Paper waste turned into green cellulose aerogel

SINGAPORE: In a world first, scientists have successfully converted paper waste into green cellulose aerogels that are non-toxic, ultralight, flexible, extremely strong and water repellent.

This novel material is ideal for applications such as oil spill cleaning, heat insulation as well as packaging, and it can potentially be used as coating materials for drug delivery and as smart materials for various biomedical applications, researchers said.

"Aerogels, which are among the lightest solid materials known to man, are one of the finest insulation materials available. Traditional aerogels are mainly made of silica, which is not environmentally-friendly," said Duong Hai from National University of Singapore ( NUS).

"Our team developed a simple, cost-effective and fast method of converting paper waste into aerogels. In addition to low thermal conductivity, these novel aerogels have several unique features, one of which is super high oil absorption capacity - it is up to four times higher than commercial sorbents available in the market," Hai said.

Researchers also developed a more eco-friendly process to convert paper waste into aerogels.

"Our fabrication process uses 70 per cent less energy, produces fewer polluting emissions into the air and water, as well as uses less dioxins in the chlorine bleaching process. It is also faster - the entire process only takes three days," said Hai.

The novel cellulose aerogels has super high oil absorption capacity. Coated with Trimethoxy-methylsilane (MTMS), the aerogels are water repellent and are capable of absorbing oil (excluding water) up to 90 times their dry weight, making them up to four times more effective than commercial oil sorbents, researchers said.

They can be squeezed to recover over 99 per cent of the crude oil absorbed.

"Oil spills are serious disasters that threaten marine ecosystems. Sorption has been considered one of the most effective ways to clean oil spills," said Hai.

"Polypropylene (PP)-based absorbents are widely used for oil absorption but they are non-biodegradable, and their absorption capabilities are both low and slow. Our novel cellulose aerogels therefore serve as an attractive alternative to current methods of oil spill cleaning," Hai added.

Another application of the aerogels is to serve as insulation materials for buildings. Their water repellent property allows them to be adaptable to both dry and rainy weather and their structure remains stable for about six months in tropical climate, researchers said.

The aerogels could also signal a change in the packing industry. Plastic-based packing materials such as the bubble wrap could be replaced with biodegradable aerogel-based foam or advanced cellulose aerogel nanosheets, which are environmentally-friendly, researchers said.

With high surface area and high porosity, the biodegradable aerogels could also be used as coating materials in drug delivery or as smart materials.