Sorption of Np(V) by synthetic hydroxyapatite

摘要

The sorption of Np(V) to synthetic hydroxyapatite was determined in batch experiments in a 0.1 M 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 x 10(-7) to 1 x 10(-6) M 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 123 L/mole at pH 6 to 69 200 L/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 = 0.032 mole/mole and K = 1.22 x 10(6) L/mole, indicating the high affinity of hydroxyapatite for Np(V) adsorption. [References: 39]