Anion exchange method

The general procedure was as follows. The anion exchange resin based on a copolymer of styrene and divinylbenzene was immersed in water for 24 h for full swelling before loading onto a column made of polyethylene. The resin was then washed with 10M HCl to convert it into the Cl — form, followed by ion exchanged water until pH 7 is reached in the water eluate.

For experiments where the main purpose was the separation of [Co(CN)6]3-, the column had dimensions 0 = 5 mm and L = 25 mm, corresponding to a resin volume of ~0.5 mL. For the experiments where the main purpose was absorption of SCN-, the column dimensions were 0 = 6 mm and L = 300 mm, corresponding to a resin volume of ~8.5 mL. A sample volume of 100-1000 mL of seawater containing radiotracer was passed through the columns. Flow rates were kept at ~0.5 mL/min.

Absorption yield (%) is expressed as:

Подпись: (24)cs, feed cs, raf

Vabs = R •i00%

Rcs, feed

where Rcsfeed denotes the net sample counting rate per mL (proportional to activity concentration (Bq/mL) of the feed solution and Rcsraf denotes the net sample counting rate per millilitre of the raffinate.

image098 Подпись: (25)

Elution yield is determined as:

where Rcs elut denotes the net sample counting rate per mL of the eluate.

image100 Подпись: Vabs,SCN • Velut,SCN V • V 1 abs,Co 1 elut,Co Подпись: (26)

The separation factor of [Co(CN)6]3- and SCN — in the complete ion exchange procedure (feed plus elution) is then defined as:

All anion exchangers are of the amine type. The main parameters are given in Table 8.

TABLE 8. ANION EXCHANGERS USED

Resin used

Type

Producer

Elution agents tested

Amberlite IR45, 50-100 mesh

Weak base, — NH2

Rohm and Haas

No elutions performed

Lewatit MP60, 50-100 mesh

Weak base, — NH2

Bayer AG

No elutions performed

Dowex 1×2, 50-100 mesh

Strong base, quaternary amine

Dow Chemical

4M NH4C1+2M HCL, 12MHCL, 65%HN03

Dowex 1×2, 200^100 mesh

Strong base, quaternary amine

Dow Chemical

NH4C1 (saturated), 65% HN03

Dowex 2×8,

Strong base,

Dow Chemical

70% НСЮ4, Ш (cone.), 96%H2S04,12MHC1, 32.5% HN03,

100-200 mesh

quaternary amine

2.5M NH4N03, 5M NH4N03, 7.5M NH4N03, 10M NH4NQ3

OO

U

image103

FIG. 48. Extraction yield for the [Co(CN)6]3 complex as a function ofpH using four different extraction agents (10%) in kerosene.