GB1585896A - Ore treatment process - Google Patents

Description

(54) ORE TREATMENT PROCESS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SWIP 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a process for the recovery of metal concentrates from metal-bearing mineral ores; and to the metal concentrates so obtained.

The recovery of metal concentrates from metal-containing ores is commonly effected by so-called froth flotation processes, by means of which valuable metal compounds, such as metal sulphides and/or oxides may be separated from the gangue materials with which they are associated in the mineral ores.

In a typical froth flotation process, the ore is first crushed and subjected to wet grinding to reduce the size of the ore particles. It is then diluted with water to give a slurry to which various frothing, conditioning and collecting agents are added. The slurry is then aerated to produce air bubbles which rise to the surface as a froth containing a concentration of the desired mineral particles, hereinafter referred to as a metal concentrate.

A number of collecting agents have been proposed; but mercaptans and xanthates are commonly used, which tend to be odorous and unpleasant to handle.

We have now devised a process for the recovery of metal concentrates which makes use of sulphur-free collectors.

According to the present invention, a process for the recovery of metal concentrates from mineral ores containing a metal or metals in the form of their sulphides and/or oxides, comprises subjecting the crushed ore to a froth flotation process in aqueous medium using, as a collector, an aliphatic aldoxime having 8 or more carbon atoms, the aqueous medium having a pH value of at least 6.

The aliphatic group of the oxide may comprise a straight or branched chain or may be alicyclic. The group may also contain carbon-carbon unsaturation.

Preferably, the aliphatic oxime is an aldoxime of general fromula C H NOH in which n is an integer having a value from 8 to 16.

It is also possible to use a mixture of aliphatic oximes in which n has different values. Examples of aliphatic oximes which may be used in our process include nonanaldoxime (n-5), dodecanaldoxime (n=12), 2-methyl dodecanaldoxime (n=13), octanaldoxime (n=8), mixed tridecan and pentadecanaldoximes (n=13 and The oximes may be readily prepared by the action of a hydroxylamine on the appropriate aliphatic aldehyde. Aldehydes which are particularly suited to this purpose are those commonly prepared by carbonylation of olefins. Such aldehydes are readily available in suitably large quantities.

The process of our invention may be applied to mineral ores containing one or more metals, for example, copper, zinc, platinum, molybdenum, nickel, lead, antimony, arsenic, silver and gold. The process is especially suitable for concentrating copper-containing ores.

Generally, the ore to be processed will contain between 0.02 and 1% by weight of the metal or metals to be recovered, but ores containing higher percentage of metal may be treated. Between 0.01 and 1 kg of aldoxime may be used for each tonne of ore processed, depending on the concentration of metal in the ore and the conditions under which the process is run.

The aldoxime is generally added, either as solid or as an aqueous emulsion, to an aqueous slurry of the ore which has been crushed to give particles < 300 m, preferably 50-150 m, the slurry containing from 20-40% solids by weight.

Alternatively, the aldoxime may be used as a concentrated solution in an organic solvent or, if appropriate, one of the other additives.

Normally, metal concentrate recovery processes include several flotation stages, and our aldoxime collectors may be added to any of these stages. They may also be added at stages prior to or subsequent to those in which other collectors are added. The metal concentrate-containing froth may be skimmed from the surface of the slurry, filtered, and the residual concentrate dried.

The metal or metals may be recovered from the metal concentrate by any extraction or refining process, including pyrometallurgical processes. The process of our invention is suitable for the froth flotation of mineral ores: containing metal sulphides. Examples of suitable sulphide mineral ores are given in Table I:: TABLE I

Empirical Metal Mineral Ore @ommula Copper Bornite Cu5FeS4 Chalcopyrite Cu FeS2 Chalcocite Cu2S Covallite CuS Antimony Stibnite Sb2S3 Cobalt Cobaltite CoAsS tend Galena PbS Molybdennm Molybdenite MoS2 Nickel Millerite NiS Zinc C Sphalerite ZnS The process of our invention may also be applied to the froth flotation of mineral ores containing metal oxides. Examples of such ores are given in Table II.

TABLE II

Empirical Metal Mineral Ore Formula Copper Cuprite Cu2O Chrysocolla CuSiO32H2O Azurite Cu3(CO3)2(OH)2 Malachite Cu2CO,(OH)2 Lead Certs site PbCO2 Molybdenum Wulfenite PbMoO4 Tin Cassiterite SnO2 Zinc Zincite ZnO Smithsonite ZnCO, For the purpose bf this specification, the term "metal oxides" is also intended to eover complex or hydrated oxides, for example carbonates and hydroxides.

The process may also be used in the froth flotation of mineral ores in which the metals are neither sulphides nor oxides. Examples of such ores are given in Table III.

TABLE III

@@@@@ @@@@@@@@ Empirical Metal Mineral Ore Formula Gold Sylvanite (AuAg)Te2 Calaverite AuTe2 Platinum Sperrylite PtAs2 Silver Hessite AgTe2 Nickel Niccolite NiAs It will be appreciated that the optimum pH of the slurry will depend on the actual ore being processed, and should thus be chosen to give optimum concentration and recovery of the desired metal-containing part of the mineral, provided always that the pH is at least 6.

The invention is illustrated by the following Examples.

Examples 1--5.

General Procedure Synthetic ores were prepared by grinding and sieving, separately, the mineral to be floated, e.g. chalcopyrite or malachite, and a gangue material of granite, collecting the fractions between 53 ,um and 150 ssm particle diameter, and then mixing to the required grade. The ore so obtained was placed in a 3 litre laboratory flotation cell, and made up to volume with water containing sodium hydroxide solution (50 ml 0.1M) to give a pH of 10.5. A solution of the collector compound in a minimum of methanol was then added, followed by an aqueous solution of a proprietary frothing agent (1 ml of 1% polypropylene glycol methyl ether) and the resulting slurry conditioned by stirring at 1000 rpm for 10 minutes.Air was then introduced at the rate of 5 litres per minute and a froth formed which was skimmed off, filtered, dried and analysed for copper. A second portion of collector and frothing agent was then added to the cell and more froth collected. The residues in the cell were also analysed. The percentages of copper in the concentated froth, given in Table IV, is in fact the average of the two froths and the recovery given is accumulative.

TABLE IV

% Cu by wt Ex. Mineral Collector Dosage # % Cu No. Ore Compound g/Kg of Cu F C T Recovery 1 CuFeS2 Dodecanaldoxime 18.2 2.75 27.9 ND 97 2 Cu2CO3(OH)2 Nonanaldoxime 18.2 5.5 15.8 0.2 97 3 Cu2CO3(OH)2 Nonanaldoxime* 18.2 5.5 16.5 0.22 92 4 Cu2CO3(OH)2 Dodecanaldoxime 18.2 5.5 32.7 0.17 97 5 Cu2CO3(OH)2 2-Methyl Dodecan- 18.2 5.5 25.2 1.7 76 aldoxime When the process was repeated with a xanthate collector, similar results were obtained.

+ = no frothing agent added F = Feed C = Concentrate T = Tailings ND = Not detectable # = dosage for first floated froth; the same weight of collector was used for all subsequent floats in all Examples.

Example 6.

A naturally-occurring copper-containing mineral ore (700 g) from the Palabora mine, South Africa, was crushed and sieved to give a fraction having particle sizes < 300 ym. This fraction (500 g) was then treated in the 3 litre flotation cell by the general procedure given under Examples 1 to 5 above. The collector compound was dodecanaldoxime and the pH of the slurry in the flotation cell was adjusted to 10.65. The results of the treatment are sumniarised in Table V below.

TABLE V

Dosage of Collector % Cu by weight % Cu g/KgCu Kg/Tonne Ore F C T Recovery 11.3 0.035 0.44 4.1 0.2 57.6 It will be seen that the concentrate was enriched approximately ten times, compared with the untreated ore.

Examples 7-9.

A sample (500 g) of ore from the Gasps Mine, Canada was jaw-crushed to a particle size < 2 mm, and then wet rod-milled in water (400 ml) until 80% of the ore particles were < 75 m . The resulting slurry was floated in a 2 litre flotation cell using the general procedure of Examples 1-5 except that a conditioning time of 3 minutes was used, the frothing agent was methyl isobutyl carbinol added after conditioning, and the aqueous medium was left at its natural pH of 7.8. In Examples 7 and 8, only the first froth was recovered. The results are given in Table VI below.

TABLE VI

Dosage % Cu by wt Ex Collector Kg/tonne % Cu No | Compound ore F C T Recovery 7 Nonanaldoxime 0.25 0.830 15.23 0.55 35.1 8 Dodecanaldoxime 0.25 0.815 13.63 0.6:7 19;0 9 Dodecanaldoxime 0.25 0.815 12.12 0.61 26.5 Cl Potassium amyl 0.25 Q*864 14.04 0.62 26.3 xanthate A comparative test (Cl) was carried out using an equivalent concentration of potassium amyl xanthate.It will be seen that the collectors according to our invention gave generally comparable results and, in Example 7, an improved grade and % recovery.

Example 10--12.

A sample (500 g) of ore from the Cyprus Pima Mine, USA, (containing approximately 0.6% Cu) was jaw crushed to a particle size of < 2 mm and then wet rod-milled in water (500 ml) until 90 /O of the particles were < 212 m > and 60% > 45 m,u. The resulting slurry was floated in a 3 litre flotation cell using the general procedure given under Examples 1-5. This time, three successive floated froths were recovered and combined 2 ml of a 1% frothing agent solution being added for each flotation. The results are given in Table VII below. The results in parenthesis are for the first float only.

TABLE VII

Collector Dosage Concentrate % Cu -Ex No Compound Kg/tonne ore % Cu by wt Recovery 10 Nonanaldoxime 0.01 3.1(8.1-) 56.8 (40.2) 11 Isodecanaldoxime 0.01 2.9(5.9) 70.0?(49.8) 12 Cl3/Cls aldoxime 0.01 5.1 (9.7) 66.3 (48.8:) Iso-decanaldoxime was prepared from the aldehyde produced by carbonylation of propylene trimer and the mixed C,3/C,s aldoxime by carbonylation of a mixed stream of C13 (66.6%) C15 (33.3%) olefins.

The results in the above Examples have not been fully optimised, in that many parameters, e.g. particle size range, pH, collector concentration, stirrer rate and variations in the composition of the flotation mixture, for example by the addition of gangue depressants, have a marked effect on the recovery and concentration obtained. However, these factors vary greatly with the precise ore being treated and the type of flotation process which is favoured at the mine in question; it is thus best that final optimisation is carried out at the site of the mine.

WHAT WE CLAIM IS: 1. A process for the recovery of metal concentrates from mineral ores containing a metal or metals in the form of their sulphides and/or oxides, in which the crushed ore is subjected to a froth flotation process in aqueous medium using, as collector, an aliphatic aldoxime having 8 or more carbon atoms, the aqueous medium having a pH value of at least 6.

2. A process as claimed in claim 1 in which the aldoxime is one of general formula CnH2nNOH in which n is an integer having a value from 8 to 16.

3. A process as claimed in claim 2 in which the aldoxime is nonaldoxime, dodecanaldoxime, 2-methyl dodecanaldoxime, octanaldoxime, or a mixture of tridecan and pentadecan aldoximes.

4. A process as claimed in any one of claims I to 3 in which from 0.01 to l kg of aldoxime is added per tonne of ore processed.

5. A process as claimed in any one of claims 1 to 4 in which a frothing agent is added to the aqueous medium.

6. A process as claimed in any one of claims l to 5 in which the ore treated is a copper-containing ore.

7. A froth flotation process as claimed in claim 1, substantially as described in any one of Examples l to 12.

8. A metal concentrate whenever produced by a froth flotation process as claimed in any one of claims l to 7.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE VII Collector Dosage Concentrate % Cu -Ex No Compound Kg/tonne ore % Cu by wt Recovery 10 Nonanaldoxime 0.01 3.1(8.1-) 56.8 (40.2) 11 Isodecanaldoxime 0.01 2.9(5.9) 70.0?(49.8) 12 Cl3/Cls aldoxime 0.01 5.1 (9.7) 66.3 (48.8:) Iso-decanaldoxime was prepared from the aldehyde produced by carbonylation of propylene trimer and the mixed C,3/C,s aldoxime by carbonylation of a mixed stream of C13 (66.6%) C15 (33.3%) olefins. The results in the above Examples have not been fully optimised, in that many parameters, e.g. particle size range, pH, collector concentration, stirrer rate and variations in the composition of the flotation mixture, for example by the addition of gangue depressants, have a marked effect on the recovery and concentration obtained. However, these factors vary greatly with the precise ore being treated and the type of flotation process which is favoured at the mine in question; it is thus best that final optimisation is carried out at the site of the mine. WHAT WE CLAIM IS:

1. A process for the recovery of metal concentrates from mineral ores containing a metal or metals in the form of their sulphides and/or oxides, in which the crushed ore is subjected to a froth flotation process in aqueous medium using, as collector, an aliphatic aldoxime having 8 or more carbon atoms, the aqueous medium having a pH value of at least 6.

2. A process as claimed in claim 1 in which the aldoxime is one of general formula CnH2nNOH in which n is an integer having a value from 8 to 16.

3. A process as claimed in claim 2 in which the aldoxime is nonaldoxime, dodecanaldoxime, 2-methyl dodecanaldoxime, octanaldoxime, or a mixture of tridecan and pentadecan aldoximes.

4. A process as claimed in any one of claims I to 3 in which from 0.01 to l kg of aldoxime is added per tonne of ore processed.

5. A process as claimed in any one of claims 1 to 4 in which a frothing agent is added to the aqueous medium.

6. A process as claimed in any one of claims l to 5 in which the ore treated is a copper-containing ore.

7. A froth flotation process as claimed in claim 1, substantially as described in any one of Examples l to 12.

8. A metal concentrate whenever produced by a froth flotation process as claimed in any one of claims l to 7.