Leaching agent

Abstract

A leaching agent comprises ammonium salt, carboxylic acid and solvent, wherein the ammonium salt is used in an amount ranging between 10% to 90% by weight of leaching agent, wherein the carboxylic acid is used in an amount ranging between 10% to 90% by weight of leaching agent and wherein the solvent is used in an amount ranging between 10% to 40% by weight of leaching agent.

Description

[0001] LEACHING AGENT

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a leaching agent, method of manufacturing and application thereof, in particular the leaching agent is used to extract rare-earth element, wherein the leaching agent is non-toxic and biodegradable as well as exhibits high affinity towards rare-earth element which results in high leaching ability in in-situ leaching extraction method.

[0004] BACKGROUND OF THE INVENTION

[0005] Rare-earth element (REE) plays a crucial role in enabling many of the technologies we rely on daily such as but not limited smartphones, computers, medical devices and wind turbines. Further, rare-earth elements have been used in applications such as but not limited to catalysts for refining petroleum, superconducting magnets for nuclear fusion reactors and permanent magnets for wind turbines. One of the most common methods of extracting rare-earth element is but not limited to in-situ leaching extraction using a leaching agent such as but not limited to ammonium sulphate.

[0006] However, the use of ammonium sulphate in rare-earth element extraction is toxic to the environment as well as it is non-biodegradable. Hence, continuous usage of ammonium sulphate as leaching agent in extraction of rare-earth elements will affect the aquatic life and human health as well as pollute the environment. Further, ammonium sulphate does not exhibit desired affinity towards the rare-earth element and leaching ability in the in-situ leaching extraction of rare-earth element which results in poor extraction.

[0007] As such, there is a need to identify a leaching agent that can overcome the abovementioned shortcomings in which the leaching agent is non-toxic and biodegradable as well as exhibits high affinity towards rare-earth element which results in high leaching ability in in-situ leaching extraction method. SUMMARY OF THE INVENTION

[0008] The present invention relates to a leaching agent comprises ammonium salt, carboxylic acid and solvent, wherein the ammonium salt is used in an amount ranging between 10% to 90% by weight of leaching agent, wherein the carboxylic acid is used in an amount ranging between 10% to 90% by weight of leaching agent and wherein the solvent is used in an amount ranging between 10% to 40% by weight of leaching agent.

[0009] Additional aspects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments of the invention.

[0010] DETAILED DESCRIPTION OF THE INVENTION

[0011] Detailed description of preferred embodiments of the present invention is disclosed herein. It should be understood, however, that the embodiments are merely exemplary of the present invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and for teaching one skilled in the art of the invention. The numerical data or ranges used in the specification are not to be construed as limiting.

[0012] The present invention relates to a leaching agent, method of manufacturing and application thereof, in particular the leaching agent is used to extract rare-earth element, wherein the leaching agent is non-toxic and biodegradable as well as exhibits high affinity towards rare-earth element which results in high leaching ability in in-situ leaching extraction method.

[0013] For the purpose of the present invention and the accompanying claims, the term “rare-earth element” is referring to scandium (Sc), yttrium (Y) and lanthanide, wherein the lanthanide consist of fifteen metallic elements which is Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), and Lutetium (Lu). For the purpose of the present invention and the accompanying claims, the term “extraction” of rare-earth element is to be understood as a dissolving or leaching process by which the rare earth element is extracted from a solid starting product such as but not limited to ion-adsorption clay (IAC).

[0014] For the purpose of the present invention and the accompanying claims, the term “Deep Eutectic Solvent” or “DES” describes a solvent system formed by combining Lewis or Bronsted acids and bases in a eutectic mixture. DES are made up of large, asymmetrical ions with low lattice energies and low melting points.

[0015] For the purpose of the present invention and the accompanying claims, the term “in- situ leaching extraction” also known as solution mining or in-situ recovery is a process used to recover minerals through boreholes drilled into the ground.

[0016] For the purpose of the present invention and the accompanying claims, the term “ultrapure water” is referring to water that contains only H2O as well as balanced number of H+and OH’ ions, has a resistivity of 18.2 MO. cm, total organic carbon of less than 10 ppb, bacterial count of less than 10 CFU / ml and must not contain detectable endotoxins.

[0017] First aspect of the present invention discusses on a leaching agent, wherein the leaching agent is a deep eutectic solvent and wherein the leaching agent is used to extract rare-earth element in in-situ leaching extraction method. The leaching agent of the present invention has a viscosity of 161.30 and pH value ranging between 1 .89 to 2.15. The leaching agent of the present invention is in the form of liquid.

[0018] The leaching agent comprises ammonium salt, carboxylic acid and solvent (composition as described in Table 1 ).

[0019] The ammonium salt is used in an amount ranging between 10% to 90%, preferably ranging between 20% to 80%, most preferably 73% by weight of the leaching agent. The ammonium salt is selected from the group consisting of choline chloride, choline hydroxide, choline nitrate, choline acetate, choline fluoride and mixtures therefrom, preferably choline chloride.

[0020] The carboxylic acid is used in an amount ranging between 10% to 90%, preferably ranging between 17% to 80%, most preferably 17% by weight of the leaching agent. The carboxylic acid is selected from the group consisting of malic acid, citric acid, malonic acid, lactic acid, phenylacetic acid, oxalic acid, propionic acid, decanoic acid and mixtures therefrom, preferably malic acid.

[0021] The solvent is used in an amount ranging between 10% to 40%, preferably ranging between 10% to 20%, most preferably 10% by weight of the leaching agent. The solvent is selected from the group consisting of deionized water, distilled water, ultrapure water, tap water and mixtures therefrom, preferably ultrapure water.

[0022] Table 1 shows the chemical components and compositions thereof (as described above) used to prepare the leaching agent of the present invention.

[0023] Table 1 : Chemical components and compositions thereof used to prepare the leaching agent of the present invention

[0024] Second aspect of the present invention discusses on a method of preparing the leaching agent of the present invention comprises the steps of: i. adding ammonium salt into carboxylic acid (as described in Table 1 ) while continuously stirring to produce a mixture, wherein the mixture is continuously stirred at a speed ranging between 200 rpm to 300 rpm, preferably 300 rpm, at a temperature ranging between 75°C to 100°C, preferably 100°C for a duration ranging between 120 minutes to 170 minutes, preferably 170 minutes; ii. cooling the mixture obtained from step (i) until a temperature ranging between 75°C to 90°C, preferably 90°C is reached to produce a cooled mixture; and iii. adding solvent (as described in Table 1 ) into the cooled mixture obtained from step (ii) while stirring to produce the leaching agent of the present invention, wherein the leaching agent of the present invention is continuously stirred at a speed ranging between 200 rpm to 300 rpm, preferably 300 rpm at a temperature ranging between 50°C to 80°C, preferably 70°C for a duration ranging between 60 minutes to 90 minutes, preferably 80 minutes.

[0025] The leaching agent of the present invention can further undergo dilution process to obtain leaching agent with desired concentration.

[0026] Third aspect of the present invention discusses on a method of leaching rare-earth element using the leaching agent of the present invention as described above and its composition summarized in Table 1 adopting any commonly known in-situ leaching extraction process, wherein the method comprising the steps of: i. adding a solvent into the leaching agent of the present invention in a ratio of 94:6 while stirring to produce a diluted leaching agent, wherein the diluted leaching agent is continuously stirred at a speed ranging between 300 rpm to 500 rpm, preferably 400 rpm at a temperature ranging between 25°C to 28°C, preferably 27°C for a duration ranging between 10 minutes to 30 minutes, preferably 20 minutes; ii. adding the diluted leaching agent obtained from step (i) into a solid product in a ratio of 10:1 while stirring to produce a mixture, wherein the mixture is continuously stirred at a speed ranging between 300 rpm to 500 rpm, preferably at 300 rpm at a temperature ranging between 25°C to 28°C for a duration ranging between 12 to 24 hours, preferably 18 hours; iii. centrifuging the mixture obtained from step (ii) to obtain supernatant, wherein the centrifugation is carried out at a speed ranging between 300 rpm to 400 rpm, preferably 300 rpm at a temperature ranging between 25°C to 28°C for a duration ranging between 30 minutes to 90 minutes and wherein the supernatant is rare-earth elements.

[0027] The method as described in the third aspect of the present invention comprises a step (ii) of adding the leaching agent obtained from step (i) into a solid product such as but not limited to an ion-adsorption clay, metal ore and magnetic waste, wherein the solid product contains high amount of rare-earth elements. Also, the method as described in the third aspect of the present invention comprises a step (i) of adding a solvent into the leaching agent of the present invention, wherein the solvent can be but not limited to ultrapure water, distilled water, deionized water, tap water and mixtures therefrom.

[0028] TEST RESULTS

[0029] The leaching agent of the present invention is prepared using the composition as described in Table 1 adopting a method as described in the second aspect of the present invention. Rare-earth elements were extracted using the leaching agent of the present invention adopting the method as described in the third aspect of the present invention.

[0030] Test results for the leaching agent of the present invention

[0031] For the purpose of Table 2 and Table 3, Set 1 refers to ammonium sulphate as conventional leaching agent in a concentration of 0.5 mol / m3. Set 2 refers to the leaching agent of the present invention in a concentration of 0.5 mol / m3.

[0032] The leaching agent of the present invention and the conventional leaching agent are tested for leaching ability on clay samples possessing high rare-earth elements, wherein the clay samples are obtained from different places i.e., Bukit Gantang, Malaysia, Lumut, Malaysia, Lumut 01 , Malaysia and Gopeng, Malaysia.

[0033] Table 2 shows the outcome of the leaching ability test for the leaching agent of the present invention.

[0034] Table 2: Outcome of the leaching ability test for the leaching agent of the present invention

[0035] Based on Table 2, it is evident that leaching agent of the present invention (Set 2) has higher leaching ability as compared to conventional leaching agent (Set 1 ) for all the clay samples in-situ leaching extraction, indicating that the leaching agent of the present invention has higher affinity towards rare-earth element.

[0036] Toxicity test

[0037] The leaching agent of the present invention and the conventional leaching agent are tested for toxicity (i.e., fish acute toxicity test (OECD 203), acute immobilization test (OECD 202) and algae growth inhibition test (OECD 201 )) based on Organization for Economic Co-operation and Development (OECD) guidelines.

[0038] Table 3 shows the outcome of the toxicity test of the leaching agent of the present invention.

[0039] Table 3: Outcome of the toxicity test of the leaching agent of the present invention According to the Globally Harmonized System of Classification and Labelling of

[0040] Chemicals (GHS), a substance with an LC50 and / or EC50 of more than 100 mg / L is considered non-toxic to aquatic organisms. Based on Table 3, it is noticeable that the leaching agent of the present invention (Set 2) has LC50 of more than 100 mg / L for acute immobilization test as well as EC50 of more than 100 mg / L fish acute toxicity test and algae growth inhibition test, indicating that the leaching agent of the present invention is non-toxic to aquatic organisms. Further, it is noticeable that the leaching agent of the present invention (Set 2) has higher LC50 for acute immobilization test and EC50 for fish acute toxicity test as compared to the conventional leaching agent (Set 1 ), indicating that the leaching agent of the present invention is less toxic than the conventional leaching agent.

[0041] Biodegradability test

[0042] The leaching agent of the present invention is tested for biodegradability properties based on Organization for Economic Co-operation and Development (OECD) guidelines. According to the OECD 301 C guidelines, the oxygen consumption of a test substance has to be more the 60% to be considered as biodegradable.

[0043] Table 4 shows the outcome of the biodegradability test of the leaching agent of the present invention.

[0044] Table 4: Outcome of the biodegradability test of the leaching agent of the present invention

[0045] In reference to Table 1 , vessels 1 , 2 and 3 contain the leaching agent of the present invention and inoculum in basal medium and vessel 4 is the control vessel which contains leaching agent in deionized water. Based on Table 1 , it is noticeable that the biodegradation rate of the leaching agent of the present invention in vessels 1 , 2 and 3 have exceeded 60% at 28 days of incubation. Thus, it is evident that the leaching agent of the present invention is biodegradable.

[0046] As a whole, the leaching agent of the present invention is able to overcome the conventional shortcomings in which the leaching agent is non-toxic and biodegradable as well as exhibits high affinity towards rare-earth element which results in high leaching ability in in-situ leaching extraction method.

[0047] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", “including” and “having” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups therefrom.

[0048] The method steps, processes and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. The use of the expression “at least” or “at least one” suggests the use of one or more elements, as the use may be in one of the embodiments to achieve one or more of the desired objects or results.

Claims

CLAIMS1 . A leaching agent comprises ammonium salt, carboxylic acid and solvent, wherein the ammonium salt is used in an amount ranging between 10% to 90% by weight of leaching agent, wherein the carboxylic acid is used in an amount ranging between 10% to 90% by weight of leaching agent and wherein the solvent is used in an amount ranging between 10% to 40% by weight of leaching agent.

2. The leaching agent as claimed in claim 1 , wherein the ammonium salt is used in an amount ranging between 20% to 80% by weight of the leaching agent.

3. The leaching agent as claimed in claim 1 , wherein the ammonium salt is used in an amount of 73% by weight of the leaching agent.

4. The leaching agent as claimed in claim 1 , wherein the carboxylic acid is used in an amount ranging between 17% to 80% by weight of the leaching agent.

5. The leaching agent as claimed in claim 1 , wherein the carboxylic acid is used in an amount of 17% by weight of the leaching agent.

6. The leaching agent as claimed in claim 1 , wherein the solvent is used in an amount ranging between 10% to 20% by weight of the leaching agent.

7. The leaching agent as claimed in claim 1 , wherein the solvent is used in an amount of 10% by weight of the leaching agent.

8. The leaching agent as claimed in claim 1 , wherein the ammonium salt is selected from the group consisting of choline chloride, choline hydroxide, choline nitrate, choline acetate, choline fluoride and mixtures therefrom.

9. The leaching agent as claimed in claim 1 , wherein the carboxylic acid is selected from the group consisting of malic acid, citric acid, malonic acid, lactic acid, phenylacetic acid, oxalic acid, propionic acid, decanoic acid and mixtures therefrom.

10. The leaching agent as claimed in claim 1 , wherein the solvent is selected from the group consisting of deionized water, distilled water, ultrapure water, tap water and mixtures therefrom.1 1 . A method of preparing a leaching agent, wherein the method comprises the steps of: i. adding ammonium salt into carboxylic acid while stirring to produce a mixture, wherein the mixture is stirred at a speed ranging between 200 rpm to 300 rpm at a temperature ranging between 75°C to 100°C for a duration ranging between 120 minutes to 170 minutes; ii. cooling the mixture obtained from step (i) until a temperature ranging between 75°C to 90°C is reached to produce a cooled mixture; and iii. adding solvent into the cooled mixture obtained from step (ii) while stirring to produce a leaching agent, wherein the leaching is stirred at a speed ranging between 200 rpm to 300 rpm at a temperature ranging between 50°C to 80°C for a duration ranging between 60 minutes to 90 minutes.

12. The method as claimed in claim 1 1 , wherein the ammonium salt is used in an amount ranging between 10% to 90% by weight of the leaching agent.

13. The method as claimed in claim 11 , wherein the carboxylic acid is used in an amount ranging between 10% to 90% by weight of the leaching agent.

14. The method as claimed in claim 1 1 , wherein the solvent is used in an amount ranging between 10% to 40% by weight of the leaching agent.

15. The method as claimed in claim 1 1 , wherein the ammonium salt is selected from the group consisting of choline chloride, choline hydroxide, choline nitrate, choline acetate, choline fluoride and mixtures therefrom.

16. The method as claimed in claim 1 1 , wherein the carboxylic acid is selected from the group consisting of malic acid, citric acid, malonic acid, lactic acid,phenylacetic acid, oxalic acid, propionic acid, decanoic acid and mixtures therefrom.

17. The method as claimed in claim 11 , wherein the solvent is selected from the group consisting of deionized water, distilled water, ultrapure water, tap water and mixtures therefrom.

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