Abstract
Samples of perchlorated and persulphated rutile were obtained by soaking the solid in aqueous solutions of HClO4 and (NH4)2S2O8 of 0.05 M, 0.10 M and 0.20 M concentration and characterized by XRD and FT-IR spectroscopic studies and by acidity and textural assessment. The XRD results indicated that the interaction of titania with the loaded anions, i.e. ClO−2 and S2O2-8, resulted in an increase in the volume of the unit cell mainly due to an increase in the c0 value of the tetragonal crystal lattice. The IR spectra showed that both ClO−2 and S2O2-8 anions were linked to the surface via bidentate bridging. Such behaviour created strong acidic sites as probed by pyridine (pKa = 5.3) whose number increased with increasing anion loading. The acidity of the perchlorated samples was higher than that of the persulphated materials. Textural analysis showed that the specific surface areas of both samples responded to the loading process to a lower extent than the total pore volume and correspondingly to the average hydraulic radius, since the latter changed in relation to the total pore volume.