Quaternary Phosphinates with Co-Solvents for Extracting C1 to C4 Carboxylic Acids from Aqueous Streams

This invention relates to solvents for extracting C1 to C4 carboxylic acids from aqueous streams. More specifically, the extraction solvents include one or more salts composed of a tetraalkylphosphonium cation and a phosphinate anion. The extraction solvents may further include one or more co-solvents as an enhancer. The co-solvents may be selected from higher carboxylic acids, ethers, esters, ketones, aromatic hydrocarbons, chlorinated hydrocarbons, and nitriles. The extraction solvents are useful for extracting aqueous mixtures containing one or more lower carboxylic acids, such as monocarboxylic acids and organofluorine carboxylic acids.