scale operations, the decomposition of the organic constituents
at the electrodes over longer periods of electrolysis hinders a
breakthrough.
5 (a) F. Endres, ChemPhysChem, 2002, 3, 144–154; (b) F. Endres, S.
Zein El Abedin and Q. X. Liu, Surf. Coat. Technol., 2006, 20, 1352–
1
356.
6
S. Zein El Abedin, M. P o¨ lleth, S. A. Meiss, J. Janek and F. Endres,
The decomposition is an important economic issue as the
lifetime of the solutions is reduced and specific recycling
strategies are required in order to remove the decomposition
products. Moreover, the conversion of the organic constituents
holds a risk for the formation of volatile or toxic products and an
uncertain state of the solution at any moment. When promoted
as ‘green’ alternatives for classic solvents, disposal of used
ionic liquids should at least be compatible with biodegradation
techniques. With the formation of an entire range of products,
this is uncertain. Especially chlorinated products, even when the
release of chlorine gas is not observed, are a concern.
When a sustainable longevity of the solutions is targeted in
processes over longer periods, there is no other way than avoiding
the decomposition. Therefore, in electrodeposition processes
soluble anodes should be preferred. Unfortunately, these are
not always available or give rise to other problems. Another
solution is the addition of ‘sacrificial agents’ i.e. components
that oxidize preferentially at the anode, thereby protecting the
solution. Most of the tested sacrificial products in this study
do not reduce the deterioration of the ionic liquid analogue.
However, the experiments in a divided cell show the addition
of water hinders the formation of chlorinated products but the
conversion of the organic components e.g. of ethylene glycol
to 2-methyl-1,3-dioxolane, remains. Formic acid inhibits the
formation of 2-methyl-1,3-dioxolane. However, the efficiency
of the zinc deposition at the cathode reduces as the deposited
zinc dissolves accompanied by hydrogen gas formation and
deterioration of the solvent via other routes remains.
Green Chem., 2007, 9, 549–553.
7 (a) A. P. Abbott, G. Capper, B. G. Swain and D. A. Wheeler, Trans.
Inst. Met. Fin., 2005, 83, 51–53; (b) A. P. Abbott, G. Capper, K. J.
McKenzie and K. S. Ryder, Electrochim. Acta, 2006, 51, 4420–
4
425.
8 A. P. Abbott, K. El Ttaib, K. S. Ryder and E. L. Smith, Trans. Inst.
Met. Fin., 2008, 86, 234–240.
A. P. Abbott, G. Capper, D. L. Davies and P. Shikotra, Mineral Proc.
Extract. Metal., 2006, 115, 15–18.
9
1
1
1
0 J. Dupont, C. S. Consorti and J. Spencer, J. Braz. Chem. Soc., 2000,
11, 337–344.
1 J. D. Holbrey and K. R. Seddon, Clean Products and Processes, 1999,
1
, 223–236.
2 A. P. Abbott and K. J. Mckenzie, Phys. Chem. Chem. Phys., 2006, 8,
4265–4279.
13 D. S. Silvester and R. G. Compton, Z. Phys. Chem., 2006, 220, 1247–
274.
4 M. Galinski, A. Lewandowski and I. Stepniak;, Electrochim. Acta,
006, 51, 5567–5580.
15 D. R. MacFarlane and K. R. Seddon, Aust. J. Chem., 2007, 60,
–5.
1
1
2
3
1
6 P. Bonhote, A. P. Dias, N. Papageorgiou, K. Kalyanasundaram and
M. Gratzel, Inorg. Chem., 1996, 35, 1168–1178.
17 J. Sun, M. Forsyth and D. R. MacFarlane, J. Phys. Chem. B, 1998,
102, 8858–8864.
1
1
2
2
8 P. J. Scammells, J. L. Scott and R. D. Singer, Aust. J. Chem., 2005,
8, 155–169.
5
9 M. Kosmulski, J. Gustafsson and J. B. Rosenholm, Thermochim.
Acta, 2004, 412, 47–53.
0 K. J. Baranyai, G. B. Deacon, D. R. MacFarlane, J. M. Pringle and
J. L. Scott, Aust. J. Chem., 2004, 57, 145–147.
1 T. J. Wooster, K. M. Johanson, K. J. Fraser, D. R. MacFarlane and
J. L. Scott, Green Chem., 2006, 8, 691–696.
22 F. Endres, S. Zein El Abedin and N. Borissenko, Z. Phys. Chem.,
2
006, 220, 1377–1394.
2
3 A. K. Burrell, R. E. Del Sesto, S. N. Baker, T. M. McCleskey and
Still, there exist possibilities to avoid decomposition in
electrochemical processes. Closed loop processes, where cathode
and anode reactions do not involve decomposition of the
ionic liquids should be searched for. Further investigation is
required to prevent the breakdown of the ionic liquid during
electrolysis over longer periods either by addition of other
sacrificial products or by using soluble anodes. In the latter
case it is not impossible organic conversions still occur in side-
reactions. If conversion of the ionic liquid, stemming from the
organic reactions at the electrodes, cannot be avoided, online
processes have to be considered in order to extract the conversion
products and to recycle the ionic liquid.
G. A. Baker, Green Chem., 2007, 9, 449–454.
24 U. Schroder, J. D. Wadhawan, R. G. Compton, F. Marken, P. A. Z.
Suarez, C. S. Consorti, R. F. de Souza and J. Dupont, New J. Chem.,
2
000, 24, 1009–1015.
2
5 K. R. Seddon, A. Stark and M. Torres, Pure Appl. Chem., 2000, 72,
275–2287.
26 P. Hapiot and C. Lagrost, Chem. Rev., 2008, 108, 2238–
264.
2
2
2
7 K. Kumai, O. Yamamoto, T. Ikeya, K. Ishihara, T. Iwahori,
N. Imanishi and Y. Takeda, J. Power sources, 1998, 70, 235–
239.
28 M. C. Kroon, W. Buijs, C. J. Peters and G. Witkamp, Green Chem.,
2
006, 8, 241–245.
2
9 (a) A. P. Abbott, G. Capper, D. L. Davies, R. K. Rasheed and V.
Tambyrajah, Chem. Comm., 2003, 1, 70–71; (b) A. P. Abbott, D.
Boothby, G. Capper, D. L. Davies and R. K. Rasheed, J. Am. Chem.
Soc., 2004, 126, 9142–9147; (c) A. P. Abbott, K. El Ttaib, K. S. Ryder
and E. L. Smith, Trans. Inst. Met. Finish., 2008, 86, 234–240; (d) A. P.
Abbott, K. S. Ryder and U. K o¨ nig, Trans. Inst. Met. Finish., 2008,
Acknowledgements
8
6, 196–204.
The authors would like to thank the EU under framework
programme 6 for funding this work through the IONMET
project (www.ionmet.eu).
3
0 K. Haerens, E. Matthijs, A. Chmielarz and B. Van der Bruggen, J. En-
viron. Management, 2009, DOI: 10.1016/j.jenvman.2009.04.013, in
press.
3
3
1 A. P. Abbott, G. Capper, K. J. McKenzie and K. S. Ryder,
J. Electroanal. Chem., 2007, 599, 288–294.
2 A. Chmielarz and co-workers, Second year report of W.P. 4 sub-
task 4.4 monitoring and control, Internal IONMET report, 2007,
14 pp.
References
1
2
3
4
N. V. Plechkova and K. R. Seddon, Chem. Soc. Rev., 2007, 37, 123–
50.
A. Fernicola, B. Scrosati and H. Ohno, Ionics, 2006, 12, 95–
02.
1
33 Taminco, Choline base technical data sheet, 2003, available on their
website.
34 T. Van der Klis, in Vademecum oppervlaktetechnieken metalen, 5e
editie, VOM, Twight B.V., 1989, pp. 223–229.
35 C. K. Mann and K. K. Barnes, in Electrochemical reactions in non-
aqueous systems, Marcel Dekker, Inc, New York, 1970, pp. 292–
294.
1
B. Li, L. Wang, B. Kang, P. Wang and Y. Qiu, Sol. Energy Mater.
Sol. Cells, 90, 549–573.
T. Sato, G. Masuda and K. Takagi, Electrochim. Acta, 2004, 49,
3
603–3611.
1
364 | Green Chem., 2009, 11, 1357–1365
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