Water contamination, particularly from chemicals used in modern technology, is a growing global concern. A recent study by the U.S. Centers for Disease Control revealed that a staggering 98 percent of tested individuals had detectable levels of PFAS, also known as “forever chemicals,” in their bloodstream. These long-lasting compounds are found in a wide array of products, from cosmetics and food packaging to firefighting foams and non-stick cookware.
Addressing this contamination is a costly endeavor. The U.S. Environmental Protection Agency estimates an annual cost of $1.5 billion for PFAS remediation alone, aiming to meet new regulations that limit these compounds to less than 7 parts per trillion in drinking water.
In a promising development, researchers at MIT have created a new filtration material that could provide a sustainable and effective solution. This innovation, detailed in the journal ACS Nano, utilizes natural silk and cellulose to remove a broad spectrum of persistent chemicals and heavy metals from water.
“Contamination by PFAS and similar compounds is a very big deal, and current solutions may only partially resolve this problem efficiently or economically,” says Yilin Zhang, an MIT postdoc and lead author of the study. “That’s why we came up with this protein and cellulose-based, fully natural solution.”
The project originated unexpectedly, explains Benedetto Marelli, professor of civil and environmental engineering at MIT. His team had developed a method for processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” for a completely different purpose—a labeling system to combat counterfeit seeds. Zhang, however, saw the potential for water filtration.
Initial attempts using only silk nanofibrils proved ineffective. The team then incorporated cellulose, an abundant material derived from agricultural wood pulp waste. Through a self-assembly process, cellulose nanocrystals were introduced as “seeds” into a water suspension of silk fibroin protein. This prompted the silk molecules to align along the seeds, creating a hybrid material with enhanced properties.
By integrating cellulose into the silk-based fibrils and fine-tuning the electrical charge of the cellulose, the researchers produced a membrane highly effective at removing contaminants in laboratory tests. The material significantly outperformed standard filtration materials like activated carbon, extracting orders of magnitude more contaminants from water.
The material’s unique composition also provides strong antimicrobial properties, a significant advantage as bacterial and fungal fouling is a major cause of filter failure. While the research demonstrates a proof of concept, the team acknowledges the need for further development, particularly in terms of durability and sourcing materials for large-scale production.
“Most of the normal materials available today are focusing on one class of contaminants or solving single problems,” Zhang says. “I think we are among the first to address all of these simultaneously.”
This innovative approach, utilizing readily available natural materials to combat pollution, has garnered praise from experts. Hannes Schniepp, professor of applied science at the College of William and Mary, who was not involved in the research, remarked, “If this can be mass-produced in an economically viable way, this could really have a major impact.”
The potential impact of this new filtration material is significant. Initially envisioned for point-of-use applications, such as faucet attachments, the technology could eventually be scaled up for municipal water supplies, offering a promising solution to the growing challenge of water contamination.
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