Enhanced extraction of Mn (II) and mass transfer characteristics in reciprocating cavity squeezing microchannel

Inspired by the mechanical reciprocating movement, a novel active microchannel device (RCSM) utilizing segmented flow and cavity squeezing technique was designed for the enhanced extraction and separation of Mn (II). The experiment evaluated the separation efficiency of Mn (II) under different conditions from two aspects: static and movement states of the reciprocating plate, and the results showed that residence time was the main factor effecting the extraction efficiency. At the same time, the movement of reciprocating plate produced a cyclic flow between oil and aqueous phases, which effectively enhanced the mixing and internal mixing of the two phases, reduced the effective mass transfer distance, and increased the effective contact area. The thermodynamics calculations indicated that the additional enthalpy was generated by the movement of reciprocating plate. And the kinetics calculations indicated that inertial forces and interfacial tensions significantly acted in the formation, fragmentation, agglomeration, and mixing of oil ∼ aqueous phases droplets in the microchannel, ultimately leading to different results in the interface and fluid flow form of the oil ∼ aqueous phases. At both high and low flow rates, regular slug flows were observed at the outlet of the RCSM, and the fusion between adjacent slugs played a positive role in improving the efficiency of extraction. In addition, the total volume mass transfer coefficient (K L a) was calculated in this experiment to further reveal the mass transfer enhancement mechanism of RCSM. Compared with static experiments, dynamic experiments demonstrated stronger mass and heat transfer performance.