Advances in Colloid and Interface Science 99 (2002) 255–264 0001-8686/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII:S0001-8686 Ž 02 . 00080-5 The significance of the difference in the point of zero charge between rutile and anatase Marek Kosmulski Department of Electrochemistry, Technical University of Lublin, Lublin, Poland Abstract The points of zero charge (PZC) of titanium dioxide reported in the literature range from 2 to 8.9. A set of 138 PZC of titanium dioxide was used to explore the effect of the crystalline structure on the PZC. The average and median PZC at pH 5.6 and 5.8, respectively, was found when the entire data set was taken into account. The PZC of anatase (31 entries, average and median 5.9 and 6, respectively) is slightly higher than that of rutile (49 entries, average and median 5.4 and 5.5, respectively), and the difference between the polymorphs corresponds to half of a standard deviation in each set of PZC.  2002 Elsevier Science B.V. All rights reserved. Keywords: Point of zero charge; Adsorption; Isoelectric point; Rutile; Anatase Contents 1. Introduction .......................................................................................... 255 2. Literature survey ................................................................................... 257 3. Materials .............................................................................................. 257 4. Experimental methods ............................................................................ 257 5. Results and discussion ........................................................................... 258 5.1. Anatase vs. rutile ............................................................................. 259 5.2. Titration versus electrokinetics .......................................................... 260 6. Conclusion............................................................................................ 260 References ................................................................................................ 260 1. Introduction Titanium dioxide is an ideal model adsorbent for studies of the relationship E-mail address: kosmulsk@hermes.umcs.lublin.pl (M. Kosmulski).