Competitive bind of anionic metals with cetylpyridinium chloride micelle in micellar-enhanced ultrafiltration

Competitive binding characteristics of anionic metals, chromate and ferriccyanide, with cetylpyridinium chloride micelles were investigated in micellar-enhanced ultrafiltration (MEUF). In MEUF process, removal of pollutants depends on the bind of pollutants to surfactant micelles which increases with the valence of anions. The valence for chromate is −2, while that for ferriccyanide is −3. In chromate/CPC and ferriccyanide/CPC system, the removal of ferriccyanide was higher than that of chromate at the same molar ratio of surfactant due to the difference of valence. In the chromate/ferriccyanide/CPC system, the removal of chromate was inhibited by the ferriccyanide at the low molar ratio of CPC (<chromate: ferriccyanide: CPC = 1:1:4) because of preferential bind of ferriccyanide to chromate.

Fig. 7A. Effect of MWCO and surfactant concentration on relative flux in chromate/ferriccyanide/CPC system. Initial concentration of both chromate and ferriccyanide: 1 mM. MWCO of 3,000. Binding characteristics of chromate and ferriccyanide with cetylpyridinium chloride micelles were investigated during micellar-enhanced ultrafiltration. The removal of chromate and ferriccyanide in the chromate/CPC and ferriccyanide/CPC systems were all >99% with the 5 molar ratio of CPC. In the co-existence of chromate and ferriccyanide, the removal of ferriccyanide was similar to that in the ferriccyanide/CPC system, while chromate removal was significantly inhibited by ferriccyanide. Ferriccyanide with greater valence bound to CPC micelles preferentially because of higher chelating ability to CPC micelles compared to chromate. Even though the bind of chromate to CPC micelles was significantly inhibited by the existence of ferriccyanide, MEUF could be a promising technology to remove or separate chromate and ferriccyanide simultaneously.