Microchannel Liquid-Liquid Extraction of Crystal Violet (CV)

Abstract

Microchannel extraction technology was used to extract crystal violet (CV) from aqueous solutions with a T-type micromixer employed for phase mixing. The extractant di(2-ethylhexyl) phosphoric acid (D2EHPA) and the diluent (n-octanol) were used as the organic phase to extract CV from the aqueous phase. The experiment was conducted with a flow rate ratio of 1:1 for the aqueous and organic phases and investigated the effects of extractant concentration, initial aqueous phase pH, residence time, and mixing speed on the extraction efficiency of CV. The results showed that the extraction rate of CV can be changed by controlling the residence time and mixing speed. When the residence time was 42.58 s, the extraction rate reached 99.39%. In batch extraction, the extraction rate of CV was 90.4% within 6 min, indicating that microchannel extraction had higher efficiency. As the phase mixing speed increased from 0.2 mL/min to 1.6 mL/min, the extraction efficiency decreased by 3.29%, although the overall volumetric mass transfer coefficient (k_La) slightly increased. In this study, the peak k_La value (0.728 s⁻¹) was 1 to 2 orders of magnitude higher than that of the batch extractor.