Value analysis of neodymium content in shredder feed: toward enabling the feasibility of rare earth magnet recycling

Exploring the potential reuse of phosphogypsum: A waste or a resource?

Phosphogypsum (PG), the main industrial by-product of phosphate fertilizer industry, primarily consists of calcium sulfate dihydrate. However, it contains various impurities with variable quantities depending on the origin of the phosphate rock. These impurities can restrict the reuse of phosphogypsum as a secondary primary resource. Consequently, large quantities of produced PG are stored in surface stockpiles that occupy extensive land areas and may pose a significant risk of ecological contamination to the surroundings. Researchers have shown growing interest in addressing the worldwide accumulation of this waste material. To gain a comprehensive understanding of the environmental impact of phosphogypsum, it is crucial to explore its properties (e.g., chemistry, mineralogy, radioactivity), and how it interacts with the surrounding environment, enabling well-informed decisions decision regarding its management and its valorization. In this review, we will i) explore the chemical, radiological and mineralogical characteristics of PG; ii) discuss the environmental concerns related to land discharge and sea disposal; and iii) examine the latest advancements in various valorization techniques developed including agriculture, REE extraction, environmental application, chemical and thermal transformation, and also construction sector. Outlining their limitations and challenges restrict in the global variability of phosphogypsum (PG), technical and economic limitations, and the potential for secondary pollution in select valorization approaches. This requires a thorough assessment and comparison with conventional disposal alternatives.

Optimization of elemental recovery from electronic wastes using a mild oxidizer

In this work, metals were recovered from electronic wastes under optimized conditions. The columnar extraction was used to increase the contact between the leachate solution and solid-state wastes. Industrial metals were recovered by an electrochemical process using a regenerated mild oxidizer under optimized operating parameters to enrich the metal concentrations and reduce waste generation. The maximum recovery rate (1.135 mg·min^-1) was recorded under the optimized conditions (160 A·m^-2 current density, 7 mL·min^-1 leachate flow rate, and 0.8 mol·L^-1 ferric concentration). The selective columnar extraction process was employed to extract gold, wherein the highest extraction efficiency (69.39%) was obtained under optimized conditions of 0.7 mol·L^-1 thiourea, 0.6 mol·L^-1 hydrochloric acid, 0.8 mol·L^-1 ferric chloride, 120 min circulation time, and 6 mL·min^-1 leachate flow rate. The adsorption process was used for the recovery of gold, which was investigated under the kinetic as well as equilibrium adsorption processes. The adsorption curves conformed to the Langmuir model and followed the first-order kinetics. The adsorption rate decreased with the increasing values of pH, temperature, adsorbent size, while the rate increased with the stirring speed and adsorbent quantity. Finally, acidic extraction under anaerobic and optimal conditions was performed to extract and selectively recover rare-earth elements. The rare-earth elements were initially precipitated in their sulfate forms and subsequently transformed into corresponding hydroxides and oxides. The total recovery efficiencies for cerium and neodymium were found to be 91.7% and 86.7%, respectively.

Dismantling of Printed Circuit Boards Enabling Electronic Components Sorting and Their Subsequent Treatment Open Improved Elemental Sustainability Opportunities

This critical review focuses on advanced recycling strategies to enable or increase recovery of chemical elements present in waste printed circuit boards (WPCBs). Conventional recycling involves manual removal of high value electronic components (ECs), followed by raw crushing of WPCBs, to recover main elements (by weight or value). All other elements remain unrecovered and end up highly diluted in post-processing wastes or ashes. To retrieve these elements, it is necessary to enrich the waste streams, which requires a change of paradigm in WPCB treatment: the disassembly of WPCBs combined with the sorting of ECs. This allows ECs to be separated by composition and to drastically increase chemical element concentration, thus making their recovery economically viable. In this report, we critically review state-of-the-art processes that dismantle and sort ECs, including some unpublished foresight from our laboratory work, which could be implemented in a recycling plant. We then identify research, business opportunities and associated advanced retrieval methods for those elements that can therefore be recovered, such as refractory metals (Ta, Nb, W, Mo), gallium, or lanthanides, or those, such as the platinum group elements, that can be recovered in a more environmentally friendly way than pyrometallurgy. The recovery methods can be directly tuned and adapted to the corresponding stream.

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

Rare earth elements (REEs) are becoming more and more significant as they play crucial roles in many advanced technologies. Therefore, the development of optimized processes for their recovery, whether from primary resources or from secondary sources, has become necessary, including recovery from mine tailings, recycling of end-of-life products and urban and industrial waste. Ionic solvents, including ionic liquids (ILs) and deep-eutectic solvents (DESs), have attracted much attention since they represent an alternative to conventional processes for metal recovery. These systems are used as reactive agents in leaching and extraction processes. The most significant studies reported in the last decade regarding the recovery of REEs are presented in this review.

A Structured Literature Review on Obsolete Electric Vehicles Management Practices

The use of electricity for transportation needs offers the chance to replace fossil fuels with greener energy sources. Potentially, coupling sustainable transports with Renewable Energies (RE) could reduce significantly both Greenhouse Gas (GHG) emissions and the dependency on oil imports. However, the expected growth rate of Electric Vehicles (EVs) could become also a potential risk for the environment if recycling processes will continue to function in the current way. To this aim, the paper reviews the international literature on obsolete EV management practices, by considering scientific works published from 2000 up to 2019. Results show that the experts have paid great attention to this topic, given both the critical and valuable materials embedded in EVs and their main components (especially traction batteries), by offering interesting potential profits, and identifying the most promising End-of-Life (EoL) strategy for recycling both in technological and environmental terms. However, the economics of EV recycling systems have not yet been well quantified. The intent of this work is to enhance the current literature gaps and to propose future research streams.

Accomplishing simple, solubility-based separations of rare earth elements with complexes bearing size-sensitive molecular apertures

Rare earth (RE) metals are critical components of electronic materials and permanent magnets. Recycling of consumer materials is a promising new source of rare REs. To incentivize recycling, there is a clear need for the development of simple methods for targeted separations of mixtures of RE metal salts. Metal complexes of a tripodal hydroxylaminato ligand, TriNOx^3-, featured a size-sensitive aperture formed of its three η²-(N,O) ligand arms. Exposure of cations in the aperture induced a self-associative equilibrium comprising RE(TriNOx)THF and [RE(TriNOx)]₂ species. Differences in the equilibrium constants K_dimer for early and late metals enabled simple separations through leaching. Separations were performed on RE1/RE2 mixtures, where RE1 = La-Sm and RE2 = Gd-Lu, with emphasis on Eu/Y separations for potential applications in the recycling of phosphor waste from compact fluorescent light bulbs. Using the leaching method, separations factors approaching 2,000 were obtained for early-late RE combinations. Following solvent optimization, >95% pure samples of Eu were obtained with a 67% recovery for the technologically relevant Eu/Y separation.

Uncovering the Recycling Potential of "New" WEEE in China

Newly defined categories of WEEE have increased the types of China's regulated WEEE from 5 to 14. Identification of the amounts and valuable-resource components of the "new" WEEE generated is critical to solving the e-waste problem, for both governmental policy decisions and recycling enterprise expansions. This study first estimates and predicts China's new WEEE generation for the period of 2010-2030 using material flow analysis and the lifespan model of the Weibull distribution, then determines the amounts of valuable resources (e.g., base materials, precious metals, and rare-earth minerals) encased annually in WEEE, and their dynamic transfer from in-use stock to waste. Main findings include the following: (i) China will generate 15.5 and 28.4 million tons WEEE in 2020 and 2030, respectively, and has already overtaken the U.S. to become the world's leading producer of e-waste; (ii) among all the types of WEEE, air conditioners, desktop personal computers, refrigerators, and washing machines contribute over 70% of total WEEE by weight. The two categories of EEE-electronic devices and electrical appliances-each contribute about half of total WEEE by weight; (iii) more and more valuable resources have been transferred from in-use products to WEEE, significantly enhancing the recycling potential of WEEE from an economic perspective; and (iv) WEEE recycling potential has been evolving from ∼16 (10-22) billion US$ in 2010, to an anticipated ∼42 (26-58) billion US$ in 2020 and ∼73.4 (44.5-103.4) billion US$ by 2030. All the obtained results can improve the knowledge base for closing the loop of WEEE recycling, and contribute to governmental policy making and the recycling industry's business development.

Tracking the Flow of Resources in Electronic Waste - The Case of End-of-Life Computer Hard Disk Drives

Recovery of resources, in particular, metals, from waste flows is widely seen as a prioritized option to reduce their potential supply constraints in the future. The current waste electrical and electronic equipment (WEEE) treatment system is more focused on bulk metals, where the recycling rate of specialty metals, such as rare earths, is negligible compared to their increasing use in modern products, such as electronics. This study investigates the challenges in recovering these resources in the existing WEEE treatment system. It is illustrated by following the material flows of resources in a conventional WEEE treatment plant in Denmark. Computer hard disk drives (HDDs) containing neodymium-iron-boron (NdFeB) magnets were selected as the case product for this experiment. The resulting output fractions were tracked until their final treatment in order to estimate the recovery potential of rare earth elements (REEs) and other resources contained in HDDs. The results further show that out of the 244 kg of HDDs treated, 212 kg comprising mainly of aluminum and steel can be finally recovered from the metallurgic process. The results further demonstrate the complete loss of REEs in the existing shredding-based WEEE treatment processes. Dismantling and separate processing of NdFeB magnets from their end-use products can be a more preferred option over shredding. However, it remains a technological and logistic challenge for the existing system.