Reaction of calcium hydroxyapatite with Cd2+ and Pb2+ ions

doi:10.1016/j.colsurfa.2006.11.042

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Volume 299, Issues 1–3, 15 May 2007, Pages 203-208

https://doi.org/10.1016/j.colsurfa.2006.11.042 Get rights and content

Abstract

Calcium hydroxyapatite (CaHap) particles with different atomic Ca/P ratios were immersed into the solutions containing Cd²⁺ or Pb²⁺ ions at 30 °C for different periods. The compositions of the solutions and particles before and after immersing were determined. The sorption of Cd²⁺ reached equilibrium within a short time of ca. 15 min without changing the morphology and crystal structure of CaHap particles. The sorption of Pb²⁺ continued for ca. 180 min, followed by coating of the CaHap particles with PbHap and formation of PbHap particles. The amount of incorporated Cd²⁺ was almost independent of the Ca/P ratio of CaHap while that of incorporated Pb²⁺ was decreased with the increase in Ca/P ratio. The reaction with Cd²⁺ took place through the surface layer dissolution of CaHap particles and recrystallization of a new layer of CdCaHap solid solution onto the particles.

Introduction

Calcium hydroxyapatite (noted as CaHap) with a formula of Ca₁₀(PO₄)₆(OH)₂ is a primary constituent of biological hard tissues in animal organisms. Synthetic CaHap is nowadays widely used as artificial bones and tooth roots, adsorbents for chromatography to separate protein, catalysts for dehydration, dehydrogenation of alcohols, powders for tooth paste and so on [1]. The apatite (Hap) structure is so tolerant to ionic substitutions that Ca²⁺ in the crystals can be replaced by various divalent cations including Mg²⁺, Cd²⁺, Sr²⁺, Pb²⁺ and Ba²⁺ [1], [2], [3], [4]. We have synthesized and characterized CaHap [3] and various Hap solid solutions such as hydroxyapatites of Mg–Ca [4], Cd–Ca [5], Sr–Ca [6], Pb–Ca [7] and Ba–Ca [8] by different wet methods. To clarify the formation mechanism of these solid solutions, the ion-exchange of Mg²⁺ in MgCaHap particles with Ca²⁺ has been investigated and it was revealed that the ion-exchange takes place by surface dissolution of the particles and recrystallization of a new layer on the particles [9]. The prominent ion-exchangeability of Hap is available for removal of noxious metal ions from industrial liquid wastes and concerns to the accumulation of metal ions in hard tissues. Thus, the exchange of Ca²⁺ ions in CaHap crystals with harmful ions such as Cd²⁺and Pb²⁺ is an important subject in medical and environmental sciences. There have been many investigations on the incorporation of Pb²⁺ [10], [11], [12] and Cd²⁺ [13], [14], [15], [16], [17] in CaHap. Several sorption mechanisms were proposed as follows; exchange with Ca²⁺, dissolution and recrystallization, and formation of new phases, that depend on the reaction conditions such as concentration of cations, solution pH, temperature, nonstoichiometry of CaHap, and so on. Unfortunately, in these studies the sorption of Cd²⁺ and Pb²⁺ was examined separately under different conditions. To compare the sorption mechanism of Cd²⁺ and Pb²⁺, the experiments should be done under the same condition. In the present study we investigated the reaction of CaHap particles with Cd²⁺ and Pb²⁺ in the same experimental condition in order to make clear the difference between the sorption mechanism of these harmful metal ions. The influence of nonstoichiometry of CaHap on the ion-exchange was also discussed.

Section snippets

Materials

CaHap particles with different Ca/P atomic ratios were synthesized by the following precipitation method [3]. Twenty cubic decimeters of solution containing 0.4 mol Ca(OH)₂ were prepared using deionized and distilled water free from CO₂ under an N₂ atmosphere and stirred for 1 h. To the Ca(OH)₂ solutions were added the solutions containing 0.240–0.269 mol H₃PO₄. The resulting suspensions were stirred at room temperature for 1 h and then aged in a 20 dm³ screw-capped Teflon vessel at 100 °C for 48 h

Crystal structure

Fig. 1 shows XRD patterns of CaHap particles (D) with Ca/P atomic ratio of 1.64 before and after the reaction with Cd²⁺ or Pb²⁺. The material before the reaction is characteristic to CaHap (JCPDS 9-432) and the crystallinity is not influenced by the reaction with Cd²⁺. The unit cell dimensions a and c obtained from the XRD pattern of the CaHap particles before the reaction were 0.944 and 0.687 nm, respectively. The a and c dimensions after the reaction were 0.945 and 0.686 nm, respectively, and

Conclusions

The reaction of CaHap particles with Cd²⁺ in the solution accompanied no change of crystal structure and particle morphology. The reaction mechanism is dissolution of the CaHap surface and recrystallization of a new CdCaHap layer on the particles. The amount of Cd²⁺ incorporated per unit surface area and the atomic (Ca + Cd)/P ratio of the particles after the reaction were independent of the nonstochiometry of CaHap. The cation/P ratio of the particle surface was lower than that of the whole

Acknowledgements

The authors thank Mr. Masao Fukusumi of Osaka Municipal Technical Research Institute for help with the TEM observation and Dr. Takenori Nakayama of Kobe Steel Ltd. with the XPS measurement. This study was supported in part by the Grant-in-Aid for Science Research Funds (B) and (C) from the Ministry of Education, Science, Sports and Culture, Japanese Government.

References (21)

A. Yasukawa et al.
Coll. Surf. A
(2005)
A. Yasukawa et al.
J. Solid State Chem.
(2002)
A. Yasukawa et al.
J. Colloid Interface Sci.
(2005)
A. Yasukawa et al.
Colloids Surf.
(2004)
J. Jeanjean et al.
J. Solid State Chem.
(1994)
J. Jeanjean et al.
J. Solid State Chem.
(1996)
T. Ishikawa
J.C. Elliott
Structure and Chemistry of the Apatites and Other Calcium Orthophosphates
(1994)
P.W. Brown et al.
Hydroxyapatite and Related Materials
(1994)
Z.H. Cheng et al.
J. Chem. Soc. Faraday Trans.
(1998)

There are more references available in the full text version of this article.

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Reaction of calcium hydroxyapatite with Cd2+ and Pb2+ ions

Abstract

Introduction

Section snippets

Materials

Crystal structure

Conclusions

Acknowledgements

Coll. Surf. A

J. Solid State Chem.

J. Colloid Interface Sci.

Colloids Surf.

J. Solid State Chem.

J. Solid State Chem.

Structure and Chemistry of the Apatites and Other Calcium Orthophosphates

Hydroxyapatite and Related Materials

J. Chem. Soc. Faraday Trans.

Reaction of calcium hydroxyapatite with Cd²⁺ and Pb²⁺ ions