Wearing face masks, use of respirators, social distancing, and practicing personal hygiene are all measures to prevent the spread of the coronavirus disease (COVID-19). This pandemic has revealed the deficiency of face masks and respirators across the world. Therefore, significant efforts are needed to develop air filtration and purification technologies, as well as innovative, alternative antibacterial and antiviral treatment methods. It has become urgent—in order for humankind to have a sustainable future—to provide a feasible solution to air pollution, particularly to capture fine inhalable particulate matter in the air. In this review, we present, concisely, the air pollutants and adverse health effects correlated with long- and short-term exposure to humans; we provide information about certified face masks and respirators, their compositions, filtration mechanisms, and the variations between surgical masks and N95 respirators, in order to alleviate confusion and misinformation. Then, we summarize the electrospun nanofiber-based filters and their unique properties to improve the filtration efficiency of face masks and respirators.

In this study, Melia azedarach fruit extract was used as a reducing agent and copper chloride dihydrate (CuCl₂·2H₂O) was used as a precursor in the synthesis of copper oxide nanoparticles (CuO NPs). The UV–visible spectrum showed a characteristic absorption peak of CuO NPs at 350 nm. The surface properties of the adsorbent were analyzed through various techniques, indicating the successful formation of CuO NPs. The impacts of several factors, including initial pH (4 to 8), a dose of CuO NPs adsorbent (0.01–0.05 g), dye initial concentration (10–50 mg·L⁻¹), and contact times ranging from 5 to 120 min, were examined in batch adsorption studies. Based on the experimental results, the Langmuir isotherm is well-fitted, indicating MB dye monolayer capping on the CuO NPs surface with 26.738 mg·g⁻¹ as a maximum adsorption capacity Q_m value. For the pseudo-second-order kinetic model, the experimental and calculated adsorption capacity values (q_e) exhibited good agreement.

A membrane composed of polyethylene terephthalate nanofiber and multi-walled carbon nanotubes (PET NF-MWCNTs) composite is used to adsorb methylene blue (MB) dye from an aqueous solution. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques are employed to study the surface properties of the adsorbent. Several parameters affecting dye adsorption (pH, MB dye initial concentration, PET NF-MWCNTs dose, and contact time) are optimized for optimal removal efficiency (R, %) by using the Taguchi L25 (5⁴) Orthogonal Array approach. According to the ANOVA results, pH has the highest contributing percentage at 71.01%, suggesting it has the most significant impact on removal efficiency. The adsorbent dose is the second most affected (12.08%), followed by the MB dye initial concentration of 5.91%, and the least affected is the contact time (1.81%). In addition, experimental findings confirm that the Langmuir isotherm is well-fitted, suggesting a monolayer capping of MB dye on the PET-NF-MWCNT surface with a maximum adsorption capacity of 7.047 mg g⁻¹. Also, the kinetic results are well-suited to the pseudo-second-order model. There is a good agreement between the calculated (q_e) and experimental values for the pseudo-second-order kinetic model.

A unique aspect of this research lies in the combination of polyethylene terephthalate (PET) nanofibers with Au^o@PPh₂-PIILP to create a nanogold composite (NGC). This NGC has proven to be highly efficient in removing methylene blue (MB) from wastewater. The prepared nanogold composite NGC was characterized by Fourier-transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FE-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDAX), and Elements Distribution Mapping (EDM). Several factors were examined in batch adsorption experiments to determine their impact on dye adsorption. These factors included the initial pH range of four to eight, the dosage of NGC adsorbent ranging from 0.001 to 0.008 g, the initial concentration of MB dye ranging from 10 to 50 mg L⁻¹, and the contact period ranging from 10 to 80 min. It has been observed that NGC is more efficient in removing MB from polluted water. The results of the pseudo-second-order model show good agreement between the calculated adsorption capacity (q_e)_cal. (4.3840 mg g⁻¹) and the experimental adsorption capacity (q_e)_exp. (4.6838 mg g⁻¹) values. Experimental findings suggest a monolayer capping of MB dye on the NGC surface with a maximum adsorption capacity Q_m of 18.622 mg g⁻¹ at 20 °C, indicating that it is well-fitted to the Langmuir isotherm.