A method of recycling nickel-rich industrial inorganic wastes to high pure nickel metal sheet

Abstract

The present invention relates to a method for recovery of metallic elements contained in industrial inorganic wastes selected from but not limited to Nickel paste. In particular, the present invention is related to a method of recycling nickel-containing low-value inorganic materials to high-value Nickel metal sheet. Further, the present method ensures a selective precipitation of Nickel in its purest form, achieving a yield of 99.9% and is free from heavy metal contaminants such as chromium, all while minimizing the consumption of chemicals.

Description

A METHOD OF RECYCLING NICKEL-RICH INDUSTRIAL INORGANIC WASTES TO HIGH PURE NICKEL METAL SHEETFIELD OF THE INVENTION

[0001] The present invention relates to a method for recovery of metallic elements contained in industrial inorganic wastes. In particular, the present invention is related to a method of recycling nickel-containing low-value inorganic materials to high-value nickel metal sheets.BACKGROUND OF THE INVENTION

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Commonly nickel leaching is done using hydrochloric acid and sulphuric acid. Present methodologies for Ni extraction is rooted need for efficient and cost-effective methods to recover valuable metals from industrial waste materials. Nickel, commonly used in batteries, electroplating, and other industrial applications, is often present in significant quantities in spent materials, like nickel paste. Traditional methods of extracting nickel from such waste involve complex processes that can be inefficient, environmentally harmful, and expensive due to the use of costly chemicals and energy-intensive techniques.

[0004] The increasing demand for nickel in industries like electric vehicle batteries has further highlighted the importance of developing more sustainable recovery methods. As industries seek to minimize waste and reduce the environmental footprint of metal extraction, a novel approach is necessary.

[0005] Extracting nickel from secondary sources like nickel paste reduces the need for mining activities, which are often associated with significant environmental degradation, including habitat destruction, soil erosion, and water pollution.

[0006] The energy consumption and carbon emissions associated with recycling nickel from waste materials are typically lower than those involved in mining and refining nickel ore. This contributes to a reduction in the overall carbon footprint of nickel production.

[0007] Technically, nickel paste often contain higher concentrations of nickel compared to natural ores. This means that less material needs to be processed to extract the same amount of nickel, increasing the efficiency of the extraction process.

[0008] Recycling nickel from industrial byproducts and alloys promotes the efficient use of existing resources, contributing to the circular economy and ensuring a more sustainable approach to resource management.

[0009] Finally individual metals are recovered using methods such as electro winning or chemical precipitation to recover pure nickel from the leachate. Similar procedures also followed for recovery of nickel, whereas secondary source of nickel is treated with an acidic solution, such as sulfuric acid (H2SO4) or hydrochloric acid (HC1), to dissolve nickel and other metals into the leachate as reported in patents and in journals.

[0010] Ore extraction requires significant initial investment in mining infrastructure, machinery, and labor. The operational costs of ore extraction include ongoing expenses for mining operations, transportation, and extensive refining processes. Ore extraction involves substantial land disturbance, deforestation, and potential contamination of water bodies due to the release of mining byproducts. Recycling nickel from waste materials avoids these environmental issues.

[0011] In conclusion, extracting nickel from nickel paste offers significant economic, environmental, and technical advantages over traditional ore extraction. These benefits include cost savings, reduced environmental impact, higher efficiency, and better alignment with sustainable resource management practices.

[0012] The proposed methodology in this invention addresses these challenges by offering a selective, efficient, and cost-effective process for extracting nickel from spent nickel paste.OBJECTS OF THE INVENTION

[0013] Objects of the present disclosure is to provide an economical method of improving the extraction of Nickel.

[0014] An object of the present disclosure is to provide an economical method for extracting Nickel from Nickel paste.

[0015] Another object of the present disclosure is to an economical method for extracting high pure Nickel metal sheet from Nickel paste.

[0016] Yet another object of the present disclosure is to provide an economical method for extracting high Nickel from Nickel paste using five- stage approach for separation of Nickel from mixed metals.SUMMARY OF THE INVENTION

[0017] The foregoing and other objects are attained by the present disclosure, which in an aspect provides an improved aluminium electrode for EDM and a method of manufacturing the same. Said improved aluminium electrode has enhanced both electrical and thermal conductivity.

[0018] Aspects of the present invention relate to a method for recovery of metallic elements contained in industrial inorganic wastes (otherwise referred to as secondary sources of metals). In particular, the present invention is related to a method of recycling nickel paste containing low-value inorganic materials to high-value nickel metal sheet.

[0019] In an aspect, a first step of the present invention is to convert metals present in the nickel paste into their metallic forms and further leaching of nickel in metallic form is easier. The method comprises the step of treating the nickel paste with a reductant selected from formic acid (HCOOH) or sodium borohydride (NaBH4) to obtain mixed metal alloys in their respective metallic forms.

[0020] In an aspect, a second step of the present invention is to convert metallic forms of nickel from the first step into their respective sulphate forms, which comprises the step of treating the metallic forms of nickel from the first step with sulphuric acid (H2SO4), followed by the addition of hydrogen peroxide and stirring the same for 3-7 hrs to obtain a leachate containing nickel sulphate (NiSO4) and an undissolved cake.

[0021] In an aspect, a third step of the present invention is treating the leachate containing nickel sulphate (Ni SO4) from the second step with sodium hydroxide (NaOH) to remove metal impurities.

[0022] In an aspect, a fourth step of the present invention is solvent extraction with 2- ethylhexyl phosphonic acid mono-2 -ethylhexyl ester to remove remaining impurities, while maintaining the pH at acidic pH to obtain 99.9 % pure NiSO4.

[0023] In an aspect, a fifth step of the present invention is to separate nickel metal sheet from the leachate having nickel sulphate from fourth step by electro winning. In some embodiments, the resulting Nickel metal sheet has a purity of >99.9%.

[0024] In an aspect, the electrowinning is effected using a Lead-Tin (Pb-Sn) anode and a stainless steel 316 (SS-316) cathode plate as electrodes in the electrowinning process.

[0025] In an aspect, the electrowinning is effected using a current density of 180 to 220 A / m2, with a cell voltage between 2.5 to 3.5 V.

[0026] In an aspect, the electrowinning process temperature is controlled within a range of 55 to 60°C.

[0027] In an aspect, the electrowinning process pH is maintained within a range of 3 to 5.

[0028] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.BRIEF DESCRIPTION OF THE FIGURES FIG. 1 schematically shows the extraction of Nickel from nickel paste. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following is a detailed description of embodiments of the present disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0030] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0031] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0032] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0033] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desiredproperties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[0034] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.

[0035] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0036] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0037] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0038] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.

[0039] Embodiments of the present invention relates to a method for recovery of metallic elements contained in industrial inorganic wastes (otherwise referred to as secondary sourcesof metals). In particular, the present invention is related to a method of recycling nickel- containing low-value inorganic materials to high-value nickel metal sheet.

[0040] In an embodiment the present invention provides a significant advancement, offering a reduction in the costs associated with the extraction of the target metal. Further, it ensures the selective precipitation of nickel in its purest form, achieving a yield of >99.9% free from heavy metal contaminants such as chromium, all while minimizing the consumption of chemicals. Furthermore, instead of depending on one or two raw materials, more and cheaper raw materials have been added.

[0041] In an embodiment of the present invention, the industrial inorganic wastes are selected from but not limited to nickel paste, or any inorganic waste containing nickel.

[0042] In an embodiment, a first step of the present invention is to convert metals present in the nickel paste into their metallic forms and further leaching of nickel in metallic form is easier. The method comprises the step of treating the nickel paste with a reductant selected from formic acid (HCOOH) or sodium borohydride (NaBH4) to obtain mixed metal alloys in their respective metallic forms.

[0043] In some embodiments of the present invention, in presence of formic acid nickel can be selectively leached with 97 to 99 %. Overall yield and purity of Nickel sulphate is greater than 97 % achieved from spent Ni material, thus obtained high purity battery grade nickel sulphate.

[0044] In one embodiment, the present invention provides a first step of treating the nickel paste with formic acid and effecting the reaction to obtain a slurry.

[0045] In an embodiment of the present invention, the formic acid (HCOOH) treatment is effected for 100 min to 150 min. For example, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150 min.

[0046] In an embodiment of the present invention, the formic acid (HCOOH) treatment is effected at 70-90 °C. For example, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90 °C.

[0047] In an embodiment of the present invention, the formic acid (HCOOH) used in the treatment has an amount of 2-15%. For example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, or 15%.

[0048] In an embodiment, a second step of the present invention is to convert metallic forms of nickel from the first step into their respective sulphate forms, which comprises the step of treating the metallic forms of nickel from the first step with sulphuric acid (H2SO4),followed by the addition of hydrogen peroxide (H?0?) and stirring the same for 3-7 hrs to obtain a leachate containing nickel and an undissolved cake.

[0049] In an embodiment of the present invention, the sulphuric acid (H2SO4) used in the treatment has concentration of 1-10M. For example, IM, 1.5M, 2M, 2.5M, 3M, 3.5M, 4M, 4.5M, 5M, 5.5M, 6M, 6.5M, 7M, 7.5M, 8M, 8.5M, 9M, 9.5M, or 10M.

[0050] In an embodiment of the present invention, the hydrogen peroxide (H2O2) used in the treatment has an amount of 3 to 5 % v / v, based on the slurry volume For example, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5%.

[0051] In an embodiment of the present invention, the stirring is effected in at 250- 300 rpm.

[0052] In an embodiment, a third step of the present invention is treating the leachate containing nickel sulphate (NiSO4) from the second step with sodium hydroxide (NaOH) to remove metal impurities.

[0053] In some embodiments, the acidic pH is selected from 0.1 to 6.9. For example, 0.1, 0.58, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, or 6.9. Preferably, the pH is maintained at 3-6.

[0054] In an embodiment, NaOH is added to bring the pH of the solution to acidic pH 4.0, which is then used for subjected for solvent extraction. In some embodiments, the concentration of NaOH is 1 M to 3 M.

[0055] In an aspect, a fourth step of the present invention is solvent extraction with2- ethylhexyl phosphonic acid mono-2 -ethylhexyl ester to remove remaining impurities, while maintaining the pH at acidic pH to obtain 99.9 % pure NiSO4.

[0056] In an embodiment, a fifth step of the present invention is to separate nickel metal sheet from the leachate having nickel sulphate from fourth step by electrowinning. In some embodiments, the resulting Nickel metal sheet has a purity of >99.9%

[0057] In a preferred embodiment, the present invention provides method for separating Nickel metal sheet from spent nickel paste (FIG. 1) comprises the steps of: a) providing spent nickel paste; b) treating the nickel paste with a reductant for 100-150 min at 70 to 90 °C to obtain a slurry; c) treating the slurry from step b) with sulfuric acid to obtain a solution, followed by addition of hydrogen peroxide to the solution at room temperature and stirring the solution to obtain a leachate containing nickel sulphate and an undissolved cake; d) purifying the nickel sulphate present in the leachate of step c) using NaOH at pH 4;e) effecting solvent extraction of nickel sulphate from step d) using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester as solvent; and f) effecting the leachate containing nickel sulphate from step d) for electrowinning process to obtain the Nickel metal sheet.

[0058] In an embodiment of the present invention, the electrowinning is effected using a Lead-Tin (Pb-Sn) anode and a stainless steel 316 (SS-316) cathode plate are as electrodes in the electrowinning process.

[0059] In an embodiment of the present invention, the electrowinning is effected using a current density of 180-220 A / m2, with a cell voltage between 2.5 to 3.5 V.

[0060] In an embodiment of the present invention, the electrowinning process temperature is controlled within a range of 55 to 60°C.

[0061] In an embodiment of the present invention, the electrowinning process pH is maintained within a range of 2 to 4.

[0062] In an embodiment of the present invention, the nickel metal sheet may be used in synthesis of Battery grade chemicals and some industrial alloys.

[0063] Although the present invention has been described hereinabove by way of specific embodiments thereof, it can be modified without departing from the teachings of the subject invention, as defined in the appended claims.EXAMPLES

[0064] The present disclosure is further explained in the form of following examples. However, it is to be understood that the foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

[0065] Example 1: Experimental description for recovery of Nickel

[0066] 100 g of Ni-paste was taken in a 2 L beaker, to this required amount of formic acid is added. Kept the solution under stirring for 2-4 h at 70-90 °C. To the obtained paste, required amount of 98 % sulphuric acid (H2SO4) in 500 mL H2O is added at RT. Followed by addition of hydrogen peroxideto the solution. The obtained solution is kept for 4-7 h stirring. Hie solution is filtered, and remaining cake was washed with the hot demineralized water. Thus, obtaining nickel-containing leachate solution. Tire leaching experiment results for different reductants are shown in Table 1.

[0067] The elemental analysis using 1CP technique is carried out for elements present in raw material and presented in Table 2. It is observed that Ni is leached into solution while negligible amounts of impurities such as Al, Ca, Mg, Fe and Zn are present in the leachate solution.5

[0068] The elementary reaction steps undergoing during the leaching process are shown below in schematic diagram. Thus, the stoichiometries amounts of various chemicals required can be calculated .

[0069] Schematic reaction steps: Elementary steps with intermediate species marked by * sign.NiO + HCOOH Ni + CO2+ H2ONi + H2SO4NiSO4+ H2NiSO4+ H2O2+ H2NiSO4+ H2O ** H2SO4+ H2O2H2SO3- + [O]* NiO + H2SO3- + [O] NiSO4+ H2* NiSO4+ H2+ [O] NiSO4+ H2O 0

[0070] For comparison, the reduction reactions were carried out with other reductant such as sodium borohydride. The leaching results with sodium borohydride are shown in Table 3. 45.93 % of Ni leaching was achieved using sodium borohydride. It can be understood that formic acid is significantly better reducing agent compared to the sodium borohydride. It is also due to higher solubility of organic compounds present in spent nickel raw material in 5 formic acid organic phase, thus highest metal reactivity is observed.Table 1: Experimental conditions and chemicals used for Ni-paste leaching:Table 2: The experimental results leaching of elements using formic acid.Table 3: The experimental results leaching of elements using NaBH4, sulphuric acid from 100 g Ni paste:5

[0071] Solvent extraction and electrowinning process

[0072] Once the leachate solution is having Nickel sulphate, it is further purified by precipitation using NaOII at pH=3-6. The obtained solution is further purified using In-house developed solvent 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester. The obtained 10 Nickel sulphate solution which is having purity above 99.9 % is taken for electrowinning to get nickel metal sheet above that 99.9 % purity. The details are given in Table 4.Table 4: Purification of leachate solution by precipitation and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, followed by electrowinningElectrowinning: For the electrowinning process under optimal conditions, a Nickel 5 concentration in the sulfate solution was maintained between 40-60 g / L. Lead-Tin (Pb-Sn) anode and a stainless steel 316 (SS-316) cathode plate were used for the process. The current density was maintained at 180-220 A / m2, with a cell voltage between 2.5 to 3.5 V, and the cell temperature was controlled within the range of 55 to 60°C. The pH of the pregnant solution fed into the electrowinning process was maintained between 2 to 4.10ADVANTAGES OF THE PRESENT DISCLOSURE

[0073] The present invention enables a highly efficient recovery of nickel from industrial byproducts, achieving approximately 99.9% nickel extraction, allowing for the conversion of low -value materials into high-purity Nickel sulfate, essential for battery grade chemicals 15 production.

[0074] In the present invention, by precisely adjusting reductant concentration, it selectively reduces the nickel, and further facilitate leaching of nickel in the form of nickel sulfate. Leached nickel sulphate is further purified by precipitation and solvent extraction. Impurities such as Al, Fe and Mg were selectively precipitates as hydroxide ensuring that 20 nickel remains in solution, thereby enhancing the purity and concentration of nickel sulfate.

[0075] The use of 2-ethylhexyl phosphonic acid mono-2 -ethylhexyl ester as a solvent to extract nickel and leaching with H2SO4, further produced high pure nickel sulphate purityabove 99.9 %. The obtained solution is sent for electrowinning process to produce metallic nickel sheet having purity greater than 99.9 %.

[0076] The process of the present invention reduces reliance on traditional nickel mining, which is often associated with environmental degradation and socio-economic challenges. By recycling nickel from waste materials, the disclosure contributes to a more sustainable and eco-friendly approach to cobalt production.

[0077] The use of a five stage process i.e. reduction, leaching, precipitation, solvent extraction, and electrowinning method allows for efficient separation and recovery of valuable nickel, while minimizing the use of chemicals and energy, making the process more economically viable compared to conventional methods.

[0078] The disclosure can be applied to various types of industrial waste materials containing nickel, making it a versatile solution for recycling nickel from different sources. Such flexibility increases its potential for widespread industrial use.

[0079] The process disclosed in the present disclosure is scalable, cost-effective, and suitable for large-scale production.

Claims

We Claim:

1. A method for separating Nickel metal sheet from spent nickel paste comprises the steps of: a) providing spent nickel paste; b) treating the nickel paste with a reductant for 100-150 min at 70 to 90 °C to obtain a slurry; c) treating the slurry from step b) with sulfuric acid to obtain a solution, followed by addition of hydrogen peroxide to the solution at room temperature and stirring the solution for 6 h to obtain a leachate containing nickel sulphate and an undissolved cake; d) purifying the nickel sulphate present in the leachate of step c) using NaOH at pH 3- 6; e) effecting solvent extraction of nickel sulphate from step d) using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester as solvent; and f) effecting the leachate containing nickel sulphate from step d) for electrowinning process to obtain the Nickel metal sheet.

2. The method as claimed in claim 1, wherein the reductant is selected from formic acid (HCOOH) or sodium borohydride (NaBH4).

3. The method as claimed in claim 1 or 2, wherein the reductant is used an amount of 3- C JO / / o.

4. The method as claimed in claim 1, wherein the sulphuric acid is used in a concentration of 2-5 M.

5. The method as claimed in claim 1, wherein the hydrogen peroxide used in the treatment has an amount of 3 to 5% v / v based on the slurry volume.

6. The method as claimed in claim 1, wherein the stirring is effected at an RPM of 250- 300 rpm.

7. The method as claimed in claim 1, wherein the undissolved material in step c) is further subjected to steps b) to f) to obtain the nickel metal sheet.

8. The method as claimed in claim 1, wherein a Lead-Tin (Pb-Sn) anode and a stainless steel 316 (SS-316) cathode plate are used as electrodes in the electrowinning process.

9. The method as claimed in claim 7, wherein the electrowinning is effected using a current density of 180-220 A / m2, with a cell voltage between 2.5 to 3.5 V.

10. The method as claimed in claim 8, wherein the electrowinning process temperature is controlled within a range of 55 to 60°C.

11. The method as claimed in claim 8, wherein the electrowinning process pH is maintained within a range of 2 to 4.

12. The method as claimed in claim 1, wherein the Nickel metal sheet has a purity of>99.9%.

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