CA2109756A1 - Basic aluminum hydroxychlorosulfate process and product therefrom - Google Patents

Abstract

IMPROVED BASIC ALUMINUM HYDROXYCHLOROSULFATE PROCESS
AND PRODUCT THEREFROM
ABSTRACT OF THE DISCLOSURE
A process for preparing an aluminum hydroxychlorosulfate (BACS) is disclosed which comprises heating a solution of a basic aluminum chloride, wherein the concentration of Al+3 is about 4.0 to about 12.5 wt.%, to a temperature of about 75 to about 98° C:
adding a sulfate anion containing compound selected from the group consisting of sulfuric acid, aluminum sulfate and mixtures there-of, at a controlled rate, in an amount such that the molar ratio of sulfate ion to aluminum in the reaction mixture is about 0.05 to about 0.20, the sulfate ion addition being carried out at a controlled rate, the temperature of the reaction being maintained at a temperature of about 75° to about 98° C two to about 24 hours after the completion of the addition of sulfate ion. A further improvement in the efficaciousness of the product is achieved by introducing iron and calcium ions into the BACS.

Description

' ~ ' ' , ,'',' IMPROVED BASIC ALUMINUM HYDROXYCHLOROSULFATE PROCESS
AND PRODUCT THEREFROM ~ ~
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FIELD OF THE INVENTION
This invention relates to an improved process for preparing basic aluminum hydroxychlorosulfates. In particu~
lar it relates to the product therefrom and its use in water treatment. ~ ~

: -.
BACKGROUND OF THE INVENTION
It ls well known that various aluminum compounds can be used as a coagulant in the treatment of water. The most common of these compounds is alum. Notwithstanding the fact that they are more expensive, basic aluminum chlorides ("BAC"j have found acceptance as coagulating agents because of their improved efficiency over alum. BAC has several advantages over alum. The BAC coagulants are effective in lower alkalinity water where alum is relatively ineffective, and BAC has a lesser impact on pH reducing the need for lime or caustic treating of water to bring it within the potable range. The coagulating plant operation is improved since with BAC there is a longer period between backwash. See for example U.S. Patent Nos. 2,858,269, and 3,270,001 incorporat-ed herein by reference. A more recent development has been the introduction of basic aluminum hydroxychloride sulfates ("BACS") for use as coagulating agents in water treatment.
BACS solutions are prepared by introducing di-valent sulfate ion into the BAC structure. Prior art methods for producing BAC are disclosed in U. S. Patent Nos. 3,497,459;
3,544,476 and 4,981,673 all of which are incorporated herein by reference.

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-~ Attorney Docket No. 442-154 U.S. Patent No. 3,544,476, discloses a method for preparing BACS by introducing an anion (Y) into the struc-ture of a basic salt compound having the general formula Mn(OH)mX3n-m M is a metal of tri or higher valency, X is an anion capable of forming a monovalent acid, 3n is greater than m and the basicity, defined as m/3nxlOO, is in the range of about 30 to 33%. Y is an anion capable of forming a di or greater valent acid. M can be aluminum, chromium or iron. Where M is aluminum and X is chlorine the basic compound is a BAC.
The anion, Y, is chemically introduced into the basic salt structure in the form of an acid or its soluble metal salt. Examples of Y are the anions of sulfuric, phosphoric, polyphosphoric, chromic, bichromic, carboxylic and sulfonic acids. X is preferably Cl, but can be I, N03 or CH3COO.
The range of the ratio Y/M is about 0.015 to about 0.4. A BACS is formed by conducting the BACS forming reac-tlon in the presence a multivalent acid ion in an acid hydro-losis solution, e.g hydrochloric acid of Al. The BACS may be obtained by the separation of an insoluble sulfate produced by the addition of the hydroxide, oxide or carbonate of calcium or barium to a solution of a normal salt of aluminum containing hydrochloric acid and sulfuric acid. the result-lng product stream contains at least lOX or more by weight of the insoluble sulfate salt by-product.
U.S. patent No. 3,497,459 discloses and claims a method for preparing a basic salt compound having the formula Rn(OH)mX3n-m wherein R can be aluminum and X can be Cl, which comprises the digestion of an oxide ore, e.g. bauxite, with a mixed acid system comprising sulfuric acid and hydrochloric acid.
-~ 1101pl54.93 .
,.

U~ ~1o3 -~ Attorney Docket No. 442-154 The resulting product solution is treated with an insoluble sulfate forming compound, e.g. calcium carbonate, to neutral~
ize the sulfuric acid used. The reaction solution is fil-tered to remove the insoluble sulfate precipitate. The mother liquor is alleged to be stable.
The prior art has recognized that BAC may be reacted with sulfuric acid to form a basic aluminum sulfate precipi-tate for ratios of S04/Al greater than 0.08. The '459 patent suggests that their process inherently passes through that reaction mechanism, but in the process of the '459 patent no such preclpitate is formed.
U.S. Patent No. 4,981,673 discloses a method for preparlng a BAC which comprises reacting a solution of alumi-num sulfate with a slurry comprising calcium carbonate and calcium chloride. The process stream is filtered to remove precipitate. The filtrate comprises a solution of a BACS of the formula Aln(oH)m(so4)kcl3n-m-2k having a basicity, m~3nxlOO, of aboùt 40% to about 60% and an Al/Cl equivalent ratio, 3n/3n-m-2k of about 2.85 to 5.
The disadvantage of prior art processes is that they result in the formation of byproduct precipitate the disposi-tion of which reduces the cost effectiveness of the process as well as creating environmental problems.
SUMMARY OF THE INVENTION
An aluminum hydroxychlorosulfate (BACS) is prepared by reacting a solution of a basic aluminum halide with a sulfate lon derived from sulfuric acid or aluminum sulfate. The resulting product solution remalns clear and no precipitate is formed. An improved product effective for the treatment of cold water is prepared by introducing calcium sulfate dihydrate in combination with calcium carbonate or calcium chloride, or a mixture thereof into the reaction mixture in amount effective to improve product efficacy while not pro~
i~ 1101pl54.93 7 ~ ~

~ Attorney Docket No. 442-154 ducing calcium sulfate precipitate by product. Utilizing calcium carbonate as the calcium salt improves floc formation effectiveness but does not impart cold water effectiveness to the ~ACS.
DETAILED DESCRIPTION OF THE INVENTION
The initial step in producing the BACS of this inven-tion is to prepare a basic aluminum chloride by any suitable known technique. In one prior art method a solution of aluminum chloride is reacted wlth aluminum to form the basic aluminum chloride. In another method of preparation of aluminum chlorhydrates, aluminum is reacted with HCl in water, the aluminum being in excess. While the concentration of basic aluminum chloride in the solution in which it is formed is not critical, generally it is made at concentra-tion of 50X w/w for practical reason6.
In the practice of this invention, the initial basici-ty of the BAC solution is not critical. BAC solutions having a basicity of 1/2 to 5/6 have been used successfully. Howev-er, the Al/Cl atomic ratio of the HAC solution must be ad-~usted to about 1.2/1 to about 0.70/1 be~ore sulfate ion addition. The BACS of this invention has the general formu-la:
..;. . , Aln(OH)mCl3n-m(s04)p wherein 3n > m and the percent basiclty, m/3nxlO0, is about 50% to about 73X. The value of p is selected such that the mole ratlo SO /Al is about 0.05 to about 0.20. In carrylng out the process of thls lnventlon the concentratlon as Al 3 18 about 4.0 to about 12.5X. It wlll be appreclated by those skllled ln the art that the source of Al+3 can be both the BAC and the alum. Where the source of sulfate ion is sulfur-lc acld, however, all of the aluminum ls supplled by the BAC.
The S04/Al ratlo may range from about 0.05 to about 0.20, preferably about 0.122 to about 0.150. The preferred BAC ls 1/2 ba~lc BAC. The preferred SO4/Al molar ratlo for ~ 1101pl54.93 7~
~ . .

~ Attorney Docket No. 442-154 thls starting materlal is about 0.10 to about 0.15. Prefera~
bly, the sulfate bonding reaction is carried out using a 1/2 basic BAC adJusted to an Al/Cl atomic ratio of about 1.0/1 to about. 0.70/1.
In carrying out the process of thls invention a solu-tion of baslc aluminum chlorlde is heated to about 75 to about 98 C. with mixing. While a reflux condenser is uti-llzed to return any water evaporated back to the system to maintaln the concentratlon of reactants constant, true reflux condltlons, per se, that ls bolling, need not occur. The concentratlon of the hot solution or lts baslclty may be ad~usted by the addltlon of water, alumlnum chlorlde hexahy-drate, hydrochlorlc acld or other baslc alumlnum chlorlde solutlons of dlfferent concentratlons or baslcity as re-gulred. Methods of ad~ustlng basiclty are well known to those skilled ln the art.
After ad~ustment the Al/Cl atomic ratlo of the solu-tlon can range between 0.70/ to about 1.2/1; typlcally about 0.75/1 to about 1.0/1, e.g., about 0.7~/1 to about 0.90/1.
If ad~ustment 18 necessary it is preferred that the solutlon be malntalned at about 90 to about 95 C. for about 10 to about 60 mlnutes after ad~ustment to ensure that the reactlon 19 completed; ~referably about 20 to about 50 minutes, e.g., 40 mlnutes. The solution is then preferably cooled to about 75 to about 90 C before sulfatlng, more preferably about 75 to about 85 C., e.g., about 80 to about 85C. Theoretlcal-ly, ad~ustment of basiclty occurs as soon as the requlred amount of HCl, alumlnum chlorlde hexahydrate or other materi-al used to make the ad~ustment 1~ added. Stolchlometrlcally, thls ls correct. Not wlshlng to be bound by theory, however, it appears that there ls some reconflguratlon or rearrange-ment of the BAC polymer or the structural dlstrlbutlon there-of upon heatlng to a temperature of about 60 to about 95 C.
Thls rearrangement or reconflguratlon apparently has a bene-flclal effect on the sulfate bondlng reactlon. Therefore, lt ls preferred that the baslcity ad~ustment be carrled out at ~ llOlpl54.93 ~ ~ " - ~ , ,, ,", " ,, ~ "" ,,"", ,, ,~ ,", ,~ , " ;, , , ~

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~ Attorney Docket No. 442-154 these elevated temperatures. While the material added to make the ad~ustment can be added at room temperature with subse-quent heating to the elevated temperatures, it i8 preferred that the temperature of the BAC solution be raised to about 60 to about 85 C. prior to such addition. The preferred temperature at which to complete this rearrangement or recon-figuration is about 90 to about 95 C. It will be appreclat-ed by those skilled in the art having access to this disclo-sure that where ad~ustment of basicity of a BAC solution ls concerned, ad~ustment in basiclty necessarily results in an ad~ustment of the Al~Cl atomic ratio by virtue of the fact that the materials used to ad~u~t baslcity are aluminum and/or chlorine containing compounds.
It will be appreciated by those skilled in the art having access to this disclosure that if no ad~ustment of the baslc aluminum chlorlde solutlon ls requlred lt ls not neces-sary to heat the solution to 90-95 C, and the solution can be heated dlrectly to about 75 to about 98 C, e.g., about 80 to about 85 C. After coollng (or heatlng dlrectly as the case may be) to about 75 to about 98 C. sulfate lon ls lntroduced either as sulfuric acld or aluminum sulfate.
Where aluminum sulfate is used, for convenience, the aluminum sulfate is added from a solution containing about 48X by wt.
of the aluminum sulfate, a commercially available product.
While concentration is not critical, sulfuric acid is prefer-ably added at concentrations of 66 Baume or less, e.g. 60 Baume'. At above 66 Baume'the sulfation reaction is too aggressive and may have a detrimental effect on the 8ACS.
The sulfate anion should be added at a temperature of about 75 to about 98 C, preferably at a temperature of about 80 to about 85 C. The sulfate anion may be added as the acld, the alumlnum salt and mixtures thereof with the follow-ing constraints:

1~ 1iOlpl54.93 J ~

- -~ Attorney Docket No. 442-154 1. The addition rate must not result in temperature excurslons of greater than 5;

2. The addition rate must not destabilize the system.
Too rapid an additlon rate will result in the formation of insoluble basic aluminum sulfate, evidenced by precipitate formation. The addition rate will depend on the concentra-tlon of the BAC solution as well as the concentration of the anlon solution. The rate required to avoid precipitation is readily determined without undue experimentation for a prede-termined reaction mixture. Generally, addition of the anion over at least a one hour period will avoid precipitation.

3. The total amount of sulfate anion added is such that the ratio of anion to total aluminum in the final reac-tlon mlxture is about 0.05/1 to about 0.20/1, preferably, about 0.122/1 to about 0.150/1 As used in the specification and claims with respect to sulfate lon addltlon, the term "controlled rate" means that the con6traints descrlbed in numbered paragraphs 1 & 2 above are met.
It will be appreciated by those skllled in the art that where the anlon ls added as the acid, the heat of solu-tlon will result ln a temperature lncrease. Conversely, the addltlon of an aluminum salt solutlon wlll result ln a tem~
perature decrease unless the solution ls heated before addl-tlon to the reactlon mlxture. However, even where the solu-tlon ls brought up to temperature to avoid a temperature excurslon. lt is necessary to add the solution at a con-trolled rate to avold the effect descrlbed in paragraph 2, above.
After addition of the sulfate ion solution the system is malntained at 75-98 C, preferably 75-85 C., for about 60 minute~ to about 24 hours; typlcally two to twenty-four hours, e.g., slx to 12 hours. Not wlshlng to be bound by -~ llOlpl54.93 ~,,,- "~

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~ Attorney Docket No. 442-154 theory, it i8 belleved that this extended heating period after sulfate ion additlon, is required in order to form sulfate llgands as evldenced by HPLC size excluslon chroma-tography. Mixing should be maintained throughout the heatlng perlod. The solution is preferably then cooled to about 40 C. over about a twelve hour to twenty four hour period.
Whlle the solution can be diluted to any desired concentra-tion at this point, it is preferred that the solution be aged for about 2 to 18 hours after its temperature has been re-duced below 40 C. before dilutlon. Dilutlon below an Al 3 concentratlon of 4.0 wt. may result in clouding of the solu-tion, and ultlmately to precipitation of insolubles. Prefer-ably, the solution is not dlluted below an Al 3 concentratlon of 4.5 wt.X.
The solutlon of product of thls invention wlll be clear, and dependlng on its characteristics can remaln clear lndefinitely. Under certaln condltlons of concentratlon, baslclty and S04/Al ratlo, fallure to dllute may result ln the generatlon of solld preclpitate after the cooled solutlon has been standlng for 24 hours or longer. The6e solutions must be dlluted to remain stable. Where the aluminum content of the solution measured as Al 3 i9 greater than 8.4X, the Al/Cl atomic ratio is in the range of about 0.8 to about l.0 and S04/Al ratios of greater than 0.12 dilution of the solu-tlon may be requlred. Generally, dilutlon to reduce the sollds concentration by about 10 to 20 wt.X of lts orlglnal value wlll be sufflclent to promote long term stablllty.
Whlle it i8 po6~ible to determine empirically whlch solutlons must be dlluted by carrylng out the process under flxed conditlons, waitlng at lea6t 24 hours, preferably, about 2 to about 5 days, to determine whether or not cloudlng occurs, and lf 90, rerunning the reactlon wlth dlfferent dllutions untll stable solutions are achieved, it 18 more practical to dilute to the Al+3 concentrations found to promote stability regardless of the reaction condltions selected. In carrylng out the dllution process the water ~} llOlpl54.93 i .~ r !~

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~ Attorney Docket No. 442-154 should be added at a moderate rate with adequate mixing to ensure that the solutlon is homogeneous wlthout stratifica-tion or areas of hlgh concentration. In general, where the source of sulfate ion is alum, it is preferred that the product stream be diluted to an Al+3 concentration of le~s than 7Ø Where the sulfate ion source ls sulfuric acid it is preferred that the solution be diluted to an Al 3 concen-tration of less than 8.0%, preferably lese than 7.5 wt.X.
The advantages of the lnstant invention may be more readily appreciated my reference to the following examples.

350.6 grams of a 50 wt.X, 5/6 basic BAC analyzing 12.39X aluminum and 8.27 wt.% chlorine was placed into a one liter flask fitted with a stirrer and reflux condenser. The solution was heated to 80 C. prior to the drop-wise addition of 136.8 grams of 20 Baume HCl over a seven minute period.
The temperature was increase to 95 C. and held there for one hour with continuous mixing. The temperature was then re-duced to 80-85 degrees.
31.3 grams of 60 Baume sulfuric acid was then added over a 12 minute period. The temperature was maintained at about 80-85 C. for an additional 30 minutes. Then heating was discontinued. The solution passively cooled to a temper-ature of 40 C. over a two hour period. Mixing was continu-ous over the entire reaction time.
281.2 grams of room temperature water was added to the reactlon mixture, with continuous mixing, after the reaction mixture had cooled to below 40 C. The finished solution was clear, and no precipltation occurred over a thirty day peri-od. The solution analysis was ae follows:

Alumlnum - 5.49% Chloride - 8.84X
Sulfate - 2.93X Al/Cl (atomic) - 0.82 S04/Al molar ratlo - 0.150 1~ llOlpl54.93 7 3 ;~
,;

-1~ Attorney Docket No. 442-154 The procedure of Example 1 was repeated using 431.5 grams of a 50X solution of BAC (Al = 12.35%, Cl=8.2~X) and 204.4B grams of HCl. The HCl addition was carried out over a ten minute period at a temperature of 60 C. The reaction temperature then was lncreased to 90-95 C., and held there for about 20 minutes. After reducing the reaction tempera-ture to 80-85 C., 164.0 grams of 48% w/w of commercial grade aluminum sulfate solution (Al = 4.45X) was added drop-wise over a 40 minute period. After an additional 30 minutes at 80-85 C., with continuous mixing, heating was discontinued.
The reactlon mixture was allowed to cool passively with continuous mixing for 16 hours until the temperature dropped to about room temperature, i.e., 24 C. 131.3 grams of water ;~
at room temperature was then added while mixing was contin-ued. The solution concentration was reduced to 85.9X of its orlginal concentration by the addition of water. The fin-ished solution was clear and free of precipltates, and ana-lyzed aB follows:

Al - 6.50X Cl = 10.69% Sulfate = 4.18% Al/Cl = 0.80 S04/A1 ~ 0.181 569.44 grams of a 50X solution of 5/6 ba~ic BAC was added to a one liter beaker fitted with a stirrer and a reflux condenser. The solutlon was heated to 60 C. with mixing, and 176.4 grams of 20 Baume HCl was then added, drop-wise, over a twenty minute period. The reaction mixture temperature was then increased to 90-95 C. and maintained at that temperature for about 45 minutes. The temperature was decreased to 80-85 C. and 54.08 grams of 60 Baume sulfuric acid was added drop-wise over a 30 minute perlod. The tem-perature was maintained at 80-85 C. for an additional 60 minutes. Heating was then discontinued, and the system wa~
allowed to cool passively over an 18 hour period to a about -1~ 1101pl54.93 7 ~ ~
-1~ Attorney Docket No. 442-154 room temperature. Aliquots of the solution were taken and each diluted to a different concentration. Dilution was made by the addition of water at room temperature, with mixlng.
Prior to dilution the solution was clear and had the following stoichiometry:
Al=8.79X Cl=12.83% Sulfate=5.00% Al/Cl=O.90 S04/Al=0.16 The effect of dilutlon i8 shown in Table I. ~.
"
TABLE I
pILUTION Al (%) 30 DAY STABILITY AT ROOM TEMPERATUR~

Neat 8.~9 5-10% precipitated solid~
90% 7.91 trace sollds, less than 0.5X `
80% ~.03 clear solutlon ~OX 6.15 clear solution 62X 5.45 clear solutlon Whlle the BAC solutions were ad~usted with HCl in the foregoing examples, it will be appreciated by those skilled ln tho art that the ad~ustment could have been made utilizing aluminum chloride hexahydrate or a BAC solution having a ~ `
dif~erent Al~Cl atomic ratio than the BAC reactant to be util$zed. A significant advantage of this invention is that, unlike prior art methods of producing BACS, there is no significant amount of insoluble byproduct produced. Such byproduct not only increases production cost, but creates environmental problems from the need to dispose of these insoluble materials.
It will be noted that the times utilized in the forego-ing examples do not conform strictly to the disclosure. This is not an inconsistency. The di~crepancy is a result of the fact that small batches are more susceptible to control of parameters such as mixing. The disclosure and claims on the other hand are directed toward a process which has commercial application on a large batch scale.
-1~ llOlpl54.93 ~ J~7 3 ~
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-l~ Attorney Docket No. 442-154 Whlle the process of this invention produces a BACS
solutlon substantially free of precipitate, it will be appre-ciated by those skilled in the art that in production runs minor fluctuations of proces~ conditions from the intended values may occur, resulting in the formation of precipitate.
These variations must be controlled so that preclpitate formation does not exceed 1% by welght of the total batch.
Preferably, reaction conditions are controlled to maintain the level of precipitate, if any, to about 0.5 wt.% or less. -~
At levels significantly greater than 1 wt.% of precipitate the process begins to become uneconomical t and sufficient precipitate is produced to begin to create the environmental problems the process of this invention seeks to avoid.
In another embodiment of the invention the process may be carried out under modified conditions. These conditions include carrying out the sulfating reaction at a temperature of about 90-95C and Al 3 concentration less than 7Ø It will be appreciated that this temperature range is above the range previously descrlbed as preferred. In order to utilize this higher temperature range effectively at the lower con-centrations, it is preferred that a double ad~ustment of the BAC be used. The first ad~ustment is carried out prior to the sulfation step, and the subsequent ad~ustment is carried out at the conclusion of the anion addition and prior to the addition of calcium ion. Unless the ad~ustment is split into two steps precipitation may occur. Additionally, only a part of the required water is added initially, the remainder being added later in the reaction process. A production run uti-lizing this modified process is illustrated for a product having the following specification~:
Aluminum 5.42 wt.%
Chloride 9.00 wt.X
Sulfate 2.90 wt.%
Al/Cl 0.80~ 0.03 S04/Al 0.148-0.153 S.G. 1.20010.01 @ 25 C.
-l~ llOlpl54.93 U~J7 -l~ Attorney Docket No. 442-154 Materlals utillzed for the proce6R were:

5~6 Baslc conventional alumlnum chloride prepared as a 50X solutlon; (BAC) 20 Baume' HCl 60 Baume sulfuric acid . Process water Slnce the sulfate lon ls supplled by sulfuric acld the total alumlnum ls supplled by the BAC. Inltially lOOX of the BAC
and 40X of the total water requirement was added to the reactor. The diluted BAC solutlon is heated to 70 C. wlth slow, non-aerating mixing. 75% of the calculated HCl requlre-ment is added over a one hour perlod. After thorough mlxlng, the temperature 18 increased to about 90-95 C. and all of the required sulfurlc acld is added over a seven to elght hour period. Since plant reactors need not be run wlth reflux condensers in place, water loss wlll occur through vents, and water must be made up by additlon. After comple-tlon of the sulfurlc acld addltlon, additlonal water 18 added slowly and contlnuou~ly untll the speclflc gravlty i9 wlthln ~ -speclflcatlon.
Durlng the heatlng perlod, the batch ls analyzed for Ad~ustments that are requlred to attain product speciflca-tlons are preferably made over the flrst 10-12 hours of heatlng after completlon of the sulfate lon addltlon. A
flnal ad~ustment of the speclflc gravlty is made after the heatlng perlod and prlor to coollng the batch.
If ad~ustment of S04/Al ratlo is requlred care must be taken not to add an excess of sulfate, slnce preclpltatlon wlll result. The remalnlng 20 Be HCl should then be added.
After thorough ~lxlng, heating ls termlnated and the batch i9 allowed to cool to about 60 C. A suspended sollds content of lX of the total batch slze by welght or les~ ls accept-able. If any suspended sollds are present flltratlon wlthout -1~ llOlpl54.93 7 ~
-1~ Attorney Docket No. 442-154 a filter aid can be carried out after the batch has cooled below 60 C.
It has be~n surprisingly found that the effectiveness of the BACS can be improved by controlling the iron content of the BACS solutlon. The total iron content should be about 75 to about 250 ppm, preferably about 160 to about 190 ppm.
Those skilled in the art will appreclate that both BAC and ;
aluminum sulfate can contain iron in varying amounts. It is therefore, necessary to first confirm the iron content of the raw materials of the reaction before making additions of iron ion to the reaction system. When required the addition of lron can be accompllshed by the addition of a water soluble lron salt. Illustratlve, non-llmiting examples of such iron salts are ferric chloride and ferric sulfate.
The additional lron is introduced prior to the sulfate addition and preferably prior to Al/Cl atomic ratio ad~u6t-ment. Ferric chloride forms a yellow solution. If the solutlon is added prior to sulfate anion addition, the yellow color dissipates. If on the other hand the solution is added to the BACS solutlon after anion addition ls completed, the solutlon remains yellow, evldencing the fact that the iron has not been lncorporated lnto the polymer formed. Such an addition has no utility for the purpose of this invention.
It has been found that while the product of the process disclosed i8 useful in water treatment, it i8 not as effica-clouc as desired for cold water treatment, e.g., water tem-peraturec of below 10 C. In order for the BACS formed from BAC to be effective in cold water it has been found necessary to introduce calcium ion into the system. The addition of calcium as calcium carbonate results in overall floc forma-tion efficiency. For improved cold water efficiency, howev-er, it is necessary to add calcium ion as calcium sulfate dihydrate. It will be appreciated by those skilled in the art having access to this disclosure, that both calcium sulfate and calcium carbonate are sparingly soluble in water.
They are, however, slightly more soluble in the BACS solution.
-1~ 1101pl54.93 :17 -1~ Attorney Doc~et No. 442-154 .
In order that the addition of calcium ion be effective for its intended purpose and to avoid any precipitate formation it is necessary to add calcium ion in a very limited concen~
tration range. The total calcium ion concentration in the BACS should be about 0.1 to about 0.4 weight percent, prefer-ably about 0.20 to about 0.25 weight percent. In the prac-tice of this invention in order to produce a BACS having improved cold water effectiveness, it is necessary that the calclum sulfate contribute about 0.04 to about 0.15 weight percent calcium, preferably about 0.08 to about 0.12 weight percent. The balance of the calcium content of the finished product is derived from calcium carbonate or calcium chlo-ride. Where the sole source of calcium is calcium sulfate dihydrate, the calcium content of the BACS is limited to the range of about 0.10 to about 0.15 because of the limited amount of the calcium sulfate which can be incorporated into the system. In one embodiment the calcium ion is added ln the form of a slurry of the sulfate and carbonate in the predetermined amounts to achieve the desired concentration.
It has also been found that water soluble calcium chlorlde can be utilized as a calcium source. It has addi-tionally been found that by using the combination calcium chloride and calcium sulfate, these compounds can contribute a portion of the anion for the purpose of achieving the desired sulfate ion concentration as well as to ad~ust the Al/Cl atomic ratio using the calcium chloride as a minor source of chloride ion. It will be appreciated by those skilled in the art having access to this disclosure that a mixture of calcium carbonate and calcium sulfate or calcium chloride, and calcium sulfate can be utllized. To ensure that the product is effective in cold water the calcium sulfate must be included, contributing calcium ion in the range ~pecified above. Calcium carbonate and chloride uti-lized in the absence of the calcium sulfate results in im-proved efficiencies over the prior art. However, the calcium sulfate is essential to produce a suitable water treatment -1~ 1101plS4.93 ~; ~

t ~ Attorney Docket No. 442-154 BACS with cold water effectiveness as is required in the northern latitudes of thls country and Canada.
Where the calclum sulfate and calcium chloride are used, the primary source of sulfate ion is the acid or alumi-num salt, and the primary source of chloride is HCl, aluminum chloride, or a BAC having a different Al/Cl atomic ratio which i5 utlllzed in ad~ustlng the Al/Cl atomlc ratio.
In calculatlng the sulfate anlon concentration to be contributed by the acid or aluminum salt it ls necessary to take into account the sulfate ion contributed by the calcium sulfate so as not to exceed the range specified in numbered paragraph 3 above. Similarly in ad~usting the Al/Cl atomic ratio the amount of chloride contributed as calcium chloride must be considered in order to maintain the Al/Cl atomic ratio within the desired range. as descrlbed above.
Preferably the calcium slurry has a solids content of about 5 to about 10 weight percent. Direct addition of the powdered calcium salts should be avoided since it will result in lnsoluble partlcles. Additionally the slurry must be added at a controlled rate to avoid lnsoluble particle forma-tlon ln the BACS solution. Typlcally, the slurry i8 added over at least a one hour interval, e.g., one to two hours, with good mixing. Mixlng i8 continued until all of the calclum salts are dlssolved, e.g., for about an additional two hours to lnsure that all of the calclum salts have been solubllzed. Further mixing may be desirable lf it appears that solublization i9 not complete. Not wishing to be bound by theory, it i9 believed that solublization occurs as a result of reaction of the calcium salts wlth the anionic residuals of the BACS. Whenever the calcium slurry contains calcium carbonate the slurry should be added at temperatures between ambient and 45 C. Higher temperatures can result in undesirable preclpltatlon reactions. Where the slurry con-talns only calcium sulfate dihydrate or the dihydrate in .

-l~ llOlpl54.93 - :.

:

J ~ 3 -1~ Attorney Docket No. 442-154 combination calcium chloride $he slurry addition can be made at the temperature at which the sulfate anion is added using -~
the acid or aluminum salt. However, such a slurry can be added at a reduced temperature.
Where the BAC solution used in the process is a 5/6 basic BAC, it is necessary to ad~ust the Al/Cl atomic ratio to about 1.2 to about 0.70. The BACS solution can be fln-ished by the addition of water to adjust the concentration of BACS in solution. The specifications for the improved BACS
of this invention are:
Broad Range Preferred Range (X w/w) (X w/w) Al = 4.5 to 8.00 % Al = 5.30 to 5.60 %
Cl = ~.8 to 11.00 % Cl - 8.25 to 9,25 %
S04 = 2.20 to 3.80 % S04 = 2.60 to 2.90 %
Ca = 0.1 to 0.4 % Ca = 0.15 to 0.25 X
Fo = 0.01 to 0.03 X Fe = 0.015 to 0.020 X
S.G.= 1.18 - 1.26 @ 25- C S.G. = 1.19 - 1.22 @ 25- C

Preferred Al/Cl atomic ratio = 0.8100/1 to 0.8225/1 Preferred S04/Al atomic ratio ~ 0.13?5 to 0.1500/1 The specific gravlty ranges shown apply whether or not calcium and iron are included in the BACS.

The following example illustrates the invention utiliz-ing aluminum sulfate as the sulfate ion source.

A one kilo batch of improved BACS was prepared in the following manner:

-1~ llOlpl54.93 ^ i.l ~73~

-l~ Attorney Docket No. 442-154 TABLE II
Quantity Component wt. X qrams 5/6 Basic BAC
50X wt.solution 40.21 402.1 20 Be' HCl 17.30 173.0 Alum 48% soln.10.98 109.8 CaS04.2H20 0.45 4.5 ~ ~
CaC03 0.25 2.5 ;
FeC13 0.12 1.2 (42.9X w/w soln.) Water 30.69 306.9 A one-liter glass reaction flask was fitted with a reflux condenser a ~tirrer and a heating mantel. 100 grams of water was charged to the flask together with the 402.1 grams of 5/6 BAC. With mixing at room temperature the 1.2 grams of ferric chloride solution was added. Mixing was continued for about thirty minutes to ensure complete inte-gration of the iron into the system. The temperature of the reactlon mixture was then increased to 60 C and 95X of the total HCl was added (164 grams) over about 30 to 45 minutes to ad~ust the basicity of the BAC. The temperature was then increased to about 82-85 C. The aluminum sulfate solutlon (lO9.B grams) was then added at a rate of approximately 1.4 ml/min., the total addition time being approximately one hour. The temperature was maintained with continuous mlxlng for about 12 hours. Then the remaining HCL (8.6 grams) was added. The temperature was reduced to 40 C. slurry com-prlsing 4.5 grams of calcium sulfate dihydrate and 2.5 grams of calcium carbonate in one hundred grams of water. The slurry was added to the reaction mixture at a rate of about 1 ml/min. with continuous mixing. The ~lurry addition was completed in about two hours. After addition of the calcium slurry was completed, heat was discontinued and mixing was maintalned for about two hours. The balance of the water (106.9 gram~) was then added to complete the batch.
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-1~ Attorney Docket No. 442-154 ~;
The HCl addition was made in two parts to avoid over-shooting the desired Al/Cl atomic ratio. Generally, the ratlo will be determined by analysis before addition of the remaining acid, or other material utilized to adjust the ratio.
~XAMPLE 5 Thls example illustrates the use of sulfuric acid as the sulfate anion source. A one kilo batch was prepared uslng the following materials:

TABLE III
Quantitv Component wt. Xqrams 5/6 BAC 50X 44.23442.3 20 Be' HCl 16.31163.1 60 Be' H2S04 3.35 33.5 ;
FeC13 soln. 0.12 1.2 CaS04-2H20 0.45 4.5 CaC03 0.25 2.5 Water 35.29352.9 A one llter glass llned reactlon vessel was fitted with a mixer, heating mantel and reflux condenser. 100 grams of water and 442.3 grams of BAC were charged lnto the vessel.
Wlth mixlng, 1.2 grams of ferric chlorlde solutlon (42.9X
FeCl3 w/w) was added at amblent temperature . Stlrrlng was continued for an addltlonal 30 mlnutes. The reactlon mixture was then heated to 60 C, and 95X of the total HCl was added -~ -(154.9 grams) over a 30-45 minutes time interval with con-stant stirring. The temperature was then increased to 82-B5 C. The sulfurlc acld (33.51 grams) was then added at approx-imately 0.35 ml/mln., the total amount belng added over a one hour interval. The temperature was maintalned for 12 hours with continuous mixing, after whlch the remainlng HCl (8.16 gram~) was added. The temperature was then lowered to 40 C.
A slurry comprising 4.5 grams of calcium sulfate dlhydrate -l~ 1101pl54.93 ~ 7 ~ ~

-2~ Attorney Docket No. 442-154 and 2.5 grams of calcium carbonate in 100 grams of water was prepared. The slurry was added to the reactlon mixture at a rate of about l.Oml/min. with continuous mixing, addition time belng about two hours. After addition of the slurry, heatlng was discontinued and mixing continued for about two hours. The reaction mixture wa~ then diluted by the addition of 152.9 grams of water.
While the above examples illustrates the invention there are certain parameters which should be met in order to achieve the ob~ectives of the invention. The BAC concentra-tion ln the lnitial reaction mixture should be about 4.0 to about 12.5X as Al 3, preferably about 9.0 to about 12.5%. At the time of addition of the sulfate ion the Al/Cl atomic ratio should be about 1.2/1 to about 0.70/1, preferably about 1.00 to about 0.70 to 1. The method of preparation of the BAC is not critical, the Al/Cl atomic ratio can be achieved directly or by ad~ustment.
As has been stated above the Al/Cl atomic ratio can be ~ -ad~usted using HCl, aluminum chloride hexahydrate or a BAC of a different Al/Cl atomic ratlo than the starting material.
In one embodiment of the invention the ad~ustment of Al/Cl atomic ratio is accompllshed in two steps. This is a partic-ularly advantageous method where the BAC concentration is such that the Al 3 is about 7.9X or greater. In this modifi-catlon of the process the BAC is ad~usted to an lnltial Al/Cl atomic ratio of about 1.2 to about 0.91. After the sulfate anion addltlon ls made and before the calcium salt addition ls made a further ad~ustment i8 made to reduce the Al/Cl atomlc ratlo to about 0.9 to 0.70.
As used in the specification and claims the term "substantlally free" as used ln reference to precipitate content of the process reaction stream, means the product stream contalns about 1.0 wt. X or less of such precipltate.
Typically the product stream will contain less than 0.5 wt.%
preclpitate. ~-~
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Claims (38)

1. A process for preparing an aluminum hydroxychloro-sulfate which comprises heating a solution of a basic alumi-num chloride, wherein the concentration of Al+3 is about 4.0 to about 12.5 wt.%, to a temperature of about 75 to about 98°
C; adding a sulfate anion containing compound selected from the group consisting of sulfuric acid, aluminum sulfate and mixtures thereof, at a controlled rate, in an amount such that the molar ratio of sulfate ion to aluminum in the reac-tion mixture is about 0.05 to about 0.20, the sulfate ion addition being carried out at a controlled rate, the tempera-ture of the reaction being maintained at a temperature of about 75° to about 98° C two to about 24 hours after the completion of the addition of sulfate ion.

2. The process according to claim 1 wherein the sul-fate ion is added as a solution of aluminum sulfate.

3. The process according to claim 1 wherein the sul-fate ion is added as a solution of sulfuric acid.

4. The process according to claim 1 including, prior to the addition of sulfate ion, the additional step of ad-justing the Al/Cl atomic ratio of the solution to about 1.2/1 to about 0.70/1 by the addition of a compound wherein the compound is, aluminum chloride hexahydrate, HCl, a basic aluminum chloride of a basicity different from that of the solution to be adjusted or mixtures thereof.

5. The process according to claim 1 including, prior to the addition of sulfate ion, the additional steps of heating the solution of basic aluminum chloride to a tempera-ture of about 60-95° C., adjusting the Al/Cl atomic ratio of the solution by the addition of a compound wherein the compound is aluminum chloride hexahydrate, HCl, a basic aluminum chloride of a basicity different from that of the solution to be adjusted or mixtures thereof; the temperature of the reaction mixture being adjusted to about 90-95°C after adjustment of basicity, maintaining that temperature for a time sufficient to complete the adjustment reaction, and subsequently cooling the reaction mixture to about 75-98° C.
prior to sulfate ion addition.

6. The process according to claim 1 wherein the sul-fate ion is added at a temperature of about 80-85° C.

7. The process according to claim 5 wherein the Al/Cl atomic ratio is adjusted at a temperature of about 90 to about 95° C.

8. The process according to claim 5 wherein the Al/Cl atomic ratio is adjusted by the addition of HCl.

9. The process according to claim 5 wherein the Al/Cl atomic ratio is adjusted by the addition of aluminum chloride hexahydrate.

10. The process according to claim 5 wherein the Al/Cl atomic ratio is adjusted by the addition of a basic aluminum chloride solution having a different Al/Cl atomic ratio from that of the solution whose Al/Cl atomic ratio is to be ad-justed.

11. The process according to claim 1 which includes the optional step of diluting the reaction mixture after completion of the sulfate addition.

12. The process according to claim 11 wherein the reaction mixture is cooled to a temperature below 40° C and aged for about 2 to about 18 hours before dilution.

13. The product prepared according to the process of claim 1.

14. A process for preparing an aluminum hydroxychloro-sulfate which comprises heating a solution of a basic alumi-num chloride, wherein the concentration of Al+3 is about 4.0 to about 12.5 wt.%, to a temperature of about 75 to about 98°
C.; the Al/Cl atomic ratio being about 1.2/1 to about 0.70/1, adding a sulfate anion containing compound selected from the group consisting of sulfuric acid and aluminum sulfate at a controlled rate, in an amount such that the molar ratio of sulfate ion to aluminum in the reaction mixture is about 0.05 to about 0.20, the sulfate ion addition being carried out over a time interval of about one hour or longer, the temper-ature of the reaction being maintained at a temperature of about 75° to about 98° C. for about two hours to about 24 hours after the completion of the addition of sulfate anion;
adding a calcium containing composition selected from the group consisting of (1) calcium carbonate, (2) calcium sul-fate dihydrate and (2) calcium sulfate dihydrate in combina-tion with a second calcium compound wherein the second calci-um compound is calcium carbonate or calcium chloride, at a controlled rate, with mixing in an amount such that the concentration of calcium ion is about 0.1 to about 0.4 wt.
percent,; provided however, that, where the calcium composi-tion includes calcium carbonate the reaction mixture is cooled down to at least 45° C prior to the addition of the calcium composition; continuing the mixing until all of the calcium salt has been solublized and recovering the BACS
solution product.

15. The process according to claim 14 wherein the Al/Cl atomic ratio of the BAC is initially greater than 1.2/l, including the additional step of making an adjustment of the Al/Cl atomic ration to about 1.2/1 to about 0.70/1 by heating the BAC solution to a temperature of about 60° C to about 98° C with the subsequent addition of an adjustment compound wherein the compound is HCl, aluminum chloride hexahydrate, a BAC of different AL/Cl atomic ratio or mix-tures thereof in an amount sufficient to cause the adjust-ment, said adjustment being made prior to the sulfate anion addition.

16. The process according to claim 14 wherein the BAC
solution is adjusted to an iron content of about 75 ppm to about 250 ppm by the addition of a water soluble iron salt, the iron content being adjusted prior to any other modifica-tion of the reaction mixture.

17. The process according to claim 14 wherein the Al/Cl atomic ratio is about 1.0/1 to about 0.70/1.

18. The process according to claim 17 wherein the Al/Cl atomic ratio of the BAC is initially greater than 1.0/1, the additional step of making an adjustment of the A//Cl atomic ratio to about 1.0/1 to about 0.70/1 by heating the BAC solution to a temperature of about 60° C to about 98°
C with the subsequent addition of HCl, aluminum chloride hexahydrate, a BAC of different Al/Cl atomic ratio or mix-tures thereof in an amount sufficient to cause the adjust-ment, said adjustment being made prior to the anion addition.

19. The process according to claim 14 wherein the sulfate anion/Al+3 atomic ratio is about 0.122/1 to about 0.150/1.

20. The process according to claim 14 wherein the sulfate anion is added at a temperature of about 80° C to about 85° C.

21. The process according to claim 14 wherein the calcium ion concentration is about 0.20 to about 0.25 wt. %.

22. The process according to claim 15 wherein the adjustment is made using HCl, aluminum chloride hexahydrate or a BAC solution having an Al/Cl atomic ratio different than that of the BAC being used in the process.

23. The process according to claim 18 wherein the adjustment is made using HCl, aluminum chloride hexahydrate or a BAC solution having an Al/Cl atomic ratio different from that of the BAC being used in the process.

24. The process according to claim 14 wherein the calcium ion concentration is about 0.20 to about 0.25 %.

25. The process according to claim 14 wherein the calcium ion is introduced from a slurry of a mixture of calcium chloride and calcium sulfate dihydrate.

26. The process according to claim 14 wherein the calcium sulfate dihydrate contributes calcium ion in an amount of about 0.04 to about 0.15 %, the balance being contributed by a second calcium compound wherein the second compound is calcium carbonate or calcium chloride.

27. The process according to claim 26 wherein the calcium sulfate dihydrate contributes calcium ion in an amount of about 0.08 to about 0.12 %, the balance being contributed by calcium carbonate.

28. The process according to claim 27 wherein the total calcium concentration is about 0.20 to about 0.25 %.

29. The process according to claim 14 which includes the optional step of diluting the reaction mixture after completion of the sulfate addition and subsequent to cooling the BACS solution to a temperature below 40° C.

30. The process according to claim 29 wherein the reaction mixture is cooled to a temperature below 40° C and aged for about 2 to about 18 hours before dilution.

31. The process according to claim l wherein the BAC
solution is adjusted to an iron content of about 75 ppm to about 250 ppm by the addition of a water soluble iron salt, the iron content being adjusted prior to any other modifica-tion of the reaction mixture.

32. The process according to claim 1 wherein the BAC
solution is adjusted to an iron content of about 150 ppm to about 200 ppm by the addition of a water soluble iron salt, the iron content being adjusted prior to any other modifica-tion of the reaction mixture.

33. The process according to claim 14 wherein the BAC
solution is adjusted to an iron content of about 150 ppm to about 200 ppm by the addition of a water soluble iron salt, the iron content being adjusted prior to any other modifica-tion of the reaction mixture.

34. The process according to claim 15 wherein the Al/Cl atomic ratio is adjusted at a temperature of about 90 to about 95° C.

35. The process according to claim 18 wherein the Al/Cl atomic ratio is adjusted at a temperature of about 90 to about 95° C.

36. The process according to claim 14 wherein the sole calcium source is calcium sulfate dihydrate and the calcium concentration is about 0.10 to about 0.15 %.

37. The process according to claim 36 wherein the calcium sulfate dihydrate contributes calcium ion in an amount of about 0.08 to about 0.12 %.

38. The product prepared according to the process of claim 14.