DESC:FORM 2

THE PATENTS ACT, 1970

(39 of 1970)

&

THE PATENT RULES, 2003

COMPLETE SPECIFICATION

[See Section 10 and Rule 13]

TITLE:

“A METHOD FOR RECOVERY OF RARE EARTH ELEMENTS AND BASE METALS FROM MAGNET SCRAP”

APPLICANT:

ATTERO RECYCLING PVT. LTD.
a company incorporated under the Indian Companies Act, 1956
having address at
173, Raipur Industrial Area, Bhagwanpur, Roorkee, Haridwar Uttarakhand - 247661, India

PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it is to be performed:
FIELD OF THE INVENTION
The present invention relates to the field of recycling of magnet scrap from electronic waste. More particularly, the present invention relates to an environment friendly and commercially feasible method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes such as hard disc drives of desktops and laptops, high-end audio headphones and speakers.

BACKGROUND OF THE INVENTION
Electronic waste (e-waste) is generated when electronic products are discarded after the end of their shelf-life. The fast-pace growth of technology and the consumption-driven society contributes to tremendous increase in e-waste production. Rare earth elements (REE) comprise of lanthanide series metals, as well as scandium and yttrium. Rare earth elements are critical materials in electronics and clean technologies. With the diminishing of easily accessible minerals for mining, the REE recovery from waste is an alternative towards a circular economy. Electronic waste contains valuable rare earth materials, making the identification and extraction of these materials critical for the electronics industry.
In recent years, concerns about the availability and sustainable recovery of rare earth elements have grown, leading to their classification as critical raw materials due to the supply risk. The earth's natural reserves are unable to meet the global demand for these strategic resources, further highlighting the importance of finding a more sustainable method for REE recovery from electronic waste. These elements play a crucial role in the manufacturing of various technologies, including fluorescent lamps, fluid catalysts, and permanent magnets used in computer hard drives, among other electrical and electronic appliances, due to their performance-enhancing features. Neodymium (Nd) magnets are among one of the prime example of the importance of rare earth elements in technology. Even though they represent only a fraction of the total weight of hard disk drives, the voice coils and spindle motors would not be able to function without them. When these products reach the end of their life cycle, they pose a significant threat to the environment.
The expanding electronics and electrical industry have led to a significant increase in the demand for rare earth elements, creating concerns about the sustainability of these materials. Mining, industrial application, and waste processing cause REE pollution as the REEs are typically dispersed at relatively low concentration and after decades of use, REEs are toxic to plants, animals, and humans at sufficient concentration. Improperly handled electronic waste is among one of the potential source of significant REE pollution. In general, REEs that are present in the e-waste are leached out into the environment. These leached out REEs enter the soil layer that is in contact with the contaminant point of origin and then, if the metals are sufficiently mobile, these metals spread into the groundwater and surrounding areas. The release of these metals from e-waste might therefore cause considerable pollution. Therefore, the use of these rare earth elements in various technological applications is causing the risk of environmental contamination as the e-waste is often not disposed in a safe and environment-friendly manner. Hence, the rare earth elements are considered to be the emerging pollutants in environment.
Conventionally, various methods have been attempted by the researchers to extract rare earth elements sustainably from electronic waste. These methods include chemical precipitation, ion exchange, solvent extraction, membrane separation, and adsorption.
IN465666 discloses about a method and a system for separation of rare earth elements from secondary sources. The method disclosed in the citation consists of: obtaining magnets from the plurality of secondary sources; crushing the obtained magnets to a coarser size using a grinder; demagnetizing the crushed magnet by heating at a first predefined temperature of 350°C for one hour; grinding the demagnetized magnet into fine powder; roasting the fine powder at a second predefined temperature of 650 to 1000°C for five hours to obtain metal oxides; dissolving the metal oxides by acid leaching to obtain leach liquor; removing iron from the leach liquor through precipitation by adjusting a pH value; separating the iron by filtration; separating the individual rare earth element by a liquid-liquid extraction method by optimally adjusting a set of experimental conditions; stripping each of the extracted rare earth elements one by one, precipitating each of the rare earth elements and drying. However, the disclosed citation involves multiple steps of grinding and heating and the method requires high temperature roasting.
CN112813264 discloses about an extraction recovery method for valuable elements in neodymium iron boron waste material. The recovery method comprises the steps as follows: first extraction is conducted on leachate of the neodymium iron boron waste materials to obtain a first organic phase and a first water phase, and first reverse extraction is conducted on the first organic phase to obtain an iron-containing solution; and second extraction on the first water phase obtained in the first step to obtain a second water phase and a second organic phase, and second reverse extraction is conducted on the second organic phase to obtain a neodymium-containing solution. However, the disclosed method in the citation is lengthy and tedious.
CN114737049 discloses about a method for removing phosphorus in rare earth leachate. The method comprises the following steps: the rare earth concentrate and concentrated sulfuric acid are uniformly mixed in the roasting section and then roasted in a rotary kiln to form rare earth roasted ore; in the leaching section, iron ions are added into the leaching solution of the rare earth roasted ore, and the iron ions react with phosphate ions to generate iron phosphate precipitate; and after solid-liquid separation of the iron phosphate precipitate and the rare earth sulfate leaching solution in the neutralization and impurity removal section, discharging the iron phosphate precipitate along with leaching residues. However, the disclosed method is applicable for ore and is silent about recycling of any of the rare earth elements from magnet scrap.
CN116949305 discloses about a method for leaching mixed rare earth compound from NdFeB waste. The method comprises the steps of wet ball milling, natural oxidizing roasting, automatic size mixing, leaching of rare earth elements and solid liquid separation. However, the method in the citation is complex that generates high-temperature flue gas waste heat that enters a waste heat boiler to prepare steam for rare earth leaching and solid slag washing.
Rabatho et al, in J Mater Cycles Waste Management (2013)15:171–178; doi 10.1007/s10163-012-0105-6 discloses about recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process. The citation investigated the possibility of dissolving the high Nd content in the magnetic waste sludge by HCl or HNO3 acid solutions, and then removing iron (Fe) as Fe(OH)3 followed by oxalic acid precipitation to recover Nd and Dy. However, the results inferred that there exists a need to improve precipitation efficiency during Fe precipitation since loss of precious metals (Nd, Dy and B) is high. There is also a loss of 10% of Nd and 20% of Dy during precipitation with oxalic acid that further needs improvement. Moreover, the recovery rate of Nd and Dy is less along with less percent purity.
Firdaus et al, in J. Sustain. Metall. (2016) 2:276–295; doi: 10.1007/s40831-016-0045-9, is a review article that discloses a systematic review of studies on the high-temperature (pyrometallurgical) recovery of rare earth elements from magnets. The features and conditions at which the recycling processes had been studied are mapped and evaluated technically. The review also highlights the reaction mechanisms, behaviors of the rare-earth elements, and the formation of intermediate compounds in high-temperature recycling processes. However, there are evident barriers or challenges such as the effects of contaminants on the recycling process; optimization for mutual separation of REs (Nd, Dy, Pr) and feasibility issue (economics and lifecycle). Besides this, further fundamental study on the thermodynamics and kinetic behavior of the magnets (including the behavior of each individual REE for mutual separation) during high-temperature processes is required to optimize the available techniques and to analyze the best option.
In view of above, the state of art discloses about the methods for recovery of REE that suffer from limitations such as lengthy method of purification, low extractability and high wastewater streams. While pyrometallurgical manufacturing offers advantages, the process generates toxic materials and dioxins from flame retardant during e-waste smelting. Some other challenges include partial metal separation achieved during e-waste smelting leading to limited value upgrading of the metals and use of harsh chemicals that are harmful for nature, less recovery rate and non-feasibility at large scale. Moreover, cyanide leaching employed in hydrometallurgy is highly toxic.
Therefore, there is a need to explore an easy to operate, environment friendly, commercially feasible and attractive method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes and to optimize the most efficient method for recovering REE from e-waste.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a method for recovery of rare earth elements and base metals from magnet scrap.
Another object of the present invention is to provide a method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap of electronic wastes.
Yet another object of the present invention is to provide an environment friendly and commercially feasible method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes.
Yet another object of the present invention is to provide a simple and easy to operate method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes.
Still another object of the present invention is to provide an efficient method for recovery of rare earth elements and base metals with high purity and recovery rate.

SUMMARY OF THE INVENTION
The present invention relates to an environment friendly and commercially feasible method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap of electronic wastes. The method of the present invention provides simple and easy to operate steps that includes demagnetization by heat treatment, ball milling, leaching, precipitation and selective extraction.
In an embodiment, the present invention provides a method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap, comprising the steps of: (a) demagnetizing Nd-magnet scrap by subjecting to heat treatment to obtain a demagnetized Nd-magnet scrap; (b) ball milling the demagnetized Nd-magnet scrap for 1-3 hours to obtain a powder having particle size in a range of 100-200 mesh; (c) agitating the powder obtained in step (b) at a pulp density of 10% with a leaching solution for 4-6 hours to obtain a leach liquor; (d) adding a solution of a precipitating agent in a pH range under agitation for 2-4 hours to obtain a precipitate of neodymium (Nd) and praseodymium (Pr) and an iron containing filtrate; (e) removing iron from the iron containing filtrate obtained in step (d) with the help of a solution of sodium hydroxide under agitation at a temperature range of 85-105? for 3-6 hours to obtain an iron free liquor; (f) treating the iron free liquor obtained in step (e) with bis(2,4,4-trimethylpentyl) phosphinic acid with a contact duration of 3-6 minutes to obtain dysprosium free solution and to selectively extract dysprosium; (g) stripping out the selectively extracted dysprosium of step (f) with 5-10% w/v sulphuric acid at an organic to aqueous layer (O/A) ratio of 1:1 with a contact duration of 3-6 minutes to obtain a stripped dysprosium; and (h) treating the stripped dysprosium of step (g) with a solution of sodium carbonate (25% w/v) for 2-4 hours at a pH range of 7-10 to obtain a precipitate of dysprosium.
The present invention relates to a simple, easy to operate and environment friendly method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap of electronic wastes that recovers 90.6% - 99% of rare earth elements with % purity of 96.3 – 99.5%.
The above objects and advantages of the present invention will become apparent from the hereinafter set forth brief description of the drawings, detailed description of the invention, and claims appended herewith.

BRIEF DESCRIPTION OF THE DRAWINGS
An understanding of the method for recovery of rare earth elements and base metals from Nd-magnet scrap of electronic wastes of the present invention may be obtained by reference to the following drawings:
Figure 1 is a schematic representation of a method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described 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.
The present invention now will be described hereinafter with reference to the detailed description, in which some, but not all embodiments of the invention are indicated. Indeed, the invention may be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. The present invention is described fully herein with non-limiting embodiments and exemplary experimentation.
The present invention provides an environment friendly and commercially feasible method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap of electronic wastes. The method of the present invention provides simple and easy to operate steps that includes demagnetization by heat treatment, ball milling, leaching, precipitation and selective extraction.
In a preferred embodiment, the present invention provides a method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap, comprising the steps of: (a) demagnetizing Nd-magnet scrap by subjecting to heat treatment to obtain a demagnetized Nd-magnet scrap; (b) ball milling the demagnetized Nd-magnet scrap for 1-3 hours to obtain a powder; (c) agitating the powder obtained in step (b) at a pulp density of 10% with a leaching solution for 4-6 hours to obtain a leach liquor; (d) adding a solution of a precipitating agent in a pH range under agitation for 2-4 hours to obtain a precipitate of neodymium (Nd) and praseodymium (Pr) and an iron containing filtrate; (e) removing iron from the iron containing filtrate obtained in step (d) with the help of a solution of sodium hydroxide under agitation at a temperature range of 85-105? for 3-6 hours to obtain an iron free liquor; (f) treating the iron free liquor obtained in step (e) with bis(2,4,4-trimethylpentyl) phosphinic acid with a contact duration of 3-6 minutes to obtain a dysprosium free solution and to selectively extract dysprosium; (g) stripping out the selectively extracted dysprosium of step (f) with sulphuric acid (5-10% w/v) at an organic to aqueous layer (O/A) ratio of 1:1 with a contact duration of 3-6 minutes to obtain a stripped dysprosium; and (h) treating the stripped dysprosium of step (g) with said solution of said precipitating agent for 2-4 hours at a pH range of 7-10 to obtain a precipitate of dysprosium.
Here, the demagnetization in step (a) is performed at a temperature range of 400-600? for 1-4 hours to avoid Nd-magnet scrap from sticking over iron ball during the step of ball milling. Further, the ball milling of the demagnetized Nd-magnet scrap is done to obtain said powder having a particle size ranging from 100 mesh to 200 mesh. The leaching solution in step (c) includes a solution of 2-4 M of sulphuric acid and 2-8% (w/v) of hydrogen peroxide (H2O2). The precipitate of Nd and Pr in step (d) is obtained by maintaining pH in a range of 1.5-2.5. The solution of the precipitating agent in step (d) and step (h) is a solution of 25% w/v sodium carbonate. The pH in step (e) is maintained at a range of 1.7-2.2. Additionally, said dysprosium free solution obtained in step (f) is further taken for recovering base metals selected from cobalt (Co) or nickel (Ni).
The present invention relates to a simple, easy to operate and environment friendly method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap of electronic wastes. Said method recovers 90.6%-99% of rare earth elements with % purity ranging from of 96.3-99.5% by steps that include demagnetization by heat treatment, ball milling, leaching, precipitation and selective extraction. Essentially, said method recovers 90.6% - 99% of neodymium (Nd) with % purity of 96.3-96.6% and recovers 92% - 99% of dysprosium (Dy) with % purity of 99.5%.
Referring to Figure 1, a schematic representation of a method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes, is illustrated.

EXAMPLE 1
For Experimentation Data
A method for recovery of rare earth elements and base metals from Nd-magnet scrap
Batch 1
100 g of Nd-magnet scrap was demagnetized by roasting at a temperature of 500°C for 2 hours. The demagnetized material was ball milled after cooling. The ball milled material was passed through 100 mesh to get a powder. The powder was agitated with a solution of 1 L of 3 M of sulphuric acid and 50 mL of H2O2 for 4 hours to obtain a leach liquor. Next, the leach liquor obtained (1.03 L) was agitated with addition of 0.18 L of a solution of sodium carbonate (25% w/v) by maintaining a pH between 1.5-1.7 for 2 hours to precipitate Nd and Pr and to obtain a slurry. The obtained slurry was filtered to get 1.09 L of a filtrate (Nd and Pr-free liquor) and 87 g of wet cake of Nd-Pr carbonate. The wet cake of Nd-Pr carbonate was washed with water and dried to obtain 61.77 g of a dry cake of Nd-Pr carbonate. The analysis of the obtained powder, leach liquor and the dry cake of Nd-Pr carbonate is presented in the Table1.
Table 1: Analysis of powder, leach liquor and the dry cake of Nd-Pr carbonate obtained in Batch 1

1.09 L of the filtrate of Nd and Pr-free liquor was agitated with addition of 0.2 L of a solution of sodium hydroxide (30% w/v) at 95°C by maintaining a pH in the range of 1.8-2.2 for 6 hours to obtain an iron containing slurry. The iron containing slurry was filtered to get 0.95 L of an iron free liquor and 136 g of an iron cake. The analysis of Nd-Pr-free liquor, the iron cake and the filtrate (iron free liquor) is given in the Table 2.
Table 2: Analysis of Nd-Pr-free liquor, the iron cake and the iron free liquor obtained in Batch 1

10% v/v of bis(2,4,4-trimethylpentyl) phosphinic acid was prepared by diluting bis(2,4,4-trimethylpentyl) phosphinic acid with a diluent (such as Exxsol d-80) by 10 times the amount of the acid. Exxsol d-80 is a mineral oil distillate which essentially is an aliphatic hydrocarbon and an odorless solvent. The iron free liquor (0.95 L) was contacted with 10%v/v of bis(2,4,4-trimethylpentyl) phosphinic acid at organic to aqueous layer (O/A) ratio of 1:1 for 5 minutes to extract dysprosium. The loaded organic layer was stripped with the help of 0.1 L of sulphuric acid (10% v/v) at organic to aqueous layer (O/A) ratio of 1:1 with multiple contacts. The strip liquor was agitated with a solution of 0.1 L of sodium carbonate for 2 hours to precipitate dysprosium. The slurry was filtered and the obtained cake was washed and dried to get dysprosium carbonate (1.37 g). The analysis of the obtained raffinate, strip liquor, dysprosium carbonate is given in Table 3.
Table 3: Analysis of raffinate, strip liquor, dysprosium carbonate obtained in obtained in Batch 1

Batch 2
500 g of Nd-magnet scrap was demagnetized by roasting at a temperature of 500°C for 3 hours. The demagnetized material was ball milled after cooling. The ball milled material was passed through 100 mesh to get a powder. The powder was agitated with a solution of 5 L of 3 M of sulphuric acid and 0.25 L of H2O2 for 5 hours to obtain a leach liquor. Next, 5.4 L of the obtained leach liquor was agitated with a solution of 0.9 L of sodium carbonate (25% w/v) by maintaining a pH between 1.5-1.7 for 2 hours to precipitate Nd and Pr and to obtain a slurry. The obtained slurry was filtered to get 5.46 L of a filtrate and a wet cake of 477 g. The obtained wet cake was washed with water and dried to obtain a dry cake of dry Nd-Pr carbonate of 310 g. The analysis of powder and leach liquor and the dry cake of Nd-Pr carbonate is presented in Table 4.
Table 4: Analysis of powder and leach liquor and the dry cake of Nd-Pr carbonate obtained in Batch 2

Further, 5.48 L of Nd and Pr-free liquor was agitated with a solution of 1 L of sodium hydroxide (30 % w/v) at 95°C by maintaining a pH in a range of 1.8-2.2 for 6 hours to obtain an iron containing slurry. The obtained iron containing slurry was filtered to get an iron free liquor (4.7 L) and an iron cake (dry wt. 722 g). The analysis of Nd-Pr-free liquor, the iron cake and the iron free liquor are given in the Table 5.
Table 5: Analysis of Nd-Pr-free liquor, the iron cake and the iron free liquor obtained in Batch 2

The iron free liquor (4.7 L) was contacted with bis(2,4,4-trimethylpentyl) phosphinic acid (10% v/v obtained by diluting with Exxsol d-80 as a diluent) at O/A ratio of 1:1 for 5 minutes to extract dysprosium. The loaded organic was stripped with the help of a solution of 0.5 L of sulphuric acid (10%, v/v) at O/A ratio of 1:1 with multiple contacts. The strip liquor was agitated with a solution of 0.35 L of sodium carbonate (30% w/v) for 2 hours to precipitate dysprosium. The slurry was filtered and the cake was washed and dried to get dysprosium carbonate (7.35 g). The analysis of the obtained raffinate, strip liquor, dysprosium carbonate are given in the Table 6.
Table 6: Analysis of the raffinate, strip liquor and dysprosium carbonate obtained in Batch 2

Batch 3
1000 g of Nd-magnet scrap was demagnetized by roasting at a temperature of 500°C for 4 hours. The demagnetized material was ball milled after cooling. The ball milled material was passed through 100 mesh to get a powder. The powder was agitated with a solution of 10.5 L of 3 M of sulphuric acid and 0.5 L of H2O2 for 6 hours to obtain a leach liquor. Next, 10.5 L of the obtained leach liquor was agitated with a solution of 1.8 L of sodium carbonate (25% w/v) by maintaining a pH between 1.5-1.7 for 4 hours to precipitate Nd and Pr to obtain a slurry. The obtained slurry was filtered to get 11.2 L of a filtrate (Nd and Pr-free liquor) and a wet cake of 870 g. The wet cake was washed with water and dried (dry wt. of 565.5 g). The analysis of powder and leach liquor and the dry cake of Nd-Pr carbonate is presented in Table 7.
Table 7: Analysis of powder, leach liquor and the dry cake of Nd-Pr carbonate obtained in Batch 3

The Nd and Pr-free liquor (11.2L) was agitated with a solution of 2 L of sodium hydroxide (30 % w/v) at 95°C by maintaining a pH in a range of 1.8-2.2 for 6 hours to obtain an iron containing slurry. The obtained iron containing slurry was filtered to get an iron free liquor (9.45 L) and an iron cake (dry wt. 722g). The analysis of Nd-Pr-free liquor, the iron cake and the iron free liquor are given in the Table 8.
Table 8: Analysis of Nd-Pr-free liquor, the iron cake and the iron free liquor obtained in Batch 3

The iron free liquor (9.45 L) was contacted with bis(2,4,4-trimethylpentyl) phosphinic acid (10% v/v obtained by diluting with Exxsol d-80 as a diluent) at 1:1 O/A ratio of 1:1 for 5 minutes to extract dysprosium. The loaded organic was stripped with the help of sulphuric acid 1 L (10%, v/v) at O/A ratio of 1:1 with multiple contacts. The strip liquor was agitated with a solution of 0.7 L of sodium carbonate (30% w/v) for 2 hours to precipitate dysprosium. The slurry was filtered and the cake was washed and dried to get dysprosium carbonate (14 g). The analysis of the obtained raffinate, strip liquor, dysprosium carbonate are given in Table 9.
Table 9: Analysis of the raffinate, strip liquor and dysprosium carbonate obtained in Batch 3

Table 10: Percent (%) recovery and %purity of recovered rare earth elements obtained in Batch 1, 2 and 3
Batch No. % Recovery % Purity
Neodymium (Nd) Dysprosium (Dy) Neodymium carbonate Dysprosium carbonate
1 98.3 92 96.3 99.5
2 99 99 96.6 99.5
3 90.6 94.6 96.6 99.5

Therefore, the present invention provides a simple, easy to operate, environment friendly and commercially feasible method for recovery of rare earth elements and base metals from magnet scrap of electronic wastes.
Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
,CLAIMS:CLAIMS

We claim:
1. A method for recovery of rare earth elements and base metals from neodymium (Nd)-magnet scrap, comprising the steps of:
(a) demagnetizing Nd-magnet scrap by subjecting to heat treatment to obtain a demagnetized Nd-magnet scrap;
(b) ball milling the demagnetized Nd-magnet scrap for 1-3 hours to obtain a powder;
(c) agitating the powder obtained in step (b) at a pulp density of 10% with a leaching solution for 4-6 hours to obtain a leach liquor;
(d) adding a solution of a precipitating agent in a pH range under agitation for 2-4 hours to obtain a precipitate of neodymium (Nd) and praseodymium (Pr) and an iron containing filtrate;
(e) removing iron from the iron containing filtrate obtained in step (d) with the help of a solution of sodium hydroxide under agitation at a temperature range of 85-105? for 3-6 hours to obtain an iron free liquor;
(f) treating the iron free liquor obtained in step (e) with bis(2,4,4-trimethylpentyl) phosphinic acid with a contact duration of 3-6 minutes to obtain a dysprosium free solution and to selectively extract dysprosium;
(g) stripping out the selectively extracted dysprosium of step (f) with sulphuric acid (5-10% w/v) at an organic layer to aqueous layer (O/A) ratio of 1:1 with a contact duration of 3-6 minutes to obtain a stripped dysprosium; and
(h) treating the stripped dysprosium of step (g) with said solution of said precipitating agent for 2-4 hours at a pH range of 7-10 to obtain a precipitate of dysprosium,
wherein,
said method recovers 90.6-99% of rare earth elements with % purity ranging from of 96.3-99.5% by steps that include demagnetization by heat treatment, ball milling, leaching, precipitation and selective extraction.
2. The method as claimed in claim 1, wherein said method recovers 90.6% - 99% of neodymium (Nd) with % purity of 96.3-96.6% and recovers 92% - 99% of dysprosium (Dy) with % purity of 99.5%.
3. The method as claimed in claim 1, wherein said solution of said precipitating agent in step (d) and step (h) is a solution of 25% w/v sodium carbonate.
4. The method as claimed in claim 1, wherein said demagnetization in step (a) is performed at a temperature range of 400-600? for 1-4 hours to avoid Nd-magnet scrap from sticking over iron ball during the step of ball milling.
5. The method as claimed in claim 1, wherein said ball milling of the demagnetized Nd-magnet scrap is done to obtain said powder having a particle size ranging from 100 mesh to 200 mesh.
6. The method as claimed in claim 1, wherein said leaching solution in step (c) includes a solution of 2-4 M of sulphuric acid and 2-8% (w/v) of hydrogen peroxide (H2O2).
7. The method as claimed in claim 1, wherein said precipitate of Nd and Pr in step (d) is obtained by maintaining pH in a range of 1.5-2.5.
8. The method as claimed in claim 1, wherein said pH in step (e) is maintained at a range of 1.7-2.2.