How to Clean Chemicals Safely

Whether in the lab or in the community, chemicals are a part of everyday life. Even when used safely, there is always a need to dispose of chemicals once finished with them. If not disposed of properly, they can creep into the water supply or damage public health in other ways. There are several common procedures for neutralizing and disposing of chemicals that, if followed, will make it easy to get rid of excess chemicals without threatening public sanitation.

Difficulty: Moderate

Instructions

Things You'll Need:

• pH paper (litmus paper)
• Sodium bicarbonate (NaHCO3) powder (copious amounts)
• Two 1000mL beakers
• Distilled water
• Hydrochloric acid
• Sodium hydroxide
• Stirring rod
• Waste beaker
• Deionized water
• Vermiculite (or a dry sand)

Neutralizing the Chemicals (Solution Method)

1. Determine what chemical species you need to dispose of. Is the solution acidic, basic or neutral? Try testing it with pH paper to find out.

2. Prepare a slurry of sodium bicarbonate. Do so by putting one half-inch of sodium bicarbonate powder into a 1000-mL beaker, and fill the beaker with distilled water until the powder is barely submerged by water.

3. Consolidate the solutions to be neutralized in a single, large beaker (provided that no reaction will occur by mixing them).

4. Slowly add the solution to the bicarbonate slurry, and stir the powder throughout the solution using a stirring rod. Continuously stop to check the pH of the resultant solution. Also note the pH of the solution after you have added the solution to be disposed of to the neutralizing slurry.

5. Continue to add sodium bicarbonate and stir if the pH paper does not indicate that the solution is about pH 7 (green).

6. Survey the chemical contents of the newly neutralized solution. If the solution does not contain any toxic cations or anions, it may be poured down the sink. If it does contain hazardous ion, pour the neutralized solution into a waste beaker for shipment to a hazardous waste facility.

Disposal of Excess Solution (Solid Method)

7. Consolidate the spilled or excess solution as best you can before attempting to dispose of it.

8. Dilute the solution with distilled, deionized water if the solution to be disposed of is highly concentrated.

9. Obtain a sufficient amount of vermiculite or a dry sand to act as a solid sponge to absorb the chemicals. It should be readily available at a pool store or garden center.

10. Spread the vermiculite or dry sand across the area (or inside the container) where the chemicals are located. It should absorb most of the liquid, leaving a solid residue behind.

11. Isolate the solid left behind, and contain the solid for disposal at a local hazardous waste facility if the waste qualifies as a biohazard.

Tips & Warnings

• Always survey the chemicals that you plan to clean up before you do so. That way, you will be able to evaluate whether neutralization or solid absorption is necessary.
• Always wear proper safety gear and equipment when handling chemicals of any kind. Never pour a chemical down the sink unless you know it is neither acidic nor basic and contains no hazardous ions in solution.

References

• Various Chemical Neutralization Methods
• About Vermiculite

Resources

• More Information on Chemical Neutralization

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