Sorption of Np(V) by synthetic hydroxyapatite

Abstract

Abstract The sorption of Np(V) to synthetic hydroxyapatite was determined in batch experiments in a 0.1M NaClO4 solution. The hydroxyapatite used was of high purity as determined by SEM, EDS, XRD, FT-IR and ICP-MS analysis. Results from kinetic experiments with an initial Np(V) concentration of 1×10-7 to 1×10-6M indicate the sorption process is relatively fast with more than 90 of the Np(V) being sorbed in approximately 3 hours. Equilibrium experiments performed over the pH range of 6 to 11 indicated sorption is strongly pH dependent with distribution coefficients, K d values (mL/g), increasing from 123L/mole at pH 6 to 69200L/mole at pH 8.5. K d values are observed to decrease as pH further increases. Data points over a range of Np(V) concentrations were collected at pH 8 and fitted to the Langmuir isotherm model for simple adsorption. The Langmuir equation gave an excellent representation of the data. Langmuir parameters were determined to be C a=0.032mole/mole and K=1.22×106L/mole, indicating the high affinity of hydroxyapatite for Np(V) adsorption.