FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
A PROCESS FOR RECOVERY OF COBALT AND MANGANESE FROM
RESIDUAL SOLID WASTE
RELIANCE INDUSTRIES LIMITED
an Indian organization of
Reliance Technology Group
Reliance Corporate Park
7B Ground Floor
Thane-Belapur Road
Ghansoli, Navi Mumbai-400 701.
Maharashtra, INDIA
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION:
The invention relates, in general, to a process for the recovery of cobalt and manganese
salts.
In particular, the invention relates to a process for the recovery of cobalt and manganese in
the form of their acetate salts from residual solid waste from catalyst recovery unit.
The process of the invention is particularly suitable for recovery of the cobalt and
manganese catalyst from the solid residue waste from the catalyst recovery unit in a form
that is acceptable for recycling as catalysts for the oxidation of alkylaromatic compounds.
BACKGROUND:
Benzene dicarboxylic acids are the starting materials in the production of polyester resins having application in the making of textile fibers, packaging films, containers and the like. These acids are manufactured by liquid phase oxidation of the corresponding dialkylbenzenes with molecular oxygen containing gas in the presence of cobalt and manganese salts as catalysts and a bromide as a promoter in acetic acid and water medium. For instance, Terephthalic acid is manufactured by continuous oxidation of p-xylene with an oxygen containing gas using catalyst comprising of salts of cobalt and manganese, and a bromide compound in acetic acid and water medium which is referred to as a mid century process.
The mother liquor after separating the terephthalic acid is continuously purged before returning it to the oxidation reactor for reuse of the catalyst. The mother liquor purge stream also contains metals such as Fe, Cr and Cu either from corrosion of process apparatus or from the original source of cobalt and manganese acetates used as catalysts. Continuous removal of the mother liquor purge stream helps maintain levels of iron, copper and chromium, and also other impurities below certain limits to prevent their detrimental effect on the oxidation reaction. The mother liquor purge stream contains cobalt and manganese salts and several organic compounds which include terephthalic acid and other aromatic carboxylic acids produced as byproducts during the oxidation reaction.

There are several patents which describe process for the recovery and recycling of the cobalt and manganese catalyst from the mother liquor purge stream from the oxidation of alkylaromatic compounds. One of the conventional processes for the catalyst recovery currently practiced in commercial plants involves adding of an alkali metal hydroxide and oxalic acid to the mother liquor purge stream and converting the cobalt and manganese into their.oxalate salts which have poor solubility in acetic acid and are easily separable by filtration. The isolated cobalt and manganese oxalates are converted into forms which are suitable for recycling as catalysts.
However, the process of recovery of cobalt and manganese catalyst by oxalate method recovers 90% or often less of these metals and about 10% and often more of the cobalt and manganese ends up in the solid residual waste and therefore remains unrecovered.
Cobalt and manganese, particularly the cobalt are expensive metals and it is desirable to recover completely these metals from the purge stream and convert them to a form acceptable for recycling as catalysts in the oxidation step of the process.
EXISTING KNOWLEDGE:
Following Patents disclose processes for the recovery of cobalt and manganese catalyst from the mother liquor after the separation of the dicarboxylic acid produced by oxidation of alkylaromatic compounds.
In US 4786621, the organic compounds in the mother liquor stream are destroyed by incineration which produces a fly ash that contains mixed metal oxides. The fly ash containing the oxides of cobalt and manganese is treated with acetic acid in the presence of a reducing agent such as cobalt metal or hydrazine which converts the cobalt and manganese to a form which is acceptable for recycling as a catalyst.

In US 3956175, the residue from the mother liquor containing cobalt and manganese mostly in the form of acetates, is contacted with water in the presence of a sulfur compound and air to isolate the metal ions into an aqueous phase. The cobalt and manganese are selectively precipitated from the aqueous solution as their carbonates which have high purity and are free from the heavy metal impurities such as iron, chromium and copper.
In US 3959449, the residue from the mother liquor containing acetates of cobalt and manganese is treated with water in the presence of a sulfur compound and air which isolates the metal ions into the aqueous solution. The cobalt and manganese ions are separated by passing the aqueous extracts through a bed of strongly acidic cation exchange resin.
In US 4312778, there is described, a process comprising of extracting the residue from the mother liquor containing acetates of cobalt and manganese, with water and contacting the aqueous extracts with a fluoropolymer membrane which is permeable to cations and contacting the other side of the membrane with a hydrohalidic acid such as hydrochloric or hydrobromic acid.
Indian Patent application 990/MUM/2001 describes a process and device for the recovery of cobalt and manganese from the mother liquor purge stream. The residue from the mother liquor is extracted with water and cobalt and manganese are selectively precipitated from the aqueous extracts. The precipitate is acidified, filtered and the filtrate is passed through an ion exchange resin comprising chelating ions. The cobalt and manganese is recovered by eluting the ion exchange resin bed with a mineral acid.
In US Patent No. 4488999, there is disclosed, a process in which cobalt and manganese are precipitated as their oxalate salts from the acetic acid mother liquor by addition of sodium, potassium or ammonium oxalate. It was found that certain amount of water facilitated formation of oxalate crystals that are easily filterable.

In US 449029, there is disclosed, a process in which cobalt and manganese are precipitated as oxalates from the acetic acid mother liquor in which they have poor solubility. The oxalate salts of cobalt and manganese are treated with hydrogen bromide, acetic anhydride and/or acetyl bromide to give corresponding salts that are soluble in acetic acid and can be recycled as catalysts.
In US 4910175, there is disclosed, a process in which the cobalt and manganese are precipitated from the mother liquor by addition of oxalic acid and an alkali metal hydroxide such a,s sodium hydroxide. The precipitated oxalate compounds of cobalt and manganese are converted to their acetates by oxidizing them in the presence of acetic acid.
Although the aforesaid patents and other state of art describe several processes for the recovery of cobalt and manganese from the mother liquor, the process for recovering the balance cobalt and manganese, after the recovery of 90% or often less of the cobalt and manganese, is not disclosed so far.
Moreover, the processes for recovery of cobalt and manganese from the mother liquor differ substantially from the process for recovery of the remaining portion of cobalt and manganese after the recovery of 90% or often less of the cobalt and manganese by oxalate process. Also, the nature of the cobalt and manganese species present in the mother liquor purge stream and those in the residual solid waste after the recovery of 90% or often less of the cobalt and manganese by oxalate process is different. Therefore, the known arts of the cobalt and manganese recovery from the mother liquor cannot be applied to the latter one for recovery of the remaining portion of cobalt and manganese after the recovery of 90% or often less of the cobalt and manganese.
Therefore, there is a need to develop a process for recovering the unrecovered portion of cobalt and manganese after the recovery of 90% or often less of the cobalt and manganese having high purity for recycling as a catalyst.

OBJECTS OF THE INVENTION:
Accordingly, the objects of the present invention are as follows:
The primary object of the present invention is to develop a process for recovery of the cobalt and manganese from the solid residual waste from catalyst recovery unit.
Another object of the present invention is to develop a process for recovery of the cobalt and manganese catalyst from the solid residual waste from the catalyst recovery unit and convert them into a form suitable for recycling as a catalyst for the oxidation of alkylaromatic compounds and other like processes.
Still another object of the present invention is to provide a process for the recovery of cobalt and manganese catalyst from the solid residual waste from the catalyst recovery unit; the recovered cobalt and manganese catalyst being of high purity.
These and other objects of this invention will become more apparent from the following detailed description of the invention and the accompanying drawings.
SUMMARY OF THE INVENTION:
In accordance with the present invention there is provided a process for recovery of cobalt and manganese salts from residual solid waste containing oxalates of cobalt and manganese; the said process comprising the following steps:
(a) treating the residual solid waste with demineralized water in a pressure reactor at a temperature ranging between 200 - 280 °C with agitation, to obtain a slurry;
(b) cooling the slurry at a temperature ranging in between 0-5 °C, to precipitate out dissolved organic solids;
(c) filtering the slurry to obtain a filtrate and a residue;
(d) washing the residue repeatedly with chilled demineralized water;
(e) mixing the washing and the filtrate to obtain a solution;

(f) neutralizing the solution with an alkali metal carbonate solution to precipitate carbonates of cobalt and manganese;
(g) treating the precipitate of cobalt and manganese carbonates with a solution containing glacial acetic acid and demineralized water, in the ratio ranging between 5:1 to 1:5 v/v, to obtain a homogeneous red solution containing acetate salts of cobalt and manganese.
The process is particularly useful to recover and recycle cobalt and manganese components in a process for the preparation of terephthalic acid by the oxidation of p-xylene and like processes.
Typically, the oxalates of cobalt and manganese constitute less than 10 %, and particularly less than 2 % of the mass of residual waste.
Typically, the contents in the reactor are agitated at an agitator speed in the range of 50-500 rpm.
Preferably, the contents in the reactor are heated at a temperature in the range of 230 - 260 °C.
Typically, the resident time of the residual waste in the reactor is in the range of 0.25 hr to 12hrs.
Preferably, the resident time of the residual waste in the reactor is in the range of 0.5 hr to 5 hrs.
Typically, the slurry in the reactor is cooled by water followed by an ice-bath at a temperature ranging in between 0-5 °C to precipitate out dissolved organic solids.
Typically, the step of washing the residue containing organic solids includes washing the residue with 5 portions of chilled demineralized water.

Typically, the chilled demineralized water at a temperature in the range of 0 to 5 °C is used for washing.
Preferably, the alkali metal carbonate is saturated aqueous sodium carbonate solution.
Typically, the said alkali metal carbonate is added slowly to the mixture and at a temperature in the range of 25 to 35 °C.
Typically, the alkali metal carbonate is added until the pH of the solution is adjusted to about 4 to precipitate any iron salts in the solution; the iron carbonate precipitate is filtered off and the alkali metal carbonate is added to raise the pH to around 9 to initiate the precipitation of cobalt and manganese salts and additional alkali metal carbonate is added to ensure complete precipitation.
Preferably, the precipitate of cobalt and manganese carbonates is dissolved in a solution containing acetic acid and water in the proportion of 1:1 v/v.
Typically, the cobalt is recovered in the range of 94.1% to 96.9% and manganese is recovered in the range of 95.1% to 97.9%.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates effect of amount of water on extraction of the solid waste Figure 2 illustrates effect of temperature on extraction of the solid waste

DETAILED DESCRIPTION OF THE INVENTION:
In the process for the production of aromatic acids such as terephthalic acid, it is conventional to perform oxidation of alkyl aromatic compounds such as P-xylene by using a molecular oxygen containing gas in the presence of the cobalt and manganese as catalysts and a bromide compound as a promoter, in acetic acid medium at high temperature and pressure. Such processes are often operated continuously, and the mother liquor containing the reaction product is continuously removed from the reactor and the desired aromatic acid separated. The acetic acid mother liquor after removal of crystals of terephthalic acid contains the cobalt and manganese catalyst, remaining terephthalic acid, and several aromatic mono and polycarboxylic acids which are byproduct impurities produced in the oxidation reactor. In addition, metals such as iron, chromium, and copper are also present either from corrosion of process apparatus or from the original source of the cobalt and manganese catalyst.
A major part of the mother liquor is sent back to the oxidation reactor for reuse of the cobalt and manganese catalyst. A small portion of the mother liquor, called mother liquor purge stream, is continuously removed to prevent the accumulation of high concentration of certain heavy metal ions such as iron, copper and chromium in the oxidation reactor which has adverse effect on the oxidation process.
The mother liquor purge stream is sent to a catalyst recovery unit where maximum 90% or often less of the cobalt and manganese is recovered as precipitates in the form of their oxalates by addition of oxalic acid and sodium hydroxide. The cobalt and manganese oxalates have poor solubility in acetic acid and are therefore easily separated by filtration. The recovery of cobalt and manganese in the catalyst recovery unit is limited to 90% to prevent coprecipitation of the undesirable metals such as Fe, Cr and Cu along with the oxalates of cobalt and manganese. Accumulation of these metals in the recycled cobalt and manganese catalysts has harmful effect on oxidation reaction.

The mother liquor from the catalyst recovery unit is sent for acetic acid recovery by distillation. The residual solid obtained from this unit still contains remaining 10% or more of cobalt and manganese, a small amount of terephthalic acid and several aromatic carboxylic acids being formed as byproducts during the oxidation reaction. This solid waste is generally sent to an incinerator for disposal.
The present invention discloses a process for recovering the remaining 10% or more of the cobalt and manganese from the solid waste in a form acceptable for recycling as a catalyst in the oxidation reactor.
Therefore, in accordance with the invention there is provided a process for recovery of cobalt and manganese salts from the solid waste residue; said solid waste residue having cobalt and manganese in the form of oxalates, produced by the use of cobalt and manganese catalyst in the oxidation of an alkyl aromatic compound to form an alkyl aromatic acid, the said process comprising the following steps:
a. treating the residual solid waste with demineralized water in a pressure reactor at a
temperature ranging between 200 - 280 °C with agitation, to obtain a slurry;
b. cooling the slurry at a temperature ranging in between 0-5 °C, to precipitate out
dissolved organic solids;
c. filtering the slurry to obtain a filtrate and a residue;
d. washing the residue repeatedly with chilled demineralized water;
e. mixing the washing and the filtrate to obtain a solution;
f. neutralizing the solution with an alkali metal carbonate solution to precipitate
carbonates of cobalt and manganese;
g. treating the precipitates of cobalt and manganese carbonates with a solution
containing glacial acetic acid and demineralized water in the ratio ranging between
5:1 to 1:5 v/v, to obtain a homogeneous red solution containing acetate salts of
cobalt and manganese.

"In accordance with the present invention, there is provided a process for recovering cobalt and manganese in the form of acetates in highly pure state.
The process according to the invention starts with residual solid waste and a solvent being charged into the reactor for extraction of the metal compounds into an aqueous phase.
The solid waste residue used in the present invention was obtained from catalyst recovery unit of a commercial terephthalic acid manufacturing unit which contains 0.24% by weight of cobalt 0.24% by weight of manganese and 1.22% by weight of sodium. HPLC analysis of the solid waste residue shows that it contains a variety of aromatic carboxylic acids. The residue also contains about 40% by weight of water which is added to the bottom of acetic acid recovery unit to facilitate transfer of the residual solid, and about 1 - 3% by weight of acetic acid.
The efficiencies of isolation of the cobalt and manganese species present in the solid waste, into water with a view to separate the inorganic salts from the organic mass are also studied. Two parameters, the water to residue ratio and temperature are studied to optimize the extraction process. To study the effect of water amount on extraction, 25 gm of the solid waste was contacted with water at 90 °C in a Parr autoclave of 450 ml capacity fitted with a mechanical agitator. After the specified time the content of the reactor were cooled and the solid was filtered and washed with water. The filtrate and washings were combined and analyzed for the metal content. The results are shown in the Table 1. The run 1 shows that isolation of cobalt and manganese was poor with water to residue ratio of 4 at 90 °C. Increasing the ratio of water to residue to 7 and 10 led only to a small increase in the isolation of cobalt and manganese (see runs 2 and 3). This effect is also shown graphically in the Figure 1. Thus, increasing water amount in the extraction process has little influence on dissolution of cobalt and manganese compounds present in the solid waste.
Another set of experiments is performed to study the effect of temperature on the isolation of cobalt and manganese into the aqueous phase. Thus, 25 gm solid waste was contacted with 100 ml water at different temperatures. The results are shown in the Table 1. Comparison of the data in the runs 1, 4, 5, and 6 shows that isolation of manganese reaches

to completion at 200 °C. Isolation of cobalt practically does not increase up to 200 °C but increases rapidly after 200 °C and reaches to completion at 250 °C. This effect is shown graphically in the Figure 2. Thus, temperature has pronounced effect on the dissolution of the cobalt and manganese compounds present in the solid waste.
Table 1: Effect of water amount and temperature on isolation of cobalt and manganese from the solid waste.

Run* Water (ml) Temp Pressure
(psig) Extraction (%)

Co Mn
1 100 90 3 17
2 175 90 - 7 25
3 250 90 - 11 36
4 100 200 80 4 100
5 100 225 160 42 99
6 100 250 270 100 100
'Extractions were performed in a Parr autoclave of 450 ml capacity with 25 gm of the solid waste for 2 h.
The residual solid waste obtained after the recovery of cobalt and manganese salts from the mother liquor purge stream in the catalyst recovery unit is used to recover the remaining portions of cobalt and manganese salts. The said residual waste from the catalyst recovery unit contains oxalates of cobalt and manganese which constitutes less than 10 % and preferably less than 2 % of the mass of the residual waste.
For complete dissolution of the cobalt and manganese salts, the contents in the reactor are agitated and heated under optimum conditions in a Parr reactor.
In accordance with the invention, temperature has pronounced effect on the dissolution of cobalt and manganese compounds present in the residue.

Typically, the contents in the reactor are agitated at an agitator speed in the range of 50-500 rpm and during agitation the said contents in the reactor are heated at a temperature in the range of 200- 280 °C
Preferably, the contents in the reactor are heated at a temperature in the range of 230 - 260 °C.
The extraction of the residue with water under optimized condition results into the complete dissolution of the cobalt and manganese oxalates presents in residue.
However, some of organic compounds also dissolve into the aqueous phase which should be separated out. Separation of the dissolved organic compounds by their precipitation from the aqueous extract is done either by concentrating them to about 1/5 of the volume or by cooling the extract at 0-5 °C.
The heating and agitating of contents of the reactor is followed by cooling the extract to about 5°C in an ice bath to separate out the dissolved organic solids.
The slurry in the reactor containing precipitated organic solids is filtered to obtain a filtrate containing salts of cobalt and manganese; the remaining solid being washed repeatedly with chilled demineralized water.
Typically, the remaining solid is washed with 5 portions of chilled demineralized water; temperature of the said chilled demineralized water having been maintained in the range of 0 to 5 °C; The aqueous washing is mixed with the filtrate containing salts of cobalt and manganese.
The cobalt and manganese oxalates can also be extracted from solid residue waste at temperature lower than 250 °C with water containing 2-5% mineral acid such as sulfuric acid and nitric acid. Typically, such extraction can be performed at temperature 100 °C to give complete isolation of cobalt and manganese into the aqueous phase. However, use of water containing mineral acid has few problems associated with it. Mineral acid present in

water may cause derivatization of the organic compounds present in solid waste and such derivatization reactions become prominent during concentration of the aqueous extract where concentration of the mineral acids goes up. The derivatization of the organic compounds in the solid waste has adverse effect in two way; Firstly, it results into the loss of organic compounds which otherwise could be isolated and marketed. The major organic compounds present in solid waste which could be isolated and marketed are benzoic acid, terephthalic acid, isophthalic acid, phthalic acid and trimellitic acid. And secondly, the presence of higher amount of acidic compounds in the extract will consume more of sodium carbonate used for neutralization and precipitation of cobalt and manganese carbonates. The derivatized organic compounds have higher solubility in water leading to increased concentration of dissolved organic acids in the extracts.
Uses of mineral acids for extraction of the solid waste bring in issue of corrosion of the processing apparatus which might be aggravated during concentration of extract where concentration of mineral acid would be higher. This may require corrosion proof apparatus such as glass-lined vessels which would add to the cost.
Although, the process for extraction of solid waste with water requires high temperature, it is free from the above problems associated with the processes that use aqueous mineral acid solution.
The aqueous solution containing combined aqueous extract and washings is subjected to selective precipitation of cobalt and manganese. Alkali metal carbonate is added to the aqueous solution to bring the pH to 4 in order to precipitate iron as iron carbonate if any iron is present in the solution. The precipitate of iron carbonate is filtered off. An aqueous alkali metal carbonate solution is added to the aqueous solution to bring the pH to 9 when a pink coloured precipitate of cobalt and manganese carbonates appears. Typically alkali metal carbonate selected is saturated aqueous sodium carbonate solution. Typically, aqueous alkali metal carbonate solution is added slowly to the filtrate at a temperature in the range of 20-35 °C.
After obtaining the pink coloured precipitate, alkali metal carbonate solution is added in excess to ensure complete precipitation of cobalt and manganese carbonates which is also confirmed by testing the supernatant liquid.

The contents are then allowed to stand for 6-10 hrs followed by filtration under suction to obtain carbonate precipitate containing cobalt and manganese. The carbonate precipitate thus obtained is washed with water to remove impurities such as sodium ions followed by dissolution in a mixture of acetic acid and water with their proportion ranging from 5:1 to 1:5 v/v to obtain a homogenous red solution of cobalt and manganese acetates. The cobalt and manganese acetate solution, obtained according to the process of the invention, has desired purity for recycle as catalyst in the oxidation of the p-xylene to terephthalic acid.
Following examples illustrate the invention, but are not intended to limit the scope of the present invention.
EXAMPLES:
Example 1:
Extraction of the solid residual waste with Demineralized water
100 ml Demineralized water and 25 gm of the solid residual waste containing 0.24% by weight of cobalt, 0.24% by weight of manganese and 1.22% by weight of sodium were charged to a Parr reactor of 450 ml capacity. The reactor was boxed up and the contents therein agitated at 240 rpm and at a temperature of 250 °C for 2 h. Thereafter the reactor was cooled initially with tap water followed by an ice-bath. The reactor was brought to atmospheric pressure by opening the vent valve. The contents of the reactor were filtered and the solid residue was washed with five portions of 10-15 ml of chilled demineralized water maintained at a temperature range of 0 to 5 °C. The washings and the filtrate were combined and analyzed further.
The results showed that cobalt and manganese were quantitatively isolated into the aqueous phase.
Example 2:
Isolation of manganese and cobalt from the aqueous solution and conversion to their
acetates

The aqueous solution obtained (the example 1) was stirred magnetically at room temperature and saturated aqueous sodium carbonate solution was added to the aqueous solution to bring its pH to 4 in order to precipitate iron carbonate if present. The sodium carbonate solution was added until the pH of the solution reached to 9 when all the cobalt and manganese precipitated out as their carbonates. Then, excess of sodium carbonate was added to the solution to ensure complete precipitation. The contents were then allowed to stand at room temperature for 6 hrs and filtered under suction. The precipitate was washed with five 20 ml portions of demineralized water and immediately treated with a solution containing glacial acetic acid and DM water in a ratio of 1:1 v/v, to obtain a homogeneous red solution of cobalt and manganese acetate. The solution was analyzed. The results showed that the overall recovery of cobalt and manganese based on the residue in accordance with the process of the invention was 95.8% and 96.4%, respectively.
Technical advancement
The process for the recovery of cobalt and manganese metals from the solid waste residue in accordance with the present invention has technical advancement over state of art. Commercially practiced processes recovers 90% or less of the cobalt and manganese from the mother liquor purge stream by converting them to the oxalate salts which have poor solubility in acetic acid and therefore are easily separated but still some portion of the metals is left unrecovered. However, the process for the recovery of cobalt and manganese from the solid residue waste, containing oxalates of cobalt and manganese, have not been reported so far. The process in accordance with the present invention recovers the balance cobalt and manganese from the solid waste residue containing cobalt and manganese in the form of their oxalates, obtained from the catalyst recovery unit with high purity.
While considerable emphasis has been placed herein on the various components of the preferred embodiment, it will be appreciated that many alterations can be made and that many modifications can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the

disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. A process for recovery of cobalt and manganese salts from residual solid waste containing oxalates of cobalt and manganese; the process comprising the following steps:
(a) treating the residual solid waste with demineralized water in a pressure reactor at a temperature ranging between 200 - 280 °C with agitation, to obtain a slurry;
(b) cooling the slurry at a temperature ranging in between 0-5 °C, to precipitate out dissolved organic solids;
(c) filtering the slurry to obtain a filtrate and a residue;
(d) washing the residue repeatedly with chilled demineralized water ;
(e) mixing the washing and the filtrate to obtain a solution;
(f) neutralizing the solution with an alkali metal carbonate solution to precipitate carbonates of cobalt and manganese;
(g) treating the precipitates of cobalt and manganese carbonates with a solution containing glacial acetic acid and demineralized water in the ratio ranging between 5:1 to 1:5 v/v, to obtain a homogeneous red solution containing acetate salts of cobalt and manganese.

2. The process as claimed in claim 1, wherein oxalates of cobalt and manganese constitute less than 10 %, and particularly less than 2% of the mass of the residual waste.
3. The process as claimed in the claim 1, wherein the contents in the reactor are agitated at an agitator speed in the range of 50-500 rpm.
4. The process as claimed in claim 1, wherein the temperature in the pressure reactor is preferably in the range of 230 - 260 °C.
5. The process as claimed in the claim 1, wherein the resident time of the residual waste in the reactor is in the range of 0.25 hr to 12 hrs, preferably 0.5 hr to 5 hrs.
6. The process as claimed in the claim 1, wherein in step (b), the cooling is performed, in two stages:

(a) in the first stage, the contents of the reactor are cooled under water; and
(b) in the second stage, the contents of the reactor are cooled in an ice-bath.

7. The process as claimed in the claim 1, wherein the step of washing the residue containing organic solids includes washing the residue with 5 portions of chilled demineralized water.
8. The process as claimed in the claim 1, wherein the chilled demineralized water at a temperature in the range of 0 to 5 °C is used for washing.
9. The process as claimed in the claim 1, wherein said alkali metal carbonate is saturated
aqueous sodium carbonate solution.
10. The process as claimed in claim 1, wherein the alkali metal carbonate is added slowly to the solution and at a temperature in the range of 25 to 35 °C.
11. The process as claimed in the claim 1, wherein in step (f), the alkali metal carbonate is added until the pH of the solution is adjusted to about 4 to precipitate any iron salts in the solution; the iron carbonate precipitate is filtered off and the alkali metal carbonate is added to raise the pH to around 9 to initiate the precipitation of cobalt and manganese salts and additional alkali metal carbonate is added to ensure complete precipitation.
12. The process as claimed in claim 1, wherein in step (g), acetic acid and water are present in the proportion of 1:1 v/v.
13. The process as claimed in any one of the preceding claims in which cobalt is recovered in the range of 94.1% to 96.9% and manganese is recovered in the range of 95.1% to 97.9%.