Chemical recycling of green poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based air filters through hydrolysis

Abstract

Sustainable alternatives based on biodegradable polymers, such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), can potentially reduce the environmental impact generated by the massive disposal of face masks. However, the destination of this biodegradable material in post-consumer landfills or composting consumes energy and does not necessarily reduce environmental damage. Therefore, it is necessary to find ways to return this material to the chemical chain, such as chemical recycling through hydrolysis. In this context, the present work aimed to produce face masks by solution blow spinning (SBS) from solutions containing 4, 6, and 8 m/v% of PHBV and assess the polymer recyclability through hydrolysis. The filters were subjected to hydrolytic reactions in aqueous solutions with pH values of 4, 7, and 10 at 40, 60, and 80 °C for three weeks based on a standard statistical design of experiments (DoE). The fibers produced with solutions containing 4 m/v% of polymer provided the highest weight loss of 68 wt% after three weeks immersed in an aqueous solution (pH = 4 at 80 °C), exhibiting the lowest environmental impact during the chemical recycling process. The ANOVA analyses showed that the fiber diameter was the most significant factor during the recycling reactions, evidencing that materials should be designed to promote the principles of the circular economy. Based on the obtained results, it can be concluded that PHBV-based face mask filters can promote the principles of the circular economy if polymer fibers are correctly designed. Finally, they can also potentially reduce the environmental damage of face mask disposal as long as the recycling process is in place with a proper collection and sorting system.