A NEW METHOD FOR THE PREDICTION OF ADSORPTION-ISOTHERMS

A universally applicable method of predicting the isotherms of pure gas physical adsorption equilibrium is proposed This makes it possible to predict the equilibrium amount of adsorption using only the thermodynamic parameters of adsorbate gases, i.e. T(c), P(c), T(nbp) and omega. This method is based on four assumptions related to the properties of the adsorption system, namely: (1) The adsorbed phase consists of two phases, i.e. a 'pseudo-liquid' phase and a 'pseudo-vapour' phase. (2) An adsorbent has a maximum available adsorption space, phi(max). (3) The density of the adsorbed at the surface of adsorbent, rho0, can be expressed as: rho0 = C1(T(c)/T)C2(P/P(c))C(3omega)C4 where, C1, C2, C3 and C4 are constants whose values depend on the characteristics of the adsorbent and T(c), P(c), T(nbp) and omega are the critical temperature, critical pressure, normal boiling temperature and Pitzer's acentric factor, respectively. T and P are the temperature and the pressure at adsorption equilibrium, respectively. (4) The volume of the 'pseudo-liquid' phase can be expressed as: phi(s) = d1(T(c)/T)d2(P/P(c))d(3omega)d4 where, d1, d2, d, and d4 are constants whose values are dependent on the characteristics of the adsorbent, while T(c), P(c), T(nbp) and omega have the same meaning as above. The equilibrium amount of adsorption predicted using the proposed method has been compared with experimental values. An average deviation of 9.3% between the two approaches is seen. The correlation equation obtained by analysis of data acquired for an individual adsorption system applies to other systems based on the same adsorbent coupled with a different adsorbate gas. An attractive feature of the proposed method is that prediction of adsorption isotherms using the proposed method only requires information relating to the thermodynamic properties of the adsorbate, i.e. T(c), P(c), T(nbp), and omega.