Abstract
— The aim of this report was to investigate the compare the potential of amino acid and galvanic interaction to reduce the formation of passivation layer and improve the overall copper recovery during chalcopyrite leaching. Sample characterization included X-Ray Fluorescence, X-Ray Diffraction, and Scanning Electron Microscopy. Manganese dioxide was used to form galvanic couple with chalcopyrite in a ratio of 4:1 respectively using sulphuric acid and glycine solutions as leaching medias. Parameters that were investigated during the leaching process were temperature (25 to 55 oC) with an increment of 10 oC, pH ranges of 1.5 – 2.5, with changes of 0.5 and time between 2 and 8 hours, with a 2-hour increment. Pregnant liquors were obtained after every 2 hours, filtered and thereafter analysed using Atomic Adsorption Spectrometry to study kinetics. During the investigation of temperature, the maximum recovery of copper using glycine and sulphuric was 37% and 42% respectively at the temperature of 55 oC, for 8 hours at the above-mentioned optimum pH. This shows that sulphuric acid remains to be the most effective acid in comparison to glycine during the leaching of chalcopyrite using galvanic action. The use of galvanic action was also effective during chalcopyrite leaching since it increased the recovery of copper from 15% up to 42%, showing that galvanic action plays a role in reducing passivation layer during the leaching process. The rate limiting step of the reaction in the leaching process using the glycine and sulphuric acid, was found to be the diffusion-controlled mechanism. This was supported by the lower activation energies for the glycine and sulphuric acid which were found to be 4 and 16 KJ/mol respectively. The mathematical validation proved that the reactions were under the control of diffusion-controlled mechanism.