Process of extracting deleterious substances, and product obtained through process of extracting deleterious substances

Abstract

To provide a method for extracting deleterious substances from ore concentrates, preferably copper sulfides.SOLUTION: The present invention provides a method for reducing the content of certain deleterious substances such as fluoride, uranium, and / or thorium in concentrates, the method comprising at least an acid leaching step and a step of reducing the internal residual acidity of the leached ore concentrate. The present invention also provides the physicochemical quality of the product obtained by this process route.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for extracting harmful substances in the mining industry, with the aim of reducing the content of certain contaminants (such as uranium, fluoride and / or thorium) in copper sulfide concentrates. The invention also relates to the physicochemical quality of the products obtained by the method of the invention. [Background technology]

[0002] In the mining industry, copper sulfide concentrates commonly obtained contain impurities, i.e., harmful substances that affect the quality of the product. Copper sulfide concentrates, such as those containing bornite (CuFeS4) or chalcocite (CuS) as the copper-containing mineral, may have a typical content of 38% Cu, 13% S, 14% Fe, and impurities such as fluoride (F=1800 ppm) and uranium (U=27 ppm). On the other hand, copper sulfide concentrates containing chalcopyrite (CuFeS2) as the main copper mineral may have a typical content of 30% Cu, 30% S, 25% Fe, and impurities such as fluoride (F=650 ppm) and uranium (U=120 ppm). Above a certain level, for example, in the case of the Chinese market, when F exceeds 1000 ppm, these impurities are subject to penalties, and very high levels of uranium and thorium can even restrict the sale of the product. Furthermore, the product obtained after reducing harmful contents by acid leaching must exhibit satisfactory stability to guarantee the physicochemical quality of the leached copper sulfide concentrate during subsequent transportation, storage and use.

[0003] In the prior art, various process routes have been used to extract harmful materials from copper sulfide concentrates, such as hydrometallurgical processes, which achieve a significant reduction in harmful content.

[0004] The paper "Kinetics of uranium leaching process using sulfuric acid for Wadi Nasib ore, Southwestern Sinai, Egypt" by MMRashad, SAMohamed, Emel Sheikh, HEMira, GMAbd el Wahab, and SAZaki, discloses a study on uranium leaching from ore using sulfuric acid solutions. However, this paper considers acid leaching of oxidized ore at high temperatures (80°C), which makes the process more expensive because such leaching is not selective, i.e., copper is leached, requiring subsequent recovery. Furthermore, it does not consider a process for removing residual acid to ensure the physicochemical quality of the leached concentrate during transportation, storage, and use.

[0005] The paper "Selective leaching of penalty elements from copper concentrates: A review" by Daniel J. Lane, Nigel J. Cook, Stephen R. Grano, and Kathy Ehrig describes several leaching systems developed to selectively extract elements that are penalized for commercialization of each copper sulfide concentrate, such as alkaline sulfide leach (ASL), sodium hypochlorite leach, sulfuric acid leach diluted with aluminum sulfate, and pressure oxidation leach (POX) combined with copper precipitation leach. However, none of the proposed routes combines room temperature leaching, the use of commercially available, low-cost acid (H2SO4), the absence of copper extraction, and the use of simple equipment such as stirred tanks, thickeners, and filters. Furthermore, no consideration is given to a process for removing residual acid to ensure the physicochemical quality of the leached concentrate during transportation, storage, and use.

[0006] As explained above, efforts have been made in the past to focus on extracting hazardous substances from ore concentrates using various methods. However, there is still a lack of a process route based on acid leaching that is thermally efficient, low cost, achieves a high removal rate of hazardous substances, mainly uranium, fluoride and / or thorium, without extracting metals that need to be subsequently recovered, uses simple equipment, and offers a step for removing residual acid to ensure the physicochemical quality of the leached concentrate during transportation, storage and use.

[0007] As will be explained in more detail below, the present invention aims to solve the above-mentioned problems of the prior art in a practical and efficient manner. Summary of the Invention

[0008] The present invention relates to a method for extracting harmful substances, mainly uranium, fluoride and / or thorium, from copper sulfide concentrates, the presence of which can lead to penalties and even restrictions on the sale of the product if the concentrations of uranium and thorium are too high.

[0009] The present invention also relates to a product obtained by the process of the present invention, which has a satisfactory stability that ensures the physicochemical quality of the leached concentrate during its subsequent transportation, storage and use.

[0010] The objectives and other advantages of the present invention will become apparent from the following description. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 shows the extraction of copper, fluoride and uranium from a copper sulfide concentrate containing bornite and chalcocite as the primary copper-bearing minerals according to Examples 1-7 using the method of the present invention. [Figure 2] FIG. 2 shows the extraction of copper, fluoride, and uranium from a copper sulfide concentrate containing chalcopyrite as the primary copper-bearing mineral according to Examples 1-7 using the method of the present invention. [Figure 3]FIG. 3 shows the extraction of copper, fluoride and uranium according to Examples 8-12 using the method of the present invention as a function of the concentration of Al2(SO4)3 in the leach solution. [Figure 4] FIG. 4 shows the extraction of copper, fluoride and uranium as a function of residence time for Examples 9, 13 and 14 using the method of the present invention. [Figure 5] FIG. 5 shows a first route option for the method of extracting harmful substances of the present invention, which includes two solid-liquid separation steps using a concentrator and a filter press. [Figure 6] FIG. 6 shows a second route option for the method of extracting contaminants of the present invention, which involves countercurrent washing of the leached copper sulfide concentrate and a single solid-liquid separation step using a thickener and filter press. DETAILED DESCRIPTION OF THE INVENTION

[0012] Copper sulfide concentrates can contain fluoride and uranium contents that exceed the standard values, with average values ​​of 2500 ppm for F and 60 ppm for U. Above a certain level, for example, above 1000 ppm for F in the Chinese market, these impurities are subject to penalties, and very high levels of uranium can even lead to product sales restrictions.

[0013] It is therefore necessary to develop process routes that selectively reduce the impurity content of concentrates in order to improve profitability by avoiding penalties and by opening up the possibility of selling products with low F, U and / or Th contents on the world market. This product must also have a satisfactory stability to guarantee the physical and chemical quality of the leached concentrate during subsequent transportation, storage and use.

[0014] In order to solve the above technical problems, the present invention provides a method for selectively extracting harmful substances from an ore concentrate, preferably copper sulfide, comprising: At a minimum, the following steps: i) subjecting the ore concentrate to acid leaching to obtain a leached ore concentrate having a reduced contaminant content and a leachate; and ii) subjecting the leached ore concentrate obtained from step i) to a treatment to reduce the internal residual acidity by washing with process water and / or neutralization by adding hydrated lime pulp. The present invention provides a method comprising:

[0015] According to the present invention, the raw material supplied to the method of the present invention consists of copper sulfide concentrate, having a solids content of about 55% to 60%, obtained from the underflow of a concentrator in a process for producing copper sulfide concentrate by flotation. The copper sulfide concentrate may contain chalcopyrite (CuFeS), bornite (CuFeS), chalcocite (CuS), enargite (CuAsS), and / or covellite (CuS). The harmful substances are preferably fluoride, uranium, and / or thorium.

[0016] The acid leaching step is preferably carried out using a sulfuric acid and / or aluminum sulfate solution, and the pH is adjusted to a range of about 1.5 to about 4.0, preferably about 2.5 to about 3.5. The acid leaching step is carried out for a residence time of about 2 to about 8 hours, preferably about 6 hours, at a temperature of about 15°C to about 35°C, preferably about 15°C to about 25°C, and at a solids content of about 10% to about 30%, preferably about 20%. The acid leaching step can be carried out using concentrated sulfuric acid (98% by mass) and / or by adding aluminum sulfate so that the concentration of Al2(SO4)3 in the leachate is about 10 g / L to about 30 g / L, preferably about 15 g / L. The use of aluminum sulfate is recommended when it is desired to reduce the fluoride content of copper sulfide concentrates containing fluorite (CaF2) as the carrier mineral for fluorine, while a low pH is recommended when it is desired to reduce the uranium and / or thorium content of copper sulfide concentrates containing uraninite (UO2) and / or thorite (ThO2) as the carrier minerals for uranium and / or thorium. The aluminum ions (Al 3+) is the fluoride ion (F - ) to form a highly stable water-soluble complex (AlF6 3- ) and are excreted in the liquid effluent.

[0017] After this step, a leached copper sulfide concentrate and a leach solution are obtained. In this process route, the main minerals containing fluorine, uranium, and / or thorium, fluorite (CaF2), uraninite (UO2), and / or thorite (ThO2), are selectively leached and removed from the product, i.e., the leached copper sulfide concentrate. In this process route, the chloride content of the leached copper concentrate is not reduced because this element is contained in the crystalline structure of silicates and phosphates such as biotite, amphibole, beryl, iron pyrosmalite, and apatite, minerals that require more aggressive acid leaching conditions (pH<1) to be leached.

[0018] The acid leaching process is carried out at room temperature and does not require heating or energy consumption. The process conditions are optimized to keep reagent consumption low. Furthermore, there is no significant copper extraction during the process, with up to 0.50% of the total mass of copper incorporated in the copper sulfide concentrate being transferred to the leachate. Because the leachate contains no copper or only very low concentrations of copper, there is no need for subsequent recovery of this metal, for example by cementation with iron powder.

[0019] The acid leaching process of the present invention has a simple construction concept since it is possible to use equipment that operates at room temperature, such as tanks, agitators, thickeners, slurry pumps and filter presses.

[0020] The majority (60%-80%) of the leachate from step i) of the dual filtration process route (Figure 5) is recycled to the acid leaching step. This ensures water reuse, reduces reagent consumption, and eliminates the generation of waste containing fluoride, uranium, and / or thorium in the liquid discharge treatment step. The remaining leachate from step i), 20%-40%, is purged and treated to remove fluoride, uranium, and / or thorium through precipitation with hydrated lime, resulting in a solid residue enriched in fluoride, uranium, and / or thorium, which is discharged and disposed of according to environmental classification. The treated leachate can then be returned to the leaching step. For the process route with countercurrent scrubbing (Figure 6), the proportion of leachate recycled to the acid leaching step ranges from 20% to 40% of the total amount produced, while the remaining 60% to 80% is purged and treated to remove fluoride, uranium, and / or thorium through precipitation with hydrated lime, resulting in a larger amount of solid waste enriched in fluoride, uranium, and / or thorium, which can be discharged and / or disposed of according to its environmental classification. The treated leachate can be returned to the leaching step of this process route.

[0021] The results after the acid leaching process of the present invention showed that the extraction of fluoride and uranium ranged from 10% to 60% and 30% to 50%, respectively. The radioactivity of the concentrate before and after leaching was measured with a Geiger counter, and the results showed that this process route reduced the uranium content and kept the radioactivity level of the leached copper sulfide concentrate unchanged (<1 mSv / year).

[0022] The resulting leached copper sulfide concentrate contains low levels of fluoride, uranium, and / or thorium, but contains residual internal acidity that must be removed to avoid deterioration of its physicochemical quality during transportation, storage, and use. Due to the residual internal acidity, the storage stability of the leached copper sulfide concentrate was unsatisfactory, resulting in high temperatures (temperatures >60°C), high oxidation levels (soluble Cu / total Cu >10%), high moisture loss (final humidity 0.15%), and the formation of lumps with high mechanical strength (Is(50) = 0.94 MPa). This deterioration in physicochemical quality was caused by sulfide oxidation reactions that occurred when the wet leached copper sulfide concentrate (moisture content 9%-11% by mass) was exposed to weathering. Sulfide oxidation reactions are promoted in acidic media. It is common in the industry to produce, store, and transport copper sulfide concentrates with moisture contents of 9%-11% by mass. These data demonstrate the importance of removing internal residual acid to ensure the stability of the physicochemical quality of the leached copper sulfide concentrate during storage, transportation and use.

[0023] The leached copper sulfide concentrate is then subjected to a process for reducing the residual internal acidity, which preferably consists of washing with process water and / or neutralization by adding slaked lime pulp, until the pH of the pulp reaches a value of 6.5 to 7.5, preferably close to 7.0, under suitable conditions, for example, at a temperature of about 15°C to about 35°C, preferably room temperature (about 20°C), a solids content of about 20% to about 50% by weight, preferably about 20% to about 40% by weight, a residence time of about 15 to about 45 minutes, preferably about 30 minutes, and an agitation speed suitable for maintaining the solids in suspension.

[0024] After the internal residual acid reduction step, a final product is obtained, which exhibits a fluoride content reduction of about 10% to about 60%, a uranium content reduction of about 30% to about 50%, and / or a thorium content reduction of about 30% to about 50%, and exhibits satisfactory stability characteristics for storage, transportation, and use, making it commercially viable.

[0025] The present invention offers several advantages by combining an acid leaching step with a process for reducing the residual acidity of the leached copper concentrate. The reduction in fluoride, uranium, and / or thorium content described above reduces fines and opens up new markets. The process of the present invention is a selective process that eliminates copper extraction, reduces reagent consumption, requires no heating, and generates less solid waste containing high levels of fluoride, uranium, and / or thorium. The process of the present invention is a process route that requires low capital and operating costs and uses simple equipment such as tanks, concentrators, and filter presses.

[0026] The present invention also relates to products obtained by the methods of the present invention. The products of the present invention exhibit a reduction in fluoride content of about 10% to about 60%, a reduction in uranium content of about 30% to about 50%, and / or a reduction in thorium content of about 30% to about 50%. The products of the present invention are free of residual acid and have satisfactory stability characteristics for storage, transportation, and use, and are therefore commercially viable. Physicochemical stability was confirmed by tests using samples of unleached copper sulfide concentrate and samples after a sulfuric acid leaching process. The products of the present invention have a low content of copper soluble in acetic acid (soluble Cu / total Cu<10%), no formation of agglomerates with high mechanical strength, and no excessive moisture loss even after storage for 60 days under controlled atmospheric conditions.

[0027] It should be understood that the above description of the subject matter of the present invention should be considered merely as one possible embodiment or embodiments, and that the characteristics set forth in the above description are merely set forth for ease of understanding, and therefore should not be construed as limiting the present invention, which is limited only by the scope of the claims.

[0028] The examples presented below illustrate the range of products that have been produced by the methods proposed herein. [Example]

[0029] Bench tests were conducted to demonstrate the effectiveness of the method of the present invention in extracting contaminants from ore concentrates under a variety of conditions.

[0030] Examples 1-7 First, tests were carried out on a copper sulfide concentrate containing bornite / chalcocite and chalcopyrite. The solids content in the pulp was 20%. Leaching was carried out without heating. Seven examples were tested under different conditions regarding the concentration of Al2(SO4)3 dissolved in the leachate (g / L), the pH of the leachate, and the leaching time. These conditions for Examples 1 to 7 are shown in Table 1.

[0031] [Table 1]

[0032] Figure 1 shows the extraction of copper, fluoride, and uranium from a copper sulfide concentrate containing bornite and chalcocite as the primary metal-bearing minerals. These are examples of the method for extracting hazardous substances of the present invention, depending on the Al2(SO4)3 concentration in the leachate, the pH of the leachate, and the leaching time at room temperature. Table 1 lists the conditions for sulfuric acid leaching tests performed on a copper sulfide concentrate containing bornite and chalcocite as the primary copper-bearing minerals. The best extraction conditions were obtained in Example 1, where a pH of 3.5 and an Al2(SO4)3 concentration of 15 g / L in the leachate resulted in an extraction rate of only 4% for copper, 43% for uranium, and 54% for fluoride.

[0033] Figure 2 shows the extraction of copper, fluoride, and uranium from a copper sulfide concentrate containing chalcopyrite as the main metal-bearing mineral. These are examples of the method for extracting harmful substances of the present invention, depending on the Al2(SO4)3 concentration in the leachate, the pH of the leachate, and the leaching time at room temperature. The best extraction conditions were obtained in Example 6, where the pH was 1.5 and no Al2(SO4)3 was added, resulting in a copper extraction rate of nearly 0%, a uranium extraction rate of 57%, and a fluoride extraction rate of 41%.

[0034] Further bench tests were carried out on the method of the present invention. To carry out these tests, a copper concentrate was used, containing values ​​of Cu (approximately 38%), F (approximately 1500 ppm), Cl (approximately 1000 ppm), and U (approximately 60 ppm). The Cu / S mass ratio was 2.72, indicating the presence of chalcocite and bornite in the mineralogical composition of the copper sulfide concentrate used. The sulfide, sulfate, and sodium sulfur contents in the copper concentrate were 12.87%, <0.61%, and 0.061%, respectively. The mass ratio of sulfide sulfur to total sulfur was 0.91, indicating that, as expected, more than 90% of the sulfur was in the form of sulfide. The sulfur content in the form of sulfate was less than 0.61%, indicating that the sample was not oxidized. The particle density measured with a pycnometer was 4.073 g / cm. 3 , the average diameter of the particles (d 50 ) is 16 μm, and 80% of the particles are 38 μm (P 80 ) was smaller.

[0035] A mineralogical analysis of the copper concentrate used was also conducted. The main minerals were bornite (31.9%), chalcocite / chalcite (23.2%), amphibole (8.7%), chlorite (6.8%), biotite / stilpnomelane (5.5%), quartz (5.4%), CuS / ganga (4.8%), iron oxide-hydroxide (4.5%), and chalcopyrite (4.1%), accounting for 95% of the mass. The copper concentrate contained the following: 38.20% Cu, 14.02% S, 15.06% Fe, 8.95% Si, 1543 ppm F, and 960 ppm Cl. It can be seen that 50% and 46% of the copper comes from bornite and chalcocite / chalcocite, respectively, and 55%, 32%, and 10% of the sulfur comes from bornite, chalcocite / chalcocite, and chalcopyrite, respectively. Iron is found in a variety of minerals, primarily bornite, iron oxide-hydroxide, and amphibole / greenalite. Silicon comes from quartz, amphibole / greenalite, chlorite, and other minerals. The main source of fluorine is fluorite, with smaller amounts found in biotite / stilpnomelane and apatite. Approximately 70% of the chloride is found in biotite / stilpnomelane.

[0036] Example 8 First, acid leaching tests (sulfuric acid and aluminum sulfate) were carried out to reduce the fluoride and uranium content in the copper concentrate used. Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, no aluminum sulfate addition, and leaching time 6 hours. After this process, the uranium content in the leached copper concentrate was 43.93 ppm (extraction rate 27.90%), and the fluorine content in the leached copper concentrate was 1428 ppm (extraction rate 11.18%).

[0037] Example 9 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 15 g / L, and leaching time 6 hours. After this step, the uranium content in the leached copper concentrate was 48.37 ppm (extraction yield 25.53%), and the fluoride content in the leached copper concentrate was 732 ppm (extraction yield 45.24%).

[0038] Example 10 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 20 g / L, and leaching time 6 hours. After this step, the uranium content in the leached copper concentrate was 47.69 ppm (28.75% extraction yield), and the fluoride content in the leached copper concentrate was 687 ppm (43.29% extraction yield).

[0039] Example 11 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 25 g / L, and leaching time 6 hours. After this step, the uranium content in the leached copper concentrate was 43.59 ppm (extraction yield 29.13%), and the fluoride content in the leached copper concentrate was 696 ppm (extraction yield 45.44%).

[0040] Example 12 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 30 g / L, and leaching time 6 hours. After this step, the uranium content in the leached copper concentrate was 41.43 ppm (extraction yield 26.07%), and the fluoride content in the leached copper concentrate was 782 ppm (extraction yield 39.97%).

[0041] Example 13 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 15 g / L, and a leaching time of 2 hours. After this step, the uranium content in the leached copper concentrate was 53.77 ppm (extraction yield 16.80%), and the fluoride content in the leached copper concentrate was 1073 ppm (extraction yield 23.82%).

[0042] Example 14 Acid leaching was carried out under the following process conditions: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to give an Al2(SO4)3 concentration in the leachate of 15 g / L, and a leaching time of 4 hours. After this step, the uranium content in the leached copper concentrate was 45.91 ppm (extraction yield 21.71%), and the fluoride content in the leached copper concentrate was 825 ppm (extraction yield 36.20%).

[0043] The acid leaching test conditions for the copper concentrate used are shown in Table 2.

[0044] [Table 2]

[0045] The chemical analysis of the leached copper concentrate after the acid leaching process is shown in Table 3.

[0046] [Table 3]

[0047] The extraction of elements from copper sulfide concentrate after acid leaching is shown in Table 4.

[0048] [Table 4]

[0049] FIG. 3 shows the extraction of copper, fluoride, and uranium from the copper concentrates of Examples 8-12 as a function of Al2(SO4)3 concentration in the leachate.

[0050] FIG. 4 shows the extraction of copper, fluoride and uranium from the copper concentrates of Examples 13, 14 and 9 as a function of residence time.

[0051] These examples showed that copper extraction rates varied little across all tests, averaging 1.0%. The fluoride extraction rate was only 11% in Example 8, where no aluminum sulfate was added. The extraction rates of F and U increased with increasing residence time, with an F extraction rate of 45% and an U extraction rate of 26% achieved at a residence time of 6 hours. Since no significant changes in the extraction rates of Cu, U, and F were observed even when the aluminum sulfate concentration in the leachate was greater than 15 g / L, the conditions in Example 9, with an aluminum sulfate concentration of 15 g / L in the leachate and a residence time of 6 hours, were considered to be the best leaching conditions. The pH during leaching was approximately 3.5, the pulp solids content was 20%, and no heating was used. Previous studies using these process conditions have shown fluorine extraction rates of 40% to 73% and uranium extraction rates of 10% to 50%.

[0052] Example 15 Next, tests were carried out to reduce the residual acidity inside the leached copper concentrate.

[0053] A conical pile containing 15 kg of unleached copper concentrate was used as a reference sample, the pH of which was 7.5.

[0054] Example 16 A conical pile containing 15 kg of leached copper concentrate was used as a reference, but without the addition of an internal residual acid reduction step. The acid leaching process followed the parameters considered most appropriate: pH 3.5 (20°C) adjusted by the addition of concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to achieve an Al2(SO4)3 concentration of 15 g / L in the leachate, and a leaching time of 6 hours. The pH of this sample was 3.5.

[0055] Example 17 A conical pile containing 15 kg of leached copper concentrate was used, and the acid leaching process followed the most suitable parameters: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to achieve an Al2(SO4)3 concentration of 15 g / L in the leachate, and a leaching time of 6 hours. The leached copper concentrate was then repulped with water and a solids content of 40%. The pH of this sample was 4.5.

[0056] Example 18 A conical pile containing 15 kg of leached copper concentrate was used, and the acid leaching process followed the most suitable parameters: pH 3.5 (20°C) adjusted by adding concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to achieve an Al2(SO4)3 concentration of 15 g / L in the leachate, and a leaching time of 6 hours. The leached copper concentrate was then repulped with water and 40% solids and neutralized with 10% by mass NaOH solution. The pH of this sample was 7.2.

[0057] Example 19 A conical pile containing 15 kg of leached copper concentrate was used, and the acid leaching process followed the most suitable parameters: pH 3.5 (20°C) adjusted by the addition of concentrated sulfuric acid (98% by mass), solids content 20%, leaching at room temperature, addition of aluminum sulfate to achieve an Al2(SO4)3 concentration of 15 g / L in the leachate, and a leaching time of 6 hours. The leached copper concentrate was then repulped with water and 40% solids and neutralized with a 10% by mass Ca(OH)2 (hydrated lime) solution. The pH of this sample was 7.2.

[0058] After 60 days, the physicochemical properties of samples 15 to 19 were measured. The atmospheric air characteristics were: average relative humidity (81±10)% and average temperature (16±13) °C. The values ​​obtained for the physicochemical properties of samples of examples 15 to 19 are shown in Table 5.

[0059] [Table 5]

[0060] The moisture contents and major element contents of the samples of Examples 15 to 19 are shown in Table 6.

[0061] [Table 6]

[0062] The moisture content of the leached concentrates was 9% to 11%, with the copper concentrate from Example 19 having the lowest moisture content (9.89%) and the copper concentrate from Example 16 having the highest moisture content (10.70%). The height, diameter and average angle of repose of the 15 kg conical pile were 23 cm, 50 cm and 50°, respectively.

[0063] The copper contents soluble in 0.20 mol / L EDTA solution measured for the initial samples and samples taken from the pile surfaces of Examples 15 to 19 after 15, 30, 45, and 60 days of exposure to the environment are shown in Table 7. The soluble copper contents were calculated as shown in Equation (1). Soluble copper content (%) = (mass of copper in the solution / mass of copper in the initial sample) x 100 (1)

[0064] [Table 7]

[0065] The initial sample of copper concentrate in Example 15 (unleached copper concentrate) had a high EDTA-soluble copper content (5.0 wt%), whereas the initial sample of leached concentrate had a lower soluble copper content, averaging 1.3 wt% EDTA-soluble copper.

[0066] The greatest increase in EDTA-soluble copper content was observed in Example 16 (leaching of copper concentrate only), where it rose from 1.0% by weight in the initial sample to 4.1% by weight after 15 days and reached 5.0% by weight after 60 days. The lowest levels of copper soluble in EDTA solution were observed in the copper concentrate that was repulped with water after leaching (Example 17) and the copper concentrate that was neutralized with hydrated lime pulp (Example 19). The soluble copper levels in Examples 17 and 19 increased from 1.3% by weight in the initial sample to only 2.5% by weight after 60 days of exposure.

[0067] The copper contents soluble in 50% by mass acetic acid solution measured for the initial samples and samples taken from the pile surfaces of Examples 15 to 19 after exposure to the environment for 15, 30, 45, and 60 days are shown in Table 8. The soluble copper contents were calculated using the above formula (1).

[0068] [Table 8]

[0069] The initial sample of Example 15 (unleached copper concentrate) had a high acetic acid soluble copper content (7.0 wt%), whereas the initial samples of leached concentrate had an average EDTA soluble copper content of 2.1 wt%.

[0070] Again, the greatest increase in acetic acid soluble copper content was observed in Example 16 (leaching of copper concentrate only), which rose from 2.0 wt% in the initial sample to 5.2 wt% after 15 days and reached 5.9 wt% after 60 days.

[0071] Additionally, the lowest levels of copper soluble in acetic acid solution were observed in the copper sulfide concentrates that were repulped with water after leaching (Example 17) and neutralized with hydrated lime pulp (Example 19). The soluble copper content in concentrates 3 and 5 increased from 2.3% by weight in the initial samples to 3.2% by weight after 60 days of exposure.

[0072] The efficiency of residual acid removal was demonstrated by monitoring the temperature, soluble copper content, and lump formation of conical piles containing leached and washed / neutralized concentrates, as described above. The use of sodium hydroxide (NaOH) as a residual acid neutralization reagent is not recommended because the pulp containing leached copper sulfide concentrate and neutralized with this agent exhibits very low settling and filtration rates, impairing the performance of downstream solid-liquid separation processes. Because NaOH is a dispersant and hydrated lime (Ca(OH)2) is a binding neutralizing agent, leached and neutralized copper sulfide concentrates with moisture contents above 11% (>13% by mass) are produced with little or no formation of highly resistant lump (CaSO4·2H2O). The water-leached and repulped copper sulfide concentrate (Example 17) showed the best results in terms of physical and chemical quality after 60 days of storage, with a low soluble copper content (2.6% by mass) and the formation of non-resistant lumps.

[0073] Furthermore, two equipment set options are proposed for the hazardous substance extraction process route of the present invention. The first equipment option, shown in Figure 5, uses a solid-liquid separation system equipped with a concentrator and a filter press to perform double filtration, which includes two solid-liquid separation steps. This option generates less waste liquid, consumes less hydrated lime, and generates less waste containing fluoride, uranium, and / or thorium, but operates intermittently due to the use of the filter press.

[0074] A copper sulfide concentrate pulp (1.1) with a solids content of 55% to 65% was diluted (1) to a solids content of 20% and acidified with 98% by weight sulfuric acid (1.2) for 30 minutes without heating to a pH of 1.5 to 3.5. The pH-adjusted diluted copper sulfide concentrate pulp (1.4) was passed through a leaching vessel (2) and leached for 6 hours without heating with or without the addition of aluminum sulfate solution (15 g / L Al2(SO4)3) (2.1).

[0075] The leached copper sulfide concentrate pulp (2.2) was then passed through thickener I (3) and the overflow from the thickener containing the leached copper sulfide concentrate (3.2) was passed through filter press I (4). The leached copper sulfide concentrate (4.1) with residual acid was then washed or neutralized using process water (5.1) or hydrated lime pulp (5.2) to reduce the residual acid (5).

[0076] The leached and washed (neutralized) copper sulfide concentrate pulp (5.3) was passed through Thickener II (6) where a flocculant (6.1) was applied. 60-80% of the overflow (6.3) from Thickener II was recycled to the process, while the remainder was subjected to chemical treatment. The underflow (6.2) of the thickener containing the leached and washed (neutralized) copper sulfide concentrate was passed through Filter Press II (7) to obtain the final product, the residual acid-free leached copper sulfide concentrate (7.1).

[0077] Furthermore, after the concentrator (3), a portion of the fluid was passed through a partition (8), and 60 to 80% by mass of the overflow (8.2) from the concentrator I was recycled to step (1) together with process water (1.3). The remaining portion, 20 to 40%, of the overflow (8.1) from the concentrator I was neutralized (9) to a pH of 9.0 by adding slaked lime pulp (9.1) and chemically treated through a filter press III or a vacuum filter (10). As a result, a residue (10.1) containing F, U, and / or Th was generated and discarded.

[0078] The second equipment option, shown in Figure 6, involves countercurrent washing of the leached copper concentrate, a single solid-liquid separation step using a thickener, and then a filter press to obtain the leached and washed product. Countercurrent washing requires more thickeners than the dual-filtration process route option. This option proved more challenging from an operational standpoint due to the larger amount of operating equipment (tanks, pumps, agitators, etc.), the larger overflow recirculation flow rate required to dilute the pulp fed to each thickener to ensure a high settling rate of the solids, and the longer it took to stabilize operating conditions if they became uncontrollable.

[0079] A copper sulfide concentrate pulp (11.1) with a solids content of 55-65% was diluted (11) to 20% solids and acidified with 98% by weight sulfuric acid (11.2) for 30 minutes without heating to a pH of 1.5-3.5. The pH-adjusted diluted copper sulfide concentrate pulp (11.4) was passed through a leaching tank (12) and leached for 6 hours without heating by adding an aluminum sulfate solution (15 g / L Al2(SO4)3) (12.1).

[0080] The leached copper sulfide concentrate pulp (12.2) was then passed through Thickener I (13) with the addition of flocculant (13.1), and the underflow pulp I (13.2) was passed through Thickener II (14). The overflow II (14.1) from Thickener II (14) was returned to Thickener I (13) to produce recycle (14.2). This same process was repeated in Thickeners III (15) and IV (16) with the addition of flocculant (15.1, 16.1) to produce underflow II pulp (14.3), underflow III pulp (15.4), and underflow IV pulp (16.5), overflow II (14.1), overflow III (15.2), and overflow IV (16.3) in the presence of recycle (15.3, 16.4) and process water (16.2).

[0081] The underflow IV pulp (16.5) was then passed through a filter press (17) to obtain residual acid-free leached copper sulfide concentrate (17.1) as the final product.

[0082] Furthermore, after the concentrator I (3), the overflow I (13.3) was passed through a partition (18), and a portion of the overflow from the concentrator I (18.2), 20% to 40% by mass, was recycled to the step (11) together with the process water (11.3). The remaining portion of the overflow from the concentrator I (18.1), 60% to 80%, was neutralized (19) to a pH of 9.0 by adding slaked lime pulp (19.1) and chemically treated through a filter press III or a vacuum filter (20). As a result, a residue (20.1) containing F, U, and / or Th was generated and discarded.

[0083] Based on the data and information contained herein, the present invention effectively solves the problem of reducing the hazardous substance content of copper sulfide concentrate, reducing the payment of imposed fines, opening up new markets, and potentially increasing the selling price. The process of the present invention is selective, without copper extraction, consumes little reagents, does not require heating, and generates little solid waste containing high levels of fluoride, uranium, and / or thorium. The process of the present invention has low capital and operating costs and uses simple equipment such as tanks, concentrators, and filter presses.

[0084] Many variations within the scope of protection of this patent application are permitted, which reinforces that the present invention is not limited to the above configurations / embodiments.

Claims

1. 1. A method for extracting hazardous materials from an ore concentrate, comprising: At least the following steps: i) subjecting the ore concentrate to acid leaching to obtain a leached ore concentrate and a leach solution; and ii) subjecting the leached ore concentrate with reduced content of harmful substances obtained from step i) to a treatment to reduce the internal residual acidity by washing with process water and / or neutralization by adding slaked lime pulp. Including, the acid leaching step is carried out at a residence time of about 2 hours to about 8 hours, a pH of about 1.5 to about 4.0, and a temperature of about 15°C to about 35°C; the internal residual acid reduction step is carried out at a residence time of about 15 minutes to about 45 minutes and a temperature of about 15°C to about 35°C; A method characterized by:

2. 2. A method for extracting harmful substances according to claim 1, characterized in that the raw material fed to the method consists of copper sulfide concentrate.

3. 3. The method for extracting hazardous materials according to claim 2, wherein the copper sulfide concentrate has a solids content of about 55% to 60%.

4. The copper sulfide concentrate is chalcopyrite (CuFeS ２ ), bornite (Cu ５ FeS ４ ), chalcocite (Cu ２ S), arsenopyrite (Cu ３ AsS ４ 4. The method for extracting harmful substances according to claim 2 or 3, characterized in that the extracting agent contains copper (CuS) and / or covellium (CuS).

5. 5. The method for extracting harmful substances according to any one of claims 1 to 4, characterized in that the leachate obtained from step i) is copper-free.

6. 6. A method for extracting hazardous substances according to any one of claims 1 to 5, characterized in that the extracted hazardous substances are fluorides, uranium and / or thorium.

7. 7. A method for extracting harmful substances according to any one of claims 1 to 6, characterized in that the acid leaching step is carried out with a residence time of about 6 hours.

8. A method for extracting harmful substances according to any one of claims 1 to 7, characterized in that the acid leaching step is carried out at a temperature of about 15°C to about 25°C.

9. A method for extracting harmful substances according to any one of claims 1 to 8, characterized in that the acid leaching step is carried out at a pH of about 2.5 to about 3.

5.

10. 10. A method for extracting harmful substances according to any one of claims 1 to 9, characterized in that the acid leaching step is carried out at a solids content of about 10% to about 30%, preferably about 20%.

11. A method for extracting harmful substances according to any one of claims 1 to 10, characterized in that the acid leaching step is carried out using sulfuric acid and / or aluminium sulfate.

12. The concentration of aluminum sulfate in the leachate is about 10 g / L to about 30 g / L. ２ (SO ４ ) ３ , preferably about 15 g / L of Al ２ (SO ４ ) ３ The method for extracting harmful substances according to claim 11, characterized in that:

13. 13. A method for extracting harmful substances according to any one of claims 1 to 12, characterized in that the internal residual acid reduction step is carried out with a residence time of about 30 minutes.

14. A method for extracting harmful substances according to any one of claims 1 to 13, characterized in that the internal residual acid reduction step is carried out at room temperature (about 20°C).

15. 15. The method for extracting harmful substances according to any one of claims 1 to 14, characterized in that the internal residual acid reduction step is carried out at a solids content of about 20% to about 50% by weight, preferably about 20% to about 40% by weight.

16. 16. The method for extracting hazardous substances according to any one of claims 1 to 15, characterized in that the product obtained exhibits a fluoride content reduction of about 10% to about 60%, a uranium content reduction of about 30% to about 50% and / or a thorium content reduction of about 30% to about 50%.

17. 17. The method for extracting harmful substances according to any one of claims 1 to 16, characterized in that the method is carried out by double filtration using a solid-liquid separation system in which a tank (2), a concentrator (3, 6) and a filter press (4, 7, 10) are present.

18. 18. The method for extracting hazardous substances according to claim 17, characterized in that 60% to 80% of the leachate produced in step i) is recycled to the acid leaching step.

19. 19. A method for extracting hazardous substances according to claim 17 or 18, characterized in that 20% to 40% of the leachate produced in step i) is purged and treated to remove fluoride, uranium and / or thorium through precipitation with hydrated lime, resulting in a solid residue rich in fluoride and uranium, which is then discharged and disposed of in accordance with environmental classification, and the treated leachate is returned to the acid leaching step.

20. 17. The method for extracting harmful substances according to any one of claims 1 to 16, characterized in that the method is carried out by countercurrent washing with the presence of a tank (12), concentrators (13, 14, 15, 16) and filter presses (17, 20).

21. 21. A method for extracting hazardous substances according to claim 20, characterized in that 20% to 40% of the leachate produced in step i) is recycled for the acid leaching step.

22. 22. A method for extracting hazardous substances according to claim 20 or 21, characterized in that 60% to 80% of the leachate produced in step i) is purged and treated to remove fluoride, uranium and thorium through precipitation with hydrated lime, resulting in a solid residue rich in fluoride and uranium, which is then discharged and disposed of in accordance with environmental classification, and the treated leachate is returned to the acid leaching step.

23. 10. A product obtained by the method for extracting hazardous materials according to claim 1, characterized in that it exhibits a reduction in fluoride content of about 10% to about 60%, a reduction in uranium content of about 30% to about 50%, and / or a reduction in thorium content of about 30% to about 50%, and is free of residual acid.

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