Nanoscale technologies for macroscale mining

Prior to this, I’d never written an article on nanotechnologies or nanoscience. So, before attempting to understand its potential applications in mining, it seemed sensible to first clarify what ‘nanotechnology’ is…

The European Commission offers a helpful explanation… “nanotechnology is the term given to areas of science and engineering where phenomena that take place at dimensions in the nanometre scale are utilised in the design, characterisation, production and application of materials, structures, devices and systems,” it states.

“Although in the natural world there are many examples of structures that exist at the nanoscale, it has only been in the last quarter of a century that it has been possible to actively and intentionally modify molecules and structures within this size range.”

While still nascent in the context of mining, nanotechnology is starting to gain traction, particularly in the mineral processing space. For example, in May, Sixth Wave Innovations announced an agreement to test its IXOS purification and extraction polymer on gold-bearing tailings samples from the Barry-Hollinger mine in Ontario, Canada.

And, in April, Canadian start-up, Litus, launched LiNC. The patent-pending lithium extraction solution based on a nanoscale composite material was initially developed at the University of Calgary in Alberta, Canada.

The power of nanobubbles

In late 2020, I came across a company called Moleaer (which means ‘tiny air’ in Latin) while researching a feature on copper processing. The company produces nanobubbles and is working to commercialise them in the mining space.

“Interesting,” I thought. I made a note to circle back round to them and learn more when the time was right.

That time is now. And, luckily for me, Brad Hice, Moleaer’s Director of Business Development, was open to a chat.

“From a definition perspective, I would consider nanotechnology anything that is completed at the atomic or nanoscale from an industrial process or chemical perspective,” he told me.

Moleaer was founded in the US in 2016 by Warren Russell and Bruce Scholten. Both have a background in water, wastewater and environmental services, and their initial mission was to apply nanobubbles to improve gas transfer efficiency in food production and water treatment applications.

That remit has now grown to incorporate other natural resources, including metal production.

“When we talk about nanotechnologies, a lot of people jump to the more common applications, like pharmaceutical delivery, inside of the human body. That can be done using nanobubbles,” Hice explained.

“In electronics, OLEDs [organic light-emitting diodes] are another example. They’re a nano polymer film applied to televisions and microchips.

“At Moleaer, with the bubbles that we create, we tend to think of them like nanoparticles, and they behave more like a particle than they do a bubble. Our focus has historically been on agriculture and water-treatment applications, specifically around the delivery of gas and hydroxyl radical formation for oxidation.

“In mining, these hydrophobic bubbles can be used to deliver oxygen into heap leaching, and they could also be applied in flotation as well. We’re optimistic that there are going to be more applications in the natural resource space too.”

Why mining? Why now?

Hice is right, nanotechnologies are more commonly associated with other industries, ones that are considered (although, in some cases, I’d argue this point) more technologically advanced.

“Why has it taken so long for them to be applied in mining processes?” I asked.

“I think that’s because, when you look at mining in general, it’s something that’s done on a very large scale, from blasting and hauling to processing,” Hice replied. “You have to move through a lot of material to extract the elements that you’re seeking. It’s just perceived at a very large scale and so it’s taken time for nanotechnologies to come to the fore.

“Where I do think nanotechnology offers benefit – whether that’s something like a nanobubble or even a biological concept – is in a more specific extraction of the ore that a mining company is targeting.

“Even though you’re doing it on a very large scale, that chemical or biological reaction is being completed at the nanoscale. So, there’s plenty of opportunity for nanotechnology to help push mining processes forward and improve efficiencies.”

Process efficiencies are music to many miners’ ears right now, as the industry stands at a crossroads between traditional, perhaps less resourceful (pun intended), ways of operating and future higher metal demand which comes with a large ESG tag attached.

“Much like in oil extraction or other natural resources, the easy stuff’s already been found, and now we’re facing the challenge of working with orebodies with more challenging compositions or that are harder to access than they have been historically,” said Hice. “Trying to find ways to be more efficient so that there’s less waste and recovery is as high as possible is really a hot topic right now.”

Gas and liquid agnostic

Today, Moleaer has over 1,000 systems deployed globally across a variety of industries.

As mentioned earlier, its nanobubbles behave more like particles than like regular bubbles when in solution. They are neutrally buoyant so don’t rise to the surface, and their tiny size means that it’s possible to create a much higher surface area with a certain volume of gas distributed over the same volume of solution.

“Between those two characteristics, we can create a very high gas transfer efficiency,” Hice explained. “The bubbles also tend to carry a negative charge which can be beneficial in certain applications, like flotation, because it helps prevent coalescing.

“Every day we’re learning new ways that these bubbles behave and how they can be leveraged to create value in a variety of industries.”

While Moleaer’s nanobubbles are tiny in size, the technology used to generate them is not. The patented bubble generators use a moving liquid stream into which a compressed gas is injected to create nano-scale cavities filled with gas.

“We are forming nanobubbles through a flow-based method,” Hice told me. “There are a number of ways that nanobubbles can be created, cavitation is a common one, but, from our perspective, the approach that we’ve developed is the most consistent and scalable, in terms of creating a high quantity of nanobubbles per given volume of liquid.”

Moleaer has tried filling them with a number of gases from to nitrogen to carbon dioxide.

“As long as the gas is compressible and we can achieve the pressures that our system requires from a gas perspective, then in theory, we can put that gas into the solution. We consider our system both gas and liquid agnostic,” said Hice.

“That said, the vast majority of our applications are water-based, and most require oxygen.”

Investigating new possibilities

Much of Moleaer’s work in mining thus far has been exploratory, investigating the potential for adding oxygen into processes to drive a chemical reaction like leaching. Whether it’s gold, silver, copper or uranium, oxygen is a necessary part of extracting many critical metals.

“What we’re trying to understand is – if we deploy oxygen via nanobubbles, not only are we delivering a dissolved gas, but can we keep oxygen in nanobubble form and allow that to carry further into the heaps to accelerate the leaching process and create a more efficient extraction over time?” said Hice.

“We’re also interested in froth flotation. That’s not something we’ve investigated yet, but there is literature from certain academic journals that suggests that small bubbles may be of benefit, in terms of mineral separation, in a froth flotation application.

“We’re still learning a lot about why nanobubbles create the benefit that they do, compared to conventional techniques.”

“Applying bubbles that don’t float in flotation… that is quite different from conventional techniques!” I said.

“Yes, there’s a lot to study,” said Hice. “In terms of whether the charge of the bubbles could allow them to behave more like a chemistry that conglomerates material, or whether there’s some sort of particle-liquid interface change that takes place. That’s something we will continue to work on.”

Driving efficiency in age old processes

I feel like we’ve been here before: historic mining industry meets new technological concept… we all know how the story often ends – with inertia.

However, the beauty of nanobubbles, and nanotechnologies in general, is that they don’t require mines to reinvent significant parts of their flowsheets or operations. They can be incorporated into existing processes to enhance their performance which means lower CAPEX and, potentially, faster payback times.

And, while the barrier to entry is still incredibly high for the commercial acceptance of new technologies, mining companies are beginning to open their minds and talk about potential new ways of operating.

That, in itself, is an important start.

“As the world moves through its high-quality ores and we start getting into more mineralogically complex deposits, nanotechnology creates an opportunity, and not just nanobubbles, but even on the biological side, in helping to improve process efficiencies,” said Hice.

“It will allow mining companies to extract more than they have historically from a given quantity of ore and improve the rate of extraction so that they can move through that ore faster.

“From both a timeliness and an efficiency perspective, those are the two ways that nanotechnology can help improve, at least on the extraction side, mining operations in the future.”

Waste management and tailings reprocessing to isolate specific minerals… In-situ mining… There are plenty more interesting potential applications.

But I’ll save those stories for another day!