Table 6. Sorption and desorption of three organic solutes by rigid PVC and PTFE

Table 6. Sorption and desorption of three organic solutes by rigid PVC and PTFE.

Initial concentration = 2000 g/L

Contact time = 6 wk (1000 hr)

Contact time = 24 hr

Contact time = 1 hr

Predicted

Amt.

amt.

Amt.

amt.

(g/L)

Analyte

Initial concentration = 50 g/L

Contact time = 6 wk (1000 hr)

Contact time = 24 hr

Contact time = 1 hr

amt.

(g/L)

Analyte

* Actual values taken from Parker et al. (1990). Desorption time was 3 days.

CDCE = cis-1,2-dichloroethylene

CLB

= chlorobenzene

MDCB = m-dichlorobenzene

ND

= no loss detected

that most analytes having a solubility of >500 mg/

These studies indicate the importance of the

L or Kow <200 (log Kow <2.3) were generally

initial concentration of the contaminants, contact

cleaned from a PVC bailer so there was no resi-

time, and the relative sorptiveness of the material

dual carryover with just one rinse with distilled

being decontaminated. We can use the data from

water. Analytes having a water solubility of >50

one of our previous studies (Parker et al. 1990) to

mg/L or Kow <2000 (log Kow <3.3) were generally

demonstrate this. Table 6 shows the amount of

effectively cleaned from a PVC bailer following

three organic solutes [cis-1,2-dichloroethylene

multiple (>6 rinses) with distilled water. They

(CDCE), chlorobenzene (CLB), and m-dichlo-

found that dimethoate was an exception and that

robenzene (MDCB)] sorbed by two rigid polymers

15 rinses were required before it was removed.

(PVC and PTFE) after 6 weeks contact with the

They concluded that in some cases it may be justi-

test solution (at ~2 ppm concentrations) and the

fiable and appropriate to rely on a distilled water

amount desorbed after the test pieces were rinsed

rinse alone. For this study, it is important to note

with fresh well water and placed in clean vials

that there was no significant loss of these analytes

with fresh well water for three days. This table

due to sorption by the bailer during the 1-min

also shows the amount that was sorbed after 1

contact time and that contaminant concentrations

hour and 24 hours contact with the test solution.

were generally less than 20 g/L. The effective-

If we use this data and assume that the relative

rate of desorption remains the same regardless of

ness of this method might be quite different if a

the amount sorbed, we can estimate the amount

longer contact time (that allowed sorption to oc-

of analyte that might be desorbed from the sam-

cur) were used or if the concentration of the

contaminants were higher (at least for the more

ples that had contact times of 24 hours and 1

water-soluble ones).

hour. (Twenty-four hours was selected to simu-

12