Evaluation of leaching behaviour of Nd from Ca10-xNdx(PO4)F2, (x = 0–1.2) matrix and its borosilicate glass-bonded analogues by neutron activation and ICP-OES analysis

• Published in: Chemical papers Vol. 77; no. 1; pp. 509 - 516
• Main Authors: Lindsay, Shirley Auxilia, Sriram, S., Chand, Manish, Annapoorani, S., Lakshmi, K. Usha, Jena, Hrudananda, Vijayalakshmi, S., Kumar, R., Jayaraman, V.
• Format: Journal Article
• Language: English
• Published: Warsaw Versita 2023
• Subjects: Biochemistry; Biotechnology; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Industrial Chemistry/Chemical Engineering; Materials Science; Medicinal Chemistry; Original Paper; Neodymium; Fluoroapatite; Nuclear waste matrices; Leaching; Borosilicate glass
• ISSN: 0366-6352; 1336-9075; 2585-7290
• DOI: 10.1007/s11696-022-02391-x

Ca
10-
x
Nd
x
(PO
4
)F
2,
(
x
 = 0–1.2) and its borosilicate glass (BSG)-bonded compositions were synthesized by solid-state reaction route and characterized by XRD and various other techniques. Leaching behaviour of Nd (simulant for rare earth) from the Nd-substituted Ca-fluoroapatite (Nd
x
CaFAp) matrix was evaluated systematically by using dynamic leaching conditions. The concentration of Nd, Ca and P in the leachate solution was determined by analysing the leachate solution using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and fluoride ions (F
−
) was quantified by ion chromatography (IC). The normalized leach rate (NLR) of each ion was determined from the chemical analysis results. The NLR of Nd was below detection limit (< 1 μg/mL); however, NLR of Ca
2+
and F
−1
ions from the matrix was of the order of 10
–4
 g.cm
−2
.day
−1
and 10
–6
 g.cm
−2
.day
−1
, respectively. Nd
x
CaFAp samples were irradiated in KAMINI reactor (neutron flux 8.0 × 10
11
 cm
−2
 s
−1
) to activate Nd to its radioisotopes. The irradiated Nd
0.3
CaFAp sample was subjected to dynamic leaching at 90 °C by using soxhlet method for 28 days.
147
Nd content in the leachate solution was determined from the γ-counting using 50% co-axial High Purity Germanium (HPGe) detector (gamma energy of
147
Nd isotope, 531 keV). Interestingly, the Ca
8.8
Nd
1.2
(PO
4
)
6
F
2
 + 20 wt% BSG composite matrix show very low NLR indicating the higher solubility of Nd in the composite phase compared to the CaFAp.