Improved Photocatalytic Air Cleaner with Decomposition of Aldehyde and Aerosol-Associated Influenza Virus Infectivity in Indoor Air

Abstract

Air pollution caused by fine particulate matter (PM 2.5 ), volatile organic compounds, and bioaerosols is a major environmental risk to health. We developed a photocatalytic air cleaner for reducing the pollution levels of indoor air; we improved the photocatalytic system by using UV-LED for the removal of acetaldehyde and PM 2.5 and by reducing the weight and size of the system. The efficiency of photocatalysis depends on the surface area and materials. Therefore, we prepared a nanosized titanium dioxide (TiO 2 )-coated aluminum plate irradiated by UV-LED lamps (wavelength: 375 nm) as a photocatalytic air cleaner. Passing air continuously through a TiO 2 -coated aluminum plate (5 × 10 × 1 cm) under black light for 200 min decomposed 90% of 5 ppm acetaldehyde (12.4 µmol h -1 ) and generated two carbon dioxide molecules (25.43 µmol h -1 ) at a molar ratio of 1:2, indicating complete decomposition of acetaldehyde with high efficiency. This photocatalytic air cleaner was applied to the decomposition of acetaldehyde and inactivation and removal of aerosolassociated influenza virus. Acetaldehyde (20 ppm) in a 1-m 3 cubic space was eliminated in 60 min at a half-life of 8 min. The aerosol-associated infectivity and the RNA genome of influenza virus A/PR/8/1934 (H1N1) produced by a nebulizer in a 779-L cubic space were eliminated within 7 min; however, they were detectable for up to 28 minutes when the functional photocatalytic air cleaner was not used. The presence of intermediate breakdown products of influenza virus indicated that the virus was broken down by photocatalysis. Thus, the photocatalytic air cleaner efficiently decomposed and eliminated organic chemicals, acetaldehyde, and aerosol-associated influenza virus infectivity and viral RNA, indicating that it can clean and detoxify the indoor air in a closed space for maintaining a safer environment.

Prevalence of Antibiotic Resistance Genes in Air-Conditioning Systems in Hospitals, Farms, and Residences

“…In recent times, humans spend the majority of time (almost 90%) indoors. There has been a growing concern over the health effects associated with indoor air quality since airborne diseases, including influenza [ 19 ], tuberculosis [ 20 ], the common cold [ 21 ], and legionellosis [ 22 ], exist in indoor air. Several studies have documented that humans who are exposed daily to these airborne particles can induce allergic and chronic inflammatory responses [ 23 ].…”

Antimicrobial TiO2 nanocomposite coatings for surfaces, dental and orthopaedic implants

“…The human influenza virus strain of A/PR8/H1N1 was treated with TiO 2 under UV light irradiation, and the efficiency of viral disinfection process was relied on the intensity of the light radiation [93] . Later, a photocatalytic air cleanser was developed using a TiO 2 -coated aluminium plate system [94] . It showed maximum efficiency against aerosol-associated influenza virus, indicating the competence of photocatalysis technology to detoxify the indoor air.…”

Review on heterogeneous photocatalytic disinfection of waterborne, airborne, and foodborne viruses: Can we win against pathogenic viruses?

“…In 2017, Shiraki et al constructed a photocatalytic air cleaner to decrease the contamination levels of indoor air. They studied the photocatalytic activity using UV-LED [85] . For this purpose, they fabricated a TiO 2 -coated aluminum plate system as a photocatalyst.…”

“… Photocatalyst Virus Operational condition Light source Disinfection efficiency Type of virus Ref. Catalystloading(mg/L) Virus level(PFU*/mL) TiO 2 Phage MS2 1000 6 × 10 4 UV 2.8-log in 65 min waterborne [41] TiO 2 Phage MS2 1000 6 × 10 5 18 W BLB* lamp 1.8-log in 180 min waterborne [61] TiO 2 Bacteriophage Qβ 1000 1 × 10 6 UV lamp 3.5-log in 2 min waterborne [64] TiO 2 Phage f2 1000 10 10 –10 11 6 W black light lamp 6-log in 15 min waterborne [78] TiO 2 Influenza virus No data 4.0 × 10 8 1 mW black light Eliminated in 5 min airborne [83] TiO 2 Influenza virus No data 0.0 or 0.1 mg ml −1 20 W black light 4-log in a short irradiation time airborne [84] TiO 2 H1N1 No data No data UV-LED lamp Eliminated in 7 min airborne [85] TiO 2 MNV-1 No data No data UV lamp 3.2-log in 10 min food...…”