Schwertmannite and synthesis method and application thereof

Abstract

The invention belongs to the technical field of electrochemical treatment of wastewater, and relates to a Schwertmannite as well as a synthesis method and application thereof. The method aims at solving the technical problems that in the prior art, a method for preparing the Schwertmannite is low in yield, and when the Schwertmannite is prepared from acid mine wastewater, the cost is high, the yield is low, and the TFe precipitation rate is low. According to the synthesis method of the Schwertmannite, a titanium ruthenium iridium electrode serves as an anode, a platinum sheet serves as a cathode, the Schwertmannite is subjected to electrochemical synthesis in acid waste water, the pH value of the acid waste water is constant in the synthesis process, the acid waste water contains TFe and # imgabs0 # TFe is Fe < 2 + > and / or Fe < 3 + >, and the pH value of the acid waste water is 2.5-3.5, according to the scheme, the TFe precipitation rate is high, and the yield of the synthesized Schwertmannite is high. The invention further provides application of the Schwertmannite synthesis method, the synthesis method is applied to treatment of acid mine wastewater, lime is added for neutralization, the addition amount of the lime is 0.09 g / 150 mL to 0.11 g / 150 mL, the usage amount of the lime is reduced, and generation of waste residues is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical wastewater treatment, and in particular, relates to a Schroeder mineral and a synthesis method and application thereof. Background Art

[0002] Schwertmannite is a secondary iron-hydroxysulfate mineral. Due to its multi-porous structure and large specific surface area, it is an environmental material with excellent adsorption performance. Schwertmannite is widely present in acid mine drainage (AMD) and can adsorb toxic heavy metals in the environment, such as arsenic, chromium, cadmium, lead, etc. Acid mine drainage (AMD) is formed by sulfide minerals (such as pyrite and chalcopyrite) in waste or tailings during the development of mineral resources under the combined action of light, air, water and microorganisms. Its low pH value, high concentration of total iron (TFe) and The dissolved heavy metal elements such as Mn and Cu will seriously damage the water and soil environment around the mining area. Direct disposal will lead to the waste of valuable metal resources, while by recovering Schroeder minerals, valuable iron ions can be recovered from wastewater; the acidity of acid mine wastewater can be reduced, the damage to water bodies and soil can be reduced, and the self-purification function of water bodies can be improved; pollutant emissions and the harm of heavy metals to the ecological environment can be reduced; at the same time, excellent environmental materials can be obtained, which has certain economic and environmental benefits.

[0003] Acid mine drainage is a worldwide environmental problem. The mainstream method for treating acid mine drainage at home and abroad is lime neutralization. The principle is to add alkali to increase the pH so that the metal is precipitated in the form of hydroxide. It includes the passive treatment process of lime ditch and the active treatment process of two-stage lime neutralization. The construction and operation and maintenance of the lime neutralization method are simple, but the high concentration of TFe and When reacting with lime water, it is easy to form a large amount of Fe(OH)3, Fe(OH)2 flocculent precipitation and CaSO4 micro-soluble substances, which coat the surface of lime to prevent the neutralization reaction. This requires more lime to participate in the reaction to achieve the effect of increasing pH, which also causes the problem of increasing the amount of neutralization slag. In addition, the heavy metal elements in the acidic mine wastewater enter the neutralization slag and make it toxic metal slag. In addition, the concentration of heavy metal elements is higher than that of TFe and This makes the heavy metals precipitated in the slag low-grade, low-efficiency and difficult to extract and recover. It is the main factor limiting the effective operation of lime neutralization. Therefore, it is necessary to remove TFe and Then, the lime neutralization method can be used to solve the problems of large amount of lime added, large amount of toxic slag produced and low heavy metal grade, and recover iron resources and environmental materials. Secondary ferric hydroxysulfate minerals can be used as TFe and By using sintered ore as raw material and synthesizing it in a certain way to form a precipitate and then recover it, we can not only obtain environmental functional materials, but also solve the limiting factors of the lime neutralization method of acid mine wastewater.

[0004] The existing technology for synthesizing Schmidtite from acidic mine wastewater has the disadvantages of high cost, low TFe precipitation rate and low Schmidtite yield. For example, the Chinese invention patent application publication number is CN105601051A, the application date is March 11, 2016, and the invention name is "A system and method for treating acidic mine wastewater based on biological mineralization", which discloses a biological oxidation mineralization method, which has a low mineralization rate and takes a long time.

[0005] For example, the Chinese invention patent application publication number is CN111186933A, the application date is January 8, 2020, and the name of the invention is "A chemical method for rapidly forming sea urchin-shaped Schrödinger mineral from acidic mine wastewater". The disclosed method adopts a chemical cyclic reaction to regulate the formation of sea urchin-shaped Schrödinger mineral: by adding zero-valent iron to the acidic mine wastewater and stirring for 30 to 90 minutes, and then adding H2O2 in batches or all at once and stirring for 4 to 7 hours, a reddish-brown sea urchin-shaped Schrödinger mineral can be formed. Although this method shortens the mineralization cycle, the zero-valent iron initially added to the reaction is expensive and needs to be added in excess. After stirring for 30 to 90 minutes, a magnet needs to be used to recover the excess zero-valent iron, which makes the process complicated. The H2O2 used is a high-value hazardous chemical with high transportation, storage, and use costs and operational risk factors.

[0006] Another example is the Chinese invention patent application publication number CN111137955A, the application date is March 4, 2020, and the invention name is "A method for rapid synthesis of Schmidt mineral using electrochemical deposition", which discloses that in a three-electrode system, a mixed solution of ferrous sulfate and acetic acid is used as the mother liquor of Schmidt mineral, a constant temperature water bath is used to control the system reaction temperature to 35-40°C, the pH value is adjusted to 3.0-3.5, and an external current is used to drive the mother liquor ions to undergo oxidation-reduction cycle reactions. The precipitated minerals are filtered, washed, and dried at low temperature to obtain finished minerals. Although this method synthesized Schmidt mineral, the TFe precipitation rate was low and the yield of Schmidt mineral was low.

[0007] Based on the above shortcomings, it is particularly urgent to seek a method to quickly synthesize Schroeder mineral from acidic mine wastewater with different TFe valence state distributions. Summary of the invention

[0008] 1. Problems to be solved

[0009] In view of the low yield of the methods for preparing Schreiber mineral in the prior art, and the high cost, low yield, and low TFe precipitation rate when preparing Schreiber mineral using acidic mine wastewater, the present application provides a method for synthesizing Schreiber mineral, which has a high TFe precipitation rate and a high yield of the synthesized Schreiber mineral. The present application also provides an application of the method for synthesizing Schreiber mineral, which is applied to the treatment of acidic mine wastewater, adding lime for neutralization, reducing the amount of lime used and reducing the generation of waste residue.

[0010] 2. Technical solution

[0011] In order to achieve the above purpose, the technical solution provided is:

[0012] A method for synthesizing a Schmidtite mineral comprises the following steps:

[0013] Using a titanium ruthenium iridium electrode as an anode and a platinum sheet as a cathode, inserting the positive and negative electrodes into acidic wastewater for electrochemical synthesis, keeping the pH value constant during the synthesis process, the pH value of the acidic wastewater being 2.5 to 3.5, and obtaining a suspension containing brown-red solid Schroeder mineral;

[0014] The suspension is filtered to obtain a brown-red solid Schmidt mineral and a filtrate, and the brown-red solid Schmidt mineral is washed and freeze-dried to obtain a Schmidt mineral;

[0015] The acidic wastewater contains TFe and The TFe is Fe 2+ and / or Fe 3+ .

[0016] Preferably, the pH value of the acidic wastewater is 2.7±0.2, for a wider range of actual natural conditions.

[0017] Preferably, the size of the cathode electrode and / or the anode electrode is 2×2 cm, and the distance between the cathode electrode and the anode electrode is 2 cm to 4 cm.

[0018] Furthermore, the concentration of TFe is 500 mg / L to 1000 mg / L. The concentration is 6000mg / L~8000mg / L.

[0019] Furthermore, the pH value of the acidic wastewater is adjusted by using a H2SO4 solution with a concentration of 1 mol / L to 4 mol / L, and / or a NaOH solution with a concentration of 1 mol / L to 5 mol / L.

[0020] Furthermore, the voltage used in the electrochemical synthesis is 5V to 10V and the time is 4h to 6h.

[0021] Furthermore, during the electrochemical synthesis process, the pH of the acidic wastewater is maintained at 2.5 to 3.5 by adding alkaline solution and / or calcium carbonate powder.

[0022] Preferably, the pH of the acidic wastewater is maintained at 2.7±0.2 for a wider range of practical natural conditions.

[0023] Furthermore, the electrochemical synthesis process is stirred at a speed of 100 r / min to 300 r / min.

[0024] Furthermore, the acidic wastewater also contains heavy metal ions Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and / or Zn 2+ One or more of .

[0025] Preferably, the heavy metal ion Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ or Zn 2+ The concentrations are 15mg / L~25mg / L, 80mg / L~100mg / L, 50mg / L~70mg / L, 40mg / L~60mg / L and 5mg / L~10mg / L respectively.

[0026] A Schmidt mineral is prepared by the synthesis method.

[0027] The invention relates to an application of the synthesis method of Schmidtite mineral, and the synthesis method is applied to the treatment of acid mine drainage.

[0028] Further, the method comprises the following steps: stirring the filtrate, adding lime to neutralize the filtrate, and obtaining a solution with a neutral pH value, wherein the amount of lime added is 0.09 g / 150 mL to 0.11 g / 150 mL.

[0029] 3. Beneficial effects

[0030] Compared with the existing known technology, the technical solution provided by the present invention has the following beneficial effects:

[0031] (1) A method for synthesizing Schmidtite of the present invention comprises: reacting TFe and Co-precipitation forms Schmidtite. During the electrochemical reaction, H + The electrons are preferentially obtained and reduced to H2. This process uses electrical energy to split the HO bond in H2O. 3+ In this process, the energy barrier of hydrolysis and mineralization reaction is overcome simultaneously. Fe in the environment 3+Can Co-precipitation forms Schmidtite, which means that after electricity is applied, Fe 3+ Direct mineralization; Fe 2+ It is first oxidized to Fe by O2 and active oxygen species produced at the anode. 3+ The Gibbs energy is released during the oxidation process, and then this part of Gibbs energy and electrical energy are used to overcome the hydrolysis mineralization energy barrier and The anode is a titanium ruthenium iridium mesh electrode, which can directly and indirectly convert Fe 2+ Oxidized to Fe 3+ , energy is released during oxidation, and the Fe 3+ It can be used to form minerals by using the hydroxyl produced by the cathode, or it can be used to use the released energy to obtain the hydroxyl of water (H2O) to form minerals. Both naturally generated and artificially synthesized Schmidtite are based on Fe 2+ Biological or chemical oxidation of raw materials to form Fe 3+ It then hydrolyzes to form Schmidtite. No method has been reported to directly convert Fe 3+ The synthesis method of the Schmidtite of the present invention is based on Fe 2+ / Fe 3+ After the ionization of the simulated acid mine wastewater solution, the TFe precipitation rate reached about 40%, and the Fe 2+ After the main acid mine wastewater simulation liquid was electrified, the TFe precipitation rate reached 74.36%. 3+ After the main acid mine wastewater simulation liquid was electrified, the TFe precipitation rate reached 37.77%, and the obtained minerals were all Schroeder minerals, which was significantly higher than that of biological oxidation Fe. 2+ Mineralization and chemical oxidation of Fe 2+ The mineralization method shows greater adaptability to changes in environmental factors.

[0032] (2) The crystal structure of the Schmidtite of the present invention is identified by XRD technology, and it has a specific diffraction peak of the Schmidtite; the morphological characteristics are observed by SEM, and it has a specific form of the Schmidtite, such as sea urchin. The Schmidtite of the present invention is an environmental material that can enrich heavy metals in acidic mine wastewater by adsorption, remove TFe and Reduce the burden of subsequent acid mine drainage treatment.

[0033] (3) Application of the synthesis method of the Schreiberite of the present invention, stirring the filtrate after the synthesis of the Schreiberite, adding lime to neutralize, forming a suspension with a neutral pH, and filtering to separate the neutralized residue and the neutralized water. Post-coupling lime neutralization reduces lime usage by 36.88% to 41.09% and neutralization slag production by 44.29% to 62.88% compared to direct lime neutralization treatment of untreated acidic mine wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Fe 2+ / Fe 3+ The simulated acid mine wastewater solution with coexistence as the main component was connected to a 7.5V voltage and powered on for 6 hours under the conditions of non-constant pH, constant pH of NaOH solution, and constant pH of calcium carbonate powder. The TFe precipitation rate and pH changed with the power-on time.

[0035] Figure 2 Fe 2+ The main acid mine wastewater simulation liquid was connected to a 7.5V voltage and powered on for 6 hours under the conditions of non-constant pH, constant pH of NaOH solution, and constant pH of calcium carbonate powder, and the changes in TFe precipitation rate and pH with power-on time.

[0036] Figure 3 Fe 2+ / Fe 3+ The mineral XRD patterns and SEM images of the simulated acid mine wastewater solution with coexistence as the main component were connected to a voltage of 7.5V for 6 hours under the conditions of non-constant pH, constant pH of NaOH solution, and constant pH of calcium carbonate powder.

[0037] Figure 4 Fe 2+ The mineral XRD patterns and SEM images were obtained by connecting the simulated acid mine wastewater liquid to 7.5V voltage for 6 hours and using calcium carbonate powder to maintain a constant pH.

[0038] Figure 5 Fe 3+ The mineral XRD patterns and SEM images were obtained by connecting the main acid mine wastewater simulation liquid to 7.5V voltage for 6 hours and keeping the pH constant with NaOH solution.

[0039] Figure 6 Fe 2+ / Fe 3+ The amount of minerals produced, the amount of subsequent lime added and the amount of neutralization slag produced in the simulated acid mine wastewater solution with coexistence as the main component was connected to a 7.5V voltage for 6 hours under the conditions of non-constant pH, constant pH of NaOH solution and constant pH of calcium carbonate powder.

[0040] Figure 7 Fe 2+ The main acid mine wastewater simulation liquid was connected to 7.5V voltage for 6 hours to measure the mineral production, subsequent lime addition and neutralization slag production at a constant pH of calcium carbonate powder. DETAILED DESCRIPTION

[0041] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.

[0042] Example 1 (Fe 2+ / Fe 3+ Coexisting AMD, using NaOH solution to maintain a constant pH)

[0043] A method for synthesizing a Schmidtite mineral in this embodiment comprises the following steps:

[0044] S1. Weigh 0.0745g FeSO4·7H2O, 0.3883g Fe2(SO4)3·xH2O and 0.8434g Na2SO4 in a 300mL beaker, add 142.5mL deionized water to dissolve, then add 7.5mL heavy metal ion mixed concentrate, adjust the pH of the solution to 2.7±0.2 with 3.68mol / L H2SO4 solution and 5mol / L NaOH solution to prepare FeSO4. 2+ / Fe 3+ The coexistence-based acid mine drainage simulation solution has a solution volume of 150 mL;

[0045] Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and Zn 2+ Each heavy metal ion is prepared by pre-dissolving the corresponding sulfate substance into a mixed concentrated solution. When used, the heavy metal ion mixed concentrated solution is directly added to obtain the Cu in the acid mine wastewater simulation solution. 2+ , Mn 2 + 、Al 3+ Mg 2+ and Zn 2+ The concentrations were 20mg / L, 90mg / L, 60mg / L, 50mg / L and 8mg / L, supplemented with Na2SO4 concentration.

[0046] Since iron and heavy metal ions are prepared by their corresponding sulfates, The concentration is lower than that in actual wastewater concentration, so Na2SO4 supplement is needed Concentration up to 6000mg / L.

[0047] S2. Place the rotor in a beaker containing simulated acid mine wastewater solution, place it on a magnetic stirrer, use a 2×2 cm titanium ruthenium iridium mesh electrode and a platinum sheet as the anode and cathode respectively and insert them into the simulated acid mine wastewater solution, connect the positive and negative electrodes to a DC power supply with a copper wire, the distance between the negative electrode and the positive electrode is 3 cm, adjust the DC power supply to apply a voltage of 7.5 V and power on for 6 hours. During the power-on process, the magnetic stirrer stirs the solution at 200 r / min, and uses a 5 mol / L NaOH solution to keep the system pH constant at 2.7±0.2.

[0048] S3. The suspension formed after the power supply is turned off is filtered to recover the brown-red solid, which is washed with deionized water for 3 to 5 times and then freeze-dried to obtain the Schmidt mineral.

[0049] In Fe 2+ / Fe 3+ In the simulated acid mine drainage solution where Fe 2+ The concentration is 100 mg / L, Fe 3+ The concentration is 500mg / L. The concentration was 6000 mg / L, and the TFe precipitation rate was 39.77% ( Figure 1 a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 48.3 mg ( Figure 6 a) by Figure 3 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0050] Example 2 (Fe 2+ / Fe 3+ Coexisting AMD, using calcium carbonate powder to maintain a constant pH)

[0051] A method for synthesizing a Schmidtite mineral in this embodiment comprises the following steps:

[0052] S1. Weigh 0.0745g FeSO4·7H2O, 0.3883g Fe2(SO4)3·xH2O and 0.8434g Na2SO4 in a 300mL beaker, add 142.5mL deionized water to dissolve, then add 7.5mL heavy metal ion mixed concentrate, adjust the pH of the solution to 2.7±0.2 with 3.68mol / L H2SO4 solution and 5mol / L NaOH solution to prepare FeSO4. 2+ / Fe 3+ The coexistence-based acid mine drainage simulation solution has a solution volume of 150 mL;

[0053] Cu 2+ , Mn 2+ 、Al 3+ Mg 2+and Zn 2+ Each heavy metal ion is prepared by pre-dissolving the corresponding sulfate substance into a mixed concentrated solution. When used, the heavy metal ion mixed concentrated solution is directly added to obtain the Cu in the acid mine wastewater simulation solution. 2+ , Mn 2 + 、Al 3+ Mg 2+ and Zn 2+ The concentrations were 20mg / L, 90mg / L, 60mg / L, 50mg / L and 8mg / L, supplemented with Na2SO4 concentration.

[0054] S2. Place the rotor in a beaker containing simulated acid mine wastewater solution, place it on a magnetic stirrer, use a 2×2 cm titanium ruthenium iridium mesh electrode and a platinum sheet as the anode and cathode respectively and insert them into the simulated acid mine wastewater solution, connect the positive and negative electrodes to a DC power supply with a copper wire, the distance between the negative electrode and the positive electrode is 3 cm, adjust the DC power supply to apply a voltage of 7.5 V and power on for 6 hours. During the power-on process, the magnetic stirrer stirs the solution at 200 r / min, and calcium carbonate powder is used to keep the system pH constant at 2.7±0.2.

[0055] S3. The suspension formed after the power supply is turned off is filtered to recover the brown-red solid, which is washed with deionized water for 3 to 5 times and then freeze-dried to obtain the Schmidt mineral.

[0056] In Fe 2+ / Fe 3+ In the simulated acid mine drainage solution where Fe 2+ The concentration is 100 mg / L, Fe 3+ The concentration is 500mg / L. The concentration was 6000 mg / L, and the TFe precipitation rate was 38.87% ( Figure 1 a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 45.2 mg ( Figure 6 a) by Figure 3 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0057] Comparative Example 1 (Fe 2+ / Fe 3+ Coexistence of AMD, non-constant pH treatment during electrochemical synthesis)

[0058] A method for synthesizing a Schmidtite mineral in this comparative example comprises the following steps:

[0059] S1. Weigh 0.0745g FeSO4·7H2O, 0.3883g Fe2(SO4)3·xH2O and 0.8434g Na2SO4 in a 300mL beaker, add 142.5mL deionized water to dissolve, then add 7.5mL heavy metal ion mixed concentrate, adjust the pH of the solution to 2.7±0.2 with 3.68mol / L H2SO4 solution and 5mol / L NaOH solution to prepare FeSO4. 2+ / Fe 3+ The coexistence-based acid mine drainage simulation solution has a solution volume of 150 mL;

[0060] Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and Zn 2+ Each heavy metal ion is prepared by pre-dissolving the corresponding sulfate substance into a mixed concentrated solution. When used, the heavy metal ion mixed concentrated solution is directly added to obtain the Cu in the acid mine wastewater simulation solution. 2+ , Mn 2 + 、Al 3+ Mg 2+ and Zn 2+ The concentrations were 20mg / L, 90mg / L, 60mg / L, 50mg / L and 8mg / L, supplemented with Na2SO4 concentration.

[0061] S2. Place the rotor in a beaker containing simulated acid mine wastewater solution, place it on a magnetic stirrer, use a 2×2 cm titanium ruthenium iridium mesh electrode and a platinum sheet as the anode and cathode respectively and insert them into the simulated acid mine wastewater solution, connect the positive and negative electrodes to a DC power supply with a copper wire, the distance between the negative electrode and the positive electrode is 3 cm, adjust the DC power supply to apply a voltage of 7.5 V and power on for 6 hours. During the power-on process, the magnetic stirrer stirs the solution at a speed of 200 r / min, and the pH value of the solution is not constant.

[0062] S3. The suspension formed after the power supply is turned off is filtered to recover the brown-red solid, which is washed with deionized water for 3 to 5 times and then freeze-dried to obtain the Schmidt mineral.

[0063] In Fe 2+ / Fe 3+ In the simulated acid mine drainage solution where Fe 2+ The concentration is 100 mg / L, Fe 3+ The concentration is 500mg / L. The concentration was 6000 mg / L, and the TFe precipitation rate was 17.77% after 6 hours of non-constant pH. Figure 1a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 11 mg ( Figure 6 a) by Figure 3 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0064] It can be seen from Example 1, Example 2 and Comparative Example 1 that Fe 2+ / Fe 3+ In the simulated solution of acidic mine wastewater with coexistence as the main component, after being powered on with a voltage of 7.5V, under the conditions of constant pH of NaOH solution, constant pH of calcium carbonate powder and non-constant pH, the Figure 1 As shown in a, the TFe precipitation rate gradually increases with time. After 6 hours of power-on, the TFe precipitation rates are 39.77% and 38.87%, 17.77%, and the final Schreiberite mass is 48.3 mg, 45.2 mg, and 11 mg, respectively. The TFe precipitation rate under the conditions of constant pH of NaOH solution and constant pH of calcium carbonate powder, as well as the mass of the synthesized Schreiberite are higher than those in Comparative Example 1 (non-constant pH). After power-on, as shown in Figure 1 As shown in b, under the condition of non-constant pH, the pH value of the whole system showed an overall downward trend. Under the conditions of constant pH of NaOH solution and constant pH of calcium carbonate powder, the pH value of the whole system was maintained at 2.7±0.2. 3+ During the hydrolysis and acid-producing process, the pH will continue to decrease, thereby inhibiting hydrolysis. Maintaining a constant pH during the reaction can promote the continued reaction and synthesize more Schreiberite minerals.

[0065] Example 3 (containing Fe 2+ AMD based on calcium carbonate powder to maintain constant pH)

[0066] A method for synthesizing a Schmidtite mineral in this embodiment comprises the following steps:

[0067] S1. Weigh 0.4469g FeSO4·7H2O and 0.9543g Na2SO4 in a 300mL beaker, add 142.5mL deionized water to dissolve, then add 7.5mL heavy metal ion mixed concentrate, adjust the pH of the solution to 2.7±0.2 with 3.68mol / L H2SO4 solution and 5mol / L NaOH solution to prepare Fe 2+ The acid mine wastewater simulation fluid is mainly composed of , and the solution volume is 150mL.

[0068] Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and Zn 2+Each heavy metal ion is prepared by pre-dissolving the corresponding sulfate substance into a mixed concentrated solution. When used, the heavy metal ion mixed concentrated solution is directly added to obtain the Cu in the acid mine wastewater simulation solution. 2+ , Mn 2 + 、Al 3+ Mg 2+ and Zn 2+ The concentrations were 20mg / L, 90mg / L, 60mg / L, 50mg / L and 8mg / L, supplemented with Na2SO4 concentration.

[0069] S2. Place the rotor in a beaker containing simulated acid mine wastewater solution, place it on a magnetic stirrer, use a 2×2 cm titanium ruthenium iridium mesh electrode and a platinum sheet as the anode and cathode respectively and insert them into the simulated acid mine wastewater solution, connect the positive and negative electrodes to a DC power supply with a copper wire, the distance between the negative electrode and the positive electrode is 3 cm, adjust the DC power supply to apply a voltage of 7.5 V and power on for 6 hours. During the power-on process, stir the solution with a magnetic stirrer at 100 r / min to 300 r / min, and use calcium carbonate powder to keep the system pH constant at 2.7±0.2.

[0070] S3. The suspension formed after the power supply is turned off is filtered to recover the brown-red solid, which is washed with deionized water for 3 to 5 times and then freeze-dried to obtain the Schmidt mineral.

[0071] In Fe 2+ In the simulated acid mine drainage solution mainly composed of Fe 2+ The concentration is 600mg / L. The concentration was 6000 mg / L. After adding calcium carbonate powder and keeping the solution pH constant for 6 hours, the TFe precipitation rate reached 74.36% ( Figure 2 a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 116.7 mg ( Figure 7 a) by Figure 4 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0072] Example 4 (containing Fe 2+ AMD, using NaOH solution to maintain constant pH)

[0073] The synthesis method of a Schreiberite in this embodiment is basically the same as that in Example 4, except that during the power-on process, a 5 mol / L NaOH solution is used to keep the system pH constant at 2.7±0.2.

[0074] In Fe 2+ In the simulated acid mine drainage solution mainly composed of Fe 2+ The concentration is 600mg / L. The concentration was 6000 mg / L, and 5 mol / L NaOH solution was added to keep the solution pH constant. After 6 hours of power on, the TFe precipitation rate was 49.33% ( Figure 2 a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 60.2 mg. Figure 4 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0075] Comparative Example 2 (containing Fe 2+ AMD, which is mainly composed of AMD, has an unstable pH during electrochemical synthesis.

[0076] The method for synthesizing a Schreiberite in this embodiment is basically the same as that in Embodiment 4, except that the pH value is not constant during the power-on process.

[0077] In Fe 2+ In the simulated acid mine drainage solution mainly composed of Fe 2+ The concentration is 600mg / L. The concentration was 6000 mg / L, and the pH of the solution was not constant. After 6 hours of electricity, the TFe precipitation rate was 36.72% ( Figure 2 a), the brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 49.6 mg, and the brown-red solid was Schroeder mineral.

[0078] It can be seen from Example 3, Example 4 and Comparative Example 2 that Fe 2+ In the acid mine wastewater simulation solution mainly composed of , after connecting 7.5V voltage to power on, under the conditions of constant pH of calcium carbonate powder, constant pH of NaOH solution and non-constant pH, Figure 2 As shown in a, the TFe precipitation rate gradually increases with time. After 6 hours of power-on, the TFe precipitation rates are 74.36%, 49.33% and 36.72% respectively. The TFe precipitation rates under the conditions of constant pH of NaOH solution and constant pH of calcium carbonate powder, as well as the quality of the synthesized Schrödinger mineral are higher than those in Comparative Example 2 (non-constant pH). Among them, the TFe precipitation rate under the conditions of constant pH of calcium carbonate powder and the quality of the synthesized Schrödinger mineral are the highest. After power-on, as shown in Figure 2 As shown in b, under the condition of non-constant pH, the pH value of the whole system showed an overall downward trend. Under the conditions of constant pH of NaOH solution and constant pH of calcium carbonate powder, the pH value of the whole system was maintained at 2.7±0.2. 3+ During the hydrolysis and acid-producing process, the pH will continue to decrease, thereby inhibiting hydrolysis. Maintaining a constant pH during the reaction can promote the continued reaction and synthesize more Schreiberite minerals.

[0079] Example 5 (containing Fe 3+ AMD, using NaOH solution to maintain constant pH)

[0080] A method for synthesizing a Schmidtite mineral in this embodiment comprises the following steps:

[0081] S1: Weigh 0.4661gFe2(SO4)3·xH2O and 0.8434gNa2SO4 in a 300mL beaker, add 142.5mL deionized water, put the beaker into an ultrasonic cleaner for ultrasonic dissolution for 5min, then transfer it to a constant temperature water bath and heat it at 45℃ for 3min. After it is completely dissolved and cooled to room temperature, add 7.5mL of heavy metal ion mixed concentrate, adjust the pH of the solution to 2.7±0.2 with 3.68mol / L H2SO4 solution and 5mol / L NaOH solution, and prepare Fe 3+ The AMD simulation solution is mainly composed of 150 mL of solution volume;

[0082] Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and Zn 2+ Each heavy metal ion is prepared by pre-dissolving the corresponding sulfate substance into a mixed concentrated solution. When used, the heavy metal ion mixed concentrated solution is directly added to obtain the Cu in the acid mine wastewater simulation solution. 2+ , Mn 2 + 、Al 3+ Mg 2+ and Zn 2+ The concentrations were 20mg / L, 90mg / L, 60mg / L, 50mg / L and 8mg / L, supplemented with Na2SO4 concentration.

[0083] S2: Place the rotor in a beaker containing AMD simulated liquid, place it on a magnetic stirrer, use a 2×2 cm titanium ruthenium iridium mesh electrode and a platinum sheet as the anode and cathode respectively and insert them into the AMD simulated liquid, use copper wires to connect the positive and negative electrodes to a DC power supply, the distance between the negative electrode and the positive electrode is 3 cm, adjust the DC power supply to apply a voltage of 7.5 V and power on for 6 hours. During the power-on process, the magnetic stirrer stirs the solution at 100 r / min to 300 r / min, and uses a 5 mol / L NaOH solution to keep the system pH constant at 2.7±0.2.

[0084] S3: The suspension formed after the power supply is turned off is filtered to recover the brown-red solid, which is washed with deionized water for 3 to 5 times, freeze-dried and weighed.

[0085] Fe 3+ Acid mine drainage simulation fluid mainly composed of Fe 3+ The concentration is 600mg / L. The concentration was 6000 mg / L. After 6 hours of electricity flow with NaOH solution at a constant pH, the TFe precipitation rate reached 37.77%. The brown-red solid recovered after filtration was freeze-dried and weighed to have a mass of 44.3 mg. Figure 5 From the XRD pattern and SEM image, it can be seen that the brown-red solid is Schroeder mineral.

[0086] The pH value of the acid mine wastewater simulation liquid configured in this application is 2.7±0.2, which is to be close to the pH value of acid mine wastewater in nature. If the pH value of the acid mine wastewater simulation liquid is kept constant at 3.0-3.5, a higher TFe precipitation rate and Schroeder mineral synthesis amount will be obtained.

[0087] Example 6 (Fe 2+ / Fe 3+ Coexisting AMD, NaOH solution with constant pH, filtrate neutralized with lime)

[0088] The application of the synthesis method of the Schmidt mineral of this embodiment comprises the following steps:

[0089] The acid mine wastewater filtrate collected after the suction filtration in step S3 of Example 1 was poured into a beaker, and a rotor was placed on a magnetic stirrer, and the speed of the magnetic stirrer was 300 r / min. Lime was added to the filtrate for neutralization to raise the pH to about 7 to form a suspension with a neutral pH. The formed neutral suspension was then suction filtered, and the neutralization residue and the neutralization water were separated. The amount of lime used and the amount of neutralization residue produced were recorded. The amount of lime used was 111.1 mg, and the amount of neutralization residue produced was 98.6 mg (as shown in Figure 1). Figure 6 b. Figure 6 c).

[0090] Example 7 (Fe 2+ / Fe 3+ Coexisting AMD, calcium carbonate powder to maintain constant pH, filtrate neutralized with lime)

[0091] The application of the synthesis method of the Schmidt mineral of this embodiment comprises the following steps:

[0092] The acid mine wastewater filtrate collected after the filtration in step S3 of Example 2 was poured into a beaker, and a rotor was placed on a magnetic stirrer, and the speed of the magnetic stirrer was 300 r / min. Lime was added to the filtrate for neutralization to raise the pH to about 7 to form a suspension with a neutral pH. The formed neutral suspension was then filtered, and the neutralization residue and the neutralization water were separated. The amount of lime used and the amount of neutralization residue produced were recorded. The amount of lime used was 109.8 mg, and the amount of neutralization residue produced was 119.1 mg (as shown in Figure 2). Figure 6 b. Figure 6 c).

[0093] Comparative Example 3 (Fe 2+ / Fe3+ Coexisting AMD, unstable pH, filtrate neutralized with lime)

[0094] The application of the synthesis method of the Schmidt mineral of this embodiment comprises the following steps:

[0095] The acid mine wastewater filtrate collected after filtration in step S3 of comparative example 1 was poured into a beaker, and a rotor was placed on a magnetic stirrer, and the speed of the magnetic stirrer was 300r / min. Lime was added to the filtrate for neutralization to raise the pH to about 7 to form a suspension with a neutral pH. The formed neutral suspension was then filtered, and the neutralization residue and the neutralization water were separated. The amount of lime used and the amount of neutralization residue produced were recorded. The amount of lime used was 150.6 mg, and the amount of neutralization residue produced was 140.9 mg (as shown in Figure 2). Figure 6 b. Figure 6 c).

[0096] Comparative Example 4 (Fe 2+ / Fe 3+ Coexisting AMD, no electricity, add lime directly to neutralize)

[0097] The method for treating acidic mine wastewater in this comparative example comprises the following steps:

[0098] Fe prepared according to step S1 of comparative example 1 2+ / Fe 3+ The coexistence is mainly acid mine wastewater simulation liquid, without electricity, put the rotor on the magnetic stirrer, and the speed of the magnetic stirrer is 300r / min. Add lime to the acid mine wastewater simulation liquid for neutralization, so that the pH is raised to about 7, forming a suspension with a neutral pH, and then filter the formed neutral suspension to separate the neutralization slag and neutralization water, and record the amount of lime used and the amount of neutralization slag produced. The amount of lime used is 176mg, and the amount of neutralization slag produced is 213.8mg (such as Figure 6 b. Figure 6 c).

[0099] From Examples 6-7, Comparative Examples 3-4 and Figure 6 It can be seen that Fe 2+ / Fe 3+ In the simulated acid mine drainage solution where the coexistence is dominant,

[0100] The NaOH solution was kept at a constant pH and the power was turned on for 6 hours to synthesize the Schmidtite. When the pH of the acidic mine wastewater filtrate was raised to 7, 111.1 mg of lime was consumed and the amount of neutralization slag produced was 98.6 mg. The amount of lime added and the amount of neutralization slag produced were compared with those in Comparative Example 4 (the acidic mine wastewater without power treatment was directly neutralized with lime). Figure 6 The control in the experiment) decreased by 36.88% and 53.88% respectively.

[0101] The calcium carbonate powder was kept at a constant pH and powered on for 6 hours to synthesize Schmidt mineral. When the pH of the acidic mine wastewater filtrate was raised to 7, 109.8 mg of lime was consumed and 119.1 mg of neutralization slag was produced. The amount of lime added and the amount of neutralization slag produced were reduced by 37.61% and 44.29% respectively compared with Comparative Example 4.

[0102] The pH value is not constant. After the power is turned on for 6 hours to synthesize the Schmidtite, 150.6 mg of lime is consumed when the pH of the acid mine wastewater filtrate is raised to 7, and the amount of neutralization slag produced is 140.9 mg. The amount of lime added and the amount of neutralization slag produced are reduced by 14.43% and 34.10% respectively compared with Comparative Example 4. Although the amount of lime added and the amount of neutralization slag produced are reduced, the reduction is less than that of Example 6 and Example 7.

[0103] Example 8 (containing Fe 2+ AMD, mainly calcium carbonate powder is used to maintain a constant pH, and the filtrate is neutralized by adding lime)

[0104] The application of the synthesis method of the Schmidt mineral of this embodiment comprises the following steps:

[0105] The acid mine wastewater filtrate collected after the suction filtration in step S3 of Example 4 was poured into a beaker, and a rotor was placed on a magnetic stirrer. The speed of the magnetic stirrer was 200 r / min to 400 r / min. Lime was added to the filtrate for neutralization to raise the pH to about 7 to form a suspension with a neutral pH. The formed neutral suspension was then suction filtered to separate the neutralization residue from the neutralization water. The amount of lime used and the amount of neutralization residue produced were recorded. The amount of lime used was 116.4 mg, and the amount of neutralization residue produced was 92.8 mg (as shown in Figure 2). Figure 7 b. Figure 7 c).

[0106] Comparative Example 5 (containing Fe 2+ AMD, without electricity, add lime to neutralize directly)

[0107] The method for treating acidic mine wastewater in this comparative example comprises the following steps:

[0108] Fe prepared according to step S1 of Example 4 2+ The coexistence is mainly acid mine wastewater simulation liquid, without electricity, put the rotor on the magnetic stirrer, and the speed of the magnetic stirrer is 200r / min~400r / min. Add lime to the filtrate for neutralization, so that the pH is raised to about 7, forming a suspension with a neutral pH, and then filter the formed neutral suspension to separate the neutralization slag and neutralization water, and record the amount of lime used and the amount of neutralization slag produced. The amount of lime used is 197.6mg, and the amount of neutralization slag produced is 250mg (such as Figure 7 b. Figure 7 c).

[0109] From Example 8, Comparative Example 5 and Figure 6 It can be seen that Fe 2+ In the acid mine wastewater simulation liquid mainly composed of calcium carbonate powder, the solution pH is constant. After the power is turned on for 6 hours to synthesize Schmidt mineral, 116.4 mg of lime is consumed when the pH of the acid mine wastewater filtrate is increased to 7, and the amount of neutralization slag produced is 92.8 mg. The amount of lime added and the amount of neutralization slag produced are compared with those in Comparative Example 5 (the acid mine wastewater without power treatment is directly neutralized with lime). Figure 6 The control in the experiment) decreased by 41.09% and 62.88% respectively.

[0110] The method for synthesizing the Schmidtite of the present invention is to react TFe and Co-precipitation forms Schmidtite. During the electrochemical reaction, H + The electrons are preferentially obtained and reduced to H2. This process uses electrical energy to split the HO bond in H2O. 3+ In this process, the energy barrier of hydrolysis and mineralization reaction is overcome simultaneously. Fe in the environment 3+ Can Co-precipitation forms Schmidtite, which means that after electricity is applied, Fe 3+ Direct mineralization; Fe 2+ It is first oxidized to Fe by O2 and active oxygen species produced by the anode. 3+ The Gibbs energy is released during the oxidation process, and then this part of Gibbs energy and electrical energy are used to overcome the hydrolysis mineralization energy barrier and The coprecipitation forms a Schmidtite. The Schmidtite synthesis method of the present application is applicable to Fe 2+ / Fe 3+ Coexistence is the main 2+ Mainly or Fe 3+ The synthesis of Schreiber mineral in the acid mine drainage simulation fluid mainly composed of Schreiber minerals is aimed at a wider range of actual natural conditions. The pH value of the acid mine drainage simulation fluid is 2.7±0.2. Various metal ions are added to make it closer to the pH value and composition of acid mine drainage in nature.

[0111] The application of the synthesis method of Schroeder mineral in the treatment of acidic mine wastewater is to firstly react TFe and The coprecipitation forms Schmidtite minerals, which are then recovered and treated with lime neutralization. 2+ with Fe 3+ )and The recovery of high concentration TFe and The problem of limiting its stable operation is solved, and the purpose of reducing the amount of lime addition and neutralization slag is achieved.

[0112] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for synthesizing a Schmidt mineral, characterized in that: The following steps are involved: Using a titanium ruthenium iridium electrode as an anode and a platinum sheet as a cathode, inserting the positive and negative electrodes into acidic wastewater for electrochemical synthesis, keeping the pH value constant during the synthesis process, the pH value of the acidic wastewater being 2.5 to 3.5, and obtaining a suspension containing brown-red solid Schroeder mineral; The suspension is filtered to obtain a brown-red solid Schmidt mineral and a filtrate, and the brown-red solid Schmidt mineral is washed and freeze-dried to obtain a Schmidt mineral; The acidic wastewater contains TFe and SO 2 4 - , the TFe is Fe 2+ and / or Fe 3+ .

2. The method for synthesizing a Schmidt mineral according to claim 1, characterized in that: The concentration of TFe is 500mg / L to 1000mg / L, and the SO 2 4 - The concentration is 6000mg / L~8000mg / L.

3. The method for synthesizing a Schmidt mineral according to claim 2, characterized in that: The pH value of the acidic wastewater is adjusted by using a H2SO4 solution with a concentration of 1 mol / L to 4 mol / L and / or a NaOH solution with a concentration of 1 mol / L to 5 mol / L.

4. The method for synthesizing a Schmidt mineral according to claim 1, characterized in that: The voltage used in the electrochemical synthesis is 5V to 10V and the time is 4h to 6h.

5. The method for synthesizing a Schmidt mineral according to claim 4, characterized in that: During the electrochemical synthesis, the pH of the acidic wastewater is maintained at 2.5-3.5 by adding alkaline solution and / or calcium carbonate powder.

6. The method for synthesizing a Schmidt mineral according to claim 1, characterized in that: The electrochemical synthesis process is stirred at a speed of 100 r / min to 300 r / min.

7. A method for synthesizing a Schmidtite mineral according to any one of claims 1 to 6, characterized in that: The acidic wastewater also contains heavy metal ions Cu 2+ , Mn 2+ 、Al 3+ Mg 2+ and / or Zn 2+ One or more of .

8. A Schmidtite mineral, characterized in that: The compound is prepared by the synthesis method according to any one of claims 1 to 7.

9. Application of the method for synthesizing the Schmidtite according to any one of claims 1 to 7, characterized in that: The synthesis method is applied to the treatment of acid mine wastewater.

10. The use of the method for synthesizing Schmidtite according to claim 9, characterized in that: The filtrate is stirred and lime is added for neutralization to obtain a solution with a neutral pH. The amount of lime added is 0.09 g / 150 mL to 0.11 g / 150 mL.

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