Magnesium hydroxide [Mg(OH)₂] is widely used in industry due to its alkaline properties, thermal stability, and non-toxicity.
1.Introduction
Magnesium hydroxide [Mg(OH)₂] is a white, inorganic compound with a wide range of industrial applications due to its alkaline nature, thermal stability, and non-toxic properties. Unlike harsher chemicals such as sodium hydroxide (NaOH), Mg(OH)₂ provides a slow-release alkalinity, making it safer and more controllable in various processes. Its ability to decompose under heat also makes it valuable as a flame retardant and environmental remediation agent.
This report explores the key industrial uses of magnesium hydroxide, detailing its role in:
Flame retardancy
Wastewater treatment
Flue gas desulfurization (FGD)
Environmental remediation
Pharmaceuticals and cosmetics
Food additives
Agriculture
Production of magnesium oxide (MgO)
2. Magnesium Hydroxide Flame Retardant
2.1 Mechanism of Action
Magnesium hydroxide flame retardant acts as an effective flame retardant in plastics, rubber, cables, and construction materials. Its flame-retardant properties stem from:
Endothermic Decomposition: At ~300–330°C, Magnesium hydroxide flame retardant decomposes into magnesium oxide (MgO) and water vapor, absorbing significant heat energy (endothermic reaction).
Mg(OH)2→MgO+H2O(Heat absorption: 1.3 kJ/g)
Dilution of Combustible Gases: Magnesium hydroxide flame retardant released water vapor dilutes flammable gases, slowing combustion.
Protective Char Layer: Magnesium hydroxide flame retardant resulting MgO forms a heat-resistant barrier, shielding the material from further burning.
2.2 Advantages Over Halogenated Flame Retardants
Non-toxic: Does not release harmful halogens or dioxins.
Smoke suppression: Reduces smoke emission compared to halogen-based retardants.
Environmental compliance: Meets strict regulations (e.g., RoHS, REACH).
2.3 Applications
Wire & cable coatings (prevents fire spread in electrical installations).
Polymer composites (used in automotive, aerospace, and construction materials).
Textiles and foams (fire-resistant fabrics and insulation).
3. Wastewater Treatment and Neutralization
3.1 Acid Neutralization
Mg(OH)₂ is widely used to treat acidic wastewater from:
Mining operations (acid mine drainage, AMD).
Metal plating & electroplating industries (neutralizes sulfuric, hydrochloric acids).
Chemical manufacturing (pH adjustment in effluent streams).
Advantages over NaOH & Ca(OH)₂:
Controlled pH adjustment: Dissolves slowly, preventing excessive alkalinity spikes.
Lower sludge production: Forms denser, more easily filterable precipitates.
3.2 Heavy Metal Removal
Mg(OH)₂ precipitates toxic metals (e.g., Pb²⁺, Cd²⁺, Ni²⁺) as insoluble hydroxides:
M2++Mg(OH)2→M(OH)2+Mg2+M2++Mg(OH)2→M(OH)2+Mg2+
Used in:
Magnesium hydroxide Electroplating wastewater treatment.
Magnesium hydroxide Battery recycling effluent processing.