Recovery of REEs, Zr(+Hf), Mn and Nb by H2SO4 leaching of eudialyte concentrate

Balinski, Adam; Atanasova, Petya; Wiche, Oliver; Kelly, Norman; Reuter, M.A.; Scharf, Christiane

doi:10.1016/j.hydromet.2019.04.007

Cited by 21 publications

(14 citation statements)

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“…Another approach for the reduction of the acid consumption is the previous separation of nepheline and zeolite from eudialyte which would reduce the required amount of acid and the process has significant costs. As it was shown in the leaching study, over 80% of the acid consumption is attributed to the leaching of these two minerals [9].…”

Section: Effect Of Roasting Time Roasting Temperature and Acid Additionmentioning

confidence: 65%

“…This indicated an insufficient amount of sulfate ions in the system. In the previous leaching study the theoretical acid consumption of 6.2 mmol/g was calculated considering Equations (8)-(10) describing the complete digestion of eudialyte (M = 1425 g/mol), nepheline (M = 584 g/mol) and zeolite (M = 352 g/mol) [9].…”

Section: Effect Of Roasting Time Roasting Temperature and Acid Additionmentioning

confidence: 99%

“…High amounts of released Si 4+ is the main drawback by leaching of eudialyte concentrates [9]. The presence of silica in solution causes problems in subsequent operations such as liquid-liquid extraction, ion exchange processes and electrolysis [23].…”

Section: Stability Of Silicamentioning

confidence: 99%

“…Several approaches have been described dealing with leaching of REEs from EGMs [9][10][11] and with REE separation from the resulting system [12][13][14][15] so far. A silica-free solution can be obtained by the pre-treatment of eudialyte with concentrated acid and subsequent water leaching.…”

Section: Introductionmentioning

confidence: 99%

“…However, during leaching high amounts of silicic acid are released, which tends to gelate. To obtain a silica-free solution more demanding methods are required [9]. Furthermore, efficient and low priced subsequent separation of individual components from resulting multi-element solutions is a big challenge.…”

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confidence: 99%

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Selective Leaching of Rare Earth Elements (REEs) from Eudialyte Concentrate after Sulfation and Thermal Decomposition of Non-REE Sulfates

et al. 2019

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Eudialyte, a sodium rich zirconosilicate, is one of the promising sources for REEs (rare earth elements), particularly for HREEs + Y (heavy rare earth elements and yttrium). The key challenge in hydrometallurgical processing is the prevention of silica gel formation and REE separation from resulting multi-element leach solutions. This study deals with the selective extraction of REE from eudialyte concentrate by selective roasting. In this method, metal ions are converted into sulfates, followed by the decomposition of non-REE sulfates in a roasting step and the water leaching of the calcine. The effect of acid addition, roasting temperature, roasting time, pulp density and leaching time is studied. For sufficient conversion of REEs into sulfates, sulfuric acid is added in excess. At a roasting temperature of ≥750 • C sulfates of zirconium, hafnium, niobium, aluminum and iron decompose into sparingly soluble compounds, while REE and manganese sulfates remain stable up to a roasting time of 120 min. The silica present in the calcine is found to be metastable even after roasting. The amount of leached Si 4+ is dependent predominantly on the pH value of the leaching medium. Applying the method, REEs can be efficiently separated from zirconium, hafnium, niobium, aluminum and iron. However, only diluted solutions can be produced. Water leaching of calcine at high solid/liquid ratios causes REE losses resulting from formation of double sulfates and gypsum. The acid excess removed from the reaction mixture in the roasting stage can be simply recovered by treatment of the gas phase.Minerals 2019, 9, 522 2 of 12 including permanent loss of ecosystem, severe soil erosion, air pollution, biodiversity loss and human health problems [5].Another promising sources for HREEs + Y are some peralkaline and apatite deposits. Generally, they contain higher amounts of REEs in comparison to ion-adsorption type deposits (peralkaline deposits ≤2 wt %; apatite deposits ≤1.5 wt %) [6]. However, due to the complex mining and extraction processes they have not gained industrial significance so far. Eudialyte group minerals (EGMs)-sodium rich silicates occurring in peralkaline deposits-are used sporadically as zirconium ore and are often enriched with REEs. The development of innovative approaches for the extraction of REEs from EGMs or apatite is of great importance for securing strategic raw materials supply and could revolutionize the rare earth market [1].EGMs are characterized by low melting temperature and high solubility in diluted mineral acids [7]. The low resistance to acids makes eudialytes amenable for cheap leaching [8]. However, during leaching high amounts of silicic acid are released, which tends to gelate. To obtain a silica-free solution more demanding methods are required [9]. Furthermore, efficient and low priced subsequent separation of individual components from resulting multi-element solutions is a big challenge. Several approaches have been described dealing with leaching of REEs from EGMs [9-11] and with REE separati...

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Section: Effect Of Roasting Time Roasting Temperature and Acid Additionmentioning

confidence: 65%

Section: Effect Of Roasting Time Roasting Temperature and Acid Additionmentioning

confidence: 99%