ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Evaluation of leaching behaviour of Nd from Ca_10-xNd_x(PO₄)F_2, (x = 0–1.2) matrix and its borosilicate glass-bonded analogues by neutron activation and ICP-OES analysis

Shirley Auxilia Lindsay, S. Sriram, Manish Chand, S. Annapoorani, K. Usha Lakshmi, Hrudananda Jena, S. Vijayalakshmi, R. Kumar, and V. Jayaraman

Homi Bhabha National Institute, Training School Complex, Mumbai, India

E-mail: hnje@igcar.gov.in

Received: 23 May 2022  Accepted: 20 July 2022

Abstract:

Ca_10-xNd_x(PO₄)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_xCaFAp) 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 Ca²⁺ 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_xCaFAp samples were irradiated in KAMINI reactor (neutron flux 8.0 × 10¹¹ cm⁻² s⁻¹) to activate Nd to its radioisotopes. The irradiated Nd_0.3CaFAp sample was subjected to dynamic leaching at 90 °C by using soxhlet method for 28 days. ¹⁴⁷Nd content in the leachate solution was determined from the γ-counting using 50% co-axial High Purity Germanium (HPGe) detector (gamma energy of ¹⁴⁷Nd isotope, 531 keV). Interestingly, the Ca_8.8Nd_1.2(PO₄)₆F₂ + 20 wt% BSG composite matrix show very low NLR indicating the higher solubility of Nd in the composite phase compared to the CaFAp.

Keywords: Leaching; Fluoroapatite; Neodymium; Nuclear waste matrices; Borosilicate glass

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02391-x

Chemical Papers 77 (1) 509–516 (2023)