Investigation on the efficiency and mechanism of Cd(II) and Pb(II) removal from aqueous solutions using MgO nanoparticles

In this study, the removal of Cd(II) and Pb(II) from aqueous solutions using MgO nanoparticles prepared by a simple sol-gel method was investigated. The efficiency of Cd(II) and Pb(II) removal was examined through batch adsorption experiments. For the single adsorption of Cd(II) and Pb(II), The adsorption kinetics and isotherm data obeyed well Pseudo-second-order and Langmuir models, indicating the monolayer chemisorption of heavy metal ions. The maximum adsorption capacities calculated by Langmuir equation were 2294 mg/g for Cd(II) and 2614 mg/g for Pb(II), respectively. The adsorption process was controlled simultaneously by external mass transfer and intraparticle diffusion. In the binary system, a competitive adsorption was observed, showing preference of adsorption followed Pb(II) >Cd(II). Significantly, the elution experiments confirmed that neither Cd(II) nor Pb(II) could be greatly desorbed after water washing even for five times. XRD and XPS measurements revealed the mechanism of Cd(II) and Pb(II) removal by MgO nanoparticles was mainly involved in precipitation and adsorption on the surface of MgO, resulting from the interaction between active sites of MgO and heavy metal ions. Easy preparation, remarkable removal efficiency and firmly adsorptive ability make the MgO nanoparticles to be an efficient material in the treatment of heavy metal-contaminated water.