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The global demand for precious metals, in chemical, petrochemical, electrical and electronic products, medical and dentistry applications, jewelry and automobile industries, against the dwindling natural deposits; demands the development of more efficient recovery methods, as well as a move towards urban mining. The latter is becoming more attractive due to the high yields compared with extraction from primary ores. Current recovery rates of precious metals and REEs from spent products are low and there is a need to drive towards a closed-loop recycling system. However; the heterogeneous nature of such secondary sources of precious metals and REEs demands the development of robust methods for the recovery of strategic metals. This Special Issue will contribute to the knowledge gap in the characterization and recycling of precious metals and REEs from spent secondary materials. Spent secondary materials include catalytic converters, electronic boards, magnet scraps, fluorescent lamps, CRTs, LCDs, PV cells, solar panels, batteries, and fly ash, among others.

Prof. Dr. Zenixole Tshentu
Dr. Durga Parajuli
Guest Editors

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Related Special Issue

Published Papers (1 paper)

Research

21 pages, 2707 KiB

Open AccessArticle

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

by Ronei Tiago Stein, Angela Cristina Kasper and Hugo Marcelo Veit

Minerals 2022, 12(6), 668; https://doi.org/10.3390/min12060668 - 27 May 2022

Cited by 7 | Viewed by 3605

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). Full article

(This article belongs to the Special Issue Recovery of Precious Metals, Rare Earth Elements and Special Metals from Spent Secondary Products, Volume II)

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