Adsorption of rare earth La3+ by α- zirconium phosphate: An experimental and density functional theory study

Abstract

The α-zirconium phosphate can act as a potential adsorbent for recycling rare earth ions in tailwater because of the abundant surface -POH groups and the layered structure. The adsorption behaviors and mechanism of rare earth La3+ on the material were studied through experimental and density functional theory (DFT) calculation methods. The experimental results show that the adsorption process conformed to pseudo-first-order kinetics and Langmuir isotherm model, with the maximum adsorption amount of 37.1 mg⋅g−1. La3+ was mainly adsorbed through ion exchange with the proton of surface -POH. The presence of impurity Al3+ had a great influence on the adsorption of La3+ on α-ZrP contrary to the case of NH4+. DFT calculations further proved that the oxygen of -ZrOP- and -POH acted as adsorption sites of α-ZrP, and the adsorption energies of La3+, Al3+ and NH4+ were −375.7, −2149.5 and −22.8 kJ⋅mol−1, respectively, in the order of Al3+ > La3+ > NH4+, consistent with the experimental results. The partial density of states (PDOS) suggested that the bonding peaks between La 4d and Os 2p orbitals occurred in the energy range of −9 to 0 eV.