Copper sulfide

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Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.

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Prominent copper sulfide minerals include Cu2S (chalcocite) and CuS (covellite). In the mining industry, the minerals bornite or chalcopyrite, which consist of mixed copper-iron sulfides, are often referred to as "copper sulfides". In chemistry, a "binary copper sulfide" is any binary chemical compound of the elements copper and sulfur. Whatever their source, copper sulfides vary widely in composition with 0.5 ≤ Cu/S ≤ 2, including numerous non-stoichiometric compounds.

Known copper sulfides

The naturally occurring mineral binary compounds of copper and sulfur are listed below. Investigations of covellite (CuS) indicate that there are other metastable Cu-S phases still to be fully characterised. [1]

Classes of copper sulfides

Copper sulfides can be classified into three groups:

Monosulfides, 1.6 ≤ Cu/S ≤ 2: their crystal structures consist of isolated sulfide anions that are closely related to either hcp or fcc lattices, without any direct S-S bonds. The copper ions are distributed in a complicated manner over interstitial sites with both trigonal as well as distorted tetrahedral coordination and are rather mobile. Therefore, this group of copper sulfides shows ionic conductivity at slightly elevated temperatures. In addition, the majority of its members are semiconductors.

Mixed monosulfide and disulfide compounds of copper contain both monosulfide (S2−) as well as disulfide (S2)n− anions. Their crystal structures usually consist of alternating hexagonal layers of monosulfide and disulfide anions with Cu cations in trigonal and tetrahedral interstices. CuS, for example, can be written as Cu3(S2)S. Several nonstoichiometric compounds with Cu:S ratios between 1.0 and 1.4 also contain both monosulfide as well as disulfide ions. Depending on their composition, these copper sulfides are either semiconductors or metallic conductors.

At very high pressures, a copper disulfide, CuS2, can be synthesized. Its crystal structure is analogous to that of pyrite, with all sulfur atoms occurring as S-S units. Copper disulfide is a metallic conductor due to the incomplete occupancy of the sulfur p band. Different stoichiometric compositions can be obtained by changing the redox atmosphere of the synthetic environment.[6]

Oxidation states of copper and sulfur

The bonding in copper sulfides cannot be correctly described in terms of a simple oxidation state formalism because the Cu-S bonds are somewhat covalent rather than ionic in character, and have a high degree of delocalization resulting in complicated electronic band structures. Although many textbooks (e.g. [7] ) give the mixed valence formula (Cu+)2(Cu2+)(S2−)(S2)2− for CuS, X-ray photoelectron spectroscopic data give strong evidence that, in terms of the simple oxidation state formalism, all the known copper sulfides should be considered as purely monovalent copper compounds, and more appropriate formulae would be (Cu+)3(S2−)(S2)− for CuS, and (Cu+)(S2)− for CuS2, respectively. [8] [9] [10] [11] [12]

Further evidence that the assignment of the so-called "valence hole" should be to the S2 units in these two formulae is the length of the S-S bonds, which are significantly shorter in CuS (0.207 nm) and CuS2 (0.203 nm) than in the "classical" disulfide Fe2+(S2)2− (0.218 nm). This bond length difference has been ascribed to the higher bond order in (S-S)− compared to (S-S)2− due to electrons being removed from a π* antibonding orbital. [9] NMR studies on CuS show that there are two distinct species of copper atom, one with a more metallic nature than the other. [13] This apparent discrepancy with the X-ray photo-electron spectrum data simply highlights the problem that NMR has in assigning oxidation states in a mixed-valence compound. The issue of the valence of copper in sulfides (as well as selenides and tellurides) continues to be revisited in the literature. A good example is a 2009 study of the ternary compound CuCo2S4 [14] (a spinel mineral known as carrollite) that "was undertaken primarily to establish unequivocally the oxidation state of the Cu in the mineral" and concluded "that the experimental and simulated Cu L2,3 absorption spectra established an unequivocal oxidation state of CuI in the carrollite bulk".

See also

Related Research Articles

Bioleaching is the extraction of metals from their ores through the use of living organisms. This is much cleaner than the traditional heap leaching using cyanide. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to recover copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.

<span class="mw-page-title-main">Thiol</span> Any organic compound having a sulfanyl group (–SH)

In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".

<span class="mw-page-title-main">Chalcopyrite</span> Copper iron sulfide mineral

Chalcopyrite ( KAL-kə-PY-ryte, -⁠koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.

Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide.

<span class="mw-page-title-main">Chalcocite</span> Sulfide mineral

Chalcocite, copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system.

<span class="mw-page-title-main">Covellite</span> Sulfide mineral

Covellite is a rare copper sulfide mineral with the formula CuS. This indigo blue mineral is commonly a secondary mineral in limited abundance and although it is not an important ore of copper itself, it is well known to mineral collectors.

<span class="mw-page-title-main">Chalcogenide</span>

A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.

Sulfur compounds are chemical compounds formed the element sulfur (S). Common oxidation states of sulfur range from −2 to +6. Sulfur forms stable compounds with all elements except the noble gases.

<span class="mw-page-title-main">Copper monosulfide</span> Chemical compound

Copper monosulfide is a chemical compound of copper and sulfur. It was initially thought to occur in nature as the dark indigo blue mineral covellite. However, it was later shown to be rather a cuprous compound, formula Cu+3S(S2). CuS is a moderate conductor of electricity. A black colloidal precipitate of CuS is formed when hydrogen sulfide, H2S, is bubbled through solutions of Cu(II) salts. It is one of a number of binary compounds of copper and sulfur (see copper sulfide for an overview of this subject), and has attracted interest because of its potential uses in catalysis and photovoltaics.

In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation (i.e. water derived from precipitation) with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. Metals that have been leached from the oxidized ore are carried downward by percolating groundwater, and react with hypogene sulfides at the supergene-hypogene boundary. The reaction produces secondary sulfides with metal contents higher than those of the primary ore. This is particularly noted in copper ore deposits where the copper sulfide minerals chalcocite (Cu2S), covellite (CuS), digenite (Cu18S10), and djurleite (Cu31S16) are deposited by the descending surface waters.

<span class="mw-page-title-main">Digenite</span> Copper sulfide mineral

Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal - hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits.

<span class="mw-page-title-main">Djurleite</span> Copper sulfide mineral

Djurleite is a copper sulfide mineral of secondary origin with formula Cu31S16 that crystallizes with monoclinic-prismatic symmetry. It is typically massive in form, but does at times develop thin tabular to prismatic crystals. It occurs with other supergene minerals such as chalcocite, covellite and digenite in the enriched zone of copper orebodies. It is a member of the chalcocite group, and very similar to chalcocite, Cu2S, in its composition and properties, but the two minerals can be distinguished from each other by x-ray powder diffraction. Intergrowths and transformations between djurleite, digenite and chalcocite are common. Many of the reported associations of digenite and djurleite, however, identified by powder diffraction, could be anilite and djurleite, as anilite transforms to digenite during grinding.

<span class="mw-page-title-main">Ammonium tetrathiomolybdate</span> Chemical compound

Ammonium tetrathiomolybdate is the chemical compound with the formula (NH4)2MoS4. This bright red ammonium salt is an important reagent in the chemistry of molybdenum and has been used as a building block in bioinorganic chemistry. The thiometallate (see metallate) anion has the distinctive property of undergoing oxidation at the sulfur centers concomitant with reduction of the metal from Mo(VI) to Mo(IV).

<span class="mw-page-title-main">Carrollite</span>

Carrollite, CuCo2S4, is a sulfide of copper and cobalt, often with substantial substitution of nickel for the metal ions, and a member of the linnaeite group. It is named after the type locality in Carroll County, Maryland, US, at the Patapsco mine, Sykesville.

<span class="mw-page-title-main">Copper(I) sulfide</span> Chemical compound

Copper(I) sulfide is a copper sulfide, a chemical compound of copper and sulfur. It has the chemical compound Cu2S. It is found in nature as the mineral chalcocite. It has a narrow range of stoichiometry ranging from Cu1.997S to Cu2.000S. Samples are typically black.

<span class="mw-page-title-main">Cubanite</span> Copper iron sulfide mineral

Cubanite is a copper iron sulfide mineral that commonly occurs as a minor alteration mineral in magmatic sulfide deposits. It has the chemical formula CuFe2S3 and when found, it has a bronze to brass-yellow appearance. On the Mohs hardness scale, cubanite falls between 3.5 and 4 and has a orthorhombic crystal system. Cubanite is chemically similar to chalcopyrite, however it is the less common copper iron sulfide mineral due to crystallization requirements.

<span class="mw-page-title-main">Cobalt sulfide</span> Chemical compound

Cobalt sulfide is the name for chemical compounds with a formula CoxSy. Well-characterized species include minerals with the formulas CoS, CoS2, Co3S4, and Co9S8. In general, the sulfides of cobalt are black, semiconducting, insoluble in water, and nonstoichiometric.

The thiospinel group is a group of sulfide minerals with a general formula AB2X4 where A is nominally a +2 metal, B is a +3 metal and X is -2 sulfide or similar anion. Thio refers to sulfur and spinel indicates their isometric spinel-like structure.

Phosphorus selenides are a relatively obscure group of compounds. There have been some studies of the phosphorus - selenium phase diagram and the glassy amorphous phases are reported. The compounds that have been reported are shown below. While some of phosphorus selenides are similar to their sulfide analogues, there are some new forms, molecular P2Se5 and the polymeric catena-[P4Se4]x. There is also some doubt about the existence of molecular P4Se10.

<span class="mw-page-title-main">Palladium(II) sulfide</span> Chemical compound

Palladium(II) sulfide is a chemical compound of palladium and sulfur with the chemical formula PdS. Like other palladium and platinum chalcogenides, palladium(II) sulfide has complex structural, electrical and magnetic properties.

References

  1. ↑ Whiteside, L.S; Goble, R.J (1986). "Structural and compositional changes in copper sulfide during leaching and dissolution". The Canadian Mineralogist. 24 (2): 247–258.
  2. 1 2 3 4 5 6 Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN   0-19-855370-6
  3. ↑ http://rruff.geo.arizona.edu/doclib/hom/villamaninite.pdf Handbook of Mineralogy
  4. 1 2 Copper sulfides from Alberta; yarrowite Cu9S8 and spionkopite Cu39S28 R. J. Goble, The Canadian Mineralogist; (1980); 18; 4; 511-518
  5. ↑ Goble, R.J.; Robinson, G. (1980). "Geerite, Cu1.60S, a new copper sulfide from Dekalb Township, New York". The Canadian Mineralogist. 18 (4): 519–523.
  6. ↑ Mumme, W. G.; Gable, R. W.; Petricek, V. (2012-04-01). "The Crystal Structure of Roxybyite, Cu58S32". The Canadian Mineralogist. Mineralogical Association of Canada. 50 (2): 423–430. Bibcode:2012CaMin..50..423M. doi:10.3749/canmin.50.2.423. ISSN   0008-4476.
  7. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  8. ↑ Folmer, J.C.W; Jellinek, F (1980). "The valence of copper in sulphides and selenides: An X-ray photoelectron spectroscopy study". Journal of the Less Common Metals. Elsevier BV. 76 (1–2): 153–162. doi:10.1016/0022-5088(80)90019-3. ISSN   0022-5088.
  9. 1 2 Folmer, J.C.W.; Jellinek, F.; Calis, G.H.M. (1988). "The electronic structure of pyrites, particularly CuS2 and Fe1−xCuxSe2: An XPS and Mössbauer study". Journal of Solid State Chemistry. Elsevier BV. 72 (1): 137–144. Bibcode:1988JSSCh..72..137F. doi:10.1016/0022-4596(88)90017-5. ISSN   0022-4596.
  10. ↑ Romero-Jaime, A.K.; Vargas-Hernández, D.; Acosta-Enríquez, M.C.; Tánori-Córdova, J.C.; Valenzuela-Badilla, J.; Castillo, S.J. (March 2020). "Novel route for simplified and efficient synthesis of spiky-like copper sulfide nanoballs by soft chemistry method and their basic physicochemical characterizations". Materials Science in Semiconductor Processing. 107: 104830. doi:10.1016/j.mssp.2019.104830. S2CID   209705124.
  11. ↑ Goh, Siew Wei; Buckley, Alan N.; Lamb, Robert N. (2006). "Copper(II) sulfide?". Minerals Engineering. Elsevier BV. 19 (2): 204–208. Bibcode:2006MiEng..19..204G. doi:10.1016/j.mineng.2005.09.003. ISSN   0892-6875.
  12. ↑ Goh, Siew Wei; Buckley, Alan N.; Lamb, Robert N.; Rosenberg, Richard A.; Moran, Damian (2006). "The oxidation states of copper and iron in mineral sulfides, and the oxides formed on initial exposure of chalcopyrite and bornite to air". Geochimica et Cosmochimica Acta. Elsevier BV. 70 (9): 2210–2228. Bibcode:2006GeCoA..70.2210G. doi:10.1016/j.gca.2006.02.007. ISSN   0016-7037.
  13. ↑ Saito, Shin-hachiro; Kishi, Hideki; Nié, Kohji; Nakamaru, Hisakazu; Wagatsuma, Fumihiko; Shinohara, Takeshi (1997-06-01). "63Cu NMR studies of copper sulfide". Physical Review B. American Physical Society (APS). 55 (21): 14527–14535. Bibcode:1997PhRvB..5514527S. doi:10.1103/physrevb.55.14527. ISSN   0163-1829.
  14. ↑ Electronic environments in carrollite, CuCo2S4, determined by soft X-ray photoelectron and absorption spectroscopy
    Alan N. Buckley, William M. Skinner, Sarah L. Harmer, Allan Pring and Liang-Jen Fan
    Geochimica et Cosmochimica Acta Volume 73, Issue 15, 1 August 2009, Pages 4452-4467
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