The present invention provides a process for the production of lithium carbonate. This invention particularly relates to a process for the production of lithium carbonate by base exchange method from lipidolite orefThe present invention will be useful for producing lithium carbonate which is widely used lithium compounds due to its applications in various enamelling of steel- as a fluxing agent and manufacturing of clay housewares, blast lining of water heaters and in the production of various grades of glass. This is also the starting materials for a wide variety of lithium chemicals such as lithium hydroxide, lithium bromide, lithium hypochlorite including lithium metal. In purer form it is used in the medicines for the treatment of certain mental diseases. In metallurgy it is used as additive to fused salt baths for the production of aluminium, magnesium and lithium and as desulphurisation agent in the iron-steel making^
The lepidolite is the chief lithium-bearing mineral in India. In the overall available reserve of the ore and in float, i.e. down to shallow depth for quarrying would be of the order of 30000 tons and it can be exceeded if there is demand for it. A recent survey reveals that the production from existing units for the manufacturing of lithium carbonate is estimated to be about 500 metric-ton per annum and its growing demand of large industries in steel, chemicals, Pharmaceuticals etc leaves a big gap of supply. In medicine some pharmaceutical companies import about 100 ton per annum from USA to meet the requirement and about 50 ton per annum of lithium chloride is imported for its use in making welding electrodes. Lithium is the lightest known metal with two stable isotopes Li6 & Li7 with relative abundance of 7.5 and 92.5 percent. It occurs as a constituent of many natural occurring in the earth crust. The average lithium content of the earth crust has been estimated as about 0.007% comprising about 14 minerals, of these only 8 minerals are commercially important viz. spodumene, amblygonite, lepidolite, zinnwaldite, petalite, triphylite, lithiophylite and cookeite.
In early days of the lithium industry lepidolite was the chief mineral for recovery. The mineral was decomposed by heating with concentrated sulphuric acid to yield a mixture of soluble lithium and other alkali sulphates. With large amount of aluminium sulphate extensive purification was necessary before the lithium could be recovered successfully. The same method is applicable to amblygonite.
Conventionally, lithium chemicals are produced from spodumene, another lithium mineral which is hard with a density of 3.15 in the conventional commercial process (Fross, Foster and Ralston, O.C.V.S. Europe Mines Report Investigation 3344 1937, Ellestad R.V. and Leute K.N.,

US Patent No.516, 109, July 25, 1950). The spodumene is heated at 1100°C to convert ct-spodumene into p-spodumene instantaneously with a density of about 2.4 and is early crushed to a very fine powder. The conversion of the mineral from a to the p form is the important step in production of lithium chemical from spodumene ore concentrate.
In an another conventional method, lithium from spodumene is recovered by subliming it as a chloride widely known as the Indian Bureau of Mines method.
Reference may be made to the US Patent No. 516109, wherein Lithium Corporation of America, USA led to the development of an entirely new method of recovering lithium from its spodumene ore. Employing sulphuric acid is a source of hydrogen under critical conditions of time and temperature, hydrogen ions can be substituted for lithium ions in spodumene without changing the physical structure of the mineral in any visible way and without extracting any of the aluminium which is a part of the spodumene structure. The water portion of the new aggregate is combined in the same manner, as was the lithia component with original spodumene.
The major disadvantage of the process is not economically viable due to the non-availability of spodumene. Besides the process steps for production of lithium chemicals using spodumene are not technically feasible with lepidolite.
In the present invention a process has been developed for the production of lithium carbonate from lepidolite ore which is abundantly available in India. The Indian lepidolite ore contains 2-3% lithium. The ore is roasted with an excess alkali sulphate to the temperature of 900-1000°C. This is followed by water leaching under the meticulously maintained conditions and displacement of lithium ions in the mineral by the cations to achieve sodium containing lithium sulphate and excess alkali sulphate. By addition of soda ash (Sodium Carbonate, Na2CO3) solution to the boiled leached liquor at high temperature to ensure maximum precipitation since the solubility of lithium carbonate (Li2CO3) decreases with increasing temperature, as given in the table below.

(Table Removed)
The main object of the present invention is to provide a process for the production of lithium carbonate which obviates the drawbacks as detailed above.
Another object of the present invention is to provide a process for the production of lithium carbonate by base exchange method from lepidolite ore.
Still another object of the present invention is to utilize the lithium bearing mineral lepidolite which is available in abundance, and thereby bridges the gap of demand and supply of lithium chemicals.
Yet another object of the present invention is to provide an eco-friendly economic process for the production of lithium carbonate.
Yet another object of the present invention is to provide a no toxic waste generating economic process for the production of lithium carbonate.
The drawing according to the specification figure (1) represents the process flow diagram for the production of lithium carbonate.
Accordingly the present invention provides a process for the production of lithium carbonate which comprises:
i) selecting lepidolite ore containing lithium oxide in the range of 1.8-3% having
size in the range of 40 to 60mm, ii) crushing and grinding the said lepidolite ore to -100 mesh size, iii) mixing with gypsum and limestone in the rate ranging between 1:0.3 : 0.3 to
1:1:1 and pelletising to the size in the range of 15 to 20 mm, iv) roasting the said pellets at a temperature ranging between 900-1000°C in a
rotary kiln or shaft kiln for a period ranging between 2 to 3 hours, v) Cooling the roasted pellets to the temperature in the rate of 150-200 C and
crushing the roasted pellets to in the range of -60+40 mesh to -100+60 mesh
size, vi) Leaching the said crushed pellets in water for 1 to 2 hours and separating
leached liquor and solids, vii) concentrating the leach liquor containing lithium sulphate in the range of 30 to
40% by the known methods including vacuum evaporation, viii) adding alkali carbonate selected from sodium carbonate, calcium carbonate
and the like of commercial grade to the concentrated leached liquor in the
ratio ranging between 1:1 to 1:1.5 and stirring for a period of 2 to 3 hours in
the temperature ranging between 40 to 100°C,

ix) filtering and drying lithium carbonate.
In an embodiment of the present invention the used lepidolite ore may have the following compositional range:

(Formula Removed)
In another embodiment of the present invention the used gypsum, limestone may be of
commercial grade.
In still another embodiment of the present invention the alkali carbonate may be selected
from sodium carbonate, calcium carbonate and the like of commercial grade.
The present invention provides a recovery of L12CO3 is about 60-96% and the
specification and typical analysis of commercial Li2CC>3 which is 98% pure comprises
impurities in the range of:

(Formula Removed)
The invention is illustrated by the following examples, which should not be construed to limit the scope of the present invention
Example -1
The lepidolite obtained from the 100 kg mineral containing 1% Li2O, 49.45% SiO2, 31.87% A12O3, 9% K2O, 1% MnO and 5% LOI ground with 30kg gypsum and 30kg limestone upto -100 + 60 mesh and is palletized and roasted at a temperature of 900°C. This is followed by size reduction of pellets upto -60+40 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the

carbonating solution (1:0.8) in a precipitator at a temperature of 60°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging . The process was effective in achieving the yield of Li2CO3of about 70%.
Example - 2
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 50.45% SiO2,32.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 30kg gypsum and 30kg limestone upto -100 + 60 mesh and is palletised and roasted at a temperature of 900°C. This is followed by size reduction of pellets upto -60+40 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 60°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging.The process was effective in achieving the yield of Li2CO3 of about 75%.
Example - 3
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 30kg gypsum and 30kg limestone upto -100 + 60 mesh and is palletised and roasted at a temperature of 1000°C. This is followed by size reduction of pellets upto -60+40 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 60°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging. The process was effective in achieving the yield of Li2CO3 of about 80%.
Example - 4
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 60kg gypsum and 60kg limestone upto -100 + 60
mesh and is palletised and roasted at a temperature of 950°C. This is followed by size reduction of pellets upto -60+40 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 60°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging. The process was effective in achieving the yield of Li2CO3 of about 80%.
Example - 5
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 60kg gypsum and 60kg limestone upto -100 + 60 mesh and is palletised and roasted at a temperature of 900°C. This is followed by size reduction of pellets upto -60+40 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 100°C. The precipitate of Na2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging The process was effective in achieving the yield of Li2CO3 of about 85 %
Example-6
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1 % MnO and 5% LOI is ground with 60kg gypsum and 60kg limestone upto -100 + 60 mesh and is palletised and roasted at a temperature of 950°C. This is followed by size reduction of pellets upto -100+60 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 100°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging . The process was effective in achieving the yield of Li2CO3 of about 90%.
Example-7
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 100kg gypsum and 100kg limestone upto -100 + 60 mesh and is palletised and roasted at a temperature of 950°C. This is followed by size reduction of pellets upto -100+60 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:1) in a precipitator at a temperature of 100°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging . The process was effective in achieving the yield of Li2CO3 of about 95%.
Example - 8
The lepidolite obtained from the 100 kg mineral containing 2% Li2O, 49.45% SiO2,31.87% AI2O3, 9% K2O, 1% MnO and 5% LOI is ground with 60kg gypsum and 60kg limestone upto -100 + 60 rnesh and is palletised and roasted at a temperature of 950°C. This is followed by size reduction of pellets upto -100+60 mesh and leached with water which is followed by solid-liquid separation by thickeners and counter current washing of the sludge and by vacuum concentration of Li2SO4 at 60°C. The concentrated liquor is treated with carbonating agent in the ratio of liquor to the carbonating solution (1:0.8) in a precipitator at a temperature of 100°C. The precipitate of Li2CO3 was recovered by separating the mother liquor in a centrifuge. The product (Li2CO3) is subsequently dried before bagging /packaging.The process was effective in achieving the yield of Li2CO3 of about 95%.
The main advantages of the present invention are :
1 The present invention uses Indian lithium bearing mineral lepidolite and it thus exploits the indigenous mineral resources of lithium.
2. The process helps produce a valuable chemical which can serve as the starting material for
other lithium chemicals including lithium metal.
3. The process is environmentally friendly.
4. The waste generated are non-toxic, which can be used for making construction bricks.
5. The product being imported can substitute the import of lithium chemicals.
6. There is no need of extensive purification to recover to Li2CO3., as it is required in other
process known hitherto

We Claim:
1. A process for the production of lithium carbonate which comprises:
i) selecting lepidolite ore containing lithium oxide in the range of 1.8-3% having
size in the range of 40 to 60mm, ii) crushing and grinding the said lepidolite ore to -100 mesh size, iii) mixing with gypsum and limestone in the rate ranging between 1:0.3 : 0.3 to
1:1:1 and pelletising to the size in the range of 15 to 20 mm, iv) roasting the said pellets at a temperature ranging between 900-1000°C in a
rotary kiln or shaft kiln for a period ranging between 2 to 3 hours, v) cooling the roasted pellets to the temperature in the rate of 150-200°C and
crushing the roasted pellets in the range of -60+40 mesh to -100+60 mesh
size, vi) leaching the said crushed pellets in water for 1 to 2 hours and separating
leached liquor and solids, vii) concentrating the leach liquor containing lithium sulphate in the range of 30 to
40% by the known methods including vacuum evaporation, viii) adding alkali carbonate selected from sodium carbonate, calcium carbonate
and the like of commercial grade to the concentrated leached liquor in the
ratio ranging between 1:1 to 1:1.5 and stirring for a period of 2 to 3 hours in
the temperature ranging between 40 to 100°C, ix) filtering and drying lithium carbonate.
2. A process as claimed in claim 1, wherein the used lepidolite ore have the following compositional range: Si02. 40-50%, A12O3- 25-35%, K2O-6-105, Li2O-1-5%, Na2O-0.1-0.2%, Fe2O3- 0.5-1%, TiO2- trace, MnO-l-2%, CaO-trace, MgO-0.2-0.8%, P2O5- trace, LOI-4-6%.
3. A process as claimed in claims 1-2 wherein used gypsum, limestone are of commercial grade.

4. A process for the production of lithium carbonate substantially as herein described with reference to the examples and drawing accompanying this specification.