RECOVERING RARE EARTH OXIDE FROM NdFeB MAGNET OF WASTE HDDs BY LEACHING AND SELECTIVE PRECIPITATION METHODS

Pham Khanh Huy

Abstract


Rare earth metal elements have been used widely in many different fields such as in fluorescence, polishing powder, nuclear, laser applications, fiber optics, superconductors, permanent magnets, capacitors and radar technology, etc. In recent years, the development and demand trend led to a large amount of electric and electronic waste (e-waste) generated annually. Faced with issues of shortage on using demand of rare earth metal, many studies have been done in order to recover, recycle and reuse this metal from e-waste. In this research, rare earth elements were recovered from permanent magnet which was dismantled from some kinds of waste hard disk drives HDDs.

Result of reseach showed that magnetic flux density of the NdFeB magnet was eliminated completely at 300 ºC in one hour. The leaching efficiency of magnet powder sample reached 99.4 % after 10 min reaction in H2SO4 acid have concentration > 0.3 M under the leaching conditions: stirring speed of 200 rpm, particle size < 0.25 mm, solid/liquid (S/L) ratio 20 g/1l and temperature reaction is 25 ºC. Total rare earth metal elements can be recovered by the using selective crystallization and precipitation method in leaching solution by Na2SO4 and oxalic acid up to 98.36 % was with purity up to 94.32 %. Nd2(C2O4) transformed into Nd2O3 after being calcinated at 700 °C.


Keywords


E-waste, rare earth magnet, FeNdB, leaching, selective precipitation.

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DOI: https://doi.org/10.15625/2525-2518/55/5B/12233

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Published by Vietnam Academy of Science and Technology