Reductive Leaching of Low-Grade Pyrolusite with Formic Acid
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TRODUCTION
MANGANESE is important in many fields, such as ferrous metallurgy, nonferrous metal production, battery production, cell, and fine chemicals.[1,2] In the past decades, more and more attention has been paid to the exploitation of low- or middle-grade ores due to the shortage of high-grade ores and the increasing demand for manganese.[3] Considerable research interests are focused on the new reduction methods of manganese from pyrolusite. Pyrometallurgy, biometallurgy, and hydrometallurgy are the main types of metallurgy method for the reduction of manganese dioxide ore. Pyrite,[4,5] CO,[6] pure sulfur,[7] H2,[8] sawdust,[9] cornstalk,[10] and bagasse pith[11] are the several common reductants used in pyrometallurgy. High energy consumption, insufficient heat and mass transfer, and severe environmental pollution are considered as the disadvantages of the pyrometallurgy process.[12] In the approach of biometallurgy, manganese-reducing bacteria can be employed to leach manganese into the acid medium. But a less expensive and more environmentally friendly bioleaching process is being expected with a higher leaching efficiency.[13] For the low- or middle-grade pyrolusite, hydrometallurgy is extensively applied in the reduction of quadrivalence manganese because of its efficiency and economy. Generally, there are three kinds of hydrometallurgical reductants: organic materials including glucose,[14–16] sucrose,[17] cellulose,[18] and methanol[19]; inorganic materials including pyrite,[20] hydrogen peroxide,[21] and sulfur dioxide[22]; biomass including YOUZHI LU, Postgraduate, AIQUN YUAN, Professor, ZENGWEI HUANG, Associate Professor, and ZEGUANG ZHOU, Senior Experimentalist, are with the School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning 530006, P.R. China. Contact e-mail: [email protected] HUAJU MA and RUNJUN HUANG, Associate Professors, are with the Guilin University of Technology at Nanning, Nanning 530001, P.R. China. Manuscript submitted November 16, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
molasses[23]and molasses alcohol wastewater,[24] sawdust,[25] corncob,[26] dried leaves,[27] waste tea-leaves,[28] and so on. Although there have been many reductants reported on hydrometallurgy, few C1 organic reductants have been investigated. We have developed a new hydrometallurgy method for reduction of low-grade pyrolusite by using formic acid as reductant in sulfuric acid solution.
II.
MATERIALS AND METHODS
A. Materials The sample of low-grade pyrolusite is obtained from Daxin manganese Mine, Guangxi, China. The other chemicals are analytical grade and used without purification. The chemical multielemental analysis results of pyrolusite are shown in Table I. X-ray diffraction (XRD) image of the ore sample is shown in Figure 1(a). It can be seen that manganese is primarily in the form of manganese dioxide in the low-grade pyrolusite, and the main gangue minerals include quart (SiO2), hematite (Fe2O3), aluminum oxide (Al2O3), kaolinite (Al2Si2O5(OH)2), and purpurite (MnFe2(PO
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