Removal of ferriccyanide using micellar enhanced ultrafiltration (MEUF)

Cyanides are used in a number of chemical synthesis and metallurgical processes (as simple salts or cyanide complexes). As a class, cyanides are highly toxic and must be destroyed or removed from wastewaters prior to being discharged. Micellar-enhanced ultrafiltration (MEUF) involves the addition of a surfactant above the critical micellar concentration in order to entrap small solutes in solution. The increased hydrodynamic size of the solutes enables their rejection by polymeric ultrafiltration membranes. Solute rejection and permeate flux depend on solute and membrane characteristics. MEUF-based separation of Fe(CN)₆^3- using regenerated cellular acetate membranes was studied in order to assess the potential of MEUF for the remediation of wastewater polluted with ferriccyanide. The solute rejection coefficient of ferriccyanide increased from 59% to 81% and to 99.9% as the molar ratio of cetylpyridinium chloride to ferriccyanide increased from 1 to 2, and 2 to 3, respectively, at a ferriccyanide concentration of 1 mM. The rejection coefficient of ferriccyanide increased from 78% to 99.9% as the molar ratio increased from 1 to 3 at a ferriccyanide concentration of 5 mM. The permeation flux and permeation of surfactant molecules across the membrane were evaluated in relation to the experimental conditions.