Catalytic ozonation of phenylamine in water with a manganese ore

Recalcitrant pollutants, which form surface complexes with surface metal sites of the catalyst, are difficult to remove by catalytic ozonation in water. Phenylamine (PA), one of the refractory pollutants, was degraded by ozone catalysis with manganese ore in this paper. And the effectiveness and the mechanism of catalytic ozonation with manganese ore for the degradation of PA in water were studied. After the BET test, the specific surface area of the raw and calcined manganese ore was 27.65 m² g^-1 and 33.49 m² g^-1, respectively. The effects of solution pH, catalyst dose and reaction time on the degradation of PA were evaluated. Results showed that the catalytic potential of calcined manganese ore was better than that of raw manganese ore and ozonation alone in the degradation of PA. It revealed that the increase of hydroxyl radicals generated on the surface of the catalyst or in the solution improved PA degradation. Oxidation of free radicals was the main mechanism of PA degradation in the catalytic ozonation process, occurring with a pseudo-first-order reaction rate at a constant of 0.0993 min^-1 (CMP) under the pH of 7.20 and catalyst dose of 3 g L^-1. Also, an activation energy of 20.4 kJ mol^-1 for PA oxidation over CMP in the presence of O₃ was estimated.