An environmental friendly Na 2 CO 3 -roasting decomposition strategy for the mixed rare earth concentrate

Zhao, Junmei; Pan, Feng; Liu, Huizhou

doi:10.1016/j.seppur.2016.05.036

Cited by 34 publications

(9 citation statements)

References 12 publications

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“…The mixed rare earth mines in Bayan Obo are some of the most critical rare earth mines in China and in the world because of their large reserves and output [3]. Mixed rare earth concentrates (MREC) commonly used in industry are composed of bastnaesite and monazite in a range from 7:3 to 8:2, containing 50-65% rare earth oxide (REO), 7-10% fluorine and some other impurie elements [4,5]. Considering their complex mineral composition, the main processes for treating MREC is the concentrated sulfuric-acid roasting method and a sodium-hydroxide decomposition process for the generation of rare earth minerals in China [6].…”

Section: Introductionmentioning

confidence: 99%

Removal of Fluorine from RECl3 in Solution by Adsorption, Ion Exchange and Precipitation

et al. 2021

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In this paper, methods of effective removal of fluorine from rare earth chloride solution by adsorption, ion exchange and precipitation with lanthanum carbonate or CO2 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 CO2, 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 RECO3(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−. The XRD spectra showed that F− was removed in the form of REFCO3 precipitates, which indicates that the adsorbed F− replaced the OH- group on the surface of RECO3(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 °C; reaction time, 2 h. Simultaneously, a fluorine-removal process by CO2 precipitation was explored. In general, RE2(CO3)3 precipitation is generated when CO2 is injected into a rare earth chloride solution. Interestingly, the results of XRD, SEM and EDS showed that the sedimentation slag was composed of REFCO3 and RE2O2CO3. It was inferred that RE2(CO3)3 obtained at the initial reaction stage had a certain adsorption effect on F− in the solution, and then F− replaced CO32− on the surface of RE2(CO3)3 by ion exchange. Therefore, F− was finally removed by the high crystallization of REFCO3 precipitation, and excess RE2(CO3)3 was aged to precipitate RE2O2CO3. The fluorine-removal percentage can reach 98.92% with CO2 precipitation under the following conditions: venturi jet; CO2 injection flow, 1000 L/h; reaction temperature, 70 °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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Section: Introductionmentioning

confidence: 99%

Removal of Fluorine from RECl3 in Solution by Adsorption, Ion Exchange and Precipitation

et al. 2021

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“…Consequently, researchers continue to explore more green rare earth extraction processes. A series of roasting processes, such as the NaOH low-temperature decomposition method, , CaO–NaCl–CaCl 2 decomposition method, and Na 2 CO 3 roasting decomposition method, − have been reported. In addition, an important process is the oxidation roasting-hydrochloric acid leaching process. , In this process, the acid leaching residue is mainly composed of REF 3 and monazite mainly.…”

Section: Introductionmentioning

confidence: 99%

Decomposition Process of Nonoxidative Microwave Radiation Roasting of a Mixed Rare Earth Concentrate with Sodium Carbonate

Tian

Guan

et al. 2021

ACS Omega

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This article introduces an efficient decomposition process that uses sodium carbonate (Na 2 CO 3 ) and activated carbon (C) as additives to decompose Bayan Obo mixed rare earth concentrate (hereinafter to be referred to as RE concentrate) by nonoxidative microwave radiation roasting. The roasting temperature, holding time, and contents of Na 2 CO 3 and activated carbon are investigated. The optimum process parameters for decomposition are 800 °C and 30 min. The ratio of m(Na 2 CO 3 )/m(RE concentrate) is 0.5, and the ratio of m(C)/m (ER concentrate and Na 2 CO 3 ) is 0.2 based on experimental data. Under the above conditions, the decomposition rate (shortened to DR) of RE concentrate is 98.58%, and the removal rates (shortened to CRs) of fluorine (F) and phosphorus (P) reached 80.35 and 46.75%, respectively. These rates are higher than traditional oxidation roasting under the same conditions. The three reasons for the result are the unique microwave heating characteristics, the overall efficient reaction of the mixture (RE concentrate, Na 2 CO 3 , and activated carbon), and the high nonoxidation rate of cerium. For these reasons and large experimental data, the reaction rate of the mixture is improved, and the efficiency of dilute hydrochloric acid for leaching rare earth elements is enhanced. In this article, the valence of rare earth elements in the roasted ore is all in the form of trivalence. Importantly, this nonoxidative roasted product can avoid the generation of chlorine in hydrochloric acid leaching. Moreover, such a short holding time is scarce in traditional roasting. When the mixture was roasted by utilizing microwave heating, the sinter phenomenon of the roasted product was avoided at high-temperature roasting. Finally, the surface morphology of RE concentrate at different conditions was observed by scanning electron microscopy (SEM) analysis, which can be used to compare the specific differences of roasting methods. According to these results, this process is beneficial for the decomposition of RE concentrate in terms of Na 2 CO 3 roasting and is helpful for improving the clean and green technology method of hydrometallurgy.

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“…Due to its high F content, about 12 000 tons of F is produced during H 2 SO 4 roasting and is then released into the atmosphere and ground water . To solve the pollution problem of fluoride, researchers proposed a way to avoid the formation of F-containing off-gas, which is adding the compounds of alkali metals in the roasting process. ,− By mixing Ca(OH) 2 and NaOH with RE concentrate, the decomposition of RE minerals was promoted and RE oxides and CaF 2 were produced, which were easily leached out with a HCl–AlCl 3 solution and the recoveries of RE elements and F reached 86.1 and 90.2%, respectively . In this work, CaO was added in the carbothermal reduction of Bayan Obo tailings for the following purposes: fluorine fixation, promoting the metallization of Fe, and the decomposition of RE minerals.…”

Section: Introductionmentioning

confidence: 99%

Novel Harmless Utilization of Bayan Obo Tailings: Separation and Recovery of Iron and Rare Earth

Yan

Xue

Yang

et al. 2020

Ind. Eng. Chem. Res.

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In this work, the carbothermal reduction and hydrochloric acid leaching were utilized for separation and recovery of iron and rare earth from the Bayan Obo tailings. The effects of temperature, addition of calcium oxide, and reaction time on the metallization rate of iron during roasting were investigated. The results showed that the metallization rate of iron reached 99.67% and the loss rate of fluorine was less than 1% under optimum roasting conditions of a temperature of 1100 °C, a coal ratio of 6.77 wt %, a calcium oxide ratio of 10 wt %, and a roasting time of 2 h. The behavior of iron and rare earth in magnetic separation was found to be controlled by the particle size after grinding. Using ball milling, 98.2% of rare earth and 96.7% of Fe were separated. A hydrochloric acid solution with a low concentration of 3 mol/L was used to leach rare earth from the magnetic separation tailings. The results showed that the leaching recovery of rare earth exceeded 99%, and more than 80% of other valuable elements were also leached out. Finally, the leaching residue contained 52.38 wt % of pure calcium fluoride, which can be used as a raw material for the flotation of fluorite.

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An environmental friendly Na 2 CO 3 -roasting decomposition strategy for the mixed rare earth concentrate

Cited by 34 publications

References 12 publications

Removal of Fluorine from RECl3 in Solution by Adsorption, Ion Exchange and Precipitation

Removal of Fluorine from RECl3 in Solution by Adsorption, Ion Exchange and Precipitation

Decomposition Process of Nonoxidative Microwave Radiation Roasting of a Mixed Rare Earth Concentrate with Sodium Carbonate

Novel Harmless Utilization of Bayan Obo Tailings: Separation and Recovery of Iron and Rare Earth

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