An integrated separation process for recovery and enantioseparation of amlodipine from wastewater: Supported liquid membrane-aqueous/organic phase crystallization

Abstract

An integrated separation process is proposed for recovery and enantioseparation of a chiral antihypertensive drug amlodipine from wastewater. Utilizing this integrated technology, both high recovery (Y) and high enantiomeric excess (ee) were obtained due to the strong enrichment ability of supported liquid membrane with strip dispersion (SLM-SD) and the good enantioseparation ability of organic phase crystallization. These two steps were coupled by an intermediate step: aqueous phase crystallization. In the SLM-SD, an extractant P204 (bi(2-ethylhexyl)phosphoric acid) was dissolved in n-heptane to form a liquid membrane phase, and hydrochloric acid was used as stripping agent. One-stage SLM-SD recycled the amlodipine from wastewater into a stripping phase with a removal (EAD) of 99.67% and a Y1,AD of 87.91% after optimizing the parameters: pH and the concentrations of P204, hydrochloric acid, and amlodipine. Sodium hydroxide and (L)-tartaric acid were added into the stripping aqueous phase to obtain amlodipine-1/2(L)-tartrate acid crystals, which were directly used in the subsequent organic phase crystallization without tedious additional steps. The Y2, AD of aqueous phase crystal reached 99% at a pH of over 6.68 and a molar ratio of over 0.5 for (L)-tartrate acid to amlodipine. Using (L)-tartaric acid or (D)-tartaric acid as resolving agent and dimethylsulfoxide as solvent, high-value-added products (R)-amlodipine and (S)-amlodipine were obtained by two steps of organic phase crystallization. The ee of products was over 99% after optimizing the dosages of dimethylsulfoxide and resolving agent. To increase the total yield, the generated mother liquors were re-treated by SLM-SD with the recovery of over 99% for residual amlodipine.