Comparison between batch and column experiments to determine the surface charge properties of rutile TiO2 powder

This paper reports a comparative study of three methods for determining the surface charge and acid-base behavior of a TiO(2) rutile material. Electrophoretic mobility measurements were performed using two different batch protocols: (i) a "static" mode that consisted of immersing the rutile powder in aqueous solutions of given pH's and ionic strengths for 10 h, and (ii) a "dynamic" mode that consisted of using an automatic titrator to continuously adjust the solution pH with a contact time of 15 min. The same apparatus (a Nanosizer from Malvern) was used to measure the zeta potential of the particles in both methods. These batch experiments were next compared to the determination of the surface charge of rutile using nonlinear chromatography in column experiments. In that case, the rutile powder was compacted to enable the formation of a proper column bed. Therefore, Raman scattering and X-ray photoelectron spectra were used, as well as other physical information such as specific surface area and morphology of the particles, to verify that the rutile powder and compacted form were identical. The three approaches were then compared and discussed in relation to the acid-base behavior of the rutile material.