AU619518B2

AU619518B2 - Basic aluminium chlorosulphate, the process for producing it, and its use as a flocculating agent

Info

Publication number: AU619518B2
Application number: AU28835/89A
Authority: AU
Inventors: Claude Aubineau; Claudine Bonnel; Jean-Pierre Cuer
Original assignee: Atochem SA
Current assignee: Arkema France SA
Priority date: 1988-01-29
Filing date: 1989-01-27
Publication date: 1992-01-30
Anticipated expiration: 2009-01-27
Also published as: FR2626567A1; JPH01226718A; IE72505B1; DK35289D0; PT89562A; NO890200L; FI890426A; FI890426A0; ATE122324T1; ES2073449T5; CN1018997B; DE68922504T2; FI98726B; ES2073449T3; FR2626567B1; DK172765B1; CN1034701A; DE68922504T3; JPH0710727B2; EP0327419A1

Abstract

A basic aluminium chlorosulphate whose basicity is between 45 and 70 % and in which more than 80 % of the SO4<2><-> ions are complexed. This product is prepared by reaction of calcium carbonate with an aluminium chlorosulphuric solution. This product can be used for coagulating and flocculating suspended matter in water, in particular with the aim of preparing potable water. An advantage of the product of the invention is that it leaves very little residual aluminium in the water produced.

Description

~J I FORM 10 19 S F 84465 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: 0 0 ni Priority: Related Art: Name and Address of Applicant: Address for Service: Atochem La Defense 10, 4 8 Cours Michelet 92800 Puteaux

FRANCE

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Basic Aluminium Chlorosulphate, The Process for Producing It, and Its Use as a Flocculating Agent The following statemrnt Is a full description of this Invention, Including the best method of perfo. 'ng It known to me/us 5845/5 No.: Initial aLl aIteration.

2- The present invention relates to a basic aluminium chlorosulphate, a process for producing it and its use as a flocculating agent. The treatment of effluents, sewages, spring waters or river waters almost always comprises a stage in which suspended materials are removed.

Products are known which have a coagulating effect on these suspended or dissolved materials in the aqueous system to be treated, these being materials which cannot be separated In a reasonable time by natural separation. Moreover, these products convert these materials into coagulated flakes which are easy to filter and separate from the liquid phase.

A chlorosulphate has now been found which is very effective and very simple to use. The chlorosulphate according to the Invention is a basic aluminium chlorosulphate which is in the form of an aqueous solution, with a composition given by the formula: Al nC (OH)3n+2k-m-2p

(S

0 4)p Xk in which: X denotes an alkaline-earth metal, preferably calcium n, m, p and k denote the molar concentrations (mol/l) of the constituents in solution less than 20% of the SO 2- can be precipitated by reacting with barium chloride at ambient temperature, whose basicity: 3n 2k m- 2p is in the range 45 to 3n Generally, the basic aluminium chlorosulphate is at least partly S po'ymerized.

Advantageously, products according to the crude formula above are Achosen, in which the ratio of a aluminium equivalent to chlorine, i.e.

3 n/m Is not greater than 2.8 and preferably not greater than 2.75.

Although it is possible to have a wide range of basicity, normally products are used which have a basicity in the range 50 to Different basicity values may be preferred, according to the product /P y5 KEH/270f Ob.- M _I _I~IC -3applications. In particular, when preparing potable water, it has been observed that the higher the basicity the lower the values of residual aluminium.

2- The nonprecipitatlon of most of the SO 4 Ions in the product by barium salts presumably indicates that this sulphate is complexed.

Determination of the total content A of sulphate contained in the product can be carried out in a customary manner by precipitating barium sulphate using a solution of barium chloride and hydrochloric acid which Is added to the sample at its boiling point. When barium chloride is Introduced at ambient temperature 15 to 25C) into a nonacidified sample, in a 2stoichlometric quantity in relation to the SO 2- ions present In the product, the dry weight of the precipitate formed after 1 hour is related to the content B of so-called "non-complexed" SO 4 2- ions.

2- The difference A-B is called the "content of complexed SO 4 ions".

KEH/270f •L -4- The product of the invention which occurs in the form of an aqueous solution generally containing from 5 to by weight expressed as Al 2 03 is mixed with an aqueous solution of barium chloride (for example from 5 to 20 g/l).

The mixture is homogenized and the precipitate allowed to form in the course of about 1 hour, then filtration is carried out through a sintered glass crucible of porosity grade No. 4. All these operations, from mixing the chlorosulphate with the BaCl 2 up to the filtration take place at ambient temperature, i.e. in the range 15 to The filtrate still contains the So 4 2- ions of the product of the invention which are not precipitated in the form of BaSO 4 and which are thus complexed. To find out this 2 quantity of complexed SO2 the product is destroyed by adding hydrochloric acid to the filtrate and bringing to the boil. Then the SO 2 ions are precipitated by a 5 to 15% by weight aqueous solution of BaCl 2 Measuring the weight of BaSO 4 precipitated gives the percentage of SO42- ions which can be precipitated by reacting with barium chloride at ambient temperature in comparison with the total amount of

SO

4 2- in the product.

Advantageously, the products have less than 10% of A SO42- ions which can be precipitated under normal conditions, and preferably less than i.e. more than 2of the SO 4 2 ions are complexed.

The present invention also relates to a process for preparing these products. The process is characterized in that: an aqueous solution is prepared containing the aluminium ion, the chloride ion and the sulphate ion, this solution is brought into contact with an alkaline-earth metal compound, the alkaline-earth metal sulphate is removed.

Step a) is advantageously carried out by bringing aluminium oxide into contact with hydrochloric acid and sulphuric acid in an aqueous medium. By "aluminium oxide" is meant all products of the alumina or aluminium hydroxide type. It is preferred to use alumina produced by the Bayer process or the aluminium hydroxides which are byproducts of the surface treatments of aluminium.

Advantageously, aluminium oxide is attacked by a mixture of concentrated hydrochloric acid and concentrated sulphuric acid at a temperature from 70 to 115 0 C. This temperature range is not essential, but corresponds only to a reaction period of one or two hours which is compatible with the industrial application of the process. It is possible to add aluminium oxide to a mixture of acids or to react aluminium oxide with one acid followed by the other, or to add the acids in several portions. It is preferred to use a mixture of hydrochloric acid and sulphuric acid to attack the aluminium oxide, then add a further amount of concentrated sulphuric acid once part of the aluminium oxide has been dissolved.

Advantageously, a solution of hydrochloric acid more concentrated than 20% by weight is used and preferably a 33% by weight solution. It is also advantageous to use

I

-6sulphuric acid having a concentration of at least 60% by weight. Generally, the quantity of hydrochloric acid, expressed in moles, is from 1.89 to 2.44 times the quantity of aluminium oxide expressed in moles of A1 2 0 3 and preferably 1.95 to 2.40.

Likewise, the quantity of sulphuric acid, expressed in moles, (used in one or more portions) is generally from 1.37 to 1.73 times the quantity of aluminium oxide expressed in moles of Al 2 0 3 and preferably from 1.42 to 1.68.

The chlorosulphuric solution of aluminium from step a) is subsequently brought ,:ito contact with the alkaline-earth metal compound. This alkaline-earth metal compound may be, for example, calcium carbonate, calcium hydroxide, calcium oxide or calcium bicarbonate. It is possible to use a mixture of these products, for example calcium carbonate and calcium hydroxide, calcium carbonate being preferred. Advantageously, the alkaline-earth metal compound is in divided form, such as a powder. Although the procedurie may be performed at any temperature, it is preferred to bring the chlorosulphuric aluminium solution to to 100 0 C for bringing it into contact with the alkaline-metal compound.

Generally 10 or 30 minutes are taken for this contacting procedure, which corresponds to customary technological conditions, but it is not beyond the scope of the invention to operate over a few minutes or over several hours.

The quantity of the alkaline-earth metal compound, I ~111_ 7 expressed in moles, Is generally from 1.63 to 1.70 times the quantity of aluminium oxide introduced in step expressed in moles of A1 2 0 3 and preferably 1.65 to 1.68. The mixture may be left stirred when all of the alkaline-earth metal compound has been mixed with the chlorosulphuric solution of aluminium. The temperature used is not specified, but generally settles at 30 to Advantageously, this lasts for from 15 minutes to 2 hours.

Subsequently, it only remains to separate the alkaline-earth metal sulphate. Customary methods may be used, such as filtration or centrifugation. This separation is preferably carried out above ambient temperature, for example from 30 to The filtrate contains the basic chlorosulphatp of the invention dissolved in water. The concentration may be modified by adding water.

The product of the invention takes the form of this solution generally containing between 5% to 15% by weight of aluminium expressed as A1 2 0 3 This form has the advantage of being stable (no appearance of a solid phase) for several months at ambient temperature.

The present invention also relates to the application of these products as coagulating and flocculating agents for water treatment, particularly water purification to produce potable water.

There is also provided according to the Invention a process for the treatment of an aqueous medium, which comprises treating the medium with the aqueous solution of the invention.

Among the basic aluminium chlorosulphates according to the invention, those which concurrently have a basicity greater than and whose weight ratio Cl/(total SO 4 is in the range EH/270f KEH/270f L.

I

-8to 8, have, when they are used for the treatment of aqueous media, a treatment characteristic which at optimal flocculation is low in the associated properties relating to the aluminium remaining in solution (residual Al).

The following Examples further illustrate the present invention.

EXAMPLE 1: PREPARATION OF A PRODUCT ACCORDING TO THE INVENTION Step 3.09 moles of a powder containing 99% Al(OH) 3 are poured into a glass reaction vessel containing 3 moles of HC1 in the form of 331.9 g of a 33% solution and 1.45 moles of H SO 4 as a 78% solution. The mixture is heated to 70 0 C and then the temperature stabilizes at 102 0

C.

After dilution with 374 g of water, 1 mole of 78% sulphuric acid is added. The temperature increases to 112°C in the course of 20 minutes. The duration of this step was about 2 hours.

Step After cooling to 93%, 2.60 moles of CACO,, i.e. 481.5 g of a 54% slurry of CACO 3 are introduced in the course of 30 minutes. The reaction vessel is left stirred for 1 hour 30 minutes, the temperature having dropped to 61 0

C.

Step After cooling to 40 0 C, the mixture is filtered in a filtration apparatus under vaccuum. The cake is washed with 100 g of water. The dry cake weighs 362 g and contains by weight 7.73% of aluminium expressed as A1 2 0 3 53.4% of SO2- 1.35% of Cl the remainder being calcium. 1,11.. g of filtrate having a density of 1.224 were 1_ collected and were diluted with 109 g of water. The product obtained is in the form of a solution.

The solution weighs 1,220 g, has a relative density of 1.201 and contains by weight 10.09% of Al expressed as A1 2 0 3 8.11% of Cl", 1.83% og SO,2-, 1.78% of complexed SO,, 2 and 1.08% of Ca 2 i.e. the ratio (Al equivalent)/Cl is 2.6, 97.3% of the SO42- ions being complexed.

The basicity is 64.18% and the weight ratio Cl/(total SO0,2) is 4.43.

EXAMPLE 2 PREPARATION OF ANOTHER PRODUCT ACCORDING TO THE INVENTION The operation was carried out as in Example 1, but using different proportions of reactants. Starting again from 3.09 moles of Al(OH) 3 the duration of step a) is hours. Step b) lasts 2 hours and begins at Step a): Final temperature 113.4oC HC1 3 moles HzSO, 2.6 moles Step b): Final temperature 63°C CaCO 3 2.6 moles in the form of a 54% slurry i After separation of the calcium sulphate (step c) and dilution with water, the following product is obtained, the percentages being by weight of the solution.

Percentaaes in the solution Al O Cl Total SO 2- 10.59% 8.35% 2.13% h 10 Complexed SO4 2 2.13% Residual Ca 0.77% Al equivalents /Cl 2.65 Basicity 61.29 Complexed SO4, 2 ions 100% Cl/(total SO,2-) 3.92 EXAMPLE 3 PREPARATION OF ANOTHER PRODUCT ACCORDING TO THE INVENTION The operation was carried out as in Example 1, but using different proportions of reactants. Starting from 3.09 moles of Al(OH) 3 the duration of step a) is 2 hours. Step b) lasts 2 hours and begins at 90 0

C.

Step a): Final temperature 112°C HC1 2.81 moles HSO, 2.25 moles Step bl: Final temperature 62°C CaCO, 2.38 moles in the form of a 54% slurry After separation of the calcium sulphate (step c) and dilution with water, the following product is obtained, the percentages being by weight of the solution.

PercentaQes in the solution

AL

2 0 3 9.96% Cl 7.72% Total SO, 2 1.50% Complexed SO0, 2 1.50% 11 Residual Ca 0.66% Al equivalent/Cl 2.69 Basicity 63.2% Complexed SO42- ions 100% Cl/(total SO42-) 5.15 EXAMPLE 4 PRODUCTS NOT ACCORDING TO THE

INVENTION

Their empirical formula is expressed in the same form as those of the products of the invention.

4a) A basic aluminium chlorosulphate is produced according to the prior art, which is in the form of a solution containing in by weight: Al 10.3 (expressed as A1 2 0 3 Cl 9.09 Total SO 2 2.49 Basicity 51.32%, the basicity being defined as for the product of the invention.

The concentration of complexed SO, 2 ions is 1.64, i.e. 1.64/2.49, i.e. 65.9% of the sulphate, is complexed.

The ratio (Al equiv.)/Cl is 2.37 and Cl/(total SO^2-) is 3.65.' The product is produced by reacting aluminium with HC1 and H 2 SO, as in the patent FR 2,036,685.

4b) Another basic aluminium chlorosulphate is produced occuring in the form of a solution containing in by weight: Al 8.3 (expressed as Al 2 0 3 Cl 5.21 12 Total SO42- 5.02 The basicity is 49.8% The concentration of complexed SO2- ions is i.e. 1.5/5.02, i.e. 29.9% of the sulphate, is complexed.

The ratio (Al equiv.)/Cl is 3.32 and Cl/(total SO 4 is 1.04.

This product is produced by a process which comprises a step in whi-h a slurry of calcium chloride and calcium carbonate (chlorocarbonate slurry) is prepared, a step in which the chlorocarbonated slurry is brought into contact with the aluminium sulphate, then a step in which the reaction mixture thus obtained is separated, this being done by separating a cake of calcium sulphate and a filtrate containing the basic aluminium chlorosulphate. This process is described in European Patent Application EP 218,487.

Using quasi-elastic light scattering, an apparent hydrodynamic diameter 4Z was measured on this product, giving 700 A.

S 20 4c) A product of the same type as in 4b) is produced. The concentrations are: Al 8 65 (as A1 2 0 3 Cl 6.82 Total SO4, 2 2.74 Complexed SO4, 2 1.93 The basicity is 57% 13 13 The percentage of complexed SO, 2 is thus 1.93/2.74 70.4% and the ratios (Al equivalent)/Cl: 2.62 and Cl/(total S04, 2 2.49.

EXAMPLE This example illustrates the application of the product according to the invention.

The product of the invention is compared with the products of Example 4.

Trials are carried out by test jars according to the following operating method: one-litre beaker temperature 15 0

C

river water test jar HYDROCURE type SLH6 rapid stirring for 1 minute 30 seconds after addition of the flocculant then slow stirring, i.e.

sufficient to produce coalescence, but avoiding separation of the flocs.

Separation is subsequently allowed to occur for 3, 10 or 20 minutes according to Tables 1 to 7.

measurement of the aluminium remaining in the water using a colorimetriC method using chromazurol, after filtration of the separated water for 20 min, on a 0.45 pm filter.

The following tables show the type of water to be treated, its pH, the turbidity expressed in NTU and the organic matter in mg of oxygen per litre of water.

14 The product used is referenced by the number of the example. The turbidity of the water at the surface after x minutes of separation, the final pH, the organic matter and the aluminium remaining in the water (residual Al) in ppb (pg/litre) are shown.

Tables 1 to 7 show the resulta.

TABLE 1 Water type Seine water pH 7.97 Turbidity 42 NTU Organic matter 6.96 mg 02/1 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al No.) A1 2 0 3 3min 10min 20min pH 4a 4 2.1 1.45 1.3 7.7 2.76 148 1 4 1.8 1.35 1.2 7.84 2.72 97 15 TABLE 2 Water type Marne water pH 8.02 Turbidity 60 NTU Organic matter 6.68 mg 0,/1 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al No.) A1 2 0 3 3min 10min 12fmin pH 4a 3 1.7 1.6 1.5 7.78 2.94 152 4c 3 1.7 1.55 1.45 7.80 2.78 152- 1 3 1.8 1.6 1.4 7.80 2.66 118 TABLE 3 Watt type Marne water pH 8.26 (was modified hydroxide) Turbidity 55 NTU Organic matter 5.94 mg 02/1 by adding sodium PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al No.) A1 2 0 3 3min 10min 20min pH 4a 3 1.55 1.55 1.35 7.90 2.12 216 4. 3 1.6 1.55 1.3 7.92 2.14 212 1 3 1.7 1.55 1.45 7.97 2.08 165 1 3 1.7 1.551 1.45 7.97 2.08 165 16 TABLE 4 Water type Oise water pH 7.99 Turbidity 9.9 NTU Organic matter 5.64 mg 02/1 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al No.) A1 2 0 3 3min 10min 20min pH 1 3 1 0.88 0.80 7.88 2.94 89 4a 3 0.98 0.93 0.91 7,84 3.10 123 4b 3 1.2 1.02 0.91 7.82 3.08 120 TABLE 20 Water type Oise water pH 8.24 (after adding sodium hydroxide) Turbidity 21 NTU Organic matter 6.92 mg 02/1 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al No.) A1 2 0 3 3min 10min 20min pH 1 3 0.94 0.83 0.72 8.08 2.86 163 4a 3 1.05 1 0.99 8.03 2.86 242 4b 3 1.25 0.99 0.93 8.02 2.88 238 It can be seen that even with a very basic water the product of the invention enables a concentration to

I

L~-r~ 17 17 be achieved which is below the maximum permissible figure of 200 pg/l given in the European Council Directive, of July 1980.

TABLE 6 Water type Seine water pH 7.97 Turbidity 42 NTU Organic matter 6.96 mg 02/1 10 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Final O.M. Al IE.) A1 2 0 3 3min 10min 20min pH 4a 4 2.1 1.45 1.3 7.7 2.76 148 2 4 2.2 1.2 1.3 7.77 2.72 117 1 4 3 1.4 1.3 7.81 2.72 104 -18 TABLE 7 Water type Marne water pH 8.02 Turbidity 60 NTU Organic matter 6.68 mg 0/l 10 PRODUCT QUANTITY TURBIDITY OF THE IN SUPERNATANT Residual (Example g/m 3 (of Fin 1 O.M. Al No.) A1 2 0 3 3min 10min 20min pH 4a 3 1.7 1.6 1.5 7.78 2.94 152 4c 3 1.7 1.55 1.45 7.80 2.78 152 2 3 1.8 1.6 1.5 7.82 2.72 128 1 3 1.8 1.6 1.4 7.80 2.66 118 EXAMPLE 6 This example consists in comparing the results for turbidity and residual aluminium with the products according to the invention from Examples 1 and 3 when they are used at low treatment concentrations: 1, 1.5, 2 and 3 g/m 3 of A0lO 3 The trials are carried out in test jars according to the operating method described in Example 5 in water of the Seine water type.

Table 8 shows the values of pH, turbidity and quantity of organic matter in the Seine water, which have been measured before treatment using the products of Example 1 and 3 (trials A to P).

L~

L

19 TABLE 8 TEST NO. WATER pH TURBIDITY (NTU) O.M. (mg 02/1) A 5.88 B-C 6.08 D-E 8.02 8.2 F-G 8.05 7.4 H-I 10 5.88 J-K 10 5.48 L 8.1 12 4.68 M-N 8 8.3 O-P 7.91 12 Table 9 sets out the mean values of the results obtained using the product from Example 3 for reference.

The percentages which are shown are obtained in the following manner: difference in parameter x value of x for Example i X 100 100 value x for Example 3 where i 1 or 3 N.B. The differences are not truly significant unless their absolute value is greater than or equal to r TAB3LE 9

PRODUCT

(Example No.)

QUANTITY

IN

g /m 3 (A1 2 0 3 TURBIDITY OF THE SUPE RNATANT O.M. Residual Al 3mi n 10min 1 14 9.3 8.9 -0.7 3 1 0 0 0 0 0 1 18 9.2 6 L. 8 3 1.5 0 0 0 0 0 1 20 9.9 3.3 3 2 0 0 0 0 0 1 5.25 0.34 -2.4 3 3 0 0 0 0 0

Claims

1. An aqueous solution of a basic aluminium chlorosulphate which has the formula: Aln Cl (OH) 3 n+2k p (SO 4 Xk in which: n, m, p and k denote the molar concentrations (mol/l) of the constituents in solution X denotes an alkaline-earth metal such that less than 20% of the SO42- can be precipitated by reacting it with barium chloride at ambient temperature, the basicity: 3n 2k m 2p being from 3n to

2. A solution according to claim 1, in which the ratio (Al equivalent)/Cl(3n/m) is not greater than 2.8.

3. A solution according to claim 1 or 2, in which the ratio Al equivalent/Cl is not greater than 2.75.

4. A solution according to any one of claims 1 to 3, in which the basicity is from 50 to A solution according to any one of claims 1 to 4, in which less than 5% of the SO 2- ions can be precipitated by reacting it with barium chloride at ambient temperature.

6. A solution according to any one of claims 1 to which is such that its basicity is at least 60% and the weight ratio Cl/SO 4 is from 4.5 to 8.

7. A solution according to any one of the preceding claims in which X denotes calcium. -22-

8. A solution according to claim 1, substantially as described in any one of Examples 1 to 3.

9. Process for producing an aqueous solution of a basic chlorosulphate, as claimed in any one of the preceding claims which comprises; a) preparing an aqueous solution containing aluminium ion, chloride ion and sulphate ion, b) bringing this solution into contact with an alkaline-earth metal compound, c) removing the alkaline-earth metal sulphate. Process according to claim 9, in which step a) is carried out by bringing aluminium oxide into contact with hydrochloric acid and sulphuric acid.

11. Process according to claim 9 or 10, in which the alkaline-earth metal compound is calcium carbonate, calcium hydroxide, calcium oxide or calcium bicarbonate.

12. Process according to claim 9, substantially as described in any one of Examples 1 to 3.

13. An aqueous solution of a basic aluminium chlorosulphate as defined in claim 1, whenever produced by a process as claimed in any one of claims 9 to 12.

14. Process for the treatment of an aqueous medium, 4 1 4 r vhich comprir-s h the medium with an aqueous solution as claimed in any one of claims 1 to 8 and .13. DATED tlhis TWENTY FOURTH day of JANUARY 198s Atochem IPt. nt Attorneys for the Applicant SPRUSON t FERI:'SON spvsOl P v