Ni(II) Sorption on the Fracture Filling Mineral Chlorite
2009 (English)In: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXXII, 2009, Vol. 1124, 531-536 p.Conference paper (Refereed)
Abundance of the mineral chlorite as fracture filling material in granitic bedrock motivates sorption studies for quantification of the retention of radionuclides on this mineral. The activation product Ni-63 is an important component in spent nuclear fuel, accounting for a large contribution to the high activity level, and further motivates sorption studies of Ni on chlorite. Earlier sorption studies have been performed on larger mineral pieces; however, it is questionable if these data are representative for fracture filling material. Chlorite from a borehole core from Oskarshamn, Sweden, from the depth of 944 m has been characterized and the chemical composition determined prior to the experiments. The thickness of the fracture filling mineral is at maximum a couple of millimeters; therefore, careful removal of the thin chlorite layer from the core was performed with a carbide tool. The fraction was sieved to a size distribution of 63-118 mu m and ultrasonically washed. The major oxides were found to be 34.4 % SiO2, 21.6 % MgO, 15.4 % Al2O3 and 12.9 % Fe2O3 determined by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis. Sorption of Ni(II) to the sample was performed in 0.1 M NaClO4 with a batch technique inside a glove-box with Ar-atmosphere, using Ni-63 as a tracer with the Ni carrier concentration of 10(-6) and 10(-8) M. The percent sorption in these experiments was 57% at pH 5.5, 85 % at pH 6.5 and 92 % at pH 8.3, with the last value corresponding to maximum sorption No significant differences between the experiments performed in the two concentrations of 10(-6) and 10(-8) M were found. The degree of sorption on this fracture filling material is of the same magnitude as earlier studies of Ni sorption on chlorite provided from larger mineral pieces, using the same size fraction of the material. Sorption of Ni is, as expected, strongly pH dependent and Ni-63 escaping a breached canister will, reaching chlorite within the surrounding bedrock, be retarded due to strong sorption.
Place, publisher, year, edition, pages
2009. Vol. 1124, 531-536 p.
, Materials Research Society Symposium Proceedings, ISSN 0272-9172
dissolution rates; ph; 25-degrees-c
IdentifiersURN: urn:nbn:se:kth:diva-24163ISI: 000270898900070ScopusID: 2-s2.0-70449382071OAI: oai:DiVA.org:kth-24163DiVA: diva2:344402
32nd Symposium on Scientific Basis for Nuclear Waste Management held at the 2008 MRS Fall Meeting Boston, MA, DEC 01-05, 2008
QC 201008192010-08-192010-08-192010-08-19Bibliographically approved