Robust iron-doped manganese oxide nanoparticles from facile fabrication to photo-catalytic degradation application of binary dyes mixture

The manganese oxide (MnO2 and iron-doped manganese oxide (Fe–MnO2) nanoparticles (NPs) with reduced band gap (Eg) were fabricated through the co-precipitation process. They used to degrade Indigo Carmine (IC) and Rhodamine B (RB) binary mixture in an aqueous medium under solar light irradiation. From FT-IR, the twisting modes of the Mn–O bond and the stretching vibrations of the Fe–Mn–O2 bond were confirmed from the peaks observed at 480 cm−1,584 cm−1,675 cm−1, and 900 cm−1, 1150 cm−1, and 1200 cm−1 respectively. The MnO2 has an optical band gap of 3.2 eV, which was decreased to 3 eV in Fe–MnO2. The zero charge (PZC) point was 8 for Fe–MnO2 and 7 for MnO2. The BET surface area for Fe–MnO2 was 398 m2/g, relatively higher than MnO2 particles, having a surface area of 384 m2/g. The average crystallite sizes calculated from Scherer formulae were 37 nm for MnO2 and 31 nm for Fe–MnO2 NPs. SEM confirmed the irregular morphology of the prepared particles. It was analyzed that agglomeration occurs in MnO2 than the Fe–MnO2. The maximum degradation of IC dye was 99%, and that of RB was 98% at the optimum conditions. The data were best fitted to second-order kinetics.