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

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 hydrothermal 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 (•OH). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging experiments. •OH, superoxide radical (•O₂^-), and singlet oxygen (¹O₂) represented the dominant reactive species for 4-CP degradation. The O₃/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.