A kind of landfill leachate treatment process

Abstract

The present invention relates to a landfill leachate treatment process, belonging to the technical field of sewage treatment. A photoelectric-Fenton oxidation treatment process is adopted, and a composite catalyst is added. Compared with the traditional Fenton process, low-cost, low-energy consumption and high-efficiency treatment of landfill leachate is achieved. The composite catalyst uses mesoporous carbon powder as a carrier, and a large number of iron-cobalt oxide and titanium oxide double heterojunctions are formed on the surface through a chemical synthesis process, which is conducive to the uniform distribution of charges on the catalyst surface. Under light conditions, electrons and holes are effectively separated at the heterojunction interface, reducing the recombination of electrons and holes and improving the electrocatalytic efficiency. At the same time, the double heterojunction provides a large number of active sites, promoting the generation of more hydroxyl radicals, forming a strong oxidation effect, effectively promoting the degradation of organic pollutants, and making photocatalysis and electrocatalysis interact with each other, greatly improving the Fenton oxidation efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a garbage leachate treatment process. Background Art

[0002] Leachate is an inevitable pollutant produced in landfills and composting sites. It contains a large amount of organic matter, suspended particles, heavy metals and other harmful substances. If these pollutants are not effectively treated, they will pose a serious threat to the water environment, soil environment and human health.

[0003] At present, the commonly used landfill leachate treatment technologies mainly include physical treatment, chemical treatment and biological treatment. Although physical treatment methods, such as filtration and sedimentation, are low in cost, they can only remove a part of the suspended particles and have limited removal effects on soluble pollutants. Biological treatment methods, such as anaerobic digestion and activated sludge, can effectively degrade organic matter, but have limited removal effects on difficult-to-degrade pollutants such as heavy metals. In addition, the existing biological treatment processes have low requirements for pollutant concentrations and are less efficient in treating leachate with high concentrations of pollution. Compared with physical treatment and biological treatment, chemical treatment methods, such as oxidation, flocculation precipitation and ion exchange, have higher treatment efficiency and fewer limitations. They are the most commonly used methods for treating landfill leachate. However, the dosage of chemicals is high and the treatment efficiency is difficult to improve. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the purpose of the present invention is to provide a landfill leachate treatment process.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A landfill leachate treatment process specifically includes the following steps:

[0007] Step S1: premixing the landfill leachate and the composite catalyst, and then adding ferrous sulfate solution to form medicated wastewater;

[0008] Step S2: pumping the medicated wastewater into the electrolytic tank, applying direct current electrolysis and photocatalysis, and intermittently adding hydrogen peroxide solution to form degraded wastewater;

[0009] Step S3: neutralize the degraded wastewater, let it stand for a first sedimentation, pump out the supernatant and add polyacrylamide to mix, let it stand for a second sedimentation, and complete the treatment of the landfill leachate.

[0010] Furthermore, Fe 2+ The concentration is 0.8-1.2mmol / L.

[0011] Furthermore, the dosage of the composite catalyst in the landfill leachate is 2.5-4 g / L.

[0012] Furthermore, the amount of hydrogen peroxide used in the landfill leachate is 6-8 mL / L, and the mass fraction of the hydrogen peroxide solution is 10%.

[0013] Furthermore, the current density of the direct current electrolysis is 30-40 mA / cm 2 The light intensity for photocatalysis is 50-80mW / cm 2 .

[0014] Furthermore, the amount of polyacrylamide in the supernatant is 1-1.5 g / L.

[0015] The composite catalyst is prepared by the following method:

[0016] Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, raise the temperature to 75-85°C, apply 60-90 rpm stirring and 150-200 W / m 2 UV irradiation, slowly adding γ-mercaptopropyltriethoxysilane, reacting for 4-6 hours, and removing toluene by vacuum rotary evaporation after the reaction to obtain a modified coupling agent;

[0017] Furthermore, the dosage ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene is 10mmol:32-35mmol:40-50mg:35-50mL. Under the initiation of ultraviolet radiation, γ-mercaptopropyltriethoxysilane and triallylamine undergo click addition reaction to form a compound with multi-branched ethoxysilane.

[0018] Step A2: Mix the modified coupling agent and ethanol solution, adjust the pH value to 3-4 with formic acid, stir and hydrolyze at room temperature for 1-1.5 hours, add mesoporous carbon powder, disperse by ultrasonication, and stand for 12 hours, centrifuge and dry to obtain modified carbon powder;

[0019] Furthermore, the dosage ratio of the mesoporous carbon powder, the modified coupling agent and the ethanol solution is 50g:3.5-4.5g:65-80mL. In the acidic alcohol aqueous solution environment, the ethoxysilane of the modified coupling agent is fully hydrolyzed and then coupled with the mesoporous carbon powder to form loose clustered carbon powder aggregates.

[0020] Step A3: dissolving cobalt nitrate and ferric chloride in deionized water, adding modified carbon powder for ultrasonic dispersion, adjusting the pH value to 8-9 with ammonia water, adjusting the temperature to 5-15°C in an ice water bath, applying stirring at 180-240 rpm, slowly adding titanium tetrachloride for reaction for 2-3 hours, centrifugally separating and drying, and calcining in a nitrogen furnace at 500°C for 3 hours to obtain a composite catalyst;

[0021] Furthermore, the dosage ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g: 0.8-1.1g: 2.5-3.5g: 0.5-0.7g: 130-160mL, and the sulfur-nitrogen organic structure introduced by the modified coupling agent in the modified carbon powder forms a chelating effect to enrich cobalt and iron ions in the clusters of the modified carbon powder. Under alkaline conditions, the iron ions are hydrolyzed to form iron hydroxide gel near the surface of the modified carbon powder, which captures the hydrolyzed titanium oxide. After roasting, a double heterojunction of iron-cobalt oxide and titanium oxide is formed on the modified carbon powder.

[0022] Beneficial effects of the present invention:

[0023] The invention discloses a composite catalyst, which cooperates with a photoelectric-Fenton oxidation treatment process and realizes low-cost, low-energy consumption and high-efficiency treatment of landfill leachate compared with a traditional Fenton process; the composite catalyst uses mesoporous carbon powder as a carrier, and is formed by click addition of γ-mercaptopropyltriethoxysilane and triallylamine to form a compound with multi-branched ethoxysilane, namely a modified coupling agent, which is hydrolyzed and coupled with the mesoporous carbon powder to form a loose clustered carbon powder aggregate, namely the modified carbon powder, wherein the sulfur-nitrogen organic structure introduced by the modified coupling agent forms a chelating effect, and cobalt and iron ions are enriched in the clusters of the modified carbon powder; under alkaline conditions, the iron ions are hydrolyzed to form iron hydroxide gel near the surface of the modified carbon powder, and the hydrolyzed Titanium oxide, after calcination, forms a large number of iron-cobalt oxide and titanium oxide double heterojunctions on the modified carbon powder; the composite catalyst uses carbon-based materials as carriers to promote the effective migration of charges under the action of the electric field. From a microscopic perspective, the double heterojunction on its surface itself is an efficient charge transfer medium, which is conducive to the uniform distribution of charges on the catalyst surface. Under light conditions, electrons and holes are effectively separated at the heterojunction interface, reducing the recombination of electrons and holes and improving the electrocatalytic efficiency. At the same time, the double heterojunction provides a large number of active sites, promoting the generation of more hydroxyl radicals, forming a strong oxidation effect, and effectively promoting the degradation of organic pollutants; the introduction of the composite catalyst allows photocatalysis and electrocatalysis to interact, greatly improving the Fenton oxidation efficiency. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention is based on the treatment of municipal domestic waste permeate. During the implementation process, the permeate of a certain waste treatment station is selected, and its water quality indicators are shown in Table 1:

[0026] Example 1

[0027] (1) Preparation of composite catalyst

[0028] Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, heat to 85°C, stir at 90 rpm and 200 W / m 2 Under ultraviolet irradiation, γ-mercaptopropyltriethoxysilane was slowly added and the reaction was carried out for 4 hours, wherein the dosage ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene was 10 mmol: 35 mmol: 50 mg: 50 mL. After the reaction was completed, toluene was removed by vacuum rotary evaporation to obtain a modified coupling agent.

[0029] Step A2: Mix the modified coupling agent and ethanol solution, adjust the pH value to 3 with formic acid, stir and hydrolyze at room temperature for 1 hour, add mesoporous carbon powder and ultrasonically disperse it, and then let it stand for 12 hours, wherein the mesoporous carbon powder is selected from MCP-4 type raw material, the volume fraction of the ethanol solution is 40%, and the amount ratio of mesoporous carbon powder, modified coupling agent and ethanol solution is 50g:4.5g:80mL. After the reaction is completed, centrifuge and dry to obtain modified carbon powder.

[0030] Step A3: dissolve cobalt nitrate and ferric chloride in deionized water, add modified carbon powder for ultrasonic dispersion, adjust the pH value to 9 with ammonia water, adjust the temperature to 5°C in an ice-water bath, stir at 240rpm, slowly add titanium tetrachloride and react for 2h, wherein the amount ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g:0.8g:3.5g:0.5g:160mL, centrifuge and dry after the reaction, place in a nitrogen furnace and roast at 500°C for 3h to obtain a composite catalyst.

[0031] (2) Treatment of landfill leachate

[0032] Step S1: Add the composite catalyst to the landfill leachate for premixing, control the amount of the composite catalyst in the landfill leachate to be 2.5 g / L, then dissolve ferrous sulfate in water, add the ferrous sulfate solution and mix, control the Fe 2+ The concentration is 1.2mmol / L, and medicated wastewater is prepared.

[0033] Step S2: Pump the dosing wastewater into the electrolytic cell, apply direct current electrolysis and photocatalysis, and control the current density to 30mA / cm 2 , light intensity is 80mW / cm 2 , dilute the hydrogen peroxide into a 10% mass fraction aqueous solution, divide the hydrogen peroxide solution into four parts, add it intermittently for 10 minutes, control the amount of hydrogen peroxide in the landfill leachate to 8mL / L, and the total reaction time of hydrogen peroxide addition is 1 hour to form degraded sewage.

[0034] Step S3: neutralize the degraded wastewater, let it stand for a precipitation, pump out the supernatant and add polyacrylamide to mix, control the amount of polyacrylamide in the supernatant to 1.5g / L, let it stand for a secondary precipitation, and complete the treatment of the landfill leachate. Example

[0035] (1) Preparation of composite catalyst

[0036] Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, heat to 75°C, stir at 60 rpm and 150 W / m 2 Under ultraviolet irradiation, γ-mercaptopropyltriethoxysilane was slowly added and the reaction was carried out for 6 hours, wherein the dosage ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene was 10 mmol: 32 mmol: 40 mg: 35 mL. After the reaction was completed, toluene was removed by vacuum rotary evaporation to obtain a modified coupling agent.

[0037] Step A2: Mix the modified coupling agent and ethanol solution, adjust the pH value to 4 with formic acid, stir and hydrolyze at room temperature for 1.5 hours, add mesoporous carbon powder and ultrasonically disperse it, and then let it stand for 12 hours, wherein the mesoporous carbon powder is selected from MCP-4 type raw material, the volume fraction of the ethanol solution is 40%, and the amount ratio of mesoporous carbon powder, modified coupling agent and ethanol solution is 50g:3.5g:65mL. After the reaction is completed, centrifuge and dry to obtain modified carbon powder.

[0038] Step A3: dissolve cobalt nitrate and ferric chloride in deionized water, add modified carbon powder for ultrasonic dispersion, adjust the pH value to 8 with ammonia water, adjust the temperature to 15°C in an ice-water bath, stir at 180 rpm, slowly add titanium tetrachloride and react for 3 hours, wherein the amount ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g:1.1g:2.5g:0.7g:130mL, centrifuge and dry after the reaction, place in a nitrogen furnace and roast at 500°C for 3 hours to obtain a composite catalyst.

[0039] (2) Treatment of landfill leachate

[0040] Step S1: Add the composite catalyst to the landfill leachate for premixing, control the amount of the composite catalyst in the landfill leachate to be 3g / L, then dissolve ferrous sulfate in water, add the ferrous sulfate solution and mix, control the Fe 2+ The concentration is 1.1mmol / L, and medicated wastewater is prepared.

[0041] Step S2: Pump the dosing wastewater into the electrolytic cell, apply direct current electrolysis and photocatalysis, and control the current density to 30mA / cm 2 , light intensity is 80mW / cm 2, dilute the hydrogen peroxide into a 10% mass fraction aqueous solution, divide the hydrogen peroxide solution into four parts, add it intermittently for 10 minutes, control the amount of hydrogen peroxide in the landfill leachate to 7mL / L, and the total reaction time of hydrogen peroxide addition is 1.2h to form degraded sewage.

[0042] Step S3: neutralize the degraded wastewater, let it stand for a precipitation, pump out the supernatant and add polyacrylamide to mix, control the amount of polyacrylamide in the supernatant to 1.2g / L, let it stand for a secondary precipitation, and complete the treatment of the landfill leachate. Example

[0043] (1) Preparation of composite catalyst

[0044] Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, heat to 80°C, stir at 90 rpm and 180 W / m 2 Under ultraviolet irradiation, γ-mercaptopropyltriethoxysilane was slowly added and the reaction was carried out for 5 hours, wherein the dosage ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene was 10 mmol: 33 mmol: 45 mg: 45 mL. After the reaction was completed, toluene was removed by vacuum rotary evaporation to obtain a modified coupling agent.

[0045] Step A2: Mix the modified coupling agent and ethanol solution, adjust the pH value to 3 with formic acid, stir and hydrolyze at room temperature for 1.2 hours, add mesoporous carbon powder and ultrasonically disperse it, and then let it stand for 12 hours, wherein the mesoporous carbon powder is selected from MCP-4 type raw material, the volume fraction of the ethanol solution is 40%, and the amount ratio of mesoporous carbon powder, modified coupling agent and ethanol solution is 50g:4g:70mL. After the reaction is completed, centrifuge and dry to obtain modified carbon powder.

[0046] Step A3: dissolve cobalt nitrate and ferric chloride in deionized water, add modified carbon powder for ultrasonic dispersion, adjust the pH value to 8 with ammonia water, adjust the temperature to 10°C in an ice-water bath, stir at 240rpm, slowly add titanium tetrachloride and react for 2.5h, wherein the amount ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g:0.9g:2g:0.6g:150mL. After the reaction, centrifuge and dry, place in a nitrogen furnace and roast at 500°C for 3h to obtain a composite catalyst.

[0047] (2) Treatment of landfill leachate

[0048] Step S1: Add the composite catalyst to the landfill leachate for premixing, control the amount of the composite catalyst in the landfill leachate to be 3.5 g / L, then dissolve ferrous sulfate in water, add the ferrous sulfate solution and mix, control the Fe 2+ The concentration is 1mmol / L, and medicated wastewater is prepared.

[0049] Step S2: Pump the dosing wastewater into the electrolytic cell, apply direct current electrolysis and photocatalysis, and control the current density to 40mA / cm 2 , light intensity is 50mW / cm 2 , dilute the hydrogen peroxide into a 10% mass fraction aqueous solution, divide the hydrogen peroxide solution into four parts, add it intermittently for 10 minutes, control the amount of hydrogen peroxide in the landfill leachate to 6mL / L, and the total reaction time of hydrogen peroxide addition is 1 hour to form degraded sewage.

[0050] Step S3: neutralize the degraded wastewater, let it stand for a precipitation, pump out the supernatant and add polyacrylamide to mix, control the amount of polyacrylamide in the supernatant to 1g / L, let it stand for a secondary precipitation, and complete the treatment of the landfill leachate. Example

[0051] (1) Preparation of composite catalyst

[0052] Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, heat to 85°C, stir at 90 rpm and 150 W / m 2 Under ultraviolet irradiation, γ-mercaptopropyltriethoxysilane was slowly added and the reaction was carried out for 4.5 hours, wherein the dosage ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene was 10 mmol: 35 mmol: 50 mg: 50 mL. After the reaction was completed, toluene was removed by vacuum rotary evaporation to obtain a modified coupling agent.

[0053] Step A2: Mix the modified coupling agent and ethanol solution, adjust the pH value to 4 with formic acid, stir and hydrolyze at room temperature for 1.2 hours, add mesoporous carbon powder and ultrasonically disperse it, and then let it stand for 12 hours, wherein the mesoporous carbon powder is selected from MCP-4 type raw material, the volume fraction of the ethanol solution is 40%, and the amount ratio of mesoporous carbon powder, modified coupling agent and ethanol solution is 50g:3.8g:75mL. After the reaction is completed, centrifuge and dry to obtain modified carbon powder.

[0054] Step A3: dissolve cobalt nitrate and ferric chloride in deionized water, add modified carbon powder for ultrasonic dispersion, adjust the pH value to 9 with ammonia water, adjust the temperature to 5°C in an ice-water bath, stir at 240rpm, slowly add titanium tetrachloride and react for 2.2h, wherein the amount ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g:0.9g:3.2g:0.6g:140mL. After the reaction, centrifuge and dry, place in a nitrogen furnace and roast at 500°C for 3h to obtain a composite catalyst.

[0055] (2) Treatment of landfill leachate

[0056] Step S1: Add the composite catalyst to the landfill leachate for premixing, control the amount of the composite catalyst in the landfill leachate to be 4 g / L, then dissolve ferrous sulfate in water, add the ferrous sulfate solution and mix, control the Fe 2+ The concentration is 0.8mmol / L, and medicated wastewater is prepared.

[0057] Step S2: Pump the dosing wastewater into the electrolytic cell, apply direct current electrolysis and photocatalysis, and control the current density to 35mA / cm 2 , light intensity is 70mW / cm 2 , dilute the hydrogen peroxide into a 10% mass fraction aqueous solution, divide the hydrogen peroxide solution into four parts, add it intermittently for 10 minutes, control the amount of hydrogen peroxide in the landfill leachate to 7mL / L, and the total reaction time of hydrogen peroxide addition is 1 hour to form degraded sewage.

[0058] Step S3: neutralize the degraded wastewater, let it stand for a first precipitation, pump out the supernatant and add polyacrylamide to mix, control the amount of polyacrylamide in the supernatant to 1.3g / L, let it stand for a second precipitation, and complete the treatment of the landfill leachate.

[0059] Comparative Example 1

[0060] This comparative example refers to Example 4, without adding the composite catalyst, and the rest of the implementation process is exactly the same.

[0061] Comparative Example 2

[0062] This comparative example refers to Example 4, except that the composite catalyst is replaced with a RHFD03 Fenton catalyst, and the rest of the implementation process is exactly the same.

[0063] The treated water quality indicators were tested and the removal rate was calculated. The specific test results are shown in Table 2:

[0064]

[0065] It can be seen from the test results in Table 2 that the embodiments have higher removal rates for COD, TOC, humic acid and chroma, and have a highly efficient and deep purification effect.

[0066] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0067] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A landfill leachate treatment process, characterized in that: The specific processes include the following: Step S1: premixing the landfill leachate and the composite catalyst, and then adding ferrous sulfate solution to form medicated wastewater; Step S2: pumping the medicated wastewater into the electrolytic tank, applying direct current electrolysis and photocatalysis, and intermittently adding hydrogen peroxide solution to form degraded wastewater; Step S3: neutralize the degraded wastewater, let it stand for primary precipitation, pump out the supernatant and add polyacrylamide to mix, let it stand for secondary precipitation, and complete the treatment of the landfill leachate; The composite catalyst is prepared by the following method: Step A1: Mix triallylamine, dimethylphenylphosphine and anhydrous toluene, raise the temperature to 75-85°C, stir and apply 150-200W / m 2 UV irradiation, slowly adding γ-mercaptopropyltriethoxysilane, reacting for 4-6 hours, and removing toluene by vacuum rotary evaporation after the reaction to obtain a modified coupling agent, wherein the amount ratio of triallylamine, γ-mercaptopropyltriethoxysilane, dimethylphenylphosphine and anhydrous toluene is 10mmol:32-35mmol:40-50mg:35-50mL; Step A2: Mix the modified coupling agent and the ethanol solution, adjust the pH value to 3-4 with formic acid, stir and hydrolyze at room temperature for 1-1.5 hours, add the mesoporous carbon powder and disperse it by ultrasonic, let it stand for 12 hours, centrifuge and dry to obtain the modified carbon powder, wherein the amount ratio of the mesoporous carbon powder, the modified coupling agent and the ethanol solution is 50g:3.5-4.5g:65-80mL; Step A3: dissolving cobalt nitrate and ferric chloride in deionized water, adding modified carbon powder for ultrasonic dispersion, adjusting the pH value to 8-9 with ammonia water, adjusting the temperature to 5-15° C. in an ice-water bath, stirring and slowly adding titanium tetrachloride for reaction for 2-3 hours, centrifugally separating and drying, placing in a nitrogen furnace for calcination at 500° C. for 3 hours to obtain a composite catalyst, wherein the amount ratio of modified carbon powder, cobalt nitrate, ferric chloride, titanium tetrachloride and deionized water is 50g: 0.8-1.1g: 2.5-3.5g: 0.5-0.7g: 130-160mL; The usage of the composite catalyst in the landfill leachate is 2.5-4 g / L.

2. A landfill leachate treatment process according to claim 1, characterized in that: The concentration of Fe2+ in the medicated wastewater is 0.8-1.2mmol / L.

3. A landfill leachate treatment process according to claim 1, characterized in that: The amount of hydrogen peroxide used in the landfill leachate is 6-8 mL / L, and the mass fraction of the hydrogen peroxide solution is 10%.

4. A landfill leachate treatment process according to claim 1, characterized in that: The current density of DC electrolysis is 30-40 mA / cm 2 The light intensity for photocatalysis is 50-80mW / cm 2 .

5. A landfill leachate treatment process according to claim 1, characterized in that: The amount of polyacrylamide used in the supernatant is 1-1.5 g / L.

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