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Recycling batteries
Chapter
14
Recycling batteries
D.C.R. Espinosa1, M.B. Mansur2 1
2
University of São Paulo, São Paulo, Brazil; Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
CHAPTER OUTLINE
14.1 Introduction 371 14.2 Main directives worldwide for spent batteries 372 14.3 Methods for the recovery of metals from spent batteries 378 14.3.1 Main processing routes 378 14.3.2 Pyrometallurgical route 379 14.3.3 Hydrometallurgical route 383
14.4 Future trends References 389
388
14.1 INTRODUCTION A battery consists of one or more electrochemical cells connected in series or parallel aimed at producing electrical energy. Each cell generally has an anode, a cathode, and an electrolyte. The electrical energy is produced by chemical reactions that result in a transfer of electrons from the anode to the cathode. The amount of power available in a battery is limited owing to the changes on the chemical species during such reactions. Primary batteries are assumed to be discharged when their chemicals are consumed. However, for a secondary or rechargeable battery, an external source of power can be used to change the direction of the flow of electrons, thus reversing the electrochemical process until the chemical species in the anode and cathode are restored to their original states, allowing its use again. Therefore, rechargeable batteries instead of primary ones are preferable from an environmental point of view because the number of spent batteries to be treated can be reduced. Batteries are the power source for portable electrical and electronic devices (computers, mobile phones, toys, and so on), tools, plug-in hybrid electric vehicles, automobile starters, light vehicles (e.g., motorized wheelchairs, electric bicycles, golf carts), etc. The use and discharge of batteries is Waste Electrical and Electronic Equipment (WEEE) Handbook. https://doi.org/10.1016/B978-0-08-102158-3.00014-8 Copyright © 2019 Elsevier Ltd. All rights reserved.
371
372 CHAPTER 14 Recycling batteries
growing throughout the world along with such devices. In fact, world demand is forecast to rise 7.8% per year to $120 billion in 2019 (World batteries, 2015). In Brazil, the annual consumption of batteries is estimated at around 1.2 billion units or nearly 6 units/year/person; in the USA, Japan, and Europe, it ranges between 10 and 15 units/year/person. The number of mobile phone users worldwide is forecast to surpass 5 billion by 2019, with approximately 50% of the total being in China and India (Statista, 2017). Although batteries are a component of electrical and electronic equipment (EEE), they must be recycled separately. They might be removable or fixed inside EEE, but should be disassembled and recycled by specific processes. Consumers and recyclers might not be aware of the existence of built-in batteries. The separation of batteries from EEE is costly because it is done manually, but nevertheless recyclers should not neglect this important operation. In some municipalities of Japan, consumers need to separate batteries from small waste EEE, especially mobile phones (Terazono et al., 2015). The main characteristics of the most-used batteries are shown in Table 14.1, including application, advantages, and disadvantages, while their typical metal composition is depicted in Table 14.2. Spent batteries may represent an important secondary source of metals that normally can be found at very high concentration levels, sometimes even higher than those found in natural ores. In addition, some metals are quite expensive, such as cobalt and nickel, and can be found in significant amounts in NiCd, NiMH, and Li-ion batteries. Therefore, the recovery of metals from spent batteries is also convenient for economic reasons because large amounts of solid waste can be reused as secondary raw material.
14.2 MAIN DIRECTIVES WORLDWIDE FOR SPENT BATTERIES Many directives have been elaborated from the beginning of the 1990s concerning the adequate destination of spent batteries in order to avoid metal contamination of soil and water resources. The very first directives were focused mainly on NiCd batteries, which were mostly used in mobile phones at that time, as well as on the progressive reduction in the use of mercury, cadmium, and lead in some types of batteries. Nowadays, issues such as collection systems, reduction of other heavy metals, banning the use of mercury in the production of batteries (according to Terazono et al. (2015), approximately 6%e10% of zinc carbon and alkaline batteries discarded in Japan still could be regarded as containing mercury), and recycling procedures are highlighted in the current directives of several countries
Table 14.1 Main characteristics of commercial batteries Type of battery
Anode/negative electrode
Cathode/positive electrode
Zincecarbon
Zn
Alkaline
Main applications
Advantages
Disadvantages
MnO2
Ammoniac, ZnCl2, and water
High gas formation; sealing system must be efficient due to high sensibility to oxygen.
Domestic general use.
Zn
MnO2
KOH
More expensive than ZneC battery.
Domestic general use.
Silver
Zn
AgO
KOH or NaOH
Low energy capacity due to its small size.
Lead
Pb
PbO
H2SO4
Current density is higher than Zneair battery; best service at low temperatures; good resistance to leaking; high efficiency with heavy discharge. Higher current density; good performance to intermittent and continuous discharges; good life and resistant to leaking; lower internal resistance; good mechanical resistance and low gas-production rate. Electrical characteristics are similar to Hg battery with higher voltage (1.55 V); very low self-discharge rate. Compared with other secondary batteries, it is the most economical; maintenance is not required.
Military use; systems that require instantaneous release of energy. Automotive use.
Contains lead; heavy.
Continued
14.2 Main directives worldwide for spent batteries 373
Electrolyte
Type of battery
Anode/negative electrode
Cathode/positive electrode
Electrolyte
Advantages
Disadvantages
Nickele cadmium
Cd
Ni(OH)2
KOH
Contains cadmium.
Wireless devices, cameras, and phones.
Nickelemetal hydride
AB5 type: MmNi3,5Co0,7 Mn0,4Al0,3 AB2 type: V15Ti15Zr20 Ni28Cr5Co5Fe6Mn6 C
Ni(OH)2, cobalt oxides, and additives
KOH
Durability is not affected when stored even at charge; some models can perform 30,000 cycles of charge and discharge. Higher energy per volume and weight compared with NiCd; does not contain cadmium.
Production cost is higher than NiCd but lower than Li-based batteries.
Portable devices, mobile phones.
LiCoO2
Organic solvents and/or salt solutions (LiPF6)
Higher current density; higher use life; higher nominal voltage.
High cost.
Li
LiFePO4 or LiMn3O6
Solid polymer electrolyte, polyethylene oxide, and LiCF3SO3
Its plastic character and hence flexibility means it can be made in different shapes and thinner configurations.
Relatively low life cycle and efficiency.
Portable devices, mobile phones, hybrid vehicles. Electronic devices, hybrid vehicles.
Lithium-ion
Lithiume polymer
Main applications
Adapted from Mantuano, D.P., 2005. Desenvolvimento de uma rota processual hidrometalúrgica para a recuperação de metais provenientes de baterias de celular descarregadas (M.Sc. thesis). UFMG, Belo Horizonte, Brazil, p. 203 (in Portuguese).
374 CHAPTER 14 Recycling batteries
Table 14.1 Main characteristics of commercial batteries Continued
14.2 Main directives worldwide for spent batteries 375
Table 14.2 Typical metal composition of commercial batteries (Veloso et al., 2005; Silva and Afonso, 2008) Element Ag Al Cd Ce Co Cr Cu Fe K La Li Mn Nd Ni Pb V Zn
Zincecarbon1
Alkaline1
Silver
NiCd2
NiMH2
Lithium2
0.019 15e20 0.43e5.5 0.6 0.017
0.5e2.0
4.6e24
2.5e4.3 0.020e0.080
12e20a
29e40
20e25
28.2e30.8
0.2e1.0
0.17 5.5e7.3
0.3e0.7
5e10 4.7e25
1.4e6.6 23e30
26e33
0.083
0.007
0.01 0.005
15e20
0.81e3.0 0.96e4.1 25e46
1.5be5.5c 10e15d 12e15e 15e20c
5 1
12e21
8.7e12.1
0.06
2
Note: Includes dry black powder only; Considering the whole battery. a Li-ion (Co). b Li-ion (Co, Ni, Mn). c Liepolymer (V). d Li-ion (Mn). e Li-ion (Ni).
as depicted in Table 14.3. According to these directives, the adequate destination of spent batteries may involve methods such as landfill disposition, stabilization, incineration, and/or recycling processes. Safe disposal in landfills and the stabilization of battery residues has become increasingly more expensive due to the increasing amount of waste produced and the limited storage capacity of sanitary landfills and special waste dumpsites. Incineration of batteries is also expensive, and it can even cause mercury, cadmium, and dioxin emissions into the environment (Bernardes et al., 2004). In fact, the recycling of spent batteries appears as the most adequate destination for this type of waste. As pointed out by Conard (1992), the recycling of wastes is important because it may contribute to the benefit of future generations and to the preservation of raw materials. In the particular case of batteries, it is still necessary to develop an efficient collection system in order to receive the spent batteries consumed worldwide (Mantuano et al., 2006).
0.092e1.6
Country
Directives
Main characteristics
Brazil
CONAMA 257 (1999), updated by CONAMA 401 (2008)
China
Regulation on Restriction of Hg in Batteries (QZHG, 1997) Universal Waste Rule (1995)
CONAMA Resolution 257 was the first law dedicated to the conscious use of batteries in Latin America. It established the requirements for the reuse, recycling, treatment, and final disposal of batteries containing Pb, Cd, Hg, and their compounds, as well as electronic products that contain integrated nonreplaceable batteries in their structures. Manufacturers and importers are responsible for processing and/or final disposal of batteries returned by users. It also imposed a gradual reduction in the limits of Hg, Cd, and Pb in the composition of batteries, from January 2000 to January 2001. In 2008 it was replaced by CONAMA Resolution 401. It established an even more significant reduction in the levels of Hg, Pb, and Cd in several types of batteries. It also intended to give more effectiveness to the postconsumption responsibility of the manufacturers and importers of batteries, according to which they become bound by the full cycle of their products, not only purchase by consumers. Manufacturers and importers must be registered, submit a technical report containing physical and chemical composition of batteries produced, and a plan for managing used batteries. Places that sell batteries must include collection points and return collected batteries to manufacturers or importers. Advertising materials and packaging of batteries must clearly show symbols indicating the appropriate destination and warnings about the risks to human health and environment. Manufacturers, importers, and distributors will be encouraged to promote environmental education campaigns for postconsumer spent batteries. Banned, from January 2001, the manufacture of ZneMn and alkaline batteries containing more than 0.0025% by weight of Hg, and 0.00001% by weight of Hg from 2005. Primary, rechargeable, and button cell batteries were excluded from these limits. Reduced the amount of waste to landfills, encouraged recycling and proper disposal of hazardous wastes, and reduced regulatory burdens on businesses that generate these wastes in order to facilitate compliance. Provided standardization for the collection, storage, and transportation of NiCd batteries, other rechargeable batteries, and certain Hg-containing batteries. Standardized the labeling of NiCd and lead-acid rechargeable batteries and products containing them. Banned the sale or offer for promotional purposes of alkaline and ZneC batteries containing intentionally introduced Hg and button cells of Hg oxide (except button cells with up to 25 mg of Hg), unless the manufacturer or importer defines the collection site for recycling or proper disposal. Manufacturers and importers must propose a chronogram to eliminate the production and marketing of certain batteries containing Hg; the label must contain information on the chemical composition, the recycling symbol, and a sentence indicating that the consumer must send it for recycling or proper disposal. Traders with annual sales exceeding $1 million must, from July 2006, install collection points and receive (free of charge) batteries of all types and brands as well as creating publicity campaigns about the benefits of recycling. For internet sales, they must inform consumers about the return of batteries or how to dispose of them properly.
USA
Mercury-containing and Rechargeable Battery Management Act (Battery Act, 1996)
376 CHAPTER 14 Recycling batteries
Table 14.3 Directives for batteries in Brazil, China, USA, Japan, and the European Union
Japan
Law for the Promotion of the Effective Utilization of Resources (1999, revised in 2001)
European Union
Directive 1991/157/EC updated by Directive 2006/66/EC
14.2 Main directives worldwide for spent batteries 377
Valid for NiCd, NiMH, Li-ion, and lead-acid batteries. Governs the positioning of recycling symbols, letters, and colors to identify each battery, including on the packages of batteries, according to specific law for the recycling of packages; labeling of the type of material used in the body of the batteries; and development of new designs for easy removal of batteries from equipment. Manufacturers are responsible for recycling collected batteries. Recycling targets were established: above 60% for NiCd, 55% for NiMH, 30% for Li-ion, and 50% for lead-acid. Electronics manufacturers must recycle or pay for it or transfer the collected batteries to the battery manufacturers, who must receive them without cost. Valid for all types of batteries except those used in security equipment, for military purposes, and to be launched into space. Batteries with Hg content higher than 0.0005% by weight (except button cells, whose Hg content can be less than 2% by weight) and portable batteries with Cd content above 0.002% by weight (except those for use in alarm systems and emergency medical equipment and cordless power tools) are prohibited from commercialization after September 2009. Adopt necessary steps to promote and maximize the selective collection of batteries and minimize household waste disposal; ensure that distributors of portable batteries accept their return free of charge, and manufacturers of industrial batteries, or third parties on their behalf, accept the return of spent batteries from consumers; collect 25% of all used batteries by September 2012, increasing to 45% by September 2016; require that the manufacture of products incorporating batteries is accomplished only on the condition that they are easily replaced after use by consumers and that they are also informed how to proceed to allow their disposal; ensure, from September 2009, that all batteries are collected and treated using the best available techniques in terms of health and environment (batteries must be handled and stored temporarily in places totally waterproof or in suitable containers; treatment must include, at least, the removal of all fluids and acids); recycle by September 2010 at least 65% of lead-acid, 75% of the NiCd, and 50% of other battery types; encourage the development of new technologies for recycling and treatment for all types of batteries; encourage technological innovations that improve the performance of batteries; inform consumers through campaigns of the effects of substances used in batteries on human health and the environment; the need to send such waste to resellers, systems for collecting and recycling available, the importance of their participation in this process, and the meaning of the symbols listed on labels and packaging. The labels on the batteries must be visible, legible, and indelible, and indicate their power, the chemical symbols Hg, Cd, and Pb for batteries containing levels higher than 0.0005% of Hg, 0.002% of Cd, and 0.004% of Pb, respectively, and symbols not to discard in the trash. All producers of batteries must be registered in the countries where they sell their products (Directive 2009/603/EC).
378 CHAPTER 14 Recycling batteries
According to CONAMA 401/2008 (Conselho Nacional de Meio Ambiente, Brazilian Environmental Agency), the most adequate destination of spent batteries must minimize environmental risks and adopt technical procedures for collecting, reusing, recycling, treating, and final disposal of such wastes. Such aspects are discussed as follows.
14.3 METHODS FOR THE RECOVERY OF METALS FROM SPENT BATTERIES Recycling processes of waste materials such as batteries must be as simple and cheap as possible. The current processes used to recycle portable batteries include pyrometallurgical and hydrometallurgical techniques (Salgado et al., 2003; Bernardes et al., 2004; Espinosa et al., 2004). Most collection programs receive all types of batteries, so the chemical composition of battery waste might be very irregular, as shown in Tables 14.1 and 14.2. Most recycling processes were developed to recycle only a few types of batteries. Therefore, initially it is necessary to sort the batteries in order to segregate the ones that cannot be treated by that specific process. For example, in general, a process that treats ZneC and alkaline cells does not admit contamination with NiCd batteries. However, the situation observed in collection systems is the mixing of different types of batteries. Unfortunately, there is no correlation between shape and size with the composition of batteries. This characteristic complicates the sorting processes. This step, allied with transportation, increases the total cost of recycling processes. With the exception of NiMH batteries, in general, battery recycling processes are viable only through funding or legal obligationdi.e., the revenue does not cover the cost of operation (Bernardes et al., 2004). The battery collection rules in municipal waste management in Japan were reviewed by Terazono et al. (2015).
14.3.1 Main processing routes Battery recycling processes are composed basically of two main steps, waste preparation and metallurgical processing. The waste preparation step begins with the screening of the waste, segregating it by chemical type. The sorting might be composed of several steps in order to improve separation efficiency. These steps might contain manual segregation and segregation using pieces of equipment developed specially for this operation. The pieces of equipment developed to this end apply several techniquesdfor example, mechanical separation, magnetic separation, X-ray imaging, and optical sensors to read bar codes located on the waste material (Bernardes et al., 2004).
14.3 Methods for the recovery of metals from spent batteries 379
After sorting, the material to be recycled is prepared for the metallurgical process through physical conditioning operations. These operations are based on typical ore dressing unit operations, such as crushing, comminution, magnetic separation, electrostatic separation, and dense medium separation (DMS). The crushing involves the fragmentation of the waste, and its main goal is to separate most of the polymeric or metallic cover from the internal material that contains the target metals to be recycled. The main goal of the comminution step is to diminish the particle size in order to liberate the several types of material. The other cited operations have the objective to separate materials according to specific characteristics. Magnetic separation is applied to separate magnetic materials (such as iron and their alloys) from nonmagnetic material. Electrostatic separation aims to separate conductive material from nonconductive, roughly metal from nonmetal. The DMS technique segregates materials having different densities. Therefore, the objective of the waste preparation step is to concentrate the fraction of waste that contains the target metals using physical methods that present relatively low costs of processing. Hence, even considering the limited efficiency of such processes, these operations might diminish the overall cost of the recycling process, thus diminishing the amount of material that should be treated by metallurgical processing. Metallurgical processing can basically follow three different routesd pyrometallurgy, hydrometallurgy, and hybrid processesdthat use techniques from pyro- and hydrometallurgy to obtain metals or metal compounds. There are several battery recycling facilities around the world. Table 14.4 presents some examples of battery recycling processes, showing the treated materials and their limitations (Bernardes et al., 2004).
14.3.2 Pyrometallurgical route Pyrometallurgical recycling processes use high temperature to process wastes, aiming at the reclamation of target metals. During heat treatment of battery waste, several reactions may take place such as decomposition of compounds, reduction, and evaporation of metals or compounds (Espinosa et al., 2004). All pyrometallurgical processes for the recycling of batteries share the common step of evaporating a metal to segregate it from other materials that have higher boiling points. Therefore, the goal of these processes is to evaporate Hg, Zn, and/or Cd.
Process
Route
Treated material
Limitation
Observation
SUMITOMO
Pyrometallurgical
NiCd and Pb-acid batteries
Lithium battery recycling process is patented.
Recytec
Pyrometallurgical
SNAM-SAVAM
Pyrometallurgical
Household cells (alkaline, ZneC, Zneair, and mercury), NiMH Most types of batteries, including fluorescent lamps NiCd, NiMH, and Li-ion batteries
INMETCO
Pyrometallurgical
Mercury
Accurec
Pyrometallurgical
Dust from furnaces containing iron, zinc, and lead and also several types of batteries: NiCd, NiMH, NiFe, Li-ion, and ZneMn NiCd, NiMH, and Zncontaining batteries
TNO BATENUS ZINCEX RECUPYL
Hydrometallurgical Hydrometallurgical Hydrometallurgical Hydrometallurgical
NiCd batteries Most types of batteries Zinc bearing materials Most types of batteries
UMICORE
Hybrid
Li-based and NiMH batteries
NiCd batteries
The process treats portable and industrial batteries.
A hydrometallurgical step is used in the process of NiMH battery recycling to reclaim rare earth metals. Li-ion recycling process is being developed. Mercury Mercury NiCd, lead, and button batteries NiCd batteries
380 CHAPTER 14 Recycling batteries
Table 14.4 Examples of battery recycling processes (Espinosa et al., 2004; Mantuano, 2005)
14.3 Methods for the recovery of metals from spent batteries 381
Zinc-containing batteries can be recycled by pyrometallurgical processes, since the boiling points of the containing metals (Hg, Zn, and Mn) are very different. During heat treatment, after water evaporation, the elimination of Hg through evaporation takes place due to its low boiling point. Frenay and Feron (1990) observed that thermal elimination of Hg, which is linked to chlorine ions of the electrolyte, should be performed at 600 C. Conversely, Xia and Li (2004) found that 450 C is enough to remove Hg under vacuum. After Hg decontamination, zinc also can be recovered through distillation but at temperatures higher than 907 C (zinc boiling point). The global discharge reaction of either an alkaline or a ZneC cell can be expressed as (Sayilgan et al., 2009): Zn þ 2MnO2 / Mn2 O3 þ ZnO
(14.1)
Therefore, one should expect to find in the waste of spent batteries not only metallic Zn, but also ZnO, MnO2, and Mn2O3. Zinc oxide, when heated above 920 C under atmospheric pressure and in the presence of a reductor (such as the carbon constituent of these types of batteries), is reduced according to the following reaction (Rosenqvist, 2004): ZnO þ CO / ZnðvÞ þ CO2
(14.2)
Since the temperature at which the reaction occurs is above the Zn boiling point, Zn is produced directly in vapor form. Consequently, the recycling process must be carried out at temperatures above 920 C in order to evaporate most of the Zn. Manganese remains solid throughout the process, but during heating, prereduction of the manganese oxides to MnO occurs due to the carbon present in the charge. The material that remains solid is composed mainly of MnO and iron (from the metallic cases). Pyrometallurgical processes for the recycling of electric arc furnace dust (and Zn-bearing materials), such as INMETCO and Waelz, accept ZneC and alkaline batteries in the charge. In such processes, the comminuted material is mixed with a carbon-based reductor. This mixture might then be agglomerated in the form of pellets depending on the process. Following this, the mixture or pellets are put into an open-hearth or a rotative furnace operating at temperatures up to 1350 C. During the process, Zn and other volatile compounds or elements are captured in the gas treatment system (Bernardes et al., 2004; Espinosa et al., 2004).
382 CHAPTER 14 Recycling batteries
Spent batteries
Sorting
Physical / mechanical treatment
Heat treatment (controlled atmosphere)
Cd
Material containing Fe, Ni and Co
n FIGURE 14.1 Generic flow sheet of operations for the pyrometallurgical recycling of NiCd batteries.
The classic recycling processes for NiCd batteries are typically pyrometallurgical and based on Cd distillation. Fig. 14.1 shows a schematic flow sheet of a theoretical pyrometallurgical recycling process for NiCd batteries. During heating, after water evaporation, the decomposition of Cd and Ni hydroxides takes place as follows (Espinosa and Tenorio, 2004): NiðOHÞ2ðsÞ / NiOðsÞ þ H2 OðgÞ T ¼ 230 C
(14.3)
CdðOHÞ2ðsÞ / CdOðsÞ þ H2 OðgÞ T ¼ 300 C
(14.4)
The recycling process can be carried out with or without the presence of a reducing agent (usually carbon based). In order to avoid the use of a reducing agent, the total pressure of the system must be about 104 bar to enable the decomposition of CdO at 850e900 C to produce Cd vapor (Espinosa and Tenório, 2004). If the process is carried out with the aid of a reducing agent, reduction of the oxides of nickel and cadmium is thermodynamically possible at relatively low temperatures. The boiling point of metallic Cd is 767 C, so above this temperature Cd is produced directly into vapor form. Generally, the pyrometallurgical process to recycle NiCd batteries is performed at temperatures of about 900 C under vacuum, under inert atmosphere, or by imposing a reducing atmosphere (Espinosa and Tenório, 2006). The controlled atmosphere is necessary to avoid the oxidation of the produced metallic Cd. Metallic cadmium is produced with 99.9% purity
14.3 Methods for the recovery of metals from spent batteries 383
and can be used in numerous applications including the production of new NiCd batteries. The material that remains solid during the treatment is composed basically of Ni, Fe, and Co and can be used in stainless steel production. Pyrometallurgical recycling processes for NiCd batteries also treat NiMH batteries mixed in the charge; however, only Ni is recovered, and the rare earth elements present in this latter type of battery are lost in the process. According to Sun et al. (2017), pyrometallurgy smelting is still the main technology used in China for spent lead-acid battery recycling. In addition, vacuum reduction technology has been evaluated to treat lead and NiCd batteries (Lin and Qiu, 2011; Huang et al., 2010).
14.3.3 Hydrometallurgical route A typical flow sheet for the recovery of metals from spent batteries using hydrometallurgical methods is shown schematically in Fig. 14.2. Firstly, batteries must be classified by type because metal composition varies significantly as shown in Tables 14.1 and 14.2. Then, after dismantling for the removal of iron scraps, plastic cases, and paper, the internal content of the battery is submitted to a leaching step in order to transfer metals of interest from the solid phase to the aqueous solution. Acid and alkaline solutions are normally used, as well as oxidant and reducing agents. Recently, organic
Spent batteries Sorting
Physical / mechanical treatment
Leaching
Solution purification
Metal reclamation
Solvent extraction Ion exchange Precipitation Cementation
Precipitation of compounds Electrolysis
Compound or metal n FIGURE 14.2 Flow sheet depicting the main steps for hydrometallurgical recycling of batteries.
384 CHAPTER 14 Recycling batteries
acids (citric and malic acids in the presence of hydrogen peroxide, H2O2) have been introduced as environmentally friendly reagents to leach cobalt and lithium from Li-ion batteries with promising results (Li et al., 2013). For example, in the leaching of Znecarbon or alkaline batteries, selective leaching of zinc and manganese can be achieved using sequential leaching steps with dilute H2SO4 solution in order to preferentially extract zinc, followed by leaching of the remaining residue with concentrated H2SO4 solution with H2O2 in order to extract manganese (Veloso et al., 2005). The following reactions may occur in the dissolution of zinc and manganese oxides: ZnO þ H2 SO4 / ZnSO4 þ H2 O
(14.5)
Mn2 O3 þ H2 SO4 / MnO2 þ MnSO4 þ H2 O
(14.6)
Mn3 O4 þ 2H2 SO4 / MnO2 þ 2MnSO4 þ 2H2 O
(14.7)
MnO2 þ H2 SO4 þ H2 O2 / MnSO4 þ 2H2 O þ O2
(14.8)
In fact, zinc oxide can be fully dissolved by sulfuric acid solutions according to Eq. (14.5). On the other hand, the dissolution of Mn2O3 and Mn3O4 oxides is partial because the MnO2 produced is insoluble (Eqs. (14.6) and (14.7)). For instance, the leaching of alkaline battery powders with 1.0% (v/v) H2SO4 at 90 C for 2 h results in the dissolution of only 43% of the total manganese originally present in the powder (Salgado et al., 2003). A similar result (dissolution of 40% of manganese and 100% of zinc oxides) was obtained using 0.7% (v/v) H2SO4 at 70 C and 3 h (Souza et al., 2001). Therefore, to leach 100% of the manganese present in the powder, the use of H2O2 as a reduction agent is a plausible alternative. In addition, the removal of potassium from the powder of Znecarbon and alkaline batteries may also contribute to reducing the consumption of H2SO4 in the acidic leaching step. In the case of Li-ion batteries, alkaline solutions of NaOH were used to leach aluminum in a selective way, followed by acid solutions of H2SO4 in order to leach cobalt and lithium (Ferreira et al., 2009). Many other aqueous systems including HCl, citric acid, malic acid, HNO3, and H2SO3 in the presence or not of H2O2 have been evaluated to leach Li-ion batteries as shown in Table 14.5. After leaching, the aqueous solution is submitted to a purification step that may comprise several separation methods such as cementation, precipitation, solvent extraction, adsorption, ion exchange, and others. Finally, the metal species are recovered from the purified solutions as pure metals or metal oxides, hydroxides, and/or salts.
Table 14.5 Summary of operational conditions for metal recovery from Li-ion batteries Leaching step
References
Leaching agents
T ( C)
S/L ratio (g/mL)
NaOH, followed by H2SO4 þ H2O2
30 to 70
1/10
Shin et al. (2005) and Swain et al. (2007)
H2SO4 þ H2O2
75
1/10 and 1/20
Li et al. (2013)
Citric acid þ H2O2 and malic acid þ H2O2
90
1/20
Mantuano et al. (2006)
H2SO4
80
1/30
Dorella and Mansur 2007)
H2SO4 þ H2O2
65
1/30
Main liquor treatment results
Main leaching results
Methods
Reagents
Alkaline leaching: Al (60%), Co (negligible), and Li (10%). Acid leaching of Al, Li, and Co around 80%e100%. H2O2 improved LiCoO2 leaching, mainly Co Co (>93%) and Li (>94%) at the presence of H2O2 (5%e15% v/v). Granulometry effect was found significant for Co leaching Co (>90%) and Li (100%) with citric acid (1.25 M) þ H2O2 (1% v/v) and with malic acid (1.5 M) þ (2% v/v) Low recovery of Co (30%). Acid concentration and temperature were found significant
Crystallization by evaporation
e
Purified CoSO4$H2O was obtained
e
e
e
e
e
e
Solvent extraction
Cyanex 272
Co (75%) and Li (100%) at the presence of H2O2 (1% v/v)
Precipitation and solvent extraction
NH4OH and Cyanex 272
Co/Li separation at pH ¼ 5. Co/Al and Co/Cu separations were found difficult Al (80%), Co (8%), and Li (13%) were precipitated at pH ¼ 5. A stripping solution Co (63 g/L) and Li (0.4 g/L) was obtained
Continued
14.3 Methods for the recovery of metals from spent batteries 385
Ferreira et al. (2009)
Liquor treatment step
Leaching step Leaching agents
T ( C)
S/L ratio (g/mL)
Lee and Rhee (2002, 2003) Zhang et al. (1998)
HNO3 þ H2O2
75
HCl, NH2OH, HCl, and H2SO3
Nan et al. (2005)
Lupi et al. (2005)
References
Liquor treatment step Main liquor treatment results
Main leaching results
Methods
Reagents
1/100
Co (95%) and Li (95%) with H2O2 (1.7% v/v)
Precipitation
Citric acid
Pure LiCoO2 was obtained
80
1/100
Co (>90%) and Li (>90%) with concentrated NH2OH HCl and HCl. Low metal recoveries obtained with H2SO3
Solvent extraction
D2EHPA and PC-88A
NaOH and H2SO4
25 and 70
1/10 and 1/5
NaOH leached Al (98%) selectively. Co (>90%), Li (>90%), and Cu (<10%) were leached with H2SO4
Precipitation and solvent extraction
Ammonium oxalate, ACORGA M5640, Cyanex 272
e
e
e
e
Solvent extraction and electrolysis
Cyanex 272
PC-88A was found more selective: Co (>99.9%) and Li (12.6%) extracted with 0.9M PC-88A Co (90%) precipitated with 0.5% impurities. Cu (97%) and Co (97%) extracted with ACORGA and Cyanex 272, respectively Co (100% extracted). Electrolysis solution obtained containing Co (<1 ppm) and Ni (<100 ppm)
Adapted from Ferreira, D.A., Prados, L.M.Z., Majuste, D., Mansur, M.B., 2009. Hydrometallurgical separation of aluminum, cobalt, copper and lithium from spent Li-ion batteries. Journal of Power Sources, 187 238e246.
386 CHAPTER 14 Recycling batteries
Table 14.5 Summary of operational conditions for metal recovery from Li-ion batteries Continued
14.3 Methods for the recovery of metals from spent batteries 387
In hydrometallurgical processes, zinc can be recovered from the aqueous solution by electrolysis, but the presence of contaminants may affect its efficiency as well as the quality of the zinc produced; for example, in the presence of cadmium, both metals will deposit, thus reducing the purity of metallic zinc. Therefore, the purification step of the leach solution is crucial for the operation’s success, so very selective methods are used for the purification of zinc such as solvent extraction (Mansur et al., 2002; Salgado et al., 2003), cementation (Feijó, 2007), ion exchange (Kentish and Stevens, 2001), and precipitation (Veloso et al., 2005). In the solvent extraction method, an organic phase containing an adequate extractant depending on the metal to be extracted is put into contact with the aqueous leach liquor. The metal is transferred to the organic phase, which is scrubbed if necessary to remove coextracted species and then submitted to the stripping step when the extracted metal is transferred to another aqueous phase. The metal of interest is separated and even concentrated depending on the aqueous/organic ratio as well as other operating conditions. This method is largely used to separate several metals such as zinc, cobalt, nickel, manganese, copper, and rare earths. A review of solvent extraction applied to metal systems is given by Ritcey and Ashbrook (1984), Habashi (1993), and Rydberg et al. (2004). Ion exchange works in a quite similar way to solvent extraction, but the leach aqueous solution is put into contact with a solid resin containing the extractant that reacts with the metal of interest. After this stage, the loaded resin is submitted to an elution step aimed at recovering the extracted metal to another aqueous solution. Ion exchange is discussed elsewhere (Zagorodni, 2006). The use of precipitation has various purposes, as in the case of water treatment for instance, but in the case of battery recycling it is mainly used in the selective separation of metals. It is carried out by controlling the pH of the aqueous phase with the addition of precipitating agents like NaOH, CaO, Ca2CO3, and many other reagents. In the treatment of spent zincecarbon or alkaline batteries, iron can be removed from the solution by precipitation in pH higher than 4.0 and with the use of an oxidizing agent. Finally, the cementation method uses a dislocating reaction to promote metal separation that is carried out by adding a less noble metal species to the solution, aiming to reduce the more noble metal species. For example, the addition of zinc powder promotes the precipitation of nickel according to the following equation: Ni2þ þ ZnðsÞ /NiðsÞ þ Zn2þ
(14.9)
388 CHAPTER 14 Recycling batteries
In the hydrometallurgical treatment of NiCd batteries, the internal material obtained from dismantling is previously milled and subsequently leached in acidic medium, resulting in an aqueous leach solution containing nickel, cadmium, and iron. After iron removal by precipitation, nickel and cadmium are separated by solvent extraction and then recovered by electrolysis. Similarly, for the case of NiMH batteries, previous treatment is required to separate the internal parts of the battery, which is leached with H2SO4 resulting in a leach solution containing rare earths, nickel, and cobalt. The former can be separated by precipitation, while the last metals are separated by solvent extraction. Some studies have revealed that hydrometallurgical routes to NiMH may include one step to recover cadmium because several NiCd batteries were found to be labeled as NiMH (Bertuol et al., 2006; Rodrigues and Mansur, 2010). Hydrometallurgical routes are commonly more complex and require a higher number of steps in comparison with pyrometallurgical routes; however, they are efficient, more flexible, more energy saving, and present high metal selectivity, so hydrometallurgical routes are becoming more frequent for treating spent batteries that contain several different metals in their composition. In addition, the leaching agents and reagents can be regenerated and reused several times in closed-circuit operation. From an environmental point of view, the generation of gases is relatively lower, so Conard (1992) has pointed out that the hydrometallurgical route to be used in the treatment of various wastes thus contributes to sustainable development. In fact, the recycling of spent batteries has advantages not only from an environmental point of view because natural resources are finite (Gupta and Mukherjee, 1990), but also from an economic standpoint because the metal content and purity present in spent batteries are usually much higher than those commonly found in their ores.
14.4 FUTURE TRENDS Future trends in battery recycling are directly related to the market for electric/electronic portable devices. In the last 2 decades, substitution of NiCd batteries in most portable devices by NiMH and lithium-based batteries has occurred. The main reasons for this change were environmental policies. Hence, technical concerns were less important in this substitution. In future decades, these systems probably should be optimized to improve their capacities.
References 389
The waste of postconsumer spent batteries is a mix of several types of batteries. So if existing recycling processes were selected to recycle this kind of waste, the spent batteries should be segregated by type prior to recycling. One possible trend is the development of a new process that treats more types of spent batteries and thus avoids this initial separation; another is improvement of segregation methods. A recent potentially important application of batteries is for electric and hybrid vehicles. The market for such vehicles is increasing, mainly in North America, China, Japan, and Western Europe (World batteries, 2015; Du and Ouyang, 2017) due to environmental concerns. The waste generated by this type of use is different from the waste of postconsumer spent batteries; the life cycle impact of such batteries has been investigated (Manzetti and Mariasiu, 2015). These vehicles are equipped with one specific type of rechargeable battery, making it easier to segregate batteries upon disposal.
REFERENCES Battery Act, 1996. Public law 104e142. Statute 110, p. 1329. https://www.govinfo.gov/ content/pkg/STATUTE-110/pdf/STATUTE-110-Pg1329.pdf (accessed 21 March 2019). Bernardes, A.M., Espinosa, D.C.R., Tenório, J.A.S., 2004. Recycling of batteries: a review of current processes and technologies. Journal of Power Sources 130, 291e298. Bertuol, D.A., Bernardes, A.M., Tenório, J.A.S., 2006. Spent NiMH batteries: characterization and metal recovery through mechanical processing. Journal of Power Sources 160, 1465e1470. CONAMA, Ministério do Meio Ambiente. http://www.mma.gov.br (in Portuguese). Conard, B.R., 1992. The role of hydrometallurgy in achieving sustainable development. Hydrometallurgy 30, 1e28. Dorella, G., Mansur, M.B., 2007. A study of the separation of cobalt from spent Li-ion battery residues. Journal of Power Sources 170, 210e215. Du, J., Ouyang, D., 2017. Progress of Chinese electric vehicles industrialization in 2015: a review. Applied Energy 188, 529e546. Espinosa, D.C.R., Tenório, J.A.S., 2004. Fundamental aspects of recycling of nickelecadmium. batteries through vacuum distillation. Journal of Power Sources 135, 320e326. Espinosa, D.C.R., Tenório, J.A.S., 2006. Recycling of nickelecadmium batteries using coal as reducing agent. Journal of Power Sources 157, 600e604. Espinosa, D.C.R., Bernardes, A.M., Tenório, J.A.S., 2004. An overview on the current process for the recycling of batteries. Journal of Power Sources 135, 311e319. Feijó, F.D., 2007. Redução das perdas de zinco associadas aos processos de purificação do licor por cementação e de tratamento dos resíduos gerados da Votorantim Metais (M.Sc. thesis). UFMG, Belo Horizonte, Brazil, p. 177 (in Portuguese). Ferreira, D.A., Prados, L.M.Z., Majuste, D., Mansur, M.B., 2009. Hydrometallurgical separation of aluminum, cobalt, copper and lithium from spent Li-ion batteries. Journal of Power Sources 187, 238e246.
390 CHAPTER 14 Recycling batteries
Frenay, J., Feron, S., 1990. Domestic battery recycling in western Europe. In: 2nd International Symposium in Recycling of Metals and Engineered Materials, vol. 2. The Minerals, Metals & Materials Society, pp. 639e647. Gupta, C.K., Mukherjee, T.K., 1990. Hydrometallurgy in Extraction Processes. CRC Press, Inc. Habashi, F., 1993. A Textbook of Hydrometallurgy. Métallurgie Extractive Québec. Huang, K., Li, J., Xu, Z., 2010. Characterization and recycling of cadmium from waste nickel-cadmium batteries. Waste Management 30, 2292e2298. Kentish, S.E., Stevens, G.W., 2001. Innovations in separations technology for the recycling and re-use of liquid waste streams. Chemical Engineering Journal 84, 149e159. Lee, K.L., Rhee, K.I., 2002. Preparation of LiCoO2 from spent lithium-ion batteries. Journal of Power Sources 109, 17e21. Lee, K.L., Rhee, K.I., 2003. Reductive leaching of cathodic active materials from lithium ion battery wastes. Hydrometallurgy 68, 5e10. Li, L., Dunn, J.B., Zhang, X.X., Gaines, L., Chen, R.J., Wu, F., Amine, K., 2013. Recovery of metals from spent lithium-ion batteries with organic acids as leaching reagents and environmental assessment. Journal of Power Sources 233, 180e189. Lin, D., Qiu, K., 2011. Recycling of waste lead storage battery by vacuum methods. Waste Management 31, 1547e1552. Lupi, C., Pasquali, M., Dell’Era, A., 2005. Nickel and cobalt recycling from lithium-ion batteries by electrochemical processes. Waste Management 25, 215e220. Mansur, M.B., Slater, M.J., Biscaia Jr., E.C., 2002. Equilibrium analysis of the reactive liquid-liquid system ZnSO4/D2EHPA/n-heptane. Hydrometallurgy 63, 117e126. Manzetti, S., Mariasiu, F., 2015. Electric vehicle battery technologies: from present state to future systems. Renewable and Sustainable Energy Reviews 51, 1004e1012. Mantuano, D.P., 2005. Desenvolvimento de uma rota processual hidrometalúrgica para a recuperação de metais provenientes de baterias de celular descarregadas (M.Sc. thesis). UFMG, Belo Horizonte, Brazil, p. 203 (in Portuguese). Mantuano, D.P., Dorella, G., Elias, R.C.A., Mansur, M.B., 2006. Analysis of a hydrometallurgical route to recover base metals from spent rechargeable batteries by liquid-liquid extraction with Cyanex 272. Journal of Power Sources 159, 1510e1518. Nan, J., Han, D., Zuo, X., 2005. Recovery of metal values from spent lithium-ion batteries with chemical deposition and solvent extraction. Journal of Power Sources 152, 278e284. QZHG, 1997. General Trade Union of Chine Light Industry, p. 14. Ritcey, G.M., Ashbrook, A.W., 1984. Solvent Extraction e Principles and Applications to Process Metallurgy, vols. I and II. Elsevier. Rodrigues, L.E.O.C., Mansur, M.B., 2010. Hydrometallurgical separation of rare earth elements, cobalt and nickel from spent nickel-metal-hydride batteries. Journal of Power Sources 195, 3735e3741. Rosenqvist, T., 2004. Principles of extractive metallurgy. In: Chapter 10 e Volatile Metals, second ed. Tapir Academic Press, pp. 271e294. Rydberg, J., Musikas, C., Choppin, G.R., 2004. Principles and Practices of Solvent Extraction. Marcel Dekker. Salgado, A.L., Veloso, A.M.O., Pereira, D.D., Gontijo, G.S., S., A., Mansur, M.B., 2003. Recovery of zinc and manganese from spent alkaline batteries by liquideliquid extraction with Cyanex 272. Journal of Power Sources 115, 367e373.
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Sayilgan, E., Kukrer, T., Civelekoglu, G., Ferella, F., Akcil, A., Veglio, F., Kitis, M., 2009. A review of technologies for the recovery of metals from spent alkaline and zincecarbon batteries. Hydrometallurgy 97, 158e166. Shin, S.M., Kim, N.H., Sohn, J.S., Yang, D.H., Young, H.K., 2005. Development of a metal recovery process from Li-ion battery wastes. Hydrometallurgy 79, 172e181. Silva, C.N., Afonso, J.C., 2008. Processamento de pilhas do tipo botão. Química Nova 31 (6), 1567e1572 (in Portuguese). Statista, 2017. Number of mobile phone users worldwide from 2015 to 2020 (in billions). https://www.statista.com/statistics/274774/forecast-of-mobile-phone-usersworldwide/ (accessed 21 March 2019). Souza, C.C.B.M., Oliveira, D.C., Tenório, J.A.S., 2001. Characterization of used alkaline batteries powder and analysis of zinc recovery by acid leaching. Journal of Power Sources 103, 120e126. Sun, Z., Cao, H., Zhang, X., Lin, X., Zheng, W., Cao, G., Sun, Y., Zhang, Y., 2017. Spent lead-acid battery recycling in China e a review and sustainable analyses on mass flow of lead. Waste Management 64, 190e201. Swain, B., Jeong, J., Lee, J., Lee, G., Sohn, J., 2007. Hydrometallurgical process for recovery of cobalt from waste cathodic active material generated during manufacturing of lithium ion batteries. Journal of Power Sources 108, 70e73. Terazono, A., Oguchi, M., Iino, S., Mogi, S., 2015. Battery collection in municipal waste management in Japan: challenges for hazardous substance control and safety. Waste Management 39, 246e257. Veloso, L.R.S., Rodrigues, L.E.O.C., Ferreira, D.A., Magalhães, F.S., Mansur, M.B., 2005. Development of a hydrometallurgical route for the recovery of zinc and manganese from spent alkaline batteries. Journal of Power Sources 152, 295e302. World batteries. Industry study #3309. Freedonia, p.515, 2015. https://www. freedoniagroup.com/World-Batteries.html (accessed 12 June 2017). Xia, Y.-Q., Li, G.-J., 2004. The BATREC process for reclaiming used batteries. Waste Management 24, 359e363. Zagorodni, A.A., 2006. Ion Exchange Materials: Properties and Applications. Elsevier. Zhang, P., Yokoyama, T., Itabashi, O., Suzuki, T.M., Inoue, K., 1998. Hydrometallurgical process for recovery of metal values from spent lithium-ion secondary batteries. Hydrometallurgy 47, 259e271.
14
Recycling batteries
D.C.R. Espinosa1, M.B. Mansur2 1
2
University of São Paulo, São Paulo, Brazil; Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
CHAPTER OUTLINE
14.1 Introduction 371 14.2 Main directives worldwide for spent batteries 372 14.3 Methods for the recovery of metals from spent batteries 378 14.3.1 Main processing routes 378 14.3.2 Pyrometallurgical route 379 14.3.3 Hydrometallurgical route 383
14.4 Future trends References 389
388
14.1 INTRODUCTION A battery consists of one or more electrochemical cells connected in series or parallel aimed at producing electrical energy. Each cell generally has an anode, a cathode, and an electrolyte. The electrical energy is produced by chemical reactions that result in a transfer of electrons from the anode to the cathode. The amount of power available in a battery is limited owing to the changes on the chemical species during such reactions. Primary batteries are assumed to be discharged when their chemicals are consumed. However, for a secondary or rechargeable battery, an external source of power can be used to change the direction of the flow of electrons, thus reversing the electrochemical process until the chemical species in the anode and cathode are restored to their original states, allowing its use again. Therefore, rechargeable batteries instead of primary ones are preferable from an environmental point of view because the number of spent batteries to be treated can be reduced. Batteries are the power source for portable electrical and electronic devices (computers, mobile phones, toys, and so on), tools, plug-in hybrid electric vehicles, automobile starters, light vehicles (e.g., motorized wheelchairs, electric bicycles, golf carts), etc. The use and discharge of batteries is Waste Electrical and Electronic Equipment (WEEE) Handbook. https://doi.org/10.1016/B978-0-08-102158-3.00014-8 Copyright © 2019 Elsevier Ltd. All rights reserved.
371
372 CHAPTER 14 Recycling batteries
growing throughout the world along with such devices. In fact, world demand is forecast to rise 7.8% per year to $120 billion in 2019 (World batteries, 2015). In Brazil, the annual consumption of batteries is estimated at around 1.2 billion units or nearly 6 units/year/person; in the USA, Japan, and Europe, it ranges between 10 and 15 units/year/person. The number of mobile phone users worldwide is forecast to surpass 5 billion by 2019, with approximately 50% of the total being in China and India (Statista, 2017). Although batteries are a component of electrical and electronic equipment (EEE), they must be recycled separately. They might be removable or fixed inside EEE, but should be disassembled and recycled by specific processes. Consumers and recyclers might not be aware of the existence of built-in batteries. The separation of batteries from EEE is costly because it is done manually, but nevertheless recyclers should not neglect this important operation. In some municipalities of Japan, consumers need to separate batteries from small waste EEE, especially mobile phones (Terazono et al., 2015). The main characteristics of the most-used batteries are shown in Table 14.1, including application, advantages, and disadvantages, while their typical metal composition is depicted in Table 14.2. Spent batteries may represent an important secondary source of metals that normally can be found at very high concentration levels, sometimes even higher than those found in natural ores. In addition, some metals are quite expensive, such as cobalt and nickel, and can be found in significant amounts in NiCd, NiMH, and Li-ion batteries. Therefore, the recovery of metals from spent batteries is also convenient for economic reasons because large amounts of solid waste can be reused as secondary raw material.
14.2 MAIN DIRECTIVES WORLDWIDE FOR SPENT BATTERIES Many directives have been elaborated from the beginning of the 1990s concerning the adequate destination of spent batteries in order to avoid metal contamination of soil and water resources. The very first directives were focused mainly on NiCd batteries, which were mostly used in mobile phones at that time, as well as on the progressive reduction in the use of mercury, cadmium, and lead in some types of batteries. Nowadays, issues such as collection systems, reduction of other heavy metals, banning the use of mercury in the production of batteries (according to Terazono et al. (2015), approximately 6%e10% of zinc carbon and alkaline batteries discarded in Japan still could be regarded as containing mercury), and recycling procedures are highlighted in the current directives of several countries
Table 14.1 Main characteristics of commercial batteries Type of battery
Anode/negative electrode
Cathode/positive electrode
Zincecarbon
Zn
Alkaline
Main applications
Advantages
Disadvantages
MnO2
Ammoniac, ZnCl2, and water
High gas formation; sealing system must be efficient due to high sensibility to oxygen.
Domestic general use.
Zn
MnO2
KOH
More expensive than ZneC battery.
Domestic general use.
Silver
Zn
AgO
KOH or NaOH
Low energy capacity due to its small size.
Lead
Pb
PbO
H2SO4
Current density is higher than Zneair battery; best service at low temperatures; good resistance to leaking; high efficiency with heavy discharge. Higher current density; good performance to intermittent and continuous discharges; good life and resistant to leaking; lower internal resistance; good mechanical resistance and low gas-production rate. Electrical characteristics are similar to Hg battery with higher voltage (1.55 V); very low self-discharge rate. Compared with other secondary batteries, it is the most economical; maintenance is not required.
Military use; systems that require instantaneous release of energy. Automotive use.
Contains lead; heavy.
Continued
14.2 Main directives worldwide for spent batteries 373
Electrolyte
Type of battery
Anode/negative electrode
Cathode/positive electrode
Electrolyte
Advantages
Disadvantages
Nickele cadmium
Cd
Ni(OH)2
KOH
Contains cadmium.
Wireless devices, cameras, and phones.
Nickelemetal hydride
AB5 type: MmNi3,5Co0,7 Mn0,4Al0,3 AB2 type: V15Ti15Zr20 Ni28Cr5Co5Fe6Mn6 C
Ni(OH)2, cobalt oxides, and additives
KOH
Durability is not affected when stored even at charge; some models can perform 30,000 cycles of charge and discharge. Higher energy per volume and weight compared with NiCd; does not contain cadmium.
Production cost is higher than NiCd but lower than Li-based batteries.
Portable devices, mobile phones.
LiCoO2
Organic solvents and/or salt solutions (LiPF6)
Higher current density; higher use life; higher nominal voltage.
High cost.
Li
LiFePO4 or LiMn3O6
Solid polymer electrolyte, polyethylene oxide, and LiCF3SO3
Its plastic character and hence flexibility means it can be made in different shapes and thinner configurations.
Relatively low life cycle and efficiency.
Portable devices, mobile phones, hybrid vehicles. Electronic devices, hybrid vehicles.
Lithium-ion
Lithiume polymer
Main applications
Adapted from Mantuano, D.P., 2005. Desenvolvimento de uma rota processual hidrometalúrgica para a recuperação de metais provenientes de baterias de celular descarregadas (M.Sc. thesis). UFMG, Belo Horizonte, Brazil, p. 203 (in Portuguese).
374 CHAPTER 14 Recycling batteries
Table 14.1 Main characteristics of commercial batteries Continued
14.2 Main directives worldwide for spent batteries 375
Table 14.2 Typical metal composition of commercial batteries (Veloso et al., 2005; Silva and Afonso, 2008) Element Ag Al Cd Ce Co Cr Cu Fe K La Li Mn Nd Ni Pb V Zn
Zincecarbon1
Alkaline1
Silver
NiCd2
NiMH2
Lithium2
0.019 15e20 0.43e5.5 0.6 0.017
0.5e2.0
4.6e24
2.5e4.3 0.020e0.080
12e20a
29e40
20e25
28.2e30.8
0.2e1.0
0.17 5.5e7.3
0.3e0.7
5e10 4.7e25
1.4e6.6 23e30
26e33
0.083
0.007
0.01 0.005
15e20
0.81e3.0 0.96e4.1 25e46
1.5be5.5c 10e15d 12e15e 15e20c
5 1
12e21
8.7e12.1
0.06
2
Note: Includes dry black powder only; Considering the whole battery. a Li-ion (Co). b Li-ion (Co, Ni, Mn). c Liepolymer (V). d Li-ion (Mn). e Li-ion (Ni).
as depicted in Table 14.3. According to these directives, the adequate destination of spent batteries may involve methods such as landfill disposition, stabilization, incineration, and/or recycling processes. Safe disposal in landfills and the stabilization of battery residues has become increasingly more expensive due to the increasing amount of waste produced and the limited storage capacity of sanitary landfills and special waste dumpsites. Incineration of batteries is also expensive, and it can even cause mercury, cadmium, and dioxin emissions into the environment (Bernardes et al., 2004). In fact, the recycling of spent batteries appears as the most adequate destination for this type of waste. As pointed out by Conard (1992), the recycling of wastes is important because it may contribute to the benefit of future generations and to the preservation of raw materials. In the particular case of batteries, it is still necessary to develop an efficient collection system in order to receive the spent batteries consumed worldwide (Mantuano et al., 2006).
0.092e1.6
Country
Directives
Main characteristics
Brazil
CONAMA 257 (1999), updated by CONAMA 401 (2008)
China
Regulation on Restriction of Hg in Batteries (QZHG, 1997) Universal Waste Rule (1995)
CONAMA Resolution 257 was the first law dedicated to the conscious use of batteries in Latin America. It established the requirements for the reuse, recycling, treatment, and final disposal of batteries containing Pb, Cd, Hg, and their compounds, as well as electronic products that contain integrated nonreplaceable batteries in their structures. Manufacturers and importers are responsible for processing and/or final disposal of batteries returned by users. It also imposed a gradual reduction in the limits of Hg, Cd, and Pb in the composition of batteries, from January 2000 to January 2001. In 2008 it was replaced by CONAMA Resolution 401. It established an even more significant reduction in the levels of Hg, Pb, and Cd in several types of batteries. It also intended to give more effectiveness to the postconsumption responsibility of the manufacturers and importers of batteries, according to which they become bound by the full cycle of their products, not only purchase by consumers. Manufacturers and importers must be registered, submit a technical report containing physical and chemical composition of batteries produced, and a plan for managing used batteries. Places that sell batteries must include collection points and return collected batteries to manufacturers or importers. Advertising materials and packaging of batteries must clearly show symbols indicating the appropriate destination and warnings about the risks to human health and environment. Manufacturers, importers, and distributors will be encouraged to promote environmental education campaigns for postconsumer spent batteries. Banned, from January 2001, the manufacture of ZneMn and alkaline batteries containing more than 0.0025% by weight of Hg, and 0.00001% by weight of Hg from 2005. Primary, rechargeable, and button cell batteries were excluded from these limits. Reduced the amount of waste to landfills, encouraged recycling and proper disposal of hazardous wastes, and reduced regulatory burdens on businesses that generate these wastes in order to facilitate compliance. Provided standardization for the collection, storage, and transportation of NiCd batteries, other rechargeable batteries, and certain Hg-containing batteries. Standardized the labeling of NiCd and lead-acid rechargeable batteries and products containing them. Banned the sale or offer for promotional purposes of alkaline and ZneC batteries containing intentionally introduced Hg and button cells of Hg oxide (except button cells with up to 25 mg of Hg), unless the manufacturer or importer defines the collection site for recycling or proper disposal. Manufacturers and importers must propose a chronogram to eliminate the production and marketing of certain batteries containing Hg; the label must contain information on the chemical composition, the recycling symbol, and a sentence indicating that the consumer must send it for recycling or proper disposal. Traders with annual sales exceeding $1 million must, from July 2006, install collection points and receive (free of charge) batteries of all types and brands as well as creating publicity campaigns about the benefits of recycling. For internet sales, they must inform consumers about the return of batteries or how to dispose of them properly.
USA
Mercury-containing and Rechargeable Battery Management Act (Battery Act, 1996)
376 CHAPTER 14 Recycling batteries
Table 14.3 Directives for batteries in Brazil, China, USA, Japan, and the European Union
Japan
Law for the Promotion of the Effective Utilization of Resources (1999, revised in 2001)
European Union
Directive 1991/157/EC updated by Directive 2006/66/EC
14.2 Main directives worldwide for spent batteries 377
Valid for NiCd, NiMH, Li-ion, and lead-acid batteries. Governs the positioning of recycling symbols, letters, and colors to identify each battery, including on the packages of batteries, according to specific law for the recycling of packages; labeling of the type of material used in the body of the batteries; and development of new designs for easy removal of batteries from equipment. Manufacturers are responsible for recycling collected batteries. Recycling targets were established: above 60% for NiCd, 55% for NiMH, 30% for Li-ion, and 50% for lead-acid. Electronics manufacturers must recycle or pay for it or transfer the collected batteries to the battery manufacturers, who must receive them without cost. Valid for all types of batteries except those used in security equipment, for military purposes, and to be launched into space. Batteries with Hg content higher than 0.0005% by weight (except button cells, whose Hg content can be less than 2% by weight) and portable batteries with Cd content above 0.002% by weight (except those for use in alarm systems and emergency medical equipment and cordless power tools) are prohibited from commercialization after September 2009. Adopt necessary steps to promote and maximize the selective collection of batteries and minimize household waste disposal; ensure that distributors of portable batteries accept their return free of charge, and manufacturers of industrial batteries, or third parties on their behalf, accept the return of spent batteries from consumers; collect 25% of all used batteries by September 2012, increasing to 45% by September 2016; require that the manufacture of products incorporating batteries is accomplished only on the condition that they are easily replaced after use by consumers and that they are also informed how to proceed to allow their disposal; ensure, from September 2009, that all batteries are collected and treated using the best available techniques in terms of health and environment (batteries must be handled and stored temporarily in places totally waterproof or in suitable containers; treatment must include, at least, the removal of all fluids and acids); recycle by September 2010 at least 65% of lead-acid, 75% of the NiCd, and 50% of other battery types; encourage the development of new technologies for recycling and treatment for all types of batteries; encourage technological innovations that improve the performance of batteries; inform consumers through campaigns of the effects of substances used in batteries on human health and the environment; the need to send such waste to resellers, systems for collecting and recycling available, the importance of their participation in this process, and the meaning of the symbols listed on labels and packaging. The labels on the batteries must be visible, legible, and indelible, and indicate their power, the chemical symbols Hg, Cd, and Pb for batteries containing levels higher than 0.0005% of Hg, 0.002% of Cd, and 0.004% of Pb, respectively, and symbols not to discard in the trash. All producers of batteries must be registered in the countries where they sell their products (Directive 2009/603/EC).
378 CHAPTER 14 Recycling batteries
According to CONAMA 401/2008 (Conselho Nacional de Meio Ambiente, Brazilian Environmental Agency), the most adequate destination of spent batteries must minimize environmental risks and adopt technical procedures for collecting, reusing, recycling, treating, and final disposal of such wastes. Such aspects are discussed as follows.
14.3 METHODS FOR THE RECOVERY OF METALS FROM SPENT BATTERIES Recycling processes of waste materials such as batteries must be as simple and cheap as possible. The current processes used to recycle portable batteries include pyrometallurgical and hydrometallurgical techniques (Salgado et al., 2003; Bernardes et al., 2004; Espinosa et al., 2004). Most collection programs receive all types of batteries, so the chemical composition of battery waste might be very irregular, as shown in Tables 14.1 and 14.2. Most recycling processes were developed to recycle only a few types of batteries. Therefore, initially it is necessary to sort the batteries in order to segregate the ones that cannot be treated by that specific process. For example, in general, a process that treats ZneC and alkaline cells does not admit contamination with NiCd batteries. However, the situation observed in collection systems is the mixing of different types of batteries. Unfortunately, there is no correlation between shape and size with the composition of batteries. This characteristic complicates the sorting processes. This step, allied with transportation, increases the total cost of recycling processes. With the exception of NiMH batteries, in general, battery recycling processes are viable only through funding or legal obligationdi.e., the revenue does not cover the cost of operation (Bernardes et al., 2004). The battery collection rules in municipal waste management in Japan were reviewed by Terazono et al. (2015).
14.3.1 Main processing routes Battery recycling processes are composed basically of two main steps, waste preparation and metallurgical processing. The waste preparation step begins with the screening of the waste, segregating it by chemical type. The sorting might be composed of several steps in order to improve separation efficiency. These steps might contain manual segregation and segregation using pieces of equipment developed specially for this operation. The pieces of equipment developed to this end apply several techniquesdfor example, mechanical separation, magnetic separation, X-ray imaging, and optical sensors to read bar codes located on the waste material (Bernardes et al., 2004).
14.3 Methods for the recovery of metals from spent batteries 379
After sorting, the material to be recycled is prepared for the metallurgical process through physical conditioning operations. These operations are based on typical ore dressing unit operations, such as crushing, comminution, magnetic separation, electrostatic separation, and dense medium separation (DMS). The crushing involves the fragmentation of the waste, and its main goal is to separate most of the polymeric or metallic cover from the internal material that contains the target metals to be recycled. The main goal of the comminution step is to diminish the particle size in order to liberate the several types of material. The other cited operations have the objective to separate materials according to specific characteristics. Magnetic separation is applied to separate magnetic materials (such as iron and their alloys) from nonmagnetic material. Electrostatic separation aims to separate conductive material from nonconductive, roughly metal from nonmetal. The DMS technique segregates materials having different densities. Therefore, the objective of the waste preparation step is to concentrate the fraction of waste that contains the target metals using physical methods that present relatively low costs of processing. Hence, even considering the limited efficiency of such processes, these operations might diminish the overall cost of the recycling process, thus diminishing the amount of material that should be treated by metallurgical processing. Metallurgical processing can basically follow three different routesd pyrometallurgy, hydrometallurgy, and hybrid processesdthat use techniques from pyro- and hydrometallurgy to obtain metals or metal compounds. There are several battery recycling facilities around the world. Table 14.4 presents some examples of battery recycling processes, showing the treated materials and their limitations (Bernardes et al., 2004).
14.3.2 Pyrometallurgical route Pyrometallurgical recycling processes use high temperature to process wastes, aiming at the reclamation of target metals. During heat treatment of battery waste, several reactions may take place such as decomposition of compounds, reduction, and evaporation of metals or compounds (Espinosa et al., 2004). All pyrometallurgical processes for the recycling of batteries share the common step of evaporating a metal to segregate it from other materials that have higher boiling points. Therefore, the goal of these processes is to evaporate Hg, Zn, and/or Cd.
Process
Route
Treated material
Limitation
Observation
SUMITOMO
Pyrometallurgical
NiCd and Pb-acid batteries
Lithium battery recycling process is patented.
Recytec
Pyrometallurgical
SNAM-SAVAM
Pyrometallurgical
Household cells (alkaline, ZneC, Zneair, and mercury), NiMH Most types of batteries, including fluorescent lamps NiCd, NiMH, and Li-ion batteries
INMETCO
Pyrometallurgical
Mercury
Accurec
Pyrometallurgical
Dust from furnaces containing iron, zinc, and lead and also several types of batteries: NiCd, NiMH, NiFe, Li-ion, and ZneMn NiCd, NiMH, and Zncontaining batteries
TNO BATENUS ZINCEX RECUPYL
Hydrometallurgical Hydrometallurgical Hydrometallurgical Hydrometallurgical
NiCd batteries Most types of batteries Zinc bearing materials Most types of batteries
UMICORE
Hybrid
Li-based and NiMH batteries
NiCd batteries
The process treats portable and industrial batteries.
A hydrometallurgical step is used in the process of NiMH battery recycling to reclaim rare earth metals. Li-ion recycling process is being developed. Mercury Mercury NiCd, lead, and button batteries NiCd batteries
380 CHAPTER 14 Recycling batteries
Table 14.4 Examples of battery recycling processes (Espinosa et al., 2004; Mantuano, 2005)
14.3 Methods for the recovery of metals from spent batteries 381
Zinc-containing batteries can be recycled by pyrometallurgical processes, since the boiling points of the containing metals (Hg, Zn, and Mn) are very different. During heat treatment, after water evaporation, the elimination of Hg through evaporation takes place due to its low boiling point. Frenay and Feron (1990) observed that thermal elimination of Hg, which is linked to chlorine ions of the electrolyte, should be performed at 600 C. Conversely, Xia and Li (2004) found that 450 C is enough to remove Hg under vacuum. After Hg decontamination, zinc also can be recovered through distillation but at temperatures higher than 907 C (zinc boiling point). The global discharge reaction of either an alkaline or a ZneC cell can be expressed as (Sayilgan et al., 2009): Zn þ 2MnO2 / Mn2 O3 þ ZnO
(14.1)
Therefore, one should expect to find in the waste of spent batteries not only metallic Zn, but also ZnO, MnO2, and Mn2O3. Zinc oxide, when heated above 920 C under atmospheric pressure and in the presence of a reductor (such as the carbon constituent of these types of batteries), is reduced according to the following reaction (Rosenqvist, 2004): ZnO þ CO / ZnðvÞ þ CO2
(14.2)
Since the temperature at which the reaction occurs is above the Zn boiling point, Zn is produced directly in vapor form. Consequently, the recycling process must be carried out at temperatures above 920 C in order to evaporate most of the Zn. Manganese remains solid throughout the process, but during heating, prereduction of the manganese oxides to MnO occurs due to the carbon present in the charge. The material that remains solid is composed mainly of MnO and iron (from the metallic cases). Pyrometallurgical processes for the recycling of electric arc furnace dust (and Zn-bearing materials), such as INMETCO and Waelz, accept ZneC and alkaline batteries in the charge. In such processes, the comminuted material is mixed with a carbon-based reductor. This mixture might then be agglomerated in the form of pellets depending on the process. Following this, the mixture or pellets are put into an open-hearth or a rotative furnace operating at temperatures up to 1350 C. During the process, Zn and other volatile compounds or elements are captured in the gas treatment system (Bernardes et al., 2004; Espinosa et al., 2004).
382 CHAPTER 14 Recycling batteries
Spent batteries
Sorting
Physical / mechanical treatment
Heat treatment (controlled atmosphere)
Cd
Material containing Fe, Ni and Co
n FIGURE 14.1 Generic flow sheet of operations for the pyrometallurgical recycling of NiCd batteries.
The classic recycling processes for NiCd batteries are typically pyrometallurgical and based on Cd distillation. Fig. 14.1 shows a schematic flow sheet of a theoretical pyrometallurgical recycling process for NiCd batteries. During heating, after water evaporation, the decomposition of Cd and Ni hydroxides takes place as follows (Espinosa and Tenorio, 2004): NiðOHÞ2ðsÞ / NiOðsÞ þ H2 OðgÞ T ¼ 230 C
(14.3)
CdðOHÞ2ðsÞ / CdOðsÞ þ H2 OðgÞ T ¼ 300 C
(14.4)
The recycling process can be carried out with or without the presence of a reducing agent (usually carbon based). In order to avoid the use of a reducing agent, the total pressure of the system must be about 104 bar to enable the decomposition of CdO at 850e900 C to produce Cd vapor (Espinosa and Tenório, 2004). If the process is carried out with the aid of a reducing agent, reduction of the oxides of nickel and cadmium is thermodynamically possible at relatively low temperatures. The boiling point of metallic Cd is 767 C, so above this temperature Cd is produced directly into vapor form. Generally, the pyrometallurgical process to recycle NiCd batteries is performed at temperatures of about 900 C under vacuum, under inert atmosphere, or by imposing a reducing atmosphere (Espinosa and Tenório, 2006). The controlled atmosphere is necessary to avoid the oxidation of the produced metallic Cd. Metallic cadmium is produced with 99.9% purity
14.3 Methods for the recovery of metals from spent batteries 383
and can be used in numerous applications including the production of new NiCd batteries. The material that remains solid during the treatment is composed basically of Ni, Fe, and Co and can be used in stainless steel production. Pyrometallurgical recycling processes for NiCd batteries also treat NiMH batteries mixed in the charge; however, only Ni is recovered, and the rare earth elements present in this latter type of battery are lost in the process. According to Sun et al. (2017), pyrometallurgy smelting is still the main technology used in China for spent lead-acid battery recycling. In addition, vacuum reduction technology has been evaluated to treat lead and NiCd batteries (Lin and Qiu, 2011; Huang et al., 2010).
14.3.3 Hydrometallurgical route A typical flow sheet for the recovery of metals from spent batteries using hydrometallurgical methods is shown schematically in Fig. 14.2. Firstly, batteries must be classified by type because metal composition varies significantly as shown in Tables 14.1 and 14.2. Then, after dismantling for the removal of iron scraps, plastic cases, and paper, the internal content of the battery is submitted to a leaching step in order to transfer metals of interest from the solid phase to the aqueous solution. Acid and alkaline solutions are normally used, as well as oxidant and reducing agents. Recently, organic
Spent batteries Sorting
Physical / mechanical treatment
Leaching
Solution purification
Metal reclamation
Solvent extraction Ion exchange Precipitation Cementation
Precipitation of compounds Electrolysis
Compound or metal n FIGURE 14.2 Flow sheet depicting the main steps for hydrometallurgical recycling of batteries.
384 CHAPTER 14 Recycling batteries
acids (citric and malic acids in the presence of hydrogen peroxide, H2O2) have been introduced as environmentally friendly reagents to leach cobalt and lithium from Li-ion batteries with promising results (Li et al., 2013). For example, in the leaching of Znecarbon or alkaline batteries, selective leaching of zinc and manganese can be achieved using sequential leaching steps with dilute H2SO4 solution in order to preferentially extract zinc, followed by leaching of the remaining residue with concentrated H2SO4 solution with H2O2 in order to extract manganese (Veloso et al., 2005). The following reactions may occur in the dissolution of zinc and manganese oxides: ZnO þ H2 SO4 / ZnSO4 þ H2 O
(14.5)
Mn2 O3 þ H2 SO4 / MnO2 þ MnSO4 þ H2 O
(14.6)
Mn3 O4 þ 2H2 SO4 / MnO2 þ 2MnSO4 þ 2H2 O
(14.7)
MnO2 þ H2 SO4 þ H2 O2 / MnSO4 þ 2H2 O þ O2
(14.8)
In fact, zinc oxide can be fully dissolved by sulfuric acid solutions according to Eq. (14.5). On the other hand, the dissolution of Mn2O3 and Mn3O4 oxides is partial because the MnO2 produced is insoluble (Eqs. (14.6) and (14.7)). For instance, the leaching of alkaline battery powders with 1.0% (v/v) H2SO4 at 90 C for 2 h results in the dissolution of only 43% of the total manganese originally present in the powder (Salgado et al., 2003). A similar result (dissolution of 40% of manganese and 100% of zinc oxides) was obtained using 0.7% (v/v) H2SO4 at 70 C and 3 h (Souza et al., 2001). Therefore, to leach 100% of the manganese present in the powder, the use of H2O2 as a reduction agent is a plausible alternative. In addition, the removal of potassium from the powder of Znecarbon and alkaline batteries may also contribute to reducing the consumption of H2SO4 in the acidic leaching step. In the case of Li-ion batteries, alkaline solutions of NaOH were used to leach aluminum in a selective way, followed by acid solutions of H2SO4 in order to leach cobalt and lithium (Ferreira et al., 2009). Many other aqueous systems including HCl, citric acid, malic acid, HNO3, and H2SO3 in the presence or not of H2O2 have been evaluated to leach Li-ion batteries as shown in Table 14.5. After leaching, the aqueous solution is submitted to a purification step that may comprise several separation methods such as cementation, precipitation, solvent extraction, adsorption, ion exchange, and others. Finally, the metal species are recovered from the purified solutions as pure metals or metal oxides, hydroxides, and/or salts.
Table 14.5 Summary of operational conditions for metal recovery from Li-ion batteries Leaching step
References
Leaching agents
T ( C)
S/L ratio (g/mL)
NaOH, followed by H2SO4 þ H2O2
30 to 70
1/10
Shin et al. (2005) and Swain et al. (2007)
H2SO4 þ H2O2
75
1/10 and 1/20
Li et al. (2013)
Citric acid þ H2O2 and malic acid þ H2O2
90
1/20
Mantuano et al. (2006)
H2SO4
80
1/30
Dorella and Mansur 2007)
H2SO4 þ H2O2
65
1/30
Main liquor treatment results
Main leaching results
Methods
Reagents
Alkaline leaching: Al (60%), Co (negligible), and Li (10%). Acid leaching of Al, Li, and Co around 80%e100%. H2O2 improved LiCoO2 leaching, mainly Co Co (>93%) and Li (>94%) at the presence of H2O2 (5%e15% v/v). Granulometry effect was found significant for Co leaching Co (>90%) and Li (100%) with citric acid (1.25 M) þ H2O2 (1% v/v) and with malic acid (1.5 M) þ (2% v/v) Low recovery of Co (30%). Acid concentration and temperature were found significant
Crystallization by evaporation
e
Purified CoSO4$H2O was obtained
e
e
e
e
e
e
Solvent extraction
Cyanex 272
Co (75%) and Li (100%) at the presence of H2O2 (1% v/v)
Precipitation and solvent extraction
NH4OH and Cyanex 272
Co/Li separation at pH ¼ 5. Co/Al and Co/Cu separations were found difficult Al (80%), Co (8%), and Li (13%) were precipitated at pH ¼ 5. A stripping solution Co (63 g/L) and Li (0.4 g/L) was obtained
Continued
14.3 Methods for the recovery of metals from spent batteries 385
Ferreira et al. (2009)
Liquor treatment step
Leaching step Leaching agents
T ( C)
S/L ratio (g/mL)
Lee and Rhee (2002, 2003) Zhang et al. (1998)
HNO3 þ H2O2
75
HCl, NH2OH, HCl, and H2SO3
Nan et al. (2005)
Lupi et al. (2005)
References
Liquor treatment step Main liquor treatment results
Main leaching results
Methods
Reagents
1/100
Co (95%) and Li (95%) with H2O2 (1.7% v/v)
Precipitation
Citric acid
Pure LiCoO2 was obtained
80
1/100
Co (>90%) and Li (>90%) with concentrated NH2OH HCl and HCl. Low metal recoveries obtained with H2SO3
Solvent extraction
D2EHPA and PC-88A
NaOH and H2SO4
25 and 70
1/10 and 1/5
NaOH leached Al (98%) selectively. Co (>90%), Li (>90%), and Cu (<10%) were leached with H2SO4
Precipitation and solvent extraction
Ammonium oxalate, ACORGA M5640, Cyanex 272
e
e
e
e
Solvent extraction and electrolysis
Cyanex 272
PC-88A was found more selective: Co (>99.9%) and Li (12.6%) extracted with 0.9M PC-88A Co (90%) precipitated with 0.5% impurities. Cu (97%) and Co (97%) extracted with ACORGA and Cyanex 272, respectively Co (100% extracted). Electrolysis solution obtained containing Co (<1 ppm) and Ni (<100 ppm)
Adapted from Ferreira, D.A., Prados, L.M.Z., Majuste, D., Mansur, M.B., 2009. Hydrometallurgical separation of aluminum, cobalt, copper and lithium from spent Li-ion batteries. Journal of Power Sources, 187 238e246.
386 CHAPTER 14 Recycling batteries
Table 14.5 Summary of operational conditions for metal recovery from Li-ion batteries Continued
14.3 Methods for the recovery of metals from spent batteries 387
In hydrometallurgical processes, zinc can be recovered from the aqueous solution by electrolysis, but the presence of contaminants may affect its efficiency as well as the quality of the zinc produced; for example, in the presence of cadmium, both metals will deposit, thus reducing the purity of metallic zinc. Therefore, the purification step of the leach solution is crucial for the operation’s success, so very selective methods are used for the purification of zinc such as solvent extraction (Mansur et al., 2002; Salgado et al., 2003), cementation (Feijó, 2007), ion exchange (Kentish and Stevens, 2001), and precipitation (Veloso et al., 2005). In the solvent extraction method, an organic phase containing an adequate extractant depending on the metal to be extracted is put into contact with the aqueous leach liquor. The metal is transferred to the organic phase, which is scrubbed if necessary to remove coextracted species and then submitted to the stripping step when the extracted metal is transferred to another aqueous phase. The metal of interest is separated and even concentrated depending on the aqueous/organic ratio as well as other operating conditions. This method is largely used to separate several metals such as zinc, cobalt, nickel, manganese, copper, and rare earths. A review of solvent extraction applied to metal systems is given by Ritcey and Ashbrook (1984), Habashi (1993), and Rydberg et al. (2004). Ion exchange works in a quite similar way to solvent extraction, but the leach aqueous solution is put into contact with a solid resin containing the extractant that reacts with the metal of interest. After this stage, the loaded resin is submitted to an elution step aimed at recovering the extracted metal to another aqueous solution. Ion exchange is discussed elsewhere (Zagorodni, 2006). The use of precipitation has various purposes, as in the case of water treatment for instance, but in the case of battery recycling it is mainly used in the selective separation of metals. It is carried out by controlling the pH of the aqueous phase with the addition of precipitating agents like NaOH, CaO, Ca2CO3, and many other reagents. In the treatment of spent zincecarbon or alkaline batteries, iron can be removed from the solution by precipitation in pH higher than 4.0 and with the use of an oxidizing agent. Finally, the cementation method uses a dislocating reaction to promote metal separation that is carried out by adding a less noble metal species to the solution, aiming to reduce the more noble metal species. For example, the addition of zinc powder promotes the precipitation of nickel according to the following equation: Ni2þ þ ZnðsÞ /NiðsÞ þ Zn2þ
(14.9)
388 CHAPTER 14 Recycling batteries
In the hydrometallurgical treatment of NiCd batteries, the internal material obtained from dismantling is previously milled and subsequently leached in acidic medium, resulting in an aqueous leach solution containing nickel, cadmium, and iron. After iron removal by precipitation, nickel and cadmium are separated by solvent extraction and then recovered by electrolysis. Similarly, for the case of NiMH batteries, previous treatment is required to separate the internal parts of the battery, which is leached with H2SO4 resulting in a leach solution containing rare earths, nickel, and cobalt. The former can be separated by precipitation, while the last metals are separated by solvent extraction. Some studies have revealed that hydrometallurgical routes to NiMH may include one step to recover cadmium because several NiCd batteries were found to be labeled as NiMH (Bertuol et al., 2006; Rodrigues and Mansur, 2010). Hydrometallurgical routes are commonly more complex and require a higher number of steps in comparison with pyrometallurgical routes; however, they are efficient, more flexible, more energy saving, and present high metal selectivity, so hydrometallurgical routes are becoming more frequent for treating spent batteries that contain several different metals in their composition. In addition, the leaching agents and reagents can be regenerated and reused several times in closed-circuit operation. From an environmental point of view, the generation of gases is relatively lower, so Conard (1992) has pointed out that the hydrometallurgical route to be used in the treatment of various wastes thus contributes to sustainable development. In fact, the recycling of spent batteries has advantages not only from an environmental point of view because natural resources are finite (Gupta and Mukherjee, 1990), but also from an economic standpoint because the metal content and purity present in spent batteries are usually much higher than those commonly found in their ores.
14.4 FUTURE TRENDS Future trends in battery recycling are directly related to the market for electric/electronic portable devices. In the last 2 decades, substitution of NiCd batteries in most portable devices by NiMH and lithium-based batteries has occurred. The main reasons for this change were environmental policies. Hence, technical concerns were less important in this substitution. In future decades, these systems probably should be optimized to improve their capacities.
References 389
The waste of postconsumer spent batteries is a mix of several types of batteries. So if existing recycling processes were selected to recycle this kind of waste, the spent batteries should be segregated by type prior to recycling. One possible trend is the development of a new process that treats more types of spent batteries and thus avoids this initial separation; another is improvement of segregation methods. A recent potentially important application of batteries is for electric and hybrid vehicles. The market for such vehicles is increasing, mainly in North America, China, Japan, and Western Europe (World batteries, 2015; Du and Ouyang, 2017) due to environmental concerns. The waste generated by this type of use is different from the waste of postconsumer spent batteries; the life cycle impact of such batteries has been investigated (Manzetti and Mariasiu, 2015). These vehicles are equipped with one specific type of rechargeable battery, making it easier to segregate batteries upon disposal.
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390 CHAPTER 14 Recycling batteries
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