Basic knowledge about magnesium oxide
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1. Basic Properties Physical Properties: Appearance: White or off-white powder, odorless and tasteless. Density: 3.58 g/cm³ (25℃). Melting Point: 2852℃, Boiling Point: 3600℃, Excellent high-temperature resistance. Solubility: Insoluble in water, slightly soluble in acids, easily soluble in ammonium salt solutions. Chemical Properties: Basic oxide, can react with acids to form magnesium salts and water (e.g.: MgO + 2HCl → MgCl₂ + H₂O). At high temperatures, can react with carbon to form elemental magnesium (MgO + C → Mg + CO). Hygroscopicity: Exposed to air, it will slowly absorb moisture and carbon dioxide, generating magnesium bicarbonate. 2. Preparation Methods Calcination Method: High-temperature calcination of magnesium carbonate (MgCO₃) or magnesium hydroxide (Mg(OH)₂) to obtain. MgCO₃ → Δ MgO + CO₂↑ MgCO₃ Δ MgO + CO₂ ↑ Precipitation Method: Through the reaction of magnesium chloride with alkali (such as sodium hydroxide) to generate magnesium hydroxide, and then calcination to obtain magnesium oxide. Other methods: Such as extracting magnesium from seawater/brine, directly oxidizing metallic magnesium, etc. 3. Classification (by purity and application) Industrial-grade Magnesium Oxide: Low purity (90-95%), used in refractory materials, metallurgy, etc. Food/Pharmaceutical-grade Magnesium Oxide: High purity (≥98%), used as an antacid, food additive. High-purity Magnesium Oxide (99.9% or above): Used in high-tech fields such as electronics, optical materials. 4. Main Applications Refractory Materials: Used as the inner lining of high-temperature equipment such as steel furnaces, cement kilns (due to high melting point). Environmental Field: Treat acidic wastewater or exhaust gas (neutralize acidic substances). Medicine and Food: Antacid (relieve excessive stomach acid). Food Additive (anti-caking agent, magnesium element supplement). Agriculture: Improve acidic soil or use as magnesium fertilizer. Others: Fillers for rubber and plastic. Raw materials for preparing other magnesium compounds (such as magnesium sulfate). High-purity magnesium oxide is used in semiconductors, ceramics, etc. 5. Safety Precautions Inhalation risk: The powder may irritate the respiratory tract. Wearing a protective mask is necessary. Contact with skin: Generally harmless, but high concentration may cause mild irritation. Storage: Sealed and protected from moisture. Avoid contact with acidic substances. 6. Extended Knowledge Nano-magnesium oxide: Has a larger specific surface area and activity, used in catalysis, antibacterial materials, etc. Difference from magnesium hydroxide: MgO is an oxide, while Mg(OH)₂ is a hydroxide (the latter is more prone to react with acids).
Introduction
1. Basic Properties
Physical Properties:
Appearance: White or off-white powder, odorless and tasteless.
Density: 3.58 g/cm³ (25℃).
Melting Point: 2852℃, Boiling Point: 3600℃, Excellent high-temperature resistance.
Solubility: Insoluble in water, slightly soluble in acids, easily soluble in ammonium salt solutions.
Chemical Properties:
Basic oxide, can react with acids to form magnesium salts and water (e.g.: MgO + 2HCl → MgCl₂ + H₂O).
At high temperatures, can react with carbon to form elemental magnesium (MgO + C → Mg + CO).
Hygroscopicity: Exposed to air, it will slowly absorb moisture and carbon dioxide, generating magnesium bicarbonate.
2. Preparation Methods
Calcination Method: High-temperature calcination of magnesium carbonate (MgCO₃) or magnesium hydroxide (Mg(OH)₂) to obtain.
MgCO₃ → Δ MgO + CO₂↑ MgCO₃ Δ MgO + CO₂ ↑
Precipitation Method: Through the reaction of magnesium chloride with alkali (such as sodium hydroxide) to generate magnesium hydroxide, and then calcination to obtain magnesium oxide.
Other methods: Such as extracting magnesium from seawater/brine, directly oxidizing metallic magnesium, etc.
3. Classification (by purity and application)
Industrial-grade Magnesium Oxide: Low purity (90-95%), used in refractory materials, metallurgy, etc.
Food/Pharmaceutical-grade Magnesium Oxide: High purity (≥98%), used as an antacid, food additive.
High-purity Magnesium Oxide (99.9% or above): Used in high-tech fields such as electronics, optical materials.
4. Main Applications
Refractory Materials: Used as the inner lining of high-temperature equipment such as steel furnaces, cement kilns (due to high melting point).
Environmental Field: Treat acidic wastewater or exhaust gas (neutralize acidic substances).
Medicine and Food:
Antacid (relieve excessive stomach acid).
Food Additive (anti-caking agent, magnesium element supplement).
Agriculture: Improve acidic soil or use as magnesium fertilizer. Others:
Fillers for rubber and plastic.
Raw materials for preparing other magnesium compounds (such as magnesium sulfate).
High-purity magnesium oxide is used in semiconductors, ceramics, etc.
5. Safety Precautions
Inhalation risk: The powder may irritate the respiratory tract. Wearing a protective mask is necessary.
Contact with skin: Generally harmless, but high concentration may cause mild irritation.
Storage: Sealed and protected from moisture. Avoid contact with acidic substances.
6. Extended Knowledge
Nano-magnesium oxide: Has a larger specific surface area and activity, used in catalysis, antibacterial materials, etc.
Difference from magnesium hydroxide: MgO is an oxide, while Mg(OH)₂ is a hydroxide (the latter is more prone to react with acids).
