Silicate Impurities Research Articles

Denudation and Weathering Rates of Carbonate Landscapes From Meteoric 10Be/9Be Ratios

AbstractKnowledge of the rates of carbonate rock denudation, the relative apportionment of chemical weathering versus physical erosion, and their sensitivity to climate, vegetation, and tectonics is essential for disclosing feedbacks within the carbon cycle and the functioning of karst landscapes that supply important services to humans. Currently, however, for carbonate lithologies, no method exists that allows to simultaneously partition denudation into erosion and weathering fluxes at spatial scales ranging from soil to watersheds. To determine total denudation rates in carbonate landscapes from an individual soil or river sample, we adapted a published framework that combines cosmogenic meteoric 10Be as an atmospheric flux tracer with stable 9Be that is released from rocks by weathering, to the limestone‐dominated French Jura Mountains. By analyzing water, soil, sediment, travertine, and bedrock for 10Be/9Be, major and trace elements, carbon stable isotopes and radiogenic strontium, we quantified contributions of Be from primary versus secondary carbonate phases and its release during weathering from carbonate bedrock versus silicate impurities. We calculated partitioning of Be between solids and solutes, and rates of catchment‐wide (from sediment) and point source (from soil) denudation, weathering and erosion. Our results indicate that average denudation rates are 300–500 t/km2/yr. Denudation is dominated by weathering intensity (W/D) ratios of >0.92, and a non‐negligible contribution from deeper (below soil) weathering. Our rates agree to within less than a factor of two with decadal‐scale denudation rates from combined suspended and dissolved fluxes, highlighting the substantial potential of this method for future Earth surface studies.

Developing a data-driven soft sensor to predict silicate impurity in iron ore flotation concentrate

Soft sensors are mathematical models that estimate the value of a process variable that is difficult or expensive to measure directly. They can be based on first principle models, data-based models, or a combination of both. These models are increasingly used in mineral processing to estimate and optimize important performance parameters such as mill load, mineral grades, and particle size. This study investigates the development of a data-driven soft sensor to predict the silicate content in iron ore reverse flotation concentrate, a crucial indicator of plant performance. The proposed soft sensor model employs a dataset obtained from Kaggle, which includes measurements of iron and silicate content in the feed to the plant, reagent dosages, weight and pH of pulp, as well as the amount of air and froth levels in the flotation units. To reduce the dimensionality of the dataset, Principal Component Analysis, an unsupervised machine learning method, was applied. The soft sensor model was developed using three machine learning algorithms, namely, Ridge Regression, Multi-Layer Perceptron, and Random Forest. The Random Forest model, created with non-reduced data, demonstrated superior performance, with an R-squared value of 96.5% and a mean absolute error of 0.089. The results suggest that the proposed soft sensor model can accurately predict the silicate content in the iron ore flotation concentrate using machine learning algorithms. Moreover, the study highlights the importance of selecting appropriate algorithms for soft sensor developments in mineral processing plants.

Quantification of Lignosulfonates and Humic Components in Mixtures by ATR FTIR Spectroscopy

The existing techniques for lignosulfonate (LS) in humate fertilizers lack selectivity to humic substances (HS) as the main component; they involve labor- and time-consuming sample preparation to separate the components at the level of detectable LS concentrations. The procedure based on attenuated total reflectance (ATR) FTIR spectroscopy with simple sample preparation for directly quantifying lignosulfonates in aqueous solutions and lignosulfonates and HS in aqueous solutions of preparations based on HS of coal origin (Sigma Aldrich, Powhumus, and Life Force) was developed. Lignosulfonate quantification is possible by exploiting the bands at 1266, 1192, 1093, and 1042 cm−1 with limits of detection of 0.4–2 g/L. Quantifying LS in a mixture with humates includes centrifugation of prepared solutions to separate interfering silicate impurities. LS quantification in the range of 10–100 g/L against HS (up to a 2-fold excess) with an error of up to 5% is possible based on the spectral absorptions at 1093 and 1042 cm−1. Simultaneous quantification of humate in the mixture with an error of up to 10% is possible by exploiting the bands at 1570 and 1383 cm−1 (carboxylates). The study shows the possibility of determining lignosulfonate against an HS background several times higher than lignosulfonate. The developed technique is applicable for analyzing fertilizers of simple composition and quality control of pure humates used for plant growth. Obtaining the most accurate results needs calibration solutions from the same brands that make up the test mixture.

Rice Husk Ash Incorporation in Calcium Aluminate Cement Concrete: Life Cycle Assessment, Hydration and Strength Development

In this research effect of rice husk ash (RHA), as silicate impurities, on the hydration reaction and mechanical strength of calcium aluminate cement (CAC) concrete, as one of the most important non-Portland cements, was investigated. Furthermore, in order to evaluate the environmental performance of mixtures, a lifecycle assessment was performed using the recipe midpoint and endpoint method. Compressive and tensile strength tests were conducted at the ages of 7, 28, and 90 days on specimens containing different contents of RHA (0, 2.5, 5, 7.5, and 10%) substituting for cement at the water-cement ratio of 0.4. Moreover, in order to calculate the hydration reaction of the specimens, thermogravimetric analysis (TGA) was performed at a rate of 10 °C/min to up to 1000 °C. The results revealed that the use of rice husk ash as a partial replacement at a concentration of 5% could reduce CO2 emission and ozone depletion by 18.75% and 31%, respectively. The findings indicate that, at 90 days, the mechanical strength of the mixes containing RHA were higher than those of the control mix, with the maximum improvement occurring at the substitution percentage of 5%. In accordance with TGA analysis the substitution of 5% RHA in CAC concrete led to a higher hydration level, which in turn improved the mechanical properties relative to the specimen without RHA at 90 days.

Silicon Contamination of the Praseodymium Doped Ceria Oxygen Surface Exchange Coefficient

Chemical oxygen surface exchange coefficients are used to quantify and rank the performance of oxygen exchange catalysts used in solid oxide fuel cell, solid oxide electrolysis cell, oxygen separation membrane, catalytic converter, and other oxygen-exchange-enabled devices. Unfortunately, during the manufacture and operation of these devices it is easy to introduce siliceous contaminants that degrade their oxygen exchange performance. Surprisingly, despite the well-known negative impact siliceous impurities have on the oxygen transport properties of ceria-based materials, quantitative measurements of how siliceous impurities impact the chemical oxygen surface exchange coefficient of praseodymium doped ceria are largely absent from the literature. In this work, the crystal structure, film thickness, surface composition, bulk composition, and chemical oxygen exchange coefficient of (100)-oriented PCO thin films with, and without, surface silica contaminants were evaluated via X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Secondary Ion Mass Spectroscopy (SIMS), and Curvature Relaxation (κR) experiments, respectively. The results show that siliceous surface phases only a few nanometers thick are capable of (1) reducing the PCO chemical oxygen surface exchange coefficient by approximately 3 orders of magnitude and (2) approximately doubling the activation energy for oxygen exchange.

Silicate impurities incorporation in calcium aluminate cement concrete: mechanical and microstructural assessment

ABSTRACT In this paper, the effect of rice husk ash (RHA), as silicate impurities, on the microstructure and mechanical properties of calcium aluminate cement concrete (CACC) is explored. Various mechanical tests, including tests for obtaining the compressive, splitting tensile, flexural strengths and elastic modulus, were performed on different mixture designs containing different volume percentages of RHA (0, 2.5, 5, 7.5, and 10%) at W/Cs of 0.4 and 0.5. Furthermore, the impact of RHA on the microstructure of this concrete was examined through careful analysis of the scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) results. The results demonstrate that, At W/C of 0.5, the microstructure and mechanical properties were improved, with the greatest improvement for the RHA substitution percentage of 5%. However, at W/C of 0.4, the addition of RHA showed no positive effect, which can be attributed to a higher specific surface area of RHA than cement.

Alkynyl-Based sp 2 Carbon-Conjugated Covalent Organic Frameworks with Enhanced Uranium Extraction from Seawater by Photoinduced Multiple Effects

Biofouling is a major obstacle to the efficient extraction of uranium from seawater due to the numerous marine microorganisms in the ocean. Herein, we report a novel amidoxime (AO) crystalline cova...

The role of polar organic components in dynamic crude oil adsorption on sandstones and carbonates

An appropriated wettability characterization is crucial for the successful implementation of waterflooding operations. Understanding how crude oil adsorption takes place on different mineral surfaces and how these processes impact reservoir wettability are essential aspects that can help unlock and produce large underground oil reserves.
 Polar organic components (POC) present in crude oil are surface-active molecules with high affinity towards mineral surfaces. POCs are quantified by the acid and base numbers (AN and BN) with units of mgKOH/g. The POC adsorption behavior is highly influenced by the type of minerals and brines present in the reservoir system.
 This study aims to shed light onto the most important features of oil adsorption on carbonates and sandstones mineral surfaces; particular attention is given to the role of acidic components. Therefore, outcrop sandstone and carbonate materials were used. The sandstone material contains various silicates, including quartz, Illite clay, and feldspars. The carbonate outcrop material came from the Stevns Klint quarry in Denmark and is considered a very pure calcium carbonate with minimum silicate impurities.
 Dynamic adsorption tests were performed at 50°C by injecting low asphaltene crude oils into core plugs, and AN and BN values of the effluent oil samples were measured and compared with the influent oil values. Furthermore, spontaneous imbibition (SI) tests were performed to assess the wettability impact of crude oil injection in oil flooded cores.
 The results showed that after crude oil injection, the cores became mix-wet. Confirmation of a reduction in capillary forces and a shift towards a less water-wet state was reported for both mineralogies, i.e., sandstones and carbonates. The acidic polar components had a substantial impact on carbonates wettability, while on sandstones, the experiments suggested that acidic polar components had a lower impact on wettability than that observed in the basic polar components.

Effects of silicate impurities on fracture behavior and microstructure of calcium aluminate cement concrete

In this paper, to accurately evaluate the effect of the variation of the silica content in Calcium aluminate cement concrete, the fracture parameters of concrete made with this cement were investigated at different substitution levels of rice husk ash (RHA), as a material containing the amorphous silica content of more than 90%. The three-point bending test was conducted on 150 notched beams with water to cement ratios (W/Cs) of 0.4 and 0.5 based on the RILEM code specifications. For all of the mix designs, the fracture parameters were determined via two different methods, i.e., the work of fracture method (WFM) and the size effect method (SEM). At W/C of 0.5, substituting RHA led to improved fracture parameters, with the maximum values seen in the mix with a substitution level of 5%. However, at W/C of 0.4, as the substitution level of RHA increased, the fracture parameters decreased. The pozzolanic property, higher specific surface area, and greater water demand of RHA relative to cement at the W/C of 0.5 (due to more free water relative to W/C of 0.4) improved the integrity, hydration, microstructure, and fracture properties of the concrete. Further, the results demonstrated that there was a significant correlation between GF and Gf (GF/Gf=2.38).

Ophiolite Chromite Deposits as a New Source for the Production of Refractory Chromite Sands

Chromite foundry sands, mixed with binding resins, are employed in the industry to form molds for high demanding casting of metals and steel. As there is no substitute, these sands highly contribute to placing chromium at the top value of the economic importance parameter in the EU classification of critical raw materials. Finding new sources to produce these sands can contribute to lowering its criticality. Chromite foundry sands must meet strict quality parameters, referred to as Cr2O3 content, Fineness Index, SiO2 content, and Acid Demand. The foundry chromite market is dominated by South Africa production deriving from layered intrusion chromite deposits. Chromite sands from ophiolite chromite deposits, normally used for the metallurgical-grade chromite market, were tested as an alternative starting raw material to produce chromite foundry sands. The study of the silicate impurities assemblage showed that its mineralogy strongly affects the result of the most crucial parameter, the Acid Demand. Ophiolite chromite with serpentine impurities should be depurated to a hardly affordable 0.31% SiO2 content to meet Acid Demand quality threshold, due to high reactivity of this silicate with the acid environment of the test. Those with olivine impurities require to be depurated to a much more easily affordable 2.11% SiO2 content. As a result, ophiolite chromite with an olivine dominated silicate assemblage can be used as an alternative source of chromite foundry sands.

Study on microstructure and tensile properties of 316L stainless steel fabricated by CMT wire and arc additive manufacturing

An austenitic stainless steel 316L part was fabricated by cold metal transfer wire and arc additive manufacturing (CMT-WAAM), and its microstructure, microhardness and tensile properties were investigated. Results showed that the as-built 316L part exhibited a multilayered structure along the building direction. In the transverse direction (perpendicular to scanning direction) of each layer, there was also a multilayered structure of alternating overlapping zone (OA) and re-melting zone (RA). Compared with the OA, the RA had higher ferrite content, smaller austenite dendrite size, more dispersed orientation and lower residual stress. The overall multilayered structure and the intra-layer non-equilibrium microstructure exhibit a great influence on the mechanical properties of as-built 316L part. Along the building and transverse direction, the microhardness distribution in the OA was uniform, while the RA showed a trend of lower hardness in the middle and higher hardness on both sides of the RA layer. The effect of multilayered structure on tensile properties was stronger in the transverse direction than that in the building direction. The deformation feature was obviously inconsistent between the OA and RA. Local necking and fracture always occurred in the OA. Microvoids trended to initiate at silicate impurity particles, grow into large cracks, and finally lead to material failure during tension.

Investigating the microwave heating behaviour of pyrrhotite tailings

Current practice is for pyrrhotite to be rejected from conventional nickel sulphide processing circuits due to its low concentration of nickel and high sulphur content. However, the nickel content of pyrrhotite tailings (up to 1 wt.% Ni) represents a significant resource, and a new flowsheet, based on the microwave heating of pyrrhotite tailings to produce FeNi and FeS phases is under development. The microwave heating properties of pyrrhotite tailings are explored in this paper through microwave heating and permittivity tests. Thermogravimetric analysis and differential scanning calorimetry were also performed to interpret the permittivity data, and the distribution of phases within the microwave treated material was investigated by scanning electron microscopy. In general, pyrrhotite heats very well upon exposure to microwave radiation. The mass loss appears to be governed by the sulphur content and the extent of heating seems to be influenced by the Ni content. The removal of silicate impurities by froth flotation had little impact on the heating behaviour.

Enhancement of flaky graphite cleaning by ultrasonic treatment.

In this study, the aim is to simplify the graphite cleaning process. In order to achieve flotation for graphite effectively, ultrasonic treatment was used as a pre-treatment technique. Flotation tests were conducted using different ultrasound power and ultrasonic treatment time. The influences of ultrasonic treatment on particle sizes, morphologies, wettability, the content of surface elements and on the flotation effect of flaky graphite were investigated. The results of ultrasonic treatment for graphite flotation were compared with the results of conventional flotation. The results showed that ultrasonic treatment not only changed the size of flaky graphite, but also eliminated impurities on the graphite surface. Additionally, the ultrasonic treatment improved the hydrophobicity of graphite. It was observed that ultrasound can remove not only silicate impurities but also most other metal impurities. The yield, carbon content and recovery of flotation concentrate were 91.46%, 95.17% and 96.12% after ultrasonic treatment for 4 min with ultrasound power 1600 W, which were 5.83%, 2.86% and 8.84% higher than that of conventional flotation, respectively. The graphite after ultrasonic treatment was conducted only one times flotation, the carbon content in concentrate products had reached 95%. This study indicates that intensifying graphite flotation by ultrasonic treatment can shorten the graphite cleaning process.

The study on desiliconization mechanism of sodium aluminate solution prepared from aluminum ash

The sodium aluminate crude solution prepared by using aluminum ash often contains a certain amount of sodium silicate impurities, and needs refined desiliconization. In this paper, desilication treatment of sodium aluminate solution by adding calcium oxide during sintering and refining. Experimental results show that the amount of calcium oxide added, desiliconization time and desiliconization temperature have an important influence on desiliconization efficiency of sodium aluminate solution. The results show that the desiliconization efficiency can reach 95.80 % under the optimal conditions, which satisfies the crystal decomposition of sodium aluminate solution.

Development of magnetically separable Cu catalyst supported by pre-treated steel slag

Wastewater contaminated with organic compounds is a serious problem; therefore, many catalysts, especially copper catalysts, have been developed to treat it and remove contaminants before discharge. However, such separation and reuse of these catalysts is often challenging. Steel slag (SS), a by-product of steel production, is produced in large quantities and requires careful disposal. Therefore, in this study, we developed a magnetically recyclable copper catalyst utilizing pre-treated magnetic steel slag (MSS) as a support. First, magnetic separation was carried out to remove calcium silicate impurities such as alite and belite in MSS up to five times, thus increasing the Fe content of the MSS. We synthesized the Cu catalyst supported by MSS (donated as Cu@MSS) and characterized the catalyst by various surface analysis techniques, showing the presence of CuO and CuCO3 nanoparticles on the MSS surface. In catalytic reduction tests of para-nitrophenol using sodium borohydride in the presence of Cu@MSS, the reaction was accelerated when using the five-times pre-treated MSS because of the removal of inhibitors such as calcium compounds, as well as the high content of iron oxides leading to a synergetic effect with metallic Cu in this study. In addition, we investigated the effects of various factors, including Cu loading, sodium borohydride concentration, and catalyst dosage, on the catalytic activity of Cu@MSS. The catalyst was found to be stable and reusable. In summary, these results suggest that treated SS can be used as a support material for copper catalysts for the treatment of contaminated wastewater and the easy separation and reuse of the catalyst.

Ceria-Based Dual-Phase Membranes for High-Temperature Carbon Dioxide Separation: Effect of Iron Doping and Pore Generation with MgO Template.

Dual-phase membranes for high-temperature carbon dioxide separation have emerged as promising technology to mitigate anthropogenic greenhouse gases emissions, especially as a pre- and post-combustion separation technique in coal burning power plants. To implement these membranes industrially, the carbon dioxide permeability must be improved. In this study, Ce0.8Sm0.2O2−δ (SDC) and Ce0.8Sm0.19Fe0.01O2−δ (FSDC) ceramic powders were used to form the skeleton in dual-phase membranes. The use of MgO as an environmentally friendly pore generator allows control over the membrane porosity and microstructure in order to compare the effect of the membrane’s ceramic phase. The ceramic powders and the resulting membranes were characterized using ICP-OES, HSM, gravimetric analysis, SEM/EDX, and XRD, and the carbon dioxide flux density was quantified using a high-temperature membrane permeation setup. The carbon dioxide permeability slightly increases with the addition of iron in the FSDC membranes compared to the SDC membranes mainly due to the reported scavenging effect of iron with the siliceous impurities, with an additional potential contribution of an increased crystallite size due to viscous flow sintering. The increased permeability of the FSDC system and the proper microstructure control by MgO can be further extended to optimize carbon dioxide permeability in this membrane system.

Dissolution Kinetics Potential of a Biotite-Rich Kaolinite Ore for Industrial Applications by Oxalic Acid Solution

The increasing demand for pure aluminum and aluminum compounds of industrial quality from kaolinite ore cannot be overemphasized. Nigeria is one of the African countries endowed with abundant solid mineral resources that have not been sufficiently exploited to assist its indigenous industries. A wide array of applications of pure aluminum and its compounds are available, such as paper filling, refractories, adsorbent, catalysis, and paint additives. In this study, the upgrading of a Nigerian biotite-rich kaolinite ore by a hydrometallurgical route was investigated in oxalic acid media. During leaching studies, the effects of parameters including reaction temperature, lixiviant concentration and particle size on the extent of ore dissolution were examined. At optimal conditions (1.0 mol/L C2H2O4, 75 °C), 92.0% of the initial 10 g/L ore was reacted within 120 min. The dissolution curves from the shrinking core model were analyzed and found to conform to the assumption of surface diffusion reaction, and the calculated activation energy of 33.2 kJ/mol supported the proposed model. The unreacted product (~8.0%) analyzed by XRD was found to contain siliceous impurities and could serve as a valuable by-product for certain industries.

Enrichment of a Nigerian chromite ore for metallurgical application by dense medium flotation and magnetic separation

This study, focused on the beneficiation of a Nigerian complex chromite ore sourced from Tunga-Kaduka, Anka Local Government of Zamfara State, Nigeria, assaying 45.85% Cr2O4 and 54.15% mineral impurities, was enriched concurrently through sink floatation and magnetic separation techniques. The chromite ore initially analyzed to contain silicate impurities was found not suitable for metallurgical purposes. Thus, enrichment was examined through gravity separation studies using organic liquid with different specific gravities at 2.8, 3.3, and 4.0. The separation of chromite ore with lowest particle size fraction was done using Mozley mineral separator followed by the magnetic separation of the sink product by magnetic separator. The results obtained revealed about 77% of the total material containing 300 μm particle size, 52% ˂ 212 μm and 17% below 75 μm. Subsequent analysis of the beneficiated ore was carried out by wet chemical analysis and atomic absorption spectrophotometer. The results showed that Cr2O4 content increased to 78.34% from initial 45.83% with maximum Cr:Fe ratio of 3.2:1, representing 84.27% of chromium metal present in the ore. The enrichment of Cr2O4 obtained in this study could be found metallurgically applicable in the electro-deposition and ferro-chromium alloy production practices.

Potential of a Nigerian biotite-rich kaolinite ore to industrial alumina by hydrometallurgical process

Increasing demands for aluminium and aluminium oxide with diverse industrial applications have prompted the development of a low-cost and eco-friendly technique as a substitute for conventional ore treatments by reduction-roasting route, requiring high energy consumption. For example, the demand for high-grade industrial alumina (Al2O3) as valuable materials in refractories, pigments, adsorbents, catalysis, water purification, aluminium production and metallurgical applications cannot be over emphasized. Thus, the upgrading of a Nigerian biotite-rich kaolinite ore containing admixture of kaolinite (Al2.00Si2.00O9.00: 96-900-9231), biotite (Mg6.55Fe3.46Al5.29Ti1.34Si11.36K4.00O48.00: 96-900-0844) and quartz (Si3.00O6.00: 96-900-9667) impurities by hydrometallurgical route was investigated in phosphoric acid media. During leaching, parameters such as leachant concentration, particle size and reaction temperature on the extent of ore dissolution were accordingly examined. At optimal leaching conditions (2.0 mol/L H3PO4, 75 °C), 87.0% of the initial 10 g/L ore reacted within 120 min. The activation energy of 16.6 kJ/mol supported the diffusion control reaction mechanism. The unreacted product (∼13.0%) analyzed by XRD was found to contain siliceous impurities including iron silicate and manganese silicate which could serve as valuable by-products for some defined industries. The leach liquor at optimal leaching conditions was accordingly treated to obtain pure aluminium solution which was further beneficiated to obtain high-grade alumina (α-Al2O3) of industrial value with 96.3% purity.

Purification of High-grade Calcite Ore by Flotation with Alkyl Diamines

A very high-grade calcite deposit located in northern Norway consists of CaCO3 ore with minor silicate and sulphide impurities. Cationic (Tallow-1,3-diaminopropane, Duomeen T) collector has been used in the purification of calcite by flotation with an aim of achieving calcite concentrate for its use in value-added products in a variety of industries. The feasibility of sulphide flotation from calcite by this cationic collector has been initially judged from Hallimond flotation and zeta potential on pure mineral systems and the results illustrate the removal of sulphide from calcite ore at neutral pH region. The adsorption mechanism of diamine on both the sulphide minerals was found to be the same by zeta potential studies. The variations in zeta potential are in good agreement with the adsorption of diamine molecular and ionic species as a function of pH. FTIR studies also showed the adsorption of diamine species in agreement with the zeta potential and Hallimond flotation results. Furthermore, the removal of sulphide impurities with selective flotation by diamine collector was performed in bench-scale flotation with the calcite ore and the results indeed showed that the calcite concentrate could meet the quality requirements for its use in the paper industry for coating and filler purposes.