Aqueous Copper Sulfide Clusters as Intermediates during Copper Sulfide Formation

Abstract

Using a combination of experimental techniques, we show that Cu(II) reduction by sulfide to Cu(I) occurs in solution prior to precipitation. EPR and 63Cu NMR data show that reduction to Cu(l) occurs during the reaction of equimolar amounts of Cu(II) with sulfide. 63Cu solution NMR data show that Cu(I) is soluble when bound to sulfide and is in a site of high symmetry. EPR data confirm that Cu(I) forms in solution and that the mineral covellite, CuS, contains only Cu(I). Mass spectrometry data from covellite as well as laboratory prepared solid and solution CuS materials indicate that Cu3S3 six-membered rings form in solution. These trinuclear Cu rings are the basic building blocks for aqueous CuS molecular clusters, which lead to CuS precipitation. In controlled titration experiments where sulfide is slowly added to Cu(II), Cu3S3 rings and tetranuclear Cu molecular clusters (Cu4S5, and Cu4S6) form; the rings are composed primarily of Cu(II). During cluster formation from Cu3S3 condensation, some Cu(II) is released back into solution, indicating that Cu(II) reduction does not occur until after Cu-S bond and higher order cluster formation. Analysis of the frontier molecular orbitals for Cu(II) and sulfide indicate that an outer-sphere electron transfer is symmetry forbidden. These results are consistent with the formation of CuS bonds prior to electron transfer, which occurs via an inner-sphere process.

Sulfidation as a Natural Antidote to Metallic Nanoparticles Is Overestimated: CuO Sulfidation Yields CuS Nanoparticles with Increased Toxicity in Medaka (Oryzias latipes) Embryos

“…CuS clusters have been reported as intermediates in the process of copper ion conversion to CuS in aqueous solution. 37 Our study visually presented the CuS clusters (1−3 nm) or particles (<12 nm) to evidently support the dissolution−precipitation mechanism.…”

Synthesis of Mesostructured Copper Sulfide by Cation Exchange and Liquid‐Crystal Templating

“…It is well known that aqueous formation of copper sulfides is complex and can produce both CuS and Cu 2 S depending on the reaction conditions. [22][23][24] Therefore, it may be possible that we have a mixture of both Cu 2 S and CuS nanoparticles, which we are currently investigating. The breadth of the peak at 375 nm can be attributed to the polydispersity of the Cu x S nanocrystals within the mesostructures.…”

Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

“…To achieve the observed suppression of cyanide oxidation one must start with copper(I) sulfide. This suggests that the reaction of cyanide with copper(I) sulfide may give a series of copper cyanide complexes in equilibrium with sulfide that stabilize the sulfide (similar compounds have been described elsewhere [33]). These sulfur compounds not only decrease the eventual limiting current below the values for non-CuO catalyzed cyanide oxidation (equations steps 1 to 4), but also, after a short delay, they inhibit the CuO catalysis.…”