Mixture Of Silica Sand Research Articles

On the undrained shear behavior of sand mixtures with non-plastic fines subjected to large shear displacement

Fluidized landslides pose significant hazards owing to the catastrophic failure and flow-like behavior with high mobility and long traveling distances. Non-plastic fines can be abundant in many fluidized landslides with 30%–40% content of relatively fine-grained particles. However, the role of fine particles in the initiation and movement of these landslides is not well understood. To investigate the effects of non-plastic fines content (FC) on the undrained shear behavior of the mixture, undrained ring shear tests were performed on mixtures of silica sand (D50 = 0.16 mm) with varying weight proportions of non-plastic fines (D50 = 0.035 mm) with different initial densities. We showed that liquefaction potential increased as fines content increased and initial density decreased. Peak strength (τp), steady-state strength (τss), and total dissipated shear energy to the steady state (Wss) increased against increasing density of the sample. Given the same initial density, τp, τss, and Wss decreased with the increases of FC. Using intergranular void ratio (es) and equivalent intergranular void ratio (es⁎), we found that plots of τp, τss, and Wss against es⁎ merged to a relatively narrow domain, indicating es⁎ can serve as a comprehensive indicator for evaluating the FC's effects on undrained shear behavior. An optimum es⁎ existed for the mixtures, which corresponds to the minimal brittleness index IB, that is used for analyzing liquefaction associated with post-failure behavior. The Wss in the log scale continuously decreased with increasing es⁎. We inferred that the addition of fine particles could change the inter-particle force transfer. When the FC increases, a greater proportion of fines can actively engage in the forces transferring structure as active fine particles, resulting in increasing liquefaction potential and reducing the energy dissipation throughout the entire shearing process of the saturated mixtures, thereby facilitating the fluidization and mobility of landslides. This study provides an evaluation of the full liquefaction process of fines-rich mixtures and further explains the fines' role in the high mobility of fluidized landslides based on the energy dissipation view.

Extraction of Silicon From Silica Sand by Carbothermic Reduction in Mini DC-EAF

This study explores silicon extraction from silica sand using different carbon sources: graphite powder, coke, and coconut shell charcoal. Experiments were conducted to assess the influence of carbon source variation and briquetting on metallic silicon production. The silica sand sample was characterized using X-ray fluorescence, while proximate analysis was performed on the coke and coconut shell charcoal reductants. Each experiment used 50 grams of silica sand with varying amounts of carbon sources at a C:SiO2 mole ratio of 1.8:1. The reductants were tested both with and without briquetting using a DC electric arc furnace for 10 minutes. SEM-EDS and X-ray diffraction were employed for result analysis, with comparisons made to other materials. The experiment using coke as a reductant with briquetting yielded the best result with a Si content in the metal of 98.15%. The experiment with a mixture of silica sand and coconut shell charcoal briquette resulted in a SiC product with Si content of 54.46%. The experiment with a mixture of silica sand and graphite briquette resulted in a SiO2 and SiC product with Si content of 43.17%. The experiment without briquetting using coke as a reductant showed a high SiO2 content, as seen from the oxygen content of 36.44%. The experiment without briquetting using coconut shell charcoal as a reductant resulted in a SiO2 and SiC with Si content of 26.64%. The mixture of silica sand and graphite without briquetting produce SiC as a product with Si content of 70.6%.

Assessing the influence of non-plastic fines on rainfall-induced landslide initiation and propagation: Flume test findings

Numerous fluidized landslides with long runout distances and fast movements have been triggered by heavy rainfall under climate change. Non-plastic fines are frequently involved in many fluidized landslides. However, the role of fines in the initiation and movement of landslides has not been well understood. This study aimed to investigate the role of non-plastic fines in the initiation and movement of rainfall-induced landslides in a flume test setup. The experiments were conducted using mixtures of silica sand (D50 = 0.16 mm) with different non-plastic fines (D50 = 0.035 mm) content under different initial densities. The results demonstrated that the behavior of landsliding greatly depends on fines content (FC) and initial packing density (presented by density index, Id) of the soil layers in the flume. The landsliding phenomena could be classified into five failure modes, including slow and fast retrogressive individual sliding, sudden multiple sliding, and deep-seated and shallow fluidized sliding. As the FC increased or Id decreased, the landsliding behavior gradually evolved from slow retrogressive individual sliding to shallow fluidized sliding. For the tests with Id ≥ −0.06, the peak velocity (Vp) of the landsliding increased continuously with FC. Conversely, for the tests with Id ≤ −0.19, an optimal FC of 30 % was identified at which Vp reached its maximum. Additionally, for FC ≤ 10 %, Vp decreased with the increasing Id, while for FC ≥ 20 %, an optional Id existed at which Vp reached its maximum for a given FC, and the value of optimal Id (−0.2 ∼ −0.04) varied with FC (20 % ∼ 40 %). The peak pore-water pressure (PWP) (up) generally increased with the increase of FC. Furthermore, an optimal Id existed at which the PWP built up after landsliding occurrence (Δu) reached its maximum. The equivalent intergranular void ratio (es*) and equivalent interfine void ratio (ef*), which are calculated by considering both FC and void ratio, are found to be appropriate indices for evaluating and explaining the role of fines in the observed landsliding behavior. In conclusion, the addition of non-plastic fines can change the structure of test materials and result in different failure modes and mobility of landslides by affecting both interparticle contacts and PWP responses. These findings provide insights into the mechanisms of landsliding behavior and have implications for the assessment and mitigation of landslides in geotechnical engineering.

Easily Pyrolyzable Biomass Components Significantly Affect the Physicochemical Properties and Water-Holding Capacity of the Pyrolyzed Biochar

The influences of feedstocks on biochar properties are widely reported. However, the influence of the transformation of biomass components (mainly cellulose, hemicellulose, and lignin) during feedstock pyrolysis on the obtained biochar has not been clearly stated. Here, biochar was pyrolyzed from four biomass types with different fractions of the three main components, of which surface area, pore structure, functional group, and thermogravimetric analyses were conducted. Further, we investigated the links among the physicochemical properties and water-holding capacity (WHC) of the biochar by measuring the WHC of a biochar–silica-sand (SS) mixture. Cellulose and hemicellulose were considered the easily pyrolyzable components of the feedstock owing to their low thermal stabilities. Additionally, the thermal decomposition of the easily pyrolyzable components caused the disappearance of most functional groups from the biochar that was synthesized at >350 °C. Moreover, the WHC of the biochar–SS mixture correlated significantly with the surface area and pore volumes of the biochar. Notably, the thermal residual mass and the WHC of the biochar–SS mixture exhibited the strongest correlation. Poplar wood sawdust (PT), which accounted for the highest mesopore volume of the biochar sample, contained the highest amount (86.09%) of the easily pyrolyzable components. The PT-derived biochar exhibited superior WHC than other biochar types, indicating that the dehydration, deoxygenation, and condensation of the easily pyrolyzable components of biomasses promoted gradual pore formation, further contributing to the increased WHC of the mixture. Rather than high-temperature-pyrolyzed biochar, PT350 demonstrated the highest WHC (599 mg/g), revealing that attention should be drawn to the contribution of low-temperature-pyrolyzed biochar to soil water retention in future research.

The Effect of Silica Powder Based on Methyltrimethoxysilane and Silica Sand as a Hydrophobic Material

In this research, a hydrophobic surface has been successfully created using a mixture of silica sand and methyltrimethoxysilane (MTMS) precursor. This research aims to determine the effect of varying the volume of MTMS on the hydrophobic surface. The MTMS as silica precursor was synthesized with Stöber method. The variation used is the volume of the MTMS precursor, while the silica from silica sand is made constant. The volume variation of the MTMS precursor is 9.5 ml, 19 ml, 28.5 ml and 38 ml. The MTMS/SiO2 composite which has been synthesized then get mixed with steel ship paint and coated on the steel plate surface as a topcoat. The MTMS/SiO2 composite was further characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Water Contact Angle (WCA), and Atomic Force Microscope (AFM) which were employed to investigate crystal structure, morphology of particle, hydrophobicity on a surface, and topography of the three-dimensional surface layer respectively. The type of liquid used in the WCA characterization is seawater. XRD characterization results show that silica sand has a quartz phase, MTMS has an amorphous phase and MTMS/SiO2 composite tends to have an amorphous phase. SEM characterization show that the particle size of silica sand that has been mixed with MTMS is around 8 – 20 μm. WCA characterization show that the addition of silica powder on the topcoat increase surface roughness and WCA, so that the steel plate surface has good hydrophobic properties. The highest water contact angle obtained in this research was 109o by seawater.

Feasibility of measuring moisture content of green sand by a low frequency multiprobe detector based on dielectric characteristics

Green sand is a mixture of silica sand, bentonite, water and coal powder, and other additives. Moisture content is an important index to characterize the properties of green sand. Based on the dielectric characteristics of green sand and transmission line theory, a method for rapidly measuring the moisture content of green sand by means of a low frequency multiprobe detector was proposed. A system was constructed, where six detectors with different arrangements and probes were designed. The experimental results showed that the voltage difference of transmission line increases with the increasing frequency before 29 MHz while decreases after 35 MHz. A voltage difference platform occurs in the range of 29–35 MHz, which is suitable for measuring the moisture content due to its insensitivity to frequency. The electric field intensity gradually decreases with the increase of the probe depth, and the intensity of central probe is always greater than that of the edge probe. When the distance of the probe away from the sand sample surface is 80 mm, the electric field intensity of the edge probe is found to be very weak. The optimal excitation frequency for measuring the moisture content of green sand is 29–33 MHz. The optimal detector is the one with one center probe and three edge probes, and their lengths are 80 mm and 60 mm, respectively. The distance between the center and edge probes is 25 mm, and the diameter of probes is 5 mm. Taking the voltage difference of transmission line, bentonite content, coal powder content and compactability as parameters of the input layer, and the moisture content as a parameter of the output layer, a three-layer BP artificial neural network model for predicting the moisture content of green sand was constructed according to the experimental results at 33 MHz. The prediction error of the model is not higher than 3.3% when the moisture content of green sand is within the range of 3wt.%–7wt.%.

Shear rate effect on the residual strength of saturated clayey and granular soils under low- to high-rate continuous shearing

The residual strength of sliding basal soils plays a pivotal role not only in the movement of bedding landslides controlled by clay-rich interlayers but also in remobilized granular deposits. Many studies have focused on better understanding the residual shear behaviors of clayey and granular soils under relatively low shear rates. However, the residual strength varies with various clay fractions for clayey soils and fine-size fractions for granular soils, as well as shear rates (especially in fast ranges) need further examined. In the present research, results of a low- to high-rate continuous ring shear test on a clayey soil and three granular soils at the shear rates ranging from 0.5 to 50.0 mm/s were reported. The clayey soil was remolded from the shear zone soil of a bedding landslide controlled by a clay-rich interlayer with main minerals of illite-smectite, and the granular soils included two silica sands and one mixture of silica sand with fine granite residual soil particles. The results show that saturated clayey soil has an obvious positive shear rate effect on its residual strength after a certain shear rate; the mechanism is the transformation of shear mode, i.e., from sliding shearing to turbulent shearing with the increasing of shear rate. The high clay fraction may promote this transformation of shear mode. In addition, the critical shear rate of the clayey soil that has a positive shear rate dependency of the residual strength (i.e., rate-strengthening) is related to the clay fraction, i.e., a smaller critical shear rate appears in the clayey soil with higher clay fraction. The residual strength of saturated granular soils with different fine-size fractions do not show any shear rate-dependent, while the fine-size fraction affects the residual strength both in drained and undrained conditions; that is, the higher the fine-size fraction is, the lower the residual strength is. Moreover, the neutral shear rate effect of granular soils in this study may be related to the low normal stress and low shear rate range. The authors believe that, results such as those obtained in this work, may be useful for developing a more suitable constitutive model to better understand the postfailure motion (or reactivation kinematics) of bedding landslides controlled by clay-rich interlayers, as well as rock avalanche deposits remobilized by heavy rainfall.

Investigation on Different Compositions of Clay and Water to the Permeability of the Silica Sand Used in Greensand Casting Mould

Greensand casting is a casting process that uses mixture of silica sand with addition of control additions which are bentonite clay and the presence of water. Control additions influence the mechanical properties of greensand casting mould, for this study focuses on the permeability. Bentonite clay acts as a binder and activated by water to develop strength and plasticity thus the greensand casting mould can be formed. Permeability is ability of gas to pass through the moulding mixture aggregates in order to reduce the defects due to trapped gasses in mould cavity such as blow holes or pin holes. The objective of this study is to investigate the effect of control addition (water and clay) on the permeability number of silica sand sample (tailing sand) from former tin mine site in Tronoh, Perak. Experiments are conducted according to American Foundrymen Society (AFS) standard of procedures. Sand sample is sieved using mechanical sieve shaker to size of 425 µm. Cylindrical test pieces dimensioning of Ø50 mm×50 mm in height from various mixtures of sand-clay–water ratios are compacted by applying three ramming blows of 6666 grams using Ridsdale-Dietert metric standard rammer. The test pieces are tested for permeability with Ridsdale-Dietert permeability meter. The results show that clay and water have affected the permeability of silica sand sample and when more water and clay added, into the moulding mixture, the permeability is found decreased. The appropriate allowable water and clay content are crucial for permeability number of greensand casting mould.

Effects of the NaCl Concentration and Montmorillonite Content on Formation Kinetics of Methane Hydrate

Most resources of natural gas hydrate (NGH) exist in marine sediments where salts and sea mud are involved. It is of great importance to investigate the effects of salts and sea mud on NGH formation kinetics. In this study, the mixture of silica sand and montmorillonite was used to mimic sea mud. The effects of the NaCl concentration of pore water and montmorillonite content on methane hydrate formation were studied. A low NaCl concentration of 0.2 mol/L and a low montmorillonite content range of 10–25 wt% is beneficial to reduce the induction time of hydrate formation. The high NaCl concentration and high content of montmorillonite will significantly increase the induction time. The average induction time for the experiments with the NaCl concentrations of 0, 0.2, 0.6, and 1.2 mol/L is 20.99, 8.11, 15.74, and 30.88 h, respectively. In the pure silica sand, the NaCl concentration of 0.2 mol/L can improve the final water conversion. In the experiments with pure water, the water conversion increases with the increase of the montmorillonite content due to the improvement of the dispersion of montmorillonite to water. The water conversion of the experiments in pure water with the montmorillonite contents of 0, 10, 25 and 40 wt% is 12.14% (±1.06%), 24.68% (±1.49%), 29.59% (±2.30%), and 32.57% (±1.64%), respectively. In the case of both montmorillonite and NaCl existing, there is a complicated change in the water conversion. In general, the increase of the NaCl concentration enhances the inhibition of hydrate formation and reduces the final water conversion, which is the key factor affecting the final water conversion. The average water conversion of the experiments under the NaCl concentrations of 0, 0.2, 0.6 and 1.2 mol/L is 24.74, 15.14, 8.85, and 5.74%, respectively.

Investigation of the Influence of Moisture Content on Fatigue Behaviour of HPC by Using DMA and XRCT.

High-performance concrete (HPC) is a topic of current research and construction projects, due to its outstanding compressive strength and durability. In particular, its behaviour under high-cycle fatigue loading is the focus of current investigations, to further pave the way to highly challenging long-lasting constructions; e.g., bridges or offshore buildings. In order to investigate the behaviour of HPC with different moisture contents in more detail, a mixture of silica sand and basalt aggregate with a maximum grain size of 8 mm was investigated with three different moisture contents. For this purpose, cyclic compressive fatigue tests at a loading frequency of 10 Hz and different maximum stress levels were performed. The main focus was the moisture influence on the number of cycles to failure and the development of concrete temperature and strain. In a further step, only the mortar matrix was investigated. For this purpose, the mixture was produced without basalt, and the moisture influence was investigated on smaller-sized test specimens using dynamic mechanical analysis (DMA) and X-ray computed tomography (XRCT). It was shown that the moisture content of HPC had a significant influence on the fatigue damage behaviour due to the number of cycles to failure decreasing significantly with increased moisture. In addition, there was also an influence on the temperature development, as well as on the strain development. It was shown that increasing moisture content was associated with an increase in strain development. XRCT scans, in the course of the damage phases, showed an increase in internal cracks, and made their size visible. With the help of DMA as a new research method in the field of concrete research, we were also able to measure damage development related to a decrease in sample stiffness. Both methods, XRCT and DMA, can be listed as nondestructive methods, and thus can complement the known destructive test methods, such as light microscopy.

Green strength properties of waterjet abrasive waste as potential composition in green mould by Taguchi and ANOVA approach

The sand casting process still continues today due to the cost-effectiveness of materials and processes. There is a wide variety of castings related to composition and size, but silica sand is widely available from coastal line mining and has a negative impact on the environment. Moreover, waste from waterjet cutting of non-ferrous and ferrous metals is practically unhazardous and may potentially be used in sand casting mould. The aim of this paper is to optimize the proportion of coal dust, water and bentonite added to the silica sand mixture and the waterjet cutting abrasive waste as a new way of handling waste with the potential to be used in sand casting manufacturing. The method used was L9 orthogonal array optimization and the composition was qualitatively measured using a green compression strength test and a green shear strength test. Factors were evaluated using the analysis of variance (ANOVA) to find the the critical factors while confirmation test was conducted for the optimal material proportion. The study concluded that the ideal ratio for silica sand mixture with waterjet abrasive waste is bentonite-12%, coal dust-5%, and water-7% for green compression strength while bentonite-12%, coal dust-6%, water-7% for green shear strength. With proper selection, the incorporation of waterjet abrasive waste into the green sand mixture is promising to potentially be used in green sand mould casting without undermine the quality of mould.

Impact of Carbon Particle Character on the Cement-Based Composite Electrical Resistivity.

Electroconductive cement-based composites are modern materials that are commonly used in many industries such as the construction industry, among others. For example, these materials can be used as sensors for monitoring changes in construction, grounding suspension, and resistance heating materials, etc. The aim of the research presented in this article is to monitor the impact of carbon particle character on cement-based electroconductive composites. Four types of graphite were analyzed. Natural and synthetic types of graphite, with different particle sizes and one with improved electrically conductive properties, were tested. For the analysis of the electrical conductivity of powder raw materials, a new methodology was developed based on the experience of working with these materials. Various types of graphite were tested in pure cement paste (80% cement, 20% graphite) as well as in a composite matrix, which consisted of cement (16.8%), a mixture of silica sand 0–4 mm (56.4%), graphite filler (20.0%) ground limestone (6.7%) and super plasticizers (0.1%). The resistivity and physical-mechanical properties of the composite material were determined. Furthermore, the resistivity of the test samples was measured with a gradual decrease in saturation. It may be concluded that graphite fillers featuring very fine particles and high specific surface are most suitable and most effective for creating electrically conductive silicate composites. The amount, shape and, in particular, the fineness of the graphite filler particles thus creates suitable conditions for the creation of an integrated internal electricity-conductive network. In the case of the use of a coarse type of graphite or purely non-conductive fillers, the presence of an electrolyte, for example, in the form of water, is necessary to achieve a low resistivity. Samples with fine types of graphite fillers achieved stable resistivity values when the sample humidity changed. The addition of graphite fillers caused a large decrease in the strength of the samples.

Evaluation of Heterogenous Oxidation Reaction of Copper Concentrate/ Silica Sand Mixture by Dropping Method

Evaluation of Heterogenous Oxidation Reaction of Copper Concentrate/ Silica Sand Mixture by Dropping Method

Metakaolin and demolition wastes in eco-based sand consolidated concrete

This study was undertaken to valorize naturally occurring silica sand in the synthesis of new consolidated concrete materials. The mixtures of silica sand, calcium sulphate, commercial metakaolin, demolition materials were designed to propose sulphate and sodium silicate/NaOH activate concretes and geopolymers, respectively. Three raw silica sand samples were collected from various locations in Tunisia. The obtained new materials were characterized by SEM and mechanical properties were investigated.The calcium sulphate-based concretes displayed good technological properties with a compressive strength close to 15MPa and 40–56% of water adsorption. When, metakaolin and demolition reject were added the mechanical resistance decreased due to the lower pozzolanic properties of these materials.Concerning the geopolymer-based sand concrete, lower compressive strength values were registered. Moreover, by incorporating demolition materials, the mechanical resistance decreased in all consolidated products. The effect of the metakaolin reactivity is more significant when it is activated with a alkaline solution. However, the sodium silicate/NaOH activation of metakaolin governs the reaction when it is highly reactive.Finally raw silica sand from Tunisia provided good consolidated concrete materials in the presence of calcium sulphate. As well, the silica sand provided good geopolymers in the presence of metakaolin and alkaline solution.

Quality of water recovered by treating acid mine drainage using pervious concrete adsorbent

In this paper, a batch experiment was conducted to evaluate the water quality obtained from using pervious concrete (PERVC) technology to treat acid mine drainage (AMD). The study proposes an innovative application of PERVC as a permeable reactive barrier liner in evaporation ponds. The effectiveness of PERVC adsorbent in removing heavy metals was compared with that of zero-valent iron (ZVI) of particle size 1.0 to 1.8 mm. The AMD used in the study was obtained from abandoned gold and coal mines. PERVC mixtures consisted of granite aggregate and ordinary Portland cement CEM I 52.5R (CEM I) or CEM I containing Class F 30% fly ash (30%FA) as a cement replacement material. ZVI was prepared from a mixture of silica sand and iron grit of specific sizes. PERVC and ZVI media were used to conduct batch reactor tests with AMD, for a period of 43 days at a ratio of 1 L of reactive material to 3 L of AMD. The quality of treated AMD was compared against effluent discharge standards. The contaminants Al, Fe and Zn were effectively removed by both PERVC and ZVI. Also, both adsorbents reduced Ni, Co and Cu to levels below those measured in raw AMD. However, PERVC was more effective in removing Mn and Mg while ZVI was ineffective. Although PERVC removed more heavy metals and with greater efficiency than ZVI, the PERVC-treated water showed high pH levels and exhibited elevated Cr6+ concentrations, owing to leaching from the cement and fly ash materials used in PERVC mixtures.

Characterization of Capillary Pressure–Saturation Relationships for Double-Porosity Medium Using Light Transmission Visualization Technique

Capillary pressure saturation (Pc–Sw) relationship plays a central role in the description of fluid flow in porous media. In this research, the light transmission visualization (LTV) technique was applied to characterize the Pc–Sw relationship in a double-porosity medium. Four experiments were conducted in two-dimensional (2-D) flow chambers packed with a double-porosity medium composed of a mixture of silica sand and sintered kaolin clay spheres. In each experiment, a different volumetric fraction of macropores and micropores was used. The experiment was also repeated by compacting the flow chamber with silica sand only to represent single-porosity medium. Variable saturations of water across the height of the system were applied by controlling the capillary pressure. Images of the 2-D model were collected using a digital camera and analyzed pixel by pixel to determine water saturation in the double-porosity medium. Results from the LTV technique showed that the Pc–Sw relationships for all experiments in double-porosity soil medium were similar in shape but varied depending on the porous media composition. Comparison with the pressure cell test results showed that the Pc–Sw curves for all experiments consistent comparable to those obtained by the LTV technique. The Pc–Sw curves were also fit to van Genuchten model for comparison and validation. For double-porosity media, the best-fit parameters were consistent with published data for sandy clay. Moreover, little variability was observed in the best-fit α and n values for the different double porosity. Overall, this study proves that the LTV technique is a noninvasive laboratory tool that can provide high-resolution spatial data for water saturation distribution in different types of porous media and is capable of producing highly resolved Pc–Sw relationships.

Removal of pharmaceutical compounds, artificial sweeteners, and perfluoroalkyl substances from water using a passive treatment system containing zero-valent iron and biochar.

Emerging contaminants are widely detected and persistent in environmental waters. Advanced oxidation processes are among the most effective methods for removing emerging contaminants from water; however, high energy consumption greatly increases the operating costs and limits large-scale applications. In this study, a passive treatment system consisting of four columns packed with mixtures of silica sand, zero-valent iron (ZVI), biochar (BC), and a mixture of (ZVI + BC) were evaluated for simultaneous removal of eight pharmaceuticals, four artificial sweeteners, and two perfluoroalkyl substances (PFASs) from water. Overall, the passive treatment system was more effective for removing target pharmaceuticals (almost complete removal) than artificial sweeteners and PFASs (partial removal). Columns ZVI, BC, and (ZVI + BC) exhibited similarly effective removal (>97%) of target pharmaceuticals, including carbamazepine, caffeine, sulfamethoxazole, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, ibuprofen, gemfibrozil, and naproxen, from ~9 to <0.25 μg L-1; pharmaceuticals were more rapidly removed by Columns ZVI and (ZVI + BC) than Column BC, except for ibuprofen. Column ZVI was more effective for removing artificial sweeteners acesulfame-K and sucralose than Columns BC and (ZVI + BC); however, BC exhibited relatively greater removal of saccharin than ZVI and (ZVI + BC). Acesulfame-K and saccharin (~110 μg L-1) were partially removed in the treatment columns. Cyclamate was not removed in any of the columns. However, >76% of input sucralose (~110 μg L-1) was removed in the three treatment columns. Reactive medium BC alone was more effective for removing target PFASs than ZVI and (ZVI + BC). Input perfluorooctanoic acid (PFOA) (~45 μg L-1) was partially removed in the columns containing BC but not ZVI alone. Between 10 and 80% of input perfluorooctane sulfonic acid (PFOS) (24 ̶ 90 μg L-1) was removed in Column ZVI; greater removals (57 ̶ 99%) were observed in Columns BC and (ZVI + BC).

Targeted nanoparticle binding & detection in petroleum hydrocarbon impacted porous media

Targeted nanoparticle binding has become a core feature of experimental pharmaceutical product design which enables more efficient payload delivery and enhances medical imaging by accumulating nanoparticles in specific tissues. Environmental remediation and geophysical monitoring encounter similar challenges which may be addressed in part by the adoption of targeted nanoparticle binding strategies. This study illustrates that engineered nanoparticles can bind to crude oil-impacted silica sand, a selective adsorption driven by active targeting based on an amphiphilic polymer coating. This coating strategy resulted in 2 mg/kg attachment to clean silica sand compared to 8 mg/kg attachment to oil-impacted silica sand. It was also shown that modifying the surface coating influenced the binding behaviour of the engineered nanoparticles – more hydrophobic polymers resulted in increased binding. Successful targeting of Pluronic-coated iron oxide nanoparticles to a crude oil and silica sand mixture was demonstrated through a combined quantitative Orbital Emission Spectroscopy mass analysis supported by Vibrating Scanning Magnetometer magnetometry, and a qualitative X-ray micro-computed tomography (CT) visualization approach. These non-destructive characterization techniques facilitated efficient analysis of nanoparticles in porous medium samples with minimal sample preparation, and in the case of X-Ray CT, illustrated how targeted nanoparticle binding may be used to produce 3-D images of contaminated porous media. This work demonstrated successful implementation of nanoparticle targeted binding toward viscous LNAPL such as crude oil in the presence of a porous medium, a step which opens the door to successful application of targeted delivery technology in environmental remediation and monitoring.

Microsilica in Sodium Silicate Bonded Sands

This paper investigates the microsilica addition value in the improvement of the sand molds and cores properties made with sodium silicate binders. There are experiments confirming the importance of the better sand mixtures mobility in the strengthening of these molds and cores. The paper explains the difference between microsilica and nanosilica in their interaction with alkaline silicate solutions and shows how the products of this interaction affect the properties of the sand mixtures. The results presented in the paper show the role of microsilica in curing sodium silicate bonded sands and demonstrate more possibilities to spread its positive complex effect on the sand molds and cores cured chemically, without heat. Conducted experiments with these sands proved the benefits of applying microsilica as a sand additive for increasing density and strength of the molds and cores, for easing their shakeout by lowering silicate level in the binder system. It is shown that the microsilica presence in the powder component allows using a hydrous sodium silicate powder also as a part of this component to replace a liquid sodium silicate in the two-component silicate binder system as well as creating pourable dry mixtures of silica sand and all solid additives of the binder system.

On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite

In order to expand the application of the induced polarization (IP) method as a technique for monitoring metallic mineral dissolution and precipitation mechanisms, we studied the effects of variations in pore water chemistry on the spectral induced polarization (SIP) response of a mixture of silica-sand and pyrite particles in the laboratory. We investigated the dependence of the SIP response on both pore water conductivity and pH for various chemical compositions: redox-passive (P) versus redox-active (A) ions, using CaCl2 as P-ions, and FeSO4 and FeCl3 as A-ion brines. The effect of pore water chemistry was evaluated by means of a recently proposed volumetric specific capacitance model. The SIP response (IP-effect) was primarily determined by the pore water conductivity and the specific capacitance was only weakly dependent on the chemical composition and pHw. We found that the specific capacitance varies to first order over a limited range and approximates a single value (≈302Fm−3 in average). However, variations in the specific capacitance as a function of active versus inactive ion chemistry might be important to consider when using IP to monitor specific mineral dissolution and precipitation processes.