Kyushu University · Environmental Science
Professor Hajime Miki's research lab specializes in hydrometallurgy and mineral processing, with a focus on the selective separation and recovery of valuable metals from complex sulfide ores, particularly copper–molybdenum ores. The lab investigates fundamental surface chemistry, electrochemical behavior, and reagent mechanisms in flotation and leaching processes, aiming to develop environmentally safer and more efficient methods for mineral processing. Key research directions include the development of alternative depressants to replace toxic reagents like NaHS, the application of electrochemical techniques to control mineral surface properties, and the use of novel lixiviants such as chloride and sulfite-based systems for selective metal extraction.
Figures are computed from collected data and may differ slightly.
Electrolysis oxidation of chalcopyrite and molybdenite was investigated, via various electrochemical methods, with the aim of realizing selective flotation of these minerals. Result of potential polarization indicated that oxidation via electrolysis affected only the chalcopyrite surface, owing mainly to the difference in conductivity of these minerals. Also measurements of contact angle after electrolysis indicated that contact angle of chalcopyrite selectively decreased whereas that of molybde
Sodium hydrogen sulfide (NaHS) is commonly used as a copper depressant in the selective flotation of copper and molybdenum ores. However, the process is facing health and safety issues because NaHS readily yields toxic hydrogen sulfide gas (H2S) under acidic conditions. In this study, Na2SO3 was proposed as an alternative copper depressant. The effect of Na2SO3 on the surface wettability and floatability of chalcopyrite and molybdenite—typical copper and molybdenum minerals, respectively—was int
An alternative approach to the heap leaching of copper sulfide minerals involves the use of chloride ions as the lixiviant. The facile oxidation of copper(I) ions in a chloride system by atmospheric oxygen offers an alternative to bio-oxidation of iron(II) in the sulfate system. In the chloride system, it is well-known that both copper(II) and iron(III) ions can act as the oxidants for these minerals. However, regeneration of these species by oxidation with dissolved oxygen is required and this
Sodium metabisulfite (MBS) was used in this study for selective flotation of chalcopyrite and molybdenite. Microflotation tests of single and mixed minerals were performed to assess the floatability of chalcopyrite and molybdenite. The results of microflotation of single minerals showed that MBS treatment significantly depressed the floatability of chalcopyrite and slightly reduced the floatability of molybdenite. The results of microflotation of mixed minerals demonstrated that the MBS treatmen
The copper ore in Chilean copper porphyry deposits is often associated with molybdenum minerals. This copper–molybdenum (Cu–Mo) sulfide ore is generally mined from various locations in the mining site; thus, the mineral composition, oxidation degree, mineral particle size, and grade vary. Therefore, in the mining operation, it is common to blend the ores mined from various spots and then process them using flotation. In this study, the floatability of five types of Cu–Mo ores and the blending of
An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and is sensitive compared with conventional electrode systems for various sulfide minerals such as pyrite, chalcopyrite, chalcocite, enargite, and tennantite. The leaching behavior of chalcopyrite was re-examined in a tes
Batch leaching behavior of ground chalcopyrite (median particle diameter 6 μ mm) was investigated anaerobically by a shaking flask method. The experiments used 0.1 mol dm-3 sulfuric acid solutions containing 0.25 mol dm-3 ferric ions and known concentrations of ferrous and cupric ions at 303 K. The initial pulp density of the chalcopyrite was 10 kg m-3.When 1.00 mol dm-3 of ferrous ions were added, copper extraction proceeded in three steps: (1) an induction period, (2) a leaching period, and (3
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