Al2O3-Based Hollow Fiber Membranes Functionalized by Nitrogen-Doped Titanium Dioxide for Photocatalytic Degradation of Ammonia Gas

In recent years, reactive ammonia (NH₃) has emerged as a major source of indoor air pollution. In this study, Al₂O₃-based hollow fiber membranes functionalized with nitrogen-doped titanium dioxide were produced and successfully applied for efficient heterogeneous photocatalytic NH₃ gas degradation. Al₂O₃ hollow fiber membranes were prepared using the phase inversion process. A dip-coating technique was used to deposit titanium dioxide (TiO₂) and nitrogen-doped titanium dioxide (N-TiO₂) thin films on well-cleaned Al₂O₃-based hollow fiber membranes. All heterogeneous photocatalytic degradation tests of NH₃ gas were performed with both UV and visible light irradiation at room temperature. The nitrogen doping effects on the NH₃ heterogeneous photocatalytic degradation capacity of TiO₂ were investigated, and the effect of the number of membranes (30, 36, 42, and 48 membranes) of the prototype lab-scale photocatalytic membrane reactor, with a modular design, on the performances in different light conditions was also elucidated. Moreover, under ultraviolet and visible light, the initial concentration of gaseous NH₃ was reduced to zero after only fifteen minutes in a prototype lab-scale stage with a photocatalytic membrane reactor based on an N-TiO₂ photocatalyst. The number of Al₂O₃-based hollow fiber membranes functionalized with N-TiO₂ photocatalysts increases the capacity for NH₃ heterogeneous photocatalytic degradation.