Fine Particles Research Articles

Impact of air pollution on depressive symptoms and the modifying role of physical activity: Evidence from the CHARLS study.

The association between air pollution and depressive symptoms has not been thoroughly investigated, and the role of physical activity (PA) is particularly unclear. Although PA has been shown to alleviate depression, it may also increase exposure to air pollution, potentially exacerbating its adverse effects. A total of 17,332 participants aged 45 years and older from the 2018 wave of the China Health and Retirement Longitudinal Study (CHARLS) were included in this study to assess the causal effect of air pollution on depressive symptoms in China and to clarify the role of PA in this relationship. Depressive symptoms were assessed using the Center for Epidemiological Studies Depression Scale (CES-D). Data on particulate matter (PM1, PM2.5, and PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO) were obtained from the ChinaHighAirPollutants (CHAP) dataset. PA levels were measured using a standardized questionnaire and categorized as low or high. An instrumental variable (IV) approach was used to estimate the causal effect of air pollution on depressive symptoms. Potential effect modification by PA was assessed. The IV estimates showed that all air pollutants were significantly and adversely associated with depressive symptoms, with a per interquartile range (IQR) increase in PM1, PM2.5, PM10, NO2, SO2, O3, and CO associated with 1.57 (95% confidence interval (CI): 1.15, 1.99), 1.49 (95% CI: 1.10, 1.89), 1.71 (95% CI: 1.26, 2.17), 2.22 (95% CI: 1.62, 2.81), 1.30 (95% CI: 0.96, 1.65), 4.67 (95% CI: 3.37, 5.98), and 0.97 (95% CI: 0.71, 1.22) units increase in CES-D scores, respectively. PA significantly modified this association, with higher PA levels mitigating the adverse effects of air pollution on depressive symptoms.

Seepage Response along with Fine Particle Migration of a Loose Soil Slope under Rainfall Infiltration

Seepage Response along with Fine Particle Migration of a Loose Soil Slope under Rainfall Infiltration

The combined effects of microplastics and their additives on mangrove system: From the sinks to the sources of carbon.

Mangrove ecosystems, a type of blue carbon ecosystems (BCEs), are vital to the global carbon cycle. However, the combined effects of microplastics (MPs) and plastic additives on carbon sequestration (CS) in mangroves remain unclear. Here, we comprehensively review the sources, occurrence, and environmental behaviors of MPs and representative plastic additives in mangrove ecosystems, including flame retardants, such as polybrominated diphenyl ethers (PBDEs), and plasticizers, such as phthalate esters (PAEs). Mangrove ecosystems have a complex influence on the behaviors of MPs and additives. Under the action of natural and unnatural factors, these pollutants exhibit complex behaviors including migration, interception, deposition and transformation, that are closely linked to those of particulate carbon, particularly carbon sequestration processes. MPs and additives hinder the CS function of mangroves by harming the growth of flora and fauna, influencing microbial nitrogen and sulfur cycles, and enhancing the degradation of organic matter in the sediment. The increasing accumulation and widespread occurrence of MPs and additives will greatly influence the carbon cycle. Future work is encouraged on systematic investigation of new alternatives to plastics and additives, and research methods to uncover the impact mechanisms of MPs and additives on BCEs. The developments of management measures and engineering technologies are also required to enhance pollutant control and mangrove CS.

Синтез самоармованого порошкового матеріалу на основі високоентропійного сплаву

In this work, the formation of a self-reinforced HEA–WC powder material during the mechanical alloying (MA) of a mixture of elemental powders of the W-Fe-Co-Ni system in a planetary ball mill in a gasoline environment was investigated. X-ray diffraction (XRD), microstructural, and energy dispersive spectral (EDS) analysis revealed that after 20 hours of MA of the powders in a carbon-containing medium, a powder material based on a high-entropy alloy was formed. HEA based powder material contains two solid solutions with BCC and FCC crystal structure, as well as a carbide WC phase formed "in-situ" owing to the large negative value of the mixing enthalpy between carbon and tungsten. The “in-situ” formation of WC particles contributes to the enhancement of interfacial bonding with the metal matrix of the HEA. All phase components of the HEA–WC powder material are in the nanostructured state. The particles of the powder material have a close to spherical shape and a bimodal particle size distribution. The powder material consists of fine particles with a size of 1–10 μm and their agglomerates with a size up to 100 μm. The microstructure of the particles consists of the main gray phase of the BCC solid solution, dark spaces of the FCC solid solution and fine WC particles with a size of 0.1 μm to 1 μm evenly distributed in the HEA matrix. High-entropy alloys with the addition of carbon are promising in terms of practical application, because carbon, having a small atomic radius, dissolves as an interstitial element in the crystal lattice of the substitutional solid solutions of the HEA principal elements and, as a result, significantly affects their structure and phase composition, and, therefore, will contribute to the improvement of the mechanical properties of the self-reinforced powder material due to the effects of both solid-solution strengthening by interstitial atoms and the precipitation strengthening by the carbide phase particles.

Disordered mesoporous silica particles: an emerging platform to deliver proteins to the lungs

Pulmonary delivery and formulation of biologics are among the more complex and growing scientific topics in drug delivery. We herein developed a dry powder formulation using disordered mesoporous silica particles (MSP) as the sole excipient and lysozyme, the most abundant antimicrobial proteins in the airways, as model protein. The MSP had the optimal size for lung deposition (2.43 ± 0.13 µm). A maximum lysozyme loading capacity (0.35 mg/mg) was achieved in 150 mM PBS, which was seven times greater than that in water. After washing and freeze-drying, we obtained a dry powder consisting of spherical, non-aggregated particles, free from residual buffer, or unabsorbed lysozyme. The presence of lysozyme was confirmed by TGA and FT-IR, while N2 adsorption/desorption and SAXS analysis indicate that the protein is confined within the internal mesoporous structure. The dry powder exhibited excellent aerodynamic performance (fine particle fraction <5 µm of 70.32%). Lysozyme was released in simulated lung fluid in a sustained kinetics and maintaining high enzymatic activity (71–91%), whereas LYS-MSP were shown to degrade into aggregated nanoparticulate microstructures, reaching almost complete dissolution (93%) within 24 h. MSPs were nontoxic to in vitro lung epithelium. The study demonstrates disordered MSP as viable carriers to successfully deliver protein to the lungs, with high deposition and retained activity.

Global big data laboratory experiment, integrated with kernel-based algorithm with an improved nonlinear ensemble for compressive strength modeling

With the continuous clamor for a reduction in embodied carbon in cement, rapid solution to climate change, and reduction to resource depletion, studies into substitute binders become crucial. These cementitious binders can potentially lessen our reliance on cement as the only concrete binder while also improving concrete functional properties. Finer particles used in cement microstructure densify the pore structure of concrete and enhance its performance properties. The compressive strength of concrete made from a mixture of ground granulated blast furnace slag (GGBFS), fly ash (FA), and ordinary Portland cement was estimated using kernel regression techniques in this work. The kernel-based method offered was support vector regression (SVR), while robust linear regression (RLR), and multi-linear regression (MLR) were used as regression methods, subsequently, nonlinear average approaches were used to improve the accuracy of the prediction. Eight variables (cement, FA, GGBFS, water, superplasticizer dose [SP], coarse aggregate [CA], fine aggregate [Fag], age) were employed as input features in 3323 data samples, and their relative value was assessed using linear correlation analysis. Following analysis, three combinations were employed to train the kernel-based models: I (inputs: cement, water, and age|output: CS), II (inputs: cement, water, FA, SP, and age|output: CS), and III (inputs: cement, water, FA, SP, CA, GGBFS, and Fag|output: CS). The third combination gave the best testing performance with all the proposed models where their R2 and MSE results after model evaluation for SVR, RLR, and MLR, are [0.984, 0.8776 and 0.8804] and [0.0019, 0.0131 and 0.0128] respectively. The study concludes that SVR with the combination III (SVR-M3) offered the best performance through effectiveness and efficiency in accurately predicting the compressive strength of the blended concrete. The prediction models should be utilized with the input variable ranges used in this work.

Nanobubbles Adsorption and Its Role in Enhancing Fine Argentite Flotation.

The efficient recovery of fine argentite from polymetallic lead-zinc (Pb-Zn) sulfide ore is challenging. This study investigated nanobubble (NB) adsorption on the argentite surface and its role in enhancing fine argentite flotation using various analytical techniques, including contact angle measurements, adsorption capacity analysis, infrared spectroscopy, zeta potential measurements, turbidity tests, microscopic imaging, scanning electron microscopy, and flotation experiments. Results indicated that the NBs exhibited long-term stability and were adsorbed onto the argentite surface, thereby enhancing surface hydrophobicity, reducing electrostatic repulsion between fine argentite particles, and promoting particle agglomeration. Furthermore, the NBs formed a thin film on the argentite surface, which decreased the adsorption of sodium diethyldithiocarbamate. Microflotation tests confirmed that the introduction of NBs considerably enhanced the recovery of argentite using flotation technology.

Effect of annealing twins on grain boundary migration in high-purity copper

The effect of grain boundary retardation by annealing twins in pure copper has been experimentally and theoretically investigated. A model that describes the influence of annealing twins on the migration of grain boundaries in pure metals has been proposed. The retarding force from the twins has been demonstrated to be analogous to the Zener retarding force created by incoherent fine particles. An equation has been derived to calculate the retarding force induced by annealing twins. The force has been demonstrated to be inversely proportional to the size of the twins and directly proportional to their volume fraction. The simulation results have been compared with the experimental results. A satisfactory correlation between the theoretical and experimental results has been achieved.

Tipos de Filtros que se Utilizan para el Tratamiento de Aguas Residuales

Filters used in wastewater treatment have the function of capturing solids, microorganisms and chemical compounds, contributing to the improvement of water quality and promoting its sustainability. Among the main filters are sand filters, used because of their low cost and effectiveness in removing suspended solids and reducing turbidity, taking advantage of biological, physical and chemical processes for water treatment. Activated carbon filters, available in granular (GAC) and powdered (PAC) forms, offer high adsorption capacity for specific chemical contaminants and are common in the final stages of water treatment in industrial plants. Membrane filters, which include microfiltration, ultrafiltration, nanofiltration and reverse osmosis, stand out for their efficiency in removing fine particles, microorganisms and salts, but require higher investment and maintenance. Gravel filters, ideal for their accessibility and capacity to remove basic contaminants through physical and biological processes. Sand and gravel filters are viable options for basic treatments, while activated carbon and membranes are reserved for advanced processes where high quality standards are required.

Temporal trends and predictive modeling of air pollutants in Delhi: a comparative study of artificial intelligence models

Air pollution monitoring and modeling are the most important focus of climate and environment decision-making organizations. The development of new methods for air quality prediction is one of the best strategies for understanding weather contamination. In this research, different air quality parameters were forecasted, including Carbon Monoxide (CO), Nitrogen Monoxide (NO), Nitrogen Dioxide (NO2), Ozone (O3), Sulphur Dioxide (SO2), Fine Particles Matter (PM2.5), Coarse Particles Matter (PM10), and Ammonia (NH3). Hourly datasets were collected for air quality monitoring stations near Delhi, India, from November 25, 2020 to January 24, 2023. In this context, five intelligent models were developed, including Long Short-Term Memory (LSTM), Bidirectional Long-Short Term Memory (Bi-LSTM), Gated Recurrent Unit (GRU), Multilayer Perceptron (MLP), and Extreme Gradient Boosting (XGBoost). The modelling results revealed that Bi-LSTM model had the best predictability performance for forecasting CO with (R2 = 0.979), NO with (R2 = 0.961), NO2 with (R2 = 0.956), SO2 with (R2 = 0.955), PM10 with (R2 = 0.9751) and NH3 with (R2 = 0.971). Meanwhile, GRU and LSTM models performed better in forecasting O3 and PM2.5 with (R2 = 0.9624) and (R2 = 0.973), respectively. The current research provides illuminating visuals highlighting the potential of deep learning to comprehend air quality modeling, enabling improved environmental decisions.

Study on the mechanism of erosion and wear of elbow pipes by coarse particles in filling slurry

Coarse particles in filling slurry are the primary factor causing wear in filling elbow pipes, and the wear mechanism of these particles on the pipes is influenced by various factors. To study the erosion and wear mechanism of elbow pipes caused by coarse particles, the motion state of coarse particles under different curvature radii, coarse particle gradations, and pipe diameters was investigated using a simulation method based on the coupling of Fluent and EDEM software, grounded in theories of fluid mechanics, rheology, and solid–liquid two-phase flow. The study explored the impact patterns and locations of wear induced by coarse particles on filling elbow pipes. The analysis results indicate that increasing the curvature radius leads to more punctate wear at the elbow and upstream wear. Increasing the proportion of finer particles in the coarse particle gradation forms a better cushioning layer and reduces erosion wear. Enlarging the pipe diameter shifts the high-low concentration boundary of coarse particles towards the elbow outlet and reduces erosion wear. The research findings provide significant references for optimizing coarse particle gradation and preventing pipe wear.

Effects of Superfine Cement on Fluidity, Strength, and Pore Structure of Superfine Tailings Cemented Paste Backfill

Advancements in mine tailings treatment technology have increased the use of superfine tailings, but their extremely fine particle size and high specific surface area limit the performance of superfine tailings cemented paste backfill (STCPB). This study investigates the effects of using superfine cement as a binder to enhance the fluidity, strength, and pore structure of STCPB. The influence of water film thickness (WFT) on STCPB performance is also examined. The results show that the cement-to-tailings ratio (CTR) and solid content (SC) significantly affect the spread diameter (SD) and unconfined compressive strength (UCS), following distinct linear/logarithmic and exponential trends, respectively. WFT has an exponential impact on SD and a non-linear effect on UCS, enhancing strength at low levels (0 μm &lt; WFT &lt; 0.0071 μm) and balancing hydration and flowability at moderate levels (0.0071 μm &lt; WFT &lt; 0.0193 μm) but reducing strength at high levels (WFT &gt; 0.0193 μm). Additionally, superfine cement significantly improves the pore structure of STCPB by reducing porosity and macropore content. These findings provide valuable insights into optimizing STCPB for enhanced performance and sustainability in mine backfilling applications.

Understanding of enhanced nitrate in fine particles at agricultural sites in summer with high ammonia level.

Nitrate is one of the major constituents of fine particles and has not been effectively alleviated in Northeast Asia. Field measurements of various gases and the chemical composition of fine particles were conducted at two agricultural sites (cropland and livestock) in ammonia-rich environments to understand the effect of ammonia on nitric acid-nitrate partitioning using a thermodynamic model and to suggest a possible strategy to control total nitrate (i.e., nitric acid formation). High nitrate levels were observed at the agricultural sites in summer compared to those at the urban sites. It was found that high level of ammonia in summer led to increased aerosol pH and nitrate fraction. At the cropland site in summer, the daily nitrate fraction was particularly sensitive to aerosol pH, suggesting that ammonia control should be effective in decreasing nitrate formation via nitric acid-nitrate partitioning (with a 50% reduction in ammonia, nitrate concentration can decrease by 34%). Aerosol water content also played a significant role in determining nitrate fraction in the aerosol pH range of 2.5-3.0. It was found that the sites were under high NOx conditions, and that the reduction of OH production (daytime) and O3 (nighttime) was important for controlling total nitrate, but this is challenging due to the high contributions of background O3. It was concluded that the reduction of ammonia emissions for the control of the nitrate fraction via gas-to-particle partitioning should be important to mitigate nitrate in fine particles at agricultural sites in summer.

Visualization of CuFeS2 Particle Ignition and Combustion Under Simulated Flash Smelting Conditions

AbstractFlash smelting involves complex reactions between copper sulfide ores, silica sand, impurities, and oxygen gas while dropping. In situ observations of particle oxidation (ignition and combustion) under simulated flash smelting conditions can promote an understanding of this phenomenon. However, previous studies were limited by technical difficulties. In this study, in situ observations, two-color temperature measurements, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS), and thermodynamic equilibrium calculations were used to characterize the oxidation of CuFeS2 particles under simulated flash smelting conditions. CuFeS2 particles changed in four phases in oxidation within 300 ms. The first process was ignition (≈ 25 ms) with an average temperature of 2100 °C. This was triggered by fine particles (several μm in diameter) on coarse particles (approximately 50 μm in diameter) and formed sphere particles consisting of two phases (sulfide and oxysulfide, Phase I) or three phases (sulfide, oxysulfide, and iron oxide, Phase II). The second process was combustion (&lt; 300 ms) with an average temperature of 1900‒2000 °C. In addition to the spherical particles, particles surrounded by a flame consisting of two phases (oxysulfide crust and oxide core, Phase III) were observed during combustion. The flame may be generated by the continuous sulfur vapor emitted from the oxysulfide crust, which vanishes after the consumption of the sulfur vapor. Finally, oxide particles (Phase IV), similar to those in the thermodynamic equilibrium phase, were formed. Graphical Abstract

Investigations into metallurgical, mechanical, and particulate matter emissions in in situ micropowder alloyed wire arc additive manufacturing process

Wire Arc Additive Manufacturing (WAAM) is an advanced manufacturing technique capable of a high deposition rate and is used for fabricating large-sized and complex components. Of specific interest in the recent past is the in-situ micropowder alloying during filler material deposition to modify the properties of each deposited layer. This study focuses on investigating the metallurgical and mechanical characteristics of the steel produced through powder-added WAAM, using characterization techniques such as optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy and Vickers microhardness testing. Additionally, changes in the size distribution of fine and ultrafine particles (UFP) emitted during WAAM deposition, with and without micropowder addition, were studied using a Scanning-Mobility-Particle-Sizer. Two single-bead multi-layered walls of ER70S6 were deposited in two conditions: as-deposited steel wall and interlayer Titanium micropowder-added steel wall. The results indicate that the microhardness of the Ti micropowder-added steel wall increased by approximately 35% due to the formation of specific microstructures, such as bainitic-ferrite, with retained austenite and mainly due to precipitation strengthening. The emission measurement results suggest that the addition of Ti micropowder during WAAM increases UFP concentration by 20%. The elevated temperature during the deposition process could be a key factor for the rise in particulate matter emissions.

Characterization of biochar produced from paperboard sludge: A sustainable approach for waste management and resource recovery

The pulp and paperboard industry are a significant industrial sector that consumes large quantities of fresh water and generates substantial volumes of wastewater. Treating this wastewater produces a considerable amount of sludge, which poses serious environmental challenges. This study proposes a sustainable solution by converting paperboard sludge (PBS) into biochar through slow pyrolysis at temperatures ?00°C, offering an alternative approach to waste management and resource conservation. The physicochemical analysis of paperboard sludge biochar (PBSB) revealed a neutral pH of 7.49, electrical conductivity of 0.09 dS m-1, an organic carbon content of 38.12%, and a calcium carbonate (CaCO3) content of 24.5%. Proximate analysis of PBSB revealed an increased fixed carbon content of 10.27 %, total organic carbon (TOC) of 7.13%, and reduced volatile matter and moisture levels. Micronutrients viz., iron (Fe) (5.06 mg L-1), Manganese (Mn) (419.3 mg L-1), Copper (Cu) (26.3 mg L-1), and Zinc (Zn) (66.1 mg L-1), were also observed in PBSB. FTIR analysis identified various carbon-containing functional groups, including C-Cl, C-N, C-C, H-C=O, C-H, and -C?C-H, indicating substantial chemical transformations during pyrolysis. Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) analysis revealed that PBSB consists of fine particles with a coarse, fluffy, spongy, porous structure, making it ideal for water adsorption. Elemental analysis through x-ray diffraction (XRD) showed high carbon and oxygen content and significant amounts of aluminosilicates, carbonates, and nutrients like phosphorus and potassium, suggesting PBSB as a potential slow-release fertilizer. This research highlights the potential of biochar derived from paperboard waste as a sustainable solution for effective waste management and resource recovery.

Response of Tree Seedlings to a Combined Treatment of Particulate Matter, Ground-Level Ozone, and Carbon Dioxide: Primary Effects.

Trees growing in urban areas face increasing stress from atmospheric pollutants, with limited attention given to the early responses of young seedlings. This study aimed to address the knowledge gap regarding the effects of simulated pollutant exposure, specifically particulate matter (PM), elevated ozone (O3), and carbon dioxide (CO2) concentrations, on young seedlings of five tree species: Scots pine (Pinus sylvestris L.); Norway spruce (Picea abies (L.) H.Karst.); silver birch (Betula pendula Roth); small-leaved lime (Tilia cordata Mill.); and Norway maple (Acer platanoides L.). The main objectives of this paper were to evaluate the seedling stem growth response and the biochemical response of seedling foliage to pollutant exposure. Four treatments were performed on two- to three-year-old seedlings of the selected tree species: with PM (0.4 g per seedling) under combined O3 = 180 ppb + CO2 = 650 ppm; without PM under combined O3 = 180 ppb + CO2 = 650 ppm; with PM (0.4 g per seedling) under combined O3 < 40-45 ppb + CO2 < 400 ppm; and without PM under combined O3 < 40-45 ppb + CO2 < 400 ppm. Scots pine and Norway maple showed no changes in growth (stem height and diameter) and biochemical parameters (photosynthetic pigments, total polyphenol content (TPC), total flavonoids content (TFC), and total soluble sugars (TSS)), indicating a neutral response to the combined PM, O3, and CO2 treatment. The chlorophyll response to PM alone and in combination with elevated O3 and CO2 exposure varied, with silver birch increasing, Norway maple-neutral to increasing, Scots pine-neutral to decreasing, and Norway spruce and small-leaved lime-decreasing. The TPC indicated stress responses in Scots pine, small-leaved lime, and Norway maple under increased combined O3 and CO2 and in Norway spruce under single PM treatment. Hence, Scots pine and Norway maple seedlings showed greater resistance to increased PM under combined O3 and CO2 with minimal change in growth, while silver birch seedlings showed adaptation potential with increasing chlorophyll under simulated pollutant stress.

Desktop 3D printers in the workplace: use, emissions, controls, and health

Abstract Desktop three-dimensional (3D) printers are used in businesses, schools, and colleges, and are generally of an unenclosed design which may give rise to injuries or inhalation exposure to emissions of small particles (&amp;lt;1 µm) and volatile organic compounds (VOCs). The aim of this work was to explore the health risks related to the use of desktop 3D printers in workplaces in the United Kingdom. A digital survey on the use of desktop 3D printers was completed voluntarily and anonymously between February and June 2023, receiving 146 responses. The most common technology and material used for printing were “filament deposition” and “polylactic acid,” respectively. The median number of printers an organisation had in use in one room was 2. A median of 10 people could be in the room during printer operation. A range of finishing techniques were reportedly applied to the printed object including the use of hand tools and solvents. General room ventilation was the most common exposure control measure stated. Measurements of airborne particles and VOCs were taken at 2 sites: a university and an engineering workshop. Airborne particle number concentrations (&amp;lt;1 µm) did not significantly increase above background levels when the printers were operating at either site. At the university, where there was the largest number of printers in operation, some VOCs could be attributed to the printing process; however, concentrations remained low. Evidence of associated respiratory symptoms was gathered by asking volunteers at the 2 sites visited to complete a questionnaire. Seventeen volunteers across the 2 sites completed the survey. None stated that they had ever experienced acute symptoms from working with 3D printers. However, they did report symptoms which included tiredness, dry/cracked skin, headache, itchy/runny nose, and a cough, with some stating that these improved on their days off. Overall, limited evidence from published literature and this study suggests that exposure to desktop 3D printing emissions could be associated with short-term respiratory health symptoms. However, static measurements in 2 workplaces where multiple desktop 3D printers were in use did not show airborne particle number concentrations in the room rising above background levels and concentrations of measured VOCs were all low. These findings may be due to effective ventilation and other control measures which over half of the workplaces surveyed stated that they had in place.

Influence of coal particle composition and maceral associations on fluidity development during the coking process

Maceral composition is a key parameter used in the assessment of metallurgical coals and coke quality prediction. However, coal particles are typically a mix of different macerals and minerals. Fluidity development in coal particles depends on particle size and the extent of association between constituent maceral grains. As such, determining the composition of coal particles is crucial to understanding the drivers of thermoplastic fluidity. In this work, coal grain analysis (CGA) was used to determine the maceral grain compositional information of individual coal particles for two pairs of metallurgical coals demonstrating different thermoplastic behaviour, as determined by standard Gieseler fluidity and dilatation testing. Each pair was comprised of coals with comparable ranks and both similar (coals A and C) and dissimilar (coals B and D) maceral compositions. The experimental results showed that coals of finer vitrinite particle size and higher degrees of maceral grain association, i.e., finely dispersed macerals within coal particles, demonstrated lower dilatation and higher permeability. It was postulated that coals with close maceral associations are more prone to volatile gas escape during thermoplasticity, hindering bubble growth and thermoswelling while also increasing melt viscosity, leading to decreased Gieseler fluidity measurements. It was also observed that coals with different degrees of maceral grain associations demonstrate different thermoplastic behaviour, where the presence of pure forms of reactive macerals enhanced coal fluidity. Results suggest that some coals possess a higher “effective fluidity” than reported from standard Gieseler testing. Conversely, coals with limited maceral grain association and high compositions of vitrinite prolific particles benefit from enhanced bubble growth and coalescence. Apparent fluidities of such coals are more accurately represented by standard Gieseler testing.

Optimization of coal slime flotation in reflux flotation cell

ABSTRACT As high-quality coal resources become increasingly scarce, the fine particle content in raw coal has risen, challenging the performance of traditional flotation equipment. Consequently, developing new flotation devices has become a critical research focus. The Reflux Flotation Cell (RFC), a novel flotation device, has shown excellent industrial performance. However, research on bubble descent behavior in the inclined section remains limited. This study examined the separation efficiency of bubbles in the inclined section and the impact of various operating parameters on the flotation performance of complex coal slime. Experimental results revealed that the bubble descent distance decreased with increasing liquid velocity but increased with higher gas velocity. Narrow channels exhibited lower overflow concentrations compared to wide ones. Flotation performance improved with higher gas and liquid velocities, although excessively high velocities led to fine particle entrainment, reducing clean coal quality. Additionally, flotation performance initially increased with concentration, peaking at 5% to 10% concentration, before decreasing beyond this range. The RFC design allows for high separation efficiency and effective flotation performance under most operating conditions.