Precipitation-stripping of yttrium oxalate powders from yttrium-loaded HDEHP organic solutions using an ultrasonic stirrer

Abstract

In previous papers, a kinetic study on the precipitation-stripping of yttrium oxalate powders from yttrium-loaded HDEHP solution had been conducted using a Lewis-type cell. In the present work, the precipitation-stripping of yttrium oxalate has been investigated in a reactor with an ultrasonic stirrer. This study shows the influence of several parameters on the precipitation yield, the solubility of yttrium in the aqueous phase, the nature, and the size distribution of the precipitated salt. The parameters which could vary were: initial concentrations of nitric (0–5 mol L −1) and oxalic (0.15–0.75 mol L −1) acids in the aqueous phase, initial concentrations of Y(HL 2) 3 (0.075–0.10 mol L −1) and HL (0.8–2.2 mol L −1) in the organic phase, nature of the organophosphorus acid used ((RO) 2PO 2H, R(RO)P0 2H with R = 2-ethylhexyl), temperature (24–60°C), ratio of the volumes of phases ( r = V o V a varying from 0.5 to 4). The nature of the precipitated salt depended on the concentrations of oxalic and nitric acids. At ambient temperature, neutral salt Y 2(C 2O 4) 3 · 10H 2O(s) was precipitated as aggregated platelets, the median diameter of which could vary from I to 4 μm according to the experimental conditions. Acidic salt YH(C 2O 4) 2 · 3H 2O(s) was precipitated in concentrated acidic aqueous media as platelets with a median diameter which could vary from 4 to 7 μm.