Dual functionalities of inexpensive Mn/TiO2 catalyst to produce oxychar for ammonia capture

This study explores the dual functionality of a manganese/titanium dioxide (Mn/TiO 2 ) catalyst in a low-temperature partial oxidation process to enhance the performance of oxychar for NH 3 capture. The Mn/TiO 2 -modified oxychar demonstrated a significant increase in NH 3 capture, achieving NH₃ uptake of 62.8 mg/g at 140°C. The superior performance is attributed to strong chemical adsorption between NH 3 and the oxygen-containing functional groups (OCFGs) associated with dissolved organic carbon. Mechanism study showed that O 2 adsorbed on Mn/TiO 2 surface can be activated for OCFG formation on oxychar. The second function of Mn/TiO 2 is to enhance the product yields by inhibiting free radical chain reactions. At 220°C, Mn ions act as free radical scavengers, converting highly reactive radicals into less reactive species, preventing uncontrolled combustion, and promoting selective oxidation. This work advances the understanding of Mn-based catalysts in oxychar production, offering a scalable pathway for NH 3 capture and sustainable waste recycling. • Mn/TiO 2 enhances oxychar for effective NH 3 capture at 140°C. • Mn/TiO 2 can activate O 2 to promote OCFG generation. • Mn ions inhibit radical chain reactions, increasing yield at 220°C. • DOC provides OCFGs as NH 3 adsorption sites. • Mn/oxychar shows high NH₃ retention with 54.8 % stability post-desorption.