Extraction and recovery of racemic amlodipine via hollow fiber supported liquid membrane

Abstract

The extraction and recovery of racemic amlodipine from chemical synthesis-based pharmaceutical wastewater as a feed solution via a hollow fiber supported liquid membrane (HFSLM) was studied. The pH and concentration of racemic amlodipine in the feed solution, types of extractants (chiral (+)-DBTA, achiral extractants D2EHPA and the synergistic extractant of (+)-DBTA and D2EHPA), concentrations of the extractants, types of the organic solvents, types and concentrations of the stripping solutions (benzenesulfonic acid and β-cyclodextrin), and the flow rates of feed and stripping solutions were investigated. The feed and stripping solutions at equal flow rates flowed counter currently in a batch operation. By using the synergistic extraction of chiral-to-achiral mixture (4 mM (+)-DBTA and 4 mM D2EHPA) at equal volumes of 1:1 dissolved in 1-decanol, the feed solution of pH 5.0, β-cyclodextrin as the stripping solution and equal flow rates of feed and stripping solutions of 100 ml/min, it was exhibited that the highest percentages of extraction and stripping were 84 and 80%, respectively, and the enantiomeric excess (% e.e.) of (S)-amlodipine of approximately 70% was observed. The aqueous-phase mass-transfer coefficient (kf) in the feed solution and the organic-phase mass-transfer coefficient (km) in liquid membrane were 4.87×10-2 and 2.89×10-2 cm/s, respectively, indicating that the diffusion of (S)-amlodipine complex through the liquid membrane was the mass-transfer controlling step. According to the investigation of the effect of temperature on the extraction of racemic amlodipine, the activation energy (Ea) of the (S)-amlodipine extraction reaction was found to be 71.10 kJ/mol. In particular, the Ea greater than 40 kJ/mol indicating that the extraction and recovery of (S)-amlodipine through the HFSLM were controlled by the chemical reaction. Furthermore, by using a mathematical model, the concentration of (S)-amlodipine in the feed solution with time can be estimated. The modeled values were found to be in good agreement with the experimental results with the average deviation of approximately 2 %.