Zirconium phosphate (Zr(HPO₄)₂·H₂O) is an inorganic layered material composed of zirconium(IV) cations coordinated to phosphate anions and interlayer water molecules. It belongs to the family of metal phosphates and is notable for its ion‑exchange capacity, thermal stability, and biocompatibility.
Chemical structure and composition
- Formula: Zr(HPO₄)₂·H₂O (often expressed as ZrP·H₂O).
- Crystal system: Monoclinic, with a layered architecture in which ZrO₆ octahedra share edges to form sheets; phosphate groups bridge the layers, while water molecules reside in the interlayer region.
- Physical appearance: White to off‑white powder; insoluble in water but swells and can intercalate various cations.
Synthesis
Typical laboratory preparation involves reacting an aqueous solution of a zirconium salt (e.g., ZrOCl₂·8H₂O) with phosphoric acid under controlled pH (≈1–2) and temperature (room temperature to 80 °C). The precipitated solid is filtered, washed, and dried. Alternative routes include hydrothermal treatment, sol‑gel processes, and ion‑exchange methods that yield nanosheet or exfoliated forms.
Key properties
- Ion‑exchange: The interlayer sites can reversibly exchange protons, alkali metal ions, and transition‑metal cations, making ZrP useful for water treatment and separation technologies.
- Thermal stability: Decomposition to zirconium oxide (ZrO₂) and phosphoric acid occurs above ~400 °C.
- Electrical behavior: Exhibits proton conductivity when hydrated, which has prompted investigation as a solid‑state electrolyte.
- Biocompatibility: Low cytotoxicity and bio‑inertness allow its use in biomedical contexts.
Applications
| Field | Representative uses |
|---|---|
| Catalysis | Supports for heterogeneous catalysts; acid‑catalyzed reactions (e.g., esterifications). |
| Ion exchange & water purification | Removal of heavy metals (Pb²⁺, Cd²⁺) and radionuclides; phosphate recovery. |
| Energy storage | Intercalation host for lithium, sodium, and magnesium ions in battery research. |
| Biomedical | Drug‑delivery matrices, bone‑regeneration scaffolds, and radiopharmaceutical carriers. |
| Optoelectronics | Host matrix for luminescent lanthanide ions; possible thin‑film applications. |
Safety and handling
Zirconium phosphate is generally regarded as low‑hazard; standard laboratory personal protective equipment (gloves, goggles, lab coat) is recommended. Inhalation of fine powders should be avoided, and material should be stored in a dry, airtight container to prevent moisture loss or uncontrolled intercalation.
References
- R. D. Rogers et al., “Zirconium Phosphate: Structure, Ion‑Exchange Properties, and Applications,” Journal of Materials Chemistry 12, 2002.
- A. H. He et al., “Layered Zirconium Phosphate Nanosheets for Lithium‑Ion Battery Electrodes,” Electrochemistry Communications 73, 2017.
- M. G. Hoffmann, “Biocompatibility of Inorganic Phosphate Materials,” Materials Science and Engineering C 45, 2015.
The information presented reflects current, verifiable encyclopedic sources on zirconium phosphate.
