Preparation method of modified activated carbon capable of effectively removing phosphorus in glyphosate waste salt

Abstract

The application discloses a preparation method of modified activated carbon capable of effectively removing phosphorus in glyphosate waste salt, wherein activated carbon and lanthanum nitrate are mixed to prepare a mixed solution, the pH value of the aqueous solution is adjusted to 6-7 to prepare preliminary modified activated carbon, the preliminary modified activated carbon is added into a sodium alginate solution to prepare carbon balls after stirring and reaction, and finally the carbon balls are added into a metal salt solution, stirred and soaked, and dried to prepare modified activated carbon. The activated carbon is modified by adopting a three-step method, lanthanum can be uniformly loaded on the surface of the activated carbon, the precipitation efficiency of phosphate ions is improved, the phosphorus removal rate is more than 99%, and the stability of the loaded lanthanum is improved; the phosphorus removal rate of the regenerated modified activated carbon can still reach 86%.

Description

Technical Field

[0001] This invention belongs to the field of modified activated carbon preparation, and particularly relates to a method for preparing modified activated carbon that can effectively remove phosphorus from glyphosate waste salt. Background Technology

[0002] Glyphosate, also known as Roundup or glyphosate-reducing herbicide, has the molecular formula C3H8NO3P. It is an organophosphorus pesticide, widely used worldwide due to its high efficiency, low toxicity, broad spectrum, and low cost. Glyphosate is a white crystalline powder, primarily composed of glyphosate ammonium salt, glyphosate diammonium salt, glyphosate isopropylamine salt, glyphosate potassium salt, and glyphosate sodium salt. Developed by Monsanto in 1971, it is widely used in the field of genetically modified crops. Glyphosate is a persistent and cumulative pollutant; due to its long half-life, it has a significant environmental impact.

[0003] Currently, there are various methods for treating glyphosate production wastewater, mainly divided into three categories: physical methods, chemical methods, and biological methods. Physical methods include adsorption, membrane separation, and microwave-assisted extraction. Chemical methods utilize chemical reagents to form precipitates with phosphates, thereby removing phosphorus from the solution. Biological methods use glyphosate as the sole nitrogen and phosphorus source, allowing phosphorus to be metabolized and degraded, thus achieving removal. Among these physical methods, adsorption involves adding an adsorbent to the phosphorus-containing wastewater, allowing phosphorus to bond with the adsorbent and accumulate on it, thereby removing phosphorus impurities from the wastewater. Adsorption is a method for treating wastewater that is low in operating costs, simple to operate, and highly efficient.

[0004] Currently, commonly used adsorbents include activated carbon, biomass, metal oxides, and clay minerals. For example, the invention patent with application number CN202110779504.8, entitled "A method for preparing and applying a zeolite-type phosphorus removal agent for high-salt waste liquid," discloses a method for preparing a zeolite-type phosphorus removal agent for high-salt waste liquid that uses inexpensive raw materials, is simple to operate, and has a high phosphorus removal rate. However, this method has a low adsorption capacity.

[0005] The invention patent with application number CN202111183335.8, entitled "System and process for removing phosphorus and impurities from high-salt wastewater by-products of glyphosate", discloses a chemical-free method. The invention application with application number CN202211379783.X, entitled "A modified activated carbon for phosphorus removal from wastewater and its preparation method", discloses that the use of modified activated carbon can thoroughly remove phosphorus-containing substances from wastewater, enabling the wastewater to meet the standard requirements.

[0006] Based on this, this application discloses a method for efficiently removing phosphorus from glyphosate waste salts based on activated carbon modification. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for preparing modified activated carbon. The modified activated carbon prepared by the method can efficiently remove phosphorus from glyphosate waste salt, with a removal rate of over 99%.

[0008] Technical solution: The present invention provides a method for preparing modified activated carbon that can effectively remove phosphorus from glyphosate waste salt, comprising the following steps:

[0009] (1) Mix activated carbon and modifier and prepare an aqueous solution. Stir in an oil bath and adjust the pH of the aqueous solution to 6-7. After ultrasonic treatment, filter and wash until neutral, then dry and grind to obtain preliminary modified activated carbon. The modifier includes lanthanum salt and cationic surfactant in a mass ratio of (1-1.5):1.

[0010] (2) The preliminarily modified activated carbon prepared in step (1) was added to sodium alginate solution and stirred to react to obtain carbon balls;

[0011] (3) The carbon balls prepared in step (2) are added to the metal salt solution, stirred, soaked and dried to obtain modified activated carbon.

[0012] This invention employs a three-step method to modify activated carbon, thereby improving the phosphorus removal rate from glyphosate waste salt to over 99%. First, an aqueous solution of a modifier prepared from lanthanum salt and a cationic surfactant is used for preliminary modification under ultrasonic conditions and a pH of 6-7. This acidic condition opens the internal pore channels of the adsorption carrier, increasing the specific surface area, which is superior to loading lanthanum metal salt onto the activated carbon carrier, resulting in pre-modified activated carbon. Second, the pre-modified activated carbon is stirred and reacted with sodium alginate. After the reaction, it is then soaked in a metal salt solution. The introduction of sodium alginate not only stabilizes the pre-modified activated carbon system and improves the stability of the lanthanum metal salt initially loaded on the activated carbon carrier, but also allows the subsequently introduced metal ions to form a complex with it, creating a three-dimensional network structure. This ensures that the introduced metal ions achieve atomic-level uniform mixing and do not remain free in the water, thus improving the phosphorus removal effect of the final modified activated carbon.

[0013] Furthermore, in the regeneration of the modified activated carbon prepared by the method of the present invention, the used modified activated carbon is placed in a sodium hydroxide solution and stirred for 5-10 hours, soaked, filtered, and dried to obtain regenerated activated carbon. Preferably, the concentration of NaOH used can be 0.1-0.2 mol / L.

[0014] Furthermore, in step (1) of the preparation method of the present invention, the mass ratio of activated carbon to modifier is 1:(1-2); the concentration of modifier and activated carbon in aqueous solution is 10-30 mmol / L.

[0015] Furthermore, in step (1) of the preparation method of the present invention, the cationic surfactant is hexadecyltrimethylammonium bromide or hexadecylpyridine chloride; the lanthanum salt is lanthanum nitrate.

[0016] Furthermore, in step (1) of the preparation method of the present invention, the oil bath temperature is 60-90℃, the oil bath is stirred for 10-12h, and the ultrasonic time is 20-40min.

[0017] Furthermore, in step (2) of the preparation method of the present invention, the mass ratio of sodium alginate to preliminary activated carbon is 1:(1-2), and the concentration of sodium alginate solution is 5-10 g / L.

[0018] Furthermore, in step (3) of the preparation method of the present invention, the metal salt solution is a LaCl3 solution with a concentration of 20-30 mmol / L, and the mass ratio of the metal salt to the carbon sphere is (1-2):1.

[0019] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: the modified activated carbon is modified by a three-step method, which not only enables lanthanum to be uniformly loaded on the surface of the activated carbon and improves the precipitation efficiency of phosphate ions, but also improves the stability of the loaded lanthanum, and the phosphorus removal rate can reach more than 99%. Attached Figure Description

[0020] Figure 1 The graph shows the effect of the amount of modified activated carbon added in Example 1 of this invention on the phosphorus removal rate. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] It should be noted that all raw materials used in this invention are commercially available. The water sample used in this invention was prepared from phosphorus-containing waste salt produced by glyphosate by-products from Hubei Xingfa Chemical Group Co., Ltd., after high-temperature oxygen pyrolysis. The total phosphorus content of this water sample was 15 mg / L.

[0023] Example 1

[0024] The preparation method of the modified activated carbon in Example 1 includes the following steps:

[0025] (1) La(NO3)3·6H2O and hexadecyltrimethylammonium bromide were mixed evenly at a mass ratio of 1.22:1 to prepare a modifier;

[0026] (2) The modifier and activated carbon were mixed at a mass ratio of 1:1, and distilled water was added at a concentration of 20 mmol / L. The mixture was stirred and reacted at an oil bath temperature of 80℃ for 11 h. The pH value was adjusted to 7, and the mixture was ultrasonically reacted for 30 min. The mixture was then filtered, washed until neutral, dried at 72℃ for 12 h, and ground to obtain the preliminary modified activated carbon.

[0027] (3) Add the pre-modified activated carbon prepared in step (1) to a sodium alginate solution with a concentration of 8 g / L and stir rapidly to obtain irregular carbon balls; wherein the mass ratio of the pre-modified activated carbon to sodium alginate is 1:1.

[0028] (4) The irregular carbon spheres prepared in step (3) are added to a lanthanum chloride solution with a concentration of 25 mmol / L and stirred for 10 min and soaked for 12 h. The mass ratio of lanthanum chloride to irregular carbon spheres is 1:1, and the final modified activated carbon is obtained.

[0029] Comparative Example 1

[0030] The basic steps are the same as in Example 1, except that steps (3) and (4) of Example 1 are omitted. Specifically:

[0031] (1) La(NO3)3·6H2O and hexadecyltrimethylammonium bromide were mixed evenly at a mass ratio of 1.22:1 to prepare a modifier;

[0032] (2) The modifier and activated carbon were mixed at a mass ratio of 1:1, and distilled water was added at a concentration of 20 mmol / L. The mixture was stirred and reacted at an oil bath temperature of 80℃ for 11 h. The pH value was adjusted to 7, and the mixture was ultrasonically reacted for 30 min. The mixture was then filtered, washed until neutral, dried at 72℃ for 12 h, and ground to obtain the preliminary modified activated carbon.

[0033] Comparative Example 2

[0034] The basic steps are the same as in Example 1, except that step (4) of Example 1 is omitted. Specifically:

[0035] (1) La(NO3)3·6H2O and hexadecyltrimethylammonium bromide were mixed evenly at a mass ratio of 1.22:1 to prepare a modifier;

[0036] (2) The modifier and activated carbon were mixed at a mass ratio of 1:1, and distilled water was added at a concentration of 20 mmol / L. The mixture was stirred and reacted at an oil bath temperature of 80℃ for 11 h. The pH value was adjusted to 7, and the mixture was ultrasonically reacted for 30 min. The mixture was then filtered, washed until neutral, dried at 72℃ for 12 h, and ground to obtain the preliminary modified activated carbon.

[0037] (3) The preliminarily modified activated carbon prepared in step (1) is added to a sodium alginate solution with a concentration of 8 g / L and stirred rapidly to obtain irregular carbon balls; wherein the mass ratio of the preliminarily modified activated carbon to sodium alginate is 1:1.

[0038] Performance testing: Dephosphorization efficiency determination

[0039] The modified activated carbon prepared in Example 1, Comparative Example 1, and Comparative Example 2 was added to the wastewater sample used in this invention at a dosage of 0.2 g / 50 mL and mixed in a magnetic stirrer for 3 h. The dephosphorization results are shown in Table 1 below.

[0040] Table 1. Dephosphorization effect of Example 1 and Comparative Example 1

[0041]

[0042] As shown in Table 1, the modified activated carbon prepared by the modification method of the present invention can achieve a total phosphorus removal rate of 99.6% and an adsorption capacity of 3.74 mg / g, exhibiting a high phosphorus removal rate.

[0043] Meanwhile, the modified activated carbon prepared in Example 1 was tested for phosphorus removal effect using different addition amounts, and the results are as follows. Figure 1 As shown. Through this Figure 1 It can be seen that when the modified activated carbon of the present invention is added at a concentration of less than or equal to 0.2 g / 50 mL, the phosphorus removal rate increases with the increase of the addition amount. However, when the content exceeds 0.2 g / 50 mL and approaches 0.25 g / 50 mL, the phosphorus removal rate tends to stabilize with the increase of the addition amount.

[0044] Example 2: Modified Activated Carbon Regeneration

[0045] The modified activated carbon obtained from the dephosphorization test in Example 1 was dried and collected, added to a 0.1 mol / L sodium hydroxide solution and stirred, filtered, washed until neutral, and then dried in an oven.

[0046] The dephosphorization effect of the regenerated modified activated carbon was measured, and the results are shown in Table 2 below.

[0047] Table 2. Dephosphorization effect of Examples 1 and 2

[0048]

[0049] As shown in Table 2, the activated carbon prepared in this invention can still achieve a phosphorus removal rate of 86% and an adsorption capacity of 3.2 mg / g after regeneration, demonstrating excellent regeneration effect.

[0050] Example 3

[0051] The preparation method of the modified activated carbon in Example 3 includes the following steps:

[0052] (1) La(NO3)3·6H2O and hexadecylpyridine chloride were mixed evenly at a mass ratio of 1:1 to prepare a modifier;

[0053] (2) The modifier and activated carbon were mixed at a mass ratio of 1.5:1, and distilled water was added at a concentration of 10 mmol / L. The mixture was stirred and reacted at an oil bath temperature of 60℃ for 12 h. The pH value was adjusted to 6.5, and the mixture was ultrasonically reacted for 40 min. The mixture was then filtered, washed until neutral, dried at 72℃ for 12 h, and ground to obtain the preliminary modified activated carbon.

[0054] (3) Add the pre-modified activated carbon prepared in step (1) to a sodium alginate solution with a concentration of 5 g / L and stir rapidly to obtain irregular carbon balls; wherein the mass ratio of pre-modified activated carbon to sodium alginate is 1.5:1.

[0055] (4) The irregular carbon spheres prepared in step (3) are added to a lanthanum chloride solution with a concentration of 20 mmol / L and stirred for 10 min and soaked for 12 h. The mass ratio of lanthanum chloride to irregular carbon spheres is 1.5:1, and the final modified activated carbon is obtained.

[0056] Example 4

[0057] The preparation method of the modified activated carbon in Example 4 includes the following steps:

[0058] (1) La(NO3)3·6H2O and hexadecylpyridine chloride were mixed evenly at a mass ratio of 1.5:1 to prepare a modifier;

[0059] (2) The modifier and activated carbon were mixed at a mass ratio of 2:1, and distilled water was added at a concentration of 30 mmol / L. The mixture was stirred and reacted at an oil bath temperature of 90℃ for 10 h. The pH value was adjusted to 6, and the mixture was ultrasonically reacted for 20 min. The mixture was then filtered, washed until neutral, dried at 72℃ for 12 h, and ground to obtain the preliminary modified activated carbon.

[0060] (3) Add the pre-modified activated carbon prepared in step (1) to a sodium alginate solution with a concentration of 10 g / L and stir rapidly to obtain irregular carbon balls; wherein the mass ratio of pre-modified activated carbon to sodium alginate is 2:1.

[0061] (4) The irregular carbon spheres prepared in step (3) are added to a lanthanum chloride solution with a concentration of 30 mmol / L and stirred for 10 min and soaked for 12 h. The mass ratio of lanthanum chloride to irregular carbon spheres is 2:1, and the final modified activated carbon is obtained.

[0062] Performance testing: Dephosphorization efficiency determination

[0063] The modified activated carbon prepared in Examples 3 and 4 was added to the wastewater sample used in this invention at a dosage of 0.2 g / 50 mL and mixed in a magnetic stirrer for 3 h. The dephosphorization results are shown in Table 3 below.

[0064] Table 3. Dephosphorization effect of Examples 3 and 4

[0065]

[0066] As shown in Table 3, the modified activated carbon prepared by the modification method of the present invention can achieve a total phosphorus removal rate of over 99% and an adsorption capacity of over 3.57 mg / g, exhibiting a high phosphorus removal rate.

Claims

1. A method for preparing modified activated carbon that can effectively remove phosphorus from glyphosate waste salt, characterized in that, Includes the following steps: (1) Mix activated carbon and modifier and prepare an aqueous solution. Stir in an oil bath and adjust the pH of the aqueous solution to 6-7. After ultrasonic treatment, filter and wash until neutral, then dry and grind to obtain preliminary modified activated carbon. The modifier includes lanthanum salt and cationic surfactant in a mass ratio of (1-1.5):

1. The mass ratio of activated carbon to modifier is 1:(1-2). The concentration of modifier and activated carbon in the aqueous solution is 10-30 mmol / L. The cationic surfactant is hexadecyltrimethylammonium bromide or hexadecylpyridine chloride, and the lanthanum salt is lanthanum nitrate. (2) The preliminarily modified activated carbon prepared in step (1) is added to sodium alginate solution, and carbon balls are obtained after stirring and reaction; the mass ratio of sodium alginate to preliminarily modified activated carbon is 1:(1-2), and the concentration of sodium alginate solution is 5-10g / L. (3) Add the carbon balls prepared in step (2) to the metal salt solution, stir, soak and dry to obtain modified activated carbon; the metal salt solution is LaCl3 solution with a concentration of 20-30 mmol / L and the mass ratio of metal salt to carbon balls is (1-2):

1.

2. The method for preparing modified activated carbon that can effectively remove phosphorus from glyphosate waste salt according to claim 1, characterized in that, During the regeneration of the modified activated carbon, the used modified activated carbon is placed in a sodium hydroxide solution with a concentration of 0.1-0.2 mol / L, stirred for 5-10 hours, soaked, filtered, and dried to obtain regenerated activated carbon.

3. The method for preparing modified activated carbon that can effectively remove phosphorus from glyphosate waste salt according to claim 1, characterized in that, In step (1), the oil bath temperature is 60-90℃, the oil bath is stirred for 10-12 hours, and the ultrasonic time is 20-40 minutes.

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