Around 200 to 300 billion disposable gloves are manufactured worldwide every year – a large proportion of them made from nitrile rubber, as used in clinics and laboratories. After a single use, most of these gloves end up in trash or incineration, releasing additional CO2 – another factor in emissions reports of more than 37 billion tons of CO2 emitted worldwide.

Researchers want to break this cycle. Instead of treating the gloves as pure waste, they chemically modify the material so that it can absorb carbon dioxide. The converted plastic will later filter CO2 from industrial exhaust gases. A new filter material could be created from a typical disposable item.

Disposable gloves become CO2 filters

The process was developed by researchers at Aarhus University in Denmark. The study appeared in the specialist journal Chem. Study leader Troels Skrydstrup and lead author Simon Stampe Kildahl speak of a clear “proof of concept” for tackling the global problem of difficult-to-recycle NBR and SBS rubbers.

These two types of rubber are produced in large quantities worldwide. Nitrile rubber is found in disposable gloves, seals or hoses. Of this, around 0.8 million tons are produced per year. A second variant, often used in shoe soles, produces around 1.8 million tonnes annually. Both materials are considered difficult to recycle.

Chemical conversion in the laboratory

The scientists chemically change the rubber. Specifically, they convert certain chemical groups in the polymer into so-called amines using a catalyst. These amines can bind CO2 – similar to the substances that are already used in industrial capture plants today.

The result is a solid, non-porous substance that absorbs CO2 through a reversible chemical reaction. When the material is heated, it releases the bound carbon dioxide. This principle is called temperature change adsorption. It allows CO2 to be specifically filtered out of a gas stream and then passed on in concentrated form.

The team achieved impressive results in the laboratory. “The amine materials derived from rubber show excellent and rapid CO2 absorption of up to an average of 3.05 millimoles per gram at 90 degrees Celsius,” the study says. In other words: Under optimal conditions, one gram of the material can bind more than three millimoles of CO2 – a value that is within the range of modern solid adsorbers.

Why 90 degrees is crucial

The temperature is particularly relevant. Many coal-fired power plants and industrial plants cool their exhaust gases to around 90 degrees Celsius before they are further processed or cleaned. This is where the new material showed its strongest performance.

With a CO2 content of ten percent – typical for exhaust gases – the converted rubber absorbed 1.68 millimoles per gram. Even with short contact times of just 15 minutes, it still achieved values ​​between 0.50 and 1.25 millimoles per gram.

For comparison: An established reference material that has been tested in industry achieves higher capacities at 20 degrees under ideal conditions. However, at 90 degrees it becomes significantly less efficient. The new rubber material closes a gap – it works particularly well where many real exhaust gas flows are anyway.

In addition, there is a high level of selectivity: nitrogen, which makes up the majority of exhaust gases, was practically not absorbed. For transport in pipelines or geological storage, a CO2 purity of more than 95 percent is usually a requirement.

Stable over many cycles

For practical use, durability is what counts most. The researchers tested the material in 40 consecutive loading and unloading cycles. CO2 was repeatedly absorbed and released through heating. The loss of performance was only between two and seven percent.

The material also withstood thermal stress well. At 150 degrees below CO2 or under a neutral gas, it retained around 95 percent of its original capacity. Only in air did the performance drop significantly, as oxygen oxidizes the amine groups and thus attacks them.

These results indicate a robust basic structure – a prerequisite for the process to be able to hold its own not only in the laboratory, but also in continuous industrial operation.

The magnitude of the problem

The approach touches on one of the biggest climate policy challenges of all: the… to limit global warming to 1.5 to 2 degrees, According to the Intergovernmental Panel on Climate Change, billions of additional tons of CO2 will have to be captured or actively removed every year by 2050.

Currently the worldwide CO2 capture at around 50 million tons per year. That is only a fraction of what would be necessary. At the same time, millions of tons of rubber products that are difficult to recycle are produced every year. If even parts of these waste streams were converted into filter material, an additional source of raw materials could be created.

However, the authors themselves emphasize that this would require production quantities on a million-ton scale. Conventional filter materials are usually based on fossil raw materials. An approach that uses existing polymer waste would at least shift the starting point.

Still a long way to go to practice

Despite the convincing laboratory values, the gap to industrial application remains large. The chemical conversion is currently carried out using special metal catalysts, including those based on ruthenium. These are expensive and must be further developed or replaced for large-scale use.

In addition, all experiments so far have been carried out on a small scale. Questions about cost-effectiveness, continuous production and integration into existing systems remain unanswered.