'Happy accident': Napier scientist's salt-trapping molecule could solve world's drinking water woes

Professor Amar Flood from Napier, is leading a team on a project which could help increase the amount of drinkable water on Earth. Photo / Supplied

A Napier scientist's "happy accident" with a molecule he was creating has the potential to solve some of the world's water issues.

Professor Amar Flood, who was born and raised in Napier and attended Napier Intermediate followed by Colenso College, graduated in 1996 with a BSc in chemistry with first class honours from Otago University.

Flood is now leading a team of scientists based at Indiana University in the US who have created a powerful new molecule for the extraction of salt from liquid.

Flood said the project began in 2008, but the creation of the molecule was the result of a "happy accident".

"I started out by wanting to make molecule shaped like a donut. What I was not expecting was for the pockets I made in the heart of the molecules to be so good at binding chloride, which is one half of table salt, the other half is sodium," Flood said.

"If you are ever going to have a positive impact on water quality, your need both the sodium and the chloride."

Ph.D student Yun Liu holds a 3D-printed model of the chloride-capture molecule. Photo / Supplied

Over the next decade, Flood was joined by other students who tinkered with his main idea and the 2D donut molecule was transformed into a 3D cage, or triazolo cage by PhD student Yun Lin.

He designed a chloride-selective receptor in the form of a cryptand-like cage using only chemical hydrogen bonding.

Although it's still in the early stages, Lin said if you were to place one-millionth of a gram of this molecule in a metric ton of water, 100 per cent of them will still be able to capture salt.

Lin and Flood both came to the realisation that the cage is the world's strongest for chloride binding strength.

As the human population continues to grow, the seepage of salt into freshwater systems is reducing access to drinkable water across the globe.

In the US alone, the US Geological Survey estimated about 272 metric tons of dissolved solids, including salts, enter freshwater streams per year.

"Everyone likes to ask me if this will be used to purify water and remove salt from all our drinking. Short answer is, not any time soon," Flood said.

"However, this discovery could be used in the short term for creating sensor technology for measuring salt concentrations accurately, which is actually the first step in any chemical remediation effort," Flood said.

Flood said the project could be also used for monitoring salt levels as a reflection of water quality.

"We also showed that this cage can be used for anti-corrosion — it stops rust.

"Chloride is known to be an aggressive ion for accelerating rust. Everyone knows living close to the ocean in Hawke's Bay makes car rust more likely, it's the chloride that does the damage not the sodium and we might have a new way to prevent it.

"Long term, our cage could help with salt removal but the exact embodiment of that technology is still in the future."