Removal Of Microspheres Research Articles

Upflow Direct Filtration and Downflow Direct Filtration: A Comparison with Emphasis on the Removal of Aerobic Spore-Forming Bacteria and Fluorescent Microspheres as Surrogates for Cryptosporidium Oocyst Removal

Monitoring the removal of Cryptosporidium oocysts in water treatment plants is a challenge, particularly in developing countries, and the use of surrogates has proven necessary. Two surrogates already investigated and recognized by the scientific community are aerobic spore-forming bacteria (ASFB) and fluorescent polystyrene microspheres (ME). In this context, this study evaluates and compares the performance of upflow direct filtration and downflow direct filtration, with emphasis on the removal of ASFB and ME as a surrogate of Cryptosporidium oocyst removal. Pilot filtration experiments were carried out with low turbidity Paranoá Lake water (average—3.7 NTU) with ASFB varying from 7 × 102 to 5.5 × 103 CFU/100 mL. In some experiments, water was spiked with microspheres, aiming for 105 ME/L. Two operational conditions were evaluated: (1) filters operating with the same filtration rate (5 m/h); (2) filters operating with the same flow rate of 59.41 L/h. In general, the downflow filter presented a slightly higher removal efficiency than the upflow filter but the differences were not considered statistically significant in most cases. The removal efficiency of microspheres (3 to 5 log) was higher than that of ASFB (1.2 to 4 log) in both filters, corroborating that the removal of ASFB is a conservative surrogate of the removal of Cryptosporidium.

Nanopatterning of the dielectric surface by a pair of femtosecond laser pulses of different colors through a monolayer of microspheres.

This paper considers the nanostructuring of the surface of dielectrics under the effect of two successive femtosecond laser pulses, one of the fundamental frequency (FF) and the other of the second harmonic (SH) of a Ti:sapphire laser, through a layer of polystyrene microspheres 1 µm in diameter, which act as microlenses. Polymers with strong (PMMA) and weak (TOPAS) absorption at the frequency of the third harmonic of a Ti:sapphire laser (sum frequency FF + SH) were used as targets. Laser irradiation led to the removal of microspheres and the formation of ablation craters with characteristic dimensions of about 100 nm. Depending on the variable delay time between pulses, the resulting structures differed in their geometric parameters and shape. Based on statistical processing of the depths of the obtained craters, the optimal delay times for the most effective structuring of the surfaces of these polymers was found.

Fast and simultaneous removal of microplastics and plastic-derived endocrine disruptors using a magnetic ZIF-8 nanocomposite

Microplastics are extremely prevalent materials, posing risks to both the environment and human health. Considerable, further impact, from the endocrine disrupting phenolic compounds generated via the degradation of plastic waste is a key concern. Magnetic sorbents have been shown to be effective in the removal of microplastics, however there is a lack of cost-effective and environmentally friendly magnetic micro/nanomaterials for integrated and efficient removal of microplastics and endocrine disrupting phenols from water. Herein, a zeolitic imidazolate framework (ZIF-8) magnetic porous nanocomposite modulated with n-butylamine (nano-Fe@ZIF-8) has been synthesised in water at room temperature. The prepared nano-Fe@ZIF-8 was characterized via scanning electron microscopy, powder X-ray diffraction and nitrogen adsorption measurements. Nano-Fe@ZIF-8 enabled the fast and simultaneous removal of both polystyrene microspheres (1.1 µm diameter) and endocrine disrupting phenols (bisphenol A and 4-tert-butylphenol). Nano-Fe@ZIF-8 showed a higher removal efficiency compared with unmodulated Fe@ZIF-8 and under optimal conditions nano-Fe@ZIF-8 (20 mg) was able to remove ≥ 98 % of polystyrene microspheres at high concentration (25 mg L-1) within 5 min, as well as remove ≥ 94 % of both bisphenol A (1 mg L-1) and 4-tert-butylphenol (1 mg L-1) within the same time frame. Nano-Fe@ZIF-8 showed comparable efficiency in the removal of polystyrene microspheres and a greatly improved extraction performance for the two selected endocrine disrupting phenols when compared with oleic and azelaic acid functionalised Fe3O4 magnetic nanoparticles. The results illustrate the synthesis of a simple, environmentally friendly, and high performing material for the fast removal of both soluble organic pollutants and microparticulated organic pollutants.

Dual-Scale Porosity Alumina Structures Using Ceramic/Camphene Suspensions Containing Polymer Microspheres

This study demonstrates the utility of thermo-regulated phase separable alumina/camphene suspensions containing poly(methyl methacrylate) (PMMA) microspheres as porogens for the production of multi-scale porosity structures. The homogeneous suspension prepared at 60 °C could undergo phase separation during freezing at room temperature. This process resulted in the 3D networks of camphene crystals and alumina walls containing PMMA microspheres. As a consequence, relatively large dendritic pores with several tens of microns size could be created as the replica of frozen camphene crystals. In addition, after the removal of PMMA microspheres via heat-treatment, micron-sized small spherical pores could be generated in alumina walls. As the PMMA content with respect to the alumina content increased from 0 vol% to 40 vol%, while the camphene content in the suspensions was kept constant (70 vol%), the overall porosity increased from 45.7 ± 0.5 vol% to 71.4 ± 0.5 vol%. This increase in porosity is attributed to an increase in the fraction of spherical pores in the alumina walls. Thus, compressive strength decreased from 153 ± 18.3 MPa to 33 ± 7.2 MPa. In addition, multi-scale porosity alumina objects with a honeycomb structure comprising periodic hexagonal macrochannels surrounded by dual-scale porosity walls were constructed using a 3D plotting technique.

Removal of polystyrene microplastic spheres by alum-based coagulation-flocculation-sedimentation (CFS) treatment of surface waters

• Real river and lake water with carboxylated PS microplastics were treated via CFS. • Higher alum doses generally benefited the removal of PS microplastics ≤ 90 μm. • Smaller PS microplastics were better removed by alum CFS treatment. • Water source affected the removal efficiency of PS microplastics. • PS microplastics did not impact the removal of turbidity, NOM fractions, or metals. Microplastics are an emerging issue in water systems, and an understanding of their occurrence and behavior is complicated by a high diversity in physical (i.e., size and shape) and chemical characteristics. To date, there have been limited studies on microplastics in drinking water treatment processes. As the coagulation-flocculation-sedimentation (CFS) process is the first step of the particle/colloid removal at many plants, its ability to remove microplastics requires further investigation. By performing alum-CFS bench tests, this study examined the removal of carboxylated polystyrene (PS) microspheres in a wide size range (3, 6, 25, 45, and 90 μm) in two types of real surface waters (Grand River and Lake Erie water) that are sources for full-scale drinking water treatment plants. Based on experiments using water from the Grand River with a variety of alum doses (10, 20, 30, 40, and 50 mg/L), a higher alum dose generally led to better removal of microspheres smaller than 90 μm, while an alum dose > 30 mg/L did not substantially improve the removal of particles between 3 and 25 μm. Further experiments indicated that smaller PS microspheres were more effectively removed in both river (Grand River_Dec 06) and lake water (Lake Erie_Nov 29). For example, with an alum dose of 30 mg/L, 75.6 and 85.2% of the 6-μm PS microspheres were removed from Grand River and Lake Erie water, respectively. Moreover, the water source significantly (p = 0.0021) affected the removal of PS microspheres, which may have been primarily related to the difference in turbidity. No impacts of PS microspheres were observed on the removal efficiency for turbidity, natural organic matter fractions, or major metal elements by alum-CFS treatment.

Conformal Electrodeposition of Co–Ni to Improve the Mechanical Properties of Three-Dimensional Ordered Macroporous Ni Films

Three-dimensional ordered macroporous Ni films, known as Ni inverse opals, are fabricated via a template approach in which polystyrene (PS) microspheres (820 nm in diameter) are assembled in closely-packed colloidal crystals via a vertical electrophoresis process, followed by electroplating of Ni into the interstitial voids within the colloidal crystals and the selective removal of PS microspheres. To improve its mechanical strength, a conformal Ni-Co layer (45 ∼ 64 nm) is electrodeposited on the skeletons of the Ni inverse opals by cyclic voltammetry. After coating, from nano-indentation tests, the hardness and reduced elastic modulus are enhanced considerably (172 ∼ 220% for hardness; 72 ∼ 79% for reduced elastic modulus), as compared to those of pristine inverse opals. After an annealing treatment for the interdiffusion of Ni and Co, the sample reveals an even stronger hardness. X-ray diffraction patterns indicate that the finite thickness of the inverse opals skeletons induces preferential growth of the (111) plane. In short, a combined effect of solid solution alloying, thickening of inverse opals skeletons for greater load bearing, and a predominant (111) plane is responsible for the improved mechanical strength of the Ni inverse opals.

Removal of micron-sized microplastic particles from simulated drinking water via alum coagulation

Microplastics are being recognized as an emerging pollutant entering wastewater and drinking water treatment plants. Microplastics are often defined as having a dimension less than 5 mm, however much smaller plastic particles have been identified in the environment. While a few studies have addressed the effectiveness of traditional water treatment processes for the removal of microplastics in the mm-size range, additional investigations that study the behavior of smaller plastic particles during water treatment are needed. The results of this work confirm that conditions which are suitable for the removal of a conventional oxide colloid, kaolin, are also effective for the removal of a model plastic sphere (density 1.3 g/cm3, 1–5 µm diameter). Coagulation using alum at concentrations between 5 and 10 mg/L Al produced water with turbidity less than 1.0 NTU from solutions containing 5 mg/L microspheres with an initial turbidity of 16 NTU. Although the presence of 20 mg/L of surfactant in solution shifted the microsphere zeta potential, it did not impair microsphere coagulation at low alum doses and all solutions showed a gradual trend toward higher residual NTU at higher alum dose. Evidence from floc photos and zeta potential measurements point to sweep flocculation as the dominant mechanism for microsphere removal for the conditions of this study. The dispersion of polyethylene microfibers (density 0.96 g/cm3, 5 µm diameter cut to 0.1 mm lengths) in water was strongly influenced by surfactants yet the fibers were still effectively removed via coagulation. Further experimentation with other plastics and solution conditions is needed to enhance understanding of the effectiveness of traditional water treatment processes for microplastic removal.

Role of sand size on bacterial retention in biochar-amended sand filters

The addition of biochar to sand columns can enhance the retention of bacteria and thus may provide a management strategy for removing bacteria from tile-drainage waters. In this study, the role of sand size as a factor in controlling microbial retention in biochar-amended sand columns was investigated. Laboratory column experiments were conducted to quantify the removal of two bacterial isolates (E. coli and Salmonella) and polystyrene microspheres in 10-cm-long columns packed with clean sand of three different sizes (0.25, 0.71, and 1.19 mm) at four biochar concentrations (0%, 5%, 10%, and 15%). Sorption studies were also performed to help identify the relative roles of sorption and physical straining on the removal of bacteria and microspheres within the columns. For the large sand, the log10 removal values (LRV) for E. coli increased from 0.22 to 0.49 for the 0% and 15% biochar concentrations, respectively, while LRV for Salmonella increased from 0.19 to 0.68. For the small sand, increasing biochar concentration from 0% to 15% increased LRV from 0.11 to 1.9 for E. coli and from 0.20 to 4.6 for Salmonella. In comparison, LRV for microspheres in the 15% biochar columns was only minimally higher than the unamended columns for all three sand sizes. Results from the sorption studies show that high sorption coefficients generally correlated with high LRV indicating that sorption rather than physical straining was the primary mechanism of retention in the columns. Results from this study further our understanding of bacterial retention in biochar-amended porous media.

Giant Vesicles with Anchored Tiny Gold Nanowires: Fabrication and Surface-Enhanced Raman Scattering.

Sensitivity and reproducibility are two major concerns to improve the performance and extend the range of practical applications of surface-enhanced Raman scattering (SERS). A theoretical report reveals that hot spots formed by gold nanoparticles with a tip-to-tip configuration would generate the maximum electric field enhancement because of the lightning rod effect. In our present study, we constructed a giant vesicle consisting of anchored tiny gold nanowires to provide a high density of sharp tip-to-tip nanogaps for SERS application. The tiny gold nanowires were directly grown and anchored onto the surfaces of polystyrene (PS) microspheres by a seed-mediated method. Then, the removal of PS microspheres by tetrahydrofuran led to the formation of the giant gold vesicles with hierarchical cage structures, providing the sharp tips and high density of hot spots for improving SERS performance. Compared with the nonwire structure (island and inhibited nanoparticle), giant gold vesicles with tiny wires showed a higher SERS enhancement factor (9.90 × 107) and quantitative SERS analysis in the range of 10-4 to 10-7 M. In addition, the large-scale giant gold vesicle array on the silica substrate resulted in a high reproducibility of SERS signals with the variation of intensities less than 7.6%.

Combination of microspheres and sol-gel electrophoresis for the formation of large-area ordered macroporous SiO2

A simple and effective fabrication scheme involving sequential electrophoretic depositions of polystyrene (PS) microspheres (500nm and 1μm in diameter) and SiO2 sols (~5nm in diameter) to produce large-area ordered macroporous SiO2 inverse opals (2×2cm2) on ITO substrates is demonstrated. The zeta potentials for PS microsphere suspension and SiO2 sols are measured to determine an optimized processing window in which both samples carry negative surface charges and sol-gel transformation can be properly implemented. Our approach entails the electrophoresis of PS microspheres to render a colloidal crystal with negligible defects. Afterward, SiO2 sols are infiltrated to the interstitial voids among the closely-packed PS microspheres via another electrophoresis process, followed by an oxidation treatment to remove the PS colloidal template and complete the densification of SiO2 gels. The resulting SiO2 inverse opals reveal impressive surface uniformity and structural integrity. Fourier transform infrared spectroscopy confirms the complete removal of PS microspheres, leaving an intact SiO2 skeleton, whereas X-ray diffraction pattern indicates its amorphous nature.

Phagocytosis of microbial symbionts balances the carbon and nitrogen budget for the deep‐water boreal sponge Geodia barretti

AbstractGeodia barretti is a massive nearly spherical sponge that forms dense assemblages on the continental shelf of the North Atlantic and the Norwegian Sea. We studied the metabolism of individual sponges collected using a remotely operated vehicle and maintained in large tanks with high volumes of unfiltered water brought from 160 m depth. We used direct methods (In‐Ex) to measure excurrent flow rates, oxygen removed, and carbon and nutrient flux through the sponges. G. barretti had very low specific filtration (0.26 mL min−1 mL−1 sponge tissue) and low respiration (5.34 ± 0.98 nmol O2 min−1 mL−1 sponge tissue; 8.44 ± 1.51 μmol O2 h−1 g C−1) rates in comparison to other sponges. A net release of nitrogen was detected as . Bacteria were removed from the water filtered with up to 99% efficiency, yet comprised only 5% of the sponges′ total carbon budget; the remainder consisted of dissolved organic carbon and detritus. High bacterial removal was aided by the presence of a tight gasket of cells that surrounds the collar of each choanocyte filter. A test for potential bypass canals showed removal of fluorescent microspheres until they were excreted 5–12 h after feeding. Electron micrographs showed active uptake of Escherichia coli “fed” to the sponge as well as phagocytosis of symbiont microbes by sponge cells in the mesohyl. These data provide the first comprehensive study of metabolism in a deep‐water high microbial abundance sponge.

Removals of cryptosporidium parvum oocysts and cryptosporidium-sized polystyrene microspheres from swimming pool water by diatomaceous earth filtration and perlite-sand filtration.

Removal of Cryptosporidium-sized microspheres and Cryptosporidium parvum oocysts from swimming pools was investigated using diatomaceous earth (DE) precoat filtration and perlite-sand filtration. In pilot-scale experiments, microsphere removals of up to 2 log were obtained with 0.7 kg·DE/m2 at a filtration rate of 5 m/h. A slightly higher microsphere removal (2.3 log) was obtained for these DE-precoated filters when the filtration rate was 3.6 m/h. Additionally, pilot-scale perlite-sand filters achieved greater than 2 log removal when at least 0.37 kg/m2 of perlite was used compared to 0.1-0.4 log removal without perlite both at a surface loading rate of 37 m/h. Full-scale testing achieved 2.7 log of microspheres and oocysts removal when 0.7 kg·DE/m2 was used at 3.6 m/h. Removals were significantly decreased by a 15-minute interruption of the flow (without any mechanical agitation) to the DE filter in pilot-scale studies, which was not observed in full-scale filters. Microsphere removals were 2.7 log by perlite-sand filtration in a full-scale swimming pool filter operated at 34 m/h with 0.5 kg/m2 of perlite. The results demonstrate that either a DE precoat filter or a perlite-sand filter can improve the efficiency of removal of microspheres and oocysts from swimming pools over a standard sand filter under the conditions studied.

A full-scale study of Cryptosporidium parvum oocyst and Cryptosporidium-sized microsphere removals from swimming pools via sand filtration

Removal of Cryptosporidium parvum oocysts and Cryptosporidium-sized microspheres was evaluated in full-scale swimming pools via high-rate sand filtration (31–34 m/h) with coagulation. Results showed that at least 90% of C. parvum oocysts and microspheres were removed by filtration with an initial dosage of coagulant B (1.56 mg/L), D (1.9 mg/L or 305 g/m2), or F (1.56 mg/L) from each swimming pool. Filtration with an initial dosage of coagulant E (0.1 mg·Al/L) achieved 82% C. parvum oocyst removal and 97% microsphere removal. Coagulants B and F had a tendency to overdose over time with continuous feeding (based on corresponding pilot-scale experiments) and did not consistently achieve removals greater than 90% in the full-scale trials. As high as 99% of C. parvum oocysts and 98% of microspheres were removed with a continuous dosage of coagulant D. Up to 98% (1.7 log) of C. parvum oocysts and 93% (1.1 log) of microspheres were removed by continuous dosing of coagulant E at 27 m/h. Consistent oocyst and microsphere removal by aluminum-based coagulants (D and E) was achieved under the tested swimming pool conditions.

Design of free‐standing microstructured conducting polymer films for enhanced particle removal from non‐uniform surfaces

ABSTRACTEfficient removal of particles from topologically‐complex surfaces is of significant import for a range of applications (e.g., explosive residue removal in security arenas). Here, we synthesize next‐generation polymeric particle removal swabs with tuned structural features to elucidate the influence of the polymer microstructure on the removal of trace particles from surfaces. Specifically, microstructured free‐standing films of the conducting polymer polypyrrole (PPy) were synthesized through template‐assisted electropolymerization techniques. The removal of polystyrene microspheres from representative aluminum surfaces of varying roughness was evaluated as a function of the PPy microstructure. PPy‐based microstructured swabs displayed increased particle trapping properties relative to non‐textured PPy‐based swabs and current commercial swabs. This increased effectiveness occurred from the more intimate particle‐swab contact, leading to increased van der Waals interactions for the microstructured swabs. Therefore, this effort provides critical design rules for the production of microstructured conducting polymer materials for their application toward advanced particle removal technologies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1968–1974

A pilot-scale study of Cryptosporidium-sized microsphere removals from swimming pools via sand filtration.

Cryptosporidium species are the most common cause of gastrointestinal illness in treated recreational water venues. In order to protect public health during swimming, Cryptosporidium-sized microsphere removals by high-rate sand filtration with six coagulants were evaluated with a 5.5 m(3) pilot-scale swimming pool. A sand filter without coagulation removed 20-63% of Cryptosporidium-sized microspheres. Cryptosporidium-sized microsphere removals exceeded 98% by sand filtration with five of the six tested coagulants. Continuously feeding coagulants A, B, and F (i.e., organic polymers) led to coagulant accumulation in the system and decreased removals over time (<2 days). Coagulant E (polyaluminum chloride) consistently removed more than 90% of microspheres at 30 m/h while the removals dropped to approximately 50% at a filtration rate of 37 m/h. Coagulant C was a chitosan-based product that removed fewer microspheres compared with other products, <75%, under the studied conditions. Results indicated aluminum-based coagulants (coagulants D and E) had an overall performance advantage over the organic polymer based coagulants primarily in terms of their tendency not to accumulate in the water and cease to be effective at improving filter efficiency.

Analysis of long- and short-range contribution to adhesion work in cardiac fibroblasts: an atomic force microscopy study.

Atomic force microscopy (AFM) for single-cell force spectroscopy (SCFS) and Poisson statistic were used to analyze the detachment work recorded during the removal of gold-covered microspheres from cardiac fibroblasts. The effect of Cytochalasin D, a disruptor of the actin cytoskeleton, on cell adhesion was also tested. The adhesion work was assessed using a Poisson analysis also derived from single-cell force spectroscopy retracting curves. The use of Poisson analysis to get adhesion work from AFM curves is quite a novel method, and in this case, proved to be effective to study the short-range and long-range contributions to the adhesion work. This method avoids the difficult identification of minor peaks in the AFM retracting curves by creating what can be considered an average adhesion work. Even though the effect of actin depolymerisation is well documented, its use revealed that control cardiac fibroblasts (CT) exhibit a work of adhesion at least 5 times higher than that of the Cytochalasin treated cells. However, our results indicate that in both cells short-range and long-range contributions to the adhesion work are nearly equal and the same heterogeneity index describes both cells. Therefore, we infer that the different adhesion behaviors might be explained by the presence of fewer membrane adhesion molecules available at the AFM tip-cell interface under circumstances where the actin cytoskeleton has been disrupted.

Titanium Oxide Anode in Inverse Structure for Dye Sensitized Solar Cell Applications by Electrophoretic Self-Assembly and Sol-Gel Processes

The aim of this study is to fabricate titanium oxide (TiO2) anode in inverse opal structure for dye sensitized solar cell (DSSC) applications via combined electrophoretic self-assembly (EPSA) and sol-gel processes. The polystyrene (PS) microspheres of 270 nm size were produced by emulsion-free polymerization. A stable colloid of PS microspheres in water-ethanol solvent was used to manufacture the 3-D photonic crystal template with periodic ordered opal structure onto the surface of indium tin oxide (ITO) coated glass substrate by EPSA. The titanium tetraisopropoxide (TTIP) sol precursor in mixture of ethanol and ethanol glycol was impregnated to fill up the voids inside PS template. The polycondensation of TiO2 was completed by absorption of ambient moisture. Further annealing at 450oC for 1 hr of samples was carried out for removal of PS microspheres and formation of TiO2 photonic crystal. The microstructure, composition, and crystalline phase analysis of obtained TiO2 in inverse opal structure were examined by SEM, EDS, and XRD.

Impact of kaolinite clay particles on the filtration of Cryptosporidium-sized microspheres

Granular filtration remains a key barrier for Cryptosporidium removal in water treatment plants without UV irradiation. To assess the impact of clay particles in source water on Cryptosporidium removal efficiency by granular filtration, this study investigated the co-transport of Cryptosporidium-sized microspheres and kaolinite particles in sand columns. To investigate the influence of clay load on microsphere transport and deposition, varying influent kaolinite concentrations (0–106particles/mL) and microsphere concentrations (102–106microspheres/mL) were tested. The spatial distribution of retained microspheres was examined subsequent to experiments via filter coring. Results demonstrate that increasing the influent microsphere concentration impaired filter performance due to a blocking mechanism whereby previously retained particles repel incoming particles. In contrast, when the particulate load was dominated by kaolinite (for an equivalent particulate load), filter performance improved as a result of filter ripening whereby previously deposited particles act as additional collectors. Thus, microsphere-kaolinite interactions proved to be favorable although both particles possessed negative zeta potentials in the tested conditions. This study demonstrates that granular filter performance is vulnerable to peak events of microbial contamination. Conversely, Cryptosporidium-sized microsphere removal by granular filtration is enhanced in the presence of kaolinite in source water.

Pulse laser particulate separation from polycarbonate: surface acoustic wave and thermomechanical mechanisms

The mechanisms of graphite particle and polystyrene-co-divinyl benzene microsphere removal from flat polycarbonate substrates by nanosecond pulse laser interaction at 532 nm were studied both experimentally and theoretically. These model contaminants exhibited an extremely contrasting behavior in respect to phase separation and collateral damage to the polycarbonate substrate. Opaque graphite particles within the irradiated spot area either desorbed due to their thermal expansion or undertook vaporization/ablation. The transparent polystyrene microspheres caused local ablation of the substrate in their optical near-field. This process led to the removal of the particles, but eradicated the available cleaning fluence window. The opaque graphite particles, on the other hand, showed efficient clearance, particularly in a practicable cleaning window above $0.5~\mathrm{J/cm}^{2}$ and low pulse numbers of about two. Besides the mechanisms occurring within the irradiated spot, a separation process in the proximity beyond the laser spot (more than double the Gaussian radius) could be related to the action of high-amplitude surface acoustic waves (SAW). A minimum surface acceleration of $10^{9}~\mathrm{cm/s}^{2}$ was calculated to be sufficient to overcome the adhesion forces in this particle separation model.

Removal Rates of Explosive Particles From a Surface by Impingement of a Gas Jet

The rate of particle removal from a surface by air jet impingement has been evaluated for 3 different types of trace explosives. Samples of research development explosive (cyclotrimethylenetrinitramine), trinitrotoluene, and C-4 were each transferred to glass surfaces and then subjected to a short burst of air from a jet with varying diameter, standoff distance, and backpressure to achieve a range of shear stresses at the surface. TNT was observed to be easiest to remove, while C-4 required the greatest shear force to resuspend. An analytical model has been developed to predict removal of spherical particles as a function of particle diameter and nondimensionalized downstream distance from a gas jet. This model was fitted to experimental data from the removal of ceramic microspheres of various sizes. The removal rate of these ceramic microspheres was observed to be much greater than that of the 3 types of explosive particles, despite the particles’ similar sizes. Copyright 2012 American Association for Ae...