Modeling of adsorption equilibria in supercritical fluids

The adsorption equilibrium of various solutes on different solid matrices in supercritical carbon dioxide was modeled. The solutes were naphthalene, hexachlorobenzene, pentachlorophenol, salicylic acid, DDT, biphenyl, anthracene and 2,6-dimethyl naphthalene. The solid matrices were soil, activated carbon, ODS, ODS-2 and NaY-Type zeolite. The model is based on numerical integration of the differential equations that express the isothermal and isobaric dependence of the adsorption equilibrium constant. The residual infinite dilution partial molar enthalpy of the solutes in supercritical fluids was determined by the Peng–Robinson equation of state with quadratic mixing rules. Based on the observation that the heat of adsorption was independent of the solute, it was shown that the adsorption equilibrium constant at various temperatures and pressures could be predicted based on a single experimental adsorption isotherm.