Ethylxanthate Adsorption on Copper Sulfide Influence of the Copper Sulfide Composition

Abstract

In this work, the influence of a mineral composition (copper sulfide) on the adsorption of a surfactant molecule used for mineral flotation is studied. Flotation is the method used to separate minerals (e.g., copper minerals) from gangue. The process is based on the adsorption of air bubbles on the particles of the mineral making them lighter than water and giving the possibility of separation. The extent of adsorption of air bubbles depends on the mineral hydrophobicity and is improved by adding a surfactant molecule (the collector) which adsorbs on the mineral particles in the ore suspension.Ethylxanthate (EtX Ϫ ) is a typical member of the o-alkyldithiocarbonates R-O-CS 2Ϫ collector family. Numerous electrochemical and spectroscopic studies of its interactions with galena PbS, 1-12 silver, 13-15 silver sulfide, 15 copper, [16][17][18][19][20] and copper sulfide 3,11,18,21-48 have been published. The generally recognized adsorption mechanism of EtX Ϫ occurs by two steps a charge transfer induced chemisorption process EtX Ϫ r EtX ads ϩ e Ϫ [1] the formation of the M-EtX compound EtX Ϫ ϩ M r M-EtX ϩ e Ϫ for a metal or [2]The ethylxanthate anion is chemically bound to the metal atom that remains in the copper sulfide crystal structure after the first step. Underpotential deposition (UPD) is invoked and can be used to explain the formation of such an adsorbed ethylxanthate. 3,11,18, After the second step, the metal has left the crystalline framework and binds to the ethylxanthate ions to form the compound M-EtX. Both steps involve electron transfer and may be observed by electrochemical methods such as voltammetry. In the case of copper, 16,18,36 the chemisorption peak (sometimes split into two subpeaks) has been observed at about Ϫ0.46 V vs. standard hydrogen electrode (SHE), followed by the Cu-EtX formation at Ϫ0.250 V vs. SHE. On copper sulfide, 3,11,18,21,25,33,36,40,44 all the authors refer to two chemisorption peaks followed by the formation of Cu-EtX multilayers. However, from one study to another the characteristic potentials vary between Ϫ0.346 and Ϫ0.130 V vs. SHE for the first peak and between Ϫ0.256 and Ϫ0.360 V vs. SHE for the second one, whereas the second step of the mechanism takes place between 0.115 and 0.120 V vs. SHE. It is known that at room temperature, the copper-sulfur phase diagram shows four stable and distinct phases: chalcocite (Cu 2 S), djurleite (Cu 1.96 S), anilite (Cu 1.75 S), and covellite (CuS). 49-57 Each phase presents a small domain of deviation from ideal composition. For instance, the chalcocite domain extends from Cu/S ϭ 2 to Cu/S ϭ 1.993. Thus, the copper sulfide formula is generally represented by Cu 2Ϫx S; x being called the deviation from stoichiometry (0 < x < 1). The exact composition of the sulfide used for these studies is not always specified; it is often referenced as chalcocite (Cu 2 S) but without a precise indication of composition verification. This indicates that according to the copper sulfide composition, the ethylxanthate adsorption is not carried out in the...

Pulverization‐Tolerance and Capacity Recovery of Copper Sulfide for High‐Performance Sodium Storage

“…[28,29] Large sodium cannot replace copper atoms unlike lithiation case in CuS due to high formation energy, which engenders formation of Na-Cu-S ternary system to generate Na 3 (CuS) 4 /Na 2 S semicoherent boundary ( Figure S13, Supporting Information). As a result, CuS nanoplates well retain the recovered capacity and the original morphology even after full disintegration.…”