Source Of CaO Research Articles

A novel strategy for low-temperature fabrication of porous CA6 ceramics using reactive CaCl2-KCl medium and its influence mechanism

This paper proposes a novel strategy to fabricate porous calcium hex-aluminate (CA6) ceramics using CaCl2-KCl as reactive medium. Effects of CaCl2-KCl content and sintering temperature on microstructure and properties of porous CA6 ceramics are systematically studied. CaCl2-KCl serves as both a pore former and an additional source of CaO, eliminating the need for additional salt-washing treatment. By optimizing CaCl2-KCl content to 20 wt%, porous CA6 ceramics with well cross-interlocking plate-like structures, possessing low thermal conductivity of 0.32 W·(m·K)−1 (1000°C), high apparent porosity of 68.28%, and desirable compressive strength of 6.76 MPa, are fabricated at 1300°C. This work not only validates the promising applicability of porous CA6 materials for thermal insulation, but also introduces an auspicious fabrication methodology for thermal insulation materials.

Fabrication of Porous Anorthite Ceramic Insulation Using Solid Wastes.

Porous anorthite (CaAl2Si2O8) ceramics, suitable for thermal insulation in buildings, were obtained using waste seashells as a source of CaO, kaolin as a source of Al2O3 and SiO2 and banana peel as a pore former. Changing the volume of banana peel as well as the processing temperature was found to be an effective approach to control the thermo-mechanical properties of the obtained anorthite ceramics. The sintering of powder compacts containing up to 30 wt% banana peel at temperatures ranging from 1100 to 1200 °C resulted in anorthite ceramics possessing up to 45% open porosity, a compressive strength between 13 and 92 MPa, a bulk density between 1.87 and 2.62 g/cm3 and thermal conductivity between 0.097 and 3.5 W/mK. It was shown that waste materials such as seashells and banana peel can be used to obtain cost-effective thermal insulation in buildings.

Production of refining alumina-containing fluxes by sintering from technogenic raw materials

Modern Russian steelmaking plants use predominantly alumina-containing materials for liquefying lime in a ladle-furnace unit, which replaced fluorspar. Alumina-containing materials currently available on the market cannot be used directly in steelmaking without preliminary preparation (refining, heat treatment or briquetting), or are simply unsuitable for ladle processing of steel. This work describes laboratory studies on the production of refining alumina-containing fluxes by sintering in units such as machines for pellets firing or producing agglomerate (in the temperature range of 1200 – 1500 °C) from clean metallurgical waste (fine dust from the production of alumina and burnt lime), meeting the requirements of steelmaking plants by chemical composition and mechanical properties. A comparison was made of sintering technological schemes with the introduction of hydra­ted lime and a mixture of hydrated lime and calcium carbonate in a 1:1 ratio as a source of CaO. We determined that the maximum permissible CaO content in sintered briquettes when using a mixture of hydrated lime and calcium carbonate in the charge, which does not lead to hydration destruction in air, is in the range of 2.3 - 3.6 %, depending on the holding temperature. The maximum permissible content of Al2O3 in sintered briquettes when using hydrated lime in the charge, which does not lead to hydration destruction in air, is in the range of 9.5 – 31.7 %, depending on the holding temperature. In existing fuel units it is possible to obtain fluxes by sintering only when using hydrated lime as a source of CaO, because adding calcium carbonate to the charge (9 – 22 %) requires an increase in holding temperature (above 1500 °C) or holding time (more than 25 min).

Mechanical properties and thermal shock resistance of anorthite ceramics obtained by slip casting

Anorthite ceramics (CaAl2Si2O8) was obtained by slip casting of water suspension of kaolin (Al2O3·2SiO2·2H2O) and CaCO3 as a source of CaO. A relative density of 87 % of the theoretical density was achieved after a 3-h-long sintering of green samples at 1200 °C. It was found that slip casting allows the fabrication of anorthite with relatively small pores (<8 μm) which was beneficial for achieving a high fracture strength of 129 MPa and good thermal shock resistance. For a quantitative measurement of thermal shock resistance, a critical temperature interval (ΔTc) was determined by a reduction in the mean fracture strength of at least 30 %. The experimentally determined ΔTc of 300 °C was higher than the value calculated by the equation assuming that the thermal stress created during quenching causes the fracture. It was found that the discrepancy between experimental and calculated values of ΔTc could be explained by an introduction of cracks of various sizes by indentation method and careful observation of crack growth initiation after quenching from various temperatures. It is believed that the reason for the discrepancy lies in the different nature of stress that was used in the theoretical calculation and the stress that acts during sample quenching.

Synthesis, structure, and hydration of stoichiometric ye’elimite and iron-bearing ye’elimite

Ye’elimite is the primary mineral component in calcium sulfoaluminate cements and is responsible for their early hydraulic reactivity. Herein, ye’elimite was synthesized using a novel method with CaSO4 as the sole CaO source to achieve high purity. Stoichiometric ye’elimite and iron-bearing ye’elimite were synthesized, with the highest purity obtained through sintering at 1250°C for 4 h. The crystal structure of iron-bearing ye’elimite was represented through dynamical disordering of the SO4 tetrahedron and Ca atom with the space group I 4 ¯ 3m. Moreover, the early hydration behaviors of stoichiometric ye’elimite and iron-bearing ye’elimite reacting with and without gypsum were studied. In the absence of gypsum, stoichiometric ye’elimite reacts faster than iron-bearing ye’elimite. However, in the presence of gypsum, the hydration of the former is faster than that of the latter and the hydration rates of both these minerals are higher than those observed in the absence of gypsum.

Thermal Decomposition Analysis of Indonesian Natural Dolomite in Air

Dolomite is widely used in the construction, glass ceramics, iron and steel, pharmaceutical industries, as a source of CaO and MgO and as thermal energy storage material. Thermal decomposition analysis of natural dolomite of the so-called Jeddih limestone has been carried out. A thermogravimetry analysis (TGA) in the air evaluates the thermal decomposition of dolomite. The natural dolomite has been analyzed by x-ray flourescence (XRF) and x-ray diffraction (XRD) to test crystal structure and decomposition phase, fourier transform infra-red (FTIR) was utilized to identify the presence of functional groups. The particle morphology was observed by scanning electron microscopy. TGA curve shows that the thermal decomposition of dolomite occurs in two stages. The first stage is in temperature range of 600 - 779°C and the second one is at the temperature 779°C. The results are in line with the XRD and FTIR measurements. Which shows that calcite begins to grow at a temperature of 600°C and MgO phase is observed at 700 - 900°C. Moreover, CaO phase starts to be found at 800°C.

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

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.

Investigation of CaO/MgO on the formation of Anorthite, Diopside, Wollastonite and Gehlenite phases in the fabrication of fast firing ceramic tiles

In this research, the effect of CaO/MgO ratio as the principal oxides activating reactions during fast firing of ceramic tiles on the transformations and formation of phases such as Anorthite, Diopside, Wollastonite, and Gehlenite was studied. Calcium carbonate and Talc/dolomite powder were selected as the sources of CaO and MgO, respectively. After forming with the press, the mixtures were dried, and the bodies were sintered. XRD, XRF, Dilatometry, and SEM/FESEM analysis methods were used to study the microstructural transformations, chemical and physical reactions in the microstructure, and final physical properties of the samples. The X-ray diffraction test identified the phases of the constructed bodies. The weight percentage of the constituent phases was calculated using the MAUD software. Studies indicated that the weight percentage of the Anorthite phase increased by decreasing the CaO/MgO ratio. In addition, the thermal expansion coefficient decreased with the reduction of the CaO/MgO ratio. The lowest coefficient of thermal expansion (7.69 × 10-6 (1/°C)) was reported. Microstructural studies demonstrated that the harmful phase of Gehlenite was removed from the final microstructure, and the Anorthite phase was increased (up to 10 wt%) by fine-graining the primary sources of calcium carbonate and Talc. Furthermore, crystals of the Anorthite phase grew more.

Use of Eggshell Waste as a source of CaO in Sm3+-Doped Na2O-B2O3-CaO-SiO2 Glass Preparation

In this research, calcium carbonate from eggshell waste was used to prepare the soda-lime borosilicate glass samples (Na2O-B2O3-CaO-SiO2) doped with samarium ions (Sm3+) at different Sm2O3 concentrations (0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol%). A conventional melt-quenching method at 1,100°C for 3 h was applied in this work to produce the glass samples. The samples were then characterized by XRD, DTA, FT-IR, UV-Vis spectrophotometer and PL techniques. The results showed that the obtained glasses had amorphous structure, and the glass density tended to increase with the addition of Sm2O3. The FTIR spectra of the main glass structure revealed that it was composed of trigonal BO3 and tetrahedral BO4 borate groups mixing with SiO4 tetrahedra and non-bridging oxygen. The addition of samarium ions to the glass resulted in a strong orange emission at 562 nm (4G5/2→6H5/2), 600 nm (4G5/2→6H7/2), 646 nm (4G5/2→6H9/2) and 708 nm (4G5/2→6H11/2) under excitation at 403 nm. The results confirmed that 0.3 mol% Sm2O3-doped glass exhibited the highest emission intensity, which suggested that eggshells have a high potential to be used as an alternative CaCO3-raw material in the production of an efficient luminescent and environmentally-friendly optical electronics material

Calcium–Magnesium oxide by the ball-milling method using eggshell as calcium source: its study for photodegradation of methylene blue

In this study, the synthesis of Calcium–Magnesium oxide through the ball milling method using eggshell as a CaO source, developing an ecological process synthesis, is presented. After ball milling, an annealing process was carried out in order to increase the crystallinity of the material to enhance its optoelectronic properties by varying the temperature from 450 to 900 °C. The samples were analyzed by X-ray diffraction, Raman and UV–Vis spectroscopy, FE-SEM, photoluminescence, and BET analysis. The ball milling process itself promoted a reduction in particle size, which increased slightly during the annealing process, achieving a more homogeneous size distribution and improving its crystallinity, according to XRD and Raman spectroscopy. The samples were tested for the photodegradation of methylene blue (100 mL of a 10 ppm solution), using LED lamps (200 W). The best photodegradation performance was recorded with the sample annealed at 750 °C, which is explained by the more homogeneous size distribution and the greater surface area, a smaller band gap, and fewer surface defects, which causes greater absorption of light, a better transport of the charge carriers and consequently a better performance in the photodegradation of MB. The complete removal of MB was achieved in 20 min under sunlight stimulation, which can be reduced to 12 min using 400 mg of the catalyst. On the other hand, the trapping experiment showed that superoxide radicals (·O2−) and holes (h+) are the key reactive species in the photodegradation process of MB. The kinetic study showed to follow a pseudo-first-order for all cases. These photodegradation results reported for the first time are better than those reported in other Calcium–Magnesium oxide synthesized by combustion or ultrasound-assisted methods.

Effect of CaO Sourced from CaCO3 or CaSO4 on Phase Formation and Mineral Composition of Iron-Rich Calcium Sulfoaluminate Clinker.

The performance of iron-rich calcium sulfoaluminate (IR-CSA) cement is greatly affected by mineral composition and mineral activity in the clinker. This study aims to identify the effect of CaO sources, either CaCO3 or CaSO4, on the phase formation and mineral composition of the IR-CSA clinker. Targeted samples were prepared with different proportions of CaCO3 and CaSO4 as CaO sources at 1300 °C for 45 min. Multiple methods were used to identify the mineralogical conditions. The results indicate that the mineral composition and performance of the IR-CSA clinker could be optimized by adjusting the CaO source. Both Al2O3 and Fe2O3 tend to incorporate into C4A3-xFxS¯ with an increase in CaSO4 as a CaO source, which leads to an increased content of C4A3-xFxS¯ but a decreased ferrite phase. In addition, clinkers prepared with CaSO4 as a CaO source showed much higher x value in C4A3-xFxS¯ and higher compressive strength than clinker prepared with CaCO3 as the sole CaO source. The crystal types of both C4A3-xFxS¯ and C2S were also affected, but showed different trends with the transition of the CaO source. The findings provide a possible method to produce IR-CSA cement at a low cost through cooperative utilization of waste gypsum and iron-bearing industrial solid wastes.

Utilization Waste Materials to Synthesize Nano Al2O3-CaO Photocatalyst using Infused Red Guava Leaves (Psidium Guajava L.)

Diazinon is a very toxic pesticide for animals and humans that is widely used in the agricultural sector, so this pollutant needs to be reduced or eliminated in the environment through photodegradation using photocatalysts derived from metal oxides. The catalytic activity of metal oxides is enhanced by adding a support material and increasing the surface area by reducing the particle size to nano size. In this study, kaolin as a source of Al2O3 and golden snail shells as a source of CaO which used to synthesize Al2O3-CaO nanoparticles (NPs) with a simple and environmentally friendly method using plant infusions. Synthesis of Al2O3-CaO NPs using infused red guava leaves (Psidium guajava L.) had been done by utilized the secondary metabolites as reducing agents and stabilizers in the nanoparticle synthesis. FTIR analysis confirmed the presence of alumina (Al-O) groups at wave numbers 850 – 650 cm-1 and CaO at 3642 cm-1. XRD analysis showed NPs Al2O3-CaO had cubic with the crystal size of 14.59 nm. The morphology of Al2O3-CaO NPs showed in the SEM pictures were agglomerated. Al2O3-CaO NPs degraded diazinon by 75% within 180 minutes under UV radiation. Thus, this research not only reduce waste material, but also reduces water pollutant.

Low-temperature fabrication and properties of porous calcium hexaluminate (CA6) ceramics with low thermal conductivity by one-step method

In this study, one-step molten salt method followed by low-temperature sintering is employed for fabricating porous calcium hexaluminate (CA6) ceramics with ideal plate-like structure and low thermal conductivity via the assistance of CaCl2. The porous CA6 ceramic containing 15 wt% CaCl2 sintered at 1400 °C for 3 h exhibits desirable compressive strength (7.14 MPa), low bulk density (1.47 g/cm3), high porosity (61.12%), and low conductivity (0.439 W/(m·K)). The results imply that CaCl2, as a pore-forming agent and an additional source of CaO, provides a large number of liquid phases and resulting in quantities of closed pores. Moreover, the reactions between molten Al2O3 and CaCl2 alter the mass transfer modes of Al2O3 and accelerate its phase transition to α-Al2O3 in addition to contributing to the conversion of CaCl2 to CaO and the subsequent formation of CA6, which results in the entire synthesis of low-temperature CA6 at around 1400 °C. Therefore, there is no need for extra salt washing treatment owing to the consumption and evaporation of CaCl2, which makes this one-step molten salt method much more advantageous in terms of its economical and highly efficient.

Synthesis of Natural Nano-Hydroxyapatite from Snail Shells and Its Biological Activity: Antimicrobial, Antibiofilm, and Biocompatibility.

Hydroxyapatite nanoparticles (HAn) have been produced as biomaterial from biowaste, especially snail shells (Atactodea glabrata). It is critical to recycle the waste product in a biomedical application to overcome antibiotic resistance as well as biocompatibility with normal tissues. Moreover, EDX, TEM, and FT-IR analyses have been used to characterize snail shells and HAn. The particle size of HAn is about 15.22 nm. Furthermore, higher inhibitory activity was observed from HAn than the reference compounds against all tested organisms. The synthesized HAn has shown the lowest MIC values of about 7.8, 0.97, 3.9, 0.97, and 25 µg/mL for S. aureus, B. subtilis, K. pneumonia, C. albicans, and E. coli, respectively. In addition, the HAn displayed potent antibiofilm against S. aureus and B. subtilis. According to the MTT, snail shell and HAn had a minor influence on the viability of HFS-4 cells. Consequently, it could be concluded that some components of waste, such as snail shells, have economic value and can be recycled as a source of CaO to produce HAn, which is a promising candidate material for biomedical applications.

Utilization of Breed Chicken Eggshells for Biodiesel Preparation from Waste Cooking Oil

Chicken eggshell waste is a promising source of CaO which can be converted into heterogeneous catalyst materials. The purpose of this study was to utilize CaO heterogeneous catalyst derived from breed chicken eggshell to produce biodiesel from waste cooking oil through the transesterification process. A total of 4 g of catalyst material was mixed with 200 g of waste cooking oil and 60 g of methanol, and then the mixture was stirred at a speed of 700 rpm for 6 h at 60 ± 40C. The produced biodiesel was analyzed using GC-MS to elucidate the various methyl ester compounds. The produced biodiesel was found to have a density of 855 kg/m3, viscosity of 3.74 mm2/s (cSt), and flash point of 135 0C. Based on these results, it can be concluded that breed chicken eggshells are potential sources for the preparation of CaO catalyst material to produce biodiesel from waste cooking oil. This finding is very useful for further optimization of mass catalysts heterogeneous CaO from breed chicken eggshells including the commercial production of biodiesel.

Dolomite-based binders manufactured using concentrated solar energy in a fluidised bed reactor

Dolomite-based binders are characterised by interesting technical and environmental features. For their synthesis, sources of both CaO and MgO are required. The idea developed in this work is to couple the synthesis of dolomite-based binders, starting from a natural dolomite, through the concept of concentrated solar energy (needed to drive the endothermal dolomite calcination process) in fluidised bed reactors. To this end, a fluidised bed system, where the concentrated solar radiation is mimicked by the use of Xe-lamps (short-arc), has been set up and operated. Natural dolomite (sieved in the 420–590 μm size range) was calcined at a nominal temperature of 850 °C, and bed temperature profiles during solar-driven calcination were investigated. Then, four binders were prepared by mixing slaked dolomite (obtained from the hydration of solar calcined dolomite) with either blast furnace slag or coal fly ash as supplementary cementitious materials. The binders were hydrated for curing times ranging from 7 to 56 days. X-ray fluorescence, X-ray diffraction and combined differential thermal and thermogravimetric analyses were employed as characterisation techniques both to analyse the chemical composition of starting materials and to investigate the evolution of the hydration in the four systems.

Recycling phosphogypsum as the sole calcium oxide source in calcium sulfoaluminate cement production and solidification of phosphorus

Because the disposal of phosphogypsum (PG) can lead to serious contamination of the air, soil, and water, recycling of PG has attracted wide attention. This study investigated the effect and solidification of phosphorus in the production of calcium sulfoaluminate (CSA) cement using PG as the sole CaO source. The effects of three phosphorus impurities (Ca3(PO4)2, CaHPO4, Ca(H2PO4)2) on the decomposition of CaSO4, formation of minerals, microstructure of the clinker, and the hydration and mechanical properties of the cement were studied. Experimental results show that Ca3(PO4)2 and Ca(H2PO4)2 promoted the decomposition of CaSO4 and the formation of clinker minerals with the increase in P2O5 content, whereas CaHPO4 showed a promoting effect only when the P2O5 content was more than 1.5 wt%. The increase in phosphorus incorporation in Ca2SiO4 leads to the transformation of β-Ca2SiO4 to α′-Ca2SiO4 and then to Ca7Si2P2O16. The presence of three phosphates in the clinker enhanced the growth of crystal grains and the generation of a liquid phase. Compared with Ca4Al6SO16 without phosphorus, the hydration reaction of phosphorus-bearing Ca4Al6SO16 started later and ended earlier, and the reaction time was shorter. The presence of phosphorus impurities reduces the 1-day strength of CSA cement but does not affect the development of the 3-day and 28-day strengths. Considering environmental aspects, the solidification of phosphorus in the production of CSA clinker were quantified by measuring the distribution of elements. The results indicated that phosphorus is solidified by Ca4Al6SO16, Ca2SiO4, and Ca4Al2Fe2O10, and Ca2SiO4 has a stronger ability to solidify phosphorus than the other two minerals. Ca3(PO4)2 is more difficult to solidify than CaHPO4 and Ca(H2PO4)2. This study is of great significant to guide the large-scale clean utilization of PG in the production of CSA cement.

Hydrogen-rich gas production from steam co-gasification of banana peel with agricultural residues and woody biomass

Steam co-gasification of banana peel with other biomass, i.e., Japanese cedar wood, rice husk and their mixture, was carried out for the hydrogen-rich gas production in a fixed-bed reactor. For the co-gasification process, the banana peels were physically mixed with rice husk, Japanese cedarwood and their mixture respectively by different mixing weight ratios. The effects of reaction temperature and the addition amount of banana peel on the gas production yield were investigated by comparing the experimental data with the calculated ones based on the individual biomass gasification at the same condition. It was found that the banana peel with a high content of alkali and alkaline earth metal (AAEM) species exhibited not only high gasification reactivity but also a significant enhancing catalytic effect on the co-gasification process at the low temperature, especially with the biomass containing no silica species. The high content of silica species in the rice husk had a negative effect on the gasification reactivity of banana peel during the co-gasification since it could hinder the release of AAEM from the biomass and/or lead to the possible formation of inactive alkaline silicates. However, the combination of these three samples with the suitable weight ratio could improve the gasification performance at the low temperature due to the synergetic effect provided by high contents of potassium and calcium from banana peel and cedarwood respectively. Moreover, the addition of calcined seashells as the CaO source could further improve the gas production yield, especially the hydrogen gas yield at a relatively low gasification temperature of 750 ℃.

Hydro-conversion of palm oil via continuously pyrolytic catalysis to biofuels over oxide-based catalyst derived from waste blood clamshell: Effect of magnesium contents

The aims of this work were (i) to develop and characterize the cheap and efficient CaO/MgO catalyst with a source of CaO from waste blood clamshell mix with MgO, and (ii) to study the catalyst efficiencies on biofuel production via continuous packed-bed reactor under atmospheric pressure without any purge gases. The chemical and physical properties of the catalyst were characterized by many techniques. The results can confirm that the ball-mill technique successfully prepared CaO and MgO catalysts. The specific surface area was increased with the increasing of Mg contents. The surface morphologies of calcined catalysts were obvious in a roughly spherical shape. The results were found that not only the Mg content was a significant effect on product and distilled yields, but also reaction temperature was a significant effect as well. The highest pyrolytic oil, derived from 10 %wt Mg catalyst with reaction temperature at 525 °C, was about 80 %, and it can be distilled almost 100 % following ASTM D86. The pyrolytic oils were purified into three types of biofuel, and then the properties of distilled products were examined. The heating values and kinetic viscosity were on standard values except for acidity. Surprisingly, the acidity was decreased comparing with raw material.

State of Art of Alkaline Earth Metal Oxides Catalysts Used in the Transesterification of Oils for Biodiesel Production

Biodiesel produced through catalytic transesterification of triglycerides from edible and non-edible oils and alcohol is considered an alternative to traditional petro-diesel. The interest in the use of alkaline earth metal oxides as heterogeneous basic catalysts has increased due to their availability, non-toxicity, the capacity to be reused, low cost, and high concentration of surface basic sites that provide the activity. This work is a compilation of the strategies to understand the effect of the source, synthesis, and thermal treatment of MgO, CaO, SrO, and BaO on the improvement of the surface basic sites density and strength, the morphology of the solid structure, stability during reaction and reusability. These parameters are commonly modified or enhanced by mixing these oxides or with alkaline metals. Also, the improvement of the acid-base properties and to avoid the lixiviation of catalysts can be achieved by supporting the alkaline earth metal oxides on another oxide. Additionally, the effect of the most relevant operation conditions in oil transesterification reactions such as methanol to oil ratio, temperature, agitation method, pressure, and catalysts concentration are reviewed. This review attempts to elucidate the optimum parameters of reaction and their application in different oils.