FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(see section 10 and rule 13)
A PROCESS FOR DISLODGING METAL FROM A MATRIX CONTAINING THE METAL
RELIANCE INDUSTRIES LIMITED
an Indian Company of 3rd Floor, Maker Chamber-IV, 222, Nariman Point, Mumbai-400021,
Maharashtra, India.
- THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE DISCLOSURE:
The present disclosure relates to a process for dislodging metals from a solid matrix. More particularly, the present disclosure relates to a process for dislodging silver metal from a silver containing catalyst.
BACKGROUND:
Catalysts find their profound use in majority of chemical reactions. The large scale use of catalysts at industrial scale puts enormous pressure on the industries to explore methods which are economically and environmentally viable for the disposal of spent catalysts. Among diverse range of catalysts available the disposal of metal containing spent catalysts is very crucial as this requires the recovery/extraction of precious metals from the spent catalysts prior to their disposal. One such catalyst is a silver based heterogeneous catalyst being extensively used in the conversion of ethylene to ethylene oxide. The global consumption of silver based heterogeneous catalysts is estimated to be around 12 million tons per year. Over a period of time, progressive generations of silver based catalysts have been developed with varying activity and selectivity. The sheer scale of use of such silver leads to tons of spent catalyst ready for disposal. The excessive high cost of silver, its sparse availability and growing concerns for the environment protection precludes disposal of. deactivated catalysts without complete recovery of silver.
EXISTING KNOWLEDGE:
Over the past few decades, extensive efforts have been devoted to provide an efficient and economically viable method for recovering silver from various sources. However, there is no universal method practiced for recovering silver from various sources. Among different methods explored hitherto for recovering silver metal from spent solid catalysts the wet chemical method is the most viable method. The wet chemical method includes leaching of silver metal from spent catalysts using concentrated nitric acid at elevated temperature. However, the strong acidic conditions and elevated

temperature cause serious operational hazards and threats to the environment and are therefore not very suitable for large scale industries.
Further to the conventional methods, the use of ultrasound sonication is becoming increasingly popular in order to provide an excellent alternative to the existing wet chemical processes which is comparatively safe and green in nature, for example, a process for leaching silver from solid waste using ultrasound assisted thiourea method as disclosed by M. Salim Oncel and his co-workers in Ultrasonic Sonochemistry 12 (2005) 237-242. The authors have selected eight process variables and monitored silver extraction from solid waste collected from silver ore processing plant. Around 98.6 % leaching of silver from 100 g/L pulp density is reported when silver containing solid waste is treated with a solution containing 7.4 g/L thiourea and 28.7 g/L H2SO4 for 24 min at 77 °C. At the particle size of 55 urn, the solid waste materials are reported to demonstrate excellent extraction efficiency. Further, the extraction efficiency decreases with increase in particle size of the solid waste. Thiourea assisted leaching of precious metals such as gold and silver from ores has several advantages when compared with the conventional cyanidation process. However, this process needs high temperature condition and considerable longer time to extract silver from the finely ground waste sample.
Also disclosed is a process for recovering metals such as Cu and Fe from Printed Circuit Board (PCB) waste sludge by using ultrasound sonication energy (see "Evaluation of Industrial Application", Fengchun Xie, Tingling Cai, Yang Ma, Haiying Li, Chuncheng Li, Zhiyuan Huang and Gaoqing Yuan, Journal of Cleaner Production 17 (2009) 1494-1498). The leaching experiment is carried out at low pH for about 60 minutes in the presence of ultrasound sonication energy. The use of ultrasound sonication energy provides high separation and high recovery efficiency without any diverse effect on environment. With the PCB waste sludge containing 3.14-4.85% copper and 3.71-4.23% iron, the recovery of copper and iron is reported to be around 97.83% and 98.5 %, respectively. The purity of recovered copper product

is reported to be around 98.0%. The recovered iron product possesses quality for using as a coagulant material for the plant on-site wastewater treatment.
In the category of solid waste materials, recovery of silver from scrap of plasma TV is also reported by A. Hoshino et.al (See Proceeding of International conference on Environmental aspects of Bangladesh (ICEAB10), Japan, Sept. 2010). The silver metal from the scrap of plasma TV is recovered by using an acidothiourea solution containing 0.05 M H2SO4 and 0.05 M thiourea. The silver contained in the extracted solution is then coagulated and precipitated by using persimmon tannin extract and cationic cellulose reagents. By virtue of said method, 100 % recovery of silver from the scrap of Plasma TV is reported. The major disadvantage allied with this process is the requirement of powdering the silver containing waste in order to achieve maximum extraction. The powdering of scrape Plasma TV demands an additional energy intensive step. Also the leaching time as disclosed in the aforementioned process is 4h.
Further, a method of recovering silver from discarded plasma display panels is reported by Pan Xiaoyong et al. (See Third International Conference on Digital Manufacturing & Automation, 2012). In the aforementioned publication, the plasma display panels are first broken into pieces of about 5-10 cm and then treated with a nitric acid solution. Both, conventional mechanical mixing and ultrasound sonication is used to dissolve silver in the nitric acid solution. The extraction of silver metal when carried out using mechanical mixing alone requires 2-days for complete extraction of silver whereas the presence of ultrasound sonication reduces the extraction time to 80 minutes. The extraction is further reduced to 20 minutes by increasing the concentration of nitric acid solution from 7 % to 15 %. The aforementioned publication further discloses that for commercial viability the required acid concentration is 25 % for achieving high extraction efficiency. The amount of extracted silver is < 0.3 %. The major disadvantage allied with the aforementioned

process is the longer reaction time and low recovery of silver at low acid strength.

United States Patent Document 6585826 discloses a method of removing residual contamination including metal nitride particles from semiconductor wafer surfaces by subjecting the wafer surface to mechanical brushing and using a carboxylic acid containing cleaning solution and sonic energy.
K.M. Swamy and co-worker have studied the effect of dual-frequency ultrasound on leaching process intensification (see Ultrason Sonochem. 2001 Oct; 8(4):341-6. The authors have established the positive influence of ultrasound on copper recovery from oxide ores in an ammonical media. The process parameters in a conventional agitation method are optimized and a maximum recovery of approximately 32% in 20 min is obtained without sonication. The recovery is increased to approximately 78% by the application of ultrasound over the same period. Further, the leaching process is intensified by studying the metal recovery variation at different ultrasonic frequencies (20, 40, 43 and 720 kHz) and intensities (up to 8 W cm-2) with sonication time. The results show that sinusoidal ultrasound even at larger intensity has some limitations with single frequency. However, simultaneous application of dual frequency 20 and 40 kHz ultrasound enhanced extraction rates along with increased yield.
Further to recovering silver metal from solid wastes by using ultrasound sonication assisted leaching process, the use of ultrasound sonication is also reported for the recovery of metals from solid materials other than the solid wastes such as spent catalysts, catalyst carriers and the like. For example, United States Patent Document 8287618 discloses a process for recovering Mo, V, Ni, Co and Al from spent hydroprocessing catalysts using ultrasound sonication assisted leaching with EDTA solution. The process as disclosed in the aforementioned US patent involves number of steps, for example, deoiling, decoking, washing, dissolving, complexing agent treatment, acid treatment, solvent extraction and the like. The aforementioned patent application further discloses that the process steps are reduced by using ultrasonic agitation in the presence of EDTA at elevated temperature. The process as disclosed in the aforementioned US patent, however, requires size of spent catalyst particles less than 500 microns.

Further, United States Patent Application 2011/0028306 discloses a process for recovering one or more precious metals from used and defective catalytic carriers by treating the carrier with a mixture of acids, such as sulfuric acid, hydrochloric acid and nitric acid. The aforementioned US patent application is, however, silent on the use of ultrasound sonication energy to facilitate the extraction of metals from the catalyst carrier.
Similarly, United States Patent Application 2008/0282843 discloses a process for removal of catalytic coating material from spent, defective or unused metal support catalytic converters. In the process as disclosed in the aforementioned US patent application the catalytic material which is coated on a metal support is removed by using ultrasound energy. The ultrasound sonication assisted dislodging of the catalytic material is accomplished by using nitric acid solution at elevated temperature.
From the foregoing disclosure of the prior-art it is evident that the use of ultrasound sonication in the recovery of precious metals such as silver from various solid wastes is explored by number of research groups. Also, the use of ultrasound sonication for recovering metals from solid materials other than the solid waste such as catalysts and the catalytic carrier is also reported. However, the metals recovered from the solid catalyst or the solid catalyst carriers are Mo, V, Ni, Co and Al. The difficulty in dislodging metal from the solid materials is largely governed by bonding between metal and matrix. Generally, it is difficult to dislodge a metal attached with the matrix by means of chemical'bonds as compared to physical bonds. Thus, the process used effectively for dislodging physically bonded metal may not be equally effective for dislodging chemically bonded metal. Besides that when solid matrix is contaminated with undesired depositions such as spent catalyst surface, the process parameters are also needed to engineer for precise removal of desired component.
Therefore, there is strongly felt a need to provide a process for dislodging metals from a solid matrix wherein dislodging of the metals which are strongly bonded with the surface of the solid matrix is accomplished under conditions which are comparatively

milder than the conventionally known conditions and wherein the process is safe, green, highly efficient, economical and provides recovered metals with high purity and in high yield.
OBJECTS:
Some of the objects of the present disclosure are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a highly efficient and environmentally benign process for dislodging metals from a matrix, particularly silver from a solid catalyst.
Still another object of the present disclosure is to provide a process for dislodging metals from a matrix, particularly silver from a solid catalyst wherein the process is simple, efficient, time saving and requires very mild reaction conditions as compared to existing wet chemical processes.
Yet another object of the present disclosure is to provide a process for dislodging metals from a matrix, particularly silver from a solid catalyst that provides dislodged metal in high yield and with high purity.
Other objects and advantages of the present invention will be more apparent from the following description, which is not intended to limit the scope of the present invention.

SUMMARY
In accordance with the present disclosure, there is provided a process for dislodging metal from a matrix containing metal, said process comprising contacting said matrix with a dilute acid having concentration of at least 0.5N in the presence of sonic energy at a temperature ranging between 10 and 50 °C for a period ranging between 4 and 15 minutes to obtain the metal into a solution.
Typically, the process for dislodging metal from a matrix containing metal further comprises the steps of: i. adding an alkali halide to the solution to precipitate said metal in the form of
metal halide; ii. separating, washing and drying the metal halide precipitate; and iii. smelting said precipitate to recover metal in pure form.
Typically, the metal is Group IB metal.
Preferably, the metal is silver.
Typically, the matrix is a silver metal catalyst.
Preferably, the matrix is a spent silver metal catalyst.
Typically, the metal is chemically bonded to the matrix.
Typically, the matrix is contacted with the dilute acid and the sonic energy for a time period varying between 4 and 15 minutes.
Typically, the dilute acid is a nitric acid solution having concentration in the range of 0.5 N to 2.5 N.

Typically, the sonic energy is supplied by using a sonic energy source that supplies sonic energy at a frequency varying between 5 to 30 KHz.
Typically, the dilute nitric acid is recycled for silver dislodging.
Typically, the alkali halide is selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide and combinations thereof.
Preferably, the alkali halide is silver halide.
Typically, the smelting of the metal halide precipitate comprises heating said precipitate mixed with sodium carbonate and borax in a furnace at a temperature varying between 950°C and 1150°C.
Typically, the silver metal recovered in process step (iii) comprises purity >99.9% without additional purification step.
DETAILED DESCRIPTION:
Accordingly, the disadvantages allied with the above described prior-art and other .. . related prior-art references, such as, use of highly acidic medium at elevated temperature and considerably prolonged reaction time which causes serious operational hazards and threat to the surrounding environment, are overcome in the present disclosure by providing a method for recoveringdislodging metals from a solid matrix which comprises the use of a considerably mild acid medium and an ultrasound sonication energy to extract metals from a solid matrix containing said metals.
The process for dislodging metals from a solid matrix, according to the present disclosure, is particularly a process for dislodging silver from a solid matrix. The solid

matrix, according to the process of the present disclosure, is a silver containing catalyst and is used for the oxidation of ethylene to ethylene oxide.
The silver containing catalyst employed in the process of the present disclosure may be unused catalyst or a spent catalyst. In accordance with one of the embodiments of the present disclosure, the silver containing catalyst is a spent catalyst.
As described earlier that in silver containing catalysts the silver metal is deposited on the surface of the catalyst support and inside the pores of the supports by strong chemical bonds. The deposited silver metal demonstrates strong solid-solid interaction with the support, for example, alumina and the like. Due to the strong chemical interaction between the silver and the support, the deposited silver metal demonstrates excellent stability and does not leach out easily during the high temperature and pressure conditions of catalytic reactions. Further, during the course of catalytic reaction, an extraneous deposition occurs on the surface of the catalysts. Therefore, recovery of silver metal from the spent catalyst under conditions which are reported in the related prior-art is not feasible.
In accordance with one of the embodiments of the present disclosure, the silver containing catalyst is treated with a diluted acid and sonic energy under predetermined reaction conditions to dislodge silver metal into a solution. Treatment of the catalyst is typically accomplished at ambient temperature and for a time period varying between 4 and 6 minutes. The sonic energy is supplied by using an ultrasound energy source that supplies sonic energy at a frequency ranging between 10 KHz to 20 KHz.
The acid employed in the process of the present disclosure is typically a dilute nitric acid solution having concentration of at least 0.5 N. In accordance with one of the embodiments of the present disclosure, the strength of the nitric acid solution is advantageously optimized in the range varying between 0.5 N and 2.5 N to satisfy

both the metal dislodging efficiency and the working conditions for the reaction container.
To the obtained solution comprising dislodged silver metal, an alkali halide is added to precipitate silver in the form of silver halide. The alkali halide is added in an amount sufficient to completely precipitate the silver from the extracted solution. The alkali halide useful for the process of the present disclosure is sodium chloride. The silver halide precipitate is then separated from the solution, washed and dried.
The process according to the present disclosure further comprises a method step of recovering silver from the silver halide precipitate. The silver from the silver halide precipitate is recovered by smelting the precipitate. For smelting, the dried silver halide precipitate is thoroughly mixed with a mixture of sodium carbonate and borax, and heated in a furnace at a temperature varying between 950°C and 1150°C to recover silver in pure form.
The purity measurement of the recovered silver is carried out as follows: The recovered silver metal after washing with water is dried and a small portion is drilled to take 0.2 g metal. 0.2 g of silver metal is then dissolved in dilute nitric acid on hot plate and after complete dissolution the contents are transferred quantitatively in 100 ml volumetric flask. Afterwards, the total volume (100 ml) is made" up with milliQ water. The presence of various elements is then estimated by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). The probable impurities likely to be present in the recovered silver are Au, Cu, Te, Fe, Pb, Na, B and Re. The purity of recovered silver is computed by subtracting total impurity from 100% silver. The purity of silver metal recovered from the solid spent catalyst in accordance with the process of the present disclosure is estimated >99.9 %.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer

or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to -facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
Example-1
12.5 gm of spent ethylene oxide catalyst containing 2.0 gm of silver was collected from industrial plant and was used without any treatment. This catalyst was placed in a 150 ml glass reactor and dipped in a mineral acid solution, for example HC1, HN03 and H2SO4. The strength of the mineral acid solution was 10%. The spent catalyst to mineral acid solution ratio was 1:4. Afterwards, an ultrasound sonication energy source (sonotrode) with sonication power of 50 % (supplying sonic energy at a frequency of 20Hz) was dipped in the mineral acid solution for 5 minute to gain

maximum dislodging of silver into the solution. At the end of run, the solution was filtered and the concentration of the dislodged silver metal was analyzed by argentometric titration. The silver metal dislodging percentage was 1.14 % to 99.5 %.
Example-2:
This example describes a process for dislodging silver metal from the spent ethylene oxide catalyst similar to the process of example-1, except the use of mineral acid solutions of varying strength. The experiments were accomplished by employing nitric acid solutions having concentrations varying from 5 % to 50 %. The silver metal dislodging percentage was 63 % to 99.8 %.
Example-3:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was carried out similar to the process of example-1, except the time of ultrasonication exposure. The sonication time was varied from 1 to 10 minutes. At the end of run, the silver metal dislodging percentage was 96 % to 99.7 %.
Example-4:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was ' carried out similar to the process of example-1, except for the sonication intensity. The sonication power was varied between 0 % and 50 %. The silver metal dislodging percentage was 1.33 % to 99.8 %.
Example-5:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was carried out in accordance with the process of example-1, except for the catalyst to mineral acid solution ratio. The catalyst to mineral acid solution ratio was varied from 1:2 to 1:8. The silver metal dislodging percentage was 60.3% to 99.9 %

Example-6:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was carried out in accordance with the process of example-1 except for the reactor geometry. The experiment was carried out using glass reactors of varying size. The glass reactors of size varying from 150 to 600 ml at optimum ratio of catalyst to mineral acid solution were used in this process. The silver metal dislodging percentage at the varying size of the glass reactor was 4 % to 99.5 %.
Example 7:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was carried out similar to the process of example-1, except for the weight of the spent ethylene oxide catalyst. The catalyst quantity was increased from 10 g to 100 g using appropriate reactor size. The catalyst to mineral acid solution ratio was 1:4. An ultrasound sonication energy source with sonication power of 50% was used for 10 min. The silver metal dislodging percentage was >97%.
Example-8:
In this example, dislodging of silver metal from the spent ethylene oxide catalyst was carried out in accordance with the process of example-1, except the nature of the mineral acid solutions used. In a first run, a first batch of spent ethylene oxide catalyst is contacted with a fresh nitric acid solution. After completion of the metal dislodging, the obtained solution containing the dislodged silver was used in a second run for dislodging of silver from a second batch of spent ethylene oxide catalyst of same weight. The catalyst to mineral acid solution ratio of 1:4 was maintained in the second run by makeup with fresh nitric acid. The solution obtained in the second run was collected and again used in a third run for dislodging of silver from a third batch of spent ethylene oxide catalyst of same weight under similar conditions. At the end of the third dislodging experiment, the obtained solution was filtered and the silver metal dislodging percentage was computed through argentometric titration. The collective

silver metal dislodging percentage was 99.1 % to 99.6 % with reduction in nitric acid solution consumption.
Example-9:
This example described a process for recovering silver from the solution comprising the dislodged silver obtained in accordance with the processes of examples 1-9.
The solution containing the dislodged silver metal was treated with sodium chloride to obtain silver chloride precipitate. The obtained precipitate was filtered, washed and dried. The silver halide precipitates was then mixed with a flux comprising a mixture of sodium carbonate and borax in a graphite crucible for isolation and purification. The graphite crucible was then heated in furnace at a temperature ranging from 980 °C to 1050°C for lh. Afterwards, the obtained melt was poured into an iron mold. After cooling, the recovered silver is separated and washed with water. Silver purity is measured through impurity testing by ICP-OES. The recovery of silver metal was 99.4 % to 99.6 % with >99.9 % purity.
Example-10:
A known amount of spent platinum catalyst containing platinum supported on alumina or refractory oxide with or without promoter metals was taken in a 150 ml glass reactor and was dipped in a hydrochloric acid solution. The hydrochloric acid solution of strength 1 M to 8 M was used. An ultrasound sonication energy source with somcation power of 50 % was then dipped in the solution for a short duration of few minutes. The spent catalyst to mineral acid solution ratio was 1:8. At the end of the run, the platinum metal dislodging percentage was calculated by ICP-OES or Visible spectrophotometry. The recovery of platinum metal was 23.0 % to 80.1 %.

Example-11:
In this example, a known amount of spent bimetallic catalyst, for example Pt-Pd/Al2O3, was introduced in a 150 ml glass reactor and. dipped in hydrochloric and nitric acid solutions, separately. An ultrasound sonication energy source with sonication power of 50 % was then immersed in the solution with variation in exposure time. The spent catalyst to mineral acid solution ratio was 1:8. At the end of run, the content were filtered and analyzed for metal dislodging percentage by ICP-OES. The recovery of platinum and palladium metals was 35.3 % and 79.6 %, respectively.
Example-12:
A known amount of spent base metal catalyst like Ni/Al2O3 was taken in a 150 ml glass reactor and dipped in 1M hydrochloric acid. An ultrasound "sonication energy source with sonication power of 50 % was immersed in the solution for 10 minute. The spent catalyst to mineral acid solution ratio was 1:8. At the end of run, the content was filtered and analyzed for nickel dislodging percentage by ICP-OES. The recovery of nickel metal was 50.0% to 66.2 %
Example-13:
A known amount of spent Ni-Mo/Al2O3 catalyst was taken in a 150 ml glass beaker and dipped in 1M aqua-regia solution. The spent catalyst to mineral acid solution ratio was 1:8. An ultrasound sonication energy source with sonication power of 50 % was dipped in the acid solution for 10 minute. At the end of run, the content was filtered and analyzed for metal dislodging percentage by ICP-OES, The recovery of nickel and molybdenum metals was 77.9 % and 81.9 %, respectively.

Example-14:
A known amount of spent palladium catalyst supported on alumina or activated carbon catalyst was treated in a manner similar to the process of example 9. The palladium spent catalyst was dipped in a suitable mineral acid solution under ultrasound sonication power of 50 % for 10 minute. The catalyst to mineral acid solution ratio was 1:8. At the end of the run, the palladium metal recovery was 20.9 % to 36.2 %.
Example-15:
A known amount of spent Pt-Sn/Al2O3 catalyst was taken in a 150 ml glass beaker and dipped in a hydrochloric acid solution. The hydrochloric acid solution of strength 1M to 8M was used. The catalyst to mineral acid solution ratio was 1:10. The spent Pt-Sn/Al2O3 catalyst dipped in the mineral acid solution was then exposed to sonic energy for 10 minute using an ultrasound sonication energy source with sonication power of 50 %. At the end of run, the content was filtered and analyzed for platinum/tin dislodging percentage by ICP-OES. The recovery of platinum and tin was 49.4 % to 80.2 % and 9.8 % to 74.6 %, respectively.
TECHNICAL ADVANCEMENT:
The present disclosure, related to a process for dislodging metal from a matrix containing the metal, has the following technical advancements:
1. A highly efficient and environmentally benign process for dislodging metals from a solid matrix, particularly silver from silver containing catalysts, and
2. Use of mild reaction conditions and sonic energy provides a fast, efficient and green process for recovering metals from a solid matrix, particularly silver from silver containing catalysts.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower

than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:
1... A process for dislodging metal from a matrix containing metal, said process
comprising contacting said matrix with a dilute acid having concentration of at
least 0.5N in the presence of sonic energy at a temperature ranging between 10
and 50 °C and for a period ranging between 4 and 15 minutes to obtain the ,
metal into a solution.
2. The process as claimed in claim 1 further comprises the steps of:
i. adding an alkali halide to the solution to precipitate said metal in the form
of metal halide; ii. separating, washing and drying the metal halide precipitate; and iii. smelting said precipitate to obtain metal in pure form.
3. The process as claimed in claim 1, wherein the metal is Group IB metal.
4. The process as claimed in claim 1, the metal is silver,
5. The process as claimed in claim 1, wherein said matrix is a silver metal catalyst.
6. The process as claimed in claim 1, wherein said matrix is a spent silver metal catalyst.
7. The process as claimed in claim 1, wherein the metal is chemically bonded to the matrix.
8. The process as claimed in claim 1, wherein said matrix is contacted with the dilute acid and the sonic energy for a time period varying between 4 and 15 minutes.

9. The process as claimed in claim 1, wherein said dilute acid is a nitric acid solution having concentration in the range of 0.5 N to 2.5 N.
10. The process as claimed in claim 1, wherein said dilute nitric acid is recycled for silver dislodging.
11. The process as claimed in claim 1, wherein said sonic energy is supplied by using a sonic energy source that supplies sonic energy at a frequency varying between 5 to 30 KHz.
12. The process as claimed in claim 2, wherein the alkali halide is selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide.
13. The process as claimed in claim 2, wherein the metal halide is silver halide.
14. The process as claimed in claim 2, wherein smelting of the metal halide precipitate comprises heating said precipitate mixed with sodium carbonate and borax in a furnace at a temperature varying between 950 °C and 1150° C.
15. The process as claimed in claim 2, wherein the silver metal recovered in process step (ii) comprises purity >99.9% without additional purification step.