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RH NIUM

The Eh-pH diagrams for rhenium species are shown in Figs. 53 and 54. The

thermodynamic

data

for important rhenium species are given in Table

39.

Figure

53

shows the stability fields for phases in the system Re-O-H.

Similar to Tc, the important species of Re VII) is soluble Re i ion, which oc

cupies much of the high-Eh part of the diagram

at

all

pH

values. Important

Re valences are

0,

III, IV, VI,

and

VII). Under mildly reducing conditions,

and

above the sulfide-sulfate boundary, Re VII) is reduced first to Re VI) and then

to Re IV,III) oxides. Native

Re

forms at lower Eh.

With the addition

of

sulfur, the phases in the system Re-S-O-H are shown

in Fig. 54. Here, the field of

native

Re is

replaced by

ReS2

and most of the

Re203 and some of the Re02 and Re03 fields are replaced by

ReS2

as well.

Not shown are phases such as Re304 and Re2S3 for which only questionable

data

exist. The total space occupied by solids as opposed to aqueous species

in

both

the Tc ±S)-O-H and Re- ±S)-O-H systems is essentially the same. Fur

ther,

Re

and Tc possess the same valences

and

exhibit almost identical crystal

chemical behavior Brookins 1984), hence Re is often used as

an

analog for

Tc in predicting Tc behavior from hypothetically breached radioactive wastes

Brookins 1986b, 1987a).

100

Table 39. Thermodynamic data for rhenium

Species state)

Re203 c)

Re0

2

c)

Re0

3

c)

ReOl aq)

ReS2 c)

LtG? kcal/gfw)

138.64

- 87.95

127.96

165.99

- 38.10

Reference

Zoubov and Pourbaix

1966)

Wagman et al.

1982)

Calculated a

Wagman et al.

1982)

Calculated

a

Abbreviations see Table 1

a

Method

of

calculation described in Brookins

1983

a)

D. G. Brookins, Eh-pH Diagrams for Geochemistry 

© Springer-Verlag Berlin Heidelberg 1988

8/18/2019 Eh PH Diagram of Rhenium Brookins1988

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