Distribution of major and trace elements concentrations in gold processing using EDXRF

Studies have been carried out on the distribution of major and trace elements concentrations in oxide and sulphide feed ores at various stages of milling and processing of gold in a goldmine at Bogoso in the western region of Ghana. The studies evaluated concentration enhancements at various stages of treatment with emphasis on understanding the typical processes leading to enhancement of concentration at each stage and ultimately the impact from discharges into the surrounding environment. The feed ore samples were analyzed using energy dispersive X-ray fluorescence spectrometry. The results show concentration enhancements of a significant number of elements at some stages of processing in the two processing plants with the highest number of elements with enhanced concentrations coming from chemically treated media of both plants. Though there are relatively high concentrations of V (max.: 284 ppm), Cr (max.: 149 ppm), Co (max.: 84 ppm), and U (max.: 26.8 ppm) at the discharge points, the concentrations of most of the toxic elements in the slurries discharged into the tailings dam are mostly within their respective world averages. The enrichment indices computed for the slurries being discharged into the tailings dam suggests that the dam is not enriched with the toxic elements Cr, Co, Ni, Zn, Cu and Pb. The enrichment index of the slurries discharged into the tailings dam decreases in the order of oxide plant > sulphide plant. Principal component analyses performed suggest that Al₂O₃, K₂O, Co, Zn, Cu, Y and Zr are geochemically associated. Results from the studies also suggest that the discharge of these elements into the tailings dam may contribute insignificant pollution of the surrounding area.     

Chitosan nanostructures deposited from solutions in carbonic acid on a model substrate as resolved by AFM

Chitosan macromolecules can be dissolved in water saturated with CO₂ under high pressure, i.e. in carbonic acid. This unique biocompatible solvent with acidity regulated by the variation of applied CO₂ pressure is rather promising for biomedical applications. In this work the main features of deposition of chitosan structures on the model substrate from solutions in this media were examined. After deposition on the mica surface, the obtained structures have been successfully visualised by atomic force microscopy (AFM). It has been found out that they adsorb as rather peculiar elongated objects with an average length of about 70?nm. Such conformations are believed to appear due to amphiphilic nature of chitosan semiflexible chains in agreement with recent theoretical findings. The well-defined geometry of the elongated monodispersed structures allows them to demonstrate some elements of liquid crystalline-like ordering.     

Spondias mombin L. as a green corrosion inhibitor for aluminium in sulphuric acid: Correlation between inhibitive effect and electronic properties of extracts major constituents using density functional theory

The inhibition of aluminium in 0.5 M H₂SO₄ by extracts of Spondias mombin L. was investigated using the standard gravimetric technique at 30–60 °C. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition. It was found that the S. mombin L. extract acts as an inhibitor for acid-induced corrosion of aluminium. Inhibition efficiency (%I) of the extract increased with an increase in concentration of the S. mombin L. extract but decreased with temperature. Furthermore, inhibition efficiency (%I) synergistically increased on addition of potassium iodide. Inhibitor adsorption characteristics were approximated by Langmuir adsorption isotherm at all the concentrations and temperatures studied. The mechanism of physical adsorption is proposed from the trend of inhibition efficiency with temperature and from the calculated values of Gibbs free energy, activation energy and heat of adsorption. Quantum chemical calculations were performed using the density functional theory at B3LYP/6-31G (d) level of theory to find out whether a clear link exists between the inhibitive effect of the extract and the electronic properties of its main constituents.