Publicação
Assessing photocatalytic asphalt mixtures: practical and laboratory methods for measuring air quality
| Resumo: | Air pollution in urban areas has become a major global concern, leading to a series of programs and regulations to be implemented to reduce it. Among the various pollutants that affect air quality is nitrogen monoxide (NO), which, once in the atmosphere, oxidizes into nitrogen dioxide (NO2). The combination of NO and NO2 refer to the nitrogen oxides (NOx), which, besides being harmful to health, have a negative impact on the environment with acid rain and intensify the greenhouse effect. This issue is exacerbated in large cities due to the high concentration of pollutant-emitting vehicles. To mitigate this problem by cleaning the air, researchers are investing in photocatalytic capability that can be applied to the surface of various substrates. Titanium dioxide (TiO2) is a highly utilized material, especially when aiming to attain both photocatalytic and self-cleaning abilities. The application of TiO2 over asphalt pavements has become an important topic in Transportation Engineering as a way of functionalized conventional pavement into a substrate where it becomes feasible to alleviate the environmental damage related to pollutant emissions, mainly NOx. The application of photocatalytic materials on asphalt pavements has the necessary conditions to increase the success of reducing pollutant levels. Pavements present a large area and are closer to vehicle exhausts. In addition, a major part of asphalt pavements is exposed to sunlight, which can activate the photocatalytic reaction. Due to these benefits, researchers have conducted studies that evaluate photocatalytic efficiency on surfaces of asphalt pavements.When evaluating photocatalytic efficiency, the literature describes a series of methods based on laboratory and field tests. In the laboratory, efficiency can be evaluated by degrading different organic dyes and degradation gas tests. For the first method, some dyes are widely used, such as methylene orange (MO), methylene blue (MB) and rhodamine B (RhB). For testing, samples of asphalt mixtures are immersed in an initial dye solution and exposed to light irradiation. Over time, changes in the solution absorbance (and, consequently, concentration) are monitored using spectrophotometry. The photocatalytic efficiency is calculated as a function of the maximum absorbance of the dye and the time. The second test follows the ISO 22197-1 standard, which specifies a test method for determining the air purification performance of materials with photocatalysis on the surface. To simulate and ensure the photocatalytic reactions occur, the experimental setup must contain an air compressor, pollutant source, humidifier, photoreactor, light source and pollutant analyzer. The photocatalytic asphalt mixture sample is placed inside the photoreactor and exposed to a controlled amount of pollutants, light and humidity. The gas flow is continuously injected into the photoreactor and subjected to light irradiation, and gas concentration is monitored over a period of time. The photocatalytic efficiency can be assessed by the net amount of pollutants that the sample removes.In field applications, one method that can be used to evaluate the efficiency is the air quality monitoring stations by conducting a comparative analysis of pollutant concentrations in a specific area before and after installing photocatalytic asphalt pavements. Those stations have sensors that collect outdoor air and distribute it through analyzers. These analyzers continuously and automatically measure various atmospheric pollutants, determining their concentrations in the ambient air "in real-time". Typically, they are fixed at strategic points in large cities, limiting assessment in more remote locations. Usually, these stations can measure several types of pollutants, such as NOx, SO2, CO2, particulate matter, among others, and the meteorological conditions, for example temperature, relative humidity, wind speed and direction , etc. Another method to evaluate the performance in field studies is to use passive sampling. The passive sampling approach is a low-cost, non-electrical, and simplified solution for the distribution of samples. The principle of the passive sampler involves gas collection through the diffusion of atmospheric air, which enters the device through one of its ends, travels through the body of the sampler (in the form of a tube) until it reaches its other end, which is sealed and contains a filter paper previously impregnated with a specific absorbent solution designed to react with the targeted pollutant to be collected. Measurement of photocatalytic efficiency is crucial in determining the performance of photocatalytic pavements and their impact on air quality. Thus, this study aims to provide a comprehensive elucidation of how to evaluate the photocatalytic efficiency of photocatalytic asphalt pavements functionalized with TiO2 nanoparticles through various methods, encompassing laboratory approaches and field studies. |
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| Autores principais: | Gomes, Igor Samuel Peixoto |
| Outros Autores: | Margalho, Élida Melo; Alcântra, Amanda; Rocha Segundo, Iran Gomes da; Castelo Branco, Verônica; Freitas, Elisabete; Carneiro, Joaquim A. O. |
| Assunto: | Air pollution Human Health Semiconductor photocatalysis technology Air quality Ciências Naturais::Ciências da Terra e do Ambiente Ação climática |
| Ano: | 2023 |
| País: | Portugal |
| Tipo de documento: | póster em conferência |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Air pollution in urban areas has become a major global concern, leading to a series of programs and regulations to be implemented to reduce it. Among the various pollutants that affect air quality is nitrogen monoxide (NO), which, once in the atmosphere, oxidizes into nitrogen dioxide (NO2). The combination of NO and NO2 refer to the nitrogen oxides (NOx), which, besides being harmful to health, have a negative impact on the environment with acid rain and intensify the greenhouse effect. This issue is exacerbated in large cities due to the high concentration of pollutant-emitting vehicles. To mitigate this problem by cleaning the air, researchers are investing in photocatalytic capability that can be applied to the surface of various substrates. Titanium dioxide (TiO2) is a highly utilized material, especially when aiming to attain both photocatalytic and self-cleaning abilities. The application of TiO2 over asphalt pavements has become an important topic in Transportation Engineering as a way of functionalized conventional pavement into a substrate where it becomes feasible to alleviate the environmental damage related to pollutant emissions, mainly NOx. The application of photocatalytic materials on asphalt pavements has the necessary conditions to increase the success of reducing pollutant levels. Pavements present a large area and are closer to vehicle exhausts. In addition, a major part of asphalt pavements is exposed to sunlight, which can activate the photocatalytic reaction. Due to these benefits, researchers have conducted studies that evaluate photocatalytic efficiency on surfaces of asphalt pavements.When evaluating photocatalytic efficiency, the literature describes a series of methods based on laboratory and field tests. In the laboratory, efficiency can be evaluated by degrading different organic dyes and degradation gas tests. For the first method, some dyes are widely used, such as methylene orange (MO), methylene blue (MB) and rhodamine B (RhB). For testing, samples of asphalt mixtures are immersed in an initial dye solution and exposed to light irradiation. Over time, changes in the solution absorbance (and, consequently, concentration) are monitored using spectrophotometry. The photocatalytic efficiency is calculated as a function of the maximum absorbance of the dye and the time. The second test follows the ISO 22197-1 standard, which specifies a test method for determining the air purification performance of materials with photocatalysis on the surface. To simulate and ensure the photocatalytic reactions occur, the experimental setup must contain an air compressor, pollutant source, humidifier, photoreactor, light source and pollutant analyzer. The photocatalytic asphalt mixture sample is placed inside the photoreactor and exposed to a controlled amount of pollutants, light and humidity. The gas flow is continuously injected into the photoreactor and subjected to light irradiation, and gas concentration is monitored over a period of time. The photocatalytic efficiency can be assessed by the net amount of pollutants that the sample removes.In field applications, one method that can be used to evaluate the efficiency is the air quality monitoring stations by conducting a comparative analysis of pollutant concentrations in a specific area before and after installing photocatalytic asphalt pavements. Those stations have sensors that collect outdoor air and distribute it through analyzers. These analyzers continuously and automatically measure various atmospheric pollutants, determining their concentrations in the ambient air "in real-time". Typically, they are fixed at strategic points in large cities, limiting assessment in more remote locations. Usually, these stations can measure several types of pollutants, such as NOx, SO2, CO2, particulate matter, among others, and the meteorological conditions, for example temperature, relative humidity, wind speed and direction , etc. Another method to evaluate the performance in field studies is to use passive sampling. The passive sampling approach is a low-cost, non-electrical, and simplified solution for the distribution of samples. The principle of the passive sampler involves gas collection through the diffusion of atmospheric air, which enters the device through one of its ends, travels through the body of the sampler (in the form of a tube) until it reaches its other end, which is sealed and contains a filter paper previously impregnated with a specific absorbent solution designed to react with the targeted pollutant to be collected. Measurement of photocatalytic efficiency is crucial in determining the performance of photocatalytic pavements and their impact on air quality. Thus, this study aims to provide a comprehensive elucidation of how to evaluate the photocatalytic efficiency of photocatalytic asphalt pavements functionalized with TiO2 nanoparticles through various methods, encompassing laboratory approaches and field studies. |
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