Photothermal effect improving the activity of spinel MnFe2O4 nanoparticles for the catalytic activation HCO3−/H2O2 to achieve the degradation of dye pollutants in low-temperature condition

Abstract

Based on the features of Mn/Fe bimetallic sites and photothermal property, spinel MnFe2O4 nanoparticles were investigated to activate HCO3−/H2O2 for the degradation of methyl orange (MO), methylene blue (MB) and rhodamine B (RhB). Compared to Mn3O4, MnO2 and Fe2O3- activated HCO3−/H2O2 systems, higher degradation rate of dyes was achieved in the spinel MnFe2O4/HCO3−/H2O2 system at 23 ± 2 °C, due to the Mn/Fe bimetallic active sites of spinel MnFe2O4. Meanwhile, the spinel MnFe2O4 nanoparticles had high stability in HCO3−/H2O2 activating for dyes degradation in 15 rounds of reaction. The co-existing ions and hardness in municipal tap water had weak influence on the HCO3−/H2O2 activating activity of spinel MnFe2O4 for dyes degradation at 23 ± 2 °C. More interestingly, although the dyes degradation activity of MnFe2O4/HCO3−/H2O2 system at low-temperature (3 ± 2 °C or 13 ± 2 °C) was weakened, the system activity at low-temperature can be obviously boosted through AM 1.5 G irradiation to activate the photothermal effect of spinel MnFe2O4. Additionally, the MnFe2O4/HCO3−/H2O2 system exhibited good practicability for dyes degradation in a 15 L of continuous reactor. In mechanism, the degradation of MB in spinel MnFe2O4/HCO3−/H2O2 system was found to be co-driven by 1O2 and OH, and the degradation of RhB and MO was co-initiated by O2−, OH and CO3−.