Adsorption of Cesium, Cobalt, and Lead onto a Synthetic Nano Manganese Oxide: Behavior and Mechanism

Synthesis parameters of nano manganese oxide (NMO) were tuned in order to maximize Cs and Co sorption efficiencies. The prepared oxide was characterized using various techniques including x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), SEM, and surface area analyzer. The sorption characteristics with respect to uptake of Cs, Co, and Pb were evaluated. An alpha - phase nano manganese oxide with a surface area of 165 m(2) g(-1) was synthesized. Maximum adsorption capacities were 230 mg g(-1) for Pb2+, 73 mg g(-1) for Cs+, and 26 mg g(-1) for Co2+. The intraparticle diffusion was the rate-limiting step in the case of Pb2+, whereas both intra-particle diffusion and film diffusion contribute to the rate-determining step in the adsorption process in the case of Cs+ and Co2+. FT-IR analyses reveled that Cs+ and Co2+ coordinated to vacancy sites of NMO as inner-sphere complexes, while Pb2+ formed bidentate corner-sharing complexes. NMO had high affinity for Pb2+ but was also effective for sorption of Cs+ and Co2+ over a wide pH range, even in the presence of Na+. HCl (0.5 mol L-1) solution could regenerate the adsorbent successfully, and the NMO could be efficiently reused with lower production of residues. Thus, the prepared NMO can be efficiently used in wastewater treatment in terms of high adsorption capacity, easy availability, and low cost.