Resulting Particle Size Distribution Research Articles

Particle size distribution of total suspended sediments in urban stormwater runoff: Effect of land uses, precipitation conditions, and seasonal variations

Understanding particle size distribution (PSD) of total suspended sediments in urban runoff is essential for pollutant fate and designing effective stormwater treatment measures. However, the PSDs from different land uses under different weather conditions have yet to be sufficiently studied. This research conducted a six-year water sampling program in 15 study sites to analyze the PSD of total suspended sediments in runoff. The results revealed that the median particle size decreased in the order: paved residential, commercial, gravel lane residential, mixed land use, industrial, and roads. Fine particles less than 125 μm are the dominant particles (over 75%) of total suspended sediments in runoff in Calgary, Alberta, Canada. Roads have the largest percentage of particles finer than 32 μm (49%). Gravel lane residential areas have finer particle sizes than paved residential areas. The results of PSD were compared with previous literature to provide more comprehensive information about PSD from different land uses. The impact of rainfall event types can vary depending on land use types. A long antecedent dry period tends to result in the accumulation of fine particles on urban surfaces. High rainfall intensity and long duration can wash off more coarse particles. The PSD in spring exhibits the finest particles, while fall has the largest percentage of coarse particles. Snowmelt particles are finer for the same land use than that during rainfall events because the rainfall-runoff flows are usually larger than the snowmelt flows.

Effect of water-methanol binary solvent system in green synthesis of copper nanoparticles with tobacco leaf extract

The increasing demand for environmentally friendly nanoparticle synthesis, as a viable strategy for pollution control, has prompted an exploration of green chemistry methods. This study meticulously investigates the synthesis of copper nanoparticles utilizing tobacco leaf extract obtained through both cold and hot extraction techniques. The primary focus lies in scrutinizing the impact of various solvents employed for plant extracts and metal ion solutions on reduction dynamics and particle size. The study employs UV-Vis and phytochemical analyses to discern differences in chemical composition and efficacy, particularly between the water and methanol-water systems, despite their resemblance in UV-Vis spectra. Intriguingly, the results unveil that the choice of solvent significantly influences the particle size distribution and stability of colloidal nanoparticles. The methanol-water system, in particular, yields smaller, more uniform particles compared to other solvent systems. This research sheds light on the pivotal role of solvent selection in nanoparticle synthesis, emphasizing its profound impact on both the reduction process and the resulting particle size distribution. The findings underscore the nuanced relationship between solvent choice and the characteristics of the synthesized nanoparticles, providing valuable insights for optimizing environmentally friendly synthesis methods. Ultimately, this study contributes to the growing body of knowledge on green chemistry approaches for nanoparticle synthesis with implications for pollution control and sustainable materials production.

Comminution of Metal–Polymer Composites for Recycling

ZusammenfassungTo increase the recycling rate of components used in electric vehicles, metal–polymer composites are to be separated. As a basis, samples of polymers are ground in a hammer mill to analyze the influence of various pretreatments. The resulting particle size distributions are related to the mechanical properties of the polymers. The results can be used for a comminution of a metal–polymer composite from an electric vehicle's battery housing and show that lower temperatures perform the best for individual materials and composites. The complexity of the components and the type of joining also influence the comminution success of composite components, as a separation of the materials is easier with low complexity and force closure.

Measurement and Analysis of Brake and Tyre Particle Emissions from Automotive Series Components for High-Load Driving Tests on a Wheel and Suspension Test Bed

A current challenge in realising clean road transport is non-exhaust emissions. Important advances regarding measurement systems, including well-defined characterisation techniques, as well as regulation, will be made in the next few years. In this work, we present the detailed results of particle emission analyses, consisting of aerosol (size distribution, particle number (PN), and mass (PM)) and electron microscopy (EM) measurements, under different load conditions on a test bed for a wheel suspension and brakes. Standard tyres and brakes from serial production were tested with a high-load driving cycle, while particle measurements were conducted by gravimetric measurements and with a TSI SMPS, a TSI APS, and a GRIMM OPS. Furthermore, samples were analysed by electron microscopy. A bimodal particle size distribution (PSD) was obtained with an SMPS, with peaks at 20 nm and around 400 nm. The results of an EM analysis of >1400 single particles from the electrostatic sampler match the PSD results. The EM analysis also showed ultrafine particles, mainly containing O, Fe, Si, Ba, Mg, and S, and also fractal particles with high-C fractions. Our results suggest, in agreement with the previously published literature, that particulate emissions are related to the brake disc temperature and occur in significant amounts above a threshold temperature.

Visible Light Activation of Gold Nanoparticles Embedded into Titanium Dioxide Surface in Electrospun Polymeric Coatings

This work reports the development of a functional photocatalytic coating based on a combination of polymeric electrospun fibres and nanoparticles that is intended to be activated in the visible light range. In this sense, the resulting fibres can act as an effective matrix for the incorporation of titanium dioxide (TiO2) particles, which are covered by gold nanoparticles (AuNPs), in the outer surface of the metal oxide precursor. In the first step of the process, the optical properties of the nanoparticles were determined by UV-Vis spectroscopy. The extension of the visible absorption can be associated to the localized surface plasmon resonance (LSPR) of the metallic AuNPs. In addition, the resultant particle size distribution and average particle diameter was evaluated by dynamic light scattering (DLS) measurements. Furthermore, the phase composition and porosity of the functional particle powder were analysed by an XRD and N2 adsorption test. In the second step, these synthesized particles have been successfully immobilized into a PAA + β-CD electrospun fibre matrix by using the two different deposition methods of dip-coating and solution-casting, respectively. The morphological characterization of the samples was implemented by means of scanning electron microscopy (SEM), showing uniform and homogeneous, free-beaded fibres with a random distribution of the synthesized particles deposited onto the electrospun fibres. Then, the functional coatings were removed from the substrate, and a thermogravimetric (TGA) analysis was carried out for each sample in order to obtain the precursor mass immobilized in the coating. Once the overall mass of precursor was obtained, the percentage of TiO2 particles and AuNPs in the precursor was calculated by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Finally, the photocatalytic activity of both functional solution and electrospun coatings were evaluated in terms of a gradual degradation of rhodamine B (RhB) dye after continuous exposition to a visible-light lamp.

Sonochemical synthesis of lignin nanoparticles and their applications in poly (vinyl) alcohol composites

Lignin is a common and abundant byproduct of the pulp and paper industry and is generally burned to produce steam. Opportunities exist to acquire greater value from lignin by leveraging the properties of this highly conjugated biomacromolecule for applications in UV absorption and polymer reinforcement. These applications can be commercialized by producing value-added lignin nanoparticles (LNPs) using a scalable sonochemical process. In the present research, monodisperse LNPs have been synthesized by subjecting aqueous dispersions of alkali lignin to acoustic irradiation. The resulting particle size distribution and colloidal stability, as determined by dynamic light scattering, transmission electron microscopy and zeta potential analysis, of LNPs can be adjusted by varying the solution pH and ultrasonication energy. As-synthesized LNPs with a mean diameter of 204 nm were incorporated into poly (vinyl) alcohol (PVA) to prepare thin and flexible nanocomposite films using a simple solvent casting method. The addition of 2.5 wt% LNP increased the material's Sun Protection Factor up to 26 compared to 0 for neat PVA, while maintaining light transmission above 75 % in the visible spectra. In addition, the tensile strength and elastic modulus of the PVA nanocomposites improved by 47 % and 36 %, respectively. The presence of LNP also enhanced the thermal stability of the materials. Significantly, the proposed sonochemical process may be generally applicable to the synthesis of a range of naturally-derived LNPs for a variety of value-added applications.

An assessment of methods used for the generation and characterization of cryomilled polystyrene micro- and nanoplastic particles

There is a critical need to generate environmentally relevant microplastics (MPs) and nanoplastics (NPs) to better investigate their behavior in laboratory settings. Environmental MPs are heterogenous in size and shape, unlike monodisperse and uniform microspheres commonly used as surrogates. Cryogenic grinding, or cryomilling, was successfully utilized to transform polystyrene (PS) bulk material into heterogenous micro and nano fragments. Fourier-Transform Infrared (FTIR) spectroscopy confirmed that this approach did not alter polymer surface chemistry. The number of milling cycles (time of milling) and frequency of grinding (intensity of milling) were varied to investigate the role cryomilling parameters had on generated MP characteristics. The resulting particle size distributions of cryomilled samples were measured and compared. Coulter Counter and Nanoparticle Tracking Analysis (NTA) were used to measure the particle size distributions at the micro and nanoparticle size ranges, respectively. Microspheres were used to determine what camera settings yielded more accurate sizing and to reduce bias in the NTA analysis. Increasing milling cycles generally increased the number of smaller particles. The evolution of the measured size distributions indicated that small nanosized fragments broke off from larger MPs during cryomilling, steadily eroding larger MP fragments. The number of milling cycles was observed to more consistently impact the size distributions of fragments compared to the frequency of milling. This study offers both analysis of the cryomilling process and recommendations for generating more realistic PS MP/NPs for examining environmental fate and effects.

A breakage model for DEM based on a probabilistic particle replacement with Voronoi fragments

Due to mechanical stress, bulk material is crushed and fines are produced. This can either be desired in comminution processes or undesired in conveying and storage processes. In this work a novel breakage model for the Discrete Element Method is presented to allow a prediction of the resulting particle size distribution after damaging events. The breakage model is based on a probabilistic particle replacement strategy. Depending on the load, the initial particle is replaced by a breakage pattern tessellated with the Voronoi algorithm. Replacement probabilities and breakage patterns follow results from breakage tests. In contrast to other replacement models, mass and volume remain constant. Initial particles are polyhedral and can be of any shape. Crushing processes with multiple breakage can be simulated. The computational scheme is described in detail. The model was verified and validated with trials of shatter tests and two conveying processes with blast furnace sinter from two different industrial partners.

Direct numerical simulation of SpraySyn burner: Impact of liquid solvent

The SpraySyn burner is a new system recently developed at the University of Duisburg-Essen to investigate experimentally nanoparticle synthesis in spray flames for a variety of materials. The current project aims at performing direct numerical simulations with detailed physicochemical models of configurations closely related to this burner. The effect of using different solvents to produce titanium-dioxide (TiO[Formula: see text]) nanoparticles is discussed in this work. The two solvents considered are o-xylene and ethanol mixed in liquid state with tetraisopropoxide to form TiO[Formula: see text]. The liquid is injected into a pilot flame as dispersed spray with a carrier flow (dispersion gas). The resulting particle size distribution is examined as well. It is in particular observed that using ethanol leads to faster agglomeration and larger nanoparticles. This effect is qualitatively similar to that found when injecting smaller liquid spray droplets.

Moisture Determination for Fine-Sized Copper Ore by Computer Vision and Thermovision Methods.

The moisture of bulk material has a significant impact on the energetic efficiency of dry grinding, resultant particle size distribution and particle shape, and conditions of powder transport. This research aims to develop computer vision and thermovision techniques for the on-site estimation of moisture content in copper ore, for use, e.g., in dry grinding installations. The influence of particle size on the results of moisture estimation is also studied. The tested granular material was copper ore of particle size 0-2 mm and relative moisture content of 0.5-11%. Both vision and thermovision images were taken at standard and macro scales. The results suggest that median-intensity vision images monotonically reflect copper ore moisture in the range of about 0.5-5%. Suitable models were identified and cross-validated here. In contrary, thermograms should not be analyzed simply for their mean temperature but treated with computer vision processing algorithms.

Centrifugal atomization of stainless-steel rotating rods melted by a high-power LASER beam

316L grade stainless steel powders were produced by centrifugal atomization during the melting of a rotating rod heated by a high-power LASER beam. The feasibility has been demonstrated by atomizing a range of stainless steel rods. The atomization process has been observed via high-speed imaging and fragmentation regimes have been identified according to a literature review on the rotating electrode process (REP). Results were compared with literature data and an existing prediction model for such a process. High-speed observation can monitor the present process and it is shown that a solidified layer of metal is formed at the edge of the rod during the process inducing metal flake ejection due to the centrifugal stresses. Effects of incident LASER beam power density, ejection speed and oxygen content of the surrounding atmosphere on the particle size distribution and the sample surface have been studied and compared with literature data on classical REP atomizers. The study focuses on the production of irregular particles during the atomization process and highlights the influence of the oxygen content in the surrounding atmosphere on the fragmentation regime and the resulting particle size distribution.

Single and multiple breakage events in fine particle breakage testing with a rigidly-mounted roll mill

For the prediction of breakage in fine grinding processes (<200 μm), simulation based on population balance models and/or discrete element method is often applied. Both numerical techniques require a deep understanding of the breakage mechanisms within the grinding process. Depending on the breakage mechanism, different devices are available to characterize the breakage behaviour of the feed material, such as the breakage function or breakage rate. For characterizing breakage specific parameters of particles in fine grinding, a new breakage tester based on a rigidly-mounted roll mill was presented in a previous study. The present work focuses on the investigation of progressive stress events in fine particle breakage testing. For this, the effect of weakening and breakage history is analysed. As a result, the shape of the resulting particle size distribution and the particle strength are influenced by previous stressing. Therefore, a new approach considering the history of particle breakage is introduced.

Limestone grindability in terms of HGI and a new approach for the understanding of grinding energy

In this study, limestone samples (a total of 108 sample) were collected from two limestone quarries. The collected samples were initially in the form of palm sized and they were crushed to −2.36 mm. Grinding experiments were conducted in standard HGI (Hardgrove Grindability Index) mill and Ring mill. PSD (Particle Size Distribution) analyzes were carried out for the samples ground with Ring mill. HGI test results were compared with the PSD results. A new method for the prediction of HGI of limestone samples from both of the quarries (Quarry-1 and Quarry-2) was proposed. Significant correlation (R2 = 0.84) was obtained with D90 size parameter. In terms of grinding energy calculations, Bond Work Index (BWI) was taken into consideration. In addition, proposed method for HGI prediction was employed to understand the possible role of microwave pre-treatment.

Effects of ultrasound-assisted enzymolysis on the physicochemical properties and structure of arrowhead-derived resistant starch

The effects of ultrasound-assisted enzymolysis on the physicochemical properties and structure of arrowhead-derived type 3 resistant starch (RS3) were investigated. Compared with the traditional enzymolysis, ultrasonic treatment significantly (p < 0.05) increased the resistant starch yield by 34.46%. Enzymolysis reaction kinetics revealed that ultrasound-assisted enzymolysis remarkably increased the enzymolysis rate and amylose content. After ultrasound treatment, RS3 displayed higher solubility, swelling power, transparency, and water absorption capacity. The results of particle-size distribution, differential scanning calorimetry, X-ray diffraction, Fourier transform-infrared spectroscopy, and scanning electron microscopy analyses demonstrated that RS3 prepared by ultrasound-assisted enzymolysis exhibited a larger granule size, higher crystallinity, a more ordered and stable double helix structure with increased surface roughness compared to those of RS3 prepared by traditional enzymolysis. These findings provide a theoretical background for the preparation of RS3 using an ultrasound-assisted enzymatic method and will promote the development of ultrasound chemistry in starch science and technology.

Rigidly-mounted roll mill as breakage tester for characterizing fine particle breakage

Fine grinding based on compression stresses is an important industrial process step, which is often applied in mineral, chemical and pharmaceutical industries, for example by using stirred media mills. For this stress mechanism, several studies investigate how to predict the breakage behavior depending on process and formulation conditions by population balance modelling. Breakage rate and breakage function are essential to describe the evolution in particle size distribution over time. Hereby, the division in a mill and a material model has already been shown to be a successful approach for different mills. Especially for fine particles the determination of the breakage function is a particular challenge. In order to predictively model breakage characteristics of materials, such as the breakage function for different energies applied to break the material, it is required to develop a new method, which is easy, fast, and inexpensive to carry out. For this purpose, we present a newly designed breakage tester consisting of a rigidly-mounted two-roll mill. First, a recommendation for the use of a breakage tester is developed. In this step, the investigated machine parameters include the gap size, feed rate, and roller velocity. Furthermore, the influence of feed particle size on the resulting particle size distribution was researched. All tests have been conducted with soda-lime glass as a model material. Second, the applicability of different models for the breakage function, focusing on the tnt10-model, is demonstrated. The breakage can be predicted for new energy values and is in very good agreement with the experimental data. This new breakage tester allows the fast characterization of particle breakage in lower micron range.

Measurement-Based Modelling of Material Moisture and Particle Classification for Control of Copper Ore Dry Grinding Process.

Moisture of bulk material has a significant impact on energetic efficiency of dry grinding, resultant particle size distribution and particle shape, and conditions of powder transport. As a consequence, moisture needs to be measured or estimated (modelled) in many points. This research investigates mutual relations between material moisture and particle classification process in a grinding installation. The experimental setup involves an inertial-impingement classifier and cyclone being part of dry grinding circuit with electromagnetic mill and recycle of coarse particles. The tested granular material is copper ore of particle size 0–1.25 mm and relative moisture content 0.5–5%, fed to the installation at various rates. Higher moisture of input material is found to change the operation of the classifier. Computed correlation coefficients show increased content of fine particles in lower product of classification. Additionally, drying of lower and upper classification products with respect to moisture of input material is modelled. Straight line models with and without saturation are estimated with recursive least squares method accounting for measurement errors in both predictor and response variables. These simple models are intended for use in automatic control system of the grinding installation.

Formation of nascent soot during very fuel-rich oxidation of ethylene at low temperatures

Soot formation during very fuel-rich oxidation of ethylene (with equivalence ratio, φ, ranging from 3 to infinity) at relatively low temperatures (1473–1673 K) was studied in a flow reactor, in which temperature was well controlled through an external heater, and φ of the reactants was adjusted by adding different amounts of O2 (0–6000 ppm) at the inlet of the reactor. Detailed sooting properties including soot volume fraction, number density, particle size distribution (PSD), and morphology were examined. The results show that at a temperature of 1673 K, the total soot yield increases monotonously with φ. However, at 1473 and 1573 K, the soot volume fraction increases first and then decreases as φ increases from 3 to infinity, which means a small amount of oxygen can promote soot formation. The PSD and number density results indicate that this promotion effect is more prominent at the nucleation stage and weakens as soot grows at longer residence times. In addition, soot morphology is affected mostly by temperature rather than φ, and the decrease of temperature leads to larger primary particles and less fractal aggregates. Kinetic modeling results indicate that the concentrations of PAHs and soot increase because a small amount of O2 addition can enhance the C3 + C3 pathways through the generation of reactive oxygenated species.

In-situ investigation of coal particle fragmentation induced by thermal stress and numerical analysis of the main influencing factors

Particle fragmentation influences thermochemical coal conversion processes in different ways, which is of great significance for process design and control. Different mechanisms are proposed for fragmentation characterization, but direct and substantial optical evidence supporting these theories is rarely reported. In the present study, the fragmentation process of two anthracites with low volatiles is investigated in-situ with the aid of an optical system. The observed fragmentation phenomenon confirms that the thermal stress is the main driving force for the fragmentation of the investigated anthracite particles. Together with a model analysis, a fragmentation pattern different from previous reports is proposed. The tensile stress causes the particles to fragment from the center. Fine particles are produced by multiple tensile failure rather than by the spalling of particles’ outer shell caused by compressive stress. Based on the model, the impact of various process- and particle-related factors on the maximum thermal tensile stress and its appearance time are quantitatively evaluated, which significantly reduces the required time and effort in comparison to experimental analysis of the fragmentation. This study provides direct visual evidence and numerical validation of the fragmentation mechanism, which can be utilized to predict the coal particle behavior and the resulting particle size distribution.

Removal of metals and hydrocarbons from stormwater using coagulation and flocculation

As the understanding of how stormwater pollutants are fractioned and need for mitigation has increased, so has the investigation into more advanced treatment techniques. The present study investigated the treatment efficiency of coagulation/flocculation and sedimentation in semi-synthetic stormwater. Five coagulants were evaluated in terms of reducing particle content, organic carbon, total and dissolved metals, hydrocarbon oil index, and polycyclic aromatic hydrocarbons (PAHs). Changes in the resulting particle size distribution as a consequence of the coagulation treatment were also investigated. The pollutants in the semi-synthetic stormwater were predominantly in the particulate phase. The medium and longer chained hydrocarbons dominated the hydrocarbon oil index, while medium to high molecular weight PAHs were most abundant. Iron chloride was the only coagulant that affected particle size distribution post-treatment, shifting the distribution toward larger particles. In terms of total metal removal, the performance of the coagulants was similar, with over 90% removal on average. Concentration of zdissolved copper, one of the metals found in the dissolved phase, was reduced by 40% via coagulation treatment. The iron chloride coagulant increased dissolved Zn, a change attributed to a considerable drop in pH resulting in higher ion mobility. Similarly, the reduction in organic content (total organic carbon, oil, and PAHs) was over 90% for most coagulants.

Ultra-Small Silver Nanoparticles Immobilized in Mesoporous SBA-15. Microwave-Assisted Synthesis and Catalytic Activity in the 4-Nitrophenol Reduction

Despite the continuous developments in the synthesis of noble metal nanoparticles, the uniformity of particle size distribution still represents a critical aspect. A fast and homogeneous nucleation is a key requirement to achieve a monodisperse particle size distribution and in this scenario, the application of alternative energy sources may constitute a winning strategy for the development of highly active nanocatalysts with unique properties. Here we present several approaches to control the synthesis of Ag nanoparticles stabilized by an anionic template, and the results evidence the advantages of adopting unconventional heating techniques such as microwave heating. The fast and selective electromagnetic heating strongly reduced the nucleation and growth times, impacting on the homogeneity of the resulting particle size distribution. In this work, we have carried out the microwave-assisted synthesis of Ag nanoparticles and the resulting nanoparticles were compared to those synthesized under conventional heating using an oil bath, showing that the differences in temperature profile and heating rates between the two synthesis pathways had a clear effect on the size distribution of the resulting nanoparticles as well as on their stability under long term storage. Finally, the synthesized ultra-small Ag nanoparticles were deposited on a mesoporous substrate, reducing undesired Ostwald ripening and facilitating their reusability. This nanocatalyst was adopted for the abatement of 4-nitrophenol, a well-known carcinogenic pollutant with adverse effects on human beings and aquatic life. The catalytic results confirm the high activity of the catalyst thanks to the high dispersion achieved afforded by ultra-small Ag nanoparticles and the accessibility provided by the wide SBA-15 mesoporous channels.