Showing papers on "Calcium oxide published in 2021"
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TL;DR: In this article, the reduction of CO2 emissions by a calcium oxide loop was investigated for pine sawdust in a mixture of N2 and CO2 in a fixed-bed reactor.
42 citations
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TL;DR: In this article, the authors present an overview of the biodiesel production advancements using calcium oxide-based catalysts (e.g., pure, supported, and mixed with metal oxides).
Abstract: Biodiesel is a clean, renewable, liquid fuel that can be used in existing diesel engines without modification as pure or blend. Transesterification (the primary process for biodiesel generation) via heterogeneous catalysis using low-cost waste feedstocks for catalyst synthesis improves the economics of biodiesel production. Heterogeneous catalysts are preferred for the industrial generation of biodiesel due to their robustness and low costs due to the easy separation and relatively higher reusability. Calcium oxides found in abundance in nature, e.g., in seashells and eggshells, are promising candidates for the synthesis of heterogeneous catalysts. However, process improvements are required to design productive calcium oxide-based catalysts at an industrial scale. The current work presents an overview of the biodiesel production advancements using calcium oxide-based catalysts (e.g., pure, supported, and mixed with metal oxides). The review discusses different factors involved in the synthesis of calcium oxide-based catalysts, and the effect of reaction parameters on the biodiesel yield of calcium oxide-based catalysis are studied. Further, the common reactor designs used for the heterogeneous catalysis using calcium oxide-based catalysts are explained. Moreover, the catalytic activity mechanism, challenges and prospects of the application of calcium oxide-based catalysts in biodiesel generation are discussed. The study of calcium oxide-based catalyst should continue to be evaluated for the potential of their application in the commercial sector as they remain the pivotal goal of these studies.
31 citations
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TL;DR: In this paper, the effects of different levels of calcium oxide and ferrous oxide on the local structural order, bonding network, transport characteristics, and other microstructures and viscosity of the aluminosilicate slag system were analyzed.
30 citations
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TL;DR: An experimental study was carried out on an expansive black cotton soil (BCS) treated with lime and bamboo ash (BA) to determine its suitability as subgrade material as discussed by the authors.
Abstract: An experimental study was carried out on an expansive black cotton soil (BCS) treated with lime and bamboo ash (BA) to determine its suitability as subgrade material. Preliminary tests cond...
30 citations
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TL;DR: In this paper, the authors have emphasized on the all the calcium rich agro industries and industrial by products, especially their processing by various approaches and focused on the properties and application of such calcium carbonate and oxide particles for the remediation of organic and inorganic pollutants from the environments.
Abstract: Every year a million tonnes of calcium rich agro and industrial waste are generated around the whole globe. These calcium rich waste like finger citron, shells of cockle, mussel, oysters etc., and egg shell are biological sources which have various organic compounds. The inorganic calcium rich waste includes gypsum, dolomite, sludge etc., which are produced in surplus amount globally. Most of these by-products are mainly dumped, while few are used for land-filling purposes which leads to the pollution. These agro and industrial by-products could be processed for the recovery of calcium carbonate and calcium oxide particles by physical and chemical method. The recovery of calcium carbonate and calcium oxide particles from such by products make them biocompatible. Moreover, the products are economical due to their synthesis from waste materials. Here, in this current review work we have emphasized on the all the calcium rich agro industries and industrial by products, especially their processing by various approaches. Further, we have also focused on the properties and application of such calcium carbonate and oxide particles for the remediation of organic and inorganic pollutants from the environments. The recovery of such particles from these byproducts is considered not only economical and eco-friendly but it also minimizes the pollution present in the form of solid waste.
29 citations
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TL;DR: In this paper, a 100% HWIR was used to prepare SiO2-Al2O3-Fe2O-3-CaO glass-ceramic samples, which exhibited a superior compressive strength, volume density, and water absorption of 204.84 MPa, 2.80 g/cm3, and 1.20% respectively.
29 citations
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01 Aug 2021TL;DR: In this article, the application of synthesized calcium oxide nanoparticles from hen eggshells for the removal of lead ions from aqueous solutions is what was investigated, and the results showed that the particle density, bulk density, porosity, point of zero charges, Fourier transform infrared radiation spectroscope, X-ray diffraction, specific surface area, thermal gravimetric analysis and scanning electron microscopy was done before batch adsorption experiments.
Abstract: Lead is an important industrial heavy metal used in various production industries. Remediation of Lead poisoned areas has both economical and technological challenges, as conventional and techniques are very expensive to apply for wastewater treatment and its operation is difficult. The adsorption method could solve the problem using sol-gel-based synthesized adsorbent since it is environmentally friendly with high-quality product produced. In the present study, the application of synthesized calcium oxide nanoparticles from hen eggshells for the removal of lead ions from aqueous solutions is what was investigated. Characterization of the adsorbent like proximate analysis, particle density, bulk density, porosity, point of zero charges, Fourier transform infrared radiation spectroscope, X-ray diffraction, specific surface area, thermal gravimetric analysis, and scanning electron microscopy was done before batch adsorption experiments. X-ray diffraction revealed that the size of synthesized calcium oxide nanoparticles was 24.34 nm and the specific surface area was 77.4m2/g. The removal of divalent lead ions from aqueous solutions was optimized by using response surface methodology. The optimum percent removal of lead (99.07) has resulted at initial concentration 75.46 ppm, pH 6.94, adsorbent dose 0.838 g, and contact time 101.97 min. The experimental removal efficiency (98.86%) agreed very well with the predicted one (99.07%), showing the suitability of the model used and the success of response surface methodology in optimizing of removal of Pb (II) ions from aqueous solutions. The lead ions removal was well fitted into the Langmuir isotherm model with correlation coefficients of 0.9963. The adsorption kinetic data were well fitted with the pseudo-second-order model with a correlation coefficient of 0.9982. The pseudo-second-order model was the rate-limiting step in the lead (II) ions adsorption process onto CaO NPs. Based on the obtained results, the calcium oxide nanoparticles prepared from eggshell have a good capacity for the removal of the lead ions from the aqueous solutions.
28 citations
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TL;DR: In this article, the authors examined the environmental impacts of eggshell limes and commercially available limes using Life Cycle Assessment (LCA) and an assessment of the strength and stiffness of a sandy soil stabilized with ground glass.
27 citations
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TL;DR: In this paper, the composition of an electrolyte was selected and optimized to induce the formation of hydroxyapatite during PEO treatment on an AZ31 alloy for application in bioabsorbable implants.
Abstract: In this work, the composition of an electrolyte was selected and optimized to induce the formation of hydroxyapatite during Plasma electrolytic oxidation (PEO) treatment on an AZ31 alloy for application in bioabsorbable implants. In detail, the PEO process, called PEO-BIO (Plasma Electrolytic Oxidation-Biocompatible), was performed using a silicate-phosphate-based electrolyte with the addition of calcium oxide in direct-current mode using high current densities and short treatment times. For comparison, a known PEO process for producing anticorrosive coatings, called standard, was applied on the same alloy. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and XPS analyses. The corrosion performance was evaluated in simulated body fluid (SBF) at 37 °C. The coating produced on the PEO-BIO sample was porous and thicker than the standard PEO one, with zones enriched in Ca and P. The XRD analysis showed the formation of hydroxyapatite and calcium oxides in addition to magnesium-silicon oxide and magnesium oxide in the PEO-BIO sample. The corrosion resistance of PEO-BIO sample was comparable with that of a traditional PEO treated sample, and higher than that of the untreated alloy.
20 citations
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TL;DR: In this article, the use of a clay/CaO heterogeneous catalyst for the production of biodiesel from waste cooking oil was investigated, where the catalyst was synthesized from clay and calcined using calcium oxide under controlled conditions.
19 citations
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TL;DR: In this paper, the influence of different concentrations of dispersed calcium oxide over ZMFA and thermal treatment at different temperatures (450-600 °C) were studied, which indicated the presence of strong active sites in a well defined pore network suitable for the reactions of bulky organic compounds.
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TL;DR: In this paper, a series of N-doped hierarchical porous carbons were successfully prepared from the direct pyrolysis process of three food waste components, and the porous biochar that derived from bone showed a high specific surface area (1405.06 m2/g) and sizable total pore volume (0.97 cm3/g).
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TL;DR: In this paper, the authors investigated the energy efficiency of catalytic microwave-assisted torrefaction with calcium oxide, where calcium oxide is employed as a microwave absorber and the results from ANOVA indicate that microwave power significantly affects the energy yield, followed by the holding time and catalyst concentration.
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TL;DR: In this article, soda sludge was used as the calcareous material to synthesize clinker binders, where the effect of temperature and times of water washing on chloride ions (Cl−) in soda sludges was investigated.
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TL;DR: In this article, the synthesis of nano calcium oxide derived from waste cockle shell (Anadara granosa) and applied as heterogenous catalyst in biodiesel production via transesterification reaction under reaction parameter 15:1 methanol to oil ratio, 5 wt.% catalyst and 3 hour reation time and constant temperature at 65 ± 2 °C.
Abstract: Present work proposes on the synthesis of nano calcium oxide derived from waste cockle shell (Anadara granosa) and applied as heterogenous catalyst in biodiesel production via transesterification reaction under reaction parameter 15:1 methanol to oil ratio, 5 wt.% catalyst and 3 hour reation time and constant temperature at 65 ± 2 °C. The waste cockle shell was prepared in nano size via ball mill technique which was run for 36 hours at 350 rpm speed and then calcined at 900 °C for 2 hours to decompose calcium carbonate, CaCO₃ into nano calcium oxide, n-CaO. The catalyst was characterized by particle size analyzer, Transmission Electron Microscopy, Field Emission Scanning Electron Microscope, Surface Area Analyser, X-Ray Diffractometer, Fourier transform infrared, Hammet indicator and benzoic acid titration. Particle size of n-CaO catalyst was found within the range of 29 nm to 67.5 nm. Specific surface area of synthesised n-CaO is 8.41 m²/g with basicity strength of 0.055 mmol/g. Methyl ester conversion of palm oil with n-CaO as a catalyst was 88.87 wt.%
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TL;DR: In this paper, the roles of calcium oxide on the release of these compounds, especially the heavy ones containing nitrogen and oxygen atoms were investigated, and it was found that calcium oxide could catalyze or react with all three components to decrease the content of light substituted polycyclic aromatic hydrocarbons.
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TL;DR: In this article, an electrochemical system is used to precipitate inorganic salts available in seawater brine, and the system consists of two graphite electrodes, a DC power source and the waste-brine works as the electrolyte.
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TL;DR: A heterogeneous catalyst alumina-doped calcium oxide nanocomposite was synthesized and used for the transesterification of pork fat into biodiesel as mentioned in this paper, which was used for animal protein processing.
Abstract: A heterogeneous catalyst alumina-doped calcium oxide nanocomposite was synthesized and used for the transesterification of pork fat into biodiesel. Calcium oxide was synthesized from waste egg shel...
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TL;DR: The thermal instability of HAp powders from a combined mechanical activation with solid-state reaction of CaCO3 or CaO and DCPD powders could result from two factors: that the pollution was released from the balls and pot mill materials during the mechanical process and another factor is a reduced level of calcium in the CaO + DCPD mixed powder due to a reaction betweenCaO and water or alcohol during mechanical milling.
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TL;DR: In this article, the effects of iron on the decomposition of gypsum, formation of phases, microstructure of the clinker, and hydration of cement paste were investigated.
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TL;DR: In this article, the main roles of calcium-based alkali materials such as calcium oxide, calcium peroxide and calcium hydroxide on the substrate pretreatment for obtaining high biodegradability, while others (e.g., calcium carbonate, lime and red muds) used as additives for maintaining process stability, thereby increasing biogas yield from anaerobic digestion and dark fermentation.
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01 Jun 2021TL;DR: In this paper, the authors used X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, AC conductivity and dielectric studies to correlate the physico-chemical behavior.
Abstract: Calcium Oxide (CaO) nanoparticles have been synthesized from waste eggshells (ES) as a source of calcium by solution combustion technique using muffle furnace and microwave oven. CaO nanoparticles obtained using muffle furnace (CaO-F) and via microwave oven (CaO-M) were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, AC conductivity and dielectric studies to correlate the physico-chemical behavior. The frequency dependence of AC conductivity, the permittivity (e′) and dielectric loss tangent (D) studies have been undertaken in the frequency range 50 Hz–5 MHz at room temperature. AC conductivity was found to enhance with an increase in the frequency. The e′ was found to decrease initially with the frequency and finally reaching a constant value at higher frequencies. The frequency dependence of D was found to exhibit a resonance peak in the studied frequency region. Catalytic activity of CaO-M was correlated with its dielectric behavior.
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TL;DR: Several metal additives (Al, Co, Cr, Er, Ga, In, La, Li, Mg, Nd, Y, and Zn) were investigated for their ability to stabilize high capacity calcium oxide nanofibers over repeated carbonation-regeneration cycles.
Abstract: Several metal additives (Al, Co, Cr, Er, Ga, In, La, Li, Mg, Nd, Y, and Zn) at nominal 3 : 10 (M : Ca) ratios were investigated for their ability to stabilize high capacity calcium oxide nanofibers over repeated carbonation–regeneration cycles. Samples containing Mg, Y, Nd, La, and Er additives had maximum sorption capacities from 0.40–0.60 gCO2 gsorbent−1, compared to 0.79 gCO2 gsorbent−1 for CaO. Y, Al, Er, and Nd were most effective for improving the stability of CaO, each had first order deactivation constants that were at least one order of magnitude smaller compared to CaO. Post-carbonation characterization revealed that particle agglomeration and structure degradation were the primary reasons for loss in capacity over repeated carbonation–regeneration cycles. Metal additives with high Tammann temperatures of the corresponding metal oxide mitigated structure degradation, leading to improved cyclic stability compared to pure CaO. Additionally, mixed oxide formation had no effect on stability albeit a deleterious effect on sorbent capacity.
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TL;DR: In this paper, the pyrolysis mechanism of Spirulina platensis with calcium oxide was investigated using a thermogravimetric analyzer and a fixed bed reactor, respectively.
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TL;DR: In this article, the influence of sodium doping in a CaO sorbent was investigated in the sorption enhanced steam methane reforming process (SE-SMR) and it was shown that the addition of sodium decreased the duration of pre-breakthrough comparing with the non-doped material.
Abstract: The addition of alkali molten salts has been reported as a strategy to overcome the sintering problem presented by calcium oxide in CO2 capture systems. In this work, the influence of sodium doping in a CaO sorbent was investigated in the sorption enhanced steam methane reforming process (SE-SMR). The goal was to increase the stability of the sorbent and, consequently, the efficiency of the process. For that, a Na-containing sorbent was prepared using the precipitation technique and a pure calcium oxide was obtained by calcination of CaCO3. The sorbents were physically mixed with 10 % Ni/Al2O3 catalyst and tested in 10 cycles of SE-SMR at 600 °C and CH4:H2O equals to 4. In general, both materials showed 100 % of CH4 conversion and H2 molar fraction of 93.5 vol.%. However, regarding the stability over the SE-SMR cycles, it was evidenced that the addition of sodium decreased the duration of pre-breakthrough comparing with the non-doped material. The XRD, SEM, and TGA results allowed us to observe an inverse relationship of particle diameter and CO2 capture performance. Na2CO3-CaO presented a larger average crystallite size compared to the pure CaO which led to a higher probability of the CaCO3 layers to inactivate the calcium oxide and, consequently, caused a strong sintering effect. Besides the presence of sodium, the precipitation method and the synthesis conditions could have favored the low initial CO2 uptake and poor stability of the Na2CO3-CaO sorbent.
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TL;DR: In this paper, the phase transition of the major ash element calcium (Ca) was studied with powder from pine as biomass model treated at temperatures 300-800°C under atmospheres of 100% N2, 3% O2 and 6% O 2 and thermodynamic equilibrium modelling.
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TL;DR: In this article, the effects of CaO particle size on the microstructure and properties of AZ91 alloy were investigated using commercial AZ91 (Mg-9Al-1Zn, wt%) alloy and CaO nano (50nm), sub-micro (200-nm, 500-nm) and micro (1000-nm), particles as grain refiners.
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TL;DR: In this article, the compressive strength of geopolymer concrete (GPC) has been investigated against the different ratios of oxides and alkaline solution (i.e. Si/Al, alkaline solutions to binder, NaOH to Na2SiO3, combined percentage of Fe2O3+CaO and molar concentration of NaOH).
Abstract: Recently, geopolymer concrete (GPC) has gained substantial consideration and commercial interest in the construction industry owing to the superior mechanical and chemical properties in comparison with the ordinary Portland cement (OPC) that it brings through the use of waste material and reduction in the CO2 emission. Previous research Studies revealed that different ratios of chemical oxide combination of the raw material (fly ash, rice husk ash, meta kaolin, sugarcane bagasse ash, GGBS etc.) strongly affect the mechanical and durability properties of GPC. Nevertheless, findings concerning different ratios of Si/Al, alkaline solution to binder, NaOH to Na2SiO3, combined percentage of Fe2O3 + CaO and molar concentration of NaOH are controversial regarding the compressive strength of GPC. Therefore, in the light of literature, this study presents the investigation of the compressive strength behavior against the different ratios of oxides and alkaline solution (i.e. Si/Al, alkaline solution/binder, NaOH/Na2SiO3, Fe2O3 + CaO and NaOH molar concentration) present in the raw material used for the production of GPC. An extensive data from previous research publications has been collected and trend of compressive strength for 7 and 28 days was developed against different ratios of Si/Al, alkaline solution/binder, NaOH/Na2SiO3, in order to conclude a typical range for the above mention parameters. It was concluded that compressive strength of GPC greatly depends on the variation in ratios of Si/Al, alkaline solution/binder, NaOH/Na2SiO3, Fe2O3 + CaO and NaOH molar concentration. It was also concluded that the compressive strength of GPC has been primarily affected by the ratio of Si/Al, alkaline solution/binder, NaOH/Na2SiO3 and molar concentration of NaOH. Besides, the oxides like CaO and Fe2O3 although smaller in quantity in comparison with the alumina and silicate oxides, have indicated a distinct influence on the compressive strength development.