Abstract

During the leaching process of the ion-adsorbed rare earth (RE) ore, the pore structure evolution of the ore body plays a vital role in the seepage of the leaching solution. To investigate the evolution of the pore structure during the leaching process, experiments have been carried out with remodelled RE ore samples based on the physical characteristics of in situ ores. The seepage rate difference between deionized water leaching solution and 2% NH4Cl leaching solution during the active leaching period was analysed. The porosity and the dynamic pore size evolution of pore structures in the ore body are discussed. Results indicate that along with ion exchange between the RE ore and the leaching solution, the porosity of the sample remains constant and the pore structure shows a decreasing trend in the first part and an increasing trend in the second part. Specifically, during the ion exchange process, the number of minimal pores (0–5 µm), small pores (5–10 µm) and medium pores (10–25 µm) increases significantly and the number of medium–large pores (25–60 µm), large pores (60–120 µm) and mega pores (greater than 120 µm) decreases dramatically. Along with the completion of the ion exchange process, the evolution of porous structure shows an opposite trend. The mechanism study reveals that the evolution of pore structure is induced by the difference of ionic strength in the leaching solution during the ion exchange process, where the RE ore microparticles will be absorbed or desorbed on to the solid phase.

Highlights

  • Ion-adsorbed rare earth (RE) ore, known as weathered crust infiltration RE ore, is a unique type of RE ore found in China

  • We focused on the influence of the leaching process on the pore structure of the ore body

  • The ion exchange process induces the shrinkage of the pore size at the beginning and with the finishing of the ion exchange process, the pore size evolves from a medium/small pore structure to a large pore structure and the pore structure of the ore body changes back to its original state

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Summary

Introduction

Ion-adsorbed rare earth (RE) ore, known as weathered crust infiltration RE ore, is a unique type of RE ore found in China. As the ion exchange process continues, the fine particles in the ore body migrate, which cause the transformation of the secondary pore structure, affecting the osmotic transport characteristics of the leaching solution and the stability of the RE ore body. This may cause safety accidents such as mine landslides. By comparing the internal pore structure evolution of the RE ore in these two leaching processes, the influence of the ion exchange process on the porous structure of the ore body is revealed and this result will provide scientific methodologies and theoretical supports to the in situ leaching of the ion absorbed RE ore

Mechanism discussion
Sample preparation
Leaching experiment
Rare earth cation concentration measurement
Porous structure test of rare earth ore
Microstructure unit test of rare earth ore
Analysis effective leaching time
Analysis of leaching time difference in leaching tests
Inversion diagrams of pore structures during leaching tests
SEM test of sample during leaching tests
Analysis of dynamic evolution law of porosity of rare earth ore
Analysis of dynamic evolution of pore structures of rare earth ore
Discussion
Conclusion
Full Text
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