Ion-pair extraction-reaction of calcium using Y-shaped microfluidic junctions: An optimized separation approach

Abstract

In this research, a continuous microsolvent extraction-reaction was developed for the efficient separation of calcium ion. This study gives a preliminary possible practical application of microfluidic devices in chemical exchange reaction for enrichment of 48Ca stable isotope. For this purpose, in the first stage, the hydrodynamic behavior of two immiscible liquids in a simple Y-shaped microfluidic junction is experimentally investigated, and then ion-pair extraction-reaction of Ca2+ using picric acid as a counter-ion and dicyclohexano-18-crown-6 (DC18C6) as a lipophilic ionophore is studied in this microfluidic and conventional batch method. The impact of main process parameters, including concentration of calcium chloride (0.001–0.1 M), picric acid (0.002–0.2 M), and DC18C6 (0.001–0.1 M) on the extraction-reaction efficiency and apparent overall volumetric mass transfer coefficient was comprehensively examined by utilizing response surface methodology (RSM), leading to an optimized condition for the separation of calcium. In addition, by changing the dimensions of microreactors, the influence of contact time and flow rates of both phases on the extraction-reaction efficiency was investigated. The results show that the efficiency varies significantly with changes in reagent concentration. Since the efficiency decreased with increasing the calcium chloride, the existence of a small amount of picric acid and DC18C6 in the organic phase facilitates the extraction-reaction. Moreover, the extraction-reaction is almost accomplished within ∼ 1.5 s with the efficiency of 98.55% by using the microfluidic device whereas the equilibrium condition is obtained in at least 30 min in a batch method. Furthermore, the higher contact time and flow rates result in the higher separation of the calcium ion.