title: Cs diffusion in local Taiwan laterite with different solution concentration, pH and packing density.
abstract: In this work we used an "in-diffusion" method to study the effects of pH, solution concentration and packing density on Cs diffusion by packing local Taiwan laterite (LTL) into modified capillary columns with 5mm diameter. These packed columns were first pre-equilibrated with synthetic groundwater (GW) for 3 weeks. The diffusion experiments were then carried out at ambient condition for 2 weeks. Our experimental results showed that the Cs diffusion profile fits Fick's second law very well in given experimental conditions, indicating the validity of modified capillary column method. Generally speaking, Cs diffusion in LTL decreases as the pH increases and as Cs concentration decreases. The apparent diffusion coefficient (D(a)) increases from 5.52 x 10(-12) (10(-7)M) to 2.18 x 10(-11) (10(-3)M)m(2)/s, while the effective diffusion coefficient (D(e)) shows slight variation as the Cs concentration changes. Both the derived D(a) and D(e) values decrease as the pH increases, implying that the diffusion mechanisms of Cs nuclide in alkaline and acid environment are different. In addition, our results show that Cs diffusion is unaffected by the given packing density, indicating the interlaminary space is not the major determinant of Cs adsorption and diffusion in LTL.
authors.affiliation: Department of Engineering and System Science, National Tsing Hua University, Hsinchu 300, Taiwan, ROC.
authors.forename: Tsing-Hai
authors.initials: TH
authors.lastname: Wang
authors.forename: Ming-Hsu
authors.initials: MH
authors.lastname: Li
authors.forename: Shi-Ping
authors.initials: SP
authors.lastname: Teng
mesh_terms: D002586:Cesium / Q000737:chemistry*; D002845:Chromatography / Q000379:methods; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry; D011850:Radioactive Waste; D012987:Soil; D012990:Soil Pollutants, Radioactive / Q000032:analysis; D014875:Water Pollutants, Radioactive / Q000032:analysis
chemical_list: D011850:Radioactive Waste; D012987:Soil; D012990:Soil Pollutants, Radioactive; D014875:Water Pollutants, Radioactive; D002586:Cesium; D007616:Kaolin