Recovery of Rare Earth Elements Present in Mobile Phone Magnets with the Use of Organic Acids

Abstract

Currently, the recovery of materials from secondary sources is increasingly necessary because of the scarcity of materials. Significant amounts of rare earth elements (REE) are found in permanent neodymium-iron-boron (NdFeB) magnets, used in various electrical and electronic equipments, such as mobile phones. However, the estimated recycling rate for REEs is only 1%. Hydrometallurgical routes are the most commonly used for REE recovery from secondary sources. This route usually uses inorganic acids, which are expensive and toxic. Thus, in this work the leaching efficiency of organic acids (acetic and citric) in leaching the REE (neodymium and praseodymium) present in magnets of obsolete or defective mobile phones was evaluated. Different concentrations of acids, solid/liquid relations, times and leaching techniques (microwave, ultrasound and conventional) are also evaluated. The results indicate that acetic and citric acids have the potential to leach Nd and Pr. Microwave leaching was the most effective method, compared to ultrasound and conventional methods. In microwaves, citric acid at 0.5 M (ratio s/l 1/100) leached 57% of Nd and 58% of Pr. Acetic acid at 0.5 M (s/l ratio—1/100) leached 48% of Nd and 65% of Pr, in 15 min. Furthermore, both citric acid and acetic acid also leached high percentages of iron (51% and 72%, respectively).

Rare Earth Elements (REE): Origins, Dispersion, and Environmental Implications—A Comprehensive Review

“…In 2020, about 23% of the global rare earths production was used for Nd-Fe-B permanent magnets, which contain about 30% of rare earths, mainly Nd with up 1/3 Pr beneath some Dy and Tb. In 2019, the volume of waste from electrical and electronic equipment reached 53.3 million tons, with an increasing tendency to contain large amounts of Cu and REE [304]. Consequently, REE play an increasingly vital role in industry, especially in green high-technology applications, such as wind turbines, hybrid cars, electric cars, and batteries [286].…”

Commercial-Scale Modification of NdFeB Magnets under Laser-Assisted Conditions

“…Their utility is diverse as they can be tailored in terms of both shape and geometry. Nevertheless, obtaining materials for manufacturing magnets from rare earth elements is not only a demanding process but is also costly and time consuming [ 3 , 4 , 5 , 6 , 7 ].…”

“…Therefore, before they find commercial applications, they must be subjected to modification to increase their resistance to external environmental factors. The search for solutions to increase this level of protection using different magnet coatings has been performed in many studies [ 3 , 4 , 8 , 9 , 10 ]. Among the most commonly used coatings are Ni-Cu-Ni, Zn, Rubber, Au, PTFE, Cr, and Ti Nitride [ 5 , 6 , 7 , 8 , 9 , 10 ].…”

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

“…Lee et al [15] carried out leaching processes with all four inorganic agents and demonstrated that hydrochloric and sulfuric acids performed best to dissolve 100% of Nd from waste magnets. In the recent study of Stein et al [16], it was demonstrated that organic acetic and citric acids also have potential as leaching agents for NdFeB magnets; however, the REE dissolution rates were found to be much lower in comparison to inorganic acids. With the additional use of microwaves, 57% of Nd and 58% of Pr were leached with 0.5 M citric acid, and 65% of Nd and 65% of Pr were leached with 0.5 acetic acid.…”