Pi	Permeability
Di	Fick’s law diffusivity
Ki	Solubility
n	Number of components
ns	Number of solutes
ci	Concentration of component i inside the membrane
ci,f	Concentration of component i in feed solution
ci,p	Concentration of component i in permeate solution
vi	Average velocity of component i
v	Reference velocity
ji	Diffusive flux relative to reference velocity
$\omega$ i	Mass fraction of component i
Mi	Molecular weight of component i
$\rho$	Total mass density
${\mu }_i$	Chemical gradient of component i
Lij	Onsager coefficient
${\Lambda }_{ij}$	Onsager diffusion coefficient
Đik	Maxwell Stefan diffusion coefficient
Dij	Multicomponent Fick diffusion coefficient
$A_{\lambda }$	Absorbance at wavenumber λ
$E_{\lambda }$	Molar absorptivity of the solute at wavenumber λ
I	Transmitted light intensity
Io	Incident light intensity
${ϵ}_{\lambda }$	Effective molar absorptivity
l	Light’s path length