[Preparation of Mn-Co/Ceramic Honeycomb Catalyst and Its Performance on Catalytic Ozonation of Hydroquinone]

In order to improve the activity and working life of metal catalysts in the heterogeneous catalytic ozonation of organic wastewater, four kinds of Mn-Co/ceramic honeycomb (CH) catalysts with different mass ratios of Mn and Co were prepared by coating method using cobalt nitrate hexahydrate [Co(NO₃)₂·6H₂O] and manganese nitrate [Mn(NO₃)₂] as precursors, respectively, and CH as the carrier. The structure of the catalysts was analyzed via X-ray diffraction (XRD), N₂ adsorption/desorption, field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The mechanical properties of the catalysts were studied. The reaction kinetics model of O₃ alone and catalytic ozonation of the hydroquinone were established and catalytic ozonation performance of catalysts was investigated. The results showed that the crystal phase of Mn₀Co₁/CH belonged to CoAl₂O₄ and that the crystal phase of the Mn-Co/CH catalyst (Mn₁Co₁, Mn₂Co₁, and Mn₃Co₁) mainly belonged to Mn₃O₄ and CoO. In particular, the Mn₁Co₁/CH catalyst had a large specific surface area of 190 m²·g^-1, high pore volume of 0.25 cm³·g^-1, and pore size of 4.8 nm. The highest catalytic activity was obtained when Mn∶Co was 1∶1 (Mn₁Co₁/CH catalyst). The catalytic activity of the Mn₁Co₁/CH catalyst was the highest, and removal efficiencies of hydroquinone and COD were 78% and 54%, respectively, using Mn₁Co₁/CH catalytic ozonation. The Mn-Co/CH catalyst had a high compressive strength (15.89-16.94 MPa). The degradation efficiency of hydroquinone decreased significantly after the addition of tert-butanol, which indicated that·OH played an important role in the Mn₁Co₁/CH catalytic ozonation. The catalytic ozonation process fitted the first-order kinetic model. The apparent rate constant k for O₃ alone was only 0.0306. Furthermore, the Mn₁Co₁/CH catalyst had the highest rate, with an apparent rate constant k of 0.0535 min^-1. The Mn-Co/CH catalyst was easy to industrialize owing to its lower consumption, excellent catalytic characteristics, and long working life.