IE72505B1

IE72505B1 - Basic aluminium chlorosulphate the process for producing it and its use as a flocculating agent

Info

Publication number: IE72505B1
Application number: IE27989A
Authority: IE
Inventors: Jean-Pierre Cuer; Claude Aubineau; Claudine Bonnel
Original assignee: Atochem Elf Sa
Priority date: 1988-01-29
Filing date: 1989-01-27
Publication date: 1997-04-23
Also published as: FR2626567B1; AU619518B2; EP0327419A1; FI98726B; JPH0710727B2; KR890011779A; ATE122324T1; CN1034701A; AU2883589A; JPH01226718A; DE68922504T2; DK172765B1; ZA89669B; DK35289D0; ES2073449T5; EP0327419B2; DE68922504T3; NO301756B1; ES2073449T3; KR910004836B1

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

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 iron 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 fora of an aqueous solution, characterized in that it comprises a product having a certain degree of polymerisation and with a composition given by the formulas Al.Cl.(03)3..2l_,_2p (SO,), X. in which: X denotes an alkaline-earth metal, preferably calcium n, a, p and k denote th® molar concentrations (mol/1) of the constituents in solution less than 20% of the SO4a can be precipitated by reacting with barium chloride at ambient temperature, whose basicity : 3 η 4- 2k - H ~ _2p Is ia the range 45 to 70%. 3a Advantageously, products according to the crude formula above are chosen, in which the ratio of a aluminium equivalent to chlorine, i.e. 3 n/a is not greater than 2.8 and preferably sot greater than 2-75.

Although it is possible to have a wide range of basicity, so>r»al!y products are used which have a basicity la the range 50 to 70%. Different basicity values may be preferred, according to the product applications, in particular, when preparing potable water, it has been observed that the higher th® basicity the lower the values of residual aluminium.

The nonprecipitation of most of the SO 2 ions in the product by barium salts presumably indicates that this sulphate is completed. 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 (i.e. 15 to 25eC) into a nonacidified sample, In a stoichiometric quantity in. relation to the SO42 ions present in the product, the dry weight of the precipitate formed after 1 hour Is related to th© content B of so-called non-complesed'5 S0^a" ions.

The difference A-3 is called th© content of completed SO4a" ions®. -4The product of the invention which occurs in the fora of an aqueous solution generally containing fro® 5 to 15% by weight expressed as AlaOs is mixed with an aqueous solution of barium chloride (for example from 5 to 20 g/1).

S The mixture is homogenized and the precipitate allowed to fora in the course of about 1 hour, then filtration is carried out through a sintered glass crucible of porosity grad® No. 4. All these operations,, from mixing th© chlorosulphate with the BaCl, up to the filtration take place at ambient temperature, i.e. in the range 15 to 25®C. The filtrate still contains the 30« 2 ions of the product of the invention which are not precipitated in the form of BaS0« and which are thus complexed. To find out this quantity of complexed SO«2~, the product is destroyed by adding hydrochloric acid to the filtrate and bringing to the boil. Then the 30« 2 ions are precipitated by a 5 to 15% by weight aqueous solution of SaCl2. Measuring the weight of BaS0« precipitated gives th© percentage of S0«2" ions which can be precipitated by reacting with barium chloride at ambient temperature in comparison with th© total amount of SO«2~ in the product.

Advantageously, the products have less than 10% of SO^2- ions which can be precipitated under normal conditions, and preferably less than 5%, i.e. more than 95% of the S0«2- ions are complexed.

The present invention also relates to a process' for preparing these products. The process is characterised in that: '«£· -5(a) an aqueous solution is prepared containing the aluminium ion, th© chloride ion and the sulphate ion, (b) this solution is brought into contact with an alkaline-earth metal compound, is) 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 th© 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®C. This temperature range is not essential, but corresponds only to a reaction period ox 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 ia 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 -S~ sulphuric 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 is moles ©£ Al, 0s „ 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 soles or Al203 , and preferably from 1.42 to 1.68.

The chlorosulphuric solution of aluminium from step a) is subsequently brought into 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 procedure may be performed at any temperature, it is preferred to bring the chlorosulphuric aluminium solution to 60 to 100°C for bringing it into contact with the alkaline-metal compound.

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

The quantity of the alkaline-earth metal compound. -7expressed ia moles, is generally from 1.63 to 1.70 times th® quantity of aluminium oxide introduced in step a), expressed in moles of &X2O3, 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 60°C.

Advantageously, this lasts for fro® 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 60°C.

Th® filtrate contains th® basic chlorosulphate of the invention dissolved in water. The concentration may be modified by adding water. The product of the invention takes the fora of this solution generally containing between 5% to 15% by weight of aluminium expressed as A1,O3. 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 th® application of these products as coagulating and flocculating agents for water treatment, particularly water purification to produce potable water.

Ar&ong the basic aluminium chlorosulphates according to the invention, those which concurrently - have a basicity greater than 60% - and whose weight ratio Cl/( total ΞΟή2_) is in the range 4.5 to 8, have, when they are used for th® treatment of aqueous media, a treatment characteristic which at optimal flocculation is low in th© 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 a): 3.09 moles of a powder containing 99% A1(OH)3 are poured into a glass reaction vessel containing 3 moles of SCI in the form of 331.9 g of a 33% solution and 1.45 moles of H,SO, as a 78% solution. The mixture is heated to 70°C and then the temperature stabilizes at 102°C. After dilution with 374 g of water, 1 mole of 78% sulphuric acid is added. The temperature Increases to 112aC in the course of 20 minutes. The duration of this step was about 2 hours.

Step b): After cooling to 93%, 2.60 moles of CAC03 , i.e. 481.5 g of a 54% slurry of CACOS 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°C.

Step c): After cooling to 40°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,O3„ 53.4% of SO42 , 1.35% of Cl, the remainder being calcium. 1,111 g of filtrate having a density of 1.224 were «· collected end 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 Al203, 8.11% of Cl', 1.63% og SO/, 1.78% of completed SO/* and 1.08% of Ca8* i.e. the ratio (Al equivalent)/Cl is 2.6, 97.3% of the S0/‘ ions being complexed.

The basicity is 64.18% and the weight ratio Cl/(total SO*2’) is 4.43. Ί θ £ΧΑΗΡΙ& ..2,..¾......gggg&RATIQKi . OF a»(MBR__gROPPCT 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 A1(OH)3# the duration of step a) is 2 hours. Step b) lasts 2 hours and begins at 90°G.

Step aj; Final temperature x 113.4 °C HCl $ 3 Boles H2SOt = 2.6 moles Step.bj: Final temperature : 63°C GaCOs x 2.6 moles in the form of a 54% slurry After separation of th© calsiuws sulphate (step c) and dilution with water, the following product is ©fe~ tained, the percentages being by weight of the solution.

Percentages in .the solution AiA 10.59% Cl 8.35% Total SO/ 2.13% Completed SO43' 2.13% Res idual Ca 0.7 7 % M equivalents /Cl 2.65 Basicity S1.2 9 Cosaplexed SO*2" ions 100% Cl/(total SO42) 3.92 EXAMPLE .. 3 ,x PREPARATION OF AWrBSR PRODUCT ACCORDING TO TOPS E «ma ?WN The operation was carried out as in Example 1, bat using different proportions of reactants. Starting from 3..09 soles of Al(0H)a, the duration of step a) is 2 hours» Step b) lasts 2 hours and begins at 90°C.

Stephan Final temperature x 112°C HCl : 2»81 soles H2SO4, s 2 »25 moles Step__bl8 Final teaaperature s 62°C CaCO3 x 2.38 moles in the foxa of a 54% slurry After separation of the calcium sulphate (step c) and dilution with water, the following product is obtained, the percentages beiaag try weight of the solution.

Percentages in the solution al2o3 S.96% Cl 7.72% Total S0/J' 1.50% Campieasad S042 1.50% *£~ Residual Ca. 0.66% Al eguivalent/Cl 2.S3 Eas ic ity 6 3.2% Oomplexed SO? ions 100% Cl/(total SO?') 5.15 BXAMPLB 4 s PRODOCTS SOT ACCORDINGTO THE, XKySWM Their eaqpirical formula is expressed ia 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 weights Al 10.3 (expressed as A12O3) Cl 9.09 Total SO? 2.49 Basicity 51.32%, the basicity being defined as for the product of the investion.

The concentration of complexed SO? ions is 1.64, i.e. 1-64/2.49, i.e. 65.9% of the sulphate, is ccsaplexed. The ratio (Al ecuiv.)/Cl is 2.37 and Cl/(total SO?') is 3.65.- The- product is produced by reacting aiusaxniw with BC1 and E2SO4 as in the patent SR 2,036,685. 4b) Another basic aluminium chlorosulphate is produced occuring in the form of a solution containing in % by weights Al Cl 8.3 (expressed as Al^Cy 5.21 Total SO?" 5,.02 The basicity is 49.8% The concentration of cceplexed SO*2" ions is 1.5, i.e. 3..5/5.02, i-e. 29.9% of the sulphate, is complexed. The ratio (Al equiv.)/Cl is 3.32 and CI/(total SO*2) is 1.04.

This product is produced by a process which comprises a step in which a slurry of calcium chloride and calcium carbonate (chlorocarbonate slurry) is prepared, a step in which the ehloxocarbonated 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 sake of calcium sulphate and a filtrate containing the basic aluminium chlorosulphate. This process is described in European Patent Application EP 218,407.

Using quasi-elastic light scattering, an apparent hydrodynamic diameter ez was measured ce this product, giving 700 A. 4c) A product of the seas type as In 4b) is produced., Th© concentrations ares Al Sj55 (as AJL2Oa) Cl 6.82 Total SO?' 2.74 Complexed SO? 1.93 The basicity is 57% 16,.

The. percentage of coeplexed SO/’ Is thus 1.93/2.74 « 70.4% and the ratios (M equivalent)/Cis 2.62 and Cl/(total β©Λ> 2.49.

RXAMPIja 5 This example illustrates the application of the product according to the inventionThe product of the invention is cceapared with the products of Bxaamle 4.

Trials are carried cut by test Jars according to the following operating methods - one-litre beaker - temperature 15°C - river water - test Jar HWROCORB type SUSS - rapid stirring for 1 minute 30 seconds after addition of the flocculast then slow stirring, i.e. sufficient to produce coalescence, but avoiding separation ©f the floes» Separation is subsequently allowed to occur for 3, 10 or 20 minutes according to Tables 1 t© 7» - measurement of the aluminium remaining in the water using a colorimetric sethod using chrosasurol, after filtration of the separated water for 20 min, on a 0.45 ^sa filter.

The following tables show the type of water to be treated, its pH, the turbidity expressed in Bffl? and the organic matter in rag of oxygen pet litre of water» a.

The- product used Is referenced bv the number of the example. The turbidity ox after ac sisstes of separation, setter and the aluminium remain the β^»Λ-τ. Α* Αΐ ·*’· 'Lb?WtSj at the surface the final pH, the organic .lag la the water (residual Al) in ppb (^g/lltre) are shown.

Tables I to 7 show results.

TABLE 1 Water type s Seine water pH 7.97 Turbidity 42 EOT Organic matter (Q.M.) 6.96 sg 0a/i PRODUCT QUANT!TT I3R WTOWTOTt^ Ομ5 TO λ^λλλΡ e"o && Residual (Examole No.) q/m3 (of A12O3) Ti 1 Crain 20ΛΧ»ί p* * 21¾,») Ί pn O.M. AJL 4ra Al 2.. 1 1.45 1.3 7.7 2.76 148 1 Al <*£ *3 Φ A » 1.35 1.2 7.84 S ff Αύ ul β c£> 97 Water s Marne water pH 8.02 Turbidity 60 KS Organic Matter (O.M.) 6.68 rag 02/l JLy PRODUCT (Exesmole 3Se.) QLWTITT X® g/W (of Al^Og) TORBIDITT OP TBS swbsnaseaw Pinal pH O.M. Residual Al SsbAs. IQsroxa 2®nta 4a 3 1.7 l.S l.S 7.73 2.94 152 lo 4c 3 1.7 1.55 1.45 7.80 2.78 152· 1 3 1.8 1.6 1.4 7.8® 2.66 118 Water type ; Marne water pH 8.26 (was racxiified by adding sodiusa hydroxide) Turbidity 55 ISO Organic Matter (O-M.) 5.94 sag 02/l PROOTS Ho.) Οο&μτιττ IN g/as (of Al/y KB3ID1TT OF TES SO3SSSST&NT Final pa 0.M. Residual Al Smxsu l©ffld.s, 2Qb1i!> 4a 3 1.55 1.55 1.35 7.90 2.12 216 4 c 3 1.6 1.55 1.3 7.92 2 -114 212 «IJ X 3 1.7 1.55 1.45 7.97 2.08 165 '5 TABLE 4 Water type : Oise water rfs 7 qg Turbidity 9.9 STU Organic matter (O-K.) 5.64 sag ©2/l PRODUCT (Example Bo.) QuAMTITT xw g/a3 (of A12O3) TOKSIDXTT Gi SUPERHATi 7» ^jT®i?2rW cm «U w3 1 7*>i«*i Q.M. Residual Al 4> irt) lOsin 2 ©sain ii e*a 3 1 0.88 0.80 η? o λ i' « t-w? M 2.94 89 15 Λ *c, "«Ci «* 0.98 0.93 0.91 «? CM 3.10 1 A «fe W 4b 3 1.2 1.02 0.91 7.82 3.08 120 Water ttoe : Oise water •g SF pH 8,.24 (after adding sodium hydroxide) Turbiditv 21 NTO Organic matter (O.M.) 6.92 sag O2/l It can be seen that even with a verr basic water :he product of the invention enables a concentration to i~...... be achieved - which is below the maximum permissible figure Oj WO /*g/l given in the Bnrope&n Council Directive, oi ISfh July 1980« TABLE 6 Water type » Seine water pH 7.97 Turbidity 42 HTU Organic matter (Θ.Μ.) 6.95 mg 0,/1 PRODUCT (Example Ho.) QUAHTITT IN g/sa3 (of Al^Og ) fejΤΪ2|ΤQ13 STOERNATANT 15" τν%ι J pH O w at aa m Residual ‘S'si^'Ti r% <ν9^'«4Λ<ι<ή»?ΛΛ 1 Chain 20aain 4sl eH ej t 1.45 1.3 7 7 S a S 2.76 148 2 51 9 Λ ω <4 1 ω 2 1.3 €SI (W Wl Λ m £ 3 2.72 117 1 4> <*# 3 •a rf X a "SE 1.3 7.01 *5 104 Water type s Marne water p3 8.02 Turbidity 60 WTO Organic matter (O-M.) 6.68 ag O2/l FRQDOCT (Exaanole Bo.) QLWTITT ZB g/sa3 (of il203) TOFJ8IDITT OF THE SOPESHATAMT Final pH 0.M. Residual Al 3min lOmin 2 Gain 4 a 3 1.7 1.6 1.5 7.78 2.94 152 15 4c 3 1.7 1.55 1.45 7.80 2.78 152 2 3 l.S 1.6 1.5 7.82 2.72 128 1 3 1-8 l.S 1.4 7.80 2.S6 118 EXAMPLE S This example consists In ccmpariag the results for turbidity and residual aluminium with the products according to the invention from Examples 1 and 3 when they axe used at low treatment concentrations $ I, 1.5, 2 and 3 g/m3 of A12O3.

The trials are carried out In test jars according to the operating aethod described in Example 5 in water of the Seise water type.

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

TEST KiO. MASER pH TURBIDIST (STO) O.M. (sag Ο·»/!) A 5.88 B-C 6., 08 D-E 8.02 8.2 3>-G 8.05 7.,4 B-I 10 5.86 J~K 10 5.48 L 8.1 12 4.68 M-M e 8.3 0-5 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 manners difference in parameter x (%) ~ value of x for Exaaaole i «. vaLSS x Fog -g-xagpIST--- x lwlw where 1 ~ 1 or 3 N,B.- The differences are not truly significant unless their absolute value is greater than or equal to 5%.

Claims

1. An aqueous solution of a basic aluminium chXorosulpbate which has the formula: (SO, ) p ia which: n, m, p and k denote the solar concentrations (mol/1) o£ the constituents in solution X denotes an alkaline-earth metal such that less than 20% of the SO., 2 can be precipitated by reacting it with barium chloride at ambient temperature, the basicity: 3n - 2k - m - 2p being from 45 3n to 70%.

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

3. » A solution according to claim X or 2, In which the ratio Al equxvalent/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 65%.

5. A solution according to any one of claims 1 to 4, ia which less than 5% of the SO 4 a ions can be precipitated by reacting it with barium chloride at ambient temperature.

6. » A solution according to any one of claims 1 to 5, which is such that its basicity is at least 60% and the weight ratio Cl/SO 9 is from 4.5 to 3.

7. A solution according to any one of the preceding claims in which X denotes calcium. -22S, A solution according to claim 1, substantially as described in any one o£ Examples 1 to 3.

8. 9. Process for producing an aqueous solution of a basic chlorosulphate, as claimed ia any on® of the 5 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, .10 c) removing the alkaline-earth metal sulphate.

9. 10. Process according to claim 9, in which step a) is carried out by bringing aluminium oxide into contact with hydrochloric acid and sulphuric acid.

10. 11. Process according to claim 9 or 10, in which 15 the alkaline-earth metal compound is calcium carbonate, calcium hydroxide, calcium oxid® or calcium bicarbonate.

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

12. 13. An aqueous solution of a basic aluminium 20 chlorosulphate as defined in. claim 1, whenever produced by a process as claimed in any one of claims 9 to 12.

13. 14.. Process for the treatment of an aqueous medium, which comprises heating the medium with an aqueous solution as claimed in any one of claims 1 to 8 and 13.