Point of Zero Charge and Isoelectric Point of Alumina

Abstract

The point of zero charge, pH_pzc, and the isoelectric point, pH_iep, of a commercial alumina sample was investigated in KNO₃ solutions. The influence of the concentration and the initial pH value of KNO₃ solution used for preparation and equilibration of the alumina suspension, as well as of the alumina/solution ratio on pH_pzc and pH_iep were investigated. The obtained results indicate that pH_iep values are dependent on initial pH values of KNO₃ solutions used for equilibration of alumina suspensions. Simultaneously with isoelectric point determination, the particle size of alumina was also measured. It was shown that the particle size of alumina increases with increasing suspension pH due to agglomeration, reaching the maximum value at pH_iep.

Keywords:

• Alumina
• Interface
• Isoelectric point
• Point of zero charge
• Surface properties

ACKNOWLEDGMENT

The authors are grateful to the Ministry of Science of the Republic of Serbia for financial support (Project No. 142004).