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

Abstract

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: ∂Γ_A/∂p < 0, ∂Γ_A/∂p > 0, ∂Γ_A/∂p= 0, where Γ_A is the surface excess of component A.

A comparison of these results with the difference in the pressure derivatives of pure-component interfacial tensions, (∂σ^o_A/∂p–∂σ^o_B/∂p=Δ_AB), has revealed that ∂Γ_A/∂p < 0 if Δ_AB takes a large positive value, ∂Γ_A/∂p > 0 if Δ_AB takes a large negative value and ∂Γ_A/∂p= 0 if Δ_AB 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.