کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
211871 462022 2016 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Catalytic and galvanic effects of pyrite on ferric leaching of sphalerite
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی مهندسی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
Catalytic and galvanic effects of pyrite on ferric leaching of sphalerite
چکیده انگلیسی


• Galvanic processes at Esol > 500 mV ensure a rapid and almost complete Zn dissolution.
• 98.9% of sphalerite dissolution was reached in 6 h at 70 °C, for fine particles.
• For coarse particle size, 75% of sphalerite dissolution was reached in 7 h.
• The difference between the mineral rest potentials promotes Zn dissolution.
• The zinc leaching rate was considerably enhanced by a synergetic effect pyrite/Fe3 +.

The catalytic and galvanic effects of pyrite on the dissolution kinetics of a zinc sulfide concentrate in an acidified ferric sulfate medium were assessed. The effects of particle size, oxidant concentration (ferric ion), and amount of pyrite added with respect to the original amount of zinc concentrate was explored, while temperature (70 °C), hydrogen potential (pH = 1.0) and agitation speed (600 rpm) of the leach solution were held constant. A process based on the galvanic coupling between pyrite and sphalerite at solution potentials above 500 mV to ensure rapid and complete sphalerite dissolution in a ferric sulfate medium is proposed. As a result, the highest zinc extraction in the shortest possible time was obtained through minimizing the formation of a passivating film, which inhibits further reaction, and by a synergetic effect between pyrite and sphalerite. The rate of zinc leaching was considerably improved by doping with pyrite in the presence of Fe3 +. The results have demonstrated that it was possible to achieve 98.9% zinc extraction with doping pyrite in 6 h and 85% zinc extraction without pyrite in 7 h, both results being for a fine grain size. Ferric leaching reached 75% Zn extraction with doped pyrite and 70% without it, both in 7 h using a coarse grain size. Scanning electron microscopy (SEM) images show a passivating layer on the sphalerite surface after ferric leaching without pyrite, while in presence of pyrite this layer was not observed and the pyrite surface was not attacked. The galvanic interaction between pyrite and sphalerite particles can be explained by the difference between their Fermi energies and the electrochemical potential of the solution. During this process pyrite remains mostly unleached, acting as a redox catalyst (electron-accepting) for sphalerite (electron-donating) dissolution. This diminishes the typical passive behavior of sphalerite in a ferric solution enhancing considerably the kinetics of sphalerite. This confirms that the difference between the rest potentials of pyrite and sphalerite is the driving force that improves zinc dissolution. For an industrial hydrometallurgical operation, using an appropriate sphalerite-pyrite concentrate does not necessarily represent a significant cost because the ore contains both sulfides.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Hydrometallurgy - Volume 163, August 2016, Pages 167–175
نویسندگان
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