Clean‐up of Oily Wastewater by Froth Flotation: Effect of Microemulsion Formation II: Use of Anionic/Nonionic Surfactant Mixtures

Abstract Froth flotation can be an effective method to remove emulsified oil from wastewater. In this series of studies, the relationship between surfactant phase behavior (the type of microemulsion that is formed between the oil and water) and efficiency of the flotation of ortho‐dichlorobenzene is being investigated. The phase behavior is related to surfactant composition and salinity in this work. Use of anionic/nonionic surfactant mixtures here permit examination of a wide range of conditions compared to the use of only anionic surfactants. Optimum oil flotation corresponds to a Winsor Type III microemulsion, which also corresponds to minimum interfacial tensions between oil and water and to maximum solubilization of water and of oil into a surfactant‐rich microemulsion phase. In this work, high selectivity for oil compared to water in the overhead froth was demonstrated, a necessary criterion for an effective separation.