A Chinese team has developed a method of converting nitrate in wastewater into ammonia. Used as a core ingredient in urea fertilizer, this new waste-to-resource process is cheaper, energy-efficient, and something of a game-changer.

Presently, agricultural and industrial wastewater runoff often contains large amounts of nitrate. This comes from things like used fertilizer, animal waste, chemical plant waste, and sewage treatment.

Too much of it can be disastrous for the local ecosystems, leading to issues like algal blooms. These in turn lead to dead zones in waterways where oxygen levels drop, killing aquatic organisms like fish.

It can also lead to groundwater contamination and associated health risks to people and animals. To counter this, most countries tend to treat wastewater to remove nitrate, but this is expensive and energy-intensive.

But, this could be missing a trick as the nitrate contains large amounts of nitrogen, a key component of fertilizer in the first place. So, one Chinese team decided to find a way to tap into this enormous potential resource.

Waste-to-fertilizer breakthrough

Ammonia, in case you are unaware, is one of the world’s most important industrial chemicals. It is used to make things like fertilizers, explosives, chemicals, refrigerants, and potentially future hydrogen energy systems.

However, converting it into these chemicals is normally very expensive and energy-intensive. This is typically done using something called the Haber–Bosch process, which blends pure nitrogen and hydrogen to make ammonia.

This process requires very high temperatures and pressures, which are typically achieved by using natural gas. According to some reports, globally, this consumes something like 1-2% of global energy consumption.

So if you can make ammonia from waste nitrate instead, you potentially reduce pollution, reduce energy usage, and reduce dependence on imported feedstocks. It could, therefore, make a kind of circular fertiliser production, and that’s a big deal.

The core of the discovery is a new super catalyst that helps the process. These, in case you don’t know, are special materials that help a chemical reaction happen faster and more efficiently.

In this case, the Chinese team used something called a dual-atom catalyst (DAC). This differs from traditional catalysts that tend to use either single atom mateirals or nanoparticles.

More work needed

For the conversion of nitrate ot ammonia, the use of two complementary atoms is key for multi-step processes like this. This is because the atomic “tag team” better allows electron transfers, intermediate molecules, bond breaking, and bond forming.

Interestingly, the team also used artificial intelligence (AI) to help find the best atom pairs for the job. So, instead of running thousands of trial-and-error physical experiments, the AI helped them narrow down the best potentials to test, saving many hours of wasted time.

And this really paid off. According to the team, the catalyst is nearly three times more efficient than other similar catalysts. If true, that means it could produce much higher ammonia yields, conversion rates, and less waste.

That all translates to more bang for your buck while also dealing with a very serious industrial and agricultural pollutant. A breakthrough, no doubt, but it is important to note that this is still work in progress.

At present, the team has only managed to showcase the catalyst under laboratory conditions in small batches. It is yet to be proven if it can work in the “real world,” can be scaled, and if the process can handle varying contaminants beyond nitrate in feed waste waters.

You can view the study for yourself in the Journal of the American Chemical Society.