Ashes from incineration of municipal solid waste contain metals, such as copper and zinc, in high concentrations. The metals can be leached out from the ashes using acids and recovered by electrolysis. To lower the energy demand of the electrolysis step, we have investigated a bioelectrochemical system for combined wastewater treatment and copper recovery from simulated ash leachate. Bacteria at the anode oxidize wastewater organics and produce a current that flows through an external circuit to the cathode, where copper is reduced and recovered. We tested a bioelectrochemical system with carbon anode and titanium cathode. With a cathode potential poised at -0.3 V, the energy required for copper reduction was reduced from 1.46 kWh/kg Cu with an abiotic anode compared to 0.23 kWh/kg Cu with a biological anode oxidizing acetate. With a cathode potential of 0.1 V, electrical energy could be recovered from the system together with copper

Karlfeldt Fedje, Karin

Modin, Oskar

Chalmers Research

Combined wastewater treatment and recovery of copper from ash leachate

Chalmers Publication Library

The paper was presented at the IWA World Water Congress & Exhibition, Busan, 
Korea, Sept. 16-31, 2012.   
Combined wastewater treatment and recovery of copper from ash 
leachate 
O. Modin, K. Karlfeldt Fedje 
Chalmers University of Technology, Department of Civil & Environmental Engineering, WET, 412 96, Göteborg, 
Sweden (Emails: oskar.modin@chalmers.se, karin.karlfeldt@chalmers.se) 
Abstract: Ashes from incineration of municipal solid waste contain metals, such as copper and zinc, in 
high concentrations. The metals can be leached out from the ashes using acids and recovered by 
electrolysis. To lower the energy demand of the electrolysis step, we have investigated a 
bioelectrochemical system for combined wastewater treatment and copper recovery from simulated ash 
leachate. Bacteria at the anode oxidize wastewater organics and produce a current that flows through an 
external circuit to the cathode, where copper is reduced and recovered. We tested a bioelectrochemical 
system with carbon anode and titanium cathode. With a cathode potential poised at -0.3 V, the energy 
required for copper reduction was reduced from 1.46 kWh/kg Cu with an abiotic anode compared to 
0.23 kWh/kg Cu with a biological anode oxidizing acetate. With a cathode potential of 0.1 V, electrical 
energy could be recovered from the system together with copper.  
Keywords: ash leachate; bioelectrochemical system; copper; metals; wastewater 
Introduction 
Valuable metals such as copper are extracted from the lithosphere at an increasing 
rate. Spatari et al. estimated that approximately 40% of the copper extracted during 
the 20th century remain in use today, while 60% has been lost or ended up in waste 
repositories such as landfills (Spatari et al. 2005). A continuing loss of metals to waste 
repositories is not sustainable.  
Incineration is an increasingly popular treatment method for municipal solid waste. 
The resulting ashes contain high amounts of metals and some valuable metals (e.g. 
Cu, Zn and Mo) are present in amounts comparable to the content in workable ores. 
The ashes are an environmental problem because of the risk for uncontrolled metal 
leaching and therefore has to be deposited into technically advanced and expensive 
lanfills. Instead, the metals can be extracted using e.g. acid and subsequently 
recovered using electrolysis. The electrolysis step, however, can be very energy 
consuming. A microbial bioelectrochemical system (BES) can be used to recover 
copper from solutions (Ter Heijne et al. 2010, Tao et al. 2011). The energy required 
for electrolysis is provided by organic compounds present in wastewater. A BES 
consists of an anode and cathode. Living microorganisms oxidize organic compounds 
and use the anode as electron acceptor. The electrons flow through an external circuit 
to the cathode where a reduction reaction takes place. The most common type of BES 
is the microbial fuel cell (MFC), which converts organic matter directly into electrical 
energy (Rabaey et al. 2003, Liu et al. 2004). In this study, we investigate 
bioelectrochemical copper recovery from simulated acid municipal solids waste 
leachates.  
Material and Methods 
A cylindrical bioelectrochemical reactor containing a carbon felt anode in 17 ml 
anode chamber and a cathode (usually titanium) in a 10 ml cathode chamber, 
separated by a Nafion 117 proton exchange membrane was used in the experiments. 
Two litres of synthetic wastewater containing acetate was circulated through the 
anode chamber whereas the cathode chamber was loaded with about 10 mL 2M 
H2SO4 containing 1 g/L Cu2+.  
Results and Conclusions 
Titanium, steel, graphite, and copper cathodes were compared using cyclic 
voltammetry (Fig. 1). The titanium electrode showed no reaction peaks with only 2M 
H2SO4 as the catholyte. With the addition of 1 g/L Cu2+, distinct cathodic and anodic 
current peaks appeared, suggesting copper was reduced and subsequently oxidized. 
The graphite electrode showed similar behavior although some, possibly oxygen-
dependent, current peaks also could be observed with 2M H2SO4 as the catholyte. The 
copper electrodes displayed a cathodic current peak similar to the titanium and 
graphite electrodes; however, a very strong anodic current was observed above 0.3 V 
as a result of the electrode itself being oxidized. The steel electrode differed from the 
other three and did not exhibit any peaks obviously related to copper in the scanned 
range. Zinc (1 g/L) did not show any peak in the scanned range for any of the 
cathodes. The titanium cathode was chosen for electrolysis tests. 
 
The anode was incubated at a set potential of initially 0.2 V and later -0.1 V until 
current production began. The current rose to a magnitude of about 3 mA (~0.1 
mA/cm2 anode surface area). The reactor was characterized using linear scan 
voltammetry and electrochemical impedance spectroscopy. The anode potential was 
around -0.2 to -0.1 V at currents from 0 to 2.5 mA (Figure 2). The cathode potential 
drops dramatically at a current of about 1 mA. This indicates that the current is 
limited by diffusion of copper ions to the cathode. At cathode potentials below -0.35 
V, the current increases again as a result of hydrogen evolution. The internal ohmic 
resistance of the cell was about 4.4 Ω.  
 
Copper recovery was examined in 2 hours tests with titanium cathode and constant 
cathode potentials of -0.3V, -0.1V, or 0.1V (Table 1). Copper recovery was calculated 
from the measured charge transfer in the system since the cyclic voltammogram 
(Figure 1) suggested that no other reactions contributed to Faradaic charge transfer in 
the range of cathode potentials used. The amount of copper deposited on the cathode 
was analysed in tests 3 and 4 by dissolving the copper in HNO3(conc). This was not 
possible in tests 1 and 2 as the deposited copper fell off from the cathode during 
handling. In test 3, the copper remained on the cathode although it was possible to 
wipe it off with paper. In test 4, with a cathode potential of 0.1 V, the copper 
remained firmly attached to the cathode and was difficult to wipe off. Thus, the higher 
the potential, the stronger the deposited copper was attached to the titanium cathode. 
The energy required for copper deposition was lower with a biological anode than 
under abiotic conditions. At a cathode potential of -0.3V copper was recovered with 
an electrical energy consumption of 1.46 kWh/kg Cu with an abiotic anode. The 
energy consumption was lowered to 0.23 kWh/kg Cu with a biologically active anode. 
At a cathode potential of 0.1 V, the tests confirmed the results of Ter Heijne et al. 
(2010) and Tao et al. (2011), i.e. showing that copper could be recovered with a net 
energy output from the system. This study has demonstrated a new concept for 
recovery of copper from simulated acid ash leachates using a bioelectrochemical 
system powered by wastewater organics.  
 References 
Spatari, S., Bertram, M., Gordon, R., Henderson, K., Graedel, T. (2005). Twentieth century copper 
stocks and flows in North America: A dynamic analysis. Ecological Economics, 54, 37-51. 
Tao, H.-C., Liang, M., Li, W., Zhang, L.-J., Ni, J.-R., Wu, W.-M. (2011). Removal of copper from 
aqueous solution by electrodeposition in cathode chamber of microbial fuel cell. Journal of Hazardous 
Materials, 189, 186-192. 
Ter Heijne, A., Liu, F., van der Weijden, R., Weijma, J., Buisman, C.J.N., Hamelers, H.V.M. (2010). 
Copper recovery combined with electricity production in a microbial fuel cell. Environmental Science 
& Technology, 44, 4376-4381. 
Rabaey, K., Lissens, G., Siciliano, S.D., Verstraete, W. (2003). A microbial fuel cell capable of 
converting glucose to electricity at high rate and efficiency. Biotechnology Letters, 25, 1531-1535. 
Liu, H., Ramnarayanan, R., Logan, B.E. (2004). Production of electricity during wastewater treatment 
using a single chamber microbial fuel cell. Environmental Science & Technology, 38, 2281-2285. 
 
 
 
 
 
Figure 1. Cyclic voltammetry tests with various cathode materials. The catholyte was either 2M H2SO4 
(thin lines), 2M H2SO4 amended with 1 g/L Cu2+ (thick lines), or 2M H2SO4 amended with 1 g/L Zn2+ 
(dashed lines). 
 
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
i 
(m
A
/c
m
2
)
Cathode potential (V vs NHE)
-10.0
0.0
10.0
20.0
30.0
40.0
50.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
i 
(m
A
/c
m
2
)
Cathode potential (V vs NHE)
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
i 
(m
A
/c
m
2
)
Cathode potential (V vs NHE)
-30.0
-20.0
-10.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
i 
(m
A
/c
m
2
)
Cathode potential (V vs NHE)
Titanium
Graphite Steel
Copper
 Figure 2. Linear scan voltammetry of bioelectrochemical cell. The cell voltage is measured as the 
cathode vs the anode, which means that a positive value suggests the system can be operated as a 
galvanic cell whereas at negative values the system requires electrical energy input. 
 
 
 
 
Table 1. Experimental conditions and results under four 2-h copper electrodeposition tests. 
Test Ecat. 
(VvsNHE) 
Cu rec.a 
(mg) 
Cu rec.b 
(mg) 
Energy cons. 
(kWh/kg Cu) 
1(abiotic) -0.3 1.56 N.M. 1.46 
2 -0.3 2.09 N.M. 0.23 
3 -0.1 2.19 1.63±0.02 0.06 
4 0.1 1.60 1.78±0.02 -0.08 
aCu recovery calculated based on measured charge transfer. 
bAmount of copper recovered from cathode surface. 
N.M. Not measured. 
 
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.0 0.5 1.0 1.5 2.0 2.5 3.0
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 v
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Current (mA)
Anode E
Cathode E
Cell V


Combined wastewater treatment and recovery of copper from ash leachate

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