The Influence of Lattice Ions on the Electrokinetic Potential of Primary and Secondary Phosphates

Abstract

Zeta potential measurements of apatite, wavellite, senegalite, and turquoise with inert and non-inert electrolytes were conducted. Sodium nitrate seems not to be an inert electrolyte with respect to fluorapatite because the increase in the nitrate concentration renders the zeta potential more negative, indicating ion-specificity towards apatite. Wavellite’s pH_IEP was achieved at 5.2, while the pH_IEP values for senegalite and turquoise were determined at 6.2 and 7.2, respectively. The preferential hydrolysis of cations and the decrease in the number of water molecules composing the crystal structure are the most probable explanation of the increment in the IEP values (IEPwavellite<IEPsenegalite<IEPturquoise).

Keywords:

• electrokinetic potential
• wavellite
• turquoise
• senegalite
• apatite
• electrolytes

Additional information

Funding

The authors acknowledge the financial support of CNPq, PROEX CAPES, and FAPEMIG.