Breakthrough: Bio-based foam absorbs 99% of microplastics

According to estimates, about 4.6 billion metric tons of non-degradable plastics pollute our environment, including primary plankton and the entire food chain. Human brains have already been found to be contaminated with microplastics and its enclosed 400 chemical additives.

Chinese researchers report to have deleoped a new biopolymer-based, reusable and biodegradable foam which absorbs four highly abundant microplastics in water with an efficiency of 98 to 99.9% in its first use. Over five cycles, its performance averaged between 95 and 98%, demonstrating its utility as a cost-effective removal tool for one of the world’s most pervasive human-made pollutants.

To assess the foam’s performance in water that already contains bacteria and other pollutants, scientists used the foam in samples from lake water, coastal water, agricultural irrigation water, and still water. Removing microplastics from water is important, as these particles pose significant risks to human and environmental health.

“Microplastics entering terrestrial and aquatic habitats are anticipated to continuously increase for thousands of years due to the alarming volumes of plastic waste in the environment,” first author Yang Wu and colleagues say. They offer a new solution: a sustainable, fibrous, microplastics-absorbing foam made of chitin from squid bone and cellulose from cotton (Ct-Cel). Cellulose and chitin are two of the most abundant polysaccharides in nature that have been widely used for pollutant elimination from wastewater due to their low cost, biocompatibility, and sustainability. To design the foam, the researchers used exfoliated β-chitin nanofiber sheets with protonated amines (Ct, from squid bone) and suspended cellulose fibers (Cel, from cotton), resulting in a pure biomass fibrous. The obtained Ct-Cel exhibited a highly porous interconnected structure, rough and positively charged surfaces, and numerous active sites (-OH, -NH3+, and -NHCO-), which assured multilevel interactions for rapid and efficient microplastic removal.

This biopolymer foam easily self-assembles into a porous structure with positively and negatively charged surfaces, enabling it to attract and interact with diverse microplastics. In preliminary tests, the foam absorbed extremely small nanometer-scale particles of polystyrene, polypropylene, polymethyl methacrylate, and polyethylene terephthalate. These plastics are ubiquitous in electronics, food packaging, textiles, and many others industrial products. Wu et al. evaluated the foam’s performance using samples from four real-world water sources to see if the foam would work in waters with microorganisms, toxic metals, chemical dyes, or other pollutants. The foam absorbed nearly 100% of microplastics in its first cycles. In fact, the presence of positively charged lead ions enhanced the foam’s performance. When averaged across 5 cycles, the foam showed a removal efficiency of 95.1% to 98.1%, demonstrating its reusability.

“The raw materials required for our functionalised foam, including chitin and cellulose, are simple to acquire and not expensive, and the instruments needed such as lyophilizer and mechanical stirrer are also common. We have demonstrated the capabilities of small-scale production in the paper. About 1 m² foam can be produced every week in our lab. We hope that a pilot production will be performed in 2025, and if the desired results are achieved, we will conduct a large-scale production in the company,” commented Prof. Hongbing Deng