A review of chloride assisted copper sulfide leaching by oxygenated sulfuric acid and mechanistic considerations

Abstract

Please cite this article as: Senanayake, G., A review of chloride assisted copper sulfide leaching by oxygenated sulfuric acid and mechanistic considerations, Hydrometallurgy (2009), doi: 10.1016/j.hydromet.2009.02.010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T AbstractThe beneficial effect of chloride on sulfide leaching in sulfuric acid has been widely reported over the last 3 to 4 decades but the reasons have not been resolved. A review of recent literature shows that sulfide leaching is complex due to alternative reaction paths, competitive reactions and interim compounds formed on solid surfaces or in solutions. This study focuses on analysis of rate data for covellite leaching by oxygenated sulfuric acid in the presence of sodium chloride and comparison with the leaching data of chalcocite. The published results for initial copper leaching from covellite are analysed on the basis of a shrinking particle kinetic model to determine the apparent rate constants and reaction orders with respect to the concentrations of chloride, dissolved oxygen, and hydrogen ions. The first stage leaching of chalcocite to an intermediate CuS appears to be controlled by the mass transport of oxygen to the sulfide surface. A comparison has been made between the second stage leaching of chalcocite and the initial leaching of pure covellite to produce elemental sulfur by considering the effect of temperature on dissolved oxygen concentration and apparent rate constants. The Arrhenius plots gave comparable values for activation energy for covellite (101 kJ. mol -1 ) and second stage leaching of chalcocite (96 kJ mol -1 ). A linear correlation of stability constants was used to determine equilibrium constants for the formation of CuS 2 and Cu(OH)(Cl). The peak potentials of voltammograms of covellite are in reasonable agreement with the predicted potentials based on thermodynamics of a range of solid phases including CuS, CuS 2 , Cu(OH)Cl, and Cu 2 Cl(OH) 3 . These observations are used to propose a reaction mechanism via mixed-ligand complex species.

Gold leaching by copper(II) in ammoniacal thiosulphate solutions in the presence of additives. Part I: A review of the effect of hard–soft and Lewis acid-base properties and interactions of ions

“…4 correspond to poor donators of electron pairs to metal ions. Thus, softness of ions can be used to rationalise the relative stability of the cation-anion interaction in water which can influence the stability of ion-pairs and metalligand complexes in water relevant to hydrometallurgical processes (Senanayake, 2004a(Senanayake, , 2008b). The measured solubility of metal ions in sea water (pH~8) can be rationalised on the basis of the solubility products (K SP ) of carbonate sediments of divalent or monovalent metal ions.…”

Leaching of Chalcopyrite in Acidified Nitrate Using Seawater-Based Media

“…Many researchers have argued that chloride ions are beneficial to leaching in the hydrometallurgical processing of chalcopyrite [1][2][3][4][5][6][7], owing to the formation of soluble copper chloro complexes [8,9]. Cupric and ferric ions have been tested as oxidants in chloride media [10][11][12][13] with beneficial results.…”

Study on the second stage of chalcocite leaching in column with redox potential control and its implications

“…Oxidative dissolution of chalcocite by Fe 3+ , O 2 or Cu 2+ , either in a sulfate or chloride system, occurs in two distinct stages with the production of secondary covellite (Cu 1.0-1.2 S) as an intermediate (Bolorunduro, 1999;Cheng and Lawson, 1991a;Dutrizac and MacDonald, 1974;Mao and Peters, 1983;Mcdonald and Langer, 1983;Miki et al, 2011;Mulak and Niemiec, 1969;Petersen and Dixon, 2003;Ruan et al, 2013;Ruiz et al, 1998Ruiz et al, , 2007Senanayake, 2007Senanayake, , 2009Sullivan, 1930;Thomas et al, 1967):…”