Abstract
Copper is a critical material for the global economy. There may be a structural supply gap that current production pipelines will struggle to address. As the primary source of the world's copper, chalcopyrite is critical to the green energy transition and to addressing this supply gap, yet its refractory nature creates significant processing bottlenecks amid surging global demand. Consequently, unlocking the full potential of chalcopyrite reserves requires urgent attention to process optimization that overcomes the mineral's inherent kinetic limitations. Recent literature demonstrates that organic biodegradable surfactants can help to overcome the refractory nature of chalcopyrite, as they significantly reduce interfacial tension and inhibit the formation of passivating layers. By modifying the mineral's surface wettability, these additives facilitate deeper lixiviant penetration and sustained dissolution kinetics, thereby unlocking superior copper recovery rates compared to conventional methods.
In this research, a non-ionic biodegradable surfactant, Tergitol 15-S-9, was tested in chalcopyrite bioleaching using non-adapted mixed mesophilic bacteria. The bioleaching results revealed that the surfactant, up to 20 ppm, significantly increased copper extraction. By adding 10 and 20 ppm of surfactant at the beginning of bioeleaching, final copper extraction increased by 2.44 and 1.66 times, respectively, compared to control tests. Increasing the surfactant concentration to 50 ppm had a minor effect on extraction. The effect at 100 ppm was negligible. Exceeding the 100 ppm threshold caused an inhibitory effect on bacterial growth and overall copper yield. At 200 ppm, dissolved copper decreased by 41%, and at 500 ppm, it decreased by more than 69%. Operational parameters such as pH, oxidation-reduction potential (ORP), bacterial count, surface tension, and ferric concentration were monitored during the experiments. It was shown that the alcohol-based surfactant could increase the lag phase of bacterial growth and metabolism at concentrations above 20 ppm and completely hinder bioleaching above 200 ppm. Bioleaching residues were subjected to various characterization analyses, such as XRD and SEM/EDS, to identify phase and morphological changes.