GB2182587A

GB2182587A - Froth flotation of nickel sulphide minerals

Info

Publication number: GB2182587A
Application number: GB08626326A
Authority: GB
Inventors: Charles Andrew Bennett; Nouraldin Mahmood Mahmood; Paul William Page; Keith Douglas Pearse
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1985-11-05
Filing date: 1986-11-04
Publication date: 1987-05-20
Also published as: GB2182587B; GB8626326D0; GB8527214D0

Abstract

Process for the selective separation of nickel sulphide minerals in the form of pentlandite from ores containing iron sulphide minerals in the form of pyrrhotite. The process involves froth flotation of an aqueous pulp of the ore; the pH of the pulp is maintained in the range 3 to 7, preferably 4 to 6. A collector having a thio group, e.g. potassium or sodium alkyl xanthate, or potassium or sodium dialkyl dithiophosphate, and an oxidant such as hydrogen peroxide or a hypochlorite are added to the pulp and the nickel sulphide minerals are floated so as to form a nickel concentrate. Aeration may be by air or nitrogen.

Description

SPECIFICATION Separation process The present invention relates to the separation of mineral ores and more particularly relates to the separation of minerals by a froth flotation process. More specifically, the invention relates to the separation of nickel sulphide containing minerals from ores or concentrates by froth flotation.

Froth flotation is a widely used method for the concentration of ores and ittakes advantage ofthedif- ferences in the surface chemical properties of different minerals. One ofthe steps in the production of nickel is the flotation ofthe nickel containing mineralsto produce a concentrate having high nickel value. in the separation of nickel containing minerals (eg pentlandite) from gangue (eg iron sulphides) minerals by froth flotation, it is desirable to maximise nickel grade and recoveryforeconomicandenviron- mental reasons (such as reduction of SO2 emission during smelting). Usuallythe process is carried out under alkaline conditions (pH 8to 9) and a relatively large proportion of pyrrhotite is recovered with the nickel concentrate.GB 2086768B discloses a process for the recovery of metal values from nickel sulphide ores or concentrates by froth flotation of an aqueous pulp of the ground ore or concentrate, characterised by the steps of adjusting the pulp pH to 9-10, adding cyanide ions in an amount sufficient to depress all the sulphide mineral content of the pulp, condition- ing the pulpfortheflotation of nickel sulphide, adding a strong sulphydryl collectorto the pulp in an amount sufficient to float the nickel sulphide, and floating and removing the nickel sulphideto provide a nickel concentrate.

The present invention relates to an improved pro cess for obtaining selective separation of nickel sulphide minerals from ores containing iron sulphide minerals in which flotation is carried outunderacidic conditions in the presence of an oxidant. There- sultantconcentratefrom the process may be used in an electrohydrometallurgical process for obtaining metallic nickel such as that disclosed in our copending UK patent application No. 8521372.

Thus according to the present invention there is provided a process for the separation of nickel sul phidemineralsfrom nickelsulphideoresorcon- centrates by froth flotation of an aqueous pulp ofthe ore or concentrate in which (a) the pH ofthe pulp is maintained in the range 3to7, (b) a collector having a thio group is added to the pulp and (c) an oxidant, preferably hydrogen peroxide, is added to the pulp either before orafterstep (b) whereby the nickel sulphide minerals are floated so as to form a nickel concentrate.

The preferred process is for the selective separation of nickel sulphide minerals in the form of pentlanditefrom ores containing iron sulphide minerals in the form of pyrrhotite.

The collector having a ohio grouping is preferably a potassium or sodium alkyl xanthate ora potassium or sodium dialkyl dithiophosphate.

The froth flotation process may be carried outcon ventionally by crushing and grinding the oreto a suit- able size to form a water based pulp, the pulp being aerated following a suitable conditioning procedure.

The aerating gas is typically air or nitrogen.

The process is carried out under acidic conditions the preferred pH being in the range 4to 6. The pH may be maintained by the use of buffer reagents and a typical buffer reagent being acetic acid/sodium acetate.

The pulp is conditioned for a suitable period with the collector and with the oxidant. Atypical oxidant for the process is hydrogen peroxide or a hypochlorite.

Afrothing agent may be used in the process but it is not always necessary.

It is envisaged thatthe process may be operated batchwise or continuously.

The preferred temperature range during the process is from 1 to 30"C.

The invention will now be described by way of example only.

The flotation process was carried out with an ore assayed at about7% nickel and consisting almost en- tirely of pentlandite and pyrrhotite, the ore originating from the Agnew field in Western Australia.

The ore was ground to a particle size of about 80% less than 75 Fm to form a water based pulp having a content of 15 to 20 g. of ore to 85 to 80 g of solution. A buffer of acetic acid/sodium acetate was used to stabilise the pH at about 4.6. The pulpwasthen conditioned with a collector (sodium or potassium ethyl xanthate) for about 2 minutes, then with an oxidant (hydrogen peroxide) for about 30 minutes. The concentrations of collector and oxidantwere 400g/tonne of ore and 15 kg/tonne of ore respectively but these are not necessarilythe optimum values. The pulp was then aerated with air or nitrogen until theflota- tion process was complete, the pentlandite being selectively recovered in the froth layer.The temperature ofthe process was ambient (about200C).

After filtering and drying,the nickel concentrate assayed 28% nickel and contained approximately 90% ofthe nickel in the original ore.

In the case of the separation of pentlandite mineral from pyrrhotite mineral, the oxidant is added to the pulp either before or after collector addition in an amountsufficientto depress the pyrrhotitecontent ofthe pulp and using sufficientthio-type collector (in theform of potassium orsodium alkylxanthateor potassium or sodium dialkyl dithiophosphate) in the pulp to float the pentlandite and produce a nickel concentrate.

During the flotation process, the redox potential of the pulp was monitored and was of the order 500 mV with respect to a standard hydrogen electrode. The electrode potential of the water based pulp/buffer solution at a pH of 4.6 in the absence of collector and oxidantwas measured at between 300to400 mV with respectto the standard hydrogen electrode.

1. Process for the separation of nickel sulphide minerals from nickel sulphide ores or concentrates by froth flotation of an aqueous pulp of the ore or concentrate in which (a) the pH ofthe pulp is main

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Separation process The present invention relates to the separation of mineral ores and more particularly relates to the separation of minerals by a froth flotation process. More specifically, the invention relates to the separation of nickel sulphide containing minerals from ores or concentrates by froth flotation. Froth flotation is a widely used method for the concentration of ores and ittakes advantage ofthedif- ferences in the surface chemical properties of different minerals. One ofthe steps in the production of nickel is the flotation ofthe nickel containing mineralsto produce a concentrate having high nickel value. in the separation of nickel containing minerals (eg pentlandite) from gangue (eg iron sulphides) minerals by froth flotation, it is desirable to maximise nickel grade and recoveryforeconomicandenviron- mental reasons (such as reduction of SO2 emission during smelting). Usuallythe process is carried out under alkaline conditions (pH 8to 9) and a relatively large proportion of pyrrhotite is recovered with the nickel concentrate.GB 2086768B discloses a process for the recovery of metal values from nickel sulphide ores or concentrates by froth flotation of an aqueous pulp of the ground ore or concentrate, characterised by the steps of adjusting the pulp pH to 9-10, adding cyanide ions in an amount sufficient to depress all the sulphide mineral content of the pulp, condition- ing the pulpfortheflotation of nickel sulphide, adding a strong sulphydryl collectorto the pulp in an amount sufficient to float the nickel sulphide, and floating and removing the nickel sulphideto provide a nickel concentrate. The present invention relates to an improved pro cess for obtaining selective separation of nickel sulphide minerals from ores containing iron sulphide minerals in which flotation is carried outunderacidic conditions in the presence of an oxidant. There- sultantconcentratefrom the process may be used in an electrohydrometallurgical process for obtaining metallic nickel such as that disclosed in our copending UK patent application No. 8521372. Thus according to the present invention there is provided a process for the separation of nickel sul phidemineralsfrom nickelsulphideoresorcon- centrates by froth flotation of an aqueous pulp ofthe ore or concentrate in which (a) the pH ofthe pulp is maintained in the range 3to7, (b) a collector having a thio group is added to the pulp and (c) an oxidant, preferably hydrogen peroxide, is added to the pulp either before orafterstep (b) whereby the nickel sulphide minerals are floated so as to form a nickel concentrate. The preferred process is for the selective separation of nickel sulphide minerals in the form of pentlanditefrom ores containing iron sulphide minerals in the form of pyrrhotite. The collector having a ohio grouping is preferably a potassium or sodium alkyl xanthate ora potassium or sodium dialkyl dithiophosphate. The froth flotation process may be carried outcon ventionally by crushing and grinding the oreto a suit- able size to form a water based pulp, the pulp being aerated following a suitable conditioning procedure. The aerating gas is typically air or nitrogen. The process is carried out under acidic conditions the preferred pH being in the range 4to 6. The pH may be maintained by the use of buffer reagents and a typical buffer reagent being acetic acid/sodium acetate. The pulp is conditioned for a suitable period with the collector and with the oxidant. Atypical oxidant for the process is hydrogen peroxide or a hypochlorite. Afrothing agent may be used in the process but it is not always necessary. It is envisaged thatthe process may be operated batchwise or continuously. The preferred temperature range during the process is from 1 to 30"C. The invention will now be described by way of example only. The flotation process was carried out with an ore assayed at about7% nickel and consisting almost en- tirely of pentlandite and pyrrhotite, the ore originating from the Agnew field in Western Australia. The ore was ground to a particle size of about 80% less than 75 Fm to form a water based pulp having a content of 15 to 20 g. of ore to 85 to 80 g of solution. A buffer of acetic acid/sodium acetate was used to stabilise the pH at about 4.6. The pulpwasthen conditioned with a collector (sodium or potassium ethyl xanthate) for about 2 minutes, then with an oxidant (hydrogen peroxide) for about 30 minutes. The concentrations of collector and oxidantwere 400g/tonne of ore and 15 kg/tonne of ore respectively but these are not necessarilythe optimum values. The pulp was then aerated with air or nitrogen until theflota- tion process was complete, the pentlandite being selectively recovered in the froth layer.The temperature ofthe process was ambient (about200C). After filtering and drying,the nickel concentrate assayed 28% nickel and contained approximately 90% ofthe nickel in the original ore. In the case of the separation of pentlandite mineral from pyrrhotite mineral, the oxidant is added to the pulp either before or after collector addition in an amountsufficientto depress the pyrrhotitecontent ofthe pulp and using sufficientthio-type collector (in theform of potassium orsodium alkylxanthateor potassium or sodium dialkyl dithiophosphate) in the pulp to float the pentlandite and produce a nickel concentrate. During the flotation process, the redox potential of the pulp was monitored and was of the order 500 mV with respect to a standard hydrogen electrode. The electrode potential of the water based pulp/buffer solution at a pH of 4.6 in the absence of collector and oxidantwas measured at between 300to400 mV with respectto the standard hydrogen electrode. CLAIMS

1. Process for the separation of nickel sulphide minerals from nickel sulphide ores or concentrates by froth flotation of an aqueous pulp of the ore or concentrate in which (a) the pH ofthe pulp is main tained in the range 3to 7, (b) a collector having a ohio group is added to the pulp and (c) an oxidant is added to the pulp either before or after step (b) whereby the nickel sulphide minerals are floated so as to form a nickel concentrate.

2. Process according to claim 1 in which the pH of the pulp is in the range 4to 6.

3. Process according to claim 1 or claim 2 in which the collector is a potassium or sodium alkyl xanthate or a potassium or sodium dialkyl dithiophosphate.

4. Process according to any of claims 1 to 3 in which the oxidant is hydrogen peroxide.

5. Process according to any ofthe preceding claims in which the pulp is conditioned for a suitable period with the collector and with the oxidant.

6. A process according to any of the preceding claims in which a frothing agent is used.

7. Process according to claim 5 in which the pulp is aerated following the conditioning step.

8. Process according to any ofthe preceding claims in which the temperature range is from 5 Cto 50"C.

9. Process forthe separation of nickel sulphide minerals from nickel sulphide ores or concentrates as hereinbefore described.