Diffusion coefficients of paraffins in a graphon membrane: the early time procedure

Abstract

The early time procedure, based upon a solution of the diffusion equation giving the transient state flow at the outgoing surface of a membrane, has been used in two ways to evaluate diffusion, coefficients of n-butane, isobutane and propane in a membrane of Graphon graphitised carbon. Even under conditions where equilibrium sorption does not obey Henry's law and so diffusion coefficients are functions of concentration, plots of log [t^1/2(dp₂/dt)] against t^–1, where t denotes time and P₂ is the outgoing pressure, are still linear for 0 < t⩽L, where L is the time-lag. Under appropriate conditions it has been established that diffusion coefficients derived in two ways from linear plots agree with each other and with values found from steady state and from time-lag measurements.