Experimental and modeling study of visible light responsive photocatalytic oxidation (PCO) materials for toluene degradation

Abstract

Only limited research has examined the development and application of visible light responsive photocatalytic oxidation (PCO), although such materials have great potential for mitigating concentrations of volatile organic compounds (VOCs) when applied to building surfaces. This study evaluates the performance and characteristics of a visible light responsive photocatalyst, specially, a co-alloyed TiNbON compound with a band energy of 2.3 eV. The PCO material was developed using urea-glass synthesis, characterized by scanning electron microscopy (SEM), diffuse reflectance spectra (DRS), powder X-ray diffraction (PXRD), and Brunauer-Emmett-Teller (BET) methods, and VOC removal efficiency was measured under visible light for toluene (1–5 ppm) at room temperature (21.5°C) and a range of relative humidity (RH: 25 to 65%), flow rate (0.78 to 7.84 cm/s), and irradiance (42 to 95 W/m2). A systematic parametric evaluation of kinetic parameters was conducted. In addition, we compared TiNbON with a commercial TiO2-based material under black light, estimated TiNbON’s long-term durability and stability, and tested its ability to thermally regenerate. Using mass transfer and kinetic analysis, three different Langmuir-Hinshelwood (LH) type reaction rate expressions were proposed and evaluated. A LH model considering one active site and competitive sorption of toluene and water was superior to others. The visible-light driven catalyst was able to remove up to 58 % of the toluene, generated less formaldehyde than the commercial TiO2, could be fully regenerated at 150°C, and had reasonable durability and stability. This evaluation of TiNbON shows the potential to remove VOCs and improve air quality for indoor applications. Further research is needed to evaluate the potential for harmful by-products, to identify optimal conditions, and to use field tests to show real-world performance.

Abatement of ammonia and butyraldehyde under non-thermal plasma and photocatalysis: Oxidation processes for the removal of mixture pollutants at pilot scale

“…However, higher concentration increases the quantity of pollutants in the reactor which potentially limits the degradation under the same experimental condition (amount of catalysts and UV intensity). Hence, efficiencies decrease at higher concentrations as reported in literature [21,35]. As for ammonia, results indicate that the RE remains low (~ 38%) compared to butyraldehyde and that category of inorganic compound is very hard to degrade by photocatalytic oxidation by itself.…”

A Review on Catalytic Nanomaterials for Volatile Organic Compounds VOC Removal and Their Applications for Healthy Buildings

“…However, the leading semiconductor photocatalyst, TiO 2 , also suffers from low photocatalytic activity under visible light activation because of its intrinsic wide band gap. Therefore, to increase the efficiency of TiO 2 in the visible light region, TiO 2 is modified with various nanomaterials including other metal oxides [40,41,42], carbonaceous nanomaterials [43] etc. Zhong et al [40] developed a TiNbON compound (band energy of 2.3 eV) using urea-glass synthesis as a visible light responsive photocatalytic oxidation material for toluene degradation.…”

“…Therefore, to increase the efficiency of TiO 2 in the visible light region, TiO 2 is modified with various nanomaterials including other metal oxides [40,41,42], carbonaceous nanomaterials [43] etc. Zhong et al [40] developed a TiNbON compound (band energy of 2.3 eV) using urea-glass synthesis as a visible light responsive photocatalytic oxidation material for toluene degradation. Experimental results showed that the visible light-driven catalyst was able to remove up to 58% of the toluene and generated less formaldehyde than the commercial TiO 2 with reasonable durability and stability.…”

Promoting ring-opening efficiency for suppressing toxic intermediates during photocatalytic toluene degradation via surface oxygen vacancies

“…The selectivity of photocatalytic conversion of VOCs to harmless final product along with control of the toxic intermediates during the reaction process has been largely ignored. The issue is the key to application and should be worth receiving high attention [10][11][12][13][14]. Some progresses have revealed that the reaction intermediates, such as aromatic oxides, epoxides, peroxides, and polyhy-droxylated compounds have high toxicity [15].…”