Fine Particles Research Articles

Study on the effect of particle shape on underflow entrainment in hydrocyclone

ABSTRACT The underflow entrainment of fine particles leads to a decline in the grading performance of hydrocyclones, which is reflected in the “fishhook” effect in grade efficiency curves. This occurrence cannot be explained by existing separation theories. The primary cause of underflow entrainment of fine particles was examined from the perspective of particle shape in this study. Experimental results showed that the degree of “fishhook” effect in grade efficiency curves was Glass frit > Quartz ≥ Mica. This suggested that the underflow entrainment effect of spherical particles is stronger than non-spherical particles. Furthermore, experiments involving mixed powders of different coarse and fine components showed that, when large particles were nonspherical and small particles replaced with spherical ones of the same proportion, the underflow entrainment of fine particles situation worsened. This demonstrated that the main factor contributing to underflow entrainment was the tracking characteristics of small particles. Using EDEM coupled with Fluent to calculate the movement of different-shaped particles in the same flow field, the relationship between particle tracking characteristics and shape were analyzed. The results showed that the tracking characteristics of nonspherical particles was significantly less than that of spherical particles.

Characterisation of the Overflow Pipe Structure on the Internal Flow Field of a Hydrocyclone

The application of cyclones can be traced back to 100 years ago. Salt, an important carrier of energy exchange in the human body, is one of the essential substances. Currently, salt surface impurities are mostly removed manually, resulting in low sorting efficiency. Cyclones, as important physical separation equipment, are widely used in separating different substances. This paper focuses on using cyclones for salt decontamination. However, due to the limitations of the cyclone’s structure, ensuring grading accuracy is challenging. The flow field, as the main power source in the cyclone grading process, significantly impacts the grading effect. The overflow pipe, where fine particles exit, has a significant effect on the internal flow field. To explore the impact of the overflow pipe structure on the cyclone’s internal flow field, five overflow pipe structures were designed and numerically analyzed. The results indicate that the improved overflow tube structure has higher static pressure than the conventional linear structure. Type 2 (Parabolic) has the highest tangential velocity, which is 27.7 percentage points higher than that of the conventional cyclone, while Type 3 (hyperbola) has the lowest axial velocity(minimum value is only 0.3 m/s) and turbulence intensity(minimum value of the cone segment is only 0.2), resulting in longer particle residence time in the cyclone for better separation. Additionally, vortices are effectively avoided, improving the stability of the flow field to some extent. The obtained data provide a theoretical basis and support for the structural design of new cyclones.

Nanoparticles: Toxicity Assessment, Health Risks and Medical Applications

With decreasing size of atmospheric aerosol particles, their ability to penetrate deeper into the respiratory system increases. Ultrafine particles (UFPs) and nanoparticles (NPs), defined as atmospheric aerosol particles smaller than 100 nm, have been identified as potentially the most dangerous to human health due to their ability to penetrate easily the lung epithelial wall into the blood, which transports them to other organs. Despite considerable toxicological evidence of the potential harmful effects of these particles on human health, the appropriate metric for assessing their health effects is still unclear. This article describes various methods used to assess particle toxicity, the mechanism of toxic action of particles and the use of NPs in medicine.

Allergology : what's new in 2024

In recent years, studies have focused on the in vitro diagnosis of immediate drug reactions, with new recommendations concerning the use of the basophil activation test. Air pollution, particularly fine particles with a diameter of less than or equal to 2.5 m (PM2.5) and less than or equal to 10 m (PM10), is contributing to an increase in emergency room visits and hospital admissions for asthma exacerbations. Skin tests and specific immunoglobulin E assays have highly variable sensitivity and specificity depending on the type of food. Finally, new collaborations between allergists and oncologists have led to the adoption of joint positions, highlighting the possible protective effect of atopy on the development of gliomas.

Fine and Ultrafine Particle Concentrations in a Cannabis Consumption Lounge

Fine and Ultrafine Particle Concentrations in a Cannabis Consumption Lounge

Structure and phase dynamics in electrospray deposited amorphous MoO3 via thermal treatment

Abstract The molybdenum oxides with distinct structure and phases have shown unique properties that are of interest in many scientific and technological applications. However, the scalability to large area deposition and in particular the deposition on the surfaces with specific topology, with a uniform and controlled structure still remains a challenge. In this work a uniform MoO$_3$ film with amorphous structure was achieved via electrospray deposition from fine particles dispersion in water.
A high vapor pressure of solvent was utilized for the progress of the deposition. As-deposited films with large thicknesses ($< 1 \mu$m) show amorphous structures with mean roughness lower than $\sim$ 32 nm. The deposited film subsequently was subject to the thermal treatment with optimal thermodynamic parameters in order to modify the structure, the phase, the defect density and subsequently the electronic properties of the final structure. It is shown that a uniform coating layer with controlled structure and defect density can be achieved. This method facilitates the deposition of the oxide layer on variety of the unconventional surfaces with large area as well as curved geometry.

The Addition of Pumpkin Flour Impacts the Functional and Bioactive Properties of Soft Wheat Composite Flour Blends

Growing interest in functional food ingredients has led to the exploration of pumpkin flour as a nutritional enhancer in wheat-based products. This study investigated the impact of pumpkin flour incorporation (0–20%) on soft wheat flour blends’ technological and bioactive properties. The comprehensive analysis included granulometric distribution, techno-functional properties (WHC, WAC, WAI, WSI, SP, OAC), pasting characteristics (RVA), gel texture (TPA), rheological behaviour (frequency sweeps), colour parameters, and bioactive compounds (TPC, DPPH, ABTS) in both water and ethanol extracts. Pumpkin flour addition systematically modified blend properties, with higher fine particle content (13.26% < 80 μm), enhancing water interaction capabilities (WHC increased from 2.52 to 3.56). Pasting behaviour showed reduced peak viscosity (2444.0 mPa·s to 1859.5 mPa·s) but enhanced gel structure stability, evidenced by increased storage modulus (112.7 Pa to 1151.0 Pa) and reduced frequency dependence. Colour parameters showed progressive darkening (L* 91.00 to 84.28) and increased yellow-orange intensity (b* 10.13 to 27.13). Bioactive properties improved significantly, with TPC increasing up to 0.57 mg/1 g DM and 0.34 GAE mg/1 g DM in water and ethanol extracts, respectively, accompanied by enhanced antioxidant activity. Pumpkin flour incorporation successfully enhanced both functional and bioactive properties of wheat flour blends, with particle size distribution and water interactions serving as fundamental determinants of technological functionality, while contributing to improved nutritional value through increased bioactive compounds.

Effect of column segment diameter ratio on flow field and separation performance of the composite column-cone hydrocyclone

To address the misplacement of fine particles in the underflow caused by structural defects in conventional hydrocyclones, a composite column-cone hydrocyclone (C-C hydrocyclone) was proposed, featuring a cone-column-cone structure. Computational Fluid Dynamics (CFD) techniques were employed to study the diameter ratio and various configurations of C-C hydrocyclone, assessing the impact on separation performance. Results indicated that increasing the column section diameter ratio from 0.5 to 0.7 reduced the cutting size by 22.96 %, enhanced sharpness by 9.87 %, and improved separation efficiency. These findings offer valuable insights for the design and application of C-C hydrocyclones based on specific requirements such as grinding classification and flotation operations.

A Laboratory Investigation into the Effect of Coarse-Grained Layer Mixing with Fine Particles on the Water Storage Capacity of a Capillary Barrier Cover

A Laboratory Investigation into the Effect of Coarse-Grained Layer Mixing with Fine Particles on the Water Storage Capacity of a Capillary Barrier Cover

CFD modelling and simulations of atomization-based processes for production of drug particles: A review.

Atomization-based techniques are widely used in pharmaceutical industry for production of fine drug particles due to their versatility and adaptability. Key performance measure of such techniques is their ability to provide control over critical quality attributes (CQAs) of produced drug particles. CQAs of drug particles produced via atomization critically depend on fluid dynamics of sprays; resulting mixing, heat and mass transfer; distribution of supersaturation and subsequent nucleation and growth of particles. It is essential to develop and use computational fluid dynamics (CFD) models for adequate understanding of multi-scale transport processes ranging from molecular scale mixing and particle scale processes, and from atomizer nozzle to overall spray chamber scale establishing relationships between CQAs and design and operating parameters of spray nozzle and chamber. In this work, we critically review past and current research efforts on CFD modelling of pharmaceutical atomization-based processes with an objective to provide clear assessment of the state of the art and to provide recommendations. An overview of the key atomization-based methods for producing drug particles with desired CQAs is presented. Key underlying physical processes and relevant concepts are then outlined. This discussion is related to the demands on CFD models; and state of the art is then discussed with respect to the process needs. Recommendations are provided towards higher fidelity and more efficient models of atomized multiphase flow dynamics and turbulence, drying modelling for the produced particles, and validation approaches. We conclude by highlighting a perceived need for numerical atomization studies with a pharmaceutical context; then, we deliver an outlook on current promising active control and machine learning strategies to augment the shift towards quality-by-design approaches in pharmaceutical manufacturing.

Particle fluxes by subtropical pelagic communities under ocean alkalinity enhancement

Abstract. Ocean alkalinity enhancement (OAE) has been proposed as a carbon dioxide removal technology (CDR), allowing for long-term storage of carbon dioxide in the ocean. By changing the carbonate speciation in seawater, OAE may potentially alter marine ecosystems with implications for the biological carbon pump. Using mesocosms in the subtropical North Atlantic, we provide first empirical insights into impacts of carbonate-based OAE on the vertical flux and attenuation of sinking particles in an oligotrophic plankton community. We enhanced total alkalinity (TA) in increments of 300 µmol kg−1, reaching up to ΔTA = 2400 µmol kg−1 compared to ambient TA. We applied a pCO2-equilibrated OAE approach; i.e., dissolved inorganic carbon (DIC) was raised simultaneously with TA to maintain seawater pCO2 in equilibrium with the atmosphere, thereby keeping perturbations of seawater carbonate chemistry moderate. The vertical flux of major elements, including carbon, nitrogen, phosphorus, and silicon, as well as their stoichiometric ratios (e.g., carbon-to-nitrogen ratios), remained unaffected over 29 d of OAE. The particle properties controlling the flux attenuation, including sinking velocities and remineralization rates, also remained unaffected by OAE. However, we observed abiotic mineral precipitation at high OAE levels (ΔTA = 1800 µmol kg−1 and higher) that resulted in a substantial increase in particulate inorganic carbon (PIC) formation. The associated consumption of alkalinity reduces the efficiency of CO2 removal and emphasizes the importance of maintaining OAE within a carefully defined operating range. Our findings suggest that carbon export by oligotrophic plankton communities is insensitive to OAE perturbations using a CO2 pre-equilibrated approach. The integrity of ecosystem services is a prerequisite for large-scale application and should be further tested across a variety of nutrient regimes and for less idealized OAE approaches.

Adverse Effects and Underlying Mechanisms of Soil Microplastics on Crops and Its Preventive Strategies

Microplastics （MPs）, as a type of emerging environmental pollutant with a particle size < 5 mm, have been frequently detected in environmental matrices. MPs pollution in soils has been attracting the scientific community due to the increasing contaminant areas and continuous accumulation, leading to a high risk to crop production. In addition, recent studies have observed that long-term exposure to MPs could seriously harm the soil ecosystem because of their fine particle size and persistence in soils. Given that, in this review, we summarized the pollution status of MPs in soils, the adverse effects and underlying mechanisms of soil microplastics on crops, and their preventive strategies. The hazardous substances that may be released by MPs and the toxic mechanisms of MPs or MPs/absorbed contaminants were reviewed. The results suggested that the main adverse effects of soil MPs on crops were mechanical damage, oxidative stress reactions, and genotoxicity to plants, eventually leading to disorders of plant growth and development and physiological metabolism. Source control and biodegradation of soil MPs were considered effective approaches to decreasing their risks. Finally, existing studies on the shortcomings of the toxic effects of MPs on crops were recapitulated, and the future research direction of MPs was prospected, aiming to provide a reference for future research in the fields of agricultural soil ecosystems and pollution control of microplastics.

How fine particles alter wave propagation in granular media: insights from micromechanical modelling

This paper presents an attempt to address an intriguing question about the role of fine particles in altering wave propagation in granular media from the micromechanical perspective. Special effort is made to examine whether the state dependency of shear wave velocity can be characterised in a unified manner and to establish micromechanical understanding on the observations from recent physical experiments. To simulate the wave propagation accurately, several novel techniques are used to build the numerical model to a scale comparable to laboratory specimens and to effectively eliminate the near-field effect and boundary reflections. It is shown that, with the presence of fines, the degradation of elastic wave velocity is directly associated with the reduction of coordination number. The dispersion relationship constructed from the space-time data of all particles reveals that even a small quantity of fines can cause severe frequency filtering and attenuation. Tied up with recent experimental work, the unified method of characterising the shear wave velocity by the state parameter in the critical state theory is confirmed by the simulations of both small-strain wave propagation and large-strain triaxial compression tests. At the microscopic level, a sound relationship is found between the mechanical coordination number and the stress-normalised shear wave velocity.

Air pollution modifies colonisation factors in beneficial symbiont Snodgrassella and disrupts the bumblebee gut microbiome

Particulate air pollutants, a major air pollution component, are detrimental to human health and a significant risk to wildlife and ecosystems globally. Here we report the effects of particulate pollutant black carbon on the beneficial gut microbiome of important global insect pollinator, the buff-tailed bumblebee (Bombus terrestris). Our data shows that exposure to black carbon particulates alters biofilm structure, gene expression and initial adhesion of beneficial bee gut coloniser, Snodgrassella alvi. Exposure of adult Bombus terrestris to non-toxic black carbon particulates significantly increased viable bacteria on MRS agar and 16S absolute abundance of beneficial bacteria Bombilactobacillus in Post-treated bumblebees compared to Pre-treated, demonstrating disruption of the bumblebee gut microbiome. These findings show that black carbon exposure has direct, measurable effects on bees’ beneficial commensal bacteria and microbiome. Together these data highlight that black carbon, a single type of particulate pollution, is an underexplored risk to insect pollinator health.

Estimating the Exposure-Response Relationship between Fine Mineral Dust Concentration and Coccidioidomycosis Incidence Using Speciated Particulate Matter Data: A Longitudinal Surveillance Study.

Coccidioidomycosis, caused by inhalation of Coccidioides spp. spores, is an emerging infectious disease that is increasing in incidence throughout the southwestern US. The pathogen is soil-dwelling, and spore dispersal and human exposure are thought to co-occur with airborne mineral dust exposures, yet fundamental exposure-response relationships have not been conclusively estimated. We estimated associations between fine mineral dust concentration and coccidioidomycosis incidence in California from 2000 to 2017 at the census tract level, spatiotemporal heterogeneity in exposure-response, and effect modification by antecedent climate conditions. We acquired monthly census tract-level coccidioidomycosis incidence data and modeled fine mineral dust concentrations from 2000 to 2017. We fitted zero-inflated distributed-lag nonlinear models to estimate overall exposure-lag-response relationships and identified factors contributing to heterogeneity in exposure-responses. Using a random-effects meta-analysis approach, we estimated county-specific and pooled exposure-responses for cumulative exposures. We found a positive exposure-response relationship between cumulative fine mineral dust exposure in the 1-3 months before estimated disease onset and coccidioidomycosis incidence across the study region [incidence rate ratio (IRR) for an increase from 0.1 to ; 95% CI: 1.46, 1.74]. Positive, supralinear associations were observed between incidence and modeled fine mineral dust exposures 1 [ (95% CI: 1.10, 1.17)], 2 [ (95% CI: 1.09, 1.20)] and 3 [ (95% CI: 1.04, 1.12)] months before estimated disease onset, with the highest exposures being particularly associated. The cumulative exposure-response relationship varied significantly by county [lowest IRR, western Tulare: 1.05 (95% CI: 0.54, 2.07); highest IRR, San Luis Obispo: 3.01 (95% CI: 2.05, 4.42)]. Season of exposure and prior wet winter were modest effect modifiers. Lagged exposures to fine mineral dust were strongly associated with coccidioidomycosis incidence in the endemic regions of California from 2000 to 2017. https://doi.org/10.1289/EHP13875.

Airway microbiota dysbiosis and metabolic disorder in ozone and PM2.5 co-exposure induced lung inflammatory injury in mice.

Co-exposure to ground-level ozone (O3) and fine particles (PM2.5, ≤ 2.5 µm in diameter) has become a primary scenario for air pollution exposure of urbanites in China. Recent studies have suggested a synergistic effect of PM2.5 and O3 on induction of lung inflammatory injury. However, the underlying mechanisms for respiratory toxicity induced by this co-exposure have not been adequately elucidated. In this study, a realistic exposure was based to set up the co-exposure condition of an animal model. Specifically, eighty male C57BL/6 mice (10 months old) were randomly divided into four groups: control, O3, PM2.5 and co-exposure (O3 + PM2.5). Mice in the co-exposure group breathed O3 and orally inhaled PM2.5 suspension. The scenario for O3 exposure was 0.6 ppm, 4 h/d, for 30 consecutive days while that for PM2.5 exposure was oral inhalation of PM2.5 suspension (5.6 mg/kg bw) once every other day and 4 h prior to O3 exposure. After last exposure, bronchoalveolar lavage fluids (BALF) were collected for inflammatory biomarker measurement, 16S rRNA sequencing and metabolite profiling. Lung tissues were processed for histological examination. The results demonstrated that co-exposure to O3 and PM2.5 exacerbated the pathological changes and inflammatory response induced by O3 or PM2.5. Further studies revealed that co-exposure to O3 and PM2.5 increased the abundance of Prevotella in the airways and caused more severe metabolic disorders compared to O3 or PM2.5 exposure. Spearman correlation analysis demonstrated correlations among airway microbiota dysbiosis, metabolic disorder, inflammation, and pathological alterations induced by co-exposure to O3 and PM2.5. In summary, co-exposure to O3 and PM2.5 worsens airway inflammatory injury, possibly through interrelated airway microbiota dysbiosis and metabolic disorder.

Possible Influence of Shipping Emissions on PAHs in Size-Segregated Particulate Matter in Guanabara Bay (Rio de Janeiro, Brazil)

Most goods in the world are transported by ships, which are powered by fossil fuels and responsible for atmospheric emissions. This study carries out an evaluation of particulate matter (PM) in the atmosphere of Guanabara Bay, Rio de Janeiro, Brazil. It involves using a MOUDI (Micro-Orifice Uniform Deposit Impactor) cascade impactor, followed by solvent extraction and subsequent chemical analysis by gas chromatography, for the determination of anthracene (ANT), benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), chrysene (CRY), fluoranthene (FLT), phenanthrene (PHE) and pyrene (PYR). Samples (57) were collected from October 2019 to January 2021 during 24 h. The average values of coarse particles ranged from 0.46 ng m-3 for FLT to 6.07 ng m-3 for PHE; in fine particles, it was from 0.518 to 4.20 ng m-3 for PHE; no FLT was detected in the ultrafine and the maximum value generated was 4.77 ng m-3 for PHE. FLT was also not detected in the nanoparticles, where the maximum value was 2.43 ng m-3 for PHE.

Key drivers and source mechanisms of oxidative potential in fine particles from an industrial city of Northern China Plain.

The oxidative potential (OP) of particulate matter (PM) is crucial for understanding its ability to generate reactive oxygen species. However, the major chemical drivers influencing OP still need to be better understood. This study investigated the seasonal variations of OP and identified key drivers and source mechanisms in the industrial city of Zibo, located in North China Plain. We used the XGBoost model and Positive Matrix Factorization (PMF) to identify key drivers and source mechanisms. In 2022, PM2.5 samples were collected from an urban site in Zibo, and major chemical components were analyzed. OP was quantified using the dithiothreitol (DTT) method. The results revealed that the annual average DTTv in Zibo City for 2022 was 1.1nmol/min/m3, with the highest DTTv levels observed in autumn, followed by spring, summer, and winter. Using the XGBoost model, we identified that metal elements such as Pb, Ba, and Cu, along with water-soluble ions NO3- and SO42-, significantly contributed to DTTv. Source apportionment analysis via PMF identified five major sources of PM2.5. Throughout the study period, secondary particles were the predominant contributors to PM2.5 (49%), while coal combustion had the lowest contribution (7%). To further elucidate the sources of OP in PM2.5, we integrated the measured OP with source contributions derived from PMF. The findings indicated that secondary particles and industrial sources contributed the most to DTTv, accounting for 40% and 21%, respectively. The OP sources exhibited seasonal variations: secondary particles were the primary contributors in winter, while dust sources dominated in spring. In summer, vehicle emissions increased substantially, and industrial emissions became the major source in autumn. This study highlighted the critical drivers and source mechanisms of OP in industrial cities and would be beneficial for future air quality control and risk reduction.

Corrigendum to ‘Fluidization of fine coal particles in an ultrasound enhanced gas-solid fluidized bed’ South African Journal of Chemical Engineering, Volume 51, January 2025, Pages 78-85, 631

Corrigendum to ‘Fluidization of fine coal particles in an ultrasound enhanced gas-solid fluidized bed’ South African Journal of Chemical Engineering, Volume 51, January 2025, Pages 78-85, 631

Effects of rapid infrared radiation heating on the warping deformation and mechanical properties of selective laser melted Co-Cr dental alloy.

Infrared radiation heating (IRH) technology has been innovatively applied to the annealing of selective laser melted (SLM) cobalt chromium (Co-Cr) frameworks. However, previous studies have not reported the effects of IRH on the warping deformation and mechanical properties of these frameworks. The purpose of this in vitro study was to investigate the effects of IRH on the warping deformation and mechanical properties of dental SLM Co-Cr alloy and to evaluate its potential applications in dental restorations. Two types of specimens, bone-shaped tensile specimens and warping deformation specimens (cantilever beam structures), were fabricated by SLM, followed by annealing using IRH and general furnace heating (GFH). The specimens were divided into 4 groups (n=6) based on the applied heat treatment method and build direction (IRH-XY; IRH-Z; GFH-XY; GFH-Z). The cantilever beam support structure of the warping deformation specimen was cut using wire cutting, and the warping deformation was measured using a digital image correlation optical extensometer. Tensile tests were used to evaluate mechanical properties, with the fracture characteristics being observed using a scanning electron microscope (SEM). A micro-Vickers hardness tester was used to measure the microhardness. The microstructures were analyzed using a metallographic microscope. All data were analyzed using a 1-way ANOVA and the Tukey Honestly Significant Difference test (α=.05). The surfaces of the SLM Co-Cr warping deformation specimens treated with IRH showed slight oxidation, while those treated with GFH exhibited a dark black appearance. No significant difference was found in deformation between the IRH group (0.412 ±0.039 mm) and the GFH group (0.379 ±0.070 mm) (P>.05). The elongation of the longitudinally built specimens was significantly higher than that of their transversely built counterparts (P<.05), while the yield strength showed an opposite trend. The longitudinally built specimens demonstrated ductile fracture characteristics, while the transversely built specimens displayed quasi-cleavage fractures. The specimens treated with IRH exhibited comparable tensile strength and microhardness with the GFH-treated specimens, with no statistically significant differences (P>.05). IRH treatment resulted in finer grains in the SLM Co-Cr alloy. Many fine second-phase particles precipitated from the matrix in the longitudinally built specimens, while few were observed in the transversely built specimens. The SLM Co-Cr specimens treated with IRH achieved comparable warping deformation and mechanical properties with those of the GFH-treated specimens. The IRH technology holds great potential for application to dental restorations.