Cleaning oil spills with paper waste

Researchers from the National University of Singapore (NUS) have converted paper waste into green cellulose aerogels that are non-toxic, ultralight, flexible, strong and water repellent. The material is suitable for oil spill cleaning, heat insulation, packaging, drug delivery and more.

The leader of the team, Assistant Professor Duong Hai Minh, described aerogels as “one of the finest insulation materials available”. Traditional aerogels are made from silica, which is not environmentally friendly, so the NUS team set out to create the material from low-cost cellulose, which is made up of 75–85% of recycled paper.

“Our team developed a simple, cost-effective and fast method of converting paper waste into aerogels,” said Assistant Professor Duong.

“Our fabrication process uses 70% less energy, produces fewer polluting emissions into the air and water, as well as uses fewer dioxins in the chlorine bleaching process. It is also faster — the entire process only takes three days.”

The aerogels also have a super-high oil absorption capacity. Coated with Trimethoxy-methylsilane (MTMS), they 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. Furthermore, they can be squeezed to recover over 99% of the crude oil absorbed.

“Sorption has been considered one of the most effective ways to clean oil spills,” said Assistant Professor Duong. “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, which has a potential market size of US$143.5 billion.”

The aerogels could also serve as insulation materials for buildings, with their absorbency and water-repellent properties making them a suitable alternative to energy-guzzling air conditioners. According to Assistant Professor Duong, the aerogels are adaptable to both dry and rainy weather and their structure remains stable for about six months in a tropical climate.

“Being extremely strong, they increase building strength,” he continued. “In addition, these aerogels are lightweight and slim, resulting in slimmer walls, thus increasing building space.”

Other potential applications include:

• the packing industry, with plastic-based packing materials such as the bubble wrap to be replaced with biodegradable aerogel-based foam or nanosheets;
• hygiene, with the absorption capabilities of MTMS-uncoated aerogels suitable for products such as nappies and sanitary napkins; and
• the biomedical industry, with compressed cellulose aerogels able to plug life-threatening wounds such as gunshots.

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