Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 63

TABLE 1.32
Organic Carbon Partition Coeffi cient Contrasts for Stabilizers with Dichloromethane

K oc Ratio
(Stabilizer:Solvent) Stabilizer Log K oc Rank

Retained in Filter
Cyclohexane 2.2 6.61 1

Amine 2.16 6.03 2

2-Methyl-2-butene 1.83 2.82 3

Cresol 1.7 2.09 4

Decreasing Retention in Carbon Filter
1,4-Dioxane 1.23 0.71 5

Phenol 1.2 0.66 6

Ethanol 1.2 0.66 6

1,3-Dioxolane 1.17 0.62 8

Thymol 0.52 0.14 9

tert- Butylamine 0.46 0.12 10

Nitromethane 0.28 0.08 11

Propylene oxide 0.03 0.04 12

Methanol − 0.77 0.01 13

Source: See Appendix 2 for a tabulation of physical and chemical properties of solvent-stabilizer compounds with full
citations.
Note: For dichloromethane, log K oc = 1.38.

around the heating coils in the boiling sump. In general, stabilizer chemicals are relatively immune
to pyrolysis within the temperatures encountered in normal degreasing, dry cleaning, and other
solvent applications. Higher temperatures may be encountered in transformers, for which the selec-
tion of suitable stabilizers requires special attention to their thermal stability.

1.2.7.6 Replenishing Solvent Stabilizers
Stabilizers were replenished in degreasers and in recycled solvent in two ways. For degreaser opera-
tors, the solvent distributors and degreasing equipment manufacturers recommended that the solvent
be periodically refreshed by adding a quantity of fresh solvent. Operators were advised to purchase
new solvent containing higher than usual levels of stabilizer to refortify the stabilizer-depleted
solvent. The new solvent was added when the degreaser was not operating and the solvent was cold
and provided enough stabilizers to restabilize the solvent (Howell and Tarrer, 1994).
In experiments conducted to simulate operating conditions in a degreaser for the purpose of
testing a solvent maintenance system, 4 L of fresh solvent were added weekly to a degreaser
whose solvent capacity was 45.4 L. * The weekly addition of almost 10% of the solvent volume
was apparently a common practice (Cormany, 1977). Testing the solvent for acid acceptance and
performing the aluminum scratch test before and after the addition of fresh solvent ensured the
success of this approach.
In the process of recycling solvents, steam stripping was used to separate the oils and other mate-
rials solubilized in the solvent during the degreasing process. Many of the stabilizer compounds,
particularly those added to methyl chloroform, are hydrophilic and are therefore siphoned off in

* A model MLW-120 stainless steel Baron-Blakeslee vapor immersion degreaser unit was used for the experiment.