The Removal of Indigo Carmine from Water by Solvent Sublation

Abstract

Indigo Carmine (IC, C₁₆H₈N₂Na₂O₈S₂), an anonic dye, was removed from an aqueous solution by solvent sublation of Indigo Carmine—Cetyltrimethyl Ammonium Bromide (CAB) complex (sublate) into 2‐octanol. A stoichiometric amount of surfactant (surfactant: dye=2∶1) was the most effective for the removal, with over 93% IC removed from the aqueous solution in 5 min by solvent sublation. The removal rate was somewhat enhanced by higher air flow rates and almost independent of the volume of the organic solvent floated on the top of the aqueous column. The effects of electrolytes (e.g., NaCl), nonhydrophobic organics (e.g., ethanol), and pH of the solution upon the process were studied. The solvent sublation process followed first‐order kinetics. A characteristic parameter, apparent activation energy of attachment of the sublate to bubbles, was estimated at a value of 1.3 kJ/mol.

This work was supported by the Natural Science Foundation of Guangdong Province (Grant No. 04300883).

Keywords:

• Solvent sublation
• Indigo carmine

Notes

This work was supported by the Natural Science Foundation of Guangdong Province (Grant No. 04300883).