pH effect on phosphate sorption by crystalline MnO2

The phosphate anions sorption on manganese dioxide was studied as a function of pH in the range 3–9 and at 293 K. The sorption was observed to increase with the increase in concentration of phosphate and decrease with the increase in pH. No effect of the phosphate adsorption upon the PZC of the solid suggested that the only outer sphere complexes were formed on the surface of the solid. The potentiometric titrations studies of the solid were also performed in the presence of different phosphate concentrations (0.53, 1.053, and 2.11 mmol L−1). The calculated pKa values showed that the solid protonation played a dominant role in the uptake of phosphate anions by the solid.

Graphical abstractThe pH changes accompanying the phosphate sorption show that it has very little effect upon the charging mechanism of the MnO2 due to the formation of outer sphere complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide