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<p>Polymetallic nodules occurring on the seabeds of the world’s oceans contain economically important metals such as Cu, Co, Ni, Pb, and Zn, primarily in the form of oxides and hydroxides. These nodules mainly consist of two intimately mixed mineral phases: manganese oxides, principally birnessite and todorokite (hydrated Mn oxides, MnOOH), and hydrated iron oxides. In the present study, 30 representative nodule samples belonging to two different size classes were analyzed. The nodules show significant enrichment of Mn, Ni, Cu, Co, and Zn, whereas comparatively lower concentrations of Fe, SiO₂, Al₂O₃, TiO₂, and P₂O₅ were observed. Alkali and alkaline earth oxides such as Na₂O, K₂O, and MgO also occur in insignificant amounts. The results further indicate that smaller nodules with rough surfaces possess relatively higher metal concentrations compared to larger nodules with smoother surfaces. The study employs chemical partition analysis to elucidate the distribution of elements among the various coexisting phases of marine sediments and polymetallic nodules. By comparing the compositions of leach solutions obtained through selective chemical reagent attacks and sequential leaching, it is possible to differentiate the chemical partitioning of elements among different geochemical fractions and their constituent mineral phases. The leaching techniques used include: EDTA for separating oxide and hydroxide phases; HCl for removing the Fe-oxide fraction of polymetallic nodules; 25% (v/v) acetic acid for separating detrital and non-detrital carbonate fractions; 2.5% (v/v) acetic acid for extracting adsorbed Co ions from clay mineral lattices; and hydroxylamine hydrochloride for separating Mn-associated metals. Rare Earth Elements (REEs) and their compounds are presently in high demand due to their extensive applications in electronics (including semiconductors and superconductors), ceramics, aerospace engineering, and medical technologies. However, the total REE concentration in polymetallic nodules is relatively low. Therefore, the development of suitable, technologically feasible techniques for the recovery and enrichment of total REE content from polymetallic nodules is essential.</p>

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Selective extraction of metals from polymetallic nodules of Central Indian Ocean Basin through chemical partitioning

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月4日

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  • Saurabh Kumar Barman,
  • Sanjay Kumar Tiwari,
  • Manvendra Singh Chauhan,
  • Vijayendra Pratap Dheeraj

摘要

Polymetallic nodules occurring on the seabeds of the world’s oceans contain economically important metals such as Cu, Co, Ni, Pb, and Zn, primarily in the form of oxides and hydroxides. These nodules mainly consist of two intimately mixed mineral phases: manganese oxides, principally birnessite and todorokite (hydrated Mn oxides, MnOOH), and hydrated iron oxides. In the present study, 30 representative nodule samples belonging to two different size classes were analyzed. The nodules show significant enrichment of Mn, Ni, Cu, Co, and Zn, whereas comparatively lower concentrations of Fe, SiO₂, Al₂O₃, TiO₂, and P₂O₅ were observed. Alkali and alkaline earth oxides such as Na₂O, K₂O, and MgO also occur in insignificant amounts. The results further indicate that smaller nodules with rough surfaces possess relatively higher metal concentrations compared to larger nodules with smoother surfaces. The study employs chemical partition analysis to elucidate the distribution of elements among the various coexisting phases of marine sediments and polymetallic nodules. By comparing the compositions of leach solutions obtained through selective chemical reagent attacks and sequential leaching, it is possible to differentiate the chemical partitioning of elements among different geochemical fractions and their constituent mineral phases. The leaching techniques used include: EDTA for separating oxide and hydroxide phases; HCl for removing the Fe-oxide fraction of polymetallic nodules; 25% (v/v) acetic acid for separating detrital and non-detrital carbonate fractions; 2.5% (v/v) acetic acid for extracting adsorbed Co ions from clay mineral lattices; and hydroxylamine hydrochloride for separating Mn-associated metals. Rare Earth Elements (REEs) and their compounds are presently in high demand due to their extensive applications in electronics (including semiconductors and superconductors), ceramics, aerospace engineering, and medical technologies. However, the total REE concentration in polymetallic nodules is relatively low. Therefore, the development of suitable, technologically feasible techniques for the recovery and enrichment of total REE content from polymetallic nodules is essential.