A novel molybdenum-based nanocrystal decorated ceramic membrane for organics degradation via catalytic wet air oxidation (CWAO) at ambient conditions

Abstract

Catalytic wet air oxidation (CWAO), one of the best-known methods for water treatment, has been intensely investigated for dyes degradation. However, the extreme operation conditions as well as the recovery of suspended catalyst are economically unattractive. In the current work, a novel Mo-based nanocrystal decorated ceramic membrane (Mo/Al2O3) has been prepared and applied for organics degradation via CWAO at ambient conditions for the first time. The catalytic Mo/Al2O3 membranes were prepared by an in-situ hydrothermal followed by calcination method. Their physical and chemical properties were characterized by field emission scanning electron microscope (FESEM), X-rays diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of Mo/Al2O3 membranes were evaluated via organics (safranine O and humic acid) degradation under a home-made membrane filtration system. The effects of calcination temperature, catalyst loading amount, and trans-membrane pressure (TMP) were systematically investigated. The stability and durability of the catalytic Mo/Al2O3 membrane were examined in a long-term filtration system. Results showed that the performance of Mo/Al2O3 membrane would decrease with increasing of calcination temperature as well as TMP. However, the catalyst loading amount was not a major effect on the removal of organics in the system. For one-time loading membrane calcined at 300 °C (1x-Mo/Al2O3 membrane@300), the removal efficiency could achieve higher than 90 % in 40 min in a recycled filtration system with an initial safranine O concentration of 10 mg L−1. The chemical quenching experiment as well as radical quantification verified the main reactive oxygen species were 1O2 and O2− in the system. The ROS generation mechanism was proposed via the characterization of the catalyst after reaction. The deliberate combination of CWAO and membrane separation represents a new strategy that offers exciting possibilities for water treatment under ambient conditions.