Showing papers on "Calcium oxide published in 2023"

Modified Calcium Oxide Nanoparticles Derived from Oyster Shells for Biodiesel Production from Waste Cooking Oil

Abstract: SiO2np derived from rice husk were chemically connected to the surface of modified Calcium Oxide (CaO) in a straightforward manner to produce fatty acid methyl ester (FAME) from waste cooking oil (WCO) with great efficiency. After 3 h at a reaction temperature of 80° C, it was discovered that WCO could produce 97.8% yield of the FAME of the modified CaO, which is much greater than the yield of 83.5% over unmodified CaO under the same reaction circumstances. The results showed that following modification, well-dispersed CaO with relatively tiny particle sizes and large surface areas was produced. Additionally, the changed CaO with very little Ca(OH)2 is produced during the modification process. The use of leftover modified CaO-nanoparticles as a heterogeneous transesterification catalyst has been identified after fourteen cycles.

Cementless ultra-high performance concrete (UHPC) using CaO-activated GGBFS and calcium formate as an accelerator

Abstract: This study proposes an innovative approach to develop cementless ultra-high performance concrete (UHPC) by activating ground granulated blast furnace slag (GGBFS) without an alkaline-activating solution. To develop cementless UHPC, calcium oxide (CaO) (5% by weight) was used to activate GGBFS, and calcium formate (CF) was used as an accelerator at concentrations ranging from 0 to 6 wt%. The results showed that CF significantly improved the mechanical properties until 5 wt% and all the samples, including CF, exhibited a compressive strength of over 150 MPa. Uniaxial tensile tests revealed strain-hardening behavior, similar to typical cement-based UHPC. The addition of CF led to an increase in hydration products and pore size refinement, resulting in improved mechanical properties. The life cycle assessment results indicated that the developed UHPC mixture had nearly 70% lower CO2 emission than cement-based UHPC. The experimental results highlight the potential of this method for sustainable UHPC development.

Role of Extracted Nano-metal Oxides From Factory Wastes In Medical Applications

Abstract: Nanometal oxides were extracted from cement factories wastes and were employed to proliferate skin cancer cells using MTT (Methyl Thiazolyl Tetraolium) assay. MTT assay results for skin cancer cell line A375,for CaO NPs the best concentration was 200 μg/mL,The viability was reduced to 57.28% while the IC50 was (69.66) g/mL for A375 and normal cell WRL68 was significantly higher (231.2 g/mL). The cytotoxicity results of CaO: MgO: Fe2O3 NPs, at higher concentrations (200 and 400) μg/mL showed a significant difference. The IC50 was (106.4) μg/mL for A375and normal cell WRL68 was significantly higher (173.3) μg/ml CaO:MgO:Fe2O3 NPs. The nanometal oxides, calcium oxide (CaO) and the mixture (CaO:MgO: Fe2O3) were extracted from wastes of cement factory, and then they were oxidized at a temperature of 400C° for (5) hours. The structural and surface properties of the prepared oxides were characterized by X-ray diffraction patterns,FE-SEM and FTIR. The X-ray data reflected that all the oxides have a polycrystalline cubic structure, with a preferred orientation along (111) for calcium oxide, with a preferred orientation along (002) for calcium oxide: magnesium oxide: iron oxide.

Preparation, characterization and experimental investigation of the separation performance of a novel CaO‐based CO 2 sorbent for direct air capture

Abstract: The capture of CO2 from air via direct air capture (DAC) is a promising way to reduce the carbon dioxide concentration in the atmosphere. The carbonation of calcium-based adsorbents using ambient conditions is particularly interesting for DAC due to its high theoretical CO2 uptake capacity and its low cost. In this paper, a new preparation method of synthetic calcium oxide-based pellets for a DAC process was investigated. Their CO2 capture performance was studied experimentally in a fixed-bed column and characterization was performed via Brunauer-Emmett-Teller (BET) analysis, mercury porosimetry, X-ray diffraction, and scanning electron microscopy. Higher heating rates during the precursor calcination process and higher relative humidities during the carbonation process were found to lead to higher CO2 capture efficiencies. All prepared pellets showed good mechanical stability.

An efficient calcium-based sorbent for flue gas dry-desulfurization: promotion roles of nitrogen oxide and oxygen

Abstract: The development of sorbents for flue gas desulfurization in a dry mode is essential to control emission of sulfur dioxide.

An Investigation on Reduction of Calcium Added Bauxite Residue Pellets by Hydrogen and Iron Recovery through Physical Separation Methods

Abstract: This study investigates the properties of H2-reduced calcium-added bauxite residue, self-hardened pellets, and the feasibility of iron recovery through electrostatic and magnetic separation methods. The oxide pellets are prepared via a mixing of bauxite residue, calcite, and quicklime. The self-hardened pellets are reduced at 1000 °C with hydrogen gas flow for 120 min. The chemical composition, phase identification, and microstructural observations are executed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. The porosity and strength of the self-hardened pellets are performed by the Mercury intrusion porosimetry and tumbling tests, respectively. The separation of iron is examined through a dry electrostatic technique, and in wet conditions, i.e., via Davis Tube and low-intensity magnetic separation (WLIMS). The effect of the magnetic field (0.1, 0.25, and 0.32 T) is tested on two different particle size fractions (−212 + 106 µm and −106 + 74 µm). It is found that most of the iron oxide in the bauxite residue is converted to metallic iron, which corresponds well with both XRD and SEM results. The Carpco electrostatic tests indicate that this approach is inefficient for the studied type of material because of the intensive association of iron with the rest of the components leading to transferring it to the middling rather than to conductive product. However, both the Davis Tube and WLIMS approve a reasonable improvement in the Fe content from 22% to 37% with acceptable recoveries. The results of the Davis Tube show that there is an optimum magnetic field and particle size for maximization of Fe grade and recovery. Finally, further suggestions are highlighted for the physical beneficiation of studied bauxite residue with the purpose of maximizing iron grade and recovery.

Producing flexible calcium carbonate from waste paper and their use as fillers for high bulk paper

Abstract: Microfibrillated cellulose (MFC) was prepared from post-consumer old corrugated container (OCC) material, which was first disintegrated in water, cleaned to remove impurities, and then fibrillated by grinding. Those processed MFCs were treated with in-situ formation of calcium carbonate by adding calcium oxide and injecting carbon dioxide into the mixture up to the ratio of 1:40 (MFC : calcium carbonate) by weight. The MFCs had a dark brown color initially but turned into high brightness materials similar to commercial ground calcium carbonate (GCC) after the in-situ formation process. The MFCs that had calcium carbonate attached on their surfaces, which were lengthy and flexible, were called flexible calcium carbonate from OCC (FCCO). Paper containing FCCO gave higher bulk, higher stiffness, and higher tensile index without lowering smoothness when compared to the paper containing commercial GCC. However, brightness was slightly lowered because of initial low brightness of the OCC. This study also demonstrated the feasibility to substitute wood fibers up to 5% with FCCO without lowering essential properties for printing paper. Benefits of the waste paper are savings of both wood resources and production cost.

Effect of Cement Type and Water-to-Cement Ratio on Fresh Properties of Superabsorbent Polymer-Modified Cement Paste

Abstract: Superabsorbent polymer (SAP) is a material with the ability to absorb liquid and desorb liquid from and to the environment, and it can ensure the internal curing of cementitious composites. Although the fresh state properties of SAP-modified mixtures (SAPCP) are affected and have been investigated nowadays, the rheological properties of SAPCP are still a virgin field and they are worth studying. Hence, the current study was aimed and conducted to observe what occurred if cements with different chemical compositions, various ratios of water/cement (w/c) and SAP were used together. Accordingly, CEM I 42.5R, CEM II/A-LL 42.5R and CEM IV/B (P) 32.5R were selected as binders in the mixtures, and w/c ratios were 0.40 and 0.50 for SAPCPs. In total, 24 mixtures were designed, produced and tested in the laboratory and spreading table tests, Vicate tests, viscosity tests and shear tests were conducted on the fresh state of the mixtures to observe the fresh behavior of SAPCPs. As a result, it was determined that the SAP, cement and w/c combinations considered in the article were effective on SAPCP fresh properties and rheology. However, it was determined that the use of high amounts of SAP in the mixture, high cement fineness and high oxide ratios in the cement (ratios of silicon dioxide/calcium oxide and aluminum oxide/calcium oxide) negatively affected not only the fresh state properties, but also the rheology. Moreover, the coexistence of the aforementioned negative conditions was the most unfavorable situation: high SAP ratio + high cement fineness + high oxide ratio in SAPCP. For these reasons, it was concluded that cement fineness and chemical composition should be taken into account in the rheology/workability-based design of SAPCPs. Then, the SAP content can be regulated for design purposes.

Maximizing biodiesel production from waste cooking oil with lime-based zinc-doped CaO using response surface methodology

Abstract: Biodiesel is one of the alternative fuels, commonly produced chemically from oil and methanol using a catalyst. This study aims to maximize biodiesel production from cheap and readily available sources of waste cooking oil (WCO) and lime-based Zinc-doped calcium oxide (Zn-CaO) catalyst prepared with a wet impregnation process. The Zn-CaO nanocatalyst was produced by adding 5% Zn into the calcinated limestone. The morphology, crystal size, and vibrational energies of CaO and Zn-CaO nanocatalysts were determined using SEM, XRD, and FT-IR spectroscopy techniques, respectively. The response surface methodology (RSM), which is based on the box-Behnken design, was used to optimize the key variables of the transesterification reaction. Results showed that when Zn was doped to lime-based CaO, the average crystalline size reduced from 21.14 to 12.51 nm, consequently, structural irregularity and surface area increased. The experimental parameters of methanol to oil molar ratio (14:1), catalyst loading (5% wt.), temperature (57.5 °C), and reaction time (120 min) led to the highest biodiesel conversion of 96.5%. The fuel characteristics of the generated biodiesel fulfilled the American (ASTM D6571) fuel standards. The study suggests the potential use of WCO and lime-based catalyst as efficient and low-cost raw materials for large-scale biodiesel production intended for versatile applications.

Effect of calcium on niobium solubility in alkaline solutions

Abstract: Abstract The solubility of niobium-94 (94Nb) in calcium alkaline solutions is one of the important parameters in safety assessment of intermediate-depth disposal which are assumed to use cementitious materials. Nb solubility and solubility-limiting solid phases of Nb in these systems remain unclear. The oversaturation solubility experiments were performed systematically in the 0.001–0.1 mol dm−3 (M) CaCl2 solutions under alkali conditions, and the characterization of precipitated solid phase controlling Nb solubility was conducted. The negative dependence of Nb solubilities on pH and calcium (Ca) concentration was observed in solubility experiments, and the Ca/Nb molar ratio of precipitated solid phase was 0.66. The pH and Ca dependence of Nb solubilities was reproduced by the reaction with Nb aqueous species Nb(OH)6− and Ca–Nb oxide with the Ca/Nb ratio of 0.66, e.g., Ca4Nb6O19 (am). With increasing pH, Nb concentrations in the 0.001–0.1 M CaCl2 solutions were significantly lower than those calculated from thermodynamic data without Ca–Nb solid. This work provides systematic evidence that the presence of Ca clearly affects Nb solubility. Since calcium is a major component of groundwater and cement pore water, the Ca–Nb solid phase should be considered in the Nb solubility assessment.

Dry so2 removal at low temperature using calcium-based sorbents

Abstract: The reaction between S0₂ and two dry calcium-based sorbents, calcium oxide (CaO) and calcium hydroxide (Ca(OH)₂), has been studied on a laboratory-scale electrically heated fluidized bed reactor at temperature below 673 K. Experimental data on CaO and Ca(OH)₂ are presented in this paper. Two calcium-based sorbents have similar reactivity curve but different sulfation rate. The results show the sulfation reactivity depends on particle size, reaction temperature and sorbent/inert ratio. From the SEM micro graphs, the external surface microstructure of calcium oxide has been obtained before and after sulfation.

Production of ferroalloys, calcium carbide, and phosphorus from high-silicon phosphorite

Abstract: The article provides information on the interaction of Chilisai phosphorite with carbon, coke, and iron with the production of ferroalloy and calcium carbide and the extraction of phosphorus into gas. Research is conducted using computer thermodynamic modeling, mathematical planning of experiments, and electric smelting of phosphorites in an arc electric furnace. It is found that under equilibrium conditions the interaction occurs with the formation of iron silicides, calcium, silicon carbides, calcium, elemental silicon, aluminum, calcium, silicon oxide (ІІ), gaseous phosphorus (P4, P2), and iron phosphides. An increase in the amount of iron at 1,500-2,000oC increases the degree of extraction of silicon in the alloy but decreases the extraction of calcium in the calcium carbide, the concentration of silicon in the alloy, and the amount of calcium carbide. In the temperature range of 1,900-2,000oC in the presence of 16.8-19.8% of iron, phosphorus completely converts to gas, and there forms an alloy with 45-47.8% of Si and 1.6- 1.9% of Al and calcium carbide in the amount of 150-215 dm3 /kg (with the extraction of 60-63.6% of Si into the alloy and 50-56.4% of Ca into calcium carbide). Electric smelting of phosphorite in an arc furnace produces ferrosilicon of grade FS45 (40-44.7% of Si) with the extraction of 73.8% of silicone into it, as well as calcium carbide up to the second grade in the amount of 200-252 dm3 /kg. Phosphorus is almost completely (99.0-99.4%) reduced during electric smelting and converted into the gas phase.

Effect of Mg/Al Oxides Supports on CaO Sorbents Prepared by Wet‐Mixing Synthesis for CO2 Capture

Abstract: Calcium looping is one of the effective methods for post-combustion CO2 capture. A key issue is choosing the appropriate supports to synthesize effective calcium-based sorbents. In this study, calcium looping sorbents incorporated with MgO, Ca3Al2O6, and MgAl2O4 supports were prepared by wet-mixing synthesis. Characterizations were made to determine the cyclic CO2 capture capacity, crystalline structure, porosity, and morphological changes of the sorbents over multiple cycles. The results showed that, at the mass ratio of CaO to support oxides of 7:3, the MgAl2O4 mixed support showed better CO2 capture performance than the MgO and Ca3Al2O6 supports. Moreover, the sorbent showed a porous and fluffy microstructure with a high specific surface area, making it a suitable candidate for cyclic CO2 capture.

Optimization of microwave-assisted biodiesel production using Iron (III) oxide - Calcium oxide / Activated charcoal derived from waste Asian green mussel shell as heterogeneous catalyst

Abstract: Abstract The primary objective of this study was to produce a heterogeneous iron (III) oxide (Fe 2 O 3 )-calcium oxide (CaO)/activated charcoal (AC) catalyst from Asian green mussel shell utilizing wet impregnation and calcination processes for biodiesel synthesis. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and the Brunauer-Emmett-Teller (BET) method were used to analyze the novel catalyst. Using a central composite design (CCD)-based response surface methodology (RSM), the process parameters such as catalyst quantity, reaction time, and microwave electrical power were optimized. The optimal reaction conditions were determined to be 1.07 wt.% of Fe 2 O 3 -CaO/AC, 6.42 min of reaction time, and 667 W of microwave electrical power. The published results imply that the heterogeneous catalyst has a great potential for the direct conversion of waste frying oil (WFO) to biodiesel, with the ability to reuse without reactivation. The development of Fe 2 O 3 -CaO/AC as a novel heterogeneous catalyst would facilitate the manufacture of biodiesel in an eco-friendly manner.

Physico-chemical characterization of snail shells powder prepared by mechanochemical processes and thermal treatment

Abstract: Natural particles are the most abundant resources exist in nature. Bio-sources of CaCO3 particles have attracted the attention of researchers for multiple cosmetics, industrial, and medical applications. This work investigates the structural evolution of CaCO3 containing in snail shell particles prepared by a mechanochemical process using methods of characterization as well as Differential scanning calorimeter (DSC), Thermogravimetric analysis (TGA), X-ray diffraction (X-RD), Fourier transformation infra-red (FT-IR), and Scanning microscopy equipped with Energy-dispersive X-Ray spectroscopy (SEM-EDXS). The result obtained from the above analysis indicates that SSP calcined between 200℃ to 400℃ undergoes an elimination of water molecules, followed by a phase transformation from Aragonite to CaCO3 Calcite. At 800℃, the SSP decomposes CaCO3, giving rise to calcium oxide crystals CaO, which release CO2 molecules. These eliminations and transformations represent a loss of 47.08% of the initial mass at 800℃. The morphological analysis shows the surface of SSP calcined at 800℃ with CaO/CaCO3 crystal formation. Also, the mechanochemical process leads to obtaining an SSP with a size between 3.311 µm to 10.140 µm. Snail shells can be a natural source of CaCO3 and CaO, thanks to their ease of extraction and processing.

Replacing Lime with Rice Husk Ash to Reduce Carbon Footprint of Bituminous Mixtures

Abstract: There have been several emphasized pathways toward a reduction in carbon footprint in the built environment such as recycling, technologies with lower energy consumption, and alternative materials. Among alternative materials, bio-based materials and nature inspired solutions have been well-received. This study examines the merits of using rice husk ash as a replacement for lime; lime has a high carbon footprint mainly associated with the decomposition of calcium carbonate to calcium oxide to form lime. Lime is commonly used in bituminous composites for roadway construction to mitigate their susceptibility to moisture damage. Replacing lime with a low-carbon alternative could allow a reduction in CO2 equivalent of bituminous composites. This paper studies the merits of using rice husk ash (RHA) as a substitute for conventional hydrated lime (HL) in bituminous composites. It should be noted that rice industries burn rice husks in a boiler as fuel, generating a substantial volume of RHA. The disposal of this ash has major environmental impacts associated with the contamination of air and water. Here, we study physical and chemical characteristics of both HL and RHA for use in bitumen mixtures. This was followed by examining the extent of dispersion of each filler in bitumen via optical microscopy to ensure their uniform dispersion. The properties of the mixtures were further studied using the Marshall mix design method. It was found that a 25.67% increase in Marshall stability and a 5.95% decrease in optimum binder content were achieved when HL was replaced by RHA at 4% filler concentration. In addition, mixtures containing RHA exhibited higher resistance to cracking and permanent deformation compared to mixtures containing HL. Additionally, 4% RHA in the mix showed stripping resistance similar to the conventional mix with HL. The mixture with 4% RHA had a lower carbon footprint with enhanced economic and environmental impacts compared to the conventional mix with HL. The study results provide insights pertaining to the merits of bio-based materials to reduce the carbon footprint of pavements.

Enhancement of Sapindus Trifoliatus Biodiesel Production and Performance using Mg-doped CaO Nanocatalyst

Abstract: Abstract The use of biodiesel can reduce dependence on diesel and stabilize the economy when using internal combustion engines. CI engine's performance with biodiesel is substantially low but could be improved by emulsifying nano-additives with biodiesel. Magnesium-doped Calcium Oxide, a novel nanocatalyst is emulsified in its nano form with the Sapindus Trifoliatus biodiesel (STBD) at B25 blend (STBD25+Mg-CaO 30ppm) and tested in the CI engine. The performance results obtained are compared to the baseline values ​​obtained using diesel, Sapindus Trifoliatus biodiesel (STBD25), and Sapindus Trifoliatus biodiesel blended with Cao nano additives (STBD25+30ppm CaO) in the CI engine. . A maximum biodiesel yield of 91.75% was achieved at 58°C, 73 min, a catalyst concentration of 4% (%w / %w) and a methanol: oil molar ratio of 15:1. From the comparison, it is revealed that (i) In-cylinder pressure found to be increased by 3.22%, 6.24% and 9.02%, (ii) HRR increases by 1.68%, 16.69% and 32.5%, (iii) BTE is found to be increased by 4.56%, 8.23% and 11.79%, (iv) UHC decreases by 21.12%, 6.06% and 11.43%, (v) CO decreases by 0.04%, 0.01% and 0.01%, (vi) Smoke decreases by 54.52%, 9.34% and 19.58%, compared with diesel, STBD25+30ppm CaO and STBD25. NOx released while using STBD25+Mg doped CaO in CI engine was observed to decrease compared with STBD25 and STBD25+CaO (by 10.72 % and 18.64 %) and increase compared with diesel (by 8.64%). Whereas an insignificant drop in NOx was observed while using STBD25+Mg doped CaO as fuel compared with STBD25+CaO and STBD25 in spite of a significant increase in HRR and BTE which might be due to the capture of excess oxygen by Mg during the combustion diffusion phase.

Evaluation of Adhesive Properties of Different Mineral Compositions in Asphalt Mixtures with Experimental and Molecular Dynamics Analyses

Abstract: The adhesion between bitumen and mineral composition plays a vital role for the performance of asphalt mixtures. This study compares the adhesion of limestone, dolomite, and granodiorite to bitumen and evaluates the effects of different mineral components on adhesion. Three kinds of aggregates were tested through rolling-bottle tests. Afterwards, the respective fillers were integrated into asphalt mastic in a 1.6:1 mass ratio with bitumen and were subjected to frequency scan tests separately. A modified Luis Ibrarra-A model, K. Ziegel-B model, and K-B-G model were used to evaluate the bitumen–filler interactions based on the rheology of the asphalt mastic. In addition, the interface behavior between eight mineral components from these fillers/aggregates and bitumen were investigated by molecular dynamics (MD) simulations. The work of the adhesion and molecule concentration profiles were obtained from MD simulations. The results showed that the limestone and dolomite had better interfacial adhesion to the bitumen than the granodiorite. The calcium oxide and titanium oxide had the highest potential adsorption effect on the bitumen. Moreover, the high calcium oxide content contributed to better bitumen adhesion with the limestone and dolomite than with the granodiorite, which was further confirmed by additional molecule concentration profile analysis. This research contributes to the in-depth understanding of the effect of different chemical properties on the performance of asphalt mastic and the selection of suitable mineral components to improve the bitumen–filler/aggregate interface and asphalt mixture performance in general.

The influence of calcium oxide doses as an activator on the compressive strength and mechanical characteristics of cement-free mortar containing ground granulated blast furnace slag

Abstract: In the construction industry, cement-based materials as aggregate binding agent are still widely used. Due to the environmental concern, researchers are working to create eco-friendly cement-free binding materials. Calcium oxide (CaO) is a reactive earth metal oxide that could serve as a potential activator for ground granulated blast furnace slag (GGBFS). In this experimental study, the cement-free mortar was produced by using GGBFS as the base material and CaO as an activator with varied doses of 5%, 15%, and 25% with a fixed water-to-binder ratio (w/b) of 0.4. The results showed that the 28-day compressive strength values of the mixture with an amount of CaO of 5%, 15%, and 25% were 21.45, 32.03, and 25.80 MPa. Moreover, the values of bulk density and porosity of free-cement mortar at the age of 28 days ranged between 1.932 - 1.939 g/cm3 and 22.66% - 24.95%, respectively. According to the research findings, the optimal additional CaO amount of 15% exhibited the series’ highest compressive strength and lowest porosity.

Observation of the Initial Interfacial Reaction between High Aluminum Molten Steel and CaO‐Al 2 O 3 Inclusion at 1873 K Using Laser Confocal Scanning Microscopy and Micro‐CT

Abstract: The slag could be entrained to molten steel during refining or continuous casting process, in which MnO, SiO2 could be reduced by Al in the molten steel to form calcium aluminate inclusions in the final product. However, there was a lack of information on reactions between pure calcium aluminates inclusions and the dissolved aluminum in the molten steel. An innovative method, utilizing synthetic inclusion-steel samples, was applied to discuss transient reactions between CaO-Al2O3 inclusions and high aluminum molten steel. The Confocal Laser Scanning Microscopy (CLSM), the X-ray computerized tomography (CT) technology and the Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) were combined in the current techniques to observe the transformation of entrained inclusions with respect to time. The influence of refractory materials on the reaction between dissolved aluminum in molten steel and inclusions can be avoided through the current method. The reaction between [Al] in the steel and calcium aluminates at 1873 K was investigated in the current study both in thermodynamics and kinetics, founding that calcium oxide in the inclusion can be reduced by the dissolved aluminum in the molten steel and the composition of inclusions changed little within 30 s. With the increase of [Al] content from 0.02 wt.% to 5.73 wt.%, the mass fraction of CaO under the equilibrium state decreased from 55% to 35%. Performed kinetic analysis indicated that the mass transfer coefficient of the calcium oxide in the inclusion was calculated as 2.95×10-5 m/s. This article is protected by copyright. All rights reserved.