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This work investigates the use of supercritical CO2, with organic acid solutions as cosolvents, for the recovery of neodymium (Nd) from the NdFeB permanent magnets of hard disk drives (HDDs). Atmospheric leaching experiments were performed at 90 °C, solid:liquid ratio of 1:20, and acid concentration of 1.0 M, using malic and citric acids. Extraction using supercritical CO2 was performed using different pressures, temperatures and extraction times. Leaching of the unroasted NdFeB powder at 90 °C resulted in Nd recoveries of 99.9% after 360 min using malic acid. With roasted NdFeB powder, low Nd recovery efficiencies of 21% and 32.1% after 900 min were obtained using malic and citric acid, respectively, at pressure of 1.01 bar and temperature of 90 °C. Extraction of the unroasted powder with supercritical CO2, at 90 °C and 120 bar, resulted in Nd recovery efficiencies of 99.4% and 50.5% after 30 min, using malic acid and citric acid, respectively. In the case of the roasted NdFeB powder, the efficiencies were 99.5% and 30.6% after 120 min using malic acid and citric acid, respectively, at 90 °C and 100 bar. The use of supercritical CO2 was highly effective for the recovery of Nd from the unroasted powder using malic acid, enabling a significant reduction of the extraction time from 360 min to 30 min. For the roasted NdFeB powder, it was possible to extract 99.5% of the Nd after 120 min using supercritical CO2 and malic acid, whereas the maximum recovery obtained with atmospheric leaching was 21.0% after 360 min.

The printed circuit boards are the fundamental components of waste electrical and electronic equipment (WEEE). The PCBs stand out due to the amount of metals in their composition as well for their complex and heterogeneous constitution that make their recycling difficult. In this context, the aims of the study was to evaluate the application of supercritical CO2 modified with ethanol in order to remove the polymers contained in PCBs from discarded mobile phones. The PCBs were characterized and an evaluation of the supercritical extraction was performed through experimental design. The characterization showed that PCBs contained 64.02 wt% of metals, 20.51 wt% of ceramics and 15.47 wt% of polymers. The fractional factorial experimental design showed that 69.53 wt% of the polymers present in the PCBs were extracted, at 170 °C and 7.5 MPa. As the remaining polymers are no longer covering the metals, they could be more easily leached and therefore more effectively recovered.

The demand for photovoltaic panels has increased in recent years and the resources used in its production such as silicon, with high production costs and silver that is becoming scarce, in addition to the presence of toxic metals such as lead, highlight the importance of recycling of these materials. One of the main challenges for recycling is the delamination of the panels, for which supercritical fluids can be an effective option. Constituents of a photovoltaic module were analyzed using SEM/EDS, XRD, XRF, TGA, DSC, and FTIR techniques. The efficiency of the delamination process was evaluated using tests carried out at atmospheric pressure, in the presence of different cosolvents. Comparative tests were performed using supercritical CO2 (ScCO2). For both processes, after delamination, the components that still showed low release of adhered materials were processed in a planetary ball mill. Determinations were then made of the recovery and purity of the delaminated fractions, as well as the separation of the adhered materials. The best results for recovery and purity of the glass, metallic filaments, and backsheet were obtained using ScCO2 with toluene, together with planetary ball milling, achieving values over 96 %. For the solar cell and EVA (cell + EVA), the recovery was greater than 85 %, including high value materials such as Si and Ag. In addition to recovering high value metals and reducing the volume of solvent, the use of ScCO2 enabled delamination of the photovoltaic panel with a time around 3.5 times shorter than at atmospheric pressure.