Reductive acid leaching of valuable metals from spent mixed-type lithium-ion batteries

Transcription

1 Reductive acid leaching of valuable metals from spent mixed-type lithium-ion batteries Gordon C. C. Yang 1,2, Yu-Chen Huang 2, Fang-Wei Yang 2 1 Center for Emerging Contaminants Research, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan 2 Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

2 Introduction Hypothesis and methodology Results and discussion Conclusions

3 Introduction (1/4) Currently, lithium-ion batteries (LIBs) are one of the most commonly used batteries over the world. Various types of LIBs have been widely used over the past 25 years and their usage is expected to grow further, particularly in automotive sector. Inevitably, a great quantity of spent LIBs will be generated in years to come (Meshram et al., 2015). 3

4 Introduction (2/4) Since LIBs are known to contain valuable metals (e.g., Co, Ni, Li, and Mn), recycling of LIBs through metal recovery is preferred to simply dispose of by landfilling (Nan et al., 2005). Among various hydrometallurgical methods employed for metal recovery from spent LIBs, reductive leaching is commonly reported in the literature (Kang et al., 2010; Meshram et al., 2015; Zeng et al., 2014). 4

5 Introduction (3/4) Many researchers also reported that such reductive acid leaching yielded a greater leached metal concentration when it was performed at elevated temperatures in the range of C in comparison with room temperature (Chen et al., 2011; Jha et al., 2013; Kang et al., 2010; Sun et al., 2012). In the literature, several reducing agents have been tested in reductive acid leaching including hydrogen peroxide, sucrose, glucose (Pagnanelli et al., 2014), and cane molasses (Su et al., 2008). 5

6 Introduction (4/4) To the best knowledge of the present authors, however, no one has compared the performance of at least three reductants in reductive acid leaching for recycling of spent LIBs in a single study. Thus, the goal of this research was set to compare the performance of recovery of valuable metals from spent mixed-type LIBs using H 2 SO 4 and various reductants. Reducing agents of interest included hydrogen peroxide (H 2 O 2 ), ascorbic acid (C 6 H 8 O 6 ), and glucose (C 6 H 12 O 6 ). 6

7 Hypothesis and methodology (1/3) Pre-treatments: The spent mixed-type LIBs are mainly The spent mixed-type LIBs collected composed from of prismatic a local recycling type and plant of spent batteries were subjected cylindrical to various pre-treatments. type. Discharge Crushing Sieving Roasting Lixiviation: H 2 SO 4 was used as a leaching agent in the acid leaching process to which a selected reductant was also added. Leaching agent: 3 M or 4 M H 2 SO 4 Reductants: Hydrogen peroxide(h 2 O 2 ) Ascorbic acid(c 6 H 8 O 6 ) Glucose(C 6 H 12 O 6 ) Solid-to-liquid ratio: 33 g/l Temperature: 80 C 7

8 Hypothesis and methodology (2/3) Presumably, the test specimen of spent LIBs contained LiCoO 2, MnO 2, and Mn 2 O 7. The stoichiometric amounts of various reductants were calculated based on the following reaction equations: LiCoO H 2 SO H 2 O 2 CoSO Li 2 SO 4 +O 2 +3H 2 O (1) 20 LiCoO 2 +30H 2 SO 4 +C 6 H 8 O 6 20 CoSO 4 +10Li 2 SO 4 +6CO 2 +34H 2 O (2) 24 LiCoO 2 +36H 2 SO 4 +C 6 H 12 O 6 24 CoSO 4 +12Li 2 SO 4 +6CO 2 +42H 2 O If the reductive acid leaching is employed, the oxidation number of the (3) MnO 2 selected +H 2 SO 4 reducing +H 2 O 2 agent MnSOhas 4 +Oto 2 be +3H taken 2 O into account so that a proper (4) 10 MnO reductant 2 +10H 2 concentration SO 4 +C 6 H 8 O 6 can 10be MnSO used. 4 +6CO 2 +14H 2 O (5) 12 MnO 2 +12H 2 SO 4 +C 6 H 12 O 6 12 MnSO 4 +6CO 2 +18H 2 O (6) Mn 2 O 7 +2H 2 SO 4 +5H 2 O 2 2 MnSO 4 +7O 2 +5H 2 O (7) 2Mn 2 O 7 +4H 2 SO 4 +C 6 H 8 O 6 4 MnSO 4 +6CO 2 +8H 2 O (8) 12 Mn 2 O 7 +24H 2 SO 4 +5C 6 H 12 O 6 24 MnSO 4 +30CO 2 +54H 2 O (9) 8

9 Table 1 The th International Conference on Sustainable Solid Waste Management, Hypothesis and methodology (3/3) Test conditions employed in reductive acid leaching of spent mixed-type LIBs using various reductants Test No. Temperature ( o C) H 2 SO 4 conc. (M) Reductant added Reductant concentration (M) None (Blank test) 0 To yield 2 a high 80 leaching of 3 Hydrogen peroxide (H 2 O 2 ) 1.87 manganese form Mn O 7 in 3 Ascorbic acid (C 6 H 8 O 6 ) 0.19 sulfuric acid, a rather high Glucose (C 6 H 12 O 6 ) 0.16 concentration of hydrogen peroxide 5 had to 80 be used as 3 Hydrogen peroxide (H 2 O 2 ) 5.92 compared 6 with M of 3 Ascorbic acid (C 6 H 8 O 6 ) 0.59 ascorbic 7 acid and M of 3 Glucose (C 6 H 12 O 6 ) 0.49 glucose 8 were used Hydrogen peroxide (H 2 O 2 )

10 Results and discussion (1/4) Table 2 Reductive acid leaching performance for the specimen of spent LIBs under various operating conditions Leaching efficiency (%) Test No. Al Fe Ni Co Mn Li When 86 a reductant was added to the leaching system, 84 a significant H 2 95 O increase 98 in C 6 H87 8 O leaching 89 efficiency for C 6 H84 12 O target metals was 100 found. 10

11 Results and discussion (2/4) H 2 O 2 C 6 H 8 O 6 C 6 H 12 O 6 Among three reductants tested, hydrogen peroxide was found to yield the highest leaching efficiency, followedbyascorbicacid(c 6 H 8 O 6 ), and glucose (C 6 H 12 O 6 )thelowest. 11

12 Results and discussion(3/4) Table 3 Comparison of reported performance for reductive acid leaching of spent lithium-ion batteries Spent LIBs Leaching media Temp., time & Leaching efficiency Reference Material pulp density LiCoO 2 4 M H 2 SO vol% H 2 O 2 85 C, 120 min, solid/liquid = 100 g/l LiCoO 2 2 M H 2 SO vol% H 2 O 2 75 C, 60 min, solid/liquid = 100 g/l LiCoO 2 2 M H 2 SO vol% H 2 O 2 60 C, 60 min, solid/liquid = 100 g/l LiCoO M C 6 H 8 O 6 70 C, 20 min, solid/liquid = 25 g/l LiCoO M H 2 SO g/l C 6 H 12 O 6 80 C, 120 min, solid/liquid = 35 g/l Mixed 3 M H 2 SO vol% H 2 O 2 80 C, 60 min, solid/liquid = 33 g/l 96% Li & 95% Co Chen et al., % Li & 70% Co Jha et al., 2013 >99% Co Kang et al., % Li & 95% Co Li et al., % Li & 88% Co Pagnanelli et al., % Li & 89% Co This study. 12

13 Results and discussion (4/4) As shown in Fig. 1(a), the solid residue obtained from Test1(i.e.,ordinaryacidleachingusingH 2 SO 4 alone) appeared to be in micro chunks. However, the solid residue obtained from Test 5 appeared to become much smaller particles as shown in Fig. 1(b). (a) (b) Fig. 1. SEM-EDS results for the solid residues obtained from acid leaching tests: (a) Test 1, and (b) Test 5 13

14 Conclusions (1/2) This study has again confirmed that reductive acid leaching yielded a much better recovery for valuable metals contained in spent mixed-type lithium-ion batteries as compared with acid leaching alone. When LIBs are leached by an acid, generally, high valent cobalt ions and manganese ions will be generated in the leached solution. 14

15 Conclusions (2/2) Like reported by many researchers, H 2 O 2 was found to be the best reductant in this work to enhance the leaching of valuable metals from spent mixed-type LIBs. In this study, the test results showed that the optimum leaching efficiencies for cobalt (Co), lithium (Li), nickel (Ni), and manganese (Mn) were 89%, 98%, 95%, and 100%, respectively. 15

16 East Taiwan - Hualien North Taiwan - Taipei West Taiwan - Taichung 16

17 South Taiwan - Kaohsiung