Effects of pH on the transformation of gypsum to carbonate apatite in the presence of ammonium hydrogen phosphate

Kunio Ishikawa, Yumiko Suzuki, Shigeki Matsuya, Masaharu Nakagawa, Kiyoshi Koyano

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Effects of pH on the transformation of gypsum to apatite in the presence of ammonium hydrogen phosphate was studied using NH4H 2PO4, (NH4)2HPO4 and (NH4)3PO4. When set gypsum was immersed to ammonium hydrogen phosphate, pH of the solution decreased regardless of the solution. Although pH of the solution decreased, no significant compositional change was observed when gypsum was immersed in NH4H 2PO4. On the other hand, apatite and small amount of dicalcium phosphate anhydrous (CaHPO4) was formed when gypsum was immersed in (NH4)2HPO4 solution. Only apatite was formed when gypsum was immersed in (NH4)3PO 4 solution. Although the detailed mechanism for the pH dependent products has not been clarified, one of the causes may be the different thermodynamical difference between gypsum and apatite. We would like to recommend the use of (NH4)3PO4 solution since this provides higher pH and thus larger thermodynamical difference between apatite and gypsum and resulting pure apatite block.

Original languageEnglish
Pages (from-to)199-202
Number of pages4
JournalKey Engineering Materials
Volume309-311 I
DOIs
Publication statusPublished - Jan 1 2006

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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