AU2011341872B2 - Method for enrichment-recovering ferronickel from raw material containing nickel, method for recovering nickel from enriched ferronickel, and method for recycling solution containing iron produced from same - Google Patents

Abstract

The present invention relates to a method for enriching ferronickel to a high density from a raw material containing nickel and iron, and more particularly comprising: a step of slurrifying for reducing the raw material containing nickel-iron and then slurrifying same by adding water; a step of acid treating for simultaneously inducing ferronickel separation and iron leaching reactions by injecting into the slurry of the reduced raw material containing nickel-iron, which is obtained from the step of slurrifying, hydrochloric acid having 0.5-1.5 times more moles or sulfuric acid having 0.25-0.75 times more moles than the moles in the reduced raw material containing nickel-iron; a step of filter-separating for eliminating a solution containing iron from the solution which is obtained from the step of acid treating by separating solids containing ferronickel by means of a filter; and a step of enriching for slurrifying the solids containing ferronickel from the step of filter-separating and mixing same with the raw material containing nickel-iron that is reduced, and enriching ferronickel by performing the step of acid treating and the step of filter-separating. Furthermore, the present invention provides a method for recycling a solution containing iron, which is produced and wasted in a method for recovering highly pure nickel from the nickel enriched product and in a method for recovering the nickel enriched product.

Description

[DESCRIPTION] [Invention Title] METHOD FOR ENRICHMENT-RECOVERING FERRONICKEL FROM RAW MATERIAL CONTAINING NICKEL, METHOD FOR RECOVERING NICKEL FROM ENRICHED FERRONICKEL, AND METHOD FOR RECYCLING SOLUTION CONTAINING IRON PRODUCED FROM SAME [Technical Field] [0001] The present invention relates to a method of enriching ferronickel at a high concentration from a raw material containing nickel (Ni) and iron (Fe), and more particularly, to a method of recovering a nickel concentrate by dissolving a raw material containing nickel and iron with an acid and precipitating ferronickel therefrom. [00021 Further, the present invention relates to a method of recovering high-purity nickel from the nickel concentrate and a method of recycling an Fe-containing solution generated and wasted during a recovery process of the nickel concentrate. [Background Art] [0003] Nickel-containing ores include limonite and saprolite, and since these ores have passive characteristics, acid dissolution reactions are slow due to a high resistance to acids. Therefore, various methods of recovering nickel by acid dissolution in an autoclave at high temperature and at high pressure have been suggested as means of effectively leaching nickel from ore and these methods are collectively known as Pan, 1 "high pressure acid leaching (HPAL)". [0004] When a nickel leaching reaction is performed at room temperature, a nickel recovery rate may not be greater than about 85% even in the case that leaching is performed for a few months or more. However, when the HPAL method is used, nickel leaching having a nickel recovery rate of 90% or more may be possible within two hours, and thus, the HPAL method may be regarded as being a typical method for nickel oxide ore hydrometallurgy. [0005] Examples of a technique related to the recovery of nickel by using the HPAL method may be disclosed in Korean Patent Application Laid-Open Publication No. 2007-7020915 and Japanese Patent Application Laid-Open Publication No. 2010 031341. However, it is commonly known in the technical field to which the current invention pertains that the HPAL method must be performed at high temperature and at high pressure in an autoclave, and only titanium may be used therefor, due to the strong resistance to acidity thereof. Therefore, HPAL equipment costs may be very high as well as maintenance costs therefor. Also, since sodium hydroxide, an expensive precipitant, or an environmentally hazard precipitant (H 2 S) must be used for enriching nickel, equipment costs for treating these precipitants may increase. [0006] In Korean Patent Application Laid-Open Publication No. 2009-0031321, the present inventors suggested a method of Pane 2 recovering nickel by acid leaching after a nickel-containing raw material is reduced by hydrogen. A technique of the foregoing patent discloses a method of preparing an iron (Fe) and nickel (Ni)-containing raw material for recycling a residue of a spent petrochemical desulfurization catalyst including: treating a residue remaining after the recovery of vanadium (V) and molybdenum (Mo) from a spent petrochemical desulfurization catalyst with an acid to remove alkaline elements therefrom; drying the residue having the alkaline elements removed therefrom and heating the residue to a temperature within a range of 600 0 C to 1300 0 C in a reducing atmosphere to reduce Ni and Fe existing in oxide forms in the residue to metals; leaching a reduced product thus obtained with an acid to selectively dissolve iron and nickel; filtering the solution to obtain a solution containing leached nickel and iron ions; neutralizing the solution containing Ni and Fe ions with alkali to prepare Fe and Ni hydroxide; and filtering and drying a product thus obtained to obtain an Fe and Ni-containing raw material. [0007] When the foregoing method is used for leaching limonite nickel ore, high-speed leaching may be possible. However, limonite ore has a high Fe content and a low Ni content, and thus, when nickel is leached therefrom by acid dissolution, a relatively large amount of Fe is leached while only a small amount of Ni is leached. Therefore, iron and Pans 3 nickel may be difficult to be separated from a leachate. [Disclosure] [Technical Problem] [00081 An aspect of the present invention provides a method of effectively concentrating nickel (Ni) from a raw material containing nickel and iron, in particular, a low-grade Ni ore, by separating and recovering nickel and iron (Fe) and recovering nickel from a concentrate. [0009] Another aspect of the present invention provides a method of innovatively decreasing an amount of byproduct generated in a nickel smelting process by recycling an Fe containing solution generated from the method of the present invention to provide a raw material for manufacturing a magnetite iron ore. [Technical Solution] [00101 According to an aspect of the present invention, there is provided a method of enriching nickel (Ni) from a nickel and iron (Fe) -containing raw material including: preparing a slurry by reducing a nickel and iron-containing raw material and adding water; acid treating the reduced nickel and iron containing raw material to prepare an acid-treated solution by adding an amount of moles of hydrochloric acid in a range of 0.5 times to 1.5 times or an amount of moles of sulfuric acid in a range of 0.25 times to 0.75 times based on an amount of moles of (Fe+Ni) in the nickel and iron-containing raw Paae 4 material to the slurry; and mixing the reduced nickel and iron-containing raw material in the acid-treated solution, wherein the reduced nickel and iron-containing raw material may include an amount of moles of iron greater than 5 times and equal to or less than 10 times based on a total amount of moles of nickel in the solution when nickel is dissolved in an amount of less than 5 g/l in the acid-treated solution, and an amount of moles of iron equal to or greater than 2.5 times and equal to or less than 5 times based on the total amount of moles of nickel in the solution when nickel is dissolved in an amount of 5 g/l or more in the acid-treated solution. [0011] The nickel and iron-containing raw material mixed in the slurry may be reduced from a limonite ore [0012] According to another aspect of the present invention, there is provided a method of recovering a nickel (Ni) concentrate from a nickel and iron (Fe)-containing raw material including: preparing a slurry by reducing a nickel and iron-containing raw material and adding water; acid treating the slurry to simultaneously generate ferronickel precipitation and iron leaching reactions and prepare a solution by adding an amount of moles of hydrochloric acid in a range of 0.5 times to 1.5 times or an amount of moles of sulfuric acid in a range of 0.25 times to 0.75 times based on an amount of moles of (Fe+Ni) in the reduced nickel and iron containing raw material to the slurry of the reduced nickel Paae 5 and iron-containing raw material obtained in the preparing of the slurry; and filtering and separating a solid content including ferronickel from the solution obtained in the acid treating of the slurry to remove an iron-containing solution. [0013] The method may further include preparing a slurry from the solid content including ferronickel obtained from the filtering and separating of the solid content and mixing the slurry with the reduced nickel and iron-containing raw material to make a slurry, and enriching ferronickel by performing the acid treating of the slurry and the filtering and separating of the solid content. [0014] The enriching of the ferronickel may be repeatedly performed until a nickel concentration reaches a range of 5 wt% to 20 wt% based on a solid content weight of a ferronickel concentrate and thus, a nickel concentrate may be recovered from the nickel and iron-containing raw material. [0015] The acid may be added to have a final pH within a range of 1 to 6 after the ferronickel precipitation and iron leaching reactions. [0016] In the method of recovering a nickel concentrate from the nickel and iron-containing raw material, the nickel and iron-containing raw material may be obtained by drying a nickel ore at a temperature suitable for removing crystallization water from the nickel and iron-containing raw material, pulverizing the nickel ore into particles having a Paae 6 diameter of 1 mm or less, and calcinating the particles within a temperature range of 2500C to 850C. [0017] The reduction of the nickel and iron-containing raw material may be performed by using a hydrogen-containing gas as a reduction gas at a temperature within a range of 550 0 C to 950 0 C, and the hydrogen-containing gas may be pure hydrogen gas or mixed nitrogen and hydrogen gas. [0018] The method may further include drying the nickel concentrate after cleaning and filtration when a content of nickel included in the nickel concentrate is in a range of 5 wt% to 20 wt% of the solid content weight of the ferronickel concentrate. [0019] According to another aspect of the present invention, there is provided a method of recovering high-purity nickel (Ni) from a nickel-containing raw material including: obtaining a high-concentration nickel solution by dissolving the nickel concentrate recovered by the method with an acid to leach nickel and filtering; and removing iron (Fe) from the high-concentration nickel solution. [0020] The acid may be hydrochloric acid and an amount of moles of the hydrochloric acid added may be in a range of 2 to 4 times of that of moles of (Fe+Ni) in the nickel concentrate, and when the acid is sulfuric acid, an amount of moles of the sulfuric acid added may be in a range of equal to 2 times of that of moles of (Fe+Ni) in the nickel concentrate. Paae 7 (00211 The removing of the iron may be performed by injecting an oxygen-containing gas to generate iron hydroxide while a pH of the high-concentration nickel solution is controlled to be within a range of 2.5 to 5.5 and filtering the generated iron hydroxide, or using a solvent extraction method. [0022) According to another aspect of the present invention, there is provided a method of recycling an iron-containing solution including: adding an alkaline component to the iron containing solution removed in the filtering and separating of the solid content to control a pH of the solution to be within a range of 9.5 to 10.5; and injecting an oxygen-containing gas to generate magnetite through oxidation. [Advantageous Effects] [00231 According to the present invention, nickel (Ni) may be effectively recovered from a raw material such as a nickel containing ore. In particular, the present invention may effectively enrich and recover nickel from a low-grade nickel ore, and thus, may be suitable for using in nickel smelting. [0024] In particular, since nickel and iron are separated and recovered from limonite, a nickel ore having a high iron (Fe) content, a nickel concentrate may be used as a raw material for stainless steel and separated and removed iron may be manufactured as a magnetite iron ore suitable for being used as a sintered ore raw material for carbon steel. As a result, an amount of byproduct generated in nickel smelting may be Pa;ne 8 innovatively reduced. [Best Model [0025] Hereinafter, the present invention will be described in detail. [0026] The present invention relates to a method of recovering a nickel (Ni) concentrate from a nickel and iron (Fe) containing raw material. In particular, in the case that nickel is leached by acid dissolution, since the raw material has a low Ni concentration and a high Fe concentration, a relatively large amount of iron is leached while only a small amount of nickel is leached. Therefore, the present invention may be suitable for the case in which iron and nickel may be difficult to be separated. [0027} Nickel and iron-containing raw materials applicable to the present invention are not particularly limited so long as the raw materials contain nickel and iron, and may include nickel ores, e.g., limonite and saprolite. Nickel ores generally include 1% to 2.5% of Ni and 15% to 55% of Fe although the nickel ores may be different according to types thereof, and among nickel ores, limonite ore has a low Ni concentration ranging from 1% to 1.8% and a high Fe concentration ranging from 30% to 55%. The present invention may be effectively used when nickel is recovered from limonite having a relatively low Ni content. [0028] In recovering nickel from the nickel ores, pretreatment P;;op 9 operations, such as drying, pulverization, and calcination, may be performed in order to effectively reduce the nickel ores in a reduction process to later be described. Hereinafter, the pretreatment operations, i.e., drying, pulverization, and calcination operations, will be described in detail. [0029] In general, leaching by a wet method has been used when nickel is recovered from nickel-containing ores and for this purpose, the nickel-containing ores have been typically pulverized in a state having moisture. However, since the present invention includes a subsequent heat treatment operation, a drying operation removing moisture in advance may be performed. Dry pulverization after the drying operation may further increase pulverization efficiency in comparison to a wet pulverization process. Further, when there is a need for uniformly controlling a particle size of the ore required for reduction and leaching reactions, air classification of particles may be performed for particles of various sizes by using wind speeds of a dust collector and thus, powder required for the reduction and leaching reactions having a uniform particle size may be obtained. [0030] In the present invention, ore powder having a particle diameter of 1 mm or less may be used. When the particle size of the ore powder is greater than 1 mm, reduction and leaching rates may be low and in particular, workability may also be poor because pump and pipe clogging may occur excessively PAnP in during an acid leaching reaction. When the particle size of the powder is 1 mm or less, the powder may be suitable for the present invention, and thus, a lower limit thereof is not particularly limited. However, the pulverization process must be performed for an unnecessarily long period of time or multiple times in order to obtain powder having a particle size less than 10 pm. Therefore, powder having a particle size of 10 pm or more may be used. [0031] In general, nickel ores contain crystallization water, and when a calcination process is not undertaken, crystallization water included in the ores may be released in a subsequent reduction process to retard a reduction reaction. Therefore, pulverized powder may be calcinated. Among the nickel ores, limonite and saprolite have characteristics of releasing crystallization water at temperatures within temperature ranges of about 2500C to 350 0 C and 6500C to 7500C, respectively. Ore powders obtained from the pulverization process are calcinated at a temperature within a temperature range of 250 0 C to 8500C and thus, crystallization water included in the nickel ores may be removed. [0032] Meanwhile, saprolite having a high content of nickel is mainly used as a raw material of nickel pyrometallurgy, and nickel may also be recovered from rotary kiln dust generated in a pyrometallurgical process by using the present invention. However, since a particle size of the dust is included in an p;;Ip I11 appropriate range suitable for the present invention and the dust has been exposed in a high-temperature state during the pyrometallurgical process, pulverization and calcination processes as in the case of the nickel-containing ores are not required. However, in the case that the particle size deviates from the range required in the present invention due to a factor such as the dust being exposed to air to take on moisture, a pulverization or calcination process may be undertaken as needed. [0033] Also, when an oil refining company uses a catalyst containing nickel, a spent catalyst residue may be generated and nickel may be enriched and recovered by using the present invention for the spent desulfurization catalyst residue including nickel. Since a particle size of the spent catalyst residue is generally included in an appropriate range suitable for the present invention, a pulverization process is not required. However, the spent catalyst residue may be pulverized by using an appropriate means when the spent catalyst residue is agglomerated. Further, the foregoing calcination process may be undertaken as needed. [00341 The following Table 1 presents main components of nickel and iron-containing raw materials. A unit of a content of each component in Table 1 is wt% and oxygen as well as trace amounts of magnesium (Mg) and manganese (Mn) being included as a remainder. Pa;ne 12 [0035] [Table 1] Ni Fe Mg Al Limonite 1.76 61.9 1.4 2.5 Saprolite 2.57 18.7 13.5 0.7 Spent catalyst residue 4.8 3.5 0.1 35.5 [0036] The present invention includes a reducing operation reducing nickel and iron after the pretreatments of the nickel and iron-containing raw materials being performed. The reducing operation may be performed by using a reduction gas including hydrogen and may be performed at a temperature within a range of 5500C to 9500C. When the reduction temperature is 5500C or less, a nickel recovery rate may decrease during subsequent leaching because a reduction may occur insufficiently, and when the reduction temperature is 950 0 C or more, the reduction rate may not increase further and only sintering may occur between particles to thereby badly affect workability. [0037] Hydrogen gas may be used alone as the reduction gas, and an inert gas may be used together therewith in order to remove oxygen in addition to hydrogen existing in a reduction furnace during the reduction reaction. Examples of the inert gas may be nitrogen. [0038] In reducing the nickel and iron-containing raw material, e.g., limonite ore (Ni:Fe = 1:30), by using hydrogen as a P;;oP 13 reduction gas, a theoretical reduction reaction is expressed as the following Reaction Formula (1). [0039] (NiO 0 Feo.

9 )OFe 2

O

3 + 4H2 = (NiO.

1 FeO, 9 ) + 2Fe + 4H20 (1) [0040] The reduced nickel and iron-containing raw material obtained from the reduction process is separated from an exhaust gas and then the reduced nickel and iron-containing raw material is discharged into an oxygen-barriered tank containing water to make into a slurry. Since a content of an iron component may be very high when the nickel ore is reduced, reoxidation may occur during extraction into air after the reduction, and an oxidation reaction may be accelerated due to the generation of heat to thus increase the risk of fire. Therefore, the slurry is prepared from the reduced nickel and iron-containing raw material, and thus, oxidation and ignition of the iron component may be prevented. [0041] The present invention includes an acid treating operation in which an acid is added to the slurry obtained to precipitate ferronickel as well as iron. In the acid treating operation, nickel ore is dissolved by introducing the nickel and iron-containing raw material into an oxygen-free reactor and adding an acid thereto. Hydrochloric acid and sulfuric acid may be used as the acid used in the acid treating operation, but the acid is not limited thereto. [0042] In general, when the nickel and iron-containing raw material reduced according to Reaction Formula (1) is leached Panr 14 with an acid, a metal-acid treatment according to the following Reaction Formula (2) is performed and thus, ferronickel is dissolved into ions. [0043] (Nio 0 Feo.

9 ) + 2Fe + 6HCl = (Nio iFeo.

9 )Cl 2 + 2FeCl 2 + 3H 2 (2) [0044] Meanwhile, when an ore having a separate limonite ore to be reduced according to the reaction of Reaction Formula (1) is added in order to precipitate the ferronickel ions dissolved in Reaction Formula (2), a reaction according to the following Reaction Formula (3) occurs. [0045] (Nio 0 Fea.

) C1 2 + { (NioiFeo 9 ) + 2Fe} = Nio.

2 Feo.

0 + 2Fe + 0.IFeCl 2 (3) [0046] That is, the dissolved ferronickel ions are substituted and precipitated into metal by reduced metal Fe. The principle of the reaction is based on a natural potential difference between iron and nickel, and a battery reaction such as a reaction described by following reaction formulas may occur. That is, since a battery is formed according to a natural potential difference between Ni ions and reduced metal Fe in an aqueous solution, a dissolution reaction is performed by the oxidation of Fe at an anodic site of the reduced ore and a precipitation reaction is performed by reduction of nickel ions in the aqueous solution at a cathodic site of the reduced ore. [0047] Anodic Reaction: Fe = Fe+ 2 + 2e E = 0.44 [00482 Cathodic Reaction: Ni2 + 2e = Ni E = -0.25 [0049] Overall reaction: Fe + Ni+ 2 = Fe+ 2 + Ni E* = 0.19 pna 1 ; [0050] Meanwhile, since the reaction of Reaction Formula (2) is very fast while the reaction of Reaction Formula (3) is slow, the reaction of Reaction Formula (3) becomes a rate controlling reaction for precipitation after leaching the ferronickel. In particular, since the solubility of iron in the aqueous solution is about 150 g/l, a concentration, in which ferronickel may be dissolved during acid leaching, is limited to 5 g/l or less. Therefore, when the concentration of ferronickel is low, a concentration of ferronickel, which may be enriched according to the reaction of Reaction Formula (3), is also limited. [0051] That is, when the reduced nickel and iron-containing raw material having a low Fe content is added to an acid treated solution having an Ni concentration of less than 5g/1, it may be difficult to precipitate the dissolved nickel ions at a high recovery rate. The reason for this is that a reaction according to Reaction Formula (3) must occur in order to allow nickel to be substituted and precipitated, but a diffusion rate in the reaction of Reaction Formula (3) may rapidly decrease when the concentration of nickel is low. [0052] Therefore, in the case that the concentration of Ni in the acid-treated solution is less than 5 g/l in the nickel precipitation reaction, the nickel recovery rate may considerably increase when the nickel and iron-containing raw material reduced at a mixing ratio (hereinafter, referred to pnP 1if; as a "mixing ratio of Fe/Ni") , in which an amount of moles of iron included in the reduced nickel and iron-containing raw material is 5 times or more based on an amount of moles of Ni in the acid-treated solution, is mixed. However, the mixing ratio may not be greater than 10. When the mixing ratio is greater than 10, an increase in the nickel recovery rate may be insignificant and the concentration of Ni may be decreased due to a high iron content in the Ni concentrate. [0053] Meanwhile, in the case that the concentration of Ni in the acid-treated solution is 5 g/l or more, an excellent nickel recovery rate may be obtained when the concentration of slurry of the reduced ore is increased even in the case that the mixing ratio of Fe/Ni is 5 or less. The reason for this is that a large amount of iron may be introduced to the solution as the concentration of slurry of the reduced ore increases. [0054] Limonite ore having a high Fe content as shown in Table 1 may be used as a nickel and iron-containing raw material suitable for obtaining the foregoing results. However, even in the case that limonite ore is used, when the concentration of Ni in the acid-treated solution is 5 g/l or more, the nickel recovery rate may not increase even in the case that the concentration of nickel in the solution is high when the Fe/Ni mixing ratio is less than 3. [00551 Meanwhile, it was described that when the raw material having a low nickel content, such as limonite, is leached with P;;np 17 an acid, substitution and precipitation of nickel may be difficult due to the low concentration of nickel in the solution, but nickel may be recovered at a high yield when the content of metal Fe in the solution is increased. In the case that the nickel and iron-containing raw material having a low nickel content is acid treated by using the foregoing principle, the same result as above may be obtained when iron is insufficiently dissolved and allowed to remain as a metal. [00561 Therefore, when a ratio of an amount of moles of acid to an amount of moles of (Fe + Ni) is less than an equivalence ratio for acid dissolution, iron will remain after the acid dissolution and the iron may substitute and precipitate nickel ions. [0057] In the present invention, hydrochloric acid and sulfuric acid may be used as an acid for the nickel leaching reaction. Since sulfuric acid may provide the same effect as that of hydrochloric acid by the same principle except a difference in chemical equivalence between hydrochloric acid and sulfuric acid, hydrochloric acid will be mainly described as an example below. [00581 As shown in Reaction Formula (2), a theoretical equivalence ratio of an amount of moles of hydrochloric acid added to an amount of moles of (Fe+Ni) in the ore during the nickel leaching is 1:2. However, in the present invention, the amount of hydrochloric acid is added less than the theoretical equivalence ratio and thus, enrichment of nickel may be promoted. Accordingly, in the present invention, the amount of moles of hydrochloric acid added is in a range of 0.5 times to 1.5 times, based on the amount of moles of (Fe + Ni) in the reduced nickel and iron-containing raw material. [0059] When the amount of moles of hydrochloric acid added is limited to a range of 0.5 times to 1.5 times based on the amount of moles of (Fe + Ni) in the reduced nickel and iron containing raw material, leaching of Fe and precipitation of ferronickel selectively and simultaneously occur and thus, ferronickel may be enriched. For example, when the ratio of the amount of moles of hydrochloric acid to the amount of moles of (Fe+Ni) is 1.0, a reaction according to the following Reaction Formula (4) occurs. [0060] (NiO 1 Feo.

9 ) + 2Fe + 3HCl = (Nio 1 Feo,) + 0.5Fe + 1.5FeCl 2 + 1.5H2 (4) [0061] That is, ferronickel and iron are dissolved according to the reaction of Reaction Formula (2), a reaction according to Reaction Formula (3) occurs for iron metal undissolved due to the insufficient equivalence ratio of hydrochloric acid, ferronickel ions are substituted and precipitated into ferronickel metal, and the reaction of Reaction Formula (4) finally occurs, in which ferronickel is entirely undissolved and only Fe is dissolved. [0062] Meanwhile, when the amount of moles of hydrochloric acid added based on the amount of moles of (Fe + Ni) in the PDno 1Q reduced nickel and iron-containing raw material is greater than 1.5 times of the amount of moles of (Fe + Ni), nickel is dissolved to decrease a nickel precipitation recovery rate, and when the amount of moles of hydrochloric acid added to the amount of moles of (Fe + Ni) is less than 0.5 times, an enrichment ratio of nickel is low and thus, the number of repetition of the reaction according to Reaction Formula (4) may increase. [0063] In the case that sulfuric acid is used as the foregoing acid, the same effect as that of hydrochloric acid may be obtained by the same principle. However, as shown in the following Reaction Formula (5), since there is a difference in chemical equivalence when sulfuric acid is used as compared to the case that hydrochloric acid is used, an amount of moles of sulfuric acid added may be in a range of 0.25 times to 0.75 times, based on the amount of moles of (Fe + Ni) in the reduced nickel and iron-containing raw material. [0064] (NiOFeo.

9 ) + 2Fe + 1.5H 2

SO

4 = (Nio 0 Fo.

9 ) + 0.5Fe + 1.5FeSO 4 + 1.5H 2 (5) [0065] Therefore, since a nickel concentrate in a ferronickel form obtained according to the reaction of Reaction Formula (4) or (5) and Fe ions dissolved as FeCl 2 or FeSO 4 may be separated through a solid-liquid separator, only nickel may be enriched by selectively removing Fe ions. [0066] Further, since the amount of moles of hydrochloric acid added to the amount of moles of (Fe + Ni) may be changed Dnrn 2Al according to the concentration of slurry and the concentration of hydrochloric acid, a final pH of the solution after the Fe leaching and Ni precipitation reactions being performed may be controlled within a range of 1.0 to 6.0. When the pH is less than 1.0, a precipitation ratio of ferronickel may decrease because a ferronickel leaching reaction is dominant, and when the pH is greater than 6.0, ferronickel hydroxide may be generated to initiate precipitation of Ni. Thus, for example, the pH at the end of the reaction may be controlled within a range of 1.0 to 6.0. [0067] The present invention includes a filtering and separating operation, in which an iron-containing solution is removed by filtering and separating a solid content including ferronickel from the solution obtained from the acid treating operation. A nickel concentrate having an increased concentration of nickel may be obtained by filtering and separating the solid content including nickel from the acid treated solution. [00683 Meanwhile, when a ferronickel concentrate including a sufficient nickel content due to the filtering and separating operation is obtained, high-purity nickel may be obtained by dissolving the ferronickel concentrate thus obtained with an acid. A content of nickel in the ferronickel concentrate may be 5 wt% or more in order to separate nickel from the ferronickel concentrate. When the content of nickel in the D-rm 91 ferronickel concentrate is less than 5 wt%, separation and recovery of nickel from the ferronickel concentrate may be difficult due to a still high content of Fe. [0069] When the content of nickel in the ferronickel concentrate including a sufficient nickel content due to the filtering and separating operation is less than 5 wt%, water may be added to the ferronickel concentrate obtained to make into a slurry and a new nickel-containing raw material is reduced and mixed with the slurry, and then acid treating operation and filtering and separating operation may be performed thereon. At this time, a content of the acid in the acid treating operation is in a range of 0.25 times to 1.5 times of a total amount of moles of (Fe+Ni) in the slurry having the reduced nickel-containing raw material added thereto. This may be expressed as the following Reaction Formula (6). [0070] (Nio 1 Feo.

9 ) + 0.5Fe + {l/2(Nio 1 Feo.9) + 2Fe} + 3HC1 = 1.5(Ni 1 Feo.

9 ) + 1.5FeCl 2 + 1.5H 2 (6) [0071] As shown in Reaction Formulas (1), (4) and (5), a content of Fe in the concentrate may be continuously reduced while nickel is continuously enriched. Therefore, nickel may be enriched as the content of Fe is continuously reduced, e.g., the ratio of Fe to Ni in the reduced ore may decrease in the sequence of 30:1, 14:1, and 10:1. [00721 In the iron-containing solution removed according to pmnn 99' the present invention, impurities such as magnesium (Mg) and manganese (Mn) existing in the ores, in which acid dissolution may be facilitated but an electrochemical substitution reaction may not occur, are also removed with Fe. Meanwhile, SiO 2 , A1 2 0 3 , and Cr 2

O

3 , being virtually undissolved by the acids are enriched with the ferronickel concentrate. [00731 When a concentration of the ferronickel concentrate obtained according to the present invention reaches a range of 5% to 20%, a raw material in a ferronickel form may be obtained. That is, inorganic and organic binders, such as cement and molasses, are added to the concentrate and then water is added to mould the concentrate, and thus, a pelletized Ni and Fe-containing raw material for stainless steel dissolution may be manufactured. [00741 Further, since the pellets are mixed with reducing agents, such as carbon and aluminum, and melted and reduced to make SiO 2 , A1 2 0 3 , and Cr 2

O

3 into a slag, a metal alloy of iron and nickel, a so-called "ferronickel", may be manufactured. [0075] When the concentration of the ferronickel concentrate obtained according to the present invention reaches a range of 5% to 20%, the ferronickel concentrate is recovered to be leached with an acid and nickel may be recovered by filtering and removing impurities, such as SiC 2 , A1 2 0 3 , and Cr 2 0 3 , which are undissolved by the acids. [0076] In removing the impurities, such as SiO 2 , Al20 3 , and Cr 2 0 3 , hydrochloric acid, sulfuric acid, and nitric acid as well as various other acids may be used as the acid used in the leaching operation, but the acid used in the leaching operation is not limited thereto. However, hydrochloric acid and sulfuric acid may be used in view of wastewater disposal and cost considerations. In the case that hydrochloric acid is used, an amount of moles of the added hydrochloric acid may be in a range of twice to four times of that of moles of (Fe+Ni) of the nickel-containing raw material, and in the case that sulfuric acid is used, an amount of moles of the sulfuric acid added may be in a range of equal to 2 times of that of moles of (Fe+Ni). [0077] When the reduced nickel-containing raw material is leached by using an acid, metal-acid reactions, such as the following Reaction Formulas (7) and (8), are performed. [0078] (NiFe) + 2Fe + 6HCl -> (NiFe)C1 2 + 2FeCl 2 + 3H2 (7) [0079] (NiFe) + 2Fe + 3H 2

SO

4 - (NiFe) S04 + 2FeSO 4 + 3H 2 (8) [0080] Accordingly, nickel and iron are selectively dissolved into ions, and A1 2 03, SiC 2 , or Cr 2 0 3 contained in the nickel containing raw material are virtually undissolved by the acids, and thus, a solid phase residue is obtained. Therefore, the nickel-containing solution obtained in the leaching operation and the solid phase residue are very easily separated by filtration and may be separated by a solid-liquid separator, such as a filter press and a decanter, to obtain a nickel pnna ')A containing solution. [0081] The nickel and iron-containing solution is obtained and high-purity nickel may then be obtained by removing the Fe component from the solution. When air is injected while a pH of the solution is controlled within a range of 2.5 to 5.5 in order to remove the Fe component, iron hydroxide having an orange color is then generated as Fe is changed into iron hydroxide, and nickel and iron may be separated by filtering the solution. Also, in addition, a solvent extraction method may be used for separating the iron ions and the nickel ions. [00821 Meanwhile, the iron component leached in the acid treating operation is removed in the filtering and separating operation, and the removed iron-containing solution may be treated to be regenerated as magnetite and recycled. When a pH of the solution is controlled to be within a range of 9.5 to 10.5 by neutralizing the iron-containing solution with an alkaline component, such as limestone or calcium hydroxide, and an oxygen-containing gas such as air is injected thereinto, iron ions may be oxidized to generate magnetite. This may be expressed as the following Reaction Formulas (9) and (10). [0083] 3FeCl 2 + 6Ca(OH) 2 + 302 = Fe 3 0 4 + 3CaCl 2 + 6H 2 0 (9) [00843 3FeSO 4 + 6Ca(OH) 2 + 302 = Fe 3 0 4 + 3CaSO 4 + 6H 2 0 (10) [00851 The magnetite thus obtained may be used as a raw material for carbon steel. However, as shown in Reaction Formulas (9) and (10), soluble calcium chloride may be Dneio )R obtained when hydrochloric acid is used, and in the case that hydrochloric acid is used, byproducts may be recycled because separation of the magnetite and the calcium chloride may be possible, and thus, generation of waste may be minimized. In contrast, gypsum may be generated when sulfuric acid is used, and since the magnetite and the insoluble gypsum are simultaneously precipitated, the precipitated product may not be recycled as a raw material for steel, but may be recycled as a raw material for cement. [Mode for Invention] [0086] Hereinafter, the present invention will be described in detail, according to embodiments. However, the following individual examples are merely provided to allow for a clearer understanding of the present invention, rather than to limit the scope thereof. [0087} Embodiment [00881 Embodiment 1 [00891 Limonite ore, saprolite ore, and a spent catalyst residue containing nickel and iron were dried and pulverized into an average particle size of 0.8 mm and the particles were calcinated at 600 OC to prepare samples. [0090] Each sample was reduced at 725 0 C with hydrogen having a molar ratio of 1:1 based on an amount of moles of (Ni+Fe) in the each sample to prepare reduced samples. A composition of the reduced each sample is presented in Table 1. A unit of a content of each component in Table 1 was wt% and oxygen as well as trace amounts of magnesium (Mg) and manganese (Mn) being included as a remainder. [00911 200 ml of water was added to 200 g of the each reduced sample to make the reduced sample into a slurry and the each reduced sample was dissolved by adding 20% hydrochloric acid in an amount of 3.75 times of the weight of the each reduced sample to the each reduced sample slurry (amount of added hydrochloric acid: 750 g) and thus, acid-treated solutions were obtained. [0092] Concentrations of nickel included in the acid-treated solutions were investigated by inductively coupled plasma (ICP). A nickel concentration in the acid-treated solution of the reduced limonite sample (acid-treated solution 1) was 4.3 g/l, a nickel concentration in the acid-treated solution of the reduced saprolite sample (acid-treated solution 2) was 6.4 g/l, and a nickel concentration in the acid-treated solution of the reduced spent catalyst residue sample (acid-treated solution 3) was 11.5 g/l. [00931 Separate reduced samples having the same compositions as those of Table 1 were prepared and mixed with the obtained acid-treated solutions at the same mixing ratios of Fe/Ni as those in the following Table 2 to prepare slurries having the same slurry concentrations (unit: g/1) as described in Table 2. n__ 17 [0094] Nickel recovery rates due to ferronickel precipitation according to mixing ratios of the acid-treated solutions and the reduced samples were calculated by investigating the concentrations of nickel by ICP. The mixing ratios of the acid-treated solutions and the reduced samples and the nickel recovery rates were calculated by using the following equations and the results thereof are presented in Table 2. [0095] Mixing ratio of Fe/Ni = an amount of moles of Fe in a reduced sample added/an amount of moles of Ni in an acid treated solution [0096] Ni recovery rate = (1 - Ni loss rate) [0097] Ni loss rate = (Ni concentration in a solution before a reaction - Ni concentration after the reaction)/Ni concentration in the solution before the reaction [0098] [Table 2] Acid Reduced Mixing Slurry Ni treated sample ratio of concentration recovery solution added Fe/Ni (g/l) rate No. Comparative 1 Limonite 3 20 60% Example 1 Inventive 1 Limonite 9 63 95% Example 1 Comparative 2 Saprolite 2 68 45% Example 2 Comparative Spent 3 1 328 35% Example 3 catalyst Inventive 2 Limonite 3 31 85% Example 2 Inventive 1 Limonite 5 92 86% Example 3 Inventive 3 Limonite 4 74 93% Example 4 [0099] As shown in Table 2, with respect to the acid-treated solution 1 in which the concentration of Ni in the acid treated solution was less than 5 g/l, a sufficient Ni recovery rate may not be obtained when an amount of the reduced sample was added at a mixing ratio of Fe/Ni of 5 or less (Comparative Example 1). However, it may be understood that Ni recovery rates were significantly improved when amounts of the reduced samples were added at mixing ratios of Fe/Ni of 5 or more (Inventive Examples 1 and 3). [00100] That is, with respect to the acid-treated solution in which the concentration of Ni in the acid-treated solution was less than 5 g/l, precipitation of dissolved nickel ions at a high recovery rate may be difficult when the reduced sample having a low Fe content was used. The reason for this is that a reaction according to Reaction Formula (3) must occur in order to allow nickel to be substituted and precipitated, but n__ nM a diffusion rate in Reaction Formula (3) was rapidly decreased when the concentration of nickel was low. [00101] Meanwhile, with respect to the acid-treated solutions 2 and 3 in which the concentrations of Ni in the acid-treated solution were 5 g/l or more, it may be understood that excellent Ni recovery rates were obtained even in the case that amounts of the reduced samples were added at mixing ratios of Fe/Ni of 5 or less, when the slurry concentrations of the reduced ores were increased (Inventive Examples 2 and 4). The reason is that the reaction of Reaction Formula (3), in which Ni is precipitated, may actively occur because a large amount of metal Fe was introduced in the solutions due to increases in the concentrations of the reduced ore slurries. In contrast, when the mixing ratios of Fe/Ni were less than 3 (Comparative Examples 1 and 2) , Ni recovery rates may not increase even in the case that the concentrations of Ni in the solutions were high. £00102] Therefore, a ratio of Fe/Ni of the reduced ore added for enriching nickel may be controlled to be 3 or more, and in particular, it may be understood that limonite having a high Fe content may be used. [00103] Embodiment 2 [00104] According to Comparative Example 1 of Embodiment 1, with respect to the reduced limonite sample having a low nickel content, substitution and precipitation of nickel may D., - .> An be difficult because the concentration of nickel during leaching was low at less than 5 g/l. In contrast, according to Inventive Example 4, it was confirmed that a high recovery rate may be obtained when the concentration of metal Fe in the solution was increased. Accordingly, the present embodiment aims to disclose that nickel may be recovered by increasing the content of nickel through performing a reaction in which only Fe is leached and Ni is precipitated from the acid treated solution of the nickel and iron-containing sample. [00105] Limonite ore was dried and then pulverized into a particle size of 0.8 mm. The particles were calcinated at 600 0 C and then reduced with hydrogen at 725 0 C to prepare reduced samples. Water was added to the reduced samples at a weight ratio of 1:2 so as to allow the reduced samples not to be oxidized and an acid having a concentration of 12% was then added thereinto. Acid treatments were performed by varying a ratio ([H+] / [Ni+Fe]) of an amount of moles of the acid to an amount of moles of (Fe+Ni) in the reduced samples as in Table 3. [00106] Fe ions and ferronickel metals, which had been respectively leached and precipitated from the acid-treated solutions thus obtained, were separated and filtered, and then ferronickel concentrates were obtained by removing iron containing solutions therefrom (enrichment order: primary). [00107] Nickel loss rates were calculated by using the Ml-0.1 equation described in Embodiment 1 from the relationships between total nickel contents in the reduced samples and contents of the lost nickel through investigating concentrations of nickel included in the removed iron containing solutions, and nickel recovery rates were then calculated therefrom. The results thereof are presented in Table 3. [00108] [Table 3] Amount of Input Ni Enrichment ore Acid type ratio of recovery order added(g) acid rate Comparative Hydrochloric 180 Primary 0.2 100% Example 4 acid Inventive Hydrochloric 180 Primary 0.5 100% Example 5 acid Inventive Hydrochloric 180 Primary 1.0 99% Example 6 acid Comparative Hydrochloric 180 Primary 1.8 83% Example 5 acid Inventive Sulfuric 180 Primary 0.5 99% Example 7 acid [00109] According to Comparative Example 4 and Inventive Example 5 in which input ratios of acid were 0.5 or less, since nickel ions were not detected in the iron-containing n___ :)solutions being separated and removed, nickel recovery rates obtained were 100%. However, with respect to Comparative Example 4 having a low input ratio of acid, since a dissolution amount of iron removed from the added ore was decreased at 10.9 g, an actual amount of nickel enriched with respect to the concentration of Fe in the ferronickel concentrate was small. In contrast, with respect to Inventive Example 5, it may be understood that since a dissolution amount of iron was 27 g, considerably higher than that of Comparative Example 4, a nickel recover rate was also high. Therefore, it may be more desirable to have a high input ratio of acid in a range of securing a nickel recovery rate. [001101 In contrast, as shown in Comparative Example 5, it may be understood that a nickel recovery rate decreased when the input ratio of acid was greater than 1.5, e.g., 1.8. According to the result of analysis, a total amount of Fe remained was 27 g including about 15 g of Fe remained as a metal in the solution, and as a result, it may be understood that a dissolution amount of Fe was about 84 g or more. Thus, a sufficient amount of metal Fe able to precipitate nickel irons did not exist in the solution because iron was excessively dissolved. That is, the reason is that precipitation of nickel was insufficient because an effect of decreasing the ratio of Fe/Ni in Embodiment 1 occurred and a potion of Ni was dissolved. Meanwhile, the reason for Fe in the sample not entirely being metal Fe is that an Fe reduction rate was not 100% and a partial oxidation reaction of Fe due to oxygen in the solution as well as acid dissolution was performed during the leaching reaction. [00111] Meanwhile, as shown in Inventive Example 7, it may be understood that an excellent nickel recovery rate, the same as that of the case of using hydrochloric acid, was obtained even in the case that the acid treatment was performed by using sulfuric acid. The same effect may be obtained because the same action as that of the case of using hydrochloric acid may be performed in the case of using sulfuric acid, except that there was only a difference in the chemical equivalence ratios between sulfuric acid and hydrochloric acid. [00112] According to the foregoing result, when a ratio of the amount of moles of the acid to that of moles of (Fe+Ni) in the acid-treated solution is controlled to be less than the equivalence ratio for acid dissolution in order that Fe was not excessively dissolved during the acid treatment of the reduced nickel and iron-containing sample having a low nickel content, i.e., hydrochloric and sulfuric acid were respectively added at molar ratio ranges of 0.5 to 1.5 and 0.25 to 0.75, only Fe was leached after the acid dissolution reaction and remaining Fe generated substitution and precipitation reactions of nickel ions to precipitate Ni, and thus, nickel may be enriched.

[00113] Embodiment 3 [00114] The iron-containing solution was removed from the acid-treated solution of Inventive Example 6 and water was then added to a remaining ferronickel concentrate at a weight ratio of 1:2 to make the remaining ferronickel concentrate into a slurry. [00115] A reduced limonite sample was prepared by using the same method as that of Embodiment 2, and water was added to 180 g of the reduced sample at a weight ratio of 1:2 so as to prevent the reduced sample from oxidation. [00116] The ferronickel concentrate slurry and the reduced sample slurry were mixed and an acid treatment was performed by adding hydrochloric acid having a concentration of 12% in an amount of moles equal to that of moles of (Fe+Ni) in the mixed slurry. [001171 Fe ions and ferronickel metal, which had been respectively leached and precipitated from the acid-treated solution thus obtained, were separated and filtered, and then a secondary enriched ferronickel concentrate was obtained by removing an iron-containing solution therefrom (Inventive Example 8). [00118] The secondary enriched ferronickel concentrate obtained in Inventive Example 8 was enriched in the same manner as Inventive Example 8 to obtain tertiary and quaternary ferronickel concentrates (Inventive Examples 9 and 10). [00119] [Table 4] Inpu t Ni Enrichmen Amount of ore added Acid type rati recover t order o of y rate acid Inventiv e Hydrochlori 180/2 + 180 Secondary 1 99% Example c acid 8 Inventiv e Hydrochlori (180+180/2)/2+180 Tertiary 1 98% Example c acid 9 Inventiv e ((180+180/2) +180) /2+1 QuaternarHydrochlori 1 97/% Example 80 y c acid 10 [00120] A content of nickel included in the quaternary enriched ferronickel concentrate according to Inventive Example 10 was investigated by inductively coupled plasma (ICP) and the content of nickel was 6.5 wt%. It may be understood that nickel was enriched at a ratio of 3 times or more based n__ or on the reduced limonite sample. A theoretical amount of nickel enriched must be 12% or more, but the amount of nickel enriched was less than 12%. The reason for this is that acid insoluble materials, such as SiO 2 , A1 2 0 3 , and Cr 2 0 3 , were enriched with the nickel concentrate in addition to nickel. [00121] Embodiment 4 [00122] Calcium hydroxide was added to the iron-containing solution removed from the acid-treated solution of Embodiment 2 to adjust a pH of the solution to be 10 and air was injected to oxidize the solution, and as a result, an iron compound was obtained. [00123] XRD analysis was performed on the iron compound obtained and it was confirmed that the iron compound was magnetite. The magnetite had a concentration of Fe of 65% or more and thus, was suitable for being used as a raw material for carbon steel. [00124] While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. [00125] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of Page 37 the common general knowledge in the art, in Australia or any other country. [00126] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. Page 37a