Investigation of the phosphate removal using octacalcium phosphate precipitation characteristics on diopside

Abstract

Octacalcium phosphate (OCP) precipitates on diopside in simulated body fluid. We investigated to remove the phosphate in solution containing phosphate by using this precipitation reaction. By immersing diopside sintered at different temperatures in a 100 μmol/L phosphate solution, it was found that the diopside sintered at 650ºC yielded a removal rate of 91.1% and removed a large amount of phosphate. Surface observation of diopside after the removal of phosphate confirmed the presence of precipitates on the surface. Further, X-ray diffraction analysis of diopside immersed in a 10 mmol/L phosphate solution showed a peak near 32°, which was considered to originate from OCP. This is presumed to be due to the superior OCP precipitation ability by adsorption by surface hydroxyl groups and consumption of phosphate. From the results of this study, it is expected that the synthesized diopside is excellent for phosphate removal and is thus useful as a phosphate-removing material.