AU2016311804B2

AU2016311804B2 - A process for initiation of copper sulfide heap bioleaching using water irrigation

Info

Publication number: AU2016311804B2
Application number: AU2016311804A
Authority: AU
Inventors: Yi GENG; Yan Jia; Renman Ruan; Heyun SUN; Jie Yu; Dongsong ZHANG
Original assignee: WANBAO MINING Ltd; Institute of Process Engineering of CAS
Current assignee: WANBAO MINING Ltd; Institute of Process Engineering of CAS
Priority date: 2015-08-27
Filing date: 2016-06-24
Publication date: 2019-01-17
Anticipated expiration: 2036-06-24
Also published as: WO2017032164A1; CN105200232B; CN105200232A; AU2016311804A1

Abstract

Disclosed is a method for starting water spraying in copper sulphide ore heap bioleaching, comprising the following steps: 1) judging the feasibility of starting copper sulphide ore water spraying: if the acid production potential of the ore is greater than the acid consumption potential, water spraying is started; and 2) starting the water praying: moisturising is performed with water in the heap construction process of the copper sulphide ore, and after the completion of the heap construction, spraying is performed with water, when the pH value of a leach liquor > 3.0, circulating spraying is performed, and when the pH value of the leach liquor is < 3.0, acidophilus iron and sulphur oxidation microorganisms are inoculated in the leach liquor as a spraying liquor, and circulating spraying is continued, to gradually increase the concentrations of acid, iron and copper in the system solution, so that the starting of the copper sulphide ore heap bioleaching is achieved.

Description

The present invention relates to the field of hydrometallurgy, and in particular to a process for initiation of copper sulfide heap bioleaching using water irrigation.

BACKGROUND OF THE INVENTION

In the process of heap bioleaching, solution containing sulfuric acid, ferric iron and acidophilic iron and sulfur oxidation microbes is used as the irrigation solution. Copper sulfide minerals are oxidized by oxidant Fe³⁺ and also under the activity of the microbes, and then Cu is released to the solution. Since the heap leaching process of low-grade copper sulfide ore or tailing involved processing of huge amount of ore, large amount of acidic solution is needed for wetting of the ore and irrigation in the beginning of the heap leaching. Besides, the gauge minerals consume acid mainly in the beginning of heap leaching. The cost in preparing of the irrigation solution by addition of sulfuric acid and ferric sulfate is costly. Metal sulfides themselves are of acid generation, and among the sulfides, pyrite is usually in much higher content. Pyrite oxidation provides the acid and iron for the heap leaching, and also the solvent extraction of Cu generates acid. The fully usage of these acid generation processes producing the cost in sulfuric acid addition to the leaching solution.

SUMMARY OF THE INVENTION

It is an objection of the invention to provide a process for initiation of copper sulfide heap bioleaching using water irrigation. Water is used directly as the irrigation solution, and the H2SO4 and Fe2(SC>4)3 are generated in heaps by oxidation of the metal sulfides under the activity of oxygen and microbial activity. This process realizes no acid addition to the irrigation solution in the initiation of heap bioleaching and cost saving.

In order to achieve the above object, the invention adopts following technical proposal.

A process for initiation of copper sulfide heap bioleaching using water irrigation, comprising the following steps:

1) feasibility test of heap bioleaching initiation using only water irrigation: if the acid generation potential exceeds the acid neutralization potential, then copper sulfide heap bioleaching is initiated by water;

2) water initiated irrigation: an ore is firstly wetted using water during stacking, and irrigated with water after being stacked. If the pH value of leachate is above 3.0, the heap is irrigated cyclically until pH value of leachate drops down below 3.0, and then the acidophilic iron and sulfur oxidation microbes are inoculated to the leachate, and the resulted leachate is irrigated cyclically as the irrigation solution to slowly increase the concentration of sulfuric acid and ferric sulfate and initiate copper sulfide heap bioleaching.

The diagnosis of net acid generation and the possibility of the water initiated irrigation are carried out by measure the acid generation potential of sulfide content (including pyrite, copper sulfide etc.) and the acid consumption potential of the gangue minerals. If the acid generation potential exceeds the acid consumption potential, the water initiated irrigation can be applied. The calculation of the acid generation as below chemical reaction equation: 4FeS2+15C>2+2H2O—>2Fe2(SO₄)3+2H2SO₄, CU2S+2.5O2+ H2SO₄=2CuSO₄+H2O. The acid consumption of the ore is measured by titration of ore powder with 100 g/L sulfuric acid, and the amount of acid consumption was calculated based on the added acid volume and acid concentration decrease.

As the heap bioleaching process described, the ore is wetted during the ore stacking in the ratio of 20-100 F/t ore. Water content of the ore is kept at the percentage of 5%-10% during the ore stacking. The height of the heap is 1-10 meter.

In the process disclosed in the invention, after the heap stacking, the water is used as the irrigation solution, and cycling irrigated until the pH dropped down to 3.0. The irrigation time and intensity (3-50 F/m² · h) is chose based on the ore character, ore size and heap height.

In the process disclosed in the invention, when the pH value of the leachate drops down to 3.0, acidophilic iron and sulfur oxidation microbes is inoculated to the solution, including one or more of the species, such as Acidithiobacillus, Leptospirillum and Ferroplasma. The source of the inoculated microbial community can be the acid mine drainage containing the acidophilic iron and sulfur oxidation microbes or the laboratory enrichment of these microbes.

In the process disclosed in the invention, nutrition for the microbes can be added to the solution ponds, to reach the concentration as below: (NH₄)₂SO₄ of 0.5-3 g/L, K2HPO4 of 0.1-0.5g/L, KC1 of 0.01-0.1 g/L, MgSO₄ of 0.1-0.5 g/L, Ca(NO₃)₂ of 0.002-0.01 g/L.

The invention also provides the process after initiation of the heap leaching using water irrigation. After the addition of the nutrient and the inoculation of the microbial groups as described in step 2), the heap is irrigated cyclically until Cu concentration in the leachate reaches to the target value, then the leachate is sent to the solvent extraction-electro winning plant, and finally the cathode copper is produced. During the solvent extraction, every 1 mol Cu extraction will return 1 mol fLSCfi to the raffinate solution, and the use of raffinate as the irrigation solution will increase the acidity in the cycling solution. According to the actual industrial condition, when the cycling solution in the leaching ponds and heaps is not enough because of the evaporation, water or acid mine drainage can be used to replenish the loss. The process of heap leaching, solvent extraction-electro winning continues until the heap reaches the target recovery, and then the heap leaching stops.

The inoculated microbes to the solution ponds usually contain acidophilic iron and sulfur oxidation microbes, such as Acidithiobacillus, Leptospirillum and Ferroplasma. The inoculated microbes comprising: enrichments of the microbial groups from acid mine drainage or the industrial heaps; or directly the acid mine drainage or the solution from industrial heap bioleaching. Normally, the iron concentration of the acid mine drainage and industrial leaching solution for the microbial enrichment is l-10g/L, pH value of it is

1.5-2.5, and containing of the acidophilic iron and sulfur oxidation microbes. The standard 9K medium for microbes enrichment ((NH₄)₂SO₄ 3 g/L, K₂HPO₄ 0.5 g/L, KC1 0.1 g/L, MgSO₄ 0.5 g/L, Ca(NO₃)₂ 0.01 g/L, pH 1.0-2.5) is used, and is added with 10 g/L FeSO₄and 2g/L elemental sulfur, respectively.

In the invention, microbial number in the leaching solution can reach the level of

8

10-10 pcs/mL after cultivation with microbial community inoculation and nutrient addition.

In the process of heap bioleaching of the metal sulfide, especially pyrite is high in amount, and can be the important source of acid and iron for the heap leaching. Under the neutral or slightly acid condition, pyrite can reacts following reaction under the effect of oxygen:

4FeS₂+15O₂+ 2H₂O->2Fe₂ (SO₄)3+2H₂SO₄

After the partially oxidation of pyrite by oxygen, small amount of Fe and sulfuric acid is generated. Ferric iron then acts as the oxidant for pyrite, and this reaction is crucial for the pyrite oxidation under acidic environment. Under the activity of acidophilic iron and sulfur oxidation microbes, Fe was replenished by Fe oxidation, and also the microbes adhere on the pyrite surface, could greatly accelerate the pyrite oxidation.

FeS₂+14Fe³⁺+ 8H2O—>15Fe²⁺+16H⁺+2SO4²' (chemical reaction)

4Fe²⁺+O2+4H⁺—>4Fe³⁺+ 2H2O (microbial reaction)

This invention takes full advantage of the pyrite oxidation under different pH condition, to solve the demands of the huge acid and iron in the process of the initiation of heap bioleaching of copper sulfides. Of the metal sulfides, the content of pyrite is usually much higher than other sulfides. Water is used as the irrigation solution, and then the pyrite is oxidized under the oxygen and activity of acidophiles. In the beginning of the leaching, pH condition of the ore is neutral, and not suitable for the acidophile growth. When the pH condition is above 3.0, oxygen is acted as oxidant to oxidize the sulfides through wetting and aeration of the ore. When the pH drops down to 3.0, microbes and nutrient are added the solution, and aeration is carried out in heaps to promote a high microbial activity, for the fast oxidation of sulfides to Cu, Fe and acid production. Under this condition, the number of Cu, Fe, acid concentration and microbial in the leaching solution gradually increased. This invention takes full advantage of the oxygen oxidation, ferric oxidation and microbial oxidation of the sulfides (copper sulfides and pyrite), to achieve the fast Cu production, acid and iron generation in the initiation of heap bioleaching, using only water as the irrigation solution without sulfuric addition. Apply of this invention in the industrial heap bioleaching plants will reduce the operation cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG

FIG,

FIG is the process flow diagram of this invention.

is the sulfuric acid concentration in leachate of the application instance 1.

is the ferric iron concentration in leachate of the application instance 1.

is copper recovery of the application instance 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be illustrated in detail below in conjunction with the drawings and specific embodiments.

As shown in figure 1, the ore is firstly diagnosed for the possibility of water initiated irrigation. After the confirmation of the possibility, ore is wetted during the ore stacking, and then water is used as the irrigation solution. Ore is slightly acidified under the oxygen oxidation of sulfides. The leachate is slightly acidified, and cycling irrigated as the irrigation solution. When the pH drops down to 3.0, the enrichment of the acidophilic iron and sulfur oxidation microbes is inoculated to the solution, and also the nutrition for the microbes is added to the solution to boost the activity of microbes. The microbes promote the oxidation of sulfides, and Cu, Fe and acid are dissolved to the solution. Their concentrations in the solution gradually increase, and the heap is cycling irrigated until Cu concentration in leachate reaches the target concentration, then the leachate is pump to solvent extraction-electro winning plant for the cathode copper production. During the solvent extraction process, 1 mol Cu extraction will return 1 mol H2SO4 to the raffinate, and help increase the acid concentration in heaps. According to the actual industrial condition, when the cycling solution in the leaching ponds and heaps is not enough, water or acid mine drainage is replenished to ponds. The process of heap leaching, solvent extraction-electro winning continues until the heap gets the target recovery, and then the leaching stops.

Embodiment 1

A column bioleaching test of the copper sulfide ore at Cu grade of 0.37%, Fe grade of 5.59% and reduce sulfur of 6.28% was carried out. The copper sulfides were dominated by chacocite (90%), and also contains small amount of covellite and enargite. Pyrite content was about 10%, and gauge minerals were mostly feldspar, quartz and sericite. The calculation of the acid generation potential and acid consumption potential proved that the ore was net acid generation, thus it was possible to initiate the heap bioleaching using water irrigation. Ore was crushed to -50mm, and stacked to a 1 meter height temperature-controlled column. During the ore filling to the column, water was used to wet the ore at the ratio of 50 L/t ore. After stacking, ore was irrigated using water at the irrigation intensity of 3 L/m h, and using the process of rest-rinse at 1 day rinse and 1 day rest. The leachate was cycling used as the irrigation solution. When the pH of leachate dropped down to 3.0, the enrichment of the microbes from the local acid mine drainage was inoculated to the leachate, and the leachate was continue used for cycling irrigation. The enriched microbial community mainly contains species of Acidithiobacillus, Leptospirillum, and Ferroplasma. The microbes was cultured in temperature controlled oscillator with the nutrition content of (NH₄)₂ SO₄of 2 g/L, K₂HPO₄of 0.3 g/L, KC1 of 0.05 g/L, MgSO₄of0.3 g/L, Ca(NO₃)₂of 0.01 g/L, FeSO₄of 10 g/L, and pH of 1.8. 500 mL enriched solution was added to the leachate, and the leachate was continued used for irrigation. When the copper concentration reached to the concentration of 3 g/L, sulfuric acid was add to the leachate at the ratio of 1.54 kg H₂SO₄/kg Cu to simulate the acid generation in the solvent extraction process of Cu. The solution was continued to be used for irrigation, and then the iron and acid concentration continued increasing (Figure 2, 3). The increasing of iron and acid concentration also promote the Cu leaching efficiency

O (Figure 4). The microbial number in the leachate reached an average of 2x10 pcs/mL during the leaching.

Embodiment 2

A commercial heap bioleaching of copper sulfide ore at Cu grade of 0.47%, Fe content of 3.59%, reduced sulfur content of 4.28% was carried out. The copper sulfide was dominated by chalcocite, and the pyrite content is about 7.8%. Based on the calculation, the acid generation potential was higher than the acid consumption potential, so it was possible for water irrigation to start the heap leaching. The ore size was crushed to

P8o=25Omm, and was stacked at the height of 6 m. Water was used to wet the ore during the stacking at the ratio of 60 L/t ore, and kept at about 5%-10% water content. After the stacking, water was used as the irrigation solution. The irrigation intensity was 6 L/m · h, and rest-rinse operation is applied at 1 day rest and 1 day rinse. After 12 days irrigation and cycling, pH value of the leachate dropped down below 3.0, the acid mine drainage (pH value of 2.5, and containing the acidophilic iron and sulfur oxidation microbes) was added to the leaching solution, and nutrition was added to the solution ponds at (NH₄)₂SO₄oflg/L, K₂HPO₄of 0.2 g/L, KC1 of 0.03 g/L, MgSO₄of 0.3 g/L, Ca(NO₃)₂ of 0.01 g/L, and continued for irrigation. Ten days later, Cu concentration in the leachate exceeded 3g/L, then the solution was pumped to solvent extraction-electro winning plant to produce cathode copper. The raffinate was returned to the leaching solution, and continued for irrigation. After another 60 days, the acid concentration was about 5g/L, and Fe was about 4g/L. Totally after 300 days, the Cu recovery reached about 81%, and the leaching completed.

Finally, it should be noted, although this invention is explained in detail with reference to the embodiments, additional advantages and modifications will readily occur to those skilled in the art. The embodiments described herein are only provided for explaining the invention and not to limite to the specific details, representative apparatus and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants' general inventive concept.

Claims

1) feasibility test of heap bioleaching initiation by water irrigation: if the acid generation potential exceeds the acid neutralization potential, then copper sulfide heap bioleaching is initiated by water;

1. A process for initiation of copper sulfide heap bioleaching using water irrigation, including following steps:

2. A process for initiation of copper sulfide heap bioleaching using water irrigation according to claim 1, wherein the acid generation potential is calculated based on reducible sulfides in the ore and all sulfides in the ore being assumed oxidized to sulfate, and acid consumption potential is calculated based on consumption of sulfuric acid being used to titrate the ore powder.

2) water initiated irrigation: an ore is firstly wetted using water during stacking, and irrigated with water after being stacked, if the pH value of leachate is above 3.0, the heap is irrigated cyclically until pH value of leachate drops down below 3.0, and thereafter an acidophilic iron and sulfur oxidation microbe is inoculated to the leachate, and the resulted leachate is irrigated cyclically as the irrigation solution to increase the concentration of sulfuric acid and ferric sulfate and initiate copper sulfide heap bioleaching

3. A process for initiation of copper sulfide heap bioleaching using water irrigation according to claim 1, wherein during the ore stacking, the ore is wetted using water at a ratio of 20-100L/ t ore, and kept with a water content of 5%-10%.

4. A process for initiation of copper sulfide heap bioleaching using water irrigation according to claim 1, wherein the said acidophilic iron and sulfur oxidation microbes mainly include one or more selected from the group consisting of the species, such as Acidithiobacillus, Leptospirillum and Ferroplasma.

5. A process for initiation of copper sulfide heap bioleaching using water irrigation according to claim 1, wherein nutrition for the microbes is added to the solution ponds or heaps during inoculation to adjust a concentration of the leaching solution as below: (NH₄)₂SO₄ of 0.5-3.0 g/L, K₂HPO₄ of 0.1-0.5g/L, KC1 of 0.01-0.1 g/L, MgSO₄ of 0.1-0.5 g/L, Ca(NO₃)₂ of 0.002-0.01 g/L.

6. A process for heap bioleaching of copper sulfides, wherein, according to claim 1-5 of the process for initiation of copper sulfide heap bioleaching using water irrigation, after step 2), the heap is irrigated cyclically until the concentration of Cu in leachate reaches target value, and Cu is then extracted from the solution by solvent extraction process, and raffinate from the solvent extraction process is used as irrigation solution to the heaps;

When the irrigation solution is not enough for irrigation, water or acid mine drainage is used to supply the irrigation solution, and irrigated cyclically until an achievement of the target recovery of the heap.