A research team from the National University of Singapore’s (NUS) Faculty of Engineering has achieved a world’s first by successfully converting 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 cleaning up oil spills, heat insulation and packaging, and it can also potentially be used as coating materials for drug delivery and as smart materials for various biomedical applications. This pioneering work was achieved by a team led by Hai Minh Duong, an assistant professor in the Department of Mechanical Engineering.

“Aerogels, which are among the lightest solid materials known to man, are one of the finest insulation materials available,” says Duong. “Traditional aerogels are mainly made of silica, which is not environmentally-friendly. In contrast, cellulose is low cost and makes up 75% to 85% of recycled paper. 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. We are very excited about the potential applications of this new material.”

The global production of paper is expected to increase to 500 million tonnes by 2020. The large amount of paper-related waste generated annually is difficult to dispose of, and so recycling or converting this waste into useful products offers a sustainable way of dealing with it. Furthermore, the technique that Duong and his team have developed for converting paper waste into aerogels is eco-friendly.

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

The novel cellulose aerogels developed by the NUS team boast super high oil absorption capacity. When coated with trimethoxymethylsilane (MTMS), the aerogels are water repellent and are capable of absorbing oil (excluding water) to 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 absorbed crude oil.

“Oil spills are serious disasters that threaten marine ecosystems,” explains Duong. “Sorption has been considered one of the most effective ways to clean oil spills. 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.”

"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 Minh Duong, NUS

Another potential application for the novel cellulose aerogels is as an insulation material for buildings. “As a heat insulation material, our novel cellulose aerogels offer a few added advantages,” says Duong. “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. Being extremely strong, they increase building strength. In addition, these aerogels are lightweight and slim, resulting in slimmer walls, thus increasing building space.”

In addition, the cellulose aerogels could prove of use to the packaging industry, where they could replace plastic-based packing materials such as bubble wrap. With its high surface area and high porosity, the biodegradable aerogel could also be used as a coating material in drug delivery or as a smart material. In its uncoated state, the cellulose aerogel is hydrophilic and so can also absorb and retain huge volumes of polar fluids such as water and alcohol. This means it could be used in products such as baby diapers and sanitary napkins.

What is more, compressed cellulose aerogels could be used to plug life-threatening wounds such as gunshot or stabbing wounds by injecting them into the wound cavity. The sponges expand inside the cavity, creating pressure that can block bleeding and life-threatening hemorrhage in 20 seconds or less.

The NUS team has even discovered a way to enhance the weight capacity of the cellulose aerogels by infusing the fibers with a solution of metallic nanoparticles. The cellulose aerogels are then hammered flat to remove most of the air, resulting in a magnetic thin film that has a weight capacity of over 28 tonnes per cm2.

The team has filed patents for their invention in the US, China, India and Southeast Asia. Meanwhile, the NUS Industry Liaison Office has already licensed the technology to Bronxculture, which intends to manufacture the cellulose aerogels for use as insulating materials for packaging boxes, insulating layers for winter garments and oil-absorption materials.

This story is adapted from material from NUS, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.