(c) The solute is uniformly distributed in the matrix before the extraction process.
(d) The mixture of solvent and solute is homogeneous. The concentration of the solute in the solvent phase is only a time
dependent variable.
(e) The extraction process is a phenomenon of diffusion in which the diffusion coefficient is a constant.
(f) The diffusion of compounds occurs in parallel and do not interact with each other.
(g) External mass transfer resistance is negligible. The concentration of solute in the bulk solvent is the same as the concentration of solute in the solvent at the interior of the solid matrix.
(h) The bulk solvent was considered a liquid of infinite volume. The slab is washed by a liquid constantly kept pure. This assumption resulted in an adjustable parameter model and was considered in this case to simplify the calculations.