{[Ce(BTC)(H^sub 2^O)]·DMF}^sub n^ metal organic framework as a new adsorbent for removal of neodymium ions

The synthesis of {[Ce(BTC)(H2O)]·DMF}n metal organic framework (MOF) and its potential application for removal of neodymium ions were studied. The effective parameters on MOF’s properties such as metal ion to ligand ration, the heat treatment temperature and pH of the synthesizing solution were investigated. The optimum condition of synthesis was determined and the product was characterized by XRD, TG, BET, and SEM methods. SEM images showed that the synthesized sample had needle-shaped particles with 40–300 nm range in diameters. The high surface area of 806 m2/g was obtained for synthesized MOF. The adsorption performance of product was evaluated by Nd ions adsorption experiments considering the influencing factors (initial solution pH, contact time, initial metal ion concentration, temperature and ionic strength). Experimental results demonstrated that the equilibrium uptake of Nd was highly pH-dependent. Elovich model fitted well with the adsorption kinetic studies. The adsorption processes were described by Freundlich model and the maximum experimental adsorption capacity of 100 mg/g. Thermodynamics parameters such as change in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also calculated. The negative values obtained for ΔG° indicated that the sorption of neodymium ion on MOF was spontaneous at all studied concentrations. The reasons of positive ΔS° are the increasing of randomness at the solid–solution interface during the fixation of ion on the adsorbent surface. These results show that natural MOF hold great potential to remove neodymium ion from nuclear waste.