Particle Size Distribution Characteristics Research Articles

Control oriented modeling of twin-screw granulation in the ConsiGmaTM-25 production plant

ConsiGmaTM-25 is a continuous production plant integrating a twin-screw granulation, fluid bed drying, granule conditioning, and a tableting unit. The particle size distribution (PSD), active pharmaceutical ingredient (API) content, and liquid content of wet granules after twin-screw granulation affect the quality of intermediate and final products. This paper proposes methods for real-time monitoring of these quantities and control-oriented modeling of the granulator.The PSD of wet granules is monitored via an in-line process analytical technology (PAT) probe based on the spatial velocimetry principle. The algorithm for signal processing and evaluation of PSD characteristics is developed and applied to the acquired PSD data. A dynamic process model predicting PSD characteristics from granulation parameters is trained via the local linear model tree (LoLiMoT) approach. The experimental data required for the model training are collected via systematically designed excitation runs. Finally, the performance of the identified model is examined and verified by means of a new set of validation runs. Furthermore, an in-line PAT probe based on Raman spectroscopy is developed and integrated after the granulator. The API- and liquid content of produced wet granules are evaluated from the spectral data by means of chemometric modeling, and chemometric models are validated on a separate set of experimental data. The solutions proposed in this research can be used as a reliable (and necessary) basis for the development of advanced quality-by-design control concepts (e.g., PSD process control). Such concepts would ultimately improve the ConsiGmaTM-25 process performance in terms of robustness against disturbances and quality of intermediate and final products.

Seasonal characteristics of particle size distribution of organic markers in atmospheric particulate matters in Beijing

Beijing is a metropolis that is quickly growing, which has significant and unusual air pollution issues. In Beijing, organic matter makes up about 40%–60% of the total mass of fine particles, making it the most prevalent portion and highlighting its crucial role in reducing air pollution. However, a thorough chemical analysis of particulate organic matter has never been reported in Beijing. In this work, the organic components of fine particles in Beijing's urban environment were examined by the Gas Chromatography and Mass Spectrometry (GC/MS) method. In 30 p.m. (Particulate matter) 2.5, more than 101 unique chemical compounds were identified and measured. Seven samples from the 2015–2016 summer, including harvest, cold, Aromatic hydrocarbons, unsaturated fats, ferulic acid, polyaromatic, and some tracer substances (hopanes, present in environmental samples, and corticosteroids) were the main ingredients, with their total concentrations being 489, 1369, and 1366 ng*m−3 in the summer, respectively. Due to their various primary pollution sources, such as combustion processes, fuel combustion, and culinary emissions, various organic compounds displayed ostensibly varied seasonal tendencies. Discussion of these organic chemicals' prevalence and a source reveals Beijing's seasonal air pollution patterns.

Solid particle size characterization by a high-frequency collision response in pneumatic particulate flow

A novel triaxial vibration method is developed for the real-time characterization of the solid particle size distribution (PSD) in pneumatic particulate flow, which is critical for chemical industry. In this work, the particle‒wall collision and friction behaviours were analysed by the time-domain statistical and time-frequency joint methods to narrow the high-frequency response range by the initial experiment of free fall for a single particle, interparticle, and multiple particles. Subsequently, verification experiments of PSD characterization in pneumatic flow were performed. First, the quantitative triaxial energy response model that considers the particle size, shape, and mass factors were established. Second, a good agreement of the particle number identification was found between the triaxial vibration energy and mean particle size of 150–550 μm. Moreover, the performance with the best accuracy was focused on a range of 42–43 kHz in the x-axis and z-axis and 36.8–38.8 kHz in the y-axis. Finally, the individual particle energy was inversely analysed by the triaxial vibration response within the optimized frequency bands, and the PSD was characterized in real-time by a low error rate, that is, 5.2% from the XZ-axis direction of sand (42–43 kHz) and 5.6% from the XYZ-axis of glass (30.9–33.9 kHz, 46.2–47.2 kHz, 38.3–41.3 kHz for each axis response). Therefore, this research complements the existing approaches for PSD characterization in particulate multiphase flow.

Cometary dust collected by MIDAS on board Rosetta

Context. The Micro-Imaging Dust Analysis System (MIDAS) atomic force microscope (AFM) on board the Rosetta comet orbiter has been dedicated to the collection and 3D topographical investigation of cometary dust in the size range of a few hundreds of nanometers to tens of micrometers with a resolution down to a few nanometers. Aims. We aim to catalog all dust particles collected and analyzed by MIDAS, together with their main statistical properties such as size, height, basic shape descriptors, and collection time. Furthermore, we aim to present the scientific results that can be extracted from the catalog, such as the size distribution and statistical characteristics of cometary dust particles. Methods. Through a careful re-analysis of MIDAS AFM images, we make a significant update and improvement to the existing MIDAS particle catalog, resulting in the addition of more particles and newly developed shape descriptors. The final product is a comprehensive list of all possible cometary dust particles detected by MIDAS. The catalog documents all images of identified dust particles and includes a variety of derived information tabulated one record per particle. Furthermore, the best image of each particle was chosen for subsequent studies. Finally, we created dust coverage maps and clustering maps of the MIDAS collection targets and traced any possible fragmentation of collected particles with a detailed algorithm. Results. The revised MIDAS catalog includes 3523 MIDAS particles in total, where 1857 particles are expected to be usable for further analysis (418 scans of particles before perihelion + 1439 scans of particles after perihelion, both after the removal of duplicates), ranging from about 40 nm to about 8 μm in size. The mean value of the equivalent radius derived from the 2D projection of the particles is 0.91 ± 0.79 μm. A slightly improved equivalent radius based on the particle’s volume coincides in the range of uncertainties with a value of 0.56 ± 0.45 μm. We note that those sizes and all following MIDAS particle size distributions are expected to be influenced by the fragmentation of MIDAS particles upon impact on the collection targets. Furthermore, fitting the slope of the MIDAS particle size distribution with a power law of a · rb yields an index b of ~−1.67 to −1.88. Lastly, based on the created dust coverage maps and clustering maps of the MIDAS collection targets, we determined the particle fragmentation ratio of 4.09 for nominal activity and 11.8 for the outburst, which underlines that parent particles with faster impact velocity are more likely to be fragmented during dust collection.

Discussion and application of ball mill in preparation of particle size samples of fine grained sedimentary rocks

The grain size of clastic rocks is one of the most important structural characteristics of clastic sediments, which can directly reflect the hydrodynamic conditions of ancient sedimentary period. The preparation of conventional clastic rock particle size samples is usually done by hand wet grinding with a grinding hammer by experienced experimenter. For the fine-grained sedimentary rocks, the conventional method for preparing grain size samples has the disadvantages of long time and low efficiency. This paper introduces a method of preparing grain size samples of fine grained sedimentary rocks by separating rock particles with ball mill. By carrying out the experiments of separating rock particles by ball mill, the influence of different sample quality and ball mill parameters on the particle size and particle size distribution of fine grained sedimentary rock in the process of rock particle fragmentation by ball mill was discussed. The conditions for separating particles of fine grained sedimentary rocks by ball mill are determined as follows: sample mass is 0.14 g ~ 0.20 g, ball mill frequency is 10 Hz, ball milling time is 3 min, the efficiency of particle size sample preparation is greatly improved. The final particle suspension samples were tested by laser particle size analyzer, and the particle size distribution characteristics of fine-grained sedimentary rocks were given, which provides a basis for the study of lithology classification, lithofacies characteristics and hydrocarbon reservoir heterogeneity, and plays an important role in the exploration and development of unconventional oil and gas.

Particle size distribution of growing media constituents using dynamic image analysis: Parametrization and comparison to sieving

AbstractGrowing media constituents have heterogeneous particle size and shape, and their physical properties are partly related to them. Particle size distribution is usually analyzed through sieving process, segregating the particles by their width. However, sieving techniques are best describing more granular shapes and are not as reliable for materials exhibiting large varieties of shapes, like growing media constituents. A dynamic image analysis has been conducted for a multidimensional characterization of particle size distribution of several growing media constituents (white and black peats, pine bark, coir, wood fiber, and perlite), from particles that were segregated and dispersed in water. Diameters describing individual particle width and length were analyzed, then compared to particle size distribution obtained by dry and wet sieving methods. This work suggests the relevance of two parameters, FeretMAXand ChordMINdiameters for assessing particle length and width, respectively. They largely varied among the growing media constituents, confirming their non‐spherical (i.e., elongated) shapes, demonstrating the advantages of using dynamic image analysis tools over traditional sieving methods. Furthermore, large differences in particle size distribution were also observed between dynamic image analysis and sieving procedures, with a finer distribution for dynamic image analysis. The discrepancies observed between methodologies were discussed (particle segregation, distribution weighing, etc.), while describing in details methodological limitations of dynamic image analysis.

Investigation on the mercury nucleation mechanism based on the release characteristics of inhalable particles during coupled combustion of sewage sludge-coal washery tailing

Establishing an integrated treatment technology system for sewage sludge and coal washery tailing by mixed combustion can effectively overcome the disadvantages of the low calorific value and utilization efficiency, realizing the efficient resource. The single-component and coupled fuel were analyzed. Aiming at the generated inhalable particulate matter during the combustion process, using multiple characterization means and the fluidized bed experimental system, the micro-characteristics and elemental distribution of coupled fuel and combustion products were obtained, and the theory based on nucleation control was analyzed to reveal particle size distribution and particulate matter emission characteristics under multiparameter coupling conditions. The nucleation mechanism of Hg on the surface of the particulate matter under mixed combustion conditions was clarified. The results show that the weight loss process of sewage sludge in the combustion process mainly includes four stages. An obvious boundary between the volatilization and combustion processes of fixed carbon does not exist; furthermore, there is some overlap between the two processes. Volatiles and minerals interact in the mixed combustion process. The constituent elements of PM1 and PM1∼10 in the generated particulate matter are mainly easily vaporizable and refractory elements, respectively. The particle size of the particles produced presents the characteristics of bimodal distribution. There is a critical value (800 °C) for the influence of combustion temperature on the emission characteristics of particulate matter. It mainly affects the emission characteristics of coarse and fine particles through dominating the occurrence forms of tar, easily gasified and refractory elements, and the collision and aggregation process between particles. Homogeneous nucleation and heterogeneous condensation are the basic pathways for the transition of Hg from the gas phase to particle nucleation, and there are different nucleation control mechanisms. The heterogeneous condensation process includes diffusion control and surface reaction control. In addition, after the coupled fuel is demineralized by acid washing, the nucleation control mechanism changes significantly from diffusion control to chemical reaction control for the particles in the continuum region.

Analysis of Influencing Factors of Gangue Ball Milling Based on Multifractal Theory

To study the heterogeneity and local heterogeneity of gangue particle size distribution (PSD) under ball milling, gangue from northern Shaanxi coal mine was taken as a research object. The multifractal pattern of PSD and the variation trend of characteristic parameters of gangue under different ball-to-gangue ratios and grinding times were analyzed by introducing multifractal theory and microscopic research methods such as laser particle size analysis and scanning electron microscopy. The results show that the multifractal characteristics of the gangue particle size distribution with different ball-to-gangue ratios and grinding time periods demonstrate obvious changes. When the ball-to-gangue ratio is 3~9, the multifractal parameters D(0), D(1), Δα, and Δf all show linear changes with grinding time. It is demonstrated that due to the phenomenon of particle agglomeration during ball milling, the multifractal characteristics of the particle size distribution of the gangue changes significantly when the ball-to-gangue ratio is 12~15. Furthermore, the results indicate that with the increase in time, D(0), Δα, and Δf show a trend of decreasing first and then increasing, and D(1) and D(1)/D(0) show a trend of first increasing and then decreasing, and both reach their extreme values at 30 min.

Physicomechanical properties of raw and comminuted pine and poplar shavings: energy consumption, particle size distribution and flow properties

The aim of this study was to assess the energy consumption during milling and cutting-milling of pine and poplar shavings and the determination of particle size distribution (PSD) characteristics and mechanical properties of these materials. Cutting-milling process required less energy (in kJ·kg–1) than milling but maximum mass flow rate of shavings was significantly higher and thus the effective power requirement of the knife mill during cutting also was higher. Comminution of plastic poplar shavings was more energy-consuming than harder pine shavings. These features influenced PSD, which was approximated with four mathematical models: Rosin–Rammler-Sperling-Bennett (RRSB), normal, logistic and lognormal. On the basis of the best fitting (Radj2) for RRSB, detailed PSD parameters were calculated and all PSDs were described as ‘mesokurtic’, ‘fine skewed’ and ‘well-graded’. In comparison to milled shavings, cut-milled shavings had higher density, but were less compressible and had lower unconfined yield strength. However, cut-milled shavings had higher flowability because of lower cohesion and internal friction angles, because after cutting-milling particles were more spherical than elongated particles after milling. Cut-milled poplar shavings had more favourable mechanical parameters and better PSD characteristics, but required more energy for comminution than pine shavings.

Hydraulic conductivity estimation of sandy soils: a novel approach

ABSTRACT In the most recent literature, predictive models for the hydraulic conductivity ( K ) estimation of sandy soils based on particle size distribution (PSD) have received harsh criticism for their inaccurate predictions outside the original study area. This study examines the best possible relationships between K and complete PSD characteristics, porosity (n), and field dry density ( ρ d ) of the 60 different samples from river deposition settings. In comparison to other grain sizes, the goodness of the nonlinear fit of K − d 50 (grain size at 50% passing) relationship was found to be the highest. Uniformity coefficient (Cu) and coefficient of curvature (Cc) were found to be the poor estimators of K . Whereas, ρ d and n showed significant nonlinear negative relations with the K. After integrating d 50 , n, and ρ d into a multivariate system and using nonlinear regression the strength of the relationship highly improved resulting in a novel equation for the K estimation. The values of statistical indicators such as R2, Adjusted R2, SSE, RMSE, and MSE i.e. 0.78, 0.77, 25.89, 0.67, and 0.45 respectively, reveal the adequacy and significant performance of the developed regression model. Also, the proposed equation, validated on an independent dataset of 21 samples, showed exceptional prediction accuracy.

Optical properties of mineral dust aerosols with non-absorptive coating: A numerical investigation

Mineral particles form complex mixed states with other anthropogenic species through a series of chemical reactions during the long-range transport and aging process, which modifies their optical properties. Traditional homogeneous particle models do not effectively describe the variability of particle size distribution, morphology and mixing structure, and the discrepancy between the simulations and experimental results is still apparent. In this paper, the impact of non-absorptive coating material on the optical properties of mineral dust particles with varying particle size distribution, morphology, and inhomogeneous characteristics is investigated by the core-shell spheroid model. The results reveal that the real part of the complex refractive index (RRI) of non-absorptive coating material has a more prominent effect on the scattering matrix elements than the particle size distribution, morphology, and inhomogeneity. The P11(π)/P11(30°) generally increases with the square of RRI, for any mean effective radius(r0), coating ratio(fcoating), and aspect ratio(α). However, the variation of -P12(θ)/P11(θ) with the r0, fcoating, and α is more complicated and depends on the RRI. The particle inhomogeneity promotes positive values of -P12(θ)/P11(θ) for lower RRI, and negative values for higher RRI in general. The maximum value of -P12(θ)/P11(θ) (Pmax) and the minimum value of -P12(θ)/P11(θ) (Pmin) are strongly depends on the RRI, r0, fcoating, and α. Moreover, the Pmax has an excellent Gaussian distribution relationship with RRI, r0, fcoating, and α. Furthermore, the parameterization scheme of the P11(π)/ P11(30°) and the Pmax as a function of RRI, r0, fcoating, and α are systematically studied. Considering further research, our study may be of great significance for the study of aerosol composition retrieval and remote sensing applications.

Characteristics of sediment particle size distribution in the Pisha sandstone area of the middle Yellow River under the effects of vegetation and complex erosion

AbstractPisha sandstone is a soft bedrock composed of sandstone, sand shale and mudstone, with very low diagenesis and erosion resistance. The sources of coarse sediment and the processes of sediment production and transportation in Pisha sandstone areas are currently little understood. Understanding these processes will help us to comprehend the characteristics of sediment particle size distribution on slopes and gullies under the effects of vegetation and complex erosion. This will provide a scientific basis for the control of coarse sediments of the Yellow River and ecological restoration of the Pisha sandstone area. In this study, the process of sediment selectivity and transportation in the slope–gully system was analyzed through soil sampling in different seasons in the Erlaohugou small watershed, China. There is a clear selectivity phenomenon in the process of transporting sediment particles from the slope to the gully, and the coarse sediment particles are transported preferentially from the slope to the gully. There is a good response relationship between the distribution characteristics of sediment particles and the multi‐dynamic interaction. The complex erosion type in different seasons has a significant impact on sediment production and transportation, and most particles were transported under hydraulic power.

Particle-size fractal dimensions and pore structure characteristics of soils of typical vegetation communities in the Kubuqi Desert

The goal of this study was to investigate the soil particle-size distribution (PSD) and pore structure characteristics in the Kubuqi Desert in order to provide basic data for gaining insights into the soil-modifying properties of the local vegetation. Based on laser diffraction analysis, we measured the soil PSD and calculated the single and multi-fractal dimensions of the soils under typical artificial forest and natural grassland vegetation. The diameters, volumes and surface areas of the soil pores were determined via nitrogen adsorption experiments. The relationships between the fractal characteristics and pore structure parameters of the soil were investigated via redundancy analysis and stepwise regression. The clay content was less than 2.0%, and the sand content was greater than 75.0%. There was variability in the PSD and fractal dimension, which was mainly observed for the 0–20 cm, 20–80 cm, and 80–100 cm soil layers. In the 0–80 cm, the fine particle content, single fractal dimension (D), entropy dimension (D1), ratio of D1 to the capacity dimension (D1/D0), and correlation dimension (D2) were smaller for the forest soils than for the grassland soils. The fine particle (clay and silt) content of the 80–100 cm soil layer was approximately 37.8% higher for the Salix psammophila-8a than for the Salix psammophila-3a, and it was approximately 161.4% higher for the Populus popular-35a than for the Pinus sylvestris var. mongolica-8a. The silt content, D1, D1/D0, and D2 were significantly positively correlated with the specific surface area (SSA), total pore volume (TPV), and average pore diameter (APD) of the nanopores (p < 0.05, 0.01, or 0.001), and they were significantly negatively correlated with the percentage of the micropore volume (PMV) (p < 0.05 or 0.01). In the Kubuqi Desert, the fine particle content and fractal dimensions of the soil layer below the root zone of shrub and arbor vegetation increased with increasing stand age, but the trend was reversed in the shallower soil layers. The variability of the soil PSD characteristics was strongly correlated with the variability of the nanopore parameters on the microscopic scale, suggesting that the total pore volume, average pore diameter, and percentage of the micropore volume may be potential indicators of the soil structure and quality.

The Influence of the Fractal Dimension on the Mechanical Behaviors of the Soil–Rock Mixture: A Case Study from Southwest China

As the typical multi-phase geotechnical material, the particle size distribution of the natural soil–rock mixture (S–RM) has a significant impact on the structural and mechanical properties. The coarse grain content used in the laboratory and simulation tests falls short of accurately describing the particle size distribution feature of the entire material. The main subject of this article is the influence of the fractal dimension on mechanical behaviors based on the fractal theory. The double fractal characteristics were principally discussed along with the typical particle size distribution characteristics of the S–RM in the Three Gorges Reservoir and southwest China. The influence of the various fractal dimensions on the mechanical behaviors of S–RM was then investigated using three groups of large–scale triaxial tests, and the responses of the linear and nonlinear strength indexes were analyzed. The results show that the stress–strain curves of S–RM in the hyperbolic shape are visible under various confining pressure, and the nonlinear strength characteristics can be observed. The coarse grain content exhibits a negative correlation to the average fraction dimension. The difference between the coarse and fine grain fraction dimensions becomes considerably more obvious as the coarse grain content increases, which also increases the error when using the average fractal dimension. The voids between the coarse grains cannot be filled with the fine grains as the grain coarseness grows, resulting in a loose structure and a contact frictional effect, which lowers cohesion and raises the peak friction angle.

Chiral Covalent-Organic Framework MDI-β-CD-Modified COF@SiO2 Core-Shell Composite for HPLC Enantioseparation.

The chiral covalent-organic framework (CCOF) is a new kind of chiral porous material, which has been broadly applied in many fields owing to its high porosity, regular pores, and structural adjustability. However, conventional CCOF particles have the characteristics of irregular morphology and inhomogeneous particle size distribution, which lead to difficulties in fabricating chromatographic columns and high column backpressure when the pure CCOFs particles are directly used as the HPLC stationary phases. Herein, we used an in situ growth strategy to prepare core-shell composite by immobilizing MDI-β-CD-modified COF on the surface of SiO2-NH2. The synthesized MDI-β-CD-modified COF@SiO2 was utilized as a novel chiral stationary phase (CSP) to explore its enantiomeric-separation performance in HPLC. The separation of racemates and positional isomers on MDI-β-CD-modified COF@SiO2-packed column (column A) utilizing n-hexane/isopropanol as the mobile phase was investigated. The results demonstrated that column A displayed remarkable separation ability for racemic compounds and positional isomers with good reproducibility and stability. By comparing the MDI-β-CD-modified COF@SiO2-packed column (column A) with commercial Chiralpak AD-H column and the previously reported β-CD-COF@SiO2-packed column (column B), the chiral recognition ability of column A can be complementary to that of Chiralpak AD-H column and column B. The relative standard deviations (RSDs) of the retention time and peak area for the separation of 1,2-bis(4-fluorophenyl)-2-hydroxyethanone were 0.28% and 0.79%, respectively. Hence, the synthesis of CCOFs@SiO2 core-shell composites as the CSPs for chromatographic separation has significant research potential and application prospects.

Study on dust suppression performance of a new spray device during drilling and blasting construction in the metro tunnel

In order to solve the problems of excessive blasting dust concentration and portal pollution in a metro tunnel of a central urban area, a new spray device is discussed and its related parameters are studied in this paper. Through field sampling and an experimental spray dust settling platform, the particle size distribution characteristics of the tunnel blasting dust and the applicability of the nozzle are analysed. The tunnel and spray device are simulated by CFD software, and the variation laws of the droplet field concentration, velocity and particle diameter under different different incident angles, pressures and wind velocity are studied. The dust suppression performance of the new partition spray device is tested through field application. The results show that the droplet field generated by the spray device can effectively cover the whole section of the tunnel. At the same angle of incidence, the high concentration area first increases and then decreases in the direction away from the device, and the maximum concentration section gradually shifts away from the spray device. With the increase of the incident angle, the growth and attenuation trend of the high concentration region gradually flattens. The best incident angle for partitioning and dust reduction is 30°. When the nozzle pressure is set to 8 MPa, the parameters such as concentration, velocity and particle size distribution are the most appropriate. The effect of the air velocity at the air outlet on the characteristics of the droplet group generated by the device is not obvious. The field application shows that when the spray device is used, the dust reduction efficiency of respiratory dust and total dust at each measuring point is higher than 70 %. Compared with the original dust control measures, the average dust reduction efficiency is increased by 30 %, which can effectively improve the working environment of constructors in the tunnel and prevent the outward diffusion of dust.

Study on Crust-Shaped Dust Suppressant in Non-Disturbance Area of Open-Pit Coal Mine-A Case Study.

Dust pollution in open-pit coal mines severely restricts the green development of mines. Therefore, dust control has become an important requirement for the sustainable development of the mining industry. With the goal of dust pollution prevention and control in open-pit coal mines, this paper puts forward the concept of a non-disturbance area of an open-pit coal mine. It clarifies the characteristics of dust generation, the coverage area, and the dust particle size distribution characteristics of the non-disturbance area. Taking the dust control at the dump site as an example, the study comprehensively utilizes indoor tests and field tests to develop a dust suppressant for the dump site and determine its dust suppression efficiency and effective service cycle. The results show that the D10, D50, and D90 particle sizes of dust in the non-disturbance area are smaller than those in the disturbance area, and the difference in particle size of D90 is the most obvious. Gelatinized starch and non-ionic polyacrylamide, as the main components of the dust suppressant, can effectively reduce dust pollution in the dump; the optimal concentration is 1.0%, and the dust suppression service cycle is more than one month. The developed dust suppressant does not contain corrosive, toxic, or heavy metal elements. Although the application of a dust suppressant will cause plant growth to lag, it does not affect plant health. The research findings serve as a reference for the zoning treatment of dust in open-pit mines.

Research on the high-efficiency crushing, sorting and recycling process of column-shaped waste lithium batteries

The efficient and environmentally friendly recycling technology of waste lithium batteries has become a research hotspot, in which mechanical crushing is an important part of the recycling process. Through experimental methods, the compressive and impact properties of columnar lithium batteries were studied, and the crushing product characteristics and crushing efficiency of the single tear crushing method, single hammer crushing method, and two-step crushing method were investigated. The study shows that the two-step crushing method could achieve 100 % dissociation of all battery components, and the crushed products can be recycled according to their particle size distribution characteristics. The power consumption of the two-step crushing method was only 23.59 % of that of a single hammer crusher, and the reduction of carbon dust emission in the crushing process was as high as 76.29 %. The high crushing efficiency and environmentally friendly of the two-step crushing method are of great practical significance for the subsequent industrial promotion of waste battery recycling.

Occurrence, partitioning and transport of perfluoroalkyl acids in gas and particles from the southeast coastal and mountainous areas of China.

Perfluoroalkyl acids (PFAA) in gas and particles were analyzed in southeast coastal and mountainous cities, including Fuzhou, Xiamen, Zhangzhou and Nanping, to study the pollution characteristics, particle size distribution, phase partitioning and atmospheric transport. PFAA ranged from 7.8 to 290pgm-3 in gaseous phase, 27 - 1200pgm-3 in particulate phase, and perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA) were main compounds. PFAA had the highest concentration in Nanping with perfluorohexanoic acid (PFHxA) dominant, which could be related to the emission of PFAS from local industrial plants. Perfluorocarboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) exhibited different particle size distribution characteristics, with PFSAs preferring to distribute on coarse particles, which could be affected by the salt, minerals and organic matter in different particle sizes. The gas - particle partitioning coefficient (KPA) had a line relationship with the fluorinated carbon chain length of PFAA, suggesting that long-chain PFAA tended to exist in particulate phase. The Winter Monsoon could transport to the study area and drive atmospheric PFAS to southern cities. HIGHLIGHTS: • Industrial plants contributed high concentrations of PFAA. • PFSAs tended to present in coarse particles. • Log KPA increased linearly with increasing carbon chain length of PFAA. • Winter Monsoon drove atmospheric PFAA to southern cities.

Characteristic Analysis on Temporal Evolution of Granulation in a Modified Anaerobic Digestion System

In the present study, the surface morphology, particle size distribution, sedimentation performance, and fractal characteristics of sludge flocs in a modified anaerobic baffled reactor (mABR) during start-up were analyzed by digital image analysis technology. The results showed that the special structure of mABR enabled successful start-up and granular sludge formation in a relatively short time. After the granular sludge was mature, the COD removal rate could quickly recover to the level before the change in organic loading rates (OLRs) within just six days, increasing from the lowest value of 76.8% to 80.2%, which indicated that the granular sludge could maintain a relatively stable micro-environment and make the metabolic process continue when the influent conditions changed suddenly. It was expected that this paper would be helpful for researchers to further develop a unified theory for anaerobic granulation and technology for expediting the formation of mABR granules.