magnesium hydroxide

Types

Magnesium hydroxide is basically an inorganic compound that contains both the magnesium cation and the hydroxide anion. It is extracted from seawater and brine. It comes in several forms, each having its own specific characteristics and uses.

• Powdered magnesium hydroxide

  Regularly known as milk of magnesia, this is a fine white powder that is often formed when magnesium ore is heated and hydrated with water. It’s usually applied in the chemical industry as a neutralizing agent for acid and in wastewater treatment plants to precipitate phosphate and hence remove it from wastewater. It is also used in the production of other forms of magnesium.

• Magnesium hydroxide suspension

  This is a liquid formulation that contains a concentrated mixture of magnesium hydroxide particles suspended in water. This form is especially popular in the production of antacid medications where the suspension is consumed to treat stomach acid-related ailments. It’s also used in toothpaste as a buffering agent.

• Magnesium hydroxide crystal

  These are typically larger, less ground forms of magnesium hydroxide. Mg(OH)2 crystals are white solids that are usually used for research and may also be applied in instances where a purer, unground form of the compound is necessary for reactions that require specific stoichiometric measurements. Mg(OH)2 crystals may also be used in catalysis and to develop other magnesium compounds.

• Coated magnesium hydroxide

  This type of magnesium hydroxide is developed by applying a thin layer of organic or inorganic substances to its surface. This form is commonly used in the plastics industry where magnesium hydroxide is coated with silica, for example, to improve its compatibility with polymer resins. Coated magnesium hydroxide is also used in the pesticide industry to help control the slow release of active ingredients.

• Nanoparticle magnesium hydroxide

  This is a very fine form of magnesium hydroxide which is around 1-100 nanometers in size. Nanoparticle magnesium hydroxide is especially popular in research and development fields as it has ideal characteristics for high reactivity and large surface area. For example, it is usually used in drug delivery systems in the pharmaceutical industry to enhance the bioavailability of drugs.

Industrial application

• Treating wastewater

  Magnesium hydroxide is a versatile compound and an essential neutralizing agent that is used in wastewater treatment. Magnesium hydroxide helps precipitate and remove heavy metals such as lead, mercury, and cadmium from industrial wastewater by neutralizing acids present in the water. It helps in providing a safer method for disposal and reducing toxic substances in the environment. It is also used to treat acidic mine drainage which is a byproduct of mining operations.

• Pulping and bleaching in paper production

  In the magnesium process of producing pulp for paper, magnesium hydroxide is used to extract lignin from wood, thus isolating cellulose fibers that are then used to make paper. Magnesium hydroxide is also used in the bleaching process to help whiten the pulp without using harsher chemical agents like chlorine.

• Flue gas desulfurization

  In power plants and industrial facilities, magnesium hydroxide is used in flue gas desulfurization systems to reduce sulfur emissions. Basically, Magnesium hydroxide reacts with sulfur dioxide in the presence of oxygen and water to form magnesium sulfate, thus helping to remove the pollutant from the atmosphere. It helps mitigate acid rain and other environmental problems associated with sulfur emissions.

• Soil stabilization and road construction

  Magnesium hydroxide is used in construction activities to help stabilize soil, especially when building roads and other infrastructure. This compound helps bind soil particles together and increases their load-bearing capacity. It is also used to stabilize clay-rich soils which are difficult to work with during construction due to their high water retention and plasticity. In road construction, magnesium hydroxide is mixed with water to form a slurry that can be injected into soft or unstable soils to improve their firmness and usability.

• Antacid and laxative in healthcare

  Magnesium hydroxide, which is prepared from seawater and brine, is usually suspended in water and applied as an antacid and laxative in medicine. It neutralizes stomach acids, providing relief from indigestion and heartburn. Due to its osmotic laxative properties, magnesium hydroxide can draw water into the intestines, helping soften stools and easing constipation.

Product specification and features

Technical specification

• Purity: Mg(OH)2 ≥ 99%
• Magnesium content: 6.5 – 7.5%
• Calcium content: < 0.5%
• Sulfate content: < 0.5%
• Heavy metals: < 0.01%
• Water insoluble substance: < 0.5%
• Particle size: > 95% pass 75μm/ 200 mesh
• pH (10% slurry): 9.5 – 11.5
• Bulk density: 0.5 – 0.9g/cm³
• Moisture content: ≤ 0.5%

How to use

Magnesium hydroxide is often prepared as a slurry of 60-70% concentration that is applied during wastewater treatment as a neutralizing agent. By adjusting the pH level, it can effectively precipitate heavy metals and other contaminants, making it easier for them to be removed from the system. Apart from wastewater treatment, magnesium hydroxide can also be used as a flocculent to help clump together solid particles, allowing them to settle out more easily.

Dosage

The specific dosage of magnesium hydroxide can vary widely depending on factors such as wastewater composition, initial pH, and target pH range. Generally, the concentration of magnesium hydroxide added is based on the stoichiometric requirement for neutralization.

To determine the appropriate dosage, the initial pH of the wastewater is measured and the amount of magnesium hydroxide required to achieve the desired pH is calculated. As a rule of thumb, 1 kg of magnesium hydroxide can be applied per ton of wastewater. However, this is very basic and the actual requirements should be determined through a jar test or small-scale pilot studies.

Product maintenance

Magnesium hydroxide should be stored in a cool dry area away from direct sunlight and incompatible materials such as strong acids. Ensure that the storage area is well-ventilated to prevent the accumulation of moisture. Seal containers properly to avoid exposure to humidity, which could result in clumping or degradation. Regularly inspect stock for signs of moisture exposure or contamination. Follow the first-in-first-out method to ensure the oldest stock is used first.

Quality and safety considerations

While processing magnesium hydroxide at scale, there are several quality and safety factors to consider so as to mitigate on risk and wastage.

• Purity and composition

  Magnesium hydroxide should contain at least 99% purity to be effective in its various uses, whether as a neutralizing agent or in papermaking. Ensure the source material, whether it’s brine or seawater, is of high quality and free from any contaminants. Also ensure that the extraction method allows for effective separation without leaving toxic residues.

• Combustibility and reactivity

  Although magnesium hydroxide itself is non-flammable, magnesium metal can pose a serious fire hazard, especially in cases where fine particles are present. When handling magnesium, be extra careful to store it away from heat sources, open flames, and strong oxidizers. Fine magnesium particles and dust should be kept away from any source of ignition and should ideally be handled in well-ventilated areas with appropriate filtration systems.

• Workplace exposure

  Magnesium hydroxide powders and dust can cause respiratory irritation, especially when inhaled over long periods. When working with the compound, wear appropriate dust masks or respirators to reduce inhalation risk. The hydroxide also has the potential to cause skin irritation and hence, skin contact with the compound should be minimized. Workers should be advised to wear gloves along with long-sleeved clothing to reduce skin exposure.

• Environmental impact

  Large-scale mining of magnesium-containing minerals can pose a serious environmental risk by disrupting ecosystems and depleting natural resources. When mining for magnesite, be extra cautious to mine sustainably and ensure to follow all local regulations regarding land use. When disposing of magnesium hydroxide waste, never release it directly into water bodies as it can disrupt aquatic life by altering pH levels.

• Transportation and storage

  Magnesium products are either highly combustible or can become hazardous when exposed to moisture or water. While transporting magnesium hydroxide, avoid shipping it with strong acids or moisture-sensitive chemicals that could potentially react with it. When storing the compound, use moisture-proof containers to reduce the risk of contamination or chemical reactions. Ensure that storage facilities are well-organized to prevent accidental mixing with incompatible substances.

Questions and Answers (Q&A) section

Q1. What industries benefit from using magnesium hydroxide?

A1. Magnesium hydroxide is commonly applied in wastewater treatment, the paper industry, flue gas desulfurization, construction, and road stabilization. It is also commonly applied in the medical industry in antacids and laxatives.

Q2. Is magnesium hydroxide an environmental pollutant?

A2. Magnesium hydroxide is actually non-toxic to the environment. In fact, it is often used to treat other more toxic forms of pollutants in industrial wastewater. However, it needs to be managed properly during disposal to avoid disruption of aquatic environments.

Q3. How is magnesium hydroxide used in the construction industry?

A3. Magnesium hydroxide is used in soil stabilization when building new roads and provides long-term durability for the constructed roads and other structures. It is mixed with water to form a slurry that binds with soft soil to improve its load-bearing capacity.

Q4. How does magnesium hydroxide prevent fires?

A4. Magnesium hydroxide is ideal for preventing fires because, when added to plastics, it can help inhibit their combustion. It releases moisture when exposed to high temperatures which helps cool the material and dilute any potentially flammable gases that are emitted.

Q5. How should magnesium hydroxide be stored in bulk outdoors?

A5. To ensure magnesium hydroxide remains effective when stored outdoors in bulk, it should be kept in a humidity-proof, moisture-proof, and waterproof environment. Use heavy-duty plastic sheets to wrap the stock and secure it tightly with ropes to avoid exposure to rain or high humidity.