Method for preparing ferrous oxalate from iron-containing industrial solid waste

Abstract

The invention belongs to the technical field of metallurgical waste recycling, and particularly relates to a method for preparing ferrous oxalate from iron-containing industrial solid waste. The method comprises the following steps that S1, the iron-containing industrial solid waste and a leaching agent are mixed, and slurry is obtained; wherein the leaching agent comprises a first acid solution and an oxalate solution; s2, the slurry is leached under microwave heating, the pH is adjusted after leaching is finished, and first filtrate and first filter residues are obtained through solid-liquid separation; and S3, mixing the first filtrate, a second acid solution and a water-soluble polymer, carrying out a hydrothermal reaction, and carrying out solid-liquid separation to obtain a second filtrate and ferrous oxalate. The method is simple in technological process. The method is simple in process, low in cost and short in time consumption, realizes resource utilization of iron-containing industrial wastes, and can help to save resources and protect the environment; iron resources in the iron-containing industrial solid waste can be fully extracted, and ferrous oxalate with small particle size and high purity can be directly prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical waste recycling, and in particular relates to a method for preparing ferrous oxalate from iron-containing industrial solid waste. Background Art

[0002] Due to the rapid growth of market demand for nickel and the increasing scarcity of nickel sulfide ore resources, laterite nickel ore has become the main raw material for extracting nickel. There are currently two mainstream laterite nickel ore smelting processes, rotary kiln drying pre-reduction-electric furnace smelting (RKEF) and sulfuric acid high-pressure leaching process (HPAL). Among them, the laterite nickel ore sulfuric acid high-pressure leaching process is widely used in industrial production due to its good leaching selectivity, high nickel and cobalt leaching rates, low energy consumption, and low carbon emissions. However, this process will produce a large amount of leaching slag. The laterite nickel ore leaching slag is rich in iron, with an iron content of 40% to 60%, but due to the extremely fine particle size of the leaching slag, mineral inclusions and coexistence, small magnetic differences, and high sulfur and water content, the iron element in it is difficult to be utilized as a resource. At present, the treatment method for leaching slag is mostly stockpiling, which will occupy a large amount of land resources and have extremely high environmental safety risks.

[0003] In the prior art, the pyrometallurgical process for extracting iron from laterite nickel ore leaching slag is mainly magnetization roasting-magnetic separation and reduction smelting. Among them, the magnetization roasting-magnetic separation process is to convert Fe2O3 in the leaching slag into highly magnetic Fe3O4, and enrich iron through magnetic separation to improve the iron grade to obtain high-grade iron concentrate. This process has high energy consumption and a long process, and the iron recovery rate of the obtained iron concentrate is low and the impurity content is high. The reduction smelting process is to granulate the leaching slag and then roast it at high temperature for desulfurization, and the obtained high-temperature roasted sand is reduced and smelted with a reducing agent and a flux to obtain molten iron for steelmaking; this process has high energy consumption, a long process, high production cost, and high pollution. When obtaining the target product, the above two processes must focus on the transfer of sulfur, and it is necessary to reduce the sulfur content in the target product by increasing the process flow.

[0004] Ferrous oxalate is now widely used in daily life, such as as a coating or ceramic colorant. It is also the main raw material required for synthesizing lithium iron phosphate positive electrode materials for lithium-ion batteries. With the development of lithium-ion batteries, its demand is also increasing day by day. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art in that the treatment of laterite nickel ore leaching residue requires focusing on the removal of sulfur, and has high energy consumption, low iron recovery rate of the final product, high impurity content, etc., thereby providing a method for preparing ferrous oxalate from iron-containing industrial solid waste.

[0006] To this end, the present invention provides the following technical solutions.

[0007] The present invention provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, comprising the following steps: S1: mixing the iron-containing industrial solid waste and a leaching agent to obtain a slurry; wherein the leaching agent comprises a first acid solution and an oxalate solution; S2: leaching the slurry under microwave heating, adjusting the pH after the leaching is completed, and performing solid-liquid separation to obtain a first filtrate and a first filter residue; S3: mixing the first filtrate, a second acid solution, and a water-soluble polymer, performing a hydrothermal reaction, and performing solid-liquid separation to obtain a second filtrate and ferrous oxalate.

[0008] Optionally, in step S2, the power of microwave heating is 300-800 W, the heating temperature is 80-95° C., and the leaching time is 15-40 min.

[0009] Optionally, in step S3, the mass of the water-soluble polymer is 0.05% to 4.00% of the mass of the first filtrate.

[0010] Optionally, in step S1, the solid-liquid ratio of the iron-containing industrial solid waste and the leaching agent is 1:8-12 g / mL.

[0011] Optionally, in step S1, the concentration of the first acid solution in the leaching agent is 3.9 to 10.0 mol / L in terms of monoacid; optionally, in step S1, the concentration of the first acid solution in the leaching agent is 6.4 to 10.0 mol / L in terms of monoacid.

[0012] Optionally, in step S1, the mass ratio of iron-containing industrial solid waste to oxalate in the leaching agent is 1:2.6-9.2; optionally, in step S1, the mass ratio of iron-containing industrial solid waste to oxalate in the leaching agent is 1:4.3-9.2.

[0013] Optionally, in step S2, the pH is adjusted to 2.5-3.5 after the leaching is completed.

[0014] Optionally, in step S2, the reagent used to adjust the pH includes oxalate; preferably, the reagent used to adjust the pH includes at least one of sodium oxalate and potassium oxalate.

[0015] Optionally, in step S2, leaching is performed under stirring; preferably, the stirring speed is 150 to 300 r / min.

[0016] Optionally, in step S3, a second acid solution is added so that the acid concentration in the system is 1.8 to 5.8 mol / L in terms of monoacid; optionally, in step S3, a second acid solution is added so that the acid concentration in the system is 3.4 to 5.8 mol / L in terms of monoacid.

[0017] Optionally, in step S3, the temperature of the hydrothermal reaction is 90-125° C., the pressure is 0.2-1.6 MPa, and the reaction time is 20-45 min.

[0018] Optionally, in step S3, the hydrothermal reaction is carried out under stirring; preferably, the stirring speed is 300 to 500 r / min.

[0019] Optionally, the water-soluble polymer includes at least one of polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2488, polyvinyl pyrrolidone K30, polyethylene glycol 10000, and polyethylene glycol 20000.

[0020] Optionally, the first acid solution includes at least one of sulfuric acid and hydrochloric acid.

[0021] Optionally, the second acid solution includes at least one of sulfuric acid and hydrochloric acid.

[0022] Optionally, in step S1, the oxalate solution includes at least one of a sodium oxalate solution and a potassium oxalate solution.

[0023] Optionally, more than 30% of the iron in the iron-containing industrial solid waste is in the form of Fe2O3, and the iron content in the iron-containing industrial solid waste is ≥20% by mass percentage; Optionally, more than 50% of the iron in the iron-containing industrial solid waste is in the form of Fe2O3, and the iron content in the iron-containing industrial solid waste is ≥40% by mass percentage; Optionally, the iron-containing industrial solid waste includes at least one of laterite nickel ore leaching residue, roasting cyanide tailings, high-phosphorus oolitic hematite, sulfuric acid slag, and Bayer process red mud; Preferably, the iron-containing industrial solid waste is laterite nickel ore leaching residue. The laterite nickel ore leaching residue can be purchased or obtained by processing the laterite nickel ore by yourself. Typically, the specific process flow for processing the laterite nickel ore includes: raw material preparation: limonite-type laterite nickel ore is used as raw material, and sulfuric acid is used as leaching agent; the laterite nickel ore particle size is 60-150 mesh, the acid-ore ratio is 250-300g / kg, and the liquid-solid volume mass ratio is 2.5:1-3.5:1 (unit: mL / g); the laterite nickel ore is mixed with the sulfuric acid solution and placed in an autoclave. High-pressure acid leaching: leaching temperature is 230-260°C, pressure is 4-5MPa, stirring rate is 400-650r / min, leaching time is 1-1.5h, and slurry is obtained after the leaching reaction is completed. Slurry flashing: solid-liquid separation is performed when the slurry is cooled to below 60°C to obtain leachate and laterite nickel ore leaching residue. Washing and drying: The laterite nickel ore leaching residue is washed and dried at a temperature of 100-120°C for 2-5 hours. As solid waste after high-pressure leaching of laterite nickel ore, the laterite nickel ore leaching residue is mostly disposed of in a stockpile manner, and the price of purchasing the solid waste is very low.

[0024] Optionally, after step S3, the method further includes washing and drying the ferrous oxalate.

[0025] Optionally, the particle size D50 of the ferrous oxalate is less than 5.0 μm.

[0026] Optionally, the step further includes adding the first acid solution and oxalate to the second filtrate and returning the second filtrate as a leaching agent to step S2 to participate in leaching.

[0027] Optionally, the use of the ferrous oxalate includes being used as a raw material for preparing a positive electrode material for a lithium-ion battery; preferably, the positive electrode material for a lithium-ion battery includes a lithium iron phosphate positive electrode material.

[0028] Optionally, the first filter residue can be used as a raw material for building materials.

[0029] The method for preparing ferrous oxalate from iron-containing industrial solid waste provided by the present invention specifically comprises the following steps:

[0030] (1) mixing iron-containing industrial solid waste and a leaching agent to obtain a slurry, wherein the leaching agent includes a first acid solution and an oxalate solution. The solid-liquid ratio of the iron-containing industrial solid waste to the leaching agent is 1:8-12 g / mL, the concentration of the acid in the leaching agent is 3.9-10 mol / L as a monobasic acid, and the mass ratio of the iron-containing industrial solid waste to the oxalate in the leaching agent is 1:2.6-9.2.

[0031] (2) The slurry is subjected to microwave heating leaching at 80-95° C. for 15-40 min, with a microwave power of 300-800 W. The leaching is carried out under stirring at a stirring speed of 150-300 r / min. After the leaching is completed, the pH value is adjusted to 2.5-3.5 using oxalate, and the first filtrate and the first filter residue are obtained by filtration. The first filter residue can be used as a raw material for building materials later.

[0032] (3) Mix the first filtrate, the second acid solution, and the water-soluble polymer so that the acid concentration in the whole system is 1.8-5.8 mol / L as monoacid, and the amount of the water-soluble polymer is 0.05%-4% of the mass of the first filtrate; put it into a reactor and carry out hydrothermal reaction under stirring for 20-45 minutes, the reaction temperature is 90-125°C, the pressure is 0.2-1.6Mpa, and the stirring rate is 300-500r / min. After the reaction is completed, filter to obtain the second filtrate and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding the first acid solution and oxalate to the second filtrate, return to the step (2) as a leaching agent to participate in the leaching step.

[0033] The beneficial effects of the present invention are:

[0034] The method for preparing ferrous oxalate from iron-containing industrial solid waste provided by the present invention comprises the following steps: S1: mixing iron-containing industrial solid waste and a leaching agent to obtain a slurry; wherein the leaching agent comprises a first acid solution and an oxalate solution; S2: leaching the slurry under microwave heating, adjusting the pH after the leaching, and solid-liquid separation to obtain a first filtrate and a first filter residue; S3: mixing the first filtrate, the second acid solution, and a water-soluble polymer, hydrothermally reacting, and solid-liquid separation to obtain a second filtrate and ferrous oxalate. The method realizes the resource utilization of iron-containing industrial waste, can help save resources and protect the environment; can fully extract the iron resources in the iron-containing industrial solid waste, the iron recovery rate can reach>98%, and directly prepare ferrous oxalate with a small particle size and high purity, the purity of ferrous oxalate is>99%, the particle size is about 3-4.5μm, and there are few by-products; and the process flow of the method is simple, there is no need to pay attention to the transfer of sulfur, it takes a short time, the cost is low, and it is suitable for industrial production.

[0035] The present invention strengthens the leaching process by microwave heating. Microwave heating has the characteristics of selectivity and rapid heating. During leaching, the absorption properties of different components in industrial solid waste are different, and there will be a temperature gradient between them. The thermal stress generated by the temperature gradient will cause cracks and cracks between the components, generate more reaction surfaces and increase the contact area between industrial solid waste and leaching agent, strengthen the leaching process, shorten the leaching time, and improve the leaching efficiency. At the same time, as the reaction proceeds, the leached product will cover the surface of industrial solid waste, occupy its surface active sites, and also hinder the leaching agent from penetrating to the surface, which has an adverse effect on the leaching reaction; microwaves can cause the reactants to produce thermal effects and high-frequency vibrations, continuously update the reaction interface on the surface of industrial solid waste, effectively maintain the contact area of ​​the reaction interface, and improve the leaching effect. In short, microwave heating has a fast heating rate, can make the reactants heated evenly, can change the thermal diffusivity and mass diffusivity, improve the leaching efficiency and shorten the leaching time, reduce the production cycle, and is low in cost and environmentally friendly.

[0036] During the leaching process, oxalate ions react with the leached calcium, magnesium and manganese ions to form insoluble CaC2O4, MgC2O4 and MnC2O4 precipitates, which are beneficial to destroy the mineral structure of the leached residue. These precipitates will enter the first filter residue through solid-liquid separation together with the unleached minerals, thereby avoiding contamination of the first filtrate.

[0037] The hydrothermal reaction has a short reaction time, low reaction temperature and controllable reaction conditions. The second acid solution is added before the hydrothermal reaction to convert part of the C2O4 2- In the hydrothermal reaction, the reducing and complexing properties of oxalic acid are used to convert Fe 3+ Reduction to Fe 2+ And with Fe 2+The reaction generates ferrous oxalate. In the hydrothermal reaction, the added water-soluble polymer can react with Fe 3+ , Fe 2+ Form a complex structure to reduce Fe 3+ In addition, water-soluble polymers can increase the viscosity of the solution, reduce the migration rate of ions, inhibit the growth and movement of ferrous oxalate, and reduce the probability of ferrous oxalate colliding and aggregating to form large particles, ultimately producing ferrous oxalate with small particle size and uniform distribution.

[0038] The method for preparing ferrous oxalate from iron-containing industrial solid waste provided by the present invention also includes adding the first acid solution and oxalate to the second filtrate, and then returning the first acid solution and oxalate to the step S2 as a leaching agent to participate in leaching, thereby realizing the recycling of wastewater.

[0039] In the method for preparing ferrous oxalate from iron-containing industrial solid waste provided by the present invention, the use of the ferrous oxalate includes being used as a raw material for preparing a positive electrode material for a lithium ion battery; preferably, the positive electrode material for a lithium ion battery includes a lithium iron phosphate positive electrode material. Ferrous oxalate with a smaller particle size can effectively control the particle size of the lithium iron phosphate positive electrode material and improve the electrochemical performance of the lithium iron phosphate positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 The present invention is a schematic diagram of the process flow of the method for preparing ferrous oxalate from iron-containing industrial solid waste. DETAILED DESCRIPTION

[0042] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0043] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0044] Example 1

[0045] This embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using directly purchased laterite nickel ore high-pressure leaching residue, which contains 41.75% iron, 2.11% chromium, 6.10% silicon, 3.94% aluminum, 0.70% magnesium, and 3.57% sulfur. The iron is mainly produced in the form of hematite (limonite), with a distribution rate of 98.63%. The process flow diagram is shown in FIG. Figure 1 As shown, the specific steps include:

[0046] (1) mixing the laterite nickel ore leaching residue and the leaching agent to obtain a slurry. The solid-liquid ratio of the laterite nickel ore leaching residue to the leaching agent is 1:10 g / mL, the concentration of sulfuric acid in the leaching agent is 3.43 mol / L, and the mass ratio of the laterite nickel ore leaching residue to the sodium oxalate in the leaching agent is 1:4.6.

[0047] (2) The slurry was subjected to microwave heating leaching at 90° C. for 25 min, with a microwave power of 650 W. The leaching was carried out under stirring at a stirring speed of 250 r / min. After the leaching was completed, the pH value was adjusted to 3.1 using sodium oxalate, and the first filtrate 1 and the first filter residue 1 were obtained by filtration. The first filter residue 1 can be used as a raw material for building materials later.

[0048] (3) Mix the first filtrate 1, sulfuric acid, and water-soluble high molecular weight polyvinyl alcohol 1799 so that the concentration of sulfuric acid in the whole system is 1.85 mol / L, and the amount of water-soluble high molecular weight polyvinyl alcohol 1799 is 2.50% of the mass of the first filtrate 1; put it into a reactor and carry out hydrothermal reaction for 30 minutes under stirring, the reaction temperature is 105°C, the pressure is 1.1Mpa, and the stirring rate is 420r / min. After the reaction is completed, filter to obtain the second filtrate 1 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding sulfuric acid and sodium oxalate to the second filtrate 1, return to the step (2) as a leaching agent to participate in the leaching step.

[0049] Example 2

[0050] The present embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using directly purchased laterite nickel ore high-pressure leaching residue, which contains 41.75% iron, 2.11% chromium, 6.10% silicon, 3.94% aluminum, 0.70% magnesium, and 3.57% sulfur. The iron is mainly produced in the form of hematite (limonite), with a distribution rate of 98.63%. The method specifically comprises the following steps:

[0051] (1) mixing the laterite nickel ore leaching residue and the leaching agent to obtain a slurry. The solid-liquid ratio of the laterite nickel ore leaching residue to the leaching agent is 1:12 g / mL, the concentration of sulfuric acid in the leaching agent is 3.30 mol / L, and the mass ratio of the laterite nickel ore leaching residue to the potassium oxalate in the leaching agent is 1:6.10.

[0052] (2) The slurry was subjected to microwave heating and leaching at 85°C for 20 min, with a microwave power of 550 W. The leaching was carried out under stirring at a stirring speed of 300 r / min. After the leaching was completed, potassium oxalate was used to adjust the pH to 2.8, and the first filtrate 2 and the first filter residue 2 were obtained by filtration. The first filter residue 2 can be used as a raw material for building materials later.

[0053] (3) Mix the first filtrate 2, sulfuric acid, and water-soluble polymer polyvinyl pyrrolidone K30 so that the concentration of sulfuric acid in the whole system is 1.79 mol / L, and the amount of water-soluble polymer polyvinyl pyrrolidone K30 is 3.20% of the mass of the first filtrate 2; put it into a reactor and carry out hydrothermal reaction for 25 minutes under stirring, the reaction temperature is 115°C, the pressure is 0.7Mpa, and the stirring rate is 480r / min. After the reaction is completed, filter to obtain the second filtrate 2 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding sulfuric acid and potassium oxalate to the second filtrate 2, return to the step (2) as a leaching agent to participate in the leaching step.

[0054] Example 3

[0055] The present embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using directly purchased laterite nickel ore high-pressure leaching residue, which contains 51.38% iron, 2.86% chromium, 3.72% silicon, 2.26% aluminum, 0.34% magnesium, and 2.01% sulfur. The iron is mainly produced in the form of hematite (limonite), with a distribution rate of 91.22%. The method specifically comprises the following steps:

[0056] (1) mixing the laterite nickel ore leaching residue and the leaching agent to obtain a slurry. The solid-liquid ratio of the laterite nickel ore leaching residue to the leaching agent is 1:8 g / mL, the concentration of hydrochloric acid in the leaching agent is 8.44 mol / L, and the mass ratio of the laterite nickel ore leaching residue to the sodium oxalate in the leaching agent is 1:5.65.

[0057] (2) The slurry was subjected to microwave heating leaching at 85°C for 35 minutes with a microwave power of 400 W. The leaching was carried out under stirring at a stirring speed of 200 r / min. After the leaching was completed, the pH value was adjusted to 3.2 using sodium oxalate. The first filtrate 3 and the first filter residue 3 were obtained by filtration. The first filter residue 3 can be used as a raw material for building materials later.

[0058] (3) Mix the first filtrate 3, hydrochloric acid, and water-soluble high molecular weight polyvinyl alcohol 1788, so that the concentration of hydrochloric acid in the whole system is 4.77 mol / L, and the amount of water-soluble high molecular weight polyvinyl alcohol 1788 is 1.50% of the mass of the first filtrate 3; put it into a reactor and carry out hydrothermal reaction for 35 minutes under stirring, the reaction temperature is 95°C, the pressure is 0.5Mpa, and the stirring rate is 350r / min. After the reaction is completed, filter to obtain the second filtrate 3 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding hydrochloric acid and sodium oxalate to the second filtrate 3, return to the step (2) as a leaching agent to participate in the leaching step.

[0059] Example 4

[0060] The present embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using directly purchased laterite nickel ore high-pressure leaching residue, which contains 41.75% iron, 2.11% chromium, 6.10% silicon, 3.94% aluminum, 0.70% magnesium, and 3.57% sulfur. The iron is mainly produced in the form of hematite (limonite), with a distribution rate of 98.63%. The method specifically comprises the following steps:

[0061] (1) mixing the laterite nickel ore leaching residue and the leaching agent to obtain a slurry. The solid-liquid ratio of the laterite nickel ore leaching residue to the leaching agent is 1:8 g / mL, the concentration of hydrochloric acid in the leaching agent is 6.4 mol / L, and the mass ratio of the laterite nickel ore leaching residue to the sodium oxalate in the leaching agent is 1:4.3.

[0062] (2) The slurry was subjected to microwave heating and leaching at 80°C for 40 minutes with a microwave power of 300 W. The leaching was carried out under stirring at a stirring speed of 150 r / min. After the leaching was completed, the pH value was adjusted to 3.5 using sodium oxalate. The first filtrate 4 and the first filter residue 4 were obtained by filtration. The first filter residue 4 can be used as a raw material for building materials later.

[0063] (3) Mix the first filtrate 4, hydrochloric acid, and water-soluble high molecular weight polyvinyl alcohol 1788, so that the concentration of hydrochloric acid in the whole system is 3.4 mol / L, and the amount of water-soluble high molecular weight polyvinyl alcohol 1788 is 0.05% of the mass of the first filtrate 4; put it into a reactor and carry out hydrothermal reaction for 45 minutes under stirring, the reaction temperature is 90°C, the pressure is 0.2Mpa, and the stirring rate is 300r / min. After the reaction is completed, filter to obtain the second filtrate 4 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding hydrochloric acid and sodium oxalate to the second filtrate 4, return to the step (2) as a leaching agent to participate in the leaching step.

[0064] Example 5

[0065] The present embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using directly purchased laterite nickel ore high-pressure leaching residue, which contains 41.75% iron, 2.11% chromium, 6.10% silicon, 3.94% aluminum, 0.70% magnesium, and 3.57% sulfur. The iron is mainly produced in the form of hematite (limonite), with a distribution rate of 98.63%. The method specifically comprises the following steps:

[0066] (1) mixing the laterite nickel ore leaching residue and the leaching agent to obtain a slurry. The solid-liquid ratio of the laterite nickel ore leaching residue to the leaching agent is 1:12 g / mL, the concentration of sulfuric acid in the leaching agent is 5.0 mol / L, and the mass ratio of the laterite nickel ore leaching residue to the potassium oxalate in the leaching agent is 1:9.2.

[0067] (2) The slurry was subjected to microwave heating and leaching at 95° C. for 15 min, with a microwave power of 800 W. The leaching was carried out under stirring at a stirring speed of 300 r / min. After the leaching was completed, potassium oxalate was used to adjust the pH to 2.5, and the first filtrate 5 and the first filter residue 5 were obtained by filtration. The first filter residue 5 can be used as a raw material for building materials later.

[0068] (3) Mix the first filtrate 5, sulfuric acid, and water-soluble high molecular weight polyvinyl alcohol 1788, so that the concentration of sulfuric acid in the whole system is 2.9 mol / L, and the amount of water-soluble high molecular weight polyvinyl alcohol 1788 is 4% of the mass of the first filtrate 5; put it into a reactor and carry out hydrothermal reaction for 20 minutes under stirring, the reaction temperature is 125°C, the pressure is 1.6Mpa, and the stirring rate is 500r / min. After the reaction is completed, filter to obtain the second filtrate 5 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding sulfuric acid and potassium oxalate to the second filtrate 5, return to the step (2) as a leaching agent to participate in the leaching step.

[0069] Example 6

[0070] This embodiment provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, using sulfuric acid slag, which contains 67.30% Fe2O3, 13.50% SiO2, 5.04% SO3, 2.38% CaO, 2.35% Al2O3, and 0.64% MgO, and specifically includes the following steps:

[0071] (1) The sulfuric acid slag and the leaching agent are mixed to obtain a slurry. The solid-liquid ratio of the sulfuric acid slag to the leaching agent is 1:9 g / mL, the concentration of hydrochloric acid in the leaching agent is 7.30 mol / L, and the mass ratio of the sulfuric acid slag to potassium oxalate in the leaching agent is 1:6.7.

[0072] (2) The slurry was subjected to microwave heating leaching at 90°C for 30 min, with a microwave power of 600 W. The leaching was carried out under stirring at a stirring speed of 200 r / min. After the leaching was completed, potassium oxalate was used to adjust the pH to 2.9, and the first filtrate 6 and the first filter residue 6 were obtained by filtration. The first filter residue 6 can be used as a building material raw material later.

[0073] (3) Mix the first filtrate 6, hydrochloric acid, and water-soluble high molecular weight polyethylene glycol 20000, so that the concentration of hydrochloric acid in the whole system is 4.4 mol / L, and the amount of water-soluble high molecular weight polyethylene glycol 20000 is 3.0% of the mass of the first filtrate 6; put it into a reactor and carry out hydrothermal reaction for 40 minutes under stirring, the reaction temperature is 100°C, the pressure is 1.3Mpa, and the stirring rate is 400r / min. After the reaction is completed, filter to obtain the second filtrate 6 and ferrous oxalate. Wash the ferrous oxalate, dry it, and store it. After adding hydrochloric acid and potassium oxalate to the second filtrate 6, return to the step (2) as a leaching agent to participate in the leaching step.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, which is different from Example 1 only in that step (2) is to heat the slurry in a water bath at 90°C for leaching for 25 minutes, and the leaching is carried out under stirring at a speed of 250 r / min. After the leaching is completed, sodium oxalate is used to adjust the pH to 3.1, and the first filtrate 7 and the first filter residue 7 are obtained by filtration. The first filter residue 7 can be used as a building material raw material later.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing ferrous oxalate from iron-containing industrial solid waste, which is different from Example 1 only in that no water-soluble polymer is added in step (3).

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing ferrous oxalate from iron-containing industrial solid waste. Compared with Example 1, the only difference is that in step (1), the leaching agent used does not contain sodium oxalate.

[0080] Test Example 1

[0081] The ferrous oxalate prepared in the embodiment and the comparative example was taken, and the content of each component was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The average particle size of the ferrous oxalate was measured by a Malvern particle size tester. The results are shown in Table 1.

[0082] Table 1

[0083]

[0084] Test Example 2

[0085] The mass of ferrous oxalate finally obtained in the embodiment and the comparative example and the mass of the laterite nickel ore leaching slag used were weighed and recorded, and the iron recovery rate was calculated by the formula: iron recovery rate = [iron content in ferrous oxalate (%) × mass of ferrous oxalate (kg)] / [iron content in laterite nickel ore leaching slag (%) × mass of laterite nickel ore leaching slag (kg)], as shown in Table 2.

[0086] Table 2

[0087] sample Iron recovery rate / % Example 1 98.62 Example 2 98.58 Example 3 98.41 Example 4 98.35 Example 5 98.78 Example 6 98.46 Comparative Example 1 71.74 Comparative Example 2 98.52 Comparative Example 3 26.34

[0088] It can be seen from the data in Table 1 and Table 2 that in the example, the method of the present application is used to prepare ferrous oxalate from iron-containing industrial solid waste, and the obtained ferrous oxalate has high purity, small particle size, and high recovery rate of iron in iron-containing industrial solid waste, thereby making full use of the iron resources in iron-containing industrial solid waste.

[0089] The only difference between Comparative Example 1 and Example 1 is that water bath heating is used for leaching in step (2), and the metal leaching rate of the leached residue within 25 minutes is lower than that of the microwave heating method, which directly leads to a lower iron recovery rate.

[0090] The difference between Comparative Example 2 and Example 1 is that no water-soluble polymer is added in step (3). 3+ , Fe 2+ Forming a complex structure can reduce Fe 3+ In addition, the water-soluble polymer can increase the viscosity of the solution, reduce the migration rate of ions, inhibit the growth and movement of ferrous oxalate particles, and reduce the probability of ferrous oxalate colliding and aggregating to form large particles. Since there is no water-soluble polymer in the system of Comparative Example 2, the particle size of ferrous oxalate obtained is relatively large.

[0091] Comparative Example 3 is different from Example 1 only in that, in step (1), the leaching agent used does not contain sodium oxalate. Due to the low activity of hematite in the laterite nickel ore leaching residue, when the leaching agent lacks oxalate, the valuable metals in the laterite nickel ore leaching residue cannot be efficiently leached under the action of acid alone, and the impurity ions cannot be removed by oxalate ions, so the purity of ferrous oxalate is poor and the iron recovery rate is extremely low.

[0092] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A method for preparing ferrous oxalate from iron-containing industrial solid waste, characterized in that: The steps include: S1: mixing iron-containing industrial solid waste and a leaching agent to obtain a slurry; Wherein, the leaching agent includes a first acid solution and an oxalate solution; S2: leaching the slurry under microwave heating, adjusting the pH after leaching, and performing solid-liquid separation to obtain a first filtrate and a first filter residue; S3: mixing the first filtrate, the second acid solution and the water-soluble polymer, performing a hydrothermal reaction and performing solid-liquid separation to obtain the second filtrate and ferrous oxalate.

2. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to claim 1, wherein in step S2, the power of microwave heating is 300-800 W, the heating temperature is 80-95° C., and the leaching time is 15-40 min.

3. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to claim 1 or 2, characterized in that: In the step S3, the mass of the water-soluble polymer is 0.05% to 4.00% of the mass of the first filtrate.

4. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 3, characterized in that: In the step S1, the solid-liquid ratio of the iron-containing industrial solid waste to the leaching agent is 1:8-12 g / mL; And / or, in the step S1, the concentration of the first acid solution in the leaching agent is 3.9 to 10.0 mol / L in terms of monoacid; Optionally, in the step S1, the concentration of the first acid solution in the leaching agent is 6.4 to 10.0 mol / L in terms of monoacid; And / or, in step S1, the mass ratio of iron-containing industrial solid waste to oxalate in the leaching agent is 1:2.6-9.2; optionally, in step S1, the mass ratio of iron-containing industrial solid waste to oxalate in the leaching agent is 1:4.3-9.

2.

5. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 4, characterized in that: In step S2, after the leaching is completed, the pH is adjusted to 2.5-3.5; And / or, in step S2, the reagent used to adjust the pH includes oxalate; preferably, the reagent used to adjust the pH includes at least one of sodium oxalate and potassium oxalate; And / or, in step S2, leaching is performed under stirring; optionally, the stirring speed is 150 to 300 r / min.

6. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 5, characterized in that: In the step S3, the second acid solution is added so that the acid concentration in the system is 1.8 to 5.8 mol / L in terms of monoacid; optionally, in the step S3, the second acid solution is added so that the acid concentration in the system is 3.4 to 5.8 mol / L in terms of monoacid; And / or, in step S3, the temperature of the hydrothermal reaction is 90-125° C., the pressure is 0.2-1.6 MPa, and the reaction time is 20-45 min; And / or, in step S3, the hydrothermal reaction is carried out under stirring; optionally, the stirring speed is 300-500 r / min.

7. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 6, characterized in that: The water-soluble polymer includes at least one of polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2488, polyvinyl pyrrolidone K30, polyethylene glycol 10000, and polyethylene glycol 20000; And / or, the first acid solution includes at least one of sulfuric acid and hydrochloric acid; And / or, the second acid solution includes at least one of sulfuric acid and hydrochloric acid; And / or, in step S1, the oxalate solution includes at least one of a sodium oxalate solution and a potassium oxalate solution.

8. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 7, characterized in that: More than 30% of the iron in the iron-containing industrial solid waste is in the form of Fe2O3 on a molar basis, and the iron content in the iron-containing industrial solid waste is ≥20% on a mass percentage basis; optionally, more than 50% of the iron in the iron-containing industrial solid waste is in the form of Fe2O3 on a molar basis, and the iron content in the iron-containing industrial solid waste is ≥40% on a mass percentage basis; optionally, the iron-containing industrial solid waste includes at least one of laterite nickel ore leaching residue, roasting cyanide tailings, high-phosphorus oolitic hematite, sulfuric acid slag, and Bayer process red mud; further optionally, the iron-containing industrial solid waste is laterite nickel ore leaching residue.

9. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 8, characterized in that: After step S3, the method further includes washing and drying the ferrous oxalate; And / or, the particle size D50 of the ferrous oxalate is less than 5.0 μm; And / or, it also includes the step of adding the first acid solution and oxalate to the second filtrate, and returning the second filtrate as a leaching agent to the step S2 to participate in leaching.

10. The method for preparing ferrous oxalate from iron-containing industrial solid waste according to any one of claims 1 to 9, characterized in that: The use of the ferrous oxalate includes being used as a raw material for preparing a positive electrode material for a lithium-ion battery; optionally, the positive electrode material for a lithium-ion battery includes a lithium iron phosphate positive electrode material; And / or, the use of the first filter residue includes being used as a raw material for building materials.

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