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

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 ( E AD ) of 99.67% and a Y 1,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 Y 2, 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.