Thesis for the Degree of Doctor of Philosophy - DTU Orbit

Table 5 HPLC-ICPMS results of iodine species in natural water samples collected in Denmark.
Sample Location Sampling
date
pH Total
iodine
(nM)
I-
(nM)
IO3- (nM) Other
iodine
species
(nM)
Seawater Færøerne
Havvand
11-12-2008 6.5 411.1 103.78 253.54 53.78
Rain water Ejby 03-02-2009 5 6.55 0.78 0.4 5.37
Lake Hostrup
Sø
26-01-2009 5.5 47.2 0.99 0.88 45.32
River Suså 03-02-2009 7 74.5 1.16 4.05 70.45
Groundwater EJ BY 27-01-2009 7 42.71 1.55 15.44 27.27
Due to the low concentrations of 129 I in the environment ( 129 I/ 127 I is about10 -12 , Fehn et al., 2007; Hou et al.,
2009), the above developed method cannot be applied for speciation analysis of anthropogenic iodine in
environmental samples but can be applied for highly contaminated 129 I water samples.
3.1.2 Quantification of total iodine-129 in freshwater and seawater samples by adsorption on activated
charcoal or DEAE 32 cellulose (unpublished results). Adsorption of iodine species onto activated
charcoal was previously applied Woittiez et al.(1991). Several studies have been conducted in order to
remove aquatic organic compound by adsorption onto activated carbon and anion exchange resin (Chen et
al., 1996; Chen 1999). Activated carbon is most often involved in the purification of water. DEAE 32
cellulose, an anion exchange resin (charge independent of pH), has also been proven very useful in isolating
humic material from fresh waters (Hiraide et al, 1994).
The results of the present study show that iodine from the studied lake water (with a total concentration of
iodine-127 of 20 ppb) can be easily adsorbed onto 5g activated charcoal washed with double distilled water
or ethanol after stirring for 2h (Table 6, experiments number 5-8 and 13-15). The sorption of iodine was not
affected by the pH (Figure 9) since the fraction of 127 I that remains in the water phase after batch
experiments (at different pH) is low. The adsorption of iodide was high over the concentration range studied
(1-30 ppb) as long as the concentration of iodate was low. The presence of iodate, a relatively large ion with
low effective charge, seems to block adsorption of iodide even at iodate levels as low as 5ppb (Figure 10). In
order to evaluate whether or not the method would be suitable for 129 I analysis, iodine trapped on the
sorbents must be able to be removed. Consequently, after adsorption of iodine species, the activated charcoal
was subjected to alkaline digestion or combustion at 900 0 C followed by extraction and back-extraction of
iodine with CHCl3 and KHSO4 solution. The chemical yield of iodine following alkaline digestion, as
measured by the added
38
125 I tracer, ranged from 46% to 56%. When activated charcoal from the batch