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1

Effect of polyacrylamide on the process of removing impurities in the rare earth leachate

Wu Xiaoyan, Zhou Fang, Liu Chufan, Feng Jian, Zhang Zhenyue, Chi Ruan

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 1

182--191

EN

The impurity removal process of the rare earth (RE) leachate is usually accompanied by the formation of flocs, and a certain amount of polyacrylamide flocculant needs to be added in this process. However, few studies have investigated the effect of the flocculant on the impurity removal process. Therefore, this paper compares the influence on the process of removing impurities with or without the adding of polyacrylamide (PAM). The results showed that the addition of PAM had little effect on the removal rate of impurities, but it was conducive to the recovery of RE. When ammonium bicarbonate was firstly adopted to regulate the solution pH to 5.0, and then sodium sulfide was used to adjust the pH to 5.2, and 0.5 mL/100 mL of PAM was added to the leachate, 96% Al3+ and 98% Zn2+ were removed from the leachate, while 95% RE was maintained. In addition, PAM could accelerate the settlement of flocs and then shorten the production cycle. The increase in RE recovery rate may be due to the addition of PAM to shorten the settling time of the flocs, thereby reducing the RE ions adsorbed during the flocculation process and increasing the recovery rate of the RE.

2

Process mineralogy of Bayan Obo rare earth ore by MLA

Xu Caili, Chi Ru’an, Zhang Yantu, Zhong Chengbin, Ruan Yaoyang, Lyu Renliang, Zhou Fang

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 4

737--745

EN

The maximum recovery of rare earth resource from the Bayan Obo ore deposit is a difficult task, especially without the sufficient data of mineralogy. In this paper the mineralogy of Bayan Obo ore deposit by comprehensively research with the application of mineral liberation analyzer (MLA) is reported. The MLA was applied to quantitatively analyze the complicated element/mineral compositions, the REE occurrence, the size distribution and the degree of liberation of the Bayan Obo ore. Mineralogical analysis of the rare earth ore has shown that REEs are present mainly as bastnaesite and monazite-(Ce) to a small extent as parisite-(Ce). 5.85% of the REEs, 34.99% of iron and 0.12% of niobium occur in the ore sample. There are 76.99% of iron occurred in hematite and the remaining iron is mainly distributed in magnetite and goethite. The degree of liberation of bastnaesite and monazite(Ce) was 79.65% and 75.67% respectively when the grinding fineness was 83.57% passing 75 μm sieves. Un-liberated or partly liberated rare earth minerals are associated closely mainly with other rare earth minerals and gangues. These theoretical data could be employed to further comprehensively utilize the rare earth ore.

3

Direct reuse of rare earth oxalate precipitation mother liquor for rare earth leaching

Wu Xiaoyan, Zhou Fang, Feng Jian, Liu Xueme, Zhang Zhenyue, Chi Ruan

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 3

760--769

EN

In the recovery process of rare earth (RE) from the weathered crust elution-deposited rare earth ore, ammonium sulfate is used as the leaching liquor to leach RE, and then the leachate containing RE3+ can be precipitated by oxalic acid and the RE oxalate precipitation mother liquor is reused for RE leaching process after removing the residual oxalic acid by precipitation with calcium hydroxide. However, the reuse process of precipitation mother liquor cannot proceed in the strong acid and alkali restricted areas and the discharge of mother liquor which contains a large amount of ammonium salt will cause ammonia-nitrogen waste and pollution. In order to realize the reuse of the precipitation mother liquor in this area, the direct reuse of RE oxalate precipitation mother liquor for RE leaching was investigated in this study. The RE oxalate precipitation process and the RE leaching process with oxalic acid were studied. The results showed that the residual oxalic acid concentration in the mother liquor can be controlled lower than 0.8 g/dm3 at pH 2-3 when the RE concentration in the leachate was 0.1- 1.5 g/dm3 and the RE precipitation rate reached to 94%. In addition, RE leaching efficiency was up to 90% while the oxalic acid concentration in the prepared mother liquor was 0.2-0.8 g/dm3, pH 2-3. Therefore, the precipitation mother liquor with oxalic acid concentration less than 0.8 g/dm3 could be directly reused for RE leaching. However, considering the different performance of RE ores, the recommended oxalic acid concentration in the direct used precipitation mother liquor was lower than 0.6 g/dm3.

4

Adsorption of lanthanum(III) and yttrium(III) on kaolinite: kinetics and adsorption isotherms

Zhou Fang, Feng Jian, Xie Xiong, Wu Baihong, Liu Qi, Wu Xiaoyan, Chi Ruan

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 4

928--939

EN

Experimental investigations were carried out using kaolinite to adsorb two rare earth ions, lanthanum ion (La3+) and yttrium ion (Y3+), which will provide some useful information and new insights on the mineralization process and fractionation phenomenon of weathered crust elution-deposited rare earth ores. The results showed that the equilibrium adsorption capacity of Y3+ is greater than La3+ under the same experimental conditions. The adsorption of rare earth ions presents strongly temperature dependent indicating an endothermic adsorption process. The pseudo-first-order kinetic model and the pseudo-second-order kinetic model were applied to discuss the adsorption kinetics. It was found that the adsorption rate of rare earth follows the pseudo-second-order kinetic model among the adsorption temperature range. Furthermore, the adsorption process of rare earth ions on kaolinite followed the Langmuir isotherm model confirmed by the correlation of experimental equilibrium data to standard isotherm model, Langmuir and Freundlich isotherms. The activation energies for the adsorption of La3+ and Y3+ on kaolinite are 28.1903 kJ/mol and 25.4190 kJ/mol, respectively. All kaolinite before and after adsorption were characterized by XRD and SEM-EDX to understand the adsorption mechanism. The obtained results suggested that the adsorption of La3+ and Y3+ on kaolinite is an endothermic and chemisorption process.