What Is Solvent Recycling?

Alex Newth

Solvent recycling is the process of taking used, dirty solvents and cleaning them until the solvent is returned to its pure form. Used solvents are placed in a solvent recycler and put through a process that fractionates and distills them from the chemicals that made them dirty — those introduced to create a reaction with the solvent. Aside from environmental reasons for solvent recycling, the main benefit is reduced costs. Laboratories do not need to buy the same amount of solvent, because it can be recycled, and disposal fees are greatly reduced, because less dirty solvent is being thrown out. This can be true for any industry that uses solvents, including laboratories, auto body shops and paint contractors.

Paint thinner, a type of solvent.
Paint thinner, a type of solvent.

Solvents are common in nearly any setting where chemicals are used. A solvent is any liquid, gas or solid chemical that dissolves in another one, forming a compound between the two chemicals. This creates a range of reactions, depending on the chemicals used, but all reactions have one thing in common: The solvent is always dirty after synthesis is complete. Once, the compound would have been thrown out, incurring disposal fees, forcing the purchase of more solvent, and greatly increasing the cost of doing business.

Dirty solvents can be made clean again via a distillation process that removes the problem chemicals.
Dirty solvents can be made clean again via a distillation process that removes the problem chemicals.

With solvent recycling, the dirty solvent compound is placed in a solvent recycler. Using a solvent recycler usually just needs the solvent to be loaded and a button pushed. Depending on how much of the compound was placed in the recycler, this can take several hours or longer to complete. The clean solvent will then be deposited in a collection bag or vat.

Solvent recycling works by fractionation and distillation. With fractionation, the chemical is pushed through small tubes and treated at different temperatures to separate the solvent from the solute. Distillation is similar and works by turning the compound into a vapor before cooling it back into a liquid, which causes the chemicals to separate and allows the solvent to be collected. Operators rarely need to do much work aside from loading the solvent, but some recyclers will require qualified operators to set the machine for certain solvents.

The target market for solvent recycling is largely laboratories, which work with solvents on a near-constant basis. Other businesses that use solvents include paint contractors and auto body shops, which use solvent-based chemicals such as paint thinners. Dry cleaners use solvents for cleaning, and beauty shops use solvents in nail polish removers and perfumes, but these markets are often use too little solvent to bother with solvent recycling.

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