The Effect of Clay
Minerals on Surfactant Biodegradability
RONALD D. BARBARO, Research Fellow
JOSEPH V. HUNTER, Associate Professor
Department of Environmental Sciences
Rutgers, the State University
New Brunswick, New Jersey
INTRODUCTION
Increased industrial and domestic use of surface active agents has caused concern over the purity of water supplies. These compounds are the active ingredients
in detergent preparations, and as such, are among the most widespread of synthetic organic pollutants. They are composed of a hydrophobic portion and hydro-
phylic portions which will ionize on addition to water, leaving a residual charge
on the active molecule. Based on this charge, surfactants may be classified as
anionic or cationic. Those surfactants that do not ionize in water are called non-
ionics. Surfactants may escape or persist through conventional waste treatment
and are readily detectable in many receiving waters. Numerous technical and
aesthetic problems have been associated with their presence (1,2,3).
Adsorption of surfactants onto particulate matter, under natural or artificial
conditions, may afford a mechanism for their removal from water supplies.
Commonly found clay minerals such as kaolinite and bentonite, are among the
materials being evaluated by the Public Health Service as adsorbents for waste
water renovation (1). However, adsorption, especially under natural conditions,
does not obviate biological utilization. It merely presents the substrate in a
modified condition.
There have been several studies dealing with the effect of clay minerals on
the bacteriological and enzymatic activity associated with the degradation of
protein (5) and organophosphates (6). However, the effect of these minerals on
the biological availability of surfactants has received little attention. The object
of this study was to observe any effect of the clay particles on the extent of degradation of several representative surfactants and to indicate the direction for further research in this area. The test materials included a relatively degradable
species and a relatively nondegradable species of the three surfactant types. The
relatively degradable species were the anionic Igopon T-77 (N-oleyl-N-methyl"
sodium taurate); the non-ionic LEA, a Lauryl alcohol adduct with three moles of
ethylene oxide and CPB the cationic cetylpyridinium bromide. The relatively
nondegradable anionic species was Ultrawet K, a branched chain dodecylbenzene
sodium sulfonate available from the Atlantic Refining Company. Both the non-
ionic Triton X 100 (P-diisobutylphenoxynonaethoxyethanol) and the cationic Hya-
mine 1622 (diisobutylphenoxyethoxyethyldimethylbenzyl ammonium chloride)
were supplied by Rohm and Haas Company. All the materials tested were of
known activity.
PROCEDURE
The tests were performed in the following manner: 20 ppm solutions of the
test surfactant and distilled water blanks were shaken with zero, 100, and 10, 000
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