Effects of environmental factors and synthesis conditions on the photocatalytic activity of titanate nanotubes for remov
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Effects of environmental factors and synthesis conditions on the photocatalytic activity of titanate nanotubes for removal of gaseous formaldehyde Thi Thanh Thuy Vo1,2 · Hong Son Nguyen1,2 · Thi Thu Tran1,2 · Pham Thanh Hien Lam1,2 · Thi Thuy Nguyen3 · Nhat Huy Nguyen1,2 Received: 20 March 2020 / Accepted: 22 July 2020 © Springer Nature B.V. 2020
Abstract The increase in indoor air pollution problems stimulates the necessity for the development of photocatalytic removal processes, especially for the application of new and effective photocatalysts. In this study, we aimed to prepare and modify various types of titanate nanotubes (TNTs) synthesized by hydrothermal method and apply them for the removal of indoor formaldehyde by photocatalysis. The effect of environmental factors such as inlet concentration, exposed surface area, residential time, light intensity, and catalyst amount was investigated. The effects of various synthesis conditions such as acid treatment (i.e., at pH 1–9) and heat treatment (i.e., at temperatures of 120–900 °C) on the properties and the photocatalytic activity of the TNTs materials were also determined. Preliminary results showed that the highest removal efficiency of around 99% was found at the condition of 2 UV light bulbs, 29 s for retention time, 0.11 g of TNTs, 15 mg/m3 of formaldehyde, and 3 glass substrates. Regarding the synthesis condition, the TNTs material treated at pH 1.6 and annealed at 400 °C had the highest formaldehyde removal efficiency, which could be due to the suitable condition of mixed nanorods and nanotubes structure, anatase crystallinity, surface area, sodium content, and surface acidity the material. Keywords Titanate nanotubes · Formaldehyde · Indoor air pollution control · Environmental photocatalysis
* Nhat Huy Nguyen [email protected] 1
Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet St., Dist. 10, Ho Chi Minh City, Vietnam
2
Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam
3
Ho Chi Minh City University of Food Industry, 140 Le Trong Tan St., Tan Phu Dist, Ho Chi Minh City, Vietnam
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Introduction Problems of indoor air quality are considered as significant risk factors for human health in all low-, middle- and high-income countries [1]. Indoor air levels of many pollutants may be 2–5 times, and sometimes 100 times higher than outdoor levels. Indoor air pollutants are of particular concern because most people spend as much as 90% of their time indoors [2]. Formaldehyde (HCHO) is determined to be one of the most popular indoor air pollutants, especially for new buildings and furniture [1]. Since 2004, the World Health Organization (WHO) has listed formaldehyde as one of the toxic chemicals for human health, which can harm the skin and respiratory system and cause lung cancer [1]. Compared to outdoor conditions, the concentration of formaldehyde indoor is usually higher, where the
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