Metal-doped alumina pellets catalyze the quick degradation of humic acid using oxygen as the oxidant at low temperatures

Low-temperature catalytic air oxidation (LTCAO) is a promising technique that utilizes oxygen to oxidize humic acid (HA) at low temperatures. Still, the fine catalyst particles are difficult to recover and reuse, hindering the actual application of this technique. This study developed a new catalyst pellet by coating Fe or Cu on small Al2O3 balls. The pellet exhibited exceptional treatment efficiency and remarkable durability. HA was adsorbed on the catalyst surface, reacted with the center dot O-2 and center dot OH species generated in oxygen activation, and finally degraded into CO2 and H2O. The total organic carbon in the HA solution was removed by 92.5 % within 90 min. During HA degradation, the primary intermediates included 2,4-dimethyl-benzaldehyde, 2,4-bis(1,1-dimethylethyl)phenol, and hexanoic acid ethyl ester. The results provided a new type of catalyst that can be used in actual bed or tower reactors, taking a big step of LTCAO toward application.