MnO2 has the advantage of being environmentally friendly and abundant in soil, but its ability to activate persulfate is poor. This study combines MnO2 with CuO into a mixed metal oxide through a one-step reaction to increase the persulfate activation efficiency of the obtained product. These mixed oxides were synthesized by alkalization of a solution containing ions of two metals and then calcined at 300°C. The obtained oxide catalysts were characterized by methods such as FTIR, SEM, BET analysis, and zeta potential. The adsorption and decomposition of methyl orange (MO) were experimentally conducted in batch form using the above mixed metal oxides as adsorbents or persulfate activators. The results showed that the mixed oxides exhibited characteristic peaks in the FTIR spectrum, and were in the form of nanorods (CuO) and amorphous small particles (3:1CuO/MnO2). The CuO catalyst has a specific surface area of 20.23m²/g and pore sizes ranging from 20 to 30Å. The zeta potentials of both CuO and MO were highly negative, e.g., -46.5mV and -24.1mV, respectively. The adsorption capacities of MO onto the mixed oxides were quite low (~13.5%) and decreased gradually as the CuO content decreased. However, the persulfate activation capacity of the mixed oxides for MO decomposition was quite high, e.g., that of 3:1CuO/MnO2 for 40mg/L MO was 74.1%. In addition, the decomposition of MO almost followed pseudo-second-order reaction kinetics.

In this paper, Mn-Fe bimetallic nanoparticles were synthesized by simultaneous reduction of a salt mixture of KMnO4 and FeCl3 with glucose as a reducing agent. Degradation of methyl orange in aqueous solution, using hydrogen peroxide as an oxidizing agent, was used to evaluate the catalytic activity of the material. The material was characterized using scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The results showed that cubic manganese oxide nanoparticles were formed at the molar ratio of KMnO4/C6H12O6·H2O = 5/5 and the hydrothermal temperature of 120-220°C, while the oval-shaped structure was formed at the molar ratio of KMnO4/C6H12O6·H2O = 5/40 and the hydrothermal temperature of 220 °C. The cubic Mn-Fe bimetallic nanoparticle was still formed at the molar ratio of Mn/Fe/C6H12O6 = 5/2/5 and the hydrothermal temperature of 120°C, and the methyl orange decomposition efficiency was found to be the highest value of 57% on this catalyst sample.