hydrometallurgical separation of rare earth elements， cobalt and nickel from spent nickel–metal–hydride batteries

1、Journal of Power Sources 195 (2010) 3735–3741Contents lists available at ScienceDirectJournal of Power Sourcesjournal homepage: www.elsevier.com/locate/jpowsourHydrometallurgical separation of rare earth elements, cobalt

2、 and nickel from spent nickel–metal–hydride batteriesLuiz Eduardo Oliveira Carmo Rodrigues, Marcelo Borges Mansur ?Departamento de Engenharia Metalúrgica e de Materiais, Universidade Federal de Minas Gerais, UFMG, A

3、v. Antônio Carlos, 6627, Pampulha, 31270-901 Belo Horizonte, MG, Brazila r t i c l e i n f oArticle history:Received 14 December 2009Accepted 15 December 2009Available online 29 December 2009Keywords:Nickel–metal–hy

4、dride batteriesRare earth elementsHydrometallurgySolvent extractionCobalt–nickel separationa b s t r a c tThe separation of rare earth elements, cobalt and nickel from NiMH battery residues is evaluated in thispaper. Ana

5、lysis of the internal content of the NiMH batteries shows that nickel is the main metal presentin the residue (around 50% in weight), as well as potassium (2.2–10.9%), cobalt (5.1–5.5%), rare earthelements (15.3–29.0%) a

6、nd cadmium (2.8%). The presence of cadmium reveals that some Ni–Cd batteriesare possibly labeled as NiMH ones. The leaching of nickel and cobalt from the NiMH battery powder withsulfuric acid is efficient; operating vari

7、ables temperature and concentration of H2O2 has no significanteffect for the conditions studied. A mixture of rare earth elements is separated by precipitation with NaOH.Finally, solvent extraction with D2EHPA (di-2-ethy

8、lhexyl phosphoric acid) followed by Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) can separate cadmium, cobalt and nickel from the leach liquor.The effect of the main operating variables of both leaching and sol

9、vent extraction steps are discussedaiming to maximize metal separation for recycling purposes.© 2009 Elsevier B.V. All rights reserved.1. IntroductionThe secondary battery nickel–metal–hydride (NiMH) is com-monly us

10、ed as power source in electronic devices like mobilephones, computers and hybrid electric vehicles (HEV). The mainparts of this battery are: a cathode made of nickel coated withnickel hydroxide; an anode made of a hydrog

11、en storage alloybased on mischmetal (mainly cerium, lanthanum, praseodymiumand neodymium) and nickel including substituents; a separatorbetween the two electrodes made of fine fibers (usually polyamide,polypropylene flee

12、ce or gauze); an electrolyte typically KOH; ametal case; and a sealing plate provided with a self-releasing safetyvent. Such structure is similar to that of Ni–Cd batteries. In fact,these two batteries have very similar

13、operating voltage but, incomparison to the Ni–Cd ones, the NiMH batteries do not containcadmium and they have about twice the energy density of the Ni–Cdbatteries.Because of such advantages, NiMH batteries have constantl

14、ysubstituted the Ni–Cd batteries. For instance, in the market ofmobile phones, the use of Ni–Cd batteries decreased from 63.8% to44.4% during this decade, those of lithium ion batteries increasedfrom 8.4% to 27.3% wherea

15、s the use of NiMH batteries were keptpractically constant at 28.0% [1]. Also, NiMH batteries currentlydominate the HEV market, with lead acid batteries finding appli-? Corresponding author. Tel.: +55 31 3409 1811; fax: +

16、55 31 3409 1815.E-mail address: marcelo.mansur@demet.ufmg.br (M.B. Mansur).cation in some mild hybrid architectures. The HEV battery marketwas estimated at $600 million in 2006 and it is expected to growto $2.3 billion b

17、y 2015 [2].As the need for electronic devices grows worldwide, the con-sumption of batteries is expected to increase in the coming years.Therefore, the continuous development of recycling battery tech-nologies may contri

18、bute to economical and environmental aspectsas pointed out by several research works with various types of bat-teries such as Zn–C, alkaline, Ni–Cd, NiMH and Li-ion [1,3–8]. Inthis context, the present paper aims to inve

19、stigate the main operat-ing variables of the hydrometallurgical route in order to maximizethe separation of the main metals commonly found in the NiMHbatteries.2. ExperimentalThe experimental work adopted in this study c

20、onsisted of thefollowing steps: (i) previous treatment, including classification ofbatteries by type (as suggested by a previous study [5]) followedby dismantling of batteries in order to separate plastic and metal-lic c

21、ases from the internal content of the NiMH batteries; (ii) metalcharacterization of the internal content of such batteries; (iii) leach-ing of the internal content of NiMH batteries with sulfuric acid;(iv) precipitation

22、of rare earth elements by pH adjustment, and (v)purification of cobalt and nickel by solvent extraction. All exper-iments were carried out using gloves, glasses and gas masks. Thecontact of battery dust with skin, eyes a

23、nd clothing requires imme-diate cleaning as suggested by previous studies [9].0378-7753/$ – see front matter © 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.jpowsour.2009.12.071L.E.O.C. Rodrigues, M.B. Mansur

24、 / Journal of Power Sources 195 (2010) 3735–3741 3737Fig. 2. Scanning electronic microscopy pictures of the internal content of NiMH batteries at different resolutions (75×, 100×, 500× and 1000×).Scan

25、ning electronic microscopic analysis of the powder of NiMHbatteries shown in Fig. 2 revealed that the powder is quite homo-geneous regarding to both color and shape of particles.The metal composition of NiMH batteries in

26、cluding and exclud-ing the metallic cases is shown in Table 1. In the first column, asemi-qualitative metal content of a randomly chosen battery deter-mined by SEM-EDS analysis is presented; the second column showsthe co

27、mposition of the powder from several batteries after milloperations which was determined by AAS and EDX. Typical compo-sitions including the metal case are also shown in the same table forthe sake of comparison. When met

28、al cases are removed, the contentof iron is significantly reduced and the composition of remainingmetals is increased. Nickel was found as the predominant metalspecies in the analyzed battery, nearby 50% in weight of the

29、 internalcontent of NiMH batteries. The presence of potassium, cobalt andrare earth elements was also found significant (2.2–10.9%, 5.1–5.5%and 15.3–29.0%, respectively), thus revealing the studied batter-ies are AB5 typ

30、e. Curiously cadmium was found in the powder ofNiMH batteries at significant amount (2.8%). As Ni–Cd and NiMHbatteries are quite similar in their structures, it seems that Ni–Cdbatteries were labeled as NiMH as evidenced

31、 also by other study[10]. Therefore, cadmium must be removed from the dust and treat-ment processes for NiMH batteries must consider the presence ofcadmium in the residue.NiMH batteries are normally classified into AB2 a

32、nd AB5 typesdepending on how metals A and B are combined in the hydrogen-absorbing alloys that constitute the anode of the battery. Suchalloys can absorb hydrogen atoms equivalent to about a thousandTable 1Metal composit

33、ion of NiMH batteries (% weight).Metal NiMHa (SEM-EDS, this work) NiMH powdera (AAS/EDX, this work) NiMHb (AB2) [3] NiMHb (AB5) [3,5,8,11]Al 1.1 0.6 0.5–1.0 0.5–2.0Cd n.d. 2.8 0.04–0.22Ce 3.4 6.1 0.4–5.5Co 5.1 5.5 1.0–3.

34、0 2.5–4.3Cr 0–1.6 0.02–0.08Cu 0.02Fe 0.9 0.3 23–25 20–25Hg 0.0072 –K 10.9 2.2 2.4–3.1La 11.5 5.4 1.4–6.6Mn 1.4 2.4 0.8–3.0Nd 10.9 3.0 1.0–4.1Ni 52.8 49.8 34–39 25–46Pb n.d. 0.0033 –Pr 3.2 0.8 0.3–1.3SiTi 1.4 2.2–3.9V 2.2