Μm Diameter Particles Research Articles

Lithiation and Delithiation of Silicon Oxycarbide Single Particles with a Unique Microstructure

Single particles (11 and 13 μm diameter) of a silicon oxycarbide (Si-O-C) glass were electrochemically analyzed using a microelectrode technique. A micromanipulator-guided nickel-plated rhodium-platinum microfilament (25 μm diameter, 13 wt % rhodium) was used to maintain electrical contact to a single Si-O-C glass particle in an organic solution containing 1 mol dm(-3) LiClO(4). The cyclic voltammograms of a single Si-O-C glass particle (11 μm diameter) featured a characteristic sharp peak at ca. 0.1 V vs Li/Li(+), along with a broad peak and a shoulder, in the anodic reaction. This result indicates that there are several electrochemically active sites for lithium storage in the single Si-O-C glass particle. The first lithiation and delithiation capacities of a single Si-O-C glass particle (13 μm diameter) were 1.67 nA h and 1.12 nA h, respectively, at 5 nA (4C rate) in the potential range 0.01-2.5 V vs Li/Li(+), leading to a Coulombic efficiency of 67%. These results are in good agreement with those observed in typical porous composite electrodes. The 13 μm diameter particle gives 75% of the full-delithiation capacity even at 100 nA (80C rate), demonstrating that its intrinsic delithiation rate capability is suitable for practical purposes. Assuming that the Tafel equation is applicable to the delithiation of the single Si-O-C glass particle, the charge-transfer resistance tended to increase as lithium was released.

On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM 10 by in-tube solid-phase microextraction coupled to capillary liquid chromatography

A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl–5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analysis of aqueous extracts of atmospheric particulate PM 10 was carried out. Moreover, the possibility of coupling IT-SPME and conventional liquid chromatography is also tested. Derivatization solution and IT-SPME coupled to capillary liquid chromatography provided the best results for achieving the highest sensitivity for carbonyl compounds in atmospheric particulate analysis. Detection limits (LODs) using a photodiode array detector (DAD) were ranged from 30 to 198 ng L −1, improving markedly those LODs reported by conventional SPME–LC–DAD.

Oil Mist Eliminator Vessel Modifications for GE 7EA Gas Turbine

With any rotating machinery as lube oil leaves bearings, a certain amount of lube oil is aerated, resulting in the formation of a mist of very small size (less than 1 μm diameter) particles. If oil mist elimination system is not sized and designed properly, it could cause various issues such as increased operation and maintenance cost, re-entry of oily air into adjacent gas turbine units, fouling of surrounding atmosphere, and creation of oil slick on concrete floors, besides impacting environmental requirements and safety hazards. This paper presents a case study involving GE 7EA gas turbines operating at the Watson Cogeneration Plant and discusses issues with the existing oil mist elimination system and steps taken for a successful replacement of the original equipment manufacturer (OEM) supplied mist elimination system with non-OEM designed and fabricated mist elimination system. The replaced system demonstrated significantly higher life expectancy than it was designed for.

Size-resolved source apportionment of carbonaceous particulate matter in urban and rural sites in central California

Abstract Very little is currently known about the relationship between exposure to different sources of ambient ultrafine particles (PM0.1) and human health effects. If human health effects are enhanced by PM0.1’s ability to cross cell membranes, then more information is needed describing the sources of ultrafine particles that are deposited in the human respiratory system. The current study presents results for the source apportionment of airborne particulate matter in six size fractions smaller than 1.8 μm particle diameter including ultrafine particles (PM0.1) in one of the most polluted air basins in the United States. Size-resolved source apportionment results are presented at an urban site and rural site in central California’s heavily polluted San Joaquin Valley during the winter and summer months using a molecular marker chemical mass balance (MM–CMB) method. Respiratory deposition calculations for the size-resolved source apportionment results are carried out with the Multiple Path Particle Dosimetry Model ( MPPD v 2.0), including calculations for ultrafine (PM0.1) source deposition. Diesel engines accounted for the majority of PM0.1 and PM1.8 EC at both the urban and rural sampling locations during both summer and winter seasons. Meat cooking accounted for 33–67% and diesel engines accounted for 15–21% of the PM0.1 OC at Fresno. Meat cooking accounted for 22–26% of the PM0.1 OC at the rural Westside location, while diesel engines accounted for 8–9%. Wood burning contributions to PM0.1 OC increased to as much as 12% of PM0.1 OC during the wintertime. The modest contribution of wood smoke reflects the success of emissions control programs over the past decade. In contrast to PM0.1, PM1.8 OC had a higher fraction of unidentified source contributions (68–85%) suggesting that this material is composed of secondary organic aerosol (SOA) or primary organic aerosol (POA) that has been processed by atmospheric chemical reactions. Meat cooking was the largest identified source of PM1.8 organic carbon (OC) at the Fresno site (12–13%) while diesel engines were the largest identified PM1.8 OC source at the rural site (5–8%). Wood burning contributions to PM1.8 OC increased during the wintertime at both sites (6–9%) but were relatively small during the summertime (∼1%). As expected, diesel engines were the dominant source of PM0.1 EC respiratory deposition at both the urban and rural site in both summer and winter (0.01–0.03 μg PM0.1 EC deposited per m3 air inhaled). Meat cooking accounted for 0.01–0.025 μg PM0.1 OC deposited per m3 air inhaled while diesel fuel accounted for 0.005–0.013 μg PM0.1 OC deposited per m3 air inhaled. Minor contributions from wood burning, motor oil, and gasoline fuel were calculated at levels

Effects and Mechanism of Pre-ozonation on Sand Filtration Performance

Diatoms were shown to be responsible for clogging the sand filtration tanks in the waterworks of Beijing treating reservoir source water. The effect of pre-ozonation on the performance of the sand filter was investigated using a continuous-flow (200 L h−1) pilot experimental system. At the optimum ozone dose of 1.0 mg L−1, the filter run time was prolonged 2.7–2.8-fold, the number of 2–5 μm diameter particles decreased from 353–829 ml−1 to 53–269 ml−1 and the turbidity in the filtrate decreased from >0.2 NTU to < 0.1 NTU. Laboratory tests showed that ozone was able to break the cells of the diatoms, including Fragilaria sp., Diatoma sp. and Navicula sp., into smaller particles, and the optimum ozone dose was also 1.0 mg L−1. Decomposition of algae is likely to be the main reason for the significantly improved performance of filtration.

Measurement of Respirable Superabsorbent Polyacrylate (SAP) Dust by Ethanol Derivatization Using Gas Chromatography-Mass Spectrometry (GC-MS) Detection

Superabsorbent polyacrylate (SAP) is an important industrial chemical manufactured primarily as sodium polyacrylate but occasionally as potassium salt. It has many applications owing to its intrinsic physical property of very high water absorption, which can be more than 100 times it own weight. SAP is commonly used in disposable diapers and feminine hygiene products and is known by a number of synonyms—sodium polyacrylate, superabsorbent polyacrylate (SAP), polyacrylate absorbent (PA), and superabsorbent material (SAM). Germany and The Netherlands have adopted a nonbinding scientific guideline value 0.05 mg/m3 (8-hr time-weighted average, TWA) as the maximum allowable workplace concentration for the respirable dust of SAP (<10 μm particle diameter). Three industry associations representing Europe, the United States, and Asia have adopted the German scientific guideline value of 0.05 mg/m3 (8-hr TWA) as a voluntary guideline. A new test method based on alcohol derivatization of the acrylate was developed and validated for the analysis of respirable superabsorbent polyacrylate dust collected on filter cassettes in the workplace environment. This method is an alternative to the commonly used sodium-based method, which is limited owing to potential interference by other sources of sodium from the workplace and laboratory environments. The alcohol derivatization method effectively eliminates sodium interference from several classes of sodium compounds, as shown by their purposeful introduction at two and six times the equivalent amount of SAP present in reference samples. The accuracy of the method, as determined by comparison with sodium analysis of known reference samples, was greater than 80% over the study range of 5–50 μg of SAP dust. The lower reporting limit of the method is 3.0 μg of SAP per sample, which is equivalent to 3 (μg/m3) for an 8-hr sampling period at the recommended flow rate of 2.2 L/min.

Development, application and validation of RP-HPLC method for the simultaneous determination of butamirate citrate and its main degradation product in pharmaceutical dosage forms

A simple, rapid and sensitive reversed phase high performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous determination of butamirate citrate (BT) and its hydrolysis product (α-ethylbenzeneacetic acid (EA)). The method was based on HPLC separation of BT from its hydrolysis product using a Shim-pack cyanopropyl column (250 mm × 4.6 mm i.d., 5 μm particle diameter) at ambient temperature with the mobile phase consisting of acetonitrile–25 mM potassium dihydrogen phosphate, pH 3.4 (40 : 60, v/v). Quantitation was achieved with UV detection at 210 nm based on peak area. The method was validated with respect to specificity, linearity, limit of detection, limit of quantitation, accuracy, precision and robustness. The method was successfully applied for the determination of BT and its hydrolysis product in syrup. The proposed method was used to investigate the kinetics of acidic and alkaline hydrolysis processes of BT at different temperatures and the apparent pseudo-first-order rate constant, half-life and activation energy were calculated. The pH–rate profile of hydrolysis of BT in Britton–Robinson buffer solutions within the pH range 1.4–12 was studied.

The Surprising Composition of the Salivary Proteome of Preterm Human Newborn

Saliva is a body fluid of a unique composition devoted to protect the mouth cavity and the digestive tract. Our high performance liquid chromatography (HPLC)-electrospray ionization-MS analysis of the acidic soluble fraction of saliva from preterm human newborn surprisingly revealed more than 40 protein masses often undetected in adult saliva. We were able to identify the following proteins: stefin A and stefin B, S100A7 (two isoforms), S100A8, S100A9 (four isoforms), S100A11, S100A12, small proline-rich protein 3 (two isoforms), lysozyme C, thymosins β(4) and β(10), antileukoproteinase, histone H1c, and α and γ globins. The average mass value reported in international data banks was often incongruent with our experimental results mostly because of post-translational modifications of the proteins, e.g. acetylation of the N-terminal residue. A quantitative label-free MS analysis showed protein levels altered in relation to the postconceptional age and suggested coordinate and hierarchical functions for these proteins during development. In summary, this study shows for the first time that analysis of these proteins in saliva of preterm newborns might represent a noninvasive way to obtain precious information of the molecular mechanisms of development of human fetal oral structures.

Influence of Oxide Particles and Residual Elements on Microstructure and Toughness in the Heat-Affected Zone of Low-Carbon Steel Deoxidized with Ti and Zr

The microstructure and toughness in Fe–0.04%C–1.85%Mn–0.03%Si–0.018%Nb steel deoxidized with Ti and Zr have been studied as functions of particle characteristics, austenite grain size and soluble Ti and Zr contents using a simulated HAZ (heat affected zone) thermal cycle (peak temperature, 1400°C; peak holding time, 60 s; time of cooling from 800 to 500°C, 70 s) and submerged arc welding (heat input of 15 kJ/mm), respectively. Microstructures were studied in samples containing 1.0 to 1.5 μm-diameter oxide particles numbering 500 to 2000 mm–2 and with a soluble oxygen content of 10 to 30 ppm (measured before casting) and soluble Ti and Zr contents of 50–150 ppm. The γ grain size after HAZ thermal cycle in the range between 200 and 600 μm is controlled by pinning and solute drag. Small γ grain size below 300 μm was obtained with high soluble Ti and Zr contents of 110–160 ppm, whereas large γ grain size above 300 μm was obtained with low soluble Ti and Zr contents of 60–110 ppm. Two types of microstructures that showed high Charpy absorbed energy (VE(–10°C)= 150–250 J and VE(–50°C)= 50–150 J) were observed independent of γ grain size: One is acicular ferrite and a small amount of grain boundary ferrite (GBF) and ferrite side plate (FSP) and the other is GBF, FSP and granular bainitic ferrite. It was observed that low VE(T) values are attributed to the formation of porosity, large-size particles, carbides (+nitrides) and lathe bainitic ferrite.

Stability indicating ion chromatography method for the simultaneous determination of ibandronate sodium drug substance and its impurities

A simple and sensitive ion chromatography method has been developed for the simultaneous assay of ibandronate sodium drug substance and the determination of its impurities. The separation was achieved on Allsep™ anion column 150 mm × 4.6 mm, 7 μm particle diameter. The mobile phase consisted of 1% (v/v) aqueous formic acid and acetone 98:2% (v/v); flow rate 1.0 ml min −1 at ambient temperature. The analytes were monitored by conductometric detector. The drug substance was subjected to stress conditions of hydrolysis, oxidation, photolytic, thermal and humidity degradation. Considerable degradation was achieved only under oxidative conditions. Mass balance was demonstrated in all stress conditions. The method was validated for specificity, precision, linearity, solution stability and accuracy. The limits of detection (LOD) and limits of quantification (LOQ) for impurities were in the range of 0.36–0.80 μg ml −1 and 1.00–2.40 μg ml −1, respectively. For ibandronate LOD was 38 μg ml −1 and LOQ was 113 μg ml −1. The average recoveries for impurities and ibandronate were in the range of 99.0–103.1% and the method can be successfully applied for the routine analysis of ibandronate sodium drug substance.

HPLC를 이용한 Isoproturon, Phenmedipham, Pyridate 및 Nitenpyram 4종 성분의 잔류농약 분석법 개발

A method for the determination of four pesticide compounds, urea (isoproturon), bis-carbamate (phenmedipham), thiocarbamate (pyridate) and vinyllidenediamine (nitenpyram) were examined and analyzed by HPLC with C-18 column (250 ㎜×4.6 ㎜, 5 ㎛ diameter particle size). Mobile phase consisted of deionized water, acetonitrile and 50 mM KH₂PO₄ (pH 2.5). Isoproturon and phenmedipham analytical condition was isocratic elution of the column with 50% solvent A (acetonitrile) and 50% solvent B (deionized water); pyridate was 85% solvent A (acetonitrile) and 15% solvent B (deionized water) at a flow rate of 1 mL/min; and nitenpyram analytical condition was 90% solvent A (50 mM KH₂PO₄, pH 2.5) and 10% solvent B (acetonitrile) at a flow rate of 1 mL/min. In results, retention times were 6.12, 8.63, 9.40 and 12.76 min for isoproturon, phenmedipham, pyridate and nitenpyram, respectively. All injection volumes were 10 μL and the limit of quantitation was 0.05 ㎎/㎏ for four pesticide compounds, respectively. Recovery rate test was performed with three farm products, rice, apple and soybean. Four pesticide compounds were spiked at concentrations of 0.05, 0.1 and 0.5 ㎎/㎏. The recovery rates were ranged from 70.18% to 118.08% and the standard deviations of all experiments were within 10%.

HPLC/DAD를 이용한 림술푸론, 에타메트설푸론메틸, 트리베누론메칠, 클로리무론에칠 4종 성분의 잔류농약 분석법 개발

Sulfonylurea계 제초제인 rimsulfuron, ethametsulfuronmethyl, tribenuron-methyl, chlorimuron-ethyl의 네 가지물질의 잔류농약 분석을 위해 HPLC를 이용한 분석방법을 개발하였다. ODS 칼럼(250 ㎜×4.6 ㎜, 5 ㎛ diameter particle size)를 사용하였으며 칼럼오븐은 35oC로 유지하고 용매 A(20 mM KH₂PO₄, pH 2.5)와 용매 B(acetonitrile)를 45:55의 비율로 1 mL/min의 유속으로 흘려주었다. 시료 주입량은 20 μL였으며 분석조건 하에서 rimsulfuron, ethametsulfuron-methyl, tribenuron-methyl, chlorimuron-ethyl의 retention time은 각각 5.92, 6.54, 9.28, 14.35분이었고 정량한계는 각각 0.02, 0.01, 0.001, 0.004 ㎎/㎏이었다. 회수율 실험은 백미, 사과, 콩에 4종의 농약 표준품을 각각 0.05, 0.1, 0.5㎎/㎏의 세 가지 농도로 spiking하여 수행하였으며 86.12∼116.26%의 회수율을 얻었고 표준오차는 모든 실험에서 10%이하였다.

Magnetic Control of Tubular Catalytic Microbots for the Transport, Assembly, and Delivery of Micro‐objects

AbstractRecently a significant amount of attention has been paid towards the development of man‐made synthetic catalytic micro‐ and nanomotors that can mimic biological counterparts in terms of propulsion power, motion control, and speed. However, only a few applications of such self‐propelled vehicles have been described. Here the magnetic control of self‐propelled catalytic Ti/Fe/Pt rolled‐up microtubes (microbots) that can be used to perform various tasks such as the selective loading, transportation, and delivery of microscale objects in a fluid is shown; for instance, it is demonstrated for polystyrene particles and thin metallic films (“nanoplates”). Microbots self‐propel by ejecting microbubbles via a platinum catalytic decomposition of hydrogen peroxide into oxygen and water. The fuel and surfactant concentrations are optimized obtaining a maximum speed of 275 µm s−1 (5.5 body lengths per second) at 15% of peroxide fuel. The microbots exert a force of around 3.77 pN when transporting a single 5 µm diameter particle; evidencing a high propulsion power that allows for the transport of up to 60 microparticles. By the introduction of an Fe thin film into the rolled‐up microtubes, their motion can be fully controlled by an external magnetic field.

Mineralogical analyses and in vitro screening tests for the rapid evaluation of the health hazard of volcanic ash at Rabaul volcano, Papua New Guinea

The continuous ash and gas emissions from the Tavurvur cone in Rabaul caldera, Papua New Guinea, during 2007–08, raised concerns regarding how exposure would affect the respiratory health of nearby populations and impact on the environment. As part of a formal evaluation of the effects of volcanic emissions on public health, we investigated the potential health hazard of the ash using a suite of selected mineralogical analyses and in vitro toxicity screening tests. The trachy-andesitic ash comprised 2.1–6.7 vol.% respirable (sub-4 μm diameter) particles. The crystalline silica content was 1.9–5.0 wt.% cristobalite (in the bulk sample) with trace amounts of quartz and/or tridymite. Scanning electron microscopy showed that the ash particles were angular with sparse, fibre-like particles (∼3–60 μm max. diameter) observed in some samples, which we confirmed to be CaSO4 (gypsum, at <6 wt.% in the bulk samples) and not asbestiform fibres. The ash specific surface area was low (0.1–2.7 m2 g−1). The leached solution from one of the ash samples was slightly acidic (pH 5.6), but did not contain high levels of toxic metals (such as F, Cu, Zn, Mn, As, Ni and Cd) when compared to previously tested volcanic ash leachates. Ash samples generated potentially-harmful hydroxyl radicals through an iron-mediated catalytic reaction, in the range of 0.15–2.47 μmol m−2 (after 30 min of reaction). However, measurement of particle oxidative capacity (potential oxidative stress reaction using ascorbic acid) and silica-like injury to red blood cells (erythrolysis assay, i.e. measurement of cell death) nevertheless revealed low biological reactivity. The findings suggest that acute exposure to the ash would have a limited potential to exacerbate pre-existing conditions such as asthma or chronic bronchitis, and the potential for chronic exposure leading to silicosis was low.

Ultrafine Particle Formation from Wear

Much attention is given to the consequences of airborne particles on human health and well-being. Wear is one source of airborne particles and contributions in the urban environments from wheel-to-rail contacts and disc brakes cannot be neglected. Traditionally, mechanical wear has been associated with the generation of particles of diameters of some microns. However, the research described has found ultrafine particle generation from wear processes.Particle generation from wear was measured under controlled laboratory conditions. The wear was created through sliding contact in a tribometer (type “pin-on-disc”) with different materials and with different sliding velocities and pressures, to represent rail traffic and automobile disc braking. Particle concentrations and size distributions in the air were determined for particle diameters from 10 nm up to more than 10 μm. For most materials and conditions three particle size modes were found: one at 50–100 nm, one at a few hundred nm and one at a few μm particle diameter.

Pressurized planar electrochromatography, high-performance thin-layer chromatography and high-performance liquid chromatography—Comparison of performance

Kinetic performance, measured by plate height, of High-Performance Thin-Layer Chromatography (HPTLC), High-Performance Liquid Chromatography (HPLC) and Pressurized Planar Electrochromatography (PPEC) was compared for the systems with adsorbent of the HPTLC RP18W plate from Merck as the stationary phase and the mobile phase composed of acetonitrile and buffer solution. The HPLC column was packed with the adsorbent, which was scrapped from the chromatographic plate mentioned. An additional HPLC column was also packed with adsorbent of 5 μm particle diameter, C18 type silica based (LiChrosorb RP-18 from Merck). The dependence of plate height of both HPLC and PPEC separating systems on flow velocity of the mobile phase and on migration distance of the mobile phase in TLC system was presented applying test solute (prednisolone succinate). The highest performance, amongst systems investigated, was obtained for the PPEC system. The separation efficiency of the systems investigated in the paper was additionally confirmed by the separation of test component mixture composed of six hormones.

Atmospheric phosphorus deposition at a montane site: Size distribution, effects of wildfire, and ecological implications

The dry deposition of atmospheric particulate matter can be a significant source of phosphorus (P) to oligotrophic aquatic ecosystems, including high-elevation lakes. In this study, measurements of the mass concentration and size distribution of aerosol particles and associated particulate P are reported for the southern Sierra Nevada, California, for the period July–October, 2008. Coarse and fine particle samples were collected with Stacked Filter Units and analyzed for Total P (TP) and inorganic P (IP) using a digestion-extraction procedure, with organic P (OP) calculated by difference. Particle size-resolved mass and TP distributions were determined concurrently using a MOUDI cascade impactor. Aerosol mass concentrations were significantly elevated at the study site, primarily due to transport from offsite and emissions from local and regional wildfires. Atmospheric TP concentrations ranged from 11 to 75 ng m −3 (mean = 37 ± 16 ng m −3), and were typically dominated by IP. Phosphorus was concentrated in the coarse (>1 μm diameter) particle fraction and was particularly enriched in the 1.0–3.2 μm size range, which accounted for 30–60% of the atmospheric TP load. Wildfire emissions varied widely in P content, and may be related to fire intensity. The estimated dry depositional flux of TP for each daily sampling period ranged between 7 and 118 μg m −2 d −1, with a mean value of 40 ± 27 μg m −2 d −1. Relative rates of dry deposition of N and P in the Sierra Nevada are consistent with increasing incidence of N limitation of phytoplankton growth and previously observed long-term eutrophication of lakes.

Development and application of a validated stability-indicating HPLC method for simultaneous determination of granisetron hydrochloride, benzyl alcohol and their main degradation products in parenteral dosage forms

A simple, rapid and sensitive reversed phase high performance liquid chromatographic method using photodiode array detection was developed and validated for the simultaneous determination of granisetron hydrochloride, benzyl alcohol, 1-methyl-1H-indazole-3-carboxylic acid (the main degradation product of granisetron) and benzaldehyde (the main degradation product of benzyl alcohol) in granisetron injections. The separation was achieved on Hypersil BDS C8 (250 mm × 4.6 mm i.d., 5 μm particle diameter) column using a mobile phase consisted of acetonitrile:0.05 M KH 2PO 4:triethylamine (22:100:0.15) adjusted to pH 4.8. The column was maintained at 25 °C and 20 μL of solutions was injected. Photodiode array detector was used to test the peak purity and the chromatograms were extracted at 210 nm. Naphazoline hydrochloride was used as internal standard. The method was validated with respect to specificity, linearity, accuracy, precision, limit of quantitation and limit of detection. The validation acceptance criteria were met in all cases. Identification of the pure peaks was carried out using library match programmer and wavelengths of derivative optima of the spectrograms of the peaks. The method was successfully applied to the determination of the investigated drugs and their degradation products in different batches of granisetron injections. The method was proved to be sensitive for the determination down to 0.03 and 0.01% of granisetron degradation product and benzaldehyde, respectively, which are far below the compendia limits for testing these degradation products in their corresponding intact drugs.

Development of a Personal Sampler for Evaluating Exposure to Ultrafine Particles

Evaluation of the exposure of humans to ultrafine, airborne particles is an important aspect of health in the workplace, especially in cases where nano-particles are present. However, portable sampling devices for efficiently collecting ultrafine particles in a worker's breathing zone are not readily available. The present study describes the design and development of a portable sampler for collecting particulates in the breathing zone, as a possible tool for this purpose. The design is based on the use of an ”Inertial Filter” to separate various-sized nano-order particles. Inertial filters consisting of SUS fiber felt (fiber diameter 5.6-13.5 μm) placed in circular nozzles (3-6 mm diameter with 4.5 mm length) were used. To achieve the smallest dp50 under the allowable pressure drop of a portable pump, the influence of fiber loading on separation performance and pressure drop were investigated. The influence of particle loading was also examined in relation to pressure drop and separation performance. The smallest dp50 under the allowable pressure drop (5.7 kPa at 6 L/min) for the battery pump employed was ~140 and 200 nm respectively for SUS fibers of 5.6 and 9.8 μm diameter (particle volume fraction ~0.013). The change in separation performance due to particle loading was confirmed to be acceptable for use under the present conditions. Under these conditions, a sufficient amount of particles can be collected for chemical analyses, e.g., particle-bound PAHs after 6-8 hours of sampling. Hence, the developed sampler has the potential for use in evaluating exposure to ultrafine particles in the breathing zone in the workplace.

Hydrometallurgical processing of a Nigerian sphalerite in hydrochloric acid: Characterization and dissolution kinetics

This study is concerned with the physio-chemical characterization and investigation of the dissolution kinetics of a Nigerian sphalerite in hydrochloric acid (HCl). The effects of HCl concentration, temperature, particle diameter, stirring speed, solid/liquid ratio on the leaching of sphalerite were investigated. The XRF analysis showed that the sphalerite mineral consists of zinc and sulphur as major elements with Fe, Sn, Ag, K, Sb, Ca and Pb occurring as minor or trace elements. The XRD examination confirmed the originality of the sphalerite sample and it revealed the presence of associated minerals such as ilmenite (FeTiO 3), pyrite (FeS 2), siderite (FeCO 3), α-quartz and cassiterite (SnO 2). Optical microscopic examination also supported the above. The leaching experiments showed that sphalerite dissolution in HCl increases with acid concentration and temperature, but decreases with particle diameter and solid/liquid ratio. In HCl 4 M and at 80 °C, about 91.80% of sphalerite was dissolved within 120 min using − 112 + 63 μm particle diameter and solid/liquid ratio of 10 g/L. The activation energy calculated from the experimental data was 39.09 kJ/mol, while the reaction order, Arrhenius constant and reaction constant of 0.24, 13.46 s − 1 and 2.21 ± 0.4 × 10 3 were computed for the process respectively. Kinetic data analysis indicated that the rate determining step for the dissolution process followed a surface chemical reaction and the reaction data fitted shrinking core model for spherical particles. Finally, the XRD analysis of the post-leaching residue provided evidence for the presence of silica and traces of sulphur in the residual solid.