Novel solution injection technology for in-situ leaching of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores are rich in the middle and heavy rare earths. The present study investigated the content of exchangeable aluminum and the exchangeable rare earth in the different layer of orebody and the partitioning of rare earth was determined as well to understand the mode of occurrence of rare earth. Furthermore, the swelling of clay minerals from different layers was investigated. The results shown that, in completely weathered layer and partly weathered layer, the content of exchangeable rare earth was more than 0.06% and the content of exchangeable aluminum was below 0.02%. However, in humic layer, the content of exchangeable rare earth was below 0.015% and the exchangeable aluminum was more than 0.03%. In the weathered crust elution deposited rare earth ore, the exchangeable aluminum is mainly found in the humic layer, whereas the rare earth elements are abundant in the completely weathered layer and partly weathered layer and the rare earth in humic layer belong to light rare earth group. Additionally, the swelling of clay minerals in humic layer was ranged between 2.5% and 2.7%, which were higher than the swelling of clay minerals in completely weathered layer and partly weathered layer. Based on these findings, a novel in situ leaching technology of weathered crust elution-deposited rare earth ores is proposed. The leaching agents were directly injected into the completely weathered layer without infiltrating through the humic layer. Avoiding the humic layer, only the completely weathered layer and partly weathered layer were leached. According to this method, the exchangeable aluminum in the rare earth leaching solution can be decreased and the purity of rare earth product can be improved. Meanwhile, the ammonium chloride was alternatively applied to leach rare earth and the choices of available leaching reagents were broadened. (C) 2016 Elsevier B.V. All rights reserved.