Copper Cobalt Oxide Research Articles

Recovery of Copper Metal through Reprocessing of Residues from a Hydrometallurgical Plant

The Chemical of Africa (CHEMAF) is a hydrometallurgical plant operated in Katanga since 2001. It produces copper metal using a process comprising the sulphuric acid leaching of copper-cobalt oxide ores under reducing conditions (Na 2 S 2 O 5 or SO 2 ) followed by the leach liquor purification by solvent extraction (SX) and electrowinning of copper. The leach liquor is recovered during the thickening of pulps from the leaching section and the scavenging of residues by washing in the counter-current decanters (CCD). The process residues were anciently dumped near the plant. With the increase in the run of mine (ROM) ores sulphide minerals content related to changes in the Kalukuluku deposit mineralogy and considering that the storage of residues may result in toxic pollutants release to the environment, their reprocessing is gaining the ground as the best option. The present research aims at recovering copper metal from residues (2.01% Cu and 0.32% Co) through their reprocessing based on the sulphuric acid leaching prior to the recovery of copper metal through cementation with iron shavings. The results from the experiments have showed that the leaching of copper (≈ 90%) and cobalt (86%) was successful when conducted during 90 minutes at 75°C using 150 g of residues subjected to stirring (500 rpm) in 1 L of H 2 SO 4 (30 g/L) in the presence of Na 2 S 2 O 5 (330 mV). Consequently, one recovers satisfactorily copper metal (2.5 g of solids assaying 93% Cu recovered at 86%) when 1 g of iron shavings was stirred (400 rpm) during 60 minutes at constant speed and at the room temperature in 250 mL of the metalliferous solution (10.84 g/L Cu and 1.73 g/L Co) prepared by the leaching of residues.

Copper oxide - perovskite mixed matrix membranes delivering very high oxygen fluxes

Here we show that copper substitution in perovskite-type barium strontium cobalt copper oxide (BSCC) membranes confers extremely high oxygen fluxes well beyond the state of art, reaching 27.5mlcm−2min−1 at 950°C. A key feature of BSCC is the formation of a mixed matrix catalyst-perovskite membrane caused by the segregation of copper, leading to the formation of an intergranular network of copper-rich oxide between perovskite grains. BSCC membranes delivered pressure normalised oxygen flux (i.e. permeance) of up to 86 times higher, above pressure difference of 18kPa, as compared to best perovskite membrane, BBSC, due to the catalytic effect of segregated copper oxide. Unlike conventional dual-phase membranes which contain ion and electron conducting phases, this work shows for the first time perovskite-type membranes consisting of a mixed matrix of oxygen ion/electron conducting (perovskite) and catalytic (copper oxide) phases, thus paving the way to the development of high performance membranes for oxygen separation from air for clean energy applications.

Malachite and heterogenite behavior during the locked-cycle recycling of process water in flotation of copper-cobalt oxide ores

The behavior of malachite and heterogenite was investigated during the process water recycling in flotation of copper-cobalt oxide ores from the deposit of Luiswishi located in Haut-Katanga province (DRC). A synthetic mill wastewater (SMWW) was utilized as feed water alone and in mixture with water recovered from the flotation tails in view to achieve at the laboratory scale the locked-cycle recycling of the industrial mill wastewater (IMWW). To simulate the chemical species presence in the pulp water and their effects on the flotation of malachite and heterogenite, calcium, magnesium and bicarbonate ions were added to the feed water and the recoveries of copper and cobalt followed during the roughing flotation stage. The concentrate XRD and SEM analyses together with the floated minerals microanalyses by EDX spectroscopy, leaching tests of mono-minerals followed by the Pourbaix diagrams construction and DRIFT spectroscopic analyses, have enabled identifying changes in the surface properties of malachite and heterogenite and describing their behaviors. It was concluded that the locked-cycle recycling of process water is inducing the build-up of chemical species in the pulp, which favors the exaggerated dissolution and hydration of malachite and heterogenite interfering on the recovery of copper (40%) and cobalt (58%) with a significant drop in their concentrate grades (7.3% Cu and 2.7% Co). The deterioration of the concentrate characteristics results also from the gangue minerals entrainment. A better description of the valuable minerals behavior in the SMWW presence could enable designing strategies in view enhancing their floatability during the locked-cycle recycling of water.

Structural Thermal Stability of Graphene Oxide-Doped Copper–Cobalt Oxide Coatings as a Solar Selective Surface

3d transition metal oxides based thin film coatings such as copper-cobalt oxides exhibit high absorption in the visible region and low emittance in the infra-red to far-infra-red region of the solar spectrum which is favourable for use as potential selective surface materials in photothermal devices. These materials have the potential to minimize heating while increasing absorption in the operative spectrum range and therefore achieve higher solar selectivity. A series of mixed copper-cobalt metal spinel oxides (CuxCoyOz) doped with graphene oxide thin films were deposited on commercial grade aluminium substrates using a sol–gel dip-coating technique at an annealing temperature of 500 °C in air for 1 h. Characterizations of the synthesized films were carried out by high temperature synchrotron radiation X-ray Diffraction (SR-XRD), UV-Vis, Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron microscopy (XPS) techniques. High thermal stability of coatings with multiple phases, binary and ternary metal oxides, was defined through SR-XRD study. FTIR analysis shows moderate (<80%) to high (up to 99%) reflectance in the infra-red region while the UV-Vis investigations demonstrate that, in the visible region, solar absorption increases gradually (up to 95%) with the addition of graphene oxide to the CuxCoyOz coatings. With the incorporation of 1.5 wt% of graphene oxide to the copper-cobalt oxide coatings, a high solar selectivity of 29.01 (the ratio of the average solar absorptance in visible and the average thermal emittance in infra-red to far infra-red region; α/e) was achieved.

Microporous sponge structure with copper-cobalt oxide hybrid nanobranches

A sponge structure featuring a micropore network and nanodendritic wall consisting of Cu-Co oxide core-shell like hybrid nanobranches is reported. First, microporous sponge structure with Cu-Co hybrid nanobranches was formed by hydrogen-templated electrolytic deposition. Next, Cu-Co branches were transformed to Cu-Co(OH)2 branches by selective anodic oxidation of Co. Cu-CoO branches were then obtained by subsequent thermal dehydration. During the selective anodization and subsequent dehydration of the as-deposited sample, the overall structures of micropore network and core-shell like nanodendritic branches were preserved.

Structural, optical, and mechanical properties of cobalt copper oxide coatings synthesized from low concentrations of sol-gel process

Thin films of CoxCuyOz have been coated on aluminum substrates via sol–gel route using low concentration of copper and cobalt precursors at annealing temperatures in range of 500–650 °C. The coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis-NIR spectrophotometry, and nanoindentation. The XRD analysis in 2θ-range of 30°–42° revealed that the coatings exhibited low crystallinity of CoCu2O3, CoCuO2, and CuCoO2. The surface bonding structure analyzed using XPS indicated that the coating contained: Cu (tetrahedral Cu+ and octahedral Cu2+), Co (octahedral Co3+, tetrahedral Co2+, and mixed Co2+ and Co3+), and O (lattice, surface, and sub-surface oxygens). The optical properties characterized using UV-Vis-NIR showed that the reflectance spectra of coatings formed a spectrally solar selective absorber profile associated with the interference peaks and the absorption edges around wavelengths of below 1.2 μm. The maximum absorptance (α = 75.8%) was shown by coating synthesized at 500 °C. The mechanical properties of coatings showed that the increase of annealing temperature increased the coating's hardness (H) and the elastic modulus (E) due to the enhancement of the [CoCuO2/CuCoO2]:[CoCu2O3] oxide phases ratio, as the result, an excellent stability of the wear resistance (H/E) of around ∼0.035 was recorded.

Simultaneous determination of epinephrene and paracetamol at copper-cobalt oxide spinel decorated nanocrystalline zeolite modified electrodes

In this study, CuCo2O4 and CuCo2O4 decorated nanocrystalline ZSM-5 materials were prepared. For comparative study, a series of MCo2O4 spinels were also prepared. Materials were characterized by the complementary combination of X-ray diffraction, N2-adsorption, UV–visible, and electron microscopic techniques. A simple and rapid method for the simultaneous determination of paracetamol and epinephrine at MCo2O4 spinels modified electrodes is presented in this manuscript. Among the materials investigated in this study, CuCo2O4 decorated nanocrystalline ZSM-5 exhibited the highest electrocatalytic activity with excellent stability, sensitivity, and selectivity. Analytical performance of the sensor was demonstrated in the determination of epinephrine and paracetamol in the commercial pharmaceutical samples.

Cu–Co–O nano-catalysts as a burn rate modifier for composite solid propellants

Abstract Nano-catalysts containing copper–cobalt oxides (Cu–Co–O) have been synthesized by the citric acid (CA) complexing method. Copper (II) nitrate and Cobalt (II) nitrate were employed in different molar ratios as the starting reactants to prepare three types of nano-catalysts. Well crystalline nano-catalysts were produced after a period of 3 hours by the calcination of CA–Cu–Co–O precursors at 550 °C. The phase morphologies and crystal composition of synthesized nano-catalysts were examined using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR) methods. The particle size of nano-catalysts was observed in the range of 90 nm–200 nm. The prepared nano-catalysts were used to formulate propellant samples of various compositions which showed high reactivity toward the combustion of HTPB/AP-based composite solid propellants. The catalytic effects on the decomposition of propellant samples were found to be significant at higher temperatures. The combustion characteristics of composite solid propellants were significantly improved by the incorporation of nano-catalysts. Out of the three catalysts studied in the present work, CuCo-I was found to be the better catalyst in regard to thermal decomposition and burning nature of composite solid propellants. The improved performance of composite solid propellant can be attributed to the high crystallinity, low agglomeration and lowering the decomposition temperature of oxidizer by the addition of CuCo-I nano-catalyst.

Laboratory Evaluation of the Flotation Response of a Copper Cobalt Oxide Ore to Gasoil-Rinkalore Mixtures

Laboratory Evaluation of the Flotation Response of a Copper Cobalt Oxide Ore to Gasoil-Rinkalore Mixtures

Supported copper and cobalt oxides on activated carbon for simultaneous oxidation of toluene and cyclohexane in air

Dispersed nano mixed copper–cobalt oxides bimetallic catalysts were prepared by deposition–precipitation method for simultaneous and complete oxidation of toluene and cyclohexane.

Optical properties and thermal durability of copper cobalt oxide thin film coatings with integrated silica antireflection layer

Copper cobalt oxide (Cu2CoO3) thin film coatings integrated with silica (SiO2) antireflection (AR) layer have been deposited on the top of aluminum substrates using a simple sol–gel dip-coating method. Reflectance spectra of the coatings were generated using spectroscopic methods while the coatings were subjected to an accelerated thermal durability test. The addition of silica changed the reflectance spectra of coatings within the wavelength range of 0.3–15.4µm. The absorptance decreased with the increase of the withdrawal rate in range of 10–40mm/min, while the emittance increased with the increase of the withdrawal rate. The optimum optical parameters for this study were absorptance, αS=84.96%; emittance, εT=5.63% corresponding to the coating with a silica AR layer at withdrawal rate of 10mm/min. The coatings with the silica AR layer were shown to be thermally durable in which no discernible ‘cracking’ phenomenon was observed. The degradation of the coatings with the silica AR layer was predominantly governed by temperature changes rather than exposure time.

Assessment of water quality effects on flotation of copper–cobalt oxide ore

Results from lab scale flotation show that when process water was re-used copper and cobalt recovery from an oxidized ore decreased respectively with 25% and 30% at the rougher stage bringing lower grade concentrate as well. The presence of thiosulphate ions contributed to slow down of NaHS consumption during sulphidisation of pure malachite and hindered collector adsorption. Elevated concentration of thiosulphate ions affected malachite surface properties and induced dissolution effects. DRIFT spectroscopy on activated malachite enabled to reveal the effects of thiosulphate ions presence with hydrophilic species being identified.

Study of correlation between activity and structural properties of Cu-(Cr, Mn and Co)2 nano mixed oxides in VOC combustion

The correlation between structure and catalytic activities of Cu-(Cr, Mn and Co)2 mixed oxides synthesized by a sol–gel combustion method was investigated for the oxidation of 2-propanol. The catalysts were characterized by FTIR, XRD, XPS, TPR and UV–vis DRS. Although the same preparation conditions were used for all the systems, obtained samples presented different pureness degrees. The structural characterization by XRD revealed that copper-chromite was pure CuCr2O4, while copper-manganese and copper-cobalt mixed oxides resulted in a mixture of the spinel (CuMn2O4 and Cu0.15Co2.85O4, respectively) and copper oxide phases. UV–vis DRS results also indicated a larger presence of small crystallites of CuO in the copper-cobalt oxide. Copper-cobalt oxide exhibited the highest activity in 2-propanol combustion which is explained, as expected for a Mars van Krevelen mechanism, by its higher reducibility at the reaction conditions and by a possible synergistic effect between this mixed oxide and CuO particles.

Tailoring the physicochemical and mechanical properties of optical copper–cobalt oxide thin films through annealing treatment

Sol–gel dip-coated optical coatings, copper–cobalt oxides on aluminum substrates, were thermally treated at different annealing temperatures in the range 500–650°C. The resulting films were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis–NIR spectrophotometry and nanoindentation techniques. The crystallinity of CoCu2O3 enhanced significantly, with increasing annealing temperature from 500 to 650°C, while the electronic structure and bonding states of the copper–cobalt oxides matrix remained unchanged. UV–Vis–NIR analysis showed that the solar absorptance (α) of the coatings changed with increase of annealing temperature and an optimum α (84.4%) was achieved at 550°C, which also coincides to the maximum tensile residual stress of the coating. Nanoindentation tests exhibited an increasing trend in both the hardness (H) and elastic modulus (E) of the coatings with increase in annealing temperature, although a slight decrease in the H/E ratio was also observed. The experimental studies were complemented by finite element modeling (FEM). The results showed that, under mechanical loading, the stress deformation and plastic deformation were concentrated within the coating layers. As such, the likelihood of delamination of the coating layer upon unloading would be reduced.

Surface Electronic Structure and Mechanical Characteristics of Copper–Cobalt Oxide Thin Film Coatings: Soft X-ray Synchrotron Radiation Spectroscopic Analyses and Modeling

Novel copper–cobalt oxide thin films with different copper/cobalt molar ratios, namely, [Cu]/[Co] = 0.5, 1, and 2, have been successfully coated on aluminum substrates via a simple and cost-effective sol–gel dip-coating method. Coatings were characterized using high resolution synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy, in combination with nanomechanical testing and field emission scanning electron microscopy (FESEM). The surfaces of both [Cu]/[Co] = 0.5 and 1 samples consisted primarily of fine granular nanoparticles, whereas the [Cu]/[Co] = 2 has a smoother surface. The analyses reveal that the increase of copper concentration in the synthesis process tends to promote the formation of octahedral Cu2+ which minimizes the development of octahedral Cu+, and these octahedral Cu2+ ions substitute the Co2+ site in cobalt structure host. The local coordinations of Co, Cu and O are not substantially influenced by the change...

Solar absorptance of copper–cobalt oxide thin film coatings with nano-size, grain-like morphology: Optimization and synchrotron radiation XPS studies

Copper–cobalt oxides thin films had been successfully coated on reflective aluminium substrates via a facile sol–gel dip-coating method for solar absorptance study. The optimum absorptance in the range of solar radiation is needed for further optimum design of this material for selective solar absorber application. Field emission scanning electron microscopy was used to characterize the surface morphology of the coating whereby nano-size, grain-like morphology was observed. Synchrotron radiation X-ray photoelectron spectroscopy was employed to analyze the electronic structure of the coated surface showing that the (i) oxygen consisted of lattice, surface and subsurface oxygen, (ii) copper consisted of octahedral and tetrahedral Cu+, as well as octahedral and paramagnetic Cu2+ oxidation states, and (iii) cobalt consisted of tetrahedral and paramagnetic Co(II), octahedral Co(III) as well as mixed Co(II,III) oxidation states. In order to optimize the solar absorptance of the coatings, relevant parameters such as concentrations of cobalt and copper, copper/cobalt concentration ratios and dip-speed were investigated. The optimal coating with α=83.4% was produced using 0.25M copper acetate and 0.25M cobalt chloride (Cu/Co ratio=1) with dip-speed 120mm/min (four cycles). The operational simplicity of the dip-coating system indicated that it could be extended for coating of other mixed metal oxides as well.

A study of recovery of copper and cobalt from copper–cobalt oxide ores by ammonium salt roasting

Copper and cobalt recovery from a copper–cobalt ore of Democratic Republic of Congo (DRC) by ammonium chloride roasting is studied. The effects of roasting temperature, roasting time, and the dosage of ammonium chloride on the leaching rate of copper and cobalt are investigated. The results show 90% copper and 95% cobalt recovery under the optimal experimental conditions of average particle diameter 0.10mm and 1:2 ammonium chloride to ore mass ratio at a roasting temperature of 300°C for 3h. After adjusting the pH of the leaching solution to 7 by ammonia addition, the copper and cobalt in the solution were precipitated by ammonium bicarbonate at 60°C for 40min. Ammonium chloride crystals obtained after absorbing the exhaust gas and filtration of the scrub liquor could be reused for the roasting process. With X-ray diffraction analysis on the calcined ore at different temperatures, the roasting mechanism of copper–cobalt oxide ores with ammonium chloride was investigated. Co(NH3)6CuCl5 was found to be the main intermediate compound formed at roasting temperatures below 320°C, above which it was further decomposed to CoCl2 and CuCl2.

CO oxidation and preferential oxidation of CO in the presence of hydrogen over SBA-15-templated CuO-Co3O4 catalysts

Copper–cobalt mesostructured spinel replicas of SBA-15 were synthesized through a hard template pathway. The catalysts, with Cu/(Co+Cu) atomic ratio in the range 0–17%, were characterized as to their structure, morphology, texture and redox features by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N2 physisorption, and temperature-programmed reduction with hydrogen. The catalysts were tested in a fixed-bed reactor for CO oxidation both in the absence of hydrogen (1.5mol% CO, 1.5mol% O2, balance He, 40–140°C) and in a hydrogen-rich atmosphere (1.5mol% CO, 1.5mol% O2, 46mol% H2, balance He, 40–200°C). In the absence of hydrogen, catalytic activity for CO oxidation was similar for all the samples for temperatures up to ca. 100°C, at which 50% CO conversion was observed. Above such temperature the copper-containing catalysts appeared more active than the pure Co3O4. All the catalysts were active for the preferential oxidation of CO in hydrogen-rich atmosphere, with 50% CO conversion occurring in the 123–138°C range. Both CO and oxygen conversions were enhanced by the presence of copper, which however also favoured the occurrence of parasite hydrogen combustion. Methanation was observed (to a limited extent, at temperatures ≥160–180°C) only on the Cu-containing catalysts. The performance of the present catalysts was compared with literature results for CO oxidation and preferential CO oxidation on cobalt and copper–cobalt oxides prepared by different methods. The hard-templated catalysts seem superior to traditionally prepared ones in the case of CO oxidation in the absence of hydrogen, whereas no clear-cut conclusion can be drawn in the case of preferential CO oxidation.

SYNTHESIS, STRUCTURE AND PHOTOELECTROCHEMICAL ACTIVITY OF MIXED COPPER-COBALT OXIDE COATINGS

The aim of the current work was to obtain photoactive copper–cobalt oxide coatings on AISI 304 type stainless steel substrate. This work is relevant to the search of new photocatalysts suitable for water photosplitting. Mixed copper–cobalt oxide coatings were synthesized by heating for 3 h at 550 °C the mixtures of copper acetate hydrate Cu(CH 3 COO) 2 ∙H 2 O and cobalt acetate tetrahydrate Co(CH 3 COO) 2 ∙4H 2 O. The obtained coatings were characterized by X–ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric–differential scanning microscopy (TG–DSC) and photovoltammetry. The experimental results revealed that mixed copper–cobalt oxide coatings are predominantly composed of spinel-type CuCo 2 O 4 phase. The average crystallite size of CuCo 2 O 4 particles was calculated to be in the range of 65–76 nm. The prepared coatings show a p -type semiconducting behavior. The value of photogenerated current depends on the molar ratio Cu:Co in the coatings. Unfortunately, photoelectrochemical measurements showed that these coatings are relatively unstable under UV irradiation in aqueous solutions. DOI: http://dx.doi.org/10.5755/j01.ct.60.2.1803

Optical and mechanical characterization of novel cobalt-based metal oxide thin films synthesized using sol–gel dip-coating method

New cobalt-based metal oxide thin films (MxCoyOz with M=Mn, Cu, Ni) have been deposited on commercial aluminum and glass substrates using sol–gel dip-coating method. The as-deposited films were characterized by a wide range of complementary techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), spectrophotometry and nanoindentation techniques. A light absorption study for coatings on glass substrates within a wavelength range of 300–1100nm was also conducted. Topographical and morphological investigations showed the presence of nano-sized, grain-like particles in the copper–cobalt oxide coatings, which consequently had the roughest surface among the three coatings. All coatings on glass substrate exhibited higher absorption of ultraviolet (UV) light compared to visible light, while coatings on aluminum substrate generally had low reflectance (<50%) of UV light, moderate reflectance (<80%) of visible light and high reflectance (up to 100%) of infrared light. Implications of optical properties as a function of film thickness controlled by dip-heating cycles were discussed. The elastic modulus (E) and hardness (H) of thin film samples compared with stand‐alone commercial aluminum substrate were also measured.