Synthesis and characterization of manganese dioxide for the removal of lead and cadmium of aqueous effluents

Full text: The contamination of water by toxic heavy metals is one of the most severe global environmental problems, besides being very difficult to solve since heavy metals are not biodegradable, they accumulate in living organisms and cause serious problems. Therefore, it is necessary to find a way to develop more efficient methods to eliminate or reduce contaminating metals to acceptable levels. Within the group of heavy metals, we can find, among others, lead and cadmium, which due to their characteristics are considered two of the most harmful to human health and to the environment. In the present research, the synthesis of a-MnO₂ was carried out using potassium permanganate as a precursor and ethanol and methanol as reducing agents, controlling the synthesis parameters according to the particle size. The XRD analysis of the samples calcined at 500°C for 2hr and 5hr showed an increase in crystallite size up to 23.65nm, which was from the sample synthesized with ethanol and calcined at 500°C for 5 hours. The FESEM microscopy analysis of the calcined samples showed crystallinity, with quasi spherical morphology in the case of the samples synthesized with methanol and with an average particle size of 20 nm, and with a thread morphology in the case of the samples synthesized with ethanol and with an average wire diameter of 10nm. Finally, the results of the removal tests of lead and cadmium ions from synthetic effluents using a-MnO₂ showed that it is feasible to use manganese dioxide for this purpose, achieving the removal of 99.99% of Pb in 5min and 99.7% of Cd in 45min of removal time. References: [1] Nilesh R. Chodankara , Girish S. Gunda , Deepak P. Dubalb , Chandrakant D. Lokhande Alcohol mediated growth of a-MnO2 thin films from KMnO4 precursor for high performance supercapacitors. Catalan Institute of Nanoscience and Nanotechnology, Barcelona, Spain (2014). (author)