A theoretical study on the selective adsorption of NH4+ and Cs+ on the phosphomolybdate ion

Abstract The adsorption mechanisms of NH 4 + and Cs + on phosphomolybdate ion were investigated in detail by density functional theory (DFT). The computational results indicate that [PMo 12 O 40 ] 3− is a cage-like structure formed by the three-membered rings and four-membered rings constructed by the Mo O bonds. Both NH 4 + and Cs + could be easily adsorbed at the bridge oxygen site of the four-membered ring on the surface of the [PMo 12 O 40 ] 3− ion. The adsorption of Cs + on [PMo 12 O 40 ] 3− is more energetically favorable than that of NH 4 + , which likely accounts for the better Cs + adsorption capability of ammonium phosphomolybdate.