Carbon Utilization Infrastructure, Markets, and Research and Development: A Final Report (2024)
Chapter: Appendix L: Extraction of Select Critical Minerals from Coal Wastes: Literature Review
L
Extraction of Select Critical Minerals from Coal Wastes: Literature Review
SUMMARY OF EXTRACTION METHODS, LEACHING AGENTS, AND LEACHING EFFICIENCY
As described in Chapter 9, the committee reviewed publications on the extraction of rare earth elements (REEs), lithium, and nickel from coal wastes since 2015. This review analyzed the extraction method and leaching agent employed in each publication, as well as the resultant leaching efficiencies of REEs, lithium, and nickel, as summarized in Table L-1.
TABLE L-1 Summary of Literature on Extraction of Rare Earth Elements (REEs), Lithium, and Nickel from Coal Wastes
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Journal Articles | ||||
| REEs | Acid leaching | H2SO4 or HCl or HNO3 | 84.3% (maximum achieved) | Yang and Honaker (2020) |
| Acid leaching | Citric acid | Y: 50% La and Ce: 40% |
Prihutami et al. (2021) | |
| Acid leaching | HCl | La: 71.9% Ce: 66% Nd: 61.9% |
Cao et al. (2018) | |
| Acid leaching | HCl | Y: 62.1% Nd: 55.5% Dy: 65.2 |
Tuan et al. (2019) | |
| Acid leaching | HNO3 + H2SO4 | No significant leachability | Lange et al. (2017) | |
| Acid leaching | HCl or HNO3 or H2SO4 or H3PO4 | La: 65.5% Ce: 64.4% Nd: 64.3% |
Znamenáčková et al. (2021) | |
| Acid leaching | Methanesulphonic acid or p-toluenesulphonic acid | 60–70% | Banerjee et al. (2022a) | |
| Acid leaching | HCl or HNO3 or H2SO4 or acetic acid or formic acid | As high as 73% | Burgess et al. (2024) | |
| Acid leaching | HCl | Dy: 73.38% Er: 76.34% Eu: 88.02% Nd: 70.08% Tb: 90.01% |
Dahan et al. (2022) | |
| Acid leaching | HF + HNO3 | Insufficient information | Hood et al. (2017) | |
| Acid leaching | HCl or HNO3 | 59% (with HNO3) 51% (with HCl) |
Deng et al. (2022) | |
| Calcination → Acid leaching | HCl | TREEs: 72% (Western Kentucky No. 13 sample); 57% (Fire Clay sample) | Ji et al. (2022a) | |
| Roasting → acid leaching | NaOH, Na2O2, CaO, Na2CO3, CaSO4, or (NH4)2SO4 → HNO3 | >90% of total REE content (with NaOH or Na2O2) <50% of total REE content (with CaO, Na2CO3, CaSO4, or (NH4)2SO4) |
Taggart et al. (2018) | |
| Roasting → acid leaching | NaOH, Na2CO3, Ca(OH)2, CaCl2, or (NH4)2SO4 → HCl, H2SO4, or HNO3 | 90% (maximum achieved) | Pan et al. (2021) | |
| Roasting → acid leaching | NaOH → HNO3 | Fe, Al, and REEs (except Ce): >90% | Wu et al. (2022) | |
| Alkali leaching | NaOH | REY: 30% (West Java coal sample); 24% (East Java coal sample) | Rosita et al. (2020c) | |
| Alkali-acid leaching | NaOH → HCl | Highest REE recovery: 95.5% | Wen et al. (2022b) | |
| Alkali-acid leaching | NaOH or (NH4)2SO4 and H2SO4 | REEs and Sc: 70–80% (after 5 h at 110°C and 5 M acid) | Shoppert et al. (2022) | |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Alkali-acid leaching | NaOH → acetic acid |
Maximum recovery of leaching:
|
Manurung et al. (2020) | |
| Alkali-acid leaching | NaOH → HCl or HNO3 or H2SO4 | >90% | Trinh et al. (2022) | |
| Alkali-acid leaching | NaOH → HCl | >85% | Kuppusamy et al. (2019) | |
| Alkali-acid leaching | NaOH → HCl | LREEs: 71% (with 5 M NaOH at 90°C) HREEs: 41% (with 5 M NaOH at 90°C) |
Li et al. (2022) | |
| Alkali fusion → acid leaching | Na2CO3 or NaCl or Na2O2 or NaOH or KOH or Ca(OH)2 → HCl | 49.25% (with Na2O2) 57.45% (with Na2CO3) 64.93% (with KOH) 74.23% (with NaOH) | Tang et al. (2022) | |
| Alkali-acid leaching | NaOH → HCl | 64.9% (at 433K with 30 wt.-% NaOH) | Żelazny et al. (2023) | |
| Alkaline-acid leaching | NaOH + citric acid | 77.6% | Rosita et al. (2023) | |
| Alkali treatment → acid leaching | NaOH → citric acid | REY recovery is 55% | Pan et al. (2023) | |
| Acid leaching | HNO3 | 1.6–93.2% (via heated HNO3 extraction) | Taggart et al. (2016) | |
| Na2O2 alkaline sintering → acid leaching | Na2O2 → HCl | The percentage recovery for total REEs for ashes was 80–90% | Middleton et al. (2020) | |
| Roasting → alkali-acid leaching | ZnO → NaOH → H2SO4 |
REEs: 87.1%
|
Fan et al. (2022) | |
| Alkaline sintering-water immersion-acid leaching method | Na2CO3 à water à HCl | up to 85.81% | Zou et al. (2017) | |
| Acid leaching or alkali leaching | HNO3 or HCl or H2SO4 or NaOH | 98% (with HNO3) | Penney and Alam (2023) | |
| Alkali fusion → acid leaching | Na2CO3 → HCl | ~72.78% | Tang et al. (2019) | |
| Water leaching → acid leaching | Deionized water → HNO3 | >50% | Modi et al. (2023a) | |
| Calcination → water leaching → acidic/basic leaching | Deionized water → H2SO4 or NaOH | Insufficient information | Modi et al. (2023b) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Subcritical water + acid leaching | Subcritical water + HCl or HNO3 or H2SO4 |
Maximum efficiencies achieved:
|
Liu and Lomanjaya (2022) | |
| Acid baking → water leaching | Sulfuric acid → water | 80% | Kuppusamy and Holuszko (2022) | |
| Acid leaching or alkali leaching or water (Millipore Milli-Q) leaching | HCl or, NaOH, or doubly deionized water | ~100% (for Powder River Basin coal samples) | King et al. (2018) | |
| Ionic liquid (IL) leaching → stripping | ([Hbet][Tf2N]) + NaNO3 → HCl | >90% (with 1, 5, or 10 mg/g betaine) | Stoy et al. (2021) | |
| Microwave pretreatment → acid leaching | HNO3 + HF + HClO4 → H3BO3 → HNO3 | Insufficient information | Liu et al. (2021) | |
| Note: This study focused on using electron paramagnetic resonance to identify rare earth elements plus yttrium (REYs) in coal fly ash. | ||||
| Microwave-assisted pretreatment → acid leaching | Carbon lampblack powder → HNO3 | 83.4% | Yakaboylu et al. (2019) | |
| Acid leaching → solvent extraction | HNO3 → DEHPA | >80% | Honaker et al. (2017) | |
| Solvent extraction | (NH4)2SO4, ionic liquid (1-butyl-3-methylimidazolium chloride) or deep eutectic solvent (2:1 molar ratio mixture of urea and choline chloride) | 89% (with (NH4)2SO4) 80% (with ionic liquid) 71% (with deep eutectic solvent) | Rozelle et al. (2016) | |
| Solvent extraction → stripping | [Hbet][Tf2N] + NaNO3/NaCl/Ca(NO3)2/CaCl2 → [Hbet] [Tf2N] + HCl | >68.6% | Stoy et al. (2022a) | |
| Citrate and EDTA leaching | Citric acid + trisodium citrate or EDTA | 11% (with citrate buffer) 33% (with EDTA) | Yang et al. (2021) | |
| Alkaline-acid leaching → stripping | NaOH → NaCl + ([Hbet] [Tf2N]) → HCl | 66% | Liu et al. (2023) | |
| Subcritical water acid leaching or microwave assisted acid leaching | Subcritical water → HCl | Y: 80.23% Sm: 68.19% | Lomanjaya and Liu (2023) | |
| Calcination extraction → acid leaching | Na2CO3 → HCl | 95.8% (coal gangue sample) 93.2% (coal ash sample) | Zhang et al. (2022) | |
| Alkali calcination → supercritical CO2 treatment → acid leaching | Na2CO3 → supercritical CO2 | >90% | Zhang et al. (2023) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Solvent extraction | Diphosphate (2-ethylhexyl) (trade name: P2O4) + kerosene | La: 89.16% Ce: 94.11% Pr: 95.56% Nd: 96.33% Y: 99.80% |
Pan et al. (2022a) | |
| Ionic liquid extraction | 1-butyl-3-methylimidazolium tetrafluoroborate | 26% | Thakare and Masud (2022) | |
| 7-step sequential extraction | H2O → MgCl2 → NaOAc (pH=5) → NH2OH•HCl (25% CH3COOH) → HNO3+H2O2 → NH4OAc → microwave digestion | Insufficient information | Nie et al. (2022) | |
| 6-step sequential extraction | MilliQ water → NH4Ac or MgCl2 → HCl or NaAc → HNO3 or NH2OH•HCl (25% CH3COOH) → (HF + HCl), (HNO3 + H2O2, H2O2 or NH4OAc in HNO3) | 92.7–113.6% for individual REEs | Wu et al. (2020) | |
| 5-step sequential extraction Or physical separation → acid leaching | MgCl2 → NaOAc/HOAc → NH2OH•HCl (25% CH3COOH) → (HNO3 + H2O2)/(NH4OAc in HNO3) → H2SO4+HF Or sieving and magnetic separation → HCl | 79.85% | Pan et al. (2020) | |
| 7-step sequential extraction Or acid leaching | Water → MgCl2 → NaOAc (pH=5) → CH3COOH + NH2OH•HCl → HNO3 + H2O2 → CH3COONH4 (pH=2) Or HCl | up to 98% | Pan et al. (2022b) | |
| 4-step sequential extraction | NaOAc → NH2OH•HCl in CH3COOH → HNO3+H2O2 → CH3COONH4 in HNO3 | ~100% (Class C fly ash) 30–70% (Class F fly ash) | Liu et al. (2019) | |
| Precipitation → redissolution → complexation | NaAlO2 → HNO3 → tributyl phosphate | Ce: 41.8% La: 40.1% Nd: 58.2% | Song et al. (2021) | |
| Trap-extract-precipitate | Na2S2O4 + Na3C6H5O7 | >98% | Miranda et al. (2022) | |
| Selective precipitation → solvent extraction | NaOH → tributyl phosphate | 97% | Talan and Huang (2020) | |
| Acid leaching → IL extraction → precipitation | HCl+HNO3+HF → [N1888] Cl / [P6,6,6,14]Cl / [P6,6,6,14] [SOPAA] / [N1888][SOPAA] → NH4HCO3/Na2C2O4 solution | 37.4% | Huang et al. (2019) | |
| Staged precipitation | NaOH | >80% Purity: 1.1% | Zhang and Honaker (2018) | |
| Acid leaching → solvent extraction → precipitation | HCl → tris-2-ethylhexyl amine → NH3(aq) | 30–90% for individual REEs | Kumari et al. (2019) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Citrate leaching → oxalate precipitation | Sodium citrate → sodium oxalate | 10% (Class F fly ash sample) 60% (Class C fly ash sample) |
Liu et al. (2023) | |
| Acid leaching → solvent extraction → stripping → precipitation | HNO3 → tributyl phosphate or di-(2-ethylhexyl)phosphoric acid in Elixore 205 → HNO3 → oxalic acid | ~100% | Wang et al. (2022) | |
| Acid leaching → biosorption | HCl → two microbe immobilization systems (polyethylene glycol diacrylate microbe beads and Si sol–gels) in immobilizing Arthrobacter nicotianae | 82–90% | Alipanah et al. (2020) | |
| Bioleaching → precipitation | Acidothiobacillus ferrooxidans → H2O2 → NaOH → HNO3 → oxalic acid | ~40–60% Purity: 36.7% | Zhang et al. (2021) | |
| Bioleaching | Candida bombicola, Phanerochaete chrysosporium, or Cryptococcus curvatus | La, Ce, Pr, and Nd: 28.1–30.7% Yb: 67.7% Er: 64.6% Sc: 63.0% Y: 62.2% |
Park and Liang (2019) | |
| Bioleaching | Mesophilic acidophilic chemolithotrophic microbial community | Sc: 52.0% Y: 52.6% La: 59.5% |
Muravyov et al. (2015) | |
| Bioleaching | Aspergillus niger | 30.91% | Ma et al. (2023) | |
| Bioweathering or acid leaching | Shewanella oneidensis or H2SO4 | Total REEs: 98.4% | Sachan et al. (2023) | |
| Hydrothermal alkali treatment → bioleaching | NaOH → Aspergillus niger | Ti: 89.20% Ga: 32.00% Sr: 54.30% Zr: 74.50% Ba: 35.40% |
Su et al. (2020a) | |
| Sieving → gravity separation → magnetic separation → flotation separation | Sieving → gravity separation → magnetic separation → flotation separation | 65% (maximum achieved) | Abaka-Wood et al. (2022) | |
| Alkali fusion → TEHDGA resin extraction | NaOH+NaNO3 → HNO3 → TEHDGA (N,N,N′,N′-tetrakis2-ethylhexyldiglycolamide) impregnated XAD-7 resin | Insufficient information | Mondal et al. (2019) | |
| Elution of ion exchange resins | Ion exchange resins | Insufficient information | Mostajeran et al. (2021) | |
| Flotation → mechanical grinding → acid leaching | HCl | 25% | Wen et al. (2022a) | |
| Physical separation | Sieving and magnetic separation | REY: 71.21% | Rosita et al. (2020b) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Absorption by high surface area carbon material | Absorbent: Microsphere Flower carbons | >85% | Brown and Balkus (2021) | |
| Acid leaching → precipitation → nanofiltration/microfiltration | Microfiltration and nanofiltration membrane | 92.8–99.3% | Kose Mutlu et al. (2018) | |
| Laser separation Electrodialytic remediation | A numerical study Distilled water, NaNO3, sodium acetate in acetic acid, or citric acid | Insufficient information 40% (with citric acid) | Phuoc et al. (2015) Lima and Ottosen (2022) | |
| Insufficient information Acid leaching | Insufficient information HCOOH leaching → Removing Ca, Mg, and Fe with NH4OH → Precipitating REEs with oxalic acid → Decomposing RE2(C2O4)3 | Purity: 99.4% in REEOs | Huang et al. (2018) | |
| Bioleaching (helped by acid and ferric ions) → solvent extraction → precipitation | Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus acidophilus, and Sulfolobus-like bacteria | Insufficient information | Sarswat et al. (2020) | |
| A review | A review | A review | Arbuzov et al. (2019) | |
| A review | A review | A review | Das et al. (2018) | |
| A review | A review | A review | Rybak and Rybak (2021) | |
| A review | A review | A review | Bagdonas et al. (2022) | |
| A review | A review | A review | Zhang et al. (2020c) | |
| A review | A review | A review | Eterigho-Ikelegbe et al. (2021) | |
| A review | A review | A review | Fu et al. (2022) | |
| A review | A review | A review | Talan and Huang (2022) | |
| A review | A review | A review | Kursun Unver and Terzi (2018) | |
| A review | A review | A review | Wilfong et al. (2022) | |
| A review | A review | A review | Liu and Chen (2021) | |
| A review | A review | A review | Mwewa et al. (2022) | |
| A review | A review | A review | Ju et al. (2021) | |
| A review | A review | A review | Dai et al. (2016) | |
| A review | A review | A review | Zhang et al. (2015) | |
| A review | A review | A review | Dodbiba and Fujita (2023) | |
| A review | A review | A review | Royer-Lavallée et al. (2020) | |
| A review | A review | A review | Peiravi et al. (2021) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| HREE (heavy REE) + LREE (light REE) | Acid leaching | Carboxylic acid (tartaric acid, malonic acid, lactic acid, citric acid, or succinic acid) | 62% | Banerjee et al. (2021) |
| Acid leaching | HCl | ~80% | Honaker et al. (2019) | |
| Calcination → acid leaching | H2SO4 | TREE: 74% | Gupta et al. (2023) | |
| Calcination → acid leaching | HCl or HClO4 or HNO3 | 98.17% | Hamza et al. (2022) | |
| Calcination → acid baking | H2SO4 | ~80% | Nawab et al. (2022) | |
| Calcination → acid leaching | HCl or citric acid or maleic acid or D,L-malic acid or oxalic acid | ~60% (with 0.05M HCl) | Ji et al. (2022b) | |
| Acid leaching → ion exchange leaching | H2SO4 → (NH4)2SO4 | TREE: 75–80% (with thermal activation or alkaline pretreatment) | Yang et al. (2019) | |
| Small-scale leaching or large-scale leaching → column separation → Precipitation and calcination | Small-scale or large-scale leaching: HCl, HNO3, or H2SO4 → bisethylhexyl diethylenetriaminepentaacetic acid (bisethylhexyl DTPA) → oxalic acid | >70% (with mineral acid leaching) Purity: >10 wt.% | Dardona et al. (2023) | |
| Desilication → microwave-assisted acid leaching | NaOH → HNO3, HCl, HClO4, or HF | 98.03% (with HNO3 + HCl + HF) | Ju et al. (2023) | |
| Acid leaching → solvent extraction | HNO3 → tributyl phosphate or Cyanex 572 or di-(2ethylhexyl)phosphoric acid (DEHPA) or their combinations | ~99% | Peiravi et al. (2017) | |
| Sequential leaching or single-step acid leaching or float-sink separations or humic acid extraction | sequential leaching; or single-step acid leaching agent: HCl or H3PO4 or H2SO4; or float-sink separations; or humic acid extraction via acetone-H2OHCl method | 70-90% | Laudal et al. (2018) | |
| Tessier sequential extraction or BCR sequential extraction | Tessier sequential extraction: NaOAc → NH2OH·HCl in CH3COOH → HNO3 + H2O2 Or BCR sequential extraction: CH3COOH → NH2OH·HCl + HNO3 → H2O2 (pH 2–3) → HNO3 + HCl | 85% (with Tessier sequential extraction) 60–70% (with BCR sequential extraction) | Park et al. (2021) | |
| 5-step sequential extraction | MgCl2 → NaOAc →NH2OH·HCl in CH3COOH → HNO3 → aqua regia + HF | 45% (maximum achieved) | Zhang and Honaker (2019b) | |
| 4-step sequential extraction | MgCl2 → NaOAc → CH3COOH + NH2OH·HCl → HNO3 + H2O2/ NH4CH3CO2 + HNO3 | 95.42% (Faer sample) 94.28% (Panbei sample) | Pan et al. (2019) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| 4-step sequential extraction | CH3COOH → NH2OH·HCl → H2O2 → Ammonia acetate (C2H7NO2) → HCl + HNO3 | 45% (maximum achieved) | Okeme et al. (2022) | |
| Acid leaching → solvent extraction → stripping → selective precipitation | H2SO4 → DEHPA → HCl → oxalic acid | REE: 75% Efficiency of recovering leached REEs via solvent extraction: 95% | Honaker et al. (2020) | |
| Deep eutectic solvents leaching → precipitation | (choline chloride (ChCl) + lactic acid (LA)) or (ChCl + para toluene sulphonic acid monohydrate [pTSA])) → oxalic acid dihydrate or NaF or Na2SO4 | 85–95% Purity: 13.8% (REE-oxalate); 7.3% (REE-fluoride) | Karan et al. (2022) | |
| Desilication → solvent extraction → stripping → precipitation | Gelatin → DEHPA solvent → HCl →Na2SO4 or sulfamic acid + NaNO3 or oxalic acid dihydrate | HREE: 94% LREE: 86% Purity: 17.6% (TREE) | Rao et al. (2022) | |
| Two-step staged precipitation | Na2CO3 | TREE: 85% | Hassas et al. (2021) | |
| Acid leaching → biosorption | HCl → biosorbent (carbonized ginkgo leaves [GL450]) | Er: 99.22% | Ponou et al. (2016) | |
| Roasting → acid leaching → Two liquid membrane separation (liquid emulsion membranes and supported liquid membranes) | NaOH → HNO3 → (DEHPA in kerosene or mineral oil) + HNO3 | Y, Tb, Dy, Ho, Er, Tm, Yb, Lu: >75% La, Ce, Pr, Nd: <50% | Smith et al. (2019) | |
| Froth flotation → magnetic separation → acid leaching | HNO3 | >80% | Zhang et al. (2018) | |
| Acid leaching or electrodialytic separation | HNO3 or electrodialytic recovery | >70% (maximum achieved) | Couto et al. (2020) | |
| HREE + LREE | Calcination → acid leaching or ion exchange leaching | HCl → (NH4)2SO4 | LREE: 80–90% | Zhang and Honaker (2019a) |
| (REE + Li + Ni) | HREE: 40–60% | |||
| HREE + LREE + MREE | Alkali fusion-acid leaching | NaOH → HCl | 32.624% (with 2 M HCl) | Mokoena et al. (2022) |
| 7-step sequential extraction Or magnetic separation → hydrothermal alkaline treatment | MilliQ water → (NH4)2SO4 → CH3COOH → hydroxylammonine chloride → ammonium oxalate + oxalic acid → ammonium oxalate, oxalic acid, and ascorbic acid → acidified H2O2 digestion + ammonium acetate extraction → LiBO2 fusion Or magnetic separation → NaOH | Total REE: 97.8% | Lin et al. (2018) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| 7-step sequential extraction or alkali-acid leaching | Deionized water → Ascorbic acid → CH3COOH → hydroxylammonium chloride → Ammonium oxalate + oxalic acid → Ammonium oxalate + oxalic acid + ascorbic acid → H2O2 or (NH4)2SO4; or NaOH/KOH → HCl/oxalic acid | Insufficient information | Choudhary et al. (2024) | |
| HREE + CREE (critical REE) | Acid leaching | H2SO4 | 80% | Honaker et al. (2018b) |
| HREE + LREE + CREE | 5-step sequential | MgCl2 → NH4CH3CO2 + CH3COOH → CH3COOH + NH2OH·HCl → HNO3 + H2O2 → microwave digestion (NaOH + HNO3) | 45–75% bounded to Fe-Mn oxides | Wang et al. (2021) |
| Acid leaching → Stagewise precipitation → solvent extraction → stripping → Oxalic acid precipitation | H2SO4 → NaOH → di-(2-ethylhexyl) phosphoric acid (DEHPA), DEHPA + tributyl phosphate, or DEHPA + H2O2 → HCl → oxalic acid | TREEs: 87.85% (average of 10 tests at pH 0.5) Purity: 80% in REO | Cicek et al. (2023) | |
| REE + Li + Ni | Biomacromolecular extraction | Lanmodulin | La: 99.5% Sc: 96% Y: 96% | Deblonde et al. (2020) |
| Sequential leaching | NH4CH3CO2→ HCl → HF → HNO3 | Insufficient information | Finkelman et al. (2018) | |
| REE + Li | Acid-alkali-based alternate extraction | HCl → NaOH → HCl → NaOH → HCl | REY: 65% Li: 84% | Ma et al. (2019) |
| 5-step sequential extraction | MgCl2 → NaOAc → NH2OH·HCl in CH3COOH | LREEs: 80-90% Li: 70% | Zhang and Honaker (2020a) | |
| Or calcination → acid leaching | → HNO3 + H2O2 → NH4CH3CO2 in HNO3 | |||
| Or calcination → HCl | ||||
| 6-step sequential extraction | MgCl2 → NaOAc → CH3COOH + NH2OH·HCl → HNO3 +H2O2 + NH4CH3CO2 → HF → HF + HNO3 | Insufficient information | Xu et al. (2022) | |
| A review | A review | A review | Sahoo et al. (2016) | |
| A review | A review | A review | Wang et al. (2020) | |
| REE + Ni | Alkaline pretreatment → IL leaching → stripping | NaOH → [Hbet][Tf2N] + NaNO3 → [Hbet][Tf2N] + HCl | LREEs: ~70–100% | Stoy et al. (2022b) |
| 7-step sequential extraction | Distilled water → (NH4)2SO4 → sodium acetate trihydrate → NH2OH·HCl → ammonium oxalate + oxalic acid + ascorbic acid → ammonium oxalate + oxalic acid → H2O2 / NH4CH3CO2 | Total REE: 2–21% | Bauer et al. (2022) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Sequential precipitation → re-dissolution → oxalic acid precipitation | NaOH → HNO3 → oxalic acid | REE: 95% Ni: insufficient information Purity: >98% in REO |
Zhang and Honaker (2020b) | |
| One-step bioleaching or two-step bleaching (hydrothermal-alkali/acid treatment + bioleaching) | Bioleaching: Acidithiobacillus thiooxidans | La: 75.08% Ce: 87.08% |
Su et al. (2020b) | |
| Books | ||||
| REE | A review | A review | A review | Zhao et al. (2019) |
| A review | A review | A review | Lai et al. (2021) | |
| A review | A review | A review | Sreenivas et al. (2021) | |
| Acid leaching by organic or mineral acids | Tartaric acid, lactic acid, HCl, or HNO3 | 62% (tartaric acid) 56% (lactic acid) ~72% (HCl or HNO3) |
Banerjee et al. (2022b) | |
| A review | A review | A review | Rao and Sreenivas (2019) | |
| Acid leaching | HCl, HNO3, or H2SO4 | >90% (with HCl) | Kumari et al. (2020) | |
| Ionic liquid extraction | Review | A review | Danso et al. (2021) | |
| A review | A review | A review | Mahandra et al. (2021) | |
| A review | A review | A review | Arellano Ruiz et al. (2021) | |
| REM | A review | A review | A review | Kumari et al. (2018) |
| REE + Li | A review | A review | A review | Vu et al. (2021) |
| Conference Papers | ||||
| REE | Alkaline digestion → acid leaching | Alkali → H2SO4 | REY: 75.25% (maximum recovery) | Rosita et al. (2020a) |
| Acid leaching | H2SO4 | Ce: 37.5% La: 33.8% Nd: 40.6% Sc: 28.1% Y: 54.5% |
Swinder et al. (2017) | |
| Alkaline treatments | Density separation → magnetic separation → size separation → NaOH treatment | REE enriching efficiency: 270% | Soong et al. (2019) | |
| Direct acid leaching | HCl or H2SO4 | Insufficient information | Taggart (2015) | |
| Sintering → acid leaching | Na2O2 → HNO3 | |||
| Pressure-digestion acid leaching | NaOH → HCl | |||
| Alkali-acid leaching | NaOH → HCl | ~90% | Roth et al. (2017) | |
| Acid leaching or roasting with chemical additives | Insufficient information | 70–100% | Taggart et al. (2017) | |
| Acid leaching | H2SO4 | 85% Purity: 50% | Honaker et al. (2018a) | |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Magnetic separation → flotation | Talon 9400, sodium oleate and oleic acid (used for pH) | 20% | Honaker et al. (2016) | |
| Acid leaching | Citric acid | Y: 83.35% (at 45°C); 51.00% (at 26°C) | Prihutami et al. (2020) | |
| Government Reports | ||||
| REE | Two stage SX rougher and cleaner circuit or roasting → acid leaching → DEHPA/TBP → stripping | H2SO4 → DEHPA/TBP → oxalic acid | >97% (with SX rougher and cleaner circuit) Purity: >90% in REO (with SX rougher and cleaner circuit) | Honaker et al. (2021) |
| Acid digestion process | HCl or HNO3 | REE + Y + Sc: 99.66% Purity: 1.04% | Peterson et al. (2017) | |
| Acid leaching → re-precipitation | HNO3 | ~100% Purity: 6% in REE | Ziemkiewicz (2020) | |
| Alkaline pretreatment → acid leaching | NaOH → HCl | 91% | Carlson (2018) | |
| Insufficient information | HF + HNO3 | Insufficient information | Hsu-Kim et al. (2020) | |
| Insufficient information | Citric acid | ~30% (at pH ~ 2) | Yang et al. (2022) | |
| Insufficient information | HF + HCl + HNO3 | 43% (maximum achieved) Purity: 54.4% (maximum achieved) | Mann et al. (2021) | |
| Insufficient information | Insufficient information | Insufficient information | Jayne et al. (2019) | |
| Insufficient information | HCl | Insufficient information | Sutterlin (2019) | |
| A review | A review | A review | Costis et al. (2019) | |
| Insufficient information | Insufficient information | Insufficient information | Bryan (2015) | |
| Insufficient information | Insufficient information | Insufficient information | Granite et al. (2016) | |
| REE + Li + Ni | Milling and caustic leaching → acid leaching → solvent leaching → stripping → purification | NaOH + HNO3 | >90–95% in TREO | Argumedo et al. (2020) |
| REE + Li | Leaching → solvent extraction → precipitation | Bacterial leaching solution → CYANEX 272, CYANEX 923, D2EPHA, or Versatic 10 → oxalic acid | Extraction efficiency: 42.5% Purity of REE oxalate in final product: 36.7% | Free et al. (2020) |
| Target Element(s) | Extraction Method | Leaching Agent | Leaching Efficiency | Citation |
|---|---|---|---|---|
| Theses/Dissertations | ||||
| REE | Alkali-acid leaching | NaOH → HCl | 74% | Choi (2018) |
| Alkaline sintering → acid leaching | Na2O2, NaOH, CaO, Na2CO3, CaSO4, or (NH4)2SO4 → HNO3 | TREE recovery efficiency: >90% (NaOH or Na2O2 sintering) | Taggart (2018) | |
| <50% (CaO, Na2CO3, CaSO4, or (NH4)2SO4 sintering) | ||||
| ~100% for PRB samples regardless of sintering agent and additive:ash ratio | ||||
| Acid baking and water leaching | H2SO4 and DI H2O | TREE: 79.1% (maximum achieved) | Kuppusamy (2022) | |
| Acid leaching Dense medium circuit → flotation | H2SO4, HCl, H3PO4 | 70–90% 60–76% (overall REE recovery) | Laudal (2017) Gupta (2016) | |
| HREE + LREE | Acid leaching → precipitation → solvent extraction → stripping → precipitation → roasting | H2SO4 → H2O2 → DEHPA → HCl → oxalic acid | 98.77% (with 0.5 M DEHPA) Purity: 80% by weight in REO | Cicek (2023) |
| Solvent extraction | DEHPA | Purity: 4.63% in TREE in solid phase | Ren (2019) | |
| Acid leaching | H2SO4 | 49.6% | Yang (2019) | |
| REE + Ni | Ionic liquid extraction | IL: [Hbet][Tf2N] | ~100% | Stoy (2021) |
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