Upcycling Waste PET Bottles Into Cu-Mn-O Mixed Oxide Decorated Catalytic Membranes for Synergistic Filtration and Persulfate-Activated Dye Degradation.

The limitation of membrane filtration is that it only filters out pollutants but does not treat them thoroughly; therefore, catalytic membranes are a synergistic combination of membrane filtration and catalytic decomposition of pollutants. This study focuses on synthesizing mixed oxides Cu-Mn-O with different ratios and coating the optimal onto a PET membrane using a dip-coating method. The materials were thoroughly characterized through FTIR, XRD, TGA, zeta potential, EDS, BET, and SEM. The 3:1CuO/MnO₂ showed a low-order structure and seems to be amorphous through XRD results. SEM results showed that the mixed oxide nanoparticles have a porous structure, ultra-small size, and uniform distribution. The large specific surface area of the 3:1CuO/MnO₂ (64.09 m²/g) enhances the surface-active sites. In adsorption and degradation tests, the 3:1CuO/MnO₂ consistently showed the highest efficiency for both Congo red (CR) and methylene blue (MB). Specifically, the CR degradation reaction followed pseudo-second-order kinetics (PSO), while the MB degradation process conformed to pseudo-first-order kinetics (PFO). In membrane filtration, the water flux reached 170.5 L/m².h for the PET membrane and decreased to 124.7 L/m².h for the 3:1CuO/MnO₂/PET membrane due to the filling of the catalytic particles. Notably, the CR rejection of the 3:1CuO/MnO₂/PET membrane surged from 74.3% to 96.7% in the presence of peroxydisulfate (PDS). ROS (reactive oxygen species) trapping tests identified singlet oxygen as the primary oxidizing agent. Finally, the catalytic membrane exhibited impressive durability with stable performance after 4 cycles, opening up potential practical applications in textile wastewater treatment.