Optimized indium solubilization from LCD panels using H2SO4 leaching.

Spent liquid crystal displays (LCDs) are a secondary source of precious/strategic metals, including indium (In). The present study involved optimizing the solubilization of this strategic element from samples of indium tin oxide (ITO) glass prepared from LCD screens of computer monitors and laptop screens. The influence of operating conditions on In solubilization, as well as optimum conditions for sulfuric acid leaching were defined by a Box-Behnken-type experimental design methodology. Optimum operating conditions include a leaching step for 30 min at a temperature of 70 °C in the presence of 0.4 N H2SO4 and a pulp density of 50% (w/v). Under these conditions, the quadratic model established to predict the solubilization of In from ITO glass samples provided an In solubilization efficiency of 89.7%, which was validated experimentally (99.5%). The analysis of direct operating costs and capital costs for the implementation of such a leaching process revealed that the process is conceivable for a high-capacity plant processing ~100 t/day of ITO glass.

Assessment of the leaching potential of flotation tailings from rare earth mineral extraction in cold climates.

Increasing use of rare earth elements (REEs) in modern technologies and existing or expected imbalances between demand and supply have led many countries, including Canada, to consider the exploitation of their own REEs primary sources. The objective of this study is a thorough characterization of the flotation tailings generated during the pre-concentration of REEs from a carbonatite type deposit with the aim of predicting their geochemical behaviour over time. These tailings were characterized based on physicochemical and mineralogical properties. Weathering cells were also used to assess the impact of temperature (3 and 19 °C) on the geochemical behaviour of the tailings exposed to a sub-arctic climate. Because the tailings consisted mainly of carbonates (97.4%) and had very high neutralization potential (859 kg CaCO3/t) relative to their acidity potential (3.94 kg CaCO3/t), no acid mine drainage (AMD) is anticipated. Compared to regional environmental standards and guidelines, the concentrations of Cd (0.20 µg/l), Zn (17 µg/l), and Pb (close to 4 µg/l) in leachates obtained during kinetic testing may be considered as potentially problematic. Finally, the results of the weathering cells at 3 °C indicate that the exposure to low temperatures may increase the concentrations of elements leached from the tailings. This study confirms that low temperatures and freeze-thaw events, which occur readily in a sub-arctic climate, may impact the geochemical behaviour of tailings produced from the extraction of REEs from carbonatite type deposit.