Drop mass transfer in a microfluidic chip compared to a centrifugal contactor

A model system was developed for enabling a multiscale understanding of centrifugal‐contactor liquid–liquid extraction. The system consisted of Nd(III) + xylenol orange in the aqueous phase buffered to pH = 5.5 by KHP, and dodecane + thenoyltrifluroroacetone (HTTA) + tributyphosphate (TBP) in the organic phase. Diffusion constants were measured for neodymium in both the organic and aqueous phases, and the Nd(III) partition coefficients were measured at various HTTA and TBP concentrations. A microfluidic channel was used as a high‐shear model environment to observe mass transfer on a droplet scale with xylenol orange as the aqueous‐phase metal indicator; mass‐transfer rates were measured quantitatively in both diffusion and reaction limited regimes on the droplet scale. The microfluidic results were comparable to observations made for the same system in a laboratory scale liquid–liquid centrifugal contactor, indicating that single drop microfluidic experiments can provide information on mass transfer in complicated flows and geometries. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3071–3078, 2014