Title of Invention

A PROCESS FOR TREATING BAUXITE TAILINGS TO NEUTRALIZE SODIUM HYDROXIDE AND A PRODUCT OBTAINED BY THE PROCESS

Abstract

The present invention relates to a process for treating bauxite tailings to neutralize a predominant proportion of sodium hydroxide present therein, comprising: pulverIzing said bauxite tailings into a homogenous powder; agitating said powder while adding sufficient water to foam a free flowing slurry; adding sufficient sulfuric acid to the slurry to neutralize said sodium hydroxide to a pH of 5.5 to 6 to form water and an aqueous solution of sodium sulfate; and separating said aqueous sodium sulfate solution from remaining insoluble slurry without washing said slurry, while permitting a residual ~ount of sodium sulfate to remain with said insoluble slurry sufficient to catalyse carbonate crystalization and further treating said insoluble slurry to form a component of cementitious building material. The present invention also relates to a product obtained by the process.

Full Text

BUILDING AMD OTHER MATERIALS CONTAINING TREATED BAUXITE TAILINGS AND PROCESS FOR MAKING SAKE TECHNICAL FIELD This invention relates to a process £or treating waste litreavs containing bauxite tailings to neutralize alkali metal -ydroxide present, ouch as sodium hydroxide to obtain a product that can be incorporated intc building or other materials, such 31* bricks to enhance their properties. Ttie invention further relates tc enhanced building materials containing tailing material treated in accordance with the process of the inven^ fc.ion. BACKGROUND ART The Layer process for alumina production from bauxite results in thti formation of large quantities of "red mud" or tailings, which are both a source of pollution and a waste of a potentially valuable mineral resource. It would, accordingly, he advantageous to have a process which efficiently utilizes •:hese ta:.Ilng« as a useful industrial product. U.S.. patent no. 3,985,567 to Iwu describes a process for combining treated bauxite tailings witn clay and heating in an oven to obtain a fcricfc product. U.S.. patent no. 4,132,866 to Lokatos, et al. describes a process :!or separating bound sodium fron red mud reflidue in i/hicf ferrLc sulfate is uEted to extract the sodium content, U.S. patent no. 5,554,352 to Jaqueo et al. describes rreating virgin bauxite to produce poszolan for uoo in concrete products. DISCLOSURE OF THE INVENTION In accordance with the present invention, a process is provided for treating waste streams containing bauxite tailings to rctnde.r them suitable for incorporation into useful construction materials, such as bricks, that are formed from cementi-tiouij material. The invention further provides an Improved building material In which bauxite tailings which have been treated with A mineral acid to neutralize alkali metal hydroxides which can then be combined with a eemantitious material and cured to provide a superior construction material* Prior to combining with cementitloua or other material, water and all o r a por tion of the alkali metal Balt6 cormea oy tnc n«uuva*-iseriion are removed. BEST MODKS FOR CARRYING OUT INVENTION AND INDUSTRIAL APPLICABILITY Initially, in accordance with the invention, bauxite 1:a::.ling'is are corainuted to a homogenous powder that can pass i:h.i:ough a 1/16" or smaller screen mesh, c^nd water is added to 1:hiJ taiLlngn. The addition of the water ta. It should be noted at this point that there are secondary a:d tertiary reactions that can and will take place when the a:id is added to the somewhat basic slurry. It is for this reason that it is preferred to have as fine a slurry as practicable until ex the prevailing circumstance* and that the fine • i.urry is in a state of vigorous agitatior: at tha moment of the Intromission of an acid, the purpose of which is to diminish the reaction time or, the 'time until exposure" of the acid to tie ttirget compound (sodium hydroxide) . Inevitably, some ] ota a ilium, magnesium and aluminum as wall as other elements trill be cfcugfht up in the process, but not enough in these olrcuiustariC'Sis to inhibit the goal, which is to remove the lodiuxn hydroxide frcm the bauxite tailing** so that the tailings can then be stabilized and Etuhseguently incorporated into the :tiatrix of common building materials. Once the Blurry has been separated from the salt solution, it is then ready to be utilized aa a component in common ovLlding materials# such as paver bricks. By way of example, tl'.a proportions of the individual components of the aggregate era the; sam-ia as would be used for a "normal" paver brick except that the "stabilized bauxite tailings* are used in place of any 2(\t jneiih fimss that would normally be present. If they (200 mush fines) .sire not used, then "stabilized bauxite tailings" would be adi®d to the mixture at the proportion of about 20% by volume. In this instance, the best mode of forming the f in-inhed product; is currently the industry standard process of utilizing hydraulic compaction in conjunction with simultaneous vibrational compaction during the forming process of the p:»mixsd aggregate. ^Tne apparatus for making the concrete brick can have at l<:nst dne visible surface having a face. the brick miy be made by filling mold with concrete mixture vibrating t: e .and u6ing descending plunger to compress c.ncrete in filled mold. at least one interior of t. can have textured us form texture it. brj::k. following ccrr.pression movable s:dew. is moved laterally away from distance sufficient for wall tci clear when raised. case paver finished face would b formed remaining place meld raised which y.siding brick.> Once formed, the bricks should preferably be kept in a iripcr saturated humidity environment and the bricks themselves nioulcl not be allowed to become "dry" during the first 168 lours of curing. The moisture levels can be maintained by hsusiug the finished brickn in an enclosure that has a mistlnq in sans that provided saturation wetting on regular intervals •iluring the ::uring process. Superior performance/utilization characteristice are achieved when tailing content does not I'xceed th»? ^:Ofc by volume level. "t is* further noted that, if there are sufficient amounts ::: iron oxide in the mixture: ««n aesthetically pleasing color in imparled to the mixture, very similar in ar.ade to that of terra :ottA. Farther, the chanqe in the pH of the aggregate, brought cm by the addition of the acidic slurry, dramatically changes Lie "wetting'1 capabilities of the a/ailable water in the nixture. This results in a homogeneous crystalline structure By using sulfuric acid a9 the pri:iui"~y rc.-ngcint, and not removing the resulting silts that crc fomed from th neu-iralizing reaction that takes place, save for what is removed oy sspara ting the excess water from the 3lurry, the remaining sodium sulfate acts, as a catalyst for the formation of the rarbendticuij crystals that characterize the internal crystalline structure of cementitious matrixes. The Ticthod of the invention is illustrated by the following procedure: One part of bauxite tailings are suspended in three: parLa of water, a titration of the mixture is performed usincf om; nolar solution of sulphuric acid per mole of sodium m the t«ilLncs, until the mixturu attains a pH 5.5-C.C. To succussfu -I v carry cut the above, the mixture should be continuous ..y ag-tated, keeping the particles of the mixture in t;usp> As & by-product of the foregoing preparation procedure of the tailings and subsequent incorporation into cementitious ■nedia, the finished product has enhanced efflorescence resistance , that is, above and beyor.d the rsw is tance levels of concrete products not incorporating bduxit? tailings as well as tho;;e th.it do. According to the present invention, when sulfuric acid is the selected mineral acid, sodium is selectively extracted from the tailings into solution as sodiun sulfate without contaroin-& .ing the solution with the sulfates of iron, titanium, silicon t: al'jmxnuirt. The residual rsd mud iron the above, free from ?he fol lowing examples further il lustrate embodiments of ;he invention. Example 1 With 30% by volume of th€* treated Red Mua added to a :i.'inerv:itiou3 aggregate using only Portland cement as the : mdi:ig ag«nt, a concrete "pave r" brick was formed, and cured lo a a. Compressive strength of 2,750 p,s.i. b. Water absorption: 13.5% Example 2 With 30% by volume of -he treated Red Mud added tc a ■rementitious a^qreyare and with 30 fc by volume of the Portland cement component replaced with the finely ground siliccte laillngs, a concrete "paver" brick can be formed, and cured to my dimenui ;m required to satisfy tne aesthetic and structural requirementt- of the building industry and the consuming public. 1'he resulting brick will have the enhanced characteristics: c. Ccnpressive strength: greater than 3,000 p.s-i. d. Water absorption : lenr. than 13 . 5* One ie.ee of a finished brick and, n "control" refractory zrick. fro:* a kiln , were exposed at ambient temperature, to the €800CF hesat of a high capacity Oxy/Acetylene "Rosebud" (large tip used expressly for heating wide area3 of workpieces). The results v«:i:e as follows: After 15 ir.inutes of direct exposure to the flans, the brick of the invention was unchanged. After 5) minutes of the sair.e treatment, the "control" brick's face had glaz»d and oecun to melt and Mdrool" off as- a liquid. A common, wast* by-product of the Bayer process is a silicate rich component generally referred to as "sand" or ' blac nent, land ('ill capping, UV shi.eldi.ng in pi • sties # pi qment for pairn, plastics, ceramics end a non-polluting marker for surface Water hydrology analysis. PCT/US02/ 12*90 IPEA/US 18 OCT 2002 CLAIMS :.. P.. process for treating waste creams containinq ■nauxite ttii lings to substantially r.e*u|:raii3e a predominant i PCTAJS 02/ 12*9(1 IPEWUS 18 OCT 2002 II. The building material of cl«iirn 10 wherein said molded component is a brick. j. The building material of claim 10 wherein said rinertil ac:i.ci. is sulfuric acid* H\0 The building material of claim 10 wherein said nlkalim* compound us sodium hydroxide. 14. The structural building material of claim 10 wherein =aid aggregate is a silicate containing component in an amount :f about £• to 50 percent relative to the weight of the cementi-t ious mat?:rial . ;3. The structural building material of claim 10 wherein said ■rementitious material is cement. 6. A proceftB ior treating bauxite tailinga comprising: pulverizing said bauxite tailings into a generally homogeneous powder; agitating said powder while adding sufficient water to form a generally free flawing slurry; and adding sufficient acid to said slurry to substantially neutralize alkaline values present therein to form water ind salts of said values. L7. The process of claim 16 which further includes separating said Gaits from remaining insoluble slurry material. 18. The process of claim 17 wherein said insoluble slurry material :.si ccmbincjd with cenentitious material, compacted and rurec. to Term a brick. 19. ivie process of claim 16 wherein said alkaline values a.re alkali metal hydroxides and said acid is a mineral acid* 20. T.ie process of claim 16 wherein said neutralization is to a pli of abou-z 5.5 to 6. PCT/US02/ 12490 ■"• IPEAAJ8 18 OCT 2002 21. A. process for forming a cismentitious material containing treated bauxite tailings comprising: pulverizing bauxite tailings containing alkaline compounds? into a generally homogeneous powder; agitating said powder while adding sufficient water tc form a generally free flowing slurry; adding sufficient acid to the slurry to neutralize said alk.-5.l~ne compounds to a pH of about 5.5 to 6 to form water ar.d an aqueous solution of the salts of said acid; separating said aqueous 3alt solution from remaining insoluble slurry material; and combining said insoluble slurry material in an amount of from about 5 to SO percent by volume with a cewcjntitious substance to form said, cementitious materia} • 22. The process of claim 2 1 wherein said cementitious sut-iitancu is cement. 23. The process of claim 21 wherein said insoluble slu;rry i& combined with said cement.itioua substance, compacted and cured to form a brick. 24. The process of claim 23 wherein said brick is cursd in a super saturated humidity environment for a predetermined time period. 25. The process of claim 24 wherein said time period is at least 168 hours. 26. The process of claim 21 wherein said acid is sulfuric acid and at least a portion of the said salts of the sulfuric acid that are formed remain with the insoluble slurry material after removal of water therefrom to catalyze subsequent formation of carbonaceous crystals in the cementitious material. 2 7. The process of claim 2 6 wherein said insoluble slurry material is not washed subsequent to separating the aqueous salt solution. 28. The process of claim b wherein said insoluble Blerry material :s not washed subsequent to separating the aqueous salt solution. 29. A process for treating waste streams substantially as herein above described and exemplified. 30. A structural building material substantially as herein above described and exemplified.

Documents:

1892-chenp-2003 abstract-duplicate.pdf

1892-chenp-2003 abstract.pdf

1892-chenp-2003 claims-duplicate.pdf

1892-chenp-2003 description (complete)-duplicate.pdf

1892-chenp-2003 form-26.pdf

1892-chenp-2003 pct search report.pdf

1892-chenp-2003 petition.pdf

1892-chenp-2003-claims.pdf

1892-chenp-2003-correspondence others.pdf

1892-chenp-2003-correspondence po.pdf

1892-chenp-2003-description complete.pdf

1892-chenp-2003-form 1.pdf

1892-chenp-2003-form 18.pdf

1892-chenp-2003-form 3.pdf

1892-chenp-2003-form 5.pdf

1892-chenp-2003-pct.pdf