Recovery and Reuse of a Surfactant in Ion Flotation

The feasibility of virtually any commercial-scale ion flotation (foam separation) process depends on the recovery and reuse of the surfactant used as the flotation agent. For aqueous solutions of acid chromate complexed with a cationic quaternary ammonium salt, ethylhexadecyl-dimethylammonium bromide, a variety of paths are investigated to split the complex and to separate and recover the surfactant. These include acid chromate reduction with NaHSO₃ or SnCl₂ followed by sorption of the surfactant by and elution from a polymeric resin, Rohm and Haas Amberlite XAD-2. The most promising path is reduction of the acid chromate with NaHSO₃ at pH 2–3, extraction with isopropanol—chloroform in a 1:1 ratio, vacuum distillation of the solvents, and redissolution of the surfactant in aqueous solution. The minimum HSO₃/Cr ratio is established, distribution coefficients for the extraction are determined, and the recovered surfactant is tested in several ion flotation experiments, making a comparison with fresh surfactant.