Transforming waste polypropylene face masks into S-doped porous carbon as the cathode electrode for supercapacitors

Upcycling of waste disposable medical masks to high value-added gasoline fuel and surfactants products by sub/supercritical water degradation and partial oxidation

The amount of waste disposable medical masks (DMMs) and the potential environmental risk increased significantly due to the huge demand of disposable medical surgical masks. In this study, two effective and environmentally friendly processes, supercritical water degradation (SCWD) and subcritical water partial oxidation (SubCWPO), were proposed for the upcycling of DMMs. The optimal conditions for the SCWD process (conversion ratio>98 %) were 410 ℃, 15 min, and 1:5 g/mL. The oil products obtained from the SCWD process were mainly small molecule hydrocarbons (C7-C12) with a content of 86 % and could be recycled as fuel feedstock for gasoline. Alkyl radicals in the SCWD reaction formed double bonds and ring structures through hydrogen capture reactions, β-scission, and dehydrogenation reactions, and aromatic hydrocarbons were formed by olefin cyclization and cycloalkane dehydrogenation. The introduction of an oxidant (H2O2) to the reaction system could significantly reduce the reaction temperature and shorten the reaction time. At 350 ℃, 15 min, 1:20 g/mL, V(H2O2): V (H2O) of 1:1, the conversion ratio of the SubCWPO process was 88 %, which was higher than that of the SCWD process at 400 ℃ (71.49 %). Oil products produced from the SubCWPO process were rich in alcohols and esters, which could be used as raw materials for nonionic surfactant of polyol and fatty acid ester. The abundant hydroxyl radical in the SubCWPO system trapped hydrogen atoms on PP and reacted with the resulting alkyl radical to form alkanols, which was oxidized to form acids. The esterification of acids and alkanols formed high level of esters. The SCWD and SubCWPO processes proposed in this study are believed to be promising strategies for DMMs degradation and the recovery of high value-added hydrocarbons.

Screen-Printed Stretchable Supercapacitors Based on Tin Sulfide-Decorated Face-Mask-Derived Activated Carbon Electrodes with High Areal Energy Density

In this work, tin sulfide nanosheets decorated on face-mask-derived activated carbon have been explored as electrode material for electrochemical supercapacitors. A hydrothermal route was employed to grow tin sulfide on the surface and inside of high-surface-area face-mask-derived activated carbon, activated at 850 °C, to produce a hierarchical interconnected porous composite (ACFM-850/TS) structure. The presence of tin sulfide in the porous carbon framework exposed the surface active sites for rapid adsorption/desorption of electrolyte ions and ensured high utilization of the porous carbon surface. Furthermore, the porous ACFM-850 framework prevented the stacking/agglomeration of tin sulfide sheets, thereby enhancing the charge-transport kinetics in the composite electrodes. Benefiting from the synergistic effect of tin sulfide and ACFM-850, the resulting ACFM-850/TS composite exhibited an attractive specific capacitance of 423 F g-1 at a 0.5 A g-1 current density and superior rate capability (71.3% at a 30 A g-1 current density) in a 1.0 M Na2SO4 electrolyte. In addition, we fabricated a planar symmetric interdigitated supercapacitor on a stretchable Spandex fabric using an ACFM-850/TS composite electrode and carboxymethyl cellulose/NaClO4 as a solid-state gel electrolyte employing a scalable screen-printing process. The as-prepared stretchable supercapacitors displayed an ultrahigh energy density of 9.2 μWh cm-2 at a power density of 0.13 mW cm-2. In addition, they exhibited an excellent cyclic stability of 64% even after 10,000 charge-discharge cycles and 42% after 1000 continuous stretch (at 25% stretching)/release cycles. Such screen-printed interdigitated planar supercapacitors with activated carbon composite electrodes and a solid-state gel electrolyte act as promising low-cost energy-storage devices for wearable and flexible integrated electronic devices.

Scalable slot-die coated flexible supercapacitors from upcycled PET face shields

Upcycling Covid19 plastic waste into valuable carbonaceous materials for energy storage applications is a sustainable and green approach to minimize the burden of waste plastic on the environment. Herein, we developed a facile single step activation technique for producing activated carbon consisting of spherical flower like carbon nanosheets and amorphous porous flakes from used PET [poly(ethylene terephthalate)] face shields for supercapacitor applications. The as-obtained activated carbon exhibited a high specific surface area of 1571 m2 g-1 and pore volume of 1.64 cm3 g-1. The specific capacitance of these carbon nanostructure-coated stainless steel electrodes reached 228.2 F g-1 at 1 A g-1 current density with excellent charge transport features and good rate capability in 1 M Na2SO4 aqueous electrolyte. We explored the slot-die coating technique for large-area coatings of flexible high-performance activated carbon electrodes with special emphasis on optimizing binder concentration. Significant improvement in electrochemical performance was achieved for the electrodes with 15 wt% Nafion concentration. The flexible supercapacitors fabricated using these electrodes showed high energy and power density of 21.8 W h kg-1 and 20 600 W kg-1 respectively, and retained 96.2% of the initial capacitance after 10 000 cycles at 2 A g-1 current density. The present study provides a promising sustainable approach for upcycling PET plastic waste for large area printable supercapacitors.

Polymer Waste Valorization into Advanced Carbon Nanomaterials for Potential Energy and Environment Applications

The rise in universal population and accompanying demands have directed toward an exponential surge in the generation of polymeric waste. The estimate predicts that world-wide plastic production will rise to ≈590 million metric tons by 2050, whereas 5000 million more tires will be routinely abandoned by 2030. Handling this waste and its detrimental consequences on the Earth's ecosystem and human health presents a significant challenge. Converting the wastes into carbon-based functional materials viz. activated carbon, graphene, and nanotubes is considered the most scientific and adaptable method. Herein, this world provides an overview of the various sources of polymeric wastes, modes of build-up, impact on the environment, and management approaches. Update on advances and novel modifications made in methodologies for converting diverse types of polymeric wastes into carbon nanomaterials over the last 5 years are given. A remarkable focus is made to comprehend the applications of polymeric waste-derived carbon nanomaterials (PWDCNMs) in the CO2 capture, removal of heavy metal ions, supercapacitor-based energy storage and water splitting with an emphasis on the correlation between PWDCNMs' properties and their performances. This review offers insights into emerging developments in the upcycling of polymeric wastes and their applications in environment and energy.

Mechanical upcycling of single-use face mask waste into high-performance composites: An ecofriendly approach with cost-benefit analysis

The COVID-19 pandemic created an unprecedented demand for PPE, with single-use face masks emerging as a critical tool in containing virus transmission. However, the extensive use and improper disposal of these single-use face masks, predominantly composed of non-biodegradable plastics, has exacerbated environmental challenges. This research presents an innovative method for mechanically upcycling PPEs used in medical sectors i.e. single use face masks. The study investigates a facile approach for reclamation of infection-free and pure polypropylene (PP) plastic from discarded single use face masks (W-PP) and blends it with various vegetable oil percentages (5, 10 and 20 %), resulting in a versatile material suitable for various applications. Melt flow index, rheological behaviour, DSC and FTIR were employed to investigate the effect of vegetable oil/radical initiator through chemical grafting on W-PP properties. The results demonstrate significant enhancements in the tensile strength and modulus of W-PP when blended with vegetable oil and a radical initiator. There was a marked increase in tensile strength (33 %) and strain (55 %) compared to untreated W-PP, rendering W-PP both robust and flexible. Furthermore, we employed this upcycled W-PP in the fabrication of glass fibre-reinforced composites, resulting in notable enhancements in both tensile strength and impact resistance. The upcycled W-PP demonstrates excellent potential for various applications, such as sheet forming and 3D printing, where the non-brittleness of plastics plays a pivotal role in manufacturing high-quality products. The cost-benefit analysis of this approach underscores the potential of upcycling PPE waste as a sustainable solution to mitigate plastic pollution and conserve valuable resources. The applications of this upcycled material span a wide range of industries, including automotive composites, packaging, and 3D printing.

Study of Zinc Diffusion Based on S, N-Codoped Honeycomb Carbon Cathodes for High-Performance Zinc-Ion Capacitors

Capacitors with zinc ions, with excellent stabilities, low cost, and high energy density, are expected to be promising energy storage devices. However, the development of zinc-ion capacitors is quietly restricted by low specific capacity and cycling stability. Herein, to overcome these limitations, honeycomb-structured S, N-codoped carbon (SNPC) is constructed by one-pot calcination of waste corn bracts and thiourea. The honeycomb structure of SNPC is demonstrated to provide abundant active sites that can enhance the extron/ion transport, conductivity for high power export, and ion adsorption capacity in energy storage applications, leading to a higher electrochemical performance achieved. The electrolytes of zinc salt have also been studied. It reveals that the SNPC electrode presents the best electrochemical performance in a 2 M ZnSO4 and 0.5 M ZnCl2 electrolyte mixture because in the electrolyte mixture, Cl- can replace the existing bound water in the solvation structure to form an anion-type water-free solvation structure ZnCl42-. The SNPC-800 electrode with a highly improved surface area (∼909.0 m2 g-1) is proved to be more suitable as the electrode than other materials. Aqueous zinc-ion capacitors (ZICs) have been assembled by the honeycomb-structured SNPC-800 as the cathode, which can achieve a relatively wide working voltage range of 0.1-1.8 V. The SNPC-800 ZICs exhibit a superior specific capacity of 179.1 mA h g-1 at 0.1 A g-1. The energy density of SNPC-800 ZICs reaches an impressive value of 89.6 Wh kg-1 at 53.8 W kg-1, and it sustains 28.3 Wh kg-1 at 1997.6 W kg-1. In addition, there is 99.8% capacity retention in the SNPC-800 ZICs over 5000 cycles. The absorption energy in SPNC is much higher than that in undoped CPC, as confirmed by density functional theory, which reveals that introducing of heteroatoms (S, N) has a comparatively active advantage at increasing the Zn-ion storage capacity. This work proposes a practical strategy for the effective recycling of waste biomass materials into honeycomb carbon electrode materials. Moreover, the honeycomb carbon-based ZICs with excellent electrochemical performance and long-term cycling stability possess great potential to be a superior cathode in practical applications.

Facemasks: An insight into their abundance in wetlands, degradation, and potential ecotoxicity

Disposable facemasks represent a new form of environmental contamination worldwide. This study aimed at addressing the abundance of facemasks in an overlooked natural environment with high ecological and economic value - the wetlands (Ria de Aveiro, Portugal, as study case), evaluating their potential biodegradation using naturally occurring fungi and assessing the potential ecotoxicity of released microfibres on local bivalves. All masks collected within 6500 m2 area of Aveiro wetland were 100 % disposable ones (PP-based, confirmed by Fourier transform infrared spectroscopy - FTIR) with an initial abundance of 0.0023 items/m2 in Sept. 2021, which was reduced by ∼40 % in Apr. 2022 and ∼87 % in Sept. 2022, as a reflection of the government policies. Analysis of the carbonyl index (0.03 to 1.79) underlined their state of degradation, primarily due to sun exposure during low tides. In laboratory conditions, 1 mm2 microplastics obtained from new disposable facemasks were prone to biodegradation by Penicillium brevicompactum and Zalerion maritimum inferred from microplastics mass loss (∼22 to -26 % and ∼40 to 50 %, respectively) and FTIR spectra (particularly in the hydroxyl and carbonyl groups). In addition, microfibres released from facemasks induced sublethal effects on the clam, Venerupis corrugata, mostly in their UV-aged form when compared to pristine ones, characterised by a decrease in cellular energy allocation (CEA) and an increase in aerobic energy metabolism (ETS). Concomitantly, clams exposed to 1250 items/L of UV-aged microplastics (similar to field-reported concentrations) expressed greater clearance capacity, indicating a need to compensate for the potential energy unbalance. This study provides the first baseline monitoring of facemasks in wetlands while bringing new evidence on their biodegradation and ecotoxicity, considering environmentally relevant conditions and keystone organisms in such environments. Such studies require scientific attention for rapid regulatory action against this emerging and persistent pollutant, also targeting remediation and mitigation strategies considering these items under pandemic scenarios.

Upcycling of surgical facemasks into carbon based thin film electrode for supercapacitor technology

Polypropylene (PP), a commonly used plastic, is used for making the outer layers of a surgical face mask. In 2020, around 3 billion surgical face masks were disposed into the environment, causing a huge threat to wildlife, aquatic life, and ecosystems. In this work, we have reported the sulfonation technique for stabilizing the surgical face masks and their conversion into carbon nanoparticles for application as a supercapacitor electrode. The electrode is fabricated by preparing a slurry paste of carbon nanoparticles and pasting it on a conductive wearable fabric. To investigate the performance of the carbon thin film electrode, electrochemical techniques are employed. The Cyclic Voltammetry (CV) analysis performed at different scan rates in a 6 molar KOH electrolyte reveals that the carbon thin film acts as a positive electrode. At 4 A g^-1, the electrode shows a specific capacitance of 366.22 F g^-1 and 100% retention of specific capacitance for 8000 cycles. A two-electrode asymmetric device is fabricated using carbon thin film as the positive electrode, NiO thin film as the negative electrode, and a KOH separator between two electrodes. The device shows a specific capacitance of 113.73 F g^-1 at 1.3 A g^-1 and glows a red LED for 6 min. This work is a step towards upcycling the waste produced from surgical face masks used during the COVID-19 pandemic and its application for energy storage.

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.

Advanced and Smart Textiles during and after the COVID-19 Pandemic: Issues, Challenges, and Innovations

The COVID-19 pandemic has hugely affected the textile and apparel industry. Besides the negative impact due to supply chain disruptions, drop in demand, liquidity problems, and overstocking, this pandemic was found to be a window of opportunity since it accelerated the ongoing digitalization trends and the use of functional materials in the textile industry. This review paper covers the development of smart and advanced textiles that emerged as a response to the outbreak of SARS-CoV-2. We extensively cover the advancements in developing smart textiles that enable monitoring and sensing through electrospun nanofibers and nanogenerators. Additionally, we focus on improving medical textiles mainly through enhanced antiviral capabilities, which play a crucial role in pandemic prevention, protection, and control. We summarize the challenges that arise from personal protective equipment (PPE) disposal and finally give an overview of new smart textile-based products that emerged in the markets related to the control and spread reduction of SARS-CoV-2.

Current knowledge on the presence, biodegradation, and toxicity of discarded face masks in the environment

During the first year of the COVID-19 pandemic, facemasks became mandatory, with a great preference for disposable ones. However, the benefits of face masks for health safety are counteracted by the environmental burden related to their improper disposal. An unprecedented influx of disposable face masks entering the environment has been reported in the last two years of the pandemic, along with their implications in natural environments in terms of their biodegradability, released contaminants and ecotoxicological effects. This critical review addresses several aspects of the current literature regarding the (bio)degradation and (eco)toxicity of face masks related contaminants, identifying uncertainties and research needs that should be addressed in future studies. While it is indisputable that face mask contamination contributes to the already alarming plastic pollution, we are still far from determining its real environmental and ecotoxicological contribution to the issue. The paucity of studies on biodegradation and ecotoxicity of face masks and related contaminants, and the uncertainties and uncontrolled variables involved during experimental procedures, are compromising eventual comparison with conventional plastic debris. Studies on the abundance and composition of face mask-released contaminants (microplastics/fibres/ chemical compounds) under pre- and post-pandemic conditions should, therefore, be encouraged, along with (bio)degradation and ecotoxicity tests considering environmentally relevant settings. To achieve this, methodological strategies should be developed to overcome technical difficulties to quantify and characterise the smallest MPs and fibres, adsorbents, and leachates to increase the environmental relevancy of the experimental conditions.

Disposal and resource utilization of waste masks: a review

Waste masks pose a serious threat to the environment, including marine plastic pollution and soil pollution risks caused by landfills since the outbreak of COVID-19. Currently, numerous effective methods regarding disposal and resource utilization of waste masks have been reported, containing physical, thermochemical, and solvent-based technologies. As for physical technologies, the mechanical properties of the mask-based materials could be enhanced and the conductivity or antibacterial activity was endowed by adding natural fibers or inorganic nanoparticles. Regarding thermochemical technologies, catalytic pyrolysis could yield considerable hydrogen, which is an eco-friendly resource, and would mitigate the energy crisis. Noticeably, the solvent-based technology, as a more convenient and efficient method, was also considered in this paper. In this way, soaking the mask directly in a specific chemical reagent changes the original structure of polypropylene and obtains multi-functional materials. The solvent-based technology is promising in the future with the researches of sustainable and universally applicable reagents. This review could provide guidance for utilizing resources of waste masks and address the issues of plastic pollution.

Abundance and characterization of personal protective equipment (PPE) polluting Kish Island, Persian Gulf

Plastic pollution is one of the major environmental threats the world is facing nowadays, which was exacerbated during the COVID-19 pandemic. In particular, multiple reports of single-use plastics driven by the pandemic, namely personal protective equipment (PPE) (e.g., face masks and gloves), contaminating coastal areas have been published. However, most studies focused solely on counting and visually characterizing this type of litter. In the present study, we complement conventional reports by characterizing this type of litter through chemical-analytical techniques. Standardized sampling procedures were carried out in Kish Island, The Persian Gulf, resulting in an average density of 2.34 × 10-4 PPE/m2. Fourier transformed infrared spectroscopy confirmed the polymeric composition of weathered face masks and showed the occurrence of additional absorption bands associated with the photooxidation of the polymer backbone. On the other hand, the three layers of typical surgical face masks showed different non-woven structures, as well as signs of physical degradation (ruptures, cracks, rough surfaces), possibly leading to the release of microplastics. Furthermore, elemental mapping through energy-dispersive X-ray spectroscopy showed that the middle layer of the masks allocated more elements of external origin (e.g., Na, Cl, Ca, Mg) than the outer and inner layers. This is likely to the overall higher surface area of the middle layer. Furthermore, our evidence indicates that improperly disposed PPE is already having an impact on a number of organisms in the study area.

A review on production and application of activated carbon from discarded plastics in the context of 'waste treats waste'

In the post-COVID scenario, the annual increase in plastic waste has taken an upsurge due to the disposal of plastic masks, gloves and other protective equipment. To reduce the plastic load ending up in landfills and oceans or dumped at roadsides, the potential of using plastic polymers in different sectors has been investigated over the years leading to their potential application in pavement laying, concrete industry, fuel generation and production of carbon-based compounds among which activated carbons (AC) is a prime example. As one of the most recommended adsorbents for removing contaminants from water and adsorbing greenhouse gases, AC creates a potential sector for using discarded plastic to further treat pollutants and approach closer to a circular economy for plastics. This paper analyses the production process, the effect of production parameters on AC characteristics and properties that aid in adsorption. The interdependence of these factors determines the surface area, porosity, relative micropore and mesopore volume, thereby defining the utility for removing contaminant molecules of a particular size. Furthermore, this work discusses the application of AC along with a summary of the earlier works leading to the existing gaps in the research area. Production costs, formation of by-products including toxic substances and adsorbate selectivity are the major issues that have restricted the commercial application of this process towards its practical use. Research aimed at valorization of plastic waste into ACs would minimize the solid waste burden, along with treating other pollutants.

A review of disposable facemasks during the COVID-19 pandemic: A focus on microplastics release

The COVID-19 epidemic seriously threats the human society and provokes the panic of the public. Personal Protective Equipment (PPE) are widely utilized for frontline health workers to face the ongoing epidemic, especially disposable face masks (DFMs) to prevent airborne transmission of coronavirus. The overproduction and massive utilization of DFMs seriously challenge the management of plastic wastes. A huge amount of DFMs are discharged into environment, potentially induced the generation of microplastics (MPs) owing to physicochemical destruction. The MPs release will pose severe contamination burden on environment and human. In this review, environmental threats of DFMs regarding to DFMs fate in environment and DFMs threats to aquatic and terrestrial species were surveyed. A full summary of recent studies on MPs release from DFMs was provided. The knowledge of extraction and characterizations of MPs, the release behavior, and potential threats of MPs derived from DFMs was discussed. To confront the problem, feasible strategies for control DFMs pollution were analyzed from the perspective of source control and waste management. This review provides a better understanding the threats, fate, and management of DFMs linked to COVID-19 pandemic.

Polyaniline/Graphene-Functionalized Flexible Waste Mask Sensors for Ammonia and Volatile Sulfur Compound Monitoring

A flexible resistive-type polyaniline-based gas sensor was fabricated by simple dip-coating of graphene combined with in situ polymerization of aniline on a flexible waste mask substrate. The prepared polypropylene/graphene/polyaniline (PP/G/PANI) hybrid sensor demonstrated a fast response (114 s) and recovery time (23 s), ppb-level detection limit (100 ppb), high response value (250% toward 50 ppm NH₃, which is over four times greater than that of the pristine PANI sensor), acceptable flexibility, excellent selectivity, and long-term stability at room temperature. The morphological and structural properties of the composite sensor materials were characterized by scanning electron microscopy and energy-dispersive spectroscopy characterization, and the surface chemistry of the hybrid sensors was analyzed by Fourier transform infrared spectroscopy. The excellent sensing performance was mainly ascribed to the larger specific surface area and efficient conducting paths of the porous PP/G/PANI network. Moreover, the PP/G/PANI hybrid gas sensor exhibited excellent sensing capability on volatile sulfur compounds contained in human breath, indicating that the hybrid sensor can be applied to breath analysis and kidney disease diagnosis.

Research on the Anti-Risk Mechanism of Mask Green Supply Chain from the Perspective of Cooperation between Retailers, Suppliers, and Financial Institutions

Against the background of the pandemic, the mask supply chain faces the risk of pollution caused by discarded masks, the risk of insufficient funds of retailers, and the risk of mask overstock. To better guard against the above risks, this study constructed a two-party game model and a cusp catastrophe model from the perspective of the mask green supply chain, and studied the strategic choices of retailers and suppliers in the supply chain affected by the risk of capital constraints and overstock. The result shows that the risk shocks will lead to the disruption of the mask green supply chain, and the main factors affecting the strategy choice of mask suppliers and retailers are mask recycling rate, deposit ratio, risk occurrence time, etc. In further research, this study involved a mechanism for financial institutions, mask retailers, and the government to jointly deal with the risk of mask overstock, the risk of retailers' insufficient funds, and the risk of environmental pollution from discarded masks. The research path and conclusion of this study reveal the risks in the circulation area of mask supplies during the pandemic, and provide recommendations for planning for future crises and risk prevention.

Upcycling face mask wastes generated during COVID-19 into value-added engineering materials: A review

Billions of disposable face masks (i.e., single-use masks) are used and discarded worldwide monthly due to the COVID-19 outbreak. The immethodical disposal of these polymer-based wastes containing non-biodegradable constituents (e.g., polypropylene) has provoked marked and severe damage to the ecosystem. Meanwhile, their ever-growing usage significantly strains the present-day waste management measures such as landfilling and incineration, resulting in large quantities of used face-covering masks landing in the environment as importunate contaminants. Hence, alternative waste management strategies are crucially demanded to decrease the negative impacts of face mask contamination. In this venue, developing high-yield, effective, and green routes toward recycling or upcycling face mask wastes (FMWs) into value-added materials is of great importance. While existing recycling processes assist the traditional waste management, they typically end up in materials with downgraded physicochemical, structural, mechanical, and thermal characteristics with reduced values. Therefore, pursuing potential economic upcycling processes would be more beneficial than waste disposal and/or recycling processes. This paper reviews recent advances in the FMWs upcycling methods. In particular, we focus on producing value-added materials via various waste conversion methods, including carbonization (i.e., extreme pyrolysis), pyrolysis (i.e., rapid carbonization), catalytic conversion, chemical treatment, and mechanical reprocessing. Generally, the upcycling methods are promising, firming the vital role of managing FMWs' fate and shedding light on the road of state-of-the-art materials design and synthesis.

Analysis of Marine Microplastic Pollution of Disposable Masks under COVID-19 Epidemic-A DPSIR Framework

Marine microplastic pollution (MMP) is becoming one of the most pressing environmental problems facing humanity today. The novel coronavirus epidemic has raised the issue of environmental contamination caused by large-scale improper disposal of medical waste such as disposable masks (DMs). To assess the impact of MMP caused by DMs and to seek solutions for the prevention and control of MMP, this study uses the Driving force-Pressure-State-Impact-Response (DPSIR) framework to establish a causal chain of MMP caused by DMs. The conclusion shows that the novel coronavirus epidemic has led to a surge in the use of DMs, which has brought pressure on resource constraints and environmental pollution at the same time. Improperly DMs enter the environment and eventually transform into MMP, which not only endangers the marine ecological system but also poses potential human health risks as well as economic and social hazards. In addition, further research on environmentally friendly masks (cloth masks and biodegradable masks) is essential to mitigate the environmental damage caused by the large-scale global use of DMs. This study provides a scientific and theoretical basis for the assessment of MMP from discarded DMs, and the findings of this study will provide a reference for the formulation of relevant policies.

Synthesis of Sulfonated Carbon from Discarded Masks for Effective Production of 5-Hydroxymethylfurfural

5-hydroxymethylfurfural (HMF), as one of the top ten important platform chemicals, can be used to produce 2,5-furandicarboxylic acid (FDCA), 2,5-dimethyl furan (DMF), levulinic acid, and other chemicals. An environmentally friendly system for the synthesis of sulfonated carbon materials from discarded masks has been proposed. A series of mask-based solid acid catalysts (bMC-SO3H) were prepared by a simple two-step process. Mechanochemical pretreatment (ball milling) of waste mask and sulfonated group precursor, followed by thermal carbonization under nitrogen gas, were used to synthesize sulfonated porous carbon. The total acid amount of the prepared bMC-SO3H was measured by the Boehm method, which exhibited 1.2–5.3 mmol/g. The addition of the sulfonated group precursor in the mechanochemical treatment (ball milling) process caused intense structure fragmentation of the discarded masks. These sulfonated porous carbons (bMC(600)-SO3H) as solid acid catalysts achieved fructose conversion of 100% and HMF yield of 82.1% after 120 min at 95 °C in 1-butyl-3-methylimidazolium chloride. The bMC-SO3H could be reused five times, during which both the HMF yield and fructose conversion were stable. This work provides a strategy for the synthesis of sulfonated carbon from discarded masks and efficient catalyzed fructose upgrading to HMF.

Recent advances and challenges in recycling and reusing biomedical materials

Medical waste has increased in the past 3 years as a result of the coronavirus disease 2019 (COVID-19) pandemic. This condition is expected to exacerbate due to the growing healthcare markets and aging population, posing health threats to the public via environmental footprints. To alleviate these impacts, there is an urgent need for medical waste management. This article highlights the drawbacks of current disposal methods and the potential of medical waste reuse and recycling, emphasizing the processes, materials, and chemistry involved in each practice. Further discussion is provided on the chemical and mechanical recycling of plastics as the dominating material in biomedical applications, and possible strategies and challenges in recycling and reusing biomedical materials are explored in this review.

Advances of Biowaste-Derived Porous Carbon and Carbon–Manganese Dioxide Composite in Supercapacitors: A Review

One of the global problems is environmental pollution by different biowaste. To solve the problem, biowaste must be recycled. Waste-free technology is also a way of saving exhaustible raw materials. Research on electrochemical energy sources is currently the most dynamically developing area of off-grid energy. Electrochemical capacitors can operate for a long time without changing performance, they have smaller dimensions, high mechanical strength, and a wide operating temperature range. These properties are effective energy-saving devices. Therefore, supercapacitors are widely used in various industries. This review discussed the methods of obtaining and the characteristics of biowaste-derived activated carbon and carbon–manganese oxide (AC-MnO2)-based supercapacitor electrodes.

Agro-residual biomass and disposable protective face mask: a merger for converting waste to plastic-fiber fuel via an integrative carbonization-pelletization framework

Incineration and landfilling offer possibilities for addressing high-rate management of COVID-waste streams. However, they can be costly and environmentally unsustainable. In addition, they do not allow to convert them to fuels and chemicals as waste-to-energy and waste-to-product technologies. Therefore, we analyzed whether integrating hydrothermal carbonization (HTC) and pelletization can allow converting the surgical face mask (SFM) and biomass to composite plastic-fiber fuel (CPFF). We blended the plastic material and corncob, peanut shell, or sugarcane bagasse at the proportion of 50:50 (%, dry mass basis) for HTC. We performed the thermal pretreatment of blends in an autoclaving reactor at 180 °C and 1.5 MPa. Then we pelletized the hydrochars in a presser machine at 200 MPa and 125 °C. By analyzing the evidence from our study, we recognized the viability of combining the SFM and agricultural residues for CPFF from comparable technical features of our products to standards for premium-grade wood pellets. For instance, the elemental composition of their low-meltable ash was not stoichiometrically sufficient to severely produce slagging and fouling in the equipment for thermal conversion. Although they contained synthetic polymers in their structures, such as polyethylene from filter layers and nylon from the earloop, they emitted CO and NOx below the critical limits of 200 and 500 mg m-3, respectively, for occupational safety. Therefore, we extended the knowledge on waste-to-energy pathways to transform SFM into high-quality hybrid fuel by carbonization and pelletization. Our framework can provide stakeholders opportunities to address plastic and biogenic waste in the context of a circular economy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-022-03285-4.

Waste-based nanoarchitectonics with face masks as valuable starting material for high-performance supercapacitors

Surgical face masks waste is a source of microplastics (polymer fibres) and inorganic and organic compounds potentially hazardous for aquatic organisms during degradation in water. The monthly use of face masks in the world is about 129 billion for 7.8 billion people. Therefore, in this contribution the utilization of hazardous surgical face masks waste for fabrication of carbon-based electrode materials via KOH-activation and carbonization was investigated. The micro-mesoporous materials were obtained with specific surface areas in the range of 460 - 969 m²/g and a total pore volume of 0.311 - 0.635 cm³/g. The optimal sample showed superior electrochemical performance as an electrode material in supercapacitor in the three-electrode system, attaining 651.1F/g at 0.1 Ag^-1 and outstanding capacitance retention of 98 % after a test cycle involving 50'000 cycles. It should be emphasized that capacitance retention is one of the most crucial requirements for materials used as the electrodes in the supercapacitor devices. In this strategy, potentially contaminated face masks, common pandemic waste, is recycled into highly valuable carbon material which can serve in practical applications overcoming the global energy crisis. What is more, all microorganisms, including coronaviruses that may be on/in the masks, are completely inactivated during KOH-activation and carbonization.

Conversion of Plastic Waste to Carbon-Based Compounds and Application in Energy Storage Devices

At present, plastic waste accumulation has been observed as one of the most alarming environmental challenges, affecting all forms of life, economy, and natural ecosystems, worldwide. The overproduction of plastic materials is mainly due to human population explosion as well as extraordinary proliferation in the global economy accompanied by global productivity. Under this threat, the development of benign and green alternative solutions instead of traditional disposal methods such as conversion of plastic waste materials into cherished carbonaceous nanomaterials such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), graphene, activated carbon, and porous carbon is of utmost importance. This critical review thoroughly summarizes the different types of daily used plastics, their types, properties, ways of accumulation and their effect on the environment and human health, treatment of waste materials, conversion of waste materials into carbon-based compounds through different synthetic schemes, and their utilization in energy storage devices particularly in supercapacitors, as well as future perspectives. The main purpose of this review is to help the targeted audience to design their futuristic study in this desired field by providing information about the work done in the past few years.

Carbon Nanotube prepared by catalytic pyrolysis as the electrode for supercapacitors from polypropylene wasted face masks

The massive global consumption and discarded face masks drove by the ongoing spread of COVID-19. Meantime, incineration and landfill discarded face masks would result in severe environmental pollution and infectious hazards. Herein a suggestion to recycle polypropylene waste masks into CNTs by an environmentally friendly and high-added value disposal process was proposed, and which was prepared as supercapacitor electrode materials for energy storage attempting. The CNTs were prepared from waste masks by catalysis pyrolysis with Ni-Fe bimetallic catalysts. Especially, the bamboo-like structure CNT was obtained with Ni/Fe molar ratio is 3. This structure owned a high specific capacitance compared to other standard CNTs. Its specific capacitance could reach 56.04 F/g (1 A/g) and has excellent cycling stability with a capacitance retention rate of the material is 85.41% after 10,000 cycles. Besides, the assembled capacitor possesses a good energy density of 4.78 Wh/kg at a power density of 900 W/kg. Thus, this work provides a sustainable and cost-effective strategy for disposing waste masks into high-valuable CNT, and their potential application for supercapacitors was also studied and exploited. It would provide a new idea for recycling and utilizing other polypropylene wastes such as medical devices.

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Porous carbon materials derived from discarded COVID-19 masks via microwave solvothermal method for lithium‑sulfur batteries

With the spread of COVID-19, disposable medical masks (DMMs) have become a significant source of new hazardous solid waste. Their proper disposal is not only beneficial to the safety of biological systems but also useful to achieve considerable economic value. The first step of this study was to investigate the chemical composition of DMMs. It is primarily composed of polypropylene, polyethylene terephthalate and iron, with fibrous polypropylene accounting for approximately 80% of the total weight. Then, DMMs were sulfonated and oxidised by the microwave-driven concentrated sulfuric acid within 8 min based on the fact that the concentrated sulfuric acid exhibits a good microwave absorption capacity. The co-doping of sulfur and oxygen was achieved while improving the thermal stability of DMMs. Subsequently, the self-activation pyrolysis of sulfonated and oxidised DMMs (P-SO@DMMs) was further realized in low-flow-rate argon. The specific surface area of P-SO@DMMs increased from 2.0 to 830.9 m²·g^-1. P-SO@DMMs sulfur cathodes have promising electrochemical properties because of their porous structures and the synergistic effect of sulfur and oxygen co-doping. The capacity of the samples irradiated by microwave for 10 min at 0.1, 0.2, 0.5, 1, 2 and 5 C were 1313.6, 1010.9, 816.5, 634.4, 513.4 and 453.1 mAh·g^-1, respectively, and after returning to 0.2 C and continuing the cycle for 50 revolutions, maintained 50.5% of the initial capacity. After 400 cycles, its capacity is 38.1% of the initial capacity at 0.5 C. It is slightly higher than the electrochemical performance of the sample treated by microwave for 8 min and significantly higher than the sample treated by 6 min. This work converts structurally complex, biohazardous DMMs into porous carbon with high specific surface area by clean and efficient microwave solvothermal and self-activating pyrolysis, which facilitates the development of carbon based materials at low cost and large scale.

Multifunctional Carbon Fibers from Chemical Upcycling of Mask Waste

Over the past years, disposable masks have been produced in unprecedented amounts due to the COVID-19 pandemic. Their increased use imposes significant strain on current waste management practices including landfilling and incineration. This results in large volumes of discarded masks entering the environment as pollutants, and alternative methods of waste management are required to mitigate the negative effects of mask pollution. While current recycling methods can supplement conventional waste management, the necessary processes result in a product with downgraded material properties and a loss of value. This work introduces a simple method to upcycle mask waste into multifunctional carbon fibers through simple steps of thermal stabilization and pyrolysis. The pre-existed fibrous structure of polypropylene masks can be directly converted into carbonaceous structures with high degrees of carbon yield, that are inherently sulfur-doped, and porous in nature. The mask-derived carbon product demonstrates potential use in multiple applications such as for Joule heating, oil adsorption, and the removal of organic pollutants from aqueous environments. We believe that this process can provide a useful alternative to conventional waste management by converting mask waste generated during the COVID-19 pandemic into a product with enhanced value.

Assessing face masks in the environment by means of the DPSIR framework

The use of face masks outside the health care facility dates back a century ago. However, face masks use noticeably soared due to the COVID-19 (Coronavirus disease 2019) pandemic. As a result, an unprecedented influx of discarded face masks is ending up in the environment. This review paper delves into face masks in the environment using the DPSIR (driving forces, pressures, states, impacts, and responses) framework to simplify and communicate the environmental indicators. Firstly, the historical, and briefly the economic trajectory of face masks are discussed. Secondly, the main driving forces of face masks use with an emphasis on public health are explored. Then, the pressures exerted by efforts to fulfill the human needs (driving forces) are investigated. In turn, the state of the environment due to the influx of masks along with the impacts are examined. Furthermore, the upstream, and downstream societal responses to mitigate the environmental damages of the driving forces, pressures, states, and impacts are reviewed. In summary, it has been shown from this review that the COVID-19 pandemic has been causing a surge in face mask usage, which translates to face masks pollution in both terrestrial and aquatic environments. This implies proper usage and disposal of face masks is paramount to the quality of human health and the environment, respectively. Moreover, further research on eco-friendly face masks is indispensable to mitigating the environmental damages occurring due to the mass use of surgical masks worldwide.

Face Mask Wastes as Cementitious Materials: A Possible Solution to a Big Concern

After more than two years wearing surgical masks due to the COVID-19 pandemic, used masks have become a significant risk for ecosystems, as they are producing wastes in huge amounts. They are a potential source of disturbance by themselves and as microplastic contamination in the water system. As 5500 tons of face masks are estimated to be used each year, there is an urgent need to manage them according to the circular economy principles and avoid their inadequate disposal. In this paper, surgical wear masks (WM), without any further pretreatment, have been introduced as addition to mortars up to 5% in the weight of cement. Mechanical and microstructural characterization have been carried out. The results indicate that adding MW to the cement supposes a decrease in the properties of the material, concerning both strength and durability behavior. However, even adding a 5% of WM in weight of cement, the aspect of the mortars is quite good, the flexural strength is not significantly affected, and the strength and durability parameters are maintained at levels that-even lower than the reference-are quite reasonable for use. Provided that the worldwide production of cement is around 4.1 Bt/year, the introduction of a 5% of WM in less than 1% of the cement produced, would make it possible to get rid of the mask waste being produced.

Synergistic effects of B/S co-doped spongy-like hierarchically porous carbon for a high performance zinc-ion hybrid capacitor

Zinc-ion hybrid capacitors (ZIHCs) are regarded as a potential candidate for large-scale energy storage devices. However, the inadequate cathode and the inferior wettability between the electrode and electrolyte hinder the construction of high-performance ZIHCs. Herein, boron (B) and sulfur (S) co-doped spongy-like hierarchically porous carbon (B₂S₃C) is first proposed as a cathode material for ZIHCs. Here, B doping is favorable for improving the wettability, while S doping contributes to enhancing the electrical properties. In addition, the density functional theory (DFT) results uncover that B and S atoms contribute to reducing the energy barrier between Zn²⁺ and the cathode, leading to boosted chemical adsorption ability of Zn²⁺ on the cathode. As a result, the assembled ZIHC based on B₂S₃C exhibits a high specific capacity of 182.6 mA h g^-1 at 0.1 A g^-1, an excellent capacity retention of 96.2% after 10 000 cycles and a remarkable energy density of 292.2 W h kg^-1 at a power density of 62.2 W kg^-1, superior to the previously reported ZIHCs. Due to the flexibility of the assembled electrodes, the solid-state ZIHC can sustain various deformations. This work paves a feasible path for the development of cost-effective and high-performance porous carbon materials.

Waste Face Surgical Mask Transformation into Crude Oil and Nanostructured Electrocatalysts for Fuel Cells and Electrolyzers

A novel route for the valorization of waste into valuable products was developed. Surgical masks commonly used for COVID 19 protection by stopping aerosol and droplets have been widely used, and their disposal is critical and often not properly pursued. This work intended to transform surgical masks into platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) as well as into crude oil. Surgical masks were subjected to controlled-temperature and -atmosphere pyrolysis, and the produced char was then converted into electrocatalysts by functionalizing it with metal phthalocyanine of interest. The electrocatalytic performance characterization towards ORR and HER was carried out highlighting promising activity. At different temperatures, condensable oil fractions were acquired and thoroughly analyzed. Transformation of waste surgical masks into electrocatalysts and crude oil can open new routes for the conversion of waste into valuable products within the core of the circular economy.

Face mask waste generation and management during the COVID-19 pandemic: An overview and the Peruvian case

The ongoing COVID-19 pandemic has driven massive consumption of personal protective equipment (PPE) worldwide. Single-use face masks are one of the most used PPE to prevent the transmission of the virus. However, mismanagement of such materials threatens the environment with a new form of plastic pollution. Researchers argue that it is necessary to develop and implement innovative ways to manage and recycle PPE in order to reduce their impacts on the environment. In the present work, we have reviewed and discussed the recent development of sustainable face mask alternatives and recycling and repurposing routes under the COVID-19 pandemic context. Moreover, we have conducted estimations of the daily face mask waste generation in Peru, a developing country struggling with a poor solid waste management framework and infrastructure. Unlike previous studies, our equation incorporates the “economically active population” variable in order to provide more precise estimations, while evaluating single-use and reusable scenarios. The scenarios of incorporating reusable face masks significantly reduced the amount of solid waste generated in Peru. In situ evidence shows that face masks are polluting the streets and beaches of Peru, probably driven by mismanagement and poor environmental awareness.

Review of the valorization options for the proper disposal of face masks during the COVID-19 pandemic

The COVID-19 pandemic has affected not only human health and economies but also the environment due to the large volume of waste in the form of discarded personal protective equipment. The remarkable increase in the global usage of face masks, which mainly contain polypropylene, and improper waste management have led to a serious environmental challenge called microplastic pollution. Potential practices for waste management related to waste valorization of discarded face masks as the major type of waste during the COVID-19 pandemic are explored in this study. Recommendations based on governmental practices, situation of state facilities, and societal awareness and engagement applicable to emergency (including COVID-19 pandemic) and postpandemic scenarios are offered while considering potential solutions and available waste management practices in different countries during emergency conditions. However, multicriteria decision making for a country must determine the optimal solution for waste management on the basis of all affecting factors. Awareness of scientific, governments, and communities worldwide will successfully eradicate this important environmental issue.

Personal protective equipment (PPE) pollution driven by the COVID-19 pandemic in Cox's Bazar, the longest natural beach in the world

The extensive use of personal protective equipment (PPE) driven by the COVID-19 pandemic has become an important contributor to marine plastic pollution. However, there are very few studies quantifying and characterizing this type of pollution in coastal areas. In the present study, we monitored the occurrence of PPE (face masks, bouffant caps, and gloves) discarded in 13 sites along Cox's Bazar beach, the longest naturally occurring beach in the world. The vast majority of the items were face masks (97.9%), and the mean PPE density across sites was 6.29 × 10^-3 PPE m^-2. The presence of illegal dumping sites was the main source of PPE, which was mainly located on touristic/recreational beaches. Fishing activity contributed to PPE pollution at a lower level. Poor solid waste management practices in Cox's Bazar demonstrated to be a major driver of PPE pollution. The potential solutions and sustainable alternatives were discussed.