Solid Separation from a Mixed Suspension through Electric-Field-Enhanced Crystallization

When applied to a pure component suspension in an apolar solvent, a strong inhomogeneous electric field induces particle movement, and the particles are collected at the surface of one of the two electrodes. This new phenomenon was used to separately isolate two organic crystalline compounds, phenazine and caffeine, from their suspension in 1,4‐dioxane. First, crystals of both compounds were collected at different electrodes under the influence of an electric field. Subsequent cooling crystallization enabled the immobilization and growth of the particles on the electrodes, which were separately collected after the experiment with purities greater than 91 %. This method can be further developed into a technique for crystal separation and recovery in complex multicomponent suspensions of industrial processes. Crystallization from a multicomponent mixture requires additional steps for product purification. The application of an inhomogeneous electric field on a mixed suspension enables simultaneous particle separation and crystal growth. Crystals of the two solutes (CAF=caffeine, PHE=phenazine) are then separately collected from the two electrodes.