In this research, rare earth elements were recovered from permanent magnet which was dismantled from some kinds of waste hard disk drives HDDs. | Vietnam Journal of Science and Technology 55 (5B) (2017) 257-264 RECOVERING RARE EARTH OXIDE FROM NdFeB MAGNET OF WASTE HDDs BY LEACHING AND SELECTIVE PRECIPITATION METHODS Pham Khanh Huy1, 2, Nguyen Thi Thu Huyen1, Tran Thi Thanh Thuy2 Huynh Trung Hai1, Mai Thanh Tung1 1 Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Ha Noi, Viet Nam 2 Hanoi University of Mining and Geology, 18 Pho Vien, Duc Thang, Bac Tu Liem, Ha Noi * Email: phamkhanhhuy@ Received: 11 August 2017; Accepted for publication: 9 October 2017 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 % after 10 min reaction in H2SO4 acid have concentration > M under the leaching conditions: stirring speed of 200 rpm, particle size M after 10 minutes of 260 Recovering rare earth oxide from NdFeB magnet of waste HDDs by leaching and selective reaction, leaching efficiency was %. Concentration of element in leaching solution depends on the concentration of H2SO4. Figure 5. Effect of: (a) Grain size powder magnet; (b) leaching efficiency of each main element. In Fig. 5 (a) it is shown that with particle size smaller than mm, leaching efficiency .
