Potentiometric titration of hematite and magnetite at elevated temperatures using a ZrO2-based pH probe

Potentiometric titration using a high temperature and high pressure ZrO2 based pH probe connected to an external pressure balanced reference electrode (EPBRE) was employed to measure the surface charge and point of zero charge (PZC) of magnetite and hematite colloids at temperatures up to 200 °C. Background-corrected titration data for magnetite and hematite particles were obtained in NaClO4 solutions at ionic strengths of 0.1 and 0.01 which permitted the approximate estimation of PZC using the inflection point of the titration plots (pHinfl). When temperature increased from 100 °C to 200 °C, the pHinfl for magnetite and hematite decreased from 6.08 ± 0.1 to 4.84 ± 0.1 and 7.17 ± 0.1 to 5.74 ± 0.1, respectively.