How to Dispose of Acid Safely

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It is important to dispose of acids with very low pH (<2) safely. If the acid doesn’t have heavy metals or other toxic substances dissolved in it, neutralizing the pH to a less acidic level (pH 6.6-7.4) allows you to dispose of the substance in the standard sewer system. If heavy metals are present, the solution must be treated as hazardous waste and disposed of through the proper channels.

Method 1
Method 1 of 3:

Working Safely

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  1. You should not throw away acids in the garbage or the sewage system as it can have dangerous consequences. [1] The ICI tells you all the important safety information about handling and storage for a chemical. You can search for the exact name of your acid in the database online and obtain all the relevant information.
  2. When handling acids or any other strong chemicals, wearing goggles, gloves, and a lab coat is very important. Splash goggles should be used as they protect the sides of the eyes as well. The gloves and lab coat will also protect your skin and clothing. [2]
    • Gloves should be made of plastic or vinyl.
    • Pull back long hair to avoid unintentional contact with the acid.
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  3. Vapors released by the acid are toxic. Use a fume hood whenever possible to limit exposure. If you don’t have access to a fume hood, open all of your windows and ventilate the area with a fan. [3]
  4. In the event that acid gets on your skin or in your eyes, you must flush them with running water for at least 15 minutes. Following this wash, immediately seek medical attention.
    • For eye splashes, keep your eyelids open moving your eyes up, down, and side to side to properly flush them.
    • For skin splashes, immerse the area of skin under running water for the full 15 minutes.
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Method 2
Method 2 of 3:

Disposing of Acid at Home

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  1. Most strong acids will degrade glass and metal, but will not react with plastics. [4] There are many different types of plastics so make sure you obtain the correct container for your acid. The acid should already be stored in such a container, but you will need a second container for diluting and neutralizing the acid.
    • Make sure the container can hold at least twice the volume of solution as the amount of acid you have. This allows you enough space for diluting and neutralizing the acid.
    • Take care not to spill any of the acid if you have to transfer it to a larger container.
  2. When diluting and neutralizing a strongly acidic solution, a large amount of heat is released. To limit the possibility of burns or melting the container, place your empty container into a bucket of ice. [5]
  3. If you have a highly concentrated acid, you’ll want to dilute it first with water. This step can be dangerous so follow all instructions carefully. Use cold water to prevent the solution from boiling and causing splashes. Add water to the empty container. Slowly, add the acid to the water paying close attention to the temperature of the container as you do.
    • The amount of water needed to dilute the acid is dependent upon how concentrated your solution is. The more concentrated, the more water you will need. You can calculate the exact amount by following the steps in how to dilute an acid .
    • Never add water directly to the acid, this can cause the water to quickly boil and splash the acid.
    • Take care not to spill any of the acid as you dilute it.
  4. pH strips can be obtained from a science supply catalog or a pool supply store. To determine how much neutralizing solution you’ll need, you must know the pH of the acid you’re trying to neutralize.
    • Dip the end of the pH strip into the solution. The strip will change color based on pH.
    • Remove the strip and compare the color to the pH chart supplied with the strips. The color that matches the strip is the pH of your solution.
    • The lower the pH of the acid, the more neutralizing solution you will need.
  5. Solutions such as sodium hydroxide or magnesium hydroxide are basic and can be added to acids to neutralize them. Sodium hydroxide is also known as lye , while magnesium hydroxide is the main ingredient in milk of magnesia. Both substances can be purchased at the store.
    • Follow the instructions on the container of lye to make your sodium hydroxide solution.
    • Milk of magnesia does not need to be altered and can be used directly to neutralize the acid.
  6. Basic solutions react with acidic solutions to neutralize the acid and produce water and a salt. [6] Slowly add your basic solution a little bit at a time to the diluted acid. Gently stir as you add. Pay attention to the temperature of the container and be careful not to splash any of the solution.
  7. Periodically test the pH with a pH strip to make sure you don’t overshoot the goal pH range of 6.6-7.4. Continue to slowly add the salt solution until you reach the desired neutral range.
    • Alternatively, you can use a universal indicator solution. The liquid will change color according to pH. [7] Add the salt solution until the indicator changes to the color around the range of pH 7.0.
    • If you go beyond the neutral range, slowly add a dilute acidic solution to get the pH back down to at least 7.4.
  8. The neutralized solution can be safely poured down the drain while running cold water. Continue to run water down the drain after the container is empty for at least 30 seconds. [8]
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Method 3
Method 3 of 3:

Disposing of Acid with Dissolved Heavy Metals

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  1. Most strong acids will degrade glass and metal, but will not react with plastics. [10] There are many different types of plastics so make sure you obtain the correct container for your acid. The acid should already be stored in such a container, but make sure it is not completely full to prevent spills.
  2. Heavy metals such as cadmium, zinc, copper, mercury, and lead are toxic and cannot be added to the water system. [11] Other inorganic compounds that are toxic and/or corrosive also cannot go down the drain.
    • If you have different containers of the same acid with different compounds dissolved in it, keep them in separate containers as they must be disposed of separately.
  3. You should use the EHS Hazardous Waste Program to dispose of most of the chemical wastes. [12] If you are at a university or work in a laboratory, there will be a department that will properly dispose of your hazardous waste for you. If this is not an option you can contact a local organization to help you with the disposal process.
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Community Q&A

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  • Question
    What are the safety precautions in the laboratory?
    Community Answer
    Dress for work in the laboratory. Wear clothing and shoes that cover exposed skin and can protect you from potential splashes. Tie back long hair, jewelry, or anything that may catch in equipment. Never eat food, drink beverages, chew gum, apply cosmetics (including lip balm), or handle contact lenses in the laboratory.
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  • Question
    Where can you take acid for disposal?
    Community Answer
    Your local pool company may be willing to dispose of the acid, or your local waste management plant may take the acid to use.
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  • Question
    Can you use a pot that had drain acid spilled in it?
    Hannah
    Community Answer
    First, look for signs of corrosion: are there any changes as to how the pot looked before (roughed up surface,...)? Foaming, bubbles or heat when the acid had contact with the pot is another sign of a chemical reaction. If this has occurred, discard the pot. If it looks fine and you have thoroughly washed it with water, you can use it again.
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      Warnings

      • If too much Milk of Magnesia is consumed, stomach acid may become basic.
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      • If you try to dilute the acid, make sure to add the acid to water and not water to the acid. If the acid is high enough in concentration, it will release a great amount of heat if you add water to it.
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      • Certain types of acid are highly corrosive and WILL damage anything weaker that it comes in contact with.
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      Things You'll Need

      • pH paper/litmus paper
      • A strong container
      • Milk of Magnesia or sodium hydroxide solution
      • Optional: universal indicator

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      References

      1. ↑ Gregory Cade, JD. Environmental & Occupational Law Attorney. Expert Interview. 13 October 2021.
      2. ↑ https://www.osha.gov/sites/default/files/publications/osha3151.pdf
      3. ↑ https://safety.uoregon.edu/physical-hazards
      4. ↑ https://research.columbia.edu/environmental-health-safety-ehs
      5. ↑ https://www.bsu.edu/-/media/www/departmentalcontent/facilities/pdf/bsu-sewer-disposal-nov-16-2011.pdf
      6. ↑ https://www.unodc.org/pdf/publications/st-nar-36.pdf
      7. ↑ https://antoine.frostburg.edu/chem/senese/101/acidbase/faq/universal-indicator.shtml
      8. ↑ https://www.unodc.org/pdf/publications/st-nar-36.pdf
      9. ↑ Gregory Cade, JD. Environmental & Occupational Law Attorney. Expert Interview. 13 October 2021.
      1. ↑ http://ehs.columbia.edu/hfPolicy.html
      2. ↑ http://cool.conservation-us.org/waac/wn/wn06/wn06-2/wn06-205.html
      3. ↑ Gregory Cade, JD. Environmental & Occupational Law Attorney. Expert Interview. 13 October 2021.

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