Separation of polymetallic sulphides by froth flotation

Description

This invention relates to the separation of sulphidic minerals by froth flotation in a mineral separation process. More particularly this invention relates to the separation of sulphidic minerals present in polymetallic sulphides by differential froth flotation.
Froth flotation is a well-known mineral processing operation for obtaining mineral concentrates of a desired compound or element. In this process a collector agent is added to the aqueous slurry of the ground ore. The collector agent for a particular mineral is preferentially adsorbed on the surface of the mineral particles containing the desired compound, thereby rendering the surface hydrophobic (non-wetting by water). In a flotation device and in the presence of a frothing agent, air bubbles will be attached to the particles of the desired mineral thereby lifting them to the surface of the slurry. The froth in most instances is collected by mechanical means. The separated froth is usually dried or dewatered, and the concentrate is treated in subsequent steps to recover the desired compound or element.
In addition to collector and frothing agents being added to an ore slurry in the mineral separation process, it is usual to add depressant agents, which will be adsorbed on the surface of particles containing unwanted compounds. The surface of the particles are thereby rendered wettable, i.e., hydrophillic and hence not flotable. The unwanted minerals may contain minerals bearing certain compounds which are to be recovered by subsequent flotation process steps, by means of additions of a collector agent specific to such a mineral. When two or more flotation circuits are operated sequentially to selectively separate desired compounds present in ores, the process is referred to as differential flotation.
The usual practice of differential flotation is to treat the ore pulp similarly to a single flotation circuit but with reagents which will permit the flotation of only one of the desired minerals by preventing or minimizing flotation of other minerals. The residue from the first flotation stage is then treated with one or more chemical reagents to bring about flotation and concentration of a second mineral. In the second flotation process the desired minerals contained in the froth will provide a concentrate of minerals which have been separated from the minerals contained in the concentrate of the first flotation step. The residue or tailing of the second flotation process step thus will contain the unwanted minerals separated from the two desired minerals present originally in the ore. Of course, more than two flotation process circuits may be introduced sequentially to result in more than two concentrates of compounds and minerals which are of use to the mineral processor.
The concentrates obtained still contain unwanted compounds, but have been substantially enriched in the desired compound or element, thereby reducing the cost of further recovery steps. It is customary to refer to the compound of metals in an ore which are to be recovered from the ore under treatment as value metals.
Massive sulphidic ores usually contain sulphides of three or more metals which are to be separated and recovered by separate process steps. Most massive sulphides contain iron sulphides which are intimately mixed and disseminated throughout the ore. The iron sulphides, quartz, silicates, are usually of no value to the metallurgist and are to be separated from the value metals and discarded. It is of great significance for economical metal recovery, that the value metals be separated into concentrates of specific metals at the early stages of the metal recovery process. The separation of value metals into concentrates is often conducted by differential flotation circuits and the final tailing, or the combined tailing of differential flotation circuits will be separated and discarded as containing various gangue minerals.
The differential flotation is usually achieved with additions of various inorganic and organic chemicals called modifiers and depressants which alter the surfaces and flotation properties of the sulphides which need to be separated. There are known collector agents for the flotation separation of copper, nickel, zinc, lead, contained in sulphidic ores but these may not be selective enough, often allowing significant portions of one value metal retained in the concentrate of another value metal. In other words, the selectivity of the collector agent is not sufficiently high. There are known depressant agents which may increase the selectivity of a collector agent, but the improvement may still not be sufficient to render the separation process economical. It may often happen that a collector-depressant combination may provide good separation in one type of sulphidic ore, but will be much less effective in the case of sulphidic ore of a different origin and nature.
By way of illustration of lack of selectivity, various sulphates of heavy metals such as zinc sulphate as well as cyanide, are used for the depression of sphalerite (ZnS) during the differential flotation of copper-zinc sulphides or copper-lead-zinc sulphidic ores. Cyanide and lime are used to separate chalcopyrite from pentlandite. In actual practice, even with additions of known depressants the sharpness of separation in complex ores of lead, copper, zinc from iron sulphides, copper-zinc sulphides or copper-nickel sulphides is often poor and results in losses in mineral values thereby substantially increasing the cost of the recovery process.
There is a need for a depressant agent which will increase the selectivity of known collector agents in the differential flotation separation of complex sulphidic ores containing copper sulphides as well as lead, zinc, and iron sulphides intimately mixed with each other.
There is also a need for a depressant agent which will increase the selectivity of known collector agents in the differential flotation separation of value metals contained in mixed sulphidic ores containing copper-nickel-iron, or copper-zinc-iron.
A new depressant has been found for the enhanced separation of metal sulphides contained in mixed polymetallic sulphidic ores consisting of:
(i) quebracho chemically reacted with one of the group consisting of: guar gum, and dextrin.
(ii) a water soluble salt of lignin sulphonate; and
(iii) at least one of the group consisting of alkali metal cyanide, alkaline earth metal cyanide, water soluble metal sulphate, and a water soluble metal sulphite containing a tetravalent sulphur atom.

BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic flowsheet representing a differential flotation separation process.
A detailed description of the preferred embodiment of the invention will be provided hereinbelow and illustrated by means of working examples. The examples will refer to the flowsheet of FIG. 1.
Quebracho is a wood extract obtained from trees by known means. It is known to use quebracho as a flotation reagent by itself and without chemically bonding it to other compounds.
The new depressant agent for use in flotation separation of polymetallic sulphidic minerals is based on a chemical compound obtained by chemically reacting quebracho and dextrin or guar gum. Quebracho is a high tannin bearing natural product and its structure may be represented schematically as shown below; ##STR1##
Dextrin is a water soluble polymeric starch gum, its molecular weight is not definable within a strict limit. It has the general formula of (C.sub.6 H.sub.10 O.sub.5).sub.n. It is believed that when quebracho and dextrin are reacted the phenolic OH groups of the phenolic nuclei of quebracho are bonded to dextrin.
Guar gum is also a natural product, it has sugar-type components such as mannose and galactose, probably combined in a polysaccharide. It is believed that the nature of the reaction between quebracho and guar gum can be considered to be similar to the hydroxide group bondings between quebracho and dextrin.
The quebracho based reaction product is further combined in a second reaction with a lignin sulphonate salt of an alkali metal or water soluble alkaline earth metal, resulting in a water soluble complex polymeric compound containing dextrin or guar gum modified quebracho and lignin sulphonate. This complex polymer will be referred to in further discussions as LS compound.
In a third process step in the preparation of the depressant agent of this invention, the LS polymer is partially monomerized by the addition of at least one of the following chemical reagents: alkali metal cyanide, water soluble alkaline earth metal cyanide, a metal sulphate either by itself or complexed with cyanide, and water soluble sulphite. For the sake of clarity, sulphites are inorganic compounds containing a metal ion and a --SO.sub.3 --.sup.-2 radical. The sulphur in the sulphite radical is tetravalent. The LS compound depending on which of the above listed reagents is utilized in monomerizing it will be referred to as a member of the LS series. For example, LS7 is an LS compound reacted with an alkali metal cyanide; specifically with sodium cyanide. LS8 is an LS compound which has been reacted with a zinc sulphate/sodium cyanide complex.
The LS series are added to the aqueous slurry or pulp of the polymetallic sulphidic mineral containing other mineral processing reagents at a rate of 50 g/t to 350 g/t, depending on the nature and type of the ore.
The polymetallic sulphidic ore is usually ground to a particle size which will allow the liberation of the desired metallic sulphides. The grinding may be wet or dry. The ground ore is usually slurried in water. The aqueous ore slurry or pulp is then conditioned by additions of conventional reagents such as pH modifiers, slime depressants and similar agents to render the surface of the ore particles receptive to collector agents and depressant agents. The addition of conditioning agents, depressants and collector agents, and frothing agents may take place in a single stage or in several subsequent stages. The agents may also be added in the wet grinding step if it is so desired. Additions of the depressant LS are usually made to the grinding and subsequent crude concentrate flotation stages. The flotation of value metal bearing minerals is carried out using conventional equipment and methods.
The depressant of the present invention improves the selective flotation separation of copper-zinc sulphide ores, copper-lead-zinc sulphidic ores, lead-zinc and copper-nickel sulphides. The LS depressants, as discussed above, are reaction products of quebracho, guar gum or dextrin with lignin sulphonate further reacted with selected inorganic compounds. The depressant is believed to form complexes in the form of monomers and these exhibit characteristics of selective and powerful depressants for specific minerals while they do not affect the flotability of other minerals. The reactions in the ore are believed to be complex and involve interaction of the organic radicals contained therein with the mineral particles.
The preparation of the depressant and the application of the depressant agent in the flotation separation of copper-zinc minerals, copper-nickel minerals, lead-zinc minerals and other massive sulphidic ores containing iron sulphides are described in the following examples.

EXAMPLE 1
This example provides a description for the preparation of an LS compound referred to hereinabove.
Dextrin and quebracho were mixed as solids in a ratio of 2.+-.0.4:1.+-.0.4 and dissolved in water to provide an aqueous solution in the of range 5-10 weight percent solid content. It is advisable that the dissolution takes place at above 40.degree. C. To this warm solution was added calcium lignin sulphonate in an amount such that the weight of calcium lignin sulphonate to the weight of quebracho+dextrin was 3:8. It is to be understood that if another water soluble salt of lignin sulphonate is to be substituted for the calcium salt, adjustment to the weight ratio is required.
The third component of the depressant was added as a solid to the prepared solution containing dextrin modified quebracho lignin sulphonate. In this example the LS8 depressant was prepared, wherein the third component is a sodium cyanide-zinc sulphate mixture in a solid weight ratio of around 3:1. The total weight of the third component to be added in the case of the LS8 depressant is equal to the weight of quebracho-dextrin mixture first dissolved in the solution. The resulting solution then contained the following solids:
______________________________________quebracho-dextrin (1:2) 42 wt. % as solidcalcium lignin sulphonate 16 wt. % as solidsodium cyanide-zinc sulphate (3:1) 42 wt. % as solid______________________________________
In the LS7 depressant sodium cyanide replaces the zinc sulphate in the mixture. The weight in the total amount of sodium cyanide added to maintain the above ratio needs to be adjusted in this case. Similarly, if another alkali metal cyanide is used to make up the LS7 or LS8 depressant, the weight requirement of the reagent needs to be adjusted to the change in the atomic weight of the alkali metal forming the cyanide, as a person skilled in the art will appreciate.
Suitable adjustments in the ratios need to be made if guar gum is to replace the dextin used for modifying quebracho.
In using the LS depressant in the flotation separation of sulphidic minerals, the rate of addition of the depressant was calculated based on the solid content of the solution prepared as described above.
EXAMPLE 2
A massive sulphidic ore from Canada which is utilized in a commercial operation for the recovery of copper, zinc and silver as major value metals, was treated in a laboratory flotation circuit using conventional flotation reagents. The ore contained the usual gangue minerals such as quartz, pyrite and minor amounts of pyrrhotite. The major difficulty in treating this ore is that the copper concentrate obtained is contaminated with zinc minerals. Using conventional zinc depressant in a flotation separation step, satisfactory separation of the value metals was not possible.
In this example, laboratory tests were conducted in continuous locked cycles on two types of ores; that is, the intermediate product in the flotation stages were recycled in order to simulate a commercial flotation plant flowsheet which incorporates several flotation stages.
The beneficiation process included the following flotation treatment steps:
(a) Grinding of the ore to obtain 80% less than 325 Tyler mesh (53 .mu.m) in the presence of lime as pH modifier, which was added at a rate of 200-400 g/t. Sodium cyanide (NaCN) for depressing zinc minerals and pyrite was added to the ore at the rate of 20-40 g/t.
(b) The slurry of the ground ore obtained in the grinding step was further conditioned with sulphur dioxide, for the depression of zinc at a rate of 400-750 g/t. The copper was then recovered by adding collector agents Cyanamid R208* (phosphate base) and Cyanamid 3418A* (phosphine base). The frothing agent used was MIBC (methylisobutyl carbinol). The crude copper concentrate was cleaned three times, i.e. in three separate stages, with extra additions of sulphur dioxide and frother MIBC. The composition of the final copper concentrate obtained using the simulated commercial plant flowsheet is shown in the following tables as copper cleaner concentrate (Cu Clean. Conc.).
(c) The copper final tailing was subsequently treated to recover zinc using a conventional lime-copper sulphate conditioning circuit. The zinc minerals contained in the copper tailing were conditioned by agitation with lime and copper sulphate additions at an alkaline pH. The zinc sulphides were then recovered by a second froth flotation step using a conventional xanthate collector agent known as Cyanamid A317* and frothing agent polyglycol ester, commercially known as Dow-DF-250.*
*Trade name
The metallurgical results obtained in the separation process for two ore types; ore A which is high in copper, and ore B which is relatively low in copper content, and using the described conventional procedure and conventional reagents are shown in Table 2.
TABLE 2__________________________________________________________________________ Weight Assays, %, g/t % DistributionOre Type Product % Cu Zn Ag Cu Zn Ag__________________________________________________________________________A CuClean. Conc. 16.55 23.9 3.29 257 97.1 11.1 88.4(High Copper) Zn Conc. 7.20 0.46 58.9 30.2 0.8 86.7 4.5 Final Tail. 76.25 0.07 0.14 4.5 2.1 2.2 7.1 Head 100.00 4.05 4.89 48.1 100.0 100.0 100.0B CuClean. Conc. 10.54 23.3 3.36 317 96.7 8.9 77.4(Low Copper) Zn Conc. 6.92 0.40 49.8 4.1 1.1 87.0 6.6 Final Tail. 82.54 0.063 0.20 8.4 2.2 4.1 16.0 Head 100.00 2.54 3.96 43.1 100.0 100.0 100.0__________________________________________________________________________
EXAMPLE 3
Laboratory locked cycle tests conducted in steps described in the previous paragraph as steps (a), (b), (c), were carried out but with additions of zinc depressant LS8 of the present invention to increase the separation of the zinc sulphide from the copper sulphide and silver containing fractions. The depressant was added to the ore in the wet grinding step and then later to the copper cleaner flotation stage. The overall addition of depressant LS8 was 170 g/tonne. The results of the flotation tests obtained with depressant LS8 are shown in Table 3.
TABLE 3__________________________________________________________________________ Weight Assays, %, g/t % DistributionOre Type Product % Cu Zn Ag Cu Zn Ag__________________________________________________________________________A Cu Clean. Conc. 14.16 27.5 1.71 295. 97.0 4.8 87.4(High Copper) Zn Conc. 7.63 0.66 59.3 31.7 1.2 91.6 5.1 Final Tail. 78.20 0.09 0.23 4.6 1.8 3.6 7.5 Head 100.00 4.02 4.95 48.0 100.0 100.0 100.0B Cu Clean. Conc. 8.22 29.3 0.99 362. 96.1 2.0 74.8(Low Copper) Zn Conc. 6.63 0.48 56.7 38.0 1.3 92.8 6.3 Final Tail. 85.15 0.08 0.25 8.8 2.7 5.2 18.9 Head 100.00 2.51 4.05 39.7 100.0 100.0 100.0__________________________________________________________________________
By comparing the flotation test results in Table 2 and 3, it is clearly observable that the additions of depressant LS8 of this invention has significantly improved zinc rejection from the copper concentrate. The rejection of iron sulphides with other gangue minerals has also been improved, as is shown by the increase in weight percent of the final tailing. The zinc sulphides that have been rejected from the copper concentrate were recovered in a second flotation recovery stage produced significantly higher zinc recovery. More zinc retained in the zinc concentrate obtained improved the economics of the entire process.
EXAMPLE 4
The ore treated in Examples 2 and 3 in laboratory tests, was treated in a commercial plant operating at a rate of 130 tonnes per hour. The following reagents were used in the operating plant.
______________________________________Grind: 80% less than 325 Tyler meshCopper Circuit: pH Modifier: Ca(OH).sub.2 = 300 g/t Depressants: NaCN = 20 g/t SO.sub.2 = 700 g/t Collectors: Aeroflot (R208)* = 40 g/t Aerophine (3418A)* = 20 g/t Frother: MIBC = 20 g/tZinc Circuit: pH Modifier Ca(OH).sub.2 = 120 g/t Zn Activator CuSO.sub.4 .times. 5H.sub.2 O = 400 g/t Collector: Xanthate (A317)* 30 g/t Frother: DF250** = 15 g/t______________________________________
The typical results obtained in the continuous plant operation are shown in Table 4.
TABLE 4__________________________________________________________________________ Weight Assays, %, g/t % DistributionProduct % Cu Zn Ag Cu Zn Ag__________________________________________________________________________Cu Concentrate 15.0 24.5 3.12 359.0 95.7 8.9 78.0Cu Tailing 85.0 0.19 5.60 17.8 4.3 91.1 22.0Zn Concentrate 8.1 0.68 52.40 50.6 1.4 81.0 5.9Zn Tailing 77.2 0.13 0.70 14.4 2.9 10.1 16.1Feed 100.0 3.82 5.18 69.3 100.0 100.0 100.0__________________________________________________________________________ *Trade name of Cyanamid collector **Trade name of Dow Chemical frother
EXAMPLE 5
The ore utilized in examples 2, 3 and 4 was treated in the same manner as is described in Example 4, in a parallel commercial circuit treating ore at the rate of 130 tonnes per hour, but with depressant LS8 added at a rate of 40 g/t in the grinding step and 30 g/t in the copper cleaner stage. Cyanide was omitted as a conditioning agent from the circuit, but was added as being incorporated in the third component sodium cyanide/zinc sulphate complex, of the depressant LS8, as described in example 1. Cyanide added in this form is complexed with zinc, whereas the addition of sodium cyanide directly as a conditioner results in the presence of unbound cyanide ions. The results obtained with the use of LS8 depressant are shown in Table 5.
TABLE 5__________________________________________________________________________ Weight Assays, %, g/t % DistributionProduct % Cu Zn Ag Cu Zn Ag__________________________________________________________________________Cu Concentrate 14.2 26.1 2.40 406 95.1 6.6 77.6Cu Tailing 85.8 0.20 5.66 19.4 4.9 93.4 22.4Zn Concentrate 8.0 0.51 54.50 46.8 1.0 83.8 5.0Zn Tailing 77.8 0.19 0.64 15.7 3.9 9.6 17.4Feed 100.0 3.82 5.18 69.3 100.0 100.0 100.0__________________________________________________________________________
As can be seen from the results shown in Tables 4 and 5, the use of zinc sulphide depressant LS8 resulted in reducing the distribution of zinc separated with the copper concentrate by 2.3% and improved both the copper concentrate grade and the zinc recovery in the zinc circuit by about 2% or more. In economic terms the values of both the copper and zinc concentrates were improved considerably.
EXAMPLE 6
A massive sulphide ore originating in British Columbia (Canada), containing copper, nickel, platinum and palladium as major value metals was treated in a laboratory batch flotation circuit using the following conventional reagents:
______________________________________Grind: 95% less than 200 Tyler meshCopper Circuit: pH Modifier Lime Ca(OH).sub.2 = 1000 g/t Ni Depressant: Sodium Cyanide (NaCN) 50 g/t Collector: M2030* = 10 g/t Frother: MIBC = 5 g/t Pyrite SO.sub.2 = 450 g/t Depressant:Nickel Circuit: pH Modifier: Na.sub.2 CO.sub.3 = 800 g/t Zn Activator: CuSO.sub.4 .times. 5H.sub.2 O = 100 g/t Collector: A350** = 50 g/t Frother: Pine Oil = 20 g/t______________________________________
*Cyanamid collector trade name **Minerec collector trade name
The results obtained when using the above conventional reagents are shown in Table 6.
TABLE 6__________________________________________________________________________ Weight Assays, % g/t % DistributionProduct % Cu Ni Pt Pd Cu Ni Pt Pd__________________________________________________________________________Cu Clean. Conc. 2.90 20.0 1.30 6.5 4.3 68.2 5.2 15.7 15.8Cu Ro. Conc. 6.90 9.25 1.40 4.54 6.30 75.1 14.0 31.6 34.9Ni Clean. Conc. 9.60 1.48 4.54 6.3 3.13 16.7 63.2 50.4 38.1Ni Ro. Conc. 12.77 1.37 4.01 5.16 3.08 20.7 74.4 55.0 49.8Ni Flot. Tail. 80.33 0.045 0.10 0.20 0.15 4.2 11.6 13.4 15.3Feed 100.0 0.85 0.69 1.20 0.79 100.0 100.0 100.0 100.0__________________________________________________________________________
EXAMPLE 7
The same ore as used in the conventional tests was treated in the same manner and under similar circumstances as described above, but without direct additions of sodium cyanide conditioner. Cyanide in this experiment was replaced by depressant LS8 prepared according to Example 1, and was added at a rate of 100 g/t to the grinding operation and 20 g/t to the copper cleaner circuit. The results obtained are shown in Table 7.
TABLE 7__________________________________________________________________________ Weight Assays, % g/t % DistributionProduct % Cu Ni Pt Pd Cu Ni Pt Pd__________________________________________________________________________Cu Clean. Conc. 2.84 23.5 0.25 10.4 5.2 77.6 1.0 24.8 18.4Cu Ro. Conc. 4.32 17.8 0.27 9.3 4.8 89.4 1.7 33.7 25.9Ni Clean. Conc. 7.81 0.55 7.07 6.41 5.20 5.0 80.0 42.1 50.7Ni Ro. Conc. 9.92 0.56 6.13 6.23 4.59 6.5 87.1 51.1 56.9Ni Flot. Tail. 85.76 0.041 0.09 0.21 0.16 4.1 11.2 15.2 17.2Feed 100.00 0.86 0.69 1.19 0.80 100.0 100.0 100.0 100.0__________________________________________________________________________
The results shown in Table 6 and Table 7 clearly demonstrate the enhanced separation of nickel from copper obtained with the use of depressant LS8 of the present invention in the selective flotation of a copper-nickel sulphide bearing ore. With additions of conventional depressants, copper values were also depressed with the nickel as shown in Table 6, resulting in low copper recovery. In the same tests, about 14% of the total nickel reported to the copper rougher concentrate. With the use of depressant LS8 (Table 7) the nickel reporting to the copper rougher concentrate was only 1.7% and the copper recovery was increased to 89.4%. 77.6% of the total copper present in the ore was recovered due to the improved separation in the copper cleaner concentrate, while nickel recovery in the nickel cleaner concentrate was increased from 63.2% to 80.0% with the use of LS8 depressant. It should be added that platinum and palladium recovery was also improved.
EXAMPLE 8
Another ore containing copper-nickel sulphides from Northern Ontario (Canada) having high copper value, was treated in conventional batch laboratory circuit using the following commercial reagents:
Grind: 55% minus 200 Tyler mesh
Copper Circuit: pH Modifier Ca(OH).sub.2 =700 g/t Ni Depressants: Cyanide (NaCN)=150 g/t Collectors: A325*=50 g/t Frother: MIBC=20 g/t
Nickel Circuit: pH Modifier H.sub.2 SO.sub.4 =200 g/t Ni Activator CuSo.sub.4 .times.5H.sub.2 O=100 g/t Collector: A317*=40 g/t Frother: MIBC =5 g/t
Results obtained using the above procedure are shown in Table 8.
*Cyanamid trade name for xanthate collectors
TABLE 8______________________________________ Weight Assays, % % DistributionProduct % Cu Ni Cu Ni______________________________________Cu Clean. Conc. 17.53 26.0 1.20 91.0 43.8Cu Ro. Conc. 26.22 18.3 1.35 95.8 73.7Ni Clean. Conc. 6.31 2.01 1.28 2.5 16.9Ni. Ro. Conc. 8.51 1.71 1.17 2.9 20.8Ni Ro. Tail. 65.27 0.10 0.04 1.3 5.5Feed 100.00 5.01 0.48 100.0 100.0______________________________________
EXAMPLE 9
The ore containing copper-nickel sulphides used in the conventional tests was treated in a same manner as described in the previous paragraph but omitting addition of cyanide conditioner and adding 150 g/t depressant LS8 instead of cyanide, in the copper circuit. The results obtained in this experiment are shown in Table 9.
TABLE 9______________________________________ Weight Assays, % % DistributionProduct % Cu Ni Cu Ni______________________________________Cu Clean. Conc. 15.77 29.0 0.23 91.1 7.7Cu Ro. Conc. 26.81 17.9 0.28 95.6 16.0Ni Clean. Conc. 3.56 2.85 8.98 2.0 68.1Ni Ro. Conc. 5.20 2.29 7.07 2.4 78.3Ni Ro. Tail. 67.99 0.15 0.04 1.3 5.5Feed 100.00 5.02 0.47 100.0 100.0______________________________________
As can be seen from the results shown in Tables 8 and 9, the depressant LS8 improved the copper-nickel selectivity very noticeably, leading to an incrase of nickel recovery in the cleaner concentrate from 16.9% to 68.1%. There was also improvement in the cleaner concentrate grades.
Examples 6 to 9 demonstrate that depressant LS8 can successfully be used for nickel depression during the selective flotation of copper-nickel sulphidic ores.
EXAMPLE 10
A massive sulphide ore containing lead and zinc as major value metals was treated in a laboratory flotation circuit using conventional reagents employed in the commercial plant operation. The major difficulty in treating this ore was that pyrite in the ore was so active that production of a lead concentrate with a commercially acceptable iron sulphide level was not attainable.
In this example laboratory tests were run in a closed circuit operation such that the commercial plant operation was simulated. A closed circuit operation is operated by recirculating the intermediate products as shown schematically in the flowsheet of FIG. 1. The reagents used in the circuit were as follows:
Grind: 65% passing 200 Tyler mesh
Lead Flotation Circuit: pH Modifier and pyrite depressant:
______________________________________ Lime Ca(OH).sub.2 = 750 g/tCollectors: Sodium Amylxanthate = 30 g/tFrother: MIBC = 15 g/t______________________________________
Zinc Flotation Circuit: pH modifier and pyrite depressant:
______________________________________ Lime Ca(OH).sub.2 = 3500 g/tSphalerite Activator: CuSO.sub.4 .times. 5H.sub.2 O = 600 g/tCollector: Sodium Amylxanthate = 60 g/tFrother: MIBC = 10 g/t______________________________________
The zinc flotation step was conducted on the lead rougher tailing as shown in FIG. 1.
The metallurgical results obtained in the conventional procedure are shown in Table 10.
TABLE 10______________________________________ Weight Assays, % % DistributionProduct % Pb Zn Pb Zn______________________________________Pb Concentrate 5.03 41.2 2.05 93.3 0.8Zn Concentrate 23.16 0.18 58.20 1.9 98.4Zn Final 71.81 0.15 0.16 4.8 0.8TailingFeed 100.00 2.22 13.70 100.0 100.0______________________________________
EXAMPLE 11
A laboratory continuous locked cycle in steps described in the previous paragraph was carried out but with addition of depressant LS7 of the present invention. The depressant was added to the grinding step at a rate of 250 g/t. The results of the flotation test using LS7 are shown in Table 11.
TABLE 11______________________________________ Weight Assays, % % DistributionProduct % Pb Zn Pb Zn______________________________________Pb Concentrate 2.81 74.06 1.05 93.4 2.0Zn Concentrate 22.60 0.12 60.56 1.2 98.6Zn Final 74.59 0.16 0.22 5.4 1.2TailingFeed 100.00 2.23 13.88 100.0 100.0______________________________________
The use of depressant LS7 in Example 11 resulted in a significantly higher lead concentrate grade that that obtained without the additions of the depressant in Table 10. This indicated that pyrite, especially oxidized pyrite was rejected from both lead and zinc concentrates into the tailing in presence of the depressant. It is to be noted that the same amount of lead sulphide as in the conventional circuit was contained in approximately half the weight of concentrate with the use of LS7, thereby significantly increasing the grade and reducing the cost of lead recovery.
EXAMPLE 12
The ore used in the previous two tests of Examples 10 and 11 was treated in a commercial plant operating at a rate of 96 tonnes per hour. Plant tests were performed with and without additions of depressant LS7. The flowsheet and reagent addition patterns were similar to those described in Examples 10 and 11 above.
The results obtained in the commercial plant with and without LS7 depressant additions are shown in Table 12.
TABLE 12______________________________________DepressantLS7 Weight Assays, % % DistributionAddition g/t Product % Pb Zn Pb Zn______________________________________0 Pb Conc. 5.03 38.84 1.60 85.3 0.6 Zn Conc. 23.56 0.41 55.25 4.2 94.0 Zn Final 71.41 0.35 1.05 10.5 5.4 Tailing Feed 100.00 2.30 13.85 100.0 100.0300 Pb Conc. 3.06 64.1 1.15 85.9 0.3 Zn Conc. 25.14 0.97 55.10 9.9 92.4 Zn Final 71.80 0.14 1.53 4.2 7.3 Tailing Feed 100.00 2.46 14.99 100.0 100.0______________________________________
It will be noted that a marked increase in lead concentrate grade was observable by the use of depressant LS7 with essentially no loss in lead recovery.
It has been shown by numerous examples conducted on a number of different massive sulphide ores that the depressant of this invention is highly superior to the conventional depressants commonly used in commercial operations.
Although the present invention has been described with reference to the preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.

Claims

1. A froth flotation process for the enhanced separation of copper bearing sulphides from polymetallic sulphidic minerals containing copper sulphide and at least one member of the group consisting of: zinc sulphide, sphalerite, nickel sulphide, pentlandite, copper-lead-zinc sulphides and iron sulphides, comprising the steps of:
(a) preparing a froth flotation reagent by first dissolving in water a mixture of quebracho and one member of the group consisting of: dextrin and guar gum, thereafter, adding to the solution so obtained, a water-soluble salt of a lignin sulphonate and so obtaining a second solution, and lastly adding for dissolution to said second solution at least one member of the group consisting of: alkali metal cyanide, alkaline earth metal cyanide, water-soluble metal sulphate, and a water soluble sulphite containing a tetravalent sulphur atom, so yielding, as the reaction product, a froth flotation reagent solution containing said ingredients added in three successive dissolution steps;
(b) adding said froth flotation reagent solution to an aqueous slurry comprising ground polymetallic sulphicid minerals containing copper sulphide and at least one member of the group consisting of: zinc sulphide, sphalerite, nickel sulphide, pentlandite, copper-lead-zinc sulphides and iron sulphides, and conditioning agents, in an amount sufficient to float the copper sulphides; and
(c) subjecting said aqueous slurry to froth flotation to yield a copper sulphide bearing froth and a tailing containing polymetallic sulphidic materials depleted in copper sulphides.
2. A froth flotation separation process according to claim 1 wherein quebracho is mixed with one member of the group consisting of dextrin and guar gum in a ratio of 1.+-.0.4:2.+-.0.4 prior to forming the first solution in water.
3. A froth flotation separation process according to claim 2 wherein the dissolution of the mixture of quebracho and one member of the group consisting of dextrin and guar gum is conducted at a temperature higher than 40.degree. C.
4. A froth flotation process according to claim 1, wherein the water-soluble salt of the lignin sulphonate added to obtain the second solution is a lignin sulphonate salt formed with one metal of the group consisting of: alkali metal and alkaline earth metal.
5. A froth flotation process according to claim 1, wherein a metal sulphate and an alkali metal cyanide are both added to said second solution.
6. A froth flotation process according to claim 5, wherein the water soluble metal sulphate added to the second solution is zinc sulfate, and the alkali metal cyanide added to the second solution is sodium cyanide.
7. A froth flotation process for the enhanced separation of lead sulphides from at least one member of the group consisting of: zinc sulphides and iron sulphides, said lead sulphides and said at least one member being contained in a polymetallic sulphidic ore, comprising the steps of:
(a) preparing a froth flotation reagent by first dissolving in water a mixture of quebracho and one member of the group consisting of: dextrin and guar gum, thereafter, adding to the solution so obtained, a water-soluble salt of a lignin sulphonate and so obtaining a second solution, and lastly adding for dissolution to said second solution at least one member of the group consisting of: alkali metal cyanide, alkaline earth metal cyanide, water soluble metal sulphate, and a water-soluble sulphite containing a tetravalent sulphur atom, so yielding, as the reaction product, a froth flotation reagent solution containing said ingredients added in three successive dissolution steps;
(b) adding said froth flotation reagent to an aqueous slurry comprising froth flotation conditioning agents, ground polymetallic sulphides containing lead sulphides and at least one member of the group consisting of: zinc sulphides and iron sulphides, in amounts sufficient to float said lead sulphides, and
(c) subjecting said aqueous slurry to froth flotation to yield a lead sulphide bearing froth and a tailing containing sulphidic ores depleted in lead sulphides.
8. A froth flotation process according to claim 7 wherein quebracho is mixed with one member of the group consisting of dextrin and guar gum in a ratio of 1.+-.0.4:2.+-.0.4 prior to forming the first solution in water.
9. A froth flotation process according to claim 8 wherein the dissolution of the mixture of quebracho and one member of the group consisting of dextrin and guar gum is conducted at a temperature higher than 40.degree. C.
10. A froth flotation process according to claim 7, wherein the water-soluble salt of the lignin sulphonate added to obtain the second solution is a lignin sulphonate salt formed with one metal of the group consisting of: alkali metal and alkaline earth metal.
11. A froth flotation process according to claim 7, wherein a metal sulphate and an alkali metal cyanide are both added to said second solution.
12. A mineral separation process for the enhanced separation of metal sulphides contained in polymetallic sulphidic ores comprising copper sulfide, iron sulfide, gangue minerals and at least one member of the group consisting of: zinc sulphide, nickel sulphide and lead sulphide, comprising the steps of:
(a) preparing a froth flotation reagent by first dissolving in water a mixture of quebracho and one member of the group consisting of: dextrin and guar gum, thereafter, adding to the solution so obtained, a water-soluble salt of a lignin sulphonate and so obtaining a second solution, and lastly adding for dissolution to said second solution at least one member of the group consisting of: alkali metal cyanide, alkaline earth metal cyanide, water-soluble metal sulphate, and a water-soluble sulphite containing a tetravalent sulphur atom, so yielding, as the reaction product, a froth flotation reagent solution containing said ingredients added in three successive dissolution steps;
(b) grinding a polymetallic sulphidic ore containing copper sulfide, iron sulfide, gangue minerals and at least one member of the group consisting of: zinc sulphide, nickel sulphide and lead sulphide;
(c) making an aqueous slurry of the ground polymetallic sulphidic ores by adding water and a predetermined amount of conditioning agent comprised of: pH modifiers, depressant agents, collector agents, and frothing agents, and also adding the froth flotation reagent obtained in step (a) in an amount sufficient to float copper sulphide contained in said polymetallic sulphidic ore;
(d) subjecting the aqueous slurry obtained in step (c) to a first froth flotation step to yield a first froth containing copper sulphides and a first tailing of polymetallic sulphides depleted of copper sulphides and, thereafter,
(e) subjecting said first tailing to a second froth flotation step to yield a second froth containing one member of the group consisting of: zinc, lead and nickel sulphides, and a tailing containing iron sulphides and gangue minerals.
13. A mineral separation process according to claim 12, wherein the grinding step is a wet grinding step, and froth flotation reagent obtained in step (a) is also added in said grinding step.
14. A mineral separation process according to claim 12, wherein said froth flotation reagent is also added to the tailing of said first froth flotation step prior to the second flotation step in an amount sufficient to float one member of the group consisting of: zinc sulphides, lead sulphides and nickel sulphides contained in said polymetallic sulphidic ore.
15. A mineral separation process for the enhanced separation of lead and zinc sulphides contained in a massive sulphidic ore, said ore containing at least zinc sulphide, lead sulphide and iron sulphide, comprising the steps of:
(a) preparing a froth flotation reagent by first dissolving in water a mixture of quebracho and one member of the group consisting of: dextrin and guar gum, thereafter, adding to the solution so obtained, a water-soluble salt of a lignin sulphonate and so obtaining a second solution, and lastly adding for dissolution to said second solution so at least one member of the group consisting of: alkali metal cyanide, alkaline earth metal cyanide, water-soluble metal sulphate, and a water-soluble sulphite containing a tetravalent sulphur atom, so yielding, as the reaction product, a froth flotation reagent solution containing said ingredients added in three successive dissolution steps;
(b) grinding a massive sulphidic ore;
(c) making an aqueous slurry of the ground massive sulphidic ore obtained in step (b), by adding water and conditioning agents comprising pH modifiers, depressant agents, collector agents and frothing agents in predetermined amounts, and also adding the froth flotation reagent obtained in step (a) in an amount sufficient to float lead sulphide contained in said massive sulphidic ore;
(d) subjecting the conditioned ore slurry to a first froth flotation separation step to yield a froth containing lead sulphide and a tailing depleted of lead sulphide; and, thereafter,
(e) subjecting the tailing of said first froth flotation step to a second froth flotation separation step in the presence of frothing agent, collector agent and depressant agent, to yield a froth containing zince sulphides and a second tailing containing iron sulphides depleted of lead and zinc sulphides and gangue minerals.
16. A mineral separation process according to claim 15, wherein the grinding step is a wet grinding step and froth flotation reagent prepared in step (a) is also added in the wet grinding step.
17. A mineral separation process according to claim 15 wherein said froth flotation reagent is also added to the tailing of said first froth flotation step prior to the second froth flotation step together with frothing agent, collector agent and depressant agent, in an amount sufficient to float zinc sulphides contained in said massive sulphidic ore.
18. A froth flotation process according to claim 11, wherein the water-soluble metal sulphate added to the second solution is zinc sulphate, and the alkali metal cyanide added to the second solution is sodium cyanide.

US Referenced Citations (8)

Number	Name	Date
1741028	Koenig	Dec 1929
2019306	Handy	Oct 1935
2070076	Brown	Feb 1937
2471384	Booth	May 1949
2919802	Drake	Jan 1960
3912623	Buza	Oct 1975
4246096	Bulatovic	Jan 1981
4702824	Abadi	Oct 1987

Separation of polymetallic sulphides by froth flotation

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