**Leaching Manganese Nodules in an Acid Medium and Room Temperature Comparing the Use of Di**ff**erent Fe Reducing Agents**

**David Torres 1,2, Luís Ayala 3, Manuel Saldaña 1, Manuel Cánovas 1, Ricardo I. Jeldres 4, Steven Nieto 4, Jonathan Castillo 5, Pedro Robles <sup>6</sup> and Norman Toro 1,3,\***


Received: 23 October 2019; Accepted: 4 December 2019; Published: 6 December 2019

**Abstract:** The deposits of Fe-Mn, in the seabed of the planet, are a good alternative source for the extraction of elements of interest. Among these are marine nodules, which have approximately 24% manganese and may be a solution to the shortage of high-grade ores on the surface. In this investigation, an ANOVA analysis was performed to evaluate the time independent variables and MnO2/reducing agent in the leaching of manganese nodules with the use of different Fe reducing agents (FeS2, Fe2<sup>+</sup>, Fe0 and Fe2O3). Tests were also carried out for the different reducing agents evaluating the MnO2/Fe ratio, in which the Fe<sup>0</sup> (FeC) proved to be the best reducing agent for the dissolution of Mn from marine nodules, achieving solutions of 97% in 20 min. In addition, it was discovered that at low MnO2/Fe ratios the acid concentration in the system is not very relevant and the potential and pH were in ranges of −0.4–1.4 V and −2–0.1 favoring the dissolution of Mn from MnO2.

**Keywords:** MnO2; acid media; ANOVA; dissolution
