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Showing papers on "Calcium oxide published in 2020"


Journal ArticleDOI
TL;DR: In this article, industrial wastes such as Granulated Blast Furnace Slag (GBFS) and Basic Oxygen Furnace SLag (BOFS) activated with calcium oxide (CaO) and medium reactive magnesia (MgO) are used for chemical stabilization of a soft clay.

81 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the carbonation process on concrete adsorbent properties and how it can influence on the removal of phosphate ions in aqueous media are studied. And the potential applicability of P loaded concrete adsorent is also evaluated.

66 citations


Journal ArticleDOI
15 Apr 2020-Fuel
TL;DR: In this article, a modified calcium oxide (CaO) is proposed as an alkaline solid catalyst, which is chemically modified using bromooctane through a microwave approach to improve its catalytic ability.

51 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of different physicochemical factors like primary dye concentration, sorption contact time, the quantity of the adsorbent, temperature, along with initial simulated solution pH, evaluated for illustrating the mechanism of adsorption.
Abstract: The natural Fly ash modified with calcium oxide has been employed to eliminate the crystal violet dyestuff from the simulated solution. Herein, the effect of different physicochemical factors like primary dye concentration, sorption contact time, the quantity of the adsorbent, temperature, along with initial simulated solution pH, evaluated for illustrating the mechanism of adsorption. Furthermore, the equilibrium study was conducted, and equilibrium models like Langmuir, Freundlich, and DubininRaduskevich (D-R) were fitted to obtain analytical results to endow with more insight into the process. The results acknowledged that the Langmuir model is well apt and suggests that the adsorption mechanism happens in a monolayer on the fly ash surface. Pseudo-first order, Pseudo-second order, and the intraparticle diffusion model evaluated, and the interpretation suggests the sorption method is obeying the Pseudo-second order and intraparticle diffusion model. The ascertained negative values of Gibbs free energy affirmed the unconstrained process for all symbiotic associations, and the obtained data 78.70 kJ mol enthalpy values manifested that exothermic mechanism was governing the reaction. The above assessment confirms the application of Calcium oxide pre-treated fly ash as a cheap adsorbent to eliminate the crystal violet dyestuff from the simulated solution.

50 citations


Journal ArticleDOI
TL;DR: In this article, a typical metal organic framework, MIL-100(Fe) and calcium acetate are employed to synthesize the high effective, stable, and magnetic CaO-based catalyst.

49 citations


Journal ArticleDOI
TL;DR: In this article, the energy band gap was calculated from the equation of Tauc for CaO and Ag-NPs@CaO and measured to be 2.1 and 2.eV, respectively.

49 citations


Journal ArticleDOI
TL;DR: Nanostructured calcium oxides supported onto biochar obtained by pyrolysis of avocado seeds were prepared, characterized and successfully used as catalysts to produce biodiesel from waste oils as mentioned in this paper.

41 citations


Journal ArticleDOI
01 Jun 2020-Fuel
TL;DR: In this article, the effects of preparation conditions (percentage of Zr stabilizer and fuel-to-metal oxide ratio) on the CO2 capture performance were investigated in a thermogravimetric analyzer.

34 citations


Journal ArticleDOI
15 Jun 2020-Energy
TL;DR: In this paper, a novel material using CaO/Ca(OH)2 and a ceramic honeycomb support composed of silicon carbide and silicon was developed to enhance the heat transfer in a reaction bed.

33 citations


Journal ArticleDOI
TL;DR: In this paper, a novel approach to sequester carbon dioxide (CO2) using industrial waste red gypsum (RG) in an accelerated mineral carbonation process was proposed.
Abstract: This study provides a novel approach to sequester carbon dioxide (CO2) using industrial waste red gypsum (RG) in an accelerated mineral carbonation process. In this study, RG samples and products were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and transmission electron microscope (TEM). The XRD analysis of RG revealed that two main constitutions of RG are gypsum (CaSO4.2H2O) and hematite (Fe2O3). From XRF analysis, RG samples consisted of calcium oxide (CaO), sulfur trioxide (SO3), and ferric oxide (Fe2O3) as major components and titanium dioxide (TiO2), manganese oxide (MnO), and europium oxide (Eu2O3) as minor components. The accelerated mineral carbonation of RG was first performed using different concentrations of sulfuric acid (H2SO4) from 0.5 M to 2 M to extract the calcium ions from the RG. Then, the mineral carbonation process was performed within an Autoclave mini reactor by preparing an aqueous solution containing RG, CO2, and 5 wt% 0.1 M to 1.4 M mono-ethanolamine (MEA). The results showed that using 1.4 M MEA could absorb the highest amount of CO2 to precipitate the calcite. The significant advantages of using MEA were related to the further absorption of CO2 than 2 M H2SO4 in the slurry and the lower consumption of energy to precipitate the calcite. The findings presented in this study shed new light on precipitating carbonate minerals like calcite from industrial wastes rich in calcium as well as ones rich in iron, barium, and magnesium.

31 citations


Journal ArticleDOI
TL;DR: In this article, the main purpose of the work reported in this paper is to use kaolin to produce one part alkali-activated cement, and thermal activation was performed on kaolin in the presence of alkalis (calcium oxide, sodium silicate, and sodium carbonate). Optimization experimental investigations were undertaken with selected alkalis to maximize the mechanical properties as well as minimize the cost of the resultant alkaliactivated cement.
Abstract: The main purpose of the work reported herein is to use kaolin to produce one-part alkali-activated cement. Thermal activation was performed on kaolin in the presence of alkalis (calcium oxide, sodium silicate, and sodium carbonate). Optimization experimental investigations were undertaken with selected alkalis to maximize the mechanical properties as well as minimize the cost of the resultant alkali-activated cement. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) test techniques were used to get insight into the binder chemical phases and their microstructure. The results showed that the optimal formulation for the alkali-activated kaolin cement developed consists of 62.5 wt.% kaolin, 30 wt.% calcium oxide, 5 wt.% sodium carbonate and 2.5 wt.% sodium silicate. The 7-day compressive strength at heat and room-curing temperatures reached 19.83 and 16.47 MPa, respectively. The competitive merits of the kaolin-based cement assessed against Portland cement considering the raw materials and production processing contributions to carbon footprint, cost, and energy content. The carbon footprint of the alkali-activated kaolin cement was 70% less than that of Portland cement. The cost and energy content of the alkali-activated kaolin cement was 45% and 70%, respectively, less than those of Portland cement.

Journal ArticleDOI
01 May 2020-Fuel
TL;DR: In this paper, the authors evaluated calcium oxide as a catalyst from calcium carbonate at different calcination temperatures and the hydration-dehydration technique was used to produce a nanocrystalline catalyst.

Journal ArticleDOI
TL;DR: A novel process and a system of preparing CSA cement by using phosphogypsum as the sole CaO source are proposed and could be employed as a reliable and environment friendly means of recycling phosphogypsypsum in the large-scale preparation of calcium sulfoaluminate cement.

Journal ArticleDOI
TL;DR: In this article, a rod-shape composite with silica (CRCS) was used for hazardous crystal violet (CV) cationic dye removal from aqueous solution.
Abstract: Fine calcium oxide (CaO) which is the main component in the fine lime and considered as a waste byproduct from the steel manufacturing industry is converted into a potential composite to be used as an adsorbent. A facile and simple impregnation between CaO and silica in the presence of H2SO4 is utilized to achieve a one-step synthesis of a highly efficient CaO-based rod-shape composite with silica (CRCS). The suitability of using this composite in hazardous crystal violet (CV) cationic dye removal from aqueous solution was evaluated in series batch experiments. The synthesized composite was characterized using various techniques including XRD, SEM, TEM, EDX, FT-IR, and Raman to determine the adsorbent physicochemical properties. Influences of various operating parameters such as contact time, initial dye concentration, adsorbent dosage, agitation speed, initial pH, and reaction temperature were examined. The results of the experimental data well fitted Langmuir and the pseudo-first-order kinetic model. Based on the thermodynamic parameters, the sorption of CV onto CRCS is a spontaneous and endothermic process. The prepared CRCS also exhibited easily regeneration and recycling at least for ten adsorption–desorption runs. This study offers new insights into promising waste management technology that is efficiently applied to treat dye-contaminated water.

Journal ArticleDOI
11 May 2020-Minerals
TL;DR: In this paper, the effects of various substances on soil contaminated with cobalt (Co) on the mass and content of cobalt in the main crop (Hordeum vulgare L.) and the after-crop (Synapis alba L.).
Abstract: This study was undertaken to determine the effects of various substances on soil contaminated with cobalt (Co) on the mass and content of cobalt in the main crop—spring barley (Hordeum vulgare L.)—and the after-crop—white mustard (Synapis alba L.). Manure, clay, charcoal, zeolite, and calcium oxide were used for phytostabilization. Cobalt was applied in the form of CoCl2 in doses of 0, 20, 40, 80, 160, and 320 mg/kg soil. Amendments in the form of manure, clay, charcoal, and zeolite were applied in an amount of 2% in relation to the weight of the soil in a pot, with calcium oxide at a dose of 1.30 g CaO/kg of soil. The highest cobalt doses resulted in a significant reduction in yield of both plants and in tolerance index for cobalt. Increasing contamination of soil with cobalt resulted in a major and significant increase in its content in plants and a reduction in cobalt translocation factor in both plants. Amendments used in phytostabilization had a significant effect on growth and development of oat and content of cobalt in plants. The strongest effect on the yield of above-ground parts was exerted by manure (both plants) and calcium oxide (white mustard), while the strongest effect on weight of roots was exerted by calcium oxide (both plants) and zeolite (white mustard). The addition of manure, zeolite and calcium oxide to soil caused an increase of the tolerance index for both plants, while the addition of clay only had a positive effect for white mustard. All substances used in phytostabilization (except zeolite) decreased cobalt content of roots, and manure and calcium oxide in above-ground parts of spring barley; manure and zeolite only in above-ground parts, and calcium oxide in both organs of white mustard. Most of them also reduced bioconcentration of cobalt in above-ground parts, calcium oxide decreased cobalt content in roots of both plants, and manure in roots of spring barley. The effect on cobalt translocation was less clear, but most substances used in phytostabilization increased the transfer of cobalt from the soil to plants. White mustard had higher ability to accumulate cobalt than spring barley.

Journal ArticleDOI
TL;DR: Experimental laboratory investigation was carried out on sediments carefully collected from the Mar Piccolo of Taranto in Southern Italy, contaminated by heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls, indicating that the addition of binders increased the pH of the mixtures with a consequent leachability of different metals.
Abstract: Among ex situ remediation technologies, stabilization/solidification (S/S) provides for the addition of a binder to dredged materials in order to chemically immobilise the contaminants and improve mechanical behaviour of sediments. The simplest form of treatment is obtained by the addition of Portland cement or lime (calcium oxide), although other additives such as adsorbents may be added. Nevertheless, the success of the S/S treatment may be affected by the contaminants present or by the salt content in the water. In this study, experimental laboratory investigation was carried out on sediments carefully collected from the Mar Piccolo of Taranto in Southern Italy, contaminated by heavy metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs); the goal was to explore the effectiveness of S/S treatment by using Portland cement/lime as binders, monitoring over time (28 days) the leaching of the different mixtures of treated sediment. It is noted that the Mar Piccolo of Taranto is one of the sites of national interest subject to remediation by the Italian government. Once taken within the first meter under the sea floor by a team of experienced divers, the samples were stored at a controlled temperature, characterised in terms of grain size and physical-chemical characteristics and treated by S/S laboratory tests. The results indicate that the addition of binders increased the pH of the mixtures with a consequent leachability of different metals. The mobility of the metals appeared to be governed also by the curing time. The performance of the mixtures in terms of immobilised metals was influenced by the presence of organic contaminants (e.g. organic matter, PAHs and PCBs). As a lesson, high organic matter and fine-grained particles can negatively affect the effectiveness of the S/S treatment in terms of metal immobilisation.

Journal ArticleDOI
TL;DR: In this paper, the effect of magnesium on the structure and chemical composition of calcium silicate hydrate at elevated temperature was investigated, and the results showed that the transformation from M−S−H to C−S-H occurs when Mg to Si molar ratio decreases to 0.4.

Journal ArticleDOI
09 Jul 2020
TL;DR: In this article, the authors demonstrate a significant improvement of the corrosion resistance of an AZ31B magnesium alloy achieved by the application of 1 μm-thin coatings generated by an environmentally friendly flash plasma electrolytic oxidation (FPEO) process in Ca-containing electrolytes.
Abstract: This study demonstrates a significant improvement of the corrosion resistance of an AZ31B magnesium alloy achieved by the application of 1 μm-thin coatings generated by an environmentally friendly flash plasma electrolytic oxidation (FPEO) process in Ca-containing electrolytes. Two compounds with different solubility, calcium oxide (CaO) or calcium glycerophosphate (CaGlyP), were used as sources of Ca in the electrolyte. Very short durations (20–45 s) of the FPEO process were employed with the aim of limiting the energy consumption. The corrosion performance of the developed coatings was compared with that of a commercial conversion coating (CC) of similar thickness. The viability of the coatings in a full system protection approach, consisting of FPEO combined with an inhibitor-free epoxy primer, was verified in neutral salt spray and paint adhesion tests. The superior corrosion performance of the FPEO_CaGlyP coating, both as a stand-alone coating and as a full system, was attributed to the formation of a greater complexity of Ca2+ bonds with SiO2 and PO43− species within the MgO ceramic network during the in situ incorporation of Ca into the coating from a double chelated electrolyte and the resultant difficulties with the hydrolysis of such a network. The deterioration of the FPEO_CaGlyP coating during immersion was found over ten times slower compared with Ca-free flash-PEO coating.


Journal ArticleDOI
Abstract: This article addresses the results of an experimental study on the behavior of soil; this soil was exposed to long-term treatment with lime and numerous wetting-drying cycles. This research investigated the effect of a wide range of lime contents on the soil volume, soil water content evolution and durability (unconfined compressive strength (UCS), plasticity index (PI) and cation exchange capacity (CEC)) for stabilized soil in contact with water. This experimental study was performed on soil treated with lime (varying from no lime to 8%) corresponding to three levels of improvement: soil improvement only, stabilization and insensitivity to water, and long-term stabilization during wetting-drying cycles. The results indicated that the UCS increases, PI and CEC decreases with the lime level. For lime levels above 4%, the behavior of the treated soil under wetting-drying was satisfactory. Mineralogical analyses indicated that the formation of calcium silicate hydrate C-S-H, ettringite C-S-A-H is responsible for the increased or decreased strength of the treated soil. CaO, SiO2 and Al2O3 were three important minerals responsible for the increase or decrease in soil sample stabilization. Simple model executed in JMP statistical software was proposed and validated. We note that CaO and SiO2 have the most influential effects by very low values of probability for the responses studied, which confirms the hypothesis of that these models can be used to model UCS and PI in curing time and wetting-drying cycles.

Journal ArticleDOI
TL;DR: In this paper, the effect of adding sodium hydroxide and calcium oxide on the mechanical properties of a kaolin-based geopolymer binder cured at room temperature was investigated.

Journal ArticleDOI
TL;DR: In this article, the authors proposed to modify calcium hydroxide powder with nanostructured flow agents to improve the powder's flowability, and the results showed that stabilisation of a moderately increased particle size without the addition of additives is recommended as a sole prevention of agglomeration by means of flow agents does not result in a manageable storage material.

Journal ArticleDOI
TL;DR: In this paper, a mesoporous silica-calcium oxide composite (slagCaO-MS) was synthesized from BFS via a facile dissolution-hydrothermal process using formic acid as a dissolving agent, while the use of mineral acids (HNO3 and HCl) resulted in the formation of ill-defined low surface-area materials with less CO2 adsorption capacities.

Journal ArticleDOI
TL;DR: In this paper, the effects of the solid-state thermal reactions at different sintering temperatures on phase transformation mechanisms and the microstructural changes, the self-disintegration mechanism as well as the efficiency of alumina percent recovery during alumina extraction from kaolin by the lime-sinter process were investigated.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the wettability of molten sodium sulfate salt on nanoscale calcium oxide surfaces at high temperature and micro-mechanisms on the molten salt promoting the performance of thermochemical energy storage.

Journal ArticleDOI
TL;DR: In this paper, the influence of ageing time on physical, structural and mechanical properties of glass Ionomer Cement (GIC) was studied using deionized water as a soaking medium.
Abstract: Glass Ionomer Cement (GIC) is produced from an acid-base reaction between various type of alkaline glass powder and polymeric acid. In this research, calcium fluoro-alumino-silicate (CFAS) glass was derived from waste materials such as soda-lime-silica (SLS) glass and clam shell (CS) which are sources of silica and calcium oxide respectively. The polyacrylic acid (PAA) is used to produced mobile carboxyl group and then, react with metal ions on the surface of CFAS glass. To study the influence of ageing time on physical, structural and mechanical properties of GIC, deionized water was used as a soaking medium. The density results increase throughout the ageing time from 7–28 days. The density of GIC at 7 days shows 1.622 g/cm3 and increasing to 1.789 g/cm3 at 28 days. However, the molar volume shows the opposite action comparing with the density of GIC. The molar volume shows continue decreasing from 357.63–324.25 cm3 mol−1. From the XRD result, GIC was indicating amorphous structure during ageing range between 7–28 days. FTIR analysis shows this phenomenon occurs due to the deformation of Si−OH bonding and formation of Si-O-Si simultaneously in the presence of water which is influence the mechanical strength of GIC. The mechanical properties of GIC increase by ageing time through the compressive test from 42.23–50.28 MPa. Thus, the observed results in this study promise the GIC derived from waste materials have a high potential in dental application due to excellence structural and mechanical properties against ageing.

Journal ArticleDOI
TL;DR: In this article, a nanosized spherical CaCO3 precursor for calcium oxide (CaO) derived from cockle shells using a sol-gel method was synthesized, which is used in bone repair, tissue scaffolds, and the development of advanced drug delivery systems.
Abstract: Cockle shells are a natural reservoir of calcium carbonate (CaCO3), which is widely used in bone repair, tissue scaffolds, and the development of advanced drug delivery systems. Although many studies report on the preparation of CaCO3, the development of a nanosized spherical CaCO3 precursor for calcium oxide (CaO) that is suitable to be incorporated in dental material was scarce. Therefore, this study aimed to synthesize a nanosized spherical CaCO3 precursor for CaO derived from cockle shells using a sol–gel method. Cockle shells were crushed to powder form and mixed with hydrochloric acid, forming calcium chloride (CaCl2). Potassium carbonate (K2CO3) was then fed to the diluted CaCl2 to obtain CaCO3. The effect of experimental parameters on the morphology of CaCO3, such as volume of water, type of solvents, feeding rate of K2CO3, and drying method, were investigated using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry (XRD), Brunauer–Emmett–Teller surface area analysis, and thermogravimetric analysis. Optimized CaCO3 was then calcined to form CaO. XRD analysis of CaCO3 nanoparticles was indicative of the formation of a calcite phase. The well-structured spherical shape of CaCO3 was obtained by the optimum condition of the addition of 50 mL of water into CaCl2 in ethanolic solution with a 1 h feeding rate of K2CO3. Less agglomeration of CaCO3 was obtained using a freeze-drying technique with the surface area of 26 m2/g and average particle size of 39 nm. Spherical shaped nanosized CaO (22–70 nm) was also synthesized. The reproducibility, low cost, and simplicity of the method suggest its potential applications in the large-scale synthesis of the nanoparticles, with spherical morphology in an industrial setting.

Journal ArticleDOI
TL;DR: SEM results showed that pits and grooves on the surface of the steel-slag aggregate, and the textural characteristics provide a framework-like function, thus strengthening the strength and adhesion of theSteel-Slag–bitumen aggregate interface, which revealed the chemical-reaction mechanism between steel- slag microcomponents and bitumen at the interface.
Abstract: In this paper, a permeable steel-slag-bitumen mixture (PSSBM) was first prepared according to the designed mixture ratio. Then, the interaction characteristics between steel slag and bitumen were studied. The chemical interaction between bitumen and steel slag was explored with a Fourier-transform infrared spectrometer (FT-IR). The influence of steel-slag chemistry, mineral composition, and bitumen reaction on phase angle, complex shear modulus (CSM), and rutting factor was explored with dynamic shear rheological (DSR) tests. The PSSBM had better properties, including high permeability, water stability, Marshall stability, high-temperature (HT) stability, and low volume-expansion rate. Bitumen-coated steel slag can prevent heavy-metal ions from leaching. In the infrared spectra of the mixture of a chemical component of steel slag (calcium oxide) and bitumen, a new absorption peak at 3645 cm-1 was ascribed to the SiO-H stretching vibration, indicating that new organic silicon compounds were produced in the chemical reaction between calcium oxide and bitumen. SiO-H had an obvious enhancement effect on the interfacial adhesion and high-temperature rheological property of the mixture. In the mineral components of steel slag, dicalcium and tricalcium silicate reacted with bitumen and generated new substances. Chemical reactions between tricalcium silicate and bitumen were significant and had obvious enhancement effects on interfacial adhesion and high-temperature rheological properties of the mixture. The results of FT-IR and DSR were basically consistent, which revealed the chemical-reaction mechanism between steel-slag microcomponents and bitumen at the interface. SEM results showed that pits and grooves on the surface of the steel-slag aggregate, and the textural characteristics provide a framework-like function, thus strengthening the strength and adhesion of the steel-slag-bitumen aggregate interface.

Journal ArticleDOI
TL;DR: In this paper, the use of magnesium salt compound leaching agent and calcium oxide precipitant can achieve the effective circulation of Ca and Mg, and finally solve the ammonia-nitrogen pollution problem in the whole extraction process.

Journal ArticleDOI
TL;DR: In this paper, the results of CO2 temperature programmed desorption and dynamic flow experiments reveal that porous calcium-based materials, synthesized through a process combining FD and AD sequentially, show high CO2 adsorption capacity (up to 26.1