Research led by RMIT University has developed an experimental invention to turn wastewater's high contaminant load into an advantage for making green hydrogen that could reduce reliance on fresh water – a scarce resource in many parts of the world.
With more than 80% of global wastewater discharged into the environment untreated, this research provides an opportunity to turn this environmental liability into boosted productivity.
The team's approach harnesses some of the contaminants in wastewater to speed up hydrogen production and overcome high contaminant loads that normally makes wastewater unusable.
The team's latest work – which involved the University of Melbourne, Australian Synchrotron, University of New South Wales – builds on previous breakthroughs, including an innovation that rapidly removes microplastics from water using magnets and a technique boosting hydrogen production using seawater.
How the innovation works
Lead researcher Associate Professor Nasir Mahmood, from RMIT's School of Science, said the team found a way to capture platinum, chromium and nickel other metals in the water and then put these elements to work to enhance green hydrogen production.
"The advantage of our innovation over others to produce green hydrogen is that it harnesses wastewater's inherent materials rather than requiring purified water or additional steps," Mahmood said.
Their experimental invention comes in the form of electrodes, which are key components for splitting water into hydrogen and oxygen. The electrode is made with an absorbent carbon surface that attracts metals from wastewater to form catalysts that are stable and efficient at conducting electricity, helping to speed up the water splitting.
The materials used to produce the special carbon surface are made from agricultural waste – another cost-effective aspect of the innovation that contributes to a growing circular economy.
"The catalyst speeds up a chemical reaction without being consumed in the process," Mahmood said.
"The metals interact with other elements in the wastewater to boost the electrochemical reactions needed for splitting water into oxygen and hydrogen.
As part of the experiments, the team used the wastewater samples in a container with two electrodes – an anode (positive) and a cathode (negative) – and powered the water-splitting process with renewable energy. When electricity flows through the water, it causes a chemical reaction.
At the cathode, water molecules gain electrons and form hydrogen gas. At the anode, water molecules lose electrons and form oxygen.
The result is a separation of water into its basic components, hydrogen and oxygen, which could then both be collected and used.
"The produced oxygen can be reintegrated into wastewater treatment plants to enhance their efficiency by reducing organic content," Mahmood said. The device enabled continuous water splitting for 18 days during experiments in the lab, with minimal decline in performance over that time. As part of the experiments, the team used wastewater that had undergone some treatment including the removal of solid waste, organic matter and nutrients.
Opportunities for industry and government collaborations
RMIT is developing a platform of catalytic systems capable of using previously difficult water resources such as wastewater and seawater and this latest proof-of-concept invention is a further example of the systems under development.
Co-lead researcher Professor Nicky Eshtiaghi said the latest RMIT innovation could potentially reduce the high cost of wastewater treatment while turning it into something valuable – a source of green hydrogen.
"Our innovation addresses both pollution reduction and water scarcity, benefiting the energy and water sectors," Eshtiaghi, from RMIT's School of Engineering, said.
"By using wastewater, the process helps reduce pollution and makes use of materials considered to be waste.
"We are keen to work with companies globally that are addressing energy and waste as cost and sustainability challenges, as well as water authorities.
"Collaborations could focus on developing commercial systems to use this technology on a large scale."
Next steps
Co-researcher Dr Muhammad Haris said further research was needed to refine the catalyst process, making it even more efficient and suitable for commercial use.
"The method needs to be tested with different types of wastewater to ensure it works universally," said Haris, from the School of Engineering.
'Harnessing wastewater as a catalyst modifier for sustainable hydrogen production' is published in ACS Electrochemistry (DOI: 10.1021/acselectrochem.5c00064).
The journal article will be available at the following link once the embargo lifts: https://doi.org/10.1021/acselectrochem.5c00064
MULTIMEDIA
Images and video of the innovation can be downloaded here: https://spaces.hightail.com/space/kHmbP6P3OX
Image/video credit: Shu Shu Zheng, RMIT University
Order of researchers in posed RMIT lab photo: Dr Muhammad Haris, Associate Professor Nasir Mahmood and Professor Nicky Eshtiaghi (left to right).
