Carbon capture with fast forming magnesite

Materials World magazine
,
24 Sep 2018

Speeding up the production of magnesite capable of capturing CO2 from the atmosphere may one day slow down global warming. Idha Valeur reports.

Magnesite is known to naturally store large quantities of CO2 at room temperature. Unfortunately, it also requires around 11,000 years to form. However, a Trent University Ontario, Canada, research team believes accelerating the production of magnesite at room temperature – in comparison with at high temperature – will potentially be a more affordable and quicker solution to combating climate change.

The efficacy of the mineral has been established – a tonne of naturally occurring magnesite can store approximately half a tonne of CO2 from the atmosphere. But the mineral was found to build-up extremely slowly. In the arid playas of northern British Columbia, Canada, the process of magnesium and carbonate ions held in groundwater eventually reacting to form magnesite began as far back as 11,000 years ago.

Research was carried out by Paul Kenward, Greg Dipple, and Mati Raudsepp at The University of British Columbia, Canada, led by Ian Power, Professor of Environmental Geoscience from Trent University. Power told Materials World, ‘Magnesite forms very slowly at Earth’s surface, but can be sped up at higher temperatures. However, higher temperatures generally mean higher costs and energy input and so there’s great value in studying CO2 mineralisation at Earth surface conditions.’

Much of the delay is because of the water, which acts as a shell around the magnesium ions, delaying its ability to bond with the carbonate ions. However, the team found that the use of tiny polystyrene microspheres coated in carboxyl, a negatively charged molecule, can pull water molecules away from the magnesium.

Power told Materials World, ‘The polystyrene microspheres have a reactive surface with a high density of carboxyl groups that target the rate-limitation in the formation of magnesite.’ The research showed that using polystyrene microspheres as the catalyst dramatically sped up the process, with magnesite able to form within 72 days.

The production process will not change the microspheres themselves, making them reusable.

Process for the future

‘Our work shows two things. Firstly, we have explained how and how fast magnesite forms naturally. This is a process which takes hundreds of thousands of years in nature at Earth’s surface. The second thing we have done is to demonstrate a pathway which speeds this process up dramatically,’ Power explained.

However, the team is still far from readying magnesite to support Paris Agreement time frames, having so far only produced one microgram. Power stated that the study was carried out at the laboratory stage and that it was impossible at this point to speculate on what it would require for the process to be developed to an industrial scale. ‘I am a strong believer that we as a society need to be developing a range of technologies, each with their advantages and disadvantages,’ he said.

‘For now,’ he concluded, ‘we recognise that this is an experimental process, and will need to be scaled up before we can be sure that magnesite can be used in carbon sequestration. This depends on several variables, including the price of carbon and the refinement of the sequestration technology, but we now know that science makes it doable.’