Removal of trinitrotoluene from aqueous media

There is provided a process for removing trinitrotoluene from waste water resulting from the manufacture of trinitrotoluene, the process comprising forming an admixture of the waste water and an amino group containing compound of the formula (C.sub.n H.sub.2n+1).sub.m (NH(CH.sub.2).sub.x).sub.y NH.sub.z, wherein n is 1 to 25, m is 1 to 3, x is 1 to 5, y is 0 to 5, z is 0 to 2 or the amine and a cationic compound of the formula (C.sub.n H.sub.2n+1).sub.4 N.sup.+ X.sup.-, wherein n is 1 to 25, and X.sup.- is Cl.sup.-, Br.sup.-, SO.sub.4 H.sup.- ; stirring the mixture to form a water insoluble reaction product of trinitrotoluene, and recovering the reaction product from the substantially trinitrotoluene free waste water.

This invention relates to a method of removing pollutants comprising TNT 
from industrial waste water. More particularly, the method of the 
invention involves admixing such waste water with certain amino group 
containing compounds alone or together with a cationic compound, and 
stirring the mixture to cause the formation of a water insoluble reaction 
product of the trinitrotoluene which can be safely and readily removed. 
BACKGROUND OF THE INVENTION 
The manufacture of polynitrotoluene compounds for munitions and explosives 
is a major industry. Large production requirements and the broad variety 
of manufactured products lead to significant pollution problems, however. 
One of the most serious of these is waste waters which are generated 
during the manufacture of explosive polynitrotoluene compounds, such as 
trinitrotoluene (TNT), including 2,4,6-trinitrotoluene (.alpha.-TNT). 
During manufacture, such compounds are subjected to a finishing process 
wherein the end product is dried, flaked and packaged. After manufacture, 
the production equipment and neighboring areas of the facilities housing 
such equipment are ordinarily rinsed thoroughly or washed down with water 
to clean away any residues of TNT which have been left behind. This 
cleaning procedure typically involves the use of considerable amounts of 
water, e.g., up to 500,000 gallons per day at a single site, and the 
resulting water wash is commonly discharged into nearby rivers or streams. 
The discharge of this water presents a major pollution problem. It has 
been found, for instance, that as little as 2.5 parts per million (ppm) of 
TNT is toxic to fish, while the concentration of TNT in industrial 
discharges is considerably higher, e.g., 50 ppm or more. 
Extensive studies of the treatment of industrial waste waters from the 
manufacture of TNT have been conducted by various academic institutions, 
defense laboratories, private industries, and others. Methods investigated 
so far include bacterial degradation, carbon-adsorption techniques, 
irradiationdecomposition and adsorption on organic resins. These are 
described in the article, "Application of Liquid Chromatography to 
Pollution Abatement Studies of Munition Wastes", by Walsh et al, 
ANALYTICAL CHEMISTRY, Vol. 45, No. 7, June 1973, pages 1215-1220, and the 
references cited therein, incorporated herein by reference. At the present 
time, carbon adsorption enjoys the widest use in industrial waste 
treatment processes to remove TNT. In general, this technique involves 
contacting TNT-containing waste water with activated charcoal or an 
activated carbon meterial, e.g., Filtrasorb-400 (Calgon Corp., Pitts., 
Pa.), which results in the adsorption of TNT and its colored decomposition 
species on the activated adsorbent material. Carbon adsorption has several 
disadvantages which limit its use, however. For instance, even after the 
TNT has been adsorbed it remains explosive and highly dangerous, 
especially when dry. As a result, regeneration of the carbon material for 
further use, which is ordinarily carried out in the case of other 
pollutants by burning the activated carbon material to oxidize the 
adsorbed pollutants, can not be accomplished with reasonable safety when 
TNT is the adsorbed material. Moreover, as a result of the afore-mentioned 
carbon regeneration difficulties, the spent carbon adsorbent must usually 
be discarded and replaced with fresh amounts, which is a costly procedure. 
Other methods involve extraction of the TNT from water by the use of water 
immiscible organic solvents, e.g., toluene. Significant amounts of TNT 
remain behind in the water layer even with extraction, however, and 
further waste treatment is required. Such further treatment often involves 
the use of the afore-mentioned carbon adsorption methods with their 
attendant disadvantages. Thus, there remains a widespread need for a 
method of removing TNT safely and efficiently from industrial discharges. 
The present invention provides a simple, safe and low cost method of 
removing TNT from waste water. The method is based on the surprising 
discovery that certain amino group containing compounds alone or together 
with cationic compounds cause the formation of water-insoluble reaction 
products with TNT. The resulting precipitates can be readily and safely 
removed and the treated waste water can then be safely discharged or 
further treated to remove other pollutants, without hazard, by 
conventional methods. 
DESCRIPTION OF THE INVENTION 
According to the present invention there is provided a process for the 
treatment of waste water from the manufacture of trinitrotoluene, the 
process comprising: 
a. forming an admixture of (i) waste water comprising an aqueous solution 
of trinitrotoluene and (ii) an amino group containing compound of the 
formula 
EQU (C.sub.n H.sub.2n+1).sub.m (NH(CH.sub.2).sub.x).sub.y NH.sub.z 
wherein n is 1 to 25, m is 1 to 3, x is 1 to 5, y is 0 to 5, z is 0 to 2, 
alone or with a cationic compound of the formula 
EQU (C.sub.n H.sub.2n+1).sub.4 N.sup.+ X.sup.- 
wherein n is 1 to 25, and X.sup.- is Cl.sup.-, Br.sup.-, SO.sub.4 H.sup.- ; 
b. stirring the mixture to form a water insoluble reaction product of 
trinitrotoluene, and 
c. recovering the water insoluble reaction product from the waste water. 
The method of the invention results in the formation of an insoluble, solid 
reaction product, which is characteristically comprised of dark colored, 
e.g., brownish, particles. By means of this invention, relatively high, 
toxic amounts of trinitrotoluene which are typically present in industrial 
waste waters from the manufacture of this compound, e.g., 50 to 150 ppm, 
can be reached in amount to harmless levels, e.g., 1 ppm or less. In 
addition, colored decomposition products of TNT, such as compounds which 
are formed when TNT containing waste water is exposed to ultraviolet 
light, are also removed by the present method. The water insoluble 
reaction product, after isolation and drying, can be burned without any 
hazard. 
By way of illustration, waste water emanating from the manufacture of TNT 
is collected at ambient pressure and temperature in a pond, tank or some 
other suitable enclosure. The collection enclosure can be outfitted, if 
desired, with conventional equipment for adjusting the temperature. The 
amino group containing compound or a mixture of the amine and cationic 
compound is added slowly, with mixing, and the mixture is stirred until 
dark colored particles begin to form, usually in a couple of hours. The 
stirring is continued for a sufficient length of time, e.g., 24 to 48 
hours, to cause substantially all of the TNT to react and to form its 
insoluble reaction products. The concentration of TNT remaining in the 
waste water can be monitored by withdrawing samples periodically and 
subjecting them to quantitative analysis, e.g., by spectrophotometry. When 
the TNT level has been reduced to 1 ppm or less, the stirring is stopped, 
and the dark colored precipitate is separated from the now substantially 
TNT-free waste water by filtering, e.g., through Diatomite or Celite 
filtering aids. Excess, unreacted amounts of the amino group containing 
compound or cationic compound can be recovered from the filtrate by a 
suitable technique, such as foam fractionation. 
The temperatures and amounts of co-reactants for the TNT in the present 
invention can vary widely. In general, higher rates of solid formation 
occur with the use of relatively large amounts of the amine or the amine 
and cationic compound and elevated temperatures, e.g., 30.degree. C. or 
above. Preferably, amounts of the amino group containing compound are used 
which provide an initial molar ratio of this compound to trinitrotoluene 
of from 1:1 to 5:1. Preferably, the cationic compound when used is present 
in amounts which provide an initial molar ratio of this compound to 
trinitrotoluene of from 0.5:1 to 2:1. 
The amino group containing compounds of the method of this invention are 
commercially available or described in the literature. Within the 
above-mentioned general formula, this compound is preferably selected from 
among 1-dodecyldiethylenetriamine, 4-dodecyldiethylenetriamine, 
N-oleyl-1,3-diaminopropane, N-tall oil fatty-1,3-diaminopropane, 
N-Coco-1,3-diaminopropane and N-tallow-1,3-diaminopropane. In the case of 
using a cationic compound as co-reactant with the amine, the amine is 
preferably selected from among n-butylamine, n-propylamine, ethylene 
diamine, diethylamine, diethylenetriamine, alkylaminobispropylamine. The 
cationic compound is preferably selected from among dodecyltrimethyl 
ammonium salt, hexadecyltrimethyl ammonium salt and dodecylpyridinum salt. 
Although the method of this invention has been described with particular 
reference to wash-down waste water, there are actually several kinds of 
waste waters generated during TNT manufacture, such as "red water" formed 
during sellite purification of TNT and "pink water" formed from the water 
washing of TNT following sellite purification. Although the so-called "red 
water" and "pink water" are normally disposed of by incineration, the 
present method is applicable for their waste treatment.

The method of the invention is further illustrated in the following 
examples, which are not intended to be limiting. 
EXAMPLE 1 
A one liter aqueous solution containing a 2:1 molar ratio of 
4-dodecyldiethylenetriamine to TNT (in pink water, concentration 140 ppm) 
was prepared and stirred continuously at ambient temperature (about 
23.degree. C.), and solid products were formed. At the end of 24 hours, 
the mixture was filtered through Celite and Diatomite and the solid free 
filtrate was analyzed for TNT content by spectrophotometry. The 
concentration of TNT in the filtrate was 1.5 ppm. 
Stirring was continued for an additional 24 hours, and the filtrate was 
again analyzed for TNT content as above. The concentration of TNT was 
about 0.5 ppm. 
EXAMPLE 2 
A one liter aqueous solution containing a molar ratio of 2:1 of 
N-tallow-1,3-diaminopropane to TNT (in pink water, concentration 140 ppm) 
was prepared and stirred continuously at 80.degree. C. After 4 hours the 
mixture was cooled and the resulting solid products were filtered through 
Celite and Diatomite. The concentration of TNT in the filtrate was 
measured as in Example 1 and found to be 1.5 ppm. 
Stirring of the mixture was continued for an additional 4 hours (8 hours 
total) at 80.degree. C., and again filtered and tested for TNT 
concentration as above. Only about 0.5 ppm of TNT was left. 
EXAMPLE 3 
A one liter aqueous solution containing a molar ratio of 1:1:1 of 
diethylenetriamine, hexadecyltriammonium bromide to TNT (concentration 140 
ppm, 5.5 .times. 10.sup.-4 M) was prepared and stirred continuously at 
ambient temperature (about 25.degree. C) and solid products were formed. 
At the end of 24 hours, the mixture was filtered through Celite and 
Diatomite and the solid free filtrate was analyzed for TNT content by 
spectrophotometry. The concentration of TNT in the filtrate was less than 
1 ppm. 
EXAMPLE 4 
The removal of TNT from aqueous solutions was carried out by adding a 
mixture of an amine and a cationic compound to "pink" water at room 
temperature. Several 1-liter solutions were prepared containing 5.5 
.times. 10.sup.-4 M of TNT, 6.0 .times. 10.sup.-4 M of N-methyl 
1,3-diaminopropane and various concentrations of hexadecyltriammonium 
bromide, as shown in the table below. The TNT concentration was determined 
by spectrophotometric analysis, after 25 hours of stirring, and the 
results are summarized below. 
__________________________________________________________________________ 
Conc. in the original solution 
Sample TNT % Removed 
No. TNT Amine Surfactant 
after 25 hr 
__________________________________________________________________________ 
1 5.5 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
2.0 .times. 10.sup.-4 M 
84% 
2 5.5 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
4.0 .times. 10.sup.-4 M 
97% 
3 5.5 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
5.0 .times. 10.sup.-4 M 
100% 
4 5.5 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
98% 
5 5.5 .times. 10.sup.-4 M 
6.0 .times. 10.sup.-4 M 
&gt;1.0 .times. 10.sup.-3 M 
.about. 0% 
(CMC) 
__________________________________________________________________________ 
It is known that the critical micelle concentration (CMC) for the bromide, 
which is a surfactant, is 9.2 .times. 10.sup.-4 M. It was unexpected, 
therefore, that precipitation occurred immediately in the solutions of TNT 
and amine by adding the bromide in amounts below its CMC. When the bromide 
was added in amounts above its CMC, no precipitation occurred. 
Although the above examples illustrated various modifications of the 
present invention, other variations and modifications will suggest 
themselves to those skilled in the art in the light of the above 
disclosure. It is to be understood, therefore, that changes may be made in 
the particular embodiments described herein which are within the spirit 
and full intended scope of the invention as defined in the appended 
claims.