Sludge conditioning method based on efficient catalytic ozonation of modified titanium film

Abstract

The invention relates to the technical field of sludge reduction, in particular to a sludge conditioning method based on efficient catalytic ozonation of a modified titanium film. According to the method, a nitrate solution of nickel, iron and cerium is adopted as an electrolyte, a titanium film is modified through electro-deposition, meanwhile, the modified titanium film serves as an aeration head and is used for catalyzing ozone oxidation conditioning of the sludge, in the process, the modified aeration head serves as a cathode, an annular titanium ruthenium net serves as an anode, and the ozone oxidation conditioning of the sludge is achieved. The sludge is conditioned under the conditions of introducing ozone and constant current, the specific resistance of the conditioned sludge can be reduced by more than 60%, and the capillary water absorption time can be reduced by more than 40%. The method is simple and efficient, medicine input to a sludge system is avoided from the source, ozone is introduced for a short time, subsequent treatment can be directly carried out after conditioning, and the time cost is saved; meanwhile, the oxidation efficiency of ozone is increased, and a good sludge conditioning effect is achieved under the condition of small ozone dosage.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge reduction, and particularly relates to a sludge conditioning method based on highly efficient catalytic ozonation of a modified titanium film. Background Art

[0002] As an important step in sludge reduction, sludge conditioning usually uses the addition of chemical agents or flocculants to improve the dewaterability of sludge. Most of the existing sludge conditioning methods involving ozonation require the introduction of a large amount of catalyst into the sludge system to achieve the effect of catalytic ozonation and realize the effective utilization of ozone, such as WO2023077882A1 (Method for preparing sludge conditioner using feed water sludge and application of sludge conditioner), CN117185619A (Method for enhancing sludge conditioning effect by ozone coupling with perborate).

[0003] WO2023077882A1 uses dried sludge and phosphoric acid, sodium hydroxide, etc. as pore-forming agents for impregnation, and then uses drying and calcination to prepare the catalyst. The application scenario of this catalyst requires first adjusting the pH of the sludge to be conditioned to a certain level, then adding a certain amount (400 mg / g sludge dry basis) of the catalyst and stirring at a certain rotation speed (800 rpm), and then pouring the sludge to be conditioned containing the catalyst into the reactor and passing ozone (dosage is 60 mg / g sludge dry basis) for conditioning for 15 minutes. This process has certain disadvantages: the preparation process of the catalyst is relatively complex and the input of external agents is large; at the same time, the application scenario is relatively strict, and it is necessary to adjust the pH of the sludge to be conditioned to acidic in advance, and a large amount of acid will be added to the original sludge here, resulting in an increase in the dosage of agents. This method has disadvantages such as complex preparation process, large dosage of agents, and large ozone dosage, which has an adverse impact on the subsequent treatment of sludge.

[0004] CN117185619A uses perborate as a catalyst, aerates ozone after adding the catalyst, and then adds a flocculant for sludge conditioning; after the conditioning method is completed, it is necessary to stand for 0.5 - 1 h according to the situation to make the solids settle sufficiently. This conditioning method first adds chemical reagents, and then adds flocculants such as polyaluminum ferric silicate after passing ozone, which makes external agents enter the sludge system. At the same time, in the experimental examples, it is necessary to stand overnight after flocculation stirring to achieve solid-liquid separation, which requires a large time cost. Therefore, this conditioning method has certain time-consuming properties and risks in the subsequent treatment of drug addition.

[0005] In summary, the existing sludge conditioning methods involving ozone oxidation have disadvantages such as complex catalyst preparation processes, large dosages of external agents, strict usage scenarios, large ozone dosages, and long time consumption. Therefore, the method of the present invention proposes a sludge conditioning method based on highly efficient catalytic ozone oxidation using a modified titanium membrane. This conditioning method uses the modified titanium membrane as a catalyst, avoiding the input of drugs into the sludge system from the source. Secondly, through the introduction of ozone for a short time, the sludge can be directly subjected to subsequent treatment after conditioning, saving time costs. At the same time, under the action of this catalyst, the oxidation efficiency of ozone increases, achieving a good sludge conditioning effect with a smaller ozone dosage. Summary of the Invention

[0006] The object of the present invention is to provide a sludge conditioning method based on highly efficient catalytic ozone oxidation using a modified titanium membrane to solve the problems of reducing the dosage of external agents and improving the sludge conditioning efficiency.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A sludge conditioning method based on highly efficient catalytic ozone oxidation using a modified titanium membrane, comprising the following steps:

[0008] S11. Modify the titanium membrane and use the modified titanium membrane as an aeration head to introduce ozone;

[0009] S12. Use the aeration head as the cathode and a circular titanium ruthenium mesh as the anode to condition the sludge under a constant current condition;

[0010] S13. Directly use the conditioned sludge for dewatering and reduction.

[0011] Further, the modification of the titanium membrane includes the following steps:

[0012] S21. Prepare an electrolyte solution;

[0013] S22. Use the titanium membrane as the cathode and a circular titanium ruthenium mesh as the anode to electro-deposit the titanium membrane under a constant current condition;

[0014] S23. Vacuum dry the electro-deposited titanium membrane to obtain the modified titanium membrane.

[0015] Further, in S21, the electrolyte solution is a nitrate solution of nickel, iron, and cerium, the total molar concentration of the solute is 1 mM, and the molar ratio of nickel, iron, and cerium is 7:2:1.

[0016] Further, in S22, the pore size of the titanium membrane is 0.2 - 0.45 μm, and the circular titanium ruthenium mesh is placed around the titanium membrane.

[0017] Further, in S22, the constant current is 10 - 30 mA / cm based on the titanium membrane 2 , and the reaction time is 300 - 500 s.

[0018] Further, in the step S11, the inlet gas flow rate of ozone is 20-50 mL / min; the concentration of the ozone generator is adjusted to 15-80 mg / L.

[0019] Further, in the step S12, the constant current for sludge conditioning is 30-50 mA, and the reaction time is 15 min to 1.5 h.

[0020] Further, in the step S13, after conditioning, the sludge specific resistance can be reduced by more than 60% compared with that before conditioning; the capillary suction time can be reduced by more than 40% compared with that before conditioning.

[0021] Beneficial effects of the present invention:

[0022] The method of the present invention avoids the input of drugs into the sludge system from the source. By introducing ozone for a short time, the sludge specific resistance after conditioning can be reduced by more than 60%, and the capillary suction time can be reduced by more than 40%, and subsequent disposal can be directly carried out, saving time costs; at the same time, the oxidation efficiency of ozone increases, achieving a better sludge conditioning effect with less ozone dosage. Description of the drawings

[0023] Figure 1 is a schematic diagram of the electrodeposition modification of the industrial titanium film of the present invention;

[0024] Figure 2 is the surface SEM images of the industrial titanium film before and after modification of the present invention; a) before modification; b) after modification;

[0025] Figure 3 is a schematic diagram of the structure of the sludge conditioning reactor of the present invention. Specific embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention.

[0027] The method of the present invention uses the electrodeposition method to perform cathode loading on the industrial titanium film, uses a nitrate solution containing nickel, iron, and cerium as the electrolyte, and a circular titanium ruthenium mesh as the anode, so that the compound of nickel, iron, and cerium is loaded on the pore surface of the titanium film, and the modification of the titanium film is completed after vacuum drying.

[0028] Subsequently, the modified catalyst titanium film is used as the cathode, and the rectangular titanium ruthenium mesh is used as the anode, and a constant current is passed under the condition of introducing ozone to perform sludge conditioning.

[0029] In the method of the present invention, the surface of the modified titanium film contains metal nickel, iron and cerium, and its surface has a certain roughness and pore structure, which makes the residence time of ozone longer when passing through; the condition of constant current increases the catalytic activity, and it is easier to generate active oxygen groups such as hydroxyl radicals, superoxide radicals and singlet oxygen in the advanced oxidation of ozone, forming an efficient chemical conditioning effect on sludge.

[0030] Free radicals attack the extracellular polymers and zoogloea in the sludge flocs, causing the physicochemical properties of the sludge such as particle size and viscosity to be reconstructed, releasing bound water, and enhancing the dewaterability of the sludge.

[0031] The schematic diagram of the electrodeposition modification of the industrial titanium film in the present invention is as Figure 1 shown.

[0032] As Figure 1 , the industrial titanium film (membrane pore Φ0.2 - 0.45μm, size Φ12 * 55mm) is used as the cathode, and the annular titanium ruthenium mesh (commercially available, Baoji Yinggao Metal Materials Co., Ltd., Φ50 * 150mm) is placed around it as the anode. The electrolyte is a mixed solution of 0.7 mM Ni(NO 3 ) 2 ·6H 2 O: 0.2 mM Fe(NO 3 ) 3 ·9H 2 O: 0.1 mM Ce(NO 3 ) 3 ·6H 2 O. The solution is circulated using a peristaltic pump at a flow rate of 0.5 rpm (≈1.1 mL / min).

[0033] The electrodeposition condition is constant current, and the current is set to 10 - 30 mA / cm 2 based on the titanium film, and the reaction time is 300 - 500 s; after electrodeposition, the titanium film is placed in a vacuum drying oven, and after drying, the modification of the titanium film is completed. The modified titanium film can be reused 2 - 10 times in the sludge conditioning system.

[0034] The modified titanium film is used as an aeration head. Subsequently, the excess sludge (water content 92 - 97%) from the sewage treatment plant is put into the reactor. The modified aeration head is used as the cathode, and the rectangular titanium ruthenium mesh is used as the anode. Ozone enters the reaction system in the form of bubbles through the modified titanium film, and an electrocatalytic ozone oxidation reaction with a constant current of 30 - 50 mA is carried out; the inlet gas flow rate of ozone is 20 - 50 mL / min; the concentration of the ozone generator is adjusted to 15 - 80 mg / L; the reaction time is 15 min - 1.5 h.

[0035] Example 1

[0036] Titanium film modification:

[0037] Prepare 350 mL of electrolyte solution in two beakers, and the dosage of the medicines is as follows: 71.3 mg of Ni(NO 3 ) 2 ·6H 2 O; 28.3 mg of Fe(NO 3 ) 3 ·9H 2 O; 15.2 mg of Ce(NO 3 ) 3 ·6H 2 O.

[0038] Use two 0.45-μm titanium membranes for electrodeposition loading, and connect wires to the titanium membranes in advance; place the titanium membranes vertically into the solution, and place and fix the annular titanium ruthenium mesh around them; connect the DC power supply and set a constant current of 420 mA, with the titanium membrane connected to the negative pole of the power supply and the titanium ruthenium mesh connected to the positive pole of the power supply.

[0039] Then, energize and start timing. The deposition times of the two titanium membranes are 300 s and 500 s respectively; after electrodeposition, take out the two modified aeration heads and put them into a vacuum drying oven, keep the pumping state and dry them at room temperature for 4 h, and then take them out, and the modification is completed.

[0040] Sludge conditioning:

[0041] Take the excess sludge from the sewage treatment plant with a moisture content of 96.8% and put 350 mL into each of the two beakers.

[0042] Set the modified titanium membrane as the cathode and the anode as a rectangular titanium ruthenium mesh. The distance between the two electrodes is 2 cm, and the DC power supply current is set to 50 mA in advance; put a magnetic stirrer rotor into the beaker and set the rotation speed to 350 rpm; turn on the ozone generator (Longevity EXT120-C) and adjust the flow rate to 30 - 50 mL / min; adjust the ozone concentration to 15 - 40 mg / L (due to instrument reasons, the flow rate and concentration will fluctuate within this range).

[0043] After ozone is introduced into the system, start energizing and time for 30 min. When the deposition times of the titanium membranes are 300 s and 500 s, after the reaction, the sludge SRF (specific resistance of sludge) of the two reactors decreases by 62.9% (300 s) and 39.1% (500 s) respectively compared with that before conditioning; the CST (capillary suction time) decreases by 41.5% (300 s) and 29.2% (500 s) respectively; the dewatering performance of the sludge is effectively improved; when the deposition time is too long, the sludge filtration performance will decrease. It is found in the test observation that when the electrodeposition time is too long, the air holes will be blocked, affecting the air outlet and thus affecting the conditioning effect.

[0044] Example 2

[0045] Modification of titanium film:

[0046] Prepare 350 mL of electrolyte solution in a beaker, and the dosage of drugs is as follows: 71.3 mg of Ni(NO 3 ) 2 ·6H 2 O; 28.3 mg of Fe(NO 3 ) 3 ·9H 3 O; 15.2 mg of Ce(NO 3 ) 3 ·6H 3 O.

[0047] Use a titanium film with a pore size of 0.2 μm for electrodeposition loading, and connect a wire to the titanium film in advance; place the titanium film vertically into the solution, and place and fix the annular titanium ruthenium mesh around it; connect the DC power supply and set a constant current of 420 mA, connect the negative pole of the power supply to the titanium film, and connect the positive pole of the power supply to the titanium ruthenium mesh.

[0048] Then, apply electricity and time for 300 s. After electrodeposition, take out the two modified aeration heads and put them into a vacuum drying oven, keep the air extraction state and dry them at room temperature for 6 h, and then take them out. The modification is completed.

[0049] Sludge conditioning:

[0050] Take 350 mL of excess sludge from the sewage treatment plant with a water content of 96.8% and put it into a beaker.

[0051] Set the modified titanium film as the cathode, the anode as a rectangular titanium ruthenium mesh, the distance between the two electrodes is 2 cm, and set the DC power supply current to 50 mA in advance; put a magnetic stirrer rotor into the beaker and set the rotation speed to 350 rpm; turn on the ozone generator (Longevity EXT120 - C) and adjust the flow rate to 30 - 50 mL / min; adjust the ozone concentration to 15 - 40 mg / L (due to instrument reasons, the flow rate and concentration will fluctuate in this range).

[0052] After ozone is introduced into the system, start applying electricity and time for 30 min. After the reaction, the SRF of the sludge in the reactor decreases by 42.2% compared with that before conditioning; the CST decreases by 34.1%; it can be seen that the dewatering performance of the sludge is effectively improved, but the effect of the titanium film with a pore size of 0.2 μm after modification is not as good as that of Example 1, indicating that to a certain extent, an increase in pore size helps to improve the dewatering performance of the sludge under the same electrodeposition time.

[0053] Example 3

[0054] In this example, the modified titanium film with a pore size of 0.45 μm and electrodeposited for 300 s in Example 1 is used.

[0055] Sludge conditioning:

[0056] Take 350mL of residual sludge (water content 96.8%) from the sewage plant and put it into a beaker. Set the modified titanium membrane as the cathode and the rectangular titanium ruthenium mesh as the anode. The distance between the two electrodes is 2cm, and the DC power supply current is set to 50mA in advance. Put the magnetic stirrer rotor in the beaker and set the speed to 350rpm; turn on the ozone generator (Longevity EXT120-C) and adjust the flow rate to 30-50mL / min; adjust the ozone concentration to 15-40mg / L (the flow rate and concentration will fluctuate in this range due to instrument reasons).

[0057] After ozone was introduced into the system, power was turned on and the time was set for 1.5 hours. After the reaction, the SRF of the sludge decreased by 40.2% and the CST decreased by 23.7%. The extension of the reaction time actually reduced the dewatering performance of the sewage, which indicates that the sludge may have been over-oxidized, affecting the dewatering performance.

[0058] Example 4

[0059] In this example, the modified titanium film with a pore size of 0.45 μm and electrodeposition time of 300 s in Example 1 was used.

[0060] Sludge conditioning:

[0061] Take 350mL of residual sludge from the sewage treatment plant in a beaker (water content 96.8%), set the modified titanium membrane as the cathode and the rectangular titanium ruthenium mesh as the anode, the distance between the two electrodes is 2cm, and the DC power supply current is set to 50mA in advance. Put a magnetic stirrer rotor in the beaker and set the speed to 350rpm. In this embodiment, ozone is not introduced. Start timing for 30min after power is turned on.

[0062] After conditioning, the SRF of the sludge increased by 15.55%, the CST increased by 9.08%, and the dehydration performance became worse, indicating that simply applying electricity will cause the dehydration performance of the sludge to deteriorate, and the addition of current alone will cause cell stress response of the microorganisms in the sludge, increasing the secretion of extracellular polymers to form a protective barrier.

[0063] Example 5

[0064] In this embodiment, an unmodified titanium membrane with a pore size of 0.45 μm is used.

[0065] Sludge conditioning:

[0066] Put 350 mL of excess sludge from the sewage treatment plant (with a moisture content of 96.8%) into a beaker; set the unmodified titanium membrane as the cathode, the anode as a rectangular titanium ruthenium mesh, with a distance of 2 cm between the two electrodes, and pre-set the DC power supply current to 50 mA. Place a magnetic stirrer rotor in the beaker and set the rotation speed to 350 rpm; turn on the ozone generator (Longevity EXT120-C) and adjust the flow rate to 30 - 50 mL / min; adjust the ozone concentration to 15 - 40 mg / L (the flow rate and concentration will fluctuate within this range due to instrument reasons).

[0067] After ozone is introduced into the system, start energizing and time for 30 min. After the reaction ends, the SRF value of the sludge decreases by 14.83%, and the CST decreases by 6.90%. The improvement of the dewatering performance is not obvious.

[0068] Example 6

[0069] In this example, the modified titanium membrane with a pore size of 0.45 μm and electroplated for 300 s in Example 1 is used, but in this example, an ordinary ceramic aeration head is used to introduce ozone, and the modified titanium membrane is not used as an aeration head.

[0070] However, in this example, the same power-on conditions and ozone introduction conditions as in Example 1 are used. After ozone is introduced into the system, start energizing and time for 30 min. After the reaction ends, the SRF value of the sludge decreases by 24.47%, and the CST decreases by 12.37%. This shows that using the modified titanium membrane as an aeration head can greatly improve the dewatering performance of the sludge.

[0071] The present invention is not limited to the above best implementation mode. Anyone can obtain various other forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as it has a technical solution identical or similar to the present application, it falls within the protection scope of the present invention.

Claims

1. A sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation, characterized in that: The following steps are involved: S11, modifying the titanium membrane, and using the modified titanium membrane as an aeration head to introduce ozone; S12, using the aeration head as cathode and the annular titanium ruthenium mesh as anode, the sludge is conditioned under constant current conditions; S13. The conditioned sludge is directly used for dehydration and weight reduction.

2. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 1 is characterized in that: The modification of titanium membrane includes the following steps: S21, preparing electrolyte; S22, using the titanium film as a cathode and the annular titanium ruthenium mesh as an anode, electro-depositing the titanium film under constant current conditions; S23. The modified titanium film can be obtained by vacuum drying the electrodeposited titanium film.

3. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 2 is characterized in that: In the S21, the electrolyte is a nitrate solution of nickel, iron and cerium, the total molar concentration of the solute is 1 mM, and the molar ratio of nickel, iron and cerium is 7:2:

1.

4. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 2 is characterized in that: In the above-mentioned S22, the membrane pore size of the titanium membrane is 0.2-0.45 μm, and the annular titanium ruthenium mesh is placed around the titanium membrane.

5. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 2 is characterized in that: In the S22, the constant current is 10-30 mA / cm based on the titanium film. 2 , the reaction time is 300 to 500 seconds.

6. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 1 is characterized in that: In the above-mentioned S11, the inlet flow rate of ozone is 20-50 mL / min; and the concentration of the ozone generator is adjusted to 15-80 mg / L.

7. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 1 is characterized in that: In the S12, the constant current of sludge conditioning is 30-50 mA, and the reaction time is 15 min-1.5 h.

8. The sludge conditioning method based on modified titanium membrane efficient catalytic ozone oxidation according to claim 1 is characterized in that: In the above S13, after conditioning, the sludge specific resistance can be reduced by more than 60% compared with that before conditioning; and the capillary water absorption time can be reduced by more than 40% compared with that before conditioning.

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