Liquid—solid adsorption from binary component mixture

Based on five thermodynamic equilibria among the components I, II, and adsorbent, a stoichiometric displacement model of adsorption (SDM-A) from binary liquid mixture with complete range of concentration in liquid-solid system is proposed and tested by using data published in literatures. The two expressions of this model show the quantitative relationships between the activity of the component I on the surface and that in the bulk solution and between its partition coefficient in two phases and its equilibrium activity in bulk solution, respectively. In some cases, the two expressions may become two linear equations, from which the correspondingly linear slopes (i.e. the adsorption parameters) are obtained with which the stoichiometric displacement relation and relative adsorption ability between components I and II can be elucidated. The effectiveness of these two expressions for different adsorption systems and the similarity and difference between SDM-A and the Freundlich Empirical Equation are also investigated. A rule illustrating a parallel relationship between 2n/Z and the property of bulk solution is also found. And, having studied the quantitative relation of the adsorption from either ideal or non-ideal liquid mixture and compaired their linear adsorption parameters, we find that SDM-A is much better than the Langmuir's.