Abstract
Adsorption behavior of perfluorooctane sulfonate(PFOS) on anatase TiO2 surfaces was studied with DFT-B3LYP method.Physisorption including hydrogen-bond interaction and chemi-adsorption including bidentate binuclear(BB) and monodentate mononuclear(MM) complexes were investigated in the study.Calculations of adsorption energy(Eads) and Gibbs free energy(ΔGads) showed that physisorption was easier to occur.Chemi-adsorption surface complexes were produced by reaction between PFOS and surface water(H2O) or hydroxyl(—OH),and the reaction to replace H2O was easier than that to replace —OH group.MM1(reacted with one H2O of surface) surface complex was the most thermodynamically favorable chemi-adsorption mode.The thermodynamically favorable and stability order of PFOS adsorbed on anatase TiO2 surfaces was H-bonded(hydrogen bonded adsorption)MM1(reacted with one H2O of surface)BB1(reacted with two H2O of surface)MM2(reacted with one —OH of surface)BB2(reacted with one H2O and one —OH of surface).Results of bond length analysis indicated that the interaction between H2O/—OH function group on TiO2 surface and sulfonate group in PFOS resulted in the formation of moderate intensity hydrogen bond.Charges transferred from PFOS molecule to TiO2 surface during chemi-adsorption process,leading to the formation of Ti—O—S bond,and transfered electrons in the process were mainly from strong electronegative atoms O and F.
Published Version
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