Characterization of Copper–Cobalt Ores and Quantification of Cu2+, Co2+, Co3+, and Fe3+ in Aqueous Leachates Using UV/Visible Spectrophotometry

Ultraviolet/visible (UV/vis) spectroscopy was used to determine qualitatively and quantitatively Cu²⁺, Co²⁺, Co³⁺, and Fe³⁺ in oxidized Cu–Co ore leachates. The mineralogical and chemical characteristics of the three oxidized Cu–Co ore samples considered were determined using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray fluorescence spectrometry (XRF). The results showed that Cu and Co in the samples were in the form of carrollite (Co₂CuS₄), malachite (Cu₂CO₃(OH)₂, and heterogenite (CoO(OH)). The samples contained (2.73% Cu and 0.19% Co), (2.82% Cu and 0.07% Co), and (0.03% Cu and 0.05% Co), respectively. Gangues were mainly constituted of quartz, goethite, and hematite. The ultraviolet/visible (UV/vis) results indicated that the wavelengths of absorbance of the metal ions in dilute ethylenediaminetetraacetic acid aqueous solution (pH ≈ 3.5) were Fe³⁺ (293 nm), Cu²⁺ (821 nm), Co³⁺ (344 nm), and Co²⁺ (512 nm). The molar concentrations of the metal ions obtained using the UV/vis method compared well with the results obtained using the atomic absorption spectroscopy (AAS) method. UV/vis spectroscopy was also used to monitor the conversion of Co³⁺ into Co²⁺ using different reducing agents. The results showed that the molar concentration of Co²⁺ in the aqueous solutions increased with the addition of reducing agents, of about 80.95% (copper foil), 61.22% (ferrous sulfate), and 20.35% (sodium sulfite), respectively.     

Optical dispersion analysis of template assisted 1D-ZnO nanorods for optoelectronic applications

Morphology and size play crucial influential roles in semiconductor nanotechnology. Capping agents have been adopted in this study for controlled fabrication of symmetrical zinc oxide (ZnO) nanostructures, with a preferred orientation and agglomeration inhibition. Elongated one-dimensional (1D) ZnO nanorods were successfully synthesised in a simple two-step process. X-ray diffraction (XRD) revealed high crystalline films with a preferred (002) plane orientation. Ethylene glycol (EG) surfactant was found to produce substantial effect on both the morphology and crystallinity as relatively small uniform nanorods with crocked ends were observed from morphological analysis. All the synthesised ZnO films depicted optical transmittance of over 50% in the visible range and a strong absorption peak in the UV proximity, at 380 nm. An evaluation of the optical parameters calculated from the measured transmittance indicated that surfactants can be used to modify the refractive index, real and imaginary dielectric constants of ZnO nanorods, to optimize the performance of optoelectronic devices.