A complexing inhibitor for inhibiting redissolution of heavy metal sulfides, and a preparation method and application thereof

Abstract

The application discloses a complexing inhibitor for inhibiting resolubilization of heavy metal sulfide and a preparation method and application thereof. The complexing inhibitor is compounded by three types of components, component A is a metal salt, component B is an organic sulfur agent, and component C is an organic non-sulfur agent, wherein the mass ratio of the component A, the component B and the component C ranges from (1-2):(1-3):(2-6); the component B is at least one selected from a dithiocarbamate, a mercaptobenzothiazole or sodium dimethyl dithiocarbamate; and the component C is at least one selected from chitosan, polyethylene imine or hydroxyethylidene diphosphonic acid. The inhibitor is especially suitable for preventing complexing and dissolution of precipitated heavy metal sulfide by excessive sulfur ions in industrial wastewater treatment, and effectively controlling the concentration rebound of heavy metal ions.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a complexation inhibitor that effectively inhibits the redissolution of heavy metal sulfides during wastewater treatment and its preparation method. Background Technology

[0002] With the acceleration of industrialization, the total amount of heavy metal wastewater discharged from industries such as electroplating, mining, smelting, and chemicals continues to rise, making heavy metal pollution a serious challenge for industrial wastewater treatment. This type of wastewater is enriched with high concentrations of toxic heavy metal ions such as Hg, Pb, Cd, Cu, and Cr. These ions are non-biodegradable, highly mobile, and bioaccumulative, leading to the transfer of pollutants through the water-soil-food chain, ultimately threatening human health. Therefore, developing efficient heavy metal removal technologies has become an urgent need in the field of environmental governance.

[0003] Currently, the main methods for treating heavy metals in industrial wastewater include electrochemical treatment, ion exchange, membrane separation, adsorption, and biological methods. However, these technologies all have significant shortcomings. While electrochemical treatment is widely used in mining wastewater treatment, its high equipment investment and energy consumption limit its widespread application. Ion exchange removes pollutants by exchanging metal ions with resin, but resins are easily saturated, and complex water environments can cause pollution, leading to increased operating costs. Membrane separation technology uses external pressure and membrane selectivity for separation, purification, and concentration. Although it has good treatment effects, membrane materials are prone to scaling and clogging, resulting in a short lifespan, and membrane separation equipment has relatively high energy consumption. Furthermore, the high-concentration membrane concentrate produced after treatment still requires further treatment and disposal. Adsorption uses adsorbents to physically or chemically adsorb and remove multiple pollutants from wastewater. Although it is highly efficient, the selection of adsorbents is complex and regeneration is difficult. Biological methods utilize microorganisms or plants to adsorb or transform heavy metal ions, offering advantages such as environmental friendliness and ease of operation. However, it requires high-level strain selection, has high treatment costs, and low removal efficiency.

[0004] Among numerous treatment methods, sulfide precipitation is widely used in wastewater treatment in industries such as mining, metallurgy, electroplating, and battery manufacturing due to its high efficiency, relatively low cost, and ability to treat various heavy metals. Its basic principle is to add sulfiding agents such as Na₂S and H₂S, causing heavy metal ions to react with sulfur ions to form extremely insoluble heavy metal sulfides, thereby achieving heavy metal removal. However, this method has a significant common problem in practical applications: excess sulfur ions can react with the already formed metal sulfide precipitates to form soluble thiocomplexes, leading to the redissolution of heavy metals and a rebound in effluent concentration. This phenomenon is particularly prominent when excessive amounts of sulfiding agents are added to ensure treatment effectiveness.

[0005] Chinese patent application CN116693115A discloses a method for treating mercury-containing wastewater. The method involves adjusting the pH of the wastewater to 8.5-9.0, then adding a sulfiding agent (Na2S / NaHS), a composite additive (iron:sulfur:silicon:aluminum:carbon = 1:(0.5-1):(0.0005-0.001):(0.0003-0.0006):(5-10)), and a flocculant to form HgS precipitate. Mercury is then removed through multi-stage filtration and adsorption. However, this invention requires multiple steps, including sand filtration, security filtration, and resin adsorption, resulting in high process redundancy and a narrow pH range of applicability. Chinese patent application CN119977120A discloses a compound heavy metal chelating agent. This chelating agent requires the synthesis of N-dithiocarboxy-aminophenylcarboxylic acid from CS2 via a dropwise addition method. This N-dithiocarboxy-aminophenylcarboxylic acid is then compounded with cyclohexyl-3,5-diene-1,2-dicarboxylic acid and propionic acid at a mass ratio of (4-5):2:1. It has been reported to stably chelate mercury ions. Experimental results show that after adding 10 g / L of this chelating agent to 100 mg / L mercury-containing wastewater, the residual mercury concentration decreased to 0.28 mg / L, and the formed chelate did not dissociate within 30 days. However, this method requires a complex synthesis process for the chelating agent and involves a high dosage, resulting in high treatment costs.

[0006] Therefore, developing a technical means that can block the formation of sulfide complexes from the source, effectively prevent the redissolution of heavy metals, and is also simple to operate, cost-effective, and widely applicable has become a key breakthrough for improving the efficiency of sulfide precipitation and expanding its application scope. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems existing in the prior art and provide a complexation inhibitor for inhibiting the redissolution of heavy metal sulfides and its preparation method, which is particularly suitable for preventing the complexation and dissolution of precipitated heavy metal sulfides by excessive sulfur ions in industrial wastewater treatment and effectively controlling the rebound of heavy metal ion concentration.

[0008] The objective of this invention can be achieved through the following technical solutions: The complexation inhibitor of the present invention is composed of the following three components: component A is a metal salt, component B is an organic sulfur agent, and component C is an organic non-sulfur agent, wherein the mass ratio of component A, component B and component C is (1-2):(1-3):(2-6); component B is selected from at least one of dithiocarbamate, mercaptobenzothiazole or sodium dimethyldithiocarbamate; component C is selected from at least one of chitosan, polyethyleneimine or hydroxyethylidene diphosphonic acid.

[0009] Preferably, component A can be selected from at least one of zinc salt, iron salt, aluminum salt, calcium salt, ferrous salt or magnesium salt, which can ionize into the corresponding metal ions in water.

[0010] More preferably, the preparation method of component A includes: dissolving the salt raw material of component A in deionized water to prepare a solution with a mass fraction of 20-35%, purging with nitrogen for protection, stirring at 100-300 r / min for 40-60 min at 40-60℃, and then spray drying.

[0011] According to a specific embodiment of the present invention, component A is selected from calcium salts or ferrous salts. For example, the calcium salt is CaCl2, and the ferrous salt is ferrous sulfate.

[0012] More preferably, the inlet air temperature of the spray dryer is controlled at 150-170℃, and the outlet air temperature is 70-90℃.

[0013] More preferably, component B is sodium dimethyl dithiocarbamate. A method for preparing sodium dimethyl dithiocarbamate includes: mixing carbon disulfide and dimethylamine in a molar ratio of 1:(1.1-1.5), reacting at 40-50 °C for 2-4 h, adjusting the pH to 10-12 with NaOH, and then crystallizing and drying.

[0014] More preferably, component C is chitosan. Its degree of deacetylation is ≥85%, and its molecular weight is 10000-50000 Da.

[0015] The preparation method of the complexation inhibitor of the present invention includes the following steps: S1: Mix component A and component B at a mass ratio of (1-2):(1-3) and stir at 200-300 r / min for 10-30 min; S2: Add component C, and control the mass ratio of component A:B:C to be (1-2):(1-3):(2-6), and continue stirring for 30-60 minutes; S3: Dry the mixture at 40-60 ℃ for 4-8 h, and then pulverize it through an 80-200 mesh sieve.

[0016] In a preferred embodiment of the present invention, in step S1, the mass ratio of component A to component B is 1:2.

[0017] In a preferred embodiment of the present invention, in step S2, the mass ratio of component A, component B and component C is 1:2:4.

[0018] In a preferred embodiment of the present invention, in step S3, the drying temperature is 50 ± 2 °C.

[0019] The reaction principle of this invention is as follows: The sulfur ion consumption mechanism of component A: Metal ions in component A preferentially react with free sulfur ions to form metal sulfides with extremely low solubility, thus reducing free sulfur ions at the source. 2-Concentration, to block its complexation pathway with target heavy metal sulfides (such as HgS, CdS).

[0020] Heavy metal chelation and fixation of component B: The organosulfur agent of component B captures residual heavy metal ions through high-affinity chelation, forming an insoluble chelated precipitate. Its chelation constant logK > 15, ensuring that the heavy metal ions are firmly fixed. Taking dithiocarbamate as an example, its chelation reaction with heavy metal ions generates a precipitate. Physical barrier construction of component C: Component C binds to heavy metal sulfides through intermolecular hydrogen bonds, forming a dense cross-linked network on the precipitate surface. This coating layer is ≥ 5 nm thick, effectively blocking the diffusion channels of sulfur ions into the interior of the precipitate and completely inhibiting the redissolution reaction. Taking chitosan (polymer-NH2) as an example, the reaction equation is shown below.

[0021] The aforementioned three-tiered synergistic mechanism works together to achieve highly efficient inhibition of heavy metal sulfide redissolution. To quantitatively evaluate the strength of the synergistic effect among components A, B, and C, this invention defines a Synergistic Efficiency Index (SEI) as follows: in The value represents the amount of heavy metal M fixed by the chelation inhibitor, in mg / g. , , These represent the fixed amount of heavy metal M when components A, B, and C are used alone at the same dosage, in mg / g; M represents heavy metals such as Cd, Hg, Pb, Zn, etc.

[0022] The physical meaning of this formula is as follows: if SEI > 1, it indicates that the combined effect is better than the simple sum of the effects of each component used alone, i.e., a synergistic effect exists; if SEI ≤ 1, it indicates that there is no synergistic effect or that there is an antagonistic effect. Within the ratio range of this invention, an SEI greater than 1 proves that a synergistic effect exists.

[0023] Compared with the prior art, the present invention has the following advantages: First, this invention exhibits wider adaptability to various operating conditions and greater stability. Compared to traditional sulfide precipitation methods, which are limited to pH 8.0-9.5 and temperatures of 15-35℃, this invention can operate efficiently and stably over a wide range of conditions, from pH 3.0-11.0 to temperatures of 10-50℃. It also significantly inhibits the redissolution of heavy metal sulfides and effectively controls the rebound of effluent concentration, demonstrating stability far superior to traditional methods. Furthermore, its unique three-stage synergistic mechanism provides excellent buffering capacity against water quality fluctuations and exhibits strong anti-interference capabilities.

[0024] Secondly, this invention significantly improves the environmental safety of sludge. The leaching concentration of heavy metals in sludge using the Toxicity Characteristic Leaching Process (TCLP) is significantly reduced, with a reduction of 50-70%. Taking cadmium-containing sludge as an example, the leaching concentration after treatment by traditional methods can reach 12.5 mg / L, while using the complexation inhibitor described in this invention can reduce it to 3.8 mg / L, a reduction of 69.6%, making it easier to meet the limit requirements of the "Standard for Pollution Control of Hazardous Waste Landfill" (GB18598-2019), facilitating subsequent sludge disposal and resource utilization.

[0025] Finally, this invention also has significant overall cost advantages. The dosage of the reagent is only about 20-50% of that of existing technical solutions (such as CN119977120A), and the efficient treatment effect eliminates the need for multiple post-treatment processes, reducing energy consumption and operating costs by about 35%, thus demonstrating good economic efficiency and promotional value.

[0026] Another aspect of the present invention provides the application of a complexing inhibitor composite material obtained according to the aforementioned complexing inhibitor or the aforementioned preparation method in the treatment of heavy metal wastewater.

[0027] When applying, follow these steps: control the pH of the wastewater to 3.0-11.0 and the concentration of heavy metals in the wastewater to 1-150 mg / L; then add the complexation inhibitor of this invention at a concentration not less than 20 times the heavy metal concentration, and stir at a speed of 150-200 r / min for 20-40 min; finally, allow it to stand and precipitate for 20-40 min for solid-liquid separation.

[0028] Preferably, when processing Cd-containing... 2+ or Hg 2+ When dealing with wastewater with a concentration of 50 mg / L, the dosage should be controlled at 2 g / L.

[0029] Preferably, a 0.45 μm filter membrane is used for solid-liquid separation. Attached Figure Description

[0030] Figure 1 This is a comparison chart of the mercury removal effects of different component inhibitors.

[0031] Figure 2 This is a graph showing the effect of different dosages of the complexation inhibitor of the present invention on the mercury concentration in the effluent.

[0032] Figure 3 The complexation inhibitor of this invention is effective against Cd in wastewater. 2+ Pb 2+ and Cr 3+ Comparison of removal effects. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the raw materials, equipment structures, or processing technologies used in the following embodiments or examples are all conventional commercially available products, equipment, or processing technologies in the art. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1: Preparation of complexation inhibitor (using calcium salt as component A) S1: Preparation of Component A. Following the aforementioned method, 100 g of calcium chloride (purity ≥95%) was dissolved in 300 mL of deionized water to prepare a solution. Under nitrogen protection, the solution was stirred at 250 r / min for 40 min in a constant temperature water bath at 50℃. The mixture was then spray-dried, with the inlet air temperature controlled at 165℃ and the outlet air temperature at 82℃, yielding a white powdery component A.

[0035] S2: Preparation of component B. 76 g of carbon disulfide and 49 g of dimethylamine were added to a reaction vessel and reacted at 45°C for 3 h. NaOH was added to adjust the pH to 11, and the mixture was allowed to crystallize at room temperature for 12 h. After filtration, the solid was dried in a vacuum drying oven at 60°C for 4 h to obtain a yellow solid, component B.

[0036] S3: Preparation of Component C. Chitosan with a degree of deacetylation ≥ 85% and a molecular weight of 30,000 Da is selected as component C.

[0037] Compounding: Mix component A and component B at a mass ratio of 1:2 and stir at 250 r / min for 20 min. Then add component C, maintaining a mass ratio of A:B:C = 1:2:4, and continue stirring for 50 min. Transfer the mixture to a 50℃ oven and dry for 6 h. Grind the mixture and pass it through a 100-mesh sieve to obtain a white powdery complexing inhibitor.

[0038] Example 2: Treatment of Mercury-Containing Wastewater Wastewater parameters: initial mercury concentration of 50 mg / L, pH of 7.5 (raw water), and temperature of 25℃.

[0039] Processing steps: S1: Without adjusting the pH, add 2.0 g / L of the complexation inhibitor prepared in Example 1 (equivalent to 40 times the mercury concentration in the wastewater).

[0040] S2: Stir at 180 r / min for 30 min on a six-unit stirrer.

[0041] S3: Let stand for 30 min to settle, then filter the supernatant through a 0.45 μm filter membrane.

[0042] S4: The total mercury concentration in the filtrate was determined by atomic fluorescence spectrometry.

[0043] S5: After allowing the supernatant to stand for another 2 h and 24 h, the total mercury concentration was measured again.

[0044] Detection results: The mercury concentration in the effluent was 0.25 mg / L after 30 min of standing, 0.26 mg / L after 2 h of standing, and 0.28 mg / L after 24 h of standing. The results indicate that the inhibitor with calcium salt as component A has a significant effect on Hg. 2+ It has excellent removal effect and no additional heavy metals are introduced into the final sludge, making it more environmentally friendly.

[0045] Example 3: Verification of Component Synergistic Effect Wastewater parameters: Mercury concentration 1.25 mg / L, pH 7.5, temperature 25℃.

[0046] Seven control groups and one experimental group were set up. Control group 1 received no inhibitor; control group 2 received component A (calcium salt) alone; control group 3 received component B (organosulfur agent) alone; control group 4 received component C (chitosan) alone; in control group 5, components A and B were combined in a 1:2 mass ratio; in control group 6, components B and C were combined in a 1:2 mass ratio; in control group 7, components A and C were combined in a 1:4 mass ratio; and in the experimental group, components A, B, and C were combined in a ternary mixture in a 1:2:4 mass ratio. The preparation of components A, B, and C is described in Example 1.

[0047] Processing steps: S1: Without adjusting the pH, add 0.40 g / L of the inhibitor prepared in the control group 2-7 and the experimental group respectively (i.e., add 0.4 g of inhibitor per liter of wastewater).

[0048] S2: Stir at 180 r / min for 30 min on a six-unit stirrer.

[0049] S3: Let stand for 30 min to settle, then filter the supernatant using a 0.45 μm filter membrane.

[0050] Test results as follows Figure 1 As shown in the figure. The mercury concentration in the effluent of control groups 1-4 was >1.10 mg / L; the mercury concentration in the effluent of control group 5 was 0.050 mg / L; the mercury concentration in the effluent of control groups 6-7 was >0.75 mg / L; and the mercury concentration in the effluent of the experimental group was 4.3 μg / L, which is less than 5 μg / L.

[0051] Conclusion: The removal rate of a single component is <12%, indicating limited effectiveness. The A+B compound has a removal rate of 96% and can partially inhibit redissolution, but it does not meet the standard. The A+B+C ternary compound has a removal rate >99.6%, demonstrating significant synergistic effect and achieving deep mercury removal.

[0052] Example 4: Optimization Experiment of Inhibitor Dosage Referring to Example 3, the fixed conditions and variable operations are as follows: Fixed conditions: wastewater mercury concentration 1.25 mg / L, pH 7.5, stirring speed 180 r / min.

[0053] Variable operation: 0.05 g / L, 0.10 g / L, 0.20 g / L, 0.40 g / L, 0.60 g / L and 1.00 g / L of the inhibitor prepared in Example 1 were added respectively, and the inhibitor concentrations were equivalent to 40, 80, 160, 320, 480 and 800 times the mercury concentration in the wastewater, respectively.

[0054] Test results as follows Figure 2 As shown, the effluent mercury concentration was 0.120 mg / L when 0.05 g / L was added; the effluent mercury concentration decreased to 0.009 mg / L when 0.10 g / L was added; the effluent mercury concentration was 0.006 mg / L when 0.20 g / L was added; the effluent mercury concentration was <0.005 mg / L when 0.40 g / L was added; and the concentration remained <0.005 mg / L even when the concentration was further increased to 0.60 g / L and 1.00 g / L.

[0055] Conclusion: At the optimal dosage of 0.40 g / L, the mercury removal rate is >99.6%, meeting the emission standards. Excessive dosage does not significantly improve the removal efficiency but increases costs.

[0056] Example 5: Wide Applicability Verification Wastewater parameters: Cadmium-containing wastewater (Cd) 2+ Concentration of 50 mg / L, pH 7.5; lead-containing wastewater Pb 2+ Concentration of 30 mg / L, pH 7.5; chromium-containing wastewater Cr 3+ The concentration was 40 mg / L, and the pH was 7.5.

[0057] Processing steps: S1: Do not adjust the pH of the raw water.

[0058] S2: According to the experimental design, the inhibitors from Example 1 were added to different wastewaters, namely, 2.0 g / L to cadmium-containing wastewater, 1.5 g / L to lead-containing wastewater, and 1.8 g / L to chromium-containing wastewater.

[0059] S3: Stir at 180 r / min for 30 min.

[0060] S4: Let stand and settle for 30 minutes.

[0061] S5: The supernatant was filtered using a 0.45 μm filter membrane to determine the residual concentration of heavy metals.

[0062] Test results as follows Figure 3 As shown, the effluent cadmium concentration was 0.21 mg / L, the effluent lead concentration was <0.01 mg / L, and the effluent chromium concentration was 0.05 mg / L.

[0063] Conclusion: The complexation inhibitor of this invention has a significant effect on Cd. 2+ Pb 2+ Cr 3+ It exhibits significant removal effects on various heavy metal ions. After treatment with this inhibitor, the concentrations of lead and chromium in the effluent are far below the limits specified in the "Integrated Wastewater Discharge Standard" (GB 8978-1996), i.e., Pb. 2+ 1.0 mg / L, Cr 3+ 1.5 mg / L. For cadmium-containing wastewater, this inhibitor can significantly reduce Cd levels. 2+ For concentrations requiring stable adherence to the stringent limit of 0.1 mg / L, secondary advanced treatment can be performed. These results indicate that the inhibitor possesses broad applicability for heavy metal treatment.

[0064] Example 6: Preparation of complexation inhibitor (using ferrous salt as component A) S1: Preparation of Component A. Following the aforementioned method, 100 g of FeSO4·7H2O was dissolved in 300 mL of deionized water to prepare a solution. Under nitrogen protection, the solution was stirred at 200 r / min for 50 min in a constant temperature water bath at 55℃. The mixture was then spray-dried, with the inlet air temperature controlled at 170℃ and the outlet air temperature at 85℃, yielding a light green powder, component A.

[0065] S2: Preparation of component B. Same as in Example 1.

[0066] S3: Preparation of component C. Same as in Example 1.

[0067] Compounding: Mix component A and component B at a mass ratio of 1:2 and stir at 250 r / min for 15 min. Then add component C, maintaining a mass ratio of A:B:C = 1:2:4, and continue stirring for 45 min. Transfer the mixture to a 50℃ oven and dry for 6 h. Pulverize and pass through a 100-mesh sieve to obtain a gray-green powdery complexing inhibitor.

[0068] Example 7: Treatment of alkaline, high-salt, mercury-containing deacidification wastewater Wastewater parameters: The wastewater was taken from the wet acid removal system of a municipal sludge incineration flue gas. The water quality was alkaline (pH 8.6 ± 0.24), with an initial total mercury concentration of (181.2 ± 55.7) μg / L. It also contained high concentrations of sulfate and chloride ions.

[0069] Processing steps: S1: Take 500 mL of the above wastewater into a beaker and maintain the original water pH≈8.6; S2: Add 10 mg / L of the complexation inhibitor prepared in Example 6 (equivalent to 55 times the mercury concentration in the wastewater). S3: Stir at 180 r / min for 30 min; S4: Let stand for 30 min to settle, then filter the supernatant through a 0.45 μm filter membrane; S5: The total mercury concentration in the filtrate was determined by atomic fluorescence spectrometry.

[0070] S6: After allowing the supernatant to stand for 2 h and 24 h, take samples again to determine the total mercury concentration.

[0071] Test results: After standing for 30 min, the total mercury concentration in the effluent decreased to (0.40 ± 0.25) μg / L; after standing for 2 h, the total mercury concentration was (0.42 ± 0.27) μg / L; after standing for 24 h, the total mercury concentration was (0.45 ± 0.30) μg / L.

[0072] Conclusion: The complexation inhibitor of this invention can still effectively inhibit HgS redissolution under alkaline, high-salt, and high-mercury conditions. The total mercury concentration in the effluent is far below the limit of 0.005 mg / L specified in the "Integrated Wastewater Discharge Standard" (DB31 / 199-2018), and the removal rate remains stable at over 99%. No significant concentration rebound was observed. It achieves effluent compliance without relying on multi-stage resin adsorption, significantly simplifying the process and reducing operating costs.

[0073] Comparative Example 1: Traditional Vulcanization Method Wastewater parameters: initial mercury concentration 0.68 mg / L, pH 7.5 (raw water), temperature 25℃.

[0074] Treatment steps: Adjust the pH of the wastewater to 8.5, add 10 mg / L sodium sulfide as a precipitant, stir at 180 r / min for 30 min, and let it stand for 30 min to settle. Then filter the supernatant through a 0.45 μm filter membrane, let the supernatant stand for 2 hours, and then take a sample again to measure the mercury concentration to observe the concentration rebound phenomenon.

[0075] Test results: The mercury concentration in the effluent was 0.05 mg / L immediately after sedimentation and separation. After standing for 2 hours, the mercury concentration rebounded to 0.62 mg / L when measured again.

[0076] Conclusion: Although the traditional sodium sulfide precipitation method can effectively precipitate mercury ions in the initial stage, it suffers from drawbacks due to excessive sodium sulfide. 2- The mercury complex reacts with the already formed HgS precipitate to form a soluble mercury thiocomplex, causing the heavy metal mercury to redissolve into the water and resulting in a severe concentration rebound. This result confirms the common technical challenges in the industry described in the background section and highlights the inherent shortcomings of traditional methods in achieving stable and compliant emissions.

[0077] Comparative Example 2: Comparison of Single-Component Treatments The same mercury-containing wastewater as in Example 3 was used, with an initial mercury concentration of 1.25 mg / L, a pH of 7.5, and a temperature of 25°C. Equal amounts of each of the three components (A, B, and C) were added individually, at a concentration of 0.4 g / L, as in the experimental group. The treatment steps were consistent with those in Example 3.

[0078] Test results: When component A was added alone, the mercury concentration in the effluent was 1.12 mg / L, with a removal rate of 10.4%; when component B was added alone, the mercury concentration in the effluent was 1.08 mg / L, with a removal rate of 13.6%; when component C was added alone, the mercury concentration in the effluent was 1.15 mg / L, with a removal rate of 8.0%.

[0079] Conclusion: The treatment effect of single components was poor, with removal rates all below 15%, far from meeting the standard, which proves the necessity of ternary compound treatment.

[0080] Comparative Example 3: Comparison of different compound ratios Using the same mercury-containing wastewater as in Example 3, with a fixed total dosage of 0.4 g / L, experiments were conducted under different A:B:C mass ratios, and the treatment steps were the same as in Example 3. The following compounding ratios were tested: Ratio 1: A:B:C = 1:1:2; Ratio 2: A:B:C = 1:3:6; Ratio 3: A:B:C = 2:1:4; Ratio 4: A:B:C = 0.1:15:20; and Ratio 5: A:B:C = 10:0.5:1. The preparation of components A, B, and C is described in Example 1.

[0081] Test results: The mercury concentration in the effluent from ratio 1 was 0.032 mg / L, with a removal rate of 97.4%; the mercury concentration in the effluent from ratio 2 was 0.018 mg / L, with a removal rate of 98.6%; and the mercury concentration in the effluent from ratio 3 was 0.025 mg / L, with a removal rate of 98.0%. These ratios all showed good treatment effects. However, the mercury concentration in the effluent from ratio 4 was as high as 0.895 mg / L, with a removal rate of only 28.4%, and the mercury concentration in the effluent from ratio 5 was as high as 0.943 mg / L, with a removal rate of only 24.6%, and their SEI was far less than 1.

[0082] Conclusion: Experimental results show that the complexation inhibitor described in this invention can effectively inhibit the redissolution of mercury throughout the entire A:B:C mass ratio range of (1-2):(1-3):(2-6). Its treatment effect is significantly better than that of Comparative Example 1 of the traditional sulfidation method and Comparative Example 2 of the single component, proving the effectiveness and rationality of this ratio range. Among them, the synergistic effect is most significant and the treatment effect is optimal when the mass ratio is close to 1:2:4. When the ratio is outside this range, although it still has a certain effect, its synergistic efficiency is weakened.

[0083] Example 8: Preparation of complexation inhibitors and wastewater treatment S1: Preparation of component A. Same as in Example 1.

[0084] S2: Preparation of component B: Mercaptobenzothiazole was selected as component B.

[0085] S3: Preparation of component C: Hydroxyethylidene diphosphonic acid is selected as component C.

[0086] Compounding: Mix component A and component B at a mass ratio of 1:2 and stir at 250 r / min for 15 min. Then add component C, maintaining a mass ratio of A:B:C = 1:2:4, and continue stirring for 45 min. Transfer the mixture to a 50℃ oven and dry for 6 h. Grind the mixture and pass it through a 100-mesh sieve to obtain a powdered complexing inhibitor.

[0087] Wastewater parameters: initial mercury concentration of 50 mg / L, pH of 7.5 (raw water), and temperature of 25℃.

[0088] Processing steps: S1: Without adjusting the pH, add 2.0 g / L of the complexation inhibitor prepared in this example (equivalent to 40 times the mercury concentration in the wastewater).

[0089] S2: Stir at 180 r / min for 30 min on a six-unit stirrer.

[0090] S3: Let stand for 30 min to settle, then filter the supernatant using a 0.45 μm filter membrane.

[0091] Detection results: The mercury concentration in the effluent was 0.26 mg / L. The results indicate that the inhibitor in this embodiment has a significant effect on Hg. 2+ It has excellent removal effect and no additional heavy metals are introduced into the final sludge, making it more environmentally friendly.

[0092] Example 9: Preparation of complexation inhibitors and wastewater treatment The preparation of the complexation inhibitor was the same as in Example 8. The wastewater treatment steps only involved adjusting the pH to 3.0 and the temperature to 10°C in step S1. The test results showed that the effluent mercury concentration was 0.30 mg / L. After the supernatant was left to stand for 7 days, the change in effluent mercury concentration was within 0.01%, indicating that even under acidic and low-temperature conditions, the inhibitor could stably inhibit the redissolution of mercury sulfides without significant concentration rebound.

[0093] Example 10: Preparation of complexation inhibitors and wastewater treatment The preparation of the complexation inhibitor was the same as in Example 8. The wastewater treatment steps only involved adjusting the pH to 11.0 and setting the temperature to 50°C in step S1. The test results showed that the mercury concentration in the effluent was 0.28 mg / L. After the supernatant was left to stand for 7 days, the mercury concentration in the effluent changed by less than 0.01%, confirming that the inhibitor of this invention maintains a highly efficient and stable heavy metal fixation capacity even under extreme alkaline and high-temperature conditions, demonstrating its technical advantage of wide adaptability to various operating conditions.

[0094] Example 11: Preparation of complexation inhibitors and wastewater treatment S1: Preparation of component A. Same as in Example 1.

[0095] S2: Preparation of component B: Sodium dithiocarbamate was selected as component B.

[0096] S3: Preparation of component C: Polyethyleneimine is selected as component C.

[0097] Compounding: Mix component A and component B at a mass ratio of 1:2 and stir at 250 r / min for 15 min. Then add component C, maintaining a mass ratio of A:B:C = 1:2:4, and continue stirring for 45 min. Transfer the mixture to a 50℃ oven and dry for 6 h. Grind the mixture and pass it through a 100-mesh sieve to obtain a powdered complexing inhibitor.

[0098] Wastewater parameters: initial mercury concentration of 50 mg / L, pH of 7.5 (raw water), and temperature of 25℃.

[0099] Processing steps: S1: Without adjusting the pH, add 2.0 g / L of the complexation inhibitor prepared in this example (equivalent to 40 times the mercury concentration in the wastewater).

[0100] S2: Stir at 180 r / min for 30 min on a six-unit stirrer.

[0101] S3: Let stand for 30 min to settle, then filter the supernatant using a 0.45 μm filter membrane.

[0102] Detection results: The mercury concentration in the effluent was 0.25 mg / L. The results indicate that the inhibitor in this embodiment has a significant effect on Hg. 2+ It has excellent removal effect and no additional heavy metals are introduced into the final sludge, making it more environmentally friendly.

[0103] Furthermore, it should be noted that the shapes and names of the components in the specific embodiments described in this specification may differ. All equivalent or simple variations made to the structure, features, and principles described in this patent concept are included within the protection scope of this patent. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific examples or use similar methods to replace them, as long as they do not deviate from the structure of this invention or exceed the scope defined in these claims, all of which should fall within the protection scope of this invention.

Claims

1. A complexation inhibitor that inhibits the redissolution of heavy metal sulfides, characterized in that, The complexation inhibitor is composed of the following three components: component A is a metal salt, component B is an organic sulfur agent, and component C is an organic non-sulfur agent, wherein the mass ratio of component A, component B, and component C is (1-2):(1-3):(2-6); component B is selected from at least one of dithiocarbamate, mercaptobenzothiazole, or sodium dimethyldithiocarbamate; and component C is selected from at least one of chitosan, polyethyleneimine, or hydroxyethylidene diphosphonic acid. Component A is selected from at least one of zinc salt, iron salt, aluminum salt, calcium salt, ferrous salt, or magnesium salt.

2. The complexation inhibitor according to claim 1, characterized in that, The calcium salt is CaCl2, and the ferrous salt is ferrous sulfate.

3. The complexation inhibitor according to claim 1, characterized in that, Dissolve the salt raw material of component A in deionized water to prepare a solution with a mass fraction of 20-35%. Purge with nitrogen for protection, stir at 100-300 r / min for 40-60 min at 40-60℃, and then spray dry.

4. The complexation inhibitor according to claim 1, characterized in that, Component B is sodium dimethyl dithiocarbamate, which is prepared by mixing carbon disulfide and dimethylamine in a molar ratio of 1:(1.1-1.5), reacting at 40-50℃ for 2-4 h, adjusting the pH to 10-12 with NaOH, and then crystallizing and drying.

5. The complexation inhibitor according to claim 1, characterized in that, Component C is chitosan with a degree of deacetylation ≥85% and a molecular weight of 10,000-50,000 Da.

6. The method for preparing the complexation inhibitor according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Mix component A and component B at a mass ratio of (1-2):(1-3) and stir at 200-300 r / min for 10-30 min; S2: Add component C, and control the mass ratio of component A:B:C to be (1-2):(1-3):(2-6), and continue stirring for 30-60 min; S3: Dry the mixture at 40-60℃ for 4-8 hours, then pulverize it through an 80-200 mesh sieve.

7. The preparation method according to claim 6, characterized in that, In step S1, the mass ratio of component A to component B is 1:2; in step S2, the mass ratio of component A, component B and component C is 1:2:

4.

8. The application of the complexation inhibitor according to any one of claims 1-5 in the treatment of heavy metal wastewater.

9. The application according to claim 8, characterized in that, When applying, follow these steps: control the pH of the wastewater to 3.0-11.0 and the concentration of heavy metals in the wastewater to 1-150 mg / L; then add the complexation inhibitor of this invention at a concentration not less than 20 times the heavy metal concentration, and stir at a speed of 150-200 r / min for 20-40 min; finally, allow it to stand and precipitate for 20-40 min for solid-liquid separation.

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