Particle Size Modification Research Articles

Engineering Active Sites of Metal/Metal Oxide Catalysts by Oxide Ligand Overlayers.

Engineering sites of supported metal catalysts is essential to enhancing activity and selectivity. Such enhancement is typically achieved by particle size modification, surface alloying, or attaching molecular ligands. Yet, control strategies for complex, multifunctional molecules and catalysts, where selectivity is crucial, are lacking. Here, we demonstrate that submonolayer WOx with tunable coverage preferentially decorates well-coordinated Pt terrace sites as a stable ligand. By combining experimental kinetics with probe molecules, in situ spectroscopies, and first-principles modeling, we show that the WOx coverage on Pt modifies the metal-to-acid site balance while retaining the acid strength intact and results in optimal reactivity for metal-acid catalyzed reactions at a specific metal, size, and support-dependent WOx coverage. The oxide can also alter the reactant adsorption mode, reversing selectivity and pathways from terrace- to step-dominated, as evidenced in furfural decarbonylation and hydrogenation. The insights open avenues for improving metal/metal oxide catalysts beyond the specific system.

Engineering Active Sites of Metal/Metal Oxide Catalysts by Oxide Ligand Overlayers

Engineering sites of supported metal catalysts is essential to enhancing activity and selectivity. Such enhancement is typically achieved by particle size modification, surface alloying, or attaching molecular ligands. Yet, control strategies for complex, multifunctional molecules and catalysts, where selectivity is crucial, are lacking. Here, we demonstrate that submonolayer WOx with tunable coverage preferentially decorates well‐coordinated Pt terrace sites as a stable ligand. By combining experimental kinetics with probe molecules, in situ spectroscopies, and first‐principles modeling, we show that the WOx coverage on Pt modifies the metal‐to‐acid site balance while retaining the acid strength intact and results in optimal reactivity for metal‐acid catalyzed reactions at a specific metal, size, and support‐dependent WOx coverage. The oxide can also alter the reactant adsorption mode, reversing selectivity and pathways from terrace‐ to step‐dominated, as evidenced in furfural decarbonylation and hydrogenation. The insights open avenues for improving metal/metal oxide catalysts beyond the specific system.

A study on thermal behaviour of thermal barrier coating: investigation of particle size, YSZ/polysilazane, time and temperature curing effect.

Thermal conductivity and adhesion strength effects were studied for thermal barrier coatings (TBCs) with different particle sizes, YSZ content, time, and temperature curing. The study involves three stages. The first step focuses on the characteristics of YSZ/polysilazane as the TBC, which is characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), and Thermal Gravimetric Analysis (TGA). The second and third steps assess thermal conductivity and adhesion strength based on variables such as particle size, YSZ/polysilazane, time, and curing temperature. Results show that there was a synergistic effect between particle size-YSZ content and time-temperature curing to obtain specimens with good thermal properties. SB270/70 showed the lowest temperature compared to other specimens, up to 160 °C. Furthermore, YSZ/polysilazane thermal conductivity and adhesion properties could be enhanced by a prolonged curing time and higher temperature. This study emphasizes that the modification of particle size, YSZ content, time, and temperature curing is a promising strategy to improve the thermal properties of TBCs.

Comparison of the Effects of Crystalline Particle Size Modified by Crystallization on the Mother Liquor Removal Profiles of Washing and Reslurry

In industrial crystallization, the mother liquor recovered with the crystalline product causes a significant decrease in product purity. Therefore, additional purification processes, such as washing or reslurry, are often necessary to remove mother liquor from the particles to produce high-purity crystalline products. Although it is important to understand the characteristics of the purification processes for effective removal, a direct comparison between these different purification processes has rarely been reported. Therefore, the characteristics of washing and reslurry were compared using particle properties determined by crystallization. Herein, the mother liquor removal profiles of washing and reslurry were investigated considering changes in the removal ratio. We compared the profiles by normalizing the operating loads in each purification process. The purification processes were characterized by analyzing the particle-size dependency on the removal profiles. The results suggested that the removal profiles of washing and reslurry depended on the particle sizes, and the removal ratio was higher for reslurry for all ranges of loading when the particle size was identical. According to the proposed classification of mother liquors, by introducing the consideration of removability, we found that a primary cause was the ratio of mother liquor segments, which can change between different states of the particles during washing or reslurry. The effect of decreasing particle size on improving mother liquor removal in reslurry was more significant compared with that of washing. Therefore, reslurry is more beneficial for mother liquor removal by particle size modification via crystallization, compared with washing. This study provides primary knowledge on the operation design of the crystallization process for purification.

Effects of biochar particle size on sorption and desorption behavior of NH4+-N

Although optimizing of particle size was a simple and low-cost method for biochar modification, the insufficient understanding of biochar particle size on sorption and desorption performance has hindered its application. In this study, apple branch biochar was mechanically grinded and dry sieved into different particle sizes to investigate the sorption mechanism, sorption and desorption characteristics at various temperature, NH 4 + -N concentrations, contact time, biochar dosages and regeneration times. The particle size modification affected the physical properties of biochar but not the sorption mechanism, which was a comprehensive process involving physicochemical sorption. The result indicated that, for all three particle sizes, the sorption process was exothermic and the Langmuir, pseudo first and second order kinetic models can provide satisfactory descriptions. The sorption capacity increased with the rising of NH 4 + -N concentrations and contact time. The decreasing biochar particle size significantly increased the sorption capacity, desorption capacity and efficiency in the first 24 h, indicating that large particle size biochar had a better slow-release effect. Moreover, both sorption capacity and slow-release effect were also affected by the ratio of NH 4 + -N to biochar. High NH 4 + -N-biochar ratios were beneficial for increasing sorption and desorption capacity of biochar, while small NH 4 + -N-biochar ratios were beneficial for increasing the slow-release effect. Considering the nutrient supply and slow-release performance, the recommended NH 4 + -N-biochar ratios for fine, medium and coarse biochar were 0.013–0.016, 0.013–0.034, and 0.009–0.124, respectively. At the same slow-release effect, coarse biochar had better nutrient supply capacity, indicating that a greater application efficiency. Compared with traditional slow-release fertilizers, biochar had excellent regeneration performance, which could be enhanced by particle size modification. In conclusion, our research provides a theoretical basis for the necessity of biochar particle size optimization. • Fine biochar (＜0.25 mm) enhances sorption capacity but lowers slow-release effect. • NH 4 + -N-biochar ratio affects the biochar sorption and desorption performance. • The recommended NH 4 + -N-biochar ratio varies with the biochar particle size. • Coarse biochar (1–2 mm) is preferred for better efficiency and regeneration.

Comparison of mechanical, chemical, and thermal activation methods on the utilisation of recycled concrete powder from construction and demolition waste

Recycled concrete powder (RCP) poses a considerable challenge with respect to effective utilisation of construction and demolition waste (CDW) resources due to its low activity, high water demand, and potential to cause dust pollution during storage. A suitable activation method is necessary for stimulating the potential activity of RCP and enhancing its utilisation. Therefore, the effect of mechanical, chemical, and thermal activation methods on the properties of RCP were investigated in this study. Mechanical and thermal activation were helpful for the activity of RCP due to the modification of particle size and distributions. RCP exhibits a higher content of SiO2 and a lower content of CaO as well as the main crystal phases of quartz, calcite, gismondine, and dolomite. After 400–800 °C thermal activation, dolomite is not observed while the RCP shows new active components (such as larnite, calcium silicate, and calcium oxide). The chemical activation test highlights that CaO (3%) is the most optimal, followed by CaSO4 (1%) and Na2SO4 (2%), while Ca(OH)2 (4%) has the least optimal activation effect on the strength activity index (SAI) of RCP mortar. For combined activation, Ca(OH)2 and CaSO4 with 1:1 ratio has the most optimal activation effect, and the SAI reaches 80.27%. Based on the mechanical performance, SAI, and micro-characteristics, the most feasible and effective activation method is thermal activation (800 °C), followed by chemical activation (Ca(OH)2+CaSO4), and mechanical activation (75 min). This study proposes a useful combined activation method for RCP that verifiably contributes to the application of CDW.

Mechanism of carbonating recycled concrete fines in aqueous environment: The particle size effect

Processing waste concrete in recycling facilities inevitably generates by-products such as very fine particles (<2.36 mm) and powders (<0.15 mm). The resourcing of these low-value recycled concrete fines (RCFs) has attracted increasing interest from the construction industry. This study attempts to elucidate the underlying mechanisms of particle size effects on carbonating RCFs via aqueous route. The results suggested that the relatively coarse particles (0.6–1.18 mm and 1.18–2.36 mm) experienced two positive effects i.e., i) improvement of surface properties by the formation of a reactive shell, and ii) significant densification of the microstructure. This was due to an initial carbonation mediated in the bulk solution, and then the internal carbonation due to the inward diffusion of carbonate species. Meanwhile, the finer particles (<0.15 mm) showed significantly different effects i.e., being totally disintegrated and converted to a calcium carbonate and silica gel composite. Such a difference was attributed to the long alkalinity maintaining ability and extensive dissolution and leaching associated with the high fineness. Whereas 0.15–0.6 mm was regarded as a transition particle size where balanced decomposition and densification were observed. Finally, after carbonating for only 6 h, the carbonated RCFs was found to enhance the compressive strength of pastes (as cement substitute) and mortars (as fine aggregate substitute) by an average of 13.2% and 9.0% in comparison with those prepared with raw RCFs.

Improving the performance of Pd based catalysts for the direct synthesis of hydrogen peroxide via acid incorporation during catalyst synthesis

The direct synthesis of hydrogen peroxide from molecular H2 and O2 offers an attractive alternative to the current means of production of this powerful oxidant, on an industrial scale. Herein we investigate the role of nitric acid addition, during catalyst preparation as a means of improving catalytic performance, under reaction conditions that have previously been found to be optimal for H2O2 production. The addition of dilute nitric acid during catalyst preparation is found to lead to a significant improvement in H2O2 synthesis activity, through the modification of particle size and control of Pd oxidation state.

Effect of Ru3+ ions on the formation, structural, magnetic and optical properties of hematite (α-Fe2O3) nanorods

Nanosized hematite (α-Fe2O3) is a widely investigated material due to its favourable properties (chemically stable, environmentally safe, inexpensive) and very good performance in several advanced applications. Properties and performance of hematite nanoparticles can be adjusted and improved by modification of particle size and shape, as well as by substitution of Fe3+ ions in the crystal structure of hematite with other metal ions. Ru3+ ions are potentially suitable metal ions for the substitution of Fe3+ ions in hematite because of the same charge and similar ionic radii. In the present work, the effects of Ru3+ ions on the formation and properties of hematite nanorods prepared by combination of hydrothermal precipitation and calcination were investigated. The influence of the molar fraction of Ru3+ ions in the hydrothermal precipitation system on the formation and properties of iron oxide phases was studied. Single-phase goethite (α-FeOOH) nanorods containing incorporated Ru3+ ions were formed in the presence of low levels of Ru3+ ions (<3 mol%), while at higher levels (4 and 5 mol% Ru) hematite nanocylinders, consisting of self-assembled and fused nanoparticles, were obtained. The mechanism of the formation of these iron oxide nanostructures in the presence of Ru3+ ions was explained and compared with the effect of other metal cations reported in the literature. Ru-doped hematite nanorods were formed after calcination of Ru-doped goethite nanorods at 500 °C. A gradual elongation of hematite nanorods with increased Ru doping to highly elongated Ru-doped hematite nanoneedles at 2 mol% Ru was observed and explained. The influence of the Ru doping level on the magnetic properties of hematite nanorods was investigated using Mössbauer spectroscopy and magnetic measurements. Temperature of the transition between antiferromagnetic (AFM) and weakly ferromagnetic (WFM) spin ordering state (Morin transition) gradually rose with increasing Ru3+-for-Fe3+ substitution in hematite. Besides, magnetization of the WFM hematite gradually decreased with Ru doping which was attributed to the reduced canting of two almost antiparallel spin sublattices in this phase. The optical band gap in hematite nanorods was found to get gradually narrower with increased Ru doping due to the modified electronic structure.

Improved Ionic Conductivity and Battery Function in a Lithium Iodide Solid Electrolyte Via Particle Size Modification

Solid electrolytes (SEs) are a promising, safe alternative to liquid electrolytes in high energy density batteries, but challenges, including low ionic conductivity and dendrite formation, remain. In a recent work, it was determined that dendrite formation within representative SEs, Li7La3Zr2O12 and Li3PS4, is due to their non-negligible electronic conductivity.[1] Notably, LiI has negligible electronic conductivity and thus the formation of lithium dendrites may be lessened, making LiI a good candidate for SE development. Our previous work on LiI SE, utilized 1:2 lithium iodide:3-hydroxypropionitrile (LiI(HPN)2) as a conductive additive, creating an 80/20 LiI/LiI(HPN)2 composite as a self-forming, rechargeable battery.[3] Additional work has demonstrated interfacial modification can effectively lower the cell impedance and improve coulombic efficiency (CE).[2, 4]In this work, a LiI SE was improved by reducing particle size via several processing methods; grinding (G), sonicating (C-S), and grinding with sonicating (G-S), and compared to a control (C) sample of LiI which underwent no processing. Partial hydration of LiI results in increased conductivity via increased defect density, and thus this parameter was controlled to ca. 34 mol% LiI monohydrate between samples. With further processing, particle size was reduced from 5 ± 1 µm to 2.0 ± 0.2 µm for the C and G-S samples. Utilized in 80/20 LiI/LiI(HPN)2 composites, reducing particle size resulted in an order of magnitude increase in ionic conductivity, from 7.7 x 10-8 to 6.1 x 10-7 S cm-1, at room temperature. Improved conductivity is attributed to an increased number of grain boundaries and defects, enabling ion transport and better mixing with the electrolyte additive, LiI(HPN)2. 3D confocal Raman spectroscopy in conjunction with non-negative matrix factorization (NMF) analysis determined the degree of HPN aggregation was lessened in the sample with smallest particle size. This LiI SE was utilized in a self-forming Li/I2 battery, where reduced particle size (improved conductivity) led to significantly reduced overpotential, allowing the coulombic efficiency to reach 100% in the first cycle. The G-S cells also exhibited improved electrochemical function when cycling at higher rates compared with the other electrolyte types. This work demonstrates the effect of particle size on solid electrolyte in a self-forming, self-healing, all solid state battery with a lithium metal negative electrode.

Improved ionic conductivity and battery function in a lithium iodide solid electrolyte via particle size modification

Solid electrolytes (SEs) are a promising, safe alternative to liquid electrolytes in high energy density batteries, but low conductivity issues remain a challenge. Herein, a lithium iodide based solid electrolyte (SE) was improved by reducing particle size via several processing methods, i.e. grinding and/or sonication. Particle size was reduced from 5 ± 1 µm to 2.0 ± 0.2 µm, resulting in an order of magnitude increase in ionic conductivity, from 7.7×10−8 to 6.1×10−7 S cm-1, at room temperature. Improved conductivity is attributed to an increased number of grain boundaries and defects, enabling ion transport and better mixing with the electrolyte additive, 1:2 lithium iodide: 3-hydroxypropionitrile (LiI(HPN)2). 3D confocal Raman spectroscopy in conjunction with non-negative matrix factorization (NMF) analysis determined the degree of HPN aggregation was lessened in the sample with smallest particle size. This LiI SE was utilized in a self-forming Li/I2 battery, where reduced particle size (improved conductivity) led to significantly reduced overpotential, allowing the coulombic efficiency to reach 100% in the first cycle. Furthermore, a more stable electrochemical response was achieved when cycled at higher current densities.

Effects of modified biochar on water and salt distribution and water-stable macro-aggregates in saline-alkaline soil

This study investigated the chemical and physical mechanisms associated with the movement of water and salt in saline-alkali soil amended with different types of biochar. Four types of biochar were selected: ordinary laboratory-prepared biochar (BC), acidified biochar (HBC), particle size modified biochar (NBC), and composite modified biochar (HNBC). The physical and chemical properties of the biochar treatments were characterized. Vertical infiltration simulation tests were conducted to analyze the effects of modification on the adsorption and distribution of salt ions on biochar, and the soil water-stable macro-aggregates in saline-alkali soil. The porous structure, specific surface area (SSA), micropore volume (VMIC), and H/C value were increased by acidification, particle size modification, and composite modification. Compared with BC, HBC and HNBC enhanced the O/C and (O+N)/C values, thereby increasing the hydrophilicity. The vertical infiltration tests showed that the depth of the soil wetting peak and cumulative infiltration were both higher than in the control (CK) after adding biochar, where HBC had the greatest water retention capacity. The modified biochar reduced the salt content and water-soluble Na+ content of the soil profile by increasing the soil water content and adsorbing Na+. The modified biochar promoted the formation and stabilization of soil water-stable macro-aggregates. Amending soil with HBC showed the greatest reduction in salt content and increased water-stable macro-aggregation. HBC improved the water retention and Na+ adsorption capacity of biochar. This enhanced the formation of soil water-stable macro-aggregates and improved the effects of biochar on saline-alkali soil by altering soil physical and chemical properties.

Supercritical Carbon Dioxide + Ethanol Extraction to Improve Organoleptic Attributes of Pea Flour with Applications of Sensory Evaluation, HS-SPME-GC, and GC-Olfactory

Supercritical carbon dioxide + ethanol (SC-CO2+EtOH) extraction, was employed as a deflavoring method to improve the sensory properties of pea flours. Furthermore, the impacts of particle size along with extraction on volatile profile and sensory attributes of pea flours were investigated using multiple approaches. These included headspace solid-phase microextraction-gas chromatography (HS-SPME-GC), GC-olfactometry (GC-O), and quantitative descriptive analysis (QDA) using a trained sensory panel. Total volatile contents of non-deflavored and deflavored whole pea flour and its fractions were in the range of 7.1 ± 0.3 to 18.1 ± 1.0 µg/g and 0.4 ± 0.1 to 2.7 ± 0.4 µg/g, respectively. The GC-O system showed that the total volatile intensity was in the range of 14.5 to 22.0 and 0 to 3.5, for non-deflavored and deflavored pea flours, respectively. Volatile analyses indicated that 1-hexanol, 1-octanol, 1-nonanol, nonanal, and 2-alkyl methoxypyrazines were major off-aroma compounds. Most off-aroma compounds were not detected in deflavored pea flours. QDA revealed less pea intensity and bitterness of deflavored pea flours. The larger particle size of flours resulted in less off-aroma compounds based on the GC data but more bitterness based on QDA. The SC-CO2+EtOH extraction at optimum conditions and particle size modifications can be a potential technology to improve the organoleptic properties of pulse ingredients.

Manipulation of the Size and Phase Composition of Yttrium Iron Garnet Nanoparticles by Pulsed Laser Post-Processing in Liquid.

Modification of the size and phase composition of magnetic oxide nanomaterials dispersed in liquids by laser synthesis and processing of colloids has high implications for applications in biomedicine, catalysis and for nanoparticle-polymer composites. Controlling these properties for ternary oxides, however, is challenging with typical additives like salts and ligands and can lead to unwanted byproducts and various phases. In our study, we demonstrate how additive-free pulsed laser post-processing (LPP) of colloidal yttrium iron oxide nanoparticles using high repetition rates and power at 355 nm laser wavelength can be used for phase transformation and phase purification of the garnet structure by variation of the laser fluence as well as the applied energy dose. Furthermore, LPP allows particle size modification between 5 nm (ps laser) and 20 nm (ns laser) and significant increase of the monodispersity. Resulting colloidal nanoparticles are investigated regarding their size, structure and temperature-dependent magnetic properties.

Physicochemical characteristics of biochars can be beneficially manipulated using post-pyrolyzed particle size modification

This work aimed to study the changes in the physicochemical properties of biochars induced by post-pyrolyzed particle size processing. Twelve distinct physicochemical attributes of four different particle sized biochars, derived from three different feedstocks, including rice husk, tea wastes and woodchips; were investigated. Amongst all of the investigated characteristics water repellency (η2 = 0.99) and mean pore diameter (η2 = 0.95) were the characteristics most affected by feedstock type and particle size, respectively. The interaction effect between biochar type and particle size was extremely significant (P < 0.001) for surface area and mean pore diameter. While feedstock mainly controlled biochar characteristics, most characteristics were also particle size dependent, where size dependency was more influential on physical than chemical properties. For most properties a significant interaction effect between biochar type and particle size was also detected.

Evaluation of Mechanical Activation and Chemical Synthesis for Particle Size Modification of White Mineral Trioxide Aggregate.

Objective:Initial setting time is one of the most important properties of calcium silicate cements (CSCs) such as white mineral trioxide aggregate (WMTA). This study aimed to evaluate the effect of two methods used to reduce the particle size of WMTA, mechanical activation and chemical synthesis.Methods:WMTA without bismuth oxide (WMTA-B) was provided and divided into four groups (n=5) including: WMTA-B, WMTA-B+10 min milling, WMTA-B+30 min milling, and sol-gel. In groups 2 and 3, the milling was performed by using tungsten carbide balls in a ratio 1:15 (w/w) and a vibration frequency of 30 Hz together with absolute ethanol. For the fourth group, polyethylene glycol (PEG), calcium acetate (Ca(C2H3O2)2), SiO2, and aluminum oxide (Al2O3) were used for the sol-gel process. After preparation, sample powders were mixed with distilled water and placed in cylindrical molds, covered with water-moistened gauze, and incubated at 37°C for 24 hours. The Vicat needle test analyzed the initial setting time. Data were analyzed by ANOVA and Tukey tests at a significance level of P<0.05. The correlation between particle size and setting time was determined.Results:Initial setting time of the sol-gel and WMTA-B+30 min milling was significantly lower than in the other two groups (P<0.05). A significant correlation was noticed between particle size and initial setting time (P<0.05).Conclusion:Sol-gel process introduces a promising alternative strategy for the reduction of initial setting time of CSC materials. While both methods increased surface area, mechanical activation was not as successful in reducing surface area and initial setting time as effectively as the sol-gel process.

Particle Packing Application for Improvement in the Properties of Compressed Stabilized Earth Blocks with Reduced Clay and Silt

Soil as a building material has been used in different forms such as mud, adobe, rammed earth and bricks. The present study focuses on producing Compressed Stabilized Earth Blocks (CSEBs) giving attention to the particle size distribution in the soil mixture. The literature established that compressive strength significantly depends on clay and silt content and 25% of clay and silt produce optimum results while no attention has been given to the amount of other, larger particles. Soil grading refers to the combination of different-size particles in a soil mixture. The correct selection of sizes in the correct proportion may cause improvements in CSEB properties. This paper explains the application of particle packing technology for the improvement of CSEB properties. The theoretical concepts provide a continuous particle size distribution, and the soil used for the experiments also has a continuous particle size distribution. The soil used in the experiments was subjected to washing to reduce the clay and silt content. Separated clay and silt and large particles of different sizes were added to the mixture to match particle size distribution to the optimization curves as explained in particle packing theories. The experimental results show that the CSEB properties can be significantly improved by modifying particle size distribution to fit the suggested optimization curves. According to the results, the compressive strength improved by more than 50% with different amounts of cement stabilization. Significant improvements in the dry densities and water absorption ratios of blocks were observed with this particle size modification.

Ascendancy of Polianthes tuberosa, Nerium oleander, Hibiscus rosa sinensis and Dalia flower Extracts on CdO Nanoparticle Morphologies and Their Effectiveness in Photocatalytic and Antimicrobial Activities

The natural biomolecules present in the plant extracts have been identified to play an active role in the formation of nanoparticles with varied morphologies and sizes which is greener and environmentally benign. The present work describes bout the synthesis of CdO nanoparticles with various morphologies with the help of flower extract mediated route using Polianthes tuberosa (PTR), Nerium oleander (NO), Hibiscus rosa sinensis (HRS) and Dalia flower (DF) as capping and stabilizing agent. The formation of good crystallinity on the basis of extracts is identified from XRD spectra. It confirms that the extracts are well supported to modify the particle size. This modification of particle size is the base to change the morphology which is visualized from FESEM. Further, the CdO nanoparticles were characterized by UV–vis-DRS, FT-IR and EDAX. The HR-TEM shows the morphologies on using these extracts like nano rod, nano wire, flower shape and spherical particles with accurate particle size. The results from the photo degradation of methylene blue (MB) dye under Solar and UV light irradiation depicts HRS based CdO nanoparticles around 91% decolorization efficiency at 120 min. The antimicrobial activities of various flower extract based CdO nanoparticles were tested for different bacterial organisms like Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Salmonella paratyphi and fungal organism of Candida albicans, Aspergillus niger and Aspergillus fumigates under the zone inhabitation method. The PTR and HRS based CdO nanoparticles are more responded for antimicrobial activity.

Approach for correcting particle size distribution measured by optical particle counter in high-pressure gas pipes.

A set of online particle detection devices was developed for the quick and accurate assessment of particle size and concentration in high-pressure natural gas that can be applied at any pressure below 10MPa. In actual site tests with P=3.42 and 2.36MPa, the online tested results of particle size and concentration are generally smaller compared to those of the offline gathered under atmospheric conditions. That is mainly due to the detection performance degradation of an optical particle counter caused by gas pressure change leading to the refractive index change of the sounding medium with which the optical paths of the incident light and scattering light are altered. Aiming to solve this problem, an analysis of the dynamic change of optical measurement volume of the optical detection system with gas pressure was conducted based on the gas state parameters and geometric optics theory, and a dynamic model of both was established that can be accompanied by a particle size modification method based on light scattering theory. After a correction of tested results, the deviations in median diameter and concentration between the modified online and offline test results were within an acceptable range. Therefore, the proposed modification is a feasible and reliable approach to enhance online particle detection.

Bioleaching process for silver recovery: Structural and rheological studies

In this work, we characterize the microstructural and rheological properties of silver manganese mineral pulps during a bioleaching process in a continuous stirred-tank reactor (CSTR). Analysis of the dissolution kinetics of Manganese in the pulp during the bioleaching process reveals a dissolution level of 20–23% during 36–48 h. This percentage allows the extraction of large percentages of silver (Ag) during the cyanidation process, thus obtaining 64 wt% of Ag. The maximum value of viscosity attained in the medium (especially between 48 and 72 h) is an important parameter, since it may cause processing setbacks such as in-homogeneous agitation and increase in transport energy. Several factors contribute to the continuous change of viscosity in the media such as mineral wearing, the presence of the excreted bacterial exopolysaccharide (EPS), pH changes, particle size modifications due to mineral wear (plus corrosion) and changes in density of the medium. For this reason, it is of great importance to monitor the rheological behavior of the mineral pulp during the bioleaching and cyanidation processes. The mineral pulp behaves as a weak gel as reported in linear viscoelastic measurements.