A latest study published in Engineering presents a novel approach to address the global issue of discarded face masks by converting them into high - value products such as carbon nanotubes (CNTs) and hydrogen. This research, led by a team of international scientists, not only offers a sustainable solution to the face - mask waste problem but also demonstrates significant economic and environmental benefits.

Since the outbreak of COVID - 19, face masks have become a daily necessity, leading to a massive amount of waste. Improper disposal of these masks poses ecological threats, including virus spread and microplastic pollution. Traditional treatment methods like high - temperature incineration and landfilling are costly and environmentally unfriendly.

The researchers proposed an economic - environmental hybrid pre - assessment method. This method, based on a coupling model, takes into account technical design, systemic economic factors, and life - cycle environmental analysis. By using process simulation software like Aspen Plus, key data for industrial - scale technologies were predicted, helping to overcome the challenge of lacking techno - economic data in the research and development stage.

In the catalyst selection process, the team compared two widely recognized catalysts: Fe/Al₂O₃ and FeNi/Al₂O₃, as well as two reaction methods: conventional heating and microwave - assisted heating. The results showed that the bimetal catalyst FeNi/Al₂O₃ exhibited higher catalytic activity and better stability. Specifically, the FeNi - MW (microwave - assisted catalysis with FeNi/Al₂O₃) had the highest catalytic activity for converting face masks into CNTs and hydrogen, with high yields of 38.49 wt% and 0.715 m³/kg respectively.

From an economic perspective, the study found that when the price of CNTs exceeds 1.49×10⁴ USD/t, microwave - assisted pyrolysis is the optimal choice due to its superior environmental performance and economic benefits. It can reduce the life - cycle greenhouse gas emissions, eutrophication potential, and human toxicity, while also increasing the system revenue.

On the other hand, conventional heating pyrolysis with the FeNi/Al₂O₃ catalyst may be more economical in some cases because of its good stability over 43 reaction regeneration cycles.

This innovative technology has multiple advantages. It aligns with the principles of a circular economy by effectively recycling waste. From an atomic economy perspective, it separates the C and H elements in face masks to produce high - value products without the need for additional methane or propylene as in conventional CVD methods for preparing CNTs.

The research not only provides a promising solution for the treatment of face - mask waste but also offers insights for the development of sustainable technologies for plastic waste management. As the market for CNTs grows and pyrolysis technology matures, this approach could play an increasingly important role in promoting environmental sustainability and economic development.

The paper “A Hybrid Pre-Assessment Assists in System Optimization to Convert Face Masks into Carbon Nanotubes and Hydrogen,” authored by Hewen Zhou, Sunwen Xia, Qing Yang, Huamei Zhong, Wang Lu, Ning Cai, Ondřej Mašek, Pietro Bartocci, Francesco Fantozzi, Chao Liu, Bo Miao, Qie Sun, Haiping Yang, Hanping Chen. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.11.016. For more information about the Engineering, follow us on X (https://twitter.com/EngineeringJrnl) & like us on Facebook (https://www.facebook.com/EngineeringJrnl).