A method for removing iron and manganese by stepwise control of pH and Eh

Abstract

The application provides a method for removing iron and manganese in a step control system pH and Eh, and relates to the field of hydrometallurgy. The method comprises the following steps: adding a neutralizing agent to a solution containing Fe 2+ and Mn 2+ to maintain the pH value at 1.5-3.0, and simultaneously, oxygen-containing gas and an additive are added to perform a synergistic catalytic oxidation reaction of Fe 2+ and Mn 2+ and maintain for 0.5-5 hours; then, the pH value of the system is adjusted to 3.0-5.0, and the oxidation-reduction potential (Eh) of the system is controlled to be maintained at more than 700 mv for 0.5-5 hours to perform a multi-ion neutralization co-precipitation reaction. In the process, SO2-containing reaction waste gas in the synergistic catalytic oxidation section and the neutralization co-precipitation section is respectively blown into a neutralizing agent slurry tank to perform SO2 absorption and recycling. The method provided by the application has the characteristics of controllable and adjustable system pH and Eh, high iron and manganese removal rate, small residual amount of iron and manganese in the solution and low loss rate of valuable metals.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgy, and more particularly to a method for removing iron and manganese by stepwise control of pH and Eh in a system. Background Technology

[0002] In the hydrometallurgical process of non-ferrous metals, acidic solutions are generally used to dissolve valuable metals from the ore. However, some iron and manganese impurities in the ore are also released along with the metals. These impurities directly affect the stability of downstream processes and product quality, and the solution generally needs to be purified to remove these impurity ions. In the hydrometallurgical process of various heavy non-ferrous metals such as copper, cobalt, zinc, and nickel, precipitation or extraction methods are mostly used to remove impurities.

[0003] Domestic and international scholars have conducted extensive research on the removal of iron and manganese ions. The main methods for iron ion removal include SO2 / O2 catalytic oxidation, jaundice alum method, goethite method, and neutralization-hydrolysis precipitation method. While these methods can effectively remove iron from the leachate, they suffer from problems such as large slag volume and generally only remove iron, not manganese. For manganese ion removal, strong oxidants (chlorine, ozone, chlorine dioxide, potassium permanganate) are mainly used to oxidize divalent manganese ions into manganese dioxide precipitate. However, the characteristics of various oxidants differ, their applicable process conditions vary significantly, and their effectiveness is not ideal, resulting in high processing costs and difficulties in industrial application.

[0004] Chinese patent CN 114317963 A discloses a process for efficient iron removal by segmented catalytic oxidation, which mainly uses segmented catalytic oxidation to remove iron ions from the solution, but does not remove manganese ions.

[0005] There are many methods for removing iron or manganese separately, but there are not many techniques for removing both iron and manganese simultaneously. The main ones are as follows:

[0006] Chinese patent CN 112978897 A discloses a method for removing iron and manganese from solutions used in zinc smelting, which removes iron and manganese ions from the zinc solution through a catalytic oxidation reaction. Although this patent describes a method for simultaneous iron and manganese removal, it is limited to removing Fe ions during the zinc smelting process. 2+ Content is 1-8 g / L, Mn 2+ Solutions with a concentration of 5–30 g / L did not achieve ideal results in removing iron and manganese; residual Mn remained in the solution after manganese removal. 2+The concentration can still reach ~1g / L, indicating insufficient removal depth. Furthermore, the patent only mentions catalytic oxidation by controlling the redox potential, without specifying the exact methods for controlling the system's redox potential and pH, resulting in unclear process control. Additionally, the catalyst dosage is primarily determined based on the total molar number of iron and manganese ions in the solution or the solution weight, without addressing the catalyst-to-oxidant ratio, the catalyst and oxidant addition rate, or the addition method. Moreover, the optimal reaction temperature is 50-90℃, and the pressure is 0.8-1.2MPa, requiring heating and a sealed container, making the reaction conditions insufficiently mild and the reaction equipment not simple enough. In conclusion, while this patented technology can remove manganese ions from the solution to a certain extent, it suffers from high residual iron and manganese ion concentrations, unclear process control, and insufficiently mild process conditions.

[0007] Chinese patent CN 113862491 A discloses a method for simultaneously removing iron, manganese, aluminum, and silicon from a high-silicon cobalt salt leaching slurry. This method involves directly adding an oxidant to the high-silicon cobalt salt leaching slurry to oxidize all the iron in the slurry to Fe. 3+ Mn 2+ The mixture is oxidized to MnO2, and then an alkaline solution is added to gradually adjust the pH of the system to 3.0–3.5 for aging. Finally, solid-liquid separation is performed to obtain a purified high-silicon cobalt salt solution and filter residue. The oxidant added in this technique introduces Na+. + and K + Impurity ions are introduced; maintaining the reaction temperature at 55-70°C will lead to high energy consumption, and there are problems of introducing impurity ions and high processing costs.

[0008] Chinese patent CN 113716759 A discloses a method for efficiently removing fluoride, iron, and manganese from rural groundwater, which involves fluoride removal through adsorption and iron and manganese removal through aeration oxidation. This technology is only suitable for water bodies with low fluoride, iron, and manganese content, limiting its application scope; moreover, its treatment capacity is relatively small, making it suitable for rural areas with limited water supply, but not for large-scale industrial applications.

[0009] In addition, existing technologies do not consider the inherent relationship between iron and manganese ions during oxidation and precipitation, nor do they consider the reuse of gases during the reaction. Summary of the Invention

[0010] The purpose of this application is to provide a method for removing iron and manganese by controlling the pH and Eh of the system in a stepwise manner. Iron and manganese ions are removed by controlling the pH and Eh of the system in two steps of synergistic catalytic oxidation and neutralization co-precipitation. At the same time, the SO2-containing reaction waste gas (where SO2 comes from the additive itself or is generated by the reaction of the additive) is returned to the neutralizing agent slurry tank for self-circulation absorption and reuse. This solves a series of problems in the existing iron and manganese removal process, such as poor removal effect of iron and manganese ions, difficulty in process control, and failure to recover and utilize residual SO2, which causes air pollution.

[0011] To achieve the above objectives, this application adopts the following technical solution:

[0012] A method for stepwise control of pH and Eh in a system for removing iron and manganese includes the following steps:

[0013] Step 1—Co-catalytic oxidation of iron and manganese ions: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 2+ and Mn 2+ A neutralizing agent is added to the solution to be treated to maintain the pH value at 1.5–3.0, while oxygen-containing gas and additives are introduced to begin Fe... 2+ and Mn 2+ The synergistic catalytic oxidation reaction of iron and manganese ions was completed after the redox potential Eh of the system reached 700 mV. The above operation was maintained while ensuring the redox potential Eh was not less than 700 mV. The solution to be treated was Mn produced during the wet copper smelting process. 2+ Concentration less than or equal to 5 g / L, Fe 2+ Acidic copper solutions with a concentration of 15 g / L or less;

[0014] Mn 2+ The redox potential is higher than that of Fe. 2+ The redox potential of Fe 2+ and Mn 2+ In a coexisting system, Fe is generally oxidized first during the oxidation process. 2+ Post-oxidation of Mn 2+ Moreover, Mn 2+ Oxidation is far more difficult than Fe 2+ This makes Fe 2+ It is constantly oxidized, while Mn 2+ However, it failed to oxidize for a long time. The applicant discovered in their research that Fe... 2+ and Mn 2+ The degree of catalytic oxidation is closely related to the pH value and redox potential Eh of the system. Further research revealed that Fe 2+ and Mn 2+ The degree of catalytic oxidation is determined by the system's redox potential (Eh), which is influenced by various factors such as system pH, gas concentration, gas-liquid mixing degree, reaction time, temperature, and ion type and concentration. Poor control makes ion oxidation difficult, and increasing pH leads to a decrease in potential, hindering its rise. Research has found that dividing the entire process into two steps—oxidation and precipitation—based on pH, makes the system's redox potential (Eh) easier to control and accelerates Fe oxidation. 2+ and Mn 2+ The catalytic oxidation rate of ions enhances Fe 2+ and Mn 2+Catalytic oxidation effect. To this end, a method for removing iron and manganese ions by stepwise control of the system's pH and Eh was proposed, which differs from existing technologies in its technical concept. Furthermore, the applicant also discovered in the research that Fe... 2+ The presence of Mn will increase 2+ The oxidation effect of Mn 2+ The presence of Fe will accelerate 2+ The oxidation rate is mainly due to Fe. 2+ and Mn 2+ There is a mutually reinforcing effect during the oxidation process. In light of this phenomenon, the applicant proposes to first perform synergistic catalytic oxidation of iron and manganese ions to further improve the iron and manganese removal rate. Specifically, this is achieved by controlling the pH value of the catalytic oxidation process and simultaneously controlling the system Eh to exceed 700mV. This allows the strong oxidizing properties of SO2 / O2 to be utilized to remove Fe... 2+ and Mn 2+ The co-catalytic oxidation of iron and manganese ions achieved by this method is one of the important technical objectives to be achieved in this application.

[0015] Step 2—Neutralization and Co-precipitation of Iron and Manganese Ions: Continue to introduce the oxygen-containing gas and the additive into the above system, maintain the redox potential Eh of the system above 700mv, and then add the neutralizing agent to adjust the pH of the system to 3.0-5.0, and carry out the neutralization and co-precipitation reaction of multiple ions to obtain iron and manganese slag slurry;

[0016] This process primarily involves adjusting the system's pH and maintaining the equilibrium temperature (Eh) to achieve the oxidation, hydrolysis, and precipitation of iron and manganese ions. Generally, higher pH leads to more complete hydrolysis and precipitation, while higher Eh results in a more significant oxidation effect. Previous researchers often improved ion removal by increasing the system's pH and Eh, which increases the loss rate of the main metal. Furthermore, according to the literature, hydrated hydroxides formed by the hydrolysis of metal ions exist in various forms, and the morphology and characteristics of hydroxide precipitation are closely related to precipitation conditions (such as pH, Eh, and concentration). For example, ferric hydroxide formed by the hydrolysis of iron ions exhibits the characteristic of colloidal particles carrying charge, and the charge of the precipitate varies at different pH levels. During the research, the applicant discovered that, in addition to iron ions, the high-valence hydrated manganese precipitate particles formed by the oxidation of manganese ions also possess charged characteristics. When the system pH is controlled between 3 and 5, the iron and manganese ion precipitates carry opposite charges, causing the precipitate particles to adsorb and approach each other, gradually agglomerating and growing into coarse grains. Therefore, the applicant controls the precipitation pH in step 2 to ensure that the ferric hydroxide particles and the high-valent hydrated manganese precipitate particles have opposite charges, thereby causing polymerization and adsorption, and co-precipitating ferric and manganese ions. During this process, it is also necessary to control the system pH to a high potential, which will promote the further oxidation of unoxidized ferric and manganese ions, ensuring complete oxidation of low-valent ferric and manganese ions, and ultimately complete precipitation.

[0017] In addition, this coprecipitation method can also aggregate silica gel and Al in solution. 3+ Charged particles. This method achieves the co-precipitation and coalescence removal of silica gel and Al from iron and manganese ions. 3+ The generation of charged particles is one of the key technical objectives that this application seeks to achieve.

[0018] Step 3—Solid-liquid separation to remove iron and manganese: The iron and manganese slurry is thickened by a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered by a filter press to form a filter wet sludge and a filter liquid. The filter liquid and the thickened supernatant are combined to form a liquid after iron and manganese removal, which is then sent to the next process. The filter wet sludge is washed and then transferred to the slag treatment process.

[0019] In addition, the additives used in this process are low-concentration SO2 gas or salts that can produce SO2. During the reaction, some SO2 participates in the reaction, while some SO2 does not participate in the reaction and rises from the top of the liquid. These SO2-containing gases will cause the SO2 concentration above the stirring tank to increase, deteriorate the operating environment, and pollute the air. Generally speaking, only alkaline solution is used to absorb the tail gas for treatment, and the recovery and utilization of this low-concentration SO2 reaction waste gas has almost never been considered. The applicant considered that SO2 dissolves in water to form H2SO3, and if CaO is present, it forms CaSO3. Both H2SO3 and CaSO3 release SO2 when they encounter acid, thus allowing the SO2 in the reaction waste gas to be absorbed and reused. The neutralizing agent in this process uses alkaline or neutral slurry such as calcium oxide. The SO2-containing reaction waste gas is bubbled into the neutralizing agent slurry tank for absorption, and then circulated back to the reaction tank with the addition of the neutralizing agent, realizing the self-circulation and reuse of SO2 in the reaction waste gas. In this way, without increasing the number of treatment steps or equipment, SO2 emissions are reduced, SO2 utilization is improved, and the operating environment is improved.

[0020] Preferably, the self-circulation and reuse of the reaction waste gas in steps 1 and 2 specifically includes:

[0021] The waste gas after the reaction in step 1 is blown into the neutralizing agent slurry tank used in step 1 for absorption and reuse. The waste gas after the reaction in step 2 is blown into the neutralizing agent slurry tank used in step 2 for absorption and reuse.

[0022] Preferably, the temperature of the iron-manganese ion synergistic catalytic oxidation reaction is 10℃-90℃, and the time is 0.5-5h.

[0023] Preferably, the temperature of the neutralization coprecipitation reaction is 10℃-90℃, and the time is 0.5-5h.

[0024] Preferably, the neutralizing agent includes one or more of calcium oxide, calcium carbonate, calcium hydroxide, sodium hydroxide, and active magnesium oxide.

[0025] Preferably, the additive includes one or more of sulfur dioxide, sulfur dioxide-containing flue gas, metabisulfite, sulfite, and thiosulfate.

[0026] Preferably, the additive is added from the bottom or lower middle part of the system.

[0027] Preferably, the oxygen-containing gas includes one or more of air, oxygen, and oxygen-containing flue gas.

[0028] Preferably, the oxygen-containing gas is air, and the air flow rate is 1-100 L / (L) 液 ·h).

[0029] Preferably, the volume ratio of sulfur dioxide provided by the additive to the volume of air is (0.5-5):100.

[0030] Compared with the prior art, the beneficial effects of this application include:

[0031] 1. This application provides a method for stepwise control of pH and Eh in a system for removing iron and manganese. By controlling the pH and Eh of the oxidation process in step 1, iron and manganese ions are kept in the system and a synergistic catalytic oxidation reaction is promoted, which simultaneously oxidizes iron and manganese ions from low valence states to high valence states, thereby further improving the oxidation effect of iron and manganese ions.

[0032] 2. This application provides a method for removing iron and manganese by stepwise control of pH and Eh in a system. Step 2 controls the pH of the precipitated system, causing the iron and manganese precipitate particles to carry opposite charges, leading to their aggregation and co-precipitation, thus accelerating the growth rate of the precipitate particles. Simultaneously, it also removes silica gel and Al. 3+ Charged particles are used to achieve the aggregation and co-precipitation of multiple ions.

[0033] 3. This application provides a method for stepwise control of pH and Eh in a system for removing iron and manganese. Through the self-circulation and reuse technology of reaction waste gas, the self-circulation and reuse of SO2-containing reaction waste gas is achieved without adding treatment processes and equipment. This reduces SO2 emissions, improves SO2 utilization, and improves the operating environment.

[0034] 4. This method can effectively improve the redox potential of the system, achieving controllable and adjustable system potential; it has advantages such as high iron and manganese removal rates and low iron and manganese residues; it can also reduce the entrainment of valuable metals in the precipitate residue, reducing the loss rate of valuable metals; in addition, this method consumes few auxiliary materials, has low cost, and is easy to industrialize. Under normal circumstances, after efficient removal of iron and manganese ions from the solution, the iron precipitation rate is greater than 99%, the manganese precipitation rate is greater than 80%, the residual iron content in the solution is reduced to below 5 mg / L, and the residual manganese content in the solution is reduced to 100 mg / L. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0036] Figure 1 A schematic diagram of the process flow for iron and manganese removal by stepwise control of pH and Eh in the system;

[0037] Figure 2 This is a schematic diagram showing the control of pH and redox potential Eh in the system of Example 3. Detailed Implementation

[0038] As used in this article:

[0039] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0040] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0041] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0042] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0043] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0044] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0045] A method for stepwise control of pH and Eh in a system for removing iron and manganese includes the following steps:

[0046] Step 1—Co-catalytic oxidation of iron and manganese ions: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 2+ and Mn 2+ A neutralizing agent is added to the solution to be treated to maintain the pH value at 1.5–3.0, while oxygen-containing gas and additives are introduced to begin Fe... 2+ and Mn 2+ The synergistic catalytic oxidation reaction of iron and manganese ions was completed after the redox potential Eh of the system reached 700 mV. The above operation was maintained while ensuring the redox potential Eh was not less than 700 mV. The solution to be treated was Mn produced during the wet copper smelting process. 2+ Concentration less than or equal to 5 g / L, Fe 2+ Acidic copper solutions with a concentration of 15 g / L or less;

[0047] Optionally, a neutralizing agent can be used to adjust the pH of the solution to be treated to any value between 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, or 1.5-3.0; the Mn content in the solution to be treated... 2+ The concentration can be 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, or any value between 0.5 and 5 g / L, Fe 2+ The concentration can be 0.1 g / L, 0.5 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, or any value between 0 and 15 g / L;

[0048] Step 2—Neutralization and Co-precipitation of Iron and Manganese Ions: Continue to introduce the oxygen-containing gas and the additive into the above system, maintain the redox potential Eh of the system above 700mv, and then add the neutralizing agent to adjust the pH of the system to 3.0-5.0, and carry out the neutralization and co-precipitation reaction of multiple ions to obtain iron and manganese slag slurry;

[0049] Optionally, in step 2, the neutralizing agent is added to adjust the pH of the system to any value between 3, 3.5, 4, 4.5, 5, or 3.0 and 5.0.

[0050] Step 3—Solid-Liquid Separation for Iron and Manganese Removal: The iron and manganese slurry is thickened using a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered using a filter press to form a wet filter sludge and a filter liquid. The filter liquid and the thickened supernatant are combined to form an iron and manganese-removed liquid, which is sent to the next process. The wet filter sludge is washed and then transferred to the sludge treatment process. Preferably, the reaction waste gas in Steps 1 and 2 is self-circulated and reused, specifically including:

[0051] The waste gas after the reaction in step 1 is blown into the neutralizing agent slurry tank used in step 1 for absorption and reuse. The waste gas after the reaction in step 2 is blown into the neutralizing agent slurry tank used in step 2 for absorption and reuse.

[0052] In steps 1 and 2, the reaction waste gas is recycled. Specifically, the waste gas after the reaction in step 1 is blown into the neutralizing agent slurry tank of step 1 for absorption and reuse, and the waste gas after the reaction in step 2 is blown into the neutralizing agent slurry tank of step 2 for absorption and reuse.

[0053] In one optional embodiment, the temperature of the iron-manganese ion co-catalytic oxidation reaction is 10℃-90℃, and the time is 0.5-5h.

[0054] Optionally, the temperature of the iron-manganese ion synergistic catalytic oxidation reaction can be any value between 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 10℃-90℃, and the time can be any value between 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h or 0.5-5h.

[0055] In one optional embodiment, the neutralization coprecipitation reaction is carried out at a temperature of 10°C-90°C for a time of 0.5-5 hours.

[0056] Optionally, the temperature of the neutralization coprecipitation reaction can be any value between 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 10℃-90℃, and any value between 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h or 0.5-5h.

[0057] The temperature control for iron and manganese removal is generally at room temperature (10-35℃), while a better iron removal effect can be obtained at 35-90℃.

[0058] In steps 1 and 2, the pH and Eh of the system are controlled in a coordinated manner, and the reaction time is determined based on the pH and Eh of the system.

[0059] In one optional embodiment, the neutralizing agent is one or more of calcium oxide, calcium carbonate, calcium hydroxide, sodium hydroxide, and active magnesium oxide.

[0060] It should be noted that the neutralizing agent can be any available and common alkaline substance; it can be added to the system in solid form or in slurry form.

[0061] In an optional embodiment, the additive includes one or more of sulfur dioxide, sulfur dioxide-containing flue gas, metabisulfite, sulfite, and thiosulfate.

[0062] In an alternative implementation, the additive is added from the bottom of the system.

[0063] The purpose of adding it to the bottom is to better achieve thorough mixing of the liquid to be treated, oxygen-containing gas, and additives, thereby improving reaction efficiency and reaction effect.

[0064] In one alternative embodiment, the oxygen-containing gas includes one or more of air, oxygen, and oxygen-containing flue gas.

[0065] The air can be natural air or processed compressed air.

[0066] In one optional embodiment, the oxygen-containing gas is air, and the air flow rate is 1-100 L / (L) 液 ·h).

[0067] The air flow rate can be 1L / (L) 液 ·h), 10L / (L 液 ·h), 20L / (L 液 ·h), 30L / (L 液 ·h), 40L / (L 液 ·h), 50L / (L液 ·h), 60L / (L 液 ·h), 70L / (L 液 ·h), 80L / (L 液 ·h), 90L / (L 液 ·h), 100L / (L 液 ·h) or 1-100L / (L 液 Any value between ·h).

[0068] It should be noted that the L here 液 This refers to the volume of the system to be treated in solution form, that is, 1-100L of air is added per hour for every liter of the system to be treated in solution form.

[0069] In an optional embodiment, the volume ratio of sulfur dioxide provided by the additive to the volume of air is (0.5-5):100.

[0070] Optionally, the volume ratio of sulfur dioxide provided by the additive to the volume of air can be any value between 0.5:100, 1:100, 2:100, 3:100, 4:100, 5:100 or (0.5-5):100.

[0071] In an alternative implementation, the oxygen-containing gas is introduced into the system through a gas dispersion coil.

[0072] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0073] First, the processing apparatus used in the embodiment will be briefly described as follows:

[0074] The device includes an additive preparation unit, an oxygen-containing gas preparation unit, a mixing unit, a monitoring unit, and a solid-liquid separation unit. The additive preparation unit is used to prepare additives and transport them to the mixing unit through pipelines. The oxygen-containing gas preparation unit is used to process gaseous raw materials to obtain oxygen-containing gas and transport the oxygen-containing gas to the mixing unit. The mixing unit is used to hold the solution containing ferrous ions and divalent manganese ions (which can be wastewater or slurry) to be treated, and to accept additives, neutralizing agents, and oxygen-containing gas. Then, the various components are thoroughly mixed and the corresponding reactions occur. The monitoring unit is used to detect the pH and redox potential of the system online. The solid-liquid separation unit is used to separate the precipitate from the system after the reaction is completed.

[0075] Understandably, in one alternative scheme, the mixing unit mainly includes a mixing tank, a stirring paddle and its power equipment, a gas dispersion coil for dispersing oxygen-containing gas, an additive input pipe, a liquid inlet pipe, and a liquid outlet pipe; the additive preparation unit includes an additive raw material tank, an additive preparation tank, a transfer pump, a flow meter, a concentration meter, and a flow rate regulating valve; the oxygen-containing gas preparation unit includes a compressed air pump, a compressed air buffer tank, a flow meter, and a flow rate regulating valve; the monitoring unit includes a redox potentiometer and a pH meter; and the solid-liquid separation unit includes a thickening device and a filter press.

[0076] The various facilities are directly connected or assembled or configured according to the process through common connection methods such as pipelines.

[0077] Example 1

[0078] like Figure 1 As shown, this embodiment provides a method for stepwise control of pH and Eh in the removal of iron and manganese. The specific operation is as follows: Take 1500ml of low copper raffinate from a wet copper smelting plant. The main components are Cu 0.27g / L, Co 0.26g / L, Fe 1.23g / L, and Mn 1.18g / L. Place the solution in a beaker and start stirring.

[0079] The first step involves the synergistic catalytic oxidation of iron and manganese ions: Calcium oxide emulsion is slowly added dropwise to the solution, maintaining the pH at approximately 2.5. Simultaneously, air is continuously bubbled into the solution, and SO2 is introduced at a controlled feed rate from the bottom, maintaining a SO2 to air volume ratio of 2%. The redox potential of the system gradually increases from 300 mV to 700 mV over 1.5 hours. This process is continued, maintaining the redox potential (Eh) above 700 mV for 2 hours. During this process, Fe in the solution... 2+ and Mn 2+ Synergistic catalytic oxidation occurs. A lid is installed on top of the reaction beaker, and the reaction waste gas is blown into the calcium oxide emulsion in this section by a vacuum device for SO2 absorption and reuse. Monitoring shows that the SO2 concentration of the waste gas emitted from above the calcium oxide emulsion is 60 mg / Nm³. 3 .

[0080] The second step involves the neutralization and co-precipitation of iron and manganese ions: Air and SO2 are continuously introduced into the system to maintain the redox potential (Eh) above 700 mV. Then, the calcium oxide emulsion is added to adjust the pH to 4.5, and this process is maintained for 4 hours. During this process, the iron precipitate particles are positively charged, while the manganese precipitate ions are negatively charged. The particles attract each other, aggregate, and form nuclei, completing the co-precipitation reaction of iron and manganese ions. A lid is installed on the top of the reaction beaker, and the reaction exhaust gas is blown into the calcium oxide emulsion in this section through an exhaust device for SO2 absorption and reuse. Monitoring of the exhaust gas emitted from the top of the calcium oxide emulsion shows an SO2 concentration of 74 mg / Nm³. 3 .

[0081] The third step involves solid-liquid separation: the iron-manganese slag slurry is thickened using a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered using a filter press to form a wet filter sludge and a filtrate. The filtrate and the thickened supernatant are combined to form a liquid after iron and manganese removal, which is then sent to the next process, the cobalt precipitation process. The wet filter sludge is then washed and transferred to a slag treatment process, namely the wet sludge washing process.

[0082] Elemental analysis of the solution after iron and manganese removal yielded the following results: Cu 0.21 g / L, Co 0.22 g / L, Fe 5.33 mg / L, Mn 0.14 g / L.

[0083] Example 2

[0084] This embodiment provides a method for stepwise control of pH and Eh in a system for removing iron and manganese. A solution with the following composition is pumped into a stirring tank and stirred for mixing. The pumping volume is 75% of the tank volume.

[0085] Calcium carbonate emulsion was slowly added dropwise to the solution to maintain a stable pH of approximately 2.0. Compressed air was continuously introduced into the solution using a blower. Sodium metabisulfite solution (concentration 150 g / L) was added to the solution using a feed pump. The addition rate of sodium metabisulfite and air was controlled by adjusting the flow meters of air and sodium metabisulfite, ensuring that the volume ratio of SO2 to air generated was 1.75%. The redox potential of the system gradually increased to 700 mV in 3.0 h. The above operation was continued, and the redox potential (Eh) was maintained above 700 mV for another 3.0 h to complete the Fe... 2+ and Mn 2+ The reaction involves a synergistic catalytic oxidation reaction. The reaction tank is a closed tank. The reaction waste gas is blown into the calcium carbonate emulsion in this section by a blower for SO2 absorption and reuse. Monitoring of the waste gas emitted from above the calcium carbonate emulsion shows an SO2 concentration of 68 mg / Nm³. 3 .

[0086] Continue the above procedure by introducing compressed air and sodium metabisulfite solution into the system to maintain the redox potential (Eh) above 700 mV. Then, add calcium carbonate emulsion to adjust the pH to 4.5 and maintain the above procedure for 3 hours. At this pH, the iron precipitate particles formed are positively charged, while the manganese precipitate ions are negatively charged. The particles attract each other, aggregate, and form nuclei, while simultaneously removing the aggregated silica gel particles, thus completing the co-precipitation reaction of iron and manganese ions. The reaction tank is a closed reaction tank. The reaction waste gas is blown into the calcium carbonate emulsion in this section by a blower for SO2 absorption and reuse. The SO2 concentration of the waste gas emitted from above the calcium carbonate emulsion is monitored to be 46 mg / Nm³. 3 .

[0087] The aforementioned iron-manganese slag slurry is thickened using a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered using a filter press to form a filter wet slag and a filter post-press liquid. The filter post-press liquid and the thickened supernatant are combined to form an iron-manganese-removed liquid, which is then sent to the next process. The filter wet slag is washed and transferred to a tailings dam for storage.

[0088] Elemental analysis of the liquid after iron and manganese removal yielded the following results: Cu 0.82 g / L, Fe 5.27 mg / L, Mn 0.64 g / L, and Si 0.08 g / L.

[0089] Example 3

[0090] This embodiment provides a method for stepwise control of pH and Eh in a system for removing iron and manganese. A slurry from a smelter is taken, with the main components being Fe 8.34 g / L, Mn 2.18 g / L, and Al 3.21 g / L. The solution is placed in a beaker and stirred.

[0091] Air and SO2 gas are blown into a gas mixing tank by a blower. The mixed gas is then passed sequentially through a primary gas mixing tank and a secondary gas mixing tank. The SO2 concentration is monitored at the outlet of the primary gas mixing tank, and air or SO2 is added to the secondary gas mixing tank as needed, ensuring that the SO2 concentration of the mixed gas output from the outlet of the secondary gas mixing tank remains stable at ~1.5%. The mixed gas is then passed into a solution to allow for a complete reaction.

[0092] Magnesium oxide and production water were added to the magnesium oxide slurry tank to prepare a slurry with a magnesium oxide concentration of 10%. Reaction waste gas was also bubbled into the tank, where magnesium oxide absorbed SO2 from the waste gas to form MgSO3 for absorption and reuse. Monitoring of the waste gas emitted from above the magnesium oxide slurry tank showed an SO2 concentration of 20 mg / Nm³. 3 .

[0093] The above magnesium oxide slurry was slowly added to the reaction solution, maintaining the pH of the solution at a stable level of ~2.2. Under the combined control of the system's pH and Eh, the redox potential of the system began to change, rising to 700 mV in 3 hours. The above operation was continued, maintaining the redox potential (Eh) above 700 mV for another 2 hours to complete the Fe... 2+ and Mn 2+ A synergistic catalytic oxidation reaction occurs.

[0094] Add magnesium oxide slurry to the solution to adjust the pH of the system to 5.0, and maintain the above operation to ensure that the redox potential (Eh) is higher than 700mV. After reacting for ~5h, the oxidized iron and manganese ions precipitate simultaneously. During the precipitation process, the precipitate ions attract each other due to the charge effect and agglomerate to form nuclei, which grow rapidly. At the same time, some charged aluminum precipitate particles are also agglomerated and removed, thus completing the co-precipitation reaction of iron and manganese ions.

[0095] The aforementioned iron-manganese slag slurry is thickened using a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered using a filter press to form a filter wet sludge and a filtrate. The filtrate and the thickened supernatant are combined to form a liquid after iron and manganese removal, which is then sent to the next process, the cobalt precipitation process. The filter wet sludge is then washed and transferred to a slag treatment process, namely the wet sludge washing process.

[0096] Elemental analysis of the solution after iron and manganese removal showed the following results: Fe 4.24 mg / L, Mn 0.37 g / L, Al 1.14 g / L.

[0097] Figure 2 This is a schematic diagram showing the control of pH and redox potential Eh in the system of Example 3.

[0098] Comparative Example 1

[0099] Compared to Example 1, the same solution was used as the raw material, namely a solution with the main components of Cu 0.27 g / L, Co 0.26 g / L, Fe 1.23 g / L, and Mn 1.18 g / L. The only difference was that the reaction was not adjusted based on the system's pH and Eh value, but only on the reaction time. Specifically, the reaction time was controlled at 2 hours in the first step and 3 hours in the second step, while other steps were performed as in Example 1. During the reaction, the system's redox potential Eh gradually increased to 560 mV, indicating partial oxidation of iron ions. Iron and manganese ions were not fully oxidized in synergistic manner. Subsequently, the pH was adjusted to carry out a co-precipitation reaction, at which point the system's Eh fluctuated between 400 and 500 mV. Analysis of samples taken after the reaction showed that, compared with the raw materials, the residual iron ion concentration in the solution was 0.25 g / L Cu, 0.28 g / L Co, 0.73 g / L Fe, and 1.12 g / L Mn. However, the residual manganese ion concentration was almost not reduced. This was mainly because the pH and Eh of the system were not adjusted according to the system, but only according to the reaction time, which failed to control the effective synergistic oxidation of iron and manganese ions.

[0100] Comparative Example 2

[0101] Compared to Example 1, the same solution was used as the raw material, namely a solution with the main components of Cu 0.27 g / L, Co 0.26 g / L, Fe 1.23 g / L, and Mn 1.18 g / L. The only difference was that the pH was not controlled within the range specified in this application in the first step; that is, the pH of the system was controlled at 0.50 in step 1. Other steps were performed as in Example 1. During the reaction, the redox potential Eh of the system remained basically stable and fluctuated around its original value without any increase. After the reaction, the sample analysis showed that the residual iron and manganese ions in the solution with Cu 0.26 g / L, Co 0.25 g / L, Fe 1.14 g / L, and Mn 1.16 g / L were almost unchanged compared to the raw material. This is mainly because the pH was not controlled within the range specified in this application in the first step, and the iron and manganese ions did not undergo synergistic oxidation and failed to precipitate.

[0102] Comparative Example 3

[0103] Compared to Example 1, the same solution was used as the raw material, namely a solution with the main components of Cu 0.27 g / L, Co 0.26 g / L, Fe 1.23 g / L, and Mn 1.18 g / L. The only difference was that Eh was not controlled within the range of this application in the first step; that is, the Eh of the system was controlled between 400 and 450 mV in step 1. Other steps were performed as in Example 1. After the reaction, the sample analysis showed that the residual iron and manganese ions in the solution of Cu 0.23 g / L, Co 0.22 g / L, Fe 1.20 g / L, and Mn 1.07 g / L were only slightly reduced compared to the raw material. This is mainly because Eh was not controlled within the range of this application in the first step, and the iron and manganese ions were not oxidized and therefore failed to precipitate effectively.

[0104] Comparative Example 4

[0105] Compared to Example 1, the same solution was used as the raw material, namely a solution with the main components of Cu 0.27 g / L, Co 0.26 g / L, Fe 1.23 g / L, and Mn 1.18 g / L. The only difference was that a one-step removal method was used throughout the process, without stepwise control of the system pH and Eh. The system pH was maintained at 5.0 throughout the entire process, and neither the oxidation nor precipitation stages were distinguished. Other steps were performed as in Example 1. During the reaction, the system potential failed to gradually increase, and the iron and manganese ions could not be effectively oxidized. Analysis of samples after the reaction showed that, compared to the raw material, the residual iron and manganese ions in the solution (Cu 0.20 g / L, Co 0.10 g / L, Fe 0.98 g / L, Mn 1.04 g / L) were slightly lower, and the amount of calcium oxide consumed was significantly increased. The concentrations of copper and cobalt in the solution were also significantly lower, while the copper and cobalt content in the slag was significantly higher. This is because maintaining a high pH level increases the loss of copper and cobalt entrained in the slag, ultimately leading to a decrease in the copper and cobalt content in the solution.

[0106] Comparative Example 5

[0107] Compared to Example 1, the raw materials used had a very low iron ion content, while other components remained largely the same, namely a solution of Cu 0.29 g / L, Co 0.24 g / L, Fe 10.08 mg / L, and Mn 1.20 g / L. The only difference was the content of ferrous iron in the raw materials. Other steps were performed as in Example 1. Analysis of samples taken after the reaction showed that the solution contained Cu 0.23 g / L, Co 0.22 g / L, Fe 4.10 mg / L, and Mn 0.94 g / L. Compared to the raw materials, the residual manganese ion content in the solution was lower, but the reduction was far less than in Example 1 (the Mn concentration in the solution after iron and manganese removal in Example 1 was 0.14 g / L).

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0109] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for stepwise control of pH and Eh in a system for removing iron and manganese, characterized in that, Includes the following steps: Step 1—Co-catalytic oxidation of iron and manganese ions: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 2+ and Mn 2+ A neutralizing agent is added to the solution to be treated to maintain the pH value at 1.5~3.0, while oxygen-containing gas and additives are introduced to begin Fe... 2+ and Mn 2+ The synergistic catalytic oxidation reaction of iron and manganese ions was carried out under the following conditions: after the redox potential Eh of the system reached 700mV, the above operation was maintained and the redox potential Eh was controlled to be no less than 700mV, and the temperature was controlled to be 10℃-90℃. The solution to be treated was Mn produced during the wet copper smelting process. 2+ Concentration less than or equal to 5 g / L, Fe 2+ An acidic copper solution with a concentration of 15 g / L or less; the additive includes one or more of sulfur dioxide, sulfur dioxide-containing flue gas, metabisulfite, sulfite, and thiosulfate; Step 2—Neutralization and Co-precipitation of Iron and Manganese Ions: Continue to introduce the oxygen-containing gas and the additive into the above system, maintain the redox potential Eh of the system above 700mv, and then add the neutralizing agent to adjust the pH of the system to 3.0~5.0, and carry out the neutralization and co-precipitation reaction of multiple ions to obtain iron and manganese slurry; the temperature of the neutralization and co-precipitation reaction is 10℃-90℃; Step 3—Solid-liquid separation to remove iron and manganese: The iron and manganese slurry is thickened by a thickener to form a thickened underflow and a thickened supernatant. The thickened underflow is then filtered by a filter press to form a filter wet sludge and a filter liquid. The filter liquid and the thickened supernatant are combined to form a liquid after iron and manganese removal, which is then sent to the next process. The filter wet sludge is washed and then transferred to the slag treatment process.

2. The method according to claim 1, characterized in that, The self-circulation and reuse of reaction waste gas in steps 1 and 2 specifically includes: The waste gas after the reaction in step 1 is blown into the neutralizing agent slurry tank used in step 1 for absorption and reuse. The waste gas after the reaction in step 2 is blown into the neutralizing agent slurry tank used in step 2 for absorption and reuse.

3. The method according to claim 1, characterized in that, The time for the iron-manganese ion synergistic catalytic oxidation reaction is 0.5-5 h.

4. The method according to claim 1, characterized in that, The neutralization and coprecipitation reaction takes 0.5-5 hours.

5. The method according to claim 1, characterized in that, The neutralizing agent includes one or more of calcium oxide, calcium carbonate, calcium hydroxide, sodium hydroxide, and active magnesium oxide.

6. The method according to claim 1, characterized in that, The additive is added from the bottom or lower middle part of the system.

7. The method according to any one of claims 1-6, characterized in that, The oxygen-containing gas includes one or more of air, oxygen, and oxygen-containing flue gas.

8. The method according to claim 7, characterized in that, The oxygen-containing gas is air, and the air flow rate is 1-100 L / (L) 液 ·h).

9. The method according to claim 8, characterized in that, The volume ratio of sulfur dioxide provided by the additive to the volume of air is (0.5-5):100.

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