LT4865B - Water composition for destabilization of disperse systems and preparation thereof - Google Patents

Abstract

The proposed water composition can be used in the destabilisation of different dispersive systems, including waste downflow polluted by heavy metals. The composition contains natrium aluminate as a coagulant where the Na2O and Al2O3 molarity ratio is from 1.5 to 4 and anionic polyacrylamide flocculant with molecular mass 3 mln., in best cases from 3.5 to 6 mln .and that has a 10% molecular ratio of sulphomethyl groups. The composition is obtained by mixing pre-prepared natrium aluminate or anionic polyacrylamide hydro solutions, when the coagulant and flocculant mass ratio is from 100 to 1.

Description

The invention relates to the field of chemical engineering and can be applied to destabilize various dispersion systems, including the treatment of wastewater, especially contaminated with heavy metals. >

Sodium aluminate NaA10 _{2 is} used for a variety of purposes and is known in water treatment as a coagulant. kn. 3anonbCKHH AK, EapaH AA KoaryjMHTbi h φηοκγπΗΗΤΜ b npoueccax ohhctkh BOflbi.-JIeHHHrparc Χημηη, 1987, 204 c.]. The composition of this coagulant is characterized by the molar ratio a of Na ₂ O and AUO3, which depends on the quantities of sodium hydroxide and aluminum oxide or hydroxide taken during production.

It is known that coagulation with aluminate for particle coagulation, water separation and acceleration of sedimentation often results in the addition of water-soluble polymers, flocculants. Such coagulation and flocculation processes apply not only to water treatment but also to the paper industry. Known paper-making techniques include the addition of polysaccharides and their derivatives by coagulation with aluminates [cf. Australian Pat. No. 2077876, IPC COB 31/00, B01D 21/01, 1978; Australian Pat. No. 508369, IPC C0B 31/00, B01D 21/01, 1980; N. Zealand Pat. No. 243348, EPC D21H 17/74, D21H 17/55, D21H 17/24, D21H 17/28, D21H 21/10, 1994], or anionic polyacrylamide flocculants [See, e.g. N. Zealand Pat. No. 243348, IPC D21H-17/74, D21H 17/55, D21H 17/24, D21H 17/28, D21H 21/10],

The disadvantage of these methods is that the solutions of the coagulant and the flocculant are prepared and used separately, so that separate capacities and dosing equipment must be provided for each. The processes would be simplified and cheaper if a pre-prepared mixture of these reagents could be used. However, aluminate solutions are highly alkaline and many substances are degraded or coagulated.

Stable solutions of sodium aluminate containing 0.1 to 1.5% of tartaric and gluconic acids in a ratio of 70:30 are known. U.S. Pat. No. 3656889, IPC C01F 7/02, 1972] or 5-50% triethanolamine [See U.S. Pat. U.S. Pat. No. 4007252, IPC C01F 7/02, 1977]. Washing compositions containing bleach dichloroisocyanurates and non-ionic detergents in addition to aluminate are also known. Japanese Pat. No. 1213400, IPC C11D 17/00, C11D 10/02, D06L 1/12, 1989],

The disadvantage of these compositions is that they are unsuitable for coagulation and / or flocculation purposes since low molecular weight organic compounds cannot perform flocculant functions.

Compositions containing water-soluble polymers are known. They are used for other purposes mentioned below and their flocculation efficiency is not mentioned. For example, dispersions of aluminosilicates (clays) are suggested to be cemented [See Am. U.S. Pat. No. 5576271, IPC C09K 7/02, 1996], containing from 0.001% to 10% of polymers - starch, carboxymethyl starch, guar thickener or polyacrylamide derivative. Such compositions contain many other inorganic salts and only 0.01 to 3% of aluminate. It is inappropriate to use them in water treatment simply because all of these additives significantly increase the mineralization of the solutions.

Composition for Textile Finishing or Bonding Paper and Wood [See Am. Japanese Pat. No. 11001595, IPC C08L 29/04, C08K 3/10, C08L 101/14, 1999], which, in addition to sodium aluminate, contains a modified polyvinyl alcohol derivative having a degree of polymerization of 50-3000 and a degree of hydrolysis> 50 mol. % and molecules contain up to 20 mol. % carboxy groups. This polymer cannot be an effective flocculant due to its low molecular weight.

The closest embodiment of the present invention is a process for preparing and stabilizing an aqueous aluminate solution by admixing a vinyl polymer having pendant type carboxylic groups. U.S. Pat. No. 4734274, IPC C01F 007/04, 1988], The polymer used has a molecular weight of> 1 min and its latex is embedded in an aluminate solution at high temperature (110 ° C). Under such conditions, hydrolysis of the carboxylic groups of the polymer occurs in strongly alkaline media and anionic carboxy groups are formed. Heating to high temperatures is a major disadvantage of this method.

It is an object of the present invention to provide a stable aqueous composition for destabilizing dispersion systems containing a coagulant sodium aluminate and an anionic polyacrylamide flocculant.

The object is achieved by mixing aqueous sodium aluminate having a molar ratio of Na ₂ O and Al ₂ O ₃ a = 1.5 - 4 and an anionic polyacrylamide of formula [(-CH ₂ - CH) _n . _m - (CH ₂ - CH-) _m ] "

I I

CONH ₂ CONH

I

CH ₂ SO ₃ Well

Containing at least 10 mol. % sulfomethyl groups, solutions. Such aqueous compositions may be used for the separation of heavy metal ions and other contaminants in waste water treatment. They avoid the separate preparation and dosing of solutions for both water treatment reagents.

The claims of the invention are illustrated by the data in Tables 1-3. Table 1 shows the time taken for solutions of coagulant to flocculant to lose stability (cloudiness or precipitation), depending on the amount of anionic groups in the polyacrylamides, the Na ₂ O and Al ₂ C> 3 molar ratio in aluminates and the dry weight ratio of flocculant to coagulant. Table 2 compares the results of the precipitation of Cr (III) from its saline solution and Table 3 compares the effluent removal of the chromium compounds by dosing the aluminate and the anionic flocculant separately and using a pre-prepared mixture of the present invention.

The data presented in Table 1 confirm that stable mixtures of aluminate and anionic flocculant with sulfomethyl groups can be prepared by varying the dry weight ratio of coagulant to flocculant (100 to 1) over a very wide range. The least stable solutions contain very little anionic polyacrylamide (1% by weight on a dry aluminate basis), but such solutions can be prepared to avoid clouding for 2-3 weeks. The data in the table show that the more stable the mixtures, the more anionic groups the flocculant has and the more alkaline the coagulant (the higher the? Value). 1 month and longer clear aqueous mixtures with a flocculant of at least 10 mol. % sulfomethyl groups and Na ₂ O and Al ₂ C> 3 molar ratio in coagulant> 1.5. For comparison, solutions containing the same degree of polymerisation (50,000) of polyacrylamide having a carboxyl group instead of a sulfomethyl group (prototype close variant, Table 1, Nos. 14 and 15). In this case, it was much more difficult to produce stable mixtures because the polymer molecules had to contain at least 25 mol. % carboxyl groups, and they became more cloudy.

The compositions of the present invention are prepared by mixing pre-prepared aqueous solutions of coagulant and flocculant. Note: Aluminum and anionic flocculant solutions and mixtures thereof as usual in this species? products, must be prepared and diluted only with softened water, preferably deionized water, since the ions of divalent and polyvalent metals form insoluble complexes therewith, and mixtures may lose their stability for this reason alone.

Table I '1

Yesterday No. Anion. groups quantity flocculant, mol% [Na ₂ O]: [Al ₂ O ₃ ] aluminate Composition stability in days, in the presence of coagulant and flocculant masses relationship 100: 1 10: 1 1: 1 1 6th 1.5 12th 10th 10th 2 6th 2 10th 14th 14th o J 6th 4 > 30 > 30 > 30 4 11th 1.5 13th 14th 15th 5 11th 2 15th > 30 > 30 6th 11th 0 > 30 > 30 > 30 7th 17th 1.5 14th > 30 > 30 8th ^17th 2 > 30 > 30 > 30 9th 20th 1.5 18th > 30 > 30 10th 20th 2 > 30 > 30 > 30 11th 43 1.3 9th 13th 12th 12th 43 1.5 > 30 > 30 > 30 13th 43 2 > 30 > 30 > 30 14th * 21 1.5 coagulates 15th * 25 1.5 4 5-6 8th

Remarks: Solutions obtained by mixing saturated solutions of aluminates and 1.5% anionic sulphomethyl-containing polyacrylamides (degree of polymerization 50000); * modified polyacrylamide containing carboxy groups.

For practical purposes, it is important to produce solutions that are as concentrated as possible, taking into account transportation costs. The concentrations of the resulting mixtures are limited by the solubility of the sodium aluminates and the viscosity of the polymer solutions. Modern water treatment technologies typically use polyacrylamide flocculants with a molecular weight greater than 2 minutes. With anionic polyacrylamide MM = 3 min, a solution of about 3.5% can be readily prepared and subsequently mixed with the aluminate solutions. Flocculants

The binding properties improve with increasing molecular weight, but due to the increased viscosity, only about 2.5% by weight of the solution was dissolved in anionic polyacrylamide with MM = 6 min. The solubility of the aluminates themselves and the stability of their solutions depend on the conditions under which they are produced, most notably on the molar ratio of Na ₂ O to AI ₂ O 3 [See kn. 3anojibCKnfi AK, BapaH AA KoarynHHTbi n φηοκγηΗΗΤΗ b npoøeccax 04HCTKH BO / Ibi.-JIeHHHrpaa: Xhmhh, 1987, 204 c.]. The highest solubility is aluminate with a Na ₂ O and Al ₂ C> 3 molar ratio of about 1.5 and can be prepared as much as 65% solution of such coagulant containing the most active ingredient (23.9% by Al ₂ O 3). As the Na ₂ O content increases, the solubility of the aluminates and, most importantly, the active substance content decreases sharply. A 50% solution of aluminate with a = 4 is almost saturated and contains only about 10.9% of the active ingredient. When diluting saturated aluminate solutions with an average of 3% flocculant solution, the latter will need to be added in a large amount so that the mixture contains at least 1% anionic polymer by weight of dry aluminate, thus further reducing the coagulant concentration. Therefore, it is not appropriate to prepare aluminates with a> 4 for the preparation of mixtures.

It is easy to calculate mathematically that saturated solutions of aluminates and 3% flocculant can form compositions containing from 20 to 1% by weight of Al ₂ O ₃ and from 0.4 to 2.5% of anionic sulfomethyl-containing polyacrylamide. The mixtures, as confirmed in Example 5 below, may be diluted prior to use to a concentration suitable for dosing.

Table 4 shows the amount of trivalent chromium remaining in the solution after precipitation, when coagulant was first added to the chromium sulphate solution and after 5 min. flocculant (precipitation method I) or a pre-mixed mixture thereof (method II). No significant differences were observed in flocculation formation and sedimentation between the two methods, and Cr (IH) precipitation results with appropriate reagent concentrations

In case II, they were even better.

table

Well aluminate, mg / l by AI2O3 Anionic flocculant, mg / l » Cr (III) concentration in solution after of precipitation, mg / l I II 50 1.5 30.4 5.7 75 2.3 1.8 0.19 1-0 3 0.1 0.13

Remarks: Initial concentration of Cr (III) in solution - 130 mg / l; a molecular weight polyacrylamide flocculant containing 43 mol. % of sulfomethyl groups.

table

Well aluminum Anionic flocculant, mg / l Cr ** after deposition, mg / l a mg / l by AI2O3 I Π 1.5 75 2.5 1.4 2 2 50 2.5 2.2 2 2 75 2.5 1.5 1.4 2 100 2.5 0.6 0.6 0 0 75 2.5 1.7 2 4 75 2.5 1.8 2.7

** - total chromium, its initial concentration in effluent - 68.8 mg / l.

Using the same mixture of coagulant and flocculant for cleaning sheepskin finishing effluent, it was observed that the floccules were slightly finer and had a longer sitting time, but the final cleaning results were not inferior to those of the individual dosing regents (Table 3). The practical benefits are derived not so much from the quality of the cleaning as from the simpler cleaning technology of the present invention.

Specific examples of preparation of aqueous coagulant and flocculant compositions are described below.

Ί Example kg of aqueous 2.6% anionic polyacrylamide of molecular weight 3.7 min, having the formula [(-CH ₂ - CH) ". _m - (CH ₂ - CH-) _m ] "

I 1 conh ₂ conh

I. '

CH ₂ SO ₃ containing 10 mol. % solution of sufomethyl groups, the solution is mixed with 450 g of an aqueous solution of 65% aqueous sodium aluminate containing 23.9% of active substance by Al ₂ O ₃ and [Na ₂ O]: [Al ₂ O ₃ ] - 1.5. A solution is obtained containing 2.5% of anionic flocculant and 2.8% of dry matter (1.0% of Al ₂ O ₃ ) coagulant. The solution remains stable for more than 1 month.

sample kg of aqueous 3.5% anionic polyacrylamide having a molecular weight of 3.1 min containing 11 mol. % solution is mixed with 5.65 kg of an aqueous solution of 62% sodium aluminate 62%, containing 20.1% of the active ingredient by Al ₂ O ₃ and [Na ₂ O]: [Al ₂ O ₃ ] - 2. A solution is obtained containing 0.53% anionic flocculant and 52.6% dry matter (17.1% A1 ₂ O ₃ ) coagulant. The solution remains stable for 14 days.

sample kg of aqueous 3.5% anionic polyacrylamide having a molecular weight of 3.1 min containing 11 mol. % solution of sufomethyl groups, the solution is mixed with 7.45 kg of an aqueous solution of 47% sodium aluminate sodium hydroxide containing 10.2% of the active substance by Al ₂ O ₃ and [Na ₂ O]: [Al ₂ O ₃ ] = 4. A solution is obtained containing 0.4% anionic flocculant and 41.4% dry matter (9% Al ₂ O ₃ ) coagulant. The solution remains stable for more than 1 month.

Example 2 kg of aqueous 2% 6 min molecular weight anionic polyacrylamide containing 31 mol. % solution of sufomethyl groups, the solution is mixed with 3.07 kg of an aqueous solution of 65% sodium aluminate 65%, containing 23.9% of active substance by Al ₂ O ₃ and [Na ₂ O]: [Al ₂ O ₃ ] = 1.5 . A solution is obtained containing 1.5% anionic flocculant and 15.3% dry matter (5.8% AI2O3) coagulant. The solution remains stable for more than 1 month.

sample kg of aqueous 3% anionic polyacrylamide of molecular weight 4.4 min containing 43 mol. % sufomethyl groups, the solution is mixed with 5.4 kg of an aqueous solution of 65% sodium aluminate containing 23.9% by weight of the active ingredient in an Al2O3 and [Na2O-tAhCb] = 1.5 'solution. A solution is obtained containing 1.95% anionic flocculant and 19.5% dry matter (7.2% AI2O3) coagulant. The solution remains stable for more than 1 month.

The reconstituted solution is further diluted 1: 9 with water and stored in a closed container. It only starts to cloud after 19 days.

The examples confirm that stable aqueous sodium aluminate with a = [Na2O]: [Al2O3] = 1.5 + 4 and an anion containing> 10 mol. % sulfomethyl groups, polyacrylamide compositions in very different weight ratios (flocculant: aluminate = 1 + 100). The concentrations of the resulting mixtures are limited only by the solubility of the sodium aluminates and the viscosity of the polymer solutions. Solutions containing (20 + 1)% by weight of active substance coagulant, based on Al 2 O 3, and (0.4 + 2.5)% by weight of flocculant having a molecular weight of 3.5-6 min are easily prepared. Therefore, a combination of both water treatment reagents can be selected for each practical waste water treatment. The resulting mixtures can be further diluted with softened water (Example 5) to obtain solutions suitable for direct dosage. The compositions are stable enough to be prepared in advance and used for a long time. Another advantage of the present invention is the fact that it has been possible to formulate compositions with a very high molecular weight anionic polyacrylamide of 6 min (Example 4). This is very important because the longer the flocculant macromolecules, the larger and mechanically resistant the flocculants are, the faster their sedimentation and the better water separation. The proposed formulations simplify in practice the wastewater treatment technology by avoiding the separate dosing of coagulant and flocculant.

Claims (5)

Definition of the Invention An aqueous composition for destabilizing dispersion systems comprising sodium aluminate and vinyl polymer, wherein the vinyl polymer is an anionic polyacrylamide of the formula [(-CH ₂ -CH) _n . _m - (CH ₂ - CH -) m] n I I CONH ₂ CONH ' I CH ₂ SO _{3 The} weight ratio of sodium to sodium aluminate in dry matter is 1 + 100. 2. The composition of claim 1, wherein the molar ratio of Na ₂ O to Al ₂ O _{3 in} sodium aluminum is 1.5 + 4. 3. A composition according to claim 1, wherein the anionic polyacrylamide has> 10 mol. % of sulfomethyl groups. Composition according to claim 1, characterized in that the anionic polyacrylamide has a molecular weight of> 3 min, preferably 3.5 - ^ - 6 min. 5. A process for preparing a composition according to claim 1, which comprises mixing pre-prepared aqueous solutions of sodium aluminate and anionic polyacrylamide.