Hydrometallurgical recovery of metal values from sulfuric acid leaching liquor of spent lithium-ion batteries

Waste Management 38 (2015) 349–356

Contents lists available at ScienceDirect

Waste Management journal homepage: www.elsevier.com/locate/wasman

Hydrometallurgical recovery of metal values from sulfuric acid leaching liquor of spent lithium-ion batteries Xiangping Chen, Yongbin Chen, Tao Zhou ⇑, Depei Liu, Hang Hu, Shaoyun Fan Key Laboratory of Resources Chemistry of Nonferrous Metals, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China

a r t i c l e

i n f o

Article history: Received 21 November 2014 Accepted 20 December 2014 Available online 22 January 2015 Keywords: Hydrometallurgical process Recovery Metal value Selective precipitation Solvent extraction

a b s t r a c t Environmentally hazardous substances contained in spent Li-ion batteries, such as heavy metals and nocuous organics, will pose a threat to the environment and human health. On the other hand, the sustainable recycling of spent lithium-ion batteries may bring about environmental and economic benefits. In this study, a hydrometallurgical process was adopted for the comprehensive recovery of nickel, manganese, cobalt and lithium from sulfuric acid leaching liquor from waste cathode materials of spent lithiumion batteries. First, nickel ions were selectively precipitated and recovered using dimethylglyoxime reagent. Recycled dimethylglyoxime could be re-used as precipitant for nickel and revealed similar precipitation performance compared with fresh dimethylglyoxime. Then the separation of manganese and cobalt was conducted by solvent extraction method using cobalt loaded D2EHPA. And McCabe–Thiele isotherm was employed for the prediction of the degree of separation and the number of extraction stages needed at specific experimental conditions. Finally, cobalt and lithium were sequentially precipitated and recovered as CoC2O42H2O and Li2CO3 using ammonium oxalate solution and saturated sodium carbonate solution, respectively. Recovery efficiencies could be attained as follows: 98.7% for Ni; 97.1% for Mn, 98.2% for Co and 81.0% for Li under optimized experimental conditions. This hydrometallurgical process may promise a candidate for the effective separation and recovery of metal values from the sulfuric acid leaching liquor. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Lithium-ion batteries (LIBs) have been widely used in portable equipment, such as mobile devices (e.g. iPad, iPhone), personal computers and video cameras, but also in hybrid and electric vehicles and other modern-life appliances. Their desirable characteristics such as modest size and weight, high cell voltage, low selfdischarge rate and high energy density may make LIBs an alternative to reduce the currently heavy dependence on fossil fuel resources (Castillo et al., 2002; Contestabile et al., 1999; Zhang et al., 1998). The drastic growth of their usage in nomadic technology market has greatly stimulated the production and consumption of LIBs. However, the consequence of the expansion of LIBs usage and the reduced life of LIBs would be an increasing demand for the disposal of spent LIBs in the forthcoming years (Contestabile et al., 1999; Zhang et al., 1998; Lupi et al., 2003; Lain, 2001). Lithium-ion batteries recently present an active research field and numerous research works are focused on the substitution ⇑ Corresponding author. Tel.: +86 731 8876605. E-mail address: [email protected] (T. Zhou). http://dx.doi.org/10.1016/j.wasman.2014.12.023 0956-053X/Ó 2015 Elsevier Ltd. All rights reserved.

products to LiCoO2 cathode material, mainly for the consideration of cost and safety. Lower valued transition metals, such as nickel, manganese and iron, were employed to substitute partially or totally for cobalt and a series of newly developed cathode materials have sprung up like mushrooms recently, such as LiFePO4, LiNi1/3Co1/3Mn1/3O2, LiNi0.8Co0.15Al0.05O2 and LiMnO2 (Ellis et al., 2010). However, these emerging materials will lead to a more complicated waste material stream (e.g. mixed waste cathode materials of LiCoO2, LiMnO2, LiNiO2, LiNi1/3Co1/3Mn1/3O2) and an increasing difficulty in the separation and recovery metal values. Spent LIBs are usually comprised of metal values (e.g. Ni, Co, Li), organic chemicals and plastics, varying from different manufacturers and different types of batteries (Chagnes and Pospiech, 2013). However, irresponsible discarding of these untreated spent LIBs may lead to environmental contamination, which cannot meet the requirement of sustainable utilization of valuable materials. This study was particularly focused on the sustainable separation and recovery of metal values from leaching liquor of spent lithium-ion batteries, regardless of battery types. Currently, pyrometallurgical and hydrometallurgical processes are the two common routes used in valuable metals recovery from

350

X. Chen et al. / Waste Management 38 (2015) 349–356

Table 1 Separation and recovery techniques investigated by some previous references. Recovery method

References

Sample

Additive

Solvent extraction

Lupi et al. (2003) Kang et al. (2010) Shen et al. (2008) Pranolo et al. (2010) Provazi et al. (2011) Zhao et al. (2011)

LiCoxNi1xO2 – LiCoO2 LiCoO2 Mixed types of batteries LiCoO2

Cyanex272 Cyanex272 AcorgaM5640, etc. PC-88A Cyanex272, etc. Cyanex272 and EDTA

Selective precipitation

Castillo et al. (2002) Contestabile et al. (2001) Kang et al. (2010) Wang et al. (2009) Dorella and Mansur (2007) Li et al. (2009) Chen et al. (2011)

LiCoO2 & LiMnO2 LiCoO2 LiCoxNi1xO2 LiCoO2, LiMnO2 & LiNiO2 LiCoO2 LiCoO2 LiCoO2

NaOH NaOH NaOH Dimethylglyoxime & KMnO4, etc. NH4OH NaOH H2C2O4

Electrochemical method

Armstrong et al. (1997) Lupi et al. (2005)

– LiCoO2 & LiCoxNi1xO2

–

Resin-ion exchange

Badawy et al. (2014)

LiCoO2

Polyamidoxime resin

Bio-hydrometallurgy

Mishra et al. (2008)

LiCoO2

Acidithiobacillus ferrooxidans

spent lithium-ion batteries (Georgi-Maschler et al., 2012; Cheret and Santen, 2005; Al-Thyabat et al., 2013). The pyrometallurgical processes, however, involve some disadvantages such as materials loss, hazardous gases release, dust emission and high energy consumption. Moreover, a hydrometallurgical process is usually needed to refine the residues into purer forms (such as salts, hydroxides and metals). Conversely, hydrometallurgical process may present an alternative and an opportunity to turn spent batteries into pure metals or metal salts with low energy requirement but produce salts as by-products. Table 1 shows the relevant recovery and separation techniques investigated by some previous references. Sustainable recycling of spent lithium-ion batteries exhibits a promising research field for both environmental protection and valuable materials re-utilization. Present study is, therefore, focused on the separation and recovery of metal values from sulfuric acid leaching liquor of mixed types of waste cathode materials (mixture of LiCoO2, LiMnO2, LiNiO2, LiNi1/3Co1/3Mn1/3O2 in this case) after the pre-treatment of spent LIBs as reported in our previous study (Chen and Zhou, 2014). First, nickel was selectively precipitated by dimethylglyoxime reagent at optimized precipitation conditions after removing of iron ions. Then manganese was selectively extracted from the leaching liquor using cobalt loaded D2EHPA (Co-D2EHPA) (Cole, 2002; Hossain et al., 2011). Finally, cobalt and lithium were sequentially precipitated and separated using ammonium oxalate solution and saturated sodium carbonate solutions (Tang et al., 2014; Wang et al., 2009), respectively. It is expected that this study can provide an effective recycling route for Ni, Co, Mn and Li recovery from leaching liquor of waste cathode materials. 2. Materials and methods 2.1. Materials and reagents In this study, the leaching liquor used was obtained from real leaching liquor of waste cathode materials (reductive leaching of mixed powders contained LiNi1/3Co1/3Mn1/3O2, LiCoO2 and LiMnO2 on conditions as follows: 2 mol L1 H2SO4 + 2 vol.% H2O2, liquid/ solid ratio of 20 ml g1, reaction temperature of 80 °C and reaction time of 60 min). Organic extraction reagents, di-(2-ethylhexly) phosphoric acid (D2EHPA, 95.7% in purity), tri-butyl phosphate

(TBP, 96.8% in purity) and sulfonated kerosene employed were kindly supplied by Luoyang Aoda Chemical Co., Ltd. (Luoyang, China). All other chemical reagents used during the experiments were of analytical grade and all the solutions at specified concentrations were prepared or diluted using deionized water. 2.2. Purification Before the separation and recovery process, iron ions were removed by adjusting pH value of the leaching liquor using 2 mol L1 sodium hydroxide solution. A pH meter (PHS-3D, 2000) was applied for pH monitoring and regulating of the leaching liquor during the purification operation. Afterwards, the pulp was filtered using vacuum suction filter machine and the residue was washed with deionized water to wash off as much valuable metals as possible. The concentrations of metal ions before and after purification were determined by ICP–OES to calculate the precipitation efficiencies of different metals. A small amount of the leaching liquor sample (2 ml) was drawn out and diluted to appropriate concentration. Then contents of different metals in the sample were detected and analyzed using an Induced Coupled Plasma Optical Emission Spectrometer (Agilent Technologies 700 Series ICP–OES). 2.3. Selective precipitation The recovery of nickel, cobalt and lithium was carried out by selective precipitation method. First, nickel was selectively precipitated by adding 0.05 mol L1 dimethylglyoxime reagent (DMG, C4H8N2O2) to the leaching liquor (Wang et al., 2009). Then manganese was extracted by Co-D2EHPA. After the separation of nickel and manganese, cobalt and lithium were sequentially precipitated using 0.5 mol L1 ammonium oxalate solution [(NH4)2C2O4] and hot saturated sodium carbonate solution (Na2CO3, 95 °C), respectively. Experimental conditions, such as equilibrium pH and molar ratio of dimethylglyoxime and nickel, were optimized to obtain the appropriate precipitation conditions. Then the nickel–DMG chelating precipitate was dissolved in 1 mol L1 hydrochloric acid solution to re-generate dimethylglyoxime. The recycled DMG will be re-used as precipitant for nickel. The precipitation and the dissolution reactions can be expressed as follows:

351

X. Chen et al. / Waste Management 38 (2015) 349–356

Cobalt was selectively precipitated using 0.5 mol L1 (NH4)2C2O4 and recovered as CoC2O42H2O after filtration and drying. Finally, lithium was treated with hot saturated sodium carbonate (prepared at 95 °C) and recovered as Li2CO3. All precipitation reactions and dissolution reaction were carried out in a 250 mL three-necked flask placed into an oil bath to control the reaction temperature. The leaching liquor was stirred at 300 rpm by an electromagnetic stirrer, and a vapor condenser was employed to prevent water evaporation. The precipitation efficiency can be calculated according to Eq. (1):

P¼

C 0 V 0  CV  100% C0V 0

ð1Þ

where P is the metal precipitation efficiency; C0 and C are the concentrations of different metals in the solution before and after precipitation, respectively; V0 and V are the volumes of the leach liquor before and after precipitation, respectively. 2.4. Solvent extraction First, di-(2-ethylhexly) phosphoric acid (D2EHPA) was 70–75% saponified using concentrated sodium hydroxide solution (10 mol L1) and then followed by pre-loading of cobalt ions into the organic (Cole, 2002; Hossain et al., 2011). Cobalt ions were pre-loaded to D2EHPA and formed a new extraction reagent, which was carried out by mixing cobalt contained solution (leaching liquor from waste LiCoO2 cathodes after removing the impurity ions such as Fe and Al) with 30 vol.% D2EHPA and 5 vol.% TBP in sulfonated kerosene. The pH values of the aqueous phase were changed from 3.0 to 6.0 with an interval of 0.5 to determine the maximum loading capacity of cobalt in the organic. And the maximum loading of cobalt was attained at pH  5.0 under conditions as follows: 30 vol.% D2EHPA and 5 vol.% TBP in sulfonated kerosene, A:O = 2:1 and mixing time of 300 s. Then the mixture was separated in a centrifugal machine to obtain Co-D2EHPA. After the stripping of manganese, the barren organic of D2EHPA will be pre-loaded with cobalt before it is re-used for manganese extraction. The content of pre-loaded cobalt in the organic was precisely measured using ICP–OES for the calculation of extraction efficiency of cobalt. All the extraction and stripping experiments were conducted in a programmable air bath shaker (Innova-43 Incubator Shaker from New Brunswick Scientific) for the control of reaction temperature, reaction time and stirring rate of the mixture. The stirring speed was maintained at 300 rpm with a stirring time varied at a range from 1 min to 30 min to obtain the optimal extraction time. Unless otherwise stated, all other experiments were carried out at room temperature (25 °C). A series of experimental conditions, including extraction time, equilibrium pH, volume ratio of the organic and aqueous phase (O:A), and volume content of the organic, were investigated to determine the optimal extraction conditions. Besides, extraction isotherm (McCabe–Thiele diagram) was studied to predict the

degree of separation and the number of extraction stages required at specific extraction conditions. The extraction efficiency of different metals can be calculated according to Eq. (2):

E¼

C1V 1  C2V 2  100% C1V 1

ð2Þ

where E is the extraction efficiencies of different metals; C1 and C2 are the concentrations of different metals in the aqueous phase before and after extraction, respectively; V1 and V2 are the volumes of aqueous phase before and after extraction, respectively. 2.5. Analytical methods The concentrations of different metals were measured by an Induced Coupled Plasma Optical Emission Spectrometer (Agilent Technologies 700 Series ICP–OES). Concentrations of metals in the organic phase were computed from the differences between initial concentrations of different metals in aqueous phase and the concentrations of different metals in raffinate. The pH meter (PHS-3D, 2000) was employed for pH monitoring and regulating. IR spectra (Thermo Scientific Nicolet iS10 FR-IR Spectrometer) were employed to identify the relevant vibrational characteristic bands of the loaded organic and predict the detailed mechanism of the extraction reaction. XRD (Rigaku, Cu Ka) was employed for phase analysis and structure determination of different precipitates (nickel–DMG chelating precipitate and CoC2O42H2O). To avoid random errors, three parallel experiments were performed during the whole selective precipitation and solvent extraction operations and the mean values of precipitation or extraction efficiencies would be treated as the final experimental results. 3. Results and discussion 3.1. Purification The main elements in the sulfuric acid leachate were Fe, Ni, Co, Mn and Li and their contents were 0.59, 6.89, 6.45, 6.31 and 1.60 g L1, respectively. Table 2 shows the effect of pH value on the precipitation of different metals between 3.0 and 7.0. The result shows that nearly all Fe ions could be removed at a low pH of 3.1. And higher pH will result in obvious loss of other metal values (e.g. 51.9% and 38.4% for Ni and Co, respectively at pH of

Table 2 Removal of iron ions by adjusting the pH of the leaching liquor (25 °C). pH

Contents of different metals (mg/L) Fe

Ni

Co

Mn

Li

3.1 4.2 5.5 6.8

2.1 <0.01 – –

6831 6405 5489 3284

6438 6092 5756 3963

6312 6294 6298 6095

1602 1596 1584 1592

352

X. Chen et al. / Waste Management 38 (2015) 349–356

6.8). Therefore, the pH was controlled at about 3.0–3.1 to prevent other metal values loss (<1% for nickel, cobalt, manganese and lithium), as well as maintaining high precipitation efficiency for Fe ions (about 99.6%).

100

% Recovery

80

Ni Co Mn Li

60 40

% Recovery

After the removal of iron ions, dimethylglyoxime reagent (0.05 mol L1) was drop-wise added to the leaching liquor to selectively precipitate nickel from other metal ions. Relatively high precipitation efficiency could be achieved at a short reaction time (10 min) and room temperature. Therefore, only effects of equilibrium pH and molar ratio of nickel to C4H8N2O2 (MRNC) were investigated under conditions of room temperature, reaction time of 20 min and stirring speed of 300 rpm. Figs. 1 and 2 show the effects of MRNC and equilibrium pH on the precipitation efficiency of nickel, cobalt, manganese and lithium. According to Fig. 1, it can be observed that a lower MRNC would be necessary to achieve higher precipitation efficiency for nickel. About 98.7% of nickel could be recovered at MRNC of 0.5 and the precipitation efficiency of nickel experienced a sharp decline to about 45.3% from MRNC 0.5 to 1.0. However, cobalt, manganese and lithium can hardly be co-precipitated, indicating the high selectivity of nickel over other metals when using DMG as precipitant. Thus MRNC of 0.5 would be the optimal molar ratio. Fig. 2 presents the effect of equilibrium pH on the precipitation efficiency of different metals at MRNC = 0.5. Only relatively low precipitation efficiency of nickel could be obtained under low equilibrium pH (e.g. about 34.2% at pH of 2), and the precipitation efficiency attained the peak (about 98.7%) at pH of 5. Then further increase of pH will lead to adverse results for the recovery of nickel due to the increasing co-precipitation of cobalt (e.g. 36.7% at pH of 7). This phenomenon can be attributed to the hydrolysis of cobalt ions at higher pH values. Actually, extra addition of base will increase the cost for the selective precipitation of nickel. However, the consumption of base will effectively promote the recovery efficiency of nickel (for example, from about 35% at pH of 2 to about 98% at pH of 5.0). The addition of base may therefore be deserved to obtain the higher valueadded nickel salt, compared with that of base. Furthermore, the optimal pH for later extraction experiments is also around 5.0 (about 3.5–4.5). In conclusion, MRNC of 0.5 and equilibrium pH of 5 would be the optimized experimental conditions, under which 98.7% nickel could be precipitated while other metal values were seldom

80

Ni Co Mn Li

60 40 20 0 2

3

4

5

6

7

Equilibrium pH Fig. 2. Effects of equilibrium pH on the precipitation efficiency of nickel, cobalt, manganese and lithium (20 min, 300 rpm, MRNC = 0.5 and 25 °C).

10000 C8H14N4NiO4/Bis(dimethylglyoxime)-nickel 8000

Intensity (Counts)

3.2. Recovery of nickel

100

Impurities

6000

4000

2000

0 10

20

30

40

50

60

70

80

Two-Theta (deg) Fig. 3. Images of XRD pattern and the precipitate product after treated with dimethylglyoxime reagent.

co-precipitated. Fig. 3 shows the images of XRD pattern and the precipitate product after treated with dimethylglyoxime reagent. It can be observed that relatively pure Bis(dimethylglyoxime)nickel chelating precipitate could be obtained, and only several small peaks for other solid phases (indicating as the impurities) can be detected. The precipitate was then dissolved in 1 mol L1 hydrochloric acid solution to re-generate DMG under conditions as follows: reaction time-30 min; reaction temperature-25 °C and liquid/solid ratio of 10 ml g1. Nickel and DMG were recovered as NiCl2 in aqueous phase and white powders of DMG, respectively. The recycled DMG will be re-used as precipitant for nickel. Table 3 exhibits

Table 3 Comparison of precipitation performance between fresh DMG and recycled DMG.

20

Elements

0 0.0

0.5

1.0

1.5

2.0

MRNC Fig. 1. Effects of MRNC on the precipitation efficiency of nickel, cobalt, manganese and lithium (20 min, 300 rpm, pH = 5 and 25 °C).

Ni Co Mn Li

a

Precipitation efficiency (%)

Fresh DMG

Recycled DMG

98.7 0.31 0.06 <0.01

97.6 0.25 0.09 <0.01

a Experimental conditions: equilibrium pH = 5, MRNC = 0.5, 20 min, 25 °C and 300 rpm.

353

X. Chen et al. / Waste Management 38 (2015) 349–356

the comparison of precipitation performance between fresh DMG and recycled DMG under the same experimental conditions. It can be observed that the recycled DMG reveals similar precipitation performance with fresh DMG under the same experimental conditions (98.7% and 97.6%, respectively), indicating that the regenerated DMG could be re-used. 3.3. Separation of manganese 3.3.1. Extraction experiments Experiments were carried out to optimize conditions for the selective extraction of manganese using Co-D2EHPA and 5 vol.% TBP as phase modifier in kerosene as the organic. Effects of extraction time, equilibrium pH, volume content of Co-D2EHPA and phase ratio (O:A) were investigated to obtain the appropriate extraction conditions (Fig. 4). The extraction kinetics study of different metals was conducted under conditions as follows: equilibrium pH of 3.2, O:A = 1:1 and the organic-15 vol.% Co-D2EHPA, 5 vol.% TBP in kerosene. As shown in Fig. 4A, the extraction of manganese is a quite rapid reaction and the extraction equilibrium could be attained within 3 min. On the other hand, the extraction kinetics of cobalt and lithium is not any faster compared to that of manganese and the loss of cobalt and lithium was not obvious with the prolonging of extraction time. Therefore the selective extraction of manganese over cobalt and lithium would not be jeopardized by different extraction times when using Co-D2EHPA. The extraction of manganese was significantly affected by equilibrium pH (Fig. 4B) under the following conditions: extraction time of 5 min, O:A = 1:1 and the organic-15 vol.% Co-D2EHPA, 5 vol.% TBP in kerosene. As the equilibrium pH varied from 1.5 to 3.5, the extraction percentage of manganese increases from 18.1% to 95.9%. The co-extraction percentages of cobalt and lithium remained a low level (less than 1%) at equilibrium pH range from

100

1.5 to 3.5. Then the extraction percentage of manganese almost levels off from pH of 3.5 to 5.5. However, the co-extraction percentages of cobalt and lithium witness a remarkable rise from 0.8% and 0.6% to 16% and 7%, indicating excessively high pH (over 3.5) would not be beneficial for the sufficient separation and extraction of manganese from other metal values. The effect of volume content of Co-D2EHPA was investigated by maintaining O:A = 1, extraction time-5 min and equilibrium pH3.5. Fig. 4C shows that the extraction percentage of manganese witnesses a steady increase from 26.1% to 95.8% with the increase of volume content from 5 vol.% to 15 vol.%. Afterwards, the extraction percentage of manganese cannot be effectively improved by further increase of volume contents of Co-D2EHPA, while the loss of cobalt and lithium become more obvious. Therefore 15 vol.% of Co-D2EHPA would be the appropriate volume content for the effective separation of manganese from the leach liquor. The effect of phase ratio (O:A) on extraction of manganese was studied on conditions of extraction time-5 min, equilibrium pH-3.5 and 15 vol.% Co-D2EHPA in the presence of 5 vol.% TBP in kerosene as organic phase. The results presented in Fig. 4D indicate that the extraction percentage of manganese increase from 14.5% to 97.1% with the increase of O:A from 0.25 to 1. Further increase of O:A from 1 to 4 could not effectively promote the extraction percentage of manganese any more, but result in a remarkable co-extraction of cobalt and lithium (about 11.7% and 6.2%, respectively). The suitable O:A ratio, therefore, would be 1:1, under which manganese could be effectively extracted and separated from the leaching liquor with little losses of other valuable metals. The loaded organic was then scrubbed with dilute oxalic acid (5 w/v H2C2O4 solution) to wash off loaded cobalt ions, and almost 100% cobalt ions can be scrubbed into the aqueous phase and manganese ions were left in the organic phase. This may be attributed to the formation of more stable CoC2O42H2O precipitate and Mn2+ cannot be precipitated in the H2C2O4 solution.

A

80

80

60

% / Extraction

% / Extraction

B

100

Co Mn Li

40 20

60

Co Mn Li

40 20 0

0 0

5

10

15

20

1

2

3

Extraction time/min 100

C

100

5

6

D

80 Co Mn Li

60 40 20

% / Extraction

80

% / Extraction

4

Equilibrium pH

Co Mn Li

60 40 20 0

0 5

10

15

20

25

Volume content / vol.%

30

0

1

2

3

4

O:A

Fig. 4. Effects of (A) extraction time; (B) equilibrium pH; (C) volume content; (D) O:A ratio on the extraction of different metals at room temperature.

354

X. Chen et al. / Waste Management 38 (2015) 349–356

16

100

A/O=5:1

14 12

[Mn]org (gL-1)

Mn stripping (%)

80

A/O=2:1

60

40

A/O=0.5 A/O=0.2 A/O=0.1

20

10

1

8

A/O=1:1

6

2

2 0 0.00

0.05

0.10

0.15

Concentration of sulfuric acid /

0

0.20

molL-1

Fig. 5. Effects of sulfuric acid concentration and A/O ratio on the stripping of Mn (25 °C, mixing time-300 s).

A/O=2:1

A/O=1:2

4

w0=6.30g/L

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

[Mn]aq (gL-1) 2+

Finally, the loaded manganese was stripped using sulfuric acid at different stripping conditions (Fig. 5). It can be concluded that the increasing of A/O ratio and sulfuric acid concentration will greatly promote the stripping efficiency of manganese under conditions of 25 °C and mixing time of 300 s. And a maximum stripping efficiency (about 99%) can be attained at A/O = 0.5 and 0.1 mol L1 H2SO4. Further increase of A/O ratio and sulfuric acid concentration cannot enhance the stripping efficiency of manganese any more. Therefore, the suitable stripping conditions are A/ O of 0.5 and 0.1 mol L1 H2SO4.

3.3.2. Extraction distribution isotherm study The McCabe–Thiele diagram for manganese extraction was constructed by determining the equilibrium isotherm (distribution isotherm showing the relative distribution of desired metal between organic and aqueous phases at specific experimental conditions) for extraction with different A:O ratios (varied from 1:2 to 5:1) through batch-wise extraction experiments. Fig. 5 shows the McCabe–Thiele diagram for manganese extraction on conditions as follows: extraction time of 5 min, A:O of 2:1, equilibrium pH of 3.5; the organic-a mixture of 15 vol.% Co-D2EHPA/D2EHPA and 5 vol.% TBP in kerosene; feed solution-6.25 g L1 cobalt, 6.30 g L1 manganese and 1.60 g L1 lithium. It can be observed that two theoretical extraction stages are needed to yield a raffinate containing less than 0.04 g L1 manganese and attain a manganese extraction efficiency over 99%.

Fig. 6. Manganese extraction McCabe–Thiele diagram with 15 vol.% D2EHPA and 5 vol.% TBP in kerosene (pH = 3.4–3.5, 25 °C, extraction time of 5 min and feed solution: 6.12 g/L manganese, 6.35 g/L cobalt and 1.49 g/L lithium).

uted to the similar properties between P–Co/O–Co bonds and P–Mn/O–Mn bonds.

3.4. Recovery of cobalt and lithium After the recovery of nickel and manganese, cobalt and lithium were sequentially precipitated using 0.5 mol L1 ammonium oxalate solution [(NH4)2C2O4] and hot saturated sodium carbonate solution (Na2CO3, 95 °C). The precipitation reactions could be expressed as follows: 2 Co2þ ðaqÞ þ C2 O4ðaqÞ þ 2H2 O ) CoC2 O4  2H2 OðsÞ

þ

2LiðaqÞ þ CO2 3ðaqÞ ) Li2 CO3ðsÞ In this study, a little excess of ammonium oxalate (1.1 times of the above stoichiometry) was added to the leaching liquor to completely precipitate cobalt at room temperate, reaction time 30 min and stirring speed of 300 rpm. About 98.2% of the cobalt ions could be recovered as CoC2O42H2O after filtration and detection the cobalt content in the filtrate. Fig. 7 shows images of XRD pattern and the precipitate product after treated with ammonium oxalate.

b 1462

T/%

3.3.3. FT-IR spectra analysis FT-IR spectra of Co-D2EHPA and the organic after extraction were determined by Thermo Scientific Nicolet iS10 FR-IR Spectrometer using KBr palate at room temperature with a range of 500–4000 cm1 (Fig. 6). Some references (Tsubaki and Yu, 1981; Nguyen et al., 2010; Darvishi et al., 2005; Jha et al., 2011, 2012) had reported the application of FT-IR spectra to investigate solvent extraction system, which revealed the identifications of phosphonic-, phosphinic- and phosphoric-acids from their relevant vibrational characteristic bands. Characteristic vibrational bands for Co-D2EHPA, such as P–O–H and C–H are identified at 1032.0 and 2925.0 cm1, respectively. As revealed in Fig. 6, some frequency shifts could be observed at the wave number range from 1000 to 1200 cm1 (as shown in the rectangle dashed box, from 1192.8 and 1032 to 1218.7 and 1033.9), which indicates that Mn2+ was loaded and extracted to the cobalt loaded organic. However, the frequency shifts are not so obvious which may be attrib-

a

2925

1462

3500

3000

1192.8 1032

Extraction Mn2+ using cobalt loaded D2EHPA

2925

4000

1218.7 1033.9

2500

2000

1500

1000

500

Wave numbers / cm-1 Fig. 7. FTIR spectra of (a) cobalt loaded D2EHPA and (b) the organic after extraction of manganese with cobalt loaded D2EHPA.

355

X. Chen et al. / Waste Management 38 (2015) 349–356 Table 4 Purity analysis for the recovered metal values: nickel, cobalt, manganese and lithium.

a

Elements

Ni powder (wt.%)

Co powder (wt.%)

Li powder (wt.%)

a

Li Ni Co Mn Others

<0.01 97.81 0.39 0.15 0.96

<0.01 – 97.47 0.87 1.66

99.18 – — — 0.82

25.7 – – 7849.3 –

Mn solution (mg/L)

Mn2+ in the stripping liquor (stripping conditions: O:A = 2:1; 5 min; CH2 SO4 = 0.1 mol L1; 25 °C).

be obtained under a relatively low pH, despite of the higher price of ammonium oxalate than NaOH.

2000

CoC2O4·2H2O

3.5. Purity analysis

Intensity (Counts)

1600

Table 4 shows the results of the purity analysis. It can be concluded that the purities for nickel, cobalt and lithium are 97.81%, 97.47% and 99.18% respectively, and the content of manganese (7849.3 mg/L) in the stripping liquor was much higher than that of lithium (25.7 mg/L). From the above results, relatively pure products with little impurities could be obtained when adopting this recovery process. These recovered metal compounds can be used as raw materials for new cathode materials of lithium-ion batteries.

1200

800

400

0 10

20

30

40

50

60

70

80

Two-theta (deg) Fig. 8. Images of XRD pattern and the precipitate product after treated with ammonium oxalate.

It can be observed that the precipitate is relatively pure CoC2O42H2O and other solid phases of metal compounds were rarely detected. For the recovery of lithium, saturated sodium carbonate with a high temperature (95 °C) was employed to precipitate lithium as lithium carbonate (Li2CO3) with a precipitation percentage of 81.0% and purity over 99%. In order to wash off Na2SO4 and furthest reduce the loss of lithium, hot deionized water (near 100 °C) was employed to wash off the impurity ions entrained. Contestabile et al. and Li et al. had reported the recovery of cobalt and lithium using NaOH and Na2CO3 solutions respectively. Usually, an extra base will be required to neutralize the H+ and adjust the pH of the leaching liquor above 7 to achieve a high cobalt precipitation efficiency, which may ultimately increase the cost. However, the usage of ammonium oxalate may effectively prevent the extra consumption of base and CoC2O42H2O can even

3.6. Flowsheet of the recovery process Based on the above experiments, a hydrometallurgical route has been proposed to recover metal values from the leachate in sulfuric acid media (Fig. 8). A combined hydrometallurgical method was adopted to separate and recover each metal value by solvent extraction and selective precipitation. Compared with other methods investigated (as reported in Table 1), this recovery process carried out in this study shows four preferable characteristics as follows:  First, each metal value in the leaching liquor can be effectively recovered, not just the high value-added metals such as cobalt and nickel.  Second, both solvent extraction and selective precipitation techniques demonstrate high selectivity towards objective metals, which indicated that purer products could be obtained without further purification operation.  Third, both the precipitant (DMG) and extraction reagent used during the separation and recovery process could be recycled and re-used, indicating the furthest avoidance of adverse impact on environment and sustainable utilization of valuable materials.

Fig. 9. Simplified flow-sheet of the hydrometallurgical recovery process.

356

X. Chen et al. / Waste Management 38 (2015) 349–356

 Finally, this hydrometallurgical process adopted during this study reveals a potential for the sustainable recovery of different metals with a wider applications, rather than limited to LiCoO2 as reported. 4. Conclusions Heavy metals contained in leaching liquor of spent LIBs can be deleterious to the environment. Meanwhile these heavy metals could be a source for cathode materials of new batteries, other nonferrous metal materials, etc. Therefore, the recovery of metal values may promise significant environmental and economic benefits (see Fig. 9). In this study, a combined hydrometallurgical process has been proposed to recover metal values from the leaching liquor of spent LIBs by selective precipitation and solvent extraction. First, nickel was precipitated using dimethylglyoxime reagent after purification operation. About 98.7% of nickel could be recovered under optimal conditions as follows: MRNC of 0.5 and equilibrium pH of 5 at room temperature. The precipitate was then dissolved in 1 mol L1 hydrochloric acid solution. After filtration, white powders of dimethylglyoxime re-generated could be re-used as precipitant and nickel ions were left in the filtrate. Subsequently, manganese was extracted using Co-D2EHPA. Extraction percentage as high as 97.1% could be attained under the following optimized conditions: extraction time-5 min, equilibrium pH-3.5, 15 vol.% Co-D2EHPA and O:A of 1:1. McCabe–Thiele diagram study for manganese extraction indicates that two theoretical counter-current extraction stages are needed to yield a raffinate containing less than 0.04 g L1 manganese and an extraction percentage over 99% manganese at specific extraction conditions. Finally, cobalt and lithium were selectively precipitated using ammonium oxalate and hot saturated sodium carbonate, respectively. About 98.2% and 81.0% of cobalt and lithium were recovered as CoC2O42H2O and Li2CO3. The impurity analysis indicates that all the recovered products present high purities as follows: 97.81%, 97.89% and 99.18% for nickel, cobalt and lithium, and a relatively pure MnSO4 solution. All metals in the leaching liquor can be effectively recovered by this process, rather than limited to high value-added metals (such as cobalt and lithium) as reported (Li et al., 2010, 2014). Furthermore, all reagents used reveal high selectivity towards metals recovery and products with high purity could also be obtained (as shown in Table 4). However, this hydrometallurgical route may be complicated to comprehensively recycle all metal values, and more sustainable and green processes may be also required to develop in our following research. Acknowledgments The authors acknowledge with gratitude for the financial support of the Fundamental Research Funds for the Central Universities of Central South University (No. 72150050350) and National Natural Science Foundation of China (No. 21176266). References Al-Thyabat, S., Nakamura, T., Shibata, E., Iizuka, A., 2013. Adaptation of minerals processing operations for lithium-ion (LiBs) and nickel metal hydride (NiMH) batteries recycling: critical review. Miner. Eng. 45, 4–17. Armstrong, R.D., Todd, M., Atkinson, J.W., Scott, K., 1997. Electroseparation of cobalt and nickel from a simulated wastewater. J. Appl. Electrochem. 27, 965–969. Badawy, S.M., Nayl, A.A., El Khashab, R.A., El-Khateeb, M.A., 2014. Cobalt separation from waste mobile phone batteries using selective precipitation and chelating resin. J. Mater Cycles Waste Manage. 16, 739–746. Castillo, S., Ansart, F., Laberty-Robert, C., Portal, J., 2002. Advances in the recovering of spent lithium battery compounds. J. Power Sources 112, 247–254.

Chagnes, A., Pospiech, B., 2013. A brief review on hydrometallurgical technologies for recycling spent lithium-ion batteries. J. Chem. Technol. Biotechnol. 88, 1191–1199. Chen, X.P., Zhou, T., 2014. Hydrometallurgical process for the recovery of metal values from spent lithium-ion batteries in citric acid media. Waste Manage. Res. 32 (11), 1083–1093. Chen, L., Tang, X., Zhang, Y., Li, L., Zeng, Z., Zhang, Y., 2011. Process for the recovery of cobalt oxalate from spent lithium-ion batteries. Hydrometallurgy 108, 80–86. Cheret, D., Santen, S., 2005. Battery Recycling. Cole, P.M., 2002. The introduction of solvent extraction steps during upgrading of a cobalt refinery. Hydrometallurgy 64, 69–77. Contestabile, M., Panero, S., Scrosati, B., 1999. A laboratory-scale lithium battery recycling process. J. Power Sources 83, 75–78. Contestabile, M., Panero, S., Scrosati, B., 2001. A laboratory-scale lithium-ion battery recycling process. J. Power Sources 92, 65–69. Darvishi, D., Haghshenas, D.F., Alamdari, E.K., Sadrnezhaad, S.K., Halali, M., 2005. Synergistic effect of Cyanex 272 and Cyanex 302 on separation of cobalt and nickel by D2EHPA. Hydrometallurgy 77, 227–238. Dorella, G., Mansur, M.B., 2007. A study of the separation of cobalt from spent Li-ion battery residues. J. Power Sources 170, 210–215. Ellis, B.L., Lee, K.T., Nazar, L.F., 2010. Positive electrode materials for Li-ion and Libatteries. Chem. Mater. 22, 691–714. Georgi-Maschler, T., Friedrich, B., Weyhe, R., Heegn, H., Rutz, M., 2012. Development of a recycling process for Li-ion batteries. J. Power Sources 207, 173–182. Hossain, M.R., Nash, S., Rose, G., Alam, S., 2011. Cobalt loaded D2EHPA for selective separation of manganese from cobalt electrolyte solution. Hydrometallurgy 107, 137–140. Jha, M.K., Lee, J.C., Kumari, A., Choubey, P.K., Kumar, V., Jeong, J., 2011. Pressure leaching of metals from waste printed circuit boards using sulfuric acid. JOM 63, 29–32. Jha, M.K., Kumar, V., Jeong, J., Lee, J.C., 2012. Review on solvent extraction of cadmium from various solutions. Hydrometallurgy 111–112, 1–9. Kang, J., Senanayake, G., Sohn, J., Shin, S.M., 2010. Recovery of cobalt sulfate from spent lithium ion batteries by reductive leaching and solvent extraction with Cyanex 272. Hydrometallurgy 100, 168–171. Lain, M.J., 2001. Recycling of lithium cells and batteries. J. Power Sources 97–98, 736–738. Li, J., Shi, P., Wang, Z., Chen, Y., Chang, C.-C., 2009. A combined recovery process of metals in spent lithium-ion batteries. Chemosphere 77, 1132–1136. Li, L., Ge, J., Chen, R., Wu, F., Chen, S., Zhang, X., 2010. Environmental friendly leaching reagent for cobalt and lithium recovery from spent lithium ion batteries. Waste Manage. 30, 2615–2621. Li, L., Zhai, L., Zhang, X., Lu, J., Chen, R., Wu, F., Amine, K., 2014. Recovery of valuable metals from spent lithium-ion batteries by ultrasonic-assisted leaching process. J. Power Sources 262, 380–385. Lupi, C., Pasquali, M., 2003. Electrolytic nickel recovery from lithium-ion batteries. Miner. Eng. 16, 537–542. Lupi, C., Pasquali, M., Dell’ Era, A., 2005. Nickel and cobalt recycling from lithiumion batteries by electrochemical process. Waste Manage. 25, 215–220. Mishra, D., Kim, D.J., Ralph, D.E., Ahn, J.G., Rhee, Y.H., 2008. Bioleaching of metals from spent lithium-ion batteries using acidithiobacillus ferrooxidans. Waste Manage. 28, 333–338. Nguyen, N.V., Lee, J.C., Kim, S.K., Jha, M.K., Chung, K.S., Jeong, J., 2010. Adsorption of gold (III) from waste rinse waste rinse water of semiconductor manufacturing industries using amberlite XAD-7HP resin. Gold Bull. 43, 200–208. Pranolo, Y., Zhang, W., Cheng, C.Y., 2010. Recovery of metals from spent lithium-ion battery leach solutions with a mixed solvent extractant system. Hydrometallurgy 102, 37–42. Provazi, K., Campos, B.A., Espinosa, D.C.R., Tenório, J.A.S., 2011. Metal separation from mixed types of batteries using selective precipitation and liquid–liquid extraction techniques. Waste Manage. 31, 59–64. Shen, Y., Xue, W., Niu, W., 2008. Recovery of Co(II) and Ni(II) from hydrochloric acid solution of alloy scrap. Trans. Nonferrous Met. Soc. China (Eng. Ed.) 18, 1262– 1268. Tang, W.J., Chen, X.P., Zhou, T., Duan, H., Chen, Y.B., Wang, J., 2014. Recovery of Ti and Li from spent lithium titanate cathodes by a hydrometallurgical process. Hydrometallurgy 147–148, 210–216. Tsubaki, M., Yu, N.T., 1981. Resonance Raman investigation of dioxygen bonding in oxycobaltmyoglobin and oxycobalthemoglobin: structural implication of splitting of the bound O–O stretching vibration. Proc. Natl. Acad. Sci. USA 78, 3581–3585. Wang, R.C., Lin, Y.C., Wu, S.H., 2009. A novel recovery process of metal values from the cathode active materials of the lithium-ion secondary batteries. Hydrometallurgy 99, 194–201. Zhang, P., Yokoyama, T., Itabashi, O., Wakui, Y., Suzuki, T.M., Inoue, K., 1998. Hydrometallurgical process for recovery of metal values from spent nickelmetal hydride secondary batteries. Hydrometallurgy 50, 61–75. Zhao, J.M., Shen, X.Y., Deng, F.L., Wang, F.C., Wu, Y., Liu, H.Z., 2011. Synergistic extraction and separation of valuable metals from waste cathodic material of lithium ion batteries using Cyanex272 and PC-88A. Sep. Purif. Technol. 78, 345– 351.