A non-specific surface area dominated catalytic ozonation with CuO modified β-MnO2 in efficient oxalic acid degradation

Abstract

In this paper, a series of copper oxide supported manganese dioxide (CuXMnT) composites were prepared by the hydrothermal and deposition precipitation methods. The effects of different hydrothermal temperatures (100 °C–180 °C) and copper doping amounts (1–10 mM) on the structural and physicochemical properties of CuXMnT composites were systematically investigated. The BET, SEM, and XRD characterizations revealed that the CuXMnT composites exhibited a typical rod-like structure. Besides, with the increscent hydrothermal temperature, the BET specific surface area decreased and the crystal form of the composites changed from α-MnO2 to β-MnO2. The Cu1Mn180 with low specific surface area (3.277 m2 g−1) exhibited the splendid catalytic ozonation activity and the oxalic acid (OA) removal rate reached 87.5% in O3/Cu1Mn180 process compared with single ozonation (3.2%). Additionally, it was noteworthy that the excellent catalytic performance of Cu1Mn180 (91.8% of OA removal rate) at pH 3.0 was resulted from the electrostatic adsorption. While, the complexation played a vital role for OA degradation at pH 6.0 and 9.0 with the OA removal efficiencies of 87.5 and 70.3% within 30 min, respectively. Furthermore, Cu1Mn180 could obtain more than 90.9% of OA removal rate during multiple consecutive cycles, representing the satisfactory stability and reusability. Moreover, the multivalent Mn, the structural oxygen species, and Cu species played the key roles for OA degradation in O3/Cu1Mn180 process at pH 6.0 via the TEM, ESR, XPS and O2-TPD characterizations. Overall, the results presented a promising alternative material for efficient catalytic ozonation application in water.