Micellar-enhanced ultrafiltration for simultaneous removal of ferricyanide and nitrate

Feasibility of micellar-enhanced ultrafiltration was investigated to study simultaneous removal of ferric cyanide and nitrate with a cationic surfactant, cetylpyridinium chloride (CPC). The removal of ferricyanide and nitrate was studied as a function of surfactant to ferricyanide/nitrate molar ratios. In the ferricyanide/CPC and nitrate/CPC systems, the removal of ferricyanide and nitrate increased gradually as the molar ratio of CPC to ferricyanide or nitrate increased. With a 10 molar ratio of CPC, the removal of ferricyanide and nitrate increased to >99.9% and 93%, respectively. In the ferricyanide/nitrate/CPC system, the removal of ferricyanide increased from 62% to 72% and to 99.9%, while that of nitrate from <2% to <2% and to 27% as the molar ratio of ferricyanide:nitrate:CPC increased from 1:1:1 to 1:1:2 and to 1:1:4, respectively. With the molar ratio of 1:1:10, the removals were >99.9% and 78% for ferricyanide and nitrate, respectively. Ferricyanide ions were more easily bound to CPC micelles because the binding power of ferricyanide was greater than that of nitrate. With the difference of binding power, selective removal of ferricyanide using micellar-enhanced ultrafiltration could be achieved.