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

• Oxygen atoms of Zr-O-P and -POH of α-ZrP acted as adsorption sites for cations. • La3+ was mainly adsorbed through ion exchange with the hydrogen of -POH groups. • La3+ was most stably adsorbed in the center of six-membered O ring of Zr-O-P. • Impurity Al3+ greatly affected the adsorption of La3+ on α-ZrP, contrary to NH4+. • Bonding of La 4d with Os 2p orbitals occured in the range of −9 to 0 eV in PDOS. 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 La 3+ 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 . La 3+ was mainly adsorbed through ion exchange with the proton of surface -POH. The presence of impurity Al 3+ had a great influence on the adsorption of La 3+ on α-ZrP contrary to the case of NH 4 + . DFT calculations further proved that the oxygen of -Zr-O-P- and -POH acted as adsorption sites of α-ZrP, and the adsorption energies of La 3+ , Al 3+ and NH 4 + were −375.7, −2149.5 and −22.8 kJ⋅mol −1 , respectively, in the order of Al 3+ > La 3+ > NH 4 + , consistent with the experimental results. The partial density of states (PDOS) suggested that the bonding peaks between La 4d and O s 2p orbitals occurred in the energy range of −9 to 0 eV.