Magnesium hydroxide vs caustic soda / sodium hydroxide demonstration

Disclaimer: This experiment was not performed in a controlled lab environment and is routinely performed safely as a benchtop demonstration to show that magnesium hydroxide provides more CaCO3 equivalent alkalinity on an equal weight basis when compared to caustic soda, which means less chemical consumption and can result in significant cost savings. Magnesium hydroxide is non-hazardous and non-corrosive which makes handling safer and easier.

1. Better for your budget

While Mg(OH)2 is typically more expensive on a “price per unit” basis, it is significantly less expensive in use. Every 1.0 kg of 50% NaOH can be replaced by 0.6 kg of 60% Mg(OH)2 to provide the same number of moles of hydroxide (OH-) for pH neutralization.

When an alkaline compound dissolves in water it produces hydroxide ions, OH-. These ions are responsible for the alkalinity of the solution.

Because Magnesium Hydroxide Mg(OH)2 provides two hydroxides for alkalinity compared to one with NaOH caustic soda, the usage rate for Mg(OH)2 is much less than that required for NaOH.

2. Safer and greener means further savings

Unlike caustic soda, Magnesium Hydroxide is non-hazardous and non-corrosive, which makes it easier and safer to handle. Spill is not reportable.

Because magnesium is a macronutrient – it is the core element of chlorophyll (makes everything green!) – it is also beneficial to the environment while sodium is a salinity hazard.

Magnesium also has coagulation properties that sodium does not. This can result in reduced sludge volume and reduced sludge hauling fees.

3. Improved solids settling

The wastewater stream for many industrial processes can be quite unpredictable and inconsistent. Dramatic changes in pH can have adverse effects on the settleability of suspended solids. To stabilise the pH, the wastewater is commonly neutralised with alkalis. The nature of the alkali selected can have a dramatic impact on the ability to settle suspended solids. Caustic soda typically provides no settling benefit and often results in gelatinous sludge that does not dewater easily. With lime (Ca(OH)2) there is typically a significant increase in sludge volume due to the formation of calcium minerals, like calcium carbonate (CaCO3).

In contrast, magnesium hydroxide assists with solids settling, providing a more compact sludge with a boost in alkaline pH to improve subsequent secondary treatment and anaerobic digestion performance.

ACTI-Mag for Caustic replacement

A safe and cost effective alternative to the use of sodium hydroxide (caustic soda) for wastewater alkalinity and pH adjustment.

Find out more about ACTI-Mag

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