Abstract:Deep-sea polymetallic nodules are widely distributed on the seafloor, rich in manganese, iron, cobalt, nickel, copper and other metal elements, and have significant economic value. In order to maximize the use of these precious metal resources, this study conducted a systematic mineralogical analysis of deep-sea polymetallic nodules. The research content covers chemical composition analysis, morphological characterization, phase structure evaluation and microscopic observation. The mineral composition of nodules was systematically studied by means of X-ray diffraction (XRD), all element chemical analysis, particle size analysis, scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). The results show that the main mineral components of polymetallic nodules are manganese olivine, manganese spinel and nepheline, with low crystallinity. The chemical phase analysis shows that manganese, iron, copper, cobalt and nickel mainly exist in the form of oxides. Iron ore mostly exists in the crust of nodules and core debris in the form of fine-grained colloid or cryptocrystalline, which makes it impossible to achieve enrichment and separation through mechanical separation. Silicon-alumina-bearing vein minerals such as quartz and feldspar are mainly concentrated in rock debris, clay clusters, or dispersed in iron rich micro layers, further increasing the difficulty of mechanical separation. The chemical composition of polymetallic nodules is extremely complex and contains many elements. The total content of cobalt, nickel, copper (CO+Ni+Cu) and other precious heavy metals was 2.28%, and the content of manganese and iron were 28.51% and 9.06%, respectively. In addition, molybdenum, zinc, vanadium, yttrium and other trace elements with potential economic value also exist in it. Because the authigenic mineral particles in the polymetallic nodules are extremely small and the metal elements such as nickel, cobalt, copper and manganese are closely symbiotic, the traditional mineral processing method is difficult to work. Therefore, metallurgical processing has become the only feasible way to extract precious metals from deep-sea polymetallic nodules.
