Heterogeneous Photocatalysis for Indoor Air Purification: Recent Advances in Technology from Material to Reactor Modeling
01 Jan 2020-pp 147-166
TL;DR: In this article, the current status of PCO material technologies, coating methods, performance test methods, and modeling for real-world indoor air-purification application is reviewed and some recommendations for the future research on improving material selection and reactor design to minimize by-product generation and to promote commercialization are also discussed.
Abstract: Heterogeneous photocatalytic oxidation (PCO) has attracted much attention in indoor air-purification applications. Recently, researches focus on developing novel photocatalyst based filters for integrating with the heating, ventilation, and air conditioning (HVAC) systems as well as portable air purifiers. A comprehensive knowledge on factors influencing the indoor volatile organic compounds (VOCs) degradation has been established both in bench-scale and pilot-scale experiments. This paper reviews the current status of PCO material technologies, coating methods, performance test methods, and modeling for real-world indoor air-purification application. Due attention to the basic principle of PCO and the effect of operating parameters is provided, followed by a discussion on the modes of PCO application for buildings. The review also concentrates on the practical limitations in scaling-up PCO air purifiers for large-scale applications. Some recommendations for the future research on improving material selection and reactor design to minimize by-product generation and to promote commercialization are also discussed.
Citations
More filters
TL;DR: In this paper, a review article describes various applications of nanomaterials in removing different types of impurities from polluted water, which carried huge potential to treat polluted water (containing metal toxin substance, different organic and inorganic impurities) very effectively due to their unique properties like greater surface area, able to work at low concentration, etc.
Abstract: Water is an essential part of life and its availability is important for all living creatures. On the other side, the world is suffering from a major problem of drinking water. There are several gases, microorganisms and other toxins (chemicals and heavy metals) added into water during rain, flowing water, etc. which is responsible for water pollution. This review article describes various applications of nanomaterial in removing different types of impurities from polluted water. There are various kinds of nanomaterials, which carried huge potential to treat polluted water (containing metal toxin substance, different organic and inorganic impurities) very effectively due to their unique properties like greater surface area, able to work at low concentration, etc. The nanostructured catalytic membranes, nanosorbents and nanophotocatalyst based approaches to remove pollutants from wastewater are eco-friendly and efficient, but they require more energy, more investment in order to purify the wastewater. There are many challenges and issues of wastewater treatment. Some precautions are also required to keep away from ecological and health issues. New modern equipment for wastewater treatment should be flexible, low cost and efficient for the commercialization purpose.
365 citations
TL;DR: In this article, the applicability of platinized titanium dioxide (Pt/TiO2) for the removal of gaseous pollutants in light of its numerous advantages (e.g., high removal efficiency, stability, regenerability, and sustainability).
39 citations
TL;DR: In this paper, a comprehensive review of the photoreactors for gas-phase reaction focusing on process intensification and recent computer simulations is provided, in which the state-of-the-art of photocatalytic air treatment providing examples such as the VOCs oxidation and NOx degradation.
Abstract: This article provides a comprehensive review of the photoreactors for gas-phase reaction focusing on process intensification and recent computer simulations. This review selected two photocatalytic gas-phase reactions, namely the oxidation of volatile organic compounds (VOCs) and the degradation of nitrogen oxides (NOx). It was also discussed two photocatalytic gas-phase reactions’ importance from a scientific and social perspective. Therefore, heterogeneous photocatalysis was applied, and it excelled itself as a promising technology for gas-phase reaction applications. However, despite the numerous advances in photocatalytic processes in recent times, there are still several challenges in their development for this technology to achieve high performance. Mass transfer and low quantum efficiency (photon transfer) are some of these challenges becoming a significant concern for the design of new photoreactors or the improvement of existing ones. Different types of photocatalytic reactors have already been designed, examined, and simulated, seeking to maximize the pollutant-catalyst contact (enhancing mass transfer) and to maximize the lighting efficiency throughout the catalyst surface (enhancing photon transfer). The process intensification has been highlighted in the development of photoreactors to ensure the improvement in mass and photons transfer. Here, we will address the monolithic photoreactors, photocatalytic membrane reactors, and photo-microreactors, in which each photoreactor has its advantages and drawbacks. CFD-based models, combined with the design of the photoreactors, are essential since they can successfully predict the performance of various geometric configurations and identify the limitations to the photon and the mass transfer with only validated virtual prototypes. From this perspective, this review presents the state-of-art of photocatalytic air treatment providing examples such as the VOCs oxidation and NOx degradation. Furthermore, this review also reports a literature exam of three different types of photoreactor designs presenting their advantages and limitations regarding the mass and the photons transfer focusing on photocatalytic process intensification. Also, it is presented a discussion of the recent applications of photocatalytic reactor modeling using computational fluid dynamics (CFD) for the gaseous pollutant degradation.
16 citations
TL;DR: In this paper, a case study was conducted to develop a support vector machine (SVM) classification model with good accuracy, and challenging compound types, inlet concentrations, and air velocity were found to be the main parameters affecting the applicability of UV-PCO.
13 citations
TL;DR: In this article , a case study was conducted to develop a support vector machine (SVM) classification model with good accuracy, and challenging compound types, inlet concentrations, and air velocity were found to be the main parameters affecting the applicability of UV-PCO.
13 citations
References
More filters
TL;DR: In this paper, the authors explored the potential environmental and energy benefits of using activated carbon fiber (ACF) filters for air cleaning in HVAC systems and found that the combination of ACF air cleaning and a 50% reduction in ventilation will decrease indoor concentrations of VOCs by 60% to 80% and reduce formaldehyde concentrations by 12% to 40%.
186 citations
TL;DR: In this article, a set of eight concretes and plasters is enriched with TiO2 photocatalyst by dip-coating and/or sol-gel methods.
173 citations
TL;DR: In this paper, the effect of polyethylene glycol (PEG) addition to the precursor solution on the photocatalytic activity and microstructure of the resultant coatings are studied.
Abstract: In this study the porous TiO2 anatase coatings are prepared from alkoxide solutions containing polyethylene glycol (PEG) by a dip-coating technique. The effects of PEG addition to the precursor solution on the photocatalytic activity and microstructure of the resultant coatings are studied. The larger amount and the larger molecular weight of PEG, the larger size and more pores produced in the resultant coatings on the decomposition of PEG during heat-treatment. The adsorbed hydroxyl content of such porous coatings is found to increase due to the larger size and more pores in the coatings. However, the transmittance of the coatings decreases due to the scattering by the larger size and more pores. Photocatalytic degradation experiments show that organophosphorous insecticide, dimethyl-2,2-dichlorovinyl phosphate (DDVP), was efficiently degraded in the presence of the porous TiO2 coatings by exposing the DDVP solution to sunlight. Photocatalytic degradation rate was related to the adsorbed hydroxyl content, transmittance and morphology of the resultant coatings.
157 citations
TL;DR: The TiO2/ACFF porous composites with synergetic adsorption and photocatalytic activities have great potentials for toluene removal.
153 citations
TL;DR: In this paper, the authors examined the effect of TiO 2 immobilized on activated carbon (AC) by co-injecting binary pollutants simultaneously since the presence of other pollutants might have an inhibition effect on the photocatalytic activity under different humidity levels.
Abstract: Previously we identified that residence time and water vapor are the vital parameters that affect the photodegradation of indoor air pollutants at parts-per-billion (ppb) levels using TiO 2 . The presence of water vapor competes with pollutants for adsorption sites on TiO 2 thus reducing the pollutant removal rate. By immobilizing TiO 2 on activated carbon (AC), a satisfactory pollutant removal rate is achieved even at high water vapor levels. This study further examines the effect of TiO 2 immobilized on AC by co-injecting binary pollutants simultaneously since the presence of other pollutants might have an inhibition effect on the photocatalytic activity under different humidity levels. 200 parts-per-billion NO, 20 ppb BTEX and 200 ppb SO 2 were co-injected under different residence time and humidity levels to investigate their mutual effect on TiO 2 and TiO 2 immobilized on AC. Results showed that no significant pollutant removal difference was observed between TiO 2 and TiO 2 immobilized on AC at longer residence time. The presence of BTEX only reduced NO conversion by 5%. At evaluated humidity levels, however, a significant different pollutant removal rate was observed. The presence of BTEX reduced NO conversion by more than 10%. The use of TiO 2 on AC, reduced both the competition effect of the pollutant and water vapor on TiO 2 . The inhibition effect of BTEX and SO 2 on NO conversion was significantly reduced when TiO 2 immobilized on AC compared to TiO 2 only. The by-product, NO 2 , from the photodegradation of NO, was also reduced despite the presence of SO 2 and BTEX under high humidity level.
150 citations