Copper-containing Minerals Research Articles

Study of the basic laws of dissolution of gold and copper in solutions with an ultra-low concentration of sodium cyanide

The work sets out to study the basic physicochemical dissolution patterns of gold, copper, and natural copper-containing minerals (chalcopyrite, bornite and azurite) in solutions with an ultra-low concentration of sodium cyanide (from 0.102∙10-3 to 4.08∙10-3 mol/L). The influence of various factors on the rate of dissolution of Au and Cu in solutions with ultra-low NaCN concentrations was studied by the rotating disk method; for natural copper minerals, the powder diffraction method was used. The concentration of gold and copper in solutions was determined by atomic absorption analysis. The chemical composition of the studied copper minerals was determined using the X-ray phase method, while the specific surface of the minerals was detected using a laser granulometer. The process of gold dissolution is shown to proceed in both diffusion and kinetic regions. In the diffusion region, the rate constant was 0.334∙10-6 L∙cm-2∙s-1/2∙rad-1/2; in the kinetic region – 0.919∙10-6 L∙cm-2∙s-1/2. The calculated value of the apparent activation energy for the diffusion region was 22.5 kJ/mol; for the kinetic region – 40.1 kJ/mol. The addition of glycine to a solution with an ultra-low concentration of sodium cyanide is shown to increase the specific dissolution rate of gold by 1.2 times: from 0.692∙10-9 to 0.82∙10-9 mol/cm2∙s. The process of copper dissolution is shown to take place in the diffusion r egion. The rate constant was 0.496∙ 10-6 L∙cm-2∙s-1/2∙rad-1/2 at an activation energy of 17.0 kJ/mol. With a fractional supply of sodium cyanide, the dissolution rate of copper minerals is reduced by 10–30% compared to a single load. The calculated apparent activation energy values for chalcopyrite, bornite, and azurite were 22.03, 24.2, and 24.1 kJ/mol, respectively. Thus, the use of ultra-low concentrations of NaCN in the process of cyanidation of gold and copper has a positive effect, which can be used i n the processing of gold-copper raw materials to significantly reduce the consumption of sodium cyanide.

Preparation of benzoxazoles and benzothiazoles utilizing naturally occurring copper-containing mineral catalyst precursors

Copper is one of the most abundant metals on Earth, and although it is mainly used in other fields, copper catalysis is also widely used in preparative organic syntheses. As copper production has recently exceeded a yearly amount of 20 million tons, using minerals instead of pure copper compounds can lower the need for such processes and can lead to more economical and environmentally friendly procedures. Such a method is the subject of our present study in which the preparation of 2-substituted benzoxazoles and benzothiazoles is presented from inexpensive starting materials in a simple setup, in the presence of naturally occurring copper-containing minerals. A total of 7 readily available minerals were tested in our model reaction and the reaction was feasible with all of them. With our method, a wide variety of benzoxazoles and benzothiazoles were prepared in good yields and high purity. The reaction could be carried out regardless of the origin of the minerals.

The Colour of Pine Needles and Nightingales. A Traditional Japanese Copper-based Green Pigment

AbstractThe article describes a historic Japanese green pigment which was identified in a painting attributed to the Kano school, dating to the Edo period. According to literature, malachite – which is the common translation of the Japanese termrokushō –has been the most widely used green pigment in Japan over a long period of time. Its colour shade could be modified by the use of different degrees of grinding and by heating the pigment. The green paint layer found in the painting was examined using XRF, SEM-EDS and XRPD, and cross sections. Examinations revealed a heterogeneous paint layer which consists of a mixture of various natural copper-containing minerals, some of which also contain arsenic and other elements. A concluding discussion of pigment nomenclature in Japan raises the question ifrokushōmay in fact be equated with pure malachite.

Efficient activation of peroxymonosulfate by copper sulfide for diethyl phthalate degradation: Performance, radical generation and mechanism

Copper-containing minerals have been extensively used in Fenton-like processes for degradation of pollutants and have exhibited great potential for environmental remediation. This work reports the first use of copper sulfide (CuS), a typical Cu-mineral, for the activation of peroxymonosulfate (PMS) for pollutant degradation; the study also elucidates the underlying mechanism of these processes. Copper sulfide effectively activated PMS to degrade diethyl phthalate (DEP). Electron paramagnetic resonance, free radical quenching, X-ray photoelectron spectroscopy, X-ray diffraction analyses and DFT calculations confirmed that ≡Cu (I)/≡Cu (II) cycling on the surface of CuS provided the main pathway to activate PMS to produce highly oxidative species. Unlike conventional sulfate radical-based PMS activation processes, hydroxyl radical (•OH) were found to be the dominant radical in the tested CuS/PMS system, which performed more efficiently than an alternative •OH-based oxidation system (CuS/H2O2) for DEP degradation. In addition, the presence of anions such Cl− and NO3− has limited inhibition effects on DEP degradation. Overall, this study provides an efficient pathway for PMS-based environmental remediation as well as a new insight into the mechanism of PMS activation by Cu-containing minerals.

Study on the A3-coupling reaction catalyzed by readily available copper-containing minerals. Synthesis of propargylamines

The highly atom efficient three-component reaction of aldehydes, secondary amines and acetylenes to form propargylamines (A3-coupling) has been studied with twelve readily available copper-containing minerals. It was found that the reaction could easily be performed in the presence of malachite, brochantite, chrysocolla and azurite in toluene at reflux. The desired products were obtained in good to excellent yields.

Chalcophile chemistry for enhanced detection of copper in its compounds and minerals

Samples of elemental copper, upon laser irradiation under negative-ion LDI-MS conditions, do not generate noticeable signals for copper-bearing gaseous ions. In contrast, a several thousand-fold enhancement of the generated ion current was observed when freshly made mixtures of copper and sulfur powders were laser-ablated. Time-of-flight mass spectra recorded showed a range of peaks with m/z ratios extending to over m/z 8000, indicating the formation in situ of an array of Cu–S ion clusters by a chemical reaction that takes place between the two elements upon laser irradiation. Evidently, sulfur acts as a potent reactive matrix and generates at least three distinguishable series of ion clusters: Cu1Sx− (x = 2, 3, 4…), Cu2Sy− (y = 3, 4, 5…), and Cu3Sz− (z = 3, 4, 5…). Laser ablation of CuS alone did not produce signals beyond m/z 600. Some of the high-mass ions formed in this manner were isobaric; consequently, composite peaks were observed under low-resolution MS conditions. Under high-resolution conditions, however, we were able to separate and determine the composition of some isobaric mixtures. For example, the peak recorded at m/z 287 was resolved to two peaks that represented primarily the 63Cu265Cu32S3− and 63Cu32S7− ions. Intriguingly, the spectra recorded from many copper-containing minerals mixed with sulfur were remarkably similar to those acquired from copper-and-sulfur mixtures, which demonstrated that elemental sulfur has the ability to extract chemically bound copper even from its compounds, and form gas-phase Cu–S clusters of varying composition.

Small‐scale distribution of copper in a Technosol horizon studied by nano‐scale secondary ion mass spectrometry

In contaminated soil, copper (Cu) is commonly distributed among various very small particles. To enlighten the qualitative distribution of Cu in a contaminated Technosol (a soil developed from deposited technogenic material) on the sub-micron scale, we used nano-scale secondary ion mass spectrometry (NanoSIMS). We studied seven areas (up to 40μm×40μm) on a thin section of a soil horizon by NanoSIMS, measuring 12 C- , 18 O- , 32 S- , 63 Cu- and 56 Fe16 O- . We evaluated the NanoSIMS measurements with a novel digital image processing tool to enlighten the composition of measured areas and thus the distribution of Cu at the sub-micron scale. Image processing comprised spatial and spectral smoothing, normalization, endmember extraction and supervised classification. Copper was present in all areas studied on the thin section in hotspots. 63 Cu- was never the ion with the highest number of mean-normalized counts (MNCs). In classes indicating Cu accumulation, Fe or S had the highest MNCs with mostly small values for O, pointing to the presence of Cu in sulfides. Copper adsorbed on Fe oxides was also indicated. Direct interaction of Cu with organic matter was less important. Copper-containing minerals were rather adjacent to or surrounded by an organic matrix. The combination of NanoSIMS analyses with digital image processing gave us new insights into the distribution of Cu in contaminated soil. We suggest this combination as a new powerful tool for the identification of ionic contaminants in soil and other solid phases in the environment.

Adsorption and flotation of copper sulfide ore with diisopropyldithiophosphate collector

The results of investigation adsorption mechanism of diisopropyldithiophosphate collector on the surface of the sulfide copper ore and flotation has been discussed. The investigation of composition and structure of sulphide copper ore has been carried out by using FT-IR-spectroscopy, Х-ray diffraction spectroscopy and ICP-MS method. The results showed that sorption capacity of ore at pH 10.5-11.5 is a maximum. The role of the oxidation-reduction processes in fixing of diisopropyldithiophosphate ion on the surface of ore was established. It was shown that data of extraction of copper to concentrate and adsorption value of diisopropyldithiophosphate ion are correlating. The IR-Fourier spectroscopic analysis showed that collector is coordinated with the ions of the metal of the crystal lattice of copper-containing minerals through the sulfur atoms of the dithiophosphate group.

Centennialite, CaCu3(OH)6Cl2.nH2O,n≈ 0.7, a new kapellasite-like species, and a reassessment of calumetite

AbstractThe new mineral centennialite (IMA 2013-110), CaCu3(OH)6Cl2·nH2O, was identified from three cotype specimens originating from the Centennial Mine, Houghton County, Michigan, USA, where it occurs as a secondary product, after acid water action upon supergene Cu mineralization in association with, and essentially indivisible from, other copper-containing minerals such as calumetite and atacamite family minerals. It forms as pale to azure blue encrustations, often taking a botryoidal form. Centennialite is trigonal,,a= 6.6606(9) Å,c= 5.8004(8) Å,V= 222.85(6) Å3,Z= 1. The strongest powder X-ray diffraction lines aredobs/Å [I%] (hkl), 5.799 [100] (001), 2.583 [75] (201), 2.886 [51] (111), 1.665 [20] (220), 1.605 [17] (023), 1.600 [15] (221), 1.444 [11] (222). The X-ray refined structure forms a kagome net of planar coordinated CuO4units with Jahn-Teller coordinated Cl apices to form octahedra that edge-share to in-plane adjacent and flattened CaO6octahedra, which are centred about the lattice origin. All oxygen sites are protonated and shared between one Ca-octahedron and one CuO4planar unit. Three protonated sites are linked, by hydrogen-bonding to Cl sites, which sit on the triad axis. Each lattice has one Cl above and one below the Ca-Cu polyhedral plane. Consequently, the layers are stacked, along ⟨001⟩, with two Cl sites between layers. In addition to this kapellasite-like topology, an extrac/2site is identified as being variably water-hosting and extends the coordination of the Ca-site to 8-fold, akin to the body-diagonal Pb-Cu sheet in murdochite. Centennialite conforms to the description of the ‘Unidentified Cu-Ca-Cl Mineral’ noted in Heinrich'sMineralogy of Michiganand is almost certainly identical to the supposed hexagonal basic calcium-copper hydroxychloride monohydrate of Erdöset al.(1981). We comment upon relationships between calumetite and centennialite and propose a substructure model for a synthetic calumetite-like phase that is related directly to centennialite.

Role of oxalic acid overexcretion in transformations of toxic metal minerals by Beauveria caledonica.

The fungus Beauveria caledonica was highly tolerant to toxic metals and solubilized cadmium, copper, lead, and zinc minerals, converting them into oxalates. This fungus was found to overexcrete organic acids with strong metal-chelating properties (oxalic and citric acids), suggesting that a ligand-promoted mechanism was the main mechanism of mineral dissolution. Our data also suggested that oxalic acid was the main mineral-transforming agent. Cadmium, copper, and zinc oxalates were precipitated by the fungus in the local environment and also in association with the mycelium. The presence of toxic metal minerals often led to the formation of mycelial cords, and in the presence of copper-containing minerals, these cords exhibited enhanced excretion of oxalic acid, which resulted in considerable encrustation of the cords by copper oxalate hydrate (moolooite). It was found that B. caledonica hyphae and cords were covered by a thick hydrated mucilaginous sheath which provided a microenvironment for chemical reactions, crystal deposition, and growth. Cryo-scanning electron microscopy revealed that mycogenic metal oxalates overgrew parental fungal hyphae, leaving a labyrinth of fungal tunnels within the newly formed mineral matter. X-ray absorption spectroscopy revealed that oxygen ligands played a major role in metal coordination within the fungal biomass during the accumulation of mobilized toxic metals by B. caledonica mycelium; these ligands were carboxylic groups in copper phosphate-containing medium and phosphate groups in pyromorphite-containing medium.