Author: Site Editor Publish Time: 22-10-2025 Origin: Site
As public awareness of indoor air quality grows, volatile organic compounds (VOCs), as one of the primary indoor pollutants, have become a focal point of research. Traditional filtration technologies have limited effectiveness in removing gaseous VOCs, whereas advanced oxidation technologies based on ultraviolet (UV) light show significant potential. This article explores the mechanisms of VOC removal using emerging UV-C LED technology through photochemical degradation and photocatalytic oxidation, as well as its significance and advantages in indoor air purification applications.
Volatile organic compounds (VOCs) are organic compounds that easily volatilize at room temperature, commonly found in building materials, furniture, cleaning agents, and personal care products. Prolonged exposure to high concentrations of VOCs can pose serious health risks, including headaches, irritation of the eyes, nose, and throat, and potential damage to the liver, kidneys, and nervous system. Certain VOCs, such as benzene and formaldehyde, are known carcinogens.
Traditional air purification technologies, such as HEPA filters, primarily target particulate matter and have minimal effect on gaseous VOCs. Activated carbon adsorption can capture some VOCs effectively but faces issues like adsorption saturation, the need for frequent replacement, and the risk of becoming a secondary pollution source. Therefore, developing advanced purification technologies that directly decompose or destroy VOC molecules is critical.
Unlike filtration or adsorption, the core mechanism of UV-C LED technology lies in utilizing the high-energy short-wavelength ultraviolet light (typically 200–280 nm) it emits to directly break the chemical bonds of VOC molecules, leading to their decomposition or conversion into harmless substances. This process occurs primarily through two pathways:
Certain VOC molecules have chemical bond energies that fall within the energy range of UV-C photons. When VOC molecules absorb UV-C photons, their internal bonds break. For example, in the case of formaldehyde (HCHO), its C-H and C=O bonds can be effectively disrupted by UV light at approximately 185 nm and 254 nm, generating highly unstable radicals such as hydrogen and formyl radicals. These radicals undergo further reactions, ultimately oxidizing into harmless carbon dioxide (CO₂) and water (H₂O).
Direct photolysis alone has limited efficiency in decomposing various VOCs. In practical applications, UV-C LEDs are often combined with photocatalysts (most commonly titanium dioxide, TiO₂) to form photocatalytic oxidation systems, which are among the most effective air purification technologies studied.
Process:
Generation of Electron-Hole Pairs: When UV-C photons with energy exceeding the bandgap of TiO₂ (approximately 3.2 eV for anatase TiO₂, corresponding to UV light at ~385 nm) strike the photocatalyst surface, they excite electrons from the valence band to the conduction band, leaving positively charged "holes" in the valence band.
Production of Reactive Oxygen Species: The photogenerated holes, with strong oxidative properties, can extract electrons from water molecules adsorbed on the catalyst surface, oxidizing them into hydroxyl radicals (·OH). Simultaneously, photogenerated electrons, with strong reductive properties, combine with oxygen in the air to form superoxide radicals (·O₂⁻).
Non-Selective Oxidative Decomposition: Hydroxyl radicals, one of the most potent oxidants in nature, can non-selectively attack nearly all VOC molecules through hydrogen abstraction or addition reactions. This process gradually degrades large, toxic VOC molecules (e.g., benzene, toluene, xylene) into smaller intermediate products, ultimately mineralizing them into CO₂ and H₂O.
Studies have shown that the combination of UV-C light (especially at 254 nm) and TiO₂ achieves removal rates of over 90% for formaldehyde, acetaldehyde, and benzene derivatives. Compared to traditional mercury-based UV-C lamps, UV-C LEDs offer advantages such as instant startup, tunable wavelengths (allowing precise matching with the optimal absorption wavelength of photocatalysts), mercury-free composition, and compact size, enabling new possibilities for optimizing photoreactor designs.
Unlike adsorption technologies, photocatalytic oxidation aims to completely mineralize pollutants rather than merely transferring them. This fundamentally eliminates the risk of secondary pollution caused by VOCs being re-released into the air after adsorption saturation.
The non-selective attack of hydroxyl radicals enables this technology to simultaneously address multiple VOCs, effectively handling complex indoor air pollution mixtures, including VOCs that are difficult to adsorb.
UV-C LEDs are mercury-free, aligning with the environmental requirements of the Minamata Convention on Mercury. With proper design (e.g., enclosing the light source to prevent direct human exposure), they can be safely used in air purification systems.
UV-C LEDs have high electro-optical conversion efficiency, low energy consumption, and a lifespan of tens of thousands of hours, significantly reducing operational and maintenance costs.
The removal of indoor VOCs using UV-C LED air disinfection technology relies primarily on photochemical direct decomposition and advanced oxidation processes triggered in synergy with photocatalysts. The latter, through the generation of highly oxidative hydroxyl radicals, efficiently and thoroughly degrades VOCs into harmless end products, representing a paradigm shift in indoor air purification from "capture" to "elimination."
Although challenges remain, such as cost and photon efficiency improvements, ongoing advancements in semiconductor technology and related research suggest that UV-C LED-based photocatalytic air purification systems, with their efficiency, environmental friendliness, and compact design, will become a key technology for creating healthy and safe indoor environments in the future.
