Method for extracting base and precious metals by a pre-treatment that leads to solubilisation of the refractory matrices thereof

Abstract

A method for extracting base and precious metals, all contained in refractory minerals, using aqueous media. The method includes mixing the mineral (Cu2S, CuS, CuFeS2, Cu5FeS4, FeS2, FeAsS.NiS, (Ni,Fe)xSy), ground to an appropriate size (2.5 centimetres), with a specific dose of solid reagent in a rotary agglomeration drum and then adding slightly acidified water to obtain a defined water content (5-8%) depending on the type of gangue contained in the metal-containing solid, thereby forming an agglomerate that will form a heap, which is subsequently allowed to stand for a period of several days (20-60 days), during which the conditions required to transform the refractory matrix into a highly soluble solid will be generated. Finally, appropriately regulated irrigation is applied, thus resulting in extraction of the metal by simple aqueous washing.

Claims

1. A method for extracting base and precious metals by using a treatment to the solubilization of refractory matrices, the method comprising the steps of: crushing a mineral to a particle size distribution between 2.5 and 5 centimetres, if the mineral contains clay, the crushing step is to a particle size of 5 cm; adding a solid lime to the crushed mineral until obtaining a homogeneous mixture with a pH>11; adding a solid reagent to the homogeneous mixture until obtaining a humidity of 5 to 8 weight %; agglomerating the humidity containing mixture to form a glomer; depositing the glomer into a leach pad to form a cell; resting the cell by standing for a length of between 5 and 60 days to reduce moisture; and irrigating with a refining solution after the resting to extract the base and precious metals in an aqueous solution.

2. The method according to claim 1, wherein in a case of an extraction of free gold particles in oxidized matrices using NaCN, the method comprising the steps of: crushing the mineral to sizes of 2.5 cm, wherein if the mineral contains clay, the crushing step is to a particle size of 5 cm; adding a solid lime to the crushed mineral until obtaining a homogeneous mixture with a pH>11; adding solid NaCN reagent to the homogeneous mixture; agglomerating the humidity containing mixture to form a glomer; depositing the glomer into a leach pad to form a cell; resting the cell between 5 to 10 days; and irrigating after resting by spraying with refining solutions to extract the gold in a cyanide solution.

3. The method according to claim 1, wherein in a case of the extraction of free gold particles in oxidized matrices, NaCl used and the method comprising the steps of: crushing the mineral to sizes of 2.5 cm, wherein if the mineral contains clay, the reduction in size is to a particle size of 5 cm; adding a solid lime to the crushed mineral until obtaining a homogeneous mixture with a pH>11; adding solid NaCl reagent to the homogenous mixture; agglomerating the humidity containing mixture to form a glomer; depositing the glomer into a leach pad to form a cell; resting the cell from 10 to 15 days; and irrigating after resting by spraying with refining solutions to extract the gold in a chlorinated solution.

4. The method according to claim 1, wherein in a case of an extraction of gold particles encapsulated in sulfide grains, including pyrite, arsenopyrite or other sulfide, contained in silicates matrices, NaCl is used, the method comprising the steps of: crushing the mineral to a particle size of 2.5 cm, wherein if the mineral contains clay, the size reduction is to 5 cm; adding a solid lime to the crushed mineral until obtaining a homogeneous mixture with a pH>11; adding a solid NaCl reagent to the homogeneous mixture; agglomerating the humidity containing mixture to form a glomer; depositing the glomer into a leach pad to form a cell; resting the cell between 20 to 30 days; and irrigating after resting by spraying with refining solutions to extract the gold in a chlorinated solution.

5. The method according to claim 1, wherein in a case of the extraction of gold particles encapsulated in sulfide grains, including pyrite, arsenopyrite or other sulfide contained in silicates matrices, NaCl and NaCN are used, the method comprising the steps of: crushing the mineral to a particle size of 2.5 cm, wherein the mineral contains clay, the size reduction is to 5 cm; adding a solid lime to the crushed mineral until obtaining a homogeneous mixture with a pH>11; adding a solid NaCl reagent to the homogeneous mixture; adding solid NaCN reagent to the product of the previous step; agglomerating the humidity containing mixture to form a glomer; depositing the glomer into a leach pad to form a cell; resting the cell between 15 to 20 days; and irrigating after resting by spraying with refining solutions to extract the gold in an aqueous solution.

6. The method according to claim 1, wherein in case of the extraction of gold particles encapsulated in sulfide grains, including pyrite, arsenopyrite or other sulfide, contained in silicates matrices, a solid reagent is used only to decapsulate the gold trapped in the sulfide grains and then leach conventionally with cyanide solutions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows three types of SCRE material processing according to the method of the present invention;

(2) FIG. 2 shows a block diagrams including a process containing various chemical elements, continues the conventional purification—precipitation stages, just to get that elements as different products; and

(3) FIG. 3 shows a diagram of Hypex/Goldest adaptation to leaching layout.

DETAILED DESCRIPTION OF THE INVENTION

(4) The method of the invention was based on the search for the reasons why it is NOT possible to leach sulfur minerals. One of the main limitations found is that the leaching mechanism is based on overcoming activation energies characteristic of the shock of reactive species, expressed by the Arrhenius equation, which to date is recognized as an empirical equation. Try to determine the leaching rate, but it does not represent the mechanism.

(5) Based on the foregoing, the method of the invention is based on the fact that given the limitation of leaching sulfur species, there is a need to develop a new method of extracting chemical elements contained in solids from different sources.

(6) The METHOD OF EXTRACTION OF CHEMICAL ELEMENTS FROM MATERIALS THROUGH A PRE-TREATMENT CONDUCTING THE SOLUBILIZATION OF ITS REFRACTORY SPECIES is an alternative and different process to conventional metal extraction processes by leaching and concentration-fusion-conversion of minerals and focuses on processing a wide range of materials, which by manipulating its electronic structure manages to transform it into a highly soluble material in water and makes it possible to simultaneously extract multiple chemical elements of commercial value.

(7) Given the versatility of the METHOD, its industrial application is perfectly feasible in the mining industry (minerals and concentrates), and in the remediation of environmental liabilities such as gravel, tailings and foundry slag of all types of origin, since the concept is based in quantum laws and their implementation does not require large investments.

(8) The METHOD delivers many benefits, namely:

(9) Allows to process wide diversity of materials and the final extraction of more than one chemical element

(10) It generates recoveries greater than 85% and reaches high kinetics of extraction by washing.

(11) Reduces washing water requirements up to 0.5 m3/ton of processed material.

(12) Reduces operating costs, extraction cycles, energy consumption by up to 50% compared to a conventional leaching process

(13) Optimizes the availability of inventories and allows the revaluation of all types of resources and environmental liabilities.

(14) Basic concepts and scope of the invention by method:

(15) Material is defined as that solid matrix that contains valuable chemical elements to be extracted. The concept of material is the same defined by the physics of condensed matter, defined by its properties, which at the same time are determined by the electronic structure, beyond its crystalline structure. To understand the personality of a material, you must study its electrons.

(16) All minerals, concentrates, tailings, rubble, slag from all types of industry, underwater minerals and materials such as meteorites and extraterrestrials will be considered as sources of multiple chemical elements, for the purposes of this invention. The diversity of the properties of these materials (semiconductors and/or topological), observed from the focus of their electronic structures, can range from SIMPLE, COMPLEX, REFRACTORY and EXOTIC materials. From now, SCRE materials.

(17) Electronic structures define several properties that can be used to facilitate the extraction of chemical elements. Two of the most important properties found in SCRE materials in general are:

(18) The energy gap of a material is the measure of its conductivity (difference between the conduction band and the valence band) and is defined by the energy of the Fermi level, which measures the energy of the electrons most bound to the solid. The positions of electrons and/or holes can be manipulated by the addition or removal of electrons

(19) The topology of a material is a phase that determines the property of allowing conductivity on the surface and at the same time electronic isolation in the bulk of the material. The removal or addition of electrons from the electronic structure of the material also allows changing the properties of the material.

(20) The invention is based on the basic identification that the electron being a quantum particle, has transport mechanisms totally different from that of an ion. An electron is transported by two specific mechanisms: tunneling and stretching.

(21) Therefore, the invention is based on the integration of three aspects:

(22) The delivery or extraction of electrons to a SCRE material, allows for example to modify the energy gap and/or activate the topological property and therefore change the property of SCRE material

(23) The supply of the donor or electron extractor, from now on DAE, is done through an external excitation.

(24) As a result of the above, SCRE materials are TRANSFORMED into highly water-soluble materials.

(25) A TRANSFORMED material suggests that each of the compounds contained therein and containing their respective chemical elements, all are in SOLUBLE form

(26) Subsequently, the water washing of this soluble material, allows to extract in solution, ALL the different types of chemical elements previously solubilized by the method.

(27) The invention provides a method to achieve maximum transformation of the original SCRE material into a highly water-soluble material. In that way, the chemical elements (metal, semimetal, etc.) will be contained in a solid that is of high water solubility compared to the original matrix and, therefore, the washing solution will contain multiple chemical elements and will be faster, more efficient and it will require a minimum of inputs and reagents, that is, it will only need a washing step.

(28) Stages of the Method

(29) a) The properly particulate SCRE material is brought into intimate contact with a certain amount of DAE agent.

(30) The granulometry of the SCRE material depends on its origin, according to:

(31) If the SCRE material is a FRESH ORE/MINERAL, it is suggested to crush up to P80=2 inches.

(32) If the SCRE material is a TAILINGS or CONCENTRATE, these already come at the micron level and will be accepted as such.

(33) If the SCRE material is a SPENT ORE, it already comes at the level of ½ to 2 inches and will be accepted as such.

(34) If the SCRE material is a SLAG from any industry, it can have several types of particle sizes ranging from millimeters to inches. If the size is larger than 3 inches, it is recommended to reduce them to a P80=2 inches, otherwise it will be accepted as is.

(35) b) The DAE agent is a solid powder type (consisting of a blending of salts) and is added at a rate of between 2 to 15 kg per ton depending on the type of SCRE material processed.

(36) Note: The DAE agent is a blending of proportions of salts calculated according to the type of SCRE.

(37) c) The mixture between DAE agent and SCRE material is carried out at a humidification range of 3 to 4%, depending on the physical quality of SCRE material, not allowing it to hydraulically saturate. The humidification can be carried out with fresh, salt water or with recirculation solutions of the integral process. The mixing between DAE agent and SCRE material is carried out in different types of reactors, depending on the granulometric profile of the SCRE.

(38) Note: At this point, it is noted that the designs of the types of mixers are being sent at the respective patent application.

(39) d) The mixture thus formed is left in electronic digestion for a period ranging from 5 to 60 days, preferable 10 to 20 days. During this period, the conditions that allow the electronic activity to transform the SCRE material into a very soluble solid that will contain the metal (s) to be extracted are generated. Resting can be done on the floor (previously prepared for this purpose).

(40) e) Once the resting time has elapsed, at this point, the metal (s) are extracted by simply washing with neutral water. The wash rate is between 0.5 to 0.7 m3 of neutral water per ton of SCRE washed. There are several types of scrubbers that will be applied depending on the granulometry of the SCRE material that was processed. The types of washers range from fixed bed to stirred reactors of 1 or 2 compartments.

(41) Note: At this point, it is noted that the designs of the types of washers are being sent at the respective patent application.

(42) f) Since the DAE agent used in the mixing stage is not a chemical reagent itself, it can be lowered from the wash solutions, to prevent some ionic loading effect of the solutions downstream of the process.

(43) g) The washing solution, from now on WS, may contain more than one chemical element to recover due to the high degree of solubility obtained in the transformation stage.

(44) h) The WS containing various chemical elements, continues the conventional purification—precipitation stages, just to get that elements as different products. See FIG. 2

(45) Applications (Hypex)

(46) 1. As described in the Detailed Description item, you can specify the SCRE materials to which the method can be applied. They are capable of being processed by the method all SCRE materials, which are detailed:

(47) Oxidized, sulphured and complex minerals of copper, zinc, iron, nickel, cobalt, molybdenum, lead, silver, gold, tin, antimony, vanadium, chromium, titanium, manganese cadmium, aluminum, bismuth, lithium and rare earths.

(48) Concentrates of the chemical elements mentioned in the previous item.

(49) Tailings and Spent Ore of the chemical elements mentioned in the previous item.

(50) Non-ferrous smelter slags

(51) Special mention for minerals containing gold encapsulated in pyrites or arsenopyrites, where the method allows to decapsulate and solubilize gold without the use of cyanide.

(52) 2. The heap leaching process of minerals will be taken as a reference, as it is the simplest to operate and has the lowest investment and operation cost. It is noted that the SCRE materials that are applied to be processed by adapting this heap leaching technology are those that comply with a particle size between % to 2 inches of P80.

(53) In relation to the above, we will detail how the method can be adapted to each of the stages that has the heap leaching of minerals.

(54) 2a. Regarding heap leaching:

(55) Leaching: processes only oxidized minerals

(56) The Method: processes any SCRE material that meets a granulometric level

(57) 2b. Regarding the unit operation of Crushing: For heap leaching, crushing plants reduce the size of the ore/rock to cause a balance between porosity of the bed of the heap and the porosity of the rock so that the chemical leaching reagent (normally the hydrogen ion), can have the ability to be transported through the bed and introduced into the rock so that the chemical reaction of dissolution develops.

(58) In the case of the METHOD, the reduction in size is defined to cause an electron transport on the surface and bulk of the rock. The ion and the electron have very different transport mechanisms.

(59) In other words:

(60) Leaching: looks for ion diffusion

(61) The Method: look for transport through tunneling and stretching of the electrons

(62) 2c. Regarding the unit operation of Mixture: the METHOD refers to the addition of an “active agent” that is the electron donor/acceptor, named DAE, as a way of protecting said agent.

(63) Regarding the unit operation of the Mixture: In the leaching of oxidized minerals, an agglomerating drum is used, as is its own definition, it is an action of mixing very fine and fine solid particles with those of larger size, so that they can form integral glomers that allow a greater porosity of the bed, when these make up the leaching stack. Therefore, it is an operation aimed at modifying physical conditions of the particulate system.

(64) In other words:

(65) Leaching: looks for the formation of glomers

(66) The Method: seeks the homogenization of the active donor/electron acceptor agent

(67) 2d. Regarding the unit operation of Rest: While a leaching heap must rest to allow the humidity supplied to generate the hydrogen bonds that ensure mechanical stability of the formed glomers/agglomerates, the METHOD is a period of electronic transformation that the SCRE material undergoes.

(68) 2e. Regarding the unit irrigation operation: Leaching continuously provides acidic solutions throughout the cycle that allows to achieve adequate levels of recovery of a single chemical element, i.e. copper. The METHOD supplies water in dosed form to dislodge all the chemical elements solubilized in the previous stage.

(69) Obtained the WS, this continues the conventional stages of purification and precipitation

(70) See FIG. 3

(71) 2f. The DAE agents are varied depending on the origin of the SCRE material that needs to be solubilized: a) They can be solid salts such as NaCl, NaNO3, MgCl2, Ureatos, Phosphates, Oxalates, Citrus; b) Mix SCRE and solid DAE agent, before the humidification stage at ambient conditions; c) The solutions for humidification at this agglomeration stage may even be the raffinate solution that circulates in the process, that is, solutions with sulfuric acid content (10 to 12 gpl) and pH less than 2.5.

(72) 2g. Once the rest period is over, the aqueous extraction of the valuable metal is carried out by drip irrigation of neutral water. Irrigation must be continuous, at a moderate flow and is done by sectors, expressed in units of liter/square meter per hour between 3 to 5. This means that in each square meter that is kept watering for one hour, 3 to 5 liters of water are being added, until ALL the metals that have been solubilized during the rest period are retrieved. The reason for being able to use neutral water is that the solubilization of the species is very high and for this fact even seawater can be used.

(73) 2h. The method of the present invention can be repeated as many times as necessary to achieve the most optimal extractions, depending on the type of matrix and the desired financial economic objective. That is, after washing the SCRE material for the first time, the heap is allowed to drain. Once drained, the site is re-humidified with highly concentrated solutions of the same DAE agent used in the first stage and/or one that is more intense. The re-humidification of the battery should be carried out at a very low rate: 2 to 3 lt/m2×hour, thus ensuring that the re-humidifying solution does not leave the heap to ensure its permanence inside the pad. It is left to rest for 10 to 20 days so that the electron transports required for the new transformation of the remaining SCRE material are generated again and finally, it is washed again to proceed to extract the complementary part of the valuable metals.

(74) 2i. If the SCRE material is polymetallic, the wash solution will contain more than one chemical element due to its degree of electronic transformation. In that case, operations downstream of purification and precipitation must be adapted as a sample

(75) FIG. 3

(76) 3. Application of the method for SCRE materials of granulometry at micron level:

(77) Mixing: The DAE agent is added in a mixer of the type mentioned in section 2. The dose is between 2 to 15 kg per ton of SCRE.

(78) Rest: Resting is done on a suitably prepared floor, in a properly conditioned pad. This period is between 10 to 20 days

(79) Washing: This is done by in a conventional hydro cyclone or a stirred reactor, at a rate of 0.5 to 0.7 m3 of water per ton of SCRE material to be washed.

(80) Method of the Invention Applied to the Specific Extraction of Gold (Goldest)

(81) Gold can be found geologically in two ways:

(82) MINERAL TYPE I: Free gold particles in oxidized matrix.

(83) MINERAL TYPE II: Gold/silver particles encapsulated in sulphide grains that can be pyrite, arsenopyrite or other sulphide, which are contained in silicate matrix.

(84) In the case of free gold particles in oxidized matrices, heap leaching with cyanide solutions is the most standard and used process. The obtaining of metallic gold is achieved by applying the Merrill Crowe process. The method of the invention considers agglomerating with solid cyanide, in the stage prior to leaching, to drastically accelerate the solubilization of gold, in such a way to drastically decrease the process cycle and increase its recovery.

(85) In the case of gold particles encapsulated in sulphide grains that can be pyrite, arsenopyrite or other sulphide, contained in silicate matrix, the conventional cyanidation process is very limited, since cyanide cannot react with sulfide grains and even then, not dissolve the gold. There are three technologies to consider in this regard:

(86) Reduce the ore to the size of microns, using crushers, ball mills and SAG, then float the pyrite/arsenopyrite, and then melt the concentrate to obtain gold bars. Process of high investment and operating costs.

(87) Reduce the ore to the size of microns, using crushers, ball mills and SAG, then concentrate the pyrite/arsenopyrite by flotation, and then said concentrate is leached using reactors built of titanium at high pressure to finally obtain gold through the Merrill Crowe process. It is also a very expensive process in investment and operation. A variant is to bioleach the concentrate to destroy the pyrite, then wash and a second cyanide leaching is performed. All of it, in mechanically agitated tanks. This is a process known as BIOX. Even so, they remain high investment processes.

(88) Reduce the mineral to the size of inches, using crushers, it is bacterially heap leached so that the microorganisms destroy the pyritic matrix, then the heap pad is washed, and a conventional cyanidation process is initiated (equivalent to that applied to MINERAL TYPE I). It is a process that requires a lot of time, excess of fresh water and is also of low efficiency.

(89) For free gold particles in MINERAL TYPE I, or MINERAL TYPE II the method of the invention considers three alternatives that consist of agglomerating the mineral with solid cyanide and/or a DAE agent (specifically defined depending on whether the matrix is pyrite or arsenopyrite), in the pre-leaching stage, to dramatically accelerate and simultaneously three aspects of the process:

(90) a) Transformation of pyrite/arsenopyrite into a soluble species, to allow agents to access and attack gold

(91) b) Achieve a high solubilization of gold, in such a way to drastically reduce the process cycle and increase its recovery.

(92) c) In this case, washing with neutral water allows the extraction of gold and silver, eliminating the concept of leaching.

(93) MINERAL TYPE I (Free gold particles in oxidized matrix):

(94) In the method of the invention, applied to the mineral type I, NaCN or DAE agent can be used and consists of the following steps:

(95) a) ALTERNATIVE 1 (Use of NaCN)

(96) CRUSHING: The mineral is reduced to a size of 2 centimeters (if the oxidized mineral contains a lot of clay, the reduction in size must be made to 4 centimeters)

(97) MIX: Before entering the mixing drum:

(98) Solid lime is added directly from a No. 1 hopper to the conveyor belt. Lime comes in powder and is added between 0.5 and 5 k/ton, depending on the purity of lime to ensure a basic pH>11 when it starts to water.

(99) Immediately afterwards the NaCN is added directly to the same conveyor belt from a Hopper No 2.

(100) The dosage will be between 1-2 kg of NaCN per ton of ore. The NaCN must be granulated to a size between 2-3 millimeters.

(101) TRANSFORMATION: At the exit of the drum, the formed mixture is transported to the pad. The material thus formed should stand for 5 to 10 days.

(102) WASHING: After the transformation period, the battery is washed with neutral water or with refining solutions to extract the gold in a cyanide aqueous solution.

(103) b) ALTERNATIVE 2 (Using DAE agent)

(104) CRUSHING: The mineral is reduced to a size of 2 centimeters (if the oxidized mineral contains a lot of clay, the reduction in size must be made to 4 centimeters)

(105) MIX: Before entering the mixing drum.

(106) Solid lime is added directly from a #1 hopper to the conveyor belt. The lime comes in powder and is added between 0.5 and 5 k/ton, depending on the purity of lime to ensure a basic pH>11 when it starts to wash.

(107) Immediately afterwards the DAE agent is added directly to the same conveyor belt from a Hopper No 2.

(108) The dosage will be between 2-3 kg of the DAE agent per ton of ore. The DAE must be granulated to size between 2 to 3 millimeters.

(109) That way the conveyor belt contains mineral, lime and DAE agent.

(110) Upon entering the mixing drum, a perfect mixture of all solids is achieved. Inside the mixing drum raffinate solutions are added to reach the determined degree of wetting.

(111) TRANSFORMATION: At the exit of the mixing drum, the formed material is transported to the pad. The material should rest for a period between 10 and 15 days.

(112) WASHING: After the transformation period, the battery is washed with neutral water or with refining solutions to extract the gold in aqueous solution.

(113) MINERAL TYPE II (Gold particles encapsulated in sulphide grains that can be pyrite, arsenopyrite or other sulphide, contained in silicate matrix):

(114) The method of the invention applied to type II mineral can be applied in 3 alternatives and consists of the following steps:

(115) b) ALTERNATIVE 1 (Using DAE agent)

(116) It consists of using a single DAE agent for both effects: solubilize pyrite/arsenopyrite, releasing gold to simultaneously solubilize gold. Proceed as follows:

(117) CRUSHING: The mineral is reduced to a size of 2 centimeters (if the oxidized mineral contains a lot of clay, the reduction in size must be made to 4 centimeters)

(118) MIXER: Add DAE agent before entering the mixing drum.

(119) Solid lime is added directly from a #1 hopper to the conveyor belt. Lime comes in powder and is added between 0.5 and 5 k/ton, depending on the purity of lime to ensure a basic pH>11 when it starts to water.

(120) Immediately after the DAE agent is added, directly to the same conveyor belt from a Hopper No 2.

(121) The dosage of DAE should be between 5-10 kg per ton of ore. The DAE should be granulated to size between 2-3 millimeters.

(122) That way the conveyor belt contains mineral, lime and DAE agent. Upon entering the mixing drum, a perfect mixture of solid reagents is achieved. Inside the mixing drum water or raffinate solutions are added to reach the determined degree of humidification, 3 to 4%.

(123) TRANSFORMATION: At the exit of the mixing drum, the material is transported to the pad. This should rest between 20 and 30 days. In that period the reagent transforms pyrite into a porous mineral and solubilizes gold, both effects simultaneously.

(124) WASHING: After the transformation period, the battery is washed with neutral water or with acidic refining solutions (around pH=2) to dislodge the gold in aqueous solution.

(125) Brief Description of the FIG. 1

(126) This scheme shows 3 types of SCRE material processing

(127) Copper leaching Spent Ore

(128) Gold ores contained in arsenopyrites (8% arsenic content)

(129) Polymetallic Concentrate Smelter Slag