Note: Descriptions are shown in the official language in which they were submitted.
LAB 105
OIL SLICK DISPERSANTS USING DIGUANIDINIUM SALT
Background of the Invention
The present invention discloses surface-active
compositions for treating and dispersing oil slicks. This
invention is also directed to a method for disposing of oil
slicks.
Pollution of seawater by oil (crude oil or
fractions o crude oil) occàsioned by accidents, off-shore
drilling operations, and/or discharge of ballast water or
spillaye from oil tankers, results in the formation of a
continuous film or slick of oil which tends to continuously
spread~ In open seas, this oily film is undesirable
because it constitutes a barrier to the transfer of air and
light from the atmosphere into the seawater, which are
indispensable to support marine life. In coastal waters,
~he oily film does damage to the crustacia beds and to the
beaches.
One way of dealing with such pollution problems
- is to use oil dispersing compositions containing
surface-active compounds. These compositions are applied
on the oil slicks, generally by spraying means. They
disintegrate the cohesive oily film into small droplets and
disperse the droplets into the water column to a depth of
several meters under the sea sufrace. The film is thus
broken and there is again a transfer of air and light from
the atmosphere. Moreover, fouling of the solid structures
and beaches along the coasts is avoided.
The oil droplets which are dispersed under the
sea surface are then biodegraded and consumed by
micro-organisms which are living in seawater and are active
in oil metabolism. This biological degradation is however
a slow process and is consequently unable to prevent the
settling of undegraded oil droplets and the formation of
oil deposits on the floor of seas, more particularly where
the water is shallow.
An active biodegradation of oil droplets needs
the presence of a high amount of micro-organisms at the
oil-water interface. However, these orgànisms are present
in seawater in limited quantities. In order to stimulate
the biodegradation, it is therefore necessary to speed up
the proliferation of the micro-organisms. To this end,
they need not only oxygen and carbon, which are present
respectively in water and in polluting oils, but also
nitrogen and phosphorous. Generally, the concentration o
these latter two elements is very low in seawater and
consequently the natural biodegradation of oil is a very
slow process.
In order to increase the biodegradation rate, it
has been proposed to add microbial nutrients to seawater.
Mineral salts, such as ammonium salts, nitrates and
phosphates, have been used. But these mineral salts are
too water-soluble and have practically no affinity for the
polluting oil. They are too quickly dissolved and
dispersed into sea water and are not maintained at the
oil-water interface where their presence is needed.
It has also been suggested to use
nitrogen-containing organic nutrients which are
oleosoluble, such as condensation products of urea or
melamine with aldehydes. However, these organic compounds
are also soluble in water. They dissociate from the oil
and are dissipated into the aqueous phase In order to
overcome this disadvantage, it has been proposed to modify
their solubility in water. For instance, condensation
products of urea and an aldehyde containing less than four
carbon atoms are first absorbed on an inert carrier and are
then rendered lipophilic by coating with a paraffin or
other protective colloid. These treatments require special
equipment and they increase the cost of nutrients.
Moreover, these latter cannot be suspended in the
surface-active compositions which are used for the
treatment of the oil slicks. Two separate applications,
one for the surac~-active composition and one for the
nutrients, are therefore required. Furthermore, the
coating might be quickly dissolved if the polluting oil,
such as a fresh crude oil, contains aromatic hydrocarbons.
Other techniques have been suggested to reduce
the solubility of the nutrients in water, but the result is
compositions which only ~loat on the water surface. These
nutrients will not then promote the development o~
micro-organisms in the water column under the sea surface
where the oil droplets are dispersed.
The difficulties encountered with prior art
dispersants have been overcome by the development of new
lipophilic nutrients for the micro-organisms w~ich are
present in sea waters and are active in oil degradation.
These new nut~ients achieve a rapid and more complete
biodegradation of the oils, at low cost.
Summary of the Invention
.
It is an object of the present invention to
provide a process for disposing of oil slic~s on seawater
by treating the polluted water with a dispersing
composition and with a water-stable nitrogen-containing
compound which is poorly soluble in water.
It is another object of the invention to improve
the biodegradation of the oil in an oil slick by treating
the polluted water with a dispersing composition and a
nitrogen-containing compound to increase the development of
micro-organisms which are active in metabolizing oil.
A further object of the invention is to provide a
nutrient for seawater micro-organisms comprising a
nitrogen- containing compound which is oleophilic and which
exhibits a low toxicity towards aquatic flora and fauna.
These and further objects have been achieved by
treating oil polluted seawater with a dispersing
composition and a nitrogen-containing nutrient for the
micro-organisms, said nutrient consisting of a
diguanidinium salt having the general formula:
1~8~
HN ~ NH
C - NH R - NH - C
XH.H2N H2.HX
wherein R is an alkyl radical containing from about 2 to
about 12 carbon atoms and X is a halogen or an acid anion~
DEECRIPTION OF PREFERRED EMBODIMENTS
The process of the present invention for
disposing of oil slicks on seawater comprises treating the
oil slicks with a dispersing composition and a
diguanidinium salt as hereinabove defined.
The digu~nidinium salts may be prepared by the
conventional method of reacting a diamine salt
(XH.H2N - R- NH2.HX) with cyanamid (H2N - C - N,
R and X being as hereinabove mentioned). An amine salt or
a mixture of amine salts may also be used. The molar ratio
between the diamine salt and the cyanamid is at least 1:2.
By way of example, 1,6-bisguanidinohexane hydrochloride,
having the formula:
HN~ ~5~ NH
/ C - NH - (CH2)6 - NH - C
ClH.H2N NH2.HCl,
is prepared from 1,6-diaminohexane and cyanamid by
introducing 1 mole of diamine, which has been previously
dried and dissolved in isopropyl alcohol, into a flask
equipt with a stirrer, a thermometer and an outlet tube
linked to a Dan and Stark decanter provided with a water
cooler. ~hen, 3 moles of hydrochloric acid are slowly
introduced into the flask. After reaction, the water and
isopropyl alcohol are removed. Xylene is then added and
the mixture is heated under reflux in order to remove any
remaining traces of water. When the mixture has cooled
down to about 80C, 2 moles of cyanamid are added to it and
the reaction mixture is heated to 140C and held there ~or
2 hours. After cooling, the reaction mixture is filtered,
washed with alcohol, stirred at 60C for 30 minutes in the
presence of alcohol containing about 1~ active carbon, and
filtered on a millipore filter. After elimination of
residual solvent, 1 7 6-bisguanidinohexane chloride is
obtained with a purity of about 98%.
The nitrogen content of the diguanidinium salts
depends upon the speciric R and X, but it lies generally in
the range of about 15 to about 40%.
Diguanidinium salts where the radical contains 12
or even more carbon atoms may be used. However, taking
into account the availability and the price of the diamine,
it is more advantageous to prepare diguanidinium salts
wherein the radical R contains only up to about 8 carbon
atoms. Moreover, depending upon the selection of the
radicals R and X, one can prepare diguanidinium salts which
are either soluble in or can be suspended in most
dispersing compositionsO Diguanidinium salts wherein R
contains from 2 to 6 carbon atoms have this characteristic
and therefore they may be applied in solution or suspension
in the dispersing composition. If the diguanidinium salt
is not soluble or cannot be suspended in the dispersant, it
~8~Z4~
can be added to the polluted water, either before or after
application of the dispersant.
In the above given formula, X may be a halogen,
more particularly chlorine, or an acid anion, such as teh
radical of su~phuric acid, nitric acid, methyl or
ethylsulphuric acid, alkylbenzenesulphonic acid, acetic
acid, lactic acid or similars. For economic reasons, it
may be advantageous to prepare diguanidinium salts where
is Cl or the radical of sulphuric acid, nitric acid or
acetic acid. The radical X may also be selected in order
to obtain diguanidinium salts which are soluble or easily
suspended in the usual dispersing compositons. For
example, diguanidinium salts, ~herein R is the dodecyl
radical, are practically insoluble in most dispersing
compsitions when X is Cl, but are soluble in these
compositions when X is the radical of lactic acid.
In order to promote the development of
micro-organisms, the diguanidinium salts are advantageously
employed in admixture with a phosphorous compound which
also acts as a nutrient to supply phosphorous. The
~phosphorous compound may be an alkaline or alkaline-earth
salt of phosphoric ester of fatty alcohol, a salt or an
ester of organophosphonic acid, or a phosphatide or similar
product having a low toxicity towards aquatic flora and
fauna. Esters obtained by neutralization of hexamethylene
diamine tetra(methylene phosphonic acid) of formula
(H2Po3c~2)2 ~ N(CH2)6N - (CH2PO3H2)2
with an amine, such as monoethanolamine or a fatty amine
containing from 12 to 18 carbon atoms, give good results.
Phosphatides or phospholipids such as lecithin or kephaline
provide both nitrogen and phosphorous, and thus reinforce
the action of the diguanidinium salts.
According to one preferred embodiment of this
invention, diguanidinium salts, wherein the radical R
contains up to 8 carbon atoms, are preferably employedO
They are used in solution with or suspended in dispersing
compositions containing at least one surface-active
compound and at least one solvent exhibiting a low toxicity
towards aquatic flora and fauna.
Useful surface-active compounds can include
ethoxylated tall oil, mono- or polyesters of polyhydroxylic
alcohols, more particularly the esters of saturated or
unsaturated aliphatic carboxylic acids containing from 12
to 20 carbon atoms and of alcohols, such as sorbitol,
glycerol and polyethyleneglycol. Mixtures of two or more
of these esters may be used, with the optional addition of
- other surface-active agents, such as ethoxylated fatty
alcohols, alkaline salts of dialkyl sulphosuccinates, or
condensation products of ethylene oxide or propylene oxide
on the above-mentioned esters.
The surface-active agents are dissolved in at
least one solvent having a low toxicity towards aquatic
flora and fauna. The solvent serves a double purpose: i~
facilitates the handling and the application of the
~5 surface- active agents, and due to its affinity, it
promotes the penetration of the composition into the oil
film. Useful solvents include liquid hydrocarbons
containing less than 5%, and preferably less than 3%
aromatic compounds~ Liquid hydrocarbons which are
preferred solvents are those having from 5 to 20 carbon
atoms, such as paraffinic hydrocarbons containing from
~1~8'~
6 to 12 carbon atoms, cycloparaffinic hydrocarbons such as
cyclopentane and cyclohexane, alkyl- cycloparaffinic
hydrocarbons, and napthenic hydrocarbons. Aliphatic
alcohols containing up to 8 carbon atoms, such as ethyl ,
propyl- and isopropyl alcohols, and glycols monoethers,
more particularly monoalkylethers (where the alkyl radical
contains from 10 to 4 carbon atoms) o glycols, such as
mono- or diethyleneglycol and mono- or di-propyleneglycol
are also suitable solvents. The organic solvent may also
contain water in an amount which does not exceed the amount
Gf organic solvent.
The weight ratio of surface-active a~ents to
solvent may vary between wide limits. It is desirable to
employ compositions which are as concentrated as possible,
but the amount of solvent in the com~osition must be
sufficient to dissolve the surface-active agents and
nutrients and also allow the application of the composition
at low temperatures. It has been found that compositions
containing more than about 85~ of surface-active agents and
~utrients are generally too viscous at low temperatures.
Moreover they do not easily penetrate the oil slick and are
therefore less act~ve. ~n the other hand, compositions
containing less than about 30~ of surface-active agents and
nutrients have a low effectiveness.
The amount of dialkylguanidinium salt in the
dispersing compositions may vary between relatively wide
limits and may be as high as 35% or even more, based on the
total weight of composition. This amount depends upon many
factors, such as the specific guanidinium salt used and its
~8~
nitrogen content, the optional presence of other nutrients
and the specific solvent used. Compositions containing
from about 2 to about 20 wt ~, and more particularly from
about 5 to about 15 wt %, of dialkylguanidinium salt are
very effective with respect to the biodegradation of oil
droplets dispersed in seawater.
The compositions of the present invention may
also contain other components such as magnesium and calcium
which are beneficial to the development of micro-organisms.
These elements may ~e present in the form of organic salts,
namely in the form of magnesium or calcium salt of alkyl~
benzenesulphonic acid. The amount of these additives
yenerally does not exceed about 3%; based on the total
weight of the composition.
The compositions are applied to oil slicks by
conventional application methods. They may be diluted with
water and sprayed on oil slicks from aircraft or boats
provided with suitable spraying means.
Exam_le 1
The following dispersing composition was prepared
(parts by weight):
53 parts diethyleneglycol monobutylether5 23 parts polyethyleneglycol monooleate (mean molecular
weight of the glycol : ~00)
6.5 parts sorbitan monolaurate
9.5 parts water
8 parts bisguanidinobutane hydrochloride
8'2~1
The toxicity of this composition was determined
by subjecting the species Artemia salina to increasin~
doses of the composition to determine the maximum amount of
composition which, after 24 hours, will still leave 50% of
the tested species alive (test CL 50 - 24 hours). It was
found that the determined 50~ toxicity level was 3,500
ppm.
Biodegradation effectiveness is determined by the
following method:
200 ppm of the tested composition is added to unsterilized
seawater (700 ml) containing topped crude oil (5000 ppm).
- This is left to incubate for 41 days at 25C, while being
stirred by air bubbling. The residual oil is then 15 extracted and ~ompared to the original amount of crude oil.
It was found that the biodegradation effectiveness with the
above composition was 1.8 times higher than that of a
similar but nutrient-free composition, and 1.4 times higher
than that of a similar composition containing ammonium
nitrate instead of bisguanidinobutane hydrochloride.
Example 2
A composition as described in Example 1 was
prepared, but by using bisguanidinoethane hydrochloride as
the diguanidinium salt.
The characteristics of this composition, with
respect to toxicity and biodegradation effectiveness, were
the same as the characteristics of the composition of
Example 1.
4~
Example 3
The following dispersing composition was prepared
(parts by weight):
16.70 parts Sorbitan monooleate
13.50 parts ethoxylated sorbitan monooleate (about 20
moles of ethylene oxide)
24 parts sodium salt of di(2-ethylhexyl)sulphosuccinate
(a 75% aqueous solution)
11.25 parts water
12 parts monoethyleneglycol monobutylether
2.5Q parts diethyleneglycol
parts bisguanidinohexane nitrate
parts monoethanolamine ester of hexamethylenediamine
tetra(methylenephosphonic acid).
With this composition, the biodegradation
effectiveness was 1.8 times higher than that of a similar,
but nutrient-free composition.
Example 4
A composition as described in Example 3 was
prepared, but by using bisguanidinohexane lactate as the
nitrogen-containing nutrient.
The biodegradation effectiveness was 1.6 times
higher than that of the nutrient-free composition.
~ 32~
13
Example 5
Bisguanidinododecane acetate was prepared from
1,4-diaminododecane acetate and cyanamid.
50 ppm of a mixture containing 65% of this
biguanidinium salt and 35% lecithin was added to
unsterilized seawater (700 ml) containing topped crude oil.
150 ppm of a commercial dispersing composition was then
added. The mixture was maintained at 25C for 41 days,
while being stirred by air bubbling. The residual oil was
extracted by methylene chloride.
It was found that the biodegradation effectiveness
was 1.7 times higher than that of the nutrient-free,
commerical dispersing composition.
-
