Abstract
The surface potential of polycrystalline hematite in aqueous sodium perchlorate environment as a function of pH was examined. Surface potential of hematite was obtained from measured electrode potential of a nonporous polycrystalline hematite electrode. Acidic solution was titrated with base, and the backward titration with acid was performed. Substantial hysteresis was obtained which enabled location of the point of zero potential and equilibrium values of surface potentials. The theoretical interpretation of the equilibrium data was performed by applying the surface complexation model and the thermodynamic equilibrium constants for the first and the second step of surface protonation was obtained aslogK1∘=11.3;logK2∘=2.8.
Highlights
Interfacial layers in heterogeneous systems exhibit special properties
This paper reports results obtained with polycrystalline (PCr) hematite electrode, made from the natural hematite being compact and nonporous agglomerate of small hematite particles
Polycrystalline hematite was connected to the copper wire with conductive glue and all contacts were isolated with plexiglas
Summary
Interfacial layers in heterogeneous systems exhibit special properties. Important systems are minerals in aqueous medium. Ionic species from aqueous solutions interact with surface sites resulting in surface charge. The problem of porosity was solved by construction of the single crystal metal oxide electrodes [5]. This approach enabled measurements of the surface potential of hematite [5, 6, 10,11,12,13], titania [14, 15], pyrite [16], sapphire [17], ice [18, 19], and silver halides [20,21,22,23]. This paper reports results obtained with polycrystalline (PCr) hematite electrode, made from the natural hematite being compact and nonporous agglomerate of small hematite particles
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