Yong Gi Jung’s research while affiliated with Chung-Ang University and other places

In this study, we verified the application of TiO2 photocatalysts on ventilation ducts used in buildings and their effects on reducing nitrogen oxide (NOx), which is a typical particulate matter precursor. The TiO2 photocatalyst produces a radical dioxide with a strong acid oxidation power through photochemical reactions with ultraviolet-A (UV-A) rays and removes NOx through oxidation. The removal experiment was conducted by applying TiO2 photocatalyst coatings inside the duct to comply with the conditions of the ISO 22197-1: 2007. In addition, changes in the NOx removal were confirmed through changes in the concentration of NOx and UV-A irradiance inside the duct. At approximately 100 min after switching on the UV-A lamp during the experiment conduced according to ISO 22197-1: 2007, the NOx concentration decreased to 0.053 ppm (by 94.87%). Moreover, it has been confirmed that the trend of reduction is proportional to the changes in UV-A irradiance and NOx concentration, that is, an increase in UV-A irradiance has a significant impact on the reduction of NOx concentration; NOx reduction increases as a secondary function due to an increase in the UV-A irradiance. Through this study, it is believed that NOx, a representative precursor material that generates particulate matter, can be removed through a building ventilation system using a TiO2 photocatalyst.

Air purifiers are a popular tool to manage indoor particulate matter; however, their effectiveness with respect to resuspending and removing particles that have been deposited on surfaces is limited. This study proposed and evaluated a method of removing both suspended and deposited particulate matter using an air purifier in conjunction with an airflow source. First, the effectiveness of the air purifier with respect to removing deposited particulate matter was determined in a static environment and under forced airflow. Then, the removal efficiency of the purification system was evaluated under varying airflow orientations and velocities. Results showed that the air purifier contributed to particulate matter resuspension and removal, and the efficiency was significantly improved under forced resuspension due to airflow generation. The orientation of the airflow was found to have an impact on the resuspension and removal efficiency of particulates, and four-way airflow was more effective compared to one-way airflow. This was attributed to four-way flow increasing the airflow diffusion radius compared to one-way flow. A flow velocity of 5 m/s or greater was necessary to resuspend deposited particulate matter. These findings illustrate that forced resuspension is an effective means of reducing deposited particulate matter in indoor environments, and four-way airflow with a wide diffusion radius and a velocity of 5 m/s or higher are the optimum conditions for this purpose.