Sorption of Uranium and Plutonium on Bentonite Altered by Highly Alkaline Water
- PDF / 350,272 Bytes
- 6 Pages / 418.68 x 637.2 pts Page_size
- 14 Downloads / 177 Views
content = 98-99 wt.% [2]) had been exposed to a solution of sodium, potassium and calcium hydroxides at approximately pH 14 under an air atmosphere at 130'C, 160'C and 200'C in order to investigate the alteration behaviour of the compacted bentonite. The dry density was 1.8 g cm"3 and the liquid:solid ratio was 40cm3 : 11.3g. It was shown by X-Ray analysis that the surface of bentonite in contact with the highly alkaline solution had been altered to analcite, a zeolite, to a depth of about 2 mm after 20 days (Figure 1). X-Ray data from samples treated at 160'C and 200'C gave almost the same pattern. It was therefore decided to use the 160°C-altered samples to prepare equilibrated water for analysis and to use the 200°C-altered samples in the sorption experiments. 5g of crushed 160°C-altered bentonite were equilibrated with 250 cm 3 saturated calcium hydroxide solution in contact with a small amount of solid calcium hydroxide (approximately 0. lg) under nitrogen at room temperature. After one month the equilibrated water was filtered under nitrogen through an Amicon DiafloTm PM-30 polysulphone filter (30,000 nominal molecular weight cut-off (NMWCO)). The pH was measured, and samples were taken for anion
analysis by ion chromatography, and for cation analysis by inductively-coupled plasma mass spectrometry (ICP-MS) (following acidification with 1 mol dm"3 nitric acid). The results of
these analyses are shown in Table 1. Based on these analytical results, a synthetic solution for use in the sorption experiments was made up to simulate the equilibrated solution.
0
10
20
30
40
50
60
Degree 20
Figure 1 XRD of Bentonite Samples
(a) unaltered sample (starting material), (b) 130°C-altered sample, (c) 160°C-altered sample, (d) 200°C-altered sample
250
Table 1 Water Analysis after Equilibration of Altered Bentonite with Calcium Hydroxide Solution Concentration / mol dm 3 4.4 x 104
Data Loading...
