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

Preparation of acid-modified waste mask-based activated carbon grafted chitosan composites and their efficient removal of uranyl ions

Resource utilization of waste masks is of great significance for environmental protection. In this study, acid-modified waste mask-based activated carbon grafted chitosan composites (CSMA) were prepared using waste masks as a carbon source, chemically modified by introducing sulphonic acid groups through sulfuric acid treatment and further loaded with chitosan, and used for the efficient removal of U(VI) from aqueous solutions. Various characterization techniques, including SEM, FTIR, BET, and XPS, were utilized to investigate the microstructure and surface chemistry of CSMA. The experimental data indicate that optimal adsorption efficiency for CSMA about U(VI) is achieved at a pH of 7, utilizing an adsorbent dosage(m/V) of 0.1 g·L-1, a reaction duration of 6 h, and a temperature of 303 K. Under these conditions, the maximum adsorption capacity reaches 467.93 mg/g. From the kinetic and thermodynamic results of adsorption, it can be seen that the process of CSMA adsorption on uranyl ions was more in line with the Langmuir isotherm model and pseudo-second-order model. Thermodynamic analysis further confirms that this adsorption process is spontaneous and endothermic. In complex aqueous environments containing various co-existing ions, CSMA demonstrates good selective adsorption capabilities. After several testing cycles, CSMA still maintains a high adsorption efficiency for U(VI). Mechanistic studies using XPS/FTIR suggested that U(VI) capture was governed by coordination/chelation with surface functional groups (-NH2, -OH, -SO3H). This study not only presents an innovative approach for resource utilization from discarded masks but also offers an efficient and cost-effective solution for removing radioactive nuclides and facilitating environmental remediation.

Laser flash pyrolysis of face mask waste to vinylidene-terminated PP wax and further functionalized as compatibilizer

During the COVID-19 pandemic, face masks, as personal protective equipment (PPE) against the coronavirus (SARS-CoV-2), have been widely used worldwide. How to properly dispose of used PPE has brought a huge challenge to the ecosystem and human health. Here we proposed a laser flash pyrolysis (LFP) strategy to upcycle the used polypropylene(PP) face mask to vinylidene-terminated PP wax (PP-VDT) and further functionalized for compatibilizer application. Carbon black (0.2 wt%) was mixed with masks as a light absorbent to improve photothermal conversion efficiency. An infrared laser was adopted as the thermal source to quickly depolymerize the used PP face mask within just several milliseconds. The pyrolysis fragments quickly vaporized out to form PP-VDT with high selectivity (average terminal vinylidene per molecular chain was up to 1.55). The PP-VDT appeared as white solid particles which were clean and high purity. In addition, PP-VDT as polymer precursors could be further functionalized by thiol-ene chemistry to hydroxyl-terminated PP (PP-OH) and isocyanate-terminated PP (PP-HMDI), which could be used as compatibilizer in PLA/PP blends to decrease the size of the dispersed PP phase and to improve tensile strength. Therefore, this LFP technique was an effective upcycling method for PP face masks to obtain value-added products.

Environmental impact of disposable face masks: degradation, wear, and cement mortar incorporation

Polypropylene (PP) disposable face masks (DFMs) are essential for limiting airborne infectious diseases. This study examines the behavior of DFMs under three scenarios: (i) exposure to the natural environment, (ii) simulated high-energy aquatic environments through an abrasion test, and (iii) incorporation into cement-based mortars. In the natural weathering experiment, after 117 days, the DFMs exhibited photodegradation, resulting in chemical alterations in carbonyl and hydroxyl groups. This degradation led to the breakdown of the polymer and the release of microplastics and nanoplastics. Controlled abrasion tests, conducted in a Denver ball with water, sand, and ceramic balls for 2 h, confirmed that water is a critical factor for fiber release from DFMs. These tests resulted in the release of 0.26 g of PP fibers from 20 DFMs (weighing 62 g in total) with a diameter of 20 µm. Weathering and abrasion tests indicated rapid release and degradation of microplastics and nanoplastics, underscoring the importance of pursuing actions like reuse. Ecotoxicological tests revealed that leachates from the DFM-incorporated mortars showed no adverse effects on Daphnia magna or Selenastrum capricornutum, unlike the reference mortar, which caused substantial toxicity to Daphnia magna. Incorporating PP fibers from DFMs into cement-based mortars showed promising potential, as indicated by favorable ecotoxicity and chemical leaching test results.

Management of COVID-19 healthcare waste based on the circular economy hierarchy: A critical review

The overall objective of this work was to conduct a critical literature review on the application of the circular economy (CE) hierarchy for the management of COVID-19 healthcare waste (HCW). To describe the problem created by COVID-19 HCW, first, the subsystems of the overall management system, including generation, segregation, classification, storage, collection, transport, treatment and disposal, were reviewed and briefly described. Then, the CE hierarchy using the 10R typology was adapted to the management of COVID-19 HCW and included the strategies Refuse, Reduce, Resell/Reuse, Repair, Reprocess, Refurbish, Remanufacture, Repurpose, Recycle and Recover (energy). Disposal was added as a sink of residues from the CE strategies. Using the detailed 10R CE hierarchy for COVID-19 HCW management is the novelty of this review. It was concluded that R-strategy selection depends on its position in the CE hierarchy and medical item criticality and value. Indicative HCW components, which can be managed by each R-strategy, were compiled, but creating value by recovering infectious downgraded materials contaminated with body fluids and tissues is not currently possible. Therefore, after applying the circular solutions, the end of pipe treatment and disposal would be necessary to close material cycles at the end of their life cycles. Addressing the risks, knowledge gaps and policy recommendations of this article may help to combat COVID-19 and future pandemics without creating environmental crises.

Virus adsorbent systems based on Amazon holocellulose and nanomaterials

The environment preservation has been an important motivation to find alternative, functional, and biodegradable materials to replace polluting petrochemicals. The production of nonbiodegradable face masks increased the concentration of microplastics in the environment, highlighting the need for sustainable alternatives, such as the use of local by-products to create efficient and eco-friendly filtering materials. Furthermore, the use of smart materials can reduce the risk of contagion and virus transmission, especially in the face of possible mutations. The development of novel materials is necessary to ensure less risk of contagion and virus transmission, as well as to preserve the environment. Taking these factors into account, 16 systems were developed with different combinations of precursor materials (holocellulose, polyaniline [ES-PANI], graphene oxide [GO], silver nanoparticles [AgNPs], and activated carbon [AC]). Adsorption tests of the spike protein showed that the systems containing GO and AC were the most efficient in the adsorption process. Similarly, plate tests conducted using the VSV-IN strain cultured in HepG2 cells showed that the system containing all phases showed the greatest reduction in viral titer method. In agreement, the biocompatibility tests showed that the compounds extracted from the systems showed low cytotoxicity or no significant cytotoxic effect in human fibroblasts. As a result, the adsorption tests of the spike protein, viral titration, and biocompatibility tests showed that systems labeled as I and J were the most efficient. In this context, the present research has significantly contributed to the technological development of antiviral systems, with improved properties and increased adsorption efficiency, reducing the viral titer and contributing efficiently to public health. In this way, these alternative materials could be employed in sensors and devices for filtering and sanitization, thus assisting in mitigating the transmission of viruses and bacteria. RESEARCH HIGHLIGHTS: Sixteen virus adsorbent systems were developed with different combinations of precursor materials (holocellulose, polyaniline (ES-PANI), graphene oxide (GO), silver nanoparticles (AgNPs), and activated carbon (AC)). The system that included all of the nanocomposites holocellulose, PANI, GO, AgNPs, and AC showed the greatest reduction in viral titration. The biocompatibility tests revealed that all systems caused only mild or moderate cytotoxicity toward human fibroblasts.

From wastewater to clean water: Recent advances on the removal of metronidazole, ciprofloxacin, and sulfamethoxazole antibiotics from water through adsorption and advanced oxidation processes (AOPs)

Antibiotics released into water sources pose significant risks to both human health and the environment. This comprehensive review meticulously examines the ecotoxicological impacts of three prevalent antibiotics-ciprofloxacin, metronidazole, and sulfamethoxazole-on the ecosystems. Within this framework, our primary focus revolves around the key remediation technologies: adsorption and advanced oxidation processes (AOPs). In this context, an array of adsorbents is explored, spanning diverse classes such as biomass-derived biosorbents, graphene-based adsorbents, MXene-based adsorbents, silica gels, carbon nanotubes, carbon-based adsorbents, metal-organic frameworks (MOFs), carbon nanofibers, biochar, metal oxides, and nanocomposites. On the flip side, the review meticulously examines the main AOPs widely employed in water treatment. This includes a thorough analysis of ozonation (O3), the photo-Fenton process, UV/hydrogen peroxide (UV/H2O2), TiO2 photocatalysis, ozone/UV (O3/UV), radiation-induced AOPs, and sonolysis. Furthermore, the review provides in-depth insights into equilibrium isotherm and kinetic models as well as prospects and challenges inherent in these cutting-edge processes. By doing so, this review aims to empower readers with a profound understanding, enabling them to determine research gaps and pioneer innovative treatment methodologies for water contaminated with antibiotics.

Masks and respirators for prevention of respiratory infections: a state of the science review

SUMMARYThis narrative review and meta-analysis summarizes a broad evidence base on the benefits-and also the practicalities, disbenefits, harms and personal, sociocultural and environmental impacts-of masks and masking. Our synthesis of evidence from over 100 published reviews and selected primary studies, including re-analyzing contested meta-analyses of key clinical trials, produced seven key findings. First, there is strong and consistent evidence for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory pathogens. Second, masks are, if correctly and consistently worn, effective in reducing transmission of respiratory diseases and show a dose-response effect. Third, respirators are significantly more effective than medical or cloth masks. Fourth, mask mandates are, overall, effective in reducing community transmission of respiratory pathogens. Fifth, masks are important sociocultural symbols; non-adherence to masking is sometimes linked to political and ideological beliefs and to widely circulated mis- or disinformation. Sixth, while there is much evidence that masks are not generally harmful to the general population, masking may be relatively contraindicated in individuals with certain medical conditions, who may require exemption. Furthermore, certain groups (notably D/deaf people) are disadvantaged when others are masked. Finally, there are risks to the environment from single-use masks and respirators. We propose an agenda for future research, including improved characterization of the situations in which masking should be recommended or mandated; attention to comfort and acceptability; generalized and disability-focused communication support in settings where masks are worn; and development and testing of novel materials and designs for improved filtration, breathability, and environmental impact.

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.

Towards environmentally sustainable management: A review on the generation, degradation, and recycling of polypropylene face mask waste

There has been a considerable increase in the use of face masks in the past years. Managing face mask waste has become a global concern, as the current waste management system is insufficient to deal with such a large quantity of solid waste. The drastic increase in quantity, along with the material's inability to degrade plastic components such as polypropylene, has led to a large accumulation of plastic waste, causing a series of environmental and ecological challenges. In addition, the growing use also imposes pressure on waste management methods such as landfill and incineration, raising concerns about high energy consumption, low value-added utilization, and the release of additional pollutants during the process. This article initially reviews the impact of mask-related plastic waste generation and degradation behavior in the natural environment. It then provides an overview of various recently developed methods for recycling face mask plastic waste. The article also offers forward-looking strategies and recommendations on face mask plastic waste management. The review aims to provide guidance on harnessing the complexities of mask waste and other medical plastic pollution issues, as well as improving the current waste management system's deficiencies and inefficiencies in tackling the growing plastic waste problem.

A cross-jurisdictional comparison on residential waste collection rates during earlier waves of COVID-19

There is currently a lack of studies on residential waste collection during COVID-19 in North America. SARIMA models were developed to predict residential waste collection rates (RWCR) across four North American jurisdictions before and during the pandemic. Unlike waste disposal rates, RWCR is relatively less sensitive to the changes in COVID-19 regulatory policies and administrative measures, making RWCR more appropriate for cross-jurisdictional comparisons. It is hypothesized that the use of RWCR in forecasting models will help us to better understand the residential waste generation behaviors in North America. Both SARIMA models performed satisfactorily in predicting Regina's RWCR. The SARIMA DCV model's performance is noticeably better during COVID-19, with a 15.7% lower RMSE than that of the benchmark model (SARIMA BCV). The skewness of overprediction ratios was noticeably different between jurisdictions, and modeling errors were generally lower in less populated cities. Conflicting behavioral changes might have altered the residential waste generation characteristics and recycling behaviors differently across the jurisdictions. Overall, SARIMA DCV performed better in the Canadian jurisdiction than in U.S. jurisdictions, likely due to the model's bias on a less variable input dataset. The use of RWCR in forecasting models helps us to better understand the residential waste generation behaviors in North America and better prepare us for a future global pandemic.

Designing super-fast trimodal sponges using recycled polypropylene for organics cleanup

Sorbent pads and films have been commonly used for environmental remediation purposes, but designing their internal structure to optimize access to the entire volume while ensuring cost-effectiveness, ease of fabrication, sufficient strength, and reusability remains challenging. Herein, we report a trimodal sorbent film from recycled polypropylene (PP) with micropores, macro-voids, and sponge-like 3D cavities, developed through selective dissolution, thermally induced phase separation, and annealing. The sorbent has hundreds of cavities per cm2 that are capable of swelling up to twenty-five times its thickness, allowing for super-fast saturation kinetics (within 30 s) and maximum oil sorption (97 g/g). The sorption mechanism follows a pseudo-second-order kinetic model. Moreover, the sorbent is easily compressible, and its structure is retained during oil sorption, desorption, and resorption, resulting in 96.5% reuse efficiency. The oil recovery process involves manually squeezing the film, making the cleanup process efficient with no chemical treatment required. The sorbent film possesses high porosity for effective sorption with sufficient tensile strength for practical applications. Our integrated technique results in a strengthened porous polymeric structure that can be tailored according to end-use applications. This study provides a sustainable solution for waste management that offers versatility in its functionality.

Sustainable Solution for Plastic Pollution: Upcycling Waste Polypropylene Masks for Effective Oil-Spill Management

The use of Polypropylene PP in disposable items such as face masks, gloves, and personal protective equipment has increased exponentially during and after the COVID-19 pandemic, contributing significantly to microplastics and nanoplastics in the environment. Upcycling of waste PP provides a useful alternative to traditional thermal and mechanical recycling techniques. It transforms waste PP into useful products, minimizing its impact on the environment. Herein, we synthesized an oil-sorbent pouch using waste PP, which comprises superposed microporous and fibrous thin films of PP using spin coating. The pouch exhibited super-fast uptake kinetics and reached its saturation in fewer than five minutes with a high oil uptake value of 85 g/g. Moreover, it displayed high reusability and was found to be effective in absorbing oil up to seven times when mechanically squeezed between each cycle, demonstrating robust oil-sorption capabilities. This approach offers a potential solution for managing plastic waste while promoting a circular economy.

Properties of Composites Based on Recycled Polypropylene and Silico-Aluminous Industrial Waste

There is an ever-growing interest in recovering and recycling waste materials due to their hazardous nature to the environment and human health. Recently, especially since the beginning of the COVID-19 pandemic, disposable medical face masks have been a major source of pollution, hence the rise in studies being conducted on how to recover and recycle this waste. At the same time, fly ash, an aluminosilicate waste, is being repurposed in various studies. The general approach to recycling these materials is to process and transform them into novel composites with potential applications in various industries. This work aims to investigate the properties of composites based on silico-aluminous industrial waste (ashes) and recycled polypropylene from disposable medical face masks and to create usefulness for these materials. Polypropylene/ash composites were prepared through melt processing methods, and samples were analyzed to get a general overview of the properties of these composites. Results showed that the polypropylene recycled from face masks used together with silico-aluminous ash can be processed through industrial melt processing methods and that the addition of only 5 wt% ash with a particle size of less than 90 µm, increases the thermal stability and the stiffness of the polypropylene matrix while maintaining its mechanical strength. Further investigations are needed to find specific applications in some industrial fields.

Unraveling the potential human health risks from used disposable face mask-derived micro/nanoplastics during the COVID-19 pandemic scenario: A critical review

With the global spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), disposable face masks (DFMs) have caused negative environmental impacts. DFMs will release microplastics (MPs) and nanoplastics (NPs) during environmental degradation. However, few studies reveal the release process of MPs/NPs from masks in the natural environment. This review presents the current knowledge on the abiotic and biotic degradation of DFMs. Though MPs and NPs have raised serious concerns about their potentially detrimental effects on human health, little attention was paid to their impacts on human health from DFM-derived MPs and NPs. The potential toxicity of mask-derived MPs/NPs, such as gastrointestinal toxicity, pneumotoxicity, neurotoxicity, hepatotoxicity, reproductive and transgenerational toxicity, and the underlying mechanism will be discussed in the present study. MPs/NPs serve as carriers of toxic chemicals and pathogens, leading to their bioaccumulation and adverse effects of biomagnification by food chains. Given human experiments are facing ethical issues and animal studies cannot completely reveal human characteristics, advanced human organoids will provide promising models for MP/NP risk assessment. Moreover, in-depth investigations are required to identify the release of MPs/NPs from discarded face masks and characterize their transportation through the food chains. More importantly, innovative approaches and eco-friendly strategies are urgently demanded to reduce DFM-derived MP/NP pollution.