Indoor low-concentration carbon monoxide (CO) exposure is widespread worldwide, and potted plants may be a potential means for CO purification. The objective is to evaluate common indoor plants’ CO ...purification and tolerance capacities.
Epipremnum aureum
(Linden ex André) G.S.Bunting,
Chlorophytum comosum
(Thunb.) Jacques,
Spathiphyllum kochii
Engl. & K.Krause, and
Sansevieria trifasciata
Hort. ex Prain with similar sizes were tested in the glass chamber with initial CO concentrations of 10, 25, 50, 100, 200, and 400 ppm, respectively. (1) The CO purification capacity of the four potted plants is ranked as
Epipremnum aureum
(Linden ex André) G.S.Bunting >
Chlorophytum comosum
(Thunb.) Jacques >
Spathiphyllum kochii
Engl. & K.Krause >
Sansevieria trifasciata
Hort. ex Prain. Under the purification effect of each plant, the CO concentration in the chamber decreases linearly and significantly (
p
< 0.05), and within a specific time period, the time-weighted average (TWA) CO concentrations can be reduced to below the corresponding permissible exposure limits specified by some countries and organizations. (2) With the increase of the stomatal number of each plant and the increase in CO concentration, the hourly and cumulative absorbed CO of each plant increase linearly and significantly (
p
< 0.05). (3) With the increase in CO concentration, the CO purification efficiency of each plant decreases exponentially and significantly (
p
< 0.05). (4) When the CO concentration was ≤ 50 ppm, all plants could effectively purify CO without damage. When the CO concentration was in the range of 100 ~ 400 ppm, within 2 weeks after the 48-h experiment, the leaf tips of
Chlorophytum comosum
(Thunb.) Jacques and
Epipremnum aureum
(Linden ex André) G.S.Bunting were damaged one after another, and the damaged leaf area increased with the increase of CO concentration. However, each plant as a whole still survived. This study demonstrated that different species of potted plants can effectively absorb low concentrations of CO to varying degrees, but higher concentrations of CO will damage the survival of specific species of potted plants.
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•Dielectric CNT@ZIF-8 nanohybrids of high surface activity were customized by a microwave-assisted approach.•Poly(lactic acid) (PLA) nanofibers were decorated by the nanohybrids via a ...combined “electrospinning‒electrospray” strategy.•The electroactive nanofibers were characterized by largely promoted surface potential and tribo-output properties.•The electroactive nanofibers exhibited a combination of remarkable PM capturing, self-sterilization and photothermal properties.
Biodegradable poly (lactic acid) (PLA) nanofibrous membranes (NFMs) are appealing to address the increasing air pollution and outbreak of epidemic diseases, as well as the drastic accumulation of plastic and microplastic pollutions. Central to the development of high-performance PLA membrane filters are the promotion of electroactivity, polarization and electret properties, which has been a roadblock toward efficient capturing of airborne particulate matters (PMs) and bacterial pathogens. Herein, we proposed a microwave-assisted synthetic approach to enable direct growth of ZIF-8 nanocrystals at carbon nanotubes (CNT@ZIF-8 nanohybrids), which were spontaneously embedded into PLA nanofibers by a combined electrospinning–electrospray technology. With uniform and affinitive anchoring of CNT@ZIF-8 (8, 10 and 12 wt%), the PLA NFMs were characterized by largely increased surface potential (up to 1.78 kV), nearly doubled dielectric constant, and excellent triboelectric properties (output voltage of 12.7 V at 10 N, 0.5 Hz). The highly electroactive PLA/CNT@ZIF-8 NFMs exhibited excellent air filtration properties (98.7 % and 99.8 % removal of PM0.3 and PM2.5, 206.9 Pa) even at the highest airflow capacity of 85 L/min, in clear contrast to the pure PLA counterpart (81.2 % and 84.1 %, 465.2 Pa). This was accompanied by 100 % perfect inhibition of both E. coli and S. aureus regardless of the CNT@ZIF-8 loadings, arising mainly from the elevated surface activity, facilitated generation of reactive oxygen species, and gradual release of zinc ions. Moreover, remarkable photothermal properties were demonstrated by temperature elevation of nearly 16 °C under near-infrared irradiation for only 20 s. The proposed methodology affords an exceptional combination of excellent air filtration, self-sterilization and photothermal properties, which may motivate development of ecofriendly and functional protective membranes for personal healthcare.
Despite the great promise in the development of biodegradable and ecofriendly air filters by electrospinning of poly(lactic acid) (PLA) nanofibrous membranes (NFMs), the as-electrospun PLA ...nanofibers are generally characterized by poor electroactivity and smooth surface, challenging the exploitation of electrostatic adsorption and physical interception that are in need for efficient removal of pathogens and particulate matters (PMs). Herein, a combined “electrospinning–electrospray” strategy was disclosed to functionalize the PLA nanofibers by direct anchoring of highly dielectric BaTiO3@ZIF-8 nanohybrids (BTO@ZIF-8), conferring simultaneous promotion of surface roughness, electret properties (surface potential as high as 7.5 kV), and self-charging capability (∼190% increase in tribo-output voltage compared to that of pure PLA). Benefiting from the well-tailored morphology and increased electroactivity, the electrospun–electrosprayed PLA/BTO@ZIF-8 exhibited excellent PM-capturing performance (up to 96.54% for PM0.3 and 99.49% for PM2.5) while providing desirable air resistance (only 87 Pa at 32 L/min) due primarily to the slip flow of air molecules over the nanohybrid protrusions. This was accompanied by excellent antibacterial properties (99.9% inhibition against both Staphylococcus aureus and Escherichia coli), arising presumably from the synergistic effects of enhanced reactive oxygen species (ROS) generation, plentiful ion release, and surface charges. Our proposed strategy opens up pathways to afford exceptional combination of high-efficiency and low-resistance filtration, excellent antibacterial performance, and mechanical robustness without sacrificing the biodegradation profiles of PLA NFMs, holding potential implications for efficient and long-term healthcare.
Pressure drop is an important indicator that affects the filtration performance of the pleated filter, and the deposition of dust particles within the pleats is crucial to the evolution of the ...pressure drop. In this study, the pressure drop during PM10 loading process was investigated for a series of V-shaped and U-shaped filters with a pleat height of 20 mm and different pleat ratios (the ratio of pleat height to pleat width: α = 0.71–3.57). In the numerical simulations, numerical models suitable for different pleated geometries were obtained through experimental verification on the local air velocity. Then, assuming that the dust cake thickness is proportional to the normal air velocity of the filters, the variation of the pressure drop with the dust deposition is derived by means of successive numerical simulations. This simulation method saved a significant amount of CPU time required for the growth of dust cake. It was found that the relative average deviations between experimental and simulated pressure drops were 3.12% and 1.19% for V-shaped and U-shaped filters, respectively. Furthermore, it was found that under the same pleat ratio and the mass of dust deposition per unit area, both the pressure drop and unevenness of normal air velocity of the U-shaped filter were lower than the V-shaped filter. Therefore, the U-shaped filter is recommended due to its better filtration performance.
Loose-fitting powered air-purifying respirators (LF-PAPRs) are increasingly used in hospitals and coal mines because of their high comfort and protection level, but the utilization faces the ...challenges of 8-hr continuous high protection requirements in the hospital environment and the coupling effects of high temperature, high humidity, high dust concentration in coal mines. Based on the self-developed powered air-purifying respirator simulation test system, this study explores the 8-hr changes of supplied airflow, the relative air pressure inside the inlet covering (ΔP), and total inward leakage (TIL) of four models of LF-PAPRs in simulated hospital and coal mine environments. Results show that: (1) In a simulated hospital environment, all four LF-PAPRs showed filter cartridge blockage within 5 ∼ 6 hr of continuous operation; while in the simulated coal mine, three models of LF-PAPRs showed filter cartridge blockage within 3 hr. (2) In both the hospital and coal mine environments, there are cases where the supplied airflow of LF-PAPRs dropped below 170 L/min within 3 hr. (3) In a simulated hospital environment, the ΔP of all LF-PAPRs maintained positive within 5-6 hr; while in the simulated coal mine, the ΔP of two LF-PAPRs, respectively, appeared negative after 1 hr and 1.6 hr operation. (4) The maximum TIL of the tested LF-PAPRs, respectively ranged from 0.5-0.9% and 1.4-3% in simulated hospital and coal mine environments. (5) In both hospital and coal mine environments, the supplied airflow and ΔP of each LF-PAPR showed a decreasing trend with increasing test duration, while the TIL significantly increased with testing time. (6) The supplied airflow, ΔP, and TIL of each LF-PAPR in the simulated hospital environment performed better than those in the coal mine. This study evaluated the performance of PAPR under the most severe operating conditions, and respirator performance may differ under in-situ conditions.
Biodegradable and renewable poly(lactic acid) (PLA) fibrous membranes have emerged as a promising approach to replace traditional polymeric air filters, but are still challenged by relatively low ...electroactivity and poor electret properties. Herein, we disclose an effective electrospinning strategy to substantially promote the electroactivity by extreme orientation of stereocomplexed PLA (OSC-PLA), conferring significant alignment and refinement of the electrospun nanofibers (diameter of ∼370 nm), as well as facilitate the formation of electroactive phases (i.e., β-phase, electrospun phase, and stereocomplex crystals). Benefiting from the well-tailored morphology and remarkable electroactivity, the OSC-PLA nanofibrous membranes (NFMs) were characterized by largely improved dielectric properties, surface potential (over 3.64 kV), and PM0.3 filtration properties (93.33% at 85 L/min) compared to the pure PLLA membrane (2.01 kV and 80.21%). It enabled the assembly of triboelectric nanogenerator (TENG) air filters using the OSC-PLA NFMs as the active layer, yielding excellent charge regeneration mechanisms and an output current of nearly 80 nA, as driven by respiratory vibrations at 85 L/min, thus permitting high humidity resistance, as exemplified by a PM0.3 removal efficiency of 95.02% at a RH of 90%. Moreover, deep machine learning and man–machine interaction were integrated with the OSC-PLA-based TENGs, demonstrating long-term monitoring and a high-precision diagnosis (accuracy of 96.88%) of various respiratory patterns. The proposed ecofriendly and electroactive ultrafine PLA nanofibers are highly appealing for sustained respiratory healthcare and self-powered intelligent diagnosis.
