A method for removing heavy metal complexes from wastewater

Abstract

The present application relates to a kind of methods for removing heavy metal complex in wastewater, comprising the following steps, S1 configuration PMS composite reagent, the PMS composite reagent is made by including the following weight percentage of raw material ball milling, persulfate 50~90%, sulfite 5~30%, hypochlorite 5~20%;S2 in the heavy metal complex-containing industrial wastewater join the PMS composite reagent obtained in the S1, heavy metal in heavy metal complex is Cu, and one or several of Co, Cr, Ni, Pb and Zn, complex in heavy metal complex is one or several of EDTA, NTA, citric acid, oxalic acid, tartaric acid, sorbic acid, stirring is dissolved, and lye is added to maintain the pH of industrial wastewater to 9.5~11.0, and carries out fenton-like oxidation and breaks the complex reaction, after reaction, aftertreatment is obtained, and the regenerated water is obtained.The present application achieves the purpose of removing heavy metal complex in wastewater by the method of in-situ activation of persulfate without additional catalyst or the application of electricity, ultraviolet and other energy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and in particular to a method for removing heavy metal complexes in wastewater. BACKGROUND

[0002] With the continuous progress of industrialization, a large amount of wastewater containing heavy metals will be produced in the production process of industries such as printed circuit boards, electroplating, leather processing and chemical production. If these wastewaters are directly discharged into the natural environment without proper treatment, they will pose a serious threat to aquatic ecosystems and may harm human health through the food chain. Therefore, how to deeply remove heavy metals has become a problem to be solved in the field of industrial wastewater treatment. Traditional treatment methods such as adsorption, precipitation and ion exchange can effectively remove free heavy metal ions, but when facing wastewater containing organic ligands with strong complexing ability, such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), citric acid and tartaric acid, these methods are not up to the task because heavy metal ions will form stable complexes with ligands, which are difficult to be removed by traditional processes. Therefore, developing and applying new and efficient heavy metal complex removal technologies has become a hot topic of widespread attention in the scientific and technological community.

[0003] Oxidative decomplexation-precipitation is one of the effective means for treating wastewater containing heavy metal complexes. Common oxidation technologies include Fenton / Fenton-like oxidation and electrochemical oxidation. Fenton / Fenton-like method produces active substances such as hydroxyl radicals (·OH) and sulfate radicals (SO4 ∙- ), which can destroy the structure of the complex and release heavy metal ions. However, the addition of Fe(II) will bring the problem of additional iron sludge production and may form more stable Fe(III) complexes, leading to secondary pollution. Given that heavy metal complexes themselves have Fenton-like catalytic properties, using these complexes as catalysts can effectively avoid the above problems.

[0004] Currently, the commonly used agents in advanced oxidation technology include hydrogen peroxide and persulfate. Compared with liquid hydrogen peroxide, persulfate, such as persulfate (PMS) and peroxodisulfate (PDS), has the advantages of easier activation and storage and transportation. The Chinese patent with the publication number CN116693007A discloses a method for electrochemically activating persulfate to degrade heavy metal complexes. The method can efficiently remove heavy metal organic complexes in various wastewater, but the device installation is complex, the energy consumption is large, the cost is high, and strict operating conditions are required. The Chinese patent with the publication number CN118388015B discloses a method for treating NTA-heavy metal complex in electroplating wastewater by Fe-C / PMS catalytic coupling chelation adsorption. The carbon-based single-atom iron catalyst prepared by the method can effectively activate PMS and has high complex breaking efficiency for NTA-heavy metal complex, but there are problems of high preparation cost and activity reduction during recycling. SUMMARY

[0005] The problem to be solved by the present application is to provide a method for removing heavy metal complexes in wastewater, which achieves the purpose of removing heavy metal complexes in wastewater by in-situ activation of persulfate without additional addition of catalyst or application of electricity, ultraviolet and other energy.

[0006] The above invention purpose of the present application is achieved by the following technical scheme:

[0007] A method for removing heavy metal complexes in wastewater, comprising the following steps,

[0008] S1, configuring a PMS composite agent, the PMS composite agent is made by ball milling of raw materials containing the following weight percentages: PMS 50-90%, sulfite 5-30%, hypochlorite 5-20%;

[0009] S2, adding the PMS composite agent obtained in S1 to industrial wastewater containing heavy metal complexes, the heavy metals in the heavy metal complexes are one or more of Cu, Co, Cr, Ni, Pb and Zn, the complexes in the heavy metal complexes are one or more of EDTA, NTA, citric acid, oxalic acid, tartaric acid and sorbic acid, stirring and dissolving, and adding lye to maintain the pH of the industrial wastewater to 9.5-11.0, carrying out oxidation and complex breaking reaction, and obtaining regenerated water after post-treatment after the reaction is completed.

[0010] Further, in S1, the persulfate is a combination of one or more of potassium monopersulfate and sodium monopersulfate.

[0011] Further, in S1, the sulfite is a combination of one or more of sodium sulfite, calcium sulfite and magnesium sulfite.

[0012] Further, in the S1, the hypochlorite is calcium hypochlorite.

[0013] Further, in the S1, the peroxymonosulfate, sulfite and hypochlorite are put into a ball mill for ball milling, and the ball-to-material ratio is controlled to be 10-25:1, the ball milling speed is controlled to be 400-800 rpm, and the ball milling time is controlled to be 30-120 min, to obtain the PMS composite reagent.

[0014] Further, in the S2, the suspended impurities in the industrial wastewater are removed in advance, and the pH of the industrial wastewater is adjusted to be 7-10.

[0015] Further, in the S2, the alkali liquor is one or a combination of several of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0016] Further, in the S2, the molar concentration ratio of the Cu complex to other heavy metal complexes in the heavy metal complex is controlled to be more than 0.5.

[0017] Further, in the S2, the molar concentration ratio of the peroxymonosulfate in the PMS composite reagent to the Cu complex in the industrial wastewater is controlled to be 20-100.

[0018] Further, in the S2, the PMS composite reagent is first added under the condition of room temperature stirring at 60-100 rpm, and the stirring is continued for 5-10 min for dissolution, then the alkali liquor is added to adjust the pH of the industrial wastewater to be 9.5-11.0, and the Fenton oxidation and complex breaking reaction are carried out under the condition of room temperature, during which the pH of the industrial wastewater is selectively maintained to be 9.5-11.0 by adding the alkali liquor, after the reaction for 20-60 min, the pH of the industrial wastewater is adjusted to be 11-12, and the regenerated water is obtained after standing and precipitation for 10-30 min.

[0019] In summary, the beneficial technical effects of the present application are:

[0020] 1. The present application activates the peroxymonosulfate and sulfite by alkali liquor to generate singlet oxygen to oxidize the copper complex, and the intermediate product has Fenton-like catalytic activity, can catalyze PMS to generate sulfate radicals, and further oxidize the heavy metal complex to achieve the purpose of complex breaking; the principle of the copper complex intermediate catalyzing PMS involves a proton-coupled electron transfer mechanism, and the catalytic activity of PMS is the highest at pH=9.8, so the pH range (9.5-11) used in the present application can ensure the rapid progress of alkali-activated PMS, Fenton-like catalytic reaction and subsequent oxidation and complex breaking. K a 1. The present application activates the peroxymonosulfate and sulfite by alkali liquor to generate singlet oxygen to oxidize the copper complex, and the intermediate product has Fenton-like catalytic activity, can catalyze PMS to generate sulfate radicals, and further oxidize the heavy metal complex to achieve the purpose of complex breaking; the principle of the copper complex intermediate catalyzing PMS involves a proton-coupled electron transfer mechanism, and the catalytic activity of PMS is the highest at pH=9.8, so the pH range (9.5-11) used in the present application can ensure the rapid progress of alkali-activated PMS, Fenton-like catalytic reaction and subsequent oxidation and complex breaking.

[0021] 2. The hypochlorite salt of the present application can coordinate and regulate the pH after the dissolution of the PMS complex agent, prevent the rapid decrease of the pH after the persulfate is dissolved in water, and the generated hypochlorite, calcium peroxide and the like can oxidize part of the organic complex with heavy metal ions to further improve the complex breaking and coagulation effect;

[0022] 3. The copper complex intermediate produced by the present application is used as a Fenton-like catalyst, generates sulfate radicals as the main active oxygen species, has a fast reaction rate and short time, avoids the secondary pollution and high cost caused by additional catalyst, and has the advantages of low price, easy storage and transportation, and convenient operation;

[0023] 4. The method provided by the present application is simple to operate, has no secondary pollution, does not need external energy input, and has low operation cost, and is an economic, efficient, universal and green technology for removing heavy metal complex in wastewater, and is suitable for treating heavy metal complex wastewater generated in processes such as printed circuit board, electroplating, leather making and chemical manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a removal comparison chart of Cu(II)-EDTA of embodiment 3 of the present application.

[0025] Figure 2 is a removal comparison chart of heavy metal complex of embodiment 4 of the present application. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, purposes and effects realized by the present application more clear and easy to understand, the present application is further described below in combination with the drawings and specific embodiments.

[0027] Embodiment 1: A method for removing heavy metal complex in wastewater disclosed by the present application, comprising the following steps,

[0028] S1: configuring a PMS complex agent, the PMS complex agent is made by ball milling raw materials containing the following weight percentages, persulfate (potassium monopersulfate) 55%, sulfite (sodium sulfite) 30%, hypochlorite (calcium hypochlorite) 15%; the above raw materials are put into a ball mill for ball milling, and the ball-to-material ratio is controlled to be 15:1, the ball milling speed is 600 rpm, and the ball milling time is 60 min to obtain the PMS complex agent;

[0029] S2 selects industrial wastewater from a certain electroplating factory, the initial pH is 4.4, the concentrations of Cu(II)-EDTA and Ni(II)-EDTA are 1.3 mmol / L and 1.2 mmol / L respectively, first remove the suspended impurities in the industrial wastewater, and adjust the pH of the industrial wastewater to 9, then add the PMS composite reagent (400 mg / L) obtained by S1 in 1L industrial wastewater under the condition of room temperature stirring at 60 rpm, stir and dissolve, then add lye (sodium hydroxide) to adjust the pH of the industrial wastewater to 9.8, and carry out oxidative decomplexing reaction under room temperature condition, during which lye is selectively added to maintain the pH of the industrial wastewater at 9.5-11.0, after 40 min of reaction, the pH of the industrial wastewater is adjusted to 12, and the regenerated water is obtained after standing and precipitating for 20 min.

[0030] Table 1 shows the removal rates of heavy metals and TOC, and it can be found that after 40 min of reaction, the removal rate of total copper in the raw water is 100%, the removal rate of total nickel is 95.43%, and the removal rate of TOC is 71.14%, and the removal effect is relatively ideal.

[0031] Table 1

[0032] Time / min 0 5 15 20 30 40 Total copper removal rate / % 0 7.32 53.58 98.92 99.25 100.00 Total nickel removal rate / % 0 1.29 21.63 85.23 89.92 95.43 TOC removal rate / % 0 5.54 7.36 28.93 54.58 71.14

[0033] Example 2: A method for removing heavy metal complexes in wastewater disclosed by the application, comprising the following steps,

[0034] S1 configures a PMS composite reagent, which is made of raw materials including the following weight percentages: persulfate (potassium monopersulfate) 65%, sulfite (sodium sulfite) 30%, and hypochlorite (calcium hypochlorite) 5%; the above raw materials are put into a ball mill for ball milling, and the ball-to-material ratio is controlled to be 15:1, the ball milling speed is 600 rpm, and the ball milling time is 60 min to obtain the PMS composite reagent;

[0035] S2 selects industrial wastewater from a certain tannery, the initial pH is 8.3, the concentrations of Cu(II)-EDTA, Ni(II)-EDTA and Cr(III)-EDTA are 1.5 mmol / L, 0.3 mmol / L and 0.1 mmol / L respectively, first remove the suspended impurities in the industrial wastewater, and adjust the pH of the industrial wastewater to 10, then add the PMS composite reagent (500 mg / L) obtained by S1 in 1L industrial wastewater under the condition of room temperature stirring at 60 rpm, stir and dissolve, then add lye (sodium hydroxide) to adjust the pH of the industrial wastewater to 9.8, and carry out oxidative decomplexing reaction under room temperature condition, during which lye is selectively added to maintain the pH of the industrial wastewater at 9.5-11.0, after 60 min of reaction, the pH of the industrial wastewater is adjusted to 12, and the regenerated water is obtained after standing and precipitating for 20 min.

[0036] Table 1 shows the removal rates of heavy metals and TOC. It can be found that the removal rate of heavy metals in raw water is more than 95% and the removal rate of TOC is 60.35% after 60 min of reaction, and the removal effect is ideal.

[0037] Table 2

[0038] Time / min 0 10 20 30 45 60 Total copper removal rate / % 0 12.25 29.52 56.28 77.67 95.43 Total nickel removal rate / % 0 11.56 26.43 45.98 79.12 96.12 Total chromium removal rate / % 0 9.74 19.56 41.98 75.28 95.87 TOC removal rate / % 0 6.78 12.52 22.55 48.69 60.35

[0039] Example 3: A method for removing heavy metal complexes in wastewater disclosed in the present application, which is different from example 1 in that in S2, industrial wastewater from a certain electroplating plant is selected, and the concentration of Cu(II)-EDTA is 0.8 mmol / L; 400 mg / L of PMS composite reagent is added to 1 L of industrial wastewater, stirred for 5 min for dissolution, then lye (sodium hydroxide) is added to adjust the pH of the industrial wastewater to 10.5, and the Fenton oxidation complex breaking reaction is carried out at room temperature, during which lye is selectively added to maintain the pH of the industrial wastewater at 9.5~11.0, after 30 min of reaction, the pH of the industrial wastewater is adjusted to 12, and the precipitate is obtained after 20 min of standing.

[0040] This example also sets up two groups of control groups, which are different from the above method in that in control group 1, after adding the PMS composite reagent, the pH is not adjusted to 9.5~11.0 by adding lye, and the pH of the reaction system is maintained at about 2.5~3.5; in control group 2, no PMS composite reagent is added.

[0041] Figure 1 The removal effect of Cu(II)-EDTA in the three groups of experiments is shown, and it can be known from the figure that according to the method provided by the present application, the removal rate of Cu(II)-EDTA is close to 94% within 30 min, while in the control group experiment, the removal rate of Cu(II)-EDTA is less than 2%. It can be found that adding PMS composite reagent and adjusting the pH between 9.5~11.0 is the key to initiating the complex breaking reaction.

[0042] Example 4: A method for removing heavy metal complex in wastewater is disclosed in the present application, which is different from example 1 in that in S2, industrial wastewater (1# water sample) from a certain circuit board factory is selected, the initial pH is 8.3, the concentrations of Cu(II)-EDTA, Ni(II)-EDTA and Cr(III)-EDTA are 1.4 mmol / L, 0.2 mmol / L and 0.3 mmol / L respectively; 600 mg / L of PMS composite reagent obtained in S1 is added to 1 L of industrial wastewater, stirred for 5 min for dissolution, then lye (sodium hydroxide) is added to adjust the pH of the industrial wastewater to 10.0, and the oxidation and complex breaking reaction is carried out at room temperature, during which lye is selectively added to maintain the pH of the industrial wastewater at 9.5~11.0, after 30 min of reaction, the pH of the industrial wastewater is adjusted to 12, and the precipitate is obtained after 20 min of standing.

[0043] In this embodiment, a group of control groups is also provided, which is different from the above method in that in control group 1, industrial wastewater (2# water sample) from a certain circuit board factory is selected, the initial pH is 8.3, and the concentrations of Ni(II)-EDTA and Cr(III)-EDTA are 1.1 mmol / L and 0.5 mmol / L respectively.

[0044] Figure 2 Time / min Total copper removal rate / % Total nickel removal rate / % TOC removal rate / % Time / min Total copper removal rate / % Total nickel removal rate / % Total chromium removal rate / % TOC removal rate / % Figure 1 Figure 2 The removal effects of heavy metal complexes in the two groups of experiments are compared, and it can be seen from the figure that according to the method provided by the present application, the removal rate of heavy metals in 1# water sample is 90~98% within 20 min, while in the control group experiment, i.e. in 2# water sample, the removal rate of heavy metals is less than 10%. It can be found that the copper complex intermediate in industrial wastewater is the key to initiate the complex breaking reaction.

[0045] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method for removing heavy metal complexes from wastewater, characterized by: The method comprises the following steps of: S1, configuring a PMS composite agent made of raw materials ball-milled in the following weight percentages: 50-90% of peroxymonosulfate, 5-30% of sulfite, and 5-20% of hypochlorite; S2, adding the PMS composite agent obtained in S1 into industrial wastewater containing heavy metal complexes, wherein the heavy metal in the heavy metal complexes is Cu and one or more of Co, Cr, Ni, Pb and Zn; the complex in the heavy metal complexes is EDTA, the solution is stirred and dissolved, and lye is added to maintain the pH of the industrial wastewater to 9.5-11.0, Fenton oxidation is performed for complex breaking reaction, and after the reaction, the regenerated water is obtained through post-treatment; In S1, the peroxymonosulfate is a combination of one or both of potassium peroxymonosulfate and sodium peroxymonosulfate, the sulfite is a combination of one or more of sodium sulfite, calcium sulfite and magnesium sulfite, and the hypochlorite is calcium hypochlorite; In S2, the PMS composite agent is first added under the condition of stirring at room temperature at 60-100 rpm, and the stirring is continued for 5-10 min for dissolution, then lye is added to adjust the pH of the industrial wastewater to 9.5-11.0, and Fenton oxidation for complex breaking is performed under the condition of room temperature, during which lye is selectively added to maintain the pH of the industrial wastewater to 9.5-11.0, after the reaction for 20-60 min, the pH of the industrial wastewater is adjusted to 11-12, and the regenerated water is obtained after standing and precipitating for 10-30 min; In S2, the molar concentration ratio of the Cu complex to other heavy metal complexes in the heavy metal complexes is controlled to be more than 0.5; In S2, the molar concentration ratio of PMS to the Cu complex in the composite agent is controlled to be 20-100.

2. The method of claim 1, wherein the method is characterized by: In S1, the peroxymonosulfate, sulfite and hypochlorite are put into a ball mill for ball milling, and the ball-to-material ratio is controlled to be 10-25:1, the ball milling speed is controlled to be 400-800 rpm, and the ball milling time is controlled to be 30-120 min, so as to obtain the PMS composite agent.

3. The method of claim 1, wherein the method is characterized by: In S2, the suspended impurities in the industrial wastewater are removed in advance, and the pH of the industrial wastewater is adjusted to 7-10.

4. The method of claim 1, wherein the method is characterized by: In S2, the lye is a combination of one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

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