*4.4. Electron Beam Treatment*

In the electron beam technology, an electron beam generated from an EB accelerator and absorbed by the background gas to ionize the air and form some active oxidizing radicals, such as ·OH and ·HO<sup>2</sup> and excited ions as O (3P), which is critical for the destruction of VOCs [216–218]. The oxidizing radicals reacted with VOCs and decomposed them to inorganic compounds. There are three types of accelerators used for VOCs decomposition, including transformer accelerator, ultrahigh frequency accelerator, and linear microwave accelerator [217]. This technology has been used for the elimination of acetaldehyde, benzene, dodecane, ethylbenzene, hexadecane, pentane, styrene, tetradecane, toluene, trimethylamine, turpentine, xylene, dimethyl sulfide, dimethyl disulfide, methyl mercaptan, and chlorinated VOCs in a lab or pilot scale [218–228]. The electron beam can treat the waste gas with a low concentration of VOCs (10 to hundreds ppm). The initial electrons from an electron beam can hardly decompose the VOCs molecules, while it can react with background gases and form active radicals. The way to improve the abatement rate of aromatic VOCs includes the addition of humidity (formation of OH·), ammonia, chlorinated VOCs, ozone, and using an absorbed dose [220,229]. The reaction temperature, VOCs molecular structure, and background gas also influence the decomposition efficiency. However, there are also some drawbacks of the electron beam technology, the generation of active oxidizing radicals, e.g., ·OH and ·HO<sup>2</sup> can lead to the creation of toxic intermediates, especially in the case of the VOCs emission with an unknown composition, such as the production of toxic byproducts (aerosol, ozone, CO, and other trace organic compounds). The equipment is also too complex. It still needs more research for the industrial application.
