Leaching method for caliche mineral heaps

Abstract

The present application relates to a caliche mineral leaching method, which comprises the steps of providing caliche with a content of fine material and applying an irrigation sequence that comprises irrigating the heap with an aqueous solution and a binding additive, in order to obtain iodine and nitrate.

Description

[0001] LEACHING METHOD FOR CALICHE ORE HEAP

[0002] Field of Invention

[0003] The present invention relates to the field of chemistry and metallurgy of non-metallic mining, in relation to heap leaching methods of caliche ore that involve the use of flocculants.

[0004] Description of the State of the Art

[0005] In the metallurgical mining industry, it is vitally important to have methodologies that allow for the optimal recovery of raw materials or products of economic interest from leaching heaps.

[0006] Prior art has disclosed processes for the removal or recovery of metallic valuables, or water-polluting compounds, and the like, for which various additives have been used. For example, document US20080196546 provides a cyanide leaching composition comprising at least one nonionic surfactant and a process for extracting gold or silver metals using the aforementioned composition.

[0007] EP0288150 seeks to leach iron ores from a low-grade ore by a process comprising washing or leaching the ore in acid, and then using the resulting enriched, acidic particulate ore for pelletizing.

[0008] Finally, document US4728537 discloses a process in which mineral granules are manufactured by adding a binder, in particles of a specific size, comprising an organic polymer to an iron or zinc mineral.

[0009] However, no leaching methodologies have been developed that use additives specifically tailored to obtain products of interest, such as iodine salts or nitrates. Therefore, methods are needed that allow the leaching of caliches containing fine material to improve the yield of iodine salts or nitrates.

[0010] Summary of the Invention

[0011] The present invention provides a method for leaching a caliche ore heap to obtain iodine salts or nitrates comprising the following steps: providing a caliche with a fine material content, and applying an irrigation sequence comprising: i) irrigating with an aqueous solution and an agglomerating additive selected from the group consisting of: polyacrylamide, a combination of calcium chloride and humic and fulvic acids; astrakanite or guar gum, or a combination thereof. Preferably, the fine material content is included up to 30% w / w. Likewise, the aqueous solution may comprise water, water from continental sources, seawater, an aqueous saline solution or brine, or dilutions thereof.

[0012] In the leaching method, step i) of irrigation is carried out up to a leaching rate (LR) between 0 and 1 m 3 / t, preferably between 0 and 0.05 m 3 / t; even more preferably at an RL of 0.05 m 3 / t.

[0013] In a preferred embodiment, the leaching method in the irrigation sequence, step i) of irrigation is carried out up to a leaching rate (LR) between 0 and 0.05 m 3 / ton; and after step i) they also include the following steps: ii) irrigate with an aqueous solution until reaching a RL between 0.05 to 0.6 m 3 / t, iii) irrigate with an aqueous solution until reaching a RL between 0.6 to 0.9 m 3 / t, iv) wash with water until reaching a RL between 0.9 and 1 m 3 / t.

[0014] Even more preferably, the irrigation sequence of steps i) to iii) is:

[0015] i) irrigate with an aqueous solution until reaching a leaching rate (LR) between 0.05 to 0.5 m 3 / t, iii) irrigate with an aqueous solution until reaching a leaching rate (LR) between 0.5 to 0.9 m 3 / t, iv) wash with water until reaching a leaching rate (LR) between 0.9 and 1 m 3 / t.

[0016] Even more preferably, the leaching method in the irrigation step i) comprises irrigation with an aqueous saline solution with a concentration range of 100 to 500 g / L of total salts. In the irrigation step iii) comprises irrigation with an aqueous saline solution with a concentration range of between 50 to 500 g / L of total salts, preferably between 100 to 500 g / L of total salts, or between 50 to 300 g / L.

[0017] The aqueous solutions in steps i) and iii) can also be water from continental sources or seawater.

[0018] In another preferred embodiment, the leaching method of the present invention, preferably in the irrigation sequence, step i) is carried out up to a leaching rate (RL) between 0 and 0.05 m3 / t; step ¡i) is carried out up to a leaching rate (RL) of 0.45 m3 / t; step iii) is carried out up to a leaching rate (RL) of 0.9 m3 / t; step iv) is carried out up to a leaching rate (RL) of 1 m3 / t.

[0019] In another preferred embodiment, the leaching method of the present invention, preferably in the irrigation sequence, step i) is carried out up to a leaching ratio (LR) between 0 and 0.07 m 3 / t; step ¡i) is carried out up to a leaching rate (LR) of 0.45 m 3 / t; step iii) is carried out up to a leaching rate (LR) of 0.95 m 3 / t; step iv) is carried out up to a leaching rate (LR) of 1 m 3 / t.

[0020] Regarding the agglomerating additives, in a preferred embodiment, said additive is preferably cationic polyacrylamide and is applied at a concentration of 0.005 to 0.05 g / L. Even more preferably, the cationic polyacrylamide is applied at a concentration of 0.01 to 0.025 g / L.

[0021] In another preferred embodiment, the agglomerating additive is anionic polyacylamide and is applied at a concentration of 0.01 to 0.05 g / L.

[0022] In another preferred embodiment, the agglomeration additive is a combination of calcium chloride and humic and fulvic acids, specifically calcium chloride at 26% w / v and humic and fulvic acids at 40% w / v, and said combination is applied between 0.05 to 1 g / L.

[0023] In another preferred embodiment, the agglomerating additive is guar gum and is applied at 0.05 g / L.

[0024] The method of the present application can be applied to leaching in heaps, columns, gabions, or pans. Preferably, it can be carried out in caliche leaching heaps. Brief description of the figures

[0025] Figure 1 shows fine material or also called clay after the agglomeration test where 1 is blank (Water), 2 is SI solution, 3 is AFA solution, 4 is Water + 3 g / L Cal, 5 is SI solution + 3 g / L Cal, 6 is AFA solution + 3 g / L Cal, 7 is Water + 50 g / L Salt, 8 is SI solution + 50 g / L Salt and 9 is AFA solution + 50 g / L Salt. (SI (intermediate solution) and AFA (weak acid water): aqueous saline solutions, see Table 2).

[0026] Figure 2 shows the results of minicolumn iodine yield tests with different binders in the irrigation stage (i) using fine-grained material or clay. (SI: aqueous saline solution or intermediate solution, see Table 2).

[0027] Figure 3 shows the results of mini-column iodine production performance tests with a mixture of fine material (claystone) and coarse material (called Breccia) (A: claystone and B: breccia).

[0028] Figure 4 shows the results of minicolumn iodine yield tests with different binders using fine material. (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2).

[0029] Figure 5 shows the results of minicolumn iodine yield tests with different binders using fine material (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2). Figure 6 shows the results of minicolumn iodine yield tests using different flocculant dosages. (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2).

[0030] Figure 7 shows a comparison of iodine concentration curves, where measurements were taken daily at a drainage composite. The concentration curve corresponds to the concentration of all drainage sampled during irrigation expressed as a function of the total leaching rate in m 3 / t. As irrigation progresses, the iodine concentration decreases according to the extraction curve for the material.

[0031] Figure 8 shows a comparison of Hydraulic Efficiency EH (fraction of solution input volume recovered at the heap exit) expressed as a function of total leaching ratio in m 3 / t.

[0032] Figure 9 shows the results of mini-column iodine yield tests with flocculant dosages (with a mixture of coarse material (70%) and fine material (30%) (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2) expressed as a function of the total leaching ratio in m 3 / t.

[0033] Figure 10 shows the results of minicolumn iodine yield tests on 100% coarse or gap material (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2) expressed as a function of the total leaching ratio in m 3 / t.

[0034] Figure 11 shows the result of the iodine production yield of industrial test No. 1 expressed as a function of the total leaching ratio in m 3 / t.

[0035] Figure 12 shows the Hydraulic Efficiency (HE) of industrial test No. 1 expressed as a function of the total leaching ratio in m 3 / t.

[0036] Figure 13 shows the result of the iodine production yield of industrial test No. 2 expressed as a function of the total leaching ratio in m 3 / t.

[0037] Figure 14 shows the Hydraulic Efficiency (HE) of industrial test No. 2 expressed as a function of the total leaching ratio in m 3 / t.

[0038] Figure 15 shows the results of minicolumn nitrate yield tests (DIS: Dilute Intermediate Solution, aqueous saline solution, see Table 2) expressed as a function of the total leaching ratio in m 3 / t.

[0039] Figure 16 shows a moisture retention curve of the material to be leached as a function of the matrix potential.

[0040] Figure 17 shows a kinetic curve of the electrical conductivity of the drained solution as a function of time. Detailed description of the invention

[0041] The present invention provides a method that allows for the leaching of a mineral heap to obtain iodine or nitrate salts, enabling the exploitation of minerals, particularly caliche, with fine material content. This mineral can also be leached in columns, gabions, or pans.

[0042] The inventors have tested and evaluated various agglomeration additives for the design of a successful irrigation protocol for a caliche ore heap. These additives are incorporated directly into the heap for leaching during irrigation, simultaneously with the leaching process. Additionally, the method provides a defined irrigation sequence based on the Leaching Rate (LR).

[0043] In this way, first, a caliche or mineral deposit of nitrate and iodine salts is provided as a starting material, preferably with a fine material content of up to approximately 30% w / w, although it may be higher than this value, to constitute or form a leaching pile. Subsequently, an irrigation sequence is applied, which essentially requires the step of i) impregnating said pile with an aqueous solution and an agglomerating additive selected from the group consisting of: polyacylamide, a combination of calcium chloride and humic and fulvic acids; astrakanite or guar gum, or a combination thereof. The addition of said agglomerating additive or flocculant can be carried out throughout the irrigation process, in any of its stages or steps, until the desired total or final leaching ratio is obtained.

[0044] Step i) of irrigation is carried out up to a leaching rate (LR) in the range between 0 to 1 m 3 / t, preferably between 0 and 0.05 m 3 / t, or even more preferably 0.05 m 3 / t. Preferably, after step i) irrigation steps are incorporated, which are defined as follows:

[0045] i) irrigate with an aqueous solution until reaching a RL between 0.05 to 0.6 m 3 / ton; preferably between 0.05 to 0.5 m 3 / t; even more preferably at 0.45 m 3 / t; iii) irrigate with an aqueous solution until reaching a RL between 0.6 to 0.9 m 3 / t, preferably until reaching a RL between 0.5 to 0.9 m 3 / t; or between 0.6 to 0.9 m 3 / t, or until reaching a RL of 0.9 m 3 / t; and iv) wash with water until reaching a leaching rate (LR) between 0.04 and 1 m 3 / t; preferably until reaching a leaching rate (LR) between 0.5 and 1 m 3 / t, or between 0.9 and 1 m3 / t. In irrigation steps i) or iii), irrigation is carried out with an aqueous saline solution with a concentration range between 50 and 500 g / L of total salts, preferably 100 to 500 or 50 to 300 g / L of total salts. Said aqueous saline solution may come from the recycling of treatment solutions of other minerals, for example, solutions with high contents of nitrate, sulfate and chlorides of sodium, calcium and magnesium; also said aqueous solution may be water from continental sources or seawater.

[0046] Regarding the irrigation steps used in this method, they can be carried out up to a value of the leaching rate RL of the total process inclusive greater than 1 m 3 / t, for example, up to 1.5 m 3 / to superior.

[0047] The terms used herein are those known to any person skilled in the art. For the sole purpose of defining the invention, the following concepts are illustrated below.

[0048] Caliche is understood to be a mineral deposit of nitrate and iodine salts, and corresponds to the raw material of the method of the present application. It consists of a mass composed of sodium nitrate mixed with other soluble salts such as chlorides and sulfates, sedimented with insoluble materials such as gravel, sand, and clayey rocks. Caliche is a type of sedimentary rock that occurs in the form of breccia or sandstone with particles cemented by salts. Caliche also contains iodine and nitrate mineral species in percentages of up to 1000 ppm or more of iodine and 8% w / w of nitrate in general, in which iodine is present as iodate. The main caliche beds for the production of iodine and fertilizers are found in the Tamarugal Pampas and the Atacama Desert in Chile. The exploitation process for this type of mineral has particular characteristics that differentiate it from traditional mining of metals such as copper and gold.This difference lies in the sedimentary origin of these deposits, which define subhorizontal mineralized layers called caliche, of variable thickness. These layers are lodged in subsurface rocks at an average depth of 1 to 3 meters and occur in large horizontal areal areas. Given this particular condition, caliche extraction requires large areas of land necessary for the development of the activities specific to this type of extraction.

[0049] In this document we will refer strictly to clastic sedimentary rocks, which are classified according to their particle size:

[0050] 1. Coarse: gravels (fragments larger than 2 millimeters and a matrix of much smaller fragments, less than 2 millimeters). a. Conglomerates (rounded clast). b. Breccias (angular clast).

[0051] 2. Medium: sand (fragments between 1 / 16 and 2 mm). a. Greywackes (>25% rock fragments). b. Arkose (Quartz with >25% feldspar).

[0052] 3. Fine: muds, called claystones, are those with a size smaller than 1 / 16 mm a. Clays. b. Slates. c. Lutites.

[0053] Fine material also refers to material with a size smaller than 200# mesh, that is, less than 0.074 mm. This material can be naturally present in the caliche or can be produced through traditional caliche mining methods, such as blasting, or through other mechanical methods that result in mineral fractionation, such as surface mining or crushing.

[0054] Similarly, it is estimated that flocculants could act on thicker materials or those larger than 0.074 mm.

[0055] Regarding the iodine salts or iodine derivatives present in the raw material to be treated, they are in the form of iodates, which can subsequently be chemically treated to be reduced to iodides and finally obtain elemental iodine using techniques known in the technical field.

[0056] Regarding the nitrate salts present in the raw material to be treated, these mainly refer to sodium or potassium nitrate salts, either simple or in combination with other salts.

[0057] Leaching is the process of extracting a substance from a solid material after it has been treated with a liquid. Caliche ore leaching processes primarily involve blasting the ground with explosives. The loosened caliche is then transported to leach pads, consisting of material piled on land. These pads are then subjected to a carefully designed irrigation process to extract the target minerals. Alternatively, caliche ore can be crushed after blasting, or it can be surface mined before processing.

[0058] An agglomerating additive is a compound or compounds added to the solutions used to irrigate the caliche leaching heap to facilitate the adhesion of certain particles. This makes it possible to agglomerate the fine material in situ, improving its stability when interacting with the leaching fluid. Similarly, an additive or flocculant allows particles to associate according to their chemical charge. The agglomerating additives and / or flocculant agents are provided in this application as detailed in the Examples section.

[0059] RL or Leaching Rate is understood as the relationship between the total irrigated solution versus the amount of irrigated material (m 3 / t). For example, an RL of 1 is equivalent to 1 m 3 of solution watered into 1 ton of caliche.

[0060] Irrigation is understood to mean the addition or spreading of an aqueous, saline, or water solution from continental or seawater sources onto a land surface or leach pad containing the material of interest, with the purpose of saturating said surface. Such irrigation may include the addition of a caking additive according to the method of the present invention.

[0061] Anyone skilled in the art will appreciate that variations can be made to the present invention, and that the detailed embodiments are merely exemplary. Dimensions and materials may vary; other forms that embody the same inventive concept would also be possible.

[0062] The following are examples of embodiments of the invention, which illustrate it and show preferred embodiments; however, they should not be considered in any way to restrict the scope of the patent application, which is limited only by the content of the appended claims.

[0063] Application Examples

[0064] Study of the mixing material and optimization.

[0065] Metallurgical tests were carried out in current and future exploitation sectors that were characterized by a certain content of fine-grained material with a clay-type lithology. 1 This unit represents a caliche 2 complex from a metallurgical point of view due to its negative implications in the operation of leaching piles (low hydraulic efficiency or EH) 3 , high inventory 4, mechanical stability problems, low irrigation rate and slow kinetics). The presence of fine materials does not allow proper percolation.

[0066] Tests were conducted to improve the leaching of these materials. The first tested the impact of fine material or claystone content on leaching, which resulted in a decrease of more than 40 percentage points in yield. A subsequent test was conducted to find a mixture of fine-sized claystone and claystone lithologies.

[0067] 1 Fine-grained lithological unit.

[0068] 2 Raw material consisting of a mass composed of sodium nitrate mixed with other salts such as chlorides, sulfates and iodine.

[0069] 3 Hydraulic efficiency (m 3 / / i): It is defined as the total % of drained solution versus the irrigated solution in a leach pad. The greater the hydraulic efficiency, the greater the drained solution.

[0070] 4 Solution that has not yet drained and is retained inside the battery (m 3 / t) thick gap size 5 that would at least mitigate these results. The result was that it is possible to work with 30% fine material in the pile (weight / weight percentage) for a deficit of no more than 10 points in iodine yield.

[0071] In addition, a way to leach the material was sought by adding additives that would promote agglomeration. Cationic and anionic polyacrylamide, guar gum (polysaccharide from the seeds of Cyamopsis tetragonoloba), calcium chloride 26% plus humic and fulvic acids 40% w / v, and lime were used as flocculants. 100% fine material (claystone) was used for this, and tests were performed in mini-columns. 6with different agglomerating additives, the cationic polyacrylamide flocculant showing the best results, increasing performance by 15.6 percentage points for 100% fine material (claystone); and by 12.6 percentage points for a mixture of 30% fine material (claystone) and 70% coarse material (breccia). These results were validated in two industrial tests.

[0072] 5 A breccia is a type of conglomerate formed by a majority fraction of clasts (angular and subangular) of size > 2 mm in diameter.

[0073] 6 Pilot leaching system consisting of a cylindrical column 36 cm high and 0.056 m 2 of circumferential area. 20 kg of caliche are loaded here, and an irrigation system is installed to emulate industrial leaching.

[0074] Table 1. Details of the additives used in the study. 7

[0075] Based on the evidence, tests were conducted to agglomerate these fine materials, adding additives to emulate the agglomeration process of piles in order to form compact masses and prevent particle segregation during the additive application stage.

[0076] The following agglomerating additives were used for the leaching tests:

[0077] 1. Polyacrylamide flocculant: Also known as a clarifier, this is a chemical that reacts in water, causing solid particles to stick together and form "clumps" or flocs that become more visible and, due to their weight, may eventually fall to the bottom. This flocculation mechanism can be by bridging, charge neutralization, or patch mechanism.

[0078] For this study, a battery of cationic polyacrylamide flocculants was used. These flocculants are composed of macromolecules with positively charged groups, allowing them to interact electrostatically with the negatively charged particles present in the water. These particles can be suspended solids, clays, organic matter, and other contaminants that cause water turbidity.

[0079] Another alternative was an anionic polyacylamide flocculant that binds with residual cationic charges on coagulants adsorbed to coagulated colloids.

[0080] 2. Cyamopsis tetragonoloba polysaccharide: A polysaccharide found in the seeds of the Cyamopsis tetragonoloba plant. This polysaccharide is water-soluble and is used in the food industry as a thickener.

[0081] 3. Calcium chloride 26% + humic and fulvic acids 40% w / v: This is a corrector of saline soils and those with weak acidic reaction and is used in agriculture. It is capable of displacing sodium and chlorides from the clay-humic complex, improving soil structure and drainage, and promoting the elimination of sodium by leaching.

[0082] 4. Lime: It is used as a binder by not allowing the migration of fine particles with the leaching solution.

[0083] 5. Astrakanite: Use of waste salts from an AFA evaporation process with high astrakanite content.

[0084] 7 The viscosity of the polyacrylamide used ranged from 700 to 1000 cP at 0.5% and 900 to 1200 cP at 0.5%, and the pH ranged from 3 to 5 at 0.5%. Experimental results

[0085] • Example 1 - Agglomeration test

[0086] Agglomeration tests were carried out with clay material, for which the following agglomeration solutions and additives were used:

[0087] Table 2. Solutions used in agglomeration tests.

[0088] The dilution is of the solution indicated on the left “solution used”.

[0089] Agglomeration tests showed a visible improvement in the physical quality of the clay. This clay exhibits the presence of glomerates that were visually detected, demonstrating that the material can be agglomerated (as shown in Figure 1).

[0090] • Example 2 - Recovery of iodine from claystone minicolumns with the application of different binders.

[0091] In order to achieve better wettability and agglomeration,

[0092] 8Aqueous saline solution in a concentration range of 100 to 500 gpl (g / L) of total salts (depending on its dilution) and low concentration of iodate (0.1-0.2 g / L).

[0093] 9 Aqueous saline solution without iodate content. When diluted, it is called a mixture. Dilute aqueous saline solution in the range of 100 to 500 g / L of total salts.

[0094] 10 Aqueous saline solution with a concentration above 75 to 85 g / L of magnesium.

[0095] 11 Salts with a majority content of astrakanite.

[0096] 12 AFA: Acidic Weak Water. Mini-column performance tests, with the addition of various additives during the irrigation stage (i). These were:

[0097] Table 3. Solutions used in performance testing.

[0098] The irrigation parameters were: 1. RL Irrigation 13 0.05 m 3 / t

[0099] 2. Irrigation SI Solution at 38% RL 0.45 m 3 / t

[0100] 3. Irrigation Solution Mixture 14 at 40% RL 0.36 m 3 / t

[0101] 4. Washing Water RL 0.04 m 3 / t.

[0102] The additive was applied from the start of irrigation until the RL was completed at 0.05 m 3 / t for each of the solutions mentioned in Table 3 (10 tests in total in parallel with their respective duplicates) 15 ).

[0103] The yield results are presented for a 100% fine clay or clayey material containing 580 ppm iodine after irrigation with various additive solutions mentioned in Table 3 of the document. These are plotted against the system's leaching rate, or LR, to obtain yield points as the caliche soil is irrigated. The test that showed the best results was the addition of astrakanite salt and water, as shown in Figure 2.

[0104] 13 Relationship between the total solution irrigated vs. quantity of irrigated material (m 3 / t) E.g.: RL = 1 means 1 m3 of solution watered in 1 ton of caliche.

[0105] 14 Diluted AFA solution. The dilution is indicated in each table.

[0106] 15 Tests performed with identical parameters help corroborate the results. • Example 3 - Mini-column performance tests with a clay-breccia mixture

[0107] The yield results for different mixtures of fine material (claystone) and coarse material (breccia) with 257 ppm iodine are presented and plotted against the system's leaching rate (LR) (total irrigation) to obtain yield points as the caliche soil is irrigated. The results in Figure 3 show that the greater the addition of fine material (claystone), the greater the decrease in yield. For example, mixtures of fine material and coarse material showed a negative impact on iodine yield (-10 percentage points) when 30% of fine material (claystone) was added; and a larger decrease (-20 percentage points) when more than 30% of this material was added.

[0108] This experiment was irrigated with the following irrigation circuit: irrigation up to a leaching rate RL 0.05 m 3 / t, followed by irrigation with intermediate solution or SI with a dilution of 38% up to a leaching rate RL of 0.5 m3 / t; subsequently a solution of Mixture with 40% dilution up to a leaching rate of RL 0.9 m 3 / t. Finally, a washing irrigation with water at a RL of 1 m 3 / t.

[0109] • Example 4 - Mini-column performance tests with different binders in impregnation with fine material - Claylite.

[0110] Tests were carried out on mini-columns with the following irrigation parameters: irrigation up to RL 0.05 m 3 / t, then irrigation with intermediate solution, SI diluted to 38% with RL 0.45 m 3 / t, followed by irrigation with a 40% diluted mixture solution with a RL of 0.9 m 3 / t. Finally, a water wash up to a RL of 1 m 3 / t adding different additives to the impregnation. These were:

[0111] Table 4. Solutions used in performance testing.

[0112] The additive was applied from the start of irrigation until impregnation was complete for each of the solutions mentioned in Table 4 (five parallel tests with their respective duplicates). The remaining irrigation was identical in all experiments.

[0113] The performance results are presented with a fine material - claystone with 225 ppm of Iodine from the addition of different solutions with additives mentioned in Table 4 of this document, which are graphed versus the leaching or total ratio of the system to obtain the performance points as the caliche is irrigated (Figure 4).

[0114] Improved iodine recoveries are observed with the addition of astrakanite salts. Calcium chloride plus humic and fulvic acids shows an additional 12 percentage points of yield. In the case of the cationic polyacrylamide flocculant, the concentration used (1 g / L) caused a plugging effect, so the tests were repeated with a lower concentration.

[0115] • Example 5 - Mini-column performance tests with different binders in the impregnation of fine material-Claystone.

[0116] Tests were carried out on mini-columns with the following irrigation parameters: irrigation up to RL 0.05 m 3 / t, then irrigation with intermediate solution, SI diluted to 38% up to a RL 0.5 m 3 / t, followed by a 40% diluted irrigation mixture up to a RL of 0.96 m 3 / t. Finally, a water wash to a RL of 1 m 3 / t adding different additives to the impregnation. These were:

[0117] Table 5. Solutions used in performance testing.

[0118] The additive was applied from the start of irrigation until impregnation was complete for each of the solutions mentioned in Table 5 (four parallel tests with their respective duplicates). The remaining irrigation was identical in all experiments.

[0119] The performance results are presented with a fine-clay material with 225 ppm of Iodine from the addition of different solutions with additives mentioned in Table 5 of this document. These are graphed versus the leaching or total system ratio (RL) to obtain the performance points as the caliche is irrigated (Figure 5).

[0120] The results showed a significant increase in iodine yield with decreasing dosage of the anionic polyacrylamide flocculant at a concentration of 0.05 g / L (+13 percentage points of yield). Calcium chloride plus humic and fulvic acids at a concentration of 0.05 g / L showed a yield increase of 6.3 percentage points.

[0121] • Example 6 - Minicolumn performance tests with different flocculant dosages in fine material - Claylite.

[0122] Considering the above results, minicolumn performance tests were conducted with different flocculants and dosages. The objective was to find the additive that most improved performance. For this test, the following were used:

[0123] Table 6. Solutions used in tests with different flocculant dosages.

[0124] The additive was applied from the start of irrigation until the target RL was reached for each of the solutions mentioned in Table 6 (7 parallel trials with their respective duplicates). The remaining irrigation time was identical in all experiments.

[0125] The performance results are presented with a fine material (claystone with 262 ppm iodine) from the addition of different solutions with additives mentioned in Table 6 of this document. These are graphed versus the leaching rate or total system (RL) to obtain the performance points as the caliche is irrigated.

[0126] After testing different additives and dosages, the best results were obtained by the cationic polyacrylamide flocculant with 0.025 g / L (+15 percentage points of yield) and calcium chloride plus humic and fulvic acids (+8.6 percentage points of yield); in addition to greater hydraulic efficiency and a higher iodide concentration in the effluent solution (0.2 g / L difference in the outlet concentration), as shown in Figures 6, 7 and 8.

[0127] • Example 7 - Minicolumn performance tests with different flocculant dosages (70% coarse material - Breccia - 30% fine material - Claylite)

[0128] Performance tests are carried out with the following irrigation parameters: up to a RL 0.05 m 3 / t, followed by irrigation with intermediate solution. SI diluted to 38% with an RL 0.45 m 3 / t is then irrigated with a 40% diluted mixture with a RL of 0.36 m 3 / t. Finally, a water wash at RL 0.04 m 3 / t; with the addition of flocculant during the impregnation stage for the 30% claystone - 70% breccia mixture. The additives used were:

[0129] Table 7. Solutions used in tests with different flocculant dosages (70% Brecha-30% Claylite).

[0130] The additive was applied from the start of irrigation until the target RL was reached for each of the solutions mentioned in Table 7 (9 parallel trials with their respective duplicates). The remaining irrigation time was identical in all experiments.

[0131] The performance results are presented with a coarse material 70% Brecha-30% fine material-Clay ita with 355 ppm of Iodine from the addition of different solutions with additives mentioned in Table 7 of this document. These are graphed versus the leaching ratio or total system (RL) to obtain the performance points as the caliche is irrigated.

[0132] The dosage that gave the best results was the cationic polyacylamide flocculant with 0.01 g / L (10 ppm) dosage (+12.6 percentage points of performance) (Figure 9).

[0133] • Example 8 - Minicolumn performance tests with different flocculant dosages (100% coarse material - Gap)

[0134] Yield tests were carried out with gap material, with the following irrigation parameters: irrigation at a RL 0.05 m 3 / t, followed by irrigation with intermediate solution, SI diluted to 38% with a RL 0.45 m 3 / t, then irrigation with a 40% diluted solution with a RL of 0.36 m 3 / t. Finally, a water wash with a RL of 0.04 m 3 / t) with different flocculant additions to evaluate whether the benefit obtained can be reproduced in coarser-grained materials. The additions used were:

[0135] Table 8. Solutions used in tests with different flocculant dosages (100% gap).

[0136] The additive was applied from the start of irrigation until the leaching rate, RL, of 0.05 m was completed. 3 / t for each of the solutions mentioned in Table 8 (3 parallel tests in total with their respective duplicates). The remaining irrigation was identical in all experiments.

[0137] The performance results are presented with a coarse-gap material with 250 ppm of Iodine from the addition of different solutions with additives mentioned in Table 8 of this document. These are graphed versus the total Leaching Rate of the system (RL) to obtain the performance points as the caliche is irrigated (Figure 10).

[0138] It is observed that for good quality materials the cationic polyacylamide flocculant has no effect on performance.

[0139] • Example 9 - Industrial Test No. 1

[0140] An industrial test of flocculant addition is carried out in a pile with material loaded directly from the mine (30% Claystone-70% Breccia) with 0.010 g / L of cationic polyacylamide flocculant in the irrigation stage i). For this, equipment is installed consisting of two 250-liter tanks where the flocculant mixture is made and injected into the irrigation line driven by dosing pumps.

[0141] The concentration curve, iodide yield, and EH are monitored. The performance of this pile is compared with a target pile, selected based on a comparative statistical study of construction parameters and pile composition.

[0142] The test is performed on industrial caliche piles and equivalent piles are compared with and without cationic polyacylamide flocculant additive.

[0143] Table 9 Comparison of batteries in industrial tests (SS: water-soluble salt content).

[0144] Once the industrial test operation was completed, an increase in iodine recovery was determined in the treated pile, in accordance with what was seen in the minicolumn tests (+6 percentage points of performance) as a consequence of an increase of 8 points in hydraulic efficiency for the pile with cationic polyacylamide flocculant, as indicated in Figures 11 and 12.

[0145] • Example 10 - Industrial Test No. 2

[0146] The test is performed on industrial caliche piles and equivalent piles are compared with and without cationic polyacylamide flocculant additive at 0.010 g / L.

[0147] Table 10 Comparison of industrial tests (SS: water-soluble salt content % w / w).

[0148] An increase in iodine yield of 4 percentage points and an increase in hydraulic efficiency of 8 percentage points is presented at RL 0.36 m 3 / t for the pile with cationic polyacylamide flocculant, as seen in Figures 13 and 14.

[0149] • Example 11 - Nitrate yield results.

[0150] The performance results are presented with a coarse material 70% Breccia-30% fine material - Claystone with 4% Nitrate from the addition of different solutions with additives mentioned in Table 7 of this document as indicated above, which are graphed versus the leaching rate or total RL of the system to obtain the performance points as the caliche is irrigated. The addition of cationic polyacylamide with 0.01 g / L (10 ppm) dosage increased the performance by 11 percentage points (Figure 15).

[0151] • Example 12 – Moisture retention characterization tests to evaluate additive performance.

[0152] Tests were performed on mini-columns with 100% clay caliche material that were instrumented with water potential, moisture content, temperature and electrical conductivity sensors.

[0153] In one test, flocculant was added during the initial irrigation stage, while the other remained as a control. Twenty-five ppm of cationic polyacrylamide flocculant was added to the clay-filled minicolumn. Both minicolumns were irrigated with water.

[0154] The effect of moisture retention in 100% caliche clay was analyzed as a function of the water potential and conductivity of the solution over time inside the minicolumns.

[0155] The results in Figures 16 and 17 indicate that the flocculant has a modifying effect on the raw material. It was verified that the physical properties improved in the minicolumns with clay-type material, since it was observed that the energy required to remove the water contained in the raw material decreased with the addition of cationic polyacrylamide flocculant, and in addition, the electrical conductivity of the drainage solution remained higher.

[0156] Conclusions

[0157] • The mixture leaching tests (claystone-breccia) show that the recovery of iodine and nitrates decreases as there is greater incorporation of claystone material.

[0158] • The negative effect of fine material on yield can be offset by using the cationic polyacrylamide flocculant, which gave the best results in mini-column tests with 30% claystone and 70% gap at 10 mg / L (13 percentage point increase in iodine recovery). Excess flocculant has an effect contrary to the objective pursued by the invention.

[0159] • The results of industrial batteries with additives show an increase in iodine yield of 4 to 6 percentage points compared to the respective comparative battery without additives. "Calcium chloride plus humic and fulvic acids is the additive whose application also improves iodine recovery.

Claims

CLAIMS 1. A method of leaching caliche ore to obtain iodine salts or nitrates, where the method comprises the following steps: - provide a caliche with a fine material content, - applying an irrigation sequence comprising: i) irrigating the caliche with an aqueous solution and a clumping additive selected from the group consisting of: polyacrylamide, a combination of calcium chloride and humic and fulvic acids; astrakanite or guar gum, or a combination thereof.

2. The leaching method according to claim 1, wherein the fine material content is included up to 30% w / w.

3. The leaching method according to claim 1, wherein step i) of irrigation is carried out up to a leaching rate (LR) between 0 and 1 m 3 / t.

4. The leaching method according to any one of claims 1 to 3, wherein step i) of irrigation is carried out up to a leaching ratio (RL) between 0 and 0.05 m 3 / t; and after step i) the following steps are included: ii) irrigate with an aqueous solution until reaching a RL between 0.05 to 0.6 m 3 / t, iii) irrigate with an aqueous solution until reaching a RL between 0.6 to 0.9 m 3 / t, iv) wash with water until reaching a RL between 0.9 and 1 m 3 / t.

5. The leaching method according to claim 4, wherein the irrigation sequence of steps ii) to iii) is: ii) irrigating with an aqueous solution until reaching an RL between 0.05 to 0.5 m 3 / t, iii) irrigate with an aqueous solution until reaching a RL between 0.5 to 0.9 m 3 / t, iv) wash with water until reaching a RL between 0.9 and 1 m 3 / t 6. The leaching method according to claim 4 or 5, wherein the irrigation step ii) comprises irrigation with an aqueous saline solution with a concentration range of 100 to 500 g / L of total salts.

7. The leaching method according to claim 4 or 5, wherein the irrigation step iii) comprises irrigation with an aqueous saline solution with a concentration range of 50 to 500 g / L of total salts.

8. The leaching method according to claim 4 or 5, wherein the aqueous solutions of steps ii) and iii) are water or seawater.

9. The leaching method according to claim 4, wherein in the irrigation sequence: step i) is performed up to a RL between 0 and 0.05 m 3 / t; step ii) is carried out up to a RL of 0.45 m 3 / t; step iii) is performed with a RL of 0.36 m 3 / t; step iv) is performed with an RL of 0.04 m 3 / t.

10. The leaching method according to claim 4, wherein in the irrigation sequence: step i) is performed up to a RL between 0 and 0.05 m 3 / t; step ii) is carried out up to a RL of 0.45 m 3 / t; step iii) is performed up to a RL of 0.9 m 3 / t; step iv) is performed up to a RL of 1 m 3 / t.

11. The method of claim 1, wherein the agglomerating additive is cationic polyacrylamide and is applied at a concentration of 0.005 to 0.05 g / L.

12. The method of claim 11, wherein the cationic polyacrylamide is applied at a concentration of 0.01 to 0.025 g / L.

13. The method of claim 1, wherein the agglomerating additive is anionic polyacrylamide and is applied at a concentration of 0.01 to 0.05 g / L.

14. The leaching method according to claim 1, wherein the agglomerating additive is the combination of calcium chloride and humic and fulvic acids, specifically calcium chloride at 26% w / v and humic and fulvic acids at 40% w / v, and this combination is applied between 0.05 to 1 g / L.

15. The leaching method according to claim 1, wherein the agglomerating additive is guar gum and is applied at 0.05 g / L.

16. The method of any of claims 1 to 15, wherein the leaching is carried out in piles, columns, gabions or trays.