Investigation of arsenic removal from copper concentrates by alkaline sulphur leaching

This study investigated the removal of arsenic from copper concentrates by alkaline sulphur leaching. The first set of mineralogical investigations was carried out as part of the study. It has been assessed that arsenic is present in the ore in the form of the tennantite and the minerals of the fahlerz group. Chemical analyses, SEM-EDS and XRD analyses support these mineralogical findings. As was observed to be associated with Cu-S. Mineralogical tests indicated that the arsenic in the concentrate could not be removed by flotation. Preliminary flotation tests also showed that arsenic could not be selectively separated from the copper concentrate. Na2S and NaOH leaching (alkaline sulphur leaching) were carried out to selectively remove arsenic from the flotation concentrate. It was observed that the arsenic contained in the copper concentrate was recovered with high efficiency (>80%) after the alkaline sulphur leaching process. Furthermore, it was observed that arsenic recovery increased further (>90%) when the flotation concentrate was regrinded and alkaline leached under the same conditions. The leaching mechanism was investigated by chemical, ore microscopy, SEM-EDS and XRD analyses. Finally, elemental sulfur (S) precipitated the arsenic from the leach solution. The production of arsenic in solid salt form (Na<sub>3</sub>AsO<sub>4</sub>) by precipitation is an advantage of the process investigated in this study, as it is environmentally friendly and has the potential to be used in different areas.