Changes In Particle Size Distribution Research Articles

Temporal Change in Particle Size Distributions of Suspended Solids Discharged from Paddy Fields

Temporal Change in Particle Size Distributions of Suspended Solids Discharged from Paddy Fields

Characterization of fine particles during the 2014 Asia-Pacific economic cooperation summit: Number concentration, size distribution and sources

To study the impacts of emission controls on aerosol physical and chemical properties, real-time measurements of size-resolved aerosol number concentration and chemical composition were conducted in urban Beijing during the 2014 Asia-Pacific Economic Cooperation (APEC) summit, in a period that a series of measures, for example shutting down or halting production from factories and power plants, and restricting the number of vehicles on the roads were implemented in Beijing and surrounding regions. Significantly, reductions in particle mass concentration (55% for PM2.5 and 48% for PM10) were observed during the APEC summit. A clear decrease in secondary inorganic aerosols (SIA), such as sulphate, nitrate and ammonium, was found during APEC, with the reduction ranged from 65.7 to 72.2% for PM1, in which sulphate showed the largest decrease compared with periods before APEC. As a comparison, organics showed a much smaller decrease of 44.3% for PM1 during APEC. These changes were mainly caused by large reductions in accumulation mode particles, which decreased by 36% compared with 19% for Aitken mode particles. The results from the positive matrix factorization (PMF) of particle number concentration indicate that regionally transported aerosols showed significant decreases (70%), similar to those of SIA during APEC, whereas primary factors from traffic and local combustion sources presented much smaller decreases, with the reduction ranged from 4 to 40%. The elevated contributions of these sources indicated the presence of strong local source emissions. The changes in particle chemical composition, size distribution and sources during the evolution of pollution episodes with and without emission controls are further illustrated. Our results highlight the importance of regional atmospheric transport in the formation of severe pollution episodes in Beijing, indicating that reducing the precursors of secondary aerosol over regional scales represent the key steps to reduce the urban particulate pollution. However, stricter emission controls on local source emissions are needed to further mitigate air pollution in Beijing.

Effect of ball milling process on the structure of local clay and its adsorption performance for Ni(II) removal

The effect of ball milling process on the properties of the natural local clay including structural changes and adsorption capacity for the removal of Ni(II) ions from aqueous solutions, was investigated. The local clay was ground at varying times from 5 to 20h with a 10:1 or 20:1 weight ratio of the balls to powder, which produced six different ball milled clays (BM-Clay1 to BM-Clay6). Ground clays were then characterized by particle size measurement, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy analysis, and adsorption experiments. These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity, and adsorption characteristics. According to XRD analysis, the degree of amorphization increased with grinding time, and the present crystalline phase in the final ball milled clay was found to be quartz, which was the associated phase in the original unmilled clay mineral. FTIR studies indicated the destruction of the layers of the montmorillonite upon milling. Adsorption experiments revealed that under similar conditions, BM-Clay2 has the most adsorption capacity for Ni(II) ions. Adsorption characteristics of this ball milled clay for the removal of Ni(II) ions from aqueous solutions was examined in batch adsorption studies under different conditions of contact time, solution pH, adsorbent dose, and initial Ni(II) concentration. The Langmuir maximum adsorption capacity was found to be 29.76mg/g at pH7 and 25°C. The adsorption kinetics data showed better agreement with the pseudo second-order kinetic model. Also, both surface adsorption and intra-particle diffusion contributed to the rate limiting steps in the adsorption of Ni(II) on clay adsorbent. In conclusion, grinding of local clay using ball milling process can significantly increase the adsorption capacity of the clay for Ni(II) removal from aqueous solutions.

Measurement of size-dependent single scattering albedo of fresh biomass burning aerosols using the extinction-minus-scattering technique with a combination of cavity ring-down spectroscopy and nephelometry

Abstract. Biomass burning (BB) aerosols have a significant effect on regional climate, and represent a significant uncertainty in our understanding of climate change. Using a combination of cavity ring-down spectroscopy and integrating nephelometry, the single scattering albedo (SSA) and Ångstrom absorption exponent (AAE) were measured for several North American biomass fuels. This was done for several particle diameters for the smoldering and flaming stage of white pine, red oak, and cedar combustion. Measurements were done over a wider wavelength range than any previous direct measurement of BB particles. While the offline sampling system used in this work shows promise, some changes in particle size distribution were observed, and a thorough evaluation of this method is required. The uncertainty of SSA was 6 %, with the truncation angle correction of the nephelometer being the largest contributor to error. While scattering and extinction did show wavelength dependence, SSA did not. SSA values ranged from 0.46 to 0.74, and were not uniformly greater for the smoldering stage than the flaming stage. SSA values changed with particle size, and not systematically so, suggesting the proportion of tar balls to fractal black carbon change with fuel type/state and particle size. SSA differences of 0.15–0.4 or greater can be attributed to fuel type or fuel state for fresh soot. AAE values were quite high (1.59–5.57), despite SSA being lower than is typically observed in wildfires. The SSA and AAE values in this work do not fit well with current schemes that relate these factors to the modified combustion efficiency of a burn. Combustion stage, particle size, fuel type, and fuel condition were found to have the most significant effects on the intrinsic optical properties of fresh soot, though additional factors influence aged soot.

The significance of powder breakdown during conveying within industrial milk powder plants

Instant whole milk powder is designed to rapidly dissolve in water, which depends on the particle size distribution (PSD). The fragile powder exiting the dryer is conveyed for packing which breaks down the particles, worsening the dissolution properties. This work investigated the effect of conveying on the final functional properties using two industrial plants with differing transport systems; a pneumatic system and bucket elevator. It was expected that the plant with the bucket elevator consistently produced powder with superior dissolution due to lower breakdown during transport. This was evaluated using the change in PSD. It was found that the plant with the bucket elevator had at least as large a change in the median particle size as the plant with the pneumatic transport system, contrary to the expectation. However, the plant with the bucket elevator had an initially larger particle size, and so the percentage of fine particles that negatively impact dissolution, remained low post transport. When quantified using the change in bulk density, having an initially low bulk density compensated for large increases in bulk density during conveying and powder with lower bulk density pre-transport showed better wettability post transport. Thus in order to produce powder with the desired functionalities the focus should be on improving the initial agglomeration and generating larger particles and lower bulk density pre-transport, as opposed to optimising the powder transport.

Fragmentation of biomass-templated CaO-based pellets

The use of biomass templating materials with a cheap production method as an enhanced sorbent for CO2 uptake has been proposed recently. However, the attrition and fragmentation behaviour of this type of material, which is a vital parameter for calcium looping sorbents, has not yet been investigated in detail. In this work the fragmentation behaviour of biomass-templated sorbents is investigated. Three types of materials were prepared using a mechanical pelletiser: 1. lime and cement (LC); 2. lime and flour (LF); and 3. lime, cement and flour (LCF). These samples were heat treated in a pressurised heated strip reactor (PHSR) and in a bubbling fluidised bed (BFB) and changes in particle size distribution were measured to assess fragmentation. Results indicated that the addition of biomass enhances the propensity to undergo fragmentation. Upon heat treatment in the PHSR the particle size of LC was not modified significantly; on the contrary the mean particle diameter of LF decreased from 520μm to 116μm and that of LCF from 524μm to 290μm. Fragmentation tests in the BFB confirmed the trend: 67% of the particles of LF fragmented, against 53% of LCF and 18% of LC samples. The addition of cement to the LF samples partially counteracts this performance degradation with respect to attrition. However, calcium aluminate pellets (LC) showed the lowest rate of fragmentation amongst all of the samples tested.

Online monitoring of nanoparticles formed during nanosecond laser ablation

The particle size distribution of dry aerosol originating from laser ablation of glass material was monitored simultaneously with Laser Ablation – Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis and two aerosol spectrometers – Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer (APS). The unique combination of LA-ICP-MS and FMPS offers the possibility of measuring the particle size distribution every 1s of the ablation process in the size range of 5.6–560nm. APS extends the information about particle concentration in the size range 0.54–17μm. Online monitoring of the dry aerosol was performed for two ablation modes (spot and line with a duration of 80s) with a 193nm excimer laser system, using the glass reference material NIST 610 as a sample. Different sizes of laser spot for spot ablation and different scan speeds for line ablation were tested. It was found that the FMPS device is capable of detecting changes in particle size distribution at the first pulses of spot laser ablation and is suitable for laser ablation control simultaneously with LA-ICP-MS analysis. The studied parameters of laser ablation have an influence on the resulting particle size distribution. The line mode of laser ablation produces larger particles during the whole ablation process, while spot ablation produces larger particles only at the beginning, during the ablation of the intact layer of the ablated material. Moreover, spot ablation produces more primary nano-particles (in ultrafine mode size range <100nm) than line ablation. This effect is most probably caused by a reduced amount of large particles released from the spot ablation crater. The larger particles scavenge the ultrafine particles during the line ablation mode.

The transformation of coal fly ash deposited on wet landfills

ABSTRACTThe stability of the ashes taken from the three heat-power plants showed that each day of storage in wet landfill causes transformation in their physical and chemical composition. At low temperatures, the spherical grains become brittle and consequently undergo cracking. The studies with a laser diffractometer have shown changes in particle size distribution during the experiment. The pozzolanic activity of the studied ashes significantly decreased under the weathering impact.

Characterizing the phytoplankton soup: pump and plumbing effects on the particle assemblage in underway optical seawater systems

Many optical and biogeochemical data sets, crucial for algorithm development and satellite data validation, are collected using underway seawater systems over the course of research cruises. Phytoplankton and particle size distribution (PSD) in the ocean is a key measurement, required in oceanographic research and ocean optics. Using a data set collected in the North Atlantic, spanning different oceanic water types, we outline the differences observed in concurrent samples collected from two different flow-through systems: a permanently plumbed science seawater supply with an impeller pump, and an independent system with shorter, clean tubing runs and a diaphragm pump. We observed an average of 40% decrease in phytoplankton counts, and significant changes to the PSD in 10-45 µm range, when comparing impeller and diaphragm pump systems. Change in PSD seems to be more dependent on the type of the phytoplankton, than the size, with photosynthetic ciliates displaying the largest decreases in cell counts (78%). Comparison of chlorophyll concentrations across the two systems demonstrated lower sensitivity to sampling system type. Observed changes in several measured biogeochemical parameters (associated with phytoplankton size distribution) using the two sampling systems, should be used as a guide towards building best practices when it comes to the deployment of flow-through systems in the field for examining optics and biogeochemistry. Using optical models, we evaluated potential impact of the observed change in measured phytoplankton size spectra onto scattering measurements, resulting in significant differences between modeled optical properties across systems (~40%). Researchers should be aware of the methods used with previously collected data sets, and take into consideration the potentially significant and highly variable ecosystem-dependent biases in designing field studies in the future.

Sn microparticles made by plasma-induced dewetting

Micrometer-scale Sn particles are produced by plasma treating Sn films from 50nm to 2000nm on silicon oxide substrates. Plasma treatment is conducted using an inductively coupled plasma source. Behaviors of spinodal dewetting as well as hole nucleation and growth are observed when analyzing the average particle size with its initial film thickness and monitoring the morphological evolution of the dewetting film. A range of RF powers are evaluated to observe changes in particle size and size distribution. When increasing the RF power of the plasma treatment, the particle size and size distribution decreases, while the number of particles per area increases. With the help of the dewetting results on smooth substrates, an attempt is made to produce an array of Sn particles using a templated substrate to imitate the Sn solder bumps used in semiconductor packaging.

Modeling the change in particle size distribution in a gas-solid fluidized bed due to particle attrition using a hybrid artificial neural network-genetic algorithm approach

Particle size distribution (PSD) is an important parameter in gas-solid fluidized bed. The change in PSD due to particle attrition can affect the long-term performance of fluidized bed. In this study, artificial neural network (ANN) with genetic algorithm (GA) as a meta-modeling tool was employed to model the change in PSD during fluidization. Experiments were conducted using incineration bottom ash (IBA) as the fluidizing particles and different mass percentage of large and small glass beads were used as the grinding medium. Rosin–Rammler (RR) distribution was used to describe the IBA PSD. The ANN-GA models developed were subsequently used to study the effect of fluidization time, mass percentage of glass beads and size of glass beads used on the IBA particle attrition during fluidization.

Ionizer induced 220Rn decay product removal in confined environment: Continuous vs. instantaneous source

This paper presents an experimental approach to evaluate the effectiveness of unipolar ionizers in indoor environment for the removal of thoron (220Rn) daughter products. Both continuous and instantaneous source conditions were simulated during these experiments. Activity and aerosol related parameters were measured for these experiments and results were interpreted. Activity concentration was found to be reduced by a factor 6.6 and 34 for continuous and instantaneous source conditions, respectively. The particle size dependency of mitigation of particles using ionizer is also discussed. The effect of ionizer on activity size distribution has been directly measured for the first time. The ionizer induced changes in particle size distributions were coupled to Dose Reduction Factor (DRF) model and significant DRF values were obtained for both source conditions. This study discusses open issues which are important for establishing ionizer induced radioactivity mitigation as a technology application.

Land-Use Conversion Changes the Multifractal Features of Particle-Size Distribution on the Loess Plateau of China.

Analyzing the dynamics of soil particle-size distributions (PSDs), soil nutrients, and erodibility are very important for understanding the changes of soil structure and quality after long-term land-use conversion. We applied multifractal Rényi spectra (Dq) and singularity spectra (f(α)) to characterize PSDs 35 years after conversions from cropland to shrubland with Caragana microphylla (shrubland I), shrubland with Hippophae rhamnoides (shrubland II), forested land, and grassland on the Loess Plateau of China. Multifractal parameters (capacity dimension (D0), entropy dimension (D1), D1/D0, correlation dimension (D2), and Hölder exponent of order zero (α0)) were used to analyze the changes of PSDs. Dq and f(α) characterized the PSDs well and sensitively represented the changes in PSDs after conversion. All types of land-use conversion significantly improved the properties of the topsoil (0–10 cm), but the effect of shrubland I and even forested land decreased with depth. All types of land-use conversion significantly increased D1 and D2 in the topsoil, and D1 and D2 in the 10–50 cm layers of shrubland II, forested land, and grassland and D1 in the 50–100 cm layers of shrubland II were significantly higher relative to the control. Both D1 and D2 were positively correlated with the contents of soil nutrients and fine particles and were negatively correlated with soil erosion, indicating that D1 and D2 were potential indices for quantifying changes in soil properties and erosion. In conclusion, all types of land-use conversion significantly improved the conditions of the topsoil, but conversion from cropland to shrubland II, forested land, and grassland, especially shrubland II and grassland, were more effective for improving soil conditions in deeper layers.

Unlocking additional value by optimising comminution strategies to process Grade Engineering® streams

Grade Engineering® comprises a range of techniques aiming to reject low grade uneconomic material (preconcentration) as early as possible within the mining value chain. It has been identified as an effective and feasible operating strategy whereby mining unit metal productivity can be significantly increased. Two Grade Engineering (G.E) levers have been assessed in a copper porphyry deposit: preferential grade by size response, and differential blasting for grade. Those are exploited through a modified blasting fragmentation coupled with screening based process on run-of-mine material to recover upgraded undersize fractions. Application of G.E inevitably alters comminution circuit typical feed particle size distributions, and consequently impact semi-autogenous (SAG) milling performance. A factorial design approach has been employed to assess the extent of this effect. A wide range of different operating scenarios, representing the possible G.E strategies and dynamic processing rock attributes, were simultaneously assessed using the Integrated Extraction Simulator (IES), a new cloud-based process simulator. This enabled the development of a G.E throughput improvement model as function of blasting fragmentation, impact hardness (Axb) and grindability (BMWi), which can be employed to conduct more detailed process modelling as well as resource optimisation.Improvements up to 14% in throughput due to changes in mill feed particle size distributions were observed under the conditions examined. The impact of this effect upon the proportion of material that is amenable to G.E is also discussed.

Characterization of 2D MoS2 and WS2 Dispersed in Organic Solvents for Composite Applications

ABSTRACTIn this work, we have explored the prospects of MoS2 and WS2, both of which are semiconducting 2D materials, for potential composite applications. In order to form 2D materials composites we have to first disperse them chemically in solution. MoS2 and WS2 powders were oversaturated in N-Methyl-2-pyrrolidone (NMP) solution at 37.5 mg/mL and sonicated at room temperature (RT) for sonication times ranging from 30 minutes to close to 24 hours. After solution processing, the samples with the 2D flakes were transferred to an Isopropyl Alcohol (IPA) bath for particle size distribution analysis. We have observed significant changes in particle size distribution spanning two orders of magnitude as a function of the sonication conditions. Specifically, the observed changes in particle size distribution for MoS2 and WS2 powders ranged from 44 microns down to 0.409 microns, and 148 microns down to 0.409, respectively, as compared to the untreated materials. Structural analysis was conducted using the SEM and X-Ray diffraction. The structural analysis using the SEM revealed morphological signatures between the two materials, where the MoS2 flakes had a randomly oriented distribution with occasional triangular flakes. In the case of the WS2, regardless of the sonication conditions, the WS2 flakes seemed to have a characteristic 120° angular distribution at the vertices, representing a rhombus with concave edges. The XRD analysis showed a minute shift in the characteristic peaks that maybe due to strain-induced effects as a result of the solution processing. Optical characterization of the materials was also conducted using Raman Spectroscopy to validate the average layer number resulting from the solution dispersions and the spatial and compositional uniformity of the two material samples.

Particle size distribution of soils (0–500 cm) in the Loess Plateau, China

To investigate the spatial variability of soil particle size distribution (PSD) in the Loess Plateau (LP) region of China, 2673 disturbed soil samples were collected in the 243 soil profiles (0–500cm) across the typical loess zone. The PSD of soil samples were determined using the laser diffraction technique and the regional spatial distribution patterns of PSD were analyzed through classical statistical and geo-statistical methods. The results showed that silt loam was the dominant soil texture (92.6%) at the 0–500cm soil layer. Sand, silt and clay contents varied slightly with increasing soil depth, suggesting that soil texture was almost homogeneous across the soil profile. Soils were overall sandy in the north and clayey in the south, but soil texture variation uneven with increasing latitude. PSD pattern across the typical LP region depicted latitudinal zonality. Fractal analysis showed a strong relationship between fractal dimension (D) and clay content (R2=0.98), demonstrating that D was controlled by the clay content rather than the coarse particles at the regional scale. The limited changes of PSD in the soil profile and the moderate variation of soil texture across the LP will provide a reference to regional scale hydrological, erosion and ecological models in the Loess Plateau of China.

Bromide ion mediated modification to digestive ripening process: Preparation of ultra-small Pd, Pt, Rh and Ru nanoparticles

Nanoparticles of catalytically important transition metals, such as Pd, Pt, Rh, and Ru have been prepared by the well-known “digestive ripening” (DR) and “modified digestive ripening” (mDR) methods. In the traditional DR process, a polydisperse colloidal dispersion is refluxed in the presence of a surface-active molecule, such as alkanethiol. The mDR method involved a small modification in the procedure, wherein refluxing was performed with an alkanethiol and a tetra-alkylammonium bromide surfactant. This minor modification led to a dramatic change in the final particle size distributions, giving access to nanoparticles in the <3 nm size regime; this was not possible with the traditional DR process. Bromide ions, which are present during refluxing, proved to be an important ingredient in the modification process. These bromide ions are revealed to act as etchants, resulting in ultra-small nanoparticles. All transition metal nanoparticles investigated displayed catalytic activity in the reduction reaction of p-nitro phenol. Pd nanoparticles, synthesized by a modified digestive ripening method, exhibited the best catalytic activity among the systems investigated.

Characteristics of Rainfall Runoff Pollutant and Initial Treatment

The spread of urbanization drives problems which distort the urban water cycle as a form of flood disaster and pollutant loads. When it comes to pollution, a lack of information on the load and characteristics of pollutants has led to insufficient reduction measures. Thus, this study discusses filtration by different types of filter media as an initial treatment to reduce pollutant loads. This study examined the effectiveness of the filtration method with different types of filter to control micro-particles from rainfall runoff water. The particle size and characteristics of pollutants were investigated. In addition, the characteristics of filter media in the filtration process, such as head loss, treatment efficiency, and changes in particle size distribution were also analyzed by lab-scale experiments. This study suggested the best filtration material to treat surface wash-off pollutants based on the results of various experiments on the treatment of real samples collected from roads and combined sewers. The results and discussions shown in this study may be useful as basic information for appropriate design and operating parameters of filtering facilities to control rainfall runoff pollutants caused by urban storms.

Cyclodextrin-based telmisartan ophthalmic suspension: Formulation development for water-insoluble drugs

In this study, cyclodextrin-based aqueous eye drop suspension of the water insoluble drug telmisartan was developed. Formation of a drug/γ-cyclodextrin complex was enabled by preventing formation of a poorly water-soluble zwitterion using a volatile base that was removed upon drying of the complex powder. Hydroxypropyl methylcellulose was shown to have the overall best effect, stabilizing the complexes without hampering the drug release from the formulation. Two strategies for preparing cyclodextrin-based aqueous eye drop suspensions of telmisartan were investigated, one where hydroxypropyl methylcellulose was added to the medium during preparation of the drug/γ-cyclodextrin complex powder (ternary complex) and the other where hydroxypropyl methylcellulose was added to the complex powder after preparation of the complex (binary complex). The complexation was characterized by DSC, FT-IR and 1H NMR and the eye drop suspensions formed were examined regarding their stability and in vitro mucoadhesion property. The ternary complex exhibited inferior mucoadhesive property compared to the binary complex. However, the ternary complex was more stable as no notable change in particle size and particle size distribution was observed during storage at 4°C over 6 months (p<0.05) with the mean particle size determined between 2.0 and 2.5μm.

Role of peach proteins in juice precipitation induced by high pressure CO2

To better understand the role of peach proteins in juice precipitation induced by high pressure CO2 (HPCD), proteins extracted from peach juice were subjected to HPCD and heat, and changes in particle size distribution (PSD) and structure were investigated. PSD analysis showed aggregations of proteins were both induced by HPCD and heat, but HPCD induced a stronger aggregation. The endotherm of HPCD- and heat-treated proteins moved to lower temperature, indicating that higher-order structures were altered after treatments. Furthermore, proteins related to HPCD- and heat-induced precipitation were analyzed by proteomics and bioinformatics. It was found that proteins with low content of α-helix and hydrogen bonds were more inclined to precipitate under HPCD, and HPCD precipitated proteins with more compact structures than heat, which might cause the stronger aggregation of proteins by HPCD. In conclusion, HPCD could induce the aggregation of peach proteins by destroying higher-order structures, which contributes to juice precipitation.