Purification of Rhodamine B by Alcohol-Modified Air Bubble Flotation

A simple and rapid method for the purification of a basic dye, Rhodamine B (RB) was developed. It was conducted by adding crude RB to an aqueous solution containing 0.2% (v/v) ethanol followed by air bubble flotation in a cylindrical glass vessel having a sintered glass filter at the bottom. By feeding air bubbles, RB was enriched into foam on the water surfaces within 3 min, while source materials (phthalic acid and N,N-diethyl-3-aminophenol), intermediate compound {2-(4-diethylamino-2-hydroxybenzoyl)}, and other organic impurities remained in the bulk aqueous solution. The foam containing enriched RB was taken up with suction and placed into another flotation vessel for repeated separation. An HPLC-grade RB was successfully obtained by 3-fold air bubble flotation.

Automated summary

A simple and rapid method was developed for the purification of the basic dye Rhodamine B using air bubble flotation. By enriching the RB into foam on the water surface within 3 minutes, impurities remained in the bulk aqueous solution. The purified RB was successfully obtained by 3-fold air bubble flotation.