Method for treating hematite type waste residues

Abstract

The invention belongs to the technical field of waste resource treatment and recovery, and provides a hematite type waste residue treatment method which comprises the steps that hematite type waste residues are sequentially pulpified and washed, and washed residues are obtained; the washing slag is leached, and a leaching solution is obtained; mixing the leachate with iron powder and sulfur, and carrying out reduction reaction to obtain reduced liquid and reducing slag; mixing the reduced liquid with a precipitant, and carrying out an aluminum precipitation reaction to obtain a purified liquid and aluminum slag; and the purified liquid is electrolyzed, and the electrolytic iron powder is obtained. According to the method, the waste residues are subjected to acid dissolution through the hydrometallurgy technology and then are prepared into the electrolytic iron powder through the electrolysis technology, iron and impurities such as aluminum and silicon can be fully separated, a high-value iron powder product is obtained, meanwhile, the impurities can be further fully utilized, and by-products of nickel and aluminum are obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste resource processing and recycling, and relates to a processing method of hematite type waste residue. BACKGROUND

[0002] In modern metallurgical industry, with the continuous growth of nickel resource demand, the hydrometallurgical process of laterite nickel ore has been widely studied and applied. Laterite nickel ore, as an important component of nickel resources, mainly includes limonite type and saprolite type. Among them, limonite type oxidized nickel ore has high crystallization water content, high iron content and low nickel grade, so high pressure acid leaching (HPAL) process is usually used for nickel extraction in the hydrometallurgical process. This process can achieve efficient leaching of nickel, but also produces a large amount of hematite residue with iron oxide as the main component. The iron content in the residue is usually more than 50%, which has a certain value for iron resource recovery. However, due to its complex composition, it contains high content of impurity elements such as aluminum, silicon and sulfur, and these impurities often form a tight phase package or intergrowth structure with iron oxide, making it difficult to effectively recover and high-value utilize the iron resource.

[0003] Currently, the resource utilization research of hematite residue produced in the hydrometallurgical process of laterite nickel ore mainly focuses on the recovery and recycling of iron resources. Among them, the process of pyrometallurgical reduction roasting combined with magnetic separation is a common technical route. The basic principle of this process is to reduce part of the high-valence iron in the oxidized iron to magnetite or metallic iron through reduction roasting of the residue at high temperature, and then separate the iron phase from other non-magnetic impurities by magnetic separation equipment to obtain iron concentrate product. However, this process faces many problems in practical application. First, the impurity elements such as aluminum, silicon and sulfur in the hematite residue are difficult to completely remove in the roasting process, and their oxides or sulfides are easy to form complex solid solutions or composite oxides with iron oxides, which increases the difficulty of phase separation between iron phase and impurities. Second, due to the strong phase intergrowth relationship between these impurities and iron oxide, it is difficult to achieve complete dissociation of impurities even under high temperature reduction conditions, which affects the grade and impurity content of iron concentrate in the magnetic separation process.

[0004] In addition, as a basic raw material for the steel industry, the market value of iron concentrate is relatively low, and the product quality is required to be high. For example, the sulfur content in the iron concentrate is generally required to be less than 0.1%, the silicon content needs to be controlled below 5%, and the aluminum content also needs to be controlled within a reasonable range. However, the impurity contents such as sulfur, silicon and aluminum in the iron concentrate obtained by roasting and magnetic separation of hematite slag are often difficult to meet the above standards, resulting in that the product is difficult to enter the mainstream steel market. If further deep purification means such as flotation, acid leaching and alkali leaching are used, the treatment cost will be significantly increased, thereby weakening the economic feasibility. Therefore, although there are a large number of research reports on the roasting and magnetic separation of hematite slag for recovering iron by pyrometallurgical method, most of the researches still remain in the laboratory stage, and no mature industrial application case has been formed.

[0005] On the other hand, the long-term stacking of hematite slag not only occupies a large amount of land resources, but also may cause potential environmental risks. Since the waste slag contains a certain amount of heavy metal elements and acidic substances, if not effectively treated, it may cause soil and water pollution under the action of rainwater erosion or groundwater infiltration. Therefore, how to realize the efficient recovery and high-value utilization of iron resources in hematite slag, while taking into account environmental protection and economic feasibility, has become one of the key problems to be solved in the current nickel laterite ore hydrometallurgical industry chain.

[0006] Therefore, it is urgent to propose a new process method, which can effectively improve the recovery rate and purity of iron in hematite slag without significantly increasing the treatment cost, and at the same time realize the efficient removal of impurities, so as to promote the resource utilization of such waste slag and improve its economic and environmental value. SUMMARY

[0007] In view of the problems in the prior art, the purpose of the present application is to provide a treatment method for hematite-type waste slag, which comprises the following steps: sequentially slurryzing and washing the hematite-type waste slag to obtain washed slag; leaching the washed slag to obtain leaching solution; mixing the leaching solution with iron powder and sulfur to perform reduction reaction to obtain reduced solution and reduced slag; mixing the reduced solution with a precipitating agent to perform aluminum precipitation reaction to obtain purified solution and aluminum slag; and electrolyzing the purified solution to obtain electrolytic iron powder. The present application uses a hydrometallurgical process to prepare electrolytic iron powder from acid-soluble waste slag, which can fully separate iron from impurities such as aluminum and silicon, obtain high-value iron powder products, and further realize the full utilization of impurities to obtain nickel and aluminum by-products.

[0008] To achieve this purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a treatment method for hematite-type waste slag, which comprises the following steps:

[0010] The hematite type waste slag is sequentially slurried and washed with water to obtain a washed slag.

[0011] The washed slag is leached to obtain a leaching solution.

[0012] The leaching solution is mixed with iron powder and sulfur to perform a reduction reaction to obtain a post-reduction solution and a reduction slag.

[0013] The post-reduction solution is mixed with a precipitation agent to perform an aluminum precipitation reaction to obtain a purified solution and an aluminum slag.

[0014] The purified solution is electrolyzed to obtain electrolytic iron powder.

[0015] The present application uses a hydrometallurgical process to produce electrolytic iron powder from waste slag after acid leaching, which can fully separate iron from impurities such as aluminum and silicon, and obtain high-value iron powder products, while further utilizing impurities to obtain nickel and aluminum byproducts.

[0016] The main components of the hematite type waste slag include iron oxide, and other impurities mainly include aluminum and silicon oxides. Silicon dioxide is insoluble in hydrochloric acid, so iron and aluminum can be leached into the solution by acid leaching, while the impurity silicon remains in the slag. In an aqueous electrolysis system, aluminum has a very low potential due to its high reactivity, so aluminum will not deposit on the cathode during electrolysis, only iron will deposit and precipitate on the cathode, and aluminum remains in the solution. Therefore, electrolysis can fully separate iron and aluminum, which is difficult to achieve by other physical separation methods. By combining acid leaching and electrolysis, iron and impurities can be fully separated. Compared to other methods of obtaining low-grade primary products such as iron concentrate, iron powder or reduced iron, electrolytic iron powder has high purity and other excellent properties, and its price is much higher than the market price of other products. Therefore, the treatment method described in the present application can obtain high-value recycled products.

[0017] The following is a preferred technical solution of the present application, but is not a limitation of the technical solution provided by the present application. By the following technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0018] As a preferred technical solution of the present application, the source of the hematite type waste slag includes the leaching tailings of the extraction of nickel from the limonite type nickel oxide ore by hydrometallurgy.

[0019] As a preferred technical solution of the present application, the method of slurry includes mixing the hematite type waste slag with water.

[0020] As a preferred technical solution of the present application, the temperature of the water washing is 40-80℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc.

[0021] The purpose of water washing is mainly to remove residual water-soluble impurities such as sulfate, nickel and other metal ions in the waste residue, so as to reduce the consumption of auxiliary materials in subsequent reduction and impurity removal steps.

[0022] As a preferred technical solution of the present application, the leaching agent used in the leaching includes hydrochloric acid with a concentration of 30% to 35%, for example, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5% or 35%, etc.

[0023] As a preferred technical solution of the present application, in the leaching, the mass ratio of the leaching agent to the water-washed residue is (2.5-3):1, for example, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1, etc.

[0024] The purpose of leaching is mainly to separate Fe and impurity silicon. Silicon dioxide is insoluble in hydrochloric acid and can therefore be retained in the residue, while iron oxide and other acid-soluble components enter the leaching solution. If the amount of acid is too small, iron cannot be fully dissolved into the solution, resulting in high residual iron in the residue and low iron recovery. If the amount of acid is too high, it will lead to high residual acid in the leaching solution, increasing the processing cost of subsequent neutralization of residual acid.

[0025] As a preferred technical solution of the present application, the temperature of the leaching is 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, etc., and the time is 4-8h, for example, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h, etc.

[0026] Hydrochloric acid is volatile, and if the temperature is too high, it will volatilize severely, the utilization rate of acid will be low, the leaching effect will be poor, and the iron recovery rate will be low. If the temperature is too low, the reaction thermodynamics will be limited, and the reaction rate will be slow. If the reaction time is short, iron will not be fully dissolved, and the recovery rate will be low. If the reaction time is too long, it is unnecessary.

[0027] As a preferred technical solution of the present application, the molar ratio of the iron powder to the trivalent iron ions in the leaching solution is (0.5-0.6):1, for example, 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1, 0.55:1, 0.56:1, 0.57:1, 0.58:1, 0.59:1 or 0.6:1, etc.

[0028] The main purpose of this step is to reduce Fe 3+ to Fe 2+ , and the reaction equation is 2Fe 3+ + Fe → 3Fe 2+ It is more difficult to directly electrodeposit trivalent iron, and divalent iron is easier to be electrodeposited and precipitated. Since the reaction is weakly acidic, H +A small amount of iron powder will also be consumed, so the iron powder needs to be in proper excess. If the iron powder is insufficient, the reduction will not be sufficient. If the iron powder is excessive, it will be wasted, and the cost of subsequent nickel recovery and impurity removal will increase, and the iron recovery rate will decrease.

[0029] As a preferred technical solution of the present application, the molar ratio of sulfur to nickel ions in the leaching solution is (1-1.1):1, such as 1:1, 1.02:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.1:1, etc.

[0030] The main purpose of this step is to remove nickel by displacement precipitation. The reaction principle is Ni 2+ + Fe + S → NiS + Fe 2+ If the sulfur is insufficient, the nickel removal will not be sufficient. If the sulfur is excessive, it will increase the loss of iron.

[0031] As a preferred technical solution of the present application, the pH of the reduction reaction is 1.5-2.5, such as 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.5, etc., the temperature is 30-50℃, such as 30℃, 33℃, 35℃, 38℃, 40℃, 42℃, 45℃, 48℃ or 50℃, etc., and the time is 1-2h, such as 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, etc.

[0032] If the pH in the reduction reaction is too low, there will be too much H + and react with the iron powder, resulting in insufficient iron powder participating in the reduction, and if the pH is too high, iron hydroxide precipitate will be easily generated, resulting in increased loss of iron precipitate. Too high a temperature will also promote the oxidation of iron, increasing the loss of iron precipitate.

[0033] As a preferred technical solution of the present application, the treatment method further comprises sequentially subjecting the reduction residue to pressure oxidation leaching and purification to recover nickel, to obtain nickel sulfate.

[0034] Preferably, the temperature of the pressure oxidation leaching is 150-180℃, such as 150℃, 155℃, 160℃, 165℃, 170℃, 175℃ or 180℃, etc., and the oxygen partial pressure is 10%-20%, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc.

[0035] Preferably, the method for purifying and recovering nickel comprises chemical precipitation and / or extraction.

[0036] In the present application, the method for purifying and recovering nickel comprises chemical precipitation and extraction, and an example is that the oxygen pressure leaching solution is first subjected to chemical precipitation to remove impurities such as Fe, and then subjected to further extraction purification to obtain nickel sulfate.

[0037] As a preferred technical solution of the present application, the precipitant comprises sodium phosphate and / or sodium fluoride.

[0038] As a preferred technical solution of the present application, when the precipitant comprises sodium phosphate, the molar ratio of the precipitant to aluminum ions in the solution after reduction is (1.0-1.2):1; for example, 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.14:1, 1.16:1, 1.18:1 or 1.2:1, etc.; when the precipitant comprises sodium fluoride, the molar ratio of the precipitant to aluminum ions in the solution after reduction is (3.0-3.5):1, for example, 3:1, 3.05:1, 3.1:1, 3.15:1, 3.2:1, 3.25:1, 3.3:1, 3.35:1, 3.4:1, 3.45:1 or 3.5:1, etc.

[0039] In this step, Al 3+ is precipitated from Fe 2+ by virtue of the difference in solubility product of phosphate or fluoride. 3+ Aluminum phosphate or aluminum fluoride is generated, which is more easily precipitated than Fe 2+ , so as to realize separation and recovery of aluminum in the solution. 3+ + PO4 3- → AlPO4↓; Al 3+ + 3F - → AlF3↓. When the amount of the precipitant is insufficient, the recovery of aluminum is insufficient, and when the amount of the precipitant is excessive, more iron is lost.

[0040] As a preferred technical solution of the present application, the pH of the aluminum precipitation reaction is 1.5-2.5, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.45, etc.; the temperature is 40-80℃, for example, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc.; and the time is 1-4h, for example, 1h, 1.3h, 1.5h, 1.8h, 2h, 2.3h, 2.5h, 2.8h, 3h, 3.3h, 3.5h, 3.8h or 4h, etc.

[0041] As a preferred technical solution of the present application, the treatment method further comprises mixing and reacting the aluminum residue with sodium hydroxide, solid-liquid separation to obtain a reaction residue, and then sequentially performing washing, drying and calcination to obtain an aluminum oxide product.

[0042] As a preferred technical scheme of the present application, the molar ratio of sodium hydroxide to aluminum element in the aluminum slag is (3-3.2):1, such as 3:1, 3.02:1, 3.04:1, 3.08:1, 3.1:1, 3.13:1, 3.154:1, 3.18:1 or 3.2:1, etc.

[0043] This step is mainly to convert aluminum in the aluminum slag into aluminum hydroxide by the action of strong alkali, so as to facilitate the subsequent sintering of aluminum oxide products.

[0044] As a preferred technical scheme of the present application, the calcination temperature is 400-600℃, such as 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃ or 600℃, etc.

[0045] As a preferred technical scheme of the present application, the current density of electrolysis is 500-3000 A / m 2 , such as 500 A / m 2 , 600 A / m 2 , 800 A / m 2 , 1000 A / m 2 , 1200 A / m 2 , 1400 A / m 2 , 1700 A / m 2 , 2000 A / m 2 , 2200 A / m 2 , 2400 A / m 2 , 2600 A / m 2 , 2800 A / m 2 or 3000 A / m 2 , and the temperature is 20-50℃, such as 20℃, 23℃, 25℃, 28℃, 30℃, 33℃, 35℃, 38℃, 40℃, 43℃, 45℃, 48℃ or 50℃, etc.

[0046] As a preferred technical scheme of the present application, the electrolytic lean solution obtained by electrolysis is returned to the leaching as bottom water for recycling.

[0047] As a preferred technical scheme of the present application, the electrolytic iron powder is subjected to water washing, fine grinding, vacuum drying and hydrogen reduction in sequence to obtain reduced iron powder.

[0048] As a preferred technical scheme of the present application, the temperature of hydrogen reduction is 600-800℃, such as 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 730℃, 750℃, 780℃ or 800℃, etc.

[0049] As a preferred technical scheme of the present application, part of the electrolytic iron powder or the reduced iron powder is used in the reduction reaction.

[0050] It should be noted that, due to the limitation of the length and in order to avoid redundancy, the present application does not exhaustively list all the point values in the above numerical range, but also is not limited to the listed values, and other unlisted values in the above numerical range are also applicable.

[0051] Compared with the prior art, the present application has at least the following beneficial effects:

[0052] The processing method of the hematite type waste residue of the present application adopts the hydrometallurgical process to obtain the electrolytic iron powder by acid dissolution and electrolysis process, and obtains the high-value electrolytic iron powder product, solving the problem of insufficient impurity separation and low product value in the prior art of treating the hematite type waste residue by roasting and magnetic separation method. The present application can further realize the resource utilization of impurities and obtain nickel and aluminum by-products, fully realizing the resource utilization of the hematite type waste residue. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a flowchart of the processing method of the hematite type waste residue of Example 1. DETAILED DESCRIPTION

[0054] The technical scheme of the present application will be further illustrated by specific embodiments.

[0055] Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as a specific limitation of the present application.

[0056] Example 1

[0057] The present embodiment provides a processing method of hematite type waste residue, as shown in Figure 1 The processing method comprises the following steps:

[0058] S1. Water washing: the hematite type waste residue is slurried by adding water and then washed to remove residual water-soluble impurity ions in the waste residue, and the water washing residue is obtained after solid-liquid separation; the source of the hematite type waste residue includes wet smelting of iron ore type nickel oxide ore to extract nickel; the temperature of the water washing is 56℃;

[0059] S2. Leaching: the obtained water washing residue is leached with hydrochloric acid, and the leaching liquid is obtained after solid-liquid separation; the hydrochloric acid is industrial grade hydrochloric acid with a concentration of 33.6%, and the addition amount of the hydrochloric acid is 2.8 times the weight of the water washing residue; the leaching temperature is 56℃, and the leaching time is 6h;

[0060] S3. Reduction: a certain amount of iron powder and sulfur are added to the obtained leaching liquid, and stirred to react, and Fe 3+ is reduced to Fe2 + At the same time, the small amount of impurity nickel ions in the solution is removed, and solid-liquid separation is performed after the reduction reaction to obtain a post-reduction liquid and a reduction residue; the addition amount of the iron powder is 0.55 times the molar amount of the nickel ions in the leaching solution, and the addition amount of the sulfur is 1.04 times the molar amount of the nickel ions in the leaching solution; the pH of the reduction reaction is 1.8-2.1, the time is 1.6 h, and the temperature is 42℃. 3+ 2+

[0061] The reduction residue is subjected to oxygen pressure acid leaching and purification to recover nickel sulfate; the temperature of the oxygen pressure acid leaching is 165℃, and the oxygen partial pressure is 15%; the method for purifying and recovering the nickel includes the following steps: first, chemical precipitation is performed to further remove impurity elements such as Fe, and then extraction purification is performed to obtain nickel sulfate;

[0062] S4. Aluminum removal: a certain amount of a precipitant is added to the post-reduction liquid, and stirring and reaction are performed to obtain a purified liquid and an aluminum residue after solid-liquid separation; the precipitant is sodium phosphate; if the precipitant is sodium phosphate, the addition amount of the sodium phosphate is 1.12 times the molar amount of aluminum in the post-reduction liquid; the pH of the aluminum removal reaction is 1.8-2.2, the temperature is 65℃, and the time is 2.8 h. 3+

[0063] The aluminum residue is mixed with a sodium hydroxide solution, and solid-liquid separation is performed after the reaction; the reaction residue obtained by the solid-liquid separation is washed with water, dried, and calcined to obtain an aluminum oxide product; the addition amount (in solid form) of the sodium hydroxide is 3.1 times the molar amount of aluminum in the aluminum residue, and the calcination temperature is 500℃.

[0064] S5. Electrolysis: the purified liquid is transferred into an electrolytic cell for electrolysis; the current density of the electrolysis is 1800 A / m 2

[0065] Example 2

[0066] The present embodiment provides a treatment method for a hematite-type waste residue, which comprises the following steps:

[0067] S1. Water washing: the hematite-type waste residue is slurried by adding water and then subjected to water washing to remove residual water-soluble impurity ions in the waste residue; solid-liquid separation is performed to obtain a water-washed residue; the hematite-type waste residue is obtained from the extraction of nickel from a hematite-type nickel oxide ore by a wet metallurgical method; the water washing temperature is 40℃.

[0068] ​​​​S2. Leaching: the obtained water washed residue is leached with hydrochloric acid, and a leaching solution is obtained after solid-liquid separation; the hydrochloric acid is industrial grade hydrochloric acid with a concentration of 30%, and the amount of the hydrochloric acid added is 3 times the weight of the water washed residue; the leaching temperature is 60°C, and the leaching time is 4h;

[0069] S3. Reduction: a certain amount of iron powder and sulfur are added to the obtained leaching solution, and stirring reaction is performed, Fe 3+ is reduced to Fe 2 + , and a small amount of impurity nickel ions in the solution are removed at the same time; after the reduction reaction, solid-liquid separation is performed, and a post-reduction solution and a reduction residue are obtained; the amount of the iron powder added is 0.6 times the molar amount of Fe 3+ in the leaching solution, and the amount of the sulfur added is 1 times the molar amount of Ni 2+ in the leaching solution; the pH of the reduction reaction is 1.5-1.9, the time is 1h, and the temperature is 50°C;

[0070] The obtained reduction residue is subjected to pressure oxidation leaching and purification to recover Ni to obtain nickel sulfate; the temperature of the pressure oxidation leaching is 150°C, and the oxygen partial pressure is 20%; the method for purifying and recovering nickel is that the impurities such as Fe are further removed through chemical precipitation, and then nickel sulfate is obtained after further extraction and purification;

[0071] S4. Aluminum removal: a certain amount of a precipitant is added to the obtained post-reduction solution, stirring reaction is performed, and solid-liquid separation is performed after the aluminum precipitation reaction to obtain a purified solution and an aluminum residue; the precipitant is sodium phosphate; if the precipitant is sodium phosphate, the amount of the sodium phosphate added is 1.0 times the molar amount of Al 3+ in the post-reduction solution; the pH of the aluminum precipitation reaction is 1.5-2, the temperature is 80°C, and the time is 1h;

[0072] The obtained aluminum residue is mixed with a sodium hydroxide solution, solid-liquid separation is performed after the reaction, the reaction residue obtained through the solid-liquid separation is washed with water and then dried and calcined to obtain an aluminum oxide product; the amount of the sodium hydroxide added (as a solid) is 3 times the molar amount of aluminum in the aluminum residue, and the calcination temperature is 400°C;

[0073] S5. Electrolysis: the obtained purified solution is transferred into an electrolytic cell for electrolysis; the current density of the electrolysis is 500A / m 2 , and the temperature is 50°C; electrolytic iron powder is obtained at the cathode, the electrolytic iron powder is scraped off from the cathode plate, part of the electrolytic iron powder is returned to step S3 as a reducing agent, and the other part is subjected to a process of water washing, fine grinding, vacuum drying, and hydrogen reduction, and the temperature of the hydrogen reduction is 600°C to obtain reduced iron powder.

[0074] Example 3

[0075] The embodiment provides a treatment method for hematite type waste residue, and the treatment method comprises the following steps:

[0076] S1. Water washing: the hematite type waste residue is slurried by adding water, and then water washing is performed to remove residual water-soluble impurity ions in the waste residue, and solid-liquid separation is performed to obtain washed residue; the source of the hematite type waste residue includes wet smelting and nickel extraction from iron ore type nickel oxide ore; the temperature of the water washing is 80℃;

[0077] S2. Leaching: the obtained washed residue is leached by adding hydrochloric acid, and solid-liquid separation is performed after leaching to obtain leaching solution; the hydrochloric acid is industrial-grade hydrochloric acid with a concentration of 35%, and the addition amount of the hydrochloric acid is 2.5 times the weight of the washed residue; the temperature of the leaching is 40℃, and the leaching time is 8h;

[0078] S3. Reduction: a certain amount of iron powder and sulfur are added to the obtained leaching solution, stirring is performed, and reaction is performed, Fe 3+ is reduced to Fe 2 + , and a small amount of impurity nickel ions in the solution are removed at the same time, solid-liquid separation is performed after the reduction reaction, and reduced residue and reduced solution are obtained; the addition amount of the iron powder is 0.5 times the molar amount of Fe 3+ in the leaching solution, the addition amount of the sulfur is 1.1 times the molar amount of Ni 2+ in the leaching solution, the pH of the reduction reaction is 2.1-2.5, the time is 2h, and the temperature is 30℃;

[0079] The obtained reduced residue is subjected to pressure oxidation leaching and purification to recover Ni to obtain nickel sulfate; the temperature of the pressure oxidation leaching is 180℃, and the oxygen partial pressure is 10%; the method for purifying and recovering nickel is that impurity Fe and the like are further removed through chemical precipitation, and nickel sulfate is obtained after further extraction and purification;

[0080] S4. Aluminum removal: a certain amount of a precipitant is added to the obtained reduced solution, stirring is performed, and aluminum removal reaction is performed, and solid-liquid separation is performed after the aluminum removal reaction to obtain purified solution and aluminum residue; the precipitant is sodium phosphate, if the precipitant is sodium phosphate, the addition amount of the sodium phosphate is 1.2 times the molar amount of Al 3+ in the reduced solution; the pH of the aluminum removal reaction is 2-2.5, the temperature is 40℃, and the time is 4h;

[0081] The obtained aluminum residue is mixed with a sodium hydroxide solution after reaction, solid-liquid separation is performed after the reaction, the reaction residue obtained through the solid-liquid separation is washed with water and then dried and calcined to obtain an aluminum oxide product; the addition amount (in solid form) of the sodium hydroxide is 3.2 times the molar amount of aluminum in the aluminum residue, and the calcination temperature is 600℃;

[0082] S5. Electrolysis: the obtained purified solution is transferred into an electrolytic cell for electrolysis; the current density of the electrolysis is 3000A / m 2, temperature 20℃, electrolytic iron powder is obtained at the cathode, after the iron powder is scraped off from the cathode plate, part of the electrolytic iron powder is returned to step S3 as a reducing agent, and the other part is subjected to the process of water washing, fine grinding, vacuum drying and hydrogen reduction, the temperature of hydrogen reduction is 800℃, and reduced iron powder is obtained.

[0083] Example 4

[0084] This example provides a treatment method of hematite type waste residue, in which the amount of hydrochloric acid in step S2 is adjusted from 2.8 times to 2.0 times, and other conditions are the same as those in Example 1.

[0085] Example 5

[0086] This example provides a treatment method of hematite type waste residue, in which the amount of hydrochloric acid in step S2 is adjusted from 2.8 times A / m 2 to 3.5 times, and other conditions are the same as those in Example 1.

[0087] Example 6

[0088] This example provides a treatment method of hematite type waste residue, in which the amount of iron powder in step S3 is adjusted from 0.55 times to 0.4 times, and other conditions are the same as those in Example 1.

[0089] Example 7

[0090] This example provides a treatment method of hematite type waste residue, in which the amount of iron powder in step S3 is adjusted from 0.55 times to 0.7 times, and other conditions are the same as those in Example 1.

[0091] Example 8

[0092] This example provides a treatment method of hematite type waste residue, in which no sulfur is used in step S3, and other conditions are the same as those in Example 1.

[0093] Comparative Example 1

[0094] This comparative example provides a method for treating hematite type waste residue by roasting and magnetic separation, in which the hematite type waste residue is mixed with coke at a ratio of 1:0.2, then roasted at 1100℃ for 2h in an inert atmosphere, and then finely ground and subjected to magnetic separation at a magnetic field strength of 300mT to obtain a magnetic concentrate (reduced iron powder).

[0095] Characterization and testing:

[0096] The main components of the hematite type waste residue used in the examples and the comparative examples have mass percentage of Fe: 43%, Al: 3.5%, and Si: 6.5%. After the method of the present application is used, the total iron content of the obtained iron powder is measured according to the method of GB / T223.7, and the recovery rate is calculated according to the input amount of the hematite type waste residue after the whole process is stabilized and the residual amount of iron in the leaching residue and the reduction residue (the recovery rate is calculated according to the iron content in the magnetic separation concentrate in Comparative Example 1). The results are shown in Table 1.

[0097] Table 1

[0098] Group Iron powder purity (%) Iron recovery (%) Example 1 99.85 95.5 Example 2 99.92 97.0 Example 3 99.65 94.6 Example 4 99.90 78.5 Example 5 96.25 90.6 Example 6 97.55 91.5 Example 7 99.95 85.8 Example 8 95.20 94.8 Comparative Example 1 91.10 85.2

[0099] As can be seen from Table 1:

[0100] As can be seen from Examples 1 to 3, through the technical scheme of the present application, high-quality electrolytic iron powder with iron grade of 99.6% or more can be obtained, and the iron recovery rate can reach 94% or more.

[0101] As can be seen from Examples 4 and 5, the amount of hydrochloric acid has a significant effect on the iron recovery rate and the purity of the iron powder. When the amount of acid is insufficient, the iron in the waste residue cannot be fully leached out, and the recovery rate decreases significantly. When the amount of acid is too much, the residual acid in the leaching solution is high, and too much iron powder is consumed by the acid during reduction, resulting in insufficient iron powder participating in the reduction reaction, incomplete removal of nickel, and excessive residual iron 3+ , which further leads to a decrease in the purity of the electrolytic iron powder and an increase in the iron precipitation loss during the aluminum removal process (Fe 3+ is more likely to react with the precipitant and precipitate), and the iron recovery rate also decreases. 2+

[0102] As can be seen from Examples 6 and 7, the amount of iron powder also has an effect on the iron recovery rate and the purity of the iron powder. When the amount of iron powder is insufficient, the reduction reaction is insufficient, the residual amounts of Fe 3+ and nickel are relatively high, which leads to an increase in the iron precipitation loss during the aluminum removal stage, a decrease in the iron recovery rate, and a decrease in the purity of the iron powder. When the amount of iron powder is too much, there is more residual iron powder in the reduction residue, which leads to the discharge of excess iron with the slag, and a decrease in the iron recovery rate.

[0103] As can be seen from Example 8, sulfur plays an important role in nickel removal by displacement precipitation. Without sulfur, the impurity removal effect is poor, and the purity of the iron powder decreases significantly.

[0104] ​It can be seen from the comparative example 1 that the iron powder obtained by the roasting and magnetic separation method has a significant gap with the iron powder obtained by the scheme of the present application, and is significantly lower than the scheme of the present application in terms of iron powder purity and recovery. This is because the roasting and magnetic separation method belongs to solid-solid separation, which cannot completely destroy the microstructure of the mutual wrapping of iron phases and impurity phases, and cannot fully dissociate the impurity particles from the iron. The scheme of the present application dissolves the iron into the solution, which can realize the deep dissociation of iron and impurity elements at the atomic or ionic level, and use the difference in chemical properties to make the separation more complete.

[0105] In summary, the treatment method of the hematite-type waste residue of the present application uses the hydrometallurgical process to obtain the electrolytic iron powder by dissolving the waste residue in acid and then through the electrolysis process, and obtains the high-value electrolytic iron powder product, solving the problem of insufficient impurity separation and low product value in the prior art. The present application can further realize the resource utilization of impurities and obtain nickel and aluminum byproducts, and fully realize the resource utilization of hematite-type waste residue.

[0106] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0107] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0108] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and it should also be considered as disclosed by the present application.

Claims

1. A method for treating hematite-type waste residue, characterized in that, The processing method includes the following steps: The hematite-type waste residue was sequentially pulped and washed with water to obtain washed residue. The water-washed residue is leached to obtain a leachate; The leachate is mixed with iron powder and sulfur to carry out a reduction reaction, resulting in a reduced liquid and a reduced residue. The reduced liquid is mixed with a precipitant to carry out an aluminum precipitation reaction, resulting in a purified liquid and aluminum dross. The purified solution is electrolyzed to obtain electrolytic iron powder.

2. The method for treating hematite-type waste slag according to claim 1, characterized in that, The source of the hematite-type waste residue includes the leaching tailings from the hydrometallurgical extraction of nickel from limonite-type nickel oxide ore.

3. The method for treating hematite-type waste residue according to claim 1 or 2, characterized in that, The pulping method includes mixing hematite-type waste residue with water; Preferably, the temperature of the water wash is 40–80°C.

4. The method for treating hematite-type waste residue according to any one of claims 1-3, characterized in that, The leaching agent used in the leaching process includes hydrochloric acid with a concentration of 30% to 35%; Preferably, in the leaching process, the mass ratio of the leaching agent to the water-washed residue is (2.5-3):1; Preferably, the leaching temperature is 40–60°C and the leaching time is 4–8 hours.

5. The method for treating hematite-type waste residue according to any one of claims 1-4, characterized in that, The molar ratio of the iron powder to the ferric ions in the leachate is (0.5-0.6):1; Preferably, the molar ratio of sulfur to nickel ions in the leachate is (1-1.1):1; Preferably, the reduction reaction is carried out at a pH of 1.5 to 2.5, a temperature of 30 to 50°C, and a time of 1 to 2 hours.

6. The method for treating hematite-type waste residue according to any one of claims 1-5, characterized in that, The processing method further includes sequentially subjecting the reduction residue to oxygen pressure acid leaching and purification to recover nickel, thereby obtaining nickel sulfate; Preferably, the temperature of the oxygen pressure acid leaching is 150–180°C, and the oxygen partial pressure is 10%–20%. Preferably, the method for purifying and recovering nickel includes chemical precipitation and / or extraction.

7. The method for treating hematite-type waste residue according to any one of claims 1-6, characterized in that, The precipitant includes sodium phosphate and / or sodium fluoride; Preferably, when the precipitant includes sodium phosphate, the molar ratio of the precipitant to the aluminum ions in the reduced solution is (1.0-1.2):1; when the precipitant includes sodium fluoride, the molar ratio of the precipitant to the aluminum ions in the reduced solution is (3.0-3.5):

1. Preferably, the pH of the aluminum precipitation reaction is 1.5 to 2.5, the temperature is 40 to 80°C, and the time is 1 to 4 hours.

8. The method for treating hematite-type waste residue according to any one of claims 1-7, characterized in that, The processing method further includes mixing and reacting the aluminum slag with sodium hydroxide, separating the solid and liquid to obtain the reaction slag, and then washing, drying and calcining it in sequence to obtain the alumina product. Preferably, the molar ratio of sodium hydroxide to aluminum in the aluminum slag is (3-3.2):1; Preferably, the calcination temperature is 400–600°C.

9. The method for treating hematite-type waste residue according to any one of claims 1-8, characterized in that, The current density of the electrolysis is 500–3000 A / m. 2 The temperature is 20–50℃; Preferably, the electrolysis yields a lean electrolyte solution, which is then returned to the leaching solution as bottom water for recycling.

10. The method for treating hematite-type waste residue according to any one of claims 1-9, characterized in that, The electrolytic iron powder is sequentially washed with water, finely ground, vacuum dried and reduced with hydrogen to obtain reduced iron powder; Preferably, the temperature for hydrogen reduction is 600–800°C; Preferably, a portion of the electrolytic iron powder or the reduced iron powder is recycled for the reduction reaction.

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