Muhammad Burhan

A Universal Isotherm Model to Capture Adsorption Uptake and Energy Distribution of Porous Heterogeneous Surface

The adsorbate-adsorbent thermodynamics are complex as it is influenced by the pore size distributions, surface heterogeneity and site energy distribution, as well as the adsorbate properties. Together, these parameters defined the adsorbate uptake forming the state diagrams, known as the adsorption isotherms, when the sorption site energy on the pore surfaces are favorable. The available adsorption models for describing the vapor uptake or isotherms, hitherto, are individually defined to correlate to a certain type of isotherm patterns. There is yet a universal approach in developing these isotherm models. In this paper, we demonstrate that the characteristics of all sorption isotherm types can be succinctly unified by a revised Langmuir model when merged with the concepts of Homotattic Patch Approximation (HPA) and the availability of multiple sets of site energy accompanied by their respective fractional probability factors. The total uptake (q/q*) at assorted pressure ratios (P/Ps) are inextricably traced to the manner the site energies are spread, either naturally or engineered by scientists, over and across the heterogeneous surfaces. An insight to the porous heterogeneous surface characteristics, in terms of adsorption site availability has been presented, describing the unique behavior of each isotherm type.

Membrane & distillation processes integration to achieve maximum recovery

P is the process that actually in the world industry is applied in majority to dehydration of organic solvents. Most generally, the mass fluxes in the pervaporation process are a function of all mass transport resistances occurring in the mass transport path. The membrane is the heart of pervaporation process and from its permeation properties depends the yield and selectivity of the process. Depending on the construction of pervaporation unit, some other mass transfer resistances can be neglected. The majority of the methods of calculation the mass fluxes in the polymer membranes based on the generalized Ficks equation, while for calculation of mass fluxes in fluid systems the generalized Maxwell-Stefan equations (GMSE) is preferably used. Recently Kubaczka proposed the method that allows prediction Maxwell-Stefan diffusion coefficients (MSD) in the membrane space for multicomponent systems using self-diffusion coefficients and binary diffusion coefficients for infinitely diluted mixtures. The purpose of this study is the test of an accuracy of the prediction of mass fluxes in the pervaporation process based on GMSE where MSD are predicted according to the proposed method. These calculations have been done for the experimental results of pervaporation of the isopropanol-water and ethanol-water mixtures in the poly (vinyl alcohol) membrane. These data were the results of the experiments conducting on the PERVAP 2210 hydrophilic membrane. The self-diffusion coefficients, which are the most important element of analyzed method, were predicted using formulas derived from the free-volume theory by Vrentas and Vrentas . The equilibrium concentrations on both sides of the separating polymer film were computed using UNIFAC-FV method with FV element modified according to the model of Kannan et al. The comparison of calculated and experimental results shows very good agreement between experimental and predicted data. The influences of free volume parameters on the mass fluxes are also analyzed.