A water disinfectant created on the spot using just hydrogen and the air
around us is millions of times more effective at killing viruses and
bacteria than traditional commercial methods, according to scientists from
Cardiff University.
Reporting their findings today in the journal Nature Catalysis, the team say
the results could revolutionize water disinfection technologies and present
an unprecedented opportunity to provide clean water to communities that need
it most.
Their new method works by using a catalyst made from gold and palladium that
takes in hydrogen and oxygen to form hydrogen peroxide—a commonly used
disinfectant that is currently produced on an industrial scale.
Over four million tons of hydrogen peroxide are made in factories each year,
where it is then transported to the places it is used and stored. This means
that stabilizing chemicals are often added to the solutions during the
production process to stop it degrading but these reduce its effectiveness
as a disinfectant.
Another common approach to disinfecting water is the addition of chlorine;
however, it has been shown that chlorine can react with naturally occurring
compounds in water to form compounds which, in high doses, can be toxic to
humans.
The ability to be able to produce hydrogen peroxide at the point of use
would overcome both efficacy and safety issues currently associated with
commercial methods.
In their study, the team tested the disinfection efficacy of commercially
available hydrogen peroxide and chlorine compared to their new catalytic
method.
Each was tested for its ability to kill Escherichia coli in identical
conditions, followed by subsequent analysis to determine the processes by
which the bacteria were killed using each method.
The team showed that as the catalyst brought the hydrogen and oxygen
together to form hydrogen peroxide, it simultaneously produced a number of
highly reactive compounds, known as reactive oxygen species (ROS), which the
team demonstrated were responsible for the antibacterial and antiviral
effect, and not the hydrogen peroxide itself.
The catalyst-based method was shown to be 10,000,000 times more potent at
killing the bacteria than an equivalent amount of the industrial hydrogen
peroxide, and over 100,000,000 times more effective than chlorination, under
equivalent conditions.
In addition to this, the catalyst-based method was shown to be more
effective at killing the bacteria and viruses in a shorter space of time
compared to the other two compounds.
It is estimated that around 785 million people lack access to water and 2.7
billion experience water scarcity at least one month a year.
In addition to this, inadequate sanitation—a problem for around 2.4 billion
people around the world—can lead to deadly diarrheal diseases, including
cholera and typhoid fever, and other water-borne illnesses.
Co-author of the study Professor Graham Hutchings, Regius Professor of
Chemistry at the Cardiff Catalysis Institute, said: "The significantly
enhanced bactericidal and virucidal activities achieved when reacting
hydrogen and oxygen using our catalyst, rather than using commercial
hydrogen peroxide or chlorination shows the potential for revolutionizing
water disinfection technologies around the world.
"We now have proven one-step process where, besides the catalyst, inputs of
contaminated water and electricity are the only requirements to attain
disinfection.
"Crucially, this process presents the opportunity to rapidly disinfect water
over timescales in which conventional methods are ineffective, whilst also
preventing the formation of hazardous compounds and biofilms, which can help
bacteria and viruses to thrive."
Reference:
A residue-free approach to water disinfection using catalytic in situ
generation of reactive oxygen species, Nature Catalysis (2021). DOI:
10.1038/s41929-021-00642-w