WO2024256057A1

WO2024256057A1 - Separation of cu and ni from ore using h2o2

Info

Publication number: WO2024256057A1
Application number: PCT/EP2024/059466
Authority: WO
Inventors: Mitchell LANCASTER; Alun Pryce James
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 2023-06-13
Filing date: 2024-04-08
Publication date: 2024-12-19
Anticipated expiration: 2025-12-13
Also published as: AR132929A1

Abstract

The present invention relates to a process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu, the process comprising the steps of: a) subjecting the ore to a first froth flotation to provide a first concentrate comprising Ni and Cu and a first underflow, b) subjecting the first concentrate to a second froth flotation to provide a second concentrate and a second underflow, and c) recovering Cu in the second concentrate and Ni in the second underflow, wherein the second froth flotation is conducted in the presence of H₂O₂.

Description

Separation of Cu and Ni from ore using H2O2

TECHNICAL FIELD

The present relates to a process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu.

TECHNICAL BACKGROUND

Ores containing Ni and Cu are of economic importance. Such Ni-and Cu- containing ores can be subjected to froth flotation to recover the desired mineral and discard any gangue minerals.

Usually, this process comprises aeration of a dispersion of the ground ore to form a froth on the surface. The froth contains hydrophobic particles whereas the underflow contains hydrophilic particles. The froth is then separated from the underflow to produce a purified concentrate. This process and the relevant reagents are described in Chapter 16 “Flotation of Nickel and Nickel-Copper Ores’" in the “Handbook of Flotation Reagents: Chemistry, Theory and Practice"", vol 2, 2007, Elsevier B.V. by S. M. Bulatovic.

Many of the flotation reagents, such as cyanides and polyamines, are, however, environmentally harmful and potentially toxic for aquatic organisms. In addition, due to the large scale of operations, even small improvements in the extraction and separation of Ni and Cu from such ores have a large overall impact. Therefore, it is an object of the present invention to provide a process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu that is environmentally-friendly and sustainable. In addition, it is an object of the present invention to provide a process that increases the recovery of Ni and/or Cu from an ore comprising Ni and Cu. Furthermore, it is an object of the present invention to provide a process that increases the separation of Ni from Cu.

SUMMARY OF THE INVENTION

These objects have been solved by a process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu, the process comprising the steps of: a) subjecting the ore to a first froth flotation to provide a first concentrate comprising Ni and Cu and a first underflow, b) subjecting the first concentrate to a second froth flotation to provide a second concentrate and a second underflow, and c) recovering Cu in the second concentrate and Ni in the second underflow, wherein the second froth flotation is conducted in the presence of H2O2.

It has been found that the above process comprising a first froth flotation (also referred to as rougher froth flotation) and a second froth flotation in the presence of H2O2 is more environmentally-friendly than the processes of the prior art. It has been found that the process of the present invention results in improved extraction of Ni and Cu and improved separation of Ni from Cu.

The present invention further relates to the use of H2O2 for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu by froth flotation.

DETAILED DESCRIPTION OF THE INVENTION

The following definitions are relevant in connection with the embodiments of the present invention.

The meaning of the term “comprising” is to be interpreted as encompassing all the specifically mentioned features as well optional, additional, unspecified ones, whereas the term “consisting of’ only includes those features as specified. Therefore, “comprising” includes as a limiting case the composition specified by “consisting of’.

The term “wt.-%” refers to the amount of the respective component by weight based on the total amount of the composition, unless noted otherwise.

As used herein, the singular forms “a”, “an”, and “the” include both singular and plural referents unless the context clearly dictates otherwise. By way of example, “a depressant” means one depressant or more than one depressant.

The term “ore” refers to a naturally occurring mineral from which a metal and other elements can be extracted. Metals are commonly present as oxides, aresenides, sulfides, sulfates or silicates.

The term “conditioning” refers to treating a ground ore with reagents, such as collectors, frothers, froth phase modifiers, dispersants, depressants, suppressants, pH regulators, and activators for a certain time period before subjecting the conditioned ore to froth flotation. Conditioning is applied to increase yield and/or ease of separation during froth flotation.

The term “froth flotation” refers to a method for separating minerals from a dispersion of ground ore by applying a gas, usually air, through the dispersion to form a froth or float on the surface. The float contains hydrophobic particles whereas the underflow contains hydrophilic particles. The float can also synonymously be called “froth” or “concentrate” and the underflow can also synonymously be called “tails” or “tailings”. The concentrate refers to material obtained after removal of gangue minerals, leaving minerals of value in the concentrate. Froth flotation can be carried out using equipment and procedures known in the art, such as a Denver, Galigher, Wemco, Outokumpo, Sala, or a Jameson cell.

The expression “ore comprising Ni and Cu” (also called Ni-Cu-ore) refers to an ore comprising minerals containing Ni and Cu ions, e.g., in the form of nickel sulfides and cupper sulfides. Such an ore may comprise as nickel containing mineral violarite, millerite, lattice substituted/doped pyrrhotite and/or pentlandite. Such an ore may comprise as copper containing mineral chalcopyrite, chalcocite, and/or bornite.

The term “collector” refers to a compound that increases the amount of desired mineral that is formed in the froth, i.e., a compound that renders the minerals water-repellents and increase attachment of the desired mineral to the air bubbles during froth flotation. Alkyl xanthate salts and dialkyl xanthogen formate are widely used collectors, in particular for Cu.

The term “frother” as used herein refers to a compound that increases the amount and/or stability of the froth that is formed during froth flotation. Frothers are surface-active compounds that commonly contain a polar group and a hydrocarbon chain. Non-limiting examples of frothers include phenols, alkylaryl sulfonates, aliphatic alcohols, alkoxy paraffins, polyglycol ethers, and polyglycol ethers. Different flotation reagents are disclosed in the “ Handbook of Flotation Reagents: Chemistry, Theory and Practice" , vol 2, 2007, Elsevier B.V. by S. M. Bulatovic.

The term “froth phase modifier” as used herein refers to a compound that controls the interaction of collectors between specific minerals. These compounds show an activating or depressing action in flotation. Thus, the term “froth phase modifier” is a generic term that may encompass depressants, pH regulators and activators. The term “dispersant” refers to compounds, usually polymers, that either increase the stability of the ore in the slurry or that prevent the formation of slimes during flotation.

The term “depressant” refers to a compound that reduces the amount of specific minerals that attach to air bubbles during froth flotation. In particular, depressants selectively inhibit the interaction of a specific mineral with the collector. As the depressant is selective for certain minerals and not others, it is preferred that the depressant is a depressant for gangue minerals and/or a Ni depressant.

The term “pH regulator” refers to a compound that regulates the pH value. Nonlimiting examples are inorganic acids, such as aqueous HC1 and inorganic bases, such as lime. It is to be understood that a reagent may have more than one function, i.e. lime can be a pH regulator and a froth phase modifier.

The term “grade” refers to the mass of a desired material based on the amount of ore: In case the grade is based on a concentrate, the grade refers to the mass of a desired material based on the amount of dried concentrate.

Preferred embodiments according to the invention are defined hereinafter. It is to be understood that the following embodiments refer to all aspects of the present invention, which includes the process for extracting and separating as well as the use of H2O2 for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu by froth flotation.

In an embodiment, the present invention relates to a process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu, the process comprising the steps of: a) subjecting the ore to a first froth flotation to provide a first concentrate comprising Ni and Cu and a first underflow, b) subjecting the first concentrate to a second froth flotation to provide a second concentrate and a second underflow, and c) recovering Cu in the second concentrate and Ni in the second underflow, wherein the second froth flotation is conducted in the presence of H2O2.

It is to be understood that the term “for extracting Ni and Cu” encompasses partial extraction of Ni and Cu. Likewise the term “for separating Ni from Cu” encompasses partial separation of Ni from Cu. Put differently, Ni and Cu do not need to be separated completely from each other and the Ni to Cu wt. -ratio in the concentrate is different than in the ore. In an embodiment, the Ni to Cu wt.-ratio in the concentrate is lower than the Ni to Cu wt.-ratio in the ore. Thus, the concentrate can be enriched with Cu. In an embodiment, the Ni to Cu wt.-ratio is larger in the underflow than the Ni to Cu wt.-ratio in the ore.

The term “recovering” comprises further process steps, such as drying and/or a further froth flotation. In particular for recovering Ni from the second underflow, it is preferred to subject the second underflow to a third froth flotation step, preferably in the presence of a Ni collector, to provide a third concentrate and a third underflow and recovering the Ni from the third concentrate.

The pH value during the froth flotation process is important, yet plays a complex role. In an embodiment, the second froth flotation is conducted at a pH value of above 10.0, preferably at a pH value of above 12.0. It is preferred that the first froth flotation is conducted at a lower pH value than the second froth flotation. In an embodiment, the first froth flotation is conducted at a pH value of 8.0 to 13.0, preferably at a pH value of 8.5 to 10.0. It is preferred that the pH value is conducted at a uniform pH value. It is further preferred that the pH value is adjusted before the ore is conditioned. Without being bound by theory, it is believed that under basic pH, the H2O2 will alter the surface structure of the Ni- containing minerals while not altering the surface structure of Cu-containing minerals, thus making the Ni-containing minerals more hydrophilic and increasing the amount of Ni-containing minerals in the underflow.

In an embodiment, the ore is conditioned before the first froth flotation to provide a conditioned ore. In an embodiment, the conditioning is conducted at a pH value of 8.0 to 13.0, preferably at a pH value of 8.5 to 10.0. It is preferred that the pH value is conducted at a uniform pH value. It is further preferred that the pH value is adjusted before the ore is conditioned.

In the process of the invention, the pH is measured by a glass pH electrode placed into the slurry present during the process step concerned (second froth flotation and/or conditioning), most often following the grind of the ore. The probe is calibrated with commercially available, certified buffer solutions.

In an embodiment, a flotation reagent selected from collectors, frothers, froth phase modifiers, dispersants, depressants, suppressants, pH regulators, activators, and two or more thereof is added during the process. A flotation reagent may be added before the first froth flotation and/or before the second froth flotation. Thus, in a preferred embodiment, a froth flotation stage is conducted, comprising a conditioning step and subsequently a froth flotation step. The first froth flotation may also be referred to as rougher stage and the second froth flotation may also be referred to as cleaning stage.

In a preferred embodiment, a collector selected from metal alkyl xanthates, preferably potassium amyl xanthate, phosphonic acids, phosphoric acid esters, carboxylic acids and salts thereof, metal alkyl sulfates, metal alkyl sulfonates, dialkyl or diaryl dithiophosphoric acids and salts thereof, mercaptobenzothiazole, xanthogen formates, alkyl ethoxycarbonyl thioureas, tertiary dodecyl mercaptans, and mixtures of two or more thereof is added to the ore before the first froth flotation. It is preferred that the collector is a Cu- and Ni-sulfide collector. It is preferred that the collector comprises a metal alkyl xanthate. The term metal preferably refers to alkali metals in this context, such as sodium and potassium. Non-limiting examples of metal alkyl xanthates are sodium isopropyl xanthate, potassium isopropyl xanthate, sodium ethyl xanthate, potassium ethyl xanthate, sodium isobutyl xanthate, potassium isobutyl xanthate, sodium amyl xanthate and potassium amyl xanthate. It is particularly preferred that sodium isopropyl xanthate is added as a collector during the process.

In an embodiment, the second concentrate contains at least 70 %, at least 75 % Cu or at least 80 % Cu based on the amount of Cu in the ore and has a total Ni content of below 2.0 wt.-% based on the dried total weight of the float. In an embodiment, the second concentrate contains at least 80 % Cu based on the amount of Cu in the first concentrate. In a preferred embodiment, the second concentrate contains at least 85 % Cu or at least 90 % Cu based on the amount of Cu in the first concentrate. Put differently, the second concentrate has a Cu recovery of at least 85 % or at least 90 % based on the first concentrate. As a nonlimiting example, if a certain amount of first concentrate contains 10 g Cu and the recovery in the second concentrate is at least 85%, then the concentrate contains at least 8.5 g Cu. The amount of Cu and Ni can preferably be determined by wavelength-dispersive XRF (x-ray fluorescence) measurements, for example measured by an Epsilon 1 benchtop XRF analyzer from Malvern Panalytical. Alternatively, the amount of Cu and Ni can be determined by ICP- OES (inductively coupled plasma optical emission spectrometry) or SIMS (secondary ion mass spectrometry) analysis.

In an embodiment, the second concentrate has a total Ni content of below 4.0 wt.-%, below 3.5 wt.-%, below 3.0 wt.-%, below 2.5 wt.-% or preferably of below 2.0 wt.-%. The total Ni content, also known as Ni grade, is based on the dried weight of the second concentrate. In an embodiment, the second concentrate has a total Cu content of at least 5 wt.-%, at least 10 wt.-%, or preferably of at least 12 wt.-%. The total Cu content, also known as Cu grade, is based on the dried weight of the second concentrate. For measuring the Ni and/or Cu grade, the first/second concentrate is dried for at 70 °C for 24 hrs to ensure that the concentrate does not contain any water. In a preferred embodiment, the first concentrate comprises 5.0 to 15.0 wt.-% Cu (Cu grade) and 3.0 to 10.0 wt.- % Ni (Ni grade) based on the dried weight of the first concentrate. In a preferred embodiment, the second concentrate comprises 12.0 to 20.0 wt.-% Cu and 1.0 to 4.75 wt.-% Ni.

In an embodiment, the ore comprises 0.01 to 10.0 wt.-%, 0.05 to 8.0 wt.- % or 0.1 to 5.0 wt.-% Cu. In an embodiment, the ore comprises 0.01 to 10.0 wt.- %, 0.05 to 8.0 wt.-% or 0.1 to 5.0 wt.-% Ni.

In an embodiment, the second concentrate has a Cu to Ni selectivity of at least 30 % at least 35 % or at least 40 %. The selectivity “S” of the second concentrate is defined as follows:

S = (amount of Cu in the second concentrate based on the amount of Cu in the first concentrate) - (amount of Ni in the second concentrate based on the amount of Ni in the first concentrate) = (Cu recovery in the second concentrate) - (Ni recovery in the second concentrate).

The type of ore is not particularly limited as long as it contains Ni and Cu. However, it is preferred that the ore comprises 0.5 wt.-% to 5.0 wt.-% Cu and 0.5 wt.-% to 3.0 wt.-% Ni, as the process is optimized for ore containing Ni and Cu in said ranges. In an embodiment, the ore comprises nickel sulfides, iron sulfides and/or copper sulfides, preferably pyrrhotite, chalcopyrite and/or pentlandite, more preferably the ore comprises pentlandite as Ni-containing mineral and chalcopyrite as Cu-containing mineral. Thus, in an embodiment, the present invention relates to a process for extracting nickel sulfide and copper sulfide from an ore comprising nickel sulfide and copper sulfide and separating the nickel sulfide from the copper sulfide, the process comprising the steps of: a) subjecting the ore to a first froth flotation to provide a first concentrate comprising sickle sulfide and copper sulfide, and a first underflow, b) subjecting the first concentrate to a second froth flotation to provide a second concentrate and a second underflow, and c) recovering copper sulfide in the second concentrate and nickel sulfide in the second underflow, wherein the second froth flotation is conducted in the presence of H2O2. In an embodiment, a depressant selected from calcium carbonate, sodium chloride, sodium cyanide, sodium silicate, sodium sulfite, sodium metabisulfite, triethylenetetramine, diethylenetriamine, starch, guar, dextrins, carboxymethyl cellulose, and mixtures of two or more thereof is added during the process, preferably before the first froth flotation. In a preferred embodiment, carboxymethyl cellulose is added as a depressant before the first froth flotation.

In an embodiment, the H2O2 is added as a 10 wt.-% to 80 wt.-% H2O2 aqueous solution. It is preferred to use the H2O2 in concentrated aqueous solution, e.g. as 50 wt.-% aqueous solution. Such concentrated aqueous solutions may comprise stabilizers.

In an embodiment, the H2O2 is used in an amount of 200 g to 2500 g H2O2 per It of the ore, preferably in an amount of 400 g to 2000 g H2O2 per It of the ore, more preferably in an amount of 800 g to 1700 g H2O2 per It of the ore. In a particularly preferred embodiment, H2O2 is used in an amount of 900 g to 1600 g H2O2 per It of the ore.

In an embodiment, the ore is provided with a particle size Pso of 10 pm to 400 pm, preferably by grinding the ore before the first froth flotation. A ground dispersion of the ore is also referred to as pulp. In a preferred embodiment, the ore is provided with a particle size Pso of 100 pm to 300 pm. The particle size may be determined by sieving, using a set of screens or meshes, e.g., a vibratory sieve shaker, to separate the various particles by their respective size. The Pso particle size refers to a weight-based particle size distribution. In an embodiment, the particle size is determined by sieve analysis, e.g., according to ASTM C136/C136M-19. Grinding can be performed by any method known in the art, such as ball or rod milling. Providing the ore with the above-mentioned particle size increases the surfaces area of the ore, thus facilitating the conditioning process. In addition, this particle size range facilitates the froth flotation process.

In an embodiment, the conditioned ore is subjected to a first froth flotation for at least 5 minutes, at least 10 minutes, or at least 25 minutes and to a second froth flotation for at least 5 minutes, at least 10 minutes, or at least 25 minutes. During froth flotation, the concentrate may be separated continuously or in a batch-wise fashion from the underflow.

In an embodiment, the ore is conditioned before the first froth flotation and/or the first concentrate is conditioned before the second froth flotation. The conditioning preferably takes place in the presence of a froth flotation reagent as described above. In an embodiment, the first concentrate contains less sulfur and more Ni and Cu compared to the respective content in the ore. The first flotation increases the Cu and Ni content in the concentrate while gangue minerals are discarded in the underflow. The second concentrate may contain less sulfur and less Ni and more Cu compared to the respective content in the first concentrate. The second froth flotation increases the Cu content while in particular the Ni content is decreased.

Examples

In the examples, pH measurements were taken on a Sensorex S200C pH probe interfaced to a ThermoFisher Orion DualStar pH meter. The pH meter was calibrated daily using pH 4, 7, and 10 buffers purchased from ThermoFisher. Calibration was completed daily prior to any flotation testing.

Ni and Cu containing ore was used comprising the minerals chalcopyrite, pentlandite and pyrrhotite. The ore contained 2.33 wt.-% Cu, 1.57 wt.-% Ni, and 11.2 wt.-% S.

1 kg of dry ore was added to a rod mill with mild steel grinding rods and ground at 60% solids. Lime was used to adjust the pH to 9-9.5. The ore was ground for 13-15 min. to a Pso of 200-250 pm and transferred to a Denver cell where tap water was added to produce a 30-40 wt.% aqueous dispersion.

A rougher flotation stage was employed to increase the Cu and Ni content while rejecting gangue minerals, such as pyrrhotite. The slurry was agitated at 1000-1100 rpm, collector (sodium isobutyl xanthate) was added and conditioned for 1-2 min., and frother (polyglycol ether-based; Dowfroth™ 250A) was added and conditioned for 1 min. Air was used as the flotation gas and turned on following the conditioning stage. A single concentrate was collected over 7 min. by scraping the froth every 15 sec. More collector was added at 3 min. and 5 min. and conditioned for 1 min. with the air turned off before resuming flotation. At the end of flotation, the collected concentrate was transferred to another Denver cell, while the tailings were filtered and dried. The Cu grade of the dried first concentrate was 8.1 wt.-%. The Ni grade of the dried first concentrate was 5.1 wt.-%. The Cu and Ni grade was measured using an ICP-OES analyzer. For the ICP-OES analysis, the metals were dissolved by acid digestion and reference samples with a predetermined concentration of metal ions were used for calibration. Subsequently the Cu/Ni separation took place using a second froth flotation step. The float from the rougher stage (15-25 wt.-% solids) was agitated at 900- 1000 rpm while the pH was raised to >12 with a lime slurry. The slurry was stirred at this pH for 10-20 min. H2O2 was then added (Comparative Example: 0 g / It ore; Example 1 : 1500 g / 1 1 ore; Example 2: 800 g / It ore) as a 50 wt.-% aqueous solution and allowed to condition for 10-30 min. prior to flotation. The H2O2 addition amount was controlled through injecting a known volume of solution into the slurry through a syringe. The air was turned on, and concentrates are collected at 1, 3, and 6 min. (cumulatively). The froth was scraped for 5 sec., 10 sec., and 15 sec., respectively for each concentrate. All concentrates and tailings were filtered dried at 70 °C for 24 hrs and assayed.

The results (recovery and grade) are summarized in the Table below. The Cu and Ni recovery are based on the amount of Cu and Ni, respectively, in the first concentrate.

Table 1 : Cu/Ni Recovery and grade in the dried second concentrate

Claims

C L A I M S

1. A process for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu, the process comprising the steps of: a) subjecting the ore to a first froth flotation to provide a first concentrate comprising Ni and Cu, and a first underflow, b) subjecting the first concentrate to a second froth flotation to provide a second concentrate and a second underflow, and c) recovering Cu in the second concentrate and Ni in the second underflow, wherein the second froth flotation is conducted in the presence of H2O2.

2. The process according to claim 1, wherein the second froth flotation is conducted at a pH value of above 10.0, preferably at a pH value of above 12.0.

3. The process according to claim 1 or 2, wherein a flotation reagent selected from collectors, frothers, froth phase modifiers, dispersants, depressants, suppressants, pH regulators, activators, and two or more thereof is added during the process.

4. The process according to any one of claims 1 to 3, wherein a collector selected from metal alkyl xanthates, preferably potassium amyl xanthate, phosphonic acids, phosphoric acid esters, carboxylic acids and salts thereof, metal alkyl sulfates, metal alkyl sulfonates, dialkyl or diaryl dithiophosphoric acids and salts thereof, mercaptobenzothiazole, xanthogen formates, alkyl ethoxycarbonyl thioureas, tertiary dodecyl mercaptans, and mixtures of two or more thereof is added to the ore.

5. The process according to any one of claims 1 to 4, wherein the second concentrate comprises at least 70 % Cu based on the amount of Cu in the ore and the second concentrate comprises less than 2.0 wt.-% Ni based on the dried total weight of the second concentrate.

6. The process according to any one of claims 1 to 5, wherein the ore comprises 0.5 wt.-% to 5.0 wt.-% Cu and 0.5wt.-% to 3.0 wt.-% Ni.

7. The process according to any one of claims 1 to 6, wherein the ore comprises nickel sulfides, iron sulfides and/or copper sulfides, preferably pyrrhotite, chalcopyrite and/or pentlandite.

8. The process according to any one of claims 1 to 7, wherein the first concentrate comprises 5.0 to 15.0 wt.-% Cu and 3.0 to 10.0 wt.-% Ni based on the dried weight of the first concentrate.

9. The process according to any one of claims 1 to 8, wherein the H2O2 is added to the first concentrate as a 10 wt.-% to 80 wt.-% H2O2 aqueous solution.

10. The process according to any one of claims 1 to 9, wherein H2O2 is used in an amount of 200 g to 2500 g H2O2 per It of the ore, preferably in an amount of 400 g to 2000 g H2O2 per It of the ore, more preferably in an amount of 800 g to 1700 g H2O2 per It of the ore.

11. The process according to any one of claims 1 to 10, wherein the ore is provided with a particle size Pso of 10 pm to 400 pm, preferably by grinding the ore before the first froth flotation.

12. The process according to any one of claims 1 to 11, wherein the ore is subjected to the first froth flotation for at least 5 minutes, at least 10 minutes, or at least 25 minutes and the first concentrate is subjected to the second froth flotation for at least 5 minutes, at least 10 minutes, or at least 25 minutes.

13. The process according to any one of claims 1 to 12, wherein the ore is conditioned before the first froth flotation and/or the first concentrate is conditioned before the second froth flotation.

14. The process according to any one of claims 1 to 13, wherein the first concentrate contains less sulfur and more Ni and Cu compared to the respective content in the ore.

15. Use of H2O2 for extracting Ni and Cu from an ore comprising Ni and Cu and separating Ni from Cu by froth flotation.