TECHNICAL PAPER Preparation of Industrial Manganese Compound from a Low-Grade Spessartine Ore by Hydrometallurgical Process Alafara A. Baba 1 • Aishat Y. Abdulkareem 1,2 • Mustapha A. Raji 1 • Kuranga I. Ayinla 1 • Folahan A. Adekola 1 • Rafiu B. Bale 3 • Malay K. Ghosh 4 Received: 9 January 2018 / Accepted: 9 July 2018 Ó The Indian Institute of Metals - IIM 2018 Abstract The increasing global demands for pure man- ganese in steel production and manganese compound as dietary additives, fertilizer, pigment, cells and fine chemi- cals production cannot be over-emphasized. Thus, contin- uous efforts in developing low cost and eco-friendly route for purifying the manganese ore to meet some defined industrial demands become paramount. Therefore, this study focused on reductive leaching and solvent extraction techniques for the purification of a Nigerian manganese ore containing admixture of spessartine (O 96.00 Mn 24.00 Al 16.00- Si 24 . 00 ) and quartz (Si 3.00 O 6.00 ). During leaching, parame- ters such as leachant concentration and reaction temperature on the extent of ore dissolution were examined accordingly for the establishment of extraction conditions. At optimal leaching conditions (1.5 mol/L H 2 SO 4 ? 0.2 g spent tea, 75 °C), 80.2% of the initial 10 g/L ore reacted within 120 min. The derived dissolution activation energy (Ea) of 35.5 kJ/mol supported the diffusion reaction mechanism. Thus, the leachate at optimal leaching was appropriately treated by alkaline precipitation and solvent extraction techniques using sodium hydroxide and (di-2- ethylhexyl) phosphoric acid (D2EHPA) respectively, to obtain pure manganese solution. The purified solution was further beneficiated to obtain manganese sulphate mono- hydrate (MnSO 4 .H 2 O, melting point = 692.4 °C: 47-304- 7403) of high industrial value. The unleached residue (* 19.8%) analyzed by XRD consisted of silicileous impurities (SiO 2 ) which could serve as an important by- product for some defined industries. Keywords Spessartine ore  Nigeria  Manganese  Manganese compound  Reductive leaching  Solvent extraction  D2EHPA 1 Introduction To date, manganese is an important nonferrous element with wide arrays of applications in steel production, preparation of dietary additives, fertilizers, pigments, cells and fine chemicals. To meet the ever increasing industrial demand for manganese, coupled with the gradual depletion of high grade manganese ore, many efforts have been made to recover this metal from low grade ores [1, 2]. However, with the extensive exploitation and consumption of high grade manganese ore (total Mn [ 35%), considerable attention is focused on the development and utilization of the low grade manganese ore (total Mn \ 35%), which has a low business value [3]. Pyrolusite (MnO 2 ) and most importantly spessartine (Mn 3 Al 2 (SiO 4 ) 3 ), are examples of industrial manganese ores that can be processed in meeting the aforementioned demands. The conventional pyro-metallurgical processes for uti- lizing manganese ores are often characterized by high energy consumption and production cost coupled with low productivity and environmental pollution [4]. Conversely, & Alafara A. Baba baalafara@yahoo.com; alafara@unilorin.edu.ng & Aishat Y. Abdulkareem iishahay876@gmail.com 1 Department of Industrial Chemistry, University of Ilorin, P.M.B 1515, 240003 Ilorin, Nigeria 2 National Mathematical Centre, Sheda-Kwali, P.M.B 118, Abuja, Nigeria 3 Department of Geology and Mineral Sciences, University of Ilorin, P.M.B 1515, 240003 Ilorin, Nigeria 4 CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, India 123 Trans Indian Inst Met https://doi.org/10.1007/s12666-018-1376-y