Capacitive deionisation (CDI) has emerged as an alternative desalination technology in recent years, not in competition with the widely accepted reverse osmosis technology, but as an alternative for certain applications, such as brackish ground water desalination. CDI has low energy and technical maintenance requirements and can overcome the scaling caused by dissolved reactive silica in the ground water.
The principle of CDI is based on imposing an external electrostatic field between the electrodes in order to force charged ions to move toward oppositely charged electrodes. The charged ions can be held within the electrical double layer formed between the solvent and the electrode interface. The salt removal efficiency is directly related to the specific surface area and conductivity of the electrodes. Porous carbons materials, such as activated carbon cloth (ACC), are typically used to make the electrodes whoever, while ACC has high specific surface area and is cheap to produce, it suffers from poor conductivity.
Graphene on the other hand, which has a unique two dimensional layer with a planar surface, has excellent conductivity and has been viewed as a potential additive for the production of more efficient CDI electrodes.
Scale up and optimise graphene nanosheet production and test two methods for preparing graphene/ACC composite electrodes. Determine the performance of the new composite electrode.
Graphene nanoflakes with desirable structural properties, such as high specific surface area and pore distribution, were produced using an innovative three-step reduction method. A novel environmentally-friendly approach for the reduction of graphene oxide was also developed to avoid the use of hydrazine, which is highly toxic. The nanoflakes were successfully assembled into monolayered films and maintained their 2D structure.
ACC electrodes were successfully coated with graphene nanosheets and the electrosorption capacity of the new hybrid electrode was found to be twice that of the ACC electrode. The scaled up production costs were shown to be economically competitive, roughly 20c per electrode.
Future work will seek to fully understand the cause-effects of the assembled layered structure. The preliminary research on layered thin film graphene electrodes showed it requires much less graphene mass but achieved higher desalting capacitance than the bulk electrode.
This technology has shown promise. For commercial success, more work needs to be undertaken to scale up the manufacture of graphene.
Total Value: $720,265 (cash and in-kind contributions)
Principal Investigator: Professor Linda Zou
Title: Developing highly conductive graphene electrodes for capacitive desalination (Phase 1 and Phase 2)
Length: 33 months (Phase 1) and 15 months (Phase 2)
Personnel: 4 collaborators contributing 2.3 FTE (Phase 1) and 3 collaborators contributing 1.3 FTE (Phase 2)
- 2016. Jia, B., and W. Zhang. Preparation and Application of Electrodes in Capacitive Deionization (CDI): a State-of-Art Review. Nanoscale Research Letters 11:64.
- 2013. 6th International Desalination Workshop. Melbourne, Australia.
- 2013. Wimalasiri, Y., and L. Zou. Carbon nanotube/graphene composite for enhanced capacitive deionization performance. Carbon 59:464-471.
- 2013. Jia, B., and L. Zou. Langmuir–Blodgett assembly of sulphonated graphene nanosheets into single- and multi-layered thin films. Chemical Physics Letters 568–569 (0):101-105.
- 2012. Jia, B., and L. Zou. Wettability and its influence on graphene nansoheets as electrode material for capacitive deionization. Chemical Physics Letters 548 (0):23-28.
- 2012. NCEDA Research Showcase, Perth, Australia.
- 2012. Jia, B., and L. Zou. Graphene nanosheets reduced by a multi-step process as high-performance electrode material for capacitive deionisation. Carbon 50 (6):2315-2321.
- 2011. Zou, L. Developing Nano-Structured Carbon Electrodes for Capacitive Brackish Water Desalination. In Expanding Issues in Desalination, InTech, 301-318.
- 2011. Li, H., et al. Synthesis of TiO2–graphene composites via visible-light photocatalytic reduction of graphene oxide. Journal of Materials Research 26 (08):970-973.
- 2011. Zou, L., and H. Li. Developing graphene-like electrodes for capacitive deionisation. In Graphene: Properties, Synthesis and Application.
- 2011. International Water Association 2nd International Specialised Conference on Nano and Micro Particles in Water and Wastewater. Zurich, Switzerland.
- 2010. Li, H., et al. Novel Graphene-Like Electrodes for Capacitive Deionization. Environmental Science & Technology 44 (22):8692-8697.
- 2010. 7th International Membrane and Science Technology Conference. Sydney, Australia.