Method for recovering sc from iron-aluminum slag in lateritic nickel ore high-pressure acid leaching process

Abstract

Disclosed in the present invention is a method for recovering Sc from an iron-aluminum slag in a lateritic nickel ore high-pressure acid leaching process, comprising the following steps: S1, leaching a raw material iron-aluminum slag by using sulfuric acid, and carrying out pressure filtration to obtain a leachate; S2, evaporating and concentrating the leachate to obtain a concentrated solution, and adding the raw material iron-aluminum slag and sodium sulfate into the concentrated solution to obtain a mixture; S3, pressurizing and heating the mixture, the pressurization pressure being 4.5-5.0 MPa and the heating temperature being 250-260°C, and then carrying out solid-liquid separation to obtain a slag phase and a liquid phase; and S4, sequentially carrying out extraction, back extraction, scandium salt precipitation, and roasting on the liquid phase to obtain scandium oxide. The recovery rate of scandium is high, and the steps are simple.

Description

A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore. Background Art

[0002] Sc, a rare element, has important industrial applications, but isolated deposits are scarce, and the Sc content in primary deposits is extremely low, making recovery difficult and costly. This is the fundamental reason for Sc's high price. Raw laterite nickel ore typically contains 0.03-0.05% Sc. Furthermore, the high levels of impurities such as iron, aluminum, manganese, magnesium, and calcium in laterite nickel ore far exceed the scandium content, which can interfere with scandium extraction. Direct extraction is cumbersome, high in impurities, and of limited practical value.

[0003] In the related art, patent publication number CN 103468979 discloses a method for recovering scandium from iron-aluminum slag produced by smelting laterite nickel ore. The method removes iron and aluminum and precipitates nickel and cobalt by adjusting the pH to obtain a sodium hydroxide scandium-nickel-cobalt precipitate, and then recovers scandium from the scandium-nickel-cobalt hydroxide precipitate.

[0004] In this method, since the impurity removal effect of each step is poor, multiple impurity removal methods need to be used for impurity removal and enrichment, resulting in a large loss of scandium and a large consumption of raw and auxiliary materials.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, which has a high scandium recovery rate and simple steps.

[0007] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0008] The present application provides a method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, comprising the following steps:

[0009] S1. The raw material iron and aluminum slag is leached with sulfuric acid and filtered to obtain a leachate;

[0010] S2. The leachate was evaporated and concentrated to obtain a concentrate, and raw iron and aluminum slag and sodium sulfate were added to the concentrate to obtain a mixture;

[0011] S3. The mixture is pressurized and heated at a pressure of 4.5-5.0 MPa and a heating temperature of 250-260 ° C. The solid-liquid separation is then performed to obtain a slag phase and a liquid phase;

[0012] S4. Extracting, stripping, precipitating scandium salt, and roasting the liquid phase in sequence to obtain scandium oxide.

[0013] Preferably, in step S4, the extractant used for extraction is a mixture of Cextrant230 extractant and N1923 extractant, the extractant uses sulfonated kerosene as a diluent, the mass ratio of the extractant Cextrant230 to N1923 is 1:1-4, the concentration of the extractant is 20-50%, and the volume ratio of the extractant to the aqueous phase is 2:1-3.

[0014] Preferably, in step S4, the stripping agent used for stripping is EDTA solution.

[0015] Preferably, in step S4, the precipitant used to precipitate the scandium salt is an ammonium salt, and the temperature for precipitating the scandium salt is 50-90°C.

[0016] Preferably, in step S4, the first organic phase obtained by extraction is washed with sulfuric acid between the extraction step and the back-extraction step.

[0017] Preferably, in step S1, the pH value of the leaching treatment is 2-3, and the leaching time is 2-3 hours.

[0018] Preferably, the calcination temperature is 800-900°C.

[0019] Preferably, in step S2, the temperature of evaporation and concentration is 90-100°C.

[0020] Preferably, the slag phase includes Fe2O3, Al2O3 and natantrolite.

[0021] Preferably, after the stripping step, a stripping solution containing scandium and a second organic phase are obtained, and the second organic phase is recycled and further subjected to extraction.

[0022] The beneficial effects of this application are as follows:

[0023] The present application prepares high-purity scandium oxide through the process of "normal pressure leaching-concentration-high pressure impurity removal-extraction-strip extraction-precipitation-roasting". The loss rate of scandium (Sc) is small and the process flow is short, which is conducive to the recovery of scandium.

[0024] The present application utilizes pressurized heating treatment to hydrolyze iron and aluminum ions. Simultaneously, unacid-leached iron and aluminum slag is added during the reaction process to promote the hydrolysis reaction. At the same time, sodium sulfate also synergistically removes iron ions to form natantolacite, further accelerating the hydrolysis reaction. The removal effect of iron and aluminum ions is good, which is beneficial to reducing interference with scandium recovery.

[0025] This application achieves further improvement in scandium recovery by adjusting the extractant system and the scandium precipitation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a process flow chart of this scheme. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] As shown in FIG1 , the present application provides a method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, comprising the following steps:

[0029] S1. The raw material iron and aluminum slag is leached with sulfuric acid and filtered to obtain a leachate;

[0030] S2. The leachate was evaporated and concentrated to obtain a concentrate, and raw iron and aluminum slag and sodium sulfate were added to the concentrate to obtain a mixture;

[0031] S3. The mixture was pressurized and heated at a pressure of 4.5-5.0 MPa and a heating temperature of 250-260 ° C for 1-2 h, and then solid-liquid separation was performed to obtain a slag phase and a liquid phase;

[0032] S4. Extracting, stripping, precipitating scandium salt, and roasting the liquid phase in sequence to obtain scandium oxide.

[0033] In this scheme, after the atmospheric pressure sulfuric acid leaching in step S1, the leaching rates of iron, aluminum, and scandium can be basically leached, and the concentration of Sc in the leachate is low at this time. Then, after the concentration in step S2, the concentration of Sc in the concentrate is increased. In step S2, sodium sulfate is used to precipitate iron ions to form sodium ferrocyanide. The reaction mechanism is as follows: 3Fe 3+ +2SO4 2- +Na + +6H2O→Na Fe3(SO4)2(OH)6+6H + ; Under the conditions of step S3, iron ions and aluminum ions undergo a hydrolysis reaction to form solid Fe2O3 and Al2O3, which enter the slag item and release sulfuric acid. The generated sulfuric acid dissolves the raw material iron-aluminum slag that has not been leached at normal pressure and newly added in step S2, which can promote the chemical equilibrium of the hydrolysis reaction in step S3 to the right, further precipitate the iron and aluminum in the iron-aluminum slag, and further reduce the Sc interference item in the liquid phase. At the same time, sodium sulfate also promotes the chemical equilibrium of the hydrolysis reaction to the right, and cooperates with the raw material iron-aluminum slag that has not been leached at normal pressure to remove iron and aluminum under high pressure and high temperature environment, which is beneficial to reducing the loss rate of Sc.

[0034] It is worth noting that after adding the raw material iron-aluminum slag and sodium sulfate to the concentrated liquid in step S2, in order to reduce the process flow, no solid-liquid separation treatment is performed, and a solid-liquid mixture is directly obtained. At the same time, the solid phase of the raw material iron-aluminum slag that has not been acid-leached can also be used as a raw material for the hydrolysis reaction in step S3.

[0035] In step S4, the extraction agent used is a mixture of Cextrant230 and N1923, the extractant uses sulfonated kerosene as a diluent, the mass ratio of Cextrant230 to N1923 is 1:1-4, the concentration of the extractant is 20-50%, and the volume ratio of the extractant to the aqueous phase is 2:1-3.

[0036] In step S4, the stripping agent used for stripping is EDTA solution.

[0037] In step S4, the precipitant used to precipitate the scandium salt is ammonium salt, and the temperature for precipitating the scandium salt is 50-90°C.

[0038] In step S4, the first organic phase obtained by extraction is washed with sulfuric acid between the extraction step and the back-extraction step.

[0039] In step S1, the pH value of the leaching treatment is 2-3, and the leaching time is 2-3 hours.

[0040] The calcination temperature is 800-900℃.

[0041] In step S2, the temperature of evaporation and concentration is 90-100°C.

[0042] The slag phase includes Fe2O3, Al2O3 and natantrolite.

[0043] After the stripping step, a stripping solution containing scandium and a second organic phase are obtained, and the second organic phase is recycled and further subjected to extraction.

[0044] Specifically, in step S4, the liquid phase obtained in step S3 is extracted with a mixture of Cextrant230 extractant and N1923 extractant to obtain a first organic phase and an extract residue, and the first organic phase is washed with dilute sulfuric acid to obtain a first impurity-removed organic phase and a washing solution containing impurities. The first impurity-removed organic phase is then back-extracted with an EDTA solution to obtain a second organic phase and a back-extract containing scandium. The back-extract containing scandium is precipitated with an ammonium salt and then calcined to obtain scandium oxide, and the second organic phase is returned to the extraction step for repeated use.

[0045] The present invention is further described below through specific examples.

[0046] Example 1

[0047] A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore comprises the following steps:

[0048] S1. The raw material iron and aluminum slag was leached with sulfuric acid, the pH value of the leaching treatment was 2, the leaching time was 3h, and after filter press, a leachate was obtained;

[0049] S2. The leachate was concentrated by evaporation at a temperature of 90°C to obtain a concentrate, and the raw materials of iron and aluminum slag and sodium sulfate were added to the concentrate to obtain a mixture;

[0050] S3. The mixture was pressurized and heated at a pressure of 4.5 MPa and a heating temperature of 250°C for 1-2 h, followed by solid-liquid separation to obtain a slag phase and a liquid phase;

[0051] S4. The liquid phase obtained in step S3 is extracted with a mixture of Cextrant230 extractant and N1923 extractant, wherein the extractant uses sulfonated kerosene as a diluent and the mass ratio of the extractant Cextrant230 to N1923 is 1:1, to obtain a first organic phase and an extract residue. The first organic phase is washed with dilute sulfuric acid to obtain a first impurity-removed organic phase and a washing solution containing impurities. The first impurity-removed organic phase is then back-extracted with an EDTA solution with an extractant concentration of 50% and a volume ratio of the extractant to the aqueous phase of 2:1 to obtain a second organic phase and a back-extract containing scandium. The back-extract containing scandium is precipitated with ammonium sulfate at 90°C and then calcined at 800°C to obtain scandium oxide. The second organic phase is reused in the extraction step.

[0052] Example 2

[0053] A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, wherein the other steps are the same as those in Example 1, except that in step S1, the pH value of the leaching treatment is 3, the leaching time is 2 h, and in step S3, the pressurizing pressure is 5.0 MPa and the heating temperature is 260°C.

[0054] Comparative Example 1

[0055] A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, wherein the other steps are the same as those in Example 1, except that in step S3, the pressurization pressure is 1 MPa and the heating temperature is 200°C.

[0056] Comparative Example 2

[0057] A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, wherein the other steps are the same as those in Example 1, except that sodium sulfate is not added in step S2.

[0058] Comparative Example 3

[0059] A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, wherein the other steps are the same as those in Example 1, except that the raw material iron-aluminum slag is not added in step S2.

[0060] Evaluation Test

[0061] The scandium oxides obtained in Examples 1-3 and Comparative Examples 1-3 were collected, and the content of scandium in the original iron-aluminum slag phase was determined by ICP. The recovery rate of scandium was calculated. The results are shown in Table 1.

[0062] Table 1 Scandium recovery rate of each scheme

[0063] From the data, it can be seen that the scandium loss in this scheme is small and the recovery rate is high.

[0064] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for recovering Sc from iron-aluminum slag in a high-pressure acid leaching process of laterite nickel ore, characterized in that: The following steps are involved: S1. The raw material iron and aluminum slag is leached with sulfuric acid, and after filter pressing, a leachate is obtained; S2. The leachate is evaporated and concentrated to obtain a concentrate, and raw iron and aluminum slag and sodium sulfate are added to the concentrate to obtain a mixture; S3. The mixture is subjected to pressurized heating treatment, the pressurized pressure is 4.5-5.0MPa, the heating temperature is 250-260°C, and then solid-liquid separation is performed to obtain a slag phase and a liquid phase; S4. Extracting, stripping, precipitating scandium salt and roasting the liquid phase in sequence to obtain scandium oxide.

2. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S4, the extractant used for the extraction is a mixture of Cextrant230 extractant and N1923 extractant, the extractant uses sulfonated kerosene as a diluent, the mass ratio of the extractant Cextrant230 to N1923 is 1:1-4, the concentration of the extractant is 20-50%, and the volume ratio of the extractant to the aqueous phase is 2:1-3.

3. The method for recovering Sc from the iron-aluminum slag in the high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S4, the stripping agent used for stripping is EDTA solution.

4. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S4, the precipitant used for precipitating the scandium salt is an ammonium salt, and the temperature for precipitating the scandium salt is 50-90°C.

5. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S4, the first organic phase obtained by extraction is washed with sulfuric acid between the extraction step and the back extraction step.

6. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S1, the pH value of the leaching treatment is 2-3, and the leaching time is 2-3 hours.

7. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: The calcination temperature is 800-900°C.

8. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: In step S2, the temperature of evaporation and concentration is 90-100°C.

9. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: The slag phase includes Fe2O3, Al2O3 and natanthal ferroalloy.

10. The method for recovering Sc from iron-aluminum slag in high-pressure acid leaching process of laterite nickel ore according to claim 1, characterized in that: After the stripping step, a stripping solution containing scandium and a second organic phase are obtained, and the second organic phase is recycled and further subjected to extraction.

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