A method for selective separation of precious metals from e-waste and spent nickel catalysts

Abstract

The present invention discloses methods for the selective recovery of precious metals from electronic waste (e-waste). An environmentally friendly oxidizing agent is developed for the selective oxidation and separation of copper from printed circuit board (PCB) metal powder. Additionally, selective recovery of gold and silver is achieved using fluxing agents. Following selective leaching, copper is recovered from the leach solution through cementation with more active metal species. Impurities, such as aluminum (Al) and iron (Fe), are subsequently removed via pH precipitation. The remaining leached elements are further separated using crystallization or additional pH precipitation processes.

Description

A METHOD FOR SELECTIVE SEPARATION OF PRECIOUS METALS FROM E- WASTE AND SPENT NICKEL CATALYSTSFIELD OF THE INVENTION

[0001] The present invention relates to the field of electronic waste (E-waste) processing, and more specifically, to methods for recovering precious metals from E-waste.BACKGROUND OF THE INVENTION

[0002] Electronic waste (E-waste) has emerged as a significant environmental challenge due to its rapid generation and complex composition. At the same time, E-waste presents a lucrative opportunity for recovering valuable metals, including precious metals such as gold, silver, and palladium. These metals are essential for various industries and have high economic value. The concentration of precious metals varies depending on the type of electronic device. Printed circuit boards (PCBs) are the primary source of these metals, containing gold, silver, palladium, and other valuable elements. Understanding the composition of E-waste is crucial for developing efficient recovery processes.

[0003] A large portion of premium E-waste, such as mobile and laptop motherboards, processor chips, RAMs, and connector pins, contains approximately 30-40% metallic content and 60-70% plastic and ceramic content. The plastics and ceramics in E-waste are typically separated through mechanical operations, leaving behind a concentrate of metallic powder. This metallic powder is a mixture of several metals, including copper (80%), lead, tin, aluminum, gold (100-1000 ppm), silver (20000 ppm), palladium (20-200 ppm), and others. The precious metals (Au, Ag, Pt, Pd, etc.) present in the PCB are highly valuable, making up 3-5% of the material but contributing significantly to the overall economic value. Therefore, efficiently recovering these precious metals without losses is critical for the profitability of PCB recycling companies.

[0004] Selective separation of plastics, ceramics, and metallic components is essential for effectively recovering precious metals from PCB waste. Various methods are employed, including mechanical separation followed by hydrometallurgical and pyrometallurgical routes, to recover these precious metals selectively. The mechanical separation of PCBs typicallyinvolves crushing, grinding, cyclone separation of plastics, and vibration screens to separate metallic from non-metallic (plastic and ceramic) components. Once the plastics and non-metallic materials are separated, the metallic powder, which contains high levels of copper and precious metals, is processed through either pyro- or hydrometallurgical methods.

[0005] Pyrometallurgy utilizes high temperatures to extract metals, allowing for rapid processing and recovery of a wide range of metals. However, this method comes with higher energy consumption, potential metal losses, and air pollution concerns.

[0006] Hydrometallurgy, on the other hand, uses aqueous solutions to dissolve and selectively extract metals at lower temperatures, offering lower energy consumption and a reduced environmental impact compared to pyrometallurgy. However, the Hydrometallurgical process has its own challenges. Hydrometallurgical processes often involve the use of nitric acid (HNO3) as a leaching agent, which serves as both an oxidizing agent and a solvent. The generation of nitrogen oxides (NOx), potent greenhouse gases and air pollutants, remains a significant concern in processes involving nitric acid.

[0007] Efforts to mitigate NOx emissions include optimizing processes, implementing efficient gas scrubbing systems, and exploring alternative leaching agents. Research has focused on using environmentally friendly oxidizing agents, such as hydrogen peroxide (H2O2), ferric iron, and ozone, in conjunction with leaching agents like sulfuric acid or hydrochloric acid, to optimize the recovery of copper and precious metals from E-waste.

[0008] The use of transition metals for cementing copper from aqueous solutions has been employed for decades. Raney nickel is a common catalyst used in various industries, including chemical and pharmaceutical sectors. After a period of use, these nickel catalysts become spent but remain largely unchanged in their basic nature and quantity. Reusing spent catalysts contributes to the concept of a circular economy, although disposal remains a challenge. Similarly, cobalt- and iron-containing spent materials can also be used for cementing copper. US3902896A discloses use of base metals, such as aluminum, zinc, cobalt, iron, and nickel, which are higher in the electromotive series than copper, to cement copper from solution.

[0009] The growing concern surrounding electronic waste in many countries, due to the lack of environmentally friendly and cost-effective processing technologies, has led to the development of the present invention. The invention addresses these concerns with a novel process for recovering copper, gold, silver, and other precious metals from E-waste in anenvironmentally friendly and cost-effective manner. This process specifically relates to the oxidative leaching of copper from E-waste and the selective separation of copper from the leach solution using purified spent catalyst metallic values. The metallic values are then precipitated as hydroxides, and precious metals such as gold, silver, and etc. are selectively extracted through pyrometallurgical methods.

[0010] In prior art, oxidizing agents like HNO3 or H2O2 have been used to recover copper from PCB waste via hydrometallurgy. However, these methods often result in the generation of significant amounts of NOx or require high investment costs to handle H2O2. The present invention addresses these issues by avoiding the hydrometallurgical process, thereby reducing pollution associated with NOx emissions.

[0011] In other prior art, the PCB metal powder is heated to temperatures above 1300°C in the presence of fluxing agents to selectively recover metallic content and separate gangue or oxides. The resulting metallic slab is then processed using electrorefining to obtain precious metal sludge and copper plating on a cathode.

[0012] Another prior art method involves the selective peeling of gold from PCBs using a leaching agent that contains a sulfoacid solute (10.1-47.0%), an oxidizing agent (3.5-11.2%), and water. This method leaches copper, nickel, and other metals, leaving behind gold foil. The gold foils are then melted to form gold ingots, and the leached copper is recycled through electro-deposition, while nickel is extracted from the recycled solution.

[0013] The present invention addresses the aforementioned pollution and environmental issues, particularly those associated with NOx generation, by eliminating the need for hydrometallurgical processes. Through this novel method, disposal problems related to PCBs, batteries, and other transition metals are effectively mitigated. Valuable metals, including copper, gold, silver, nickel, and cobalt, are efficiently extracted from solid waste using a low-energy, low-pollution process.SUMMARY OF INVENTION

[0014] The present invention provides a novel method for recovering copper, gold, silver, and other precious metals from the electronic waste (e-waste). The method specifically includes an oxidative leaching of copper from e-waste and the selective separation of copper from the leach solution using the metallic values of purified spent catalyst. Subsequently, the metallic values in the leach solution are precipitated as hydroxides.

[0015] The primary objective of the present invention is to develop process steps for the recovery of copper and precious metals (such as gold, silver, palladium, etc.) from e-waste using an environmentally friendly oxidizing agent. In this study, the term "oxidizing agent" refers to any source of transition metal oxides with an oxidation state greater than three.

[0016] Another objective of the invention is to pre-treat copper-containing PCB waste by dissolving through acidic or alkaline treatment, thereby removing unwanted metals such as zinc (Zn), iron (Fe), and aluminum (Al) to prevent contamination during the copper leaching process.

[0017] Another objective of the present invention is to develop a processing step for recovering nickel from spent pharmaceutical waste or Raney nickel, and converting into a valuable material without the need for excessive acid addition. Additionally, the invention aims to convert the dissolved nickel into useful battery cathode materials.

[0018] Aspects of the present invention provides a method for the selective recovery of precious metals from waste PCBs. An environmentally friendly oxidizing agent has been developed for the selective oxidation and separation of copper from PCB metal powder. Furthermore, selective recovery of gold and silver is achieved using fluxing agents. After selective leaching, copper is cemented from the leach solution using more active metal species. Subsequently, impurities such as aluminum (Al) and iron (Fe) are separated using pH precipitation. The remaining leached elements are selectively separated using crystallization or further pH precipitation.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above-mentioned and other features and advantages of this present disclosure, and the manner of attaining them, will become more apparent and the present disclosure will be better understood by reference to the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein:

[0020] Fig.l is a flow chart of a method for overall metal recovery from electronic waste (e-waste), according to embodiments of the present invention;

[0021] Fig.2a is a flow chart for preparation of oxidation agent from the electronic waste (e-waste), according to an embodiment of the present invention;

[0022] Fig.2b is another flow chart for preparation of oxidation agent from the electronic waste (e-waste), according to an embodiment of the present invention;

[0023] Fig.3 is a flow chart for pre-treatment of spent catalyst;

[0024] Fig.4 is a flow chart for obtaining nickel and other materials present in the leach liquor;

[0025] Fig.5 is a flow chart for purifying or selectively recovering metals from the leach liquor; and

[0026] Fig.6 is a flow chart for iron precipitation present in the leach liquor.DETAILED DESCRIPTION

[0027] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.

[0028] In this document, the terms "comprises," "comprising," or “including” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a system, method, article, device or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such system, method, article, device, or apparatus. An element proceeded by "comprises ...a" does not, without more constraints, preclude the existence of additional identical elements in the process, product, method, article, device or apparatus that comprises the element.

[0029] Any embodiment described herein is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this detailed description are illustrative, and provided to enable persons skilled in the art to make or use the disclosure and not to limit the scope of the disclosure, which is defined by the claims.

[0030] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[0031] In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention can be practiced without these specific details. In other instances, structures and systems are shown in the flow chart form only in order to avoid obscuring the present invention.

[0032] The present invention provides a method for selective recovery of precious metals from electronic waste (e-waste) such as Printed circuit boards (PCBs), motherboards, processorchips, RAMs or likes. The method includes a selective oxidation with an oxidizing agent and separation of copper (Cu) from the PCB metal powder. Additionally, the selective recovery of gold and silver is achieved using fluxing agents. Following selective leaching, copper is recovered from the leach solution by cementation with more active metal species. Subsequently, impurities such as aluminum (Al) and iron (Fe) are removed through pH precipitation. The remaining leached elements are selectively separated using either crystallization or pH precipitation.

[0033] A novel feature of the present invention is an environmentally friendly oxidizing agent is developed from electronic waste (e-waste) for the selective oxidation and separation of copper from PCB metal powder.

[0034] A novel feature of the present invention is the enrichment of precious metal content in the PCB after the selective removal of plastics, ceramics, and copper from the PCB boards.

[0035] Another novel feature of the present invention is the selective recovery of copper (Cu) using environmentally friendly oxidizing agent.

[0036] Yet another novel feature of the present invention is the utilization of industrial wastes, such as Mn dust, battery waste, and pharmaceutical waste, in a single process flow with minimal chemical usage.

[0037] Embodiments of the present invention are described herein with reference to the figures. In an embodiment of the present invention, as shown in Fig. l is a method / process for overall metal recovery. The method for the recovery of copper, silver, gold, and other metals from the electronic waste, as well as the recovery of nickel from spent raney nickel, is carried out according to the following sequence of steps:

[0038] Step 1 : First, plastics and ceramic compounds present in the PCB boards are separated from the metallic components using any combination of the following physical separation steps: crushing, milling, density media separation, flotation, jigging operations, and cyclone separation. Approximately 60% of the material is sorted as plastics and ceramics from the PCB boards, while 40% consists of metallic content. A magnetic separation step is then employed to selectively separate ferrous materials, such as iron, from the metallic content. The metal powder obtained after the magnetic separation step primarily consists of copper (>80%), lead,tin, silver, gold, and other precious metals. These steps result in an enrichment of gold, silver, and other precious metals by approximately 2.5 times.

[0039] Step 2 : A hydrometallurgical leaching step is employed to remove highly reactive impurities, such as residual iron, aluminum, zinc, and others, to prevent contamination in the subsequent leaching, purification, or precipitation processes. The leaching mediums used in this step can include minerals, organic acids, alkalies, sulfuric acid, or hydrochloric acid. The operational parameters, such as a temperature range of 0 to 100 °C and a time range of 5 minutes to 12 hours, are applicable.

[0040] Step 3 : To further enrich the precious metal content, the remaining metallic powder obtained after Step 1 is subjected to an oxidative leaching step to selectively remove the major element such as copper (Cu). Oxidizing agents such as hydrogen peroxide, sodium hypochlorite, transition metal oxides, and aqueous solutions containing trivalent or higher oxidation states, such as CO2O3, N12O3, Mn02, Fe2O3, and Fe2(SO4)3, as well as salts or compounds of Mz+(where M is a transition metal and Z is an integer with a value of 3 or higher) are used in the presence of mineral or organic acids. In this step, sulfuric acid is used as the leaching medium, with a temperature range of 0 to 100 °C and a time range of 5 minutes to 12 hours being applicable. The chemical reaction occurring during this step is given below:(i) Cu + Oxidizing agent + 2 H2SO4 + Pb + [Sn, Au, Ag, Pt, etc] — CuSO4 + PbSO4 (solid) + [Sn, Au, Ag, Pt, etc] (solid) + 2 H2O + derivatives of oxidizing agent(ii) Cu + MnO2 / Co2O3, Ni2O3 + 3 H2SO4 + Pb + [Sn, Au, Ag, Pt, etc] CuSO4 + MnSO4 / NiSo4 / CoSO4 + PbSO4 (solid) + [Sn, Au, Ag, Pt, etc] (solid) + 2 H2O

[0041] After this step, the precious metal content in the residue is approximately 5 to 10 times that of the feed PCB material.

[0042] Fig.2a and Fig.2b show the process of preparation of the oxidizing agent from the waste, as described in Step 4.

[0043] Step 4 : A pre-processing step based on either physical or physico-chemical treatment is employed to remove the impurities from the oxidizing agent used for the leaching of copper in Step 3.

[0044] Step 5 : The selective separation of copper metal from the leach liquor obtained in Step 3 is achieved using either electro-winning or cementation processes. The current densities in the process can range from 10 to 150 A / cm2, and the voltage will be less than 3.5, preferably below 3. The electrochemical reactions of this step are given below:(i) Cu2++ 2 e" — Cu (cathode)(ii) Mn2++ 2 O2MnCh + 2 e (anode)(iii) O2+ 2 e" — 1 / 2 O2 (anode)

[0045] The cementation agent can be a transition metal, and the reaction is given below:(i) Cu2++ M M2++ Cu

[0046] Step 6 : The precious metal residue obtained from Step 3 is processed using a sequence of pyrometallurgical steps: oxidative roasting and smelting in the presence of borax and sodium carbonate as fluxing agents to remove lead and tin from the precious metals, or any conventional processes used for the recovery of precious and other metals from copper anode slimes. The temperature in the oxidation roasting process can range from 500 to 800°C. After oxidation, the impurity oxides are removed using borax and Na2COs fluxing agents in the temperature range of 1000-1300°C. After smelting, the slag and metal parts (which consist of precious metals) are separated. The chemical reaction of this step is given below:(i) PbSC>4 + Sn + O2 — PbCh + SnCh + SO2 (gas)

[0047] In another embodiment of the present invention, as shown in Fig. 3, is a flow chart for the pre-treatment of the spent catalyst, which is described below.

[0048] Step 7 : A process is provided comprising the pre-treatment of the spent Raney nickel obtained from pharmaceutical waste to neutralize the organics and residual alumina. In this step, the spent Raney nickel is treated with alkali leaching. The process parameters in this step can vary, with NaOH content ranging from 50 to 250 g / L, spent Raney nickel to liquid ratio ranging from 1:1 to 1:10, temperature from 50 to 150°C, and time from 1 to 5 hours. The leach liquor consists of alumina and organics, which are separated from the solid nickel. The leached alumina is precipitated as alumina hydroxide by regulating the pH of the solution to 4-5 using acid. The chemical reactions that occur during these steps are given below:(i) Ni-A12O3 + 2 NaOH Ni (solid) + 2 NaA102 + H2O

[0049] Step 8 : The copper from the leach liquor obtained from Step 3 is cemented using the nickel residue obtained from Step 7. The chemical reaction of this step is given below:(i) CuSC + Ni (solid) -^NiSC + Cu (solid)

[0050] In another embodiment of the present invention, as shown in Fig. 4, is a flow chart for obtaining nickel and the other materials present in the leach liquor, as described below.

[0051] Step 9 : The nickel and other materials present in the leach liquor are selectively precipitated using any of the pH precipitation or selective crystallization techniques to obtain the respective metal oxides or sulphates.

[0052] In another embodiment of the present invention, as shown in Fig. 5, is a flow chart for purify or selectively recover the metals from the leach liquor, as described below.

[0053] Step 10: In another aspect of the present invention, a process is defined to purify or selectively recover the metals from the leach liquor obtained from Step 3. The copper leached in the leach liquor of Step 3 is precipitated using metallic iron as the cementation agent. In this step, the pH of the solution is maintained below 2 to prevent the oxidation of copper-to-copper oxide. The reactions that occur in this step are given below:(i) Cu2++ Fe (solid) — Fe2++ Cu (solid)

[0054] In another embodiment of the present invention, as shown in Fig. 6, is a flow chart for iron precipitation from the leach liquor, as described below.

[0055] Step 11: In another aspect of the present invention, the iron present in the leach liquor is selectively separated using oxidation and pH precipitation. In this step, the oxidizing agents can be H2O2, CO2O3, N12O3, MnCh, or oxidants obtained in Step 4, or their representative compounds. After the oxidation of Fe2+to Fe3+, the pH of the solution is raised to between 3 and 4 for the selective precipitation of iron oxide. The temperature in this step is maintained between 80°C and 100°C to precipitate iron as crystalline hematite. The time can vary between 1 hour and 6 hours. The reactions that occur in this step are given below:(i) 2 FeSO4 + CO2O3 or N12O3 or MnCh Fe2(SO4)s + CoSO4 or NiSO4 or MnSO4(ii) Fe2(SO4)3+ 6 NaOH Fe2O3(solid) + 3 Na2SO4+ 3 JLO

[0056] After iron precipitation, the remaining leach liquor is sent to Step 9.

[0057] Examples:

[0058] Raw Materials: The chemical composition of the feed mobile PCB scrap and spent Raney nickel used in the present study is provided in Table 1 and Table 2, respectively. In present invention, two MnO2sources are used as oxidizing agents: ferro-manganese dust waste and NMC battery black mass. The chemical composition of these two oxidizing agents is given in Table 3 and Table 4.&Table 1. Chemical composition of the PCB scrap obtained from mobile wasteTable 2. Chemical composition of the Raney-nickelTable 3. Chemical composition of manganese dustTable 4. Chemical composition of NMC blackmass

[0059] Example 1:

[0060] One kg of metal powder from Step 1 and 1.3 kg of the oxidizing agent obtained from the residue of Step 3 are taken as feed materials in this case study. Additionally, 2.5 kg of acid diluted in 4 L of water is used as the leaching medium. After feeding these materials into a 20 L glass reactor, the temperature is raised to 80°C, and the stirring speed is maintained at 100 rpm. Once the set temperature is reached, the reaction continues for 4 hours. After the reaction time is complete, the reactor is cooled to 40°C, and the contents are tapped from the reactor. The tapped slurry is filtered in a Halar-coated centrifuge using 1 pm filter cloth at an rpm of 1000.

[0061] The filtrate obtained after filtration is sent to the electrolysis step (Step 4). An AC / DC converter is used, with the cathode connected to a copper plate (5 cm length and 1 cm width) and the anode connected to a graphite plate. The current density is maintained at 40 mA / cm2The dissolved copper ions are deposited on the cathode, and manganese ions are deposited as MnCh on the anode plate.

[0062] The filtered residue obtained is dried and weighs approximately 400 g. This residue mostly consists of unreacted materials from the metal powder (Sn, Au, Ag, Pd, Pb, etc.) and the oxidiser (SiCh). The total mass is sent to Step 7, an oxidation roasting process in a tubular furnace, to convert Pb and Sn to their oxide forms. The roasting operation is maintained at a temperature of 800°C for 2 hours. During the process, oxygen gas is purged into the system. After the completion of the reaction, the mass is transferred to a graphite crucible. Borax (30%) and Na2COs (10%) are added to the graphite crucible as fluxing agents. The graphite crucible is then heated in an open-hearth furnace at 1000°C for 30 minutes. The impurities like SiCh, PbCh, SnCh, etc., go into the slag, while the precious metals form a metallic phase. The slag and precious metals are easily separated due to their density differences. After slag-metal separation, the precious metal liquid is poured into a mould and cast into a billet form.

[0063] Example 2:

[0064] One kg of metal powder from the Step 1 and approximately 2.5 kg of the oxidizing agents (LIB cathode material) are used as feed materials in this case study. Additionally, 5 kg of acid diluted in 10 L of water is used as the leaching medium. After feeding these materialsinto a 20 L glass reactor, the temperature is raised to 80°C, and the stirring speed is maintained at 100 rpm. Once the set temperature is reached, the reaction continues for 4 hours. After the reaction time is complete, the reactor is cooled to 40°C, and the contents are tapped from the reactor. The tapped slurry is filtered in a Halar-coated centrifuge using 1 pm filter cloth at an rpm of 1000.

[0065] The filtrate obtained is transferred into a glass reactor. Approximately 740 g of nickel residue metal powder obtained from the Step 5 is used as the cementation agent to separate copper metal powder from the solution. The operation conditions are maintained as follows: temperature 60°C, time 1 hour, and stirring speed 100 rpm. After copper cementation, the nickel and other valuable metals precipitate as hydroxides by changing the pH of the solution. In this case, sodium hydroxide is used as a medium to increase the pH of the solution.

[0066] The filtered residue obtained is dried and weighs approximately 200 g. This residue mostly consists of unreacted materials from the metal powder (Sn, Au, Ag, Pd, Pb, etc.). The total mass is sent to Step 7, an oxidation roasting process in a tubular furnace, to convert Pb and Sn to their oxide forms. The roasting operation is maintained at a temperature of 800°C for 2 hours. During the process, oxygen gas is purged into the system. After the completion of the reaction, the mass is transferred to a graphite crucible. Borax (30%) is added to the graphite crucible as a fluxing agent. The graphite crucible is then heated in an open-hearth furnace at 1000°C for 30 minutes. The impurities like PbCh, SnCL, etc., go into the slag, while the precious metals form a metallic phase. The slag and precious metals are easily separated due to their density differences. After slag-metal separation, the precious metal liquid is poured into a mould and cast into a billet form.

[0067] Example 3:

[0068] The copper from the leach liquor obtained after the oxidative leaching in Example 2 is selectively precipitated using the metallic iron powder. The pH in this step is maintained below 1, and 10% excess iron metal is used in the cementation process according to the stoichiometric equation. After that, the cathode material from LIB waste is used as the oxidizing agent to oxidize Fe2+to Fe3+form. The operational parameters, such as temperature and time, are maintained at 80°C and 3 hours, respectively. The leach liquor and the unreacted mass are filtered using a centrifuge. Afterward, a 45 wt.% sodium hydroxide solution is used to increasethe pH of the solution, precipitating dissolved iron as hematite. The operational parameters in this step are maintained as follows: pH 3.5, temperature 85°C, and time 1 hour.

[0069] In one advantage of the present invention is that the precious metals from PCB waste are recovered using environmentally friendly oxidizing agents.

[0070] In another advantage of the present invention is that the method minimizes the losses of precious metals and avoids the use of corrosive and harmful effluents, such as H2O2 and cyanides.

[0071] Yet another advantage of the present invention enables the recovery of valuable metals, such as manganese, from industrial wastes and electronic waste.

[0072] Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent methods or processes.

[0073] The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.We Claim:1. A method for selective separation of precious metals from electronic waste (e-waste), the method comprising:separating metallic components from the electronic waste using physical separation techniques;obtaining metallic powder by selectively separating ferrous components using a magnetic field;characterized in that,employing a leaching operation to remove highly reactive impurities, such as residual iron, aluminum, and zinc;performing an oxidative leaching step to selectively separate a major element, such as copper (Cu), and precious metals, wherein a leach liquor obtained from the oxidative leaching step is further employed to selectively separate copper from the leach liquor using either electro-winning or cementation processes; andprocessing precious metal residue obtained from the oxidative leaching step using a sequence of pyrometallurgical steps, including oxidative roasting and smelting in the presence of borax and sodium carbonate as fluxing agents to remove lead and tin from the precious metals.2. The method according to claim 1, wherein the method is for the selective recovery of precious metals from the electronic waste (e-waste), such as printed circuit boards (PCBs), motherboards, processor chips, RAMs, or the like.3. The method according to claim 1, wherein in the leaching step, leaching mediums are used, including minerals, organic acids, alkalies, sulfuric acid, or hydrochloric acid, and the operational parameters, such as a temperature range of 0 to 100°C and a time range of 5 minutes to 12 hours, are applicable.4. The method according to claim 1, wherein in the oxidative leaching step, oxidizing agents include but are not limited to hydrogen peroxide, sodium hypochlorite, transition metal oxides, and aqueous solutions containing trivalent or higher oxidation states, such as CO2O3,N12O3, MnCh, Fe20s, and Fe2(SO4)3, as well as salts or compounds of Mz+(where M is a transition metal and Z is an integer with a value of 3 or higher), used in the presence of mineral or organic acids.5. The method according to claim 1, wherein electro-winning is carried out to remove copper (Cu), where electrochemical reactions being:(i) Cu2++ 2 e" — Cu (cathode)(ii) Mn2++ 2 O2MnCh + 2 e (anode)(iii) O2+ 2 e" — 1 / 2 O2 (anode).6. The method according to claim 1, wherein in the cementation process, the cementation agent is a transition metal, and the reaction is given below:(i) Cu2++ M M2++ Cu.7. The method according to claim 1, wherein nickel and other materials present in the leach liquor are selectively precipitated using pH precipitation or selective crystallization techniques to obtain the respective metal oxides or sulphates.8. The method according to claim 1, wherein the temperature in the oxidation roasting process ranges from 500 to 800°C, and after oxidation, the impurity oxides are removed using borax and Na2COs fluxing agents at a temperature range of 1000-1300°C.9. The method according to claim 1, wherein a process is further employed to purify or selectively recover metals from the leach liquor obtained from the oxidative leaching step, where the copper leached in the leach liquor is precipitated using metallic iron as the cementation agent, the reaction that occurs being:Cu2++ Fe (solid) — Fe2++ Cu (solid).10. The method according to claim 1, wherein iron present in the leach liquor is selectively separated using oxidation agents and pH precipitation, the reactions that occur in this step being:(i) 2 FeSO4 + CO2O3 or N12O3 or MnCh Fe2(SO4)3 + CoSO4 or NiSC or MnSO4(ii) Fe2(SO4)3+ 6 NaOH Fe2O3(solid) + 3 Na2SO4+ 3 JLO.11. The method according to claim 1, wherein the precious metals from PCB waste are recovered using environmentally friendly oxidizing agents.12. The method according to claim 1, wherein the method minimizes the loss of precious metals and avoids the use of corrosive and harmful effluents, such as H2O2and cyanides.Dated this the 27thday of January 2025.Digitally signed by Name: Suchitra B IN / PA No-5090 Designation: Patent Agent for the ApplicantA Method for Selective Separation of Precious Metals from E-Waste and Spent Nickel CatalystsABSTRACTThe present invention discloses methods for the selective recovery of precious metals from electronic waste (e-waste). An environmentally friendly oxidizing agent is developed for the selective oxidation and separation of copper from printed circuit board (PCB) metal powder. Additionally, selective recovery of gold and silver is achieved using fluxing agents. Following selective leaching, copper is recovered from the leach solution through cementation with more active metal species. Impurities, such as aluminum (Al) and iron (Fe), are subsequently removed via pH precipitation. The remaining leached elements are further separated using crystallization or additional pH precipitation processes.Reference Fig: Fig. 1

Claims

Claims:

1. A method for selective separation of precious metals from electronic waste (e-waste), the method comprising:separating metallic components from the electronic waste using physical separation techniques;obtaining metallic powder by selectively separating ferrous components using a magnetic field;characterized in that,employing a leaching operation to remove highly reactive impurities, such as residual iron, aluminum, and zinc;performing an oxidative leaching step to selectively separate a major element, such as copper (Cu), and precious metals, wherein a leach liquor obtained from the oxidative leaching step is further employed to selectively separate copper from the leach liquor using either electro-winning or cementation processes; andprocessing precious metal residue obtained from the oxidative leaching step using a sequence of pyrometallurgical steps, including oxidative roasting and smelting in the presence of borax and sodium carbonate as fluxing agents to remove lead and tin from the precious metals.

2. The method according to claim 1, wherein the method is for the selective recovery of precious metals from the electronic waste (e-waste), such as printed circuit boards (PCBs), motherboards, processor chips, RAMs, or the like.

3. The method according to claim 1, wherein in the leaching step, leaching mediums are used, including minerals, organic acids, alkalies, sulfuric acid, or hydrochloric acid, and the operational parameters, such as a temperature range of 0 to 100°C and a time range of 5 minutes to 12 hours, are applicable.

4. The method according to claim 1, wherein in the oxidative leaching step, oxidizing agents include but are not limited to hydrogen peroxide, sodium hypochlorite, transition metaloxides, and aqueous solutions containing trivalent or higher oxidation states, such as CO2O3, N12O3, MnCh, Fe20s, and Fe2(SO4)3, as well as salts or compounds of Mz+(where M is a transition metal and Z is an integer with a value of 3 or higher), used in the presence of mineral or organic acids.

5. The method according to claim 1, wherein electro-winning is carried out to remove copper (Cu), where electrochemical reactions being:(i) Cu2++ 2 e" — Cu (cathode)(ii) Mn2++ 2 O2MnCh + 2 e (anode)(iii) O2+ 2 e" — 1 / 2 O2 (anode).

6. The method according to claim 1, wherein in the cementation process, the cementation agent is a transition metal, and the reaction is given below:(i) Cu2++ M M2++ Cu.

7. The method according to claim 1, wherein nickel and other materials present in the leach liquor are selectively precipitated using pH precipitation or selective crystallization techniques to obtain the respective metal oxides or sulphates.

8. The method according to claim 1, wherein the temperature in the oxidation roasting process ranges from 500 to 800°C, and after oxidation, the impurity oxides are removed using borax and Na2COs fluxing agents at a temperature range of 1000-1300°C.

9. The method according to claim 1, wherein a process is further employed to purify or selectively recover metals from the leach liquor obtained from the oxidative leaching step, where the copper leached in the leach liquor is precipitated using metallic iron as the cementation agent, the reaction that occurs being:Cu2++ Fe (solid) — Fe2++ Cu (solid).

10. The method according to claim 1, wherein iron present in the leach liquor is selectively separated using oxidation agents and pH precipitation, the reactions that occur in this step being:(i) 2 FeSO4 + CO2O3 or N12O3 or MnCh Fe2(SO4)3 + CoSO4 or NiSC or MnSO4(ii) Fe2(SO4)3+ 6 NaOH Fe2O3(solid) + 3 Na2SO4+ 3 JLO.

11. The method according to claim 1, wherein the precious metals from PCB waste are recovered using environmentally friendly oxidizing agents.

12. The method according to claim 1, wherein the method minimizes the loss of precious metals and avoids the use of corrosive and harmful effluents, such as H2O2and cyanides.

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