DESC:FIELD OF THE INVENTION
The present invention relates to a method to convert solid waste generated in copper manufacturing process into copper nanoparticles. More precisely the invention relates to a methodology of synthesising copper nanoparticles from the solid wastes of the copper manufacturing plant.

BACKGROUND OF THE INVENTION
Copper manufacturing plant always faces a challenge of treatment of solid wate and effluent. The waste stream of copper often is a source of pollution which may contaminate ground water and soil. Conventionally, Copper manufacturers treat the effluent with lime to precipitate various contaminants viz. Cu, As Fe, Ni, Zn etc inform their hydroxide derivatives by neutralization. As a result, huge amount of hazardous gypsum containing heavy metals like copper is produced and its disposal has posed another environmental challenge. Other wastes such as mil-scales, slag and rejected cathodes are recycled back in the process for copper recovery. The recycled copper deteriorates the quality of the copper bullions / copper wire being produced in the copper manufacturing process.
In this context, copper manufacturing plants generates large amount of solid waste which contains heavy and toxic metals such as Arsenic, Cadmium, Nickel, Lead, Iron, Zinc and Copper etc., as shown in Table-1.

Table-1 Range of elemental Compositions of solution prepared from solid waste.
Element Cu, % As, ppm Si, ppm Al, ppm Ca, ppm Cr, ppm Fe, ppm K, ppm Mg, ppm Mn, ppm Na, ppm Ni, ppm Pb, ppm Zn, ppm
Solution 0.1 - 99.6 0-500 0-60 0-4000 0-3000 0-40 0-7000 0-500 0-200 0-100 0-300 0-10 0-10 0-600

Presently, there are various chemical processes available to remove various metals ions from waste streams. One of the majorly used methods is precipitation of metal oxide by carbonates, sulphite & hydroxide (Treatability Manual, Vols. 1 -5, Monsanto Research Corporation, EPA 600 8 80 042a, July 1980). Generation of hydroxides, sulphites of metals need to be stored and it cannot be used directly for any application. Therefore, it requires secondary chemical treatment to prepare its copper salts (copper chloride (CuCl2), copper acetate Cu(Ac)2, Copper Sulfate (CuSO4), Copper acetylacetonate (Cu(ACAC)2) (IN2011MU01616 A). The secondary treatment of copper hydroxide and sulphate acts as secondary source of pollution. Hence the process become ecological & economically non-viable. In this context, the creation of value-added products directly from waste stream is an attractive way to treat the waste stream. Thus, there is need of developing novel process for converting solid waste generated during copper manufacturing process into copper nanoparticles as value added product. Although there are various reports available in literature for process of preparing copper nanoparticles using chemical processes. Most of these processes are preparing nanoparticles by using wet chemical process using highly pure salts of copper as a copper source are copper chloride (CuCl2), copper acetate Cu(Ac)2, Copper Sulfate (CuSO4), Copper acetylacetonate (Cu(ACAC)2) (JP2005281781A). Therefore, the present invention focused on preparing copper nanoparticles from solid waste which does not require high purity salts of copper. The synthesis of copper nanoparticles from the waste stream helps in reduction of hazardous waste, improve quality of copper wire and also enables the production of value-added products (copper nano-particles) for large-scale industrial applications without needing high purity copper salt. Due to nanosized of copper particles, the electronic, optical, and surface properties are greatly enhanced as compared to the bulk counterpart. Moreover, because of its high surface area to volume ratio, it could be used as antibacterial agent in coating, paints, and formulations.

OBJECT OF THE INVENTION
The object of the present invention is to retrieve copper from wastes in the form of value added copper nanoparticles.

SUMMARY
The present invention relates to a method to convert solid waste generated in copper manufacturing process into copper nanoparticles. More precisely the invention relate to a methodology of synthesising copper nanoparticles from the solid wastes of the copper manufacturing plant.

The method of converting solid waste from copper manufacturing plant into copper nanoparticles comprising the following steps:
Dissolution of solid waste aqueous solution using mineral acids;
neutralization of acidic solution of copper by base to reach ph= 7;
reduction of Cu (2+) ions to Cu (0) using various reducing agents in presence of dispersing agent to obtain the copper nanoparticles.

Mineral acids used can be Hydrochloric acid, Sulphuric acid, Phosphoric acid, Hydrofluoric acid, and Hydrobromic acid. The base used can be Ammonium Hydroxide (NH4OH), Methyl Amine (CH3NH2), Ethylamine, Triethylamine, Ethanolamine, Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH), Sodium bicarbonate (NaHCO3), and lithium Hydroxide (LiOH). The reducing agent can be Sodium Borohydride (NaBH4), LiAlH4 (Lithium Aluminium Hydride), Hydrazine (N2H4), Sodium citrate, Ascorbic acid, Malonic acid, and Glucose. The dispersing agent can be small molecule or polymer - Polyethylene glycol, Polyacrylamide, Polyacrylic acid, Tannic acid, Oleic acid.The rate addition of the reducing solution varies upon reducing strength of reducing agent - dropwise, moderate, and fast addition.

BRIEF DESCRIPTION OF DRAWING
Figure 1 shows the flow diagram represents process of preparation of copper nanoparticles from waste stream.
Figure 2 shows PXRD graph of copper nanoparticles.
Figure 3 shows SEM images of copper nanoparticles prepared from the waste stream.

DESCRIPTION
For promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as would normally occur to those skilled in the art are to be construed as being within the scope of the present invention.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other, sub-systems, elements, structures, components, additional sub-systems, additional elements, additional structures, or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the accompanying figures.

The waste generated from industry is major concern due to it is one of the major sources of water & soil pollution. More precisely, the waste generated of metal/steel industry need to be treated or converted into non-toxic material. Conventionally, this waste solid or non-toxic material is disposed is in secured landfill which can cause secondary source of pollution. This non-toxic material can act secondary source of pollution which generate chemical wastage and land-fill issues which further lead to water and soil pollution. The present invention relates to the treatment of copper waste stream & method of producing copper nanoparticles from waste stream of copper manufacturing plants. More specifically, direct conversion of waste copper stream into copper nanoparticles is achieved through modification of wet chemical process. Our process alleviates need of usage of pure copper salts for the preparation of nanoparticles. Furthermore, this process enables the retrieval of copper from the waste into a value-added product.

The current disclosure claims the methods for producing various sized copper nanoparticle from waste stream ranging from 20 nm to 200 nm. This disclosure solves the problem of treatment copper wastage & converts it into the valued added products such as copper nanoparticles which could be used as antibacterial additive in paints and coatings. Hence, formation of copper nanoparticle is an alternative method to retrieve copper in the form of copper nanoparticles.

Copper salts are conventionally used in synthesis of copper nano-particles. The present invention claims the replacement of copper slats with mill scale, slag, rejected cathodes etc. generated in copper manufacturing processes for synthesis of copper nanoparticles. The present invention also claims the process developed for synthesis of copper nano-particles from the waste generated such as mil-scales, slag and rejected cathodes from copper manufacturing processes. The present invention also claims the control over the size of copper nano-particles in the range of 50 to 500 nm during the synthesis of copper nano-particles from the waste generated such as, mil-scales, slag and rejected cathodes from copper manufacturing processes. The method of converting solid/liquid waste into copper nanoparticles, Sequence of treatment of waste is selected such as:
Dissolution?Neutralization? Reduction, or
Dissolution?Reduction?Neutralization, or
Dissolution?Neutralization?Reduction?Neutralization

As mentioned above converting solid/liquid waste into copper nanoparticle, for reduction Cu2+ ions, reducing agent were selected based on optimization of reduction rates and particles size of copper nanoparticles. The method of converting solid waste into copper nanoparticles, to avoid possible aggregation smaller size particle, the selective stabilizing agent is selected on basis of its capacity to form a complex with copper metal. The method of converting solid waste into copper nanoparticles, the size of the copper nanoparticles can be varied by adjusting reaction conditions including, for example, surfactant systems, addition rates, and temperatures. The method of converting solid waste into copper nanoparticles, controlling the size of copper nanoparticles is achieved through changing concentration selected stabilizer ( Cu2+: Stabilizer ratio = 0.5, 1, 2,….10).

The invention relates to demonstration of synthesis of copper nanoparticles from the solid wastes of the copper manufacturing plant such as mil-scales, slag and rejected cathodes. The process relates to retrieval of copper from wastes in the form of value added copper nanoparticles which could be used as an additive in paints and coatings for an antibacterial, antiviral, antifungal properties and in conducting inks for enhancing conductivity. The present invention is first of its kind of work wherein, synthesis of copper nanoparticles is successfully achieved from copper wastes instead of using copper salts as a copper precursor (CuCl2, Cu(NO3)2 and Cu(Ac)2). More than 98% of copper is recovered from the waste in the form of copper nanoparticles with particle size less than 300 nm. This process involves neutralisation followed by reduction in a non-oxidising atmosphere. The present invention is not only environmentally friendly but also economical viable solution for recovery of copper in usable and value-added form.

According to invention, the method of retrieving copper from waste stream of copper manufacturing plant in the form copper nanoparticles is provided herein. However, the traditional treatment of copper wastage stream is a precipitation of copper. This invention involves two steps, neutralization of acidic stream of copper wastage and reduction of Cu (2+) ions to Cu (0) using various reducing agents in presence of dispersing agent to obtain the copper nanoparticles.

Initial solid waste is leached out in aqueous solution using mineral acids such as Hydrochloric acid, Sulphuric acid, Phosphoric acid, Hydrofluoric acid, and Hydrobromic acid. The resulting acidic solution of copper is neutralized by base to reach to PH=7. Base can be Ammonium Hydroxide (NH4OH), Methyl Amine (CH3NH2), Ethylamine, Triethylamine, Ethanolamine, Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH), Sodium bicarbonate (NaHCO3), and lithium Hydroxide (LiOH). Maintaining the PH of Acidic aqueous solution of copper could provide optimal condition for the formation copper nanoparticles. The amount of base added can change the reaction condition to obtain copper nanoparticles. After the addition of sufficient quantity of bases, the reaction solution was exposed to various reducing agents. These reducing agent solutions were prepared freshly and rate addition of the reducing solution varies upon reducing strength of reducing agent - dropwise, moderate, and fast addition. Reducing agent can be Sodium Borohydride (NaBH4), LiAlH4 (Lithium Aluminium Hydride), Hydrazine (N2H4), Sodium citrate, Ascorbic acid, Malonic acid, and Glucose. By reducing copper ions to metallic copper, we can obtain variable sized copper nanoparticles. The elemental compositions of copper nano particles are shown in Table-2. Pure metallic nano powered was thus obtained. These particles have high surface energy due to very surface area to volume ratio hence particles may undergo agglomeration. To avoid agglomeration or coalescence of particle, the addition of the right quantity of stabilizing or dispersing agent is required to arrest the growth/agglomeration of particles in nanoscale regime. The stabilizing agent may be small molecule or polymer - Polyethylene glycol, Polyacrylamide, Polyacrylic acid, Tannic acid, Oleic acid.

Table-2 Range of elemental Compositions of copper nano particles
Element Cu, % As, ppm Si, ppm Al, ppm Ca, ppm Cr, ppm Fe, ppm K, ppm Mg, ppm Mn, ppm Na, ppm Ni, ppm Pb, ppm Zn, ppm
Cu NPs >99 0-2 0-60 0-15 0-50 0-1 0-14 0-6 0-13 0-0.4 <3000 0-17 0-2 0-300

Example 1
Before neutralization of Cu2+ ions solution, it is necessary to dissolve solid wastage (miliscale, slag and cathode) to obtain Cu2+ solution for further treatment. For dissolution of copper solid wastage, in 100 mL beaker placed 2.23 g of copper wastage obtained from copper manufacturing plant. Simultaneously, acidic solution was prepared in separate beaker using 24 mL HNO3, 25 mL H2SO4. The ratio of these acids is decided on the basis of dissolution rate of copper solid. Then optimal ratio of acidic mixture is poured into beaker containing copper solid wastage (Such Miliscale, slag and copper cathode). After addition of acid, the resulting solution were transferred on magnetic stirrer for heating at 60 °C and 300 rpm for 2h or stirred until waste solid is completely dissolved. Then reaction solution allowed to cool at room temperature and taken for next step. The resulting copper solution then diluted to 1000 mL (1Litre). Diluted solution of copper ion is acidic in nature which need to be neutralized further to get optimal level of pH. This dissolved solid of copper, the reaction solution is neutralized using strong bases. Adding 25.4 mL solution of polyacrylamide-6000 (3.7 grams) into 1 Litre solution of copper (7GPL) in round bottom flask (reactor) & is stir well in Nitrogen atmosphere. Then adjust the pH using 6 mL solution of Ammonia while reaction mixture is stirred at PH=7. Add 1 litre ascorbic acid solution with stirring and again adjust pH using 6M NaOH (50 mL) hence the resulting solution becomes basic. Place the reactor or round bottom flask in hot oil bath (80°C) & maintain the temperature 80°C and stirring for 2 hrs. After 2hrs, allow the solution to cool at room temperature. Transfer this solution in centrifuge bottle. Resulting copper nanoparticles centrifuged at 4000 rpm for 30 min in centrifuge bottle. After centrifugation, mother liquor is thrown away (Discarded) by decantation and all the particles are settled at bottom of centrifuge bottle. In settled particles, add 30 mL of water and sonicate for 10 min till particle gets dispersed in 30 mL water and add 30 mL acetone. Again, centrifuge the solution at 4000 rpm for 30 min. Repeat this procedure twice. Finally add acetone to remove particle from centrifuge bottle to round bottom flask for rota-evaporation. Evaporate acetone on rota & evaporate hence particle remains in dry in round bottom flask.

Example 2
Before neutralization of Cu2+ ions solution, it is necessary to dissolve solid wastage (miliscale, slag and cathode) to obtain Cu2+ solution for further treatment. For dissolution of copper solid wastage, in 100 mL beaker placed 2.23 g of copper wastage obtained from copper manufacturing plant. Simultaneously acidic solution was prepared in separate beaker using 24 mL HNO3, 25 mL H2SO4. The ratio of these acids is decided based on faster dissolution rate of copper solid. Then optimal ratio of acidic mixture is poured into beaker containing copper solid wastage (Such Miliscale, slag and copper cathode). After addition of acid, we observe brown fumes. After addition of acid, the resulting solution were transferred on magnetic stirrer for heating at 60 °C and 300 rpm for 2h. Then reaction solution allowed and taken for next step. The resulting copper solution then diluted to 1000 mL (1Litre). After Dissolution of copper, the reaction solution was neutralized using strong bases. Diluted solution of copper ion is acidic in nature which need to be neutralized further to get optimal level of pH. Adding 25.4 mL solution of PVP (4.2 grams) into 1 Litre solution of copper rods (7GPL) in round bottom flask (reactor) & is stir well in Nitrogen atmosphere. Then again adjust the pH using 6 mL solution of Ammonia while reaction mixture is stirring PH=7. Add 1 litre ascorbic acid solution with stirring and again adjust pH using 6M NaOH (50 mL) hence the resulting solution becomes basic. Place the reactor or round bottom flask in hot oil bath (80°C) & maintain the temperature 80°C and stirring for 2 hrs. After 2hrs, allow the solution to cool at room temperature. Transfer this solution in centrifuge bottle. Resulting copper nanoparticles centrifuged at 4000 rpm for 30 min in centrifuge bottle. After centrifugation, mother liquor is thrown away (Discarded) by decantation, you will observe all the particles are settled at bottom of centrifuge bottle. In settled particles add 30 mL of water and sonicate for 10 min till particle gets dispersed in 30 mL water and add 30 mL acetone. Again, centrifuge the solution at 4000 rpm for 30 min. Repeat this procedure twice. Finally add acetone to remove particle from centrifuge bottle to round bottom flask for rota-evaporation. Evaporate acetone on rota & evaporate hence particle remains in dry in round bottom flask.

Example 3
For dissolution of copper solid wastage, in 100 mL beaker placed 2.23 g of copper wastage obtained from copper manufacturing plant. Simultaneously acidic solution was prepared in separate beaker using 24 mL HNO3, 25 mL H2O2. The ratio of these acids is decided based on faster dissolution rate of copper solid. Then optimal ratio of acidic mixture is poured into beaker containing copper solid wastage (Such Mili-scale, slag and copper cathode). After addition of acid, we observe brown fumes. After addition of acid, the resulting solution were transferred on magnetic stirrer for heating at 60 °C and 300 rpm for 2h. Then reaction solution allowed and taken for next step. The resulting copper solution then diluted to 1000 mL (1Litre). After Dissolution of copper, the reaction solution was neutralized using strong bases. Diluted solution of copper ion is acidic in nature which need to be neutralized further to get optimal level of pH. Adding 25.4 mL solution of polyacrylamide-6000 (3.7 grams) into 1 Litre solution of copper rods (7GPL) in round bottom flask (reactor) & & stir well in Nitrogen atmosphere. Then adjust the pH using 6 mL solution of Ammonia while reaction mixture is stirring PH=7. Add 1 litre ascorbic acid solution with stirring and again adjust pH using 6M NaOH (50 mL) hence the resulting solution becomes basic. Place the reactor or round bottom flask in hot oil bath (80°C) & maintain the temperature 80°C and stirring for 2 hrs. After 2hrs, allow the solution to cool at room temperature. Transfer this solution in centrifuge bottle. Resulting copper nanoparticles centrifuged at 4000 rpm for 30 min in centrifuge bottle. After centrifugation, mother liquor is thrown away (Discarded) by decantation, you will observe all the particles are settled at bottom of centrifuge bottle. In settled particles add 30 mL of water and sonicate for 10 min till particle gets dispersed in 30 mL water and add 30 mL acetone. Again, centrifuge the solution at 4000 rpm for 30 min. Repeat this procedure twice. Finally add acetone to remove particle from centrifuge bottle to round bottom flask for rota-evaporation. Evaporate acetone on rota & evaporate hence particle remains in dry in round bottom flask.

Example 4
For dissolution of copper solid wastage, in 100 mL beaker placed 2.23 g of copper wastage obtained from copper manufacturing plant. Simultaneously acidic solution was prepared in separate beaker using 24 mL HNO3, 25 mL H2O2. The ratio of these acids is decided based on faster dissolution rate of copper solid. Then optimal ratio of acidic mixture is poured into beaker containing copper solid wastage (Such Mili-scale, slag and copper cathode). After addition of acid, we observe brown fumes. After addition of acid, the resulting solution were transferred on magnetic stirrer for heating at 60 °C and 300 rpm for 2h. Then reaction solution allowed and taken for next step. The resulting copper solution then diluted to 1000 mL (1Litre). After Dissolution of copper, the reaction solution was neutralized using strong bases. Diluted solution of copper ion is acidic in nature which need to be neutralized further to get optimal level of pH. Adding 25.4 mL solution of PVP (3.7 grams) into1 Litre solution of copper rods (7GPL) in round bottom flask (reactor) & & stir well in Nitrogen atmosphere. Then again adjust the pH using 6 mL solution of Ammonia while reaction mixture is stirring PH=7. Add 1 litre ascorbic acid solution with stirring and again adjust pH using 6M NaOH (50 mL) hence the resulting solution becomes basic. Place the reactor or round bottom flask in hot oil bath (80°C) & maintain the temperature 80°C and stirring for 2 hrs. After 2hrs, allow the solution to cool at room temperature. Transfer this solution in centrifuge bottle. Resulting copper nanoparticles centrifuged at 4000 rpm for 30 min in centrifuge bottle. After centrifugation, mother liquor is thrown away (Discarded) by decantation, you will observe all the particles are settled at bottom of centrifuge bottle. In settled particles add 30 mL of water and sonicate for 10 min till particle gets dispersed in 30 mL water and add 30 mL acetone. Again, centrifuge the solution at 4000 rpm for 30 min. Repeat this procedure twice. Finally add acetone to remove particle from centrifuge bottle to round bottom flask for rota-evaporation. Evaporate acetone on rota & evaporate hence particle remains in dry in round bottom flask.

Example 5
Before neutralization of Cu2+ ions solution, it is necessary to dissolve solid wastage (mili-scale, slag and cathode) to obtain Cu2+ solution for further treatment. For dissolution of copper solid wastage, in 100 mL beaker placed 2.23 g of copper wastage obtained from copper manufacturing plant. Simultaneously acidic solution was prepared in separate beaker using 24 mL HNO3, 25 mL H2SO4. The ratio of these acids is decided based on faster dissolution rate of copper solid. Then optimal ratio of acidic mixture is poured into beaker containing copper solid wastage (Such Miliscale, slag and copper cathode). After addition of acid, we observe brown fumes. After addition of acid, the resulting solution were transferred on magnetic stirrer for heating at 60 °C and 300 rpm for 2h. Then reaction solution allowed and taken for next step. The resulting copper solution then diluted to 1000 mL (1Litre). After Dissolution of copper, the reaction solution was neutralized using strong bases. Diluted solution of copper ion is acidic in nature which need to be neutralized further to get optimal level of ph. Adding 25.4 mL solution of PAA (4.2 grams) into 1 Litre solution of copper rods (7GPL) in round bottom flask (reactor) & is stir well in Nitrogen atmosphere. Then adjust the pH using 6 mL solution of Ammonia while reaction mixture is stirring PH=7. Add 1 litre ascorbic acid solution with stirring and again adjust pH using 6M NaOH (50 mL) hence the resulting solution becomes basic. Place the reactor or round bottom flask in hot oil bath (80°C) & maintain the temperature 80°C and stirring for 2 hrs. After 2hrs, allow the solution to cool at room temperature. Transfer this solution in centrifuge bottle. Resulting copper nanoparticles centrifuged at 4000 rpm for 30 min in centrifuge bottle. After centrifugation, mother liquor is thrown away (Discarded) by decantation, you will observe all the particles are settled at bottom of centrifuge bottle. In settled particles add 30 mL of water and sonicate for 10 min till particle gets dispersed in 30 mL water and add 30 mL acetone. Again, centrifuge the solution at 4000 rpm for 30 min. Repeat this procedure twice. Finally add acetone to remove particle from centrifuge bottle to round bottom flask for rota-evaporation. Evaporate acetone on rota & evaporate hence particle remains in dry in round bottom flask.
,CLAIMS:I/we claim
1. A method of converting solid waste from copper manufacturing plant into copper nanoparticles comprising the following steps:
• adding 2.23 g of copper wastage to an acidic solution;
• the solution obtained in (a) is heated and stirred at 300 rpm for 2 h;
• solution obtained in step (b) is kept at room temperature to cool down;
• the solution obtained in step (c) is diluted to 1 L;
• adding strong base to neutralize the solution obtained in step (d) in presence of dispersing agent and reducing agent while stirring the solution in nitrogen atmosphere;
• placing a container containing basic solution of copper obtained in step (e) in a hot oil bath and stirring for 2 hrs and then cooling down at room temperature;
• the solution obtained in step (f) is centrifuged at 4000 rpm for 30 min;
• mother liquor is thrown away by decantation and then 30 mL of water is added to the solution and sonication is carried out for 10 min till particle gets dispersed in 30 mL water and thereafter 30 mL acetone is added to the solution, and the solution is centrifuged at 4000 rpm for 30 min. and step (h) is repeated twice;
• adding acetone to remove copper particles and further evaporation is carried out and thereafter acetone is evaporated and the dry copper particles are obtained.

2. The method as claimed in claim 1, wherein ratio of acids is depends on the basis of dissolution rate of copper solid.
3. The method as claimed in claim 1, wherein acid solution can be nitric acid, Hydrochloric acid, Sulphuric acid, Phosphoric acid, Hydrofluoric acid, and Hydrobromic acid.
4. The method as claimed in claim 1, wherein in step (b) the solution obtained in step (a) is kept in a magnetic stirrer, wherein the temperature of magnetic stirrer is maintained at 60 ? while stirring.
5. The method as claimed in claim 1, wherein base can be Ammonium Hydroxide (NH4OH), Methyl Amine (CH3NH2), Ethylamine, Triethylamine, Ethanolamine, Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH), Sodium bicarbonate (NaHCO3), and lithium Hydroxide (LiOH).
6. The method as claimed in claim 1, wherein the amount of base added in step (e) is 50 ml.
7. The method as claimed in claim 1, wherein the PH of the solution is neutral.
8. The method as claimed in claim 1, wherein reducing agent can be Sodium Borohydride (NaBH4), LiAlH4 (Lithium Aluminium Hydride), Hydrazine (N2H4), Sodium citrate, Ascorbic acid, Malonic acid, and Glucose.
9. The method as claimed in claim 1, wherein dispersing agent can be small molecule or polymer - Polyethylene glycol, Polyacrylamide, Polyacrylic acid, Tannic acid, Oleic acid.
10. The method as claimed in claim 1, wherein temperature of the hot oil bath is 80 ?.