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.

A comparative study on electrochemical performance of KOH activated carbons derived from different biomass sources - Musa acuminata stem, Pongamia pinnata seed oil extract cake, cajanus cajan stem and Asclepias syriaca floss

In the present scenario of research, the recycling of inexpensive widely available agricultural waste/biowaste to activate carbon (AC) and procurement of value-added product has significant impact on energy storage systems, particularly in Electrochemical double layer capacitors (EDLCs). Herein, we report the production of KOH activated carbons from different biomass sources such as Musa Acuminata stem (MAC), Pongamia pinnata seed oil extract cake (PPC), Cajanus Cajan stem (CCC) and Asclepias syriaca floss (ASC) for the said purpose. Initially, the biomass materials were pyrolyzed at 550 °C and then activated with KOH at 800 °C. All the carbon materials were characterized for their physico-chemical properties by various analytical techniques and compared. Further, these materials were studied for their electrochemical performance using suitable electro-analytical techniques in 1 M KOH solution. ACs (Activated carbons) derived from MAC, PPC, CCC & ASC were estimated in three electrode system and were found to exhibit a specific capacitance (Cs) of 358, 343, 355 & 540 F/g at a scan rate of 2 mV/s and 102, 188, 253 & 256 F/g at a current density of 2.5 A/g respectively. The main novel objective of this work is to correlate the morphological and surface properties of these ACs obtained from different biomass sources with electrochemical performance. A symmetric coin cell constructed with ASC material exhibited Cs of 67 F/g at a current density of 2.5 A/g with maximum energy & power densities (ED & PD) of 37.2 W h/kg and 19.9 kW/kg respectively. Further the cell showed 25,000 cycles stability with 86% Cs retention and 100% coulombic efficiency.