Method for producing polyferric sulfate by using mine waste liquid

Abstract

The invention relates to a method for producing polyferric sulfate by using mine waste liquid, which comprises the following steps: S1, adding a certain amount of iron powder into mine leaching waste liquid, adjusting the pH value to 1-2, and filtering to obtain a stock solution; s2, adding the filtered stock solution into a reaction kettle, starting stirring, raising the temperature to 70-80 DEG C, and performing negative pressure evaporation for volume concentration; s3, stopping concentration when the concentration density of the feed liquid reaches 1.45 g / cm < 3 >, closing the negative pressure vacuum device, and adding a certain amount of catalyst; s4, continuously stirring, introducing air as an oxidizing agent, converting into positive pressure operation, controlling the temperature within the range of 40-60 DEG C, and oxidizing the feed liquid; s5, after the oxidation reaches the end point, continuously stirring, maintaining the positive pressure operation, introducing air, raising the temperature to 80-100 DEG C, and polymerizing for a certain time to obtain liquid polymeric ferric sulfate; and S6, carrying out spray drying on the polymerized feed liquid to obtain a solid polymeric ferric sulfate product. According to the invention, the production efficiency is improved, the cost is reduced, the generation of pollutants is reduced, and the cooled and recycled sulfuric acid can be reused in a wet copper smelting system.

Description

Technical Field

[0001] This invention relates to a method for producing polyferric sulfate using mine wastewater, belonging to the fields of flocculant manufacturing technology and hydrometallurgical technology. Background Technology

[0002] Polyferric sulfate (PFLS) is an excellent flocculant and water purifier, widely used in the treatment of source water, drinking water, natural water, industrial water, industrial wastewater, and municipal sewage. Its water purification effect is significantly better than traditional inorganic water purifiers such as aluminum sulfate and polyaluminum sulfate, with the effect being more pronounced the higher the water turbidity. PFLS products are available in liquid and solid forms. Liquid PFLS is reddish-brown and has a certain viscosity, while solid PFLS is a light yellow powder, which is easier to store and transport. Common preparation methods for PFLS include direct oxidation, catalytic oxidation, biological oxidation, and electrochemical methods.

[0003] Direct oxidation involves using a strong oxidizing agent in an acidic solution to oxidize Fe. 2+ Oxidized to Fe 3+ This method involves directly oxidizing the material to prepare polyferric sulfate. This process does not require the introduction of additional oxygen or air into the reaction system. Commonly used oxidants in direct oxidation methods include H₂O₂, KClO₃, NaClO₃, NaClO, and HNO₃. This method has a simple process route, can be carried out at room temperature and pressure, and has a fast reaction rate, but it suffers from the problems of large oxidant consumption and high cost.

[0004] Catalytic oxidation is a process in which Fe is oxidized using air or oxygen as an oxidant in the presence of a catalyst. 2+ Oxidized to Fe 3+ The method involves hydrolysis and polymerization to obtain polyferric sulfate. Commonly used catalysts include KNO2, NaNO2, and HNO3. Among them, NaNO2 has a relatively low cost and is widely used in actual production, but the reaction needs to be carried out under high temperature and pressure conditions, and the reaction takes a long time.

[0005] The process of preparing polyferric sulfate by bio-oxidation is as follows: FeSO4 is used as raw material, the pH is adjusted with H2SO4, air is introduced at room temperature as an oxidant, suitable nutrients are added, and a bacterial strain (usually acidophilic and aerobic ferrooxidizing ammoniac) is introduced as a biocatalyst. Under the action of microorganisms, FeSO4 undergoes a series of oxidation, hydrolysis, and polymerization reactions, and finally the finished product, bio-polyferric sulfate, is obtained. The bio-oxidation method is still in the early stage of research and has not been put into large-scale production application.

[0006] The electrochemical method utilizes bipolar membrane electroosmosis to drive the membrane separation process. Its core component, the bipolar membrane, can dissociate water molecules into OH groups under the action of a DC electric field. - and H +Under the influence of an electric field, the bipolar film continuously generates OH-. - It participates in the preparation process of polyferric sulfate. Compared with traditional preparation methods, this method has the advantages of high product basicity, continuous operation, simple operation, high efficiency, and environmental friendliness. However, the cost of the electrochemical method is often slightly higher than other preparation methods.

[0007] Hydrometallurgical copper smelting is a metallurgical process commonly used to process oxide copper ores, lean ores, and low-grade ores. It mainly includes three key steps: leaching, extraction, and electrowinning, and is an important method for modern environmentally friendly copper smelting. This process has advantages such as low investment, low pollution, and simple operation, and is widely used in the field of comprehensive resource utilization. Leaching is the first step in hydrometallurgical copper smelting. Through a chemical reaction, under the action of acid, copper in the ore is converted into soluble copper sulfate, which then enters the solution. Methods such as heap leaching, stirred leaching, or microbial leaching can be selected. Extraction utilizes organic extractants to selectively extract copper ions from the aqueous phase, forming a copper-containing organic phase. Then, through back-extraction, the copper is transferred back to the acidic aqueous phase, yielding a high-concentration electrowinning solution. Electrowinning occurs in an electrolytic cell where an external current is applied, causing copper ions to be deposited as pure copper metal at the cathode. The anode is usually an insoluble material. The copper produced by electrowinning has high purity, reaching over 99.99%.

[0008] Cathode copper is produced using a bioleaching-solvent extraction-electrowinning process. The copper-bearing mineral is mainly low-grade chalcocite, and the iron-bearing mineral is mainly pyrite. Due to the action of bacteria and microorganisms, iron is continuously leached from the iron-bearing minerals and oxidized to a higher valence state. As copper ore production continues, the heap leaching solution circulates in a closed loop within the system, leading to a continuous increase in the concentration of iron ions. This high concentration of iron ions affects the production efficiency of the solvent extraction process. How to remove iron ions from the leaching solution or to utilize the impurity iron elements has become a challenging problem for hydrometallurgical copper smelting mines using bioleaching. The main components of the heap leaching raffinate are Fe2(SO4)3, FeSO4, and H2SO4, with small amounts of other metal salt ions. The main components of the heap leaching waste liquor (raffinate) are shown in Table 1 below.

[0009]

[0010] The direct production of solid polyferric sulfate from mine wastewater fully utilizes the iron and acid in the wastewater, saving raw material costs. The bioleaching process of Acidobacterium ferrosulfonum converts most of the iron into a high valence state, shortening production time, reducing oxidation time and oxidant usage, improving production efficiency, reducing costs, and minimizing pollutant generation. The use of negative pressure evaporation and concentration shortens the concentration time, and the cooled and recovered sulfuric acid can be reused in the hydrometallurgical copper smelting system. Summary of the Invention

[0011] The purpose of this invention is to provide a production process for solid polyferric sulfate, utilizing mine leaching wastewater as raw material, thus solving the problem of most iron and acid sources, achieving waste utilization, and significantly reducing production costs. Due to the bioleaching process of *Thiobacillus ferrooxidans*, most of the iron is converted to a higher valence state, shortening the production time of polyferric sulfate, reducing the amount of catalyst and oxidant used, and minimizing pollutant generation. Employing negative pressure evaporation concentration and positive pressure oxidative polymerization methods, the cooled and recovered sulfuric acid can be reused in the hydrometallurgical copper smelting system. Positive pressure oxidative polymerization improves oxidation and polymerization efficiency, enhancing product performance.

[0012] This invention is achieved using the following technical solution:

[0013] A method for producing polyferric sulfate from mine wastewater includes the following steps:

[0014] S1 adds a certain amount of iron powder to the leaching waste liquid from the mine, adjusts the pH value to 1-2, and obtains the original solution after filtration;

[0015] S2 adds the filtered stock solution to the reaction vessel, starts stirring, raises the temperature to 70-80℃, and concentrates the volume by evaporation under negative pressure.

[0016] The concentration of the S3 feed solution reached 1.45 g / cm³. 3 Stop the concentration, turn off the negative pressure vacuum device, and add a certain amount of catalyst;

[0017] S4 continues to run and stir, introduces air as an oxidant, switches to positive pressure operation, and controls the temperature in the range of 40-60℃ to oxidize the liquid.

[0018] After the S5 oxidation reaches its endpoint, continue stirring, maintain positive pressure, introduce air, raise the temperature to 80-100°C, and polymerize for a certain time to obtain liquid polyferric sulfate.

[0019] S6 spray-dries the polymerized liquid to obtain solid polyferric sulfate product.

[0020] Furthermore, iron powder with a particle size of 100–500 μm is added to S1.

[0021] Furthermore, the reactor described in S2 has a jacketed structure, with steam or water allowed to be introduced into the outer layer to regulate the temperature. The reactor is equipped with a stirrer and a gas pipeline, with the gas pipeline leading to the bottom of the reactor.

[0022] Furthermore, the reactor is connected to a water jet vacuum pump to provide a negative pressure environment.

[0023] Furthermore, during the negative pressure evaporation process, when the acidity of the circulating liquid in the water jet vacuum pump reaches 18-20 g / L, fresh water is replaced, and the acid is recovered for use in the copper smelting system.

[0024] Furthermore, the negative pressure control range in S2 is -50 to -100 kPa, and the stirring speed is 50-100 rpm.

[0025] Furthermore, the amount of catalyst used in S3 is 1% of the mass of the feed liquid, and the catalyst is prepared as a 50% aqueous solution and added.

[0026] Furthermore, the catalyst described in S3 is one of KNO2, NaNO2, or HNO3.

[0027] Furthermore, in S4, the stirring speed is 100–200 rpm and the air flow rate is 1–3 m³ / min. 3 / S, pressure control range 100~150kPa, oxidation time greater than 4h.

[0028] Furthermore, the oxidation endpoint condition in S5 is: Fe in the feed solution 2+ If the mass concentration is less than 1%, extend the oxidation time.

[0029] Furthermore, in S5, the stirring speed is 150–300 rpm, and the air flow rate is 1–3 m³ / min. 3 / S, pressure control range 100~150kPa, polymerization time 4h.

[0030] Compared with the prior art, the present invention has the following advantages or beneficial effects:

[0031] 1. The production of polyferric sulfate using mine leaching solution realizes the resource utilization of waste, and the production cost of polyferric sulfate is low and the pollution is minimal;

[0032] 2. The negative pressure evaporation and concentration method was used to increase the iron concentration of the feed liquid and recover a portion of the acid for reuse in the hydrometallurgical copper smelting system;

[0033] 3. The positive pressure oxidation polymerization method improves oxidation and polymerization efficiency, shortens production time, and improves product performance;

[0034] 4. The solid polyferric sulfate prepared by the method of the present invention has the characteristics of high performance, good stability, and convenient storage and transportation. Detailed Implementation

[0035] This invention discloses a method for producing polyferric sulfate from mine wastewater, comprising the following steps:

[0036] S1 adds a certain amount of iron powder to the leaching waste liquid from the mine, adjusts it to a certain pH value, and then filters it to obtain the original solution;

[0037] S2 adds the filtered stock solution to the reaction vessel, starts stirring, raises the temperature to a certain level, and uses negative pressure evaporation to concentrate the volume.

[0038] S3 Once the specific gravity of the feed liquid has been concentrated to a certain value, stop the concentration, turn off the negative pressure vacuum device, and add a certain amount of catalyst.

[0039] S4 continues to run and stir, introduces air as an oxidant, switches to positive pressure operation, controls the temperature within a certain range, and oxidizes the liquid.

[0040] After the S5 oxidation reaches its endpoint, continue stirring, maintain positive pressure, introduce air, raise the temperature, and polymerize for a certain period of time to obtain liquid polyferric sulfate.

[0041] S6 spray-dries the polymerized liquid to obtain solid polyferric sulfate product.

[0042] Specifically:

[0043] In S1, iron powder with a particle size of 100-500 μm is added, and the pH value is adjusted to 1-2.

[0044] In S2, the reactor has a jacketed structure, with steam or water allowed to be introduced into the outer layer to regulate the temperature. The reactor is equipped with a stirrer and gas pipelines, with the gas pipelines leading to the bottom of the reactor. The reactor is connected to a water jet vacuum pump to provide a negative pressure environment. The negative pressure evaporation temperature control range is 70–80℃, the negative pressure control range is -50–-100 kPa, and the stirring speed is 50–100 rpm.

[0045] In step S3, the catalyst is one of KNO2, NaNO2, or HNO3. The catalyst dosage is 1% of the feed solution mass, and the catalyst is prepared as a 50% aqueous solution before addition. The concentrated feed solution density reaches 1.45 g / cm³. 3 This means that the concentration has reached its endpoint.

[0046] The operating conditions for S4 are: temperature control range of 40–60℃, stirring speed of 100–200 rpm, and air flow rate of 1–3 m³ / min. 3 / S, pressure control range 100~150kPa, oxidation time greater than 4h.

[0047] In S5, the oxidation endpoint condition is: Fe in the feed solution 2+ If the mass concentration is less than 1%, extend the oxidation time. S5 operating conditions are: temperature control range 80–100℃, stirring speed 150–300 rpm, air flow rate 1–3 m³ / min. 3 / S, pressure control range 100~150kPa, polymerization time 4h.

[0048] During the negative pressure evaporation process, when the acidity of the circulating liquid in the water jet vacuum pump reaches 18-20 g / L, fresh water is replaced, and the acid is recovered for use in the copper smelting system.

[0049] The polymerized liquid is immediately spray-dried to obtain solid polyferric sulfate, which is then ground and sieved to produce a finished product of a certain particle size.

[0050] The present invention provides a method for producing polyferric sulfate using leaching wastewater from hydrometallurgical copper mines. This wastewater contains a certain amount of iron and sulfuric acid. By supplementing the iron source and adjusting the acidity, followed by evaporation and concentration, the iron content of the leaching solution meets the requirements for producing polyferric sulfate. During the bioleaching process, *Thiobacillus ferrooxidans* converts most of the iron to a higher valence state, significantly reducing the amount of oxidant and catalyst used in the production process. High pressure, high temperature, enhanced stirring, and continuous aeration are beneficial for the oxidation and polymerization reactions. The leaching wastewater contains small amounts of Ca, Mg, Al, and Si salts, which not only do not affect product quality but also modify the product, resulting in superior performance compared to ordinary polyferric sulfate. The liquid polyferric sulfate is then spray-dried to directly produce a high-performance solid product, improving stability, extending shelf life, and facilitating storage and transportation.

[0051] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0052] Example 1:

[0053] This embodiment provides a high-efficiency, high-concentration polyferric sulfate production process, which includes the following steps:

[0054] S1 Take 1L of mine leaching waste liquid, slowly add 500μm iron powder while stirring, and measure the pH value change. When the pH value reaches 1.5, stop adding iron powder and filter the solution.

[0055] S2 adds the filtered solution to the reactor, starts stirring at 50 rpm, heats the reactor to 70-80°C, and controls the negative pressure to -50--100 kPa to evaporate and concentrate the liquid.

[0056] During the S3 evaporation and concentration process, the density of the liquid was continuously measured until it reached 1.45 g / cm³. 3 Turn off the negative pressure vacuum device and add 1% by weight of the liquid material of a 50% NaNO2 solution;

[0057] S4 switches to positive pressure operation, continues stirring, introduces air as an oxidant, switches to positive pressure operation, controls the temperature within a certain range, and oxidizes the liquid.

[0058] S5 measures Fe every hour. 2+ Content, when Fe 2+ When the content is less than 0.1%, the temperature is increased, stirring is continued, positive pressure is maintained, and air is introduced. After polymerization for 4 hours, liquid polyferric sulfate is obtained.

[0059] The main chemical reactions involved are as follows:

[0060] pH adjustment reaction:

[0061] Fe + H₂SO₄ → FeSO₄ + H₂

[0062] Catalytic oxidation reaction:

[0063] 2FeSO4+H2SO4+2NaNO2→Fe2(SO4)3+Na2SO4+2NO+H2O

[0064] 2NO + O2 → 2NO2

[0065] 2FeSO4+H2SO4+NO2→Fe2(SO4)3+NO+H2O

[0066] 2FeSO4+(1 / 2)O2+H2SO4→Fe2(SO4)3+H2O

[0067] Hydrolysis reaction: Fe2(SO4)3 + nH2O → mFe2(OH) n (SO4) 3-n / 2 +nH2SO4

[0068] Polymerization reaction: mFe2(OH) n (SO4) 3-n / 2 →[Fe2(OH) n (SO4) 3-n / 2 ] m

[0069] Example 2:

[0070] This embodiment follows the same steps as Example 1. Based on the completion of Example 1, in S6 the polymerized liquid is spray-dried to obtain solid polyferric sulfate product.

[0071] Comparative Example 1:

[0072] Dissolve 30g of FeSO4·7H2O in 20mL of distilled water. In a 40℃ constant temperature water bath, add 98% concentrated sulfuric acid at a ratio of n(Fe):n(H2SO4) = 1:0.4 while stirring continuously until the solid is fully dissolved. Turn on the magnetic stirrer and slowly add 50% H2O2 at a ratio of n(Fe):n(H2O2) = 1:0.8, completing the addition within 30 minutes. Then raise the temperature to 60℃ and add NaHCO3 to maintain the pH of the solution at 1.5-2.5. Stir and polymerize for 2 hours. After cooling, filter to obtain liquid polyferric sulfate product.

[0073] According to GB / T 14591—2016 standard, the liquid polyferric sulfate product obtained in Example 1, the solid polyferric sulfate product obtained in Example 2, and the solid polyferric sulfate product prepared by ferrous sulfate heptahydrate in Comparative Example 1 were analyzed for key indicators such as basicity, total iron content, Fe2+ content, pH value, and density. The analysis results are shown in the table below:

[0074] Table 2. Sampling analysis results of the examples and comparative examples

[0075]

[0076] Table 2 shows the basicity, total iron content, and Fe content of the liquid and solid polyferric sulfate produced in Examples 1 and 2. 2+ The main indicators such as content, pH value, and density all meet the first-grade standard of GB / T 14591—2016. Liquid polyferric sulfate prepared using FeSO4·7H2O, when combined with excess oxidant H2O2, exhibits Fe... 2+ The content still exceeds the standard, indicating insufficient utilization of the oxidant. Compared to using FeSO4·7H2O as a raw material to prepare polyferric sulfate, this embodiment utilizes mine leaching wastewater, saving a significant amount of raw materials iron and sulfuric acid. The use of high pressure, high temperature, enhanced stirring, and continuous aeration facilitates the oxidation and polymerization reactions, resulting in complete oxidation, a high degree of polymerization, a short and efficient production process, and a compact workflow. This directly produces a high-performance solid product, improving stability, extending shelf life, and facilitating storage and transportation.

[0077] This invention utilizes mine wastewater to directly produce solid polyferric sulfate, making full use of the iron and acid in the wastewater and saving raw material costs. The *Thiobacillus ferrosulfonii* bioleaching process converts most of the iron into a higher valence state, shortening production time, reducing oxidation time and oxidant usage, improving production efficiency, lowering costs, and reducing pollutant generation. The use of negative pressure evaporation concentration, along with high pressure, high temperature, enhanced stirring, and continuous aeration, facilitates the oxidation and polymerization reactions. The liquid polyferric sulfate is then spray-dried directly to produce a high-performance solid product, improving stability, extending shelf life, and facilitating storage and transportation.

[0078] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for producing polyferric sulfate using mine wastewater, characterized in that: Includes the following steps: S1 adds a certain amount of iron powder to the leaching waste liquid from the mine, adjusts the pH value to 1-2, and obtains the original solution after filtration; S2 adds the filtered stock solution to the reaction vessel, starts stirring, raises the temperature to 70-80℃, and concentrates the volume by evaporation under negative pressure. The concentration of the S3 feed solution reached 1.45 g / cm³. 3 Stop the concentration, turn off the negative pressure vacuum device, and add a certain amount of catalyst; S4 continues to run and stir, introduces air as an oxidant, switches to positive pressure operation, and controls the temperature in the range of 40-60℃ to oxidize the liquid. After the S5 oxidation reaches its endpoint, continue stirring, maintain positive pressure, introduce air, raise the temperature to 80-100°C, and polymerize for a certain time to obtain liquid polyferric sulfate. S6 spray-dries the polymerized liquid to obtain solid polyferric sulfate product.

2. The method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: S2 The reactor described herein has a jacketed structure, with steam or water allowed to be introduced into the outer layer to regulate the temperature. The reactor is equipped with a stirrer and a gas pipeline, with the gas pipeline leading to the bottom of the reactor.

3. The method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: The reactor is connected to a water jet vacuum pump to provide a negative pressure environment.

4. A method for producing polyferric sulfate from mine wastewater according to any one of claims 1-3, characterized in that: During the negative pressure evaporation process, when the acidity of the circulating liquid in the water jet vacuum pump reaches 18-20 g / L, fresh water is replaced, and the acid is recovered for use in the copper smelting system.

5. The method for producing polyferric sulfate from mine waste liquid according to claim 1, characterized in that: the negative pressure control range in S2 is -50 to -100 kPa, and the stirring speed is 50-100 rpm.

6. The method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: In S3, the amount of catalyst used is 1% of the mass of the feed liquid, and the catalyst is prepared as a 50% aqueous solution and added.

7. A method for producing polyferric sulfate from mine wastewater according to claim 1 or 6, characterized in that: S3 The catalyst described herein is one of KNO2, NaNO2, or HNO3.

8. The method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: in step S4, the stirring speed is 100-200 rpm and the air flow rate is 1-3 m³ / s. 3 / S, pressure control range 100~150kPa, oxidation time greater than 4h.

9. A method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: S5 The oxidation endpoint condition is: Fe in the feed solution 2+ If the mass concentration is less than 1%, extend the oxidation time.

10. A method for producing polyferric sulfate from mine wastewater according to claim 1, characterized in that: S5 In the middle stage, the stirring speed is 150-300 rpm, and the air flow rate is 1-3 m³ / h. 3 / S, pressure control range 100~150kPa, polymerization time 4h.

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