Photocatalytic Oxidation of Escherischia coli, Aspergillus niger, and Formaldehyde under Different Ultraviolet Irradiation Conditions

Abstract

Ultraviolet (UV) light irradiation, including the type of light source, light intensity, and irradiation dosage, directly affects the photocatalytic reaction rate and energy consumption. In this study, we investigated the photocatalysis effect of decomposing organic matter and inactivation bacteria and fungi under various conditions of UV sources (UVA and UVC) and light intensities (from 0.01 to 10 W/m2). The effect of light intensity was evaluated by photocatalytic reaction rate and UV dosage defined as a product of light intensity and irradiation time necessary to achieve a certain reduction. The results confirmed the positive effect of increased light intensity on photocatalytic reactions and suggested that within the light intensity range applied in this study low light intensity with long exposure time has higher light utilization efficiency compared to that of high light intensity with short exposure time. A conception for selection of the appropriate light intensity and dosage for effective degradation of pollutants, while saving energy, was provided.

Photocatalytic oxidation of gaseous ammonia over fluorinated TiO2 with exposed (001) facets

“…Selective catalytic oxidation (SCO) is an effective method to degrade NH 3 , but the oxidation reaction generally requires a high temperature [5][6][7]. Photocatalytic oxidation (PCO) could eliminate the indoor air pollutants such as formaldehyde and volatile organic compounds under ultraviolet (UV) light irradiation at ambient temperature; therefore, it is a promising method for indoor air NH 3 destruction [8][9][10][11]. A few studies have been focused on the photocatalytic removal of gaseous NH 3 .…”

Removal of Low-Concentration Formaldehyde by a Fiber Optic Illuminated Honeycomb Monolith Photocatalytic Reactor

“…and Fujishima, 1998;Ao et al, 2004;Yu et al, 2006a;Zuo et al, 2006;Hodgson et al, 2007;Wang et al, 2007;Yang et al, 2007a;Shie et al, 2008;Zhang and Liu, 2008;Chen et al, 2009;Mo et al, 2009;Lu et al, 2010;Aïssa et al, 2011;Bourgeois et al, 2012;Han et al, 2012;Dozzi et al, 2013). In the photocatalytic oxidation, the ultraviolet (UV) radiation with energy above the band-gap of titanium dioxide (TiO 2 ) (wavelength < 385 nm) can induce the formation of electron-hole pairs and generate hydroxyl radicals further on the UV-illuminated TiO 2 surface, and then the oxidation of organic contaminants to H 2 O, CO 2 and other final products is mediated by hydroxyl radicals (Anpo et al, 1991;Yu et al, 2006b;Zuo et al, 2006;Hodgson et al, 2007;Yu and Lee, 2007;Mo et al, 2009Sun et al, 2010Yu et al, 2010;Kandiel et al, 2013;Klementova and Zlamal, 2013;Silva et al, 2013).…”

“…In the photocatalytic oxidation, the ultraviolet (UV) radiation with energy above the band-gap of titanium dioxide (TiO 2 ) (wavelength < 385 nm) can induce the formation of electron-hole pairs and generate hydroxyl radicals further on the UV-illuminated TiO 2 surface, and then the oxidation of organic contaminants to H 2 O, CO 2 and other final products is mediated by hydroxyl radicals (Anpo et al, 1991;Yu et al, 2006b;Zuo et al, 2006;Hodgson et al, 2007;Yu and Lee, 2007;Mo et al, 2009Sun et al, 2010Yu et al, 2010;Kandiel et al, 2013;Klementova and Zlamal, 2013;Silva et al, 2013). The key photocatalytic oxidation and reduction processes in the degradation of formaldehyde can be expressed as what follows (Noguchi and Fujishima, 1998;Ao et al, 2004) A variety of photocatalytic reactors have been designed for indoor air purification, such as plate (Yu et al, 2006b;Zuo et al, 2006;Yang et al, 2007b;Yu and Lee, 2007;Chen et al, 2009;Yu et al, 2010), honeycomb monolith (Hodgson et al, 2007;Wu et al, 2013;Yu et al, 2014), annular (Yang et al, 2007a;Shie et al, 2008), packed-bed (Han et al, 2012), and optical fiber (Bourgeois et al, 2012). Among these reactors, the performances of plate [once-flow removal efficiency (ORE): 11-19.6% (Yang et al, 2007b); 50% (Chen et al, 2009)] and annular [ORE: 8-14% (Yang et al, 2007a)] reactors on formaldehyde decomposition were lower than those of the packed-bed [ORE: 40-90% (Han et al, 2012)], optical fiber [ORE: 60% (Bourgeois et al, 2012)] and the honeycomb monolith type [ORE: 35-86% (Hodgson et al, 2007;…”

Effect of TiO2 calcination temperature on the photocatalytic oxidation of gaseous NH3

“…NH 3 can be completely removed by selective catalytic oxidation using various catalysts such as metals, metal oxides and zeolites, but they cannot realize effective abatement of gaseous NH 3 at room temperature (Akah et al, 2005;Zhang et al, 2009;Cui et al, 2010). Photocatalytic oxidation (PCO) is a promising method for removing indoor air pollutants such as formaldehyde, volatile organic compounds, etc, under ultraviolet (UV) light irradiation at ambient temperature (Guo et al, 2008;Chen et al, 2009;Mo et al, 2009). TiO 2 is a very effective photocatalyst known for the stability of its chemical struc-ture, biocompatibility and physical, optical and electrical properties (Chen and Mao, 2007).…”