Cs absorption capacity and selectivity of crystalline and amorphous Hf and Zr phosphates

Journal Article · Tue Apr 06 00:00:00 EDT 2021 · Polyhedron

DOI:https://doi.org/10.1016/j.poly.2021.115199· OSTI ID:1778895

Nagasaka, Cocoro A. ^[1]; Kozma, Karoly ^[1]; Brunson, Kieran G. ^[1]; Russo, Chris J. ^[1]; Alam, Todd M. ^[2]; Nyman, May ^[1]

---

1. Oregon State Univ., Corvallis, OR (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Removal of radioactive Cs from sodium-rich solutions is a technical challenge that goes back to post World War II nuclear waste storage and treatment; and interest in this topic was reinvigorated by the Fukushima-Daiichi nuclear power plant disaster, 10 years ago. Since the 1960's there has been considerable focus on layered Zr phosphates as robust inorganic sorbents for separation of radionuclides such as Cs. Here we present synthesis and characterization, and direct comparison of Cs sorption capacity and selectivity of four related materials: 1) crystalline α-Zr phosphate and α-Hf phosphate, and 2) amorphous analogues of these. Powder X-ray diffraction, thermogravimetry, solid-state 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and compositional analysis (inductively coupled plasma optical emission spectroscopy and mass spectroscopy, ICP OES and ICP MS) provided formulae; respectively M(HPO4)2∙1H2O and M(HPO4)2∙4H2O (M = Hf, Zr) for crystalline and amorphous analogues. Maximum Cs loading, competitive Cs-Na selectivity and maximum Cs-Na loading followed by the above characterizations plus 133Cs MAS-NMR spectroscopy revealed that amorphous analogues are considerably better Cs-sorbents (based on maximum Cs-loading and selectivity over Na) than the well-studied crystalline Zr-analogue. Additionally, crystalline α-Hf phosphate is better Cs-sorbent than crystalline α-Zr phosphate. All these studies consistently show that Hf phosphate is less crystallize than Zr phosphate, when obtained under similar or identical synthesis conditions. We attribute this to lower solubility of Hf phosphate compared to Zr phosphate, preventing ‘defect healing’ during the synthesis process.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); University of Notre Dame, IN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)
• Grant/Contract Number: AC04-94AL85000; NA0003525; NA0003763
• OSTI ID: 1778895
• Alternate ID(s): OSTI ID: 1778001; OSTI ID: 1815161
• Report Number(s): SAND-2021-4540J; 695552; TRN: US2209585
• Journal Information: Polyhedron, Vol. 202; ISSN 0277-5387
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Ion exchange
Zirconium
Hafnium
Layered materials
Radioactive Cs