Adsorption from binary solutions on activated charcoal at high pressures up to 490 MPa

Effects of pressure on surface excesses for twelve adsorption systems each consisting of a binary solution of components A and B and activated charcoal have been studied at pressures up to 490 MPa and at a temperature of 298.2 K. The following three types of pressure dependence have been observed: ∂ΓA/∂p < 0, ∂ΓA/∂p > 0, ∂ΓA/∂p= 0, where ΓA is the surface excess of component A.A comparison of these results with the difference in the pressure derivatives of pure-component interfacial tensions, (∂σoA/∂p–∂σoB/∂p=ΔAB), has revealed that ∂ΓA/∂p < 0 if ΔAB takes a large positive value, ∂ΓA/∂p > 0 if ΔAB takes a large negative value and ∂ΓA/∂p= 0 if ΔAB is small.General criteria for determining the directions of the pressure dependences of adsorption have been derived theoretically and are utilized to discuss the experimental results.