Showing papers on "Calcium oxide published in 2015"
TL;DR: In this paper, a CaO catalysts derived from waste obtuse horn shells were utilized in the transesterification of palm oil into biodiesel, and the resulting CaO catalyst was characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), temperature-programmed desorption of CO2 (TPD-CO2), Brunauer-Emmett-Teller surface area analysis, and scanning electron microscopy (SEM).
144 citations
TL;DR: In this paper, the authors investigated the mechanism of vanadate formation when vanadium slag was roasted with calcium oxide, and the effects of heating rate, added amount of CaO, holding temperature and holding time on oxidation efficiency were investigated.
119 citations
TL;DR: In this article, the authors present results of a study on chemical acceleration of a neutral granulated blast-furnace slag activated using sodium carbonate. And they show that with accelerators, compressive strength up to 15MPa can be achieved within 24h in comparison to 2.5MPa after 48h for a mix without an accelerator.
106 citations
TL;DR: In this article, the adsorption of gas-phase As2O3 by CaO, FeO, and Al2O 3, using a fixed-bed reactor with an arsenic continuous generation device, was investigated.
Abstract: This research studies the adsorption of gas-phase As2O3 by CaO, Fe2O3 and Al2O3, using a fixed-bed reactor with an arsenic continuous generation device. The adsorption of gas-phase arsenic on CaO and Fe2O3 is mainly chemical adsorption at 600–900 °C. The adsorption quantity and efficiency decreases as the temperature increases. Iron(III) oxide has the best arsenic adsorption ability, followed by calcium oxide and then aluminum oxide. The incoming arsenic concentration was varied, from 4.5 × 10–6 v/v to 13.5 × 10–6 v/v, to determine if this had any effect on adsorption, which revealed that the adsorbent did not become saturated under the experimental conditions used. The adsorption efficiency for each adsorbent was affected by the adsorption temperature, and the same adsorption efficiency was achieved regardless of the inlet arsenic concentration. Intrinsic reaction kinetics of CaO and Fe2O3 with arsenic oxide was studied. The activation energies of CaO and Fe2O3 are 12.17 kJ/mol and 25.99 kJ/mol, respecti...
91 citations
TL;DR: In this paper, the authors used PKS solid residues which had been subjected to thermal treatment in a gasifier were used as raw materials for the production of a calcium oxide (quicklime/burnt lime) catalyst.
87 citations
TL;DR: In this paper, the synthesis of mixed calcium oxide-alumina compositions as candidate materials for a cyclic thermochemical hydration-dehydration scheme at moderate to high temperatures (e.g. 400-600°C) was investigated.
80 citations
TL;DR: In this paper, the effectiveness of fly ash (FA) and lime kiln dust (LKD) in soft clays subgrade stabilization is examined, and the results revealed that the addition of Class C FA could increase the dry unit weight of the FA treated soil, enhance the unconfined compressive strength, and improve the resilient modulus.
Abstract: Soft clays are widely distributed in Missouri, United States. Due to their relatively low strength and high compressibility, subgrade construction in soft clays has encountered many difficulties. In recent practice, the use of fly ash (FA) along with lime to tackle soft subgrade problems has shown promising results. The effectiveness of Class C FA and lime kiln dust (LKD) in clay subgrade stabilization is examined in this research. Scanning electron microscopic (SEM) analysis, proctor compaction tests, unconfined compression tests, and resilient modulus tests were carried out on the FA and LKD modified soil mixtures. Test specimens were prepared at optimum water content and tested at various curing periods. The test specimens were reconstituted by static compression. Test results revealed that the addition of Class C FA could increase the dry unit weight of the FA treated soil, enhance the unconfined compressive strength, and improve the resilient modulus. Regression equations were developed to co...
76 citations
TL;DR: In this paper, the authors investigated the effects of reaction temperature and pressure, moisture content of DSS, and calcium oxide (CaO) additive on evolution profile and characteristics of gas, solid, and liquid products.
72 citations
TL;DR: In this article, seven commercially available reactive MgOs, whose characteristics vary widely, were chosen to activate ground-granulated blast-furnace slag (GGBS), which is one of the most widely used by-products in the cement industry.
Abstract: Reactive MgO has recently emerged as a potential activator for ground-granulated blast-furnace slag (GGBS), which is one of the most widely used by-products in the cement industry. However, it is known that the characteristics of reactive MgO vary significantly, which may affect the activation process and hence the performance of MgO-GGBS blends. In this study, seven commercially available reactive MgOs, whose characteristics vary widely, were chosen to activate GGBS. The unconfined compressive strength (UCS) of MgO-GGBS pastes up to 90 days was measured, and the hydration products were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The primary hydration products were identified as calcium silicate hydrate (C-S-H) and hydrotalcitelike phases (Ht). Minor hydration products included magnesium silicate hydrate (M-S-H) and ettringite. The reactivity and calcium oxide content of the MgO samples were found to be the two major factors affecting the hydration process of the MgO-GGBS blend. Higher reactivity did not change the hydration products, but resulted in more hydration products in the same time. Sufficient CaO content increased the pH of the system, which enhanced the slag dissolution degree and was beneficial to the strength development.
65 citations
TL;DR: In this article, the Aerosil® additive for thermochemical storage is investigated during cycling in an indirect operating pilot-scale thermochemical reactor with regard to side reactions, stability on the surface and various coating configurations.
62 citations
TL;DR: In this paper, the effect of adding limestone on the metallurgical properties (reducibility, swelling, cracking, softening temperature, Low-Temperature Disintegration, Cold Crushing Strength) of acid iron ore pellets was investigated using a comprehensive set of metallogical laboratory tests.
TL;DR: In this paper, the authors used shrimp shells as a green source of precursors to produce calcium oxide nano-plates ranging from 40 to 130 nm (in length) and 30 to 100 nm(in width).
TL;DR: In this paper, a combined kinetic and nanostructural research on CaO oriented to two key processes for different systems, i.e., hardening of construction materials and carbon mineral sequestration, is presented.
TL;DR: In this article, the authors demonstrated that nanoscale calcium oxide particles (n-CaO) could transport through phloem tissue of groundnut unlike the corresponding bulk materials.
Abstract: Nanoscale materials, whose size typically falls below 100 nm, exhibit novel chemical, physical and biological properties which are different from their bulk counterparts In the present investigation, we demonstrated that nanoscale calcium oxide particles (n-CaO) could transport through phloem tissue of groundnut unlike the corresponding bulk materials n-CaO particles are prepared using sol–gel method The size of the as prepared n-CaO measured (699 nm) using transmission electron microscopic technique (TEM) Results of the hydroponics experiment using solution culture technique revealed that foliar application of n-CaO at different concentrations (10, 50, 100, 500, 1,000 ppm) on groundnut plants confirmed the entry of calcium into leaves and stems through phloem compared to bulk source of calcium sprayed (CaO and CaNO3) After spraying of n-CaO, calcium content in roots, shoots and leaves significantly increased Based on visual scoring of calcium deficiency correction and calcium content in plant parts, we may establish the fact that nanoscale calcium oxide particles (size 699 nm) could move through phloem tissue in groundnut This is the first report on phloem transport of nanoscale calcium oxide particles in plants and this result points to the use of nanoscale calcium oxide particles as calcium source to the plants through foliar application, agricultural crops in particular, as bulk calcium application through foliar nutrition is restricted due to its non-mobility in phloem
TL;DR: In this article, a density functional theory was employed to examine the binding mechanism of SO3 to several metal oxides that compose coal fly ash, including calcium oxide, magnesium oxide, sodium oxide and potassium oxide, to understand the interactions between the gaseous SO3 and the metal oxide surfaces.
TL;DR: In this article, the liquid precursors of calcium hydroxide and diammonium hydrogen phosphate were injected into the plasma jet generated by the SG-100 torch to synthesize the hydroxyapatite (HA) coatings.
Abstract: The liquid precursors of calcium hydroxide and diammonium hydrogen phosphate were injected into the plasma jet generated by the SG-100 torch to synthesize the hydroxyapatite (HA) coatings. Three operational deposition process parameters, namely: (i) electric power, (ii) spray distance, and (iii) scan speed were varied. The process enabled synthesization of coatings with HA as major phase onto stainless steel substrates. The coatings were deposited to reach the thickness of about 50 μm with high rate ranging from 3 μm to nearly 7 μm by pass of torch. The X-ray diffraction (XRD) analysis of coatings enabled finding of HA accompanied by calcium phosphates, calcium oxide, and calcium carbonate. The presence of the carbonates was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and by elemental mapping made with the use of Electron Dispersive X-ray Spectroscopy (EDS). The morphology of coatings, observed using scanning electron microscope (SEM), revealed fine-grained microstructure and porosity in the range of 1.3 to 5.1%. The adhesion of coatings obtained using scratch test characterized by critical force was in the range of 2.5 to 3.6 N.
TL;DR: In this paper, a set of CO2 absorption experiments were conducted in a high temperature reaction capillary with a controlled atmosphere (CO2 partial pressure of 1 bar), in the temperature range between 450 1C and 750 1C using CaO based sorbents obtained by calcination of commercial calcium carbonate.
Patent•
18 Nov 2015
TL;DR: In this paper, a heavy metal stabilizer consisting of sodium bentonite, zeolite powder, sulfydryl-iron base modified charcoal, reduced iron powder and calcium oxide is presented.
Abstract: The invention discloses a heavy metal stabilizer which comprises sodium bentonite, zeolite powder, sulfydryl-iron base modified charcoal, reduced iron powder and calcium oxide. By carrying out sulfydryl-iron base modification on charcoal, the adsorption property of the heavy metal stabilizer to heavy metal is improved greatly; by mixing the sulfydryl-iron base modified charcoal with sodium bentonite, zeolite powder, reduced iron powder and calcium oxide, the heavy metal stabilizer is obtained. Compared with other materials, the heavy metal stabilizer has a better heavy metal adsorption property, can be applied to soil of different pH and combined pollution of multiple pollutants such as lead, zinc, copper, cadmium and arsenium at different degrees through reasonable proportioning, can simultaneously and effectively reduce exchangeable form quantity of pollutants such as lead, zinc, copper, cadmium and arsenium in soil, and is high in efficiency, stable and effective for a long term.
TL;DR: In this paper, the feasibility of calcium oxide for hydroxyapatite preparation was evaluated by the chemical precipitation with phosphoric acid, and X-ray diffraction confirmed that single phase of hydrophylla was obtained.
Abstract: Calcium oxide was successfully derived from eggshell waste. It was employed as a calcium precursor in order to prepare hydroxyapatite. It can be noted that eggshell presented high thermal stability, and it was calcined from 700 to 1000 °C for 3 h for calcium oxide formation. Morphological properties were investigated, and it presented the irregular shape with a variation on size. The feasibility of calcium oxide for hydroxyapatite preparation was evaluated by the chemical precipitation with phosphoric acid. X-ray diffraction confirmed that single phase of hydroxyapatite was obtained.
TL;DR: In this article, a transesterification catalyst, labeled as CS-850, gains surface area of 8.00m 2 ǫg −1, functional groups of vanishing O C O and O H bonds, surface morphology of tenuous branch and porous structure.
TL;DR: Screened multiwire, PVC insulated tinned copper cable was gasified with steam at high temperature (HTSG) under atmospheric pressure for recovery of cooper and it was found that 28% of chlorine reacted to form CaCl2, 71% was retained in aqueous condensate and only 0.6% was absorbed in alkaline scrubber.
TL;DR: In this article, the catalytic performance of natural dolomitic rock as an environmentally friendly catalyst in the reaction of Jatropha Curcas oil with methanol under microwave-assisted transesterification was analyzed.
TL;DR: In this paper, the effect of long-term soaking and leaching on the stability properties of fine-grained soil with and without gypsum content was studied, and the results showed that the longterm soaking (up to 180 days) effect on the unconfined compressive strength, and volume change of the stabilised soil samples.
Abstract: This paper aims to study the effect of long-term soaking and leaching on the stability properties of fine-grained soil with and without gypsum content. The soil samples were stabilised with 3% lime and cured for 28 days at 20°C. The results showed the long-term soaking (up to 180 days) effect on the unconfined compressive strength, and volume change of the stabilised soil samples. These properties are degraded when compared to the initial properties of the unsoaked samples. Further, the gypsum content has significant effects on the geotechnical properties of soil samples during soaking process. The effect of soaking on the cured samples (28 days) seems to be more important than the benefits induced by lime–clay reactions. The permeability of soil samples is strongly related to the gypsum content during the leaching test, and the effect of leaching on the permeability increased with gypsum content.
TL;DR: In this article, a Lime Mud (LM) based transesterification catalyst is prepared through calcinations and then it is hydrated and desiccated to simulate the contamination by H2O and CO2.
TL;DR: In this article, a CaO-based expansive agent was added to fiber reinforced cement-based composites in order to help in reducing the cracking induced by drying shrinkage, and the effect on mechanical performance of thermal pre-treatment at 80°C was evaluated.
Abstract: In this project several fiber reinforced cement-based composites (FRCCs) were studied, in which a CaO-based expansive agent was added in order to help in reducing the cracking induced by drying shrinkage. Two different kinds of fibers were tested: brass-coated hooked steel fibers and flat and flexible amorphous metallic fibers. All the mixtures were characterized for fresh and hardened state, by measuring the consistency of fresh mixtures, compressive and flexural strength, as well as length changes under drying shrinkage test condition for the hardened state. Their microstructures were also investigated by mercury intrusion porosimeter and SEM observations. The effect on mechanical performance of thermal pre-treatment at 80 °C was also evaluated. Results obtained confirmed the effectiveness of CaO addition (even at a low-dosage) on the stability of mixtures under drying shrinkage. It also proved to be effective in terms of flexural strength improvement when used with brass-coated fibers. The reason of this synergy probably lies in the formation of calcium hydroxyzincate (CHZ) crystals at the interface between the fibers and surrounding cement paste. These CHZ crystals, as observed by SEM, are likely able to noticeably improve the quality of the interface of the fiber-matrix by increasing adhesion.
TL;DR: An attempt was made to recycle oil shale fly ash (OSFA), a by-product obtained from the extracting of shale oil in the oil shale industry, into a value-added glass-ceramic material via melting and sintering method, showing that it could be used as a substitute material for construction applications.
TL;DR: In this paper, the authors investigated batch reactions and phase transitions in a simulated nuclear waste glass melter feed heated at 5 k/min up to 700 k/m using optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and Xray diffraction.
Abstract: To understand feed-to-glass conversion for the vitrification of nuclear waste, we investigated batch reactions and phase transitions in a simulated nuclear waste glass melter feed heated at 5 K/min up to 700°C using optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray diffraction. To determine the content and composition of leachable phases, we performed leaching tests; the leachates were analyzed by inductively coupled plasma atomic emission spectroscopy. By 400°C, gibbsite and sodium borates lost water and converted to amorphous phase, whereas other metallic hydroxides dehydrated to oxides. Between 400°C and 700°C, carbonates decomposed before 500°C; amorphous aluminum oxide and calcium oxide reacted with the sodium borate and formed the more durable amorphous borate phase along with intermediate crystalline products; above 500°C, quartz began to dissolve, and hematite started to convert to trevorite.
TL;DR: In this article, the authors developed new composite materials for application in chemical heat storage (CHS) systems based on the calcium oxide/water/calcium hydroxide (CaO/H2O/Ca(OH)2) reaction.
Abstract: New composite materials were developed for application in chemical heat storage (CHS) systems based on the calcium oxide/water/calcium hydroxide (CaO/H2O/Ca(OH)2) reaction. It was found that the mixtures of expanded graphite (EG) and Ca(OH)2 enhance the reaction performance and moldability, which are important factors for the application in a packed-bed CHS heat exchanger. The reaction kinetics was investigated by thermogravimetric analysis. The maximum mean heat output of a mixture containing 11 wt% EG was 1.76 kW (kg-material), which is twice as high as that of the pure Ca(OH)2 (0.85 kW (kgmaterial)). A repetitive dehydration-hydration experiment was carried out and it was confirmed that the positive effect of EG was preserved during the investigated 10 cycles. Therefore, based on our results, these composite materials can enhance the thermal performance of the CaO/H2O/Ca(OH)2 reaction cycle in CHS systems.
TL;DR: In this paper, three types of bauxites containing aluminum hydroxide of 58.1% gibbsite and 19.3% boehmite were used with lime at 95% of CaO through solid state sintering in one stage to prepare a refractory clinker.
Journal Article•
TL;DR: In this article, seven commercially available reactive MgOs, whose characteristics vary widely, were chosen to activate ground granulated blastfurnace slag (GGBS), which is one of the most widely used by-products in the cement industry.
Abstract: Reactive MgO has recently emerged as a potential activator for ground granulated blastfurnace slag (GGBS), which is one of the most widely used by-products in the cement industry. However, it is known that the characteristics of reactive MgO vary significantly, which may affect the activation process and hence the performance of MgO-GGBS blends. In this study, seven commercially available reactive MgOs, whose characteristics vary widely, were chosen to activate GGBS. The unconfined compressive strength (UCS) of MgO-GGBS pastes up to 90 days was measured and the hydration products studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The primary hydration products were identified as calcium silicate hydrate (C-S-H) and hydrotalcite-like phases (Ht). Minor hydration products included magnesium silicate hydrate (M-S-H) and ettringite. The reactivity and calcium oxide content of the MgO samples were found to be the two major factors affecting the hydration process of the MgO-GGBS blend. Higher reactivity did not change the hydration products but resulted in more hydration products in the same time. Sufficient CaO content increased the pH of the system, which enhanced the slag dissolution degree and was beneficial to the strength development.