A single solute, , is being transferred from a feed into an immiscible fresh solvent, , in a batch two-phase extraction system. This Demonstration displays the dynamic approach to equilibrium for values of the linear equilibrium distribution constant, the solvent to feed-charge ratio, and the mass-transfer capacity coefficient, all to be set by the user.

The solute balances in the feed and solvent are given by

and

,

where is the mass transfer capacity coefficient expressed in , and are the concentrations of solute in the feed and solvent (), respectively, and is the feed to solvent charge ratio. Assuming a linear equilibrium relationship gives , where is the equilibrium distribution constant.

Values of the fractional extraction, defined as , are also determined. The red and blue curves correspond to the solute concentrations in the feed and solvent phases, respectively.

Observe that both and have an effect on the system time constant. Indeed, the steady-state concentration is reached faster when, for instance, you increase

As expected, has no effect on the values of the fractional extraction. On the other hand, the fractional extraction is affected by the choice of and .