Establishing correlation between effective diffusivity coefficient and the mass transfer for Zn2+ column extraction by D2EHPA: An experimental and theoretical investigation

Mass transfer coefficient is an all-important parameter for the design of columns. This paper was aimed at analyzing mass transfer in the columns with counter-current flow. Considering that the available theoretical models have focused on the prediction of a single drop diffusion in nonionic systems and show poor agreement with the experimental data of an ionic or reactive extraction system, it is of interest to develop a new correlation for effective diffusion coefficient. In this regard, ZnSO4/D2EHPA (Zinc sulphate/Di(2-ethylhexyl) phosphoric acid)/Kerosene extraction system, involving chemical reaction, was investigated in spray and packed columns with counter-current flows. This proposed correlation was derived in the form of dimensionless parameters, in which the effects of operational parameters, e.g. dispersed phase flow rate, and packing height (for packed column) or nozzle inner diameter (for spray column), were taken into account. Interestingly, for the first time, the effect of temperature was explored and incorporated into the final correlation. The promising results of our model with R-square of ∼98% and 95% for spray and packed column respectively, suggest its applicability for the prediction of mass transfer coefficient in similar systems and, subsequently, improving the column design.