A method for treating wastewater containing high concentration of Cu(II)-EDTA by using ball-milling zero-valent manganese

Abstract

This invention provides a method for the efficient and low-cost treatment of wastewater containing high concentrations of Cu(II)-EDTA by ball milling zero-valent manganese, utilizing zero-valent manganese (ZVMn) obtained through simple mechanical ball milling. bm This study investigated the performance and mechanism of Cu(II)-EDTA as the target pollutant. The concentration of Cu(II)-EDTA was 100 ppm, and ZVMn was used. bm At a concentration of 1 g / L, after a reaction time of 5 minutes, the removal rate of pollutants reached over 98%, with a recovery rate as high as 90%. Cost calculations showed that the energy consumption of zero-valent manganese after ball milling was 1.41 times lower than that of untreated zero-valent manganese. The effects of adding different coexisting substances to the reaction system were investigated. bm The environmental adaptability of ZVMn was demonstrated, with pollutant removal rates exceeding 90% after 5 minutes, indicating that ZVMn... bm It maintains good removal performance under the influence of different coexisting substances and has good environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation of industrial heavy metal wastewater, specifically to a method for the efficient and low-cost treatment of wastewater containing high concentrations of Cu(II)-EDTA by ball milling zero-valent manganese. Background Technology

[0002] This section provides only background information relevant to this disclosure and is not necessarily prior art.

[0003] With industrial progress and social development, heavy metal pollution has become a key focus and challenge for national pollution control. Statistics show that my country's electroplating industry alone generates approximately 4 billion tons of heavy metal wastewater annually, primarily containing copper (Cu), nickel (Ni), and cadmium (Cd). The presence of complexing agents (pesticides, fertilizers, detergents, plasticizers, etc.) further complicates the composition of industrial heavy metal wastewater. Heavy metal ions readily combine with organic ligands such as ethylenediaminetetraacetic acid (EDTA), nitrotriacetic acid (NTA), humic acid (HA), and citric acid (CA) to form stable metal complexes with different structures and toxicities. Therefore, in addition to existing in ionic form, over 90% of heavy metals in wastewater exist in complexed forms. These stable heavy metal complexes are non-biodegradable and exhibit both natural persistence and bioaccumulation. Once it enters a higher organism through bioaccumulation, it is very difficult to excrete or completely eliminate it naturally. It will react with proteins or enzymes in the organism, causing them to lose their activity, damaging internal organs, and causing acute, subacute, and chronic poisoning, resulting in irreversible damage to the organism.

[0004] Cu(II)-EDTA, a typical pollutant in electroplating wastewater, is composed of the heavy metal Cu. 2+ A stable complex formed by complexing Cu with EDTA in a 1:1 molar ratio. EDTA contains four carboxyl groups and two amino groups. 2+ The resulting complex has a stability constant as high as 18.7. Copper, as one of the essential elements for the human body, plays a vital role, but excessive intake can lead to acute copper poisoning, which in severe cases can cause hepatitis, hypotension, acute renal failure, and even death. Complexed copper, due to the stable coordination bond formed with EDTA, is more toxic to the environment and microorganisms than metal ions.

[0005] Previous studies have shown that, similar to most methods for removing free heavy metals, the removal of complexed heavy metals also includes electrolysis, adsorption, and photocatalysis. However, in practical operation, it is necessary to consider both treatment effectiveness and operating costs, while also avoiding the introduction of secondary pollutants. Electrolysis is energy-intensive and prone to leaving organic ligands that can lead to secondary pollution. Adsorption is reliable, relatively economical, and produces less sludge compared to coagulation-filtration, and is widely used for the treatment and remediation of water bodies containing heavy metals. However, the adsorbent will reach adsorption saturation and must be regenerated. Additionally, there are membrane separation methods such as reverse osmosis, but all of these have drawbacks to varying degrees, including high cost, high energy consumption, and operational difficulties.

[0006] Zero-valent metals, as green remediation materials, have a large specific surface area and strong electron-donating ability, and are widely used in water purification processes. Manganese is one of the most abundant elements in the first transition series and one of the most active and important geochemical elements. Mn has a rich variety of valence states, ranging from 0 to +7, and its electronic structure is 3d. 5 4s 2 With a redox potential of -1.18V, it has a strong affinity for oxygen and can reduce and fix most heavy metal ions in water. Mn 0 The surface is easily oxidized to form MnO x @Mn 0 The core-shell structure exhibits more persistent catalytic activity compared to manganese oxides and has a strong adsorption capacity for heavy metals and organic matter.

[0007] However, in practical applications, we have found that zero-valent manganese also has many drawbacks. The oxide layer on its surface significantly hinders the outward transfer of internal electrons, leading to a decrease in its reduction activity for target pollutants. Compared with chemical modification, the method of surface modification of zero-valent manganese through mechanical ball milling is easier to scale up and apply due to its advantages of simple operation, low cost, and no waste liquid generation. Summary of the Invention

[0008] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for treating wastewater containing high concentrations of Cu(II)-EDTA by ball milling zero-valent manganese at high efficiency and low cost, in order to address the shortcomings of the existing technology.

[0009] To solve the above-mentioned technical problems, the present invention discloses the following technical solution:

[0010] An application of zero-valent manganese in the removal of Cu(II)-EDTA, specifically a ball-milled zero-valent manganese (ZVMn) bm A method for efficiently and cost-effectively treating wastewater containing high concentrations of Cu(II)-EDTA.

[0011] The zero-valent manganese is obtained by ball milling manganese powder; the manganese powder is commercial manganese powder.

[0012] The grinding balls used in the ball mill are stainless steel grinding balls.

[0013] The diameter of the grinding beads is 2-6 mm, preferably 2-4 mm and 4.1-6 mm, and more preferably 3 mm and 5 mm.

[0014] Furthermore, the ratio of the number of grinding balls with a diameter of 2-4 mm to the number of grinding balls with a diameter of 4.1-6 mm is 1-3:1, preferably 2:1.

[0015] For every 4g of manganese powder, 15-25 grinding balls with a diameter of 4.1-6mm and 35-45 grinding balls with a diameter of 2-4mm are used, preferably 20 grinding balls with a diameter of 5mm and 40 grinding balls with a diameter of 3mm.

[0016] The total ball milling time is 0.5-4 hours, preferably 1.5-3 hours, and more preferably 2 hours.

[0017] The ball mill rotates at a speed of 200-800 rpm, preferably 300-600 rpm, and more preferably 350-500 rpm.

[0018] The ball milling is performed using a planetary ball mill, with the milling direction changed every 20-40 minutes, preferably every 30 minutes. The operating power of the ball mill is 20-46W, such as 25W, 30W, 35W, or 40W, preferably 33.33W.

[0019] Among them, ball-milled zero-valent manganese (ZVMn) bm It is added to wastewater containing Cu(II)-EDTA to remove Cu(II)-EDTA; wherein, during the process of removing Cu(II)-EDTA, it is stirred, such as by mechanical stirring.

[0020] The mass ratio of zero-valent manganese to Cu(II)-EDTA is 8-12:1, preferably 10:1.

[0021] The zero-valent manganese removes Cu(II)-EDTA under conditions where the initial pH is 2-5, such as when the initial pH of the reaction is 3.4.

[0022] The ball-milled zero-valent manganese (ZVMn) described in this invention bm Store in an inert gas for later use.

[0023] The ball-milled zero-valent manganese (ZVMn) described in this invention bm The removal rate of Cu(II)-EDTA and Cu(II) was as high as 98% within 5 minutes.

[0024] Beneficial effects:

[0025] 1. The method of the present invention utilizes ball milling to weaken the outer oxide layer of commercial manganese powder, allowing the electrons of the zero-valent manganese inside to be efficiently transferred outward, captured and utilized by the pollutants adsorbed on the outside, thereby reducing the pollutants.

[0026] 2. The ball-milled zero-valent manganese (ZVMn) synthesized by the method of this invention bm The removal effect of high-concentration Cu(II)-EDTA is better than that of unmodified zero-valent manganese (ZVMn) material, which significantly improves the removal efficiency and reduces energy consumption.

[0027] 3. Preparation of ball-milled zero-valent manganese (ZVMn) by the method of the present invention bm The reaction conditions are minimal and can be carried out at room temperature and pressure.

[0028] 4. The method of the present invention is simple in technology, highly practical, has mild reaction conditions, is easy to operate, has low equipment requirements, is conducive to large-scale promotion, and has significant economic and environmental benefits. Attached Figure Description

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0030] Figure 1 ZVMn in Example 1 bm XRD pattern.

[0031] Figure 2 ZVMn in Example 1 bm SEM images of ZVMn.

[0032] Figure 3 ZVMn in Example 2 bm Comparison of Cu(II)-EDTA removal effects between ZVMn and ZVMn.

[0033] Figure 4 ZVMn in Example 2 bm Comparison of Cu(II) removal effects between ZVMn and ZVMn.

[0034] Figure 5 ZVMn in Example 2 bm Comparison of Cu(II) recovery effects between ZVMn and ZVMn.

[0035] Figure 6 ZVMn in Example 2 bm Comparison of SEM-mapping before and after the reaction.

[0036] Figure 7 ZVMn in Example 2 bm Energy consumption comparison chart between ZVMn and ZVMn.

[0037] Figure 8 Different inorganic anion pairs ZVMn in Example 3 bm Comparison of treatment effects on wastewater containing high concentrations of Cu(II)-EDTA.

[0038] Figure 9 The natural organic compound (HA) in Example 4 affects ZVMn bm Comparison of treatment effects on wastewater containing high concentrations of Cu(II)-EDTA.

[0039] Figure 10 The reaction of ZVMn with different initial pH values ​​in Example 5 bm Comparison of treatment effects on wastewater containing high concentrations of Cu(II)-EDTA. Detailed Implementation

[0040] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0041] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0042] The main raw materials involved in the following examples, such as zero-valent manganese (ZVMn), were all from Maclean (Shanghai, China). All reagents were of analytical grade, and the particle size of zero-valent manganese was 200 mesh.

[0043] Example 1

[0044] This embodiment provides a method for ball milling zero-valent manganese, the specific steps of which are as follows:

[0045] 4.0 g of zero-valent manganese was weighed and milled using a planetary ball mill from Nanjing Boyuntong Instrument Technology Co., Ltd. at 400 rpm for 2 hours. The operating power was 33.33 W, and the mill rotated once every 30 minutes. The milling jar contained 20 medium-sized milling beads (5 mm in diameter) and 40 small milling beads (3 mm in diameter). The milling process resulted in a 10.1% mass loss of ZVMn. The processed sample was denoted as ZVMn. bm Stored in inert gas.

[0046] from Figure 1 It can be seen that ball milling did not change the main phase of the material, which remained Mn. 0 Phase structure; from Figure 2 It can be seen that ball milling reduces the particle size of ZVMn, increases the specific surface area of ​​the material, and is beneficial for pollutant removal.

[0047] Example 2

[0048] Add 100 ppm (100 mg / L) Cu(II)-EDTA aqueous solution to a 100 mL beaker, bringing the total reaction solution volume to 50 mL. The initial pH is 3.4. Add 0.05 g ZVMn to the reaction solution. bm Alternatively, ZVMn is mixed at a concentration of 1 g / L in an open aerobic environment using mechanical stirring. The mixture is placed on a constant-temperature rotary mixer with a rotation speed of 200 r / min and a temperature of 25 °C. Samples are taken at regular intervals to determine the residual amount of Cu(II)-EDTA or Cu(II) in the system.

[0049] Experimental results are as follows Figure 3 and Figure 4 As shown, ZVMn bm Within 5 minutes, the removal rates of Cu(II)-EDTA and Cu(II) were 98% and 93%, respectively, which were higher than those of ZVMn (54% and 38%). Figure 6 It can be seen that the copper signal was significantly enhanced after the reaction, thus achieving copper recovery.

[0050] Energy consumption calculation: The commercial retail price of manganese is 1.01 yuan / gram, and the Nanjing commercial electricity price is 0.67 yuan / kWh. The calculation method is as follows: formulas (1)(2)(3). The calculation results are as follows: Figure 7 The ball mill consumes 0.045 yuan of electricity when running at 33.33W for 2 hours. Considering the loss rate of 10.1% caused by the ball mill, 4.45g of raw materials are needed to obtain 4g of processed sample, and the material cost is 4.495 yuan. The total cost is 4.495 + 0.045 = 4.54 yuan (material cost + electricity cost). Therefore, the unit sample processing fee is 4.54 ÷ 4 = 1.135 yuan / gram.

[0051] With ZVMn bm Taking the treatment of 1L of 100ppm Cu(II)-EDTA wastewater as an example, using 1g / L ZVMn bm The removal rate of 100ppm Cu(II)-EDTA within 5 minutes is 98%. Complete removal would require 1g / L × 1L × 100% ÷ 98% = 1.02g, costing 1.02 × 1.135 = 1.158 yuan. The electricity cost of the constant-temperature rotary mixer running at 860W for 5 minutes is 0.048 yuan. Considering the above costs, ZVMn... bm The energy required to treat 1L of 100ppm Cu(II)-EDTA wastewater is 1.158 + 0.048 = 1.206 yuan. It can be seen that ball milling significantly reduces the energy consumption of the material, achieving low-cost treatment.

[0052]

[0053] For the reacted ZVMnbm Alternatively, ZVMn can be recovered by dissolving it in 0.1 mol / L hydrochloric acid and then bringing the volume to 50 mL. The amount of Cu(II) recovered in the system is then determined. The experimental results are as follows: Figure 5 As shown, the recovery rate of Cu(II) from zero-valent manganese after ball milling can reach over 90%, which is much higher than the 35% recovery rate of untreated zero-valent manganese.

[0054] Example 3

[0055] Add 100 ppm Cu(II)-EDTA aqueous solution to a 100 mL beaker, bringing the total reaction solution volume to 50 mL with an initial pH of 3.4. Add 0.029 g NaCl, 0.042 g NaNO3, and 0.071 g NaSO4 to the reaction solution to achieve an initial anion concentration of 10 mM. Add 0.05 g ZVMn. bm The concentration was adjusted to 1 g / L, and the mixture was mechanically stirred in an open aerobic environment on a constant-temperature rotary mixer at a speed of 200 r / min and a temperature of 25 °C. Samples were taken at regular intervals to determine the residual amount of Cu(II)-EDTA in the system.

[0056] Experimental results are as follows Figure 8 As shown, the presence of inorganic anions affects ZVMn bm The removal of Cu(II)-EDTA has little effect.

[0057] Example 4

[0058] Add 100 ppm Cu(II)-EDTA aqueous solution to a 100 mL beaker, bringing the total reaction solution volume to 50 mL. The initial pH is 3.4. Add 5 mg of humic acid (HA) to the reaction solution to bring the initial concentration to 10 ppm, and add 0.05 g of ZVMn. bm The concentration was adjusted to 1 g / L, and the mixture was mechanically stirred in an open aerobic environment on a constant-temperature rotary mixer at a speed of 200 r / min and a temperature of 25 °C. Samples were taken at regular intervals to determine the residual amount of Cu(II)-EDTA in the system.

[0059] Experimental results are as follows Figure 9 As shown, the presence of natural organic matter, represented by HA, affects ZVMn. bm The removal of Cu(II)-EDTA has little effect on ZVMn bm It has good environmental adaptability.

[0060] Example 5

[0061] Add 100 ppm Cu(II)-EDTA aqueous solution to a 100 mL beaker, adjust the initial pH of the solution with 3 mM KOH, and the total volume of the reaction solution is 50 mL. Add 0.05 g ZVMn to the reaction solution. bm The concentration was adjusted to 1 g / L, and the mixture was mechanically stirred in an open aerobic environment on a constant-temperature rotary mixer at a speed of 200 r / min and a temperature of 25 °C. Samples were taken at regular intervals to determine the residual amount of Cu(II)-EDTA in the system.

[0062] Experimental results are as follows Figure 10 As shown, different initial pH values ​​affect ZVMn bm The removal of Cu(II)-EDTA has little effect on ZVMn bm It has good environmental adaptability.

[0063] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An application of zero-valent manganese in the removal of Cu(II)-EDTA, characterized in that, The zero-valent manganese is obtained by ball milling manganese powder; the mass ratio of the zero-valent manganese to Cu(II)-EDTA is 8-12:

1.

2. The application according to claim 1, characterized in that, The grinding balls used in the ball mill are stainless steel grinding balls.

3. The application according to claim 2, characterized in that, The diameter of the grinding beads is 2-6 mm.

4. The application according to claim 2, characterized in that, The diameter of the grinding beads is 2-4 mm and 4.1-6 mm.

5. The application according to claim 4, characterized in that, The ratio of grinding balls with a diameter of 2-4 mm to grinding balls with a diameter of 4.1-6 mm is 1-3:

1.

6. The application according to claim 4, characterized in that, The ratio of grinding beads with a diameter of 2-4 mm to those with a diameter of 4.1-6 mm is 2:

1.

7. The application according to claim 1, characterized in that, Use 15-25 grinding balls with a diameter of 4.1-6 mm and 35-45 grinding balls with a diameter of 2-4 mm for every 4 g of manganese powder.

8. The application according to claim 7, characterized in that, Use 20 5 mm grinding balls and 40 3 mm grinding balls for every 4 g of manganese powder.

9. The application according to claim 1, characterized in that, The total ball milling time is 0.5-4 h.

10. The application according to claim 1, characterized in that, The total ball milling time is 1.5-3 hours.

11. The application according to claim 1, characterized in that, The total time for ball milling is 2 hours.

12. The application according to claim 1, characterized in that, The ball mill rotates at a speed of 200-800 rpm.

13. The application according to claim 1, characterized in that, The ball mill rotates at a speed of 300-600 rpm.

14. The application according to claim 1, characterized in that, The ball mill rotates at a speed of 350-500 rpm.

15. The application according to claim 1, characterized in that, The ball milling is performed using a planetary ball mill, and the direction of the ball milling is changed every 20-40 minutes.

16. The application according to claim 1, characterized in that, The mass ratio of zero-valent manganese to Cu(II)-EDTA is 10:

1.

17. The application according to claim 1, characterized in that, The zero-valent manganese removes Cu(II)-EDTA under pH conditions of 2-5.

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