Method for removing heavy metal complex in wastewater

Abstract

The invention relates to a method for removing heavy metal complexes in wastewater, which comprises the following steps: S1, preparing a PMS composite agent which is prepared by ball-milling the following raw materials in percentage by weight: 50-90% of persulfate, 5-30% of sulfite and 5-20% of pypocholoride; s2, the PMS composite agent obtained in the S1 is added into industrial wastewater containing a heavy metal complex, heavy metal in the heavy metal complex is Cu and one or more of Co, Cr, Ni, Pb and Zn, complex in the heavy metal complex is one or more of EDTA, NTA, citric acid, oxalic acid, tartaric acid and sorbic acid, the mixture is stirred and dissolved, alkali liquor is added to maintain the pH of the industrial wastewater to be 9.5-11.0, and the PMS composite agent is obtained after the reaction is completed. Carrying out Fenton-like oxidation complex breaking reaction, and carrying out post-treatment after the reaction is finished, so as to obtain the reclaimed water. According to the method, the purpose of removing the heavy metal complex in the wastewater by the in-situ activation of the persulfate is achieved under the condition of not additionally adding a catalyst or applying energy sources such as electricity, ultraviolet and the like.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a method for removing heavy metal complexes in wastewater. Background Art

[0002] With the continuous progress of industrialization, industries such as printed circuit boards, electroplating, leather processing, and chemical production will produce a large amount of wastewater containing heavy metals during the production process. If these wastewaters are discharged directly into the natural environment without proper treatment, they will pose a serious threat to aquatic ecosystems and may cause harm to human health through the food chain. Therefore, how to deeply remove heavy metals has become an urgent problem to be solved in the field of industrial wastewater treatment. Although traditional treatment methods, such as adsorption, precipitation, and ion exchange, can effectively remove free heavy metal ions, these methods are powerless when faced with organic ligands with strong complexing ability in wastewater, such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), citric acid, and tartaric acid, because heavy metal ions will form stable complexes with ligands, which are difficult to be removed by traditional processes. Therefore, the development and application of new and efficient heavy metal complex removal technologies has become a hot topic of widespread concern in the scientific and technological community.

[0003] Oxidative decomposition-precipitation is one of the effective methods for treating wastewater containing heavy metal complexes. Common oxidation technologies include Fenton / Fenton-like oxidation and electrochemical oxidation. Fenton / Fenton-like methods use metal ions (such as Fe(II), Cu(II)) to catalyze peroxides (such as hydrogen peroxide, persulfate) to produce active substances such as hydroxyl radicals (∙OH) and sulfate radicals (SO4 ∙- ), these active substances can destroy the complex structure and release heavy metal ions. However, the addition of Fe(II) will bring additional iron sludge problems 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] At present, the commonly used agents in advanced oxidation technology include hydrogen peroxide and persulfate. Compared with liquid hydrogen peroxide, persulfate, such as permonosulfate (PMS) and peroxydisulfate (PDS), has the advantage of being easier to activate and store and transport. The Chinese patent with 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 wastewaters, but its device installation is complex, energy consumption is high, cost is high, and strict operating conditions are required. The Chinese patent with authorization announcement number CN118388015B discloses a method for treating NTA-heavy metal complexes in electroplating wastewater using Fe-C / PMS catalytic coupling chelating adsorption. The carbon-based single-atom iron catalyst prepared by the method can effectively activate PMS and has a high decomposition efficiency for NTA-heavy metal complexes, but there are problems of high preparation cost and decreased activity during recycling. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a method for removing heavy metal complexes in wastewater in view of the above-mentioned deficiencies in the prior art, which achieves the purpose of removing heavy metal complexes in wastewater by in-situ activation of persulfate without adding additional catalysts or applying energy such as electricity or ultraviolet rays.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions: A method for removing heavy metal complexes from wastewater comprises the following steps: S1 prepares a PMS composite agent, wherein the PMS composite agent is prepared by ball milling raw materials containing the following weight percentages: PMS 50-90%, sulfite 5-30%, hypochlorite 5-20%; S2 adds the PMS composite agent obtained in S1 to the industrial wastewater containing heavy metal complexes, wherein the heavy metals in the heavy metal complexes are Cu, and one or more of Co, Cr, Ni, Pb and Zn, and the complex in the heavy metal complexes is one or more of EDTA, NTA, citric acid, oxalic acid, tartaric acid and sorbic acid, stir to dissolve, and add alkali solution to maintain the pH of the industrial wastewater to 9.5-11.0, to carry out oxidation and decomposition reaction, and after the reaction is completed, post-treatment is carried out to obtain recycled water.

[0007] Furthermore, in S1, the peroxymonosulfate is one or a combination of potassium peroxymonosulfate and sodium peroxymonosulfate.

[0008] Furthermore, in S1, the sulfite is one or a combination of several of sodium sulfite, calcium sulfite and magnesium sulfite.

[0009] Furthermore, in S1, the hypochlorite is calcium hypochlorite.

[0010] Furthermore, in S1, permonosulfate, 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 400-800 rpm, and the ball milling time is 30-120 min to obtain a PMS composite agent.

[0011] Furthermore, in S2, suspended impurities in the industrial wastewater are removed in advance, and the pH of the industrial wastewater is adjusted to 7-10.

[0012] Furthermore, in S2, the alkali solution is one or a combination of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0013] Furthermore, in S2, the molar concentration ratio of the Cu complex to other heavy metal complexes in the heavy metal complex is controlled to be greater than 0.5.

[0014] Furthermore, in S2, the molar concentration ratio of the persulfate in the PMS composite agent to the Cu complex in the industrial wastewater is controlled to be 20-100.

[0015] Furthermore, in the S2, the PMS composite agent is first added under room temperature stirring conditions of 60-100 rpm and stirring is continued for 5-10 minutes to dissolve, and then alkali solution is added to adjust the pH of the industrial wastewater to 9.5-11.0, and Fenton oxidation decomposition reaction is carried out under room temperature conditions. During this period, alkali solution is selectively added to maintain the pH of the industrial wastewater to 9.5-11.0. After reacting for 20-60 minutes, the pH of the industrial wastewater is adjusted to 11-12, and the wastewater is allowed to stand and settle for 10-30 minutes to obtain recycled water.

[0016] In summary, the beneficial technical effects of the present invention are: 1. The present invention activates persulfate and sulfite by alkali solution to produce singlet oxygen copper oxide complex, wherein the intermediate product has Fenton-like catalytic activity, can catalyze PMS to produce sulfate radicals, further oxidize heavy metal complexes, and achieve the purpose of decomplexation; wherein the principle of the copper complex intermediate product catalyzing PMS involves a proton-coupled electron transfer mechanism, in which the PMS K a The highest catalytic activity is at pH = 9.8, so the pH range (9.5-11) used in the present invention can ensure the rapid progress of alkali activation of PMS, Fenton-like catalytic reaction and subsequent oxidation and decomposition; 2. The hypochlorite of the present invention can coordinate and adjust the pH after the PMS composite agent is dissolved, preventing the pH from rapidly decreasing after the persulfate is dissolved in the water, and after the calcium hypochlorite enters the water, the hypochlorite radicals, calcium peroxide, etc. generated can cooperate with the heavy metal ions to oxidize part of the organic complex, so as to further improve the complex breaking and coagulation-aiding effects; 3. The copper complex intermediate produced by the present invention is used as a Fenton-like catalyst to generate sulfate radicals as the main active oxidizing species, with a fast reaction rate and a short reaction time, thus avoiding the secondary pollution and high cost caused by the additional addition of catalysts, and has the advantages of low price, easy storage and transportation, and convenient operation; 4. The method provided by the present invention is simple to operate, has no secondary pollution, does not require external energy input, and has low operating costs. It is an economical, efficient, universal, and green technology for removing heavy metal complexes in wastewater, and is suitable for the treatment of heavy metal complex wastewater generated in processes such as printed circuit boards, electroplating, leather making, and chemical manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a comparison chart of the removal of Cu(II)-EDTA in Example 3 of the present invention.

[0018] Figure 2 It is a comparison chart of the removal of heavy metal complexes in Example 4 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0020] Example 1: A method for removing heavy metal complexes in wastewater disclosed in the present invention comprises the following steps: S1 prepares a PMS composite agent, which is prepared by ball milling raw materials containing the following weight percentages: 55% permonosulfate (potassium permonosulfate), 30% sulfite (sodium sulfite), and 15% hypochlorite (calcium hypochlorite); 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 minutes to obtain the PMS composite agent; S2 selected industrial wastewater from an electroplating plant with an initial pH of 4.4 and Cu(II)-EDTA and Ni(II)-EDTA concentrations of 1.3 mmol / L and 1.2 mmol / L, respectively. First, the suspended impurities in the industrial wastewater were removed and the pH of the industrial wastewater was adjusted to 9. Then, under room temperature stirring conditions of 60 rpm, the PMS composite agent (400 mg / L) obtained in S1 was added to 1L of industrial wastewater and stirred to dissolve. Then, alkali solution (sodium hydroxide) was added to adjust the pH of the industrial wastewater to 9.8, and an oxidative decomposition reaction was carried out at room temperature. During the reaction, alkali solution was selectively added to maintain the pH of the industrial wastewater at 9.5~11.0. After 40 minutes of reaction, the pH of the industrial wastewater was adjusted to 12 and allowed to stand for 20 minutes to obtain recycled water.

[0021] Table 1 shows the removal rates of heavy metals and TOC. It can be found that after 40 minutes 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%. The removal effect is relatively ideal.

[0022] Table 1 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 Example 2: A method for removing heavy metal complexes in wastewater disclosed in the present invention comprises the following steps: S1 prepares a PMS composite agent, which is prepared by ball milling raw materials containing the following weight percentages: 65% permonosulfate (potassium permonosulfate), 30% sulfite (sodium sulfite), and 5% hypochlorite (calcium hypochlorite); 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 minutes to obtain the PMS composite agent; S2 selected industrial wastewater from a tannery. When the initial pH was 8.3, the concentrations of Cu(II)-EDTA, Ni(II)-EDTA, and Cr(III)-EDTA were 1.5mmol / L, 0.3mmol / L, and 0.1mmol / L, respectively. The suspended impurities in the industrial wastewater were removed in advance, and the pH of the industrial wastewater was adjusted to 10. Then, under room temperature stirring conditions of 60rpm, the PMS composite agent (500mg / L) obtained by S1 was added to 1L of industrial wastewater, stirred to dissolve, and then alkali solution (sodium hydroxide) was added to adjust the pH of the industrial wastewater to 9.8. An oxidative decomposition reaction was carried out at room temperature. During the reaction, alkali solution was selectively added to maintain the pH of the industrial wastewater at 9.5~11.0. After 60 minutes of reaction, the pH of the industrial wastewater was adjusted to 12, and the wastewater was allowed to stand for 20 minutes to obtain recycled water.

[0023] Table 1 shows the removal rates of heavy metals and TOC. It can be found that after 60 minutes of reaction, the removal rate of heavy metals in the raw water is more than 95%, and the removal rate of TOC is 60.35%. The removal effect is relatively ideal.

[0024] Table 2 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 Example 3: A method for removing heavy metal complexes in wastewater disclosed in the present invention is different from Example 1 in that, in S2, industrial wastewater from a certain electroplating plant is selected, and the Cu(II)-EDTA concentration is 0.8 mmol / L; PMS composite agent (400 mg / L) is added to 1L of industrial wastewater, stirred for 5 minutes to dissolve, and then alkali solution (sodium hydroxide) is added to adjust the pH of the industrial wastewater to 10.5, and Fenton oxidation complex breaking reaction is carried out at room temperature, during which alkali solution is selectively added to maintain the pH of the industrial wastewater at 9.5-11.0. After reacting for 30 minutes, the pH of the industrial wastewater is adjusted to 12, and the solution is allowed to stand and precipitate for 20 minutes to obtain recycled water.

[0025] This embodiment also provides two control groups, wherein the difference from the above method is that in control group 1, after adding the PMS compound agent, no alkali solution is added to adjust the pH to 9.5-11.0, and the pH of the reaction system is maintained at approximately 2.5-3.5; in control group 2, no PMS compound agent is added.

[0026] Figure 1 The comparison of the removal effect of Cu(II)-EDTA in three groups of experiments is shown. It can be seen from the figure that according to the method provided by the present invention, the removal rate of Cu(II)-EDTA within 30 minutes is close to 94%, 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 agent and adjusting the pH between 9.5 and 11.0 are the key to initiating the decomposition reaction.

[0027] Example 4: A method for removing heavy metal complexes in wastewater disclosed in the present invention is different from Example 1 in that, in S2, industrial wastewater from a circuit board factory (1# water sample) is selected. When the initial pH is 8.3, the concentrations of Cu(II)-EDTA, Ni(II)-EDTA, and Cr(III)-EDTA are 1.4mmol / L, 0.2mmol / L, and 0.3mmol / L, respectively; the PMS composite agent (600 mg / L) obtained in S1 is added to 1L of industrial wastewater, stirred for 5 minutes to dissolve, and then alkali solution (sodium hydroxide) is added to adjust the pH of the industrial wastewater to 10.0, and an oxidative complex breaking reaction is carried out at room temperature. During the reaction, alkali solution is selectively added to maintain the pH of the industrial wastewater at 9.5~11.0. After reacting for 30 minutes, the pH of the industrial wastewater is adjusted to 12, and the solution is allowed to stand and precipitate for 20 minutes to obtain recycled water.

[0028] This embodiment also provides a control group, in which the difference from the above method is that in the control group 1, industrial wastewater from a circuit board factory (water sample #2) is selected. When the initial pH is 8.3, the concentrations of Ni(II)-EDTA and Cr(III)-EDTA are 1.1 mmol / L and 0.5 mmol / L, respectively.

[0029] Figure 2 The comparison of the removal effect of heavy metal complexes in two groups of experiments is shown. It can be seen from the figure that according to the method provided by the present invention, the removal rate of heavy metals in water sample 1# is 90-98% within 20 minutes, while in the control group experiment, the removal rate of heavy metals in water sample 2# is less than 10%. It can be found that the copper complex intermediate in industrial wastewater is the key to triggering the decomposition reaction.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for removing heavy metal complexes from wastewater, characterized in that: The following steps are included: S1 prepares a PMS composite agent, wherein the PMS composite agent is prepared by ball milling raw materials containing the following weight percentages: PMS 50-90%, sulfite 5-30%, hypochlorite 5-20%; S2 adds the PMS composite agent obtained in S1 to the industrial wastewater containing heavy metal complexes, wherein the heavy metals in the heavy metal complexes are Cu, and one or more of Co, Cr, Ni, Pb and Zn, and the complex in the heavy metal complexes is one or more of EDTA, NTA, citric acid, oxalic acid, tartaric acid and sorbic acid, stir to dissolve, add alkali solution to maintain the pH of the industrial wastewater to 9.5-11.0, carry out Fenton oxidation decomposition reaction, and obtain recycled water after post-treatment after the reaction is completed.

2. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In S1, the peroxymonosulfate is one or a combination of potassium peroxymonosulfate and sodium peroxymonosulfate.

3. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In S1, the sulfite is one or a combination of sodium sulfite, calcium sulfite and magnesium sulfite.

4. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In S1, the hypochlorite is calcium hypochlorite.

5. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In the S1, 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 400-800 rpm, and the ball milling time is 30-120 min to obtain a PMS composite agent.

6. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In S2, suspended impurities in the industrial wastewater are removed in advance, and the pH of the industrial wastewater is adjusted to 7-10.

7. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In S2, the alkali solution is one or a combination of sodium hydroxide, potassium hydroxide and calcium hydroxide.

8. A method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In the step S2, the molar concentration ratio of the Cu complex to other heavy metal complexes in the heavy metal complex is controlled to be greater than 0.

5.

9. A method for removing heavy metal complexes in wastewater according to claim 8, characterized in that: In the step S2, the molar concentration ratio of PMS to Cu complex in the composite agent is controlled to be 20-100.

10. The method for removing heavy metal complexes in wastewater according to claim 1, characterized in that: In the S2, first, under the stirring condition of 60-100 rpm at room temperature, the PMS composite agent is added and the stirring is continued for 5-10 minutes to dissolve, and then an alkali solution is added to adjust the pH of the industrial wastewater to 9.5-11.0, and a Fenton oxidation complex breaking reaction is carried out under room temperature. During this period, an alkali solution is selectively added to maintain the pH of the industrial wastewater to 9.5-11.

0. After reacting for 20-60 minutes, the pH of the industrial wastewater is adjusted to 11-12, and the wastewater is allowed to stand and settle for 10-30 minutes to obtain recycled water.

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