Is Potassium Hydroxide Harmful to the Environment?

by Kate Onissiphorou

Just like many inorganic substances, potassium hydroxide doesn’t contain degradable functional groups. This means that it does not have a detrimental impact on the biological oxygen demand in water.

It does, however, dissociate into ions when dissolved in water, which can elevate the pH level of systems that do not have sufficient buffers. If a large quantity of an alkaline substance like potassium hydroxide was to be deposited into a pond or lake, the pH will increase significantly. Although usually temporary, this rise can be moderately toxic to nearby aquatic organisms. 

The good news is that it’s relatively uncommon for large amounts of potassium hydroxide to find their way into contained bodies of water. With a wide range of industrial applications, potassium hydroxide is more likely to be converted into other substances or used as feedstocks before any residue is disposed of. Its harmful effects on the environment are therefore minimal.

Is potassium hydroxide toxic?

A bowl of solid, white crystal potassium hydroxide
As a strong base, potassium hydroxide is highly caustic. It can cause severe injuries to organic tissue like skin and the inner linings of the digestive tract. It can also damage the eyes, nasal cavity and lungs. If ingested, the estimated lethal dose of potassium hydroxide is about five grams, while the airborne value should not exceed two mg/m3.

At lower concentrations, potassium hydroxide is useful in the food industry. For example, it’s used to remove fruit and vegetable peels and to caramelise various sugar-based products. It can also be used to thicken ice cream and extract chocolate from cocoa. Ice cream being made in a factory

Is potassium hydroxide dangerous?

All substances, no matter how seemingly harmless (including water), have thresholds of toxicity to humans and other organisms. However, caustic substances like potassium hydroxide have a relatively lower threshold of toxicity.

Potassium hydroxide has a toxicity threshold which, if exceeded, may be immediately dangerous. Low-dose, long-term exposure can also be hazardous.

How potassium affects the environment

Although potassium has some essential natural functions, it can have a detrimental impact on the environment. Read more about the environmental effects of potassium below.

High energy consumption

One of the primary industrial methods of producing potassium hydroxide is through the electrolysis of an aqueous solution of potassium chloride. In this process, an electric current splits the compound into potassium and chlorine. The chlorine is released as a gaseous by-product while the potassium reacts with water to form potassium hydroxide. Potassium hydroxide manufacturing tends to use a lot of energy and therefore has a relatively large carbon footprint.

Essential to plants

Along with nitrogen and phosphorus, potassium is one of the most important micronutrients for plant life. Its main function in plants is maintaining osmotic pressure, which allows the movement of water and nutrients in and out of the plant cells. This helps to maintain the size and structure of the cells. It also indirectly regulates the amount of carbon dioxide entering the plant by controlling the opening and closing of the stomata.

Unhealthy soil pH

Plants tend to grow best at a certain soil pH, with most generally needing soil that has a pH range of between 5.5 and 7.5. This is slightly acidic and near the neutral pH level. Releasing excessive potassium hydroxide into the soil can disrupt the pH balance and make the soil highly alkaline. This change could kill a wide range of plant species and essential bacteria. A soil meter measuring the pH of the soil it's in.

Moderately toxic to aquatic organisms

When released into enclosed bodies of water like ponds and lakes, potassium hydroxide causes the pH level of the surrounding water to rise suddenly. This can immediately kill some of the nearby aquatic organisms. However, the level decreases as the substance dissipates, meaning the increase in pH is usually only short-lived. As a result, the overall toxicity of potassium hydroxide is generally considered to be mild.

Harmful to humans

At certain levels, potassium hydroxide can be harmful to humans. This is particularly the case for workers in factories that use potassium hydroxide as feedstocks. Airborne particulates of potassium hydroxide with a concentration above two mg/m3 can damage lung tissue and irritate the skin.

Is potassium hydroxide biodegradable?

Potassium hydroxide is less toxic than other alkali metal hydroxides such as sodium hydroxide. It can be caustic and harmful to organic living tissues, but is technically non-biodegradable.

Like most inorganic compounds, potassium hydroxide cannot degrade through organic means of decomposition. That’s because bacteria, fungi and other microorganisms cannot directly consume it and break it down into its components. There is simply no organic functional group to attack. However, it can easily be neutralised by the acidic byproducts of metabolism.

How to dispose of potassium hydroxide safely

Chemical safety data sheets (SDS) contain specific recommendations on how to dispose of certain chemicals safely. The SDS for potassium hydroxide sets out the following recommendations:

  • Collect the powdered material and place it in a sealed container
  • For solutions, use dry sand, earth, sawdust, or a similar material to absorb the solution and place it in the disposal container
  • Ventilate and wash the spillage area completely
  • Never throw the residues or spilt material into the sewer
  • Factories must have a processing system that will neutralise the excess potassium hydroxide before the effluent is disposed of
  • If a large amount of potassium hydroxide needs to be disposed of, contact the environmental office or a qualified disposal company.


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