Method for removing copper ions in water by combining phosphorylated micron iron and green rust

Abstract

The invention belongs to the field of water treatment, and relates to a method for removing copper ions in water by combining phosphorylated micron iron and green rust. The method comprises the following steps: adding phosphorylated micron iron and green rust into to-be-treated water containing copper ions, and carrying out stirring reaction to remove the copper ions. According to the method, the phosphorylated micron zero-valent iron can efficiently remove the bivalent copper ions in the water within a short time under the synergistic effect of the green rust, the method is a novel water treatment method for removing the copper ions in the water, a new method is provided for water pollution treatment, and the method has important significance on water pollution treatment.

Description

Technical Field

[0001] The invention belongs to the field of water treatment and relates to a method for removing divalent copper ions in water by combining phosphorylated modified micron zero-valent iron with green rust. Background Art

[0002] Copper pollution mainly comes from electroplating and dye wastewater discharge. A large amount of copper-containing wastewater is discharged into the water environment, which is toxic to aquatic plants and animals, and eventually harms humans through the food chain. Since copper ions are highly enriched and cannot be naturally degraded, copper ions in water bodies will continue to accumulate, causing serious environmental pollution. Therefore, an efficient and harmless water treatment technology is needed to control copper ions in water.

[0003] At present, the methods commonly used to remove copper ions in water bodies include adsorption method: using mineral adsorption materials (zeolite, bentonite), biological adsorption materials (algae, fungi), carbon-based adsorption materials (activated carbon) or nanomaterials (iron tetroxide nanocomposites) to adsorb copper ions in water, and a large number of active groups in the surface structure of the adsorbent play a key role; electrochemical method: under the action of electric current, copper ions undergo reduction reaction at the cathode to generate copper element deposited on the cathode surface; or under the action of electric current, copper ions move in a directional manner, through a selective ion exchange membrane, and are separated from raw water by electrodialysis; chemical precipitation method: adding alkaline neutralizer, sulfiding agent or ferrous sulfate to water, and removing copper ions by precipitation. Although the above methods can well remove copper ions in water, they all have certain disadvantages, such as the selectivity of adsorbents, the consumption and passivation of electrodes, the dosage of chemical agents and secondary pollution problems. Therefore, there is still a need for an environmentally friendly and simple water treatment method in the field to effectively reduce the copper ion content in water. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems and provide a method for removing copper ions in water by combining phosphate-modified zero-valent iron with green rust, which can effectively improve the removal effect of copper ions, thereby controlling the copper ion content in water and ensuring the safety of the water environment; and the method is green and convenient, and provides a new direction for metal treatment in the field of water treatment.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is as follows:

[0006] A method for removing copper ions in water by combining phosphated micron iron with green rust is disclosed. The method comprises adding phosphated micron iron and green rust into water to be treated containing copper ions, stirring the reaction and removing the copper ions.

[0007] Preferably, the preparation method of the phosphated micron iron comprises: ball milling the reduced iron powder and potassium dihydrogen phosphate to obtain the phosphated micron iron. More preferably, the molar ratio (iron-phosphorus ratio) of the reduced iron powder and potassium dihydrogen phosphate is 20:1-5:1; more preferably, the ball-to-material ratio of the ball milling is 4.5:1; more preferably, the grinding balls of the ball milling include 3mm grinding balls and 5mm grinding balls, and the number ratio of the two is 2 (3 mm small balls): 1 (5 mm small balls); more preferably, the ball milling speed is 300-500r, and the ball milling time is 1-4h. The phosphated micron iron obtained by the technical scheme can be effectively applied to the removal of copper ions in the present invention. The condition parameters outside the scope of the technical scheme may also be able to obtain phosphated micron iron, but the removal effect of copper ions in water applied to the present invention may not be good. More preferably, the particle size of the phosphated micron iron is 100-500 mesh.

[0008] More preferably, the phosphorylated micron iron P-ZVI bm The material preparation method specifically includes: adding potassium dihydrogen phosphate and reduced iron powder in a molar ratio of 1:10 into a ball mill, then adding 60 grinding balls with a diameter of 3 mm and 30 grinding balls with a diameter of 5 mm, and the ball-to-material ratio is 4.5:1, placing the grinding jar in a planetary ball mill for ball milling at a speed of 500 r / min, rotating forward for 30 minutes and reverse for 30 minutes as one cycle, and repeating the cycle 4 times for a total of 4 hours.

[0009] More preferably, the reduced iron powder is micron-sized, with a particle size of 100 to 500 meshes.

[0010] Preferably, the green rust is prepared by a coprecipitation method. More preferably, the method for preparing the green rust comprises: mixing a ferrous salt and a ferric salt to obtain a mixed solution, and adding an alkaline precipitant NaOH solution to prepare the green rust. More preferably, the ferrous salt is selected from FeSO4, the ferric salt is selected from FeCl3, and the concentration of the ferrous salt in the mixed solution is 0.132 mol·L -1 , the iron salt concentration is 0.066 mol·L -1 More preferably, the concentration of the NaOH solution is preferably 0.1 to 1 M; More preferably, the NaOH solution is added dropwise to the mixed solution until the pH value reaches 8 and the addition is stopped.

[0011] Preferably, the copper ion concentration in the water to be treated is 10 to 50 mg·L -1 , more preferably 20 mg·L -1 .

[0012] Preferably, the feeding amount of the phosphated micronized iron is 0.5-2 g·L -1 , more preferably 1 g·L -1 The amount of green rust is 0.1-0.5 g·L -1, more preferably 0.1 g·L -1 .

[0013] Preferably, the pH value of the reaction is 4 to 5.4, more preferably 5.4.

[0014] Preferably, the reaction temperature is 20-30°C, more preferably 25°C.

[0015] Preferably, the stirring rate of the reaction is 30-50 r / min, more preferably 45 r / min, and the reaction time is not less than 10 min, more preferably 10-60 min.

[0016] Preferably, the copper ion concentration in the water to be treated is 20 mg·L -1 The feed amount of phosphated micronized iron is 1-2 g·L -1 The amount of green rust is 0.1 g·L -1 , at pH 5.4 and temperature 25°C, at 45 r·min -1 A stirring rate of 10 minutes can achieve a removal effect of 90%, and a reaction time of 50 minutes can achieve a removal effect of more than 95%.

[0017] Zero-valent iron reduction technology has a wide range of raw materials, is cheap and easy to obtain, and after years of research, it has been proven to have good prospects in the treatment of heavy metal ions. However, ordinary commodity zero-valent iron has the defects of low reaction activity and easy surface passivation. In order to overcome the above shortcomings, many scientific researchers have been committed to zero-valent iron modification technology such as sulfidation in recent years. Phosphorylation modification is a new type of zero-valent iron modification technology. Phosphate modification can enhance the ability of zero-valent iron to release electrons, thereby achieving the effect of quickly removing copper ions in water. At the same time, green rust has adsorption and reduction effects on copper ions due to its layered double hydroxide structure and high reduction activity, and it is an iron mineral containing divalent iron and trivalent iron in its structure. There is a potential difference between it and phosphorylated zero-valent iron. Using it in combination with it will promote electron transfer and improve the reduction effect. Therefore, phosphorylated zero-valent iron under the synergistic effect of green rust will greatly increase the rate of removing copper ions in water. The present invention achieves an efficient and convenient copper ion removal effect by using phosphorylated modified zero-valent iron and green rust in combination to remove copper ions in water. This is a new water treatment method for removing copper ions from water, which can broaden the application range of zero-valent iron and green rust.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the method provided by the present invention, the phosphated micron zero-valent iron can efficiently remove divalent copper ions in water in a short time under the synergistic effect of green rust, is a new water treatment method for removing copper ions in water, and provides a new method for water pollution treatment, which is of great significance for water pollution treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The comparison of the removal effects of copper ions by different systems. In the figure, [Cu(Ⅱ)]0=20mg·L -1 , [P-ZVI bm ]0=0.5g·L -1 , [GR]0=0.1g·L -1 , [ZVI bm ]0=0.5g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0020] Figure 2 The pseudo-first-order kinetics fitting diagram for removing copper ions from different systems is shown in Figure 2.

[0021] Figure 3 The initial pH value of the solution affects the P-ZVI bm / GR removes copper ions. In the figure, [Cu(Ⅱ)]0 = 20 mg·L -1 , [P-ZVI bm ]0=0.5g·L -1 , [GR]0=0.1g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0022] Figure 4 The amount of phosphorylated zero-valent iron added to P-ZVI bm / GR removes copper ions. In the figure, [Cu(Ⅱ)]0 = 20 mg·L -1 , [GR]0=0.1g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0023] Figure 5 The amount of green rust added to P-ZVI bm / GR removes copper ions. In the figure, [Cu(Ⅱ)]0 = 20 mg·L -1 , [P-ZVI bm ]0=0.5g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0024] Figure 6 The ratio of Fe and P in ball milling is P-ZVI bm / GR removes copper ions. In the figure, [Cu(Ⅱ)]0 = 20 mg·L -1 , [P-ZVI bm ]0=0.5g·L -1, [GR]0=0.1g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0025] Figure 7 This is the SEM image of phosphorylated micronized zero-valent iron;

[0026] Figure 8 This is the SEM-Mapping surface spectrum of phosphorylated micronized zero-valent iron;

[0027] Fig. 9 For ZVI bm and P-ZVI bm Particle size distribution diagram;

[0028] Fig.10 This is the SEM image of green rust;

[0029] Fig.11 This is a comparison chart with the effect of ordinary micron zero-valent iron / green rust system. In the figure, [Cu(Ⅱ)]0=20mg·L -1 , [GR]0=0.1g·L -1 , [ZVI]0=0.5g·L -1 , speed = 45r·min -1 , temperature = 25°C;

[0030] Fig.12 This is a comparison chart of the effect of the sulfide micron zero-valent iron / green rust system. In the figure, [Cu(Ⅱ)]0 = 20 mg·L -1 , [GR]0=0.1g·L -1 , [S-ZVI]0=0.5g·L -1 , speed = 45r·min -1 , temperature = 25℃. DETAILED DESCRIPTION

[0031] In order to better clarify and understand the purpose, process scheme and advantages of the present invention, the technical scheme and implementation method of the present invention are further described clearly, completely and in detail through specific examples and in combination with the accompanying drawings. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operating processes are given, but they are only part of the embodiments of the present invention, not all of the embodiments. The specific implementation methods described are limited to explaining and interpreting the present invention, and do not limit the present invention. Based on the embodiments in the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] The experimental methods and conditions used in the following examples are conventional methods and conventional conditions unless otherwise specified. The materials, reagents or instruments used in the examples, unless otherwise specified, can be obtained from commercial sources or prepared by conventional methods. The reaction conditions embodied in the content of the invention of the present invention can achieve the reaction and obtain the product of the expected effect. Due to space limitations, only some embodiments are listed below to further illustrate the advantages of the technical solution of the present invention.

[0033] Example 1

[0034] Phosphated micronized iron and green rust are prepared by conventional preparation methods. The specific preparation process is as follows:

[0035] Phosphorylated ZVI bm ) The preparation process is as follows: Reduced iron powder (reduced iron powder (99%) purchased from Shanghai MacLean Biochemical Technology Co., Ltd.) and potassium dihydrogen phosphate are weighed and mixed at a molar ratio of 10:1 (a total of 5 g) and placed in a stainless steel ball mill, and 30 stainless steel balls (3 mm grinding balls: 5 mm grinding balls are in a ratio of 2:1) are placed in the ball mill. The ball mill is placed in a ball mill, the speed is 500 r / min, forward rotation for 30 min, reverse rotation for 30 min as one cycle, the cycle is repeated 4 times, the time is 4 hours, and after the ball milling is completed, it is stored for use. Figure 7 This is the SEM image of the prepared phosphorylated micronized zero-valent iron. Figure 8 This is the SEM-Mapping surface spectrum of phosphorylated micron zero-valent iron.

[0036] The preparation process of green rust (GR) is as follows: 0.0079 mol of FeCl3·6H2O and 0.0158 mol of FeSO4·7H2O are weighed into a 250 mL beaker, and 120 mL of deoxygenated deionized water is added. After dissolving, 1 mol·L -1 The NaOH solution was added dropwise into the continuously stirred mixed solution of FeCl3·6H2O and FeSO4·7H2O. When the pH value of the mixed solution reached 8.0, the addition of NaOH was stopped, the prepared suspension was filtered and separated, and then transferred to a freeze dryer for freeze drying for 8 hours and stored for later use. Fig.10 This is the SEM image of green rust.

[0037] Test method: Add phosphorylated micron zero-valent iron and green rust to a 40 mL brown extraction bottle, then add 20 mg·L -1 Cu(Ⅱ) solution, the concentration of phosphorylated micronized iron in the reaction system was 0.5 g·L -1 , green rust concentration 0.1g·L -1 , cover the bottle cap tightly, place it on a rotating incubator and rotate at 45 r / min -1The reaction was carried out at a speed of 5.4, the initial pH value was 5.4, and the reaction temperature was 25°C. The sampling time points were 10, 20, 30, 40, and 50 min. The reaction solution was extracted with a 5 mL syringe and filtered through a 0.45 μm water filter membrane. The concentration of the liquid sample was measured using an atomic absorption spectrometer.

[0038] Calculation formula for copper ion removal rate:

[0039]

[0040] Where η is the removal rate of copper ions at time t, C0 is the initial concentration of copper ions, C t is the concentration of copper ions at reaction time t.

[0041] Example 2

[0042] Based on Example 1, the phosphorylated micron iron / green rust P-ZVI in the test method bm / GR system replaced by micronized zero-valent iron ZVI bm , Phosphorylated micronized iron P-ZVI bm , green rust GR, micron zero valent iron / green rust ZVI bm / GR system, and ordinary micron zero-valent iron ZVI (commercially available reduced iron powder) / GR system were used to test the removal effect of copper ions in water.

[0043] Among them, micron zero-valent iron (ZVI bm ) The preparation process is as follows: Reduced iron powder (reduced iron powder (99%) purchased from Shanghai MacLean Biochemical Technology Co., Ltd.) is placed in a stainless steel ball mill, and 30 stainless steel balls (3 mm grinding balls: 5 mm grinding balls are in a ratio of 2:1) are placed in the ball mill. The ball mill is placed in a ball mill, the speed is 500 r / min, forward rotation for 30 min, reverse rotation for 30 min as one cycle, the cycle is repeated 4 times, the time is 4 hours, and after the ball milling is completed, it is stored for later use.

[0044] Fig. 9 For ZVI bm and P-ZVI bm Particle size distribution diagram.

[0045] Figure 1 For ZVI bm 、P-ZVI bm ,GR,ZVI bm / GR and P-ZVI bm / GR five systems respectively remove copper ions from water. ZVI after 60 minutes of reaction bm 、P-ZVI bm , GR, ZVI bm / GR and P-ZVI bmThe removal rates of copper ions by the five / GR systems were 10.4%, 77.6%, 26.1%, 57.4% and 96.2%, respectively.

[0046] Fig.11 The effect of ordinary micron zero-valent iron ZVI (commercially available reduced iron powder) and green rust GR on removing copper ions from water was investigated, and only 38% of the removal rate was achieved after 50 minutes of reaction. This shows that the combined system of ordinary micron zero-valent iron ZVI and green rust GR cannot quickly remove copper ions from water.

[0047] Figure 2 For ZVI bm 、P-ZVI bm , GR, ZVI bm / GR and P-ZVI bm Pseudo-first-order kinetics fitting diagram of copper ion removal by five systems of GR. The results showed that ZVI bm The two systems of ZVI and GR do not conform to the pseudo-first-order kinetics, while bm / GR, P-ZVI bm and P-ZVI bm / GR three systems are consistent, and the kinetic constant k obs 0.0166min respectively -1 , 0.0239min -1 and 0.0488min -1 , the combined system is a single P-ZVI bm The combined use of phosphated micron iron and green rust can quickly remove copper ions in water, and the combined system has an advantage in removing copper ions compared with the single system.

[0048] Example 3

[0049] On the basis of Example 1, the pH value in the test method was adjusted to obtain the copper ion removal effect under the conditions of pH values ​​of 2, 3, 4, and 5, respectively.

[0050] Figure 3 For P-ZVI bm / GR removal of copper ions under different initial pH values. It can be seen that the removal rate of copper ions by the combined system is low under pH = 2-3, and high under pH = 4-5, indicating that this technology has a certain pH application range, and the removal effect of copper ions is better under the condition of pH not less than 4.

[0051] Example 4

[0052] Based on Example 1, adjust the P-ZVI in the test method bm Dosage, get P-ZVI bmThe dosage was 0.25 g·L -1 , 0.5g·L -1 , 1g·L -1 , 2g·L -1 The removal effect of copper ions under the following conditions:

[0053] Based on Example 1, the GR dosage in the test method was adjusted to obtain GR dosages of 0.1 g·L -1 , 0.2g·L -1 , 0.3g·L -1 , 0.4g·L -1 , 0.5g·L -1 Copper ion removal effect under different conditions.

[0054] Figure 4 and Figure 5 The effects of different material dosages on the removal of copper ions from water by the combined system were investigated. bm Dosage is less than 0.25g·L -1 When P-ZVI bm Dosage greater than 0.25g·L -1 When the reaction time is 50 minutes, the removal rate can reach more than 95%, and the reaction rate increases with the increase of the dosage. For example, when the dosage is 2g·L -1 Under the following conditions, the removal rate can reach 95% after 10 minutes of reaction. The dosage of green rust GR is 0.1g·L -1 -0.5g·L -1 A high removal effect can be achieved under all conditions.

[0055] Example 5

[0056] On the basis of Example 1, the iron-phosphorus ratio in the preparation process of phosphated micron iron was adjusted to obtain copper ion removal effects of materials with a molar ratio of reduced iron powder to potassium dihydrogen phosphate of 2:1, 5:1, 10:1, 15:1, and 20:1, respectively.

[0057] Figure 6 The effects of different molar ratios of Fe and P on the removal of copper ions in water by the combined system were investigated. When the iron-phosphorus ratio was 5:1 or above, especially in the range of 5 to 20:1, the combined system could remove copper ions in water well. This shows that it is not only one fixed molar ratio of phosphorylated micron iron that can remove copper ions in water under the synergistic effect of green rust, but there is a relatively wide ratio range. This greatly improves the application ability of the combined system.

[0058] Comparative Example 1

[0059] Another common modification method for zero-valent iron is sulfidation modification. The present invention sets sulfided zero-valent iron as a comparative example. The preparation method of sulfided micron zero-valent iron is as follows: (1) Acid washing: In an anaerobic glove box, use deoxygenated deionized water (high-purity nitrogen is introduced into the deionized water for 30 minutes) and prepare a concentration of 50 mmol·L -1 Take 20mL of dilute hydrochloric acid and add it to a 40mL extraction bottle. Then add 5.6g of commercial micronized zero-valent iron. Shake well and let it stand for 1 hour to remove the iron oxide on the surface. (2) Sulfurization: Add 20mL or 10mL of 0.5mol·L -1 (3) Drying: The filtered solid was freeze-dried (12 h) to obtain S-ZVI powders with sulfur-iron ratios of 1:10 and 1:20.

[0060] Fig.12 The effects of two groups of sulfided micron zero-valent iron ZVI and green rust GR with different sulfidation ratios on removing copper ions from water were investigated. After 50 minutes of reaction, the removal rates were only 69% and 74%, respectively. It can be seen that both are far lower than the phosphated micron iron P-ZVI of the present invention. bm The removal effect of the system combined with green rust GR. This reflects the phosphorylated micron iron P-ZVI of the present invention. bm Unexpected superiority of the system combined with Green Rust GR.

[0061] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for removing copper ions in water by combining phosphated micron iron with green rust, characterized in that: The method comprises adding phosphated micron iron and green rust into water to be treated containing copper ions, stirring the water to react and removing the copper ions.

2. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The method for preparing phosphated micron iron comprises: ball milling reduced iron powder and potassium dihydrogen phosphate to obtain phosphated micron iron.

3. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 2, characterized in that: The molar ratio of the reduced iron powder to potassium dihydrogen phosphate is 20:1 to 5:

1.

4. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 2, characterized in that: The particle size of the reduced iron powder is 100-500 meshes.

5. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The preparation method of phosphated micron iron specifically comprises: adding potassium dihydrogen phosphate and reduced iron powder in a molar ratio of 1:10 into a ball mill, then adding 60 grinding balls with a diameter of 3 mm and 30 grinding balls with a diameter of 5 mm, with a ball-to-material ratio of 4.5:1, placing the grinding jar into a planetary ball mill for ball milling at a speed of 500 r / min, rotating forward for 30 min and reverse for 30 min as one cycle, repeating 4 times for a total of 4 hours.

6. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The green rust is prepared by a co-precipitation method.

7. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The copper ion concentration in the water to be treated is 10 to 50 mg·L -1 .

8. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The feeding amount of the phosphated micron iron is 0.5-2 g·L -1 The amount of green rust is 0.1-0.5 g·L -1 .

9. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The pH of the reaction is 4-5.

10. The method for removing copper ions in water by combining phosphated micron iron with green rust according to claim 1, characterized in that: The stirring rate of the reaction is 30-50 r / min, and the reaction time is not less than 10 min.

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