Calcium carbonate hydrogel can be moulded, hardened and recycled – just add water

Scientists in Germany and China may have found a solution to the burgeoning problem of plastic pollution and recycling. The team has made a mouldable hydrogel that adopts a transparent, rigid shape when dried and can be recycled after immersing it in water.

© Wiley-VCH

Common plastics, such as polyethylene terephthalate (PET), have revolutionised food storage and transport. But they have had a lasting environmental impact, with industries struggling to recycle the growing mounds of plastics at landfill sites and found washed up along coastlines.

Research groups have developed novel ways to recycle such waste, be it with bacteria or converting it into cigarette filters, but on a relatively small scale.

Shengtong Sun from the University of Konstanz and his colleagues have taken a different approach and attempted to design a new class of recyclable plastics. Made from amorphous calcium carbonate nanoparticles cross-linked with poly(acrylic acid), the team’s ‘mineral plastic’ can be shaped and stretched like dough.

Once the gel is freeze-dried, it adopts a rigid and transparent shape. The team found the plastic returns to its original gel form if it is soaked in water for a day, making it easier to recycle or dispose of.