Chromatographic characterisation of ordered mesoporous silicas: part I. Surface free energy of adsorption.

The ordered mesoporous siliceous materials: MCM41C16, MCM41C16-SH and MCM41C16-NH(2) (known as MCMs) having different surface functionalities were studied by inverse gas chromatography at infinite dilution of chromatographed substances to elucidate their adsorption and adhesive properties. The free energies of adsorption, DeltaG(ads), were calculated in two ways on the basis of the primary chromatographic data. The van der Waals component of the surface free energy, gamma(S)(vdW), was calculated by employing the Dorris-Gray method and the Schultz method. The van der Waals, gamma(S)(vdW), and specific, I(SP), components of the surface free energy were temperature dependent, and were expressed as the linear dependences. The suggested approach was also employed for non-ordered silica adsorbents on the basis of various literature data.