“…In one-dimensional diffusion, the mass diffusion coefficient could be considered constant because of the relatively small variation of the mass diffusion coefficient in an isothermal free diffusion process. Therefore, applying Fick’s law, the diffusion process can be expressed as (Unatrakarn et al , 2011; Gholami et al , 2015): where c(z, t) is the concentration of the diffusant in liquid, mol · m −3 ; z is the axis of diffusion, m; t is the diffusion time, s; v is the velocity of the liquid, m · s −1 ; D is the mass diffusion coefficient, m 2 · s −1 .…”