Adsorption of Tributyl Phosphate on Silica Gel

Abstract

The adsorption behaviour of tributyl phosphate (TBP) on silica gel was studied. It was found that the adsorption isotherm shapes were complicated, being considered as S- and L-type isotherms according to the Giles classification. Adsorption itself was polymolecular and of a physical nature, the first adsorptive layer involving hydrogen bonding between the protons of surface silanol groups and the electron-donating oxygen atom of the adsorbate molecule. Subsequent adsorption layers were formed via van der Waals interaction. The free energy of adsorption of the system lay between −22.1 kJ/mol and −23.8 kJ/mol. The enthalpy change was negative and very small, i.e. −6.3 kJ/mol, while the entropy change was positive and in the range 53.9 J/(mol K) to 55.4 J/(mol K). The increase in entropy was explained in terms of the mobility of the TBP molecules in the adsorptive layer arising from their replacement on the silica gel surface by water molecules derived from the aqueous medium.

Adsorption of Tri‐n‐Butyl Phosphate (TBP) from NaClO4 Aqueous Solution on Hg Electrode

“…The adsorption occurs in the potential range from approximately 0 V up to À 1.3 V vs. SCE. Adsorption of TBP was also reported on silica gel [6], mineral surfaces [7], Amberlite XAD-4 resin [8] and clay [9].…”

Phosphate Coating on the Surface of Carbonyl Iron Powder and Its Effect in Magnetorheological Suspensions

“…They call "no bridging" the absence of hydrophilic silica network: "the solvent attaches itself to the surface silanol group of the fumed silica rendering it inactive for further network formation" [ 1 11. Sazanova et al, studying the adsorption of tributyl-phosphate on silica gel, concluded that the first layer adsorbed on the particle is due to the hydrogen bonding between the protons of silanol groups at surface and the electron-donating oxygen atom of the adsorbate molecule [12]. So, it is reasonable that FeP04 over the surface of HSI will changes the network between hydrophilic silica nanoparticles.…”