Method for preparing ferrous sulfate from iron-containing solid waste

Abstract

The invention provides a method for preparing ferrous sulfate from iron-containing solid waste, and relates to the field of solid waste treatment. The method for preparing ferrous sulfate from the iron-containing solid waste comprises the following steps: mixing concentrated sulfuric acid and the iron-containing solid waste, and curing in a reducing atmosphere or a protective atmosphere to obtain a cured material; the cured material is subjected to water leaching and centrifugal separation, and silicon-containing slag and leachate are obtained; carrying out deepening treatment on the silicon-containing slag to obtain white carbon black; the leachate and iron powder are mixed for a reduction reaction, then a vulcanizing agent is added for vulcanization, precipitation and impurity removal, and copper sulfide slag and a ferrous sulfate solution are obtained through solid-liquid separation; treating the copper sulfide slag to recover valuable metals; and crystallizing the ferrous sulfate solution to obtain ferrous sulfate crystals. According to the method for preparing the ferrous sulfate from the iron-containing solid waste, low-cost, short-process and high-efficiency treatment of the iron-containing solid waste is achieved, and the ferrous sulfate product is obtained.

Description

Technical Field

[0001] The present application relates to the field of solid waste treatment, and in particular to a method for preparing ferrous sulfate from iron-containing solid waste. Background Art

[0002] Iron-containing solid waste, such as copper smelting slag such as molten pool smelting slag and suspended smelting slag produced in the copper smelting process, and iron-containing tailings obtained by electric furnace or slag selection, contain rich valuable resources such as iron and copper. Among them, the representative components of copper smelting iron-containing tailings are: Fe: 29-40%, SiO2: 20-30%, Al2O3: ≤10%, CaO: ≤6%, Cu: 0.1-1.0%. If it is simply stored in the form of solid waste, it will inevitably cause a large amount of valuable resources to be wasted and occupy a large amount of land resources. Therefore, it is necessary to treat it as a resource and recycle it to prepare high-value products, such as ferrous sulfate, copper sulfide and other products, to maximize the utilization of iron-containing solid waste resources.

[0003] The main methods for recovering iron from iron-containing solid wastes are pyrometallurgical depletion, mineral processing and enrichment, and wet leaching. Pyrometallurgical depletion mainly includes electric furnace depletion, vacuum furnace depletion, reverberatory furnace depletion, etc. Based on carbon thermal reduction, the metals and part of the iron in the copper slag are enriched in the iron-rich alloy. Although this method can achieve the recovery of valuable metal resources such as iron and copper, it has the disadvantages of high energy consumption, large slag volume, and high safety risk factor; the main methods for mineral processing and enrichment of iron-containing solid wastes are magnetic separation and flotation, which can achieve separation and enrichment without destroying the original chemical properties of the materials, and have the advantages of low cost, low pollution, and high recovery rate; wet leaching mainly uses leaching agents to convert valuable metals from solid to ionic state, and then refines the products through "filtration-impurity removal", which can achieve a high recovery rate of metals, but if you want to achieve selective leaching of metals, the requirements for leaching agents are relatively high.

[0004] In order to achieve the optimal treatment of iron-containing solid waste, many scholars have adopted a combined approach to treat it. For flash smelting slag with a high copper content, the copper is first recovered by beneficiation. The iron-containing tailings (also known as copper smelting beneficiation tailings) are prepared by a hydrometallurgical route to produce ferrous sulfate products. Patent CN 114149031A adopts the main process of "sulfuric acid aging-leaching-neutralization-fluoridation to remove calcium and magnesium-sulfidation to remove zinc-evaporation crystallization" to prepare high-purity ferrous sulfate products. Patent CN 116514178 A adopts the main process of "tailings slurry adjustment-sulfuric acid leaching-sulfidation impurity removal-iron reduction-cooling crystallization" to prepare ferrous sulfate products. Although these two routes can better achieve the treatment of iron-containing solid waste, there are several disadvantages. First, the consumption of concentrated sulfuric acid and impurity removal reagents is large, and the reagent cost is high; second, the colloidal silica produced in the production process will lead to difficulty in filtration, low production efficiency, and low product rate; third, the use of fluoride for impurity removal will introduce a large amount of F - , resulting in an increase in wastewater treatment costs. Summary of the invention

[0005] The purpose of this application is to provide a method for preparing ferrous sulfate from iron-containing solid waste to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] A method for preparing ferrous sulfate from iron-containing solid waste, comprising:

[0008] Mixing concentrated sulfuric acid and iron-containing solid waste, and aging them in a reducing atmosphere or a protective atmosphere to obtain a slaking material;

[0009] The slaking material is subjected to water immersion, and centrifugal separation is performed to obtain silicon-containing slag and leachate; the silicon-containing slag is subjected to further treatment to obtain white carbon black;

[0010] The leachate is mixed with iron powder to carry out a reduction reaction, and then a sulfiding agent is added to carry out sulfidation precipitation to remove impurities, and solid-liquid separation is performed to obtain copper sulfide slag and ferrous sulfate solution; the copper sulfide slag is treated to recover valuable metals;

[0011] The ferrous sulfate solution is crystallized to obtain ferrous sulfate crystals.

[0012] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste satisfies any one of the following conditions:

[0013] (1) The amount of concentrated sulfuric acid used is 1-2 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-2h;

[0014] (2) The amount of concentrated sulfuric acid used is 1-1.3 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-0.5h.

[0015] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste meets one or more of the following conditions:

[0016] (1) The aging is carried out under closed conditions;

[0017] (2) The reducing atmosphere includes sulfur dioxide and / or hydrogen, and the protective atmosphere includes argon and / or nitrogen.

[0018] Preferably, the solvent used in the water immersion is clean water or the mother liquor and / or condensed water obtained from the crystallization.

[0019] Preferably, the mass ratio of the solvent to the slaking material is (3-6):1, and the water immersion time does not exceed 4 hours.

[0020] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste meets one or more of the following conditions:

[0021] (1) The reduction reaction temperature is 20-90°C, the time is 1-4h, and the system pH is 0-3;

[0022] (2) The amount of iron powder is 3+ The reaction is 1-1.5 times the theoretical amount.

[0023] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste meets one or more of the following conditions:

[0024] (1) The reduction reaction temperature is 50-80°C, the time is 1-2h, and the system pH is 1.8-3;

[0025] (2) The amount of iron powder is 3+ The reaction is 1-1.2 times of the theoretical amount.

[0026] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste meets one or more of the following conditions:

[0027] (1) The vulcanizing agent comprises sodium sulfide and / or sodium hydrosulfide;

[0028] (2) The concentration of the vulcanizing agent is 20-40 wt %, and the amount used is 1-3 times the theoretical amount of sulfur and metal for sulfidation precipitation;

[0029] (3) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-3 hours.

[0030] Preferably, the method for preparing ferrous sulfate from iron-containing solid waste meets one or more of the following conditions:

[0031] (1) The amount of the vulcanizing agent is 1-1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation;

[0032] (2) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-2 hours.

[0033] Preferably, the crystallization comprises cooling crystallization or vacuum evaporation crystallization;

[0034] The mother liquor or condensate obtained from the crystallization is partially or completely used as the absorption liquid for the tail gas generated by the sulfidation precipitation and impurity removal.

[0035] Compared with the prior art, the beneficial effects of this application include:

[0036] During the aging process, the introduction of reducing gas can achieve the reduction of trivalent iron and reduce the oxidation of divalent iron, thereby improving the product conversion rate, reducing the amount of iron powder added in the subsequent iron powder reduction process, and reducing reagent costs. The use of concentrated sulfuric acid to treat iron-containing waste slag solves the problems of iron-containing waste slag storage and concentrated sulfuric acid sales in the factory area, and the SO2 gas produced by pyrometallurgical copper smelting can be used as a reducing agent, achieving the purpose of waste treatment and low-cost resource recovery in a short process. DETAILED DESCRIPTION

[0037] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows:

[0038] A method for preparing ferrous sulfate from iron-containing solid waste, comprising:

[0039] Mixing concentrated sulfuric acid and iron-containing solid waste, and aging them in a reducing atmosphere or a protective atmosphere to obtain a slaking material;

[0040] The slaking material is subjected to water immersion, and centrifugal separation is performed to obtain silicon-containing slag and leachate; the silicon-containing slag is subjected to further treatment to obtain white carbon black;

[0041] The leachate is mixed with iron powder to carry out a reduction reaction, and then a sulfiding agent is added to carry out sulfidation precipitation to remove impurities, and solid-liquid separation is performed to obtain copper sulfide slag and ferrous sulfate solution; the copper sulfide slag is treated to recover valuable metals;

[0042] The ferrous sulfate solution is crystallized to obtain ferrous sulfate crystals.

[0043] The maturation process uses the intelligent closed reaction equipment developed by us, which is wear-resistant, strong acid-resistant, high-temperature-resistant, and has a controllable and adjustable reaction speed. This equipment solves the problem of short life and low efficiency of the core equipment in the resource utilization of iron-containing tailings industry.

[0044] The solid-liquid separation after water immersion uses centrifugal equipment with high-efficiency purification, which can solve the difficult problems of liquid-solid separation of silicon-containing slag slurry and entrainment of qualified products to reduce the product rate.

[0045] The amount of reducing atmosphere gas used is based on Fe 3+ Basically reduced to Fe 2+ It is appropriate.

[0046] (1) Iron-containing solid waste contains some Fe3O4 and Fe2O3, which will generate Fe2(SO4)3 after reacting with concentrated sulfuric acid. If reducing gas is not introduced, the subsequent iron powder reduction process will cause excessive iron powder consumption and increase costs. If reducing gas is introduced (the gas source can be SO2 produced by copper smelting or H2 produced by the process of the present invention), comprehensive treatment and utilization of waste gas can be achieved, greatly reducing costs. The reactions involved are:

[0047] ①Fe2O3+SO2(g)+H2SO4(l)=2FeSO4+H2O(g)

[0048] △G θ =-201646.73+201.83T

[0049] ②Fe3O4+SO2(g)+2H2SO4(l)=3FeSO4+2H2O(g)

[0050] △G θ =-303757.97+252.91T

[0051] ③Fe2O3+H2(g)+2H2SO4(l)=2FeSO4+3H2O(g)

[0052] △G θ =-208341.86+14.63T

[0053] ④Fe3O4+H2(g)+3H2SO4(l)=3FeSO4+4H2O(g)

[0054] △G θ =-310447.22+65.7T

[0055] △G θ is Gibbs free energy, in J; T is temperature, in K. From the Gibbs free energy of each reaction, it can be seen that at 100-300℃, the Gibbs free energy is <0, and all are spontaneous reactions. That is, the introduction of reducing gas can achieve the reduction of trivalent iron.

[0056] (2) In the water immersion-liquid-solid separation process, insoluble silicon slag, lead sulfate, etc. exist in the slag in solid form, and iron, nickel, cobalt, copper and other ions exist in the solution in ionic form, thus achieving separation.

[0057] (3) Because some Fe may still exist in the solution 3+ , the main reaction equation for adding iron powder is: 2Fe 3+ +Fe=3Fe 2 + , which can achieve Fe 3+ of restoration.

[0058] (4) During the sulfide precipitation process, nickel, cobalt, copper and other ions react with sulfur to form insoluble sulfides, while divalent iron exists in the form of ions, thereby removing impurities.

[0059] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies any one of the following conditions:

[0060] (1) The amount of concentrated sulfuric acid used is 1-2 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-2h;

[0061] (2) The amount of concentrated sulfuric acid used is 1-1.3 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-0.5h.

[0062] Optionally, the amount of concentrated sulfuric acid used can be 1 times, 1.5 times, 2 times or any value between 1-2 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time can be 0.1h, 0.5h, 1.0h, 1.5h, 2h or any value between 0.1-2h.

[0063] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies one or more of the following conditions:

[0064] (1) The aging is carried out under closed conditions;

[0065] (2) The reducing atmosphere includes sulfur dioxide and / or hydrogen, and the protective atmosphere includes argon and / or nitrogen.

[0066] In an optional embodiment, the solvent used for the water immersion is clean water or the mother liquor and / or condensed water obtained from the crystallization.

[0067] The water immersion process is stirring at room temperature.

[0068] In an optional embodiment, the mass ratio of the solvent to the slaking material is (3-6):1, and the water immersion time does not exceed 4 hours.

[0069] Optionally, the mass ratio of the solvent to the matured material can be 3:1, 4:1, 5:1, 6:1 or any value between (3-6):1, and the immersion time can be 1h, 2h, 3h, 4h or any value not exceeding 4h.

[0070] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies one or more of the following conditions:

[0071] (1) The reduction reaction temperature is 20-90°C, the time is 1-4h, and the system pH is 0-3;

[0072] (2) The amount of iron powder is 3+ The reaction is 1-1.5 times the theoretical amount.

[0073] Optionally, the temperature of the reduction reaction can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or any value between 20-90°C, the time can be 1, 2, 3, 4 or any value between 1-4h, and the system pH can be 0, 0.5, 1, 1.5, 2, 2.5, 3 or any value between 0-3; the amount of the iron powder can be about the same as that of Fe 3+ The reaction amount is 1 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times or any value between 1-1.5 times the theoretical amount.

[0074] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies one or more of the following conditions:

[0075] (1) The reduction reaction temperature is 50-80°C, the time is 1-2h, and the system pH is 1.8-3;

[0076] (2) The amount of iron powder is 3+ The reaction amount is 1-1.2 times of the theoretical amount.

[0077] Optionally, the reduction reaction temperature may be 50°C, 60°C, 70°C, 80°C or any value between 50-80°C, the reaction time may be 1h, 1.5h, 2h or any value between 1-2h, the system pH may be 1.8, 2, 2.5, 3 or any value between 1.8-3; the amount of iron powder may be about the same as Fe 3+ The reaction amount is 1 times, 1.1 times, 1.2 times or any value between 1-1.2 times the theoretical amount.

[0078] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies one or more of the following conditions:

[0079] (1) The vulcanizing agent comprises sodium sulfide and / or sodium hydrosulfide;

[0080] (2) The concentration of the vulcanizing agent is 20-40 wt %, and the amount used is 1-3 times the theoretical amount of sulfur and metal for sulfidation precipitation;

[0081] (3) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-3 hours.

[0082] Optionally, the concentration of the vulcanizing agent can be 20wt%, 30wt%, 40wt% or any value between 20-40wt%, and the amount used can be 1 times, 2 times, 3 times or any value between 1-3 times the theoretical amount of sulfur and metal for sulfidation precipitation; the temperature of the sulfidation precipitation impurity removal is room temperature, and the time can be 1h, 2h, 3h or any value between 1-3h.

[0083] In an optional embodiment, the method for preparing ferrous sulfate from iron-containing solid waste satisfies one or more of the following conditions:

[0084] (1) The amount of the vulcanizing agent is 1-1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation;

[0085] (2) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-2 hours.

[0086] Optionally, the dosage of the vulcanizing agent can be 1 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times or any value between 1-1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation; the temperature for sulfidation precipitation impurity removal is room temperature, and the time can be 1h, 1.5h, 2h or any value between 1-2h.

[0087] In an optional embodiment, the crystallization includes cooling crystallization or vacuum evaporation crystallization;

[0088] The mother liquor or condensate obtained from the crystallization is partially or completely used as the absorption liquid for the tail gas generated by the sulfidation precipitation and impurity removal.

[0089] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0090] The raw materials of the following examples are copper smelting tailings, and the experimental sampling raw material components are: Fe: 31.55%, SiO2: 23.41%, Al2O3: 6%, CaO: 4%, Cu: 0.2%.

[0091] Example 1

[0092] This embodiment provides a method for preparing ferrous sulfate from iron-containing solid waste, comprising the following steps:

[0093] Step 1) Reduction sulfuric acid aging: Concentrated sulfuric acid and iron-containing solid waste are mixed and aged in a certain proportion. The equipment is an intelligent closed high-speed reactor. Reducing gas SO2 is introduced into the process to achieve the reduction of trivalent iron / reduce the oxidation of divalent iron, thereby promoting the leaching of iron and reducing the consumption of subsequent reducing agents.

[0094] The amount of concentrated sulfuric acid used is 1.1 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.5h.

[0095] Step 2) the slaking material is leached with ferrous sulfate crystallization mother liquor - liquid-solid separation: under a certain liquid-solid ratio, the slaking material obtained in step 1) is directly stirred and leached. After the leaching is completed, liquid-solid separation is performed using a high-efficiency centrifugal device. The filter residue is silicon-containing slag. After further in-depth treatment of the silicon-containing slag, the product white carbon black is obtained.

[0096] The solvent used for leaching is ferrous sulfate crystallization mother liquor; the mass ratio of solvent to slaking material is 4:1, and the leaching time is 2h.

[0097] Step 3) filtrate iron reduction - sulfidation impurity removal - liquid-solid separation: the residual trivalent iron in the filtrate obtained in step 2) is reduced with iron powder, then sulfidation precipitation and impurity removal are carried out with a sulfiding agent, and finally liquid-solid separation is performed to obtain valuable copper sulfide slag and ferrous sulfate filtrate respectively. The copper sulfide slag is returned to the copper smelting system to recover copper and other metals.

[0098] The temperature of the reduction reaction is 30°C, the time is 2h, and the pH of the system is 1.8-2.0; the amount of iron powder used is about the same as Fe 3+ The concentration of the sulfiding agent is 40wt%, and the amount used is twice the theoretical amount of sulfur and metal for sulfidation precipitation. The temperature for sulfidation precipitation and impurity removal is room temperature, and the time is 1.5h.

[0099] Step 4) Cooling crystallization / vacuum crystallization: The ferrous sulfate solution obtained in step 3) is cooled to 15-18° C. for crystallization, and centrifuged for solid-liquid separation to obtain ferrous sulfate crystals.

[0100] Example 2

[0101] Step 1) Reduction sulfuric acid aging: Concentrated sulfuric acid and iron-containing solid waste are mixed and aged in a certain proportion. The equipment is an intelligent closed high-speed reactor. Reducing gas SO2 is introduced into the process to achieve the reduction of trivalent iron / reduce the oxidation of divalent iron, thereby promoting the leaching of iron and reducing the consumption of subsequent reducing agents.

[0102] The amount of concentrated sulfuric acid used is 1.1 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.5h.

[0103] Step 2) The matured material is leached by crystallization mother liquor - liquid-solid separation: under a certain liquid-solid ratio, the matured material obtained in step 1) is directly stirred and leached. After the leaching is completed, liquid-solid separation is performed using a high-efficiency centrifugal device. The filter residue is silicon-containing residue. After further in-depth treatment of the silicon-containing residue, the product white carbon black is obtained.

[0104] The solvent used for leaching is ferrous sulfate crystallization mother liquor; the mass ratio of solvent to slaking material is 4:1, and the leaching time is 2h.

[0105] Step 3) filtrate iron reduction - sulfidation impurity removal - liquid-solid separation: the residual trivalent iron in the filtrate obtained in step 2) is reduced with iron powder, then sulfidation precipitation and impurity removal are carried out with a sulfiding agent, and finally liquid-solid separation is performed to obtain valuable copper sulfide slag and ferrous sulfate filtrate respectively. The copper sulfide slag is returned to the copper smelting system to recover copper and other metals.

[0106] The temperature of the reduction reaction is 30°C, the time is 2h, and the pH of the system is 2.5-3.0; the amount of iron powder used is 3+ The concentration of the sulfiding agent is 40wt%, and the amount used is 1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation. The temperature of sulfidation precipitation and impurity removal is room temperature, and the time is 1.5h.

[0107] Step 4) Cooling crystallization / vacuum crystallization: The ferrous sulfate solution obtained in step 3) is cooled to 15-18° C. for crystallization, and centrifuged for solid-liquid separation to obtain ferrous sulfate crystals.

[0108] Example 3

[0109] Step 1) oxygen-free sulfuric acid aging: concentrated sulfuric acid and iron-containing solid waste are mixed and aged in a certain proportion. The equipment is an intelligent closed high-speed reactor. Protective gas N2 is introduced into the process to reduce the oxidation of divalent iron, thereby reducing the consumption of subsequent reducing agents.

[0110] The amount of concentrated sulfuric acid used is 1.1 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.5h.

[0111] Step 2) the slaking material is leached with ferrous sulfate crystallization mother liquor - liquid-solid separation: under a certain liquid-solid ratio, the slaking material obtained in step 1) is directly stirred and leached. After the leaching is completed, liquid-solid separation is performed using a high-efficiency centrifugal device. The filter residue is silicon-containing slag. After further in-depth treatment of the silicon-containing slag, the product white carbon black is obtained.

[0112] The solvent used for leaching is ferrous sulfate crystallization mother liquor; the mass ratio of solvent to slaking material is 4:1, and the leaching time is 2h.

[0113] Step 3) filtrate iron reduction - sulfidation impurity removal - liquid-solid separation: the residual trivalent iron in the filtrate obtained in step 2) is reduced with iron powder, then sulfidation precipitation and impurity removal are carried out with a sulfiding agent, and finally liquid-solid separation is performed to obtain valuable copper sulfide slag and ferrous sulfate filtrate respectively. The copper sulfide slag is returned to the copper smelting system to recover copper and other metals.

[0114] The temperature of the reduction reaction is 30°C, the time is 2h, and the pH of the system is 2.5-3.0; the amount of iron powder used is 3+The concentration of the sulfiding agent is 40wt%, and the amount used is 1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation. The temperature of sulfidation precipitation and impurity removal is room temperature, and the time is 1.5h.

[0115] Step 4) Cooling crystallization / vacuum crystallization: The ferrous sulfate solution obtained in step 3) is cooled to 15-18° C. for crystallization, and centrifuged for solid-liquid separation to obtain ferrous sulfate crystals.

[0116] Comparative Example 1

[0117] The difference from Example 1 is that there is no reducing atmosphere / protective atmosphere in the sulfuric acid aging process, and the process is carried out in an air atmosphere, and the other conditions are the same.

[0118] Comparative Example 2

[0119] The difference from Example 1 is that the pH of the reduction reaction system is >3, and the other conditions are the same.

[0120] The conditions and results of each embodiment and comparative example are shown in Table 1 below.

[0121] Table 1 Conditions and results of each embodiment and comparative example

[0122]

[0123] In the above Examples 1 to 3 and Comparative Example 1, the Fe recovery rate of the iron-containing solid waste can reach more than 99%, and the Fe recovery rate in Comparative Example 2 is 94%. Compared with Example 1, when no reducing gas is introduced into Example 3, the consumption of iron powder increases significantly, which is mainly due to the Fe content of the raw material. 3+ Compared with Examples 1 and 3, the consumption of iron powder in Comparative Example 1 increased without any protective atmosphere, which was mainly related to the reaction process Fe 2+ Converted to Fe 3+ Compared with Example 1, Example 2 / 3 has a lower sodium sulfide consumption, mainly because the iron powder will react with Cu at a higher pH. 2+ reaction, reducing the solution Cu 2+ Comparative Example 2 compared with Example 1, the recovery rate of iron is lower, mainly when the pH value of the reduction reaction end point is higher, Fe 2+ Easily converted to Fe 3+ , Fe 3+ The loss is caused by the formation of Fe(OH)3 precipitate.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing ferrous sulfate from iron-containing solid waste, characterized in that: include: Mixing concentrated sulfuric acid and iron-containing solid waste, and aging them in a reducing atmosphere or a protective atmosphere to obtain a slaking material; The slaking material is subjected to water immersion, and centrifugal separation is performed to obtain silicon-containing slag and leachate; the silicon-containing slag is subjected to further treatment to obtain white carbon black; The leachate is mixed with iron powder to carry out a reduction reaction, and then a sulfiding agent is added to carry out sulfidation precipitation to remove impurities, and solid-liquid separation is performed to obtain copper sulfide slag and ferrous sulfate solution; the copper sulfide slag is treated to recover valuable metals; The ferrous sulfate solution is crystallized to obtain ferrous sulfate crystals.

2. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 1, characterized in that: Meet any of the following conditions: (1) The amount of concentrated sulfuric acid used is 1-2 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-2h; (2) The amount of concentrated sulfuric acid used is 1-1.3 times the theoretical amount of metal in the iron-containing solid waste that can react with sulfuric acid, and the aging time is 0.1-0.5h.

3. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 1, characterized in that: One or more of the following conditions are met: (1) The aging is carried out under closed conditions; (2) The reducing atmosphere includes sulfur dioxide and / or hydrogen, and the protective atmosphere includes argon and / or nitrogen.

4. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 1, characterized in that: The solvent used in the water immersion is clean water or the mother liquor and / or condensed water obtained from the crystallization.

5. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 4, characterized in that: The mass ratio of the solvent to the slaking material is (3-6):1, and the water immersion time does not exceed 4 hours.

6. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 1, characterized in that: One or more of the following conditions are met: (1) The reduction reaction temperature is 20-90°C, the time is 1-4h, and the system pH is 0-3; (2) The amount of iron powder is 3+ The reaction is 1-1.5 times the theoretical amount.

7. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 6, characterized in that: One or more of the following conditions are met: (1) The reduction reaction temperature is 50-80°C, the time is 1-2h, and the system pH is 1.8-3; (2) The amount of iron powder is 3+ The reaction amount is 1-1.2 times of the theoretical amount.

8. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 1, characterized in that: One or more of the following conditions are met: (1) The vulcanizing agent comprises sodium sulfide and / or sodium hydrosulfide; (2) The concentration of the vulcanizing agent is 20-40 wt %, and the amount used is 1-3 times the theoretical amount of sulfur and metal for sulfidation precipitation; (3) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-3 hours.

9. The method for preparing ferrous sulfate from iron-containing solid waste according to claim 8, characterized in that: One or more of the following conditions are met: (1) The amount of the vulcanizing agent is 1-1.5 times the theoretical amount of sulfur and metal for sulfidation precipitation; (2) The temperature of the sulfide precipitation impurity removal is room temperature and the time is 1-2 hours.

10. The method for preparing ferrous sulfate from iron-containing solid waste according to any one of claims 1 to 9, characterized in that: The crystallization includes cooling crystallization or vacuum evaporation crystallization; The mother liquor or condensate obtained from the crystallization is partially or completely used as the absorption liquid for the tail gas generated by the sulfidation precipitation and impurity removal.

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