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Calcium oxide

Calcium oxide, commonly known as quicklime or lime, is an inorganic compound with the chemical formula CaO and a molecular weight of 56.077 g/mol. It appears as an odorless, white or gray-white solid, often in the form of hard lumps or powder, and is highly caustic and alkaline, reacting vigorously with water to form calcium hydroxide and generate significant heat. This compound is a strong irritant to skin, eyes, and mucous membranes, necessitating careful handling in industrial and laboratory settings.^[1]^[2]^[3] Calcium oxide is primarily produced industrially through the calcination of calcium carbonate (limestone, CaCO₃) in rotary kilns at temperatures between 900°C and 1,200°C, following the reaction CaCO₃ → CaO + CO₂. This process, known as lime burning, has been utilized for millennia and remains the dominant method due to the abundance of limestone deposits worldwide. The resulting quicklime is then processed into various forms, including hydrated lime (Ca(OH)₂), for diverse applications.^[4]^[5] Key physical properties include a high melting point of approximately 2,613°C, a boiling point around 2,850°C, and a density of 3.34 g/cm³, making it suitable for high-temperature processes. Chemically, it exhibits basic properties with a pH of about 12.5 in aqueous suspension and is sparingly soluble in water (about 1.65 g/L at 20°C), but it readily absorbs moisture and carbon dioxide from the air, reverting to calcium carbonate over time.^[3]^[2] In industry, calcium oxide serves as a fundamental material in construction, where it is a key ingredient in Portland cement and lime mortar for binding aggregates. It is also essential in steelmaking as a flux to remove impurities like phosphorus and sulfur, and in water treatment for softening, pH adjustment, and sludge conditioning. Additional applications include agriculture as a soil amendment and fertilizer, pulp and paper production for bleaching, and chemical manufacturing for processes like the Solvay soda production. Historically, it has been used in incendiary devices, and in modern contexts for self-heating food packaging due to its exothermic hydration reaction.^[6]^[7]^[1]

Properties

Physical properties

Calcium oxide is an odorless, white or gray-white crystalline solid, typically appearing as hard lumps, fine powder, or granules in its pure form.^[1]^[8] It exhibits a caustic and alkaline nature due to its basic properties, with a density of 3.34 g/cm³ at 20 °C.^[9] This compound demonstrates high thermal stability, with a melting point of 2613 °C and a boiling point of 2,850 °C, at which it tends to sublime rather than boil in a conventional sense.^[10]^[9] Its specific heat capacity is approximately 0.75 J/g·K for the solid phase near room temperature.^[11] Regarding solubility, calcium oxide is practically insoluble in water—reacting instead to form calcium hydroxide with significant heat evolution—but it dissolves in glycerol while remaining insoluble in ethanol and acetone.^[12] In commercial quicklime products, particle morphology varies by processing, often featuring irregular crystalline granules or lumps with sizes ranging from fine powder (less than 0.1 mm) to larger aggregates up to 150 mm, influencing handling and reactivity.^[13]

Chemical properties

Calcium oxide, with the chemical formula CaO, has a molar mass of 56.077 g/mol.^[14] It is an ionic compound consisting of calcium cations (Ca²⁺) and oxide anions (O²⁻), where calcium exhibits an oxidation state of +2 and the oxide ion serves as a strong Lewis base.^[14] The crystal structure of calcium oxide is face-centered cubic, adopting the rock salt (NaCl) structure with space group Fm³m, in which each Ca²⁺ ion is octahedrally coordinated to six O²⁻ ions and vice versa. This ionic lattice contributes to its high melting point and stability under standard conditions. Calcium oxide is a strong base owing to the basicity of the oxide ion, which readily accepts protons; an aqueous suspension exhibits a pH of approximately 12.8.^[14] Key chemical reactions of calcium oxide highlight its reactivity. It undergoes slaking with water in an exothermic process:

\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2

releasing significant heat, up to 65 kJ/mol.^[14] With carbon dioxide, it forms calcium carbonate:

\text{CaO} + \text{CO}_2 \rightarrow \text{CaCO}_3

a reaction driven by the affinity of the oxide ion for CO₂. Calcium oxide also reacts vigorously with acids, such as hydrochloric acid, in a neutralization reaction:

\text{CaO} + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2\text{O}

demonstrating its utility as a basic reagent.^[14] Calcium oxide is hygroscopic, readily absorbing atmospheric moisture and CO₂ to form surface layers of hydroxide and carbonate, which can cause crumbling.^[14] It remains stable under ambient conditions but decomposes into elemental calcium and oxygen at extremely high temperatures above 2500 K, as dictated by its thermodynamics.^[15]

Production

Industrial production

Calcium oxide, commonly known as quicklime, is primarily produced on an industrial scale through the calcination of limestone (calcium carbonate, CaCO₃) in large rotary kilns at temperatures ranging from 900°C to 1,200°C, following the reaction CaCO₃ → CaO + CO₂.^[16]^[17] This endothermic process decomposes the carbonate, releasing carbon dioxide gas and leaving behind the oxide, with rotary kilns favored for their efficiency in handling high volumes of material in continuous operation.^[18] The primary raw material is high-purity limestone, often sourced from quarries, though marble can also serve as a suitable alternative due to its similar calcium carbonate composition; impurities such as silica or clay in the feedstock can lead to reduced product purity and affect downstream applications by forming silicates or other contaminants.^[19]^[20] Various kiln types are employed depending on scale and desired product characteristics, including shaft kilns for smaller or intermittent operations and advanced flash calcination processes that rapidly heat fine limestone particles to produce highly reactive quicklime with greater surface area.^[21]^[22] Energy consumption for these processes typically ranges from 5 to 7 GJ per ton of lime produced, primarily from fuels like natural gas or coal used to sustain the high temperatures required.^[23]^[24] Global production of lime, including quicklime, reached 424 million metric tons in 2023 and an estimated 420 million metric tons in 2024, underscoring its status as a major commodity chemical essential to industries like steelmaking and construction; leading producers include China (310 million tons), India (17 million tons), the United States (16 million tons), and several European countries.^[25]^[26]^[27] A significant by-product of calcination is CO₂, with the lime industry accounting for about 1% of global industrial CO₂ emissions, predominantly from the inherent process reaction; mitigation efforts include carbon capture and storage technologies integrated into kiln operations to reduce these emissions.^[28]^[29] Produced lime is classified into quality grades based on reactivity, with quicklime offering high reactivity for applications requiring rapid slaking and dead-burned lime, achieved through prolonged high-temperature exposure, exhibiting lower reactivity and suited for refractory materials due to its denser structure.^[30]^[31]

Laboratory preparation

Calcium oxide is commonly prepared in the laboratory through the thermal decomposition of calcium carbonate, a method analogous to but scaled down from industrial calcination processes. Analytical-grade calcium carbonate (CaCO₃) is heated in a muffle furnace at temperatures between 900 and 1000 °C for 1–2 hours, leading to the reaction:

\mathrm{CaCO_3(s) \rightarrow CaO(s) + CO_2(g)}

This produces a white, powdery residue of calcium oxide with yields typically approaching the theoretical value of 56% based on the molar mass ratio, often achieving 90–95% practical recovery when using pure reagents and monitoring weight loss to confirm CO₂ evolution.^[32]^[33] The equipment includes porcelain or platinum crucibles to hold the sample and a muffle furnace for controlled high-temperature heating, ensuring even decomposition without contamination. An alternative route involves the thermal decomposition of calcium hydroxide, which is heated to 500–600 °C in a similar furnace setup. The reaction proceeds as:

\mathrm{Ca(OH)_2(s) \rightarrow CaO(s) + H_2O(g)}

This method yields high-purity calcium oxide, with decomposition initiating around 512 °C and completing efficiently at higher temperatures, providing yields of 80–90% depending on the hydroxide's initial purity. It is particularly useful when starting from slaked lime, and the water vapor produced can be vented to prevent hydrolysis of the product. Calcium oxide can also be synthesized by direct oxidation of calcium metal in an oxygen atmosphere. Finely divided calcium is ignited or heated in a dry oxygen stream within a controlled inert setup, such as a quartz tube furnace, following:

$2\mathrm{Ca(s) + O_2(g) \rightarrow 2CaO(s)}

This exothermic reaction requires careful temperature control (around 300–500 °C) to avoid excessive sintering, yielding nearly stoichiometric calcium oxide with purity exceeding 95% if high-purity metal is used.^[34] Safety precautions include using an inert atmosphere initially to prevent premature ignition and handling the reactive metal with tongs in a glove box. Other methods utilize the calcination of calcium salts like oxalate or nitrate for specialized applications. Calcium oxalate (CaC₂O₄) is decomposed at 600–800 °C to form CaO, CO, and CO₂, while calcium nitrate (Ca(NO₃)₂) decomposes around 600 °C to CaO, NO₂, and O₂; both require analytical-grade precursors and yield 85–95% CaO after purification steps like washing to remove impurities.^[35]^[36] Throughout these preparations, purity is ensured by using reagent-grade starting materials and post-reaction treatments such as sieving or acid washing, with overall yields ranging from 80–95%. Equipment like muffle furnaces and crucibles is standard, but safety notes emphasize wearing heat-resistant gloves, using fume hoods for gaseous byproducts, and avoiding direct contact with hot samples to prevent burns or reactions with moisture.

Applications

Construction and materials

Calcium oxide, commonly known as quicklime, plays a pivotal role in the production of Portland cement, where it reacts with silica and alumina from clay or shale at high temperatures to form clinker, the primary component of cement. This clinker is then ground with gypsum to produce the final cement powder used extensively in concrete for building foundations, bridges, and infrastructure.^[37] In lime mortar applications, quicklime is slaked with water to form calcium hydroxide, which is mixed with sand to create a breathable binder suitable for historic restorations and modern eco-friendly buildings, allowing moisture vapor to pass through walls and prevent damage from trapped water.^[38] The high reactivity of calcium oxide enables rapid setting and strong adhesion in these mortars, contributing to their durability and flexibility compared to rigid cement-based alternatives.^[39] In steel manufacturing, calcium oxide serves as a flux in basic oxygen furnaces (BOF), where it combines with impurities such as phosphorus and sulfur to form slag, which is then removed to purify the molten steel.^[40] This process, essential for producing high-quality steel used in construction beams, rebar, and structural components, consumes significant quantities of quicklime to maintain the basicity of the slag and facilitate efficient impurity removal.^[41] Calcium oxide is also employed in water treatment processes within construction to soften hard water used for concrete mixing, where it reacts with calcium and magnesium ions to precipitate them as insoluble carbonates, preventing adverse effects on cement hydration and concrete strength.^[42] In glass and ceramics production, calcium oxide acts as a flux to lower the melting point of silica, enabling the formation of stable soda-lime glass through the lime-soda process, which combines limestone (source of CaO), soda ash, and sand for windows, bottles, and containers used in building materials.^[43] Similarly, in ceramics, it stabilizes glazes and bodies by adjusting viscosity and promoting vitrification at lower temperatures, enhancing the quality of tiles and sanitary ware for construction interiors.^[44] The construction industry is the largest end-user of calcium oxide, accounting for over half of global demand as of 2025.^[45] The material's advantages, such as its high reactivity for quick setting and its historical application in Roman concrete—where unslaked quicklime created self-healing properties—continue to influence modern sustainable construction practices.^[46]

Chemical manufacturing

Calcium oxide serves as a versatile reagent and catalyst in numerous industrial chemical processes, leveraging its strong basicity and reactivity to facilitate the synthesis of key compounds. In the production of calcium carbide, a critical intermediate for acetylene and other chemicals, calcium oxide reacts with carbon at high temperatures. The reaction proceeds as follows:

\mathrm{CaO + 3C \rightarrow CaC_2 + CO}

This endothermic process typically occurs in electric arc furnaces at approximately 2,000°C, with lime derived from calcined limestone providing the calcium source and petroleum coke or anthracite serving as the carbon input.^[47] The resulting calcium carbide is then hydrolyzed to produce acetylene gas, which is essential for welding and organic synthesis.^[48] In the pulp and paper industry, calcium oxide plays a pivotal role in the kraft process's chemical recovery cycle, specifically during the causticizing step. Here, quicklime (CaO) reacts with sodium carbonate in green liquor to regenerate sodium hydroxide, the active cooking agent for wood pulping:

\mathrm{CaO + Na_2CO_3 \rightarrow CaCO_3 + 2NaOH}

This reaction precipitates calcium carbonate mud, which is subsequently calcined in a lime kiln to recover CaO, enabling a closed-loop system that minimizes waste. The process efficiency depends on the slaking of CaO to calcium hydroxide prior to reaction, ensuring high conversion rates of sodium carbonate to hydroxide.^[49]^[50] Calcium oxide is widely employed as a heterogeneous base catalyst in biodiesel production via the transesterification of vegetable oils or animal fats with methanol or ethanol. Typically, 1-2% CaO loading by weight of the oil is used, promoting the conversion of triglycerides to fatty acid methyl esters (biodiesel) and glycerol at temperatures around 60-65°C. Yields exceeding 90% are achievable under optimized conditions, such as a 6:1 methanol-to-oil ratio and 2-3 hours reaction time, with the catalyst's activity stemming from its Lewis basic sites. Waste-derived CaO, like from eggshells, enhances sustainability while maintaining efficacy.^[51]^[52]^[53] In petroleum refining, calcium oxide functions as a desulfurization agent to remove sulfur compounds from fuels and as a drying agent to eliminate moisture from hydrocarbons. It neutralizes acidic impurities and absorbs water in processes like caustic washing or additive formulations, with specialized grades like PetroCal O tailored for these applications. Its role supports compliance with low-sulfur fuel standards by facilitating the conversion of sulfur oxides or mercaptans.^[54]^[55] For organic synthesis, calcium oxide acts as a dehydration agent to remove water from reaction mixtures and as a base in esterification reactions, promoting the formation of esters from acids and alcohols. In transesterification variants, it catalyzes the exchange of alkyl groups, often at mild conditions, while its dehydrating properties prevent hydrolysis side reactions. These applications benefit from CaO's mild basicity, avoiding over-alkalinity issues seen with homogeneous catalysts.^[56]^[57] High-grade calcium oxide, with purity exceeding 95%, is essential for catalytic applications to ensure minimal impurities that could deactivate sites or contaminate products. Commercial lime for these uses typically contains 90-95% free CaO when properly stored, but catalytic processes demand refined grades approaching 99% to optimize activity and selectivity.^[1]^[58]

Agriculture and environmental uses

Calcium oxide, commonly known as quicklime, plays a vital role in agriculture by neutralizing acidic soils through liming, which raises soil pH and enhances nutrient availability for crops. This process counters soil acidity caused by factors such as acid rain, fertilizer application, and crop nutrient uptake, thereby improving plant growth and yield. Application rates typically range from 1 to 5 tons per hectare, determined by soil tests that assess buffering capacity, target pH, and crop needs; quicklime's high neutralizing value (150-175% calcium carbonate equivalent) allows for lower quantities compared to agricultural limestone.^[59]^[60]^[61] In animal feed, calcium oxide serves as a supplemental source of calcium for livestock and poultry, supporting bone health, eggshell formation, and overall metabolic functions. It is generally recognized as safe (GRAS) when incorporated into formulations at low levels, such as 1% of dry matter in cattle rations to improve feed digestibility and reduce acidity in by-products like distillers grains. Quicklime is often slaked to calcium hydroxide for safer integration into feed blocks or supplements containing molasses, minerals, and non-protein nitrogen.^[1]^[62]^[63] Calcium oxide is widely employed in water and wastewater treatment for its ability to precipitate phosphates and heavy metals, aiding in pollution control. In phosphate removal, lime raises pH to form insoluble calcium phosphate, effectively reducing phosphorus levels in effluents from sources like agricultural runoff or sewage. For heavy metals such as lead, cadmium, and zinc, quicklime precipitates them as hydroxides at concentrations exceeding 1000 mg/L, enabling efficient separation from industrial wastewater. Additionally, in flue gas desulfurization (FGD) systems at power plants, calcium oxide reacts with sulfur dioxide to form calcium sulfite, mitigating acid rain precursors:

\text{CaO} + \text{SO}_2 \rightarrow \text{CaSO}_3

This dry or wet scrubbing process captures up to 90% of SO₂ emissions.^[64]^[65]^[66]^[67] In sugar refining, particularly for beet juice clarification, calcium oxide is added to raw juice after heating, where it neutralizes organic acids and facilitates impurity removal through subsequent carbonation. The addition of CO₂ converts excess lime to calcium carbonate precipitates, which trap proteins, colorants, and other non-sugars, producing clear juice for evaporation and crystallization. This step enhances sugar purity and yield, with quicklime preferred for its rapid reactivity in industrial-scale operations.^[68]^[69]^[70] For odor control in sewage treatment, calcium oxide neutralizes ammonia and reduces volatile compounds like hydrogen sulfide by elevating pH above 12, creating an alkaline environment inhospitable to odor-producing bacteria. In biosolids stabilization, quicklime addition minimizes off-gassing of amines and ammonia during processing and storage, improving handling safety and land application viability. This application also aids pathogen reduction, aligning with regulatory standards for wastewater residuals.^[71]^[72] The use of calcium oxide in agriculture and environmental applications promotes sustainability by enhancing soil fertility and reducing reliance on synthetic fertilizers, as improved pH optimizes natural nutrient cycling and microbial activity. These sectors represent a significant portion of global calcium oxide production, underscoring its role in eco-friendly practices that lower chemical inputs and mitigate environmental pollution.^[73]^[74]

Historical and miscellaneous uses

Calcium oxide, known historically as quicklime, has been utilized since ancient times in construction for its binding properties when slaked to form lime mortar. Archaeological evidence indicates its use in Egyptian pyramids around 2600 BCE, where lime-based mortars helped bond limestone blocks, contributing to the enduring structures of the Old Kingdom.^[75] The Romans advanced this application by combining quicklime with pozzolana, a volcanic ash, to create hydraulic concrete that set underwater and exhibited superior durability, as described in Vitruvius's engineering texts and evidenced in structures like the Pantheon.^[75] In military contexts, quicklime is speculated to have served as an incendiary component in Byzantine Greek fire, a petroleum-based weapon deployed from the 7th century onward, where its exothermic reaction with water intensified flames and caused burns upon contact.^[76] During the medieval period, lime mortars incorporating quicklime were widely employed in European fortifications, such as castle walls and cathedrals, providing flexible yet strong bonding that accommodated structural shifts over time.^[77] For applications requiring adjusted reactivity, substitutes like magnesium oxide have been used in place of calcium oxide, particularly in steelmaking fluxes where higher refractoriness is needed, and dolomitic lime (containing both calcium and magnesium oxides) offers slower slaking for controlled pH adjustments in soil treatment.^[78] Magnesium oxide provides similar basicity but with greater thermal stability, making it preferable in high-temperature processes.^[79] Among miscellaneous uses, quicklime plays a key role in leather tanning through depilation, where it swells and loosens hair from hides via alkaline hydrolysis, a process dating back to ancient civilizations and still employed today.^[80] Slaked lime, derived from calcium oxide, is essential in nixtamalization, the traditional Mesoamerican processing of corn, where it enhances nutritional bioavailability by breaking down cell walls and adding calcium.^[81] Recent research since 2010 has explored calcium oxide nanoparticles for catalytic applications, particularly in biodiesel production via transesterification, where their high surface area enables efficient conversion of triglycerides with yields exceeding 95% under mild conditions.^[51] These nanomaterials also show promise in CO2 capture and organic synthesis, leveraging their basic sites for enhanced reactivity.^[82] Culturally, quicklime held symbolic significance in alchemy as a emblem of transformation, representing the calcination stage where base materials were purified into higher forms, akin to spiritual enlightenment in medieval esoteric texts.^[83] This metaphor of rebirth through fire underscored its role in alchemical pursuits of the philosopher's stone.^[84]

Safety and environmental considerations

Health and safety hazards

Calcium oxide, commonly known as quicklime, is highly corrosive and acts as a severe irritant to the skin, eyes, and respiratory tract. Upon contact with moist tissues, it undergoes exothermic hydration, generating significant heat that can cause chemical burns and tissue damage.^[1] This reactivity makes it particularly hazardous in handling, as even brief exposure can lead to painful blisters, ulceration, or perforation of affected areas.^[10] Primary exposure routes include inhalation of dust particles, which can irritate the upper respiratory tract and, in cases of impure calcium oxide containing silica, pose a risk of silicosis—a chronic lung disease characterized by scarring of lung tissue. Skin contact often results in dermatitis, with symptoms ranging from redness and itching to severe burns, while eye exposure can cause immediate pain, swelling, and potential vision impairment. Ingestion is less common but can lead to gastrointestinal irritation and burns in the mouth and esophagus.^[85]^[10] Toxicity assessments indicate low acute oral toxicity, with an LD50 greater than 2000 mg/kg in rats, suggesting it is not highly poisonous when swallowed in small amounts. The International Agency for Research on Cancer (IARC) does not classify calcium oxide as a carcinogen. However, chronic inhalation exposure has been associated with lung issues, including pneumoconiosis and nasal septum ulceration, due to prolonged irritation of respiratory passages.^[86]^[87]^[88] To mitigate risks, personal protective equipment (PPE) such as chemical-resistant gloves, safety goggles, protective clothing, and respirators approved for particulate matter is essential during handling. Storage should occur in cool, dry, well-ventilated areas to prevent moisture absorption and spontaneous reactions, and workplaces must adhere to the OSHA permissible exposure limit (PEL) of 5 mg/m³ as an 8-hour time-weighted average for calcium oxide dust. Engineering controls like local exhaust ventilation further reduce airborne concentrations.^[89]^[85]^[10] In case of exposure, immediate first aid is critical: for skin or eye contact, flush thoroughly with water for at least 15-20 minutes while removing contaminated clothing, and seek medical attention; for inhalation, move the affected person to fresh air and provide oxygen if breathing is difficult; if ingested, do not induce vomiting but rinse the mouth and contact poison control.^[90]^[85] Historical incidents in lime kilns frequently involved severe burns from hot calcium oxide or dust exposure, contributing to worker injuries before modern safeguards. Under EU REACH regulations, calcium oxide is classified as causing skin irritation (Category 2), serious eye damage (Category 1), and specific target organ toxicity from single exposure (respiratory tract irritation, Category 3), mandating strict handling protocols across member states.^[91]^[92]

Environmental impact

The production of calcium oxide through calcination of limestone releases approximately 0.78 tons of CO₂ per ton of CaO, primarily due to the decomposition of calcium carbonate, contributing significantly to global greenhouse gas emissions and climate change.^[93] Airborne lime dust from production and handling processes can degrade local air quality by forming fine particulates that scatter sunlight and deposit on ecosystems, while alkaline runoff from sites elevates water pH levels, potentially causing oxygen depletion and disrupting aquatic habitats.^[94]^[95] Limestone quarrying for calcium oxide feedstock results in habitat fragmentation and loss, leading to biodiversity declines as vegetation is cleared and soil structures are altered, with long-term effects on local flora and fauna populations.^[96]^[97] To mitigate these impacts, carbon capture and storage (CCS) technologies are being integrated into lime kilns, capturing up to 99% of process CO₂ for geological sequestration, while recycling waste materials such as eggshells—calcined to produce CaO—reduces reliance on virgin limestone and diverts organic waste from landfills.^[98]^[99]^[100] Regulatory measures like the European Union Emissions Trading System (EU ETS) impose caps on CO₂ emissions from lime production facilities, requiring allowances for verified outputs and incentivizing reductions through trading, while life-cycle assessments indicate a global warming potential of approximately 1.0 kg CO₂ equivalent per kg of calcium oxide, encompassing extraction, production, and transport stages.^[101]^[102] On a positive note, calcium oxide's application in SO₂ scrubbing processes neutralizes sulfur dioxide emissions from industrial sources, thereby reducing acid rain formation and associated ecosystem damage.^[103]^[104]

Natural occurrence

Associated minerals

Calcium oxide, mineralogically known as lime (IMA symbol: Lm), is an extremely rare naturally occurring mineral due to its high reactivity, which causes it to rapidly form hydrated or carbonated compounds in the presence of water or atmospheric CO₂.^[1]^[105] It has been documented in trace amounts as a product of high-temperature processes, such as coal-seam fires where limestone decomposes, and in altered limestone xenoliths within volcanic ejecta or sublimates.^[106] Additionally, pure CaO has been identified in calcium-aluminum-rich inclusions within meteorites like Allende.^[107] A related mineral is portlandite (Ca(OH)₂), the hydrated form of calcium oxide, which occurs more frequently in natural environments such as altered ultramafic rocks and combustion metamorphosed limestones, though it differs from pure CaO by incorporating water of hydration.^[108] This hydration reflects the instability of anhydrous CaO under typical terrestrial conditions. When naturally occurring quicklime is found, it is typically impure, often containing significant magnesia (MgO) in dolomitic varieties derived from magnesium-bearing limestones, along with minor traces of silica (SiO₂) and alumina (Al₂O₃) from the parent rock composition.^[109]^[110] Over 99% of calcium oxide in existence is anthropogenic, produced via industrial calcination, underscoring the negligible role of natural sources.^[111] The identification of calcium oxide in potential natural samples relies on techniques like X-ray diffraction (XRD), which detects its cubic crystal structure through characteristic peaks at 2θ values of approximately 32°, 37°, 54°, 64°, and 67°; such analyses often reveal it in industrial residues or slags that may be erroneously classified as minerals.^[112]^[113]

Geological formation

Calcium oxide, commonly known as lime, primarily forms in geological settings through the metamorphism of precursor minerals such as limestone (calcium carbonate, CaCO₃), where heat and pressure drive decarbonation reactions that release carbon dioxide.^[114] This process occurs during contact or regional metamorphism, typically at temperatures exceeding 700–900°C under low-pressure conditions, decomposing calcite into CaO and CO₂.^[115] Similarly, in meteoritic contexts, CaO appears as a minor oxide phase within calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites, representing early condensates from the solar nebula formed at high temperatures over 4.5 billion years ago. The geological stability of calcium oxide is limited by its rapid hydration in the presence of atmospheric moisture, forming calcium hydroxide (Ca(OH)₂) and preventing the accumulation of large natural deposits.^[116] Exploration for potential CaO sources focuses on geophysical surveys targeting limestone precursors, such as seismic and magnetic methods to map carbonate layers, given the rarity of pure lime, which constitutes less than 0.01% of Earth's crust as a distinct mineral phase.^[117]

References

[1]
Calcium Oxide | CaO | CID 14778 - PubChem - NIH
Calcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in ...
[2]
calcium oxide - the NIST WebBook
calcium oxide · Formula: CaO · Molecular weight: 56.077 · IUPAC Standard InChI: InChI=1S/Ca.O Copy · IUPAC Standard InChIKey: ODINCKMPIJJUCX-UHFFFAOYSA-N Copy
[3]
Calcium oxide | 1305-78-8 - ChemicalBook
Sep 25, 2025 · Calcium oxide Properties ... Melting point, 2570 °C ... Boiling point, 2850 °C (lit ... bulk density, 800-1200kg/m3 ... Density, 3.3 g/mL at 25 °C (lit ...
[4]
An Innovative Approach to Prepare Calcium Oxide from Calcium ...
Jun 6, 2024 · The calcination of P-CS is the change process of the recrystallization of the calcium hydroxide lattice into calcium oxide crystals of the main ...Introduction · Materials and Methods · Results and Discussion · Conclusions
[5]
Calcination of industrial products in general - onejoon
During calcination, calcium carbonate (CaCO3) is decomposed to calcium oxide (CaO). This is how the process works in industrial production ...
[6]
Calcium - Element information, properties and uses | Periodic Table
Calcium oxide (also known as lime or quicklime) is a major component of mortar and cement. The production of cement using calcium oxide has long been known ...
[7]
[PDF] Water Treatment Chemical Supply Chain Profile - Calcium Oxide
Calcium oxide (quicklime) is used in water treatment for precipitative softening and sludge treatment, and as a precursor to calcium hydroxide.
[8]
CALCIUM OXIDE - CAMEO Chemicals - NOAA
An odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.
[9]
Calcium Oxide - an overview | ScienceDirect Topics
Calcium oxide is defined as a product of the thermal decarbonation of ... Its melting point is 2572 °C and its boiling point is 2853 °C. It is soluble ...
[10]
Calcium oxide - NIOSH Pocket Guide to Chemical Hazards - CDC
Calcium oxide ; Molecular Weight. 56.1 ; Boiling Point. 5162°F ; Melting Point. 4662°F ; Solubility. Reacts ; Vapor Pressure. 0 mmHg (approx).
[11]
calcium oxide - the NIST WebBook
calcium oxide · Formula: CaO · Molecular weight: 56.077 · IUPAC Standard InChI: InChI=1S/Ca.O Copy · IUPAC Standard InChIKey: ODINCKMPIJJUCX-UHFFFAOYSA-N Copy · CAS ...Missing: physical | Show results with:physical
[12]
Calcium‐fortified foods in public health programs - PubMed Central
Sep 28, 2020 · Calcium oxide (quicklime), CaO, 71, 56. Soluble in water, forming calcium hydroxide; soluble in acids, glycerol, and sugar solution; practically ...
[13]
Lime FGD Systems Data Book - epa nepis
STANDARD SIZES OF QUICKLIME Size Description 1. ... Each quicklime particle is surrounded by a layer of relatively impervious and unreactive calcium hydroxide.<|control11|><|separator|>
[14]
https://pubchem.ncbi.nlm.nih.gov/compound/14778
[15]
https://webbook.nist.gov/cgi/cbook.cgi?ID=C1305788
[16]
Quicklime - | Lhoist
Quicklime is produced by heating limestone (calcium carbonate, CaCO3) to approximately 900°C (1,652°F). This process, known as calcination or lime-burning, ...
[17]
Making Lime
Industrial mineral lime is produced by heating limestones or chalks, formed of calcium carbonates, at high temperatures above 900°C in industrial kilns that ...
[18]
https://www.eula.eu/kiln-types/
[19]
How does calcium oxide manufacturing process occurs - Echemi
Sep 8, 2022 · The main raw material required for producing calcium oxide is limestone. The steps involved in the manufacturing process are as follows: Pre- ...
[20]
Calcium oxide – Knowledge and References - Taylor & Francis
It is basically a quicklime – calcium oxide – produced by heating impure limestone to a high temperature. The impurities, usually siliceous or clay, lead to the ...
[21]
Kiln Types - European Lime Association
Shaft Kilns. Shaft kilns can burn stone from a minimum of 20mm diameter up to 175mm. · Rotary Kiln. Rotary kilns consist of a rotating cylinder inclined at an ...
[22]
Flash Calcination of Lime Mud from the Forest Industry: Influence of ...
Jun 6, 2025 · Flash calcination was performed at a wide range of temperatures between 800 and 1300 °C and different gas mixtures containing N 2 , CO 2 , and H 2 O in the ...
[23]
Oxyfuel combustion in rotary kiln lime production - Wiley Online Library
Oct 8, 2014 · The reference case modeled in this study has an energy consumption of ~7 GJ/t lime produced. The energy consumption for oxygen production is ...
[24]
[PDF] A COMPETITIVE AND EFFICIENT LIME INDUSTRY
with the average fuel use for the production of quicklime of 4.25 GJ/tonne quicklime (paragraph ... Technology, 2012) remarks: “However, achieving an energy ...
[25]
Lime Market Size, Share, Analysis & Growth Report, 2033
Oct 21, 2025 · In 2023, global lime production was estimated at approximately 430 million metric tons. This substantial output underscores the material's ...Missing: statistics | Show results with:statistics
[26]
[PDF] LIME1 - Mineral Commodity Summaries 2024 - USGS.gov
Domestic Production and Use: In 2023, an estimated 17 million tons of quicklime and hydrated lime was produced. (excluding independent commercial hydrators2) ...
[27]
[XLS + PDF] Top Lime Producing Countries - Report Linker
In 2023, China dominated lime production with 230 million metric tons, showing its significant role in the global lime market. The United States and India ...
[28]
Carbon Footprint | Carmeuse
The lime industry accounts for on average 1% of global industrial CO2 emissions. ... The vast majority of these emissions originate directly from the lime ...
[29]
[PDF] CO2 Mitigation - Calix
... CO2, trapped in the rock, and which is released when making lime. These “process” CO2 emissions account for nearly 2/3 of lime's total CO2 emissions. Lime and ...
[30]
What is exactly dead-burnt lime, and why is less reactive than ...
Mar 25, 2023 · The over heated lime is termed dead burnt lime or overburned lime. Grinding will certainly help by increasing the surface area and improve the acceptable range ...
[31]
https://lancasterlimeworks.com/learning-center/types-of-lime/
[32]
[PDF] LIME: CALCIUM OXIDE - On scifun.org
CaO(s) + CO2(g). This reaction is reversible; calcium oxide will react with carbon dioxide to form calcium carbonate. The reaction is driven to the right by ...
[33]
[PDF] PRODUCTION OF IMPROVED CALCIUM-BASED SORBENTS FOR ...
It was found (Boynton, 1980) that the feed limestone particle size greatly influenced the quality of the product quicklime. Complete calcination required ...
[34]
A CANDIDATE TO EXPLAIN THE 6.8 m BAND - IOP Science
When the calcium metal grains contact oxygen gas, oxidation occurs on the surface of the calcium metal grains. Since the grains are extremely small, most, but ...
[35]
Reactivity of lime and related oxides. I. Production of calcium oxide
The production of calcium oxide from calcium carbonate (precipitated or prepared from calcium oxalate) involves types of physical changes similar to those in ...
[36]
(PDF) Preparation of nano-CaO using thermal-decomposition method
In order to make use of CaO, nano-CaO was prepared by thermal-decomposition method using Ca(NO 3 ) 2 .4H 2 O as precursor, NaOH aqueous solution as precipitant, ...
[37]
[PDF] 11.6 Portland Cement Manufacturing - EPA
Calcium, the element of highest concentration in portland cement, is obtained from a variety of calcareous raw materials, including limestone, chalk, marl, ...
[38]
[PDF] Preservation Brief 2: Repointing Mortar Joints in Historic Masonry ...
Up until about the mid-19th century, lime or quicklime (sometimes called lump lime) was delivered to construction sites, where it had to be slaked, or combined ...
[39]
Lime Mortar | MATSE 81: Materials In Today's World
Lime produced in this matter is referred to as quicklime or burnt lime. If water is added, this quicklime or burnt lime hydrates to form a white pasty ...
[40]
Steel Slag - Material Description - FHWA-RD-97-148
The open hearth furnace process is no longer used. In the basic oxygen process, hot liquid blast furnace metal, scrap, and fluxes, which consist of lime (CaO) ...
[41]
[PDF] 12.5 Iron And Steel Production 12.5.1 Process Description - EPA
During refining, the primary particulate compound emitted is calcium oxide from the slag. ... Basic oxygen furnace c. 69. 138. Electric arc furnace c. 9. 18 a.
[42]
Water Handbook - Precipitation Softening | Veolia
Precipitation softening reduces water hardness, alkalinity, and silica using lime or lime and soda ash, forming insoluble compounds removed by sedimentation ...
[43]
[PDF] AP-42, CH 11.15: Glass Manufacturing
May 25, 2007 · Soda-lime glass consists of sand, limestone, soda ash, and cullet (broken glass). The manufacture of such glass is in four phases: (1) ...
[44]
GLAZE COMPOSITION - Glendale Community College
All GLAZES are composed of three components: SILICA - the glass former, ALUMINA - the portion that 'shrinks-to-fit' the clay, FLUX - to lower the melting point.
[45]
Global Calcium Oxide Market | 2019 – 2030 - Ken Research
Global Calcium Oxide Market valued at USD 8.0 billion, driven by construction, metallurgy, and environmental demands. Key growth in emerging economies with ...
[46]
Riddle solved: Why was Roman concrete so durable? - MIT News
Jan 6, 2023 · Masic wondered: “Was it possible that the Romans might have actually directly used lime in its more reactive form, known as quicklime?” ...
[47]
[PDF] 11.4 Calcium Carbide Manufacturing 11.4.1 General Calcium ... - EPA
Lime for the reaction is usually made by calcining limestone in a kiln at the plant site. The sources of carbon for the reaction are petroleum coke, ...
[48]
https://pubs.acs.org/doi/abs/10.1021/ie403981j
[49]
[PDF] 10.2 Chemical Wood Pulping - EPA
The smelt is dissolved in water to form green liquor, which is transferred to a causticizing tank where quicklime (calcium oxide) is added to convert the ...
[50]
Kraft Pulping Process - an overview | ScienceDirect Topics
The smelt from the furnace is dissolved in water to form green liquor which is reacted with lime (CaO) to produce white liquor and calcium carbonate “mud”. The ...
[51]
Advances in CaO-based catalysts for sustainable biodiesel synthesis
CaO exhibits high catalytic activity to perform transesterification reactions. Additionally, CaO is a cheap and eco-friendly catalyst that can also be used as ...
[52]
Biodiesel Production from Castor Oil by Using Calcium Oxide ...
May 4, 2016 · 91.17% of biodiesel yield was obtained with catalyst loading of 2 w/w%, time of 3 h, temperature of 60°C, and methanol-to-oil ratio of 6 : 1.
[53]
An Overview of Biodiesel Production via Calcium Oxide Based ...
This review focuses on biodiesel generation via transesterification reactions from a catalytic standpoint.
[54]
Quicklime - MLC
At MLC, our calcium oxide (CaO), or commonly referred to as quicklime, is a high calcium content derivative of our 98.5% pure calcium carbonate (limestone).
[55]
CHEMICAL DATA NOTEBOOK SERIES #87: CALCIUM OXIDE
Aug 1, 1993 · It is used to make fluxes; in the manufacture of such metals as aluminum, magnesium, and steel; as a refining agent for metals, petroleum, and ...
[56]
Efficient Process for the Production of Alkyl Esters | ACS Omega
Aug 4, 2022 · It is known that the esterification reaction slows down in the presence of calcium oxide.
[57]
Calcium oxide as a solid base catalyst for transesterification of ...
Transesterification of edible soybean oil with refluxing methanol was carried out in the presence of calcium oxide (CaO), -hydroxide (Ca(OH) 2 ), or -carbonate ...Missing: dehydration | Show results with:dehydration<|separator|>
[58]
Calcium Oxide: Key Uses, Properties & Suppliers in 2025 - Accio
Rating 5.0 (26) · Free 14-day returnsIndustrial applications require ≥95% purity, while food/pharmaceutical sectors need 99% USP/FCC compliance. Verify adherence to ISO 9001, ASTM C911, or EN 459-1 ...Missing: catalysis | Show results with:catalysis
[59]
Understanding Value in Lime | Ohioline - The Ohio State University
Oct 2, 2002 · The cost of each product is $15/ton. If our soil test calls for an application of 2,000 lbs/A of calcium carbonate equivalent, what is the ...
[60]
Facts about Soil Acidity and Lime - MSU Extension
Nov 9, 2015 · Lime, calcium oxide, reduces soil acidity by neutralizing it and raising pH. Soil acidity is caused by hydrogen ions, measured by pH below 7.0.
[61]
Clemson Lime Rate Calculator
The agricultural limestone rates calculated here are applicable for raising soil ... Calcium oxide (burnt or quick lime): 150-175; Calcium silicate: 86 ...
[62]
Distillers grains with calcium oxide improve cattle diets
Nov 3, 2014 · Adding the calcium oxide, or CaO, directly to the ration mix at a rate of 1 percent of the total dry matter made the distillers grains less ...
[63]
Animal feed block made of molasses and calcium oxide
The molasses-calcium oxide animal feed block can be used as an animal feed supplement and can also include minerals, non-protein nitrogen, salt, vitamins, and ...
[64]
Precipitation and recovery of phosphorus from the wastewater ...
Mar 20, 2022 · Phosphorus can be removed from wastewater chemically and biologically. Iron or aluminum salts are often used to precipitate phosphate and ...
[65]
An unconventional lime for phosphate removal - Envirotec Magazine
May 16, 2018 · Chemical precipitation is used to remove inorganic forms of phosphate by adding a coagulant. Calcium is usually added to the process as hydrated ...
[66]
Removal of heavy metal ions from wastewater - Nature
Jul 8, 2021 · One of the most effective hydroxide precipitates for treating inorganic effluents of heavy metal concentration of 1000 mg/L is lime (CaO or Ca( ...
[67]
Sorbacal ® Q - Lhoist
Sorbacal® Q quicklime, or calcium oxide (CaO), is widely used in a large variety of flue gas desulfurization (FGD) processes. Sorbacal® Q is used to produce ...
[68]
Sugar Industry - Carmeuse
By adding lime, the juice becomes less acidic, creating an environment where impurities, such as proteins and colorants, can easily coagulate and be removed.
[69]
Preparation, Characterization and Application of Calcium Oxide ...
Jul 2, 2022 · The final carbonation mud resulted from sugar beet clarification process has been and still represents the most common waste problem in ...
[70]
US6051075A - Process for sugar beet juice clarification
The raw juice is heated to high temperature, and a solution/suspension of calcium oxide and water (milk of lime) is added to the juice. The juice is then ...
[71]
[PDF] Biosolids Technology Fact Sheet: Alkaline Stabilization of Biosolids
Materials that may be used for alkaline stabilization include hydrated lime, quicklime (calcium oxide), fly ... used. C. Odor control equipment at the processing.
[72]
Disinfection & Animal Waste - Carmeuse
Reduce Pathogen Growth – The use of high calcium quicklime, hydrated lime, or lime slurry can reduce pathogens by raising the pH of the material over 12.
[73]
Calcium Oxide Market Growth Opportunities & Trends - ReAnIn
Fertilizer and chemical sectors represent close to 15% of the market. Calcium oxide is widely applied as a soil amendment and in various chemical manufacturing ...Missing: percentage | Show results with:percentage
[74]
CaOH₂ and the Future: How Calcium Hydroxide Will Shape a ...
Apr 2, 2025 · Sustainability impact: By balancing soil pH, CaOH₂ enhances soil fertility naturally. This process reduces the need for synthetic fertilizers, ...
[75]
The History of Concrete: Textual
Natural cement was used first, then Egyptians used mud and lime. Romans used pozzolana. Joseph Aspdin invented portland cement, and I.K. Brunel first used it ...Missing: ancient | Show results with:ancient
[76]
[PDF] Lectures on Materials Science for Architectural Conservation
Ancient Roman bricks and tiles frequently contain pozzolana as a filler ... the gypsum mortar between the stones of the Egyptian pyramids);. • smoothing ...<|separator|>
[77]
[PDF] Lime and Cement Technology: Transition from Traditional to ...
Feb 5, 2001 · This influenced traditional work methods involving lime mortars as well as creating new methods for preparation of cement.
[78]
[PDF] Lime Data Sheet - Mineral Commodity Summaries 2020 - USGS.gov
Magnesium hydroxide is a substitute for lime in pH control, and magnesium oxide is a substitute for dolomitic lime as a flux in steelmaking. as U.S. production ...
[79]
Soil Acidity and Liming: Basic Information for Farmers and Gardeners
Compared to standard ag lime: 0.61 ÷ 0.44 = 1.39; thus 1.39 tons of this material should be used for every 1.0 ton of lime recommended on the soil test. If this ...
[80]
Applying Lime to Raise Soil pH for Crop Production (Western Oregon)
For established perennial or no-till crops, a top-dress lime application (1 to 2 t/a) may be beneficial. When very different soils are present within a field, ...
[81]
Review on the modifications of natural and industrial waste CaO ...
Mar 15, 2024 · This work comprehensively reviews the CO 2 capture capacity of sorbent improvement based on various CaO sorbents.
[82]
[PDF] Art of Alchemy
Feb 12, 2017 · Alchemy employed a systematic set of symbols and technical terms, commonly ... Quicklime. Alum. Lodestone. Realgar. Sal gemmae (Rock-crystal ...
[83]
The Revolution | Amplified Edition - The Pulter Project
25-27), and the verb she uses twice for this process, “calcine”, is alchemical, meaning to purify a substance to quicklime by burning it. When Pulter's speaker ...
[84]
CALCIUM OXIDE CAS Number - NJ.gov
OSHA: The legal airborne permissible exposure limit. (PEL) is 5 mg/m3 averaged over an 8-hour workshift. NIOSH: The recommended airborne exposure limit is. 2 mg ...
[85]
[PDF] SAFETY DATA SHEET - Fisher Scientific
Jul 11, 2014 · OSHA PEL. NIOSH IDLH. Mexico OEL (TWA). Calcium oxide. TWA: 2 mg/m3 ... Calcium oxide. >2000 mg/kg (female Rat). Not listed. LC50 > 6.04 mg/L ...
[86]
List of Classifications - IARC Monographs
Sep 18, 2025 · IARC Monographs on the Identification of Carcinogenic Hazards to Humans ... Agents classified by the IARC Monographs, Volumes 1–139. Copy
[87]
ICSC 0409 - CALCIUM OXIDE
Repeated or prolonged inhalation of dust particles may cause effects on the lungs. Repeated or prolonged inhalation may cause nasal ulceration. This may result ...Missing: chronic issues
[88]
https://chemicalsafety.ilo.org/dyn/icsc/showcard.display?p_card_id=0409
[89]
Calcium Oxide - ESPI Metals
4 FIRST AID MEASURES. General Measures: Remove patient from area of exposure. INHALATION: Remove to fresh air, keep warm and quiet, give oxygen if breathing ...
[90]
Lime Kilns - A silent killer - Tides & Tales
Aug 15, 2021 · Now speaking of bodies, Lime Kilns were decidedly dangerous to be around. While burning, the structures emitted noxious fumes which were prone ...
[91]
Calcium oxide - Substance Information - ECHA - European Union
The precautionary measures and guidance on safe use are as submitted to ECHA by registrants under the REACH Regulation. Information on precautionary measures ...
[92]
[PDF] An investigation of the global uptake of CO2 by lime from 1930 to 2020
Jun 9, 2023 · In the present study, 0.77, 0.683, and 0.75 t CO2 per tonne of lime produced were adopted as emis- sion factors for the US, China, and ROW, ...
[93]
Alkaline industrial wastes – Characteristics, environmental risks, and ...
Apr 15, 2023 · Typical pHs of these waste materials range between 6 and 13 (Table 1) and they can cause environmental pollution by generating fugitive dust ...
[94]
Alkaline residues and the environment: a review of impacts ...
Jan 20, 2016 · Impacts of alkaline leachates include increased water pH, high chemical oxygen demand and oxygen depletion in the water column, high sulphate ...
[95]
Biodiversity offsets in limestone quarries: Investigation of practices in ...
Direct impacts result arises from vegetation clear cut and earth and rock excavation, resulting in habitat loss and fragmentation.
[96]
Assessing the Impact of Quarrying as an Environmental Ethic Crisis
The loss of trees also disrupted biodiversity since it eliminated some species' habitats. The engineering processes involved in blasting and extraction are ...
[97]
Carbon Capture, Storage and Utilisation in lime manufacturing
Dec 14, 2022 · Carbon Capture is the only known way to limit climate impact in those chemical processes, where CO 2 -emissions cannot be reduced by electrification.
[98]
exploring alternatives for small to medium-scale carbon capture in ...
This study investigates two concepts for carbon capture in combination with lime kilns in Kraft pulp mills: oxyfuel combustion and electric arc plasma ...
[99]
Calcium oxide nanoparticles from eggshell waste - ScienceDirect.com
Upon calcination, eggshells are converted into CaO NPs, offering an eco-friendly and cost-effective route for nanoparticle production. Several studies have ...
[100]
EU Emissions Trading System (EU ETS) - European Lime Association
The EU ETS puts a cap on the carbon dioxide (CO2) emitted by business and creates a market and price for carbon allowances. It covers 45% of EU emissions.
[101]
[PDF] Methodology for the free allocation of emission allowances in the EU ...
The focus of this study is on preparing a first blueprint of an allocation methodology for free allocation of emission allowances under the EU Emission Trading ...
[102]
[PDF] Section 5 - Chapter 1: Wet and Dry Scrubbers for Acid Gas Control
Lime (CaO) is usually the sorbent used in the spray drying process, but hydrated lime (Ca(OH)2) is also used and can provide greater SO2 removal. Slurry ...
[103]
Dry scrubbing of gaseous HCl and SO2 with hydrated lime in ...
Lime slurry is usually used in semi-dry process to remove the acid gas in the air pollution control systems (Han et al., 2021). Because the temperature was ...
[104]
[PDF] Mineral carbonation and industrial uses of carbon dioxide
Mineral carbonation is based on the reaction of CO2 with metal oxide bearing materials to form insoluble carbonates, with calcium and magnesium being the most ...
[105]
[PDF] Chemistry of Ash and Leachates from the May 18, 1980 Eruption of ...
of oxides MgO, CaO, Ti02, and Fe2O3. These oxides are associated with ... 1974, The chemistry of sublimates collected directly from lava fountains at ...<|separator|>
[106]
Corundum, Rutile, Periclase, and CaO in Ca,Al-Rich Inclusions from ...
All inclusions contained at least two of the oxides periclase (MgO), rutile (TiO2), calcium oxide (CaO), and corundum (Al2O3).
[107]
[PDF] Morphology of Calcium Hydroxide in Cement Paste
Tilley suggests the name "portlandite" for crystalline calcium hydroxide occurring naturally. It is of interest that the natural mineral tobermorite and other ...
[108]
Lime - Quicklime & Limestone - 911Metallurgist
Oct 29, 2020 · The chief impurities are silica, alumina, and iron, which react ... It was common practice in the manufacture of dolomitic finishing lime ...
[109]
Impact of Limestone Surface Impurities on Quicklime Product Quality
During thermal processing in a kiln, impurities such as Si, Mg, Al, Fe, and Mn react with Ca, reducing quicklime product quality. Which reactant phases are ...
[110]
[PDF] Lime | 2019 Minerals Yearbook - USGS Publications Warehouse
May 4, 2024 · The two high-calcium forms of lime are high-calcium quicklime. (calcium oxide, CaO) and high-calcium hydrated lime. [calcium hydroxide, Ca(OH)2] ...<|separator|>
[111]
shows that the XRD pattern of calcium oxide has characteristic ...
shows that the XRD pattern of calcium oxide has characteristic peaks at 2 values of 32.2, 37.3, 53.8, 64.1, and 67.3 degree. Calcium carbonate has a XRD powder ...
[112]
XRD data of CaO, Ca(OH) 2 and CaCO 3 - ResearchGate
XRD results revealed that SLS calcined at 1000 °C displayed a Ca(OH)2 phase, while those calcined at other temperatures showed a CaCO3 phase. The ...
[113]
15 Metamorphism of Calcareous Rocks – Open Petrology
Key reactions that occur during carbonate metamorphism include decarbonation ... They are mostly limestones and dolostones, dominated by carbonate minerals.
[114]
Decarbonation - an overview | ScienceDirect Topics
Decarbonation is defined as a reaction involving the decomposition of carbonate minerals, such as calcite and dolomite, resulting in the release of carbon ...
[115]
Fumarolic Minerals: An Overview of Active European Volcanoes
Sep 21, 2016 · The leaching of lava by aggressive fumarolic gases can lead to material consisting exclusively of oxides of Si, Al, Fe, and Ti, opal- ...
[116]
Fumarole mineral - Wikipedia
Historical lava flows of Vesuvius volcano contain fumarolic minerals. Various fumarole minerals have been discovered at Vulcano volcano in Italy, where ...
[117]
The mechanism of vapor phase hydration of calcium oxide - PubMed
Oct 21, 2014 · Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic ...Missing: rare nature skarn deposits
[118]
[PDF] MINERALOGY AND PETROLOGY OF SKARN DEPOSITS
Anhydrite-bearing assemblages are rare in skarns, probably due to the relatively high low temperature solubility of anhydrite. In any case, early~formed Ca ...
[119]
[PDF] WC/98/001 Procedures for the rapid assessment of limestone ...
Certain geophysical techniques may be applied to field exploration for limestone ... The ASTM publish a test method to measure carbonate content, expressed as the ...
[120]
Impact-related chemical modifications of the Chang'E-5 lunar regolith
Dec 15, 2023 · In this study, we conducted detailed petrographic and mineralogical analyses on a diverse set of lunar regolith samples, including thirty-three ...