Graphene for effective desalination

Leader


Challenge

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.

Investigation

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.

Outcomes 

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 Direction

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.

Technology Readiness

This technology has shown promise. For commercial success, more work needs to be undertaken to scale up the manufacture of graphene.

Partners 


 

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)

Related Project: Application of capacitive deionisation in inland brackish water desalination

Further Information

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