FIELD OF THE DISCLOSURE:

The present disclosure relates to a process for the extraction of noble metals from the soil of Mangalwedha, India.

BACKGROUND:

The soil of Mangalwedha, a district of Solapur, Maharashtra, India is found to contain the rich contents of precious noble metals. The soil of Mangalwedha is basaltic in nature. The basalt of Mangalwedha is highly compacted, siliceous, friable and chromatic with greenish and grey color. The Geographical Survey of India has tried to detect the presence of gold (Au) metal in the Mangalwedha basalt by employing conventional Neutron Activation Method. However, the team of Geographical Survey of India could not arrive at significant conclusion regarding the presence of gold metal in the Mangalwedha basalt. The Mangalwedha basalt also contains silver metal. During Neutron Activation Analysis carried out for the detection of gold metal in the Mangalwedha basalt, the silver metal absorbs most of the gold radiations thereby providing the negative result for the presence of gold metal in the Mangalwedha basalt.

In 2004, a team of Dr. N.J. Sathe under the able guidance of Dr. R. R. Patil, from Geology Department of Solapur University has reported the presence of gold (Au) in the basalt of Mangalwedha. Another scientist Kum. R.N. Vanarote from Geology Department of Solapur University has reported the presence of platinum (Pt) in the basalt of Mangalwedha, under the able guidance of Dr. R. R. Patil.

On the name of these scientists, the basalt of Mangalwedha containing gold (Au) and platinum (Pt) is named as NJS-basalt and RNV-basalt, respectively. Other than these precious noble metals, the basalt of Mangalwedha also contains copper (Cu) and silver (Ag) metals. The presence of yellow spots or dots, and white spots or dots, shining in sunlight, indicates the presence of gold and platinum, respectively, in the basalt of Mangalwedha.

The chromatic and hard nature of the Mangalwedha basalt makes the extraction of these noble metals very challenging. The reaction temperature is one of the most important criteria for the separation of noble metals. In due course several efforts have been made to extract these precious noble metals from the Mangalwedha basalt, however, no significant results have been obtained.

Therefore, there is felt a need to provide a process for the extraction of precious noble metals from the basalt of Mangalwedha.

OBJECTS:

Some of the objects of the present disclosure are described herein below:

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 process for the extraction of noble metals from the basalt of Mangalwedha, Maharashtra, India.

Still another object of the present disclosure is to provide a process for the extraction of noble metals from the basalt of Mangalwedha, Maharashtra, India, which is simple, efficient and economic.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. SUMMARY:

In accordance with the present disclosure there is provided a process for the separation of noble metals contained in basalt, said process comprising the following steps:

i. grinding a basalt sample to obtain its fine particulate matter;

ii. concentrating the fine particulate matter of the basalt sample;

iii. smelting the concentrated fine particulate matter of the basalt obtained in method step (ii) along with a flux for a pre-determined period of time at a predetermined temperature to form a melt comprising slag and a mixture of noble metals;

iv. cooling the melt to a room temperature and recovering the mixture of noble metals; and

v. dissolving the mixture of noble metals in an aqua-regia solution and subjecting the obtained solution to an electro-winning process to separate noble metals.

The basalt sample in accordance with the process of the present disclosure is grinded to obtain its fine particulate matter having particle size ranging from 100 to 200 mesh.

Typically, the method step of concentrating the fine particulate matter of the basalt includes at least one concentration method selected from the group of methods consisting of a gravity separation, magnetic separation and chemical separation.

In accordance with one of the embodiments, the method step of concentrating the fine particulate matter of the basalt comprises the following steps:

i. subjecting the fine particulate matter of the basalt to a magnetic separation to remove magnetic impurities present therein;

ii. subjecting the fine particulate matter of the basalt obtained from method step (i) to a separation under gravity using a Willfley's Table technique to remove water soluble salts present therein; and

iii. treating the fine particulate matter of the basalt obtained in method step (ii) with a dilute nitric acid to remove Cu and Ag impurities. The flux used in the process of the present disclosure can be borax which is added in an amount varying from 15 to 25 wt%..

The method step of smelting the concentrated fine particulate matter of the basalt further comprises the addition of at least one flux initiator selected from the group consisting of starch, sodium carbonate and silver.

In accordance with one of the embodiments, the flux initiator includes a mixture of sodium carbonate, starch, and optionally silver in amounts varying from 15 to 25 wt%; 1 to 2 wt%; and 10 to 12 wt%, respectively, based on total weight of the concentrated fine particulate matter of the basalt.

Typically, the smelting of the concentrated fine particulate matter of the basalt is carried out in a Blast-furnace at a temperature ranging from 1000 to 1800 °C for a time period ranging from 1.5 to 2 hours.

In method step (iv) of the process of the present disclosure, the mixture of noble metals is recovered by mechanical means.

The noble metals separated from the basalt in accordance with the process of the present disclosure include gold, platinum and silver.

DETAILED DESCRIPTION:

The description herein after 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.

In accordance with the present disclosure, there is provided a process for the extraction of noble metals present in the basalt of Mangalwedha, Maharashtra, India, as descried herein below:

The process for the extraction of noble metals from the Mangalwedha basalt is a series of metallurgical process which comprises the step of collecting a basalt sample, concentrating the sample to remove undesired impurities present therein, subjecting the concentrated sample to at least one extraction method to extract noble metals; and purifying the extracted noble metals to obtain extracted noble metals in pure form.

In the first process step, a sample collected from the Mangalwedha basalt is subjected to a concentration process to remove undesired species present therein. The concentration of minerals/ores is a well known technique in the metallurgy prior-art and accordingly conventional methods that are suitable for the purification of the Mangalwedha basalt sample can be employed in the process of the present disclosure.

Prior to concentration, the sample collected from the Mangalwedha basalt is grinded to obtain its fine particulate matter. The grinding of the basalt sample is typically accomplished by using conventional methods known in the metallurgy prior-art such as by using a ball mill, autogenous mill, semiautogenous mill and the like. In accordance with one of the embodiments of the present disclosure, the grinding of the basalt sample is carried out by a ball mill method. The grinding of the Mangalwedha basalt is typically accomplished to obtain its fine particulate matter having particle size varying from 100 to 200 mesh.

The fine particulate matter of the Mangalwedha basalt is then subjected to a concentration process. The concentration of minerals/ores is well known process in the related prior art and is usually accomplished to separate impurities from the minerals/ores so as to obtain mineral/ores having relatively high contents of desirous metals.

The concentration of the fine particulate matter of the Mangalwedha basalt in accordance with the present disclosure is carried out by using at least one method selected from the group of methods consisting of separation under gravity, magnetic separation, chemical separation and the like.

In accordance with one of the embodiments of the present disclosure, the concentration of the fine particulate matter of the Mangalwedha basalt is a multistep process in which the fine particulate matter of the Mangalwedha basalt is treated with a magnetic separator first to remove iron impurities. The iron free fine particulate matter of the Mangalwedha basalt thus obtained is then purified by using a Willfley's Table technique to remove water soluble salts present therein. The Willfley's Table technique is a well known technique for a person skilled in the art. In the next step, iron and water soluble salts free fine particulate matter of the Mangalwedha basalt is treated with a dilute nitric acid. The copper (Cu) and silver (Ag) impurities present in the Mangalwedha basalt get dissolved in the dilute nitric acid. The concentrated fine particulate matter of the Mangalwedha basalt thus obtained is significantly free from iron, silver, copper and water soluble salts.

The next step of the process of the present disclosure comprises the extraction of noble metals from the concentrated fine particulate matter of the Mangalwedha basalt. The extraction of noble metals in accordance with the process of the present disclosure is a two step process. The first step typically includes a Fire-Assay Treatment method wherein a mixture of noble metals is recovered/extracted from the concentrated fine particulate matter of the Mangalwedha basalt. The Fire-Assay treatment is a trusted technique used for the quantitative determination of precious metals contained in the ores such as gold (Au), silver (Ag) or Platinum group metals like as platinum, palladium, ruthenium, rhodium, and osmium. In the Fire-Assay treatment method of the present disclosure, the concentrated fine particulate matter of the Mangalwedha basalt is mixed with a flux and smelted in a furnace at a pre-determined temperature for a pre-determined period of time to extract a mixture of noble metals present therein. The choice and selection of flux used for the purpose of the present disclosure depends on the type of gangue materials present in the concentrated fine particulate matter of the Mangalwedha basalt. The flux material which is useful for the purpose of the present disclosure includes borax (Na ₂ B ₄ 0 ₇ ). In addition to borax, the inventor of the present disclosure advantageously uses starch (maize grains), sodium carbonate (Na ₂ C0 ₃ ), and silver/silver nitrate as a flux initiator to enhance the flux properties. In some instances when silver metal has to be determined in the sample, the use of silver/silver nitrate as the flux material is avoided.

In accordance with one of the embodiments of the process of the present disclosure, the concentrated fine particulate matter of the Mangalwedha basalt is mixed with borax, sodium carbonate (Na ₂ C0 ), starch (maize grains) and silver to obtain a mixture. All the components are typically mixed in a pre-determined weight proportion. In accordance with one of the embodiments of the present disclosure, the borax, sodium carbonate, starch (maize grain) and silver are typically added in amounts varying from 15 to 25 wt%; 15 to 25 wt%; 1 to 2 wt%; and 10 to 12 wt%, respectively, based on per kg weight of the concentrated fine particulate matter of the Mangalwedha basalt.

The obtained mixture is then charged in a crucible and placed in a Blast-Furnace. The Blast-furnace is then heated at a pre-determined temperature of about 1000 °C. The temperature of the Blast-Furnace is maintained at about 1000 °C by using coke as a fuel. At a high temperature of about 1000 °C, the concentrated fine particulate matter of the Mangalwedha basalt reacts with the flux; since the reaction is highly exothermic, it leads to a high temperature rise of the crucible placed inside the Blast- Furnace. The crucible placed inside the Blast-Furnace achieves a high temperature of about 1800 °C. At this high temperature, the concentrated fine particulate matter of the Mangalwedha basalt and the flux melt together and form a melt. The melt thus formed comprises slag and a mixture of noble metals. The melt is then cooled down to a room temperature and the slag is then separated from the mixture of noble metals. During the fire-assay treatment method, the unwanted materials (conventionally known as gangue) present in the concentrated fine particulate matter of the Mangalwedha basalt react with the flux and form the slag. The term 'slag' in the context of the present disclosure refers to a vitreous mass left as a by-product/residue during the smelting of the concentrated fine particulate matter of the Mangalwedha basalt carried out in the presence of the flux.

The separation of slag can be accomplished by using any conventional methods known in the related prior-art. The slag in accordance with the process of the present disclosure is separated by mechanical means, for example, by crushing the slag.

The next extraction process typically includes a separation of the individual noble metals from the mixture of noble metals recovered from the fine particulate matter of the Mangalwedha basalt. The noble metals are separated by following a series of chemical/electrochemical treatment.

The mixture of noble metals is first treated with an Aqua-regia solution. The gold and platinum metals have strong affinity towards Aqua-regia solution. The aqua-regia solution containing gold and platinum noble metals is typically subject to an electro- winning process to separate gold and platinum metals. The electro-winning process is a well known process to person skilled in the art for the extraction of metals, particularly gold from its liquefied solution. Alternatively, the aqua-regia solution of the gold and platinum noble metals is treated with concentrated nitric acid solution followed with concentrated sulfuric acid. The precipitate thus formed is mixed with concentrated hydrochloric acid. The platinum metal present in the precipitate gets dissolved in the concentrated hydrochloric acid whereas gold present in the precipitate remains insoluble. 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.

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:

A sample collected from Mangalwedha basalt was subjected to a grinding process to obtain a fine particulate matter having the particles of 100 mesh size. The fine particulate matter was treated with a magnetic separator followed by Willfley Table technique. Afterwards, the fine particulate matter of the Mangalwedha basalt was treated with a dilute nitric acid. The concentrated fine particulate matter of the Mangalwedha basalt (1 kg), thus, obtained was mixed borax (0.25 kg), sodium carbonate (0.25 kg), starch (0.02 kg) and silver (0.001 kg), and was charged in a preheated crucible placed in a Blast-Furnace, at a temperature of 1000 °C. At this high temperature, the concentrated fine particulate matter of the Mangalwedha basalt has reacted with flux and other materials. Due to exothermic nature of the reaction, the temperature of the crucible placed inside the Blast-Furnace increased to about 1800 °C. At a high temperature of about 1800 °C, the concentrated fine particulate matter of the Mangalwedha basalt melt completely with the flux and formed a melt that comprised of a mixture of noble metals and slag. The melt thus obtained was cooled down to a room temperature. The slag was then separated from the mixture of noble metals by mechanical means. The mixture of noble metals thus obtained was treated with a dilute nitric acid and hen with an aqua-regia solution. The aqua-regia solution containing gold and platinum noble metals was then subjected to an Electro- winning process to separate gold metal from the platinum metal. Alternatively, the aqua-regia solution of the gold and platinum noble metals was treated with concentrated nitric acid solution and then with concentrated sulfuric acid. The precipitate thus formed was mixed with concentrated hydrochloric acid. The platinum metal present in the precipitate gets dissolved in the concentrated hydrochloric acid whereas gold remains insoluble.

TECHNICAL ADVANCEMENTS:

A process for the extraction of noble metals from Mangalwedha basalt, as disclosed in the present disclosure has several technical advantages including but not limited to the realization of:

• extraction of precious noble metals such as Gold (Au), Platinum (Pt), and silver (Ag) from Mangalwedha basalt;

• simple and economic process for the extraction and purification of Platinum (Pt) noble metal from the basalt of Mangalwedha;

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.