Waste Surgical Masks as Precursors of Activated Carbon: A Circular Economy Approach to Mitigate the Impact of Microplastics and Emerging Dye Contaminants

The COVID-19 pandemic has caused a surge in the use of disposable surgical masks, primarily composed of polypropylene (>86% carbon), whose improper disposal contributes to persistent microplastic pollution. In alignment with circular economy principles, this study explores the valorization of surgical masks into carbonaceous adsorbent materials (ACMs) for dye removal from water. The masks were chemically treated with concentrated H2SO4 at 85 °C for 2 h and subsequently activated with air (400 °C), CO2, or steam (800 °C, 1 h). The resulting ACMs were characterized by SEM, FT-IR, nitrogen adsorption at -196 °C, and pH of the aqueous carbon suspension (pHSus, 1.96-9.25). CO2 and steam activation yielded the highest surface areas (525 and 632 m2·g-1, respectively). FT-IR confirmed the introduction of sulfonic groups, enhancing dye interactions. Adsorption tests using methylene blue (MB), methyl orange (MO), and orange G (OG) in ultrapure and river water showed removal efficiencies up to 100% for MB with ACM-WV and ~94% with ACM. All dyes followed pseudo-second-order kinetics. These findings demonstrate that surgical mask waste can be effectively transformed into high-value adsorbents for water treatment applications.