title: The isoelectric point/point-of zero-charge of interfaces formed by aqueous solutions and nonpolar solids, liquids, and gases.
abstract: From our previous work on the role of the electrostatic field strength in controlling the pH of the iso-electric point (iep)/point-of-zero-charge (pzc) of polar solids we have extended the analysis to predict that the pH of the iep/pzc of a nonpolar solid, liquid or gas-aqueous interface should occur at pH 1.0-3.0, dependent on the value assigned to water molecules or clusters at the interface. Consideration of a wide range of experimental results covering nonpolar solids such as molybdenite, stibnite, paraffin, etc. as well as hydrocarbon liquids such as xylene, decalin, and long chain (>C8) alkane oils, as well as nitrogen and hydrogen gases, all in various simple 1:1 electrolyte solutions confirm the general validity of the result. We further consider various models of the origin of the charge on nonpolar material-water interfaces.
authors.affiliation: Particulate Fluids Processing Centre, Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria 3010, Australia. tomhealy@unimelb.edu.au
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Healy
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Fuerstenau