CA2222996C - Method of depressing non-sulfide silicate gangue minerals - Google Patents

Abstract

A method for the depression of non-sulfide, silicate gangue minerals is provided wherein the depressant is either (1) a polymeric material comprising recurring units of the formula: -[-X-]-x -[-Y-]-y -[-Z-] -z wherein X is the polymerization residue of an acrylamide or mixture of acrylamides, Y is an hydroxy group containing polymer unit, Z is an anionic group containing polymer unit, x represents a residual mole fraction of at least about 35 %, y represents a residual mole fraction of from about 1 to 50 % and z represents a residual mole fraction of from about 0 to about 50 %, or (2) a mixture of said polyme r and a polysaccharide.

Description

METHOD OF DEPRESSING NON-SULFIDE SILICATE GANGUE MINERALS
BACKGROUND OF INVENTION

The present invention relates to froth flotation processes for recovery of value sulfide minerals from base metal sulfide ores. More particulariy, it relates to a method for the depression of non-sulfide silicate gangue minerals in the beneficiation of value sulfide minerals by froth flotation procedures.
Certain theory and practice states that the success of a sulfide flotation process depends to a great degree on reagents called collectors that impart selective hydrophobicity to the mineral value which has to be separated from other minerals.
Certain other important reagents, such as the modifiers, are also responsible for the successful flotation separation of the value sulfide and other minerals.
Modifiers include, but are not necessarily limited to, all reagents whose principal function is neither collecting nor frothing, but usually one of modifying the surface of the mineral so that it does not float.
In addition to attempts at making sulfide collectors more selective for value sulfide minerals, other approaches to the problem of improving the flotation separation of value sulfide minerals have included the use of modifiers, more particularly depressants, to depress the non-sulfide gangue minerals so that they do not float along with sulfides thereby reducing the levels of non-sulfide gangue minerals reporting to the concentrates.
A depressant is a modifier reagent which acts selectively on certain unwanted minerals and prevents or inhibits their flotation.
In sulfide value mineral flotation, certain non-sulfide silicate gangue minerals present a unique problem in that they exhibit natural floatability, i.e. they float independent of the sulfide value mineral collectors used. Even if very selective sulfi(Je value mineral collectors are used, these silicate minerals report to the sulfide concentrates. Talc and pyrophyllite, both belonging to the class of magnesium silicates, are particulariy troublesome in that they are naturally highly hydrophobic. Other magnesium silicate minerals belonging to the classes of olivines, pyroxenes, and serpentine exhibit various degrees of floatability that seems to vary from one ore deposit to the other. The presence of these unwanted minerals in sulfide value mineral concentrates causes many problems i.e. a) they increase the mass of the concentrates thus adding to the cost of handling and transportation of the concentrate, b) they compete for space in the froth phase during the flotation stage thereby reducing the overall sulfide value mineral recovery, and c) they dilute the sulfide concentrate with respect to the value sulfide mineral content which makes them less suitable, and in some cases unsuitable, for the smelting thereof because they interfere with the smelting operation.
The depressants commonly used in sulfide flotation include such materials as inorganic salts (NaCN, NaHS, S02, sodium metabisulfite etc) and small amounts of organic compounds such as sodium thioglycolate, mercaptoethanol etc. These depressants are known to be capable of depressing sulfide minerals but are not known to be depressants for non-sulfide minerals, just as known value sulfide collectors are usually not good collectors for non-sulfide value minerals. Sulfide and non-sulfide minerals have vastly different bulk and surface chemical properties. Their response to various chemicals is also vastly different. At present, certain polysaccharides such as guar gum and carboxy methyl cellulose, are used to depress non-sulfide silicate gangue minerals during sulfide flotatibn.
Their performance, however, is very variable and on some ores they show unacceptable depressant activity and the effective dosage per ton of ore is usually very high (as much as 1 to 10 Ibs/ton). Their depressant activity is also influenced by their source and is not consistent from batch to batch. Furthermore, these polysaccharides are also valuable sources of food i.e. their use as depressants reduces their usage as food and, storage thereof presents particular problems with regard to their attractiveness as food for vermin.
Lastly, they are not readily miscible or soluble in water and even where water solutions thereof can be made, they are not stable. U.S. Patent 4,902,764 (Rothenberg et al.) describes the use of polyacrylamide-based synthetic copolymers and terpolymers for use as sulfide mineral depressants in the recovery of value sulfide minerals. U.S.
Patent 4,720,339 (Nagaraj et al) describes the use of polyacrylamide-based synthetic copolymers and terpolymers as depressants for silicious gangue minerals in the flotation beneficiation of non-sulfide value minerals, but not as depressants in the beneficiation of sulfide value minerals. The '339 patent teaches that such polymers are effective for silica depression during phosphate flotation which also in the flotation stage uses fatty acids and non-sulfide collectors. The patentees do not teach that such polymers are effective depressants for non-sulfide silicate gangue minerals in the recovery of value sulfide minerals. In fact, such depressants do not exhibit adequate depressant activity for non-sulfide silicate minerals during the beneficiation of sulfide value minerals. U.S. Patent 4,220,525 (Petrovich) teaches that polyhydroxyamines are useful as depressants for gangue minerals including silica, silicates, carbonates, sulfates and phosphates in the recovery of non-sulfide mineral values. Illustrative examples of the polyhydroxyamines disclosed include aminobutanetriols, aminopartitols, aminohexitols, aminoheptitols, aminooctitols, pentose-amines, hexose amines, amino-tetrols etc. U.S. Patent 4,360,425 (Lim et al) describes a method for improving the results of a froth flotation process for the recovery of non-sulfide mineral values wherein a synthetic depressant is added which contains hydroxy and carboxy functionalities. Such depressants are added to the second or amine stage flotation of a double float process for the purpose of depressing non-sulfide value minerals such as phosphate minerals during amine flotation of the siliceous gangue from the second stage concentrate. This patent relates to the use of synthetic depressant during amine flotations only.
In view of the forgoing and especially in view of the teachings of U.S.
4,902,764 which teaches the use of certain polyacrylamide-based copolymers and terpolymers for sulfide mineral depression during the recovery of value sulfide minerals, we have unexpectedly found that certain polymers, alone or in conjunction with polysaccharides, are indeed excellent depressants for non-sulfide silicate gangue minerals (such as talc, pyroxenes, olivines, serpentine, pyrophyllite, chlorites, biotites, amphiboles, etc). This result is unexpected because such depressants have been disclosed only as sulfide gangue depressants. These synthetic depressants have now been found to be excellent altematives to the polysaccharides used currently alone since they, and the blends with polysaccharides, are readily miscible or soluble in water, are non-hazardous and their water solutions are stable. The use thereof will increase the availability of the polysaccharides as a valuable human food source and their performance is not variable. They can be manufactured to adhere to stringent specifications and, accordingly, batch-to-batch consistency is guaranteed. The synthetic polymers lend themselves readily to modification of their structure, thereby permitting tailor-making of depressants for a given application.

SUMMARIo OF THE INVENTION
In accordance with the present invention there is provided a method which comprises beneficiating value sulfide minerals from ores with the selective rejection of non-sulfide silicate gangue minerals by:
a. providing an aqueous pulp slurry of finely-divided, liberation-sized ore particles which contain said value sulfide minerals and said non-sulfide silicate gangue minerals;
b. conditioning said pulp slurry with an effective amount of non-sulfide silicate gangue mineral depressant, a value sulfide mineral collector and a frothing agent, said depressant comprising either (1) a polymer comprising:
(i) x units of the formula:

X

(ii) y units of the formula:

(iii) z units of the formula:

Z

wherein X is the polymerization residue of an acrylamide monomer or mixture of acrylamide monomers, Y is an hydroxy group containing polymer unit, Z is an anionic group containing polymer unit, x represents a residual mole percent fraction of at least about 35%, y is a mole percent traction ranging from about 1 to about 50% and z is a mole percent fraction ranging from about 0 to about 50% or (2) a mixture of said polymer and a polysaccharide, and c. coliecting the value sulfide mineral having a reduced content of non-sulfide silicate gangue minerals by froth flotation.
In embodiments, glyoxylated polyacrylamide can be used as depressant, provided that it contains less than 50 mole percent glyoxylated amide units as the y units.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS
The polymer depressants of the above formula may comprise, as the (i) units, the polymerization residue of such acrylamides as acrylamide per se, alkyl acrylamides such as methacrylamide, ethacrylamide and the like.
The (ii) units may comprise the polymerization residue of monoethylenically unsaturated hydroxyl group containing copolymerization monomers such as hydroxyalkylacrylates and methacrylates e.g. 1,2-dihydroxypropyl acrylate or methacrylate;
hydroxyethyl acrylate or methacrylate; glycidyl methacrylate, acrylamido glycolic acid;
hydroxyal kylacrylam ides suchas N-2-hydroxyethylacryiamide; N-1-hydroxypropylacrylamide;
N-bis(1,2-dihydroxyethyl)acrylamide; N-bis(2-hydroxypropyl)acrylamide; and the like.
It is preferred that the (ii) units monomers be incorporated into the polymeric depressant by copolymerization of an appropriate hydroxyl group containing monomer, however, it is also permissible to impart the hydroxyl group substituent to the already polymerized monomer residue by, for example, hydrolysis thereof or post-reaction of a group thereof susceptible to attachment of the desired hydroxyl group with the appropriate reactant material e.g. giyoxal,.such as taught in U.S. 4,902,764.
Glyoxylated polyacrylamide should, however, contain less than about 50 mole percent glyoxylated amide units, i.e. preferably less than about 40 mole percent, more preferably less than 30 mole percent, as the Y units. It is preferred that the Y units of the above formula be a non-a-hydroxyl group of the structure -ECH2 CH~-Ca0 A-CHR- (CHR~)n OH

wherein A is 0 or NH, R and R' are, individually, hydrogen or a C1-C4 alkyl group and n is 1-3, inclusive.
The (iii) units of the polymers useful in the depressants herein comprise the polymerization residue of an anionic group containing monoethylenically unsaturated, copolymerzable monomer such as acrylic acid, methacrylic acid, alkali metal or ammonium salts of acrylic and/or methacrylic acid, vinyl sulfonate, vinyl phosphonate, 2-acrylamido-2-methyl propane sulfonic acid, styrene sulfonic acid, maleic acid, fumaric acid, crotonic acid, 2-sulfoethylmethacrylate; 2-acrylamido-2-methyl propane phosphonic acid and the like.

Altematively, but less desirably, the anionic substituents of the (iii) units of the polymers used herein may be imparted thereto by post-reaction such as by hydrolysis of a portion of the (i) unit acrylamide poiymerization residue of the polymer as also discussed in the above-mentioned '764 patent.
The effective weight average molecular weight range of these polymers is surprisingly very wide, varying from about a few thousand e.g. 5000, to about millions e.g.
million, preferably from about ten thousand to about one million.
The polysaccharides useful as a component in the depressant compositions used in the process of the present invention include guar gums; modified guar gums;
cellulosics 10 such as carboxymethyl cellulose; starches and the like. Guar gums are preferred.
The ratio of the polysaccharide to the polymer in the depressant blend should range from about 9:1 to about 1:9, respectively, preferably from about 7:3 to about 3:7, respectively, most preferably from about 3:2 to 2:3 respectively.
The dosage of the polymer depressant alone or in combination with the polysaccharide, useful in the method of the present invention, ranges from about 0.01 to about 10 pounds of depressant per ton of ore, preferably from about 0.1 to about 5 lb./ton, most preferably from about 0.1 to about 1.0 Ib./ton.
The concentration of (i) units in the depressants used herein should be at least about 35% as a mole percent fraction of the entire polymer, preferably at least about 50%.
The concentration of the (ii) units should range from about 1 to about 50%, as a mole percent fraction, preferably from about 5 to about 20%, while the concentration of the (iii) units should range from about 0 to about 50%, as a mole percent fraction, preferably from about 1 to about 50% and more preferably from about 1 to about 20%. Mixtures of the polymers composed of the above X, Y and Z units may also be used in ratios of 9:1 to 1:9.
The new method for beneficiating value sulfide minerals employing the synthetic depressants of the present invention provides excellent metallurgical recovery with improved grade. A wide range of pH and depressant dosage are permissible and compatibility of the depressants with frothers and sulfide value mineral collectors is a plus.
The present invention is directed to the selective removal of non-sulfide silicate gangue minerals that normally report to the value sulfide mineral flotation concentrate, either because of natural floatability or hydrophobicity or otherwise. More particulariy, the instant method effects the depression of non-sulfide magnesium silicate minerals while enabling the enhanced recovery of sulfide value minerals. Thus, such materials may be treated as, but not limited to, the following:
Talc Pyrophyllite .-Pyroxene group of Minerals Diopside Augite Homeblendes Enstatite Hypersthene Ferrosilite Bronzite Amphibole group of minerals Tremolite Actinolite Anthophyllite Biotite group of minerals Phlogopite Biotite Chlorite group of minerals Serpentine group of minerals Serpentine Chrysotile Palygorskite Uzardite Anitgorite Olivine group of minerals Olivine Forsterite Hortonolite Fayalite The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified. In the examples, the following designate the monomers used:
AMD = acrylamide DHPM = 1,2-dihydroxypropyl methacrylate HEM = 2-hydroxyethyl methacrylate AA = acrylic acid MAMD = methacrylamide VP = vinylphosphonate GPAM = glyoxylated poly(acrylamide) APS = 2-acrylamido-2-methylpropane sulfonic acid VS = vinyisulfonate CMC = carboxymethyl cellulose t-BAMD = t-butylacrylamide HPM = 2-hydroxypropyl methacrylate HEA = 1-hydroxyethyl acrylate HPA = 1-hydroxypropyl acrylate = DHPA = 1,2-dihydroxypropyl acrylate NHE-AMD = N-2-hydroxyethylacrylamide NHP-AMD = N-2-hydroxypropylacrylamide NBHE-AMD = N-bis(1,2-dihydroxyethyl)acrylamide NBEP-AMD = N-bis(1-hydroxypropyl)acrylamide SEM = 2-sulfethylmethacrylate AMPP = 2-acrylamido-2-methylpropane phosphonic acid C = comparative Examples 1-41 Test Procedures Pure Talc Flotation The depressant activity of the aolymers is tested using a high grade talc sample in a modified Hallimond tube. 1 Part of talc of size -200+400 mesh is suspended in water and conditioned for 5 min. at the desired pH. A known amount of polymer depressant solution is added and the talc is further conditioned for 5 min. The conditioned talc is then transferred to a flotation cell, and flotation is conducted by passing nitrogen gas for a prescribed length of time. The floated and unfloated talc are then filtered separately, dried and weighed. Per cent flotation is then calculated from these weights.
The depressant activity (as measured by % talc flotation; the lower the talc flotation, the greater is the depressant activity) of depressants having varying molecular weights is shown in Table 1. These examples clearly demonstrate that the polymer depressants of the present invention depress talc flotation. In the absence of any polymer, talc flotation is 98%; in the presence of the polymers, talc flotation is in the range of 5 to 58%. The depressant activity, in general, is greater at the high molecular weight. The depressant activity also increases with the proportion of the hydroxy group containing comonomer.

Table 1 Depressant Concentration: 100 ppm; 8 min. flotation; pH 9 Example Depressant % Talc Flotation = 1 C None 98 2 AMD/DHPM, 95/5, MW 10,000 31 3 AMD/DHPM, 90/10, MW 10,000 22 4 AMD/DHPM, 80/20, MW 10,000 19 5 AMD/DHPM, 50/50, MW 10,000 20 6 AMD/HEM, 95/5, MW 10,000 56 7 AMD/HEM, 90/10, MW 10,000 23 8 AMD/DHPM, 90/10, MW 3,000 58 9 AMD/DHPM, 90/10, MW 10,000 32 10 AMD/DHPM, 90/10, MW 20,000 25 11 AMD/DHPM, 90/10, MW 297,000 22 12 AMD/DHPM, 90/10, MW 397,000 5 13 AMD/DHPM, 90/10, MW 878,000 7 14 AMD/HEM, 90/10, MW 3000 45 15 AMD/HEM, 90/10, MW 10,000 12 16 AMD/HEM, 90/10, MW 20,000 13 17 AMD/HEM, 90/10, MW 116,000 15 18 AMD/HEM, 90/10, MW 286,000 20 19 AMD/HEM, 90/10, MW 458,000 18 20 AMD/HEM, 90/10, MW 656,000 18 21 AMD/DHPM/AA 80/10/10, MW 7000 24 22 AMD/HEM/AA 80/10/10, MW 8800 38 The depressant activity at varying dosage of various polymer depressants of the present invention at molecular weights of 10,000 and 300,000 is given in Table 2. In general, the depressant activity increases with the dosage of the polymer. At the high molecular weight, the dosage of the polymer required for a given depression is significantly = low.

Table 2 pH 9; 8 min. Flotation Example Depressant % Talc Flotation 23C None 98 24 AMD/DHPM, 90/10, MW 10,000, 5 ppm 70 25 AMD/DHPM, 90/10, MW 10,000, 10 ppm 59 26 AMD/DHPM, 90/10, MW 10,000, 40 ppm 40 27 AMD/DHPM, 90/10, MW 10,000, 100 ppm 21 28 AMD/HEM, 90/10, MW 10,000, 5 ppm 52 29 AMD/HEM, 90/10, MW 10,000, 10 ppm 28 30 AMD/HEM, 90/10, MW 10,000, 100 ppm 22 31 AMD/DHPM, 90/10, MW 300,000, 1 ppm 30 32 AMD/DHPM, 90/10, MW 300,000, 2.5 ppm 12 33 AMD/DHPM, 90/10, MW 300,000, 100 ppm 5 34 AMD/HEM, 90/10, MW 300,000 1 ppm 42 35 AMD/HEM, 90/10, MW 300,000 10 ppm 20 36 AMD/HEM, 90/10, MW 300,000 100 ppm 20 The depressant activity of a 90/10 acrylamide/dihydroxypropylmethacrylate copolymer at different pH values is given in Table 3. These results demonstrate that the depressant activity is maintained in the wide pH range of 3.5-11.

Table 3 AMD/DHPM 90/10: MW 10,000; DOSAGE 100 PPM; 8 MIN. FLOTATION
NO DEPRESSANT: 95-98% FLOTATION IN THE pH RANGE USED
Example pH % Talc Flotation 37 3.5 20 41 11 26 =

Examples 42-45 Natural Sulfide Ore Flotation Ore 1 This ore containing approximately 2.25% Ni and 28% MgO (in the form of Mg silicates) is ground in a laboratory rod mill to obtain a pulp at size of 80% -200 mesh.
This pulp is transferred to a flotation cell, conditioned at the natural pH (-8.5) with 200 parts/ton of copper sulfate for 4 min., then with 175 parts/ton of sodium ethyl xanthate for 2 min., followed by conditioning with the desired amount of the polymer depressant and an alcohol frother for 1 min. Flotation is then carried out by passing air at approximately 5.5 I/min., and four concentrates are taken. The concentrates and the tails are then filtered, dried and assayed.
The results for two terpolymers depressants of the present invention are compared with those of guar gum in Table 4. The objective here is to decrease the Mg-silicate recovery (as identified by MgO as an indicator) into the sulfide flotation concentrate while maintaining as high a Ni recovery and Ni grade as possible. The results in Table 4 demonstrate that the two terpolymer depressants of the present invention provided about 3 units lower MgO
recovery while providing equal of slightly better Ni recovery and Ni grade at only 75% of the guar gum dosage. In the absence of any depressant, the NIgO recovery is much higher (27%) which is unacceptable.
Table 4 Feed Assay: 2.25% Ni and 27.7 MgO

Example Depressant p/t Cum. Ni Rec. Ni MgO
Wt.%. Grade Rec.

42C None 0 36.87 80.5 5.0 27.0 43C Guar Gum 175 31.10 76.1 5.4 21.5 44 AMD/DHPM/AA 130 27.88 77.6 6.4 18.6 80/10/10, 7K
45 AMD/HEM/AA 130 26.98 75.1 6.3 18.5 80/10/10, 9K
.

Examples 46-65 Ore 2 This ore containing approximately 3.3% Ni and 17.6% MgO (in the form of Mg silicates) is ground in a laboratory rod mill for 5 min. to obtain a pulp at a size of 81 % -200 mesh. The ground pulp is then transferred to a flotation cell, and is conditioned at the natural pH (-8-8.5) with 150 parts/ton of copper sulfate for 2 min., 50 to 100 parts/ton of sodium ethyl xanthate for 2 min. and then with the desired amount of a depressant and an alcohol for 2 min. First stage flotation is then conducted by passing air at approximately 3.5-5 Vmin. and a concentrate is collected. In the second stage, the pulp is conditioned with 10 parts/ton of sodium ethyl xanthate, and desired amounts of the depressant and the frother for 2 min. and a concentrate is collected. The conditions used in the second stage are also used in the third stage and a concentrate is collected. All of the flotation products are filtered, dried and assayed.
In Table 5, the depressant activity of several copolymer and terpolymer depressants is compared with that of guar gum at two different dosages. In the absence of any depressant, the Ni recovery is 96.6% which is considered very high and desirable; the MgO
recovery is 61.4% which is also very high, but considered highly undesirable.
The Ni grade of 4.7% obtained is only slightly higher than that in the original feed. With guar gum at 420 and 500 parts/ton, the MgO recovery is in the range of 28.3 to 33.5% which is considerably lower than that obtained in the absence of a depressant, and Ni recovery is about 93%
which is lower than that obtained in the absence of depressant. A reduction in Ni recovery is to be expected in the process of reducing MgO recovery since there is invariably some mineralogical association of Ni minerals with the Mg-silicates; when the latter are depressed, some Ni minerals are also depressed. The synthetic polymer depressants of the present invention show much stronger depressant activity than guar gum;
the MgO
recoveries are in the range of 6.3 to 15.3% compared with 28.3-33-5% for guar gum.
These results indicate that significantly lower dosage of the synthetic depressants can be used if results similar to those of guar gum are desired. The terpolymer containing 10 parts each of methacrylamide and dihydroxypropyl methacrylate provides depressant activity that is similar to that of guar gum. Similarly, a terpolymer of AMD, DHPM and vinyl phosphonate provides metallurgy that is similar to guar gum.
It is pertinent to note here that polyacrylamide reacted with glyoxylic acid, containing pendant hydroxyl and carboxyl groups, shows depressant activity at a degree of substitution of 10% (i.e. 10 parts of the amide groups in the polyacrylamide are reacted with glyoxylic acid.) At a degree of substitution of 50%, depressant activity is weaker.

Table 5 Feed Assay: 3.31% Ni and 17.58% MgO

Example Depressant p/t Ni Ni MgO
Rec. G rade Rec.
46C None 0 96.6 4.7 61.4 47C Guar Gum 350+70+80 93.0 7.7 28.3 48C Guar Gum 300+60+60 92.9 6.7 33.5 49 AMD/DHPM 90/10, 397K 350+60+60 84.5 10.5 12.6 50 AMD/DHPM 90/10, 878K 350+70+80 81.8 12.6 8.2 51 AMD/DHPM 90/10, 878K 280+56+64 84.2 8.0 15.3 52 AMD/DHPM 80/20, 500K 350+70+80 80.3 11.5 9.8 53 AMD/DHPM 80/20, 800K 350+70+80 71.4 11.8 6.3 54 AMD/MAMD/DHPM 350+85+ 92.3 7.2 37.6 80/10/10, 6.23K 100 55 AMD/MAMDNP 80/10/10, 350+85+ 93.1 7.8 31.8 12.1 K 100 56 G PAM (90/10) 350+70+80 93.3 6.3 43.7 57C GPAM (50/50) 350+70+80 99.0 4.7 63.4 58 AMD/HPM 90/10 350+85+ 94.6 6.4 44.0 59 AMD/HEM 90/10, 656K 250+60+70 86.4 7.0 27.9 60 AMD/DHPM/HEM 95/5/5 280+56+64 84.1 6.9 23.9 61 AMD/DHPM/AA 80/10/10, 250+60+70 91.8 5.6 39.2 62 -do- 280+56+64 89.6 6.2 28.1 63 AMD/DHPM/AA 85/10/5, -do- 89.6 7.2 24.6 64 AMD/DHPM/APS 250+60+70 95.0 6.5 47.5 80/10/10, 11.7K
65 AMD/DHPMNS 80/10/10, -do- 94.1 7.0 42.9 7.78K
65A Polymer of Examples 59 350+70+80 92.5 10.3 16.8 and 61 in a ratio of 1:1 Examples 66-79 Ore 3 This ore has approximately 2.1 % Ni and 17% MgO. 1000 Parts of ore is ground in a rod mill to obtain a pulp that has a size of 80% passing 20 mesh. The ground pulp is conditioned for 2 min. with 200 parts/ton of copper sulfate, 2 min. with 100 parts/ton of sodium ethyl xanthate and the required amount of frother, and then for 2 min. with the desired amount of the depressant. Flotation is then conducted by passing air, and a concentrate is taken. In the second stage, the pulp is conditioned with 40 parts/ton of xanthate and additional amounts of the same depressant, and a second concentrate is taken. A third stage flotation is conducted similarly and a concentrate is taken. All of the flotation products are filtered, dried and assayed.
The results for the depressant activity of several of the synthetic copolymer and terpolymer depressants of the present invention are compared with that of guar gum (at two dosages) in Table 6. These results demonstrate clearly that the depressants provide metallurgy that is equal or better than that of guar gum at 40 to 70%
of the guar gum dosage. In many examples, improved Ni recovery is obtained while maintaining a low MgO recovery indicating gangue silicate mineral depression.

Table 6 Feed Assay: Ni 2.06%; MgO 17% - Xanthate Rougher Float Dose Cum. Grade Cum. Rec. %
Example Depressant P/t Wt=% Ni Ni MgO
66C GUAR 200 27.9 6.11 84.6 13.1 67C GUAR 250 27.0 6.31 84.4 12.1 68 AMD/DHPM 90/10, 397K 100 29.4 6.20 86.6 13.5 69 AMD/DHPM 90/10, 397K 140 27.5 6.29 85.6 12.7 70 AMD/DHPM 90/10, 878K 100 28.0 6.45 85.6 12.5 71 AMD/DHPM 90/10, 878K 180 28.3 6.39 84.8 12.8 72 AMD/HEM 90/10, 286K 140 27.9 6.22 85.1 12.8 73 AMD/HEM 90/10, 286K 180 26.7 6.66 84.4 10.9 74 AMD/HEM 90/10, 656K 100 27.9 6.54 85.2 12.1 75 AMD/HEM 90/10, 656K 180 26.6 6.50 83.7 11.2 76 AMD/DHPM/AA 80/10/10, 140 28.3 6.15 84.5 12.6 77 AMD/DHPM/AA 80/10/10, 180 27.8 6.48 85.4 12.4 78 AMD/HEM/AA 80/10/10, 140 28.9 6.18 86.0 13.8 79 AMD/HEM/AA 80/10/10, 180 27.4 6.33 84.2 12.5 Eicamples 80-83 Ore 4 This ore containing approximately 0.6% Ni and about 38% MgO (in the form of Mg silicates) is ground in a laboratory rod mill to obtain a pulp at a size of 80% -200 mesh.
This ground pulp is deslimed, conditioned for 20 min. with 120 parts/ton of sodium ethyl xanthate and the desired amount of frother. Flotation is then conducted and a concentrate is collected for 4 min. This concentrate is then conditioned for 1 min. with 20 parts/ton of sodium ethyl xanthate and with the specified amount of the depressant. A
cleaner flotation is then carried out for 3.5 min. The concentrate and tails are then filtered, dried and assayed.
The results for the depressant activity of three synthetic polymer depressants are compared with that of guar gum in Table 7. It is again evident from the results in Table 7 that the synthetic depressants of this invention provide metallurgy that is equal to or better than guar gum at 40 to 80% of the guar dosage. With two of the depressants the Ni recovery is significantly improved while maintaining low MgO recoveries.

Table 7 Example Depressant Dose Cum. Grade Cum.
(p/t) Wt.% Recovery Ni Ni MgO
80C Guar 30 3.8 9.2 62.6 2.3 81 AMD/DHPM 90/10, 397K 15 4.4 9.1 65.8 2.6 82 AMD/DHPM 90/10, 397K 12.5 4.7 7.5 66.2 3.0 83 AMD/HEM/AA 80/10/10, 24 3.8 9.0 61.7 2.4 Examples 84-96 Ore 5 This ore containing small amounts of Ni, Cu and Fe in the form of sulfides, small amounts of platinum and palladium, and approximately 7.5% MgO (in the form of Mg silicates) is ground in a laboratory rod mill with 15 parts/ton of potassium amyl xanthate and 12.5 parts/ton of diisobutyl dithiophosphate for 10 min. to obtain a pulp at a size of 40% -200 mesh. The ground pulp is then transferred to a flotation cell, and is conditioned for 2 min. at the natural pH (-8.2) with the same amounts of collectors as in the grind, followed by conditioning with the specified amount of depressant and an alcohol frother for 2 min.
Flotation is then conducted by passing approximately 3.5-5 Vmin. of air and a concentrate is collected. The procedure used in the first stage of flotation is followed in the second stage and a second concentrate is collected. The flotation products are then filtered, dried and assayed.
The results for the depressant activity of a variety of synthetic polymer depressants of the present invention are compared in Table 8 with that of two carboxy methyl cellulose -samples from different sources. The objective here is to obtain high recovery and grades of Pt and Pd in the concentrate. In the absence of any depressant, the recovery of Pt and Pd is indeed very high (97.5% and 94-95% respectively), but the concentrate grades are unacceptably low. With the CMC depressants, the Pt and Pd recoveries are 95-96.5% and 92-94.6%, respectively, and the grades are 3-3.1 for Pt and 12.7-13 for Pd. It is evident from the results that the synthetic polymer depressants provide Pt and Pd metallurgy that is equal to or better than that of CMC samples and at significantly lower dosages (60-80%
of the CMC dosage). It is also evident that the synthetic polymer depressants provide better grades for the Pt which is a more important and much higher value metal than Pd.
In Example 88, a polymer containing only 0.5 part of the t-butyl acrylamide in addition to DHPM provides Pt metallurgy that is equal to that of CMC(B) but at 80% of the dosage of CMC.
Table 8 Feed Assay: 5.8 p/t Pt; 22 p/t Pd Example Depressant pk Pt Rec. Pt Pd Pd Grade Grade Rec.
84C None 0 97.5 1.6 95.0 6.0 85C None 0 97.6 2.3 94.4 7.2 86C CMC-A 500 95.2 3.1 92.0 12.7 87C CMC-B 500 96.5 3.0 94.6 13.0 88 AMD/DHPM/t-BAMD 89.5/10/0.5 400 96.5 3.1 93.1 11.6 89 AMD/DHPM/AA 80/10110, 750K 400 96.6 2.1 93.2 7.4 90 AMD/DHPM/AA 80110/10, 750K 500 92.9 4.6 88.3 14.7 91 AMD/HEM/AA 80110/10, 224K 370 94.5 3.8 92.1 13.9 92 AMD/HEM/AA 80110/10, 224K 300 95.3 42 91.4 16.4 93 AMDlHEM/AA 80110/10. 224K 400 96.6 2.7 94.1 10.6 94 AMD/DHPM/AA 85/10/5 400 96.8 32 93.4 11.2 95 AMD/DHPMNP 80/10l10, 12K 370 96.9 2.8 94.1 10.4 96 AMD/DHPM/MAMD 80/10/10 400 94.8 1.6 91.9 6.5 Examples 97-99 Ore 6 This ore contains 0.85% Ni and 39% MgO. 1000 Parts of the ore are ground in a rod mill to give a flotation feed of size 80% passing 200 mesh. The ground pulp is conditioned for 30 min. with the desired amount of a depressant along with 500 parts/ton 4 sodium ethyl xanthate. Rougher flotation is then carried out for 25 min. The rougher concentrate is then conditioned with the specified amount of depressant and 10 parts/ton of sodium ethyl xanthate and a cleaner flotation is carried out for 15 min.
The flotation products are filtered, dried and assayed.
The results for two synthetic copolymers of AMD/DHPM are compared with that of CMC in Table 9. These results demonstrate that the synthetic depressants provide metallurgy that is equal to or better than that of CMC, but at about 27% of the CMC
dosage. In the case of the copolymer with a molecular weight of 878,000, the MgO
recovery in both the regular and cleaner concentrate is significantly lower than that obtained with CMC.
Table 9 Feed Assay: Ni 0.85%; MgO 39%

Dose Cum. Recovery, %
Example Depressant p/t Product Grade Total Ni Wt Ni MgO
97C CMC 275 1 CICon 15.44 3.48 60.8 2.3 RoCon 3.21 21.17 76.8 20.6 98 AMD/DHPM 90/10, 878K 75 1CICon 18.01 2.73 59.3 1.5 RoCon 3.78 15.92 72.6 14.6 99 AMD/DHPM 90/10, 397K 75 iCiCon 14.48 3.41 61.6 2.1 RoCon 2.83 21.96 77.6 J 20.7 Examples 100-109 Ore 7 This ore containing small amounts of Ni, Cu, and Fe in form of sulfides and about 17% MgO (in the form of Mg silicates) is ground in a laboratory ball mill for 12 min. to obtain a pulp at a size of 40% -200 mesh. The ground pulp is then transferred to a flotation cell, and is conditioned at the natural pH (-7.2) with the specified amount of a depressant for 3 min., followed with 16 parts/ton of sodium isobutyl xanthate and 34 parts/ton of a dithiophosphate and a polyglycol frother for 3 min. Flotation is then conducted by passing air at approximately 3.5 Vmin. and two concentrates are collected. The flotation products are then filtered, dried and assayed.
The results for the depressant activity of a variety of synthetic polymer depressants of the present invention are compared with that of a modified guar in Table 10. The objection here is to minimize the recovery of Si02, CaO, MgO, A1203 - all of which represent the silicate minerals present in the sulfide concentrates - and to maintain or improve the recovery of Ni and Cu which constitute the value sulfide minerals.
In the absence of any depressant, the Ni and Cu recoveries are 49.5% and 79%, respectively, but the recovery of the gangue constituents is very high (9.4% for Si02, 7.4% for CaO, 10.6%
for MgO and 5.8% for A1203). With guar, both the Ni and Cu recoveries are slightly reduced, perhaps because of depression of some silicate minerals that carry Ni and Cu sulfides as mineral locking, but recovery of the gangue constituents is also reduced. With all of the synthetic polymer depressants tested, there is a significant reduction in the recovery of the gangue constituents, and with some of them the reduction is far greater than that obtained with guar. All of the depressants of the present invention (except one) give higher copper recoveries than guar, in some cases the copper recoveries are higher than that obtained in the absence of the depressant. Also the Ni recoveries obtained with the synthetic depressants are either equal to or much greater than that obtained with guar. In the best case, AMD/HEM 90/10, 10,000 MW, there is more than 50% reduction in Si02 compared to the test with no depressant, and 44% reduction in Si02 compared to that with guar. Similarly significant reductions are also observed for other gangue constituents.
Table 10 Calculated Head Assays: Cu - 0.07%, Ni - 0.20%; Si02 - 48.8%; CaO - 5.8%
MgO - 17%; A1203 - 9%

Example Depressant p/t Orsier of Copper Nickel Si02 CaO MgO A1203 Addn.
Rec Rec Rec Rec Rec Rec 100C None 0 - 79.0 49.5 9.4 7.4 10.6 5.8 101 C Guar 60 Depr 1 st 77.2 46.2 7.5 5.9 8.6 4.8 102 AMD/HEM 95/5 100k 60 Depr 1st 75.9 46.3 8.5 6.8 9.5 5.6 103 AMD/HEM 90110 20k 60 Depr 1st 78.3 48.6 8.0 6.4 9.2 5.2 104 AMD/HEM 90/10 10k 70 Depr Ist 81.3 51.0 7.3 5.9 8.2 4.9 105 AMD/HEM 90/10 10k 70 Reverse 82.4 50.1 4.2 5.1 7.5 3.9 106 AMD/DHPM 80/20 10k 67 Depr 1st 79.4 46.5 6.5 4.9 7.4 3.8 107 AMD/DHPM 90/10 10k 60 Depr 1st 79.3 48.2 7.4 5.9 8.5 4.7 108 AMD/D1-IPM 90/10 10k 60 Reverse 80.2 47.5 6.5 5.0 7.5 4.0 109 AMD/DHPM/AA 80/10/10 60 Depr 1st 78.4 46.3 72 5.9 8.2 4.9 10k Example 110 Following the procedure of Example 50 except that ttie DHPM is replaced by an equivalent amount of HEA. Similar results are attached.

Example 111 Replacing the HEM of Example 45 with DHPA achieves substantially similar results.

Examples 112 Example 53 is again followed but the DHPM is replaced by HPA to achieve similar recovery.

Example 113 When the HEM of Example 73 is replaced by NHE-AMD similar cumulative recovery of nickel and magnesium is observed.

Example 114 NBHE-AMD is used to replace DHPM in the Example 88 procedure. The results are similar.

Example 115 The DHPM of Example 96 is replaced by NHP-AMD to yield similar platinum and palladium recoveries.

Example 116 Metal recoveries are similar when the HEM of Example 102 is replaced by NBEP-AMD.
Example 117 Replacement of the AA of Example 22 by SEM results in similar % talc flotation.
Example 118 When the VP of Example 55 is replaced by AMPP, similar results are achieved.
Examples 119-127 An ore containing approximately 3.3% Ni and 16.5% MgO (in the form of Mg silicates) is ground in a laboratory rod mill for 5 minutes to obtain a pulp at a size of 81 /a -200 mesh. The ground pulp is then transferred to a flotation cell, and is conditioned at the natural pH (-8-8.5) with 150 parts/ton of copper sulfate for 2 minutes, 50 to 100 parts/ton of sodium ethyl xanthate for 2 minutes and then with the desired amount of depressant blend and an alcohol frother for 2 minutes. First stage flotation is then conducted by passing air at approximately 3.5-5 Vmin. and a concentrate is collected. In the second stage, the pulp is conditioned with 10 parts/ton of sodium ethyl xanthate, and desired amounts of depressant blend and the frother for 2 minutes and a concentrate is collected.
The conditions used in the second stage are also used in the third stage and a concentrate is collected. All of the flotation products are filtered, dried and assayed.
The depressant activity of a 1:1 blend of AMD/DHPM and guar gum is compared with the individual depressants in Table lI. With guar alone the Ni recovery is 93% and MgO recovery is 28.3%. With the synthetic polymer depressant alone, the Ni recovery is 84.5% and the MgO recovery is 12.6% which is less than half of that of guar gum, thereby indicating a very strong depressant activity of the synthetic depressant. In the case of the blend, there is a further reduction in MgO recovery and the Ni recovery and grade improve slightly over that of the synthetic depressant. These results demonstrate the greater depressant activity obtained with the blend and also suggest that much lower dosages can be used compared to those of the individual components.
The depressant activity of a 1:1 blend of AMD/HEM polymer and guar gum is compared with that of the individual depressants in Table 2. With guar gum alone, as before, the Ni recovery is 93% and the MgO recovery is 28.3%. With the AMD/HEM
copolymer at the same dosage, the MgO recovery is only 7.7% indicating a very strong depressant activity; the Ni recovery is also significantly reduced (68.3% vs.
93% for guar).
With the blend, however, the Ni recovery improves significantly (82.8%) while the MgO
recovery is maintained at the low level of 8.3%. The results also suggest that a considerably lower dosage can be used with the blend to obtain enhanced performance.
In fact, when the dosage is lowered to 430 parts/ton, the Ni recovery increases to 86%
(from 82.8%) while the MgO recovery increases to 11.5% (from 8.3%).

Table II

FEED ASSAY: 3.31% Ni and 17.58% MgO

Ni Ni Mgo Example Depressant 9/t Rec Grade Rec.
119C None 0 96.6 4.7 61.4 120C Guar Gum 350+70+80 93.0 7.7 28.3 121C AMD/DHPM 90/10; 397K, 300+60+60 84.5 10.5 12.6 122 Guar Gum and AMD/DHPM 350+70+80 85.7 11.0 10.3 1:1 90/10; 397K
123C None 0 96.6 4.7 61.4 124C Guar Gum 350+70+80 93.0 7.7 28.3 125C AMD/HEM 90/10; 656K 350+70+80 68.3 11.4 7.7 126 Guar Gum and AMD/HEM 1:1 300+70+80 82.8 12.2 8.3 90/10; 656K
127 Guar Gum and AMD/HEM 1:1 30+60+70 86.0 10.3 .5 11.5 90/10; 656K

Examples 128-143 When the procedures of Examples 119-127 are again followed except that the depressant components are varied, as are their concentrations, as set forth in Table 12, below, similar results are achieved.

Table 12 Polysaccharide PM:PS
Example Polymer (PM) (PS) Ratio 128 AMD/MAMD/DHPM 80/10/10; 623K Guar Gum 9:1 129 AMD/DHPM/AA 80/10/10; 7K Starch 1:1 130 -do- 750K CMC 4:1 131 AMD/MAMDNP 80/10/10; 12K Modified Guar 2:3 132 GPAM (90/10) -do- 1:4 133 AMD/HEM/AA 80/10/10; 9K CMC 1:1 134 AMD/HEM/t-BAMD 89.5/10/0.5 Guar Gum 1:9 135 AMD/DHPM/APS 80/10/10; 11.7K Starch 2:1 136 AMD/DHPMNS 80/10/10; 7.78K Guar Gum 3:2 137 AMD/HPA 80/20 Guar Gum 1:1 138 AMD/DHPA/AA 80/10/10 Guar Gum 1:1 139 AMD/NHE-AMD 90/10 CMC 1:1 140 AMD/NBHE-AMD/BAMD 89.5/10/0.5 Starch 1:1 141 AMD/NHP-AMD/MAMD 80/10/10 Guar Gum 1:1 142 AMD/NBEP-AMD 95/5 Guar Gum 1:1 143 AMD/HEM/SEM 80/10/10 Guar Gum 1:1

Claims (20)

CLAIMS:

1. A method which comprises beneficiating value sulfide minerals from ores with selective rejection of non-sulfide silicate gangue minerals by:
a. providing an aqueous pulp slurry of finely-divided, liberation-sized ore particles which contain said value sulfide minerals and said non-sulfide silicate gangue minerals;
b. conditioning said pulp slurry with an effective amount of non-sulfide silicate gangue mineral depressant, a value sulfide mineral collector and a frothing agent, respectively, said depressant comprising either (1) a polymer or a mixture of polymers comprising:

(i) x units of the formula:

(ii) y units of the formula (iii) z units of the formula:

wherein X is the polymerization residue of an acrylamide monomer or mixture of acrylamide monomers, Y is an hydroxy group containing polymer unit, Z is an anionic group containing polymer unit, x represents a residual mole percent fraction of over about 35%, y is a mole percent fraction ranging from about 1 to about 50% and z is a mole percent fraction ranging from about 0 to about 50% or (2) a mixture of said polymer or polymers and a polysaccharide, with the proviso that in case glyoxylated polyacrylamide is used as depressant, it contains less than 50 mole percent glyoxylated amide units as the y units, and c. collecting the value sulfide mineral having a reduced content of non-sulfide silicate gangue minerals by froth flotation.

2. A method according to Claim 1 wherein Y has the formula wherein A is O or NH, R and R1 are, individually, hydrogen or a C1 - C4 alkyl group and n is 1-3, inclusive.

3. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of 1,2-dihydroxypropyl methacrylate and z is 0.

4. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of 1, 2-dihydroxypropyl methacrylate, Z is the polymerization residue of acrylic acid and z is a mole percent fraction ranging from about 1 to about 50.

5. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of hydroxyethyl methacrylate and z is 0.

6. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of hydroxyethyl methacrylate, Z is the polymerization residue of acrylic acid and z is a mole percent fraction ranging from about 1 to about 50%.

7. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of 1,2-dihydroxypropyl methacrylate, Z is the polymerization residue of vinyl sulfonate and z is a mole percent fraction ranging from about 1 to about 50%.

8. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of 1,2-dihydroxypropyl methacrylate, Z is the polymerization residue of vinyl phosphonate and z is a mole percent fraction ranging from about 1 to about 50%.

9. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of hydroxyethyl methacrylate, Z is the polymerization residue of vinyl sulfonate and z is a mole percent fraction ranging from about 1 to about 50%.

10. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of hydroxyethyl methacrylate, Z is the polymerization residue of vinyl phosphonate and z is a mole percent fraction ranging from about 1 to about 50%.

11. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of 1, 2-dihydroxypropyl methacrylate, Z is the polymerization residue of 2-acrylamido-2-methyl propane sulfonic acid and z is a mole percent fraction ranging from about 1 to about 50.

12. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, Y is the polymerization residue of hydroxyethyl methacrylate, Z is the polymerization residue of 2-acrylamido-2-methyl propane sulfonic acid and z is a mole percent fraction ranging from about 1 to about 50%.

13. A method according to Claim 1 wherein X is the polymerization residue of acrylamide and t-butylacrylamide, Y is the polymerization residue of 1,2-dihydroxypropyl methacrylate and z is 0.

14. A method according to Claim 1 wherein X is the polymerization residue of acrylamide, and methacrylamide, Y is the polymerization residue of 1,2-dihydroxypropyl methacrylate and z is 0.

15. A method according to Claim 1 wherein X is the polymerization residue of acrylamide and methacrylamide, Y
is the polymerization residue of hydroxyethyl methacrylate and z is 0.

16. A method according to Claim 1 wherein Y represents a glyoxylated acrylamide unit and y is less than about 40.

17. A method according to Claim 1 wherein X is the polymerization residue of acrylamide and t-butylacrylamide, Y is the polymerization residue of hydroxyethyl methacrylate and z is 0.

18. A method according to any one of Claims 1 to 17 wherein the polysaccharide is guar gum.

19. A method according to any one of Claims 1 to 17 wherein the polysaccharide is carboxymethyl cellulose.

20. A method according to any one of Claims 1 to 17 wherein the polysaccharide is starch.