Extraction process for reducing alunite content from tailings, product, and its use

Abstract

To provide a process for extracting aluminum, potassium and alunite sulfate from sulfide copper ore tailings to reduce the alunite content in the ore tailings.SOLUTION: A process according to the present invention includes at least a step of heat treatment of a raw material and a leaching step. The method generates a first coproduct rich in quartz and a second coproduct rich in aluminum and / or potassium sulfates. The proposed process route has a high percentage of aluminum, potassium and alunite sulfate extraction, with effective reduction of the alunite content in ore tailings, low cost and obtaining of coproducts that can be subsequently marketed and / or disposed of in an environment in a safe manner and contributes to practice of circular economy.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for extracting aluminum, potassium and alumite sulfate from mining tailings, in particular those intended for disposal in the environment, and to a method for reducing the alumite content in these tailings. The present invention also relates to the products obtained by this method and their use. [Background technology]

[0002] In the mining industry, tailings are an unavoidable product of the ore processing process, and are generated along with the desired useful materials. Tailings have various impacts on the environment, requiring large-scale disposal sites, suppressing vegetation, and adversely affecting the physical and chemical properties of surface and groundwater. Here, alumite can be present in tailings obtained by the flotation of copper ore. Alumite is potassium aluminum sulfate hydroxide (KAl3(SO4)2(OH)6). Alumite is soluble in water, and when it comes into contact with water, it releases Al into the liquid effluent. 3+ ions and H + It releases ions, lowers the pH and reduces the Al content in the liquid effluent. 3+ This increases the concentration of ions and other metals / non-metals. If such liquid effluents are disposed of in the environment, they may cause a strong environmental burden.

[0003] Conventionally, there are several options for reducing the alumite content in discarded tailings, such as hydrocyclone separation and flotation, but these options do not result in tailings with a sufficiently low alumite concentration in the composition. However, prior art efforts have also been made to extract alumite using various routes (e.g., pyrometallurgical and / or hydrometallurgical process routes) that achieve more effective alumite content reduction.

[0004] Document CN105217658 discloses a method for extracting aluminum and potassium from alumite by direct pressure acid leaching. The proposed method does not require thermal treatment of the raw material, as pressure leaching is believed to be sufficient to remove the target compounds. However, pressure leaching is known to be expensive, requiring expensive sealed and pressurized tanks, high energy consumption, and the use of more complex equipment in the solid-liquid separation step of the pulp.

[0005] Meanwhile, WO2019149293 discloses a method for processing alumite ore, which involves crushing, grinding, and flotation of the raw alumite ore. The concentrated alumite ore is calcined and leached with a 5% to 20% by weight aqueous sodium carbonate solution. However, sodium carbonate is a very expensive reagent and is difficult to obtain commercially, making this method economically unfeasible. Furthermore, the process route proposed in this document produces a liquid effluent rich in sodium sulfate. This effluent requires special and expensive treatment for disposal or to produce marketable by-products.

[0006] US 4,031,182 discloses a method for recovering aluminum from alum ore. The method comprises the steps of calcining the alum ore to remove sulfur in the form of water molecules and SOx gases and converting potassium aluminum sulfate hydroxide (alumite) to alumina (Al2O3), leaching the calcined product with water and filtering to remove potassium sulfate and other soluble sulfates, leaching the water leach residue with sulfuric acid solution at high temperature to convert the alumina to soluble aluminum sulfate, followed by filtering to remove silicon dioxide (SiO2) and other solid impurities, crystallizing the aluminum sulfate and further removing impurities, heating the residue to convert the aluminum sulfate to alumina and removing residual sulfur as SOx gases, and digesting the calcined alumina with sodium hydroxide under standard Bayer process conditions at a high A / C ratio (aluminum / caustic soda) to precipitate "sandy" aluminum hydroxide from the resulting high A / C ratio solution. The proposed process operates at high temperatures to thermally decompose alumite to obtain SO2 and Al2O3 + SiO2. This involves complete thermal decomposition with the evolution of gases containing SO2, followed by the production of aluminum by leaching with sulfuric acid solution, which involves high energy consumption and requires either the treatment of the SO2 gas to produce sulfuric acid or washing with an alkaline solution such as hydrated lime.

[0007] A paper by Meng-Jie Luo, Cheng-Lin Liu, Jin Xue, Ping Li, and Jian-Guo Yu, entitled "Leaching kinetics and mechanism of alunite from alunite tailings in highly concentrated KOH solution," discloses the direct leaching of alunite from tailings using a highly concentrated KOH solution. Under appropriate leaching conditions (e.g., temperatures below 90°C and KOH concentrations above 13.5 mol / L), most of the alunite dissolves, while kaolinite, dickite, and quartz remain as residue. This paper discusses the extraction of alunite by alkaline leaching, but like sodium carbonate, potassium hydroxide is not a readily available or low-cost raw material on the market.

[0008] As noted above, the prior art has addressed the extraction of alumite using various methods and raw materials. However, there remains a need for a thermally efficient, low-cost process route that can efficiently remove alumite from copper ore tailings and reduce the environmental impact of disposing of these tailings in the natural environment.

[0009] As will be described in detail below, the present invention aims to practically and efficiently solve the problems of the prior art described above. Summary of the Invention

[0010] The present invention relates to a method for extracting aluminum, potassium and alumite sulfate from copper sulfide ore tailings, with the aim of reducing the alumite content in the ore tailings. Such tailings are typically disposed of in the environment and are often used to extract aluminum, potassium and alumite sulfate. 3+ ions and H + The release of ions into the liquid effluent causes significant environmental impacts, which is why the extraction of alumite using the method proposed in this invention is of great importance.

[0011] The present invention also relates to quartz-rich products, aluminum sulfate and / or potassium sulfate-rich products obtained by the process of the present invention, and to their uses.

[0012] The objectives and other advantages of the present invention will become more apparent from the following description. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an operational flow chart of the alumite extraction process route of the present invention showing how a first quartz-rich by-product is obtained. [Figure 2] FIG. 2 is an operational flow chart of the alumite extraction process route of the present invention showing the processing of the aluminum sulfate and / or potassium sulfate rich liquid and the obtaining of a second by-product rich in aluminum sulfate and / or potassium sulfate. [Figure 3] FIG. 3 shows a comparison of the extraction rates of Al, Cu, and K from different ore tailings according to an embodiment of the present invention after carrying out the alumite extraction process of the present invention. [Figure 4] FIG. 4 shows the characterization of two fractions of aluminum sulfate and / or potassium sulfate rich by-products obtained after the alumite extraction process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Given the existing problems with the disposal of ore tailings into the environment and the real possibility of contamination, the need to process and extract metals from these tailings is a recurring and serious challenge.

[0015] In particular, the tailings of alumite-rich copper sulfide ores release Al when in contact with water. 3+ ions and hydrolyzes to form H +By releasing ions, they lower the pH of the effluent and promote the leaching of other metals and non-metals. If such liquid effluents are disposed of in the environment, they can cause serious environmental impacts.

[0016] In order to solve such existing technical problems, the present invention proposes a method for extracting alumite from the tailings of copper sulfide ore.

[0017] In order to achieve the above object, the present invention provides a method for extracting alumite from tailings, comprising at least the following steps: i) subjecting the raw material (1.1) to a mild heat treatment (1) with controlled temperature and residence time to promote only the dehydroxylation of the alumite, resulting in a calcined product with low crystallinity; ii) subjecting the calcined product obtained in step i) to acid leaching (3) using a mineral acid (3.1), which may be hydrochloric acid, nitric acid, sulfuric acid, similar acids or mixtures thereof, with sulfuric acid being preferred; iii) obtaining from the copper sulfide tailings about 75% by weight to about 100% by weight, preferably about 85% by weight to about 95% by weight of the extract and a by-product pulp; The method of the present invention produces co-products from the by-products, which can be used in a variety of applications. Thus, the proposed process makes it possible to treat waste, reduce environmental impact, find use for by-products that would otherwise be discarded, and promote the implementation of a circular economy.

[0018] According to the present invention, the raw material (1.1) in the method of the present invention comprises tailings obtained by the flotation of copper sulfide ore. Preferably, the tailings obtained by the flotation of copper sulfide ore have a quartz content of about 20% to about 80% by weight and an alumite content of about 5% to 90% by weight, and may also contain small amounts of sulfide minerals (pyrite, chalcopyrite, bornite, covellite, chalcocite) of about 0.5% to about 5.0% by weight and clay minerals (kaolinite, pyrophyllite, dickite) of about 5% to about 25% by weight.

[0019] Figure 1 shows an operational flow chart of the extraction method for reducing alumite content described in this invention. The initial heat treatment step (1) of the raw material (1.1) consists of a mild heat treatment of the copper tailings to remove hydroxyl groups from its molecules (dehydroxylation). This heat treatment is carried out in equipment that can withstand high temperatures, preferably a rotary kiln or oven. The residence time and temperature in the heat treatment step must be properly controlled to avoid the formation of refractory crystalline structures that would inhibit the extraction of alumite in the subsequent leaching step. Therefore, the temperature used in this step may be about 550°C to about 850°C, preferably about 650°C to about 750°C, and the residence time may be about 0.5 hours to about 2 hours, preferably about 1 hour.

[0020] The solids obtained in the heat treatment step are then cooled (2) and subjected to acid leaching (3) in a tank without heating, with a residence time and solids content (preferably 10% to 50%, more preferably 30%) appropriate to maximize the extraction of alumite. The mineral acid (3.1) used in this step may be hydrochloric acid, nitric acid, sulfuric acid, similar acids, or mixtures thereof, with sulfuric acid being preferred. In this step, the residence time in the tank may be from about 1 hour to about 8 hours, preferably from about 2 hours to about 4 hours, and the temperature may be from about 25°C to about 90°C, preferably from about 60°C to about 80°C. The pH of the reaction should be less than 3.0, preferably greater than 1.5 and less than 2.5. The specific consumption is about 150 kg to about 450 kg of acid (3.1) per ton of raw material (1.1), preferably about 250 kg to about 350 kg of acid (3.1) per ton of raw material (1.1), resulting in a rate of about 300 kg of acid (3.1) per ton of raw material (1.1). The raw material (1.1) may be copper tailings, and the acid (3.1) may be 98% by weight sulfuric acid.

[0021] After this step, a liquor containing aluminum sulfate and potassium sulfate is obtained, which corresponds to an extraction rate of alumite from the copper tailings of about 80% to about 95%, preferably about 85% to about 90%. Advantageously, the process of the present invention also produces, as a by-product, a pulp containing quartz-rich solids and a liquor rich in aluminum sulfate and potassium sulfate. This pulp is then thickened and filtered (4) to separate the quartz-rich solids from the liquor rich in aluminum sulfate and potassium sulfate (4.1). Thickening is carried out in a thickener with the addition of a flocculant, the thickening rate being about 0.010 m 2 / t / day ~ approx. 0.020m 2 / t / day, preferably about 0.015m 2 The thickener underflow, which contains pulp with a solids content of about 30% to about 60%, preferably about 45%, is then sent to the filtration step (4) using a filter press or vacuum filter. The filtration rate is about 200 kg / h / m 2 ~About 400kg / h / m 2 , preferably about 300 kg / h / m 2 This results in a quartz-rich solid having a moisture content of about 10% by mass to about 30% by mass, preferably about 20% by mass.

[0022] The quartz-rich solids are then processed through additional steps, including washing the solids with process water (5), producing a poor liquor (5.1), drying (6), and cooling, to produce a quartz-rich first by-product (6.1). The quartz-rich first by-product (6.1) has an SiO2 content of about 75% to about 100% by weight, preferably about 85% to about 95% by weight, and can be used for disposal in the environment, used in the construction of dam slopes, or sold for civil engineering construction in the production of blocks, ceramics, or road paving. In this way, the quartz-rich first by-product (6.1) obtained by the method of the present invention can be safely disposed of in the environment, as well as commercialized to generate revenue and reduce the environmental impact of copper ore processing. It is estimated that 700 to 750 kg of quartz-rich by-product (SiO2 content: >88% by weight) is produced per 1,000 kg of raw ore.

[0023] As shown in the operational flow chart of FIG. 2, the aluminum sulfate and potassium sulfate-rich liquid (4.1) obtained in step (4) is then subjected to thermal evaporation (7), producing a first salt consisting of aluminum and potassium double sulfate and water vapor during the crystallization process. The water vapor is condensed, and the heat energy and water are recovered and recycled. In this process, approximately 75% of the total solvent volume is reduced. The liquid is then crystallized by cooling (8, 9), and the additional vapor generated is condensed to recover additional heat energy and water. This process yields a first portion (9.1) of a second by-product rich in aluminum sulfate and / or potassium sulfate. The first portion (9.1) is a salt. These steps are carried out in an evaporator and a crystallizer.

[0024] The remaining liquid volume is then subjected to a new evaporation (10) and a drying, flocculation and cooling process (11) to obtain a second portion (11.1) of a second by-product enriched in aluminum sulfate and / or potassium sulfate, which is also a salt.

[0025] The two fractions (9.1, 11.1) obtained from the second by-product may have the same or different compositions and may be potassium sulfate (K2SO4), aluminum sulfate (Al2(SO4)3·15-20H2O), and / or a mixture of potassium sulfate and hydrated aluminum (KHSO4·Al2(SO4)3·10-20H2O). The aluminum sulfate- and / or potassium sulfate-rich second by-product (9.1, 11.1) has an aluminum content of about 3.5% to about 8.5% by weight, a potassium content of about 1.0% to about 5.0% by weight, and a sulfate content of about 25% to about 50% by weight. It can be sold for use in pool water treatment, as a raw material for the production of aluminum sulfate and / or potassium sulfate, or as an antibacterial, disinfectant, and therapeutic agent in the health and beauty fields. It is estimated that 150-250 kg of by-products rich in aluminum sulfate and / or potassium sulfate are produced per 1000 kg of ore feedstock.

[0026] The overall alumite extraction process can remove from about 75% to about 100%, by weight, and preferably from about 85% to about 95%, by weight of the alumite from the copper sulfide tailings.

[0027] The method for extracting alumite from copper sulfide tailings described in this invention can reduce the amount of tailings discarded at ore processing sites by 20% to 30%, reducing environmental impacts and the cost of raising the dam, and extending the life of the mine by increasing the recoverable reserves of the deposit. Furthermore, quartz-rich by-products and aluminum sulfate and / or potassium sulfate-rich by-products are produced, which can be sold and generate additional revenue. Even if the quartz-rich by-product, which does not contain alumite in its composition, is not sold, its disposal into the environment does not generate acidic liquid discharges containing dissolved metals / non-metals and does not pose serious environmental damage.

[0028] Furthermore, industrial operations to obtain copper sulfide concentrates from alumite-containing copper sulfide ores will be more sustainable. Circular economy technologies will be directly applied, and 20% to 80% of the total mass of copper sulfide ore will be utilized to generate products for domestic and international markets. Generally, the overall mass recovery rate in copper sulfide ore flotation projects is very low, ranging from 2% to 5%.

[0029] The present invention also relates to products obtained by the method of the present invention and their respective uses. The obtained first product has an SiO2 content of more than 88% by mass and is relevant for commercialization in civil engineering construction, such as in the construction of dam bodies or in the production of blocks, ceramics, or road paving. Furthermore, this first product can be safely disposed of in the environment without generating acidic liquid discharges containing dissolved metals / non-metals, and its commercialization can generate revenue and reduce the environmental burden of copper ore processing. The second product comprises potassium sulfate, aluminum sulfate, and / or a mixture of acidic potassium sulfate and hydrated aluminum and can be used for the treatment of pool water, as a raw material for the production of aluminum sulfate and / or potassium sulfate, or as an antibacterial, disinfectant, and therapeutic agent in the health and beauty fields.

[0030] The present invention has been described above merely as an example of one or more embodiments, and the features described are merely for ease of understanding, and therefore should not be construed as limiting the present invention, which should be limited only by the scope of the claims. [Example]

[0031] The examples presented here are illustrative of the range of products produced by the methods proposed in this invention.

[0032] example Laboratory tests were carried out to show the effect of the alumite extraction method on various parameters.

[0033] Example 1 First, two control tests were conducted without a heat treatment step on the raw material. Copper sulfide tailings were directly subjected to sulfuric acid leaching under the following conditions: a temperature of 80°C, two sulfuric acid dosages (155 kg / t and 312 kg / t), a residence time of 4 hours, and a pulp solids content of 30% by mass. The results of these tests showed that the extraction rate of aluminum was only 1%, the extraction rate of copper was 22%, and the extraction rate of potassium was 0%. In other words, when acid leaching was performed alone without a heat treatment step on the raw material, the extraction rate of alumite was extremely low. This demonstrates that a heat treatment step is essential for the present invention.

[0034] Example 2 Next, tests were conducted to determine the optimal conditions for the thermal treatment of the raw material. The raw material was pyrolyzed in an oven at a temperature of 750°C and a residence time of 1 hour. Subsequently, leaching was carried out using 98% by mass sulfuric acid (312 kg / t) at a temperature of 80°C, a residence time of 4 hours, and a solids content of 30% by mass in the pulp. The results of this test showed that the extraction rates of aluminum, copper, and potassium were 46%, 52%, and 96%, respectively.

[0035] Example 3 The raw material was pyrolyzed in an oven at 750°C for a residence time of 3 hours. It was then leached using 98% by mass sulfuric acid (312 kg / t) at 80°C for a residence time of 4 hours with a pulp solids content of 30% by mass. The results of this test showed an aluminum extraction rate of 41%, a copper extraction rate of 51%, and a potassium extraction rate of 96%. This result is similar to that of Example 2, except that the residence time in Example 2 was shorter.

[0036] Therefore, it was determined that a residence time of 1 hour (Example 2) in the heat treatment step of the raw material was more advantageous.

[0037] Example 4 Next, tests were conducted to determine the optimal conditions for the acid leaching process. The raw material was thermally decomposed in a rotary kiln at 750°C for a residence time of 1 hour. Subsequently, leaching was carried out using sulfuric acid at a temperature of 80°C for a residence time of 4 hours, with 312 kg of sulfuric acid per ton of raw material and a solids content of 30% by mass in the pulp. The results of this test showed that the extraction rates of aluminum, copper, and potassium were 53%, 73%, and 97%, respectively.

[0038] Therefore, the extraction of aluminum and potassium is more favorable under dynamic conditions using a rotary kiln instead of an oven (static conditions) in the heat treatment process.

[0039] Example 5 The raw material was pyrolyzed in a rotary kiln at 750°C for a residence time of 1 hour. Subsequently, sulfuric acid was used for leaching at 80°C for a residence time of 4 hours, with 312 kg of sulfuric acid per ton of raw material and a pulp solids content of 40% by mass. The results of this test showed an aluminum extraction rate of 56%, a copper extraction rate of 59%, and a potassium extraction rate of 96%. Because the rheology of the pulp with a solids content of 40% by mass made it difficult to maintain a suspension, which interfered with the subsequent concentration and filtration processes, it was decided to maintain a solids content of 30% by mass.

[0040] Example 6 The raw material was pyrolyzed in a rotary kiln at 750°C for a residence time of 1 hour. It was then leached using sulfuric acid at 25°C for a residence time of 4 hours, with 312 kg of sulfuric acid per ton of raw material and a solids content of 30% by mass in the pulp. The results of this test showed that the extraction rates of aluminum, copper, and potassium were 26%, 49%, and 83%, respectively.

[0041] Therefore, a temperature of 80° C. (Example 4) is important to ensure a high extraction rate of aluminum and potassium, and therefore of alumite.

[0042] Example 7 Example 4 was repeated to produce a product for testing on subsequent steps in the process route. The raw material was pyrolyzed in a rotary kiln at 750°C with a residence time of 1 hour. It was then leached using sulfuric acid at 80°C for a residence time of 4 hours, with 312 kg of sulfuric acid per ton of raw material and a solids content of 30% by mass in the pulp. The results of this test showed an aluminum extraction rate of 53%, a copper extraction rate of 61%, and a potassium extraction rate of 97%.

[0043] FIG. 3 shows a comparison of the extraction rates of Al, Cu, and K in Examples 1 to 7 above.

[0044] As shown, the best extraction results were obtained in Examples 4 and 7. The extracted Al / K mass ratios were closest to the stoichiometry of alumite, indicating that the extraction rate of alumite was close to 100%. The lowest Al, Cu, and K extraction results were obtained in Example 6, where the acid leaching temperature was 25°C. On the other hand, Example 5 had the highest Al / K mass ratio, possibly due to additional aluminum extracted from other minerals.

[0045] Example 8 The pulp obtained by the acid leaching under the above-mentioned optimal conditions was then subjected to evaporation, crystallization, and solid-liquid separation processes. Evaporation of the solvent (water) and crystallization were carried out in the laboratory by controlling the heating of the pulp obtained after leaching on an electric heating plate. Solid-liquid separation was carried out using a Buchner funnel, filter paper, and a vacuum pump. A first by-product rich in quartz and a second by-product rich in potassium sulfate and / or aluminum sulfate were obtained. In the first step, 75% of the solvent (water) evaporated, and in the second step, 100% of the solvent (water) evaporated. The properties of the two fractions of the by-products rich in aluminum sulfate and / or potassium sulfate obtained by these processes are shown in Figure 4.

[0046] It is clear from the data and information in this paper that the present invention can effectively reduce the alumite content in tailings, achieve a high extraction rate of alumite, low cost, and obtain by-products that can be sold or safely disposed of in the environment in the future, generating future benefits and supporting the application of circular economy technologies in the processing of copper sulfide ores.

[0047] Numerous variations are permitted within the scope of protection of this patent application, which reinforces that the present invention is not limited to the above configurations / specific examples.

Claims

1. 1. An extraction process for reducing alumite content from tailings, comprising: At least the following steps: i) subjecting the raw material (1.1) to a heat treatment (1); ii) subjecting the calcined product obtained in step i) to acid leaching (3) using a mineral acid (3.1) selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, similar acids or mixtures thereof; iii) extracting about 75% to about 100% by weight of the alumite from the tailings. Including, The heat treatment step (1) of the feedstock (1.1) is carried out at a temperature of about 550°C to about 850°C and a residence time of about 0.5 hours to about 2 hours; leaching step (3) is carried out at a residence time of about 1 hour to about 8 hours, a temperature of about 25°C to about 90°C, and an acidic pH; The extraction process produces a metal and mineral rich pulp as a by-product; An extraction method comprising:

2. 2. A process for reducing the alumite content according to claim 1, characterized in that the raw material (1.1) fed to the extraction process consists of tailings obtained by flotation of copper sulfide ores.

3. 3. The extraction method for reducing the alumite content according to claim 2, characterized in that the tailings obtained by the flotation of copper sulfide ore have a quartz content of about 20% to about 80% by weight and an alumite content of about 5% to about 90% by weight, and may also contain, in small amounts, about 0.5% to about 5% by weight of sulfide minerals (pyrite, chalcopyrite, bornite, covellite, chalcocite) and about 5% to about 25% by weight of clay minerals (kaolinite, pyrophyllite, dickite).

4. 4. The extraction method for reducing the alumite content according to claim 1, wherein the heat treatment step (1) of the raw material (1.1) is carried out in a rotary or static furnace (oven).

5. 5. The extraction method for reducing the alumite content according to any one of claims 1 to 4, characterized in that the heat treatment step (1) of the raw material (1.1) is carried out at a temperature of between about 650 °C and about 750 °C.

6. 6. The extraction process for reducing the alumite content according to any one of claims 1 to 5, characterized in that the heat treatment step (1) of the raw material (1.1) is carried out with a residence time of about 1 hour.

7. 7. The extraction method for reducing the alumite content according to any one of claims 1 to 6, characterized in that the leaching step (3) is carried out in a tank.

8. 8. The extraction method for reducing the alumite content according to any one of claims 1 to 7, characterized in that the leaching step (3) is carried out at a temperature of from about 60°C to about 80°C.

9. 9. The extraction process for reducing the alumite content according to any one of claims 1 to 8, characterized in that the leaching step (3) is carried out with a residence time of from about 2 hours to about 4 hours.

10. 10. The extraction method for reducing the alunite content according to any one of claims 1 to 9, characterized in that the leaching step (3) is carried out at a reaction pH greater than 1.5 and less than 2.

5.

11. 11. The extraction method for reducing the alumite content according to any one of claims 1 to 10, characterized in that the leaching step (3) is carried out using sulfuric acid.

12. 12. The extraction process for reducing the alumite content according to claim 1, wherein the leaching step (3) is carried out at a rate of about 150 kg to about 450 kg of acid (3.1) per ton of raw material (1.1), preferably about 250 kg to about 350 kg of acid (3.1) per ton of raw material (1.1), resulting in a rate of about 300 kg of acid (3.1) used per ton of raw material (1.1).

13. 13. The extraction method for reducing alumite content according to any one of claims 1 to 12, characterized in that the amount of extracted alumite is about 85% to about 95% by weight.

14. 14. A method for extracting alunite to reduce its content according to any one of claims 1 to 13, characterized in that the metal- and mineral-rich pulp obtained in step iii) is subsequently concentrated and filtered (4) to obtain a quartz-rich solid and a liquid (4.1) rich in aluminum sulfate and / or potassium sulfate.

15. 15. The extraction method for reducing alumite content according to claim 14, characterized in that the quartz-rich solids are treated by additional steps including washing the solids with process water (5), drying (6) and cooling to produce a first quartz-rich by-product (6.1).

16. The quartz-rich first by-product (6.1) is about 75% to about 100% by weight, preferably about 85% to about 95% by weight, of SiO ２ 16. The extraction method for reducing alumite content according to claim 15, characterized in that it has a content of

17. 15. The extraction method for reducing the alumite content according to claim 14, characterized in that the liquid (4.1) rich in aluminum sulfate and potassium sulfate is treated by additional steps including thermal evaporation (7) to produce a first salt consisting of a double salt of aluminum sulfate and potassium sulfate and water vapor, condensation of the water vapor with recovery of energy and water, crystallization of the liquid (4.1) by cooling (8, 9) with production of additional water vapor, and additional condensation with recovery of energy and water, to obtain a first portion (9.1) of a second by-product rich in aluminum sulfate and potassium sulfate.

18. 18. The extraction method for reducing the alumite content according to claim 17, characterized in that the remainder of the liquid volume is subjected to additional steps consisting of evaporation (10), drying and cooling (11) to obtain a second portion (11.1) of a second by-product enriched in aluminum sulfate and / or potassium sulfate.

19. 19. The extraction method for reducing the alumite content according to claim 17 or 18, characterized in that the second by-product (9.1, 11.1) consists of potassium sulfate, aluminum sulfate and / or a mixture of potassium acid sulfate and aluminum hydrate.

20. 20. The extraction method for reducing the alumite content according to any one of claims 17 to 19, characterized in that the second by-product (9.1, 11.1) rich in aluminum sulfate and / or potassium sulfate is in the form of a salt.

21. 10. The product obtained by the extraction method of claim 1, comprising about 75% to about 100% by weight of SiO ２ A product characterized by having a content.

22. About 85% to about 95% by weight of SiO ２ 22. The product of claim 21, characterized in that it has a content of:

23. 10. The product obtained by the extraction method of claim 1, comprising potassium sulfate, aluminum sulfate, and / or a mixture of acidic potassium sulfate and hydrated aluminum, characterized in that the aluminum content is about 3.5% to about 8.5% by weight, the potassium content is about 1.0% to about 5.0% by weight, and the sulfuric acid content is about 25% to about 50% by weight.

24. 22. Use of a product according to claim 21 for the construction of dam slopes, civil engineering works or road paving.

25. 24. Use of a product according to claim 23 for the treatment of swimming pool water, for the production of aluminium sulphate and / or potassium sulphate or as an antibacterial, disinfectant and therapeutic agent in the health and beauty sector.

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