Abstract
In order to investigate the influence of the ion exchange process on the permeability of rare earth ore bodies in the leaching process, a laboratory-scale comparative experiment with ammonium sulfate solution and deionized (DI) water as leaching solutions is conducted. Compared with the DI water leaching test, the permeability coefficient of the rare earth ore sample leached by the ammonium sulfate solution gradually decreases at the beginning and then increases with the completion of leaching. The physical and morphological evolutions of rare earth ore samples in this comparative experiment are also monitored by nuclear magnetic resonance and scanning electron microscopy. It is concluded that the change in the permeability coefficient arises from the adsorption–desorption of a large number of clay microparticles, resulting in a dynamic evolution of pore structures. Further mechanism analysis suggests that the change in internal ionic strength caused by ion exchange and leaching solution seepage promotes the adsorption–desorption behavior of clay microparticles.
Highlights
The ion-adsorption type rare earth deposit is a unique type of heavy rare earth element deposit.This type of deposit is formed by granite or volcanic rock after years of weathering, and it is mainly composed of clay minerals, quartz sand, feldspar, etc. [1,2]
The permeability coefficient of the rare earth ore sample is influenced by the adsorption–desorption behavior of a large number of clay microparticles, which is induced by the ion exchange reaction between NH4 + in the leaching solution and RE3+ in the rare earth ore sample
By comparing the data obtained from the comparative experiment, it can be concluded that the ion exchange reaction between the leaching solution and the rare earth ore promotes a decrease in the permeability coefficient of the sample
Summary
The ion-adsorption type rare earth deposit is a unique type of heavy rare earth element deposit.This type of deposit is formed by granite or volcanic rock after years of weathering, and it is mainly composed of clay minerals, quartz sand, feldspar, etc. [1,2]. The ion-adsorption type rare earth deposit is a unique type of heavy rare earth element deposit. This type of deposit is formed by granite or volcanic rock after years of weathering, and it is mainly composed of clay minerals, quartz sand, feldspar, etc. Since rare earth ions are mainly adsorbed on clay minerals, such as halloysite, kaolinite and montmorillonite in the deposit, chemical technology is the only method for extraction of rare earth elements from the ion-adsorption type rare earth deposit [3,4]. In situ leaching is the main mining method for this type of rare earth deposit for its great advantages in terms of mining costs and environmental protection [5]. To enhance the leaching efficiency, the study of the permeability of the ion-adsorption type rare earth deposit has received much attention from researchers
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