Leaching of niobium- and REE-bearing iron ores: Significant reduction of H2SO4 consumption using SO2 and activated carbon

Abstract

An innovative process was developed for the leaching of niobium-and rare earth elements-bearing pyrochlores ores and the subsequent separation of Nb from the REE. Compared to the conventional Nb hydrometallurgical methods, the proposed leaching process is based on a triphasic system: H 2 SO 4(aq)-SO 2(g)-activated carbon/ore. The implementation of this leaching step allows the selective dissolution of the non-valuable phases while significantly reducing the H 2 SO 4 consumption. The results obtained in continuous operation, at the pilot scale, show a reduction of the sulfur consumption by 48% when compared to the classical H 2 SO 4 pasting-roasting process. The presence of activated carbon, at concentration as low as 0.4% (w/w), was found to considerably fasten the dissolution reactions and allows optimizing the SO 2 utilization to a nearly quantitative rate. The triphasic leaching also affords concentrating the Nb stream which decreases the energy consumption of the downstream operations and especially for the subsequent Nb-REE-bearing pyrochlores roasting step. The process was optimized at the laboratory scale and then tested in continuous operation for 15 days at a flow of 15 kg h −1 of dry equivalent of non-magnetic Nb-REE pyrochlore ore from the Gabonese Mabounié deposit and the equivalent of 8.25 kg h −1 of H 2 SO 4 and 0.15 kg h −1 of activated carbon.

Facile method for the selective recovery of Gd and Pr from LCD screen wastes using ultrasound-assisted leaching

“…The development of REE recovery strategies has been trending in recent years; most of the proposed processes employ inorganic acids such as HCl, H 2 SO 4 or HNO 3 for leaching [13][14][15], which can damage the environment and human health, if they are not adequately controlled. Additionally, more environmentally friendly reagents, such as sulfate-roasting followed by water leaching [16] and ionic liquids [17] have also been studied, to leach the REE.…”

A fluoride-free liquid-liquid extraction process for the recovery and separation of niobium and tantalum from alkaline leach solutions

“…We previously showed by UV-vis spectrophotometry that the speciation of Nb in industrial solutions mainly consists of hexaniobate ions [45,48] x-8 (1 ≤ y ≤ 5), after a several hours or upon heating [55][56][57]. Taking these observations into account, given the high ratio Nb/Ta in the studied industrial samples, and due to the process by which they have been produced [45,51] Figure 2). This is due to the fact that the extraction of hexaniobates by Aliquat® 336 is mainly an anion exchange mechanism ( Table 2) The stripping solution for the selective back-extraction of niobium was finally optimized by fixing the total concentration of nitrates and using mixtures of H 2 C 2 O 4 , HNO 3 , and NH 4 NO 3 .…”

A Deep Insight into the Selectivity Difference Between Y(III) and La(III) Ions Toward D2EHPA Ligand: Experimental and DFT Study

“…For rare earth elements extraction and separation, diverse extractants, including D2EHPA [7][8][9][10], Cyanex 272 [11][12][13][14], Cyanex 921 [15][16], PC88A [17][18][19][20], TBP [21][22][23][24], EHEHPA [25][26][27][28], and various ionic liquids [29][30][31][32], have been utilized in operational conditions and different aqueous sulfate, chloride, and nitrate mediums. All trivalent lanthanide ions have extremely similar properties owing to the coverage of 4f electrons.…”