scholarly journals PROBABILITY-DETERMINED DESIGN PLANNING FOR DECOMPOSITION OF SILICON-CONTAINING SAMPLES

2020 ◽  
Vol 8 (2) ◽  
pp. 49-55
Author(s):  
Anna V. Troeglazova
Keyword(s):  
Hydrofluoric Acid ◽  
Contact Time ◽  
Solid Phase ◽  
Size Fraction ◽  
Acid Leaching ◽  
Temperature Phase ◽  
Ultrasonic Vibrations ◽  
Particle Size Fraction ◽  
Laboratory Studies ◽  
Phase Contact Time

An alternative method of acid leaching of silicon-containing metallurgical samples using ultrasonic vibrations is proposed in order to extract Si quantitatively from the solid phase into the solution. The effect of ultrasonic vibration, leaching temperature, phase contact time, weight of the sample, particle size, fraction of hydrofluoric acid in the reaction mixture was investigated. The results of laboratory studies showed that acid leaching assisted by ultrasonic vibrations is an efficient, safe and economically profitable way of sample preparation of silicon-containing metallurgical samples.

scholarly journals Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 20
Author(s):  
Deniz Talan ◽  
Qingqing Huang
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Contact Time ◽  
Separation Efficiency ◽  
Ph Value ◽  
Solid Phase ◽  
Separation Performance ◽  
Solution Ph ◽  
Zeolite Sample ◽  
Alternative Sources

The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

Distribution of total bacteria and staphylococci in PM2.5, PM10 and total dust in the emission of two fattening pig houses/Verteilung von Gesamtbakterien und Staphylokokken in PM2,5, PM10 und Gesamtstaub in der Emission von zwei Mastschweineställen

Gefahrstoffe ◽  
2020 ◽  
Vol 80 (09) ◽  
pp. 344-348
Author(s):  
M. Clauß ◽  
S. Linke ◽  
A. C. Springorum
Keyword(s):  
Particle Size ◽  
Size Fraction ◽  
Airborne Bacteria ◽  
Dispersion Modelling ◽  
Particle Size Fraction ◽  
Collection System ◽  
Total Dust ◽  
Dust Distribution ◽  
Selective Collection ◽  
Total Bacteria

The particle size distribution of airborne bacterial conglomerates is an important factor in calculating possible spread distances of the bacteria over the air. Therefore, a size-selective collection system based on an emission impinger was developed to compare the distribution of total bacteria and staphylococci in particle fractions PM2.5, PM10 and total dust in the emission of two fattening pig stables. Mean emissions of 7.2 × 104 cfu/m³ total bacteria, 6.1 × 104 cfu/m³ staphylococci and 2.8 × 106 cells/m3 measured. About 30% of total bacteria and staphylococci were found in the PM2.5 particle size fraction and about 60% in PM10. The average dust distribution was 80% PM10 and 60% PM2.5. The results show that airborne bacteria from fattening pig units mainly occur on larger particles and do not correlate with dust fractions. The found conditions should be considered in future dispersion modelling.

scholarly journals PURIFICATION OF INDONESIAN NATURAL GRAPHITE AS CANDIDATE FOR NUCLEAR FUEL MATRIX BY ACID LEACHING METHOD: CHEMICAL CHARACTERIZATION

2020 ◽  
Vol 26 (3) ◽  
Author(s):  
Deni Mustika ◽  
Torowati Torowati ◽  
Arbi Dimyati ◽  
Sudirman Sudirman ◽  
Adel Fisli ◽  
...  
Keyword(s):  
Sulphuric Acid ◽  
Nuclear Fuel ◽  
Hydrofluoric Acid ◽  
Acid Leaching ◽  
Chemical Characterization ◽  
Ash Content ◽  
Natural Graphite ◽  
Nuclear Graphite ◽  
Purity Level ◽  
Graphite Matrix

PURIFICATION OF INDONESIAN NATURAL GRAPHITE AS CANDIDATE FOR NUCLEAR FUEL MATRIX BY ACID LEACHING METHOD: CHEMICAL CHARACTERIZATION. Graphite matrix in Pebble Bed Reactor (PBR) – High Temperature Gas Cooled Reactor (HTGR) has an important role as heat transfer medium, neutron moderator and structural material to protect fuel. Thus, graphite matrix must fulfill chemical and physical characteristics for PBR-HTGR fuel. Indonesia has graphite sources in several regions that can potentially be purified. This research aimed to purify Indonesian natural graphite by several variation of acids and to perform chemical characterizations. Natural graphite from flotation process was purified by several variations of acid, i. e., hydrofluoric acid (HF), sulphuric acid + nitric acid (H2SO4 + HNO3) and hydrofluoric acid + hydrochloric acid + sulphuric acid (HF + HCl + H2SO4) and subsequently followed by chemical characterizations such as purity level, ash content, and boron quivalent. The highest purity was obtained in the purification process by HF with carbon content up to 99.52%; this purity level fulfills the specification of nuclear graphite (>99%). Ash content analysis shows a value in compliance with the specification requirement, i.e., < 100 ppm, and boron equivalent value also fulfills the specification value of < 1 ppm. It can be concluded from this study that the graphite purified by acid leaching with HF can be used as fuel matrix candidate but is qualified as low quality. Futher research is required to produce high quality nuclear graphite, particularly research in the minimization of the impurity by evaporation at temperatures over 950 oC to by far lower the ash content.Keywords:  Indonesian natural graphite, purification, nuclear fuel matrix, acid leaching, chemical characterization.

Optimization of Laser Hardening Processes for Industrial Parts With Complex Geometry via Predictive Modeling

2009 ◽  
Author(s):  
Neil S. Bailey ◽  
Yung C. Shin
Keyword(s):  
Phase Transformation ◽  
Thermal Model ◽  
Complex Geometry ◽  
Solid Phase ◽  
Three Dimensional ◽  
Laser Hardening ◽  
Temperature History ◽  
Temperature Phase ◽  
Laser Systems ◽  
History Of

A predictive laser hardening model for industrial parts with complex geometric features has been developed and used for optimization of hardening processes. A transient three-dimensional thermal model is combined with a three-dimensional kinetic model for steel phase transformation and solved in order to predict the temperature history and solid phase history of the workpiece while considering latent heat of phase transformation. Further, back-tempering is also added to the model to determine the phase transformation during multitrack laser hardening. The integrated model is designed to accurately predict temperature, phase distributions and hardness inside complex geometric domains. The laser hardening parameters for two industrial workpieces are optimized for two different industrial laser systems using this model. Experimental results confirm the validity of predicted results.

1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

1995 ◽  
Vol 50 (8) ◽  
pp. 742-748 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien­ tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

scholarly journals Influence of Hydrofluoric Acid Leaching and Roasting on Mineralogical Phase Transformation of Pyrite in Sulfidic Mine Tailings

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 513 ◽  
Author(s):  
Babak Koohestani ◽  
Ahmad Khodadadi Darban ◽  
Pozhhan Mokhtari ◽  
Esmaeel Darezereshki ◽  
Erol Yilmaz ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Phase Transformation ◽  
Iron Oxides ◽  
Mine Tailings ◽  
Hydrofluoric Acid ◽  
Surface Characterization ◽  
Acid Leaching ◽  
Roasting Process ◽  
Pyrite Content ◽  
Mineralogical Phase

Under the oxidative roasting process, pyrite, as a major mineral in sulfidic mine tailings, can transform to iron oxides. Generated iron oxides, if exhibiting enough magnetic properties, can be recovered via magnetic separation resulting in partial mine tailings valorization. However, due to the presence of various minerals and sintering possibility, it is advantageous to remove impurities and increase the pyrite content of mine tailings prior to the roasting procedure. In this case, hydrofluoric acid that has no influence on pyrite can be used to leach most inorganic minerals, including aluminosilicates. Therefore, this study investigated and compared the influence of the roasting process with and without hydrofluoric acid leaching pretreatment on mineralogical phase transformation of pyrite and magnetic properties of thermally generated minerals. Several tests and analyses were performed to study mineralogical phase transformation, morphology, elemental composition, surface characterization, and magnetic properties. Results of this study indicated that without acid leaching pretreatment, pyrite was mainly transformed to hematite. However, via acid leaching, fluorine, as a more electronegative element over oxygen, entered the compound and neglected the role of oxygen in thermal oxidation, instead reducing sulfur content of pyrite to only form pyrrhotite.

scholarly journals Laser Diffraction as An Innovative Alternative to Standard Pipette Method for Determination of Soil Texture Classes in Central Europe

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1232
Author(s):  
Dušan Igaz ◽  
Elena Aydin ◽  
Miroslava Šinkovičová ◽  
Vladimír Šimanský ◽  
Andrej Tall ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Soil Texture ◽  
Polynomial Regression ◽  
Texture Classification ◽  
Size Fraction ◽  
Laser Diffraction ◽  
Classification Systems ◽  
Particle Size Fraction

The paper presents the comparison of soil particle size distribution determined by standard pipette method and laser diffraction. Based on the obtained results (542 soil samples from 271 sites located in the Nitra, Váh and Hron River basins), regression models were calculated to convert the results of the particle size distribution by laser diffraction to pipette method. Considering one of the most common soil texture classification systems used in Slovakia (according to Novák), the emphasis was placed on the determination accuracy of particle size fraction <0.01 mm. Analysette22 MicroTec plus and Mastersizer2000 devices were used for laser diffraction. Polynomial regression model resulted in the best approximation of measurements by laser diffraction to values obtained by pipette method. In the case of particle size fraction <0.01 mm, the differences between the measured values by pipette method and both laser analyzers ranged in average from 3% up to 9% and from 2% up to 11% in the case of Analysette22 and Mastersizer2000, respectively. After correction, the differences decreased to average 3.28% (Analysette22) and 2.24% (Mastersizer2000) in comparison with pipette method. After recalculation of the data, laser diffraction can be used alongside the sedimentation methods.

scholarly journals 14C Dating of Carbonate Mortars from Polish and Israeli Sites

Radiocarbon ◽  
2009 ◽  
Vol 51 (2) ◽  
pp. 857-866 ◽  
Author(s):  
Danuta Nawrocka ◽  
Justyna Czernik ◽  
Tomasz Goslar
Keyword(s):  
Radiocarbon Dating ◽  
Size Fraction ◽  
Acid Leaching ◽  
Building Construction ◽  
14C Dating ◽  
Preliminary Processing ◽  
Small Scales ◽  
Quartz Aggregates ◽  
Leaching Reaction ◽  
Good Agreement

The presented research involves the analysis and radiocarbon dating of 2 different groups of carbonate mortars, from Kraków, Poland and Hippos, Israel. Differences in composition of the mortars are reflected in different rates of their acid leaching. The Israeli mortars contain carbonate-basaltic aggregates, which may cause overestimation of 14C age. Preliminary processing of these samples (choice of selected grain-size fraction and collection of CO2 released during the first phase of the acid-leaching reaction), enabled us to obtain good agreement between the 14C dates and the age derived from historical contexts. A similar method of preliminary processing was applied to the carbonate mortars of the Medieval building in Kraków. The Polish samples represent carbonate mortars with some admixture of quartz aggregates, suggesting that they would be an ideal material for 14C dating. However, these samples contained white lumps of carbonates, the structure of which differed from that of the binder. These admixtures, possibly related to the hydrological conditions at the site and to the character of the ingredients, appeared modern, and if not removed prior to acid leaching, they could cause underestimation of the age of samples. The 14C dates of the mortars from the walls of the Small Scales building in Kraków are the first obtained for this object, and their sequence does not contradict archaeological indications on several phases of the building construction.

Tacoma controls tastes and odours with ozone

2007 ◽  
Vol 55 (5) ◽  
pp. 137-144 ◽  
Author(s):  
M. Carlson ◽  
T. Chen ◽  
C. McMeen ◽  
I.H. Suffet ◽  
M. Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Analytical Methods ◽  
Contact Time ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
First Order ◽  
Ozone Dose ◽  
Gorge Reservoir ◽  
Flavour Profile ◽  
As Solid Phase

The study is focussed on the conditions that would provide the best ozone oxidation to decrease the taste and odour of the water from Eagle Gorge Reservoir. This study incorporated advanced analytical methods, such as solid phase microextraction (SPME) and flavour profile analyses (FPA), to evaluate the best method for improving taste and odour. The study developed first-order relationships between ozone dose and the oxidation of several taste and odour compounds. The results focussed on the importance and interactions between ozone dose, pH, hydrogen peroxide and contact time.

Sign in / Sign up

Export Citation Format

Share Document