CA1254588A - Method and composition for waste disposal - Google Patents
Method and composition for waste disposalInfo
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- CA1254588A CA1254588A CA000509045A CA509045A CA1254588A CA 1254588 A CA1254588 A CA 1254588A CA 000509045 A CA000509045 A CA 000509045A CA 509045 A CA509045 A CA 509045A CA 1254588 A CA1254588 A CA 1254588A
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Abstract
METHOD AND COMPOSITION FOR WASTE DISPOSAL
ABSTRACT
The absorbing and solidifying or chemical fixation agents of the present invention comprise a substantially homogeneous mixture containing a major amount of an absorptive, granular clay with minor amounts of cement and a soluble alkali metasilicate.
Typically the mixture contains from about 60 to about 95% by weight of an absorptive granular clay, such as fuller's earth;
from about 5 to about 15% by weight of cement, such as Portland cement; and, from about 0.1 to about 5.0% by weight of an alkali metal metasilicate, such as sodium metasilicate. In a preferred, range the mixtures comprise from about 80 to about 90% by weight clay, from about 8 to about 12% by weight cement and from about 0.5 to about 1.5% by weight silicate. The mixtures may include up to about 30% by weight of fly ash, cement dust or mixtures thereof. The agents are mixed with a liquid or semi-liquid waste material in an amount of between about 3 and about 8 pounds per gallon of waste material. The resultant mixture is allowed to harden to form a substantially water insoluble solid having a consistency ranging from that of dirt to that of a plaster or cement-like solid.
ABSTRACT
The absorbing and solidifying or chemical fixation agents of the present invention comprise a substantially homogeneous mixture containing a major amount of an absorptive, granular clay with minor amounts of cement and a soluble alkali metasilicate.
Typically the mixture contains from about 60 to about 95% by weight of an absorptive granular clay, such as fuller's earth;
from about 5 to about 15% by weight of cement, such as Portland cement; and, from about 0.1 to about 5.0% by weight of an alkali metal metasilicate, such as sodium metasilicate. In a preferred, range the mixtures comprise from about 80 to about 90% by weight clay, from about 8 to about 12% by weight cement and from about 0.5 to about 1.5% by weight silicate. The mixtures may include up to about 30% by weight of fly ash, cement dust or mixtures thereof. The agents are mixed with a liquid or semi-liquid waste material in an amount of between about 3 and about 8 pounds per gallon of waste material. The resultant mixture is allowed to harden to form a substantially water insoluble solid having a consistency ranging from that of dirt to that of a plaster or cement-like solid.
Description
5~ ExpreY~ Mail M~ilin~
Label No. B57967714 LWP : 1 04 METHOD AN~ COMPOSITXON FO~ WAST~ DISPOSAL
BACKGROUND OF THE INV~NTION
The pre~ent invention relates to methods and compositions useful in the field of wa~te dispo~al. The present invention facilitate~ the detoxification and delisting of was~e materials.
Aq u~ed herein the term "dellsting" means the treatment of the waste to remove the waste from a defined category, c1888, or ~ype, e.g., hazardous, and enable cla~sLfication o~ the waQte in~o a lower category, cla~s, or type, e.gO, nonhazardous, under the EPA regulationQ, e.g., the Resource Conservation and Recovery Act (RCRA?, 40 CFR 260 and 261. More in particul~r? ~he present invention provides a mean~ for the ~afe snd ~fficient permanent disposal o~ waste materials in the forms o liquids or semi-liquid~, (which includes slurrie~ or sludges), and may or may not contain soluble or in~oluble hazardous, toxic, or nuisance material~. ;
The terms "waste" or "waQte material" as used herein, includes inductrial wastes, for example, those generated by the metallurgical or mining indu~trie~, generally sludges and leacha~es; tkose generated by the chemical indu~tries, typicalLy process by-products which are not economically useful, and; those generated by the petroleum indu~trie~, generally oily or greasy materlals. It will be understood that the term~ "waste" or "waste material" also encompas~ commercial or indus~rial .. , ~"~ 3 nonhazardous wastes and arP inclu~ive of for example, municipal products and by-products, iaboratory wa~te~, hou~ehold wa~tes, landfill leacha~es and product 5pill8.
Previously a number of propo~Plu have ~een made rela~ing to useful compositions and to method~ for the treatment of waste liquids and sludges. Typically the waste i8 absorbed ln or on t~he composition, the mixture solldified, and the solid hold$ng the waste material in a more stable condltion is sub~equently disposed of in a landfill. For exa~ le, U.S. Patent 2,665,259 descri~es a mixture of fuller's earth and cement useful in a~sorbing oils and grease, u.s. Patent 3,~37,872 teaches the use of a solu~cion of an alkali metal silicate, such as sodium sillcate, and a silicate setting agent, such as Portland cement, to form a golid u3eful in the treatment of wa~te materials. u-s- Patent 3,841,1()2 relates to the treatment of wastes with a mixture of soluble silicaee3 and cement to prepare a solid material ~uitable to entrap waste msterial t:herein. u.s. Patent 3,980,558 uses a variety of hydralllic cements as binders for wa~e msterlQl8. u.s. Patent 3,988,258 teaches the use of a mixture of cement and water glas~ for the en~rapment of ~adwa~te. u.s. Patent 4,028,130 describes the use of fly ash to fonn a solid with sewage wastes. u.S. Patent 4,067,894 teaches the use of waste clay with an organic binder and a pelletizing agent to trea~ effluents containing, heavy metals. u.s. Patent ~,101,332 descrlbes the use of fl~ ash and cement kiln du~t to ~orm a ~olld useful in water treatment. u.s. Patent 4,113,504 teaches the use of a mixture of vermiculite and cement ~o form a solld matrix for the ~.54~.3 entrapment of heavy metal wastes. u.s. Pa~rJt ~ ,705 descr~fJ~ the use-of alum$num sillcate or alumina ~ilicate and Por~land Cement to encapsulate hazardous wa~te- u-S. P~tent ~,Z29,~g5 rel~-te.c, ~ the use of clay and silica which 1~ gelled to ent~ap wa~te material~
therein. U.S. Re. 31,267 teachea the u~e oE fuller'3 earth to form a paste with oil reclaiming sludge which facilltate~ easier disposition of the sludge.
The major disadvantages of the prior art which have no~
heretofore been ~ati~factorily remedied are: a) the large increases in material volume resulting from the prior ~rt was~e treatments also result3 in large increases in dispo~al costs;
b) the stron~ tendency of the final prior art mix~ure~ to release absorbed materials, or form aqueou~ solutlons of the absorbed material~, when exposed to water, or to dilute acid o,r slkaline solutions; c) bleeding of entrapped or absorbed materials when the mixture~ are placed under pre~sure or are exposed to freeze-thaw cycles, or to elevated temperatures; and, d) the class or type of was~e, s defined by the EPA regulations, i8 not changed which would allow a delisting and facilitate disposal of the treated waste in a sanitary landfill at a substantially less cost than the disposal .of the same wa~te $n a hazardous waste landfill.
The increase ln volume of material in some of the prior art proposals reaches as high as t,wenty times the volume of the original waste. If such treatment takes place at a plant or a spill s$te, the increased volume enta$1~ a sub~tnnti~l increa~e in the amount of bulk handling, s~ora~e, ~ransporta~ion and subsequent disposal space. If the treatment takes pl~ce at a landfill &ite, the available volume of the landfill ls substantially decrea~ed by large amoun~s of flller or matrix material. The problem of leaching has not been fully met by the prior art proposals. In many situations the prior art ~olid mixtures having ~he waste material entrapped therein, must be maintained out of contact with liquids, such BS water, in order to maintain ~he integrity of the mixtures. Many of the prior art mixtures- are not phy3ically, or structurally stable, under pres~ure, or through freeze-thaw cycle~ or a~ elevated temperatures. In such situations the entrapped mater~als are exuded out of the matrix materlal. Temperature ch~nges can create breaches in the matrix m~terial which allow~ the previou~ly en~rapped materials to escape. The ~tr~ctural integrity of wastes, or mlxture3 of waste ~nd a filler or matrix mater$al, may be determined by standardlzed tests, namely those recited in 40 CFR 261, App. II. The prior art mixture3 have been unable to consistently meet such ee~t requlrements which would enable a delisting, or lower listing of ~he waste material.
BRIEF DESCRIPTION OF THE INVENTION
The ~olidifying or chemicsl fixation ~gent~ oE the present invention ~re absorbent materi~l3 which are compri3ed of a substantialLy homogen~l~ mixture of an absorptive, granular, pre~erably a finely divided, particulate, clay with minor amount~
of cement and a soluble alkali metasilicate. The present Mlxtures con~ain a major amount of absorp~ive, granular clay, such a3 fuller's earth, that i~, the particulate clay i~ ~rcsen~ in an amount greater than any other component, In a pre~erred rAnge, the mixture contains from about 60 tO about 95~/oby weight of an absorptive grsnular clay, such as fuller's earth; from about 5 to ~bout 15~/o by weight of cement,such as Portland cement;and, from about 0.1 to about 5.0% by welght of an alkall metal metasilicate, such a~ sodium metasilicate. In a narrower, and more preferred, range the mixtures compr$se from about 80 tO
about 90% by weight clay, from about 8 to about 12% by weight cemen~ and from about 0.5 to about 1.5% by weight silicate.
The present mixtures may also contain up to aboue 30V/., and more preferably up to about 25%, by weight of fly ash or cement tust. ~ixtures of fly a~h and cement du~t are useful.
The preferred absorptive granular clay i8 fuller's earth.
Fuller'~ earth is a colloid~l clay, hydrated calcium magne~ium aluminum silicate. The term "fuller's earth" includes highly porous clays, ~uch as montmorillonites , attapulgites, sepialites, polygorskites and opalites. Fuller's earth i8 known to be available from suppliers such as, Mid-Flor$da Mining Company, ITT-Flordian, Englehard Minerals and Chemicals, Oil Dri Corporation, Excel Minerals, Waverly Dres~er Industries, Mill White, Georgia Tennessee Mining, Wyandotte Chemical Company, ~ennet~ Mineral Company, Belcane Mineral Company and the Absorbent Clay Company.
~: , A fine particle ~ize of the compounds of ~he pre~en~
compogition i~ desirable in order that the mix~ure can be made as homogen~ous as possible and not ~epar~te during tran~porta~ion or stors~e7 The particle 8ize of the clay component i~ the presenr invention is particularly important in that a lar~e amount of absorbent surface is required, and a flnely divided absorptive clay material will provide ~uc~ surface. However, if the psrticle size i3 ultrs-fine, the mixture i8 sub~ect to dusting, in which case the surface ares advantage 18 lost and the composition may create more problems than i~ solves. Generally a particle size range of from about +20 mesh i8 useful, that is th~
compo ition will Bll p~88 through a 20 mesh standard Tyler screen. For most purposes it $8 preferred that A majority of the particle~ be of a ~ize to be retained on a 100 mesh screen.
The cemen~ component suitable for u~e in the pre~ent composition includes all materials which harden by a combination of hydrolysis and hydration reactions upon the addi~ion of water.
Such ma~erials include ~11 types of Portland cements, natural cements, masonry cements, gypsum, gypsum cements and plasters, Plaster of Parl~ and Poæzolans. A particularly preferred cement is ASTM Type II Portland cement. The particle size of the cement component i8 generally finex thsn the clay component discussed above.
The alkali metal metasilicate component may be ~elected from any o the alk~li metal metssilicate3, however, sodium met~silicate i~ preferred because of it~ low CoGt and ready ~ailability. Therefore, in the following discus~ions it will be understood that reference to godium me~a~ilicate refers only ~o a preferred metasilicate. The sodium meta~llicates are normally solids and are also known ag soluble silicates or a~ dry wa~er glass. Sodium metasilicate, Na2SiO3 (~Ja20'Si~2) i~ commercially available in the anhydrous form, or as hydrate~, such as, Na2SiO3 5 H20~ 6 H20. ~ ~2 and ~ H20. Sodium ~esqui~ilicate and anhydrous orthosilicate are mixture~ of sodium metasilicate and caustic soda and are su$ted ~o use, although no~ preferably. The particle size of the metasilicate componen~ is 3imilar to the particle size of the clay and cement components discussed above.
Fly ash i~ a well known waste materlal. Typically fly ash is the finely divided re~idual product produced by the combustion of pulverized coal which is carried off with the ~tack gase~
exi~in~ the furnace. Fly ash may be collected from such gase~ by a process of precipitation, typically utilizing electr~s~atic precipitators. Fly ash is mostly comprised of Yilica, aluminum and iron compounds pre~ent in a variety of forms. Cement dust i5 a finely divided solid waste material generated by cement manufacture. Primarily it is kiln dust. The dust is a mixture of raw cement, kiln feed, partly calcined material, finely divided cement klinker, metallic and nonmetallic oxide~, and alkali materials, typicaLly alkali sulfates. Mlxtures of fly ash and cement dust may be utilized.
The componen~s may be mixed in accord wi~.h any conventional technique in the absence of wa~er to provide an intimate, ~i5 ~ ^3 substantially homogeneou~ mixture. It hag been found ln practice that ~f the cement component and the metasilicate component~ are inieially thoroughly mixed and the clay component ~ubaequen~ly added and mixing continued, a ~ub~t~ntially homogeneo~5, 1uent mixture is obtained.
The compositions of the absorbing and eolidifying agents of the present invention may include minor smount~ of inert or complementary materials. Such materials typically unction ts a$d in ~he absorption of liquid3, contribute ~trength, add early hardening characteristic~, or as binding alds.
DETAILED DESCRIPTION OF THE INVENTION
~ _ , The particulate, or ~ranular, compo~itlons of the present invention have improved absorbent properties and are p~rtlcularly adapted to use in proces3es involving the solidificatlon and/or chemical fixation of liquids and ~ludges. The present composition~ comply with the current and presently proposed federal regulation~ pertaining to the ~olidification and/or chemical fixation of hazardous waste~.
The present compbsitions are useful in the field7 thst 1~, at the site of a chemical 8pill or B clean-up operation. They are, however, equally useful in the proces~ing of chemical waste by-products at or near the polnt of generatlon. In the latter ca~e the by-products may be treated on a periodlc basiY, e.g., on a daily or weekly schedule, to avoid the accumulation of larg~
quantities of untreated wastes. Although, the C09t of ~,~ rj f~
transportation of the trea~ed waste may be 31ightly increased, such disadvantage i~ offset by the expen~e of handling and ~toring ~he raw wa~te ma~erial, and the ri~k oP having such untreated wastes presen~ in a produc~ion faciLity.
The present invention seeks to remedy the shortcomings of the prior art by providing a substantially improved ab~orptive and solidifying or chemical fixation agent that facilitates a minimum volume final product, that is not soluble, or reliquefiable, in the presence of liquids, especially water, and that is~--chemically, mechanically and temperature s~able. The present agents are particularly useful in ~reating waste materials containing heavy me~als. Heavy metals may be defined as those metals in Groups I B, II B, IV B~ V B, VI B, VII B, VIII, III A, IV A, V A, the lanthanides and the actinldes.
Generally the heavy metal content of the waste material is les~
than 1% by weight. The heavy metal component of thè waste material may be present in either a liquid or a solid phase.
Typically the heavy metal component i~ in the solid phase in slurries and sludgeq. The pre~ent agents are also particularly u~eful in treating wastes, either orgsnic or inorganic having hydroxyl groups~
The final produc~ with entrapped materials ~ypically ranges in form from a friable clay, or so~t dirt to a hard plaster or cement-like material. ALthough the present absorbing and solidifying agents are particularly suited to be bagged and stored for use at the site of a chemical spill, they are aptly ~ 3 suited to u~e in bulk at plant, landfill, or other site~ The pre~ent solidifying compo~ltions are slso particularly ~ulted to use as sanltary landfill covers which are applied, or layered, over ~he top oE the land~11 and allowed to slnk into the landfill material and solldify liquid ma~.erial ln pl~ce.
In the presen~ method the compositions are mlxed with ~he Iiquid or semi-liquid waste material to be dispo~ed of to ~srm a solid, ~toreable product. Generally the compo3itlons are utilized in amount~ between abou~ 3 and sbou~ 8 pounds per gallon of waste. The ratio will vary, dependent upon the charac~eristics of the waste material. Generally purely liquid waste material~ require larger amounts o~ absorb~nt ma~erial than semi-liquid materiaLs, e.g., sludges. Tgpically about 5 pounds per gallon is useful to treat most liquid waste materlals. The exact, or more exact ~mount may be easily determined by empirical means.
The l$quid or ~eml-liquid waste and the solidifying agent may be mixed by conventional techniques, for example, in a~gregate mixing devices, by mechanical stirring or manually by shovel or paddle. The mixing i8 continued, or additional absorbent material added and mixed, until a mixture of paste-like consi~tency is obtained.
The hardening process may take place in situ, that is the mixture i8 not moved after mixing. Typically the mixture is poured 9 shoveled or dumped in its uLtimate location. The mixtures may be poured, or otherwise loaded, into container~ to harden. In this embodiment the fllll con~ainers are subsequen~ly disposed of, or ~heir conten~s separately di~posed of and the containers reused. Hardening takes place a~ amhient temperature generally between abou~. 20F and 100F, and more typically between about 40F and about 90F, over a period o~ from about l~
tO about 72 hours, and more typically from about 12 to about 24 hours. A solid, substantially completely water insoluble, storable product is produced.
The product ater hardening may have a dirt-like consistency or, and most usually, it haY a hard rock-like chara~ter~ The volume increase, that is, the volume of the final hardened mixture as compared to the volume of the original waste, i8 typically between about 20 and about 80~/o and usually between about 30 and about 60%.
In some instances the starting waste material may be classified under regulations a~ hazardous, but after treatment may qualify for, and be classified as having, a nonhazardous status~ In such cases a subqtantial saving in disposal cost may be realized.
While it will be~understood that the pre~ent invention is not to be interpreted ln the llght of a particular theory, it is postulated that the liquld waste is absorbed and/or adsorbed on and in the finely divided component, e.g., the clay particles, subsequently the solid metasilicate component became~ partly soluble tieing the waste material and finely divided material.
The partly soluble silicate component ~ubsequently promotes the setting of the cement component, possibly acting a~ a hydraulic cement by forming silicates and other rnaterials similar to et~ringite. The re~ul~ is a solid material having the waste material encapsulated therein.
It will be furthe~ understood that numerous modlication~
and variations of the invention may be made without departin~
from the spirit and scope theréof, therefore, only such lim-itat~ons should be imposed as are indicated by the appended claims.
Label No. B57967714 LWP : 1 04 METHOD AN~ COMPOSITXON FO~ WAST~ DISPOSAL
BACKGROUND OF THE INV~NTION
The pre~ent invention relates to methods and compositions useful in the field of wa~te dispo~al. The present invention facilitate~ the detoxification and delisting of was~e materials.
Aq u~ed herein the term "dellsting" means the treatment of the waste to remove the waste from a defined category, c1888, or ~ype, e.g., hazardous, and enable cla~sLfication o~ the waQte in~o a lower category, cla~s, or type, e.gO, nonhazardous, under the EPA regulationQ, e.g., the Resource Conservation and Recovery Act (RCRA?, 40 CFR 260 and 261. More in particul~r? ~he present invention provides a mean~ for the ~afe snd ~fficient permanent disposal o~ waste materials in the forms o liquids or semi-liquid~, (which includes slurrie~ or sludges), and may or may not contain soluble or in~oluble hazardous, toxic, or nuisance material~. ;
The terms "waste" or "waQte material" as used herein, includes inductrial wastes, for example, those generated by the metallurgical or mining indu~trie~, generally sludges and leacha~es; tkose generated by the chemical indu~tries, typicalLy process by-products which are not economically useful, and; those generated by the petroleum indu~trie~, generally oily or greasy materlals. It will be understood that the term~ "waste" or "waste material" also encompas~ commercial or indus~rial .. , ~"~ 3 nonhazardous wastes and arP inclu~ive of for example, municipal products and by-products, iaboratory wa~te~, hou~ehold wa~tes, landfill leacha~es and product 5pill8.
Previously a number of propo~Plu have ~een made rela~ing to useful compositions and to method~ for the treatment of waste liquids and sludges. Typically the waste i8 absorbed ln or on t~he composition, the mixture solldified, and the solid hold$ng the waste material in a more stable condltion is sub~equently disposed of in a landfill. For exa~ le, U.S. Patent 2,665,259 descri~es a mixture of fuller's earth and cement useful in a~sorbing oils and grease, u.s. Patent 3,~37,872 teaches the use of a solu~cion of an alkali metal silicate, such as sodium sillcate, and a silicate setting agent, such as Portland cement, to form a golid u3eful in the treatment of wa~te materials. u-s- Patent 3,841,1()2 relates to the treatment of wastes with a mixture of soluble silicaee3 and cement to prepare a solid material ~uitable to entrap waste msterial t:herein. u.s. Patent 3,980,558 uses a variety of hydralllic cements as binders for wa~e msterlQl8. u.s. Patent 3,988,258 teaches the use of a mixture of cement and water glas~ for the en~rapment of ~adwa~te. u.s. Patent 4,028,130 describes the use of fly ash to fonn a solid with sewage wastes. u.S. Patent 4,067,894 teaches the use of waste clay with an organic binder and a pelletizing agent to trea~ effluents containing, heavy metals. u.s. Patent ~,101,332 descrlbes the use of fl~ ash and cement kiln du~t to ~orm a ~olld useful in water treatment. u.s. Patent 4,113,504 teaches the use of a mixture of vermiculite and cement ~o form a solld matrix for the ~.54~.3 entrapment of heavy metal wastes. u.s. Pa~rJt ~ ,705 descr~fJ~ the use-of alum$num sillcate or alumina ~ilicate and Por~land Cement to encapsulate hazardous wa~te- u-S. P~tent ~,Z29,~g5 rel~-te.c, ~ the use of clay and silica which 1~ gelled to ent~ap wa~te material~
therein. U.S. Re. 31,267 teachea the u~e oE fuller'3 earth to form a paste with oil reclaiming sludge which facilltate~ easier disposition of the sludge.
The major disadvantages of the prior art which have no~
heretofore been ~ati~factorily remedied are: a) the large increases in material volume resulting from the prior ~rt was~e treatments also result3 in large increases in dispo~al costs;
b) the stron~ tendency of the final prior art mix~ure~ to release absorbed materials, or form aqueou~ solutlons of the absorbed material~, when exposed to water, or to dilute acid o,r slkaline solutions; c) bleeding of entrapped or absorbed materials when the mixture~ are placed under pre~sure or are exposed to freeze-thaw cycles, or to elevated temperatures; and, d) the class or type of was~e, s defined by the EPA regulations, i8 not changed which would allow a delisting and facilitate disposal of the treated waste in a sanitary landfill at a substantially less cost than the disposal .of the same wa~te $n a hazardous waste landfill.
The increase ln volume of material in some of the prior art proposals reaches as high as t,wenty times the volume of the original waste. If such treatment takes place at a plant or a spill s$te, the increased volume enta$1~ a sub~tnnti~l increa~e in the amount of bulk handling, s~ora~e, ~ransporta~ion and subsequent disposal space. If the treatment takes pl~ce at a landfill &ite, the available volume of the landfill ls substantially decrea~ed by large amoun~s of flller or matrix material. The problem of leaching has not been fully met by the prior art proposals. In many situations the prior art ~olid mixtures having ~he waste material entrapped therein, must be maintained out of contact with liquids, such BS water, in order to maintain ~he integrity of the mixtures. Many of the prior art mixtures- are not phy3ically, or structurally stable, under pres~ure, or through freeze-thaw cycle~ or a~ elevated temperatures. In such situations the entrapped mater~als are exuded out of the matrix materlal. Temperature ch~nges can create breaches in the matrix m~terial which allow~ the previou~ly en~rapped materials to escape. The ~tr~ctural integrity of wastes, or mlxture3 of waste ~nd a filler or matrix mater$al, may be determined by standardlzed tests, namely those recited in 40 CFR 261, App. II. The prior art mixture3 have been unable to consistently meet such ee~t requlrements which would enable a delisting, or lower listing of ~he waste material.
BRIEF DESCRIPTION OF THE INVENTION
The ~olidifying or chemicsl fixation ~gent~ oE the present invention ~re absorbent materi~l3 which are compri3ed of a substantialLy homogen~l~ mixture of an absorptive, granular, pre~erably a finely divided, particulate, clay with minor amount~
of cement and a soluble alkali metasilicate. The present Mlxtures con~ain a major amount of absorp~ive, granular clay, such a3 fuller's earth, that i~, the particulate clay i~ ~rcsen~ in an amount greater than any other component, In a pre~erred rAnge, the mixture contains from about 60 tO about 95~/oby weight of an absorptive grsnular clay, such as fuller's earth; from about 5 to ~bout 15~/o by weight of cement,such as Portland cement;and, from about 0.1 to about 5.0% by welght of an alkall metal metasilicate, such a~ sodium metasilicate. In a narrower, and more preferred, range the mixtures compr$se from about 80 tO
about 90% by weight clay, from about 8 to about 12% by weight cemen~ and from about 0.5 to about 1.5% by weight silicate.
The present mixtures may also contain up to aboue 30V/., and more preferably up to about 25%, by weight of fly ash or cement tust. ~ixtures of fly a~h and cement du~t are useful.
The preferred absorptive granular clay i8 fuller's earth.
Fuller'~ earth is a colloid~l clay, hydrated calcium magne~ium aluminum silicate. The term "fuller's earth" includes highly porous clays, ~uch as montmorillonites , attapulgites, sepialites, polygorskites and opalites. Fuller's earth i8 known to be available from suppliers such as, Mid-Flor$da Mining Company, ITT-Flordian, Englehard Minerals and Chemicals, Oil Dri Corporation, Excel Minerals, Waverly Dres~er Industries, Mill White, Georgia Tennessee Mining, Wyandotte Chemical Company, ~ennet~ Mineral Company, Belcane Mineral Company and the Absorbent Clay Company.
~: , A fine particle ~ize of the compounds of ~he pre~en~
compogition i~ desirable in order that the mix~ure can be made as homogen~ous as possible and not ~epar~te during tran~porta~ion or stors~e7 The particle 8ize of the clay component i~ the presenr invention is particularly important in that a lar~e amount of absorbent surface is required, and a flnely divided absorptive clay material will provide ~uc~ surface. However, if the psrticle size i3 ultrs-fine, the mixture i8 sub~ect to dusting, in which case the surface ares advantage 18 lost and the composition may create more problems than i~ solves. Generally a particle size range of from about +20 mesh i8 useful, that is th~
compo ition will Bll p~88 through a 20 mesh standard Tyler screen. For most purposes it $8 preferred that A majority of the particle~ be of a ~ize to be retained on a 100 mesh screen.
The cemen~ component suitable for u~e in the pre~ent composition includes all materials which harden by a combination of hydrolysis and hydration reactions upon the addi~ion of water.
Such ma~erials include ~11 types of Portland cements, natural cements, masonry cements, gypsum, gypsum cements and plasters, Plaster of Parl~ and Poæzolans. A particularly preferred cement is ASTM Type II Portland cement. The particle size of the cement component i8 generally finex thsn the clay component discussed above.
The alkali metal metasilicate component may be ~elected from any o the alk~li metal metssilicate3, however, sodium met~silicate i~ preferred because of it~ low CoGt and ready ~ailability. Therefore, in the following discus~ions it will be understood that reference to godium me~a~ilicate refers only ~o a preferred metasilicate. The sodium meta~llicates are normally solids and are also known ag soluble silicates or a~ dry wa~er glass. Sodium metasilicate, Na2SiO3 (~Ja20'Si~2) i~ commercially available in the anhydrous form, or as hydrate~, such as, Na2SiO3 5 H20~ 6 H20. ~ ~2 and ~ H20. Sodium ~esqui~ilicate and anhydrous orthosilicate are mixture~ of sodium metasilicate and caustic soda and are su$ted ~o use, although no~ preferably. The particle size of the metasilicate componen~ is 3imilar to the particle size of the clay and cement components discussed above.
Fly ash i~ a well known waste materlal. Typically fly ash is the finely divided re~idual product produced by the combustion of pulverized coal which is carried off with the ~tack gase~
exi~in~ the furnace. Fly ash may be collected from such gase~ by a process of precipitation, typically utilizing electr~s~atic precipitators. Fly ash is mostly comprised of Yilica, aluminum and iron compounds pre~ent in a variety of forms. Cement dust i5 a finely divided solid waste material generated by cement manufacture. Primarily it is kiln dust. The dust is a mixture of raw cement, kiln feed, partly calcined material, finely divided cement klinker, metallic and nonmetallic oxide~, and alkali materials, typicaLly alkali sulfates. Mlxtures of fly ash and cement dust may be utilized.
The componen~s may be mixed in accord wi~.h any conventional technique in the absence of wa~er to provide an intimate, ~i5 ~ ^3 substantially homogeneou~ mixture. It hag been found ln practice that ~f the cement component and the metasilicate component~ are inieially thoroughly mixed and the clay component ~ubaequen~ly added and mixing continued, a ~ub~t~ntially homogeneo~5, 1uent mixture is obtained.
The compositions of the absorbing and eolidifying agents of the present invention may include minor smount~ of inert or complementary materials. Such materials typically unction ts a$d in ~he absorption of liquid3, contribute ~trength, add early hardening characteristic~, or as binding alds.
DETAILED DESCRIPTION OF THE INVENTION
~ _ , The particulate, or ~ranular, compo~itlons of the present invention have improved absorbent properties and are p~rtlcularly adapted to use in proces3es involving the solidificatlon and/or chemical fixation of liquids and ~ludges. The present composition~ comply with the current and presently proposed federal regulation~ pertaining to the ~olidification and/or chemical fixation of hazardous waste~.
The present compbsitions are useful in the field7 thst 1~, at the site of a chemical 8pill or B clean-up operation. They are, however, equally useful in the proces~ing of chemical waste by-products at or near the polnt of generatlon. In the latter ca~e the by-products may be treated on a periodlc basiY, e.g., on a daily or weekly schedule, to avoid the accumulation of larg~
quantities of untreated wastes. Although, the C09t of ~,~ rj f~
transportation of the trea~ed waste may be 31ightly increased, such disadvantage i~ offset by the expen~e of handling and ~toring ~he raw wa~te ma~erial, and the ri~k oP having such untreated wastes presen~ in a produc~ion faciLity.
The present invention seeks to remedy the shortcomings of the prior art by providing a substantially improved ab~orptive and solidifying or chemical fixation agent that facilitates a minimum volume final product, that is not soluble, or reliquefiable, in the presence of liquids, especially water, and that is~--chemically, mechanically and temperature s~able. The present agents are particularly useful in ~reating waste materials containing heavy me~als. Heavy metals may be defined as those metals in Groups I B, II B, IV B~ V B, VI B, VII B, VIII, III A, IV A, V A, the lanthanides and the actinldes.
Generally the heavy metal content of the waste material is les~
than 1% by weight. The heavy metal component of thè waste material may be present in either a liquid or a solid phase.
Typically the heavy metal component i~ in the solid phase in slurries and sludgeq. The pre~ent agents are also particularly u~eful in treating wastes, either orgsnic or inorganic having hydroxyl groups~
The final produc~ with entrapped materials ~ypically ranges in form from a friable clay, or so~t dirt to a hard plaster or cement-like material. ALthough the present absorbing and solidifying agents are particularly suited to be bagged and stored for use at the site of a chemical spill, they are aptly ~ 3 suited to u~e in bulk at plant, landfill, or other site~ The pre~ent solidifying compo~ltions are slso particularly ~ulted to use as sanltary landfill covers which are applied, or layered, over ~he top oE the land~11 and allowed to slnk into the landfill material and solldify liquid ma~.erial ln pl~ce.
In the presen~ method the compositions are mlxed with ~he Iiquid or semi-liquid waste material to be dispo~ed of to ~srm a solid, ~toreable product. Generally the compo3itlons are utilized in amount~ between abou~ 3 and sbou~ 8 pounds per gallon of waste. The ratio will vary, dependent upon the charac~eristics of the waste material. Generally purely liquid waste material~ require larger amounts o~ absorb~nt ma~erial than semi-liquid materiaLs, e.g., sludges. Tgpically about 5 pounds per gallon is useful to treat most liquid waste materlals. The exact, or more exact ~mount may be easily determined by empirical means.
The l$quid or ~eml-liquid waste and the solidifying agent may be mixed by conventional techniques, for example, in a~gregate mixing devices, by mechanical stirring or manually by shovel or paddle. The mixing i8 continued, or additional absorbent material added and mixed, until a mixture of paste-like consi~tency is obtained.
The hardening process may take place in situ, that is the mixture i8 not moved after mixing. Typically the mixture is poured 9 shoveled or dumped in its uLtimate location. The mixtures may be poured, or otherwise loaded, into container~ to harden. In this embodiment the fllll con~ainers are subsequen~ly disposed of, or ~heir conten~s separately di~posed of and the containers reused. Hardening takes place a~ amhient temperature generally between abou~. 20F and 100F, and more typically between about 40F and about 90F, over a period o~ from about l~
tO about 72 hours, and more typically from about 12 to about 24 hours. A solid, substantially completely water insoluble, storable product is produced.
The product ater hardening may have a dirt-like consistency or, and most usually, it haY a hard rock-like chara~ter~ The volume increase, that is, the volume of the final hardened mixture as compared to the volume of the original waste, i8 typically between about 20 and about 80~/o and usually between about 30 and about 60%.
In some instances the starting waste material may be classified under regulations a~ hazardous, but after treatment may qualify for, and be classified as having, a nonhazardous status~ In such cases a subqtantial saving in disposal cost may be realized.
While it will be~understood that the pre~ent invention is not to be interpreted ln the llght of a particular theory, it is postulated that the liquld waste is absorbed and/or adsorbed on and in the finely divided component, e.g., the clay particles, subsequently the solid metasilicate component became~ partly soluble tieing the waste material and finely divided material.
The partly soluble silicate component ~ubsequently promotes the setting of the cement component, possibly acting a~ a hydraulic cement by forming silicates and other rnaterials similar to et~ringite. The re~ul~ is a solid material having the waste material encapsulated therein.
It will be furthe~ understood that numerous modlication~
and variations of the invention may be made without departin~
from the spirit and scope theréof, therefore, only such lim-itat~ons should be imposed as are indicated by the appended claims.
Claims (16)
1. A solidifying or chemical fixing agent comprised of a substantially homogeneous mixture of:
a) a major amount by weight of an absorptive, granular clay;
b) from about 5 to about 15% by weight cement;
c) from about 0.1 to about 5% by weight alkali metal metasilicate; and d) said components having a size less than 20 mesh standard Tyler screen.
a) a major amount by weight of an absorptive, granular clay;
b) from about 5 to about 15% by weight cement;
c) from about 0.1 to about 5% by weight alkali metal metasilicate; and d) said components having a size less than 20 mesh standard Tyler screen.
2. The mixture of Claim 1 wherein the mixture contains between about 60 and about 90% by weight of an absorptive, granular clay.
3. The mixture of Claim 1 wherein the said clay is fuller's earth.
4. The mixture of Claim 1 wherein the said cement is Portland cement.
5. The mixture of Claim 1 wherein the said alkali metal metasilicate is sodium metasilicate.
6. The mixture of Claim 1 wherein the majority of the particles range in size between about +20 mesh and -100 mesh standard Tyler screen.
7. The mixture of Claim 1 which further includes up to 30% by weight of fly ash, cement dust or mixtures thereof.
8. The mixture of Claim 7 wherein the mixture contains up to about 25% by weight of fly ash, cement dust or mixtures thereof.
9. A method for the solidication or chemical fixation of liquid or semi-liquid waste materials to produce a solid, storable product comprising the steps of:
a) mixing 8 liquid or semi-liquid waste material with a solidifying or chemical fixation agent consisting of major amount by by weight of an absorptive; granular clay; from about 5 to about 15% by weight cement; and, from about 0.1 to about 5% by weight alkali metal metasilicate, in an amount of between about 3 and about 8 pounds of solidifying agent per gallon of waste material; and b) allowing the mixture to harden to form a substantially water insoluble solid.
a) mixing 8 liquid or semi-liquid waste material with a solidifying or chemical fixation agent consisting of major amount by by weight of an absorptive; granular clay; from about 5 to about 15% by weight cement; and, from about 0.1 to about 5% by weight alkali metal metasilicate, in an amount of between about 3 and about 8 pounds of solidifying agent per gallon of waste material; and b) allowing the mixture to harden to form a substantially water insoluble solid.
10. The method of Claim 9 wherein the amount of absorptive clay ranges between about 60 And about 95% by weight of the mixture.
11. The method of Claim 9 wherein said absorptive granular clay is fuller's earth.
12. The method of Claim 9 wherein said cement is Portland cement.
13. The method of Claim 9 wherein said alkali metal metasilicate is sodium metasilicate.
14. The method of Claim 9 wherein said solidifying agent has a particle size of less than 20 mesh standard Tyler screen.
15. The method of Claim 9 wherein the solidifying or chemical fixation agent includes up to 30% by weight of fly ash, cement dust, or mixtures thereof.
16. The method of Claim 15 wherein the solidifying or chemical fixation agent contains up to 25% by weight of fly ash, cement dust, or mixtures thereof.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US76849285A | 1985-08-22 | 1985-08-22 | |
US768,492 | 1985-08-22 |
Publications (1)
Publication Number | Publication Date |
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CA1254588A true CA1254588A (en) | 1989-05-23 |
Family
ID=25082651
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA000509045A Expired CA1254588A (en) | 1985-08-22 | 1986-05-13 | Method and composition for waste disposal |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5948157A (en) * | 1996-12-10 | 1999-09-07 | Fording Coal Limited | Surface treated additive for portland cement concrete |
-
1986
- 1986-05-13 CA CA000509045A patent/CA1254588A/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5948157A (en) * | 1996-12-10 | 1999-09-07 | Fording Coal Limited | Surface treated additive for portland cement concrete |
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