Hydrothermally Synthesized MnO2 Nanowires and Their Application in Lead (II) and Copper (II) Batch Adsorption

Manganese oxide (MnO2) nanowires with diameters of 20 nm to 100 nm are synthesized by hydrothermal method. Chemical characterization of these nanostructures demonstrates the formation of Mn(IV), corroborating the MnO2 compound. The nanowires were used as adsorbents of Pb(II) and Cu(II) ions from water in batch system at room temperature. The results indicate faster adsorption rates and better affinity towards Pb(II) compared to Cu(II), since the adsorption capacity (3.730 [mg·g−1]) and the percentage of removal (99.99%) at equilibrium for Pb(II) are higher than those for Cu(II), 2.972 [mg·g−1] and 75.48%. The kinetics of adsorption was described by a pseudo-second order rate model for both ions, and Weber and Morris intra-particle diffusion model was used to a better understanding of the process. In addition, the Langmuir and Freundlich models were used to describe the isotherms, the first model was better adjusted for Cu(II) adsorption and the later for Pb(II) adsorption.