Phosphorus removal agent for landfill leachate and preparation method thereof

Abstract

The application relates to the field of water body phosphorus removal agents, and particularly discloses a phosphorus removal agent for landfill leachate and a preparation method thereof. The phosphorus removal agent at least comprises hydrophilic modified activated carbon, and the hydrophilic modified activated carbon is prepared by reacting activated carbon in a mixed solution containing polyether amine, polyethylene polyamine and an acidic catalyst. The phosphorus removal agent is not prone to accumulating dirt in the adsorption process, and can improve and maintain a relatively stable phosphorus adsorption capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water phosphorus removal agent, especially to a garbage leachate phosphorus removal agent and a preparation method thereof. BACKGROUND

[0002] Garbage leachate is a kind of wastewater with high concentration and high pollution, which contains a large amount of organic matter, ammonia nitrogen, phosphorus and other pollutants. In order to reduce the harm to the environment and human health, it needs to be treated. In the process of treating garbage leachate, phosphorus removal process is very important.

[0003] Common phosphorus removal processes include chemical phosphorus removal, biological phosphorus removal and physical phosphorus removal. Chemical phosphorus removal is to add chemical reagents to wastewater to combine with phosphate to form insoluble phosphate precipitate, thereby removing it from wastewater. Common chemical reagents include aluminum salt, iron salt, etc. Biological phosphorus removal is to convert organic matter and ammonia nitrogen in wastewater into biological solids through the action of microorganisms, and at the same time, phosphorus is precipitated in the form of phosphate. Physical phosphorus removal is to use porous solid materials to selectively adsorb phosphorus in wastewater to achieve the purpose of removing phosphorus. Among them, activated carbon adsorption method is one of the common physical adsorption methods for phosphorus removal.

[0004] Activated carbon has high specific surface area, rich pore structure and good adsorption performance, which can effectively adsorb phosphorus in wastewater. However, activated carbon is easy to accumulate organic matter, suspended particles and other dirt on the surface during the treatment of garbage leachate, which seriously affects its adsorption performance and is not conducive to improving the phosphorus adsorption capacity. SUMMARY

[0005] In order to alleviate the problem that activated carbon is easy to accumulate dirt during water phosphorus removal process and affect the phosphorus adsorption capacity, the present application provides a garbage leachate phosphorus removal agent and a preparation method thereof.

[0006] In the first aspect, the present application provides a garbage leachate phosphorus removal agent, which comprises hydrophilic modified activated carbon, and the hydrophilic modified activated carbon is prepared by reacting activated carbon in a mixed solution containing polyether amine, polyethylene polyamine and acidic catalyst.

[0007] Preferably, the concentration of polyether amine in the mixed solution is 1-10 g / L, and the concentration of polyethylene polyamine is 1-3 g / L.

[0008] Preferably, the reaction temperature is 40-80 DEG C, and the reaction time is 4-6 h.

[0009] Preferably, the concentration of acidic catalyst in the mixed solution is 0.1-1 mol / L.

[0010] Preferably, the acidic catalyst is at least one of hydrochloric acid, nitric acid and acetic acid.

[0011] Preferably, the D50 particle size of the activated carbon is 0.1mm-5mm, more preferably 1mm-5mm.

[0012] Preferably, the molecular weight of the polyether amine is 1000-5000.

[0013] Preferably, the polyethylene polyamine is selected from at least one of diethylene triamine, triethylene tetramine, and tetraethylene pentamine.

[0014] In the water body phosphorus removal process, the activated carbon is always immersed and suspended in the water body. The present application can significantly reduce the water wetting angle of the activated carbon by hydrophilic modification of the activated carbon, greatly improving the wetting and spreading ability of water to the activated carbon in the landfill leachate system, thereby taking away the organic matter and other dirt attached to the surface of the activated carbon, reducing the accumulation of dirt, and protecting the phosphorus adsorption capacity.

[0015] Specifically, the hydrophilic modification raw material of the present application includes polyether amine and polyethylene polyamine. Under the catalysis of an acidic catalyst, both the polyethylene polyamine and the polyether amine contain active amine groups, which can react and bond with the active groups such as carboxyl groups on the surface of the activated carbon, thereby forming a hydrophilic modified layer on the surface of the activated carbon. During the modification process, the polyether amine can effectively improve the strength and firmness of the hydrophilic modified layer due to its long-chain macromolecular structure, and the polyethylene polyamine can act as a crosslinking agent. The combination of the two can improve the firmness and anti-washing ability of the hydrophilic modified layer, thereby protecting the phosphorus adsorption capacity of the activated carbon.

[0016] The aforementioned obtained hydrophilic modified layer contains a large number of amine groups, which can obtain positively charged groups after dissociation in water, and has adsorption effect on anions such as phosphate. Therefore, the phosphorus adsorption capacity of the activated carbon after hydrophilic modification is further improved. Therefore, when the raw material is polyether amine or polyethylene polyamine with higher amine value content, the phosphorus removal rate of the hydrophilically modified activated carbon will be improved in the same time.

[0017] In addition, the acidic catalyst can not only improve the rate of hydrophilic modification reaction, but also increase the content of active groups such as carboxyl groups and phenolic hydroxyl groups on the surface of the activated carbon, providing more reaction sites for hydrophilic modification.

[0018] It should be noted that the composite phosphorus removal agent of the present application can be hydrophilically modified activated carbon alone, or can be used in combination with other phosphorus removal materials, such as phosphorus removal bacteria with biological phosphorus removal effect, and materials such as zeolite, diatomite, aluminum salt, and iron salt.

[0019] Preferably, the mixed solution further contains vinyl imidazole, an initiator, and a siloxane monomer containing a carbon-carbon double bond; the concentration of the siloxane monomer containing a carbon-carbon double bond is 0.1-1g / L, and the concentration of the vinyl imidazole is 0.1-0.5g / L.

[0020] Preferably, the vinyl imidazole is at least one of 1-vinylimidazole, 2-vinylimidazole.

[0021] Preferably, the siloxane monomer containing carbon-carbon double bond is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, gamma-(methacryloyloxy)propyltrimethoxysilane and gamma-(methacryloyloxy)propyltriethoxysilane.

[0022] By adding the siloxane monomer containing carbon-carbon double bond, the vinyl imidazole and the initiator, the vinyl imidazole with nitrogen-containing heterocyclic structure can be grafted on the surface of the activated carbon, the complexing capacity of the activated carbon for heavy metal ions in wastewater is improved, and the wastewater treatment performance of the activated carbon is expanded.

[0023] During the reaction, the siloxane monomer containing carbon-carbon double bond is first bonded to the surface of the activated carbon through silicon hydroxyl, and then the siloxane monomer containing carbon-carbon double bond and the vinyl imidazole are subjected to copolymerization reaction through free radical reaction, so that the nitrogen-containing heterocyclic structure is introduced to the surface of the activated carbon.

[0024] In a second aspect, the application provides a preparation method of a phosphorus removal agent for landfill leachate, characterized in that the method comprises the following steps:

[0025] Pretreatment: adding an acidic catalyst, a siloxane monomer containing carbon-carbon double bond, an initiator and a vinyl imidazole into water to prepare a mixed solution, heating and warming, adding activated carbon and stirring for 3-5 hours;

[0026] Hydrophilic modification: adding polyether amine and polyethylene polyamine into the mixed solution and stirring to react, and then washing with water and drying to obtain the hydrophilically modified activated carbon.

[0027] The application does not have specific requirements for the order of adding raw materials, and the reaction can be completed. In the above preparation steps, the acidic catalyst is mixed and stirred with the activated carbon before the hydrophilic modification, which can increase the number of active reaction sites such as carboxyl groups on the surface of the activated carbon and improve the hydrophilic modification effect.

[0028] It should be noted that when the modification raw materials do not contain the siloxane monomer containing carbon-carbon double bond, the initiator and the vinyl imidazole, the corresponding raw materials are not added in the pretreatment step.

[0029] In summary, the application has the following beneficial effects:

[0030] 1. In the application, polyether amine and polyethylene polyamine are used to hydrophilically modify the activated carbon under acidic conditions, a firm hydrophilic modification layer can be obtained, the problem of dirt accumulation on the surface of the activated carbon is effectively alleviated, and the phosphorus adsorption capacity of the activated carbon in the water body phosphorus removal process is improved.

[0031] 2、The application introduces vinyl imidazole with nitrogen-containing structure on the surface of activated carbon through free radical copolymerization, effectively improving the adsorption capacity of activated carbon for heavy metal elements. DETAILED DESCRIPTION

[0032] Example raw material selection: polyether amine (molecular weight 2000, amine value 514 g / eq), activated carbon is coconut activated carbon (D50 particle size 2-4 mm, specific surface area 950-1200 m 2 / g).

[0033] Example

[0034] Example 1, a kind of phosphorus removal agent for landfill leachate, is prepared according to the following method:

[0035] Pretreatment: hydrochloric acid, vinyl trimethoxysilane, initiator and 1-vinylimidazole are added to water to prepare a mixed solution with a hydrochloric acid concentration of 0.5 mol / L, a vinyl trimethoxysilane concentration of 0.5 g / L, a 1-vinylimidazole concentration of 0.35 g / L, and an azobisisobutyronitrile concentration of 0.02 g / L. The solution is heated to 70°C, and activated carbon is added to make the mass concentration of activated carbon 100 g / L. Stirring is carried out at 1000 rpm for 3.5 h.

[0036] Hydrophilic modification: polyether amine and triethylenetetramine are added to the above-mentioned mixed solution to make the concentration of polyether amine in the solution 8 g / L, and the concentration of triethylenetetramine 2 g / L. Stirring is continued at 70°C, and after 4 h, the activated carbon is centrifuged and washed with water three times. Drying is carried out at 60°C to obtain hydrophilically modified activated carbon.

[0037] Example 2, a kind of phosphorus removal agent for landfill leachate, is prepared according to the following method:

[0038] Pretreatment: hydrochloric acid, vinyl trimethoxysilane, initiator and 1-vinylimidazole are added to water to prepare a mixed solution with a hydrochloric acid concentration of 1 mol / L, a vinyl trimethoxysilane concentration of 0.9 g / L, a 1-vinylimidazole concentration of 0.5 g / L, and an azobisisobutyronitrile concentration of 0.03 g / L. The solution is heated to 40°C, and activated carbon is added. Stirring is carried out at 1000 rpm for 5 h.

[0039] Hydrophilic modification: polyether amine and triethylenetetramine are added to the above-mentioned mixed solution to make the concentration of polyether amine in the solution 5 g / L, and the concentration of triethylenetetramine 1 g / L. Stirring is continued at 40°C, and after 6 h, the activated carbon is centrifuged and washed with water three times. Drying is carried out at 60°C to obtain hydrophilically modified activated carbon.

[0040] Example 3, a kind of phosphorus removal agent for landfill leachate, is prepared according to the following method:

[0041] Pre-treatment: hydrochloric acid, 1-vinyltrimethoxysilane, initiator and 1-vinylimidazole were added into water to prepare a mixed solution with a hydrochloric acid concentration of 0.2 mol / L, a vinyltrimethoxysilane concentration of 0.3 g / L, a 1-vinylimidazole concentration of 0.2 g / L and an azobisisobutyronitrile concentration of 0.01 g / L. The solution was heated to 80℃, activated carbon was added and stirred at 1000 rpm for 3 h.

[0042] Hydrophilic modification: polyether amine and triethylenetetramine were added into the above mixed solution to make the polyether amine concentration in the solution 10 g / L and the triethylenetetramine concentration 3 g / L. The reaction was continued at 80℃, and after 5 h, the activated carbon was separated by centrifugation, washed with water three times and dried at 60℃ to obtain the hydrophilic modified activated carbon.

[0043] Example 4, a phosphorus removal agent for landfill leachate, was prepared according to the following method:

[0044] Pre-treatment: hydrochloric acid was added into water to prepare a mixed solution with a hydrochloric acid concentration of 0.5 mol / L. The solution was heated to 70℃, activated carbon was added and stirred at 1000 rpm for 3.5 h.

[0045] Hydrophilic modification: polyether amine and triethylenetetramine were added into the above mixed solution to make the polyether amine concentration in the solution 8 g / L and the triethylenetetramine concentration 2 g / L. The reaction was continued at 70℃, and after 4 h, the activated carbon was separated by centrifugation, washed with water three times and dried at 60℃ to obtain the hydrophilic modified activated carbon.

[0046] Example 5, a phosphorus removal agent for landfill leachate, differed from Example 4 in that in the pre-treatment step, an equal amount of vinyltrimethoxysilane was used to replace 1-vinylimidazole.

[0047] Comparative Example

[0048] Comparative Example 1, a phosphorus removal agent for landfill leachate, differed from Example 4 in that in the hydrophilic modification step, an equal amount of polyether amine was used to replace triethylenetetramine.

[0049] Comparative Example 2, a phosphorus removal agent for landfill leachate, differed from Example 4 in that in the hydrophilic modification step, an equal amount of triethylenetetramine was used to replace polyether amine.

[0050] Comparative Example 3, a phosphorus removal agent for landfill leachate, differed from Example 4 in that unmodified activated carbon was used.

[0051] Performance test

[0052] 1. Water wetting angle test

[0053] The water wetting angle of the activated carbon in the above examples and comparative examples was detected according to the method in GB / T 14216-2008 "Determination of Wetting Tension of Plastic Film and Sheet".

[0054] 2. Phosphorus adsorption capacity test

[0055] The phosphorus removal agent prepared in the above examples and comparative examples was taken and added into a beaker containing distilled water to prepare a sample solution of 2 g / L. Sodium dihydrogen phosphate was added into the sample solution to make the initial phosphorus concentration reach 50 mg / L. The sample solution was subjected to constant temperature oscillation. Samples were taken from the sample solution at 10 min, 30 min and 60 min of oscillation. The residual phosphorus content was detected by molybdenum ammonium spectrophotometry, and the phosphorus removal rate was calculated.

[0056] 3. Dirt resistance test

[0057] Clay with a D50 particle size of 1-10 microns was taken and added into distilled water to prepare a sewage solution of 5 g / L. The phosphorus removal agent prepared in the above examples and comparative examples was added into the sewage solution and soaked for 8 h. After the soaking was completed, sodium dihydrogen phosphate was added into the sewage solution to make the initial phosphorus concentration in the solution reach 50 mg / L. The sample solution was subjected to constant temperature oscillation. Samples were taken from the sewage solution at 10 min, 30 min and 60 min of oscillation. The residual phosphorus content was detected by molybdenum ammonium spectrophotometry, and the sewage phosphorus removal rate was calculated.

[0058] Table 1. Test results of phosphorus removal performance test

[0059]

[0060] 4. Heavy metal ion adsorption capacity

[0061] The phosphorus removal agent prepared in the above examples and comparative examples was taken and added into a beaker containing distilled water to prepare a sample solution of 2 g / L. Potassium chromate and copper sulfate were added into the sample solution to make the initial hexavalent chromium and copper ion concentrations reach 10 mg / L. The sample solution was subjected to constant temperature oscillation. Samples were taken from the sample solution at 20 min of oscillation. The residual metal ion content was detected by ultraviolet spectrophotometry, and the hexavalent chromium and copper ion removal rates were calculated.

[0062] Table 2. Test results of heavy metal ion adsorption capacity

[0063]

[0064] Analysis of test results:

[0065] (1) According to the combination of Embodiments 1-5 and Comparative Examples 1-3 and Table 1, it can be seen that the polyether amine and polyethylene polyamine are used to modify the activated carbon in the present application, which significantly reduces the probability of dirt accumulation in the process of removing phosphorus from water body, and effectively improves the phosphorus removal rate. Moreover, neither of the polyether amine and polyethylene polyamine alone can achieve excellent phosphorus removal effect. The reason may be that the polyether amine and polyethylene polyamine can form a firm and washable hydrophilic layer on the surface of activated carbon, which can improve the wetting and spreading effect of water on the surface of activated carbon, and is beneficial to the stripping of dirt on the surface of activated carbon and the prevention of dirt accumulation and reduction of adsorption capacity. However, either of the polyether amine and polyethylene polyamine alone has lower hydrophilicity and adhesion strength of the hydrophilic layer, and cannot maintain stable adsorption effect.

[0066] In addition, the hydrophilic modification layer contains rich amine groups, which can be dissociated in water to obtain positively charged groups, and the anions such as phosphate groups have adsorption effect, which improves the phosphorus removal rate.

[0067] (2) According to the combination of Embodiments 1 and 4-5 and Table 2, it can be seen that the activated carbon is grafted and modified by using vinyl imidazole, initiator and siloxane monomer containing carbon-carbon double bond in the present application, which can effectively improve the adsorption effect of heavy metal ions. The reason may be that the vinyl imidazole, initiator and siloxane monomer containing carbon-carbon double bond can undergo copolymerization reaction, and introduce nitrogen-containing heterocyclic ring into the surface of activated carbon, thereby realizing effective adsorption of heavy metal ions.

[0068] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A phosphorus removal agent for landfill leachate, characterized in that, The hydrophilic modified activated carbon is prepared by reacting activated carbon in a mixed solution containing polyether amine, polyethylene polyamine and acidic catalyst; the concentration of the polyether amine in the mixed solution is 1-10 g / L, the concentration of the polyethylene polyamine is 1-3 g / L, and the concentration of the acidic catalyst in the mixed solution is 0.1-1 mol / L; the mixed solution further contains vinyl imidazole, initiator and siloxane monomer containing carbon-carbon double bond, the concentration of the siloxane monomer containing carbon-carbon double bond is 0.1-1 g / L, and the concentration of the vinyl imidazole is 0.1-0.5 g / L.

2. The phosphorus removal agent for landfill leachate according to claim 1, characterized by, The reaction temperature is 40-80 ℃, and the reaction time is 4-6 h.

3. The phosphorous removal agent for landfill leachate according to claim 1, characterized by, The D50 particle size of the activated carbon is 0.1 mm-5 mm.

4. The phosphorous removal agent for landfill leachate according to claim 1, characterized by, The polyethylene polyamine is at least one selected from diethylene triamine, triethylene tetramine and tetraethylene pentamine.

5. The phosphorous removal agent for landfill leachate according to claim 1, characterized by, The vinyl imidazole is at least one of 1-vinyl imidazole and 2-vinyl imidazole.

6. The phosphorous removal agent for landfill leachate according to claim 1, characterized by, The siloxane monomer containing carbon-carbon double bond is at least one of vinyl trimethoxysilane, vinyl triethoxysilane, γ-(methacryloyloxy) propyl trimethoxysilane and γ-(methacryloyloxy) propyl triethoxysilane.

7. The method for producing a phosphorous removal agent for landfill leachate according to any one of claims 1 to 6, characterized by, The method comprises the following steps: Pre-treatment: the acidic catalyst, siloxane monomer containing carbon-carbon double bond, initiator and vinyl imidazole are added into water to prepare a mixed solution, heated to a certain temperature, and then the activated carbon is added and stirred for 3-5 h; Hydrophilic modification: the polyether amine and polyethylene polyamine are added into the mixed solution and stirred for reaction, and then washed with water and dried to obtain the hydrophilic modified activated carbon.

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