Silica Sand Samples Research Articles

Interaction of micro/nano-metric size of Jordanian aluminosilicate raw materials with high pH solution

This study analyses the influence of particle size on the dissolution behaviour of three Jordanian raw materials. Kaolin, volcanic tuff and silica sand samples were dissolved in sodium hydroxide solution 10 M at 25 °C, and shaken for 168 h. To better understand the dissolution process, the alkaline solution was renewed after the desired time in order to know the degree of Al-Si raw material removed to the dissolution. The concentrations of leached Al and Si was used to evaluate the dissolution behaviour of the studied raw materials. The three raw materials have higher extent of leaching of Si4+ and Al3+ with decreasing the particle size.

Physical Modeling of Cone Penetration in Layered Sand

AbstractThis paper presents the results of cone penetration tests performed in layered, uniformly graded silica sand samples prepared inside a calibration chamber specifically designed for digital ...

Chemical Evaluation of the Glass Making Potentials of Silica Sand Deposits Along Cross River in Cross River State, South–East of Nigeria

Analytical techniques such as X–ray Fluorescence Spectroscopy (XRF) and Atomic Absorption Spectroscopy (AAS) coupled with statistical package for multivariate analyses were used to characterize silica sand deposit obtained along Cross River in Cross River State, South Eastern Nigeria. Samples were collected from five locations along the river which include: Ikom-Okuni, Obubra-Ofumbogha, Abi-Ediba, Biase-Agwagune and Etung-Effraya. The results of analyses revealed that silicon dioxide (SiO2) forms the predominant metal oxide in the entire samples followed by iron oxides (Fe203), sodium oxide (Na20). Other Oxides such as aluminum oxide (AI2O3), potassium oxide (k2O) etc were also present. Further beneficiation of the silica sand samples gave increased silica dioxide content across all the samples and increase and decrease of other metal oxides. The acid demand value (ADV) and pH value of the silica sand determination revealed a moderately low ADV and neutral pH value of all the samples. A correlation between the mean values of SiO2 and Fe2O3 in all the samples across all the sampling locations showed an inverse relationship between SiO2 and Fe2O3. Furthermore, comparison using population t – test of observed mean of SiO2 and Fe2O3, with their observed minimum standard (90.52%, 0.005%) shows that the silica sand samples from Ediba and Agwagune can be used as a source of SiO2 for glass making due to their high SiO2 and low levels of Fe2O3 content.

Chemical Evaluation of the Glass Making Potentials of Silica Sand Deposits Along Cross River in Cross River State, South–East of Nigeria

Analytical techniques such as X–ray Fluorescence Spectroscopy (XRF) and Atomic Absorption Spectroscopy (AAS) coupled with statistical package for multivariate analyses were used to characterize silica sand deposit obtained along Cross River in Cross River State, South Eastern Nigeria. Samples were collected from five locations along the river which include: Ikom-Okuni, Obubra-Ofumbogha, Abi-Ediba, Biase-Agwagune and Etung-Effraya. The results of analyses revealed that silicon dioxide (SiO2) forms the predominant metal oxide in the entire samples followed by iron oxides (Fe203), sodium oxide (Na20). Other Oxides such as aluminum oxide (AI2O3), potassium oxide (k2O) etc were also present. Further beneficiation of the silica sand samples gave increased silica dioxide content across all the samples and increase and decrease of other metal oxides. The acid demand value (ADV) and pH value of the silica sand determination revealed a moderately low ADV and neutral pH value of all the samples. A correlation between the mean values of SiO2 and Fe2O3 in all the samples across all the sampling locations showed an inverse relationship between SiO2 and Fe2O3. Furthermore, comparison using population t – test of observed mean of SiO2 and Fe2O3, with their observed minimum standard (90.52%, 0.005%) shows that the silica sand samples from Ediba and Agwagune can be used as a source of SiO2 for glass making due to their high SiO2 and low levels of Fe2O3 content.

Silica Sand Identification using ALOS PALSAR Full Polarimetry on The Northern Coastline of Rupat Island, Indonesia

Silica sand is one of the minerals which relatively abundant in Indonesia. One of the areas with abundant of silica sand distribution is the northern coastline of Rupat Island, Bengkalis district, Riau province, Indonesia. The distribution of silica sand in this island identified only on the northern coastline in this island. Some selected sample of silica sand was measured to get the percentage of silica sand mineral’s content using X-Ray Fluorescence (XRF). Two adjacent scenes of ALOS PALSAR full-polarimetry were used. The physical properties of silica sand sample such as dielectric constant were measured using dielectric probe kit in the frequency range from 0.3 to 3.0 GHz and used for calculating the backscattering coefficient and the difference characteristics of silica sand with another object. Freeman-Durdeen and Yamaguchi techniques were used to get the scattering decomposition of physical scattering from the incoherent object model based. Surface scattering is the clearest of Scattering decomposition to show silica sand identification compares with other decompositions. From surface scattering, the backscattering coefficient value of silica sand was calculated starting from -59 dB until -52 dB. These values were given by the surface roughness condition, where the roughness is slightly rough planar. The flat condition supported by the grain size of silica sand particles that have almost the same size and shape, that were conducted by using microscopic photograph testing.

고수압 해저터널에 급속 인공동결공법 적용시 간극수의 염분 농도가 동결속도에 미치는 영향 평가: 실내 동결챔버시험 위주로

고수압 조건의 해저터널 공사에 기존의 그라우팅 공법은 제한을 받게 되어 굴착작업이 어려울 수 있으나, 인공동결공법을 적용할 경우 신속한 차수 및 지반보강 효과를 얻을 수 있다. 인공동결공법을 적용할 경우, 동결 조건에 따라 동결토의 거동이 크게 변화하므로 기존의 연구 사례를 바탕으로 해저지반 등 특수한 조건에서 동결토의 역학적 거동을 예측하는 것에는 한계가 있다. 또한, 인공동결공법의 설계를 위해서는 동결체 형성에 필요한 소요시간 및 동결범위를 산정해야 하며, 해저지반의 경우 간극수 내 염분의 영향을 반영해야 한다. 본 논문에서는 동결토의 열적 특성을 파악하기 위해 인조규사 시료에 대한 실내 열전도도 측정시험과 동결챔버시험을 수행하였다. 동결토와 비동결 포화토 간극수의 염도를 조절하여 동결 과정과 염분에 따른 유효 열전도도를 비정상 열선법을 적용하여 측정하였다. 인조규사 간극수의 염도에 의한 동결특성 변화를 파악하기 위해 동결챔버를 설계 및 제작하였고 이를 통하여 동결 조건을 변화시키며 동결챔버시험을 수행하였다. 동결 조건에 따른 시료내 온도 변화를 분석하고 이를 통해 동결 조건이 사질토의 열전달 특성에 미치는 영향을 평가하였다. 비동결 포화토의 경우는 간극수가 담수(염도 0%)인 조건과 염수(염도 3.5%)인 조건 모두 유효 열전도도가 유사하게 평가되었으나, 동결토의 경우는 간극수가 염수인 조건이 보다 큰 유효 열전도도를 보였다. 이는 동결챔버시험에서 간극수가 염수인 조건이 담수인 조건보다 동결속도가 더 빠른 결과와 일치한다. It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.

Enhancing the Technical Qualifications of Egyptian White Sand Using Acid Leaching; Response Surface Analysis and Optimization

White silica sand samples were collected from Zafarana area along the Red sea coast, Egypt. The samples were mixed and quartered to obtain representative sample for characterization. The silica content in the sample is 99.441% and the iron content is 0.112%. Such geochemical qualifications don't match the technical specification of ceramic, optics, silicon metals and solar cells. RSM in conjunction with CCRD was used to study the removal of iron from silica sand using oxalic acid in terms of three operating parameters (Contact time, Acid concentration, Temperature). The model F values indicated the high significance of the design, also the good agreement between the Actual and the predicted results (R2 > 0.9) indicated suitability of second order quadratic polynomial model to represent the removal process. The best removal process (82%) was achieved at 8gm per ton oxalic acid concentration, 95°C temperature and 120 min leaching time. The final product exhibit high silica content (99.683% SiO2) and lower iron content of (0.017%) which match the requirements of ceramic, silicon carbide, silicon metal and the production of silicon for solar cells.

Imaging of Silica Sand to Evaluate Its Quality to Use It as Foundry Core Sand

Silica sand is a major mineral commodity for foundries, specifically for sand casting. Suppliers of foundry sand located near consumers would keep costs low production. Gray cast iron in Mexico demands large amounts of silica sand for the manufacture of core molds, currently supplied by the USA. This sand must meet industrial specifications for core sand to reach adequate strength, such as grain shape, grain size distribution, pH and ADV. In the last years, a high demand for silica sand for fracking in the USA has obligated Mexican foundries to search for new sources of this commodity. In this research, seven samples of silica sand from different areas Northeast and Southeast in Mexico were analyzed by microscopy imaging using metallography microscopy and SEM, to compare with core commercial sands. Also, semi-qualitative chemical composition by energy dispersive X-ray spectroscopy was analyzed. Surprisingly, results showed some silica sands from Mexico have textural surface and chemical composition similar to samples from the USA. A source of silica sand located in Mexico could be developed to meet local demand.

Effect of surface roughness on the shaft resistance of non-displacement piles embedded in sand

This paper presents the results of axial load tests performed on instrumented model piles pre-installed in a large-scale, half-circular chamber with a viewing window in its flat-side wall. Uniform silica sand samples were prepared with different densities using dry pluviation. The effects of pile surface roughness and soil density on the response of the soil during loading of the model piles were studied by analysing sequences of digital images using the digital image correlation technique. Test results show that the extent of the zone next to the pile that is affected by loading of the pile increases as the pile surface roughness and soil density increase. The development of a shear band next to the pile shaft was also studied by carefully analysing images taken with a digital microscope during loading of the model piles. The average thickness of the shear band is in the 3·2D50–4·2D50range for rough model piles, whereas no shear band was observed for smooth model piles. Understanding of shear band formation along the pile–soil interface provides insights into the calculation of the shaft resistance of the pile as a function of initial soil density and stress as well as pile surface roughness.

Optimizing the performance of the RER magnetic separator for upgrading silica sands

ABSTRACTFeed fractionation of a silica sand sample to a rare earth roll separator (RER) magnetic separator was found to be much more favorable for separation than the whole batch. The performance of the separator depends on both the size and the size distribution of the feed. The correlation between the different size fractions of the feed, e.g., −0.6 + 0.106, −0.6 + 0.211, and −0.211 + 0.106 mm and the RER magnetic parameters, e.g., belt speed and splitter angle of inclination was statistically verified using the central composite design (CCD) to achieve the optimum performance of the separator to reduce the Fe2O3 content of the sand concentrate. About 56.6% removal of this contaminant was achieved with the whole feed −0.6 + 0.106 mm at belt speed of 100 rpm and splitter angle inclination of 95°, whereas 84.3% reduction of Fe2O3 content was achieved with the separate size fractions under different belt speed and splitting angle inclination optima. The quality of the silica sand concentrate produced satisfies the requirement for both colorless glass and insulating glass fibers production.

Geoelectrical characterization of carbonate and silicate porous media in the presence of supercritical CO2–water flow

The relative permittivity (er) and the electrical conductivity (σ) of porous media are known to be functions of water saturation (S). As such, their measurements can be useful in effective characterisations and monitoring of geological carbon sequestration using geoelectrical measurement techniques. In this work, the effects of pressure, temperature and salt concentration on bulk er–S and σ–S relationships were investigated for carbonate (limestone) and silicate porous media (both unconsolidated domains) under dynamic and quasi-static supercritical CO2 (scCO2)-brine/water flow. In the silica sand sample, the bulk er (eb) for scCO2–water decreases as the temperature increases. On the contrary, slight increase was seen in the eb with temperature in the carbonate sample for the scCO2-water system. These trends are more conspicuous at high water saturation. The eb–S curves for the scCO2–water flow in the silica sand also show clear dependency on the domain pressure, where eb increases as the domain pressure increases. Furthermore, the bulk σ (σb), at any particular saturation for the scCO2-brine system rises as the temperature increases with more significant increase found at very high water saturation. Both eb and σb values are found to be greater in the limestone than silica sand porous samples for similar porosity values. Based on different injection rates investigated, we do not find significant dynamic effects in the eb–S and σb–S relationships for the scCO2-brine/water system. As such, geoelectrical characteristics can be taken as reliable in the monitoring of two-phase flow system in the porous media. It can be inferred from the results that the geoelectrical techniques are highly dependent on water saturation. This dependence is more conspicuous at higher water saturation. Different mathematical models examined show their reliability at different water saturation ranges. The polynomial fit developed in this work takes into consideration the fluid pressure in the system as well as the initial bulk relative permittivity prior to the injection of CO2. The polynomial fit shows a good reliability in the prediction of the geo-electrical properties of the CO2–water–porous media system, especially at higher water saturation. In comparison, the mixing model from the literature shows more reliability in the prediction of similar property at lower water saturation.

A Study on Silica Sand Quality in Yazaram and Mugulbu Deposits for Glass Making

The suitability of silica sand deposits of Yazaram and Mugulbu in Mubi South Local Government Area of Adamawa State, Nigeria for commercial glass production were assessed based on the chemical and physical properties of the silica sand samples collected along the river side’s. Test was carried out at the National Metallurgical Development Centre (NMDC), Jos. The chemical analysis was carried out using X-ray florescence spectrometer (XRFS) and the physical properties such as the particle size, grain morphology and the specific gravity examinations were carried out using mechanical shaker (sieving method), electronic microscope to reveal the shape of the samples and the specific gravity testing machine respectively. The results obtained were assessed and compared with the standard requirements for glass making. Mugulbu had the highest percentage of silica content of 77.70% and Yazaram had the lowest percentage of silica content of 77.60% and the grain morphology was found to be angular with specific gravity of 2.50 for both the samples, which were found to be within the acceptable limits for glass making. The iron oxide content in all the samples was found to be high, with highest value of 1.94% for Mugulbu and lowest value of 1.05% for Yazaram. However, the iron content for all the samples was above 1% thereby limiting the range of applications to coloured and amber glass manufacturing. The physical properties for all the samples were found to satisfy the standard requirements for glass making. http://dx.doi.org/10.4314/njt.v34i1.13

The Prospect of Bipinganj Sand in High Tech Applications

This study investigates the possibility of using the Bipinganj silica sand in high-tech industries such as semiconductors, telecommunications and optics, microelectronics, solar applications etc. Silica sand sample, collected from the locality named Bipinganj (Sub district Durgapur, District Netrokona) in Bangladesh, was characterized by its mineralogy, composition, crystalinity etc and the characteristics are compared with the high purity silica characteristics. The sand sample being studied is sized mostly from 106μm to 600μm, the bulk density is 2.60g/cc and contains around 0.58% moisture. No clay binder was found in the sand while a negligible amount of organic matter could be detected. The x-ray diffraction analysis showed that the major component was the quartz phase. XRF analysis showed that after acid washing the silica content was enhanced from 97.04% in the as-received sample to 99.05% in the processed condition.

Temperature Increase during the Depressurization of Partially Hydrate-Saturated Formations within the Stability Region

Depressurization experiments of methane-hydrate-bearing sediments were conducted to measure changes within the hydrate stability region before dissociation started. Pore-filling hydrate with a saturation of about 40% was formed in water-saturated silica sand samples with a porosity of 0.4. The initial pressure was kept constant at around 14.5 MPa, and the initial temperature was varied between 281.3 and 283.7 K. When the samples were depressurized at rates ranging from −1.2 to −3.9 MPa/min, temperature increases of 0.26–0.37 K on average were measured. These were caused by a decreasing aqueous methane solubility as well as the liberation of isolated free gas, leading to additional heat-releasing hydrate formation (ΔHMH-f = −51.86 kJ mol–1 of CH4 at 280 K). The results suggest that the solubility obeys Henry’s law as long as free methane is present in the pore space. The temperature changes during depressurization shift the equilibrium pressure, leading to an anticipated dissociation during the process. The increase in hydrate saturation, in turn, reduces the effective permeability of the formation, reducing the extent to which a formation can be depressurized by a single vertical wellbore. Sensitivity studies for the above state sediment conditions show that the induced increase in the temperature raises the equilibrium pressure of up to 0.7 MPa and raises the hydrate saturation by 7%, for an initial in situ pressure of 35 MPa and varying temperatures.

Phase equilibrium condition of marine carbon dioxide hydrate

The phase equilibrium of ocean carbon dioxide hydrate should be understood for ocean storage of carbon dioxide. In this paper, the isochoric multi-step heating dissociation method was employed to investigate the phase equilibrium of carbon dioxide hydrate in a variety of systems (NaCl solution, submarine pore water, silica sand+NaCl solution mixture). The experimental results show that the depression in the phase equilibrium temperature of carbon dioxide hydrate in NaCl solution is caused mainly by Cl− ion. The relationship between the equilibrium temperature and freezing point in NaCl solution was discussed. The phase equilibrium temperature of carbon dioxide hydrate in submarine pore water is shifted by −1.1K to lower temperature region than that in pure water. However, the phase equilibrium temperature of carbon dioxide hydrate in mixture samples of coarsed-grained silica sand and NaCl solution is in agreement with that in NaCl solution with corresponding concentrations. The relationship between the equilibrium temperature and freezing point in mixture samples was also discussed.

X-ray computed-tomography imaging of gas migration in water-saturated sediments: From capillary invasion to conduit opening

[1] The strong coupling between multiphase flow and sediment mechanics determines the spatial distribution and migration dynamics of gas percolating through liquid-filled soft granular media. Here, we investigate, by means of controlled experiments and computed tomography (CT) imaging, the preferential mode of gas migration in three-dimensional samples of water-saturated silica-sand and silica-silt sediments. Our experimental system allowed us to independently control radial and axial confining stresses and pore pressure while performing continuous x-ray CT scanning. The CT image analysis of the three-dimensional gas migration provides the first experimental confirmation that capillary invasion preferentially occurs in coarse-grained sediments whereas grain displacement and conduit openings are dominant in fine-grained sediments. Our findings allow us to rationalize prior field observations and pore-scale modeling results, and provide critical experimental evidence to explain the means by which conduits for the transit of methane gas may be established through the gas hydrate stability zone in oceanic sediments, and cause large episodic releases of carbon into the deep ocean.

Uncertainties in determining microbial biomass C using the chloroform fumigation–extraction method

We tested the accuracy of the chloroform fumigation–extraction method, which is commonly used to determine soil biomass C concentrations. Accurate and precise determination of total microbial biomass is important in order to characterize soil properties and to develop predictive metal transport models for soils. Two natural soils, and individual soil components, including silica sand, montmorillonite, kaolinite, a humic acid, and Bacillus subtilis bacterial cells, were fumigated for 24 h. Following the fumigation, C from fumigated and unfumigated samples was extracted using a 0.5 M K 2SO 4 solution. The difference between the C content in the fumigated and unfumigated samples ideally represents C due to biomass because the fumigation procedure should lyse cells and release biomass C. We observed increased C release upon fumigation for bacteria-only samples, confirming the ability of fumigation to lyse cells. There was no difference in extracted C concentration between fumigated and unfumigated samples of silica sand and of humic acid, confirming that the fumigation process does not introduce additional organic C to samples of these soil components. However, the fumigated clay samples both showed increased C release relative to the unfumigated controls, indicating that significant concentrations of the fumigant, chloroform, adsorbed onto the clay minerals studied here. Additionally, we found significant chloroform remaining in the extracts from two fumigated natural soils. Attempts to remove the chloroform from the soils or soil components prior to extraction by increasing the evacuation time, or to remove chloroform in the extracts by sparging them vigorously with nitrogen gas, both failed. This research reveals that chloroform gas may adsorb significantly to clays and the clay fraction of natural soils. Thus, the fumigation–extraction method must be corrected to account for the added chloroform C and accurately assess the concentration of biomass C in soils that contain significant concentrations of clays.

Comparison of the water change characteristics between the formation and dissociation of methane hydrate and the freezing and thawing of ice in sand

Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.

The minimum bubbling velocity of fluidized beds operating at high temperature

The paper studies the influence of operating temperature on the transition of a fluidized bed to the bubbling regime. Fluidization experiments and collapse tests were performed in a 54mm i.d. transparent column on samples of FCC, silica sand and corundum, at temperatures ranging from 30 to 500°C. All the solids investigated, included in group A of Geldart classification, exhibited homogeneous expansion after fluidization at all temperatures. Depending on the technique adopted to identify the velocity at which the bed enters the bubbling regime, different trends of u mb versus T are observed. Such results are analysed together with the expansion behaviour of particle systems of various densities, illustrated by diagrams built with data of fluidization and collapse experiments. The role exerted by thermally induced interparticle forces in delaying the onset of steady bubbling is highlighted, as well as the opportunity of adopting a definition of u mb of practical meaning.

The influence of grading on the shear strength of loose sands in stress-controlled ring shear tests

Three silica sand samples—well graded, intermediately graded, and narrowly graded—having different uniformity coefficients, were constituted to allow the investigation of the influence of particle size distribution on their mechanical behavior. Using a ring shear apparatus, samples were tested under a wide range of laboratory conditions. Results of the tests clearly indicate that, for specimens confined under identical stress conditions, well-graded specimens have higher values of peak and steady state strengths than the rest of the specimens. A relationship between uniformity coefficient and shear strengths shows that the higher the uniformity coefficient, the higher the shear strength. On account of these, well-graded specimens have higher static liquefaction resistance than the poorly graded specimens. Within the range of normal stresses employed in the tests, results reveal that not only are poorly graded sands more likely to suffer higher postfailure strength reduction, but that their steady-state strengths are easily reduced to zero, the magnitude of the confining stress notwithstanding. This reduction of shear resistance to zero has been described as complete liquefaction in this paper. While almost all of the narrowly graded specimens suffered complete liquefaction, widely graded ones did not; an observation that seem to highlight the influence of grading on the mechanical behavior of the sands.