Measurements of adsorption for membranes <i>in situ</i> with the use of time-lags and steady state flows

Abstract

Abstract Isotherms, steady state flows, the four time-lags, the kinetics of sorption and of the approach to the steady state of flow have been measured and analysed to investigate the properties of a graphitized carbon membrane. Sorption isotherms determined on the membrane in situ by a kinetic pro­cedure involving the time-lags and steady state flows were in agreement with isotherms determined by a standard procedure. Analysis of the time-lag and other results left the possibility of a small dependence of the diffusion coefficient, D, upon positional coordinate or upon time, but the dominant influence upon D was its dependence upon concentration, C. Differential diffusion coefficients increased very rapidly with C outside the range of the Henry law. Uptakes of diffusant in the steady state of flow, measured directly, through time-lag measurements and from steady state concentration contours across the membrane were in good agreement.