No abstract

There is a global need for efficient and environmentally sustainable processes to close the life cycle loop of waste electrical and electronic equipment (WEEE) through recycling. Conventional WEEE recycling processes are based upon pyrometallurgy or hydrometallurgy. The former is energy-intensive and generates greenhouse gas (GHG) emissions, while the latter relies on large volumes of acids and organic solvents, thus generating hazardous wastes. Here, a novel “aeriometallurgical” process was developed to recycle critical rare earth elements, namely, neodymium (Nd), praseodymium (Pr), and dysprosium (Dy), from postconsumer NdFeB magnets utilized in wind turbines. The new process utilizes supercritical CO2 as the solvent, which is safe, inert, and abundant, along with the tributyl-phosphate–nitric acid (TBP–HNO3) chelating agent and 2 wt % methanol as a cosolvent. Nd (94%), Pr (91%), and Dy (98%) extraction was achieved with only 62% iron (Fe) coextraction and minimal waste generation. Fundamental investigations into the extraction mechanism demonstrated that metal ion charge has an important impact on the extraction efficiency. Fundamental investigations indicate that extraction proceeds by corrosion of the magnet particle’s surface layer. This work demonstrates that supercritical fluid extraction would find widespread applicability as a cleaner, a more sustainable option to recycle value metals from end-of-life products to enable the circular economy.

With the growing awareness to protect the urban environment and the increasing demand for strategic materials, recycling of postconsumer lithium-ion batteries has become imperative. This study aims to recover lithium, cobalt, nickel, and manganese from a LiNi 0.15 Mn 0.15 Co 0.70 O 2 cathode material of spent lithium-ion batteries of an electric vehicle. By utilizing systematic experimental and theoretical approaches based on the design of experiment and response surface methodology, the best leachant between HCl and H 2 SO 4 + H 2 O 2 and the optimal operating conditions are determined. Leaching with 1.0 M H 2 SO 4 mixed with 0.62 wt % H 2 O 2 at a liquid-to-solid ratio of 25.8 mL g −1 and a temperature of 51 °C for 60 min results in ∼100% recovery of all four metals. After leaching, cobalt, nickel, and manganese are coprecipitated as Ni 0.15 Mn 0.15 Co 0.70 (OH) 2 at pH above 11, while lithium is precipitated as lithium carbonate. These precipitates are mixed and sintered to generate a new cathode material, which is used to make a battery with high electrochemical performance. Valorization of spent lithium-ion batteries from electric vehicles enables conserving natural resources and protecting ecosystems, both of which enable the long-term sustainability of the biosphere while at the same time contributing to the circular economy.

The critical need for cost‐effective and sustainable large‐scale battery technologies for harvesting renewable energy has led to a new research wave on novel batteries made of low‐cost, high‐abundance, high‐performance, and safe components. Among the emerging candidates for post‐lithium‐ion batteries, aluminum‐based batteries are particularly promising due to the high theoretical capacities, low cost, and high abundance of raw materials. Most advanced nonaqueous rechargeable Al batteries rely on costly dialkylimidazolium chloride‐based chloroaluminate ionic liquids and this added cost inevitably diminishes various benefits of utilizing Al as the anode material. Here, a high‐performance Al battery made of Al anode, graphene nanoplatelets (GNPs) cathode, and a cost‐effective AlCl3‐trimethylamine hydrochloride (AlCl3‐TMAHCl) ionic liquid electrolyte is reported. The battery delivers a high specific capacity of 134 mAh g−1 at 2000 mA g−1 while maintaining Coulombic efficiency (CE) above 98% over 3000 cycles. Moreover, it delivers a specific capacity of 83 mAh g−1 with a CE of 97% under ultrafast charging at 4000 mA g−1 (1 min) and slow discharging at 100 mA g−1 (50 min) conditions. Considering the low cost and high performance, AlCl3‐TMAHCl electrolyte opens up a new avenue for the development of next‐generation Al batteries.

Some rare earth elements (REEs) are classified as strategic materials because of their increasingly high demand, supply uncertainty, and near zero recycling. For tackling the sustainability challenges associated with REEs, their technospheric mining, i.e., recovery from secondary sources, is imperative. Characterization results indicate that phosphogypsum, a byproduct of the fertilizer industry, contains about 0.03− 0.4 wt % REEs. Here, a novel process was developed that utilizes microwave irradiation to enhance the leaching efficiency of REEs from phosphogypsum. Optimal REE leaching was achieved by either microwaving at low power (600 W) and short duration (5 min) or at high power (1200 W) and long duration (15 min). The former creates cracks and pores in the particles, enhancing the infiltration of lixiviant, with minimal conversion of gypsum into less soluble crystals. The latter results in thermal degradation of the PG particles and the release of REEs at the cost of changing the PG crystal structure to less soluble phases. In all cases microwave pretreatment had a positive effect (more than 20% increase) on REE leaching efficiency. At the optimum microwaving conditions [15 min irradiation (2.45 GHz) at 1200 W], 80% Nd, 99% Y, and 99% Dy leaching efficiency was achieved.