1.Shandong Institute of Geological Sciences,Jinan 250013,China; 2.Key Laboratory of Ministry of Land and Resources for Mineralization Processes of Gold Mine and Resources Utilization,Jinan 250013,China
Abstract：Manganese oxide is an important class of mineral in manganese ore, and it is also a class of manganese ore which is most widely used in industry. At present, however, the studies of manganese oxide in manganese ore are only limited to the specific mineral in one mine area. Many manganese oxide ores in most mine areas in China cannot be covered.Various kinds of manganese oxide ores from different mine areas were selected to screen out the monomineral of pyrolusite, manganite and braunite. Five types of leaching agents were added, including hydroxylamine hydrochloride-hydrochloric acid, oxalic acid-sulfuric acid, sulfinic acid (H2SO3), sulfuric acid-hydrofluoric acid-potassium fluoride (H2SO4-HF-KF) and metaphosphoric acid(HPO3). The leaching rates of all samples were higher than 98% for hydroxylamine hydrochloride-hydrochloric acid system, which was applicable for all monominerals used. In order to further obtain the optimal leaching conditions, three types of monomineral were tested with different leaching time (10 min~1.5 h), hydroxylamine hydrochloride mass concentration (5-40 g/L) and hydrofluoric acid(0.2+99.8)-(3+97) (in other words, the volume fraction range of HCl was 0.2%-3%). The results showed that the leaching rates of three monominerals were higher than 99.5% when the leaching time was 10 min-1.5 h, the hydroxylamine hydrochloride mass concentration was higher than 20 g/L and the acidity was not less than HCl (1+99) (i.e., the volume fraction of HCl was not less than 1%). Since the original minerals were complicated, the following conditions were finally determined: 50 mL of 20 g/L hydroxylamine hydrochloride-hydrochloric acid (1+99) was added into manganese oxide ore and the sample was leached in boiling water bath for 1.0 h,Mn3+ and Mn4+ in mineral were reduced to Mn2+, the original mineral structure was destroyed to release manganese. After filtration, the content of manganese in solution was determined by inductively coupled plasmas atomic emission spectrometry (ICP-AES). The detection limit was 0.7 μg/g. The proposed method was applicable for the analysis of manganese oxide ores in most mine areas in China. The original manganese ore sample was determined according to the experimental method. The relative standard deviations (RSD, n=12) were 0.39% and 1.1%. The recoveries of monomineral were between 99.7% and 102.3%.
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