Leakage and swell in emulsion liquid membrane systems: Comparing continuous stirred-tank reactor and batch experiments

Abstract

Emulsion liquid membrane (ELM) systems can efficiently extract and concentrate dilute solutes in a variety of applications and chemistries. Internal phase leakage and swell reduce extraction efficiency and concentration, which limits their use. Nearly all studies of ELM leakage and swell have been conducted in batch systems, although continuous flow systems are preferred for industrial applications. The objective of this investigation was to assess the ability of batch experiments to predict continuous system performance with respect to internal phase leakage and swell. The effects of five factors (surfactant concentration, osmotic pressure, membrane viscosity, internal phase volume fraction, and extraction vessel stir rate) on leakage and swell were measured in a continuous stirred-tank reactor (CSTR) system without solute extraction. The results were compared with those reported previously for a batch system with the same experimental conditions and vessel geometry. Overall, the effects of the five factors in the CSTR system are qualitatively consistent with the batch system observations, suggesting that the influential variables in the batch system are similarly influential in the CSTR system. Leakage and swell in the CSTR and batch systems are correlated with similar amounts of swell in both systems but consistently smaller leakage in the CSTR configuration.