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Recovery of Rare Earth Elements in Hard Disk Drives Out of Desktop Computers

In the context of the general discussion about the recovery of technology metals in WEEE, hard disk drives out of desktop computers came into focus of optimized recycling processes due to high contents of rare earth elements (REE).

In Germany 2009, the quota of desktop computers in collection group three "IT, telecommu-nication equipment and consumer equipment" was about 3.9 %. These devices are sorted out and manually disassembled in primary treatment facilities to separate single components, which will be processed mechanically later on. A share of over 3 % represents hard disk drives, which consist of aluminum, iron, copper, plastics and REE containing components, like printed circuit boards and Neodymium-Iron-Boron (NdFeB) permanent magnets. The commonly used recycling strategy for these components in primary treatment facilities is shredding. This process dilutes and disperses the REE into the main output flows and leads to a total loss.
This case study points out REE containing components in hard disk drives, investigates the dismantling feasibilities and analyzes the REE contents. For this purpose, over 30 hard disk drives of different manufacturers and production dates were disassembled and compared.
The effort of a manual disassembly is high, due to a large number of connection elements, which constitutes a very compact and solid design of hard disk drives. Printed circuit boards with a share of 6 % can be easily separated, as these components are located outside of the hard disk drive bodies. Containing high rates of precious metals like gold, printed circuit boards consist of small quantities of Cerium, Lanthanum, Scandium and Europium. Higher concentrations of REE like Neodymium, Praseodymium, Dysprosium and Terbium are hold by two different NdFeB magnets inside the hard disk drive. Responsible for the precise movement of the read/write head and for the drive of the disc spindle these permanent magnets hold a share of over 3 % of hard disk drives (2.69 % linear motor magnet, 0.43 % spindle motor magnet). For a more detailed estimation of REE potentials, NdFeB magnets were analyzed. Digestion methods with nitric acid, sulfuric acid and aqua regia were tested for samples of linear and spindle mag-nets. Ten elements were determined for further analyses with an inductively-coupled plasma optical emission spectroscopy (ICP-OES): Boron (0.81 %), Cobalt (2.09 %), Dysprosium (1.39 %), Iron (63.81 %), Neodymium (23.56 %), Praseodymium (3.39 %) and Terbium (0.01 %) as constituents of the alloy and Nickel (3.3 %), Tin (0 %) and Zinc (0.01 %) as coating materials.

Copyright:	© Lehrstuhl für Abfallverwertungstechnik und Abfallwirtschaft der Montanuniversität Leoben
Quelle:	Depotech 2012 (November 2012)
Seiten:	8
Preis:	€ 4,00
Autor:	Dipl.-Ing. Maximilian Ueberschaar Prof. Dr.-Ing. Vera Susanne Rotter
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