Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation
In this paper, methods of effective removal of fluorine from rare earth chloride solution by adsorption, ion exchange and precipitation with lanthanum carbonate or CO<sub>2</sub> gas as fluorine-removal agent, respectively, were studied. The relevant parameters studied for fluorine-remov...
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MDPI AG
2021-12-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/12/1/31 |
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| author | Dongliang Zhang Kai Gao Xiaowei Zhang Mitang Wang |
| author_facet | Dongliang Zhang Kai Gao Xiaowei Zhang Mitang Wang |
| author_sort | Dongliang Zhang |
| collection | DOAJ |
| description | In this paper, methods of effective removal of fluorine from rare earth chloride solution by adsorption, ion exchange and precipitation with lanthanum carbonate or CO<sub>2</sub> gas as fluorine-removal agent, respectively, were studied. The relevant parameters studied for fluorine-removal percentage were the effects of the type and dosage of fluorine-removal agent, the injection flow and mode of CO<sub>2</sub>, the initial concentration of rare earth solution and initial pH value, contact time, temperature and stirring. XRD, SEM and EDS were used to analyze and characterize the filter slag obtained after fluorine removal. SEM and EDS results showed that RECO<sub>3</sub>(OH) with a porous structure was formed in rare earth chloride solution when lanthanum carbonate was used as fluorine-removal agent, and it had strong selective adsorption for F<sup>−</sup>. The XRD spectra showed that F<sup>−</sup> was removed in the form of REFCO<sub>3</sub> precipitates, which indicates that the adsorbed F<sup>−</sup> replaced the OH<sup>−</sup> group on the surface of RECO<sub>3</sub>(OH) by ion exchange. The experimental results showed that a fluorine-removal percentage of 99.60% could be obtained under the following conditions: lanthanum carbonate dosage, 8%; initial conc. of rare earths, 240 g/L; initial pH, 1; reaction temperature, 90 <inline-formula><math display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C; reaction time, 2 h. Simultaneously, a fluorine-removal process by CO<sub>2</sub> precipitation was explored. In general, RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> precipitation is generated when CO<sub>2</sub> is injected into a rare earth chloride solution. Interestingly, the results of XRD, SEM and EDS showed that the sedimentation slag was composed of REFCO<sub>3</sub> and RE<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>. It was inferred that RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> obtained at the initial reaction stage had a certain adsorption effect on F<sup>−</sup> in the solution, and then F<sup>−</sup> replaced CO<sub>3</sub><sup>2−</sup> on the surface of RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> by ion exchange. Therefore, F<sup>−</sup> was finally removed by the high crystallization of REFCO<sub>3</sub> precipitation, and excess RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> was aged to precipitate RE<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>. The fluorine-removal percentage can reach 98.92% with CO<sub>2</sub> precipitation under the following conditions: venturi jet; CO<sub>2</sub> injection flow, 1000 L/h; reaction temperature, 70 <inline-formula><math display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C; initial pH, 1; reaction time, 1.5 h; initial conc. of rare earths, 240–300 g/L; without stirring. The above two methods achieve deep removal of fluorine in mixed fluorine-bearing rare earth chloride solution by exchanging different ionic groups. The negative influence of fluorine on subsequent rare earth extraction separation is eliminated. This technology is of great practical significance for the further development of the rare earth metallurgy industry and the protection of the environment. |
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| institution | Directory Open Access Journal |
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| language | English |
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| spelling | doaj.art-17c3c1cc76c54e6394ce7103070f5eff2023-11-23T14:49:12ZengMDPI AGMinerals2075-163X2021-12-011213110.3390/min12010031Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and PrecipitationDongliang Zhang0Kai Gao1Xiaowei Zhang2Mitang Wang3School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, ChinaState Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization, Baotou Research Institute of Rare Earths, Baotou 014010, ChinaSchool of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, ChinaSchool of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, ChinaIn this paper, methods of effective removal of fluorine from rare earth chloride solution by adsorption, ion exchange and precipitation with lanthanum carbonate or CO<sub>2</sub> gas as fluorine-removal agent, respectively, were studied. The relevant parameters studied for fluorine-removal percentage were the effects of the type and dosage of fluorine-removal agent, the injection flow and mode of CO<sub>2</sub>, the initial concentration of rare earth solution and initial pH value, contact time, temperature and stirring. XRD, SEM and EDS were used to analyze and characterize the filter slag obtained after fluorine removal. SEM and EDS results showed that RECO<sub>3</sub>(OH) with a porous structure was formed in rare earth chloride solution when lanthanum carbonate was used as fluorine-removal agent, and it had strong selective adsorption for F<sup>−</sup>. The XRD spectra showed that F<sup>−</sup> was removed in the form of REFCO<sub>3</sub> precipitates, which indicates that the adsorbed F<sup>−</sup> replaced the OH<sup>−</sup> group on the surface of RECO<sub>3</sub>(OH) by ion exchange. The experimental results showed that a fluorine-removal percentage of 99.60% could be obtained under the following conditions: lanthanum carbonate dosage, 8%; initial conc. of rare earths, 240 g/L; initial pH, 1; reaction temperature, 90 <inline-formula><math display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C; reaction time, 2 h. Simultaneously, a fluorine-removal process by CO<sub>2</sub> precipitation was explored. In general, RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> precipitation is generated when CO<sub>2</sub> is injected into a rare earth chloride solution. Interestingly, the results of XRD, SEM and EDS showed that the sedimentation slag was composed of REFCO<sub>3</sub> and RE<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>. It was inferred that RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> obtained at the initial reaction stage had a certain adsorption effect on F<sup>−</sup> in the solution, and then F<sup>−</sup> replaced CO<sub>3</sub><sup>2−</sup> on the surface of RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> by ion exchange. Therefore, F<sup>−</sup> was finally removed by the high crystallization of REFCO<sub>3</sub> precipitation, and excess RE<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub> was aged to precipitate RE<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>. The fluorine-removal percentage can reach 98.92% with CO<sub>2</sub> precipitation under the following conditions: venturi jet; CO<sub>2</sub> injection flow, 1000 L/h; reaction temperature, 70 <inline-formula><math display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C; initial pH, 1; reaction time, 1.5 h; initial conc. of rare earths, 240–300 g/L; without stirring. The above two methods achieve deep removal of fluorine in mixed fluorine-bearing rare earth chloride solution by exchanging different ionic groups. The negative influence of fluorine on subsequent rare earth extraction separation is eliminated. This technology is of great practical significance for the further development of the rare earth metallurgy industry and the protection of the environment.https://www.mdpi.com/2075-163X/12/1/31mixed rare earth chloride solutionfluorinerare earth hydroxy-carbonaterare earth fluoro-carbonateion exchangeCO<sub>2</sub> precipitation |
| spellingShingle | Dongliang Zhang Kai Gao Xiaowei Zhang Mitang Wang Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation Minerals mixed rare earth chloride solution fluorine rare earth hydroxy-carbonate rare earth fluoro-carbonate ion exchange CO<sub>2</sub> precipitation |
| title | Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation |
| title_full | Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation |
| title_fullStr | Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation |
| title_full_unstemmed | Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation |
| title_short | Removal of Fluorine from RECl<sub>3</sub> in Solution by Adsorption, Ion Exchange and Precipitation |
| title_sort | removal of fluorine from recl sub 3 sub in solution by adsorption ion exchange and precipitation |
| topic | mixed rare earth chloride solution fluorine rare earth hydroxy-carbonate rare earth fluoro-carbonate ion exchange CO<sub>2</sub> precipitation |
| url | https://www.mdpi.com/2075-163X/12/1/31 |
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