Removal of Pb(II) and Cu(II) Ions From Aqueous Solutions by Manganese Phosphonate

Abstract

An inorganic-organic hybrid material manganese phosphonate (NH4)Mn(hedpH) (hedp = 1-hydroxyethylidenediphosphonate) (denoted as MnP) was successfully synthesized under hydrothermal conditions, and it was used to remove heavy metal ions Pb(II) and Cu(II) from aqueous solutions. This adsorbent contained anionic double chains of , composed of {MnO6} octahedra and {CPO3} tetrahedra. Strong hydrogen bonds existed between the neighboring chains, and the layers in the ab plane were formed. The counterions occupied the cavities within the layer; hence these layers were further connected by hydrogen bonds to develop a three-dimensional network. Moreover, the adsorption research results revealed that MnP had excellent adsorption capacity for Pb(II) and Cu(II), especially for Pb(II). It was found that the Langmuir model was better than the Freundlich model to fit the adsorption isotherms of MnP for Pb(II) and Cu(II), and the maximum adsorption capacities for Pb(II) and Cu(II) were 740.74 mg/g and 154.32 mg/g, respectively. The kinetics data indicated that the adsorption processes were governed by the film diffusion and followed pseudo-second-order rate model for MnP.