Oil Removal from Produced Water during Laboratory- and Pilot-Scale Gas Flotation: The Influence of Interfacial Adsorption and Induction Times

The significance of interfacial chemistry for the oil removal efficiency during flotation was demonstrated in a series of laboratory flotation and pilot-scale compact flotation unit (CFU) tests. Three crude oils with different physicochemical properties were used in the investigations. The differences in drop size distributions and densities of the oils could not fully account for the observed oil removal. However, taking the time for drainage and rupture (i.e., induction time) of the thin aqueous film separating the drops and bubbles into consideration resulted in good agreement with the oil removal. Moreover, it was demonstrated in a modified CFU setup that water-soluble hydrocarbons adsorbed onto the bubbles and reduced the oil removal. This was most likely as a result of increased induction times caused by the adsorbed components.