title: Neptuniumnn(V) sorption and diffusion in opalinus clay.
abstract: The sorption and diffusion behavior of 8 x 10(-6) M Np(V) in Opalinus Clay (OPA) with synthetic pore water (pH 7.6) as mobile phase was studied under ambient conditions by batch and diffusion experiments, respectively. The Kd value determined by batch experiments with OPA suspensions is equal to 0.025 +/- 0.005 m3/kg. The diffusion-accessible porosity epsilon of intact OPA as determined by through- and out-diffusion experiments with tritiated water (HTO) is equal to 0.15 +/- 0.01. The diffusion coefficient De and the rock capacity factor alpha of 22Na+ in OPA were measured by through-, out-, and in-diffusion experiments and asserted the reliability of these diffusion techniques. For the diffusion of Np(V) in synthetic pore water, the capillary method gave Dw = (6.0 +/- 1.0) x 10(-10) m/s. Due to the strong sorption of Np(V) on CPA, the diffusion of Np(V) was investigated bythe in-diffusiontechnique.The diffusion parameters for Np(V) in OPA are De = (6.9 +/- 1.1) x 10(-12) m2/s and alpha = 243 +/- 4. This corresponds to Kd = 0.10 +/- 0.01 m3/kg for the sorption of Np(V) in intact OPA.
authors.affiliation: Intitue of Nuclear Chemistry, Jhannes Gutenberg-Universität Mains, 55099 Mains, Germany. twu@hutc.zj.cn
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.forename: Samer
authors.initials: S
authors.lastname: Amayri
authors.forename: Jakob
authors.initials: J
authors.lastname: Drebert
authors.forename: Luc R
authors.initials: LR
authors.lastname: Van Loon
authors.forename: Tobias
authors.initials: T
authors.lastname: Reich
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D004058:Diffusion; D008962:Models, Theoretical; D009405:Neptunium / Q000032:analysis / Q000737:chemistry*; D016062:Porosity; D011850:Radioactive Waste / Q000032:analysis; D013557:Switzerland; D018505:Waste Management
chemical_list: D000538:Aluminum Silicates; D011850:Radioactive Waste; D009405:Neptunium; D000077215:Clay