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 and 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, nickel, and 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.
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