Hydrothermally improved natural manganese-containing catalytic materials to degrade 4-chlorophenol

Abstract

Natural manganese-containing mineral (NMM) was used as a catalyst in heterogeneous catalytic ozonation for 4-chlorophenol (4-CP) degradation. The surface and structural properties of NMM were modified by the hydro-thermal aging process and called H-NMM. The catalytic activity of NMM and H-NMM were evaluated for the catalytic ozonation process (COP). The synergistic effect of NMM and H-NMM in ozonation processes for 4-CP degradation under optimal conditions (pH of 7, 1 g/L of NMM and H-NMM, 0.85 mg/min of O3, and 15 min of reaction time) was measured by 3.04 and 4.34, respectively. During the hydrothermal process, Mn4+ and Fe2+ were converted to Mn2+ and Fe3+, which caused better performance of the H-NMM than the NMM. During the catalytic ozonation process, Mn2+ is completely oxidized, which increases the production of Hydroxyl radical (center dot OH). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging experiments. center dot OH, superoxide radical (center dot O-2(-)), and singlet oxygen (O-1(2)) represented the dominant reactive species for 4-CP degradation. The O-3/H-NMM process indicated a powerful ability in the mineralization of 4-CP (66.31 of TOC degradation). H-NMM exhibited excellent stability and reusability in consecutive catalytic cycles, and the NMM exhibited desirable performance. This study offers NMM and H-NMM as effective, stable, and competitive catalysts for hastening and enhancing the ozonation process to mitigate environmentally related pollutants of high concern.