Upcycling discarded cellulosic surgical masks into catalytically active freestanding materials

Abstract

The COVID-19 pandemic outbreak has resulted in the massive fabrication of disposable surgical masks. As the accumulation of discarded face masks represents a booming threat to the environment, here we propose a solution to reuse and upcycle surgical masks according to one of the cornerstones of the circular economy. Specifically, the non-woven cellulosic layer of the masks is used as an environmentally sustainable and highly porous solid support for the controlled deposition of catalytically active metal-oxide nanoparticles. The native cellulosic fibers from the surgical masks are decorated by titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles following a simple and scalable approach. The abundant surface –OH groups of cellulose enable the controlled deposition of metal-oxide nanoparticles that are photocatalytically active or shown enzyme-mimetic activities. Importantly, the hydrophilic highly porous character of the cellulosic non-woven offers higher accessibility of the pollutant to the catalytically active surfaces and high retention in its interior. As a result, good catalytic activities with long-term stability and reusability are achieved. Additionally, developed free-standing hybrids avoid undesired media contamination effects originating from the release of nanoscale particles. The upcycling of discarded cellulosic materials, such as the ones of masks, into high-added-value catalytic materials, results an efficient approach to lessen the waste´s hazards of plastics while enhancing their functionality. Interestingly, this procedure can be extended to the upcycling of other systems (cellulosic or not), opening the path to greener manufacturing approaches of catalytic materials. Graphical abstract A novel approach to upcycle discarded cellulosic surgical masks is proposed, providing a solution to reduce the undesired accumulation of discarded face masks originating from the COVID-19 pandemic. The non-woven cellulosic layer formed by fibers is used as solid support for the controlled deposition of catalytically active titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles. Cellulosic porous materials are proven useful for the photocatalytic decomposition of organic dyes, while their peroxidase-like activity opens the door to advanced applications such as electrochemical sensors. The upcycling of cellulose nonwoven fabrics into value-added catalytic materials lessens the waste´s hazards of discarded materials while enhancing their functionality.

Disposal and resource utilization of waste masks: a review

“…The –OH groups also provide strong, sustainable, and recyclable support for the deposition of metal/metal oxide nanoparticles (Mousli et al 2020 ; Tang et al 2020 ). The inner layer of the mask was immersed in the precursor solution containing TiO 2 , CoO x , and Fe x O y catalytic nanoparticles (Reguera et al 2022 ). Then, the nanoparticles were embedded in the three-dimensional porous structure of the cellulose membrane successfully to attain catalytic activity.…”

Designing Highly Photoactive Hybrid Aerogels for In-Flow Photocatalytic Contaminant Removal Using Silica-Coated Bacterial Nanocellulose Supports

“…Due to their excellent mechanical properties, stability, and water permeability, nanocellulose-based materials are particularly interesting candidates as support materials for obtaining porous nanostructured membranes and free-standing materials for catalytic and water purification applications. − BC is obtained through a biosynthetic process by bacteria from the genus Komagataeibacter xylinus (considered Gram-negative, strictly aerobic, and non-photosynthetic), which converts glucose, glycerol, and other organic substrates into cellulose within a few days. , Even though BC has the same chemical structure as its plant-derived equivalents, it exhibits a non-woven, highly hydrophilic, fibrous, and three-dimensional network with no secondary biomass components, such as lignin and hemicellulose . BC is composed of thin and tangled nanofibers (5–100 nm diameters) and exhibits a large surface area (98 m 2 /g), high crystallinity (60–80%), good transparency (>80% T in UV–visible region), adequate mechanical stability, and reasonable flexibility (Young’s modulus = 15 GPa, tensile strength 200–300 MPa, elongation = 1.5–2%) and a high density of hydroxyl groups on its surface (allowing its surface functionalization and anchoring of reactive nanomaterials and thus promoting a superior interaction with the anchored inorganic nanostructures , ).…”

Study on the use of waste polypropylene-based mask in crude oil as viscosity reducer

“…The degradation conditions of polypropylene materials are harsh, requiring high temperatures or strong ultraviolet rays [4]. They are very stable under natural conditions and can exist for a long time in the environment [5,6]. Currently, the main disposal measure for waste masks is incineration, which can cause a large amount of resource waste and emit a large amount of air pollutants such as carbon dioxide.…”