Sorption Of Np Research Articles

Sorption and Colloidal Behavior of Np(IV) in a Bentonite-Carbonate Solution System

Abstract Sorption of Np(IV) on bentonite in the presence of carbonate was studied by a batch method. The sorption was considered mainly due to Np(OH)2(CO3)2 2- and Np(OH)4(CO3)2 4- The distribution coefficient (Kd of Np(OH)2(CO3)2 2- and Np(OH)4 (CO3)2 4- was determined to be 104.01±0.24 ml/g and 103.93±0.37 ml/g respectively. The increasing Kd at high pH was attributed to the sorption of NpO2(OH)-2 with the Kd of 105.82±0.39 ml/g The formation of colloidal species was observed under a reducing condition. By assuming Np(OH)4 as the colloidal species, the formation constant was evaluated to be βc≤1053.85 Under an oxidizing condition, the formation of the colloidal species was less observed possibly due to the transformation of Np(OH)4 to NpO2OH.

Sorption and Colloidal Behavior of Np(IV) in a Bentonite-Carbonate Solution System.

Abstract Sorption of Np(IV) on bentonite in the presence of carbonate was studied by a batch method. The sorption was considered mainly due to Np(OH)2(CO3)2 2- and Np(OH)4(CO3)2 4- The distribution coefficient (Kd of Np(OH)2(CO3)2 2- and Np(OH)4 (CO3)2 4- was determined to be 104.01±0.24 ml/g and 103.93±0.37 ml/g respectively. The increasing Kd at high pH was attributed to the sorption of NpO2(OH)-2 with the Kd of 105.82±0.39 ml/g The formation of colloidal species was observed under a reducing condition. By assuming Np(OH)4 as the colloidal species, the formation constant was evaluated to be βc≤1053.85 Under an oxidizing condition, the formation of the colloidal species was less observed possibly due to the transformation of Np(OH)4 to NpO2OH.

EXAFS spectroscopic study of neptunium(V) sorption at the .alpha.-iron hydroxide oxide (.alpha.-FeOOH)/water interface

The sorption of aqueous Np(V) on crystalline α-FeOOH (goethite) has been studied at the molecular level by synchrotron-based X-ray absorption spectroscopy. Sodium nitrate solutions (pH 7.2, ionic strength 0.08 M) having a Np(V) concentration of 1.3×10 -5 M were reacted with high surface area goethite (50 m 2 /g), resulting in ∼95% uptake of the Np and a sorption density of 10 -5 mol of Np/g of goethite

Sorption Behavior of Neptunium(V) Ion on Clay Sorbent

Sorption of Np(V) ion on a tuffaceous loam was studied under static and flowing conditions. The obtained results revealed that the distribution ratio of Np ion was influenced by pH and Ca ion concentration of the solution, probably because of the change in surface charge of loam with pH and of the coprecipitation due to the formation of calcium carbonate. The Np ion flowing down the column of the sorbent showed a breakthrough curve which enabled one to calculate the distribution ratio and the dispersion coefficient of the ion in the clay using the model for the process limited by the one-dimensional dispersion.

Sorption behavior of neptunium(V) ion on clay sorbent.

Sorption of Np(V) ion on a tuffaceous loam was studied under static and flowing conditions. The obtained results revealed that the distribution ratio of Np ion was influenced by pH and Ca ion concentration of the solution, probably because of the change in surface charge of loam with pH and of the coprecipitation due to the formation of calcium carbonate. The Np ion flowing down the column of the sorbent showed a breakthrough curve which enabled one to calculate the distribution ratio and the dispersion coefficient of the ion in the clay using the model for the process limited by the one-dimensional dispersion.

Technetium and Neptunium Reactions in Basalt/Groundwater Systems

AbstractSorption isotherms and apparent concentration limits for Tc(VII) and Np(V) for a variety of groundwater/basalt systems were determined using Grande Ronde basalt samples representative of the Hanford Site candidate high-level waste repository. Under oxic redox conditions (air present), little or no sorption of technetium was observed; neptunium exhibited low to moderate sorption ratios. Under anoxic redox conditions (oxygen-free), low to moderate sorption of technetium was often observed, but the extent of sorption was highly dependent upon the groundwater composition and the method of pretreatment (if any) of the basalt. Sorption isotherms for technetium under reducing redox conditions (hydrazine added) indicate an apparent concentration limit of approximately 10−6mol/L Tc. No apparent concentration limit was found for neptunium for concentrations in groundwater up to.∼10−6mol/L and 8 × 10−7mol/L under oxic and reducing (hydrazine added) redox conditions, respectively.Valence control and valence analysis experiments suggest that the sorption or precipitation of Tc and Np from groundwater in the presence of basalt may result from a heterogeneous reaction occurring on the surface of the basalt. One of the critical factors of this reduction reaction appears to be the accessibility of the reactive ferrous iron component of the basalt. The laboratory simulation of groundwater redox conditions representative of the repository environment through the use of solution phase redox reagents is of questionable validity, and information obtained by such experimental methods may not be defensible for site performance assessment calculations. Anoxic experiments conducted in an argon-filled glove box appear better suited for the laboratory simulation ofin situredox conditions.

Sorption behaviour of some actinides on silica gel from mineral acids and alcoholic solutions

Sorption of Th, Pa, U, Np and Pu on silica gel from HNO3, HCl and HCl−ROH solutions was investigated. Equilibrium studies indicated sorption behaviour to vary greatly with the acid used. In mixtures of HCl with different alcohols, distribution coefficints were found to depend on alcohol percentage as well as on acidity. Results were discussed and conditions for possible separations were indicated.