term sustained release over 14 days. The antibacterial properties of the supraparticles were determined against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, where complete antibacterial inhibition was achieved using a Cu concentration of 5.0 wt%. In addition, cell viability assays of the different CaP supraparticles with human telomerase-immortalized mesenchymal stromal cells (hMSC-TERT) exhibited high biocompatibility with particle concentrations of 0.01 mg mL-1 over 72 hours.

Interaction of Cooking-Generated Aerosols on the Human Nervous System and the Impact of Caloric Restriction Post-Exposure

Background: The inhalation of cooking-generated aerosols could lead to translocation to the brain and impact its function; therefore, the effects of cooking-generated aerosols on healthy adults were investigated using an electroencephalograph (EEG) during the 2 h period post-exposure. Methods: To explore any changes from the impact of exposure to cooking-generated aerosols on the human brain due to the absence of food intake during exposure, we divided the study participants into three groups: (A) no food intake for 2 h (2 h-zero calorie intake), (B) non-zero calorie intake, and (C) control group (simulated cooking). Results: The ultrafine particle concentrations increased from 9.0 × 103 particles/cm3 at the background level to approximately 8.74 × 104 particles/cm3 during cooking. EEGs were recorded before cooking (step 1), 60 min after cooking (step 2), 90 min after cooking (step 3), and 120 min after cooking (step 4). Comparing the non-zero calorie group with the control group, it was concluded that exposure to cooking-generated aerosols resulted in a 12.82% increase in the alpha band two hours post-exposure, compared to pre-exposure. The results revealed that zero calorie intake after exposure mitigated the impacts of cooking-generated aerosols for the alpha, beta3, theta, and delta bands, while it exacerbated effects on the whole brain for the beta1 and beta2 bands. Conclusions: While these are short-term studies, long-term exposure to cooking-generated ultrafine particles can be established through successive short-term exposures. These results underscore the need for further research into the health impacts of cooking-generated aerosols and the importance of implementing strategies to mitigate exposure.

The efficiency of portable air cleaners in reducing cross-exposure through respiratory aerosols: Effects of flowrate, location, and unit type

This study evaluates the efficacy of portable air cleaners (PACs) in a controlled climate chamber that simulates an office environment, assessing their impact on respiratory particle transmission between two thermal manikins (representing an infected and an exposed individual) as well as on the noise level in the chamber. The study explores three types of PAC, namely floor-type (PAC1), table (PAC2) and personalized (PAC3) in various locations and operation modes. The particles were generated using an aerosol generator and introduced into the infected manikin's exhalation; the particle concentration at the exposed manikin's breathing zone (BZ) was measured using an aerodynamic particle sizer. The results showed that the PAC2, operating at a flow rate of 97 m³/h, significantly reduced the intake fraction (IF) by over 90 % within the first hour, proving to be the most effective in minimizing cross-exposure risks while maintaining sound levels within the acceptable limits for office rooms. In contrast, PAC3, with a lower flow rate of 13 m³/h, reduced IF by only 21.6 % after 60 min. The result also showed that settings with higher flow rates (higher than 134 m3/h) resulted in noise levels above the maximum allowable for office spaces for all tested PACs. Additionally, prolonged operation did not further decrease IF significantly after reaching optimal reduction levels within 30–60 min, depending on the PAC type and settings. Further, the study showed that strategic placement away from direct alignment with occupants' BZ is recommended to optimize aerosol removal and noise management.

Improvement of the microstructure and corrosion behavior of Ni-TiO2 composite coatings electrodeposited at various amounts of TiO2 powder

The purpose of this study was to produce efficient Ni-TiO2 composite coatings at different concentrations of TiO2 particles to enhance BS2 microstructure and corrosion resistance in 3.5 wt. % NaCl. % NaCl solution. EDS analysis shows that the Ti and O content increases by increasing the amount of TiO2. XRD results reveal that the preferential growth plane of pure Ni is (100), which corresponds to the (111) and (100) planes for Ni-TiO2 composite coatings. SEM shows that the substrates are coated homogeneously. In addition to the microstructural improvements, the corrosion resistance efficiency was enhanced significantly with the inclusion of TiO2 particles. Specifically, the study showed that 10 g/L of TiO2 provided the optimal balance, achieving a corrosion resistance efficiency of 74.6%, along with a marked reduction in porosity. Furthermore, the surface morphology confirmed a uniform and defect-free distribution of the TiO2 particles, contributing to the overall anti-corrosion properties. These findings suggest that Ni-TiO2 composite coatings are a promising candidate for industrial applications, particularly in environments where materials are exposed to harsh conditions, such as marine environments. The outcomes of this research have the potential to inform the development of advanced anti-corrosion strategies for various industries.

Direct and Indirect Effects for Radiosensitization of Gold Nanoparticles in Proton Therapy.

The radiosensitization characteristics of gold nanoparticles (GNPs) have been investigated in a single cell irradiated with monoenergetic beams of protons of various energies using TOPAS-nBio, an advanced toolkit of TOPAS. Both direct and indirect effects against single-strand breaks (SSBs) are investigated and their double-strand breaks (DSBs) have been calculated. A single spherical cell interaction with a detailed DNA structure has been modeled and simulated under different conditions such as particle sizes and concentrations of GNPs, their biodistributions and associated proton energies. The physical interaction among protons, suspension water and GNPs has been simulated using a dual physics approach, while the interaction between water radiolysis and OH radicals was considered in the chemical process to save computational time. The present simulations involve irradiating the cell geometry with a dose of 1 Gy. The range of DSBs (Gy-1 Gbp-1) obtained was 2.1 ± 0.09 to 21.74 ± 0.4 for all GNPs of sizes 6-50 nm the proton energies in the range of 5-50 MeV. Regardless of proton energy and GNP size, the calculations showed that the contribution of indirect and hybrid DSBs remains higher in all simulation types than that of direct DSBs. New simulation outcomes of the indirect DSBs illustrate a percentage increase, while we cannot get an increase in the direct and hybrid DSBs in most cases when compared with no GNPs cases. The indirect DSBs provide the highest enhancement factor of 1.89 at 30 nm GNPs in size for 30 MeV protons energy, and the direct and hybrid DSBs indicate a slight increase in enhancement. The work indicates that the use of GNPs increased indirect DNA DSBs, while hybrid DSBs show only a slight increase in enhancement, and no enhancement is shown in direct DNA DSBs. It is significant to consider other mechanisms such as DNA damage repair when investigating DNA damage.

Interaction of a Dense Layer of Solid Particles with a Shock Wave Propagating in a Tube

A numerical simulation of an unsteady gas flow containing inert solid particles in a shock tube is carried out using the interpenetrating continuum model. The gas and dispersed phases are characterized by governing equations that express the concepts of mass, momentum, and energy conservation as well as an equation that shows the change of the volume fraction of the dispersed phase. Using a Godunov-type approach, the hyperbolic governing equations are solved numerically with an increased order of accuracy. The working section of the shock tube containing air and solid particles of various sizes is considered. The shock wave structure is discussed and computational results provide the spatial and temporal dependencies of the particle concentration and other flow quantities. The numerical simulation results are compared with available experimental and computational data.

Effect of droplet charge density on stabilization of oil‐in‐dispersion emulsions co‐stabilized by binary mixed surfactants and nanoparticles

AbstractIonic surfactant and similarly charged nanoparticles can co‐stabilize oil‐in‐dispersion (OID) emulsions at extremely low concentrations (0.001 cmc/0.001 wt%), in which particles do not adsorb at the oil/water interface but distribute in the aqueous phase forming a dispersion. In this paper, the effect of droplet charge density on stabilization of the n‐decane‐in‐water OID emulsion was examined by using a cetyl trimethyl ammonium bromide (CTAB)/C12B (dodecyl dimethyl carboxyl betaine) binary mixture at a low fixed total concentration (0.01 mM) with varying molar fractions of CTAB. A model based on the Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory is proposed to calculate interaction energies between droplets and between droplets and particles. It is found that the droplet charge density can be well compensated by particle concentration along the stabilization boundary, and the OID emulsion still follows the DLVO stabilization. Particles tend to surround droplets at large distances but may form a monolayer between approaching droplets at shorter distances, which significantly reduces the van der Waals attraction between droplets. In addition, the induced auxiliary droplet–particle repulsion is proportional to the number of particles per unit area of droplet surfaces, which together with the droplet–droplet repulsion ensures a large total repulsion preventing droplets from flocculation and coalescence. This work explains quantitatively the stabilization of OID emulsions, which have potential applications in emulsion products such as foods, cosmetics, pesticides, and various industrial emulsion systems. Moreover, the development of the OID emulsions represents an important advancement in green chemistry as it substantially reduces the required amounts of emulsifiers and their environmental impact after use.

Comparison and selection of flotation processes for the separation of fine and difficult-to-float coal particles

ABSTRACT This work compares the performance of two coal preparation plants (CPPs) with similar flotation feeds to study the compatibility between flotation process and coal slime properties and to guide the design of flotation process and equipment selection. The two plants process coal slimes using “flotation column + flotation machine” and “flotation machine + flotation machine” flowsheet, respectively. The migration rules of different size and density fractions in the flotation were experimentally studied. The operation performance between the two flotation processes was comprehensively compared. The results show that, for feedstocks with high concentration of high-ash fine slimes and intergrown particles, the dual flotation processes can effectively reject intergrown particles and high-ash fine slimes, thereby reducing the ash of flotation concentrate to meet quality requirements. In the rougher flotation column, the flotation perfection index of < 0.045 mm size fraction is 55.67%, which is 4.74% higher than that of the rougher flotation machine. In the sorting of cleaner flotation machine, the particles with low density of < 1.3 g/cm3 are collected preferentially. With the extension of the flotation process, the intergrown particles and high-ash fine slimes gradually report to the clean coal products. The flotation recovery of > 0.25 mm size fraction is relatively poorer compared to other fractions. When the feed has high content of high-ash fine slimes, the process of “flotation column + flotation machine” is preferred. When the feed has high content of middle density fraction, the process of “flotation machine + flotation machine” is preferred for dual flotation. The upper limit of feed size should be strictly controlled in flotation.

Traffic Intensity as a Factor Influencing Microplastic and Tire Wear Particle Pollution in Snow Accumulated on Urban Roads

Traffic-related roads are an underestimated source of synthetic particles in the environment. This study investigated the impact of traffic volume on microplastic (MP) and tire wear particle (TWP) pollution in road snow. An examination was conducted in a medium-sized city situated in northeastern Poland, known for being one of the cleanest regions in the country. MPs and TWPs were found at all 54 sites, regardless of the intensity of traffic. The average concentration for all samples was 354.72 pcs/L. Statistically significant differences were found between the average values of the particle concentration on low, medium, and heavy traffic roads, amounting to 62.32 pcs/L, 335.97 pcs/L, and 792.76 pcs/L, respectively. Within all three studied groups of roads, MPs and TWPs with the smallest size, ranging from 50 to 200 μm, were prevalent. In all of the studied groups of roads, four analyzed shapes of particles were found, with irregular fragments being the most abundant form (89.23%). The most frequently recorded color among the collected samples was black (99.85%), and the least frequently recorded color was blue, constituting only 0.01%. This study suggests that snow cover on the roads may act like a temporary storage of pollutants during winter particularly in the temperate climate zone and, after thawing can significantly increase the concentration of MPs and TWPs in surface waters. Possible measures to decrease the release of MPs and TWPs into the environment in the city may include reducing the traffic volume and speed, implementing street sweeping, utilizing filtration chambers, and installing stormwater bioretention systems or settling ponds.