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Rare earth elements (REEs) are commercially used in an increasing number of critical or widely popular consumer and industrial products. Neodymium (Nd) element has emerged in recent years as one of the most critical REE, due to risks associated with its security of supply at required amounts. It has been widely reported that end of life (EoL) consumer electrical products contain significant amounts of metals and plastics. Thus, recovery of Nd from magnet scraps, EoL appliances or industrial applications is gaining even more strategic importance nowadays. In this study, an ex-ante life cycle assessment (LCA) of the hydrometallurgical recovery of Nd from waste electric and electronic equipment (WEEE) was conducted. The hydrometallurgical Nd recovery route consists of pretreatment, chemical leaching and Nd metal precipitation The feasibility and environmental performance of Nd metal recycling experiment model was investigated with an LCA scenario focusing on neodymium-iron-boron (Nd-Fe-B) magnet production. The LCA results were compared to that due to Nd-Fe-B magnet production from bastnäsite/monazite mineral ores using the traditional sintered magnet route. LCA sensitivity analysis and cost analysis were also performed. It was found out that, from both an economical and environmental point of view, magnet production from recovered Nd performed better than that of virgin magnet production. The scaled-up Nd metal recovery system reduced environmental impacts of Nd-Fe-B magnet production system by up to 65% for eight of the eleven environmental impact categories. Nd recycling reduced production cost from 8.55 to 3.98 USD/kg.
BACKGROUND: The waste printed circuit boards (WPCBs), today, offer a wide array of metals and are of great importance because their metal concentration is much more than that in the ores. Largely, studies have been devoted to Cu bioleaching from WPCBs because it has the highest ratio among all metallic elements ( ̴ 10-30%). In the present study, an intensified mixed meso-acidophilic bacterial leaching of multi-metals has been studied from WPCBs of spent mobile phones, with the system operating under high oxido-reductive potentials (HORPs). ICP-OES, XRD and SEM-EDX characterization indicated the sample to have recoverable contents of Cu, Al, Ni & Zn which were targeted for bioleaching. RESULTS: Shake flask optimization studies, under HORP of >750 mV indicated dissolutions of Cu – 98.1%, Al – 55.9%, Ni – 79.5% and Zn – 66.9% under optimized conditions of 9 g/L Fe (II), 10% pulp density, 1.8 initial pH and 10% (v/v) as initial inoculum. Under these conditions, at ORP >650 mV, Cu – 97.3%, Al – 55.8%, Ni – 79.3% and Zn – 66.8% were achieved in bench scale (1L) bioreactor systems without any significant reduction in efficiency (compared to shake flasks) in 8 days of operation. CONCLUSION: Variations in the co-relatable parameters, to metal leaching, such as pH, ORP and Fe (II) concentrations indicated that these parameters significantly contributed to metal leaching. Operating the system under high and controlled ORPs is a faster and efficient way to leach multi-metals from WPCBs.
Abstract Waste electrical and electronic equipments (WEEE or e-waste) are an important source for rare earth elements (REEs). Among various type of WEEE, NdFeB magnets are known for their high content of neodymium (Nd) and dysprosium (Dy). Recovery of REEs from NdFeB magnets is of prime interest for the industry to meet the ever-growing demand for REEs. In this study, some physical and hydrometallurgical approaches including demagnetization, grinding, screening, leaching, precipitation and extraction have been adopted to study the Nd and Dy recovery from spent NdFeB magnets. Various inorganic (HCl, HNO₃, H₂SO₄ and aqua regia) and organic reagents (acetic acid and oxalic acid) were tested as lixiviants for leaching of the magnets. As a new approach, the recovery of Nd and Dy in the leaching solution was tested by eliminating the iron by a solution purification process involving precipitation of ferric iron in solution as a hydroxide and solvent extraction with ionic liquids (ILs). The comparative batch system studies between ionic liquids (ILs) demonstrated that the extraction efficiency of di-2-ethylhexyl phosphoric acid (D2EHPA) was higher than trihexyltetradecylphosphonium chloride (CYPHOS® IL101) after leaching stage. Nd and Dy were successfully extracted with complete recovery from the optimized system. H₂SO₄ leaching solution using ILs. Keywords: Hydrometallurgy; Ionic Liquids; NdFeB Magnets; Neodymium; Dysprosium
In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus.
Rare earth metals (REMs) are a series of 17 elements, for instance, neodymium is much less common than lanthanum or cerium and a very large amount of mining is needed for small amounts of neodymium. On the other hand, recovery of REMs is interesting due to its high market prices along with various industrial applications. Waste of electric and electronic equipment (WEEE), or electronic waste (ewaste) is a potential and important secondary source of base metal, precious metal and REMs. In the last decade, recovery of metals using bioprocess technology has been one of the most promising technologies. Biosorption represents a biotechnological innovation as well as a cost effective excellent tool for the recovery of REMs from aqueous solutions. In this study, Nd was removed from a mixed leachate solution derived from neodymium magnets in batch and continuous sorption systems by using dried green microalgae (Chlorella vulgaris). The maximum Nd uptake (q=157.21 mg/g) was determined at pH 5 with a biosorbent dosage of 0.5 g/L and an initial neodymium concentration in the mixed leachate solution was 250 mg/L at 35 °C in the batch test. Therefore Chlorella vulgaris was found to have a good potential in its role as a biosorbent for neodymium out of a mixed leachate solution derived from neodymium magnets. The use of the studied biosorbent in the removal of Nd in continuous mode was successful. Due to the slow kinetics of Nd sorption onto Chlorella vulgaris, the sorption capacity in batch assays was higher than that in continuous assays.
Compact Fluorescent Lamps (CFLs) are a relatively old but efficient lighting technology that has resulted from the innovations using rare earth elements (REEs). Fluorescent lamp waste represents a great potential source of yttrium and europium ores as well as other secondary raw materials that could be repurposed to aid the future demand and deal with waste metal disposal issues. The main goal of this study was to investigate and compare the Rare Earth Element leaching performance of selected mineral acids (HCl, HNO3, H2SO4, Aqua Regia) during microwave and hot plate digestion methods, required in order to separate yttrium and europium from waste lamp fluorescent phosphor powders. Also, base metals leached from fluorescent lamp powders were studied since they composed a considerable digested fraction present in the samples. Specifically, this study is proposed: • to investigate hot plate and microwave assisted digestion methods in order to break down yttrium and europium containing phosphors from waste fluorescent lamp powders; • to identify key leaching characteristics among acids and methods in this study; • to establish a qualitative and quantitative comparison between the microwave and the hot plate acid digestion methods.