Quartz Mass Research Articles

Unraveling the electronic properties in SiO2 under ultrafast laser irradiation

First-principles simulations were conducted to explore various electronic properties of crystalline SiO2 (α-quartz) under ultrafast laser irradiation. Employing Density Functional Perturbation Theory and the many-body (GW) approximation, we calculated the impact of thermally excited electrons on the electronic specific heat, electron pressure, effective mass, deformation potential, electron-phonon coupling and electron relaxation time of quartz, covering a wide range of electron temperatures, up to 100,000 K. We show that the electron-phonon relaxation time of highly-excited quartz becomes twice faster compared to low-excited states. The deformation potential, which dictates atomic displacement, has a non-monotonic behavior with a well-pronounced minimum at around 16,000 K (2.7 × 1021 cm−3 of excited electrons) where the bond ionicity of the Si-O starts decreasing followed by a cohesion loss at 35,000 K due to the pressure exerted by the excited electrons on the lattice. Consequently, our calculated data, illustrating the evolution of physical parameters, can facilitate simulations of laser-matter interactions and provide predictive insights into the behavior of quartz under experimental conditions.

Thin seams and small mines are associated with higher exposures to respirable crystalline silica in US underground coal mines

ObjectivesPrevious radiologic and histopathologic studies suggest respirable crystalline silica (RCS) overexposure has been driving the resurgence of pneumoconiosis among contemporary US coal miners, with a higher prevalence of severe disease...

Andesite Quality based on Compressive Strength Tests in the Ulujadi area, Palu City and the Banawa Area, Donggala Regency

The research location is located in the Ulujadi area, Palu City, Central Sulawesi Province, which is one of the areas that has abundant andesite mineral content. This research aims to optimizing use of andesite rocks in the Ulujadi area of ​​Palu City. The research was carried out using qualitative and quantitative methods in the form of rock sampling and laboratory analysis, namely compressive strength test analysis to determine the technical properties of rocks and petrographic analysis to determine the quality of andesite based on the minerals that make up it. The results of petrographic analysis show that the andesite rocks in the study area are composed of minerals that have a good level of resistance. ST 07 has a mineral composition of plagioclase (38%), pyroxene (5%), biotite (5%), hornblende (7%), and soil mass (45%), and has a compressive strength test of 123 MPa, included in the classification strong, and is used as a foundation for light to medium buildings (SNI 03-0394-1989). ST 08 has a mineral composition of plagioclase (32%), ground mass (50%), opaque minerals (5%), orthoclase (5%), quartz (4%), and hornblende (4%), with a compressive strength test value of 97MPa, including in the strong classification, and can be used as a foundation for light to medium buildings. Meanwhile, ST 09 has a mineral composition of plagioclase (30%), hornblende (12%), quartz (3%), biotite (3%), orthoclase (7%), pyroxene (5%), and soil mass (40%). ), it is included in the weak category due to the relatively high degree of weathering, and can only be used as an ornamental stone.

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

Abstract. Soil dust aerosols are a key component of the climate system, as they interact with short- and long-wave radiation, alter cloud formation processes, affect atmospheric chemistry and play a role in biogeochemical cycles by providing nutrient inputs such as iron and phosphorus. The influence of dust on these processes depends on its physicochemical properties, which, far from being homogeneous, are shaped by its regionally varying mineral composition. The relative amount of minerals in dust depends on the source region and shows a large geographical variability. However, many state-of-the-art Earth system models (ESMs), upon which climate analyses and projections rely, still consider dust mineralogy to be invariant. The explicit representation of minerals in ESMs is more hindered by our limited knowledge of the global soil composition along with the resulting size-resolved airborne mineralogy than by computational constraints. In this work we introduce an explicit mineralogy representation within the state-of-the-art Multiscale Online Nonhydrostatic AtmospheRe CHemistry (MONARCH) model. We review and compare two existing soil mineralogy datasets, which remain a source of uncertainty for dust mineralogy modeling and provide an evaluation of multiannual simulations against available mineralogy observations. Soil mineralogy datasets are based on measurements performed after wet sieving, which breaks the aggregates found in the parent soil. Our model predicts the emitted particle size distribution (PSD) in terms of its constituent minerals based on brittle fragmentation theory (BFT), which reconstructs the emitted mineral aggregates destroyed by wet sieving. Our simulations broadly reproduce the most abundant mineral fractions independently of the soil composition data used. Feldspars and calcite are highly sensitive to the soil mineralogy map, mainly due to the different assumptions made in each soil dataset to extrapolate a handful of soil measurements to arid and semi-arid regions worldwide. For the least abundant or more difficult-to-determine minerals, such as iron oxides, uncertainties in soil mineralogy yield differences in annual mean aerosol mass fractions of up to ∼ 100 %. Although BFT restores coarse aggregates including phyllosilicates that usually break during soil analysis, we still identify an overestimation of coarse quartz mass fractions (above 2 µm in diameter). In a dedicated experiment, we estimate the fraction of dust with undetermined composition as given by a soil map, which makes up ∼ 10 % of the emitted dust mass at the global scale and can be regionally larger. Changes in the underlying soil mineralogy impact our estimates of climate-relevant variables, particularly affecting the regional variability of the single-scattering albedo at solar wavelengths or the total iron deposited over oceans. All in all, this assessment represents a baseline for future model experiments including new mineralogical maps constrained by high-quality spaceborne hyperspectral measurements, such as those arising from the NASA Earth Surface Mineral Dust Source Investigation (EMIT) mission.

73 Performance of Analytical Laboratories Undertaking Silica on Filter Analysis: What Proficiency Testing Data Tells Us

Abstract Silicosis, one of the oldest recorded occupational diseases, is a form of lung disease caused by the inhalation of respirable crystalline silica (RCS) within occupational settings such as quarrying, foundries, potteries and stone masonry. Hence worker exposure studies, involving sampling airborne dust onto a filter for subsequent silica analysis in the laboratory, are often conducted. Laboratories use either X-ray diffraction (XRD) or Fourier-Transform Infrared (FTIR) spectroscopy for measurements and follow validated procedures set out in either national regulatory methods or in international consensus standards. But how well do these published methods work in routine occupational hygiene laboratories? The AIR proficiency testing (PT) programme, a partnership between HSE and LGC Standards, offers test items where participants receive samples prepared through the aerosolisation of defined masses of quartz onto air filters. Are there differences between laboratories using direct on filter assays and those that use methods which require a sample preparatory step? Are instrumental measurements by XRD and FTIR comparable? In this presentation, we will attempt to answer these questions using returned PT data.

HIGH STRENGTH MANGO LEAF WASTE/POLYURETHANE COMPOSITE REINFORCEMENT USING QUARTZ MATERIAL

Quartz stone contains silica components (SiO2) which have the ability as a reinforcement material for composite materials. Quartz SEM-EDX testing shows that the quartz silica comonent is 69%. Other components contained in quartz are 34% MgO and 2% CaO. Therefore, quartz stone is used as a reinforcing material in mango leaf waste composite materials. Meanwhile, compressive strength testing of composite materials was carried out with variations of Polyurethane (PU) polymers, namely 1, 2, 3, 4, 5, 6, and 7 grams, obtaining the highest maximum pressure at 6 grams polymer mass, which is 38.91 grams. Testing of composite materials that have been given a mixture of quartz stone with a mass of Polyurethane (PU) 6 grams and a quartz stone variation of 0.03; 0,06; 0,09; 0,12; 0,15; and 0.18 grams obtained the maximum power most optimally there is a quartz mass of 0.06 grams of 40.47 grams. The strength of mango leaf composite meets the strength standard for building materials, namely concrete with a value of 20-150 MPa. This shows that quartz stone can be a composite reinforcement comprehenent for mango leaf waste.

SPODUMENE AND BERYL FROM CONȚU LITHIUM - PEGMATITES, CINDREL (CIBIN) MOUNTAINS, CENTRAL GROUP, SOUTH CARPATHIANS, ROMANIA

Spodumene, now in the everyday life, represent a critical source of the chemical element known as lithium. For principle reducing emissions of CO2, now and in the future, we can find an alternative resource like green resources – spodumene. The first step is to identify the field with minerals - prospecting, then the second is exploration, and culminates with exploitation. In Romania, we find probably the only fields with lithium pegmatites in Conțu. Pegmatitic bodies are known as Conțu Superior and Conțu Inferior. Spodumene appears in the form of crystals and massive aggregates, with long habitus – prismatic, sometimes tabular, and with dimensions of 25 cm – 70 cm. Its color varies from white–greenish with vitreous luster, to gray – greenish, color due to the alteration processes, which led to the appearance in green – yellow colors on the spodumene has a good cleavage on the plane (010). Spodumene has monoclinic symmetry and C2/c space group (15), and cell parameters: a = 9.466 Å, b = 8.394 Å, c = 5.221 Å. The analytical method (EPMA) indicated a lithium oxide content between 7.43 % and 7.50 %, these percentages were calculated. Beryl (the emerald variety) macroscopically, has a greasy luster, colors in light green to dark green tones, in the mass of quartz and albite. Beryl crystallizes in the hexagonal system, space group P6/mcc (192), and the cell parameters are a = 9.267 Å, b = 9.187 Å. Infrared transmittance spectroscopy indicated the presence of beryl. BeO4 vibrates at frequencies around 900 cm-1 and 1000 cm-1, we find in sample N118, valence vibrations at: 1094 cm-1, 1039 cm-1, and 957 cm-1.

Kinetics of the transformations occurring during the firing process of an industrial spray-dried porcelain stoneware body

Pressed compacts of an industrial spray-dried porcelain stoneware powder, consisting mainly of albite, quartz, kaolinite, and illite, were thermally treated at different temperatures and times. Fired test piece bulk density and water absorption, in addition to phase content (using X-ray diffraction (XRD) data and Rietveld refinements) and microstructure (using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDS)), were determined. The isothermal kinetics of densification, mullite precipitation, and feldspar and quartz dissolution were obtained. The evolution of the mullite, quartz, feldspar, and vitreous phase mass percentages with the dissolved feldspar fraction was independent of thermal treatment. The evolution of water absorption, linear shrinkage, and bulk density with vitreous phase content was also independent of thermal treatment. Water absorption decreased linearly as vitreous phase content increased, until it cancelled out at a vitreous phase content of 66% by weight.

Reactor scale simulations of ALD and ALE: Ideal and non-ideal self-limited processes in a cylindrical and a 300 mm wafer cross-flow reactor

We have developed a simulation tool to model self-limited processes such as atomic layer deposition (ALD) and atomic layer etching inside reactors of arbitrary geometry as well the output of in situ quartz crystal microbalance and mass spectrometry. We have applied this model to two standard types of cross-flow reactors: a cylindrical tube reactor and a model 300 mm wafer reactor, and explored both ideal and nonideal self-limited kinetics. The model results are in agreement with experimental results and analytic expressions obtained using a simple plug-flow model for the cylindrical tube reactor. We also extended the simulations to consider two nonideal self-limited processes: soft-saturating processes characterized by a slow reaction pathway and processes where surface by-products can compete with the precursor for the same pool of adsorption sites. Our results show that it is possible to have a self-limited process with saturated yet inhomogeneous growth profiles due to the competition of reactor by-products. This is in agreement with experimental observations for titanium dioxide ALD from titanium tetraisopropoxide and titanium tetrachloride precursors.

Adsorption of gold in gold-thiosulfate solution onto a quartz surface

Experimental research and quantum chemical calculations were used to study the adsorption of gold-thiosulfate ions on a quartz surface from a solution. The adsorption rate of gold-thiosulfate ions from a quartz-containing solution was 9.52% when a stirring time of 30 min, a stirring speed of 500 r·min−1, a 30% quartz mass ratio in the slurry, and an initial gold concentration of 56.50 mg·L−1 were used. Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) were used to study the interaction mechanism of quartz and gold-thiosulfate ions in the gold-containing solution. The results showed that quartz and gold-thiosulfate underwent both physical and chemical adsorption in solution under different conditions. The CASTEP module in Materials Studio was used to perform quantum chemical calculations. The band structure, density of states, and Mulliken population analysis of the optimized quartz crystal structure showed that the p orbital of quartz was the most active. The calculated adsorption energy of gold-thiosulfate onto the (101) surface of quartz was −386.70 kJ·mol−1. The calculated S2–O36 distance was 1.628 Å, and the S3–O44 distance was 1.622 Å. The results of the Mulliken charge population analysis and bond population analysis showed that gold-thiosulfate ions adsorbed via the formation of relatively stable bonds on the (101) surface of quartz. Some gold was adsorbed by quartz when thiosulfate was used to leach gold ore, which affected the extraction of gold. These results indicate that quartz has the ability to “rob” gold during the thiosulfate gold leaching process, thereby affecting the leaching efficiency.

Design and characterization of a new oxidation flow reactor for laboratory and long-term ambient studies

Abstract. Oxidation flow reactors (OFRs) are frequently used to study the formation and evolution of secondary aerosol (SA) in the atmosphere and have become valuable tools for improving the accuracy of model simulations and for depicting and accelerating realistic atmospheric chemistry. Driven by rapid development of OFR techniques and the increasing appreciation of their wide application, we designed a new all-Teflon reactor, the Particle Formation Accelerator (PFA) OFR, and characterized it in the laboratory and with ambient air. A series of simulations and experiments were performed to characterize (1) flow profiles in the reactor using computational fluid dynamics (CFD) simulations, (2) the UV intensity distribution in the reactor and the influence of it and varying O3 concentration and relative humidity (RH) on the resulting equivalent OH exposure (OHexp), (3) transmission efficiencies for gases and particles, (4) residence time distributions (RTDs) for gases and particles using both computational simulations and experimental verification, (5) the production yield of secondary organic aerosol (SOA) from oxidation of α-pinene and m-xylene, (6) the effect of seed particles on resulting SA concentration, and (7) SA production from ambient air in Riverside, CA, US. The reactor response and characteristics are compared with those of a smog chamber (Caltech) and of other oxidation flow reactors: the Toronto Photo-Oxidation Tube (TPOT), the Caltech Photooxidation Flow Tube (CPOT), the TUT Secondary Aerosol Reactor (TSAR), quartz and aluminum versions of Potential Aerosol Mass reactors (PAMs), and the Environment and Climate Change Canada OFR (ECCC-OFR). Our studies show that (1) OHexp can be varied over a range comparable to that of other OFRs; (2) particle transmission efficiency is over 75 % in the size range from 50 to 200 nm, after minimizing static charge on the Teflon surfaces; (3) the penetration efficiencies of CO2 and SO2 are 0.90 ± 0.02 and 0.76 ± 0.04, respectively, the latter of which is comparable to estimates for LVOCs; (4) a near-laminar flow profile is expected based on CFD simulations and suggested by the RTD experiment results; (5) m-xylene SOA and α-pinene SOA yields were 0.22 and 0.37, respectively, at about 3 × 1011 molec. cm−3 s OH exposure; (6) the mass ratio of seed particles to precursor gas has a significant effect on the amount of SOA formed; and (7) during measurements of SA production when sampling ambient air in Riverside, the mass concentration of SA formed in the reactor was an average of 1.8 times that of the ambient aerosol at the same time.

Comprehensive two-dimensional gas chromatography mass spectrometry with a solid-state thermal modulator for in-situ speciated measurement of organic aerosols

Thermal desorption aerosol gas chromatography mass spectrometry is capable of online measuring speciated organics in atmospheric aerosols. Compared to the one-dimensional gas chromatography, comprehensive two-dimensional gas chromatography increases the resolution and the sensitivity, mitigates the unresolved complex mixture and co-elution occurred in one-dimensional gas chromatography. In this study, we report a quartz filter-based thermal desorption aerosol comprehensive two-dimensional gas chromatography mass spectrometry (2D-Q-TAG). It combines a solid-state thermal modulator with a quartz filter-based thermal desorption aerosol gas chromatography mass spectrometry. The solid-state thermal modulator conducts modulation independently from the chromatographic oven without using cryogens or compressed air, which makes the system readily adaptive for field measurement. The 2D-Q-TAG was evaluated using C7-C40 n-alkanes and 16 polycyclic aromatic hydrocarbons (PAHs). It has low limits of detection from 0.001 to 0.104 ng. The instrument was then deployed to measure atmospheric PM2.5 (particulate matter with an equivalent aerodynamic diameter ≤ 2.5 μm) in urban Beijing. It allows in-situ detection of speciated organics in atmospheric aerosols with hourly time resolution. Organic classes including alkanes, furanones, alcohols, aldehydes, ketones, acids, PAHs, oxy-PAHs, and alkyl-naphthalenes were well separated and detected. The total mass concentration of n-alkanes ranged from 122.1 to 629.9 ng/m3. Diurnal variation of n-alkanes was captured due to the high time resolution of the instrument.

Ring-by-ring analysis and models of retained mass of quartz in a laboratory Knelson Concentrator

The basic principle of a Knelson Concentrator (KC) is the differential settling velocities of particles in a medium under a centrifugal field. Whether the ore particles remain in the KC bowl depends on the terminal settling velocity (v) of the particles and the fluidization water flow velocity (V). Both variables are functions of the material properties and the operating parameters. This study reports the relations between the retained mass of quartz in each ring of the KC bowl (obtained by measuring the quartz mass ring by ring) and the rotational speed, fluidization water flow rate, and particle size. The retained mass of quartz in each ring was then modeled by approximating the fluidization water velocity and defining a new ratiov/V. Based on the experimental data, the functional relation between the quartz mass in each ring of the KC bowl and the feed particle properties/operating conditions was fitted by a Weibull model. The model established by the ring-by-ring approach gives more accurate predictions than a previous model, and a model based on the quartz mass in the entire bowl.

Respirable coal mine dust at surface mines, United States, 1982-2017.

Exposure to respirable coal mine dust can cause pneumoconiosis, an irreversible lung disease that can be debilitating. The mass concentration and quartz mass percent of respirable coal mine dust samples (annually, by occupation, by geographic region) from surface coal mines and surface facilities at U.S. underground mines during 1982-2017 were summarized. Mine Safety and Health Administration (MSHA) collected and analyzed data for respirable dust and a subset of the samples were analyzed for quartz content. We calculated the respirable dust and quartz concentration geometric mean, arithmetic mean, and percent of samples exceeding the respirable dust permissible exposure limit (PEL) of 2.0 mg/m3, and the average percent of quartz content in samples. The geometric mean for 288 705 respirable dust samples was 0.17 mg/m3 with 1.6% of the samples exceeding the 2.0 mg/m3 PEL. Occupation-specific geometric means for respirable dust in active mining areas were highest among drillers. The geometric mean for respirable dust was higher in central Appalachia compared to the rest of the U.S. The geometric mean for respirable quartz including 54 040 samples was 0.02 mg/m3 with 15.3% of these samples exceeding the applicable standard (PEL or reduced PEL). Occupation-specific geometric means for respirable quartz were highest among drillers. Higher concentrations of respirable dust or quartz in specific coal mining occupations, notably drilling occupations, and in certain U.S. regions, underscores the need for continued surveillance to identify workers at higher risk for pneumoconiosis.

Respirable coal mine dust in underground mines, United States, 1982-2017.

This study summarized the mass concentration and quartz mass percent of respirable coal mine dust samples (annually, by district, and by occupation) from underground coal mines during 1982-2017. Respirable dust and quartz data collected and analyzed by Mine Safety and Health Administration (MSHA) were summarized by year, coal mining occupation, and geographical area. The older (before August 2016) 2.0 mg/m 3 respirable dust MSHA permissible exposure limit (PEL) was used across all years for comparative purposes. For respirable dust and quartz, geometric mean and percent of samples exceeding the respirable dust PEL (2.0 mg/m 3 or a reduced standard for samples with >5% quartz content) were calculated. For quartz samples, the average percent quartz content was also calculated. The overall geometric mean concentration for 681 497 respirable dust samples was 0.55 mg/m 3 and 5.5% of the samples exceeded the 2.0 mg/m 3 PEL. The overall respirable quartz geometric mean concentration for 210 944 samples was 0.038 mg/m 3 and 18.7% of these samples exceeded the applicable standard. There was a decline over time in the percent of respirable dust samples exceeding 2.0 mg/m 3 . The respirable dust geometric mean concentration was lower in central Appalachia compared to the rest of the United States. However, the respirable quartz geometric mean concentration and the mean percent quartz content were higher in central Appalachia. This study summarizes respirable dust and quartz concentrations from coal mine inspector samples and may provide an insight into differences in the prevalence of pneumoconiosis by region and occupation.

Quantitative relation between the ESR signal intensities in Ge and E’ centers and quartz mass

Establishing the quantitative relation between electron spin resonance (ESR) signal intensity and quartz mass can help both to improve ESR signal measurement and to allow a greater understanding of the characteristics of ESR color centers. However, this relation has not as yet been clearly defined. We measured the ESR signal intensities in the Ge and E′ centers in the pure quartz in our samples. We applied both standard and additional doses of irradiation by using two different types of spectrometers across different timeframes in an attempt to establish the quantitative relation between the ESR signal intensities in Ge and E’ centers and quartz mass. The linear correlation established between ESR signal intensity and quartz mass was significant for the samples treated with additional irradiation, but there was, overall, no close correlation between ESR signal intensity and quartz mass for samples which were not given additional irradiation doses. A significant correlation between ESR signal intensity and quartz masses of weight ≥0.35 g was established for Ge center, but this was not the case for quartz masses of weight ≤0.3 g. This would suggest that the apparent instability of Ge center is likely aroused by the application of weak signals. The quantitative relation between ESR signal intensity and quartz mass might therefore provide a possible solution for the correction of signal intensities in aliquots of unequal weight in laboratory measurements, particularly for non-irradiated aliquots on the dose growth curve. We would propose that larger quartz masses be used for the clear identification of Ge center signal, for enhancing ESR signal intensity, and for improving the quality of signal measurement.

Geology, fluid inclusions, and geochemistry of the Zhazixi Sb–W deposit, Hunan, South China

The Zhazixi Sb–W deposit in the Xuefeng uplift, South China, exhibits a unique metal association of W and Sb, where the W orebodies are hosted by interlayer fractures and the Sb orebodies are contained within NW-trending faults. This study proposes that the W and Sb mineralization took place in two separate periods. The mineral paragenesis of the W mineralization reveals a mass of quartz, scheelite and minor calcite. The mineral assemblage of the Sb mineralization developed after W mineralization and consists of predominantly quartz and stibnite, and small amounts of native Sb, berthierite, chalcostibnite, pyrite, and chalcopyrite. Fluid inclusions in quartz and coexisting scheelite are dominated by two-phase, liquid-rich, aqueous inclusions at room temperature. Microthermometric studies suggest that ore-forming fluids for W mineralization are characterized by moderate temperatures (170–270°C), low salinity (3–7wt% NaCl equiv.), low density (0.75–0.95g/cm3), and moderate to high pressure (57.2–99.7MPa) and these fluids experienced a cooling and dilution evolution during W mineralization. Ore-forming fluids for Sb mineralization are epithermal types with low temperatures (150–230°C), low salinity (4–6wt% NaCl equiv.), moderate density (0.82–0.94g/cm3), and high pressure (42.2–122.5MPa) and these fluids display an evident decline in homogenization temperature during Sb mineralization. Laser Raman analyses of the vapor phase indicate that the ore-forming fluids for both W and Sb mineralization contain a small amount of CO2.The ore-forming fluids for Sb mineralization are identified as predominantly originating from the continental crust, as suggested by the low 3He values (0.009×10−12cc.STP/g) and 3He/4He ratios (0.002–0.056Ra) as well as high 36Ar values (1.93×10−9cc.STP/g) and 40Ar/36Ar ratios (909.5–2279.7). The source of S is identified to be the Neoproterozoic Wuqiangxi Formation, as traced by the δ34SV-CDT values of stibnite (3.1–9.4‰). The 208Pb/204Pb (37.643–40.222), 207Pb/204Pb (15.456–15.681), and 206Pb/204Pb (17.093–20.042) ratios suggest a mixture of lower crustal and supracrustal Pb sources.It is thus concluded that the ore genesis of the Zhazixi Sb–W deposit is related to the intracontinental orogeny during the early Mesozoic. Fluid mixing is considered to be the critical mechanism involved in W mineralization, whereas a fluid cooling process is responsible for Sb mineralization. Furthermore, the absence of Au is attributed to the low Σas content in Sb-mineralizing fluids.

An investigation on laboratory Knelson Concentrator separation performance: Part 2: Two-component feed separation modelling

In the previous study, a mathematical model was proposed to predict retained mass inside a laboratory Knelson Concentrator bowl. In this part, a model is proposed to describe the particle separation performance of the laboratory Knelson Concentrator. The separation model considers the main forces (fluid drag force, Fd, centrifugal force, Fc, and buoyancy force, Fb) acting on particles inside the concentrating bowl, which are functions of material properties as well as the operating condition parameters. Several materials with different densities including magnetite, zinc, ferromolybdenum, lead, and tungsten were used as valuable components to simulate minerals with the same densities in two-component synthetic feeds with various size fractions. The modelling of component separation in the Knelson Concentrator was performed based on the ratio of Fd/(Fc-Fb). Based on an extensive experimental database, practical and simple models were proposed as predictors of recovered mass of valuable components from tailings and the mass of quartz (as gangue) in the Knelson Concentrator versus the ratio of Fd/(Fc-Fb) for quartz.

Feasibility of the quantification of respirable crystalline silica by mass on aerosol sampling filters using Raman microscopy

Airborne respirable crystalline silica (RCS) is a hazard that can affect the health of workers, and more sensitive measurements are needed for the assessment of worker exposure. To assess the use of Raman microscopy for the analysis of RCS particulate collected on filters, aliquots of quartz or cristobalite suspended in isopropanol were pipetted onto silver filters. Samples were measured by arbitrarily selecting positions along the filter and collecting spectra at 50 discrete points. The calculated limits of quantification on test samples were between 0.066–0.161 and 0.106–0.218 μg for quartz and cristobalite, respectively. Three respirable quartz calibration dusts (A9950, NIST 1878 and Quin 1B) with different mass median aerodynamic particle sizes obtained similar Raman response relationships per unit mass. The difference between NIST 1878 and Quin 1B was not significant (p = 0.22). The intermediate measurement precision of replicate samples was 10–25% over the measured range for quartz (0.25–10 μg) and could potentially be improved. Results from mixtures of quartz and cristobalite were mostly within 10% of their theoretical values. Results from samples of 6% quartz in calcite were close to the theoretical quartz mass. The upper measurement limit for a mixture of 20% RCS in the light absorbing mineral hematite (Fe2O3) was 5 μg. These data show that Raman spectroscopy is a viable option for the quantification of the mass of respirable crystalline silica on filters with a limit of detection approaching 1/10th of that obtained with other techniques. The improvement in sensitivity may enable the measurement of particulate in samples from low concentration environments (e.g. inside a mask) or from miniature samplers operating at low flow rates. ©2017 Crown copyright. Journal of Raman Spectroscopy published by John Wiley & Sons, Ltd. © 2017 Crown copyright. Journal of Raman Spectroscopy published by John Wiley & Sons, Ltd.

In Situ Real-Time Quantitative and Qualitative Monitoring of Molecular Contamination

The quantitative and qualitative monitoring of contamination is an important issue for the mitigation of the risks induced by contamination. In situ and real-time measurements of contamination levels are currently performed with good accuracy by using quartz microbalances. However, they have to be completed by chemical analyses to identify the nature of the contaminants. Unfortunately, in situ techniques are limited to a very rough characterization. A transfer of the samples is then required, which prohibits real-time monitoring and may lead to the partial degradation of the samples. To tackle this challenge, an experimental technique, coupling thermogravimetric analysis and mass spectrometry, has been developed at ONERA. This method takes advantage of a preseparation of the species through the thermogravimetric analysis. A numerical tool was moreover developed to process automatically experimental thermogravimetric analysis/mass spectrometry data. It enables determination of the contribution of each species (deconvolution of thermogravimetric analysis measurements species by species, both for quartz crystal microbalance measurements and mass spectrometry spectra) and extraction of the mass spectrum of each of these species. The results of this analysis are presented for the characterization of an adhesive widely used for space applications. The deconvolution in species matches very well the experimental data.