Experimental Study of the Nickel Solubility in Groundwater and Cement Water Under Anoxic Conditions
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Groundwater and cement water In this study, two different groundwaters were used, emanating from boreholes PVA2 and KR8 in the Ollciluoto VLJ repository. The waters were stored at 4 TC until used. Both waters contained brownish precipitates of, probably, iron oxyhydroxides. About four litres of the two waters were vacuum filtered (Millipore 0.45 pm) under normal laboratory conditions, and subsequently flushed with N2, while the rest was stored untreated at 4 'C until later. Half of the filtered and N 2-flushed waters was stored for two weeks under N2 without any further treatment. In the following, these are referred to as PVA2 and KR8. The rest of the waters were contacted with the above cement under N2 atmosphere using a water:cement ratio of 10:1. After a contact time of two weeks, the bottles with the cement waters were opened and filtered (Millipore 0.45 pm) under N2. During storage, all the bottles were covered with Al foil in order to minimize eventual light-induced disturbances. In the following, the filtered cement waters are referred to as C-PVA2 and C-KR8. Except for the storage at 4 'C, all pretreatment of the samples as well as the subsequent experiments took place at ambient room temperature. The chemical composition of the four stock solutions - PVA2, C-PVA2, KR8 and C-KR8 was determined with regard to the main relevant elements, see Table I. The nickel association with the colloid particles in the waters used was determined with two different techniques, centrifugation and ultrafiltration. The colloid determination was made on samples that had been stored under N2 for two months. The centrifugation (1.5 h at 9 800 G) was performed in the laboratory under normal atmospheric conditions, while the ultrafiltration was made under N2 using filter membranes (Amicon Diaflo XM50, approximate pore size, 3 nm) and cross-flow technique. The results suggest that, for the groundwaters PVA2 and KR8,
Table I. The chemical composition of the groundwaters PVA2 and KR8 and the corresponding cement-waters C-PVA2 and C-KR8. The pH was measured under N2. (N.d. = not detected.) Component pH, Conductivity (mS/m) TOC (mg C /L) HCO3 (mg/L) CO3 (mg/L) Si (mg/L) Cl (mg/L) S04 (mg/L) Al (mg/L) Ca (mg/L) Fe2 +(mg/L) Fe3+ (mg/L) K (mg/L) Mg (mg/L) Na (mg/L) Ni(mg/L)
PVA2 8.8 120 13.0 280
C-PVA2 12.7 1160 6.2 140 0.69 122 24 0.07 550 0.05 0.54 230 0.4 550
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