Method for treating pyrophosphate heavy metal wastewater and application thereof

Abstract

The present application relates to the technical field of pyrophosphate heavy metal treatment, and discloses a treatment method for pyrophosphate heavy metal wastewater and application thereof, the treatment method for pyrophosphate heavy metal wastewater comprises the following steps: adding waste manganese slag into the pyrophosphate heavy metal wastewater, adding a hydrolysis agent, fully reacting, and obtaining a mixed solution; the hydrolysis agent comprises at least one of potassium peroxymonosulfate, potassium persulfate, potassium sulfite, hydrogen peroxide and peroxyacetic acid. Wherein, the waste manganese slag serves as a reaction carrier, provides a catalytic surface and an adsorption site for degradation of pyrophosphate heavy metal complexes; the hydrolysis agent is activated under the catalysis of the manganese slag, attacks the pyrophosphate P-O-P bond to hydrolyze into orthophosphate, simultaneously destroys the metal complex structure, releases metal ions, and subsequently adds iron salt for co-precipitation, thereby breaking through the problems of slow treatment and low efficiency of traditional treatment methods for stable complexes.

Description

Technical Field

[0001] This invention relates to the field of pyrophosphate heavy metal wastewater treatment, specifically to a method for treating pyrophosphate heavy metal wastewater and its application. Background Technology

[0002] In the electroplating process, pyrophosphate (P2O7) 4- Due to its excellent complexing and buffering properties, pyrophosphate is widely used in printed circuit board electroplating processes to replace highly toxic cyanide electroplating processes, such as copper pyrophosphate, nickel pyrophosphate, and zinc pyrophosphate. Pyrophosphate ions can form stable complexes with metal ions, ensuring the stability of metal ions in the electroplating solution and preventing rapid precipitation or hydrolysis, resulting in thick and dense plating layers. Wastewater generated from pyrophosphate electroplating mainly includes rinsing wastewater from the plated parts and electroplating wastewater. The main components of the electroplating wastewater are potassium pyrophosphate and pyrophosphate-heavy metal complexes, and the presence of potassium pyrophosphate significantly improves the solubility of these complexes in the wastewater.

[0003] Pyrophosphate-heavy metal complexes are relatively stable under neutral and alkaline conditions; for example, the instability constant of copper pyrophosphate is approximately 10. -9 Under conventional treatment methods, copper pyrophosphate is not easily decomposed, resulting in the concentration of heavy metals in the effluent failing to meet standards. In addition, the use of large amounts of pyrophosphate in the electroplating process leads to extremely high concentrations of total phosphorus in the wastewater, posing a double challenge to wastewater treatment.

[0004] Currently, the mainstream methods mainly rely on alkali precipitation, oxidation, ferrous reduction, and induced precipitation to treat pyrophosphate heavy metal complex wastewater.

[0005] Traditional alkali precipitation methods mainly rely on the reaction of heavy metal ions with hydroxide ions to form hydroxide precipitates. However, they are extremely inefficient at removing metal ions in the stable complex state of pyrophosphate, making effective removal difficult.

[0006] Oxidation methods, such as the Fenton process and ozone method, are primarily effective against organic-heavy metal complexes. They utilize reactive species like hydroxyl radicals and ozone to disrupt the organic chelate bonds in organic complexing agents (such as EDTA and citric acid). However, oxidation methods are not significantly effective against inorganic-heavy metal complexes, such as pyrophosphate-heavy metal complexes. The oxidizing agents in oxidation methods cannot destroy the POP structure in pyrophosphate.

[0007] The main mechanism of ferrous reduction is through Fe 2+ The reducing effect reduces heavy metals, breaking down their complex structures, while simultaneously causing heavy metals to co-precipitate with Fe(OH)3; iron ions can also be removed by forming ferric pyrophosphate precipitate with pyrophosphate. However, due to the solubility product of ferric pyrophosphate precipitate being 2 × 10⁻⁶...-13 It has a relatively large solubility, while the solubility product of ferric phosphate precipitate is approximately 1.3 × 10⁻⁶. -22 Ferrous phosphorus has low solubility and is easier to separate and remove. Therefore, the removal effect of total phosphorus in pyrophosphate wastewater by the ferrous reduction method is usually not ideal, and it is easy to lead to a high residual concentration of total phosphorus.

[0008] Currently, based on the tendency of dissolved copper pyrophosphate to precipitate, some researchers have proposed inducing the gradual conversion of dissolved copper pyrophosphate complexes into insoluble copper pyrophosphate precipitates by adding excess divalent copper salts (CN104108812A) or mixing in discarded copper-containing wastewater (CN109354259A) to copper pyrophosphate wastewater. The removal efficiency can then be optimized by adjusting the pH, and excess copper ions can be recovered subsequently through solid-liquid separation or iron powder replacement. However, this method requires precise control of the copper salt dosage. Improper dosage can easily lead to an increase in the concentration of free copper ions in the wastewater, increasing the burden on subsequent treatment and potentially causing secondary copper pollution. Summary of the Invention

[0009] This invention provides a method for treating pyrophosphate heavy metal wastewater and its application, in order to solve the problems of incomplete removal of total phosphorus and the high stability of pyrophosphate-heavy metal complexes in pyrophosphate heavy metal wastewater, making it difficult to break down and remove the complexes.

[0010] In a first aspect, the present invention provides a method for treating pyrophosphate heavy metal wastewater, comprising the following steps:

[0011] Waste manganese slag was added to pyrophosphate heavy metal wastewater, followed by the addition of a hydrolyzing agent. The mixture was allowed to react fully to obtain a mixed solution. Iron salt was then added to the mixed solution to adjust the pH, causing precipitation and solid-liquid separation.

[0012] The hydrolysing agent includes at least one of potassium peroxymonosulfate (KHSO5), potassium persulfate (K2S2O6), potassium sulfite (K2SO3), hydrogen peroxide (H2O2), and peracetic acid (C2H4O3).

[0013] In one optional embodiment, the waste manganese slag includes at least one of manganese dioxide (MnO2), manganese tetroxide (Mn3O4), manganese trioxide (Mn2O3), and manganese oxide (MnO);

[0014] And / or, the particle size of the waste manganese slag is 0.5 to 5 mm;

[0015] And / or, the manganese content in the waste manganese slag is 30wt% to 50wt%.

[0016] In one optional embodiment, the iron salt includes at least one of ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), and ferric nitrate (Fe(NO3)3);

[0017] In one alternative implementation, the pH is adjusted to 7-8;

[0018] In one optional embodiment, the solid-liquid separation method includes any one of gravity sedimentation, plate and frame filtration, centrifugal separation, membrane separation, and adsorption.

[0019] In one optional embodiment, before adding the waste manganese slag, the step of adjusting the pH of the pyrophosphate heavy metal wastewater to 1-11 is further included.

[0020] Furthermore, the pH of the pyrophosphate heavy metal wastewater can be adjusted to any one of the following values ​​or a range between any two values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 6.5, 7, 8, 9, 9.5, 10, and 11.

[0021] And / or, the concentration of pyrophosphate in the pyrophosphate heavy metal wastewater is 0.1–1 mM;

[0022] Furthermore, the concentration of pyrophosphate can be any one of the following values ​​or a range between any two values: 0.1, 0.13, 0.15, 0.2, 0.26, 0.28, 0.3, 0.36, 0.4, 0.45, 0.48, 0.5, 0.55, 0.6, 0.7, 0.75, 0.77, 0.8, 0.88, 0.9, 0.93, and 1 mM.

[0023] And / or, the pyrophosphate heavy metal wastewater includes, but is not limited to, at least one of copper pyrophosphate, nickel pyrophosphate, and zinc pyrophosphate.

[0024] In one optional embodiment, the reaction conditions are: temperature 20~25°C, time 1~24h;

[0025] Furthermore, the temperature can be any one of the following values ​​or a range between any two values: 20, 20.3, 20.6, 20.8, 21, 21.5, 21.9, 22, 22.5, 23, 23.5, 24, 24.3, 24.6, and 25°C.

[0026] Furthermore, the time can be any one of the following values: 1, 1.5, 3, 7, 8, 10, 12, 15, 18, 20, 22, 24h, or a range between any two values.

[0027] In one optional embodiment, the amount of waste manganese slag added is 0.5 to 4 g / L.

[0028] In one optional embodiment, the amount of the hydrolysant added is 1 to 10 mM.

[0029] In one optional embodiment, the amount of iron salt added is 1 to 5 mM.

[0030] Secondly, the present invention provides the application of the above-described method for treating pyrophosphate heavy metal wastewater in wastewater treatment.

[0031] The technical solution of this invention has the following advantages:

[0032] 1. The present invention provides a method for treating pyrophosphate heavy metal wastewater, comprising the following steps:

[0033] Waste manganese slag is added to pyrophosphate heavy metal wastewater, followed by the addition of a hydrolyzing agent. The mixture is allowed to react fully to obtain a mixed solution. The hydrolyzing agent includes at least one of potassium peroxymonosulfate (KHSO5), potassium persulfate (K2S2O6), potassium sulfite (K2SO3), hydrogen peroxide (H2O2), and peracetic acid (C2H4O3).

[0034] This method utilizes waste manganese slag for the treatment of pyrophosphate heavy metal wastewater, including complex breaking, phosphorus removal, and heavy metal removal. The waste manganese slag, containing active manganese oxides, serves as a reaction carrier, providing a catalytic surface and adsorption sites for the efficient degradation of pyrophosphate-heavy metal complexes. A hydrolyzing agent is added to promote rapid hydrolysis of pyrophosphate. Activated by the manganese slag catalysis, the hydrolyzing agent attacks the POP bonds of pyrophosphate ions, converting them into orthophosphate ions. Simultaneously, it disrupts the metal complex structure, releasing metal ions. This overcomes the slow and inefficient treatment of stable complexes by traditional methods. After the reaction is complete, iron salts are added to further remove phosphorus and heavy metals through co-precipitation, resulting in a relatively small amount of sludge produced, which is beneficial for subsequent treatment.

[0035] 2. The method for treating pyrophosphate heavy metal wastewater provided by this invention employs a mechanism of "hydrolyzing agent + manganese slag synergistic catalysis + iron salt precipitation" to treat pyrophosphate heavy metal wastewater. Due to the activation of the hydrolyzing agent, Mn(IV) on the surface of manganese slag is converted into Mn(III) intermediates, and ≡Mn(III) sites can selectively complex heavy metal-pyrophosphate ions. Because it is necessary to maintain the balance of surface charge, the formation of Mn(III) intermediates will simultaneously create a large number of oxygen vacancies on the surface of manganese slag. This not only reduces the stability of POP bonds by changing the electronic structure of surface active sites, but also promotes the formation of a large number of Lewis acid sites on the Mn surface, adsorbing more water molecules and surface hydroxyl groups (≡Mn-OH). The abundant water molecules and hydroxyl groups at the manganese slag interface act as nucleophiles, attacking the pyrophosphate groups complexed at nearby Mn(III) sites, leading to the breakage of POP bonds and hydrolysis into two orthophosphate ions;

[0036] Furthermore, the addition of ferric salts, through the co-precipitation of iron with phosphorus and heavy metals, further achieves deep removal, effectively removing total phosphorus and pyrophosphate heavy metal complexes from the pyrophosphate heavy metal wastewater.

[0037] Furthermore, this invention utilizes smelting waste manganese slag containing manganese oxides as a reaction carrier, eliminating the need for additional high-cost materials and achieving the resource utilization of waste. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 This is a process flow diagram of the present invention for treating pyrophosphate heavy metal wastewater;

[0040] Figure 2 This refers to the amount of orthophosphate released in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of Test Example 1 of this invention;

[0041] Figure 3 This refers to the change in orthophosphate concentration over 24 hours in Examples 1, 2, and 3 of Test Example 1 of this invention;

[0042] Figure 4 This refers to the change in orthophosphate concentration over 24 hours in Examples 1, 4, 5, and 6 of Test Example 1 of this invention.

[0043] Figure 5This refers to the change in orthophosphate concentration over 24 hours in Examples 1, 7, and 8 of Test Example 1 of this invention. Detailed Implementation

[0044] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0045] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0046] To address the problems existing in the aforementioned related technologies, according to a first aspect of the present invention, a method for treating pyrophosphate heavy metal wastewater is provided, comprising the following steps, the process flow diagram of which is shown below. Figure 1 As shown:

[0047] S1. Pyrophosphate heavy metal wastewater is introduced into a reaction vessel containing waste manganese slag. The pH is adjusted or not, a hydrolysis agent is added, and the reaction is allowed to proceed fully to obtain a mixed solution.

[0048] S2. Pass the mixed solution into the deep treatment tank, add iron salt, adjust the pH to 7-8, precipitate, and separate the solid and liquid.

[0049] The waste manganese slag includes at least one of manganese dioxide (MnO2), manganese tetroxide (Mn3O4), manganese trioxide (Mn2O3), and manganese oxide (MnO); wherein the manganese content is 30wt% to 50wt%; and the particle size is 0.5 to 5mm.

[0050] The hydrolyzing agent includes at least one of potassium peroxymonosulfate (KHSO5), potassium persulfate (K2S2O6), potassium sulfite (K2SO3), hydrogen peroxide (H2O2), and peracetic acid (C2H4O3);

[0051] The preferred hydrolysing agent is potassium peroxymonosulfate (KHSO5), which can increase the Lewis acid sites on the surface of waste manganese slag and promote the hydrolysis of pyrophosphate to orthophosphate.

[0052] The iron salt includes at least one of ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), and ferric nitrate (Fe(NO3)3).

[0053] Adjust the pH of pyrophosphate heavy metal wastewater to 1–11;

[0054] The concentration of pyrophosphate in the pyrophosphate heavy metal wastewater is 0.1–1 mM; the wastewater includes, but is not limited to, at least one of copper pyrophosphate, nickel pyrophosphate, and zinc pyrophosphate.

[0055] In step S1, the amount of waste manganese slag added is 0.5-4 g / L;

[0056] In step S1, the amount of hydrolysant added is 1-10 mM;

[0057] In step S1, the reaction conditions are: temperature 20~25℃, time 1~24h;

[0058] In step S2, the amount of iron salt added is 1-5 mM;

[0059] In step S2, the solid-liquid separation method includes any one of gravity sedimentation, plate and frame filtration, centrifugal separation, membrane separation, and adsorption.

[0060] Secondly, the present invention provides an application of the treatment method for pyrophosphate heavy metal wastewater described in the first aspect in wastewater treatment.

[0061] The waste manganese slag used in the embodiments and comparative examples of this application mainly comes from electrolytic manganese slag, purchased from a manganese smelter, and its main components include manganese dioxide (MnO2), manganese tetroxide (M3O4), manganese oxide (MnO), and manganese trioxide (Mn2O3); the manganese content in this waste manganese slag is 46.43 wt%.

[0062] The wastewater containing pyrophosphate heavy metals in the following examples and comparative examples comes from simulated wastewater prepared in the laboratory. The pH of the simulated wastewater is 9, which is consistent with the pH of conventional wastewater containing pyrophosphate heavy metals. The pH of the simulated wastewater is adjusted by adding a certain amount of sulfuric acid or sodium hydroxide.

[0063] Example 1

[0064] This embodiment provides a method for treating pyrophosphate heavy metal wastewater, including the following steps:

[0065] (1) Add waste manganese slag to the wastewater containing copper pyrophosphate at a dosage of 2 g / L, and add potassium persulfate (KHSO5) hydrolysant to make the concentration of potassium persulfate (KHSO5) in the system 1 mM.

[0066] The concentration of pyrophosphate in the wastewater was 0.48 mM, the concentration of total copper was 0.48 mM, and the pH was 9.

[0067] (2) The wastewater is continuously circulated, allowing the waste manganese slag, hydrolysate and pyrophosphate-heavy metal complex in the wastewater to react fully at 24°C for 24 hours to obtain a mixed solution;

[0068] (3) Pass the mixed solution into the deep treatment tank, add ferric chloride to make the concentration of ferric chloride in the system 1mM, adjust the pH to 7-8, and after half an hour of coagulation and sedimentation, separate the solid and liquid by gravity sedimentation to obtain the supernatant and precipitate.

[0069] Example 2

[0070] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), the concentration of pyrophosphate in the wastewater is 0.48 mM, the concentration of total copper is 0.48 mM, and the pH of the wastewater is adjusted to 4.

[0071] Example 3

[0072] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), the concentration of pyrophosphate in the wastewater is 0.48 mM, the concentration of total copper is 0.48 mM, and the pH of the wastewater is adjusted to 7.

[0073] Example 4

[0074] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), waste manganese slag is added to the wastewater containing copper pyrophosphate at a dosage of 0.5 g / L.

[0075] Example 5

[0076] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), waste manganese slag is added to the wastewater containing copper pyrophosphate at a dosage of 1 g / L.

[0077] Example 6

[0078] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), waste manganese slag is added to the wastewater containing copper pyrophosphate at a dosage of 4 g / L.

[0079] Example 7

[0080] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), the concentration of potassium persulfate (KHSO5) in the system is 5 mM.

[0081] Example 8

[0082] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in Embodiment 1, except that in step (1), the concentration of potassium persulfate (KHSO5) in the system is 10 mM.

[0083] Example 9

[0084] This embodiment provides a method for treating pyrophosphate heavy metal wastewater, the specific steps of which are as follows:

[0085] (1) Add waste manganese slag to wastewater containing copper pyrophosphate and zinc pyrophosphate at a dosage of 2 g / L, and add potassium persulfate (K2S2O6) hydrolysant to make the concentration of potassium persulfate (K2S2O6) in the system 1 mM;

[0086] The wastewater contained 1 mM of pyrophosphate, 0.5 mM of total copper, 0.5 mM of total zinc, and had a pH of 4.

[0087] (2) The wastewater is continuously circulated, allowing the waste manganese slag, hydrolysate and pyrophosphate-heavy metal complex in the wastewater to react fully at 20°C for 24 hours to obtain a mixed solution;

[0088] (3) Pass the mixed solution into the deep treatment tank, add ferric sulfate (Fe2(SO4)3) to make the concentration of ferric sulfate (Fe2(SO4)3) in the system 5mM, adjust the pH to 7-8, and after half an hour of coagulation and precipitation, separate the solid and liquid to obtain the supernatant and precipitate.

[0089] Example 10

[0090] This embodiment provides a method for treating pyrophosphate heavy metal wastewater, the specific steps of which are as follows:

[0091] (1) Add waste manganese slag to wastewater containing copper pyrophosphate and nickel pyrophosphate at a dosage of 3 g / L, and add hydrogen peroxide (H2O2) hydrolysant to make the concentration of hydrogen peroxide (H2O2) in the system 1 mM;

[0092] The wastewater had a pyrophosphate concentration of 1 mM, a total copper concentration of 0.5 mM, a total nickel concentration of 0.5 mM, and a pH of 4.

[0093] (2) The wastewater is continuously circulated, allowing the waste manganese slag, hydrolysate and pyrophosphate-heavy metal complex in the wastewater to react fully at 25°C for 24 hours to obtain a mixed solution;

[0094] (3) Pass the mixed solution into the deep treatment tank, add ferric nitrate (Fe(NO3)3) to make the concentration of ferric nitrate (Fe(NO3)3) in the system 5mM, adjust the pH to 7-8, and after half an hour of coagulation and precipitation, separate the solid and liquid to obtain the supernatant and precipitate.

[0095] Example 11

[0096] This embodiment provides a method for treating pyrophosphate heavy metal wastewater, the specific steps of which are as follows:

[0097] (1) Add waste manganese slag to wastewater containing copper pyrophosphate, nickel pyrophosphate and zinc pyrophosphate at a dosage of 3 g / L, and add peracetic acid (C2H4O3) hydrolysant to make the concentration of peracetic acid (C2H4O3) in the system 1 mM;

[0098] The wastewater contained 0.6 mM pyrophosphate, 0.2 mM total copper, 0.2 mM total nickel, 0.2 mM total zinc, and had a pH of 4.

[0099] (2) The wastewater is continuously circulated to allow the waste manganese slag, hydrolysing agent and pyrophosphate-heavy metal complex in the wastewater to react fully for 24 hours to obtain a mixed solution;

[0100] (3) Pass the mixed solution into the deep treatment tank, add ferric chloride (FeCl3) and ferric sulfate (Fe2(SO4)3) to make the concentration of ferric chloride (FeCl3) in the system 2mM and the concentration of ferric sulfate (Fe2(SO4)3) 3mM. Adjust the pH to 7-8, and after half an hour of coagulation and sedimentation, separate the solid and liquid to obtain the supernatant and precipitate.

[0101] Example 12

[0102] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 2, except that in step (1), potassium peroxymonosulfate (KHSO5) is replaced with potassium sulfite (K2SO3) so that the concentration of potassium sulfite (K2SO3) in the system is 1mM.

[0103] Example 13

[0104] This embodiment provides a method for treating pyrophosphate heavy metal wastewater, including the following steps:

[0105] (1) Add waste manganese slag to the wastewater containing copper pyrophosphate at a dosage of 4 g / L, and add potassium persulfate (KHSO5) hydrolysant to make the concentration of potassium persulfate (KHSO5) in the system 1 mM.

[0106] The concentration of pyrophosphate in the wastewater was 0.48 mM, the concentration of total copper was 0.48 mM, and the pH was adjusted to 7.

[0107] (2) The wastewater is continuously circulated to allow the waste manganese slag, hydrolysing agent and pyrophosphate-heavy metal complex in the wastewater to react fully for 24 hours to obtain a mixed solution;

[0108] (3) Pass the mixed solution into the deep treatment tank, add ferric chloride to make the concentration of ferric chloride in the system 1mM, adjust the pH to 7-8, and after half an hour of coagulation and sedimentation, separate the solid and liquid to obtain the supernatant and precipitate.

[0109] Example 14

[0110] This embodiment provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in embodiment 1, except that in step (1), the concentration of pyrophosphate in the wastewater is 0.48 mM, the concentration of total copper is 0.48 mM, and the pH of the wastewater is adjusted to 11.

[0111] Comparative Example 1

[0112] This comparative example provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in Example 1, except that in step (1), waste manganese slag is added to the wastewater containing copper pyrophosphate at a dosage of 0 g / L.

[0113] Comparative Example 2

[0114] This comparative example provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in Example 1, except that in step (1), the concentration of potassium persulfate (KHSO5) in the system is 0 mM.

[0115] Comparative Example 3

[0116] This comparative example provides a method for treating pyrophosphate heavy metal wastewater. The specific steps are the same as in Example 1, except that in step (1), waste manganese slag is added to the wastewater containing copper pyrophosphate at a dosage of 0 g / L, and the concentration of potassium persulfate (KHSO5) in the system is 0 mM.

[0117] Test Example 1

[0118] In step (2) of the examples and comparative examples, the concentration of orthophosphate in the wastewater was determined by molybdate spectrophotometry during the 24-hour reaction; the results are shown in Table 1.

[0119] Table 1. Concentration of orthophosphate during the 24-hour reaction in the examples and comparative examples (unit: mM).

[0120]

[0121] According to Table 1 and Figure 2 As shown, after 24 hours of treatment, under the conditions of adding 1 mM potassium persulfate (KHSO5) hydrolysant and 2 g / L waste manganese slag (Example 1), the conversion rate of pyrophosphate to orthophosphate reached about 42%, with only about 18% of the total phosphorus remaining as pyrophosphate. About 40% of the total phosphorus was adsorbed by the manganese slag. The pyrophosphate hydrolysis rate under other conditions did not exceed 3%. However, Comparative Examples 1-3 showed that when only manganese slag, only hydrolysant, or neither was added, the pyrophosphate in the system could only be converted to orthophosphate through natural hydrolysis, which was extremely inefficient and could not be used for subsequent iron salt precipitation.

[0122] According to Table 1 and Figure 3 As shown, after 24 hours of treatment, under the conditions of adding 1 mM potassium persulfate (KHSO5) and 2 g / L waste manganese slag, the highest conversion rate of pyrophosphate to orthophosphate was achieved at pH 7, reaching approximately 63%, with only about 2% of the total phosphorus remaining as pyrophosphate, and about 35% of the total phosphorus being adsorbed by the manganese slag (Example 3). At pH 4, the pyrophosphate hydrolysis rate was the fastest, but it reached its maximum value after 2 hours (Example 2). This is because the adsorption capacity of manganese oxides under acidic conditions quickly saturates, and the catalyst cannot desorb quickly. Therefore, although the hydrolysis rate is fast at pH 4, premature saturation limits the final conversion rate of orthophosphate. At pH 9, the pyrophosphate... The conversion rate of pyrophosphate to orthophosphate was approximately 42% (Example 1); at pH 11, the conversion rate of pyrophosphate to orthophosphate was approximately 27% (Example 14); considering practical process applications, adjusting the pH to 7 at a wastewater pH of 9 or with a small amount of sulfuric acid is a preferred, lower-cost, and relatively economical option at this stage; while maintaining the original wastewater pH, manganese oxide was used as a catalyst, and a hydrolyzing agent was added to promote the formation of intermediates such as ≡Mn(III), oxygen vacancies, and ≡Mn-OH at the interface, which triggered the breakage of the POP bond of pyrophosphate, causing it to be rapidly converted to orthophosphate, thereby inducing the decomposition of the pyrophosphate-heavy metal complex, and the total phosphorus and heavy metals in the system were removed by coagulation and precipitation in the subsequent deep treatment process.

[0123] According to Table 1 and Figure 4 As shown, after 24 hours of treatment, under the condition of adding 4 g / L of waste manganese slag, the conversion rate of pyrophosphate to orthophosphate was the highest, reaching about 94%, with only about 1% of the total phosphorus remaining as pyrophosphate and about 5% of the total phosphorus being adsorbed by the manganese slag (Example 6); under the condition of adding 0.5 g / L of waste manganese slag, the hydrolysis rate of pyrophosphate was the slowest, with a conversion rate of only 17% (Example 4).

[0124] According to Table 1 and Figure 5As shown, after 24 hours of treatment, the highest conversion rate of pyrophosphate to orthophosphate was achieved when 1 mM potassium persulfate (KHSO5) was added, reaching approximately 42%, with only about 18% of the total phosphorus remaining as pyrophosphate and about 40% of the total phosphorus being adsorbed by manganese slag (Example 1). Under the condition of 10 mM potassium persulfate (KHSO5), the hydrolysis rate of pyrophosphate was the slowest, with a conversion rate of approximately 17% (Example 8). This was because the addition of a large amount of persulfate hydrolysate agent lowered the pH of the solution, enhanced the adsorption capacity of the manganese slag, and affected the conversion rate of pyrophosphate.

[0125] Examples 9-12 used waste manganese slag in conjunction with different types of hydrolysants to treat pyrophosphate heavy metal complex wastewater. Among them, potassium persulfate (K2S2O6) and potassium sulfite (K2SO3) hydrolysants had high conversion efficiency of pyrophosphate, while hydrogen peroxide (H2O2) and peracetic acid (C2H4O3) had low conversion efficiency.

[0126] Test Example 2

[0127] In the examples and comparative examples, the supernatant obtained in step (3) was used to determine the removal effect of heavy metals and total phosphorus in the pyrophosphate heavy metal complex wastewater; the concentrations of total phosphorus, total copper, total zinc and total nickel in the supernatant were tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0128] The results are shown in Table 2.

[0129] Table 2. Effluent concentrations of pyrophosphate heavy metal complexes in the examples and comparative examples (unit: mg / L)

[0130]

[0131] In Example 1, the dosage of manganese slag was 2 g / L, the dosage of hydrolysing agent potassium peroxymonosulfate (KHSO5) was 1 mM, the pH of the wastewater was 9, the total phosphorus concentration in the effluent was 0.44 mg / L, and the total copper concentration was 0.31 mg / L, all of which met the discharge standards of the municipal wastewater treatment plant.

[0132] In Examples 2 and 3, the pH of the wastewater was adjusted to 4 and 7, respectively. The removal rates of total phosphorus and total copper were better than those under the condition of pH 9. The main reason is that the adsorption of manganese oxides in manganese slag was enhanced, but the pH of the influent needs to be changed.

[0133] In Examples 1 and 4-6, the dosage of manganese slag was different, and the removal rates of total phosphorus and total copper increased with the increase of the dosage of manganese slag. This is because a higher dosage of manganese slag can provide more surface sites to combine with hydrolysing agents and pyrophosphate-heavy metal complexes, promoting the formation of intermediates such as interface ≡Mn(III), oxygen vacancies and ≡Mn-OH, which triggers the breaking and hydrolysis of POP bonds of pyrophosphate.

[0134] In Examples 1, 7, and 8, the dosage of potassium peroxymonosulfate (KHSO5) was different, resulting in different removal effects of total phosphorus and total copper. This is because excessive hydrolysate adsorbed on the surface of manganese slag, reducing the outer layer adsorption of pyrophosphate-heavy metal complex and decreasing the conversion rate of hydrolysis.

[0135] Examples 9-12 show the treatment of wastewater containing complex pyrophosphate heavy metal complexes. It can be seen that waste manganese slag, in combination with different hydrolyzing agents and coupled with iron salt coagulation for deep treatment, can also achieve different degrees of hydrolysis and removal of different pyrophosphate heavy metal complexes.

[0136] Overall, the removal efficiency of total phosphorus and heavy metals is significantly correlated with the hydrolysis efficiency of pyrophosphate in the pretreatment process.

[0137] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for treating pyrophosphate heavy metal wastewater, characterized in that, Includes the following steps: Adjust the pH of the pyrophosphate heavy metal wastewater to 1-11, add waste manganese slag to the pyrophosphate heavy metal wastewater, add a hydrolysant, and allow it to react fully to obtain a mixed solution. The hydrolysant is activated under the catalysis of manganese slag, hydrolyzing pyrophosphate into orthophosphate, while destroying the metal complex structure and releasing metal ions. Add iron salt to the mixed solution, adjust the pH, precipitate, and separate the solid and liquid phases; The hydrolyzing agent includes any one of potassium persulfate, potassium persulfate, potassium sulfite, hydrogen peroxide, and peracetic acid; The waste manganese slag includes at least one of manganese dioxide, manganese tetroxide, manganese trioxide, and manganese oxide.

2. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The particle size of the waste manganese slag is 0.5–5 mm; And / or, the manganese content in the waste manganese slag is 30wt% to 50wt%.

3. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The iron salt includes at least one of ferric chloride, ferric sulfate, and ferric nitrate; And / or, the pH is adjusted to 7-8; And / or, the solid-liquid separation method includes any one of gravity sedimentation, plate and frame filtration, centrifugal separation, membrane separation, and adsorption.

4. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The concentration of pyrophosphate in the pyrophosphate heavy metal wastewater is 0.1–1 mM; And / or, the pyrophosphate heavy metal wastewater includes at least one of copper pyrophosphate, nickel pyrophosphate, and zinc pyrophosphate.

5. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The reaction conditions are: temperature 20~25℃, time 1~24h.

6. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The amount of waste manganese slag added is 0.5–4 g / L.

7. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The dosage of the hydrolysing agent is 1–10 mM.

8. The method for treating pyrophosphate heavy metal wastewater according to claim 1, characterized in that, The amount of iron salt added is 1-5 mM.

9. The application of the method for treating pyrophosphate heavy metal wastewater according to any one of claims 1-8 in wastewater treatment.

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