Controlling the rheology of a metal ore residue

Abstract

A method for preparing an aqueous mineral suspension from an aqueous metal ore residue may include introducing into the aqueous metal ore residue a polymer (P) having a molecular mass Mw measured by GPC ranging from 2,000 to 20,000 g/mol. The polymer (P) may be prepared by radical polymerization of at least one anionic monomer (M). The suspension produced by such a method may have a Brookfield viscosity of which is lower than 1,800 mPa.Math.s or a yield point of lower than 80 Pa.

Claims

1. A method for preparing an aqueous mineral suspension, the method comprising: combining, with an aqueous metal ore residue, a material comprising a polymer (P), wherein the polymer (P) has a molecular mass Mw, measured by GPC, in a range of from 2,000 to 20,000 g/mol, wherein the polymer (P) is prepared by a process comprising a radical polymerization, at a temperature greater than 50 C., of a monomer comprising an anionic monomer (M) comprising a polymerizable olefinic unsaturation and a carboxylic acid group, optionally in salt form, in the presence of a reagent comprising hydrogen peroxide, benzoyl peroxide, acetyl peroxide, laurel peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, an alkaline metal persulfate, and/or an azo compound, optionally as a combination or association comprising an Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion, as a radical-generator, and wherein the aqueous mineral suspension has a dry solid content greater than 40 wt. % of the aqueous mineral suspension, and wherein the aqueous mineral suspension has: (i) a Brookfield viscosity, measured at 100 rpm and at 25 C., of less than 1,800 mPa.Math.s, and/or (ii) a flow threshold, measured at a temperature of 25 C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, of less than 80 Pa.

2. The method of claim 1, wherein the aqueous mineral suspension has a viscosity of less than 1,500 mPa.Math.s.

3. The method of claim 1, wherein the aqueous mineral suspension has a flow threshold of less than 70 Pa.

4. The method of claim 1, wherein the aqueous mineral suspension has a dry solids content greater than 50 wt. %.

5. The method of claim 1, wherein the aqueous mineral suspension comprises the polymer (P) in a range of from 0.01 to 2 wt. % dry, relative to dry aqueous metal ore residue weight.

6. The method of claim 1, wherein the polymer (P) is one polymer.

7. The method according to claim 1, wherein the aqueous metal ore residue comprises a lithium, strontium, lanthanide, actinide, uranium, rare earth, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, tin, and/or lead ore.

8. The method of claim 1, wherein the combining of the polymer (P) with the aqueous metal ore residue occurs: before pumping the aqueous metal ore residue; during pumping the aqueous metal ore residue; after pumping the aqueous metal ore residue; before flocculation of the aqueous metal ore residue; during flocculation of the aqueous metal ore residue; after flocculation of the aqueous metal ore residue; before concentration of the aqueous metal ore residue; during concentration of the aqueous metal ore residue; after concentration of the aqueous metal ore residue; before conveying the aqueous metal ore residue; before storing the aqueous metal ore residue, or during storing the aqueous metal ore residue.

9. The method of claim 1, wherein, in the radical polymerization, the reagent further comprises a first compound comprising phosphorus in the oxidation I state, a second compound comprising phosphorus in the oxidation III state, a third compound comprising a bisulfite ion, a xanthate derivative, a mercaptan compound, and/or a compound of formula (I) in a range of from 0.05 to 5 et. %, relative to a total monomer weight: ##STR00003## X independently being H, Na, or K, and R independently being a C.sub.1-C.sub.5-alkyl group; or wherein the radical polymerization is carried out at a temperature in a range of from 50 to 98 C.; or wherein the radical polymerization is carried out in a medium comprising water and/or a solvent; or wherein the monomer in the radical polymerization comprises: the anionic monomer (M) in 100 wt. %; or the anionic monomer (M) in a range of from 70 to 99.5 wt. % and a second monomer in a range of from 0.5 to 30 wt. %.

10. The method of claim 1, wherein the anionic monomer (M) comprises a first carboxylic acid group.

11. The method of claim 1, wherein the monomer in the radical polymerization further comprises: a second anionic monomer; 2-acrylamido-2-methylpropanesulfonic acid, a salt of 2-acrylamido-2-methylpropanesulfonic acid, 2-(methacryloyloxy)ethanesulfonic acid, a salt of 2-(methacryloyloxy)ethanesulfonic acid, and/or sodium methallyl sulfonate, styrene sulfonate; a non-ionic monomer comprising a polymerizable olefinic unsaturation; and/or a monomer of formula (II): ##STR00004## wherein: R.sup.1 and R.sup.2, are independently H or CH.sub.3, L.sup.1 is independently C(O), CH.sub.2, CH.sub.2CH.sub.2, or OCH.sub.2CH.sub.2CH.sub.2CH.sub.2, L.sup.2 is independently (CH.sub.2CH.sub.2O).sub.x, (CH.sub.2CH(CH.sub.3)O).sub.y, and/or (CH(CH.sub.3)CH.sub.2O).sub.z, and x, y, and z, are independently an integer or decimal in a range of from 0 to 150, with a sum of x, y, and z being in a range of from 10 to 150.

12. An aqueous mineral suspension, comprising: an aqueous metal ore residue; and a polymer (P) with a molecular mass Mw, measured by GPC, in a range of from 2,000 to 20,000 g/mol, wherein the polymer (P) is prepared by a process comprising radically polymerizing, at a temperature greater than 50 C., a monomer comprising an anionic monomer (M) comprising a polymerizable olefinic unsaturation and a carboxylic acid group, optionally in salt form, in the presence of a reagent comprising hydrogen peroxide, benzoyl peroxide, acetyl peroxide, laurel peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulphate, an alkaline metal persulphate, and/or an azo compound, optionally as combination or association comprising an Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion, as a radical generator, wherein the aqueous mineral suspension has a dry solids content greater than 50 wt. %, and has (i) a Brookfield viscosity, measured at 100 rpm and at 25 C., of less than 1,800 mPa.Math.s, and/or (ii) a flow threshold measured at a temperature of 25 C. using a rheometer with imposed shearing, equipped with a bladed spindle, for a particular torsional loading, of less than 80 Pa.

13. The method of claim 1, wherein the aqueous mineral suspension has a flow threshold greater than 10 Pa and less than 80 Pa.

14. The method of claim 1, wherein the aqueous mineral suspension has a flow threshold greater than 10 Pa and less than 70 Pa.

15. The method of claim 1, wherein the polymer (P) comprises a first polymer and a second polymer, the first and second polymers being different.

16. The method of claim 1, wherein the polymer (P) comprises a first polymer, a second polymer, and a third polymer, the first, second, and third polymers being different.

17. The method of claim 1, wherein the material in the combining further comprises a lignosulfonate derivative, a silicate, an unmodified polysaccharide, and/or a modified polysaccharide, optionally combined separately from the polymer (P).

18. The method according to claim 1, wherein the aqueous metal ore residue comprises a metal oxide, a metal sulfide, or a metal carbonate.

19. The method according to claim 1, wherein the aqueous metal ore residue comprises a residual amount of a metal of less than 2,000 g dry per ton, relative to total aqueous metal ore residue dry weight.

20. The method of claim 1, wherein the polymer (P) has a molecular mass Mw, measured by GPC, in a range of from 2,200 to 10,000 g/mol, and/or wherein the polymer (P) is at least partially neutralized.

Description

EXAMPLES

(1) The following examples illustrate the various aspects of the invention.

(2) The polymers used in the method according to the invention are prepared.

(3) Polymer (P1) is prepared by placing 156 g of water and 0.013 g of iron sulphate heptahydrate into a one-litre glass reactor with mechanical stirring and oil bath heating.

(4) Using a dosing pump, 271 g of acrylic acid at 100% by weight are weighed into a 500 mL beaker.

(5) Using a dosing pump, 3.3 g of persulphate diluted with 15 g of water are weighed into a 20 mL test tube.

(6) Using a dosing pump, 115 g of sodium bisulphite at 40% by weight are weighed into a 200 mL test tube.

(7) The reactor is heated to 80 C.

(8) 30% of the persulphate solution is injected rapidly and then the remainder of this solution, the acrylic acid and the bisulphite solution are injected in parallel in: 3 h for the acrylic acid and 3.5 h for the persulphate and the bisulphite.

(9) The reaction medium is kept at 80 C.

(10) The medium is then heat-treated for 30 minutes with a solution of 0.3 g of persulphate in 4 g of water and then 4.5 g of hydrogen peroxide at 130 V.

(11) Lastly, the pumps are rinsed with water.

(12) The medium is heated again for 60 min at 80 C.

(13) The solution is then neutralised using 50% by weight of sodium hydroxide in water until it reaches pH 8 and then diluted to a solids content of 42% by weight. Polymer (P1) is obtained, with a molecular mass Mw, measured by GPC, of 2,500 g/mol.

(14) Polymer (P2) is prepared by placing 212 g of water and 0.08 g of iron sulphate heptahydrate into a one-litre glass reactor with mechanical stirring and oil bath heating.

(15) Using a dosing pump, 303 g of acrylic acid at 100% by weight and 15 g of water are weighed into a 500 mL beaker.

(16) Using a dosing pump, 25.6 g of sodium hypophosphite monohydrate diluted with 30 g of water are weighed into a 100 mL test tube.

(17) Using a dosing pump, 21 g of hydrogen peroxide at 130 V and 35 g of water are weighed into a 100 mL test tube.

(18) The reactor is heated to 95 C. and the monomer, the hypophosphite solution and the hydrogen peroxide solution are added in parallel in 120 min while keeping the temperature of the reaction medium at 95 C.

(19) Lastly, the pumps are rinsed with water.

(20) The medium is heated again for 60 min at 95 C.

(21) The solution is then neutralised using 50% by weight of sodium hydroxide in water until it reaches pH 8 and then diluted to a solids content of 42% by weight. Polymer (P2) is obtained, with a molecular mass, measured by GPC, of 4,500 g/mol.

(22) The raw material used for this series of tests is an aqueous metal ore residue from a Chilean copper mine located in the north of the country. This is waste resulting from the separation of the ore containing the useable metal from the rock extracted from the mine. This aqueous copper ore residue is in the form of a water-based suspension.

(23) Various measures were taken beforehand on the aqueous residue in the absence of the polymer according to the invention: particle size distribution using a Mastersizer 2000 laser granulometer (Malvern), solid content using a Mettler-Toledo dry balance, Brookfield viscosity at 100 rpm using a Brookfield DV3T viscometer with a suitable spindle, flow limit value using a Brookfield DV3T viscometer using a winged module and flow speed using a No. 4 Ford Cup viscometer.

(24) The particle size distribution by volume shows the presence of multiple particle populations with different sizes: D(0.1)=1.6 m, D(0.5)=25 m, D(0.84)=195 m, D(0.9)=252 m, and D(0.99)=501 m.

(25) The other characteristics are shown in Table 1.

(26) TABLE-US-00001 TABLE 1 % Solids content 55.8 Brookfield viscosity at 100 rpm, in mPa .Math. s 1,220 pH 10.0 Conductivity in S/cm 2,700 Viscosity, No. 4 Ford cup, in s 25

(27) A concentration of the aqueous residue is then prepared by decanting and separating a portion of the supernatant water to form an aqueous residue whose characteristics are shown in Table 2.

(28) TABLE-US-00002 TABLE 2 % Solids content 60.5 Brookfield viscosity at 100 rpm, in mPa .Math. s 3,016 pH 10.1 Conductivity in S/cm 2,320 Viscosity, No. 4 Ford cup, in s /

(29) A sample of suspension of aqueous residue of reconcentrated copper ore is transferred into a 500 mL beaker and then mechanically stirred with a Raynerie mixer. Stirring varies from 800 to 1,000 rpm.

(30) Then, a polymer (P1) according to the invention is added (0.1% by weight dry/dry) and the mixture is left under stirring for 5 to 10 min.

(31) Stirring is then stopped to allow the Brookfield viscosities, pH and conductivity measures to be taken. The test is repeated, adding different amounts of polymer. The results are shown in Table 3.

(32) TABLE-US-00003 TABLE 3 Polymer (P1) % by weight dry/dry of Brookfield viscosity at Conductivity polymer 100 rpm (mPa .Math. s) pH (S/cm) 0 3,032 9.9 2,410 0.07 1,374 9.9 2,580 0.09 1,186 9.9 2,560 0.1 1,070 9.9 2,590

(33) A dose of 0.1% by weight dry/dry of polymer (P1) makes it possible to significantly reduce the viscosity of the aqueous residue. The aqueous suspension of copper ore residue can then be handled easily.

(34) Another test is conducted without any polymer and with two polymers (P1) and (P2) according to the invention at this dose of 0.1% by weight dry/dry. The results are shown in Table 4.

(35) TABLE-US-00004 TABLE 4 Residue without with polymer with polymer additive (P1) (P2) % by weight dry/dry 0 0.1 0.1 pH 10.1 9.9 9.3 Conductivity in 2,320 2,590 2,940 % Solids content 60.5 60.9 60.5 Brookfield viscosity at 3,016 1,070 1,188 100 rpm (mPa .Math. s)

(36) A dose of 0.1% by weight dry/dry of polymer (P1) or of polymer (P2) thus also makes it possible to significantly reduce the viscosity of the aqueous residue.

(37) The flow threshold of this aqueous copper ore residue with a solids content of 61% was then measured at a temperature of 25 C. using a Brookfield DV3T rheometer with imposed shearing, equipped with a spindle with suitable blades. Without destroying the underlying structure, the bladed spindle is immersed into the material up to the first immersion mark.

(38) After a five-minute wait time, the measure is taken without pre-shearing at a speed of 0.5 rpm. This relatively low speed is preferred so as to minimise the inertia effect of the bladed spindle. The variation in torsional loading measured by the instrument in order to maintain a spin speed of 0.5 rpm is tracked over time.

(39) The value of the flow limit or flow threshold of the aqueous residue is indicated by the instrument when this variation is zero. The results obtained are shown in Table 5.

(40) TABLE-US-00005 TABLE 5 Residue Flow Threshold (Pa) Time without with polymer with polymer (min) additive (P1) (P2) 0 55 32 26 2 60 48 37 4 58 46 36 6 55 42 33 8 / 38 31 10 / 33 30 12 54 31 27 14 / 29 28 16 / / / 18 / / / 20 50 28 28

(41) Aqueous suspensions of aqueous copper ore residue with a solids content of 58%, with or without polymers (P1) and (P2), are then prepared according to the invention. The characteristics of these suspensions are measured. The results obtained are shown in Table 6.

(42) TABLE-US-00006 TABLE 6 Residue without with polymer with polymer additive (P1) (P2) % by weight dry/dry 0 0.1 0.1 pH 9.8 10.0 10.0 Conductivity in 2,160 2,770 2,820 Brookfield viscosity at 2,196 838 824 100 rpm (mPa .Math. s)

(43) It can thus be seen that aqueous suspensions of reference copper residue with a solids content of 55%, 61% or 58% have high viscosities.

(44) The addition of polymer (P1) or of polymer (P2) according to the invention makes it possible to significantly lower these viscosities as well as to control the flow threshold of these suspensions.

(45) With the polymers according to the invention, it is therefore possible to disperse aqueous copper ore residues, in particular at the output of a thickener, which have high solids contents while controlling their rheology.