Warning Model of the Ionic Rare Earth Mine Slope Based on Creep Deformation Time Series

This paper takes the actual working conditions of leaching mining, with the Xikeng Rare Earth Mine in Anyuan County as the research object. The slope surface monitoring as a technical means is used to analyze the deformation characteristics, including cumulative displacement, velocity, and acceleration, and the leaching slope and establish an early warning system to assist with leaching production. The study shows that there are three stages in the process of ionic rare earth mine slope deformation, i.e., the initial stage with deformation velocity in 0.15 to 0.30 mm∙h-1, the speed of the uniform deformation stage fluctuating but maintaining at -0.15 to 0.15 mm∙h-1, and the accelerated deformation stage when the velocity and acceleration are 3 to 10 times or more than those of the initial deformation stage. The practice had proved that the monitoring system responded positively when an alarm based on the Local Outlier Factor (LOF) was issued so that the production process was in a safe state and no large-scale landslide disaster occurred. This study will provide theoretical and technical support for the safe and efficient mining of rare earth in situ leaching.

Conditioning with Lime and Fertilizer Improves Ionic Rare Earth Mine Tailings

To explore rare earth mine tailings improvement technology without soil dressing, we planted Chinese cabbage in pots to determine the effect of different amounts of lime combined with fertilizer on the improvement of ionic rare earth mine tailings, aiming to provide a scientific basis for the reclamation of abandoned ionic rare earth mines. The results showed that the soil substrate of the tested rare earth tailings exhibited four forms of degradation: soil acidification, soil desertification, nutrient depletion, and heavy metal contamination by rare earth elements (REEs). The application of fertilizer alone (CK treatment) did not support Chinese cabbage growth, whereas different amounts of lime combined with fertilizer supported plant growth and significantly reduced the activity of the rare earth heavy metals. The height, fresh weight, and REE content of the Chinese cabbage plants were significantly reduced with an increase in the amount of lime applied. Addition of lime not only significantly improved the soil pore space and reduced soil acidification but also significantly increased the soil nutrient content. Our findings suggest that lime combined with fertilizer can improve ionic rare earth mine tailing soil degradation, thus promoting plant growth and achieving the improvement of ionic rare earth mine tailings without soil dressing.

Assessment of natural irradiation doses in rare earth mines of Muong Hum, Bat Xat district, Lao Cai province

The rare earth mine containing high concentrations of natural radionuclides (238U, 232Th, and 40K) in Muong Hum commune, Nam Pung, Bat Xat district, Lao Cai province, a mine with large reserves of rare earth resources in Vietnam, will be exploited and processed in the near future. The activity of natural radionuclides in the environment of air, soil, water, and effective annual dose are important parameters in assessing the impact of radiation on the environment when the mine goes into operating and processing rare earth ore. Investigating and determining radioactivity in soil, water, and plants at Muong Hum rare earth mine by means of radioactive gas measurement (RAD-7), gamma radiation dose rate (DKS-96), sample analysis using an ICP-MS mass spectrometer, will be performed in this study. The results showed that some soil samples had radionuclides activity 238U, 232Th higher than the allowed standard. The annual effective dose value in the region is 6.1 times higher than the world average (2.4 mSv/year). The obtained results are the basis for monitoring the impact of the radioactive environment and providing solutions to minimize the effects of radioactive substances on the ecological environment when the mine goes into mining and processing of rare earth ores.

Accumulation and Distribution of Rare Earth Elements (REEs) and Non-REEs With Vetiver Grass in The Abandoned Ion-Absorbed Rare Earth Mine

Overexploitation of rare earth elements (REEs) has caused serious desertification and environmental pollution, and ecological restoration of mines has attracted increasing national attention. In this paper, experiments involved land plowing, organic fertilizer broadcasting and vetiver cultivation were carried out to repair abandoned ion-absorbed rare earth mines (REM). Toxic metals content and pH in mining soil, distribution and transportation of toxic metals in the soil – vetiver grass system were investigated in detail.Results revealed that the abandoned REM soil was weakly acidic (pH=4.09) and rich in various toxic metals composed of REEs (La, Ce, Nd, Y, Gd, Dy) of 657.57mg/kg and Non-REEs (Pb, Cu, Se, As, Cd) of 109.98mg/kg. The distribution pattern in vetiver grass illustrated that toxic metals accumulation was mainly concentrated in the roots instead of shoot, and then the cumulative concentration of REEs in roots were much greater than that of Non-REEs. Furthermore, vetiver grass exhibited preferential accumulation of Cd, Se and REEs during the absorption process (from soil to root) and preferential accumulation of Pb, Cu and As during the translocation process (from root to leaf). The adsorption behavior of toxic metals by vetiver was confirmed due to these observed irregular particles in the scanning electron microscopy.