Degradation of rhodamine B with manganese dioxide nanorods

This is an investigation on oxidative degradation of rhodamine B (RhB) by manganese dioxide (MnO₂) nanorods synthesized by redox co-precipitation method. Field emission scanning electron microscopy of MnO₂ nanorods at an electron voltage of 10 kV revealed a rod-like morphology for the synthesized nanoparticles. Fourier transform infrared spectra exhibited characteristic peaks of MnO₂. Surface area of MnO₂ nanorods was 277 m²/g. Effect of various parameters like initial concentration and pH of RhB solution, time of contact between MnO₂ nanorods and RhB, dosage of MnO₂, and stirring speed on decolouration of RhB was evaluated in batch experiments. Rapid decolouration in the initial period of the reaction was observed due to the adsorption of RhB molecules onto the surface of MnO₂ nanorods followed by oxidative degradation. Percentage decolouration decreased with increase in initial concentration and increased with increase in dosage, speed of stirring the mixture and with increase in pH up to pH 7. Near complete decolouration was achieved at a dose of 0.5 g/L of MnO₂ nanorods from 20 mg/L RhB solution within 3 min. Observations fitted best to the pseudo second order kinetic model. This study could pave the way for development of cost-effective, nontoxic nanostructures for treatment of wastewaters containing RhB.