comparative leaching of spent zinc-manganese-carbon
TRANSCRIPT
MURDOCH RESEARCH REPOSITORY
This is the author’s final version of the work, as accepted for publication following peer review but without the publisher’s layout or pagination.
The definitive version is available at :
http://dx.doi.org/10.1016/j.hydromet.2010.07.004
Senanayake, G., Shin, S-M., Senaputra, A., Winn, A., Pugaev, D., Avraamides, J., Sohn, J-S. and Kim, D-J. (2010) Comparative leaching of spent zinc-
manganese-carbon batteries using sulfur dioxide in ammoniacal and sulfuric acid solutions. Hydrometallurgy, 105 (1-2). pp. 36-41.
http://researchrepository.murdoch.edu.au/3392/
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Comparative leaching of spent zinc-manganese-carbon batteries using sulfur dioxide in ammoniacal and sulfuric acid solutions
G. Senanayake a*, S-M. Shinb , A. Senaputraa, A. Winna, D. Pugaeva, J. Avraamidesa,
J-S. Sohnb , M-J. Kimb
aParker Centre, Faculty of Minerals and Energy, Murdoch University, WA 6150, Australia.bMinerals & Materials Processing Division, Korea Institute for Geoscience & Mineral Resources (KIGAM),92 Kwahak-no, Yuseong-gu, Daejeon, Korea.
AbstractThe non-magnetic fraction of spent zinc-manganese-carbon batteries containing 20.8% Zn, 22.7% Mn, 2.65% Fe, and <0.1% Hg, Ni, Co, Cu and Pb was leached in H2SO4, H2SO4/SO2, NH3 and NH3/SO2 at 30-60 oC. In acid media the complete dissolution of zinc is unaffected by SO2. However, the reductive role of SO2 increases the leaching of manganese in H2SO4 from 25% to 100% and iron from 1% to 25%. Literature results of leaching with other reductants are compared. The XRD analysis of leach residues from ammonia solutions shows the conversion of Zn5(OH)8Cl2·H2O in the feed to ZnO with low dissolution of zinc, manganese and iron. Low leaching of iron in NH3/SO2 is due to the formation of Fe(NH4)2(SO3)2 and Fe(NH4)2(SO4)2 identified by XRD analysis of leach residues. However, the formation of Zn(NH3)4
2+ facilitates the selective leaching of zinc in buffered SO2/NH3 solutions that contains NH4
+. Complete dissolution of copper also occurs in both H2SO4/SO2 and NH3/SO2. The dissolution of mercury by H2SO4 is retarded in the presence of SO2, and enhanced by NH3/SO2. Lead remains insoluble in all media, whilst the partial dissolution of nickel and cobalt is retarded by NH3/SO2.
Keywords: Zinc-manganese-carbon battery recycling; Leaching; Sulfuric acid; Ammonia; Sulfur dioxide.
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1. Introduction
Zinc-manganese-carbon batteries (ZMCBs) consist of a carbon rod cathode with a
moist paste of MnO2 and NH4Cl mixed with carbon (acetylene black) to improve
conductivity and retain moisture in the acid electrolyte (McComsey, 2001). These
components are contained in a zinc case which acts as the anode. A plastic or
paperboard separator and an asphalt seal are usually present. These non-rechargeable
batteries (primary cells) are designed to be fully discharged once, according to Eq. 1. A
simplified overall cell reaction is presented in Eq. 2.
Discharge of ZMCBsZn + 2MnO2 + 2NH4Cl = Zn(NH3)2Cl2 + Mn2O3 + H2O (1)Zn + 2MnO2 = Mn2O3 + ZnO (2)
The spent ZMCB material consists of graphite, Zn, ZnO, MnOOH, Mn2O3, Mn3O4,
MnO2 and Fe2O3 along with traces of Hg, Pb and other heavy metals which prohibit the
landfill disposal of spent batteries due to environmental concerns (De Michelis et al.,
2007; Ferella et al., 2008; Shin et al., 2009; Furlani et al., 2009; Sayilgan et al., 2009a).
This also highlights the necessity and advantage of reutilisation and recycling of spent
batteries (Espinosa et al., 2004). The dissolution of zinc and manganese oxides/salts
and associated metals from fully discharged ZMCBs is controlled by the reactivity of
these oxides in acid or alkali media and the presence of complexing ligands and/or
reducing agents in the lixiviants.
The amphoteric nature of zinc is an advantage as its leaching and separation can be
conducted in acid or alkaline media, which provides several hydrometallurgical options
to recycle spent ZMCBs and recover a range of value added products such as Zn,
Mn2O3, Mn3O4 and Zn-Mn ferrites at a low production cost depending on the metal
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grades of starting material (Panero et al., 1995; Pietrelli et al., 1999; Rabah et al., 1999;
Salgado et al., 2003; Xi et al., 2004; De Souza and Tenario, 2004; Nan et al., 2006;
Avraamides et al., 2006; El-Nadi et al., 2007; Freitas et al., 2007; Shin et al., 2007; De
Michelis et al., 2007; Peng et al., 2008; Ferella et al., 2008; Kim et al., 2009; Shin et al.,
2009; Sayligan et al., 2009a,b; Furlani et al., 2009). Reagents and unit operations used
in recycling processes of ZMCBs are summarised in Table 1. Ferella et al. (2008)
reported a summary of economic evaluation of recycling and further studies required
for the economic balance of a processing plant.
Ammonia forms a series of complexes of the general formula M(NH3)n2+ with n =
1-6 and M = Zn(II), Mn(II), Fe(II) and minor elements in spent ZMCBs. The stability
constants of complexes of metal ions of a given coordination number (n) follow the
descending order Zn(II) > Fe(II) > Mn(II), as demonstrated in Table 2, suggesting the
possibility of selectively leaching zinc according to Eqs. 3-5. Equilibrium constants for
Eqs. 3-7 based on the HSC 6.1 data base at 60oC are 100.3, 101.1, 1014 , 10-4.7 and 106.1
respectively (Roine, 2002).
ZnO + 2NH4+ + 2NH3 = Zn(NH3)4
2+ + H2O (3)Zn(OH)2 + 2NH4
+ + 2NH3 = Zn(NH3)42+ + 2H2O (4)
Zn + 2NH4+ + 2NH3 = Zn(NH3)4
2+ + H2 (5)NH3 + H2O = NH4
+ + OH- (6)NH3 + H2O + SO2 = NH4
+ + HSO3- (7)
Thus, the presence of dissolved SO2 enhances the formation of NH4+ (Eq. 7) which
favours zinc leaching (Eqs. 3-5). Ammoniacal sulfur dioxide also offers the reducing
agent S(IV) for high-valence Mn(III/IV)-Fe(III) oxides as well as ammonia which can
form complexes and affect the solubility of certain major/minor metals in spent ZMCBs
during leaching.
In comparison to the wealth of information on the leaching behaviour of the zinc,
manganese and iron in spent ZMCBs (Table 1), information on minor metals is scarce.
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The scope of this work is a comparative study of leaching of zinc, manganese and iron
as well as minor metals from spent ZMCBs in H2SO4, H2SO4/SO2, NH3, and NH3/SO2
based upon previously reported results and measured data in this study.
2. Experimental
Spent ZMCB material of minus 8 mesh was prepared according to the procedure
described in previous publications (Shin et al., 2009; Kim et al., 2009). The leaching
studies on major/minor metals were conducted at 30-60oC in H2SO4 or NH3 solutions in
the absence or presence of SO2. Leach tests were conducted using a 170 mm x 75 mm
glass reactor and accessories. The reactor had four baffles and an impeller with three
wings of 6.5 cm diameter and was operated in a fume hood. The solid/liquid ratio was
maintained at 100 g/L using a liquid volume of 0.8 L. Sulfur dioxide was sparged
through the liquor 30 minutes prior to adding the spent ZMCB solids and continued
during each experiment. Care was taken to flush the reactor vessel of air and allow gas-
liquid equilibrium to be established before addition of the spent ZMCB material.
Stirring speed was controlled at 1000 rpm and regularly checked by a tachometer. The
SO2 gas was first passed through a Drescher bottle containing “blank” lixiviant solution
before it went to a special glass tip that was used in order to produce uniform bubbles in
the reaction vessel. Sampling was carried out at regular time intervals using a syringe
fitted with a No.4 filter paper. In some cases the slurry sample was filtered using a
clean No. 4 sintered porous crucible, which was reused after being soaked in
hydrochloric acid (50% v/v) overnight and placed in an ultrasonic cleaner for 30 min to
remove solids. The solution pH was checked using a calibrated standard pH probe
(ORION pH/Eh meter, model 420A). The concentrations of metal ions in solutions
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were determined using Atomic Absorption (GBC Avanta AAS Model 933AA) or
Inductively Coupled Plasma (Varian ICP model Liberty 200) Spectroscopy.
3. Results
Table 3 lists the chemical composition of the minus 8 mesh fraction of spent ZMCBs
and shows the presence of Zn, Mn and Fe along with the minor transition/base metals
Hg, Ni, Co, Cu, Pb, Ti, Al and Mg. The leaching results for the major/minor metals
obtained in the present study using H2SO4 or NH3 solutions in the presence or absence
of SO2 are summarized and compared in Figs. 1 and 2 and in Tables 4 and 6. The
results based upon leaching in H2SO4, NaOH or (NH4)2CO3 in the absence or presence
of reducing agents such as SO2, H2O2, H2C2O4, sugars, reported in the literature are
listed in Table 5. The XRD patterns of feed and leach residues obtained under various
leaching conditions are shown in Figs. 3-5.
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4. Discussion
4.1 Reductive acid leaching
A solution of 1 mol/L H2SO4 at 30 oC and S/L ratio of 100 g/L dissolved about 98%
Zn, 35% Mn and <1% Fe. Unlike ZnO and Zn(OH)2, which can be quantitatively
dissolved in acid, Mn(III/IV) oxides can only be partially dissolved in acid due to their
low solubility in the absence of reducing agents (Ferella et al., 2008; El Nadi et al.
2007; Sayilgan et al., 2009b; Zhang and Cheng, 2007). As shown in Table 4, the
presence of SO2 enhances the leaching of manganese from 35% to 98% and iron from
<1% to to 25% due to the reductive role of SO2 which produces Mn(II) and Fe(II).
These results are consistent with the reported data on the effect of various reducing
agents listed in Table 5. For example, the leaching efficiencies of manganese in H2SO4
in the absence of H2O2 are 25% in Test H and 35% in Test E. These values increase to
97% in Test G and 82% in Test F, respectively, in the presence of H2O2. The presence
of lactose increases the manganese leaching efficiency from 21% in Test N to 100% in
Test P. Oxalic acid and low pH increases the leaching efficiency of manganese from
21% in Test J to 97% in test K, although zinc is insoluble in Test K even at low pH due
to the precipitation of ZnC2O4 (De Michelis et al., 2007).
Any iron dissolved as Fe(II) in acid can also act as a reducing agent for manganese
oxides, resulting in the precipitation or adsorption of Fe(III) (Senanayake, 2003,
Avraamides et al., 2006). Moreover, the low extraction of iron (~0%) compared to
manganese (21%) and zinc (~100%) when leached in 1.1 mol/L H2SO4 at 30oC, in the
absence of reducing agents, is due to the high final pH (Test J, Table 5). The leaching
of zinc in acid is generally unaffected by most reducing agents, except for oxalic acid
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as noted above. However, H2O2 reduces manganese(IV) oxides but oxidises Fe(II) to
Fe(III) resulting in some oxidative precipitation of iron (compare Test H and Test G).
Other reducing agents enhance iron leaching.
4.2 Reductive alkaline leaching
Results from previously reported work on alkaline leaching of spent ZMCBs listed
in Table 5 show selective leaching of 82% Zn compared to ≤ 0.1% Mn in solutions of
NaOH (Test V) or (NH4)2CO3 (Test R) (Shin et al., 2007). Despite the high stability of
Zn(NH3)n2+ complexes noted in Table 2, the leaching of zinc in 1-2.5 mol/L NH3
solutions in the absence of NH4+ is only between 2-39% (this study,Table 4). Moreover,
the dissolved zinc(II) undergoes partial precipitation after 5-40 minutes depending upon
the ammonia concentration and temperature (Fig. 1). In contrast, the SO2/NH3 system
offers over 95% Zn dissolution (Figs. 1 and 2).
The presence of SO2, examined in this study (Table 4), and the presence of H2O2 as
reported by Shin et al. (2007) show little manganese and iron leaching in ammoniacal
solutions, despite the possibility of formation of Mn(NH3)42+ and Fe(NH3)4
2+ noted in
Table 2.
4.3 XRD patterns of feed and leach residues
The XRD pattern of the feed shown in Fig. 3 indicates the presence of
Zn5(OH)8Cl2·H2O. However, in Fig. 4 the XRD pattern of the leach residue produced in
2.5 mol/L NH3 solutions without SO2 shows the presence of ZnO instead of
Zn5(OH)8Cl2.H2O. The peaks for both Zn5(OH)8Cl2·H2O and ZnO are absent in the
XRD pattern of the leach residue produced in ammoniacal SO2 solutions (Fig. 5) but
peaks for (NH4)2Fe(SO4)2 and (NH4)2Fe(SO3)2 appear.
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4.4 Comparison of trace metal leaching in acid and alkaline media
Despite the weak association or complexation with sulfate (PbSO40, K298 K = 102.7)
and ammonia (Pb(NH3)2+ , K298K = 101.6), the dissolution of Pb(II) is negligible in both
sulfuric acid and ammonia solutions (Table 6). This is a result of the low solubility
products of PbSO4 (KSP ~10-7.7) and Pb(OH)2 (KSP ~10-14) at 60oC causing co-
precipitation with other solids (Muir and Senanayake, 1985; Senanayake 2008). Whilst
the sulfuric acid dissolution of copper and nickel remains unaffected by SO2, cobalt
dissolution increases (Table 6) as expected from the reductive role of SO2/H2SO4
(Senanayake and Das, 2004).
Xi et al. (2004) proposed the addition of iron powder to cement out mercury from
filtered pregnant leach liquor. One of the advantages of the H2SO4/SO2 system is the
removal of mercury from solution. This appears to be a result of reductive precipitation
of Hg(II) as Hg2SO4 in a reaction which has an equilibrium constant of K333 K ~ 1028 (Eq.
8).
2Hg2+ + SO2 + 2H2O = Hg2SO4(s) + 4H+ (8)
The partial dissolution of Hg, Ni and Co (50-73%) compared to Cu (100%) in the
NH3/SO2 leach system, despite the formation of strong M(II)-NH3 complexes (Table 1),
is probably due to surface oxide passivation and/or adsorption of metal ions on Mn-Fe
residue, but this warrants further studies.
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5. Conclusions
This study explored the reducing ability of SO2 and the complexing ability of the
NH4+/NH3 system on the leaching Zn(II), Fe(II) and Mn(II) from spent ZMCBs.
Aqueous sulfur dioxide reduces Fe(III), Mn(IV)/(III) to Fe(II) and Mn(II) and enhances
the leaching of these two metals along with zinc in acid media. In NH3/SO2 solutions,
despite the complexation of Fe(II) and Mn(II) with NH3, they are not leached to any
significant extent, as a result of their precipitation as oxides/hydroxides. The XRD of
the residue shows the presence of Fe(NH4)2(SO3)2 and Fe(NH4)2(SO4)2. Zinc is
completely leached in the buffered NH3/NH4+/SO2 system but it is only partially leached
in NH3 solution due to ZnO formation under higher pH conditions.
Considering the minor elements in ZMCBs, the NH3/SO2 system lowers the
dissolution of nickel and cobalt but enhances the dissolution of mercury compared to
the H2SO4/SO2 system, whilst copper dissolution is complete and lead is insoluble in all
cases.
Future work will focus on the separation of iron, manganese and trace metals from
pregnant leach solutions and recovery of other value added commodities from spent
ZMCBs and other types of spent batteries.
Acknowledgements
Financial assistance and support from the Parker CRC for Integrated
Hydrometallurgy Solutions and the Korean Institute for Geoscience and Mineral
Resources under the Korean Government’s Global Partnership Program (GPP) are
gratefully acknowledged.
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Figure titles
Fig. 1. Zinc dissolution in ammoniacal solution (50 mL/min SO2 flow rate, S/L = 100 g/L, solution analysis based on AAS)
Fig. 2. Zinc and trace metal dissolution in 2.5 mol/L NH3 and SO2 (50 mL/min) system at S/L = 100 g/L, solution analysis based on ICPS)
Fig. 3 XRD patterns for the feed material and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
Fig. 4 XRD patterns for leach residues in 2.5 M NH3, T = 60 °C and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
Fig. 5 XRD patterns for leach residue in 2.5 M NH3 , SO2 (50 mL/min) and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
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Fig. 1
0
25
50
75
100
0 15 30 45 60 75 90
Time / (minutes)
Leac
hing
eff
icie
ncy
(%) o
f Zn
2.5 M NH3/60 oC/ SO2
1 M NH3/30 oC/ SO2
2.5 M NH3/60 oC1 M NH3/60 oC
1 M NH3 /30 oC
Fig. 1. Zinc dissolution in ammoniacal solution (50 mL/min SO2 flow rate, S/L = 100 g/L, solution analysis based on AAS)
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Fig. 2
0
20
40
60
80
100
0 30 60 90Time (min)
Leac
hing
eff
icie
ncy
(%
)Zn
Cu
Co
Ni
Hg
Fig. 2. Zinc and trace metal dissolution in 2.5 mol/L NH3 and SO2 (50 mL/min) system at S/L = 100 g/L, solution analysis based on ICPS)
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Fig. 3
Fig. 3 XRD patterns for the feed material and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
17
Feed
Zn5(OH)8Cl2·H2O
GraphitePeak
inte
nsity
, %
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Fig. 4
Fig. 4 XRD patterns for leach residues in 2.5 M NH3, T = 60 °C and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
18
Leach residue in NH3
ZnO
Graphite
Peak
inte
nsity
, %
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Fig. 5
Fig. 5 XRD patterns for leach residue in 2.5 M NH3 , SO2 (50 mL/min) and standards (line bars); KαCu (λ=1.54059Å), scanning rate 1°/min, step size 0.08 °/step.
19
(NH4)2Fe(SO4)2·6H2O
(NH4)2Fe(SO3)2·H2O
Peak
inte
nsity
, %Leach residue in NH3 + SO2
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Table 1Summary of spent ZMCB leaching or recycling procedures and products
Reagents and other commodities
Unit Operations(or flowsheet)
Products and References
Water, H2SO4/H2O2 Redox Leaching, Precipitation, Electrolysis
Zn, MnO2
(Bartolozzi et al., 1994)Water, H2O2, (NH4)2S Water leaching,
Oxidative leaching with H2O2, precipitation of ZnS, flotation and wet sieving etc.
ZnS, NH4Cl, γ-MnO2
(Rabah et al., 1999)
Water Solvent extraction to separate Zn and Mn
Purified electrolytes of ZnSO4
and MnSO4
(Salgado et al., 2003)H2SO4/SO2 Leaching Pregnant leach liquors
containing ZnSO4, MnSO4 and FeSO4
(Avraamides et al., 2006)
H2SO4, H2C2O4 Reductive acid leaching, purification, filtration
Leach liquor and sludge (De Michellis et al., 2007)
H2SO4, (NH4)2CO3 or NaOH
Selective leaching with or without H2O2 as reductant
Leach liquors(Shin et al., 2007)
H2SO4 or HCl, Cyanex 301
Acid leaching, Solvent extraction, stripping
Zn(II) and Mn(II) solutions(El-Nadi et al., 2007)
Water, H2SO4 Washing, Leaching, Precipitation, Purification, Electrolysis, Calcination of Leach residues
Electrolytic Zn and calcined Mn2O3-Mn3O4 (Ferella et al., 2008)
Water, H2SO4, carbohydrates
Washing, Leaching Leach liquor of ZnSO4 and MnSO4 (Furlani et al., 2009)
Water, H2SO4, HCl, SX reagents, IX resins
Washing, Leaching, Solvent extraction, Ion exchange
Electrolytic Zn, Mn-oxides, MnCO3, Cu, Pb, Cd(Sayilgan et al., 2009a,b)
NaOH Selective Zn Leaching Leach liquor of Zn(OH)42-
(Shin et al., 2009)H2SO4, H2O2 Reductive leaching,
precipitationMnZnFe4O8 nanoparticles(Kim et al., 2009)
NH3 Alkaline leaching Zn(NH3)42+ solution and ZnO
in leach residue (this work)NH3, SO2 Alkaline reductive
leachingZn(NH3)4
2+ solution and Fe(NH4)2(SO3)2 , Fe(NH4)2(SO4)2 in leach residue (this work)
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Table 2
Stability constants (log βn) for metal ion ammine complexes____________________________________________________________________________________n Zn(II) Mn(II) Fe(II) Cu(I) Cu(II) Ni(II) Hg(II) Co(II) Co(III) Pb(II)____________________________________________________________________________________1 2.38 1.00 1.4 5.93 4.16 2.80 8.80 2.11 7.30 1.602 4.88 1.54 2.51 10.9 7.47 5.04 17.5 3.74 14.0 -3 7.43 1.70 2.68 - 10.8 6.77 18.5 4.79 20.1 -4 9.65 1.30 3.26 - 13.1 7.96 19.3 5.55 25.7 -5 - - 3.25 - 12.9 8.71 - 5.73 30.7 -6 - - - - - 8.74 - 5.11 35.2 -____________________________________________________________________________________βn defined as equilibrium constants for Mz+ + nNH3 = M(NH3)n
z+, data at 18-25 oC and ionic strength 0-2 from Sillen and Martell (1964, 1971), Smith and Martell (1976), Isaev et al. (1990), and Hancock (1997).
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Table 3. Chemical composition of minus 8 mesh spent ZMCBs
Element mass%a b c
Element mass%
a b cZn 20.8 13.2 13.6d Mg 0.02 eMn 22.7 26.6 27.6d K 0.4 0.15 5.1d
Fe 2.65 1.58 e Na 0.07Cl 3.25 4.26 Hg 0.02Ti 0.66 0.01 Cr <0.01Si 0.29 1.35 Pb 0.07Al 0.28 0.44 Ni 0.04S 0.16 Co 0.01Ca 0.06 e Cu 0.04
a. This work, analysed by Ultratrace Laboratories in Perth, Western Australia. b. Unwashed spent ZMCB paste (Sayilgan et al., 2009a). c. Unwashed spent ZMCB paste (Furlani et al., 2009).d. Washed product contained 19.3% Zn, 33.6% Mn and 1.37% K. e. 0.2-0.6%.
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Table 4Effect of SO2/H2SO4 and NH3/SO2 on Zn, Mn and Fe leaching efficiency from spent ZMCBs______________________________________________________________________________________________________T S/L ratio Acid/ base Conc. Reductant Time Zn Mn Fe pH pH(oC)a (g/L) (h) (%) (%) (%) initial final______________________________________________________________________________________________________
Acid leaching and effect of SO2
30-32 100 H2SO4 1 none 1.5 98(±2) 35(±2) <1 0 -30-40 100 H2SO4 0.5 50 ml/min SO2 1.5 95(±5) 98(±2) 25(±2) 0.3 0.930-40 100 H2SO4 1 50 ml/min SO2 1.5 98(±2) 98(±2) 25(±2) - -
Alkaline leaching and effect of SO2
30-32 100 NH3 1 none 1.5 6(±1) <1 <1 11.5 10.530-35 100 NH3 1 50 ml/min SO2 1.5 65(±2 <1 <1 11.6 8.560-60 100 NH3 1 none 1.5 2(±1) <1 <1 10.4 6.960-60 100 NH3 2.5 none 1.5 39(±2) <1 <1 12.1 10.960-60 100 NH3 2.5 50 ml/min SO2 1.5 90(±5)b <1 <1 10.8 8.8________________________________________________________________________________________________________
a. Temperature range indicates initial and final temperature, 1000 rpm.b. After 0.25 h (Fig. 2).
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Table 5Literature data on Zn, Mn and Fe leaching efficiency from spent ZMCBs______________________________________________________________________________________________________T S/L ratio Acid/ base Conc. Reductant Time Zn Mn Fe Test(oC) (g/L) (h) (%) (%) (%)______________________________________________________________________________________________________Acid leaching and effect of reducing agents50c 200 H2SO4 1 none 2 75 4.2 - A
200 H2SO4 2 none 2 88 6.7 - B200 H2SO4 3 none 2 92 7.5 - C200 H2SO4 4 none 2 89 8.0 - D
25d 100 H2SO4 1 none 92 35 - E100 H2SO4 1 6% H2O2 93 82 - F
60e 100 H2SO4 2 0.39 mol H2O2 97 97 55 G80f 100 H2SO4 2 none 3 100 25 100 H80g 200 H2SO4 1.1 none 3 99 21 0 (final pH 5.3) J80g 100 H2SO4 2 0.74 M H2C2O4 5 0 97 98 (final pH 1.24) K45h 100 H2SO4 +30%f -30%f 3 100 91 - L30i 100 H2SO4 0.1 200 ml/min SO2 0.25 99 99 10 M70j 100 H2SO4 2 none 4 100 21 - N70j 100 H2SO4 2 5 g/L lactose 4 100 100 - P90j 100 H2SO4 2 9 g/L lactose 3 98 100 - Q
Alkaline leaching and effect of reducing agents60d 100 (NH4)2CO3 2 none 0.5 82 0.1 - R
100 (NH4)2CO3 2 6% H2O2 no change - S60d 100 NaOH 4 none 0.5 83 0.1 - T
NaOH 4 6% H2O2 no change - U80k 100 NaOH 4 none 0.5 82 <0.1 - V_________________________________________________________________________________________________________
c. El Nadi et al., 2007;d. Shin et al. (2009) e. Kim et al., 2009; 200 rpmf. Ferella et al., 2008, 300 rpmg. De Michelis et al., 2007h. Sayilgan et al. (2009b); spent alkaline and ZCB; 30% less than stoichiometric oxalic acid to avoid precipitation MC2O4;
30% more than stoichiometric H2SO4; HCl had comparable effect.i. Avraamides et al., 2006j. Furlani et al., 2009; 200 rpm, washed spent zinc alkaline battery feed (see Table 2); twice stoichiometric glucose
required to extract over 97% Zn and Mn due to caromolization at high temp.k. Shin et al. (2007); ZCB feed composition: 24.4% Zn, 19.8% Mn, 11.8% Fe; 200-250 rpm
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Table 6. Comparison of trace transition metal leach efficiencies
Lixiviant Co% Hg% Ni% Cu% Pb%H2SO4 /30-32 oC 44 29 98 98 <0.1
SO2/H2SO4 /30-32 oC 89 0.7 98 98 <0.1SO2/NH3 /60 oC 63 50 73 98 <0.1
After 90 min leaching with 1 mol/L H2SO4 or 2.5 mol/L NH3 in the absence or presence of SO2 (50 mL/min), also see Fig. 3 (solution analysis based on ICPS)
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