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.

Role of Nanomaterials in the Treatment of Wastewater: A Review

Platinized titanium dioxide (Pt/TiO2) as a multi-functional catalyst for thermocatalysis, photocatalysis, and photothermal catalysis for removing air pollutants

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.

An Overview of Photoreactors and Computational Modeling for the Intensification of Photocatalytic Processes in the Gas-Phase: State-of-Art

Ultraviolet photocatalytic oxidation technology for indoor volatile organic compound removal: A critical review with particular focus on byproduct formation and modeling.

Ultraviolet photocatalytic oxidation technology for indoor volatile organic compound removal: A critical review with particular focus on byproduct formation and modeling

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.

Mohan V. Lekshmi

Papers

Heterogeneous Photocatalysis for Indoor Air Purification: Recent Advances in Technology from Material to Reactor Modeling