Liquid-Liquid Extraction for Recovery of Chemicals from Dilute Aqueous Streams

Liquid-liquid extraction (LLE) can often be applied to separation problems involving the removal of chemicals from dilute aqueous streams, especially when these chemicals are higher boiling than water.  The cost to boil water can be prohibitive for systems with low concentrations of high boiling components.  However, when the proper solvent and equipment is selected, economical solutions can be developed for extracting and recovering these chemicals.  This presentation will outline where, when and how LLE can be applied to these types of separation problems.  It will look at the basic steps towards implementation of an extraction process.  The first step is solvent selection and generating liquid-liquid equilibrium data.  This data can be used to make a preliminary design for the production equipment and also to determine the economic feasibility of the extraction process.  If it is economically feasible, then pilot plant testing is performed to generate accurate scale-up data.  Finally, the test data is used to design of the production extraction equipment.  Several examples will be presented, including pilot plant data and subsequent scale up to production size equipment.