Discarded disposable face masks can easily cause environmental pollution, and microbial-induced calcium carbonate precipitation (MICP) technology can lead to soil brittleness. This article attempted to combine discarded disposable face masks with MICP technology by adding the shredded face mask (SFM) with six different percentages (0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight) to ISO standard sand. The test results showed that the optimal content of SFM was 0.2%. Compared with the sand samples without SFM, the water absorption rate decreased by 26.99%, the dry and saturated unconfined compressive strengths (UCS) increased by 145.11% and 252.38%, respectively, and the failure strain increased by 127%, and the calcium carbonate content increased by 20.1%. Meanwhile, 0.2% SFM fiber can form a three-dimensional network structure, which restricts the displacement and deformation of sand particles, improves the brittleness of the sand samples, and enhances the strength of the sand samples. This study provides an effective method for recycling discarded disposable face masks while promoting the application of fiber-reinforced MICP-treated sand in geotechnical engineering.

This study rigorously examined the enhancement of the mechanical properties of clay through the application of disposable face mask fibers (DFMF). By subjecting the reinforced specimens to a comprehensive series of unconfined strength tests, it was found that adding DFMF to the base soil decreased the maximum dry unit weight (MDUW) and increased the optimum moisture content (OMC). The study examined the effects of DFMF content on the compounds, revealing that a maximum increase of 0.2 in DFMF content improves their unconfined compressive strength (UCS); Therefore, 0.2% mask DFMF content was noticed to be the optimum DFMF content, which constituted maximum strength.

Due to their extensive use during and after the COVID-19 pandemic, many disposable face masks are irresponsibly deposited into the water environment, threatening the health of people living nearby. However, the effects of water conditions on the degradation and potential hazards of these masks are generally unclear. This paper entailed the release and cellular toxicity of micro/nano plastics from disposable face masks once discarded in different waters, including soil water, river water, and tap water, with deionized (DI) water as control. At first, polypropylene (PP) was confirmed to be the major component of disposable face masks with Raman and Fourier transform infrared (FTIR) techniques. To monitor the release rate of PP from masks, a silver nanoparticle (AgNP)-based surface-enhanced Raman scattering (SERS) method was established by employing the unique Raman fingerprint of PP at 2882 cm(-1). During 30-d incubation in different waters, the release rates of PP, sizes of PP aggregates, length of fibers, and proportions of plastics smaller than 100 nm were in the order of soil water > river water > tap water > DI water. All the obtained PP exhibited significant toxicity in human lung cancer (A549) cells at concentrations of 70 mg/L for 48 h, and the ones obtained in soil water exhibited the most severe damage. Overall, this paper revealed that environmental waters themselves would worsen the adverse effects of disposable face masks, and the key compounds affecting the degradation of masks remain to be clarified. Such information, along with the established methods, could be beneficial in assessing the health risks of disposable face masks in different waters.