1,4-Dioxane Chemistry, Uses, and Occurrence - Environmental Investigation and Remediation - page 82

deodorants, production of fumigants, reagents to provide the mobile phase in some laboratory chro-
matography applications, reagents for measuring optical activity, reagent for cryoscopic analysis,
and as a polymerization catalyst (ATSDR, 2005).
This chapter explores the various uses of 1,4-dioxane and its occurrence as a by-product in dif-
ferent industries by providing examples of how 1,4-dioxane was used or generated, with discussion
of the relative quantities involved. Appreciation for the many ways 1,4-dioxane has been used or
generated and released to the environment can assist with site investigations in locations where
multiple industries have operated.

2.3.1 C ELLULOSE A CETATE M EMBRANE P RODUCTION FOR R EVERSE O SMOSIS
AND K IDNEY D IALYSIS F ILTERS
Cellulose acetate membranes and cellulose triacetate membranes are used to i lter small particles from
water in reverse osmosis water treatment applications, from blood in kidney dialysis applications, and
from water and other liquids in a variety of additional technological applications. Austrian chemist
Karl Weissenberg recognized that cellulose acetate will l ow when dissolved in 1,4-dioxane in rheo-
logical studies published in 1929 (Philippoff, 2006). 1,4-Dioxane was used to produce artii cial silk in
England in 1932 by treating cellulose acetate yarn with 1,4-dioxane (Barber, 1934, in USEPA, 2002).
The concept of reverse osmosis was i rst demonstrated in the late 1950s with cellulose acetate
membranes. Reverse osmosis membranes are produced via solution deposition and hollow i ber
extrusion. Solution deposition involves spreading a mixture of cellulose, a solvent, and a swelling
agent over a smooth surface. As the solvent evaporates, the air-dried surface hardens and pores form
within the cellulose layer. Reverse osmosis membranes are made with a very thin layer of polymer
i lm applied on top of the porous cellulose acetate substrate. After the solvent evaporates from the
cellulose membrane surface, the membrane is quenched by immersing in water, which precipitates
the polymer (Klein and Smith, 1972).
The solvents used in this process are selected for their solubility in water. The solvent was com-
monly a mixture of 1,4-dioxane and acetone in ratios ranging from 1.5:1 to 2.5:1. Swelling agents
include methanol and ethanol, used at between 2 wt% and 10 wt% of the i nal solution (Yashushi,
1977). Wastewater efl uent from cellulose acetate and triacetate membrane production facilities has
often included 1,4-dioxane. Several 1,4-dioxane groundwater contamination incidents have been
caused by efl uent from membrane production facilities, as described further in the case studies
presented in Chapter 8.
Cellulose acetate and triacetate membranes produced by using 1,4-dioxane as a deposition sol-
vent may contain residual 1,4-dioxane and thus require a California Proposition 65 warning label.
Manufacturers acknowledge that trace amounts of 1,4-dioxane may be present and recommend
l ushing with water to purge 1,4-dioxane from the system. Because 1,4-dioxane is ini nitely soluble,
it is quickly removed from i lters by l ushing with water. Nearly all residual 1,4-dioxane is now
l ushed out in the manufacturing process, though this may not have always been the case. Most
manufacturers no longer use 1,4-dioxane for producing reverse osmosis or kidney dialysis i lters.
Cellulose acetate i bers are also used to produce some varieties of cigarette i lters. 1,4-Dioxane
is among the solvents listed in the patent literature for the process used to create the i ber bundles
that remove tar from cigarette smoke (Matsumura et al., 1997).

2.3.2 L IQUID S CINTILLATION C OCKTAILS
Numerous experiments and routine measurements in the medical and life sciences are made by
injecting or orally administering a radio-labeled solution containing -emitting nuclides and then

counting the radioactivity in blood, tissue, excreted urine, or other media. The process of counting
levels of radiation often involves the use of liquid scintillation “cocktails.” Samples selected for
radiation measurement are dissolved in a solvent mixture, called a liquid scintillation cocktail,

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