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Low-Temperature Synthesis and Characterization of Iron Whitlockite (Ca18Fe2(HPO4)2(PO4)12) †

Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
Rudolfs Cimdins Riga Biomaterials Innovations and Development Centre of RTU, Faculty of Materials Science and Applied Chemistry, Institute of General Chemical Engineering, Riga Technical University, LV-1007 Riga, Latvia
Baltic Biomaterials Centre of Excellence, Headquarters at Riga Technical University, LV-1658 Riga, Latvia
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030/8, 128 43 Prague, Czech Republic
Author to whom correspondence should be addressed.
Presented at the International Conference EcoBalt 2023 “Chemicals & Environment”, Tallinn, Estonia, 9–11 October 2023.
Proceedings 2023, 92(1), 25;
Published: 21 November 2023
(This article belongs to the Proceedings of International Conference EcoBalt 2023 "Chemicals & Environment")
Calcium phosphates (CPs) represent the most widespread class of bioceramic materials used for bone regeneration purposes due to their excellent biological performance and similarity to the natural bone. Synthetic CPs substituted with other biologically active ions can be considered as a sub-group of the CP family while possessing specific biological or physical properties provided by incorporated foreign ions. Magnesium whitlockite (Mg-WH, Ca18Mg2(HPO4)2(PO4)12) is a Mg-substituted CP, which naturally occurs in humans. This material is assumed to be the second most abundant biomineral in the human body. Although the ionic radius of Mg2+ is very similar to those of the first-row transition-metal ions (Zn2+, Mn2+, Fe2+, Cu2+), reports on the synthesis of such materials are very rare [1,2,3]. At the same time, transition-metal ions can provide some very specific properties (e.g., magnetic properties). To the best of our knowledge, there is only one work describing the synthesis and characterization of iron whitlockite (Fe-WH, Ca18Fe2(HPO4)2(PO4)12) [4]. The authors prepared Fe-WH by treating Ca9Fe(PO4)7 with H2 or D2 at elevated temperatures. In our work, Fe-WH was synthesized at low temperature by the dissolution–precipitation method in aqueous medium under hydrothermal conditions. Phase conversion from brushite to Fe-WH took place in slightly acidic medium in the presence of Fe2+ ions just in 1 h. The crystal structure of synthesized products was confirmed by XRD analysis, FTIR, Raman and Mössbauer spectroscopies. The magnetic ordering and oxidation state information were determined using magnetic susceptibility. Morphological features were studied by means of SEM analysis. Cytotoxicity experiments were performed with MC3T3-E1 cells.

Author Contributions

Conceptualization, A.Z. and D.G.; methodology, A.Z. and D.G.; formal analysis, D.G., A.D., D.Z. and V.T.; investigation, D.G., A.D., D.Z. and V.T.; writing—original draft preparation, A.Z.; writing—review and editing, A.Z.; visualization, D.G.; supervision, A.Z.; funding acquisition, A.Z. All authors have read and agreed to the published version of the manuscript.


This work was funded by the grant WHITCERAM (No. S-LJB-22-1) from the Research Council of Lithuania. A.D. acknowledge the access to the infrastructure and expertise of the BBCE H2020 GA857287.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Kizalaite, A.; Grigoraviciute-Puroniene, I.; Asuigui, D.R.C.; Stoll, S.L.; Cho, S.H.; Sekino, T.; Kareiva, A.; Zarkov, A. Dissolution–Precipitation Synthesis and Characterization of Zinc Whitlockite with Variable Metal Content. ACS Biomater. Sci. Eng. 2021, 7, 3586–3593. [Google Scholar] [CrossRef]
  2. Kizalaite, A.; Klimavicius, V.; Versockiene, J.; Lastauskiene, E.; Murauskas, T.; Skaudzius, R.; Yokoi, T.; Kawashita, M.; Goto, T.; Sekino, T.; et al. Peculiarities of the formation, structural and morphological properties of zinc whitlockite (Ca18Zn2(HPO4)2(PO4)12) synthesized via a phase transformation process under hydrothermal conditions. Crystengcomm 2022, 24, 5068–5079. [Google Scholar] [CrossRef]
  3. Heng, C.; Liu, W.; Zheng, X.; Ma, X.; Hui, J.; Fan, D. Dopamine and DNA functionalized manganese whitlockite nanocrystals for magnetic resonance imaging and chemo-photothermal therapy of tumors. Colloids Surf. B Biointerfaces 2023, 222, 113120. [Google Scholar] [CrossRef]
  4. Belik, A.A.; Izumi, F.; Stefanovich, S.Y.; Lazoryak, B.I.; Oikawa, K. Chemical and Structural Properties of a Whitlockite-like Phosphate, Ca9FeD(PO4)7. Chem. Mater. 2002, 14, 3937–3945. [Google Scholar] [CrossRef]
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MDPI and ACS Style

Zarkov, A.; Griesiute, D.; Dubnika, A.; Zakutna, D.; Tyrpekl, V. Low-Temperature Synthesis and Characterization of Iron Whitlockite (Ca18Fe2(HPO4)2(PO4)12). Proceedings 2023, 92, 25.

AMA Style

Zarkov A, Griesiute D, Dubnika A, Zakutna D, Tyrpekl V. Low-Temperature Synthesis and Characterization of Iron Whitlockite (Ca18Fe2(HPO4)2(PO4)12). Proceedings. 2023; 92(1):25.

Chicago/Turabian Style

Zarkov, Aleksej, Diana Griesiute, Arita Dubnika, Dominika Zakutna, and Vaclav Tyrpekl. 2023. "Low-Temperature Synthesis and Characterization of Iron Whitlockite (Ca18Fe2(HPO4)2(PO4)12)" Proceedings 92, no. 1: 25.

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