Porous carbon tubes from recycling waste COVID-19 masks for optimization of 8 mol% Y2O3-doped tetragonal zirconia polycrystalline nanopowder

Disposable polypropylene medical masks are widely used to protect people from injury caused by COVID-19 worldwide. However, disposable medical masks are non-biodegradable materials, and the accumulation of waste masks can pollute the environment and waste resources without a reasonable recycling method. The aims of this study are to transform waste masks into carbon materials and to use them as a dispersant in preparing high-quality 8 mol% Y₂O₃-doped tetragonal zirconia nanopowders. The waste masks were carbonized to get a carbon source in the first step, then KOH was used to etch the carbon source creating a micropores structure in the carbon material after the carbon-bed heat treatment method. The resulting carbon material is a porous tube structure with a high specific surface area (1220.34 m²/g) and adsorption capacity. The as-obtained porous carbon tubes were applied as a dispersant to produce 8 mol% Y₂O₃-doped tetragonal zirconia nanopowders, and the resulting nanopowders owned well-dispersed and had the smallest particle size than that prepared by activated carbon as a dispersant. Besides, the sintered 8 mol% Y₂O₃-doped tetragonal zirconia ceramic possessed high density, which resulted in higher ionic conductivity. These findings suggest that waste face masks can be recycled to prepare high-added-value carbon materials and provide a green and low-cost method to reuse polypropylene waste materials.