The Recovery of Valuable Metals from Ocean Polymetallic Nodules Using Solid-State Metalized Reduction Technology

Feng Zhao,Da Li,Linyong Feng,Shengdong Wang,Xunxiong Jiang

doi:10.3390/min10010020

Feng Zhao, Da Li + Show 3 more

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https://doi.org/10.3390/min10010020

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Abstract

Ocean polymetallic nodules are oxide ores rich in Ni, Co, Cu, and Mn, which are valuable metals found in deep-sea mineral resources. Such non-ferrous metals do not exist in isolation, and producing concentrates using conventional mineral separation techniques is challenging without pre-treatment. We propose an effective, environmentally-friendly recovery technology combined with solid-state metalized reduction treatment and magnetic separation to recycle these metals from ocean polymetallic nodules. We conducted single-factor tests to investigate the effects of additives, anthracite dosage, duration, and reduction temperature on metal recovery and to obtain optimal operating parameters. We found that valuable metals in ocean polymetallic nodules may be selectively reduced to a metallic state. Only a fraction of Mn was reduced to metal. The reduced metals were recovered to concentrates using magnetic separation. More than 80% of these metals were concentrated to magnetic concentrates with mass ratios of 10–15%. The recovery rates of Ni, Co, Cu, Mn, and Fe in concentrates were optimum at 86.48%, 86.74%, 83.91%, 5.63%, and 91.46%, respectively, when using CaF2 4%, anthracite 7%, SiO2 dosage 5%, and FeS 6% at 1100 °C for 2.5 h. This approach to non-ferrous metal extraction using conventional hydrometallurgical processes could be a step toward practical industrial-scale techniques for the recovery of metals from polymetallic nodules.

Highlights

Due to rapid economic growth and technological advances, greater attention has been paid to the exploration and investigation of deep-sea resources
We found that CaF2 decreased the surface tension of alloy particles and the mineral melting point, and promoted the migration and aggregation of metalized valuable metals
The results show that with the increase in temperature, the alloy particles size increases, and the

Summary

Introduction

Due to rapid economic growth and technological advances, greater attention has been paid to the exploration and investigation of deep-sea resources. This is driven by an increasing need for alternative sources of metals, and much research has focused alternative extraction methods [1]. Besides containing Fe and Mn, polymetallic nodules are comprised of other non-ferrous metals, such as Ni, Co, and Cu with a total content of approximately 3% of these three metals. The crystallization degree of polymetallic nodules is poor, existing as semi-crystalline, crypto-crystalline, or amorphous forms. Fe and Mn are the main constituent metallic elements of nodules, found in the form of 10-Å phyllomanganate (δ-MnO2 ) and goethite, in which Ni, Co, and

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