Occurrence and screening- flotation separation for the beneficiation of rare earth elements and yttrium (REY) in core sediments from the Pacific Ocean

Abstract

Rare earth elements (REE) and yttrium (termed as REY), as a significant strategic resource, are recently found to be extremely enriched in deep-sea sediments, which is expected to be an important REY resource in the future. However, the efficient development and utilization of deep-sea REY-rich sediments are greatly limited by the current common beneficiation and metallurgy method. In this study, detailed grain size analysis, mineral identification and geochemical measurement aiming at deep-sea sediments collected from a station in the Central Pacific Basin were employed to determine the occurrence of deep-sea REY-rich sediments. Based on that, the Screening-flotation separation was adopted to achieve efficient enrichment of REY in the sediments. The ΣREY contents in the samples can reach 790 ppm, and sieve analysis reveal that bioapatite (fish teeth and bones) and Fe-Si-Mn oxide (oxyhydr) on the micro-nodule surface are the major REY carriers. About 87.27% REY was scavenged by bioapatite fossils. The REE patterns show distinct negative Ce/Ce* and slightly positive Eu/Eu* anomalies, similar to the Western and central North Pacific seawater, indicating a promising source of REY in the samples may be pore water in sediments, taking into account other studies as well. The grain size analysis suggests that REY enrichment can be achieved by removing the fine-grained particles (<15 μm). Screening-flotation separation, as a newly developed approach for the beneficiation, uses the pre-screening method to pre-detach the clay-size fraction (<15 μm), and combines flotation and magnetic separation, which further upgrades REY concentrate to achieve about 9 times enhancement of REY recovery from marine sediments. Although further research is needed, the study we determined can provide reference for industrial exploitation of rare earth resources in deep-sea REY-rich sediments.