Sulfuric acid is one of the most common acidifying reagents and sulfur sources, essential across multiple industries. At the same time, it is also a toxic and highly hazardous chemical reagent, requiring safe handling and disposal by trained personnel. For this reason, it’s important to understand how to safely dispose of sulfuric acid. 

A major use of sulfuric acid in the United States is in phosphate fertilizer production. This is an example of an application where sulfuric acid is “used up.” By contrast, many of the other uses of sulfuric acid employ sulfuric acid as an acid catalyst, meaning that it is not incorporated into the final product. As we’ll see in this article, this has important implications for sulfuric acid recovery and disposal. For example, petroleum refineries use sulfuric acid as a catalyst in the production of alkylates.

Other common uses of sulfuric acid include:

•       Explosives
•       Dyes
•       Chemical manufacture
•       Parchment paper
•       Glue
•       Metal pickling
•       Electroplating
•       Storage batteries
•       Food additive
•       Rubber and plastics

In this article, we’ll discuss how to safely and efficiently dispose of waste sulfuric acid. Additionally, we’ll take a look at the regeneration process for sulfuric acid, and how it helps to cut back on chemical waste.

Neutralizing sulfuric acid for safe disposal

For most labs and businesses, the safest and most economical way to safely dispose of sulfuric acid is to neutralize it with a base. The neutralization reaction removes the hazards associated with the strong, corrosive acid. Additionally, it can save on costs because the neutralized product need not be picked up by your hazardous waste disposal company.

Here is an example of a reaction that would neutralize sulfuric acid. In this case, we have shown the reaction of sulfuric acid with potassium hydroxide, a common base in many laboratories. However, you have many options for basic reagents. All the reactions will follow the same format: the acid and the base react to produce a salt and water.

H2SO4 (aq) + 2KOH (aq) → K2SO4 (aq) + H2O (l)

This neutralized solution can then be safely and legally flushed down the sink in most localities. However, always check with your state and local regulations for proper waste management.

Remember when performing the reaction that acid should always be added to water, not the other way around. Adding water to acid may release heat, causing the water to vaporize and the acid to splatter.

As a highly corrosive material, sulfuric acid has the ability to cause thermal burns, permanent organ damage, and even death. Therefore, only trained personnel should handle it, and personnel protective equipment is a must.

Sulfuric acid should be stored separately from incompatible chemicals, including the following:

•       Bases
•       Sodium hypochlorite
•       Hydrochloric acid
•       Nitric acid
•       Halides
•       Nitrates
•       Cyanides
•       Chlorates
•       Permanganates
•       Azides

Regenerating spent sulfuric acid for reuse

It is also possible to regenerate virgin sulfuric acid from sulfuric acid waste. This technology dates back to World War II, when sulfuric acid was required for the use of ammunition and explosives. During this time, the government put limits on the commercial use of sulfuric acid to help the supply keep up with the demand. Regenerative sulfuric acid became an innovative way to simultaneously satisfy the war effort and the industrial demand.

Sulfuric acid regeneration is mainly employed in the refinery industry. Refineries use sulfuric acid as a catalyst in the production of alkylates. Alkylates are a high-value gasoline blending stock.

Since the sulfuric acid is a catalyst in the production of alkylates, that means that it is necessary to drive or speed up the reaction, but it is not ultimately a part of the final product. However, it may pick up impurities during the reaction, dropping the chemical purity by as much as 10%.

Refineries often employ sulfuric acid regeneration methods, meaning they can continue to reuse sulfuric acid without waste.

Other uses of regenerated sulfuric acid include water treatment and metal extraction. Regenerated sulfuric acid helps save on substantial volumes of chemical waste.

Alternatively, another way to recycle sulfuric acid is to use a sulfate-reducing bacteria to produce hydrogen sulfide, a new chemical product which can be used as a fuel.

Where to buy sulfuric acid

Out of stock? Lab Alley has you covered. As the industry leader in all things chemical supply, Lab Alley keeps sulfuric acid in stock and ready to ship. Shop sulfuric acid today on our easy-to-navigate website, and enjoy transparent pricing, no-hassle ordering, and fast delivery. All of our chemical products are offered in multiple concentrations and sizing options, from small to bulk, to satisfy our diverse clientele.