FELD OF THE INVENTION
The present invention relates to a process for the recovery of gold metal from manually dismantled gold coated E-Waste. More specifically the process is related to recovery of gold from gold coated parts (pins) of the printed circuit boards (PCBs), which is used in all electronic products, are plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper PCBs.
BACKGROUND OF THE INVENTION
PCBs are plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper. After PCBs are etched and then copper is coated with solder, nickel/gold, or some other anti-corrosion coating because untreated copper oxidizes quickly.
Asia's largest and world's one of the biggest Alang / Sosiya Ship recycling Yard, 50 KM away from the city of BHAVNAGAR, has been generated significant amount of electronic wastes which is economically attractive because of presence of precious metals (PMs) like Gold, silver palladium and platinum.
Sodium or potassium Cyanide, the most dangerous reagent for the human life is commonly used for the recovery of gold from mines and gold plated electronic waste like connectors, fingers, jewellery and any other stuff which has gold polish on it. Aqua regia and reducing agent are commonly used for the recovery of gold from gold plated electronic waste like connectors; computer central processes units (CPUs), jewellery and any other stuff which has gold polish on it. Before aqua regia treatment, nitric acid is also used for recovery of gold from different kinds of gold plated connectors and pins. If the gold plated is thick and base metals (copper, iron, or nickel etc.) are present in it, gold could be extracted from a solution of hydrochloric acid using some ketone such as methyl butyl ketone, phosphate such as tributyi phosphate,
iPo^-.ttELHX i2-e^-2ex& 17:4.7-

alkyl amine, and long-chained ether such as diethyl glycol dibutyl ether (DBC) as extractant in industrial processes. The chemistry involved in such processes is reduction and oxidation of the metals in order to extract and bring them into solution.
Reference may be made to the US 6,164,571, wherein they have disclosed plastics of the printed circuit boards (PCB) was broken by heating at 150° C to about 300° C. under a pressure of 3.4x10 Pascals in the presence of 2-butanol as a solvent. The remaining undissolved fiberglass material and precious metal is removed by filtration, decanting or centrifugation. This patent is only related to the separation of plastic parts of the PCB.
Reference may be made to the WO2006013568 A2, wherein they have disclosed hydrometallurgical process for the extraction of non-ferrous precious metals originating from electronic waste, mineral earth, and mineral materials. In this patent, PCB was crushed in to powder and then treated with concentrated hydrohalogen acid containing a halogen salt of magnesium. Undigested solid after filtering the reaction mixture is mixed with an aqueous solution containing a strong acid Mg2X and with a strong oxidizing agent for the recovery of gold. All of the gold and a minor amount of palladium were recovered by precipitation through adjusting the pH to a range of about 2 to 4.
Reference may be made to the CM. Madelines et al, Hydrometallurgy, 35: (1994), wherein pressure leaching with cyanide ion was examined for recovery of silver, gold and palladium from precious metals containing scrap. The remarkable success of cyanide as lixiviate for gold is due to the enormous stability of the dicyanoaurate ion. However, the high concentration of copper in initial raw material might interfere with the selective recovery of silver, gold and palladium. In addition, in cyanide process, a substantial care is needed to prevent evolution of the hazardous HCN gas and destruction of the remaining cyanide in the waste solution
TPB- D:ELH:X 1 ^-82 - Z616 17: :■ 4.?

Reference may be made to the DD 253048 (1988), wherein they have disclosed the recovery of copper, gold, silver, palladium, tin and lead from electronic scrap that also includes plastics (e.g., connectors and printed circuits). The scrap is treated with a 30-50% HNOi solution at 35°C to yield metal nitrates in solution, solid gold and H2O; The solution is cooled, sulfates are added to water, forming a solution containing copper, palladium, silver, and the insoluble material (Au, Sn02 and H2SO4) is filtered off. The filter cake is melted with Na2C03 to yield gold metal.
Reference may be made to the US 4,997,532, wherein they have suggested a process based on treating precious metal-bearing scrap with a polar organic solvent where bromine is dissolved to form non-aqueous precious metals complexes. The organic solvent is subjected to electrolysis to recover the extracted metals. This process is not suitable for use with combined scraped metal second material. This is because of the high flash point of polar organic solvent at temperature 80-90°C which the optimal condition of platinum and rhodium dissolution in bromine/bromide system. Besides polar organic solvent so possess necessary selectivity in liquid- liquid extraction process by respective precious metals recovering from leaching solution, containing also copper, metal, iron, zinc, etc.
Reference may be made to the US 5,989,311, wherein they have disclosed a method for the recovery of various metals by combined use of nitrate and halogen salts in the presence of oxygen. In this technology copper and precious metals are extracted from their elemental states using bromine/bromide or iodine/iodide plus sodium nitrate and oxygen. At the same time, the halogen ions, such as bromide or iodide, and nitrogen oxide generated from the pressure leading process are continuously converted from respectively, to bromide or iodide and to nitrate, which are the major reagents for the production of copper and gold ions in the leaching solution. However pressure leaching is expensive and can render the process complicated with respect to materials and handling.
:PO. D.ELttX- 12 - e2: - 2B-18 IT : 47

Other methods for recovering gold, silver and platinum group metals consist of oxidation and lixiviation of the precious metals by liquid solvents such as hydrochloric acid and hydrogen peroxide mixtures, acid chlorine solutions, and hyper chlorite. These methods yield low recovery rates and are only useful for specific source materials. They also require sophisticated machinery and the process themselves are very time-consuming, and require large amounts of energy.
According to the prior art, the chemistry involved in such processes is reduction and oxidation of the metals in order to extract them and bring them into solution. Metal recovery from E-Waste are the mechanically dismantles of metals parts and then recovery and separation of metals by hydrometallurgical or pyrometallurgical routes. Pyrometallurgical routes generate hazardous gas depend on the quantities and types of E-waste and can be economical and eco-efficient if the hazardous emissions are controlled. Pyrometallurgical route is initially used for reduce the E-waste and followed by hydrometallurgical route for leaching of metals and then electrometallurgical processing for the recovery of pure metals. The main steps in hydrometallurgical processing consist of a series of acid or caustic alkali treatment of finely divided solid material. The solutions are then subjected to separation procedures such as electrowinning, solvent extraction, precipitation, cementation, ion exchange, filtration and distillation to isolate and concentrate the metals of interest. All these processes suffer from high reagent consumption corrosion problems and the need for scrubbing emitted hazardous gases.
In the present invention, E-waste is obtained from the Alang / Sosiya ship recycling Yard which is 50 KM away from the city of Bhavnagar, which has been generating significant amount of electronic wastes. E-waste comprises of metals of gold, iron, nickel, copper and tungsten.
XPQt. BBLM X 1 2 - 0-2 - 2e IS 17 : 47

Each radio room of the ship has ~250Kg E-waste (75Kg precious metals like silver, gold, palladium and platinum, % of the precious metals varied for each ship). Most of the people working for metal recovery are doing job work using aqua regia for the recovery of gold from E-Waste. The gold containing electronic waste from Alang contains more corrosive resistive metal/alloys, which require highly corrosive mineral acid to separate precious metal from other metals.
OBJECTS OF THE INVENTION
The main objective of the invention is to provide a process for the recovery of gold metal from manually dismantled gold coated E-waste.
Another objective of the invention is to recover gold from E-Waste available from Asia's largest Ship recycling Yard at Alang.
Yet another objective of the invention is to provide a process for the recovery of gold metal from manually dismantled E-Waste, which obviates the drawbacks as detailed above.
Still another objective of the present invention is to provide a batch scale process for the recovery of gold from gold coated pins of the PCBs especially gold is coated on copper.
Yet another objective of the present invention is to provide the process for the recovery of gold from computer central processes units (CPUs).
Still yet another objective of the present invention is to provide a process for enabling 100% recovery of gold with more than 99% purity.
IFO Q-ELBI, .1 2 - 8-2. - 28.16 1,7 : 47

Still another objective of the present invention is to generate in situ hypochlorous acid as potential leachnat for the recovery of highly corrosive metal like nickel, iron and nickel alloy.
Yet another objective of the present invention is to separate out iron as iron alkoxide with high purity.
SUMMARY OF THE PRESENT INVENTION
Accordingly, the present invention provide a process for the recovery of gold metal from manually dismantled gold coated E-Waste, said process comprises the steps of:
i. manually separating gold coated parts of E-Waste and digesting in
acetic acid with sodium chloride and hydrogen peroxide at a temperature in the range of range of 60-85°C for a period in the range of 20-30 h under constant stirring (400 rpm) in container fitted with a mechanical stirrer, a temperature sensor and a refluxing condenser,
ii. separating the gold particles/ flakes on the surface of reaction mixture
of step i) by filtration,
iii. optionally recovering other metals Fe, Ni, W and Cu as their acetates
by filtration from the reaction mixture of step i).
In an embodiment of the invention, the E-waste is pins, parts or central processing
units of gold coated part of printed circuit boards (PCBs) or transistor.
In another embodiment of the invention, the E-waste comprises of metals of copper,
gold, nickel, iron and tungsten.
In still another embodiment of the invention, the volume ratio of acetic acid to
hydrogen peroxide is in the range of 1:1 or 1:2.
In yet another embodiment of the invention, the weight/volume ratio of E-waste to
acetic acid is in the range of 1:0.7 to 1:2.
XPO. eELHX 12. - aZ - 2.0.16.-' 1 7 "4.7

In still another embodiment of the invention, the weight ratio of E-waste to sodium chloride is in the range of 1:0.024 to 1:0.045.
In yet another embodiment of the invention, the reaction temperature is 75°C. In still another embodiment of the invention, the recovery and purity of gold is >99.5%.
In yet another embodiment of the invention, the combination of acetic acid, hydrogen peroxide and sodium chloride produce in situ hypochlorus acid which is responsible for leaching of corrosive resistive metal like nickel/nickel-iron/nickel-copper/copper-tungsten.
The present invention provides a process for the recovery of gold from spent E-Waste or PCBs, specifically the process concerns with the recovery of Gold from manually dismantled gold coated pins and CPU of PCBs. lOOg pins were digested with acetic acid (1:2 solid to acid wt ratio) and NaCl (1:0.0125 acid to salt mole ratio) in two neck round bottom flask (250 ml) fitted with condenser and calculated amount of H2O2 (1:1 acid to H2O2 mole ratio) were added slowly and then reaction mixture was kept at 80 °C for the recovery of Gold for 24h. Small amount of copper metals were dissolved and were separated by simple filtration. Gold particles were separated by simply pouring and then by filtration. Recovery and purity of gold was found >99.5%, was confirmed by ICP-OES analysis.
BRIEF DESCRIPTION OF FIGURES
Fig 1: Process flow diagram for gold recovery from E-Waste
Fig 2: Process flow diagram for gold recovery from transistor
Fig 3: UV spectrum of hypocholorus acid( CH3COOH (98%)+NaCI + H2O2(50%))
8
XPO; DEL.H1. 1Z - Q 2: - ZQle 17:47'

DETAILED DESCRIPTION OF THE INVENTION
Experimental details for the recovery of gold at laboratory scale with optimized condition are summarized below.
lOOg manually separated gold coated part of printed circuit boards (PCBs) was digested in lOOmL of organic acid like acetic acid, chloro- and dichloro-acetic acid etc., in the presence of hydrogen peroxide (lOOmL) at room temperate. After stipulated time the reaction mixture was analyzed by ICP-OES analysis with proper dilution. Only 1% metals were dissolved except gold when acetic acid used as a reactant cum solvent. Negligible amount of metals were dissolved in chloroacetic acid, and dichloroacetic. It was conformed form the above experimental that acetic acid is a best solvent for the gold recovery, further experiment was done at different (50, 75 and 100 °C) using acetic acid. lOOg manually separated gold coated part of PCBs in organic acid were digest at 50, 75 and 100 °C in the presence of hydrogen peroxide (lOOmL). Maximum metal leaching efficiency (4%) was observed at 75 °C. No leaching of gold was observed in the solution. No further leaching efficiency was observed at higher temperature. It was conformed form the above experimental that 75 °C is a best temperature for the gold recovery, further experiment was done with sodium chloride (Ig). lOOg manually separated gold coated part of printed circuit boards (PCBs) was digested in acetic acid (lOOmL) with sodium chloride (Ig) and hydrogen peroxide(lOOmL) at room temperate. Reaction mixture was further kept at 75 °C for 24h under constant stirring (400rpm). Gold particles/ flakes were separated on the surface of reaction mixture as shown in Figure 1. 0.4g of gold particles is recovered using above method. Recovery and purity of gold was found >99.5%, confirmed by ICP-OES analysis.
Above experiment was repeated in the absence of acetic acid also. No metals were dissolved in the reaction mixture. No gold particles were separated from the reaction mixture.
:F0^ OELBX 12 - QZ- ZBIS 1.7 : 47

Above experiment was repeated for the recovery from computer processor of mother board (CPB) of the PCB.. 23.4g CPU was digested in acetic acid (lOOmL) with sodium chloride (Ig) and hydrogen peroxide (lOOmL) at room temperate. Reaction mixture was further kept at 75 °C for 24h under constant stirring (400rpm). 78mg of gold was recovered as metallic gold flakes by simple filtration, and 9.4g of (59.46% Fe, 37.93% Ni, 2.06% W and 0.05% Cu present as their acetates. Recovery and purity of gold was found >99.5%), was confirmed by ICP-OES analysis.
Above experiment was repeated for the manually dismantle transistor for Gold recovery. 1.5g GOLD withlOO% purity was recovered and characterized by Powder-XRD pattern (Fig 3).
The present invention provides a process for the recovery of gold metal coated on the copper metal in PCBs, said process comprising:
a) lOOg pins were digested with acetic acid (200ml) and NaCl (2.4g) in two neck round bottom flask (1000 ml) fitted with condenser and calculated amount of H2O2 (50%) (1:1 acid to H2O2 mole ratio) were added slowly and then reaction mixture was kept at 80 °C for the recovery of Gold for 5 to 8h.
b) About 17 wt % of copper and nickel metals were dissolved and were separated by simple filtration.
c) gold particles were separated by simply decantation (pouring) and then by filtration.
d) recovery and purity of gold was found >99.5%, was confirmed by ICP-OES analysis.
In an embodiment, the invention provides a process for the recovery of gold using organic acid particularly, acetic acid or substituted acetic acid, mere particularly acetic acid
10
IP a. B.BLM1 12-8 2.-201.6 1/ : 47

Another embodiment of the invention is, -17 wt % copper and nickel is dissolved from I50g gold coated pins except gold
Another embodiment of the present invention is dissolution of substantial amount of Cu, W, Ni and other metals when di- and tri-chloro acetic acid is used as a leachant with sodium chloride and hydrogen peroxide.
Another embodiment of the present invention is the maximum separation of gold in acetic acid, hydrogen peroxide and sodium chloride.
Another embodiment of the present invention is, to provide a batch scale process for enabling > 97% recovery of gold with more than 99% purity.
Another embodiment, recovery and purity of gold was found >99.5%) (confirmed by ICP-OES analysis).
Yet another embodiment of the present invention is that the same protocol is applicable for the recovery of 99% gold from computer processor of mother board (CPB)
Typical Metal analysis of gold coated pins*
Metal Wt.%
Cu ' 99^
Ni 0.1
Au 0.6
*Total metal content in one kg E-waste is ~ 13% by weight
11

a B-ELB X i 2^ - Q--2 - 2 0 16: 1

Novelty and inventive steps
In this work insitu formation of hypochlorous acid is used as a leachant for the recovery of gold from highly corrosive resistive metal like nickel, tungsten, iron and nickel alloy, iron-nickel-tungsten alloy of the E-Waste.
The formation of hypochlorus acid is confirmed by UV-Vis spectra (fig 4).
Inventive steps are,
a) Use of acetic acid as leaching solvent in combination with sodium chloride and hydrogen peroxide
b) Insitu formation of hypochlorus acid as an active leaching reagent
c) recovery of gold flaks by simply decantation
The Following examples are given by of illustration and therefore should not be constructed to limit the scope of the present invention.
Example 1
lOOg of manually separated gold coated pins from printed circuit board (PCB) was digested in 200 mL acetic with 200 mL hydrogen peroxide and 2.4g sodium chloride.. After 5h the reaction mixture was analyzed by ICP-OES. Only 1% metals were dissolved except gold. 630 mg of gold was recovery
Example 2
lOOg of manually separated gold coated pins from printed circuit board (PCB) was digested in 200 mL chloroacetic acid or dichloroacetic with 200 mL hydrogen peroxide and 2.4g sodium chloride.. After 5h the reaction mixture was analyzed by
12
19 O. D-ELH-X 12-" Q^2. - ZG 1S 17 ■. 47

ICP-OES. Only 1% metals were dissolved except gold. Negligible amount of metals were dissolved in chloroacetic or dichloroacetic acid and gold is not separated out.
Example 3
Example 1 was repeated without adding NaCl. No leaching of gold was observed in the solution.
Example 4
Example 1 was repeated at different reaction temperatures. lOOg manually separated gold coated part of PCBs in acetic acid (200 mL) were digested at 50, 75 and 100 °C in the presence of hydrogen peroxide (240 mL) and NaCl (2.4 g). Maximum metal leaching efficiency (16%) was observed at 75 °C. No separation of gold was observed at 50 °C.
Example 5
150 g manually separated gold coated part of printed circuit boards (PCBs) was digested in acetic acid (300mL) with sodium chloride (3.6g) and 300 mL hydrogen peroxide at 75 °C for 8h under constant stirring (400rpm). Gold particles/ flakes were separated on the surface of reaction mixture as shown in Figure 1. 860 milligram of gold particles is recovered. Recovery and purity of gold was found >99.5%, confirmed by ICP-OES analysis.
13

Tl

IE LHX 12-82-2 0 16 1.1 :

Example 6
Example 1 was repeated in the absence of acetic acid. lOOg manually separated gold coated part of printed circuit boards (PCBs) was taken in the round bottom flask having stirring and heating facility. To this was added sodium chloride (2.4 g) and hydrogen peroxide (200 mL) at 75 °C for 24h under constant stirring (400rpm). No dissolution of metals was observed and also no gold particles were separated from the reaction mixture.
Example 7
Example 1 was repeated for the recovery of gold from computer processor of mother board (CPB) of the PCB. 23.4g CPU was digested in acetic acid (70 mL) with'sodium chloride (Ig) and hydrogen peroxide (70 mL) at 75 °C for 8 h under constant stirring (400rpm). Negligible flaks of gold were separated as metallic gold flakes. Also negligible amount of other metals were digested.
Example 8
Example 7 was repeated for the recovery of gold from computer processor of mother board (CPB) of the PCB. 23.4g CPU was digested in acetic acid (70 mL) with sodium chloride (Ig) and hydrogen peroxide (70 mL) at 75 °C for 24 h under constant stirring (400rpm). 78 mg of gold was recovered as metallic gold flakes by simple filtration, and 9.4g of other metals (59.46% Fe, 37.93% Ni, 2.06%o W and 0.05% Cu present as their acetates) were digested. Recovery and purity of gold was >99.5%), was confirmed.by ICP-OES analysis
Example 9
Example 8 was repeated for the manually dismantle transistor for Gold recovery.
lOOg transistors were digested in acetic acid (lOOmL) with sodium chloride (2.4g)
14
feELHX 1,2- 02 - 2e.l,S 17 : 47

and hydrogen peroxide (240 mL) at 75 °C for 24h under constant stirring (400rpm). 630 mg of gold was recovered as metallic gold flakes by simple filtration. The purity of gold was >99.5%, as confirmed by ICP-OES analysis
Advantages of the invention
1. Sodium or potassium Cyanide, the most poisonous reagent commonly used for the recovery of gold from mines and gold plated electronic waste like connectors, fingers, jewellery and any other stuff which has gold polish on it for the human life are not used in the this invention.
2. Aqua regia or nitric acid commonly used for the recovery of gold from gold plated electronic waste like connectors; computer processor of mother board (CPB), jewellery and any other stuff are not used in this invention
3. The process involved in the invention is use of organic acid and oxidizing agent which are less hazardous.
4. In situ generated hypochlorus acid have been effectively employed for the recovery of gold from many types of E-waste

We Claim:
1. A process for the recovery of gold metal from manually dismantled gold
coated E-Waste, said process comprises the steps of:
i. manually separating gold coated parts of E-Waste and digesting in
acetic acid with sodium chloride and hydrogen peroxide at a
temperature in the range of range of 60-85°C for a period in the range
of 20-30 h under constant stirring (400 rpm) in container fitted with a
mechanical stirrer, a temperature sensor and a refluxing condenser,
ii. separating the gold particles/ flakes on the surface of reaction mixture
of step i) by filtration,
iii. optionally recovering other metals Fe, Ni, W and Cu as their acetates
by filtration from the reaction mixture of step i).
2. The process as claimed in claim 1, wherein the E-waste is pins, parts or central processing units of gold coated part of printed circuit boards (PCBs) or transistor.
3. The process as claimed in claim 1, wherein E-waste comprises of metals of copper, gold, nickel, iron and tungsten.
4. The process as claimed in claim 1, wherein volume ratio of acetic acid to hydrogen peroxide is in the range of 1:1 or 1:2.
5. The process as claimed in claim 1, wherein the weight/volume ratio of E-waste to acetic acid is in the range of 1:0.7 to 1:2.
6. The process as claimed in claim 1, wherein weight ratio of E-waste to sodium chloride is in the range of 1:0.024 to 1:0.045.
7. The process as claimed in claim 1, wherein the reaction temperature is 75°C.
8. The process as claimed in claim 1, wherein the recovery and purity of gold is
>99.5%.
16

9. The process claimed in claim 1, wherein combination of acetic acid, hydrogen peroxide and sodium chloride produce in situ hypochlorus acid which is responsible for leaching of corrosive resistive metal like nickel/nickel-iron/nickel-copper/copper-tungsten.