A method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation

Abstract

The present invention belongs to the technical field of wastewater treatment, and specifically discloses a method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation, which is used for wastewater treatment. This method synthesizes a conductive adsorption filler with a hierarchical structure. The filler has a large specific surface area and can improve the adsorption efficiency of thiourea. Conductive adsorption fillers with gradually increasing density are layered and filled in the absorption tower, and wastewater is fed from the top of the tower to achieve step-by-step adsorption and filtration of the wastewater. On this basis, an external power supply is connected between the conductive adsorption filler and the filler support plate in the packed absorption tower to form an electrolytic cell, so that organic matter in the wastewater is enriched at the conductive adsorption filler, and in-situ electrocatalytic oxidation is completed, thereby achieving continuous adsorption and improving degradation efficiency. The invention couples processes such as conductive adsorption fillers, packed absorption towers, and in-situ electrocatalytic oxidation to solve the problem of low efficiency of wastewater treatment by the original single method. It does not require complex equipment and has strong adaptability.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation. Background Art

[0002] Water is the source of life and one of the most important material resources for human survival and development. No industry is without water. The control of water pollution is a major problem that needs to be solved urgently.

[0003] Adsorption is a green and environmentally friendly method for wastewater treatment, which includes physical adsorption and chemical adsorption. The driving forces of adsorption include van der Waals forces, electrostatic interactions, hydrogen bonds, and π-π stacking. The materials used for adsorption generally have a large specific surface area and a developed pore structure. Commonly used adsorption materials include zeolite, activated carbon, diatomaceous earth, and some natural mineral materials. The adsorption method is characterized by simple operation, no secondary pollution, and environmental friendliness. However, conventional adsorption is difficult to remove thiourea from wastewater, and the adsorption capacity and efficiency also need to be further improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation, which effectively solves the problem that thiourea in wastewater is difficult to remove and the existing method has low adsorption efficiency of thiourea in wastewater.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation, comprising the following steps:

[0006] S1. Synthesis of conductive adsorption filler: soaking the foam metal filler in an alkaline organic solvent, allowing it to react, then adding a metal precursor solution dropwise to the alkaline organic solvent in which the foam metal filler is soaked, ultrasonically dispersing it, allowing it to react, then taking out the foam metal filler and placing it in a muffle furnace, reacting it at high temperature for a period of time, to obtain a conductive adsorption filler with a hierarchical structure.

[0007] S2. Building an absorption tower: arranging a plurality of adsorption layers from top to bottom inside the absorption tower, wherein the adsorption layers include the conductive adsorption filler and a filler support plate, and the filling density of the conductive adsorption filler gradually increases from top to bottom.

[0008] S3. Build an electrocatalytic device: connect the conductive adsorption filler of each adsorption layer and the filler support plate carrying the conductive adsorption filler through an external power supply to form an electrolytic cell, with the conductive adsorption filler serving as the positive electrode and the filler support plate serving as the negative electrode.

[0009] S4. The wastewater enters the absorption tower. When the electrolytic cell is powered, the wastewater flows through each adsorption layer from top to bottom and then flows out. The organic matter in the wastewater is physically adsorbed and in-situ electrocatalytically oxidized.

[0010] Furthermore, in step S1, the concentration of the metal precursor solution is 10-30 wt%, and the metal precursor solution is at least one of a copper sulfate solution, an aluminum sulfate solution, and a ferric sulfate solution.

[0011] Furthermore, in step S1, the alkaline organic solvent is prepared by mixing an organic solvent with a sodium hydroxide solution, and the organic solvent is at least one of ammonium persulfate, sodium persulfate and trimesic acid.

[0012] Furthermore, the concentration of the organic solvent is 50-75 wt%.

[0013] Furthermore, in step S1, the foam metal filler is at least one of foam copper, foam iron and foam nickel.

[0014] Furthermore, in step S2, the filler support plate is at least one of a silicon-based material, a carbon material, and an alloy.

[0015] Furthermore, in step S1, the foam metal filler is first cleaned and then immersed in an alkaline organic solvent. The cleaning method is: placing the foam metal filler in isopropyl alcohol, stirring and cleaning, and then cleaning the surface of the foam metal filler with hydrochloric acid solution, continuing to stir and clean, and ultrasonically oscillating.

[0016] Furthermore, in step S2, a liquid distributor is provided in the absorption tower, and the liquid distributor is provided between below the liquid inlet of the absorption tower and above the top adsorption layer. A liquid redistributor is provided below the filler support plate of each adsorption layer except the bottom adsorption layer.

[0017] The present invention also provides an application of a method combining an in-situ electrocatalytic oxidation technology and an adsorption method in wastewater treatment.

[0018] The beneficial technical effects of the present invention are:

[0019] (1) The present invention uses a porous coordination compound with a highly regular structure formed by a foam metal filler and an organic ligand through coordination bonds and other action modes as an absorption tower filler, which can greatly improve the adsorption rate of thiourea in wastewater.

[0020] (2) The conductive adsorption filler of the present invention has a simple preparation method, strong stability, and a hierarchical nanostructure, which can effectively increase the specific surface area and improve the adsorption efficiency.

[0021] (3) The present invention combines the electrocatalytic oxidation method with the absorption tower to solve the problem of low catalytic efficiency due to low organic matter concentration on the electrode surface, which is conducive to achieving in-situ electrocatalytic oxidation after efficient capture and improving degradation efficiency.

[0022] (4) The method of the present invention can adsorb most of the thiourea from the wastewater, and the thiourea removal rate in the wastewater reaches 98%, thereby reducing wastewater pollution. It is suitable for the field of wastewater recycling and environmental protection and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a cross-sectional view of the absorption tower constructed in Example 1 of the present invention;

[0024] Figure 2 is a line graph showing the change in thiourea removal rate from wastewater as a function of the mass of the conductive adsorption filler in Test Example 2 of the present invention;

[0025] Figure 3 1 is a scanning electron microscope image of the copper foam (a1, a2), the copper foam with clustered nanosheet structure (b1, b2), and the conductive adsorption filler (c1, c3) in Test Example 2 of the present invention;

[0026] Figure 4 It is a bar graph of the thiourea removal rate in wastewater in Test Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] A method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation comprises the following steps:

[0029] S1. Synthesis of a conductive adsorbent filler: Soaking a copper foam filler in an alkaline organic solvent and allowing it to react for a period of time. Then, dropwise adding a metal precursor solution to the alkaline organic solvent containing the copper foam filler, ultrasonically dispersing the metal, and allowing it to react for a period of time. The copper foam filler is then removed from the muffle furnace and reacted at high temperature for 1 to 6 hours to obtain a conductive adsorbent filler having a hierarchical structure. The conductive adsorbent filler has a structure of at least one of a pyramid, a nanosheet, and a nanoneedle.

[0030] In this embodiment, the foam copper filler is first cleaned, and then the cleaned foam copper filler is immersed in an alkaline organic solvent. The cleaning method is: placing the foam copper filler in isopropyl alcohol, stirring and cleaning, and then cleaning the foam copper surface with hydrochloric acid solution, continuing to stir and clean, and ultrasonic oscillation.

[0031] The alkaline organic solvent is prepared by mixing an organic solvent with a sodium hydroxide solution, wherein the organic solvent is at least one of ammonium persulfate, sodium persulfate and trimesic acid, and the concentration of the organic solvent is 50-75 wt%.

[0032] The concentration of the metal precursor solution is 10-30 wt %, and the metal precursor solution is at least one of a copper sulfate solution, an aluminum sulfate solution, and a ferric sulfate solution.

[0033] S2. Build absorption tower: Figure 1 As shown, a top adsorption layer, a middle adsorption layer, and a bottom adsorption layer are arranged from top to bottom within the absorption tower. Each adsorption layer includes a filler support plate, and each filler support plate is filled with the conductive adsorbent filler 5. The packing density of the conductive adsorbent filler 5 increases gradually from top to bottom. That is, the packing density of the conductive adsorbent filler 5 on the top filler support plate 41 is less than the packing density of the conductive adsorbent filler 5 on the middle filler support plate 42, and less than the packing density of the conductive adsorbent filler 5 on the bottom filler support plate 43.

[0034] like Figure 1 As shown, in this embodiment, a liquid distributor 2 for evenly diverting the liquid is provided below the liquid inlet 1 adjacent to the absorption tower in the absorption tower. A filler support plate is provided at a certain interval from below the liquid distributor 2 in the absorption tower to above the liquid outlet 3 of the absorption tower. In this embodiment, a total of three filler support plates are provided in the absorption tower. Each filler support plate is filled with conductive adsorption filler 5, and a liquid redistributor 6 is provided below the top filler support plate 41 and the middle filler support plate 42 to evenly distribute the wastewater passing through the liquid redistributor 6 on the conductive adsorption filler 5 in the lower layer. The density of the conductive adsorption filler 5 in the top layer is less than the density of the conductive adsorption filler 5 in the middle layer and less than the density of the conductive adsorption filler 5 in the bottom layer.

[0035] S3. Build an electrocatalytic device: Figure 1 As shown, the conductive adsorption filler 5 of each adsorption layer and the filler support plate carrying the conductive adsorption filler 5 are connected through an external power supply 7 to form an electrolytic cell, the conductive adsorption filler 5 serves as the positive electrode, and the filler support plate serves as the negative electrode.

[0036] S4, such as Figure 1 As shown, wastewater enters the absorption tower through the liquid inlet 1 at the top of the absorption tower. When the electrolytic cell is powered, the wastewater is evenly distributed through the liquid distributor 2 before flowing through the conductive adsorption fillers 5 of each adsorption layer from top to bottom, exiting the absorption tower through the liquid outlet 3. Organic matter in the wastewater is physically adsorbed and simultaneously undergoes in-situ electrocatalytic oxidation. After treatment in the absorption tower, thiourea, polymers, and heavy metal ions are removed from the wastewater by adsorption. The electrolytic cell is powered for 2-6 hours.

[0037] The invention combines copper ion complexation, conductive adsorption filler and electrocatalytic oxidation electrolytic cell, and increases the specific surface area of ​​the adsorbent and improves the adsorption efficiency of thiourea in wastewater through the combined action of adsorption, gravity sedimentation, filtration, catalytic oxidation and other methods.

[0038] The present invention is further described below with reference to the accompanying drawings and test examples.

[0039] Test Example 1: Testing the removal rate of thiourea from wastewater by complexing the copper ions in the copper chloride solution with the thiourea in the wastewater to cause the thiourea to settle. The specific steps include:

[0040] (1) Preparation of metal salt solution: Weigh 1 g of copper chloride solid and dissolve it in 20 mL of deionized water to prepare a 5% copper chloride solution.

[0041] (2) Reacting the wastewater with a copper chloride solution: 10 mL of copper chloride solution was slowly added dropwise to 10 mL of wastewater, while observing the reaction in the solution. After stirring for 5 minutes, the flocculated precipitate was separated by filtration. The filtrate was centrifuged at 8000 r / min for 15 minutes to obtain a centrifuged supernatant. The supernatant obtained after centrifugation was titrated to determine the thiourea content in the supernatant.

[0042] The test results show that the removal rate of thiourea in wastewater is 30%. The mechanism of this test example is that copper ions form a coordination bond with thiourea to form a stable complex. Thiourea, as a reducing agent, reacts with Cu 2+ The reaction generates formamidine disulfide and Cu + Thiourea forms a complex with copper chloride and also with Cu + Formation of complex, Cu + It also forms a complex with formamidine disulfide.

[0043] Test Example 2: Testing the removal rate of thiourea from wastewater using the conductive adsorption filler synthesized by the present invention. The specific steps are as follows:

[0044] (1) Prepare a metal precursor solution: Dissolve 0.046 mol copper sulfate and 0.04 mol aluminum sulfate in 50 mL of water and stir until dissolved. This is referred to as solution A.

[0045] (2) Preparation of alkaline organic solvent: Dissolve 0.02 mol of ammonium persulfate and 0.2 mol of sodium hydroxide in 200 mL of deionized water, referred to as solution B.

[0046] (3) Cleaning the foam copper filler: 1*1cm 2 The foam copper filler was placed in isopropyl alcohol and stirred for 15 minutes. The surface of the foam copper filler was then cleaned with 0.1 mol / L hydrochloric acid. The stirring and cleaning was continued for 10 minutes, and ultrasonic vibration was performed for 5 minutes.

[0047] (4) Preparation of a conductive adsorption filler with a hierarchical structure: The cleaned foam copper filler was placed in solution B and allowed to react for 2 hours. Then, solution A was slowly added dropwise to solution B soaked with the cleaned foam copper filler, and ultrasonically dispersed for 10 minutes. After standing at room temperature for 1 hour, a foam copper filler with a clustered nanosheet structure was obtained. The foam copper filler with a clustered nanosheet structure was taken out and placed in a muffle furnace, and reacted at 200°C for 2 hours to obtain a conductive adsorption filler with a hierarchical structure.

[0048] (5) reacting the wastewater with the conductive adsorption filler: adding a certain amount of the conductive adsorption filler to 10 mL of wastewater, stirring and reacting for 4 h to allow it to fully contact with the thiourea in the wastewater, stirring and then allowing it to stand, taking the supernatant for titration, and determining the thiourea content in the supernatant.

[0049] The results of the test are as follows Figure 2 It shows that as the mass of the conductive adsorption filler increases, the removal of thiourea from the wastewater first increases rapidly and then gradually stabilizes, with the highest thiourea removal rate in the wastewater reaching 63%. The mechanism of this test case is:

[0050] In the reaction system of this test example, sodium hydroxide is added as an alkaline medium to form copper hydroxide, OH - and Cu 2+ Under alkaline conditions, copper hydroxide nanosheets form coordination and nucleation structures. These structures form a network through van der Waals forces and hydrogen bonds. The reaction process is shown below, where s in brackets represents solid and aq represents solution:

[0051] Cu(s)+(NH4)2S2O8(aq)+2NaOH(aq)→Cu(OH)2(s)+Na2SO4(aq)+(NH4)2SO4(aq);

[0052] Cu(OH)2→CuO+H2O.

[0053] Depend on Figure 3 The SEM image shows that the branched nanosheets in the clustered nanosheet structure grow in different directions on the copper foam structure with almost uniform size. The nanosheets are assembled in multiple layers, interconnected and fixed in a center, forming a spherical shape similar to a flower bud (see Figure 3 (b1) and Figure 3 (b2)). The structure of the conductive adsorption filler is that the nanowires are interwoven and entangled to form a highly regular network structure (see Figure 3 (c1) and Figure 3 (c3)), the structure of the conductive adsorption filler significantly increases the surface area compared to the foam copper structure and the clustered nanosheet structure, thereby increasing the adsorption efficiency.

[0054] Test Example 3: Testing the removal rate of thiourea from wastewater by an absorption tower composed of conductive adsorption fillers. The specific steps are as follows:

[0055] (1) Prepare a metal precursor solution: Dissolve 0.046 mol copper sulfate and 0.04 mol aluminum sulfate in 50 mL of water and stir until dissolved. This is referred to as solution A.

[0056] (2) Preparation of alkaline organic solvent: Dissolve 0.02 mol of ammonium persulfate and 0.2 mol of sodium hydroxide in 200 mL of deionized water, referred to as solution B.

[0057] (3) Cleaning the foam copper filler: 1*1cm 2 The foam copper was placed in isopropanol and stirred for 15 minutes, then the surface of the foam copper was cleaned with 0.1 mol / L hydrochloric acid, and the stirring and cleaning was continued for 10 minutes, and ultrasonic vibration was performed for 5 minutes.

[0058] (4) Preparation of a conductive adsorption filler with a hierarchical structure: The cleaned copper foam was placed in solution B and allowed to react for 2 h. Then, solution A was slowly added dropwise to solution B containing the cleaned copper foam, and ultrasonic dispersion was performed for 10 min. After standing at room temperature for 1 h, the copper foam was taken out and placed in a muffle furnace, and reacted at 200 ° C for 2 h to obtain a conductive adsorption filler with a hierarchical structure.

[0059] (5) Building an absorption tower: a top adsorption layer, a middle adsorption layer, and a bottom adsorption layer are respectively arranged inside the absorption tower from top to bottom, each of the adsorption layers includes a filler support plate, and each of the filler support plates is filled with the conductive adsorption filler, and the filling density of the conductive adsorption filler gradually increases from top to bottom.

[0060] (6) The wastewater passes through the conductive adsorption packing in the absorption tower under the action of gravity. The conductive adsorption packing with gradually increasing density gradually adsorbs and filters the thiourea in the wastewater. The wastewater at the outlet of the absorption tower is titrated to determine its thiourea content.

[0061] The test results show that the removal rate of thiourea in wastewater reaches 88%.

[0062] Test Example 4: Testing the removal rate of thiourea from wastewater by the method of the present invention, the specific steps are as follows:

[0063] (1) Prepare a metal precursor solution: Dissolve 0.046 mol copper sulfate and 0.04 mol aluminum sulfate in 50 mL of water and stir until dissolved. This is referred to as solution A.

[0064] (2) Preparation of alkaline organic solvent: Dissolve 0.02 mol of ammonium persulfate and 0.2 mol of sodium hydroxide in 200 mL of deionized water, referred to as solution B.

[0065] (3) Cleaning the foam copper filler: 1*1cm 2 The foam copper filler was placed in isopropyl alcohol and stirred for 15 minutes. Then the surface of the foam copper filler was cleaned with 0.1 mol / L hydrochloric acid, and the stirring and cleaning was continued for 10 minutes, and ultrasonic vibration was performed for 5 minutes.

[0066] (4) Preparation of a conductive adsorption filler with a hierarchical structure: The cleaned copper foam filler was placed in solution B and allowed to react for 2 h. Then, solution A was slowly added dropwise to solution B soaked with the cleaned copper foam filler, and ultrasonically dispersed for 10 min. After standing at room temperature for 1 h, the copper foam filler was taken out and placed in a muffle furnace, and reacted at 200 ° C for 2 h to obtain a conductive adsorption filler with a hierarchical structure.

[0067] (5) Building an absorption tower: a top adsorption layer, a middle adsorption layer and a bottom adsorption layer are respectively arranged inside the absorption tower from top to bottom, each of the adsorption layers includes a filler support plate, and each of the filler support plates is filled with the conductive adsorption filler 5, and the filling density of the conductive adsorption filler gradually increases from top to bottom.

[0068] (6) Building an electrocatalytic device: The conductive adsorption filler of each adsorption layer and the filler support plate carrying the conductive adsorption filler are connected through an external power supply to form an electrolytic cell, wherein the conductive adsorption filler serves as the positive electrode and the filler support plate serves as the negative electrode.

[0069] Wastewater is fed from the top of the tower and, with electricity flowing through the electrolytic cell, flows through three layers of packing. Organic matter in the wastewater is physically adsorbed and simultaneously undergoes in-situ electrocatalytic oxidation.

[0070] like Figure 4 As shown, the thiourea removal rates measured in test examples 1-4 are summarized and compared and analyzed. It can be seen that the thiourea removal rate of test example 4 is the highest, that is, the wastewater is passed through an absorption tower filled with multi-layer conductive adsorption fillers and an external power supply for deep treatment, which can significantly improve the adsorption efficiency of thiourea in the wastewater and increase the thiourea removal rate in the wastewater by three times.

[0071] In summary, the conductive adsorption filler with a hierarchical structure synthesized by the present invention has a large specific surface area and can improve the thiourea adsorption efficiency. The conductive adsorption filler with gradually increasing density is layered and filled in the absorption tower, and the wastewater is fed from the top of the tower to achieve step-by-step adsorption and filtration of the wastewater. On this basis, an external power supply is connected between the conductive adsorption filler and the filler support plate in the absorption tower to form an electrolytic cell, so that the organic matter in the wastewater is enriched at the adsorption filler, and in-situ electrocatalytic oxidation is completed to achieve continuous adsorption and improve the degradation efficiency. The invention couples the processes of conductive adsorption filler, absorption tower and in-situ electrocatalytic oxidation to solve the problem of low efficiency of wastewater treatment by the original single method. It does not require complex equipment, has strong adaptability, is suitable for the field of wastewater treatment technology, and has good industrial application prospects.

[0072] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation, characterized in that: The following steps are involved: S1. Synthesis of a conductive adsorbent filler: soaking a foam metal filler in a solution prepared by a mixed reaction of ammonium persulfate and sodium hydroxide solution, allowing the mixture to react, then dropwise adding a metal precursor solution to the solution soaked with the foam metal filler, performing ultrasonic dispersion, allowing the mixture to react, and then removing the foam metal filler from a muffle furnace and reacting at high temperature for a period of time to obtain a conductive adsorbent filler having a hierarchical structure; S2. Building an absorption tower: arranging multiple adsorption layers from top to bottom inside the absorption tower, wherein the adsorption layers include the conductive adsorption filler and a filler support plate, and the packing density of the conductive adsorption filler gradually increases from top to bottom; S3. Build an electrocatalytic device: Connect the conductive adsorption filler of each adsorption layer and the filler support plate carrying the conductive adsorption filler through an external power supply to form an electrolytic cell, with the conductive adsorption filler serving as the positive electrode and the filler support plate serving as the negative electrode; S4, the wastewater enters the absorption tower. Under the condition that the electrolytic cell is powered, the wastewater flows through each adsorption layer from top to bottom and then flows out. The organic matter in the wastewater is physically adsorbed and in-situ electrocatalytically oxidized; In step S1 , the concentration of the metal precursor solution is 10-30 wt %, and the metal precursor solution is at least one of a copper sulfate solution and an aluminum sulfate solution.

2. The method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation according to claim 1, characterized in that: The concentration of the ammonium persulfate is 50-75 wt %.

3. The method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation according to claim 1, characterized in that: In step S1, the foam metal filler is at least one of foam copper, foam iron and foam nickel.

4. The method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation according to claim 1, characterized in that: In step S2, the filler support plate is at least one of a silicon-based material, a carbon material, and an alloy.

5. The method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation according to claim 1, characterized in that: In step S1, the foam metal filler is first cleaned and then soaked. The cleaning method is: placing the foam metal filler in isopropyl alcohol, stirring and cleaning, and then cleaning the surface of the foam metal filler with hydrochloric acid solution, continuing to stir and clean, and ultrasonically oscillating.

6. The method for continuously treating thiourea in wastewater by adsorption-enhanced electrocatalytic oxidation according to claim 5, characterized in that: In step S2, a liquid distributor is further provided in the absorption tower, and the liquid distributor is arranged between below the liquid inlet of the absorption tower and above the top adsorption layer. A liquid redistributor is provided below the filler support plate of the other adsorption layers except the bottom adsorption layer.

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