Chapter 4 Results and discussion
4.4 Second-stage solvent extraction for lithium recovery
4.4.3 Lithium recovery in Solution B
52
53
These two reactions occur competitively, and then the uncharged metal chelate, MRn, is distributed in the aqueous and organic phases. During the reaction, if the coordination number of the metal ion is not satisfied by the extractant, the insufficient part can be stocked with water molecules, resulting in the creation of a hydrated complex, HRn∙xH2O. In this case, the distribution ratio of this metal cation is low. In this situation, if the base, B, is added, the reaction of the hydrated complex and base will occur as in the following formula:
MRn(H2O)a+ B(H2O)h ↔ MRnB + (a + h)H2O (19)
It can be assumed that, in the first extraction, the sodium and especially the magnesium ions formed the hydrated chelate complex with D2EHPA.
This assumption can be supported by the extraction result of first-stage extraction, because the magnesium and sodium ions showed relatively low distribution ratios. Accordingly, this hydrated complex was located in the aqueous phase, and then it moved to the second-stage extraction system.
In the second-stage extraction, the TBP, which contains basic phosphorus, was added to the extraction reaction. These TBP molecules substituted for water molecules with equation (19). From the study of Choi (2009), the extractability of TBP decreases in the order of Ca2+ > Li+ > Sr2+
>Na+, and especially, magnesium and sodium ions cannot be extracted by TBP (distribution ratio is less than 10-2). In addition, as explained in Section 2.4 equation (4), the TBP molecule can react with a D2EHPA molecule and form a HRTBP complex. Consequently, the substitution of water molecules by TBP molecules occurred, but the TBP molecule has a low affinity with
54
magnesium and sodium ions. Therefore, the metal chelate complex is resolved, and it forms a HRTBP complex. By this process, the concentrations of magnesium and sodium in the aqueous phase could be increased during second-stage extraction.
55
Figure 16. Repetitive extraction of lithium inSolution B with 1.5 M D2EHPA + 0.5 M TBP
-80%
-60%
-40%
-20%
0%
20%
40%
0 2 4 6 8 10 12
Extraction efficiency [ %]
Repetition [cycle]
Li Mg Na
56
Chapter 5. Conclusion
A study of lithium recovery from shale gas-produced water was conducted to determine the applicability of the solvent extraction method. The extraction efficiency of cations, except calcium ion, was low due to the high TDS level of produced water. Therefore, extraction experiments with different dilution rates were conducted, and then 50X was selected as an appropriate dilution rate. Then, metal cation extraction was tested using D2EHPA in kerosene to explore the separation trend of D2EHPA and find favorable conditions for selective lithium recovery.
(1) Metal cation extraction trend of D2EHPA
In all the extraction experiments, D2EHPA showed that the extraction efficiency decreased in the following order: Ca2+> Sr2+> Ba2+> Mg2+> Li+>
Na+. Therefore, the multi-stage solvent extraction was proposed to reduce the effect of divalent cations on lithium extraction. The first-stage extraction was conducted to remove divalent cations in shale gas-produced water, and the second-stage extraction was performed to selectively recover lithium ion.
(2) Effect of TDS of shale gas-produced water on extraction
The extraction did not occur for cations, except calcium ion, because of the high TDS of shale gas-produced water. Therefore, extraction experiments with different dilution rates (1, 10, 25, and 50X) were conducted to determine the most efficient dilution rate. From the results, up to 25X diluted produced water showed relatively low extraction efficiency compared to the final concentration of lithium ion in the aqueous phase. Thus, 50X was selected as an appropriate dilution rate.
(3) First-stage extraction for divalent cation removal
57
The first-stage solvent extraction was tested by varying repetition numbers and D2EHPA concentrations with 50X diluted shale gas-produced water. The results showed that the extractability increased with increased extractant concentrations, and the effective repetition number varied with the applied D2EHPA concentrations. Eight cycles with 1 M of D2EHPA and five cycles with 1.5 M were selected as appropriate repetition numbers and extractant concentrations.
(4) Second-stage extraction for lithium recovery
The aqueous phase solution obtained after the appropriate number of first-stage extraction repetitions was applied for lithium recovery. In addition, to see the effect of TBP concentrations, three different concentrations (0.5, 1, and 1.5 M) were tested. From the results of repetition tests with eight repeated extractions aqueous solution using 1 M of D2EHPA, the lithium ion was extracted selectively, and the total extraction efficiencies of lithium ion were 26.46%, 25.21%, and 15.55% with the TBP concentrations of 0.5, 1, and 1.5 M, respectively. It showed that the TBP concentration of 0.5 M was the most efficient, so the experiment with five repetitions of first-stage extraction with 1.5 M D2EHPA was conducted with 1.5 M D2EHPA and 0.5 M TBP. The total extraction efficiency of lithium ion was 25.26%.
The highest extraction efficiency of lithium ion with D2EHPA and TBP was 26.46%. It may appear that the efficiency is not that high. However, almost all of the divalent cations were removed in the first-stage extraction, and the extractant, D2EHPA, has more affinity to lithium ion compared to other monovalent cations. Thus, in the second-stage extraction, only lithium ion was extracted, and the selectivity of lithium is very high. In conclusion, this multi-stage solvent extraction method can be applied for selective lithium recovery.
58
References
1. Beckwith Robin. 2011. Proppants: Where in the world. JPT. Chagnes Alexandre, Swiatowska Jolanta. 2015. Lithium Process Chemistry:
Resources, Extraction, Batteries, and Recycling. Elsevier 248-249
2. Bis (2-ethylhexyl) phosphate. MSDS No. 237825. Sigma Aldrich Korea.
Yongin-city. July 15, 2014. http://www.sigmaaldrich.com
3. Bukowsky H., Uhlemann E., Gloe K., and Muhl P.. 1992. The separation of calcium and magnesium from lithium chloride by liquid-liquid extraction with di (2-ethylhexyl) phosphoric acid. Hydrometallurgy. 28 323-329 4. Cabeza Luisa F., Gutierrez Andrea, Barreneche Camila, Ushak Svetlana,
Fernandez Angel G., Fernadez A. Ines, and Grageda Mario. 2015. Lithium in thermal energy storage: A state-of-the-art review. Renewable and Sustainable Energy Reviews 42 1106-1112
5. Cheng Chuyong. 2000. Purification of synthetic laterite leach solution by solvent extraction using D2EHPA. Hydrometallurgy. 56 369-386
6. Chitraker Ramesh, Kanoh Hirofui, Miyai Yoshitaka, and Ooi Kenta. 2001.
Recovery of Lithium from Seawater Using Manganese Oxide Adsorbent (H1.6Mn1.6O4) Derived from Li1.6Mn1.6O4. Ind. Eng. Chem. Res. Vol. 40 2054-2058
7. Choi Yunseok (translation), Tanaka Motoharu, and Akaiwa Hideo. 2009.
Solvent extraction chemistry (용매추출화학). Freeacademy. 2nd edition 8. DEHPA. Web. (n. d). SNF Flomin.
Retrieved from http://www.flomin.com/es/SNF.nsf/DEHPA_Flomin.pdf 9. Gabra G. G..1978. Lithium Chloride Extraction by n-Butanol.
Hydrometallurgy 3 23-33
59
10. Goodenough Robert D., andGaska Remigius A.. Extraction of lithium halides form calcium-containing brines in the presence of urea and alcohol- ketone. U. S. Patent 3,306,712, issued date February 28, 1967
11. Gregory Kelvin B., Vidic Radisav D., and Dzombak David A.. 2011.
Water Management Challenges Associated with the Production of Shale Gas by Hydraulic Fracturing. Elements Vol. 7 181-186
12. Haluszczak Lara O., Rose Arthur W., and Kump Lee R.. 2012.
Geochemical evaluation of flowback brine from Marcellus gas wells in Pennsylvania, USA. Applied Geochemistry 55-61
13. Hano T., Matsumoto M., Ohtake T., Egashira N. and Hori F.. 1992.
Recovery of Lithium from Geothermal Water by Solvent Extraction Technique. Solvent Extraction and Ion Exchange vol. 10 195-206
14. Hoshino Tsuyoshi. 2013. Preliminary studies of lithium recovery technology from seawater by electrodialysis using ionic liquid membrane.
Desalination. 317 11-16
15. International Energy Agency (IEA). November 2012. Golden Rules for a Golden Age of Gas.World Energy Outlook Special Report on
Unconventional Gas 30-32
16. Jakubec K., Haman J., and Rod V.. 1986. Separation of calcium from concentrated magnesium chloride solutions by solvent extraction with di(2- ethylhexyl) phosphoric acid. Hydrometallurgy. 17 15-26
17. Kielland Jacob. 1937. Individual activity coefficients of ions in aqueous solutions. Journal of the american chemical society. 59 1675-1678
18. Kim Seoni, Lee Jaehan, Kang Jin Soo, Jo Kyusik, Kim Seonghwan, Sung Yung-Eun, and Yoon Jeyong. 2015. Lithium recovery from brine using a λ- MnO2/activated carbon hybrid supercapacitor system.Chemosphere. 125 50-56
60
19. Kislik Vladimir S.. 2012. Solvent extraction: classical and novel approaches. Elsevier scientific Publishing Company. 5-8Nishihama Syouhei, Onishi Kenta, and Yoshizuka Kazuharu. 2011. Selective Recovery Process of Lithium from Seawater Using Integrated Ion Exchange Methods.
Solvent Extraction and Ion Exchange, 29: 421-431
20. Koopman C., Witkamp G. J., and Rosmalen G. M. Van. 1999. Removal of heavy metals and lanthanides from industrial phosphoric acid process liquors. Separation science and technology. 34 2997-3008
21. Sadakane Akira, Iwachido Tadashi, and Toei Kyoji. 1975. The extraction of alkali metal picrates with dibenzo-18-crown-6. Bulletin of the chemical society of Japan. Vol. 48 60-63
22. Shevchenko V. B., Smelov V. S., Kozlov A. G., Chubukov V. V., Lanin V.
P., and Smetanin E. Ya.. 1974. Extraction of americium, curium, strontium, and the rare earth elements from aqueous waste solutions of the reprocessing of spent fuel cells of VVER reactors. Soviet atomic energy.
Vol. 37 No. 5 1133-1137
23. Spellman Frank R.. 2012. Environmental impacts of hydraulic fracturing.
CRC Press Taylor & Francis Group. Boca Raton, London and New York.
120
24. Tributyl phosphate. MDSD No. 240494. Sigma Aldrich Korea. Yongin- city. August 26, 2015. http://www.sigmaaldrich.com
25. Triburyl phosphate. Web.June 04, 2016. Pubchem CID: 31357. Retrieved from
https://pubchem.ncbi.nlm.nih.gov/compound/tributyl_phosphate#section=T op
26. Umetani Shigeo, Maeda Kohji, Kihara Sorin and Matsui Masakazu. 1987.
Solvent extraction of lithium and sodium with 4-benzoyl or 4-
61
perfluoroacyl-5-pyrazolone and TOPO. Talanta Vol. 34 No.9 779-782 27. U.S. Department of Energy, Ground Water Protection Council. 2009.
Modern Shale Gas Development in the United States: A Primer.
28. U.S. Geological Survey. 2012. Mineral commodity summaries 2012. 94- 95
29. U.S. Geological Survey. 2014. Mineral commodity summaries 2014. 94- 95
30. U.S. Geological Survey. 2016. Mineral commodity summaries 2016. 100- 101
31. Yang Wei-fan, Yuan Shuanggui, Xu Yanbing, Xiao Yonghou, Fang Ke- ming, and Xong Bing. 2003. Extraction of thorium traces from hydrochloric acid media by 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5.
Journal of radioanalytical and nuclear chemistry. Vol. 256 No. 1 149-152
62
초 록
셰일가스는 수압파쇄법을 통해 개발되는데, 이 과정에서 다량의 물이 셰일 지층으로 주입된다. 이후, 파쇄용수와 셰일 지층수가 결합된 환류수가 배출되며, 이를 셰일가스 생산수라고 한다.
셰일가스 생산수는 셰일가스 개발 중에 발생하는 고염도의 폐수이다. 셰일가스 생산수에는 셰일암의 점토광물로부터 기인하는 리튬이 상대적으로 많이 포함되어있다. 최근, 리튬의 수요가 증가함에 따라 해수에서 리튬을 회수하는 다양한연구가 진행 중인데, 해수 내 리튬의 농도는 0.17 mg/L로, 마셀러스 (Marcellus) 셰일 지역에서 발생하는 생산수가 약 95 mg/L의 리튬을 함유하고 있는 것과 비교하면 생산수 내 리튬 함량이 매우 높은 것을 알 수 있다. 그러므로 셰일가스 생산수에서 리튬을 선택적으로 회수할 수 있다면, 해수에서의 리튬 추출보다 효과적일 것으로 보인다. 본 연구는 희석된 셰일가스 생산수에 용매추출법을 적용하여 선택적인 리튬 회수가 가능한지 알아보기 위해 진행되었다. 셰일가스 생산수는200,000 mg/L에 이를 만큼 매우 높은 농도의 총 용존 고형물(Total Dissolved Solids: TDS)을 함유하고 있으며, 그에따라 용매추출 과정 시에 리튬 이온과 경쟁적으로 작용하는 양이온들의 농도도 매우 높다. 따라서 리튬 이온과 경쟁적으로 작용하는 다른 양이온들의 영향을 줄이고 리튬 이온 선택성을 향상시키기 위해 다단계 용매추출법을 적용하였다.
첫 번째 단계 추출에서는 추출제로di(2-ethylhexyl) phosphoric acid (D2EHPA)를 사용하였으며, 두 번째 단계 추출에서는 추출제 D2EHPA에 보조첨가제 tri-butyl phosphate