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Recovery of rare earths and lithium from rare earth molten salt electrolytic slag by lime transformation, co-leaching and stepwise precipitation

Li Xinglan, Luo Peidi, Liu Zishuai, Tang Xuekun, Zhang Baqun, Guo Jiangfeng

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 2

art. no. 186333

EN

The rare earth molten salt electrolytic slag (REMSES) has recently attracted significant attention due to its potential environmental hazards and high content of rare earths and lithium, leading to a surge in recycling efforts. In this study, we propose and demonstrate a novel and straightforward process for the simultaneous extraction of rare earths and lithium from REMSES through lime transformation and sulfuric acid leaching at low temperatures. Firstly, during the lime transformation process, REMSES is converted into hydroxides that can be easily dissolved in acids. Secondly, REEs and Li present in the slag are co-extracted using a conditional sulfuric acid leaching method, resulting in 95.72% REEs leaching efficiency and 99.41% Li leaching efficiency under optimal conditions. Finally, REEs and Li in the solution are precipitated using oxalic acid and trisodium phosphate with precipitation efficiencies of 99.02% for REEs and 94.85% for Li respectively. This innovative process enables the conversion of REEs and lithium from REMSES into high-purity products (a mixture of REOs with 99.31% purity; Li3PO4 with 98.93% purity), thereby facilitating their valuable utilization.

2

Effective flotation separation of scheelite and calcite by applying methylene phosphonic acid sodium as a novel and green depressant

Zhou Hepeng, Wu Handan, Guo Jiangfeng, Tang Xuekun, Huang Wen, Luo Xianping

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 3

art. no. 168517

EN

It is known that the flotation separation of scheelite and calcite is quite difficult due to their similar surface properites. To slove the problem, ethylenediaminetetra (methylene phosphonic acid) sodium (EDTMPS), an environmentally friendly reagent, was employed as an efficient depressant for flotation separation of calcite for the first time. In flotation experiments, it demonstrates that EDTMPS could strongly inhibit the flotation of calcite but barely affect the flotaiton behavior of scheelite, showing excellent dpress ability and selectivity. Based on a series of measurements including contact angle analysis, zeta potential, and XPS analysis, it was found that large amout of EDTMPS could be absorbed on the surface of calcite through strong chemical chelation reaction and thus inhibiting the further adsorption of NaOL. On the contrary, little EDTMPS was absorbed on that of scheelite owing to the negatively charged tungstate ions on the surface in relative terms. All in all, these results exhibit EDTMPS has excellent selective inhibition ability on calcite, which can be potentially applied in actual scheelite and calcite flotation separation process.

3

Application of diethylenetriaminepenta pentasodium salt as an eco-friendly depressant to effectively improve the flotation separation of scheelite and calcite

Zhou Hepeng, Wu Handan, Guo Jiangfeng, Tang Xuekun, Huang Wen, Luo Xianping

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 6

art. no. 174718

EN

Diethylenetriaminepenta (methylene-phosphonic acid) pentasodium salt (DTPMPA), an eco-friendly reagent, was tried for the first time as a depressant for flotation separation of scheelite from calcite. Micro-flotation tests show that DTPMPA can selectively depress the floatability of calcite. In contrast, DTPMPA barely affects the flotation behavior of scheelite. Based on the selective depress effect, floatation separation of scheelite and calcite can be effectively achieved by using DTPMPA as depressant in artificially mixed minerals flotation tests. Based on a series of measurements, it found the surface of calcite was positively charged due to the existence of Ca ion site, which can be chelated with -PO3H- functional group on the surface of DTPMPA. In the flotation process, DTPMPA can be chemically absorbed on the surface of calcite to inhibit further collector adsorption. On contrast, little DTPMPA was adsorbed on the surface of scheelite due to the spatial site resistance and electrostatic repulsion induced by surface WO42+. All in all, these results exhibit DTPMPA has excellent selective depression ability on calcite, which can be potentially applied in the actual scheelite flotation process.

4

Enhancing flotation of smithsonite by using 1,3,5-Triazinane-2,4,6-trithione as sulfidation

He Kunzhong, Zhou Hepeng, Zhang Yongbing, Tang Xuekun, Luo Xianping, Han Haisheng

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 5

1--14

EN

1,3,5-Triazinane-2,4,6-trithione (TMT) was used for the first time as a sulfidation agent in the flotation of smithsonite. Results showed that 80.5% recovery rate could be obtained in the presence of TMT (5 × 10-5 mol/L) and butyl xanthate (5 × 10-4 mol/L). However, the recovery rate was only 59.4% when sodium sulfide (5 × 10-5 mol/L) was used. Micro-flotation test and contact angle measurement showed that TMT activation was better than sodium sulfide activation. Besides, the contact angle increased from 32.44° (untreated) to 89.58° (treated with TMT), which was significantly higher than 50.2° (treated with sodium sulfide). Fourier Transform Infrared spectroscopy(FT-IR) and Zeta potential test showed the chemisorption of TMT on the smithsonite surface. The results of ICP spectral detection and solution chemistry calculation revealed that Zn3TMT complex precipitates in the smithsonite pulp were formed on the mineral surface at pH 6.5. A hydrophobic film was also formed on the mineral surface after TMT treatment, and more adsorption sites were provided for butyl xanthate. Thus, the adsorption of collector was significantly enhanced.