METHOD FOR TREATING SUSPENSIONS OF SOLID PARTICLES IN WATER USING AMPHOTERIC POLYMERS

Abstract

The present invention relates to an effluent treatment method for treating an aqueous effluent having solid particles, the method including the addition to the effluent of at least one water-soluble polymer comprising at least one non-ionic monomer and at least one anionic monomer obtained by controlled radical polymerization, the said polymer having a UL viscosity of between 2 and 4.5 cps.

Claims

1. An effluent treatment method for treating an aqueous effluent that contains solid particles, the method including the addition to the effluent of at least one water-soluble polymer comprising at least one non-ionic monomer and at least one anionic monomer obtained by controlled radical polymerization, the said polymer having a UL viscosity of between 2 and 4.5 cps.

2. A method according to claim 1 wherein the controlled radical polymerization is a polymerization by reversible addition-fragmentation chain transfer, RAFT (Reversible Addition Fragmentation Chain Transfer Polymerization).

3. A method according to claim 2 wherein the controlled radical polymerization is carried out with a control agent having the formula (I): ##STR00004## in which Z═O, S or N; R.sup.1 and R.sup.2, being identical or different, represent: a group (i): alkyl, acyl, alkenyl or alkynyl, linear or crosslinked, optionally substituted; or a carbon ring (ii), either saturated or unsaturated, optionally substituted or aromatic; or a heterocycle (iii), either saturated or unsaturated, optionally substituted or aromatic, it being possible for these groups and rings (i), (ii), and (iii) to be substituted by substituted aromatic groups; or the groups: alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxy (—COOH), acyloxy (—O.sub.2CR), carbamoyl (—CONR.sub.2), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (—OH), amino (—NR.sub.2), halogen, allyl, epoxy, alkoxy (—OR), S-alkyl, S-aryl; groups that are hydrophilic or ionic in nature such as the alkali salts of carboxylic acids, the alkali salts of sulfonic acid, polyalkylene oxide chains (polyoxyethylene POE, polyoxypropylene POP), cationic substituents (quaternary ammonium salts), R representing an alkyl or aryl group.

4. A method according to claim 1, wherein the controlled radical polymerization is carried out with a control agent having the formula (I): ##STR00005## in which Z═O, S or N; R.sup.1 and R.sup.2, being identical or different, represent: a group (i): linear or branched alkyl comprising from 1 to 20 carbons, preferably from 1 to 10 carbons, optionally substituted; linear or branched acyl comprising from 1 to 20 carbons, preferably from 1 to 10 carbons, optionally substituted; linear or branched alkenyl comprising from 2 to 20 carbons, preferably from 2 to 10 carbons, optionally substituted; or linear or branched alkynyl comprising from 2 to 20 carbons, preferably from 2 to 10 carbons, optionally substituted; or a carbon ring (ii), either saturated or unsaturated, optionally substituted or aromatic, comprising from 4 to 7 carbons, preferentially from 5 to 6 carbons; or a heterocycle (iii), either saturated or unsaturated, optionally substituted or aromatic, comprising 1, 2 or 3 heteroatoms selected from O, N or S, and from 3 to 6 carbons, preferentially from 4 to 5 carbons; it being possible for these groups and rings (i), (ii), and (iii) to be substituted by substituted aromatic groups; or the groups: alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxy (—COOH), acyloxy (—O.sub.2CR), carbamoyl (—CONR.sub.2), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (—OH), amino (—NR.sub.2), halogen, allyl, epoxy, alkoxy (—OR), S-alkyl, S-aryl; groups that are hydrophilic or ionic in nature such as the alkali salts of carboxylic acids, the alkali salts of sulfonic acid, polyalkylene oxide chains (polyoxyethylene POE, polyoxypropylene POP), cationic substituents (quaternary ammonium salts); R representing a linear or branched alkyl group comprising from 1 to 20 carbons, preferably from 1 to 10 carbons, or aryl comprising from 6 to 10 carbon atoms.

5. A method according to claim 4 wherein in formula (I) Z═O.

6. A method according to claim 5 wherein in formula (I) R.sup.1 and R.sup.2, being identical or different, represent a group (i): linear or branched alkyl comprising from 1 to 20 carbons, preferably from 1 to 10 carbons; linear or branched acyl comprising from 1 to 20 carbons, preferably from 1 to 10 carbons; linear or branched alkenyl comprising from 2 to 20 carbons, preferably from 2 to 10 carbons; or linear or branched alkynyl comprising from 2 to 20 carbons, preferably from 2 to 10 carbons; these groups being optionally substituted by one or more substituted aromatic groups comprising from 4 to 7 carbons; or the groups: alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxy (—COOH), acyloxy (—O.sub.2CR), carbamoyl (—CONR.sub.2), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (—OH), amino (—NR.sub.2), halogen, allyl, epoxy, alkoxy (—OR), S-alkyl, S-aryl; groups that are hydrophilic or ionic in nature such as the alkali salts of carboxylic acids, the alkali salts of sulfonic acid, polyalkylene oxide chains (polyoxyethylene POE, polyoxypropylene POP), cationic substituents (quaternary ammonium salts); R representing a group: linear or branched alkyl comprising from 1 to 20 carbons, preferably from 1 to 10 carbons; or aryl comprising from 6 to 10 carbon atoms.

7. A method according to claim 1, wherein the controlled radical polymerization is carried out with a control agent having the formula (II): ##STR00006##

8. A method according to claim 1, wherein the effluent is: A mining operation effluent, deriving from coal mines, diamond mines, phosphate mines, metal mines such as aluminum, platinum, iron, gold, copper, silver; or An effluent from bituminous sands or oil sands mining operations; or An effluent that contains from 5 to 70% by mass, preferably from 20 to 50% by mass, more preferentially from 30 to 40% by mass, of solid particles; or An effluent that comprises sand, clay and water; or An effluent that comprises sand, clay, water and residual bitumen; or An effluent that comprises fresh tailings; or An effluent that comprises fine tailings; or An effluent that comprises fresh fine tailings (FFT or RFF for ‘résidus fins frais’); or An effluent that comprises mature fine tailings (MFT or RFM for ‘rësidus fins mûrs’).

9. A method according to claim 1, wherein the said polymer has a UL viscosity of between 2.5 and 4.2 cps.

10. A method according to claim 1, wherein the non-ionic monomer is selected from acrylamide, methacrylamide; N-isopropylacrylamide; N,N-dimethylacrylamide; N,N diethylacrylamide; N-methylolacrylamide; N-vinylformamide; N-vinyl acetamide; N-vinylpyridine; N-vinylpyrrolidone; acryloyl morpholine (ACMO), glycidyl methacrylate, glyceryl methacrylate, and diacetone acrylamide.

11. A method according to claim 1, wherein the anionic monomer is selected from among acrylic acid; methacrylic acid; itaconic acid; crotonic acid; maleic acid; fumaric acid; 2-acrylamido-2-methylpropane sulfonic acid; vinyl sulfonic acid; vinylphosphonic acid; allylsulfonic acid; allylphosphonic acid; styrene sulfonic acid, the said anionic monomer being non-salified, partially or totally salified, and the salts of 3-sulfopropyl methacrylate.

12. A method according to claim 1, wherein the polymer is obtained from acrylamide and acrylic acid.

13. (canceled)

14. A composition comprising an aqueous effluent that contains solid particles, at least one water-soluble polymer comprising at least one non-ionic monomer and at least one anionic monomer obtained by controlled radical polymerization, the said polymer having a UL viscosity of between 2 and 4.5 cps.

Description

LIST OF FIGURES

[0090] FIG. 1 represents the NWR (Net Water Release) according to the dosage of the counterexample and the CRP polymers

[0091] FIG. 2 represents the NWR according to the dosage of the counterexample and of the CRP polymer 1

[0092] FIG. 3 represents the NWR according to the dosage of the counterexample and of the CRP polymers

[0093] FIG. 4 represents the NWR according to the dosage of the polymers A and A′

[0094] FIG. 5 represents the NWR according to the dosage of the polymers B and B′

[0095] FIG. 6 represents the NWR according to the dosage of the polymers C and C′

[0096] FIG. 7 represents the NWR according to the dosage of the polymers D and D′

[0097] FIG. 8 represents the NWR according to the dosage of the polymers E and E′

[0098] FIG. 9 represents the NWR according to the dosage of the polymers F and F′

[0099] FIG. 10 represents the reversible equilibrium between a dormant and an active species

EXAMPLES

[0100] Protocol for UL Viscosity Test:

[0101] 500 mg of polymer are added to 490 ml of a solution of deionised water. After complete dissolution of the polymer, 29.25 grams of NaCl are added therein.

[0102] The viscosity is measured making use of a digital Brookfield Viscometer DVII+ with a rotational speed of 60 revolutions/minute at 25° C. (module UL).

[0103] Protocol for Flocculation Test:

[0104] First, the polymers are dissolved in deionised water in order to obtain aqueous solutions having a concentration of 0.4% by weight of polymer relative to the total weight of the solution. All of these solutions are mechanically agitated at 500 rpm until the polymers are completely dissolved and clear and homogeneous solutions are obtained. For each test, the appropriate volume of polymer solution is added to 200 g of MFT and then the complete mixture is mixed manually until such time as flocculation and optimum water release are observed.

[0105] The NWR represents the “Net Water Release”. It corresponds to the total amount of water recovered during the flocculation test minus the amount of water that gets added unduly during incorporation of the aqueous polymer solution in the suspension.

Example 1: Synthesis of a Poly(Acrylamide-Co-Sodium Acrylate) Copolymer by the Uncontrolled Conventional Free Radical Polymerization Route (Counter-Example)

[0106] A 1.5 l reactor equipped with a mechanical agitator, a thermometer, and a nitrogen inlet is loaded with distilled water, acrylamide (AM) and acrylic acid (AA) based on the following composition: [0107] Acrylamide: 70 mole % [0108] Acrylic acid: 30 mole %

[0109] The mixture obtained is homogenized and then cooled, neutralized with sodium hydroxide to pH=7.6-7.7 and finally degassed under a stream of nitrogen. The polymerization is then initiated using a redox system (initiator). The resulting gel obtained after polymerization is subsequently ground and dried in a drying kiln so as to obtain a powder.

[0110] The UL viscosity of the reference polymer is 3.5 cps.

Example 2: Synthesis of Poly(Acrylamide-Co-Sodium Acrylate) Copolymers by CRP According to the Invention (CRP 1)

[0111] A 1.5 l reactor equipped with a mechanical agitator, a thermometer, and a nitrogen inlet is loaded with distilled water, acrylamide (AM) and acrylic acid (AA) based on the following composition: [0112] Acrylamide: 70 mole % [0113] Acrylic acid: 30 mole %

[0114] The mixture obtained is homogenised and then cooled, neutralised with sodium hydroxide to pH=7.6-7.7 and finally degassed under a stream of nitrogen. The polymerisation is then initiated using a redox system (initiator), but in the presence of a radical polymerisation control agent having the formula (II). The resulting gel obtained after polymerisation is subsequently ground and dried in a drying kiln so as to obtain a powder. The UL viscosity of the polymer CRP 1 is 3.5 cps.

Example 3: Synthesis of Poly (Acrylamide-Co-Sodium Acrylate) Copolymers by CRP According to the Invention (CRP 2)

[0115] The copolymer CRP 2 is synthesised under the same conditions as in Example 1, while replacing the sodium hydroxide with potassium hydroxide.

[0116] The UL viscosity of the polymer CRP 2 is 3.5 cps.

Example 4: Flocculation of an MFT (29.2% by Weight of Dry Extract)

[0117] The flocculation tests are carried out on a suspension of mature fine tailings (MFT) derived from bituminous sands mining operations with a solids content of 29.2% by weight. The results obtained with the reference sample and the products CRP 1 and 2 are grouped together in FIG. 1. The results of these experiments show that the effect of overdosing of the two products CRP 1 and CRP 2 occurs at dosages that are much higher than that of the counter-example.

Example 5: Flocculation of an MFT (33.2% by Weight of Dry Extract)

[0118] The flocculation tests are carried out on a suspension of mature fine tailings (MFT) derived from bituminous sands mining operations with a solids content of 33.2% by weight. The results obtained with the reference sample and the product CRP 1 are grouped together in FIG. 2. The results of these experiments show that the effect of overdosing of the product CRP 1 occurs at dosages that are higher than that of the reference product. In addition, the increase in the dosage of the polymer CRP 1 makes it possible to achieve LNE (NWR) values that are higher and never achieved by the reference product.

Example 6: Flocculation of an MFT (31.7% by Weight of Dry Extract)

[0119] The flocculation tests are carried out on a suspension of mature fine tailings (MFT) derived from bituminous sands mining operations with a solids content of 31.7% by weight. The results obtained with the reference sample and the products CRP 1 and 2 are grouped together in FIG. 3. The results of these experiments show that the products CRP 1 and 2 have an optimal dosage that is much lower than that of the reference product and thus lead to LNE (NWR) values that are significantly higher and never achieved by the reference product.

Example 7: Flocculation of an MFT (32.0% by Weight of Dry Extract)

[0120] Two series of six water-soluble polymers having UL viscosity of between 3.0 and 6.3 cps were prepared. One counter-example series wherein the water-soluble polymers are obtained according to the method described in Example 1 and one series referred to as “CRP” wherein the water-soluble polymers are obtained according to the method described in Example 2. The flocculation tests are carried out on a suspension of mature fine tailings (MFT) derived from bituminous sands mining operations with a solids content of 32.0% by weight. For each test, the results obtained are compared with a counter-example water-soluble polymer and a “CRP” water-soluble polymer having similar UL viscosities.

TABLE-US-00001 TABLE 1 Counter- Example CRP Water- UL Water- UL Soluble Viscosity Soluble Viscosity Polymer (cps) Polymer (cps) A 3 A’ 3 B 3.8 B’ 3.8 C 4.2 C’ 4.2 D 5.2 D’ 5.2 E 5.7 E’ 5.7 F 6.3 F’ 6.3 UL viscosity of the counter-example polymers and of the CRP polymers according to the invention

[0121] It is observed that, at equivalent UL, the CRP water-soluble polymers systematically lead to better performance than the reference water-soluble polymers (higher NWR values and wider dosage range) as long as the UL viscosity remains lower than or equal to 4.20 cps (FIGS. 4, 5 and 6). Above this value, there is almost no difference observed between the CRP water-soluble polymers and the reference water-soluble polymers (FIGS. 7, 8 and 9).