Insights of water vapor sorption onto polymer based sorbents

Abstract

Two polymer based sorbents PS-I and PS-II are analyzed for water sorption applications. Adsorption/desorption isotherms of water vapor onto PS-I and PS-II have been experimentally measured using a magnetic suspension adsorption measurement unit for adsorber temperature ranges 20–80 °C and evaporator temperature ranges 2–73 °C. The equilibrium adsorption uptake of water vapors corresponding to saturation condition at 30 °C by PS-I and PS-II was found nearly 2 and 2.5 times higher than the conventional silica-gel, respectively. Adsorption data has been analyzed for various adsorption models which include Brunauer–Emmett–Teller (BET); Freundlich; Dubinin–Astakhov (D–A); Oswin; and Guggenheim–Anderson–de Boer (GAB) model. The GAB and BET model give the good fit for relative pressure range of 0.10–0.90 and 0.05–0.35, respectively. At all adsorption temperatures of both sorbents, the monolayer uptake by the GAB model is found higher than the BET model. Effect of adsorption potential on adsorption uptake is highlighted in relation with water vapor adsorption mechanism. The isosteric heat of water vapor adsorption is determined for both sorbents using Clausius–Clapeyron equation.