Recovery of Lithium, Nickel, and Cobalt from Spent ... - ACS Publications

Oct 31, 2017 - National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Key Laboratory of Green Process and. Engineering ...
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Research Article pubs.acs.org/journal/ascecg

Recovery of Lithium, Nickel, and Cobalt from Spent Lithium-Ion Battery Powders by Selective Ammonia Leaching and an Adsorption Separation System Hongyan Wang,†,‡,# Kai Huang,‡,# Yang Zhang,† Xin Chen,† Wei Jin,† Shili Zheng,† Yi Zhang,† and Ping Li*,† †

National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, 1 North Second Street, Zhongguancun, Haidian District, Beijing, 100190, People’s Republic of China ‡ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Road, Haidian District, Beijing 100083, People’s Republic of China S Supporting Information *

ABSTRACT: A novel hydrometallurgical route was developed to recover valuable metals from spent lithium-ion battery (LIB) powders. An ammonia media was utilized to selectively leach lithium, nickel, and cobalt from the pretreated spent LIB powders. Subsequently, an adsorption method was adopted to effectively separate lithium from Co2+−Ni2+−Li+−NH4+-containing leaching solutions using manganese type lithium ion-sieves as adsorbents. The results showed that the direct recovery efficiencies of lithium, nickel, and cobalt from the spent LIB powders reached 76.19%, 96.23%, and 94.57%, respectively. Also, ammonia could be closedloop recycled, while Li2CO3, NiSO4, and CoSO4 could be obtained as products. This study provides a new pathway for recycling utilization of spent LIB powders. KEYWORDS: Spent lithium-ion ternary batteries, Recovery, Ammonia leaching, Adsorption separation, Manganese type lithium ion-sieves



Ni2+−Co2+−Al3+−Mn2+-containing leaching solutions employed the multistep chemical precipitation17−19 and solvent extraction20−23 to obtain the desired products. However, such indiscriminate leaching behavior and complex separation process caused high cost and potential heavy metal-containing hazard emission, weakening their application prospects. Selective leaching and an effective separating process would be more suitable for recycling spent LIB powders.24 Recently, ammonia leaching has aroused much concern because of its selective leaching characteristics between the desired metals (Li, Ni, Co) and undesired metals (Al and Mn). In view of Eh-pH diagrams, ammonia leaching is thermodynamically feasible for transition metals such as Ni and Co which possessed high complexation ability with ammonia.25 On account of this principle, Sun et al. used ammonia−ammonium sulfate solutions to leach the pretreated spent LIB powders in the presence of sodium sulphite.5 Kwon et al. investigated the leaching behavior of spent LIB powders with ammonia, ammonium carbonate, and ammonium sulfite as leaching

INTRODUCTION Ternary lithium ion batteries (LIBs) have become an indispensable part in electric vehicles, taking advantage of their high voltage, light weight, and long cycle lifetime.1−3 Their fast-growing consumption generates large amounts of spent LIBs owing to their short average service lifetime (1−3 y).4 In general, the main metals of spent LIB powders (LiNixCoyMnzO2) include Li, Ni, Co, Al, and Mn with the approximate contents of 5−7, 5−10, 5−20, 1−3, and 10−15 wt %, respectively, and the main residues are graphite and organics after dismantling, separation, and grinding.5,6 Recovery of desired metals (Li, Ni, and Co) from spent LIB powders becomes an important issue from the viewpoint of resource conservation and hazard prevention of heavy metal pollution. The conventional technology for recovering Li, Ni, and Co from spent LIB powders mainly involves pyrometallurgical process, hydrometallurgical process, or the combination of both.7−9 The hydrometallurgical process is more positive in the reduction of hazardous gas emissions and effective recovery of lithium.10 Generally, leaching agents of HCl,11 HNO3,12 H2SO4,4,13 CO2,6 and various organic acids14−16 in the presence of H2O2 or NaHSO3 are adopted to leach Li, Ni, Co, Al, and Mn from the spent LIB powders. Then, the as-prepared Li+− © 2017 American Chemical Society

Received: August 7, 2017 Revised: October 26, 2017 Published: October 31, 2017 11489

DOI: 10.1021/acssuschemeng.7b02700 ACS Sustainable Chem. Eng. 2017, 5, 11489−11495

Research Article

ACS Sustainable Chemistry & Engineering agents and proved that the ammonium sulfite acted as a reductant while the ammonium carbonate was a buffer solution.26 However, these methods still suffer from the difficulties such as separation of valuable metals in Co2+− Ni2+−Li+−NH4+-containing leaching solutions, ammonia media recycling and extra wastewater emission of sulfates produced from sulfites. In this study, a carbon reduction heating was first used to replace routine heating in the pretreatment of spent LIB powders, not only eliminating the graphite and organics residues in the spent LIB powders, but also transforming LiNixCoyMnzO2 into resources such as lithium (Li) or nickel (Ni) or cobalt (Co) compounds and evading the usage of sulfites as the reductants. Second, the pretreated spent LIB powders were leached by ammonia−ammonium hydrocarbonate (NH3·H2O−NH4HCO3) solutions to form Co2+−Ni2+− Li+−NH4+-containing leaching solutions in the presence of hydrogen peroxide (H2O2) as the reductant. Third, Li+ ions were preferentially separated by lithium ion-sieves adsorption from the leaching solutions since adsorption has been widely investigated as a sustainable technique to separate lithium from lithium-containing solutions such as brines and seawater.27−29 The NH4+ ions was further recycled into the leaching step by distillation of ammonia. After ammonia distillation, the Co2+− Ni2+-containing mixtures were collected for the following conventional solvent extraction separation method. The results showed that Ni, Co, and Li of spent LIBs could be simultaneously leached by the NH3·H2O−NH4HCO3−H2O2 solutions, and the leaching yields of Ni, Co, and Li reached 96.4%, 96.3% and 81.2%, respectively, while the Al and Mn were hardly leached out. The prepared manganese type lithium ion-sieves can selectively adsorb Li from the Li+−Ni2+−Co2+− NH4+-containing leaching solutions, reaching the Li/Ni and Li/ Co separation factors of about 212 and 983, respectively. At last, Li2CO3, NiSO4, and CoSO4 could be obtained as products. Thus, a novel integrated route were established to dispose the spent LIB powders, realizing closed-loop recycling of leaching agents, selective leaching, and effective separation of desired metals to obtain target products.

Figure 1. XRD patterns of the pristine materials (a), the LIB powders (b), carbothermal reduction heating pretreatment powders (c), and leaching residues (d).

separately determined by ICP-OES, was 5.52%. After carbothermal reduction heating pretreatment of spent LIB powders, the LiNi0.5Co0.2Mn0.3O2 was found to transform to Ni and Co as major phases and MnO and Li2CO3 as minor phases (Figure 1c). Morphology of particles, distribution, and contents of Li, Ni, Co, and Mn changed little (Figure S1(b)). Ammonia leaching tests were carried out to determine the leaching efficiency. ICP-OES results showed that Li, Ni, and Co could be leached out by the NH3·H2O−NH4HCO3 solutions (NH3·H2O 367.5 g/L, NH4HCO3 140 g/L) in the presence of H2O2 (63.24 g/L) with yields of 81.2%, 96.4%, and 96.3%, respectively, while Mn and Al were practically insoluble. Only 0.96% Ni, 0.40% Co, and 2.82% Li existed in the residues, under the experimental conditions. SEM-EDX (Figure S2(b)) results also verified that little Ni and Co could be found in the residues particles. Thermodynamically, the Ni and Co had stronger complexation ability with ammonia than Mn and Al.30,31 Expect for the ammonia complexation effect, the addition of H2O2 is believed to oxidize the Ni and Co metals to Ni2+ and Co2+ ions, facilitating the Ni2+− and Co2+−ammine complex formations, respectively. On the other hand, the synergistic effect between NH3 and HCO3− can also selectively inhibit the leaching of Mn and Al. Specifically, the Mn2+, which was originated from MnO, was first dissolved into NH3·H2O solutions to form Mn2+−ammine complexes, and then precipitated in the form of manganese carbonate (MnCO3) due to its lower solubility than manganese hydroxide (MnOH), which was further confirmed by XRD patterns of leaching residues (Figure 1d) and previous study.32 After selective ammonia leaching, the obtained Li+−Ni2+−Co2+−NH4+-containing leaching solutions, which contain 1.04 g/L of Li+, 5.66 g/L of Ni2+, 1.91 g/L of Co2+, and 120 g/L of NH4+ ions, will be used for the following adsorption separation step. Characteristics of Lithium Ion-Sieve Adsorbents. Manganese type lithium ion-sieves were synthesized to selectively adsorb Li+ ions from the Li+−Ni2+−Co2+−NH4+containing leaching solutions. As observed, all peaks of the precursors (Figure 2a) were very sharp and matched with the peaks of the standard Li1.27Mn1.73O4 (JCPDS 51-1582) very well.33 Peaks of the lithium ion-sieves (Figure 2b) were in correspondence with that of precursors, showing that such structure was stable during the process of acid treatment. Mn and O contents of precursors were measured by EDX (Figure



RESULTS AND DISCUSSION Carbothermal Reduction Pretreatment and Selective Ammonia Leaching. The spent LIB powders were prepared by dismantling of spent LIBs to remove the plastic and steel cases, manual separating anodes and cathodes foils, and then grinding the cathodes foils which generally contained Al foils, pristine cathode materials (LiNi0.5Co0.2Mn0.3O2 powders), small amounts of graphite powders, and organics residues. All the diffraction peaks of spent LIB powders can be indexed to LiNi0.5Co0.2Mn0.3O2 as the major phase and aluminum (JCPDS-99-0005) as the minor phase (Figure 1b), similar to the previous studies.4,17 Cu and large amounts of graphite were removed in the dismantling step, compared to the pristine materials (Figure 1a) which were obtained by directly crushing anodes and cathodes foils. SEM-EDX analysis was further used to characterize the spent LIB powders. As shown in Figures S1(a) and S2(a), surface morphology appeared to be agglomerated particles with 5−15 μm size, Ni, Co, and Mn were evenly distributed in the particles, and their chemical contents were 18.71, 7.02, and 10.06 wt %, respectively. Differently, Al was randomly distributed in the observed area with the content of 1.36 wt %, related to dismantling and separating process of spent LIBs. Lithium content, which was 11490

DOI: 10.1021/acssuschemeng.7b02700 ACS Sustainable Chem. Eng. 2017, 5, 11489−11495

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ACS Sustainable Chemistry & Engineering

with H+ during the acid treatment. SEM images of both precursors and lithium ion-sieves (Figure S4(c) and (d)) indicated that the particles were agglomerated and the average diameter of the particles was in the range of 5−20 μm. The textures of precursors and lithium ion-sieves which were deduced from nitrogen adsorption−desorption isotherms and pore size distribution (Figure S4(b)) showed their specific surface area and average pore diameters resembled the previous reported results.37 Adsorption Separation of Lithium. To effectively separate Li+ ions, we conducted various experiments to investigate the adsorption behaviors of lithium ion-sieves from the Li+−Ni2+−Co2+−NH4+-containing leaching solutions. The effect of Li+ ions concentration were carried out by changing the initial concentration of Li+ ions from 0.5 to 2.5 g/ L at constant concentration of Ni2+ (2 g/L), Co2+ (2 g/L), and NH4+ (150 g/L) at 30 °C for 6 h, considering the variation range of lithium concentration in the different leaching conditions. It could be found from Figure 3a that the adsorption capacity of Li+ increased from 25.27 to 30.40 mg/ g with the increase of initial concentration of Li+ from 0.5 to 2.5 g/L, while the adsorption capacities of Ni2+ and Co2+ decreased from 0.76 to 0.23 mg/g and from 0.41 to 0.060 mg/g, respectively. A higher Li+ ion concentration accelerates the attainment of Li+/H+ ion-exchange equilibrium, the Li+ ions can easily get into the active sites of lithium ion-sieves leading to the increase of adsorption capacity of Li+. Meanwhile, the active sites and space are occupied by Li+ ions resulting in less space and active sites for Co2+ and Ni2+.38 Figure 3b showed the effect of lithium ion-sieves amounts on the adsorption capacities of Li+, Ni2+, and Co2+ under the constant

Figure 2. XRD patterns of precursors (a) and lithium ion-sieves before (b) and after lithium adsorption (c).

S3), and the mass ratio of Mn to O was 1.04, close to the theoretical mass ratio of Mn to O of Li1.27Mn1.73O4 (1.06). The FT-IR spectra of both precursors and lithium ion-sieves (Figure S4(a)) exhibited two distinct bands at 1631 and 3400 cm−1, which could be attributed to the bending modes of water molecule and stretching modes of OH−, respectively.34 Two bands which were located at approximately 520 and 630 cm−1 were assigned to the asymmetric stretching modes of MnO6 group.35 Different from the precursors, a band at 900 cm−1, which was observed in the FT-IR spectrum of lithium ionsieves, could be ascribed to a proton coupling vibration peak,36 demonstrating that the Li+ in the precursors was exchanged

Figure 3. Adsorption of Li+, Ni2+, and Co2+ ions onto lithium ion-sieves as a function of initial Li+ ions concentration (a), the amount of lithium ionsieves (b), initial pH (c), and temperature (d). 11491

DOI: 10.1021/acssuschemeng.7b02700 ACS Sustainable Chem. Eng. 2017, 5, 11489−11495

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ACS Sustainable Chemistry & Engineering concentrations of Li+−Ni2+−Co2+−NH4+-containing leaching solutions (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L, and NH4+ 150 g/L) at 30 °C for 6 h, and the results showed that Li+ uptake amount decreased from 28.00 to 25.37 mg/g and adsorption capacity of Ni2+ and Co2+ changed little with the increase of amounts of lithium ion-sieves increased from 2.5 to 12.5 g/L. Most of the Li+ ions in the leaching solutions had been adsorbed onto the lithium ion-sieves with the suitable amounts, and the remanent Li+ ions could no longer be removed despite the growth of unoccupied active adsorption sites number, resulting in the decrease of adsorption capacities of lithium ion-sieves.39 Lithium ion-sieves had a much higher affinity for Li+ ions than Ni2+ and Co2+, which was confirmed by the constant (KL) related to adsorption energy calculated from the following Langmuir model. The concentration of NH4+ ions from 75 g/L (pH 9.35) to 200 g/L (pH 10.89) was further changed under the constant concentrations of Li+, Ni2+, and Co2+ (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L) at 30 °C for 6 h. As shown in Figure 3c, the Li+ adsorption capacity increased from 22.70 to 26.10 mg/g while the adsorption amount of Ni2+ decreased from 0.14 to 0.060 mg/g and the adsorption amount of Co2+ decreased from 0.030 to 0.013 mg/g, with the increase of NH4+ concentration from 75 to 200 g/L. These results are closely related to higher complexation ability between NH3 and Ni2+ and Co2+ and the increased pH values. At the higher pH, lithium ion-sieves possessed the lower surface charge which brought the stronger electrostatic interactions between the Li+ and H+.40 The temperature variations results (Figure 3d) also showed that the adsorption capacities of Li+, Ni2+, and Co2+ increased when the temperature increased from 20 to 50 °C at constant concentrations of Li+, Ni2+, and Co2+ (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L, NH4+ 150 g/L) in the leaching solutions for 6 h, similar to the previously reported results.41,42 To evaluate the adsorption behaviors of Li+, Ni2+, and Co2+ ions onto lithium ion-sieves, Li+, Ni2+, and Co2+ ion adsorption isotherms were determined by separately altering the concentration of Li+, Ni2+, and Co2+ ions from 0.5 to 2.5, 0.5 to 2.0, and 0.5 to 2.5 g/L, respectively, under constant NH4+ concentrations in the NH4+-containing aqueous solutions (NH4+ 150 g/L) with 5 g/L of lithium ion-sieves at 30 °C for 6 h. The obtained adsorption data were simulated by the Langmuir model, Freundlich model, and Temkin−Pyzhev model,43−45 as shown in the Supporting Information (Part 1.1). As observed, the coefficient values (Table S2 and Figures S5−S8) suggested that the Langmuir model described the adsorption equilibrium of Li+, Ni2+, and Co2+ ions well, indicating that the adsorption of Li+, Ni2+, and Co2+ ions in the NH4+-containing aqueous solutions belonged to dominantly monolayer adsorption.46 The maximum adsorption capacities (qm) for Li+, Ni2+, and Co2+ ions were 38.82, 0.862, and 0.685 mg/g, respectively. In the Li+−Ni2+−Co2+−NH4+-containing leaching solutions (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L, NH4+ 150 g/L), the generated curves of Li+ ions confirmed that the Langmuir model still fit the experimental data well, while the curves of Ni2+ and Co2+ ions fit the Langmuir and Temkin− Pyzhev models moderately. The magnitude of adsorption heats (B1) results (Table S2) demonstrated that the strong affinity of the lithium ion-sieves for Li+ (B1 = 2.81) and the weak affinity of the lithium ion-sieves for Ni2+ (B1 = 0.051) and Co2+ (B1 = 0.159), indicating the high selectivity for Li+ ions. The maximum adsorption capacity (qm) for Li+, Ni2+, and Co2+ ions decreased to 31.63, 0.74, and 0.221 mg/g, respectively.

The phenomenon of the decreased Li+ adsorption capacity may be attributed to the active adsorption sites on the lithium ionsieves occupied by Ni2+ and Co2+ due to their competitive affinity.47 To determine the efficiency of Li+ ions adsorption onto lithium ion-sieves, the kinetics of adsorption was investigated by performing adsorption experiments onto lithium ion-sieves under the constant concentrations of Li+, Ni2+, and Co2+ (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L) at 20 °C with different equilibration times. Both the pseudo-first-order model and pseudo-secondorder kinetic model48−50 as shown in the Supporting Information (Part 1.2) were used to fit the experimental data (Figure S9). The results suggested that pseudo-second-order kinetic model better fit to the adsorption data and was more suitable to describe the adsorption kinetics of Li+ ions by evaluating the determination coefficients (R2 > 0.99, Figure S10, Table S3). This indicated that the Li+ ion adsorption onto lithium ion-sieves was a chemisorption process. Besides, the adsorption kinetics of Ni2+ and Co2+ showed that the pseudosecond-order kinetic model also better fit the adsorption data. However, the initial adsorption rates of Ni2+ (2.284 mg/g·min) and Co2+ (116.114 mg/g·min) were higher than that of Li+ (0.12 mg/g·min), indicating that Ni2+ and Co2+ ion adsorption onto lithium ion-sieves might be a physical adsorption in the competitive adsorption of Li+, Ni2+, and Co2+, which was similar to competitive adsorption of V(V) and Cr(VI).51,52 Thermodynamic parameters were further determined by the Clausius−Clapeyron equation as shown in Supporting Information (Part 1.3), and the results (Table S4 and Figure S11) showed that the ΔHo of Li+, Ni2+, and Co2+ ions adsorbed were 0.332, 0.00815, and 0.0059 kJ/mol, respectively, indicating that the Li+, Ni2+, and Co2+ adsorptions onto lithium ion-sieves were all endothermic. Equilibrium distribution coefficients (Kd) and selectivity coefficients (αLi Me) were adopted to investigate the selective adsorption of Li+ ions since the Kd represented the adsorption affinity of ions for the lithium ion-sieves and the αLi Me was one of the important considerations for realizing the ions selectivity. The Kd and α could be estimated from the following equation: (C0 − Ce)V MCe

Kd = Li αMe =

(1)

KdLi KdMe

(2) +

2+

Where C0 represents the initial concentration of Li , Ni , and Co2+; Ce is the equilibrium concentration of Li+, Ni2+, and Co2+; V represents the volume of leaching solutions; and M represents the amount of lithium ion-sieves. Table 1 shows equilibrium adsorption capacity, Kd and αLi Me of + Li , Ni2+, and Co2+ in the Li+−Ni2+−Co2+−NH4+-containing leaching solutions (Li+ 1 g/L, Ni2+ and Co2+ 2 g/L). At the 150 Table 1. Comparison of Cation Uptake from Li+−Ni2+− Co2+−NH4+-Containing Leaching Solutions by Lithium IonSieves

11492

ion

C0/(g/L)

Ce/(g/L)

qe/(mg/g)

Kd/(mL/g)

αLi Me

Li Ni Co

0.993 2.077 2.111

0.7485 2.0738 2.1103

24.45 0.317 0.070

32.665 0.154 0.0332

1 212.11 983.89

DOI: 10.1021/acssuschemeng.7b02700 ACS Sustainable Chem. Eng. 2017, 5, 11489−11495

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ACS Sustainable Chemistry & Engineering g/L of NH4+, the adsorption affinities of Li+, Ni2+, and Co2+ onto lithium ion-sieves were 32.665, 0.154, and 0.0332, respectively. The Kd order of Li+ > Ni2+ > Co2+ indicated high selectivity for Li+. More importantly, the selectivity Li Li coefficients α Ni and α Co reached 212.11 and 983.89, respectively. Such excellent selectivity between Li+, Ni2+, and Co2+ could be explained by the “ion memory” effect of lithium ion-sieves and larger ionic radii of Ni2+ and Co2+ which hindered them access to adsorption sites.53 Selective Adsorption Separation and Adsorbent Regeneration. Based on the findings above, we performed selective adsorption experiments from the actual Li+−Ni2+− Co2+−NH4+-containing leaching solutions (Li+ 1.039 g/L, Ni2+ 5.762 g/L, Co2+ 1.948 g/L, NH4+ 120 g/L) under the optimized leaching conditions to evaluate the separation effect of Li. In the measurement, the selective adsorption experiment was carried out in 250 mL polytetrafluoroethylene bottles containing 100 mL of leaching solutions mixed with 8 g lithium ion-sieves to form suspensions. The suspensions samples were shaken in a thermostatic water bath vibrator with a speed of 150 rpm at 30 °C for 24 h to complete adsorption without pH adjustment and then filtered through 0.22 μm filters. It was found that above 99.9% Li+ ions were adsorbed while only 0.17% Ni2+ and 1.79% Co2+ were adsorbed onto the lithium ion-sieves. After adsorption, the Li+-adsorbed leaching solutions contained only 0.18 mg/L Li+ ions, 5.662 g/L Ni2+, and 1.913 g/L Co2+, indicating that the Li+ ion could be effectively separated by lithium ion-sieves from the leaching solutions (Table 2).

Figure 4. Cycle performance of lithium ion-sieves in actual Li+−Ni2+− Co2+−NH4+-containing leaching solutions.

Table 2. Concentration Variations of Li+, Ni2+, and Co2+ before and after Adsorption in the Li+−Ni2+−Co2+−NH4+Containing Leaching Solutions ions

concentration before adsorption/mg/L

concentration after adsorption/mg/L

adsorption efficiency

Li+ Ni2+ Co2+

1039 5762 1948

0.18 5662 1913

99.9% 0.17% 1.79%

Li+ -adsorbed lithium ion-sieves are amenable to efficient reusability by HCl solution. Reusability of the lithium ion-sieves was determined through several adsorption−desorption cycles. The adsorption cycle experiments were the same as the abovementioned adsorption procedure. After each cycle, 10 g lithium ion-sieves were regenerated by washing with 1 L HCl solution (0.5 mol/L) at room temperature for 24 h, washed by distilled water, and then centrifuged to remove the residual ions. The HCl solution was used for next desorption step to concentrate Li+ ions and other impurities. Five adsorption−desorption cycles results (Figure 4) showed that the Li+ adsorption capacity were kept in the range of 25−28 mg/g while Ni2+ and Co2+ adsorption capacity was kept in the range of 1.0−1.5 and 0.3−0.5 mg/g with the desorption yields of Li+, Ni2+, and Co2+ of 92.36%−95.60%, 66.20%−75.5%, and 11.33%−13.95%, respectively. After the five adsorption−desorption cycles, concentrations of Li+, Ni2+, and Co2+ in the HCl solution (Figure S12) increased to 0.883, 10, and 0.72 mg/L, respectively. Recovery Process. At last, we proposed a novel hydrometallurgical flow sheet of the recovery of Li, Ni, and Co from the spent LIB powders as presented in Figure 5. During the selective ammonia leaching, 81.2% Li, 96.4% Ni, and 96.3% Co

Figure 5. Flowsheet of the recovery of Li, Ni, and Co from the spent LIB powders.

can be leached out and diluted to a desired concentration (1− 10 g/L) without Mn and Al. After solid−liquid separation, the diluted Li+−Ni2+−Co2+−NH4+-containing leaching solutions were disposed with the lithium ion-sieves to selectively separate Li+ ions, and the lithium separation efficiency reached 99.9%. The Li+-adsorbed lithium ion-sieves were separated and desorbed by HCl solution for regeneration. The desorption solutions were then neutralized by NaOH and carbonized by Na2CO3 to obtain Li2CO3 product with more than 99.5% purity (Figure S13,S14 and Table S5). On the other hand, the Ni2+−Co2+−NH4+-containing leaching solutions was distilled to realize closed-loop recycling of ammonia and the remnents were mixtures of NiCO3 and CoCO3 or their hydrates (Figure S15). Under the experimental conditions, the mixtures, which contained 11.34% Co and 25.1% Ni without Mn, Al, and Li, 11493

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could be easily dissolved by H2SO4 and extracted by P507, cyanex 272, etc., to obtain NiSO4 and CoSO4 products.54,55 Overall, the whole process realized effective recovery of Li, Ni, and Co from the spent LIB powders with the direct recovery efficiencies of 76.19%, 96.23%, and 94.57%, respectively, and closed-loop recycling of ammonia.



CONCLUSIONS A novel hydrometallurgical method was developed for recovering Li, Ni, and Co from spent LIB powders. 81.2% Li, 96.4% Ni, and 96.3% Co were selectively leached from the pretreated spent LIB powders by NH3·H2O−NH4HCO3 solutions in the presence of H2O2. And then the 99.9% lithium was efficiently separated from leaching solutions using manganese type lithium ion-sieves. The maximum amount of lithium adsorbed was 31.62 mg/g, and the selectivity coefficients of Li+ to Ni2+ and Li+ to Co2+ reached 212.11 and 983.89, respectively. Furthermore, Li2CO3, NiSO4, and CoSO4 could be obtained as products and ammonia could be closed-loop recycled. This sustainable process for recovering high valued metals from the spent LIBs will enable conservation and recycling of resources.



ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b02700. Additional experiments and results as discussed in the text and shown in Experimental, Characterization, Parts 1.1−3, Figures S1−S15, and Tables S1−S5 (PDF)



AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +86-10-82544856. Fax: +86-10-82544856. ORCID

Shili Zheng: 0000-0001-9474-9503 Ping Li: 0000-0002-9536-6210 Author Contributions #

H.W. and K.H. contributed equally to this study

Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was supported by the National Nature Science Foundation of China (No. 51574212, U1403195).



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Research Article

ACS Sustainable Chemistry & Engineering

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