What Is A Good Caustic Soda Replacement?

You may have heard about caustic soda while you were studying. In fact, you may have used it, with caution, in some of your science experiments. Scientifically known as sodium hydroxide (NaOH), caustic soda is used in many industrial applications, such as in manufacturing cleaning and pharmaceutical products, as well as in wastewater treatment, ore processing, metal cleaning, and in other essential processes. 

While it has many uses, caustic soda is considered a dangerous substance, and several eco-friendly and sustainability-driven industries have decided to use a replacement for caustic soda that’s equally effective yet less harmful to humans and the environment. 

Caustic soda and lime are typically used in neutralizing acidic metal bearing industrial waste. But they’re highly corrosive and harmful to humans. An inorganic compound, it’s capable of decomposing proteins and may cause chemical burns if mishandled. 

Magnesium Hydroxide as Caustic Soda Replacement 

Magnesium hydroxide Mg(OH)2 is a great alternative for caustic soda, as it’s cost-effective, less harmful, and equally effective. 

Like caustic soda, Mg(OH)2, may come in powdered and crystalline forms, and is generated mainly from seawater mixed with calcium hydroxide or milk of lime. When mixed with water, it forms a popularly known mixture called milk of magnesia which is used to neutralize stomach acid, and as a laxative. This further proves that magnesium hydroxide is gentle and safe for humans. 

Below are the advantages of Magnesium Hydroxide over Sodium Hydroxide (Caustic Soda):

  • Safe for humans. When ingested or comes in contact with skin, magnesium hydroxide does not cause major problems. 
  • Non- corrosive. Unlike its more hazardous counterpart, magnesium hydroxide does trigger a chemical reaction that could cause chemical burns or tissue damage.    
  • Has higher alkaline levels. An alkaline substance is capable of neutralizing an acid and is useful in industrial processes including waste water treatment. Magnesium Hydroxide Mg(OH)2 is composed of two hydroxides for alkalinity, while caustic soda (NaOH) only has one.
  • Offers better pH control. Controlling a pH level involves the addition of an alkaline or acidic substance to bring a measured pH to its ideal levels. For instance, a wastewater system needs to control the pH range of wastewater that’s discharged from commercial or industrial sites to reduce the corrosive effects of gaseous contaminants. 
  • Non-Toxic. As a non-toxic substance, magnesium hydroxide is used in pharmaceutical applications and may be ingested by humans as an antacid or a laxative. 
  • Environment-safe. Magnesium is a major element of chlorophyll, making it friendly and beneficial to the environment. 
  • Cheaper to use. Because it has higher alkalinity levels, a smaller amount of Magnesium Hydroxide is needed to achieve the ideal pH control as compared to caustic soda, translating to lower costs 

Caustic soda causes skin and eye irritation and burns, according to the Centers for Disease Control and Prevention. Its replacement, magnesium hydroxide, does not react negatively with water. It won’t burn or damage your skin on contact. 

When industrial accidents occur, such as a large-scale caustic soda spill, an environmental clean-up service is required, because apart from being highly corrosive, caustic soda is highly combustible, too. On the contrary, if magnesium hydroxide is involved in such accidents, only minor cleaning like pumping or shoveling is needed.

Applications for Magnesium Hydroxide    

One of the most useful and prevalent application of caustic soda or lime in the past decades is in waste water treatment facilities.  

  • Biological Treatment Plants 

Industrial waste water relies on pH control to reduce the harmful effects of gaseous acidic contaminants. Several manufacturing companies process their wastes via anaerobic digesters and later, an aerobic activated sludge system. The digester and sludge systems function to breakdown the dangerous substances and gases produced by the wastes coming from the manufacturing processes and making them safer to the environment.   

The sludge system is “cleaned” before getting discharged. To provide phosphorus and nitrogen as nutrients, phosphoric acid and urea are then added to the system. In the past, lime was used for pH control and to increase alkalinity but more and more treatment plants are turning to magnesium hydroxide as a caustic soda replacement.

Using magnesium hydroxide instead of caustic soda, industrial waste water produces reduced sludge volume density, making it easy to de-water.

  • Bleaching agent 

Magnesium hydroxide may also be used as a caustic soda replacement in bleaching paper. A research found that the use of the said compound reduces the need for other chemicals and was able reduce the volume of wastes produced. However, as magnesium hydroxide appeared as a solid suspension, it reacted slowly compared to caustic soda.  Magnesium sulfite and oxide, however, is being used in pulping and bleaching paper.


The use of magnesium hydroxide as a caustic soda replacement is a better option for industrial applications, particularly in the treatment of wastes. Besides lowering the overall costs and producing less volume of hazardous waste, magnesium hydroxide is less harmful to humans and the environment. 

Adam Hansen

Adam is a part time journalist, entrepreneur, investor and father.