Note: Descriptions are shown in the official language in which they were submitted.
10, This lnvention re`lates to a process for converting hazardous wastes
into an inert non-polluting material. The process will treat waste
~- streams which for some economic or hazardous reason cannot be disposed
of in any other manner. The term hazardous wastes includes any type of
industrial wastewater, sludge, or any other waste material generated by
15. any industrial process. This includes pickling acids, spent caustic
solutions, plating wastes, sludges resulting from the neutralization,
oxidation, and/or precipitation of heavy metal wastes " s-~t~dgesn from
the chemical or physical treatment of waste products, refinery wastes,
sulfur d;oxide removal sludges, sewerage sludges, water treatment plant
2Q sludges, tannery wastes, organic manufacturing wastes, paint and pigment
wastes, polymer production wastes, and any other wastes, liquid or
solid, resulting from any manufacturing process.
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Attempts have been made in the past to convert wastes into non-
polluting material, such as the use of an aqueous solution of an alkali
metal silicate mixed with the waste material and a silicate setting
agent, as described in U. S. Patent No. 3,837,872, dated September 24, 1974.
5. However, certain outstanding disadvantages have been found in such a
solidification method, - namely, such silicatesare soluble in water and
the soluble salts could leach out and pollute. Moreover, the sludge upon
drying, dehydrates the silica gel which will not reabsorb water to any
appreciable degree; instead, it dries into a powdery high surface area
10. dust which can be blown by the wind. Also it has a nigh pH value, and
a greater amount of reagent is needed for the above process, therefore
;~ involving a greater expense.
The object of the present invention is to overcome the above-named
disadvantages by providing a process for converting hazardous wastes,
15. both liquids and sludges or slurries, into an inert, non-pollut;ng
material, wherein an insoluble rather than a soluble material is used
and wherein the~ions do not leach out to any appreciable extent, there-
fore will not pollute the water, - also wherein the resulting inert
product is spongy and will reabsorb water, and wherein the pH value is
20. ~ relatively iow, about 8 to 9, with the formation of insoluble compounds,
good resulting sludge, therefore is not dangerous to handle - also
wherein only about 5% by weight per volume is needed for the conversion
process and wherein the materials used are relatively inexpensive,
therefore cutting costs by 30% or more, - also wherein the resultant
25. product greatly simulates soil in both color and physical character-
istics and may be actually used as soil for growing vegetation, in-
cluding grass, therefore, in effect, recycling soil to natural and
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useful condition to enable grass to be grown thereon, thus avoiding
marring of the natural appearance of the landscape bearing such wastes.
The principal material used in the present invention is bentonite,
which is a colloidal native hydrated aluminum s;licate (clay) found in
: 5. the midwest of the U.S.A. and Canada. The colloid is from yellowish-
~; white to almost pale brown. It forms highly viscous suspensions or gels
- , with not less than ten times its weight of water.
A suitable range for the conversion mixture of the present inven-
~;~ tion is ~ to 30% bentonite, ~ to 50% Portland Cement and the balance,
10. waste material, (by weight).
Outstanding benefits of this process are the abilities to use
treated toxic wastes for subterranean disposal, for fill material to
- improve undesirable land areas, or for the reclamation and revegetation
of strip mine areas. The process will produce the above results in a
15. manner which is safe and desirable from all environmental aspects.
The concentrations of bentonite, portland cement, and wastewater or
sludge are highly dependent upon the type of material being treated.
Based upon the eventual use and disposal of the treated wastes, the
~ mixture can be prepared in a manner which will suit the ultimate dis-
.~ 20. posal. If the material is to be land fill, less reagents are required
than if the material is to be used as a base for a building site.
Interactions between the setting agents and the industrial wastes
are extremely complex with ion exchange reactions taking place on the
bentonite clay and various hydration and setting reactions taking place
25~ in the cement matrix.
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The purpose of this invention is to provide a
simple, economical method of treating hazardous wastes to
produce an inert material that will dispose of these wastes
in an environmentally acceptable fashion at a minimum of
cost by the addition of only a small volume of treatment
chemicals.
The invention uses two materials, which after
wetting and aging, can absorb and contain hazardous wastes
with a minimal amount of leaching to the environment and
contain only minor quantities of dissolvable material.
This invention does not use any highly ionized materials
which, in themselves, could create an environmental hazard.
The invention has unique chemical characteristics
and encapsulates hazardous materials rendering them nearly
inert and non-leachable. This process will encapsulate
organic and/or inorganic waste materials and render them
fit for disposal to the environment.
The inert product of this process is a clay-like
material and has the ability to encapsulate hazardous
wastes in a cement-bentonite matrix, and produce a material
that has the ability to retain and re-absorb moisture.
The produced inert solid has the appearance of soil and
can be easily mistaken for a clay varying in color from a
red to a gray or bl~ck-brown.
The treated waste material has the ability to
support vegetation. Grasses grown on solidified waste
materials resulted in vegetation of a luxurious green.
These treated industrial wastes provide excellent media
for grass growth because of their high ability to hold
moisture, and the lack of many ions which would destroy
plant life.
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A. The reaction of bentonite clay with water results in the
bentonite clay exhibiting an affinity for water and absorbing
12 to 15 times its volume in water. Bentonite clays exhibit
basic ion exchange properties in water solutions, and quite
5. readily gives up sodium and potassium ions in the adsorption
of metallic ions. The result of this property of bentonite
makes it highly desirable as an inorganic ion exchange media.
Also, bentonite clays enter very strongly into base exchange
with various basic organics, thereby extracting them from
10, solutions of their salts. When bentonite clay is mixed with,
by vo lume,
one part bentonite to ten parts of water/ it creates a gelat-
inous ion exchange medium which exhibits the above mentioned
properties. The avid absorption of bentonite of other sub-
stances, both inorganic and organic, is due to the great
15. surface area of the bentonite clay, the spongy structure,
mobility, the basic exchange, and the strong negative polarity
of the material.
Portland cement undergoes several reactions with water in
setting. These reactions begin with the hydrolysis of
20. certain chemicals in the Portland cement and continue through
hydration and other reactions. By combining Portland cement
with a mixture of industrial wastes and bentonite clays, a
physical stability is acquired, which has the ability to
entrap and bind all contained waste materials.
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B. By combining the bentonite clay, cement, and industrial wastes
in an alkaline pH range, there are chemical reactions that
occur with metal salts to form insoluble metal hydroxides
which are permanently coated or encapsulated into the matrix.
5. Many organic salts and acids can be converted to the sodium
derivative and these can be avidly trapped into the matrix to
form insoluble compounds.
By selectively varying the ratio of reagents, any desirable
consistency can be obtained from a soft clay to a dense, hard
10. rock-like material. In combining bentonite and Portland
cements, to induce a solidified system, only small quantities
of bentonite and Portland cement are required which is another
outstanding feature, namely economy, of the present invention.
In most instances, the total percent by weight of fixation
15. reagents to wastes is less than lO% and often times is in the
range of l% to 6%. Normal reaction time for the bentonite
clay and cement mixtures range from 30 minutes to five hours,
depending upon the consistencies of the industrial waste being
treated. The material after treatment is still fluid, and it
20. is normally pumped from the treatment site to a holding pond
to solidify and then removed with earth moving equipment or left in
place.
Example No. 1. Industrial waste materials resulting from the
pickling of steel were brought to a central disposal area and
treated by lime neutralization. The resulting sludge was then
25. treated by the process of the present invention, with the
resulting product being a clay-like material which totally
absorbed, chemically bound, and encapsulated all of the water
Z8~
B. By combining the bentonite clay, cement, and industrial wastes
in an alkaline pH range, there are chemical reactions that
occur with metal salts to form insoluble metal hydroxides
which are permanently coated or encapsulated into the matrix.
S. Many organic salts and acids can be converted to the sodium
derivative and these can be avidly trapped into the matrix to
form insoluble compounds.
By selectively varying the ratio of reagents, any desirable
consistency can be obtained from a soft clay to a dense, hard
10. rock-like material. In combining bentonite and Portland
cements, to induce a solidified system, only small quantities
of bentonite and Portland cement are required which is another
outstanding feature, namely economy, of the present invention.
In most instances, the total percent by weight of fixation
15. reagents to wastes is less than lO% and often times is in the
range of l% to 6%. Normal reaction time for the bentonite
clay and cement mixtures range from 30 minutes to five hours,
depending upon the consistencies of the industrial waste being
treated. The material after treatment is still fluid, and it
20. is normally pumped from the treatment site to a holding pond
to solidify and then removed with earth moving equipment or left in
place .
Example No. 1. Industrial waste materials resulting from the
pickling of steel were brought to a central disposal area and
treated by lime neutralization. The resulting sludge was then
25. treated by the process of the present invention, with the
resulting product being a clay-like material which totally
absorbed, chemically bound, and encapsulated all of the water
1 1 1q~2 8 1
- and 6%~ 9%~ 12%~ 15%~ 18%, and 20Yo Portland cement; 4% bentonite
w;th 6Yo~ 9%~ 12%~ 15Yo~ 18%, 20Yo~ and 24% Portland cement. The
samples were solidified and penetrations ranged from a maximum
greater than 5 kilograms per square centimeter to approximately
5. 0.8 kilograms per square centimeter. The material closely
resembled a clay and was impermeable to water.
A field study was then established using various ratios of
bentonite and clay mixtures. Test cells were constructed to
study the leaching characteristics and the following reagents
10. were added to the sludge: (3 6 represents 3% by weight of
bentonite and 6% by weight of Portland cement) 3 6~ 3 9~ 3 12
4 6~ 4 9~ 4 12~ 1~4 4~ 2~2 6~ 3~7 2~ Readings were taken on
the samples and the penetrations were all in the range greater
than 2~ kilograms per square centimeter. The material was
15. clay-like in appearance and did not permit water penetration.
Leachate analyses of these test cells were obtained, and the
data shows that the material is relatively leach free and
complexes all heavy metals, and retainssulfates, and chlorides.
Grass was then grown on this treated material and it fluorished.
20. Additional investigations were conducted using bentonite clay
in ~ to 30YO by weight mixes, and Portland cement in ~ to 50YO
by weight mixes, and was found that the hardness of the solidified
sludge was a function of the total solids of the mixed material,
and of the concentration of reagents added to the system.
25. Example No 2~ Numerous samples of organic waste products
were subjected to the process of the present invention under
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simulated treatment conditions. These were treated with
bentonite and Portland cement. The sludges produced by this
process adsorbed the organlc waste materials in a bentonite
cement matrix and also produced a sludge which was clay-like
5. in consistency.
The organic materials contained in the waste stream were
adequately treated using this system, and no evidence of their
presence was noted after the sludges had been treated with the
Portland cement-bentonite mixture. More specifically, several
10. samples of organic wastes such as oil tank bottoms, organic
sludge resulting from paint manufacturing, and oils and
greases were subjected to the solidification technique. The
ratios of bentonite and Portland cement were varied until a
dense clay-like material was formed. It was determined that~bywe;ght
15. in all instances, no more than 30% bentonite and 50% Portland
cement were required to solidify the wastes. Depending upon
the solids, and the water concentration, solidifications were
performed that used a minimum of reagents. For example, a
paint sludge required 2% bentonite and 4% Portland cement to
20. create a solidified product that was capable of withstandingl.5 kg/sq. cm bearing strength. Once again, it was noted that
the product was more highly colored and was highly dependent
upon the color of the waste materials. In all instances,
dense clay-like materials were formed that were impermeable
25. and relatively free from leaching.
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Example No. 3. Samples of the sludge resulting from acid
mine drainage treatment were solidified using the herein
described process. The resulting sludge had a clay-like
consistency, was orange in nature, and complexed all of the
metals present in the mine drainage sludge. The leachate
characteristics of the neutralized sludge were extremely
good with the leachate emanating from the solidified
material containing no parameters that would adversely
after water quality. This sludge was successfully treated
and produced an environmentally acceptable waste product.
r~ore specifically, samples of effluent of clarifier sludge
were subjected to the process and satisfactory solidification
occurredin the range, by weight of 2% bentonite and 4%
Portland cement. The color of the sludge produced in this
instance was yellow, red and closely resembled the original
wasteproduct. The materials were solidified under various
concentrations ranging from 1% bentonite to 20% Portland
cement, to 10~ bentonite and 20% Portland cement, by weight.
Example No. 4. Samples of the sludges resulting from fly
ash and sulfur dioxide scrubbing were treated and produced
a material that was of a clay-like consistency and black in
color. The leachate characteristics of the neutralized
sludges were extremely good and contained no parameters that
would adversely affect water quality. More specifically,
test ratios of bentonite to Portland cement in the range
of 1/2:1, by weight 1:2, 1:3,1 1/2;3, 2:4 and 3:6 were
used on a clarifier effluent resulting from the sulfur
dioxide scrubbing process at a local generating station.
The material had a pH of 5.5, a specific . . . . . . . . .
-~b.
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gravity of 1.43, and a moisture content of 49%. The v æ ious
test ratios produced a product that was very soft at the lower
concentrations to a product that was rock hard at 3.6. The
bearing strength of the 1/2:1, 1:2, and 1:3 mixtures was less
than 0.25 Kilograms per square centimeter, or tons/ft2, while
the 3:6 ratio provided 3.5 kilograms per square centimeter.
Additional samples of sulfer dioxide scrubbing sludges were
obtained and treated using bentonite and Portland cement for
solidification reagents. The test ratios used in this study
were 1.25%: 2~5~/o~ 1.25%: 3.75%, 2.5~/o: 7~5%, 3.75%: 7.5%, 3.75%: 11.25%?
6.25%: 11.25%. Fifty grams of fly ash was ~ded to 200 milliliters
of sludge which had a specific gravity of 1.35, a density of
11.27 pounds per gallon, and a moisture of 56%. To this the
bentonite and Portland cement were added until fixation took
place. After a period of one week, the penetrometer readings
of tons/ft2 ranged from 7.92 to greater than 50.4. After two
weeks aging, the results showed 190 to greater than 50.4. After
four weeks, the results showed the 1.25%:2.5% showing a bearing
strength of 25.2 tons/ft2. The 1.25%:3.75% showed a bearing
capacity of 460 per square centimeter. All of the other results
showed bearing capacities greater than 50.4. The solidified
material had a black color and the consistency varied from a
watery clay to a silty clay structure.
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Thus it will be seen that we have provided an efficient and
very inexpensive method of converting hazardous industrial
wastes into an inert, non-polluting and very useful soil-like
product having the characteristics of ordinary soil so as to
permit growing of grass or vegetation thereon and thus greatly
improving the environment; furthermore we have provided a
resulting product which is chemically and physically stable
and almost completely insoluble in water.
While we have illustrated and described several embodiments
of our invention, it will be understood that these are by way
of illustration only and that various changes and modifications
are contemplated in our invention, within the scope of the
following claims.
