Page 170 - Partition & Adsorption of Organic Contaminants in Environmental Systems

SORPTION FROM WATER SOLUTION 161

TABLE 7.12. BET-N 2 Surface Areas (SA) and
Percents of Organic Carbon (OC) of Peat and
Fractionated Organic Matters
2
Sample OC (%) SA (m /g)
Peat 49.3 1.4
Peat HA 47.3 0.16
Muck HA 46.3 0.17
HM 51.4 4.5
Source: Data from Chiou et al. (2000).

20

Peat HA
Uptake by Sorbent, Q (mg/g) 10 2 1
Muck HA
15

5

0
0 0.02 0.04
0
0 0.2 0.4 0.6
Relative Concentration, C /S w
e
Figure 7.23 Sorption of EDB from water on peat HA and muck HA. [Data from
Chiou et al. (2000). Reproduced with permission.]

mechanism. In contrast, the EDB isotherms on whole peat and (peat-derived)
HM display a noticeable nonlinearity at low C e /S w values. The apparent non-
linear capacity (Q ans ) of EDB with HM is much greater than with whole peat;
the extent of EDB sorption nonlinearity at low C e /S w , as characterized by
the Freundlich n exponent in Table 7.13, is also somewhat higher with HM
than with whole peat. The increased linearity at moderate to high C e /S w reflects
the dominance of solute uptake by partition into SOM. The partition capaci-
ties of EDB on the two HAs are practically equal. The uptake capacity of EDB
on whole peat at all but low C e /S w values is also about the same as that on peat
HA.
The sorption isotherms of moderately polar DUN on the same four
sorbents are illustrated in Figure 7.25, in which the sorption to HM exhibits