Enhanced leaching recovery of rare earth elements from a phosphatic waste clay through calcination pretreatment

Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay seams. Part II: Re-investigation on the effect of calcination

“…13 and Fire Clay seams. Apatite can be leached under weakly acidic conditions (e.g., 0.1 M HCl, corresponding final pH of around 1.5-2.0 [33]); however, zircon, crandallite-group minerals, monazite, and xenotime are difficult to leach even under strongly acidic conditions (e.g., 1.2 M HCl in the present study). In addition, a large portion of the REE-bearing minerals in the coal wastes are encapsulated in clay particles and, thereby, have no access to hydrogen ions during the leaching reaction.…”

Una perspectiva global de las tierras raras

“…En la Figura 1 se muestra un diagrama general del proceso de obtención de óxidos de tierras raras (Zaimes, Hubler, Wang & Khanna, 2015). Uno de los principales contaminantes en este proceso es la utilización de ácido sulfúrico (H2SO4) (Mwewa, Tadie, Ndlovu, Simate & Matinde, 2022), empleado para el proceso de digestión del mineral molido (utilizando un molino de bolas) y a temperaturas entre 200 y 220 °C, lo cual genera grandes cantidades de sulfatos ácidos dando como resultado un alto nivel de contaminación tanto del agua como de emisiones a la atmósfera (Pillai, 2007) sin embargo, aunque se han propuesto otros reactivos para la digestión y/o calcinación del mineral molido tales como ácido clorhídrico (HCL), ácido nítrico (HNO3), hidróxido de sodio (NaOH) o aun con ácido sulfúricoco (H2SO4) a bajas molaridades, es necesario aumentar el tiempo del proceso o incluso aumentar por lo menos al doble la temperatura de la digestión o calcinación del mineral (Suwanmanee & Ratthanapra, 2019;Ji, Li , Huang & Zhang, 2021) y esto a su vez genera mayor cantidad de contaminantes al agua, a la tierra y a la atmósfera.…”

Leaching of phosphate ores with lower dissolution of metallic impurities: the dual role of sodium oleate

“…In the production of wet-process phosphoric acid, PO is reacted with sulfuric acid to produce phosphoric acid and phosphogypsum (PG) via the dihydrate process, as described by the reaction below. 8,9 Ca 5 (PO 4 ) 3 F + 5H 2 SO 4 + 10H 2 O / 3H 3 PO 4 + 5CaSO 4 $2H 2 O + HF However, reserves of high grade PO are depleting due to the extensive utilization, compelling the use of medium and low grade PO. 10 There are a number of approaches to improve the quality of medium and low grade PO, including grinding and classifying, 11 gravity concentration, 12 and otation.…”

“…In the production of wet-process phosphoric acid, PO is reacted with sulfuric acid to produce phosphoric acid and phosphogypsum (PG) via the dihydrate process, as described by the reaction below. 8,9 Ca 5 (PO 4 ) 3 F + 5H 2 SO 4 + 10H 2 O → 3H 3 PO 4 + 5CaSO 4 ·2H 2 O + HF…”