Conference Paper

Characterization of physico-chemical changes during the alkali roasting of niobium and tantalum oxides

Conference Proceeding cp
TMS Annual Meeting
  • Volumen: 0
  • Número: CONFCODENUMBER
  • Fecha: 01 January 2015
  • Páginas: 51-58
  • ISBN: 9781119073376
  • Source Type: Conference Proceeding
  • Document Type: Conference Paper
  • Publisher: Minerals, Metals and Materials Society184 Thorn Hill RoadWarrendalePA 15086
Niobium and tantalum are considered critical materials because the increasing demand in the energy sector which is reliant on limited abundance of these two metals in minerals. Traditionally, niobium and tantalum mineralsare digested using hydrofluoric acid at moderate temperatures, producing oxy-fluorides which are separated by solvent extraction, involving the use ofhazardous chemicals. The increasing environmental pressures are forcing the industry to search for alternative low carbon processing methods. In this paper alkali roasting based separation and beneficiation, which is not well understood in the literature, is proposed, for which the kinetics and thermodynamic equilibria for the formation of sodium tantalate and niobate with sodium hydroxide are analyzedat the temperature range of 400°C to 700°C. The apparent activation energy of formation.changes from 31.0±0.8 to 22.3±1.2 kJ mol-1 and from 23.8±1.2 toll0.2±12.8 kJ mol-1, for tantalate and niobate, respectively. The reaction mechanism is examined on the basis of the analysis of reaction products using X-ray powder diffraction (XRPD) and X-ray fluorescence (XRF).

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