Abstract

The particularities of cesium incorporation into synthetic calcium phosphates with either apatite or whitlockite-type structures were investigated using the sorption process from aqueous solution and further heating to 700 °C. The nanoparticles for sorption were prepared by wet precipitation from aqueous solutions at a fixed molar ratio of Ca/P = 1.67 and two different ratios of CO32−/PO43− (0 or 1). The obtained substituted calcium phosphates and corresponding samples after the sorption of cesium from solutions with different molar concentrations (c(Cs+) = 0.05, 0.1 and 0.25 mol L−1) were characterized by powder X-ray diffraction, FTIR spectroscopy, scanning electron microscopy and elemental analysis. Based on the combination of X-ray diffraction and elemental analyses data for the powders after sorption, the cesium incorporated in the apatite- or whitlockite-type structures and its amount increased with its concentration in the initial solution. For sodium-containing calcium phosphate even minor content of Cs+ in its composition significantly changed the general principle of its transformation under annealing at 700 °C with the formation of a mixture of α-Ca3(PO4)2 and cesium-containing apatite-related phase. The obtained results indicate the perspective of using of complex substituted calcium phosphates nanoparticles for immobilization of cesium in the stable whitlockite- or apatite-type crystal materials.

Highlights

  • Calcium phosphates with apatite ­(Ca10(PO4)6(OH)2) and whitlockite (β-Ca3(PO4)2) type of structure have been extensively studied in recent years for potential applications as biomaterials [1,2,3,4,5], fluorescing probes [6,7,8], drug-carriers [9, 10], catalysts [11,12,13] and hosts for luminescent materials [14, 15]

  • The nanoparticles of calcium phosphates as initial material for sorption were obtained by wet precipitation from aqueous solutions and characterized

  • Obtained results showed the influence of molar ratio of C­ O32−/PO43− in initial solution on composition and structure-type of prepared calcium phosphate

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Summary

Introduction

Calcium phosphates with apatite ­(Ca10(PO4)6(OH)2) and whitlockite (β-Ca3(PO4)2) type of structure have been extensively studied in recent years for potential applications as biomaterials [1,2,3,4,5], fluorescing probes [6,7,8], drug-carriers [9, 10], catalysts [11,12,13] and hosts for luminescent materials [14, 15] Such compounds and their complex substituted analogues possess a variety of useful properties such as a high biocompatibility and bioactivity, osteoconductivity, antimicrobial effect, thermal and chemical stability [16, 17]. Most studies of cesium adsorption have been carried out on rocks, soils, sediments and minerals but only a few studies have evaluated the immobilization of cesium on the complex calcium phosphates [31,32,33]

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