DESC:FORM 2

THE PATENT ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006

COMPLETE SPECIFICATION
(See section 10 and rule 13)

TITLE OF THE INVENTION
A PROCESS FOR RECOVERY OF VANADIUM AND NICKEL FROM A COMPOUND CONTAINING VALUABLE METALS.

APPLICANTS
Aditya Birla Science and Technology Company Pvt Ltd, Plot number 1 and 1-A/1, Taloja, MIDC, Taluka- Panvel, District- Raigad- 410208, Maharashtra, India.

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is
to be performed:

FIELD OF THE INVENTION
[001] The present invention relates to a process for recovery of vanadium and nickel from a compound containing valuable metals.
BACKGROUND OF THE INVENTION

[002] Vanadium is a rare element and mainly used in the production of ferrovanadium, vanadium-bearing chemicals, speciality alloys, vanadium metal, and vanadium pentoxide. Vanadium mainly occurs in phosphate rock, titaniferrous magnetite, bauxite, coal and petrochemical residues. 80% of the vanadium in the form of ferrovanadium is currently consumed for steel production. Vanadium is also used for nonferrous alloys production, ceramics, paint, chemicals and redox flow batteries.

[003] Petroleum residues and carbon residues such as coal gasification slag, petroleum ash, metal-containing petroleum residue, vanadium-containing spent catalyst or any other solid (feed) material containing vanadium and nickel is treated as hazardous waste and disposing of this material is a big concern. Moreover, these residues contain high amount of carbon, sulfur, together with vanadium, iron and nickel. Hence, recovery of metals from this material would be viable and environmentally friendly.

[004] In conventional methods, petroleum residues are roasted at about 600°C to burn off carbon and also for the removal of sulfur to produce metal oxide rich product that can be used as a raw material for ferrovanadium production. However, the concentration of carbon and sulfur should be very low for ferrovanadium production. Furthermore, nickel limits the amount of the roasted residue in raw material as the nickel content should be below a critical limit for ferrovanadium grade. Moreover, the sulfur present in the petroleum residue is in the form of metal sulfates, which needs high energy for decomposition. In addition, the SOx gases generated in the process need to be appropriately collected and neutralized.

[005] Therefore, there is a need of a process for recovery of these valuable metals that overcomes some of the problems of the prior art.
BRIEF DESCRIPTION OF DRAWINGS

[006] Figure 1 shows a process flowsheet of water leaching-precipitation-roasting process for recovering vanadium and nickel from a vanadium compound, in accordance with an embodiment of the present invention;

[007] Figure 2 shows a process flowsheet of acid leaching-precipitation-energy recovery process for recovering vanadium, nickel and energy from the vanadium compound, in accordance with another embodiment of the present invention;

[008] Figure 3 shows a process flowsheet of water leaching-precipitation-alkali roasting process for recovering vanadium and nickel from the vanadium compound, in accordance with an embodiment of the present invention;

[009] Figure 4 shows XRD of the roasted product obtained after water leaching followed by roasting, in accordance with the embodiments of the present invention;
[010] Figure 5 shows XRD of the roasted vanadium product produced from vanadium compound by acid leaching followed by precipitation, in accordance with the embodiments of the present invention; and

[011] Figure 6 shows the XRD of the calcined nickel product produced from vanadium compound by acid leaching followed by precipitation, in accordance with the embodiments of the present invention.

SUMMARY OF INVENTION
[012] In an aspect the invention provides a process for recovery of valuable metals from a compound containing vanadium and nickel. The process comprises of leaching the compound containing vanadium and nickel to obtain a leached slurry and filtering the leached slurry to separate a mother liquor and a residue.

[013] In another aspect, leaching of is carried out by water and/or dilute mineral acid for a duration of leaching is in the range of 1-4 hours at a pH in the range of 0.1 to 4at a temperature of leaching is in the range of 25oC to 90oC.

[014] In yet another aspect, the ratio of compound containing vanadium and nickel to water and/or dilute mineral is in the range of 1:2 to 1:5.

[015] The process further comprises of adjusting pH of mother liquor of step (b) in the range of 4.5 - 6.0 to obtain a tetravalent vanadium containing precipitate and a supernatant. Subsequently, pH of the supernatant is adjusted in the range of pH 8-10 to obtain a nickel containing precipitate.

BRIEF DESCRIPTION OF THE EMBODIMENTS
[016] The invention summarized above and defined by the enumerated claims may be better understood by referring to the following description, which should be read in conjunction with the accompanying claims. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the invention, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention.

[017] It is to be noted that, as used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[018] The expression of various quantities in terms of “%” or “% w/w” means the percentage by weight, relative to the weight of the total solution or composition unless otherwise specified.

[019] The present invention discloses pyro and hydrometallurgical processes for the recovery of one or more valuable metals from a vanadium compound by water leaching, acid leaching and/or roasting and precipitation. Target metals include vanadium (V), nickel (Ni), and iron (Fe).

[020] The vanadium compound comprises of coal gasification slag, petroleum ash, metal-containing petroleum residue, vanadium and nickel-containing spent catalyst or any other solid (feed) material containing vanadium and nickel. Usage of all these alternatives of vanadium compound are considered to be within the scope of the present invention.

[021] In an embodiment of the invention, as shown in Figure 1, the process comprises the step of water or dilute acid leaching of vanadium compound to dissolve metal sulphates (VOSO4, FeSO4, NiSO4 etc.) present in the vanadium compound and a resultant obtaining a residue with reduced content of target metal and sulphur. The vanadium in leach liquor is selectively separated by ion exchange, adsorption and desorption, solvent extraction or precipitation. However, in the current embodiment, this leach solution is sent for a precipitation step wherein the leach solution is contacted with an alkali solution to increase the pH to about 5 so as to selectively precipitate tetravalent Vanadium rich compound. The equation for chemical precipitation of vanadium is given below:
a. VOSO4 + 2 NaOH + H2O = VO2.xH2O + Na2SO4

[022] This tetravalent vanadium rich compound is used in Ferro-vanadium production with or without a prior roasting step. After removal of vanadium, nickel is selectively removed by techniques such as solvent extraction, precipitation, ion exchange or adsorption. In the current embodiment, nickel is precipitated from vanadium leach solution by increasing the pH to 9. Nickel together with iron is precipitated at this pH. This compound is used for ferronickel production or for selective separation of nickel. The precipitation reaction for nickel is given below:
a. NiSO4 + 2NaOH = NiO.xH2O + Na2SO4

[023] The residue generated after leaching contains low amount of metals and negligible sulphur with high amount of carbon. This residue is combusted in presence of oxygen at around 650°C to remove carbonaceous compounds. The residue generated after combustion contains oxides of vanadium, iron and nickel. This residue can be replaced with V2O5 in the charge mix of FeV production process.

[024] The process of the present invention not only decreases the energy consumption for roasting but also increases the ratio of vanadium compound usage in FeV production. Furthermore, about 60% of nickel can be recovered from this process.

[025] In an embodiment, the tetravalent vanadium rich compound generated after water leaching is converted to pentavalent vanadium compound by oxidation at high temperature or by using an oxidizing agent such as H2O2 in the slurry.

[026] In another embodiment of the invention, shown in Figure 2, the process comprises the step of acid leaching of vanadium compound to dissolve metal sulphates and metal compounds present in the VC and a resultant residue with very low content of target metal and sulphur. The residue generated after leaching contains mainly carbonaceous material that is used as a source of energy. The vanadium in leach liquor is selectively separated by ion exchange, adsorption and desorption, solvent extraction or precipitation. However, in the current embodiment, precipitation technique that is used is to selectively separate vanadium rich oxide and nickel rich compound from the solution.

[027] At pH 5, tetravalent vanadium hydroxide compound precipitates out from the leach solution. After removal of vanadium, nickel can be selectively removed by techniques such as solvent extraction, precipitation, ion exchange or adsorption. In the current embodiment, nickel was precipitated by increasing the pH to 9. Nickel together with iron is precipitated at pH 9. This compound is used for ferronickel production or for selective separation of nickel.

[028] This process decreases the energy consumption for roasting and also increases the ratio of vanadium compound usage in FeV production. Furthermore, about 90% of nickel can be recovered from this process. In addition, carbonaceous residue can be used elsewhere for energy production.

[029] In yet another embodiment of the invention, shown in Figure 3, the process comprises the step of water or dilute acid leaching of vanadium compound to dissolve metal sulphates present in the VC and a resultant residue with reduced content of target metal and no sulphur. The vanadium in leach liquor is selectively separated by ion exchange, adsorption and desorption, solvent extraction or precipitation. However, in the current embodiment, the leach solution is sent for a precipitation step wherein the leach solution is contacted with an alkali solution to increase the pH to about 5, so as to selectively precipitate tetravalent vanadium rich compound. This tetravalent vanadium rich compound is used in ferrovanadium production with or without a prior roasting step at 650°C.

[030] The residue generated after leaching contains low amount of metals and negligible sulphur with high amount of carbon. This residue is combustion roasted in the presence of alkali compounds such as NaCl, NaOH, Na2CO3, KCl, KOH, K2CO3 etc. at around 6500C to remove carbonaceous compounds in presence oxygen and to convert vanadium compounds to alkali compounds such as sodium vanadate or potassium vanadate. The residue generated after combustion contains alkali vanadates and iron and nickel oxides.

[031] This residue generated after combustion roasting is dissolved in water to dissolve alkali vanadate compounds. The solution after alkali vanadate dissolution is treated with ammonium salts to precipitate ammonium metavanadate. This ammonium metavanadate is roasted at around 650°C to produce V2O5, which is used for FeV production or other applications. The vanadium residue generated after water leaching of combustion roasted residue is rich in nickel and iron, which can be used for ferronickel production or selective separation of nickel.

[032] This process decreases the energy consumption for roasting and also increases the ratio of vanadium compound usage in FeV production. Furthermore, about 90% of nickel can be recovered from this process. In addition, this process can produce about 40% of vanadium oxide in the pure form (with no iron)

WORKING EXAMPLES:
[033] Advantages and benefits of the present process according to the embodiments of the present invention would become more apparent from the below experimental details to a person skilled in the art.
EXAMPLE 1:

[034] 5 g of VC was added to 25 ml of water and stirred for 1 hour to obtain a slurry containing dissolved sulfate compounds. The leached solution had pH <1. After leaching, a solid-liquid separation process was performed to separate the leach solution from insoluble residue. About 60% of metal values, without much significant selectivity for a particular metal, were dissolved into the leach solution. Then this leach solution was treated with NaOH, to obtain pH 5-5.5, to precipitate tetravalent vanadium rich compound (rich in VO2. xH2O) after which a solid-liquid separation process was performed. This precipitate was roasted at 650°C in oxygen environment to produce flakes of V2O5. This product contained some impurities of iron oxides. The solution after vanadium precipitation was rich in nickel and iron. This solution was again treated with NaOH to increase the pH to 9 to precipitate nickel rich compound. However, the solution obtained after vanadium removal could also be used for selective nickel recovery by solvent extraction, adsorption, ion exchange etc.

[035] The residue after leaching (2.5 g) contains a low amount of metals and insignificant quantity of sulfur and it is rich in carbonaceous material. This residue was roasted at 650 0C to burn off the carbon and the roasted product contains mainly the oxides of iron, nickel and vanadium. XRD of this product after roasting is shown in the Figure 4, which shows the presence of vanadium, iron, nickel and sodium compounds. This product can be mixed as one of the vanadium sources for the production of ferrovanadium. However, its fraction in the raw mix needs to be limited based on final nickel content allowed in FeV.
EXAMPLE 2:

[036] 5 g of VC was added to 25 ml of 2M sulfuric acid solution and stirred for 1 hour at 600C to dissolve metals into the solution. This process dissolved >95% of metals in to the solution. After leaching, a solid-liquid separation process was performed to separate the leach solution from insoluble residue. Then this leach solution was treated with NaOH, to obtain pH 5-5.5, to precipitate tetravalent vanadium rich compound (rich in VO2. xH2O) after which a solid-liquid separation process was performed. This precipitate was roasted at 650 0C in oxygen environment to produce flakes of V2O5. XRD of this product is shown in the Figure 5, which shows peaks of V2O5 and iron vanadate and same can be used for FeV production. The solution after vanadium precipitation is rich in nickel and iron. This solution was treated with NaOH to increase the pH to 9 to precipitate nickel rich compound. XRD of this product after roasting is shown in the Figure 6, which shows only peaks of nickel ferrite. The residue after leaching (about 1.8 g) was rich in carbonaceous material and contained a very low amount of metals, which can be used as an energy source.
EXAMPLE 3:

[037] 5 g of VC was added to 25 ml of water and stirred for 1 hour to dissolve sulfate compounds. After leaching, a solid-liquid separation process was performed to separate the leach solution from insoluble residue. About 60% of metal values were dissolved into the leach solution. Then this leach solution was treated with NaOH, to obtain pH 5-5.5, to precipitate tetravalent vanadium rich compound (rich in VO2. xH2O) after which a solid-liquid separation process was performed. This precipitate was roasted at 650°C in oxygen environment to produce flakes of V2O5. This product contained some amount of iron. Hence, it can be used for FeV production. The solution after vanadium precipitation is rich in nickel and iron. This solution was treated with NaOH to increase the pH to 9 to precipitate nickel rich compound, which can be used for ferronickel production or selective recovery of nickel.

[038] The residue (about 2.5 g) after leaching contained a low amount of metals and insignificant quantity of sulfur and rich in carbonaceous material. This residue was roasted at 650°C, in presence of sodium carbonate with a ratio of sodium carbonate to residue is 2:5, to burn off the carbon and to convert vanadium oxides to sodium vanadate. The roasted product contained mainly the sodium vanadate and oxides of iron and nickel. This roasted product was leached with water at 60°C for 1h to dissolve sodium vanadates. This process recovered more than 90% of vanadium. The filtration of the leach solution generates a residue (~0.2 g) rich in iron and nickel oxides. This residue can be used for ferronickel production or selective nickel recovery. The sodium vanadate solution was mixed with ammonium salt to precipitate ammonium vanadate in a known process, which was roasted at 650°C to produce vanadium pentaoxide flakes.

[039] The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application thereby enabling others, skilled in the art, to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.

,CLAIMS:We Claim:

1) A process for recovery of valuable metals from a compound containing vanadium and nickel comprising the steps of:
(a) leaching the compound containing vanadium and nickel to obtain a leached slurry; and
(b) filtering the leached slurry to separate a mother liquor and a residue,

wherein said leaching of step (a) is carried out by water and/or dilute mineral acid.

2) The process as claimed in claim 1, wherein pH during leaching is in the range of 0.1 to 4.

3) The process as claimed in claim 1, wherein the duration of leaching is in the range of 1-4 hours.

4) The process as claimed in claim 1, wherein the temperature of leaching is in the range of 25oC to 90oC.

5) The process as claimed in claim 1, wherein the ratio of compound containing vanadium and nickel to water and/or dilute mineral is in the range of 1:2 to 1:5.

6) The process as claimed in claim 1, wherein said dilute mineral acid is selected from a group consisting of dilute sulphuric acid, dilute hydrochloric acid, dilute nitric acid or mixture thereof.

7) The process as claimed in claim 1, wherein said valuable metals is selected from a group vanadium, nickel, iron and the like.

8) The process as claimed in claim 1, wherein said compound containing vanadium and nickel is selected from a group consisting of coal gasification slag, petroleum ash, metal-containing petroleum residue, metal-containing spent catalyst or combination thereof.

9) The process as claimed in claim 1, further comprising of adjusting pH of mother liquor of step (b) in the range of 4.5 - 6.0 to obtain a tetravalent vanadium containing precipitate and a supernatant.

10) The process as claimed in claim 9, further comprising of roasting said tetravalent vanadium precipitate at a temperature in the range of 600oC to 700oC to obtain vanadium(V) flakes.

11) The process as claimed in claim 9, further comprising adjusting pH of said supernatant in the range of pH 8-10 to obtain a nickel containing precipitate.

12) The process as claimed in claim 9 and 11, wherein the adjustment of pH is facilitated by an alkaline agent, selected from a group comprising of sodium hydroxide, lime, limestone, potassium hydroxide, ammonia.

13) The process as claimed in claim 1, further comprising roasting said residue of step (b) at a temperature in the range of 600°C -700°C to burn off carbon for energy recovery.

14) The process as claimed in claim 1, wherein said residue of step (b) is further processed comprising the steps of:
(a) roasting said residue at 600°C -700°C in the presence of a sodium salt;
(b) water leaching the roasted residue from step (a) for a duration of 20-30 hours;
(c) precipitating ammonium metavanadate from leached residue of step (b) by adding ammonium sulphate; and
(d) roasting ammonium metavanadate at 400°C-600°C to obtain vanadium flakes.

Dated this 05th Day of March 2021
-Digitally Signed-
M. Kisoth
IN/PA-2259
Agent for the Applicant