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The acidified ferrous sulfate leachi...

Perpich, Michael James,

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The acidified ferrous sulfate leaching of copper sulfides in the presence of oxygen and sulfur dioxide gas mixtures /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	The acidified ferrous sulfate leaching of copper sulfides in the presence of oxygen and sulfur dioxide gas mixtures // Michael James Perpich.
作者:	Perpich, Michael James,
面頁冊數:	1 electronic resource (227 pages)
附註:	Source: Dissertations Abstracts International, Volume: 59-06, Section: B.
Contained By:	Dissertations Abstracts International59-06B.
標題:	Chemistry. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9809761
ISBN:	9780591603101

The acidified ferrous sulfate leaching of copper sulfides in the presence of oxygen and sulfur dioxide gas mixtures /
Perpich, Michael James,

The acidified ferrous sulfate leaching of copper sulfides in the presence of oxygen and sulfur dioxide gas mixtures /Michael James Perpich. - 1 electronic resource (227 pages)

Source: Dissertations Abstracts International, Volume: 59-06, Section: B.

Past work on the use of oxygen and sulfur dioxide gas mixtures in acidified ferrous sulfate solutions to dissolve metal sulfides has been reviewed. This approach has proved useful since oxygen-sulfur dioxide gas mixtures have the ability to regenerate ferric ion after it has been reduced in the electrochemical dissolution of the sulfide. Evaluation of the ferric/ferrous iron ratio during metal sulfide dissolution has shown this to be true. Specifically, the use of this system has led to improved recoveries and faster dissolution kinetics for ZnS, FeS$\\sb2$, and NiS under laboratory conditions. In this study the above system was used to oxidize chalcocite (Cu$\\sb2$S), covellite (CuS) and chalcopyrite (CuFeS$\\sb2$). Significant improvements in the kinetics and recoveries of Cu$\\sb2$S and CuS were observed when using the oxygen-sulfur dioxide gas mixture and ferrous sulfate over systems which use ferric sulfate. However, little improvement was observed in the case of CuFeS$\\sb2$. Electrochemical tests (redox potential measurements, anodic and cathodic polarization curves and polarization resistance) were run on copper sulfide electrodes in order to better understand the mechanisms controlling copper sulfide leaching behavior. It was shown that Cu$\\sb2$S oxidizes by a process which is cathodically controlled while CuS and CuFeS$\\sb2$ oxidize by processes which are anodically controlled. In the case of CuS, the oxygen-sulfur dioxide system was able to overcome the anodic inhibition by maintaining high redox potentials in the solution. These high potentials act as a driving force for electron flow despite the formation of highly protective and semi-insulating reaction product films in the later stages of leaching. In the absence of oxygen-sulfur dioxide gas mixtures, the ratio of Fe$\\sp{+++}$/Fe$\\sp{++}$ would decrease with time leading to low redox potentials and low leaching rates. In the case of CuFeS$\\sb2$, the anodic inhibition is so high that despite the high redox potentials, little improvement in the leaching rate is observed. However, the situation changes when a small amount of Ag$\\sp+$ is added to the system. Under these conditions the Ag$\\sp+$ ion effectively prevents the formation of a highly protective reaction product film. This in combination with the high redox potentials leads to very rapid and complete oxidation of the CuFeS$\\sb2$. Based on the experimental data obtained from both chemical and electrochemical tests, models are proposed for the leaching of the three sulfides. In addition, electrochemical dissolution rates obtained using both mixed potential theory and polarization resistance are shown to correlate well with dissolution rates obtained from chemical leaching tests during the initial stages of leaching.

English

ISBN: 9780591603101Subjects--Topical Terms:

516420
Chemistry.

The acidified ferrous sulfate leaching of copper sulfides in the presence of oxygen and sulfur dioxide gas mixtures /
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520 $a Past work on the use of oxygen and sulfur dioxide gas mixtures in acidified ferrous sulfate solutions to dissolve metal sulfides has been reviewed. This approach has proved useful since oxygen-sulfur dioxide gas mixtures have the ability to regenerate ferric ion after it has been reduced in the electrochemical dissolution of the sulfide. Evaluation of the ferric/ferrous iron ratio during metal sulfide dissolution has shown this to be true. Specifically, the use of this system has led to improved recoveries and faster dissolution kinetics for ZnS, FeS$\\sb2$, and NiS under laboratory conditions. In this study the above system was used to oxidize chalcocite (Cu$\\sb2$S), covellite (CuS) and chalcopyrite (CuFeS$\\sb2$). Significant improvements in the kinetics and recoveries of Cu$\\sb2$S and CuS were observed when using the oxygen-sulfur dioxide gas mixture and ferrous sulfate over systems which use ferric sulfate. However, little improvement was observed in the case of CuFeS$\\sb2$. Electrochemical tests (redox potential measurements, anodic and cathodic polarization curves and polarization resistance) were run on copper sulfide electrodes in order to better understand the mechanisms controlling copper sulfide leaching behavior. It was shown that Cu$\\sb2$S oxidizes by a process which is cathodically controlled while CuS and CuFeS$\\sb2$ oxidize by processes which are anodically controlled. In the case of CuS, the oxygen-sulfur dioxide system was able to overcome the anodic inhibition by maintaining high redox potentials in the solution. These high potentials act as a driving force for electron flow despite the formation of highly protective and semi-insulating reaction product films in the later stages of leaching. In the absence of oxygen-sulfur dioxide gas mixtures, the ratio of Fe$\\sp{+++}$/Fe$\\sp{++}$ would decrease with time leading to low redox potentials and low leaching rates. In the case of CuFeS$\\sb2$, the anodic inhibition is so high that despite the high redox potentials, little improvement in the leaching rate is observed. However, the situation changes when a small amount of Ag$\\sp+$ is added to the system. Under these conditions the Ag$\\sp+$ ion effectively prevents the formation of a highly protective reaction product film. This in combination with the high redox potentials leads to very rapid and complete oxidation of the CuFeS$\\sb2$. Based on the experimental data obtained from both chemical and electrochemical tests, models are proposed for the leaching of the three sulfides. In addition, electrochemical dissolution rates obtained using both mixed potential theory and polarization resistance are shown to correlate well with dissolution rates obtained from chemical leaching tests during the initial stages of leaching.
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