Browsing by Author "Thomas Kivevele"

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Selective extraction of uranium from nitric acid leachate of Minjingu rock phosphate
(2025-04) Kariim, Ishaq; Bakari, Ramadhani; Syed, Muhammad; Park, Ji-Yeon; Lee, In-Gu; Thomas Kivevele
A sample of beneficiated rock phosphate from Minjingu Mine and Fertilizer Plant, Tanzania was analysed by energy-dispersive X-ray fluorescence (ED-XRF) spectroscopy and found to contain 15.8 % and 5.30 × 10−2 % w/w P2O5 and U, respectively. The U content of the same sample was estimated to be 3.70 × 10−2 % w/w when the digested mass was analysed by inductively coupled plasma mass spectrometry (ICP-MS). The rock was leached with three different mineral acids at 65–70 °C. The outlet liquid and solid streams were analysed by ICP-MS and ED-XRF, respectively. Maximum leaching of P2O5 and U occurred with 8.9 M HNO3. Their respective concentrations in the leachate were 6.69 % w/w (99.0 g L−1) and 1.80 × 10−2 % w/w (0.27 g L−1). The leachate also contained 1.90 × 10−2 % w/w (0.28 g L−1) rare earth elements (REEs). Selective extraction of U was attempted employing Di-2-ethyl hexyl phosphoric acid (D2EHPA) and Tri-butyl phosphate (TBP) as co-extractants. A 2-stage cross-current solvent extraction (10 g scale; 30 °C) with 1:6 mol ratio of D2EHPA:TBP (0.14 M total extractant concentration; 1:1 w/w organic/aqueous ratio) gave 81–89 % U extraction without co-extraction of REEs. The extraction of U increased to 95.6 % after four stages of solvent extraction but there was a noticeable co-extraction of Y beyond the first two stages. Production of fertilizers from U-free leachate is environmentally safer and the recovered U, in pure form, can be used for fuel production.