HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Salingar, Y. Articles by Kochva, M. Search for Related Content PubMed Articles by Salingar, Y. Articles by Kochva, M. Agricola Articles by Salingar, Y. Articles by Kochva, M.

Solute Partitioning in a Calcium Carbonate-Phosphoric Acid-Water System

Keren Kayemeth LeIsrael (JNF), Land Development Authority, Soil Reclamation Dep., P.O. Box 45, 26103 K. Hayim, Israel

Malik Kochva

Faculty of Agricultural Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel

* Corresponding author.

ABSTRACT

A range of Ca phosphates form in a time-dependent process, when calcite interacts with a dilute orthophosphate solution. This study was conducted to ascertain the possible formation of a stable CaCO₃-PO₄ compound on calcite surfaces and to characterize its precursors. The solution's ionic speciation provided evidence of the formation of a CaHCO₃-PO₄ compound (CBP) with a stoichiometric Ca/P ratio of 3 and a solubility product, K_sp, of (Ca²⁺)³(HCO^–₃)³(PO^3–₄) = 10^–28.36. This hypothesis was also supported by electron spectroscopy analyses of the surface layers of the final solid product and scanning electron microscopy (SEM). Prior to the CBP formation, either a compound with the same Ca/P ratio as dicalcium phosphate (DCP, CaHPO₄) formed, or CBP was in quasi-equilibrium at a Ca/P ratio of 1.5 to 2.3. Another possibility is that a poorly crystalline or amorphous Ca phosphate solid phase was formed. Finally, the newly formed CBP converted to hydroxyapatite (HAP, Ca₅ (PO₄)₃OH).

This study conducted at Technion-Israel Inst. of Technology.

Received for publication January 14, 1992.