Hydrometallurgical Leaching of Manganese Using Hydrochloric Acid in The Presence of Thiourea from Um Bogma Area, Sinai, Egypt

The current study provides a new technological process for leaching manganese from a low-grade ore from Um-Bogma, Sinai, Egypt utilizing HCl acid in presence of thiourea as decreasing agent. The sample was analyzed utilizing wet chemical, XRD, and SEM techniques. The XRD data indicated the presence of many manganese minerals, including pyrolusite and jacobsite, as well as iron minerals including hematite and gibbsite, as well as dolomite and quartz crystals. The wet analysis proved that the primary ore components are MnO (37.72%) and Fe₂O₃ (26.81%). The leaching conditions were fully optimized in terms of HCl concentration, thiourea quantity, solid/liquid ratio, reaction time, temperature and stirring speed. Leaching parameters were studied and optimized as 4M HCl in the presence of thiourea (0.1 g) within a solid/liquid ratio of 1:5 at 80 °C for 45 min. Under the optimized conditions, the manganese recovery efficiency attained 96%, with low iron dissolution efficiency. The role of the leaching process is based on formation of thiourea radical in the acidic medium. The formed radical is responsible for the reduction of the unsoluble Mn (IV) to soluble Mn (II) form. The generated radical is responsible for the conversion of insoluble Mn (IV) to soluble Mn (II). The obtained leach liquor was then precipitated with various alkaline solutions include NaOH or Na₂CO₃. The resultant precipitate was dried at 100 °C and calcinated at 800 °C then subjected to chemical analysis. The kinetic data were examined using the shrinking core model, which revealed that the film diffusion and chemical reaction were more suited to the leaching process.