The accelerated growth in global demand for Manganese coincides with the continuing depletion of high-grade ores on the earth's surface. This element is essential for diverse markets such as steel production, dietary additives, fertilizers, cells, fine chemicals, and some chemical reagents. Interestingly, there are large mineral reserves in the ocean's depths, where marine nodules are an attractive option due to their high manganese content (between 16 and 24%). The dissolution of MnO₂ from manganese nodules needs a reducing agent. Iron is a feasible alternative with a low cost and can even be recycled from scrap or industrial waste like smelting slag, tailings, or scrap steel. This paper provides a comprehensive review of Manganese acid-reducing processes from marine nodules using different iron-reducing agents that include FeS₂, Fe²⁺, Fe⁰, Fe₂O₃, and Fe₃O₄. Fe⁰ has displayed the best performance in terms of dissolution kinetics and Mn extraction. This review further confers the chemistry and reactions involved in the reductive leaching and stresses the critical parameters that could be considered for optimization. In this sense, the concentration of reducing agent and temperature are highlighted as the most influential, making other parameters (e.g., particle size, stirring speed, acid concentration, and leaching time) almost irrelevant. Finally, it is concluded that the best way to extract Mn from marine nodules is to reuse steel scraps, working with high Fe⁰/MnO₂ ratios (2/1), low concentrations of sulfuric acid (0.1 mol/L), and short times (5 min), achieving extractions of 90%.

全球对锰需求的加速增长与地球表面高品位矿石的持续枯竭相吻合。该元素对于多样化的市场至关重要，例如钢铁生产，膳食添加剂，肥料，细胞，精细化学品和某些化学试剂。有趣的是，海洋深处蕴藏着大量的矿藏，由于其锰含量高（16％至24％），因此海洋结核是一种有吸引力的选择。MnO ₂的溶解从锰结核中需要还原剂。铁是一种低成本的可行替代品，甚至可以从废料或工业废料（如冶炼炉渣，尾矿或废钢）中回收。本文全面综述了使用不同的铁还原剂，包括FeS ₂，Fe ₂ ⁺，Fe ⁰，Fe ₂ O ₃和Fe ₃ O ₄，从海洋结核中还原锰酸的过程。铁⁰在溶解动力学和锰萃取方面表现出最好的性能。这篇综述进一步赋予了还原浸出所涉及的化学和反应，并强调了可以考虑进行优化的关键参数。从这个意义上讲，还原剂的浓度和温度是最有影响力的，其他参数（例如粒度，搅拌速度，酸浓度和浸出时间）几乎无关紧要。最后，得出的结论是，从海洋结核中提取锰的最佳方法是重复使用废钢，以高的Fe ⁰ / MnO ₂比（2/1），低浓度的硫酸（0.1 mol / L）和短的时间工作。次（5分钟），提取率达到90％。