Ammonia (NH3) emissions from livestock facilities pose significant environmental challenges, particularly under high-humidity conditions where conventional adsorption efficiency significantly declines. This study investigates the photocatalytic removal of NH3 using TiO2-coated zeolite LTA supports (3A and 4A) under relative humidity (RH) levels typical of farm environments. The composites were synthesized via controlled dip-coating cycles and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analyses. At 55% RH, zeolite 3A exhibited higher NH3 removal efficiency than zeolite 4A, owing to its smaller pore size and superior intrinsic adsorption selectivity. However, adsorption-only systems underwent rapid deactivation over repeated cycles. While TiO2 coatings enhanced the photocatalytic activity of both supports, zeolite 3A composites showed a more pronounced decline in efficiency over time. In contrast, at 95% RH, the TiO2-coated zeolite 4A achieved superior photocatalytic efficiency and operational stability. This performance is attributed to the 4A framework’s greater water uptake and faster diffusion kinetics, which promoted the generation of hydroxyl (•OH) and hydroperoxyl (HO2•) radicals under UV-A irradiation. These findings suggest that while TiO2–zeolite 3A is effective at moderate humidity, TiO2–zeolite 4A is more robust for high-humidity livestock environments, providing a sustainable strategy for effective NH3 emission control.
Lee et al. (Wed,) studied this question.