SIMPLIFIED LOCAL-DENSITY MODEL FOR ADSORPTION OVER LARGE PRESSURE RANGES

A mean-field model is developed that superimposes the fluid-solid pote ntial on a fluid equation of state to predict adsorption on a flat wal l from vapor, liquid, and supercritical phases. A van der Waals-type e quation of state is used to represent the fluid phase, and is simplifi ed with a local density approximation for calculating the configuratio nal energy of the inhomogeneous fluid. The simplified local density ap proximation makes the model tractable for routine calculations over wi de pressure ranges. The model is capable of prediction of Type II and III subcritical isotherms for adsorption on a flat wall, and shows the characteristic cusplike behavior and crossovers seen experimentally n ear the fluid critical point.