Modeling mass transfer enhancement in pulsed contained liquid membranes

This study theoretically explores the technique of membrane pulsing as a novel method to enhance the performance of contained liquid membranes. To assess the effect of pulsing on the capacity and selectivity of a given contactor, a mathematical model was developed for the competitive permeation of two solutes, copper and nickel ions, across hollow-fiber-contained liquid membranes (HFCLMs) with di(2-ethylhexyl) phosphoric acid as a carrier and kerosene as a diluent. The effect of pulsing is incorporated in the model by using dispersion instead of diffusion coefficients in the membrane diffusion resistance. It is found that membrane pulsing can significantly enhance transport in HFCLMs and can be exploited in a number of ways such as extending the capacity of a contactor or making it more tolerant to feed streams with low pH. In addition, predictions indicate that the capacity is more effectively extended by pulsing than by increasing the carrier concentration as the latter approach causes more deterioration in separation selectivity. The required pulsing conditions are attainable especially if the pore size of the supporting fibers is large.