| Work Detail |
Researchers at James Cook University have developed a process to synthesize graphene from tangerine peel oil, which they then used to recover silver from photovoltaic waste. To demonstrate the quality of the recovered silver and the synthesized graphene, they fabricated a dopamine sensor that appeared to outperform reference devices.
A team at Australia’s James Cook University has synthesized “stand-alone” graphene using nontoxic and renewable tangerine peel oil that can reportedly be used for silver recovery from end-of-life organic photovoltaic devices.
“Not only was high-quality graphene obtained, but a remarkable ability to selectively recover silver from PV waste was also demonstrated. One of the most surprising findings was the exceptional selectivity of graphene with respect to silver,” Mohan Jacob, author of the paper, explains to pv magazine .
The quality of the recovered and synthesized materials was then demonstrated in a silver-enhanced SPE dopamine sensor device, which outperformed two reference dopamine sensors fabricated without the graphene-silver composite.
Graphene synthesis
The team began their research by synthesizing graphene “using downstream microwave plasma” under atmospheric conditions. “The main components of the system include a 2.45 GHz microwave generator, a matching network, a cooling system, and a reaction chamber,” it says.
A Raman spectrum analysis of graphene showed “a characteristic 2D peak” at microwave powers between 200 W and 1000 W. “Transmission electron microscopy images revealed an interstitial spacing of 0.34, which was consistent with the X-ray diffraction value calculated using Bragg’s law,” the team noted.
Silver Recovery from PV
The team then recovered silver from the organic PV devices by leaching in a nitric acid solution. The PV coating contained indium tin oxide (ITO), zinc oxide (ZnO), molybdenum oxide (MoO3) and silver (Ag).
After leaching was complete, the solution was cooled and used as a stock solution to create graphene-coated SPE. “After 10 min of electrodeposition, the Ag concentration decreased slightly to 1.69 ppm. This decrease suggests that some Ag ions were being reduced and deposited on the electrode surface during the electrochemical process. After 20 min of electrodeposition, the Ag ion concentration decreased again to 1.62 ppm, indicating a continuous reduction in Ag ion concentration,” the academics note.
“These results suggest that longer electrodeposition duration may lead to a greater reduction in silver concentration.” Ag deposition was confirmed by cyclic voltammetric detection.
“Despite the presence of other diverse compounds in the PV waste solution, graphene showed an extraordinary ability to isolate and recover silver with high precision. This dual benefit of producing valuable graphene and selectively recovering silver from a complex mixture was an exciting and somewhat unexpected result,” Mohan said.
The team says the study “highlights the remarkable effectiveness” of graphene in recovering valuable metals such as silver from electronic waste.
“We chose to demonstrate with waste PV material because PV waste is a rapidly growing concern due to the increasing adoption of solar energy. Disposing of PV panels, which contain valuable metals such as silver, poses environmental and economic problems. By focusing on PV waste, we set out to develop a sustainable solution that addresses the urgent need for effective recycling methods while also recovering valuable resources,” explains Jacob.
Dopamine Sensor Demonstration
To illustrate the quality of the composite in a real-world application, the team fabricated a graphene-silver electrode (SPE/graphene-Ag) detector and compared it to a bare SPE detector and a graphene/SPE detector. Test results showed that the SPE/graphene-Ag electrode exhibited “significant improvement in peak current” compared to the other two samples.
The researchers suggested other applications of graphene-silver composites, such as corrosion-resistant coatings, conductive inks for use in flexible devices in the electronics industry, antimicrobial coatings for use in biomedical industries, as well as sensors to detect gases, biomolecules and contaminants.
Their work is detailed in the article “ Green synthesis of graphene for targeted recovery of silver from photovoltaic waste ,” published in Chemosphere .
So far, the response to the research has been positive. “Our work has just gotten underway and we are overwhelmed by the response from our colleagues and their interest in our research,” Jacob said, adding that the group has received encouraging feedback about the “broader applicability and potential impact” of the work in the battery and e-waste fields.
The team’s next steps are to optimize the green synthesis process to improve its scalability and economic viability, with the goal of achieving a process that can be integrated into existing PV and e-waste recycling infrastructure. “We are actively pursuing commercialization to bring these advancements to market and make a significant impact on the industry,” Jacob said. “We are also exploring partnerships with industry stakeholders and investors to pilot larger-scale deployments.” |
