Method for treating mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid

Abstract

The invention relates to the technical field of chemical engineering, and provides a method for treating mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, which comprises the following steps: S1, carrying out acidification, vacuum dechlorination, secondary blow-off dechlorination, neutralization, filtration and sedimentation treatment on the mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, and adding liquid caustic soda to obtain a pretreatment solution; and S2, adding sodium hypochlorite into the pretreatment liquid, uniformly mixing, and carrying out catalytic oxidation by using a copper oxide doped carbon nitride composite molecular sieve as a catalyst to obtain a mother solution treated by sodium hypochlorite. According to the technical scheme, the problem that the total ammonium content of the treated dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor is too high in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor. Background Art

[0002] In the production process of chloroisocyanuric acid products, the catalyst technology involved in using sodium hypochlorite to treat dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors faces challenges, which directly restricts the environmental protection and economic efficiency of the sodium hypochlorite treatment process of dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors. The core problem of the catalyst system currently used for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors with sodium hypochlorite is mainly: in the complex chemical environment formed by high concentrations of cyanuric acid, sodium chloride and inorganic ammonium salts in the mother liquor, the traditional catalyst used for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors with sodium hypochlorite is easily occupied due to ion exchange or ion exchange, resulting in a decrease in the catalytic efficiency of the sodium hypochlorite treatment of dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors, and is unable to play the role of reducing the total ammonium content of the mother liquor, which leads to excessively high total ammonium content in the mother liquor after catalytic oxidation.

[0003] Therefore, developing a new catalyst that can reduce the total ammonium content in dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors and developing an efficient method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors have become the key to breaking through the bottleneck of chloroisocyanuric acid mother liquor treatment technology. Summary of the Invention

[0004] The present invention provides a method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor, which solves the problem that the total ammonium content of the treated dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor is too high.

[0005] The technical solutions of the present invention are as follows: The present invention provides a method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor, comprising the following steps: S1, acidifying the mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, vacuum dechlorination, secondary blow-off dechlorination, neutralization, filtration, sedimentation treatment, adding liquid alkali to obtain a pre-treated liquid; S2, adding sodium hypochlorite to the pre-treated liquid, mixing evenly, catalytically oxidizing, and filtering to obtain a mother liquor treated with sodium hypochlorite; The catalytic oxidation is performed using a catalyst; The preparation method of the catalyst comprises the following steps: A1. Mixing molecular sieves, melamine, and dimethylformamide uniformly, concentrating, drying, and calcining to obtain a catalyst precursor; A2. Soaking the catalyst precursor in alkali solution, filtering, washing, drying, and performing H exchange to obtain an H-type molecular sieve; A3. Exchanging the H-type molecular sieve with copper ions to obtain a catalyst.

[0006] As a further technical solution, the mass ratio of the molecular sieve to melamine is 10:1-10, preferably 10:3-5.

[0007] As a further technical solution, copper ion exchange is performed using a cupric chloride solution; The concentration of the copper chloride solution is 0.05~1 mol / L; The mass volume ratio of the H-type molecular sieve and the copper chloride solution is 0.05-0.2 g / mL.

[0008] As a further technical solution, the mass ratio of the catalyst to the sodium hypochlorite is 1:20~30.

[0009] As a further technical solution, the molecular sieve is ZSM-5 molecular sieve.

[0010] As a further technical solution, the mass volume ratio of the molecular sieve to dimethylformamide is 1g:10~15mL.

[0011] As a further technical solution, in step A1, the calcination temperature is 500-570° C. and the calcination time is 5-7 hours.

[0012] In the method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor of the present invention, during the preparation of the catalyst, the calcination temperature is 500-570° C., so that melamine can be converted into carbon nitride and interact with the active sites on the surface of the molecular sieve. The calcination time is 5-7 hours to ensure that the above process can be completed.

[0013] As a further technical solution, the alkali solution is sodium hydroxide with a concentration of 0.05 to 0.1 mol / L; The H exchange process is as follows: adding the dried catalyst precursor into an ammonium salt solution, stirring, filtering, washing, drying, and calcining at 500-650° C. for 3-4 hours.

[0014] As a further technical solution, the ammonium salt solution is ammonium nitrate with a concentration of 0.05-0.1 mol / L.

[0015] The stirring speed is 500-600 rpm, the temperature is 70-80° C., and the time is 20-28 h.

[0016] As a further technical solution, the copper ion exchange process is: immersing the H-type molecular sieve in a copper chloride solution for exchange, filtering, washing, drying, and calcining at 500-600° C. for 3-5 hours.

[0017] As a further technical solution, the soaking temperature is 40-50°C and the soaking time is 18-20 hours.

[0018] As a further technical solution, the mass volume ratio of the catalyst precursor to the alkali solution is 1-1.2 g / mL.

[0019] As a further technical solution, the mass volume ratio of the catalyst precursor to the ammonium salt solution is 0.1-0.2 g / mL.

[0020] As a further technical solution, step A4 is also included, specifically: impregnating an equal volume of the copper ion-exchanged molecular sieve with a mixed solution of ferric chloride, nickel chloride, and manganese chloride, drying, and calcining to obtain a catalyst.

[0021] As a further technical solution, in the mixed solution of ferric chloride, nickel chloride and manganese chloride, the mass ratio of water, ferric chloride, nickel chloride and manganese chloride is 95:2:2:3~4.

[0022] As a further technical solution, in step A4, the calcination temperature is 600-650° C. and the calcination time is 4-5.5 h.

[0023] In the method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor of the present invention, during catalyst preparation, an equal volume impregnation method is used to compound ferric chloride, nickel chloride, and manganese chloride in a molecular sieve after copper ion exchange. The ferric chloride, nickel chloride, and manganese chloride are calcined to obtain three metal oxides: ferric oxide, nickel oxide, and manganese dioxide. Due to its variable oxidation state, ferric oxide promotes the oxidation of ammonium ions through redox cycles, thereby enhancing the adsorption and activation capacity of ammonium ions. Nickel oxide utilizes its redox activity to synergistically accelerate the conversion of ammonium ions with ferric oxide. Manganese dioxide provides various electron transfer pathways by virtue of its multiple oxidation states, cooperates with other components to oxidize ammonium ions, and promotes the decomposition of sodium hypochlorite to produce strongly oxidizing active oxygen species, thereby enhancing the oxidation effect on ammonium ions and further reducing the total ammonium content of the dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors.

[0024] As a further technical solution, the pH of the pretreatment liquid is 11-12.

[0025] As a further technical solution, in step S2, the molar ratio of cyanuric acid to sodium hypochlorite in the pretreatment solution is 1:7-8; The temperature of the catalytic oxidation is 60-80° C., and the time is 2-3 hours.

[0026] The working principle and beneficial effects of the present invention are: In the present invention, a catalyst is introduced during the process of treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors with sodium hypochlorite. The catalyst is prepared by first compounding molecular sieve with carbon nitride, then sequentially performing H exchange and copper ion exchange, and further compounding with copper oxide. Due to the special electronic structure and chemical activity of carbon nitride, after combining with the molecular sieve, active centers with excellent adsorption function can be formed, and the adsorption selectivity and adsorption capacity for ammonium-containing substances in the mother liquor are high. In addition, the introduction of copper oxide improves the treatment efficiency of the catalyst for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors with sodium hypochlorite, thereby effectively reducing the total ammonium content in the treated mother liquor. DETAILED DESCRIPTION

[0027] 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 embodiments described 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 making any creative efforts are within the scope of protection of the present invention.

[0028] In the following examples and comparative examples, melamine was purchased from Suzhou Tejingsi Chemical Co., Ltd. with the product number T-12, and the specific surface area of ​​the ZSM-5 molecular sieve was 350 m 2 / g, pore size of 0.5 nm, purchased from Raodong (Liaoning) New Materials Co., Ltd.

[0029] Example 1 A method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor comprises the following steps: S1, acidifying the mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, vacuum dechlorination, secondary dechlorination by blowing, neutralization, filtration, sedimentation treatment, adding liquid alkali to adjust the pH to 12, to obtain a pre-treated solution; S2. Sodium hypochlorite is added to the pretreatment liquid and mixed evenly (the molar ratio of cyanuric acid to sodium hypochlorite in the pretreatment liquid is 1:8), and catalytic oxidation is performed at 80° C. for 2 h to obtain a mother liquor treated with sodium hypochlorite; A catalyst is used during catalytic oxidation, and the mass ratio of the catalyst to sodium hypochlorite is 1:30. The catalyst preparation method includes the following steps: A1. Mix ZSM-5 molecular sieve, melamine, and dimethylformamide (the mass volume ratio of molecular sieve to dimethylformamide is 1 g:10 mL, and the mass ratio of molecular sieve to melamine is 10:1), and calcine at 570°C for 5 hours to obtain a catalyst precursor; A2. Soak the catalyst precursor in 0.1 mol / L sodium hydroxide (the mass volume ratio of the catalyst precursor to the alkali solution is 1.2 g / mL), wash, and dry. Add the dried catalyst precursor to 0.1 mol / L ammonium nitrate solution (the mass volume ratio of the catalyst precursor to the ammonium nitrate solution is 0.2 g / mL), stir at 80°C and 600 rpm for 20 hours, filter, wash, dry, and calcine at 650°C for 3 hours to obtain an H-type molecular sieve; A3. Soak the H-type molecular sieve in a 0.1 mol / L copper chloride solution at 50°C for 18 hours (the mass volume ratio of the H-type molecular sieve to the copper chloride solution is 0.2 g / mL), concentrate, dry, and calcine at 600°C for 3 hours to obtain a catalyst.

[0030] Example 2 A method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor comprises the following steps: S1, acidifying the mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, vacuum dechlorination, secondary dechlorination by blowing, neutralization, filtration, sedimentation treatment, adding liquid alkali to adjust the pH to 11, to obtain a pre-treated liquid; S2. Sodium hypochlorite is added to the pretreatment liquid and mixed evenly (the molar ratio of cyanuric acid to sodium hypochlorite in the pretreatment liquid is 1:7), and catalytic oxidation is performed at 60° C. for 3 h to obtain a mother liquor treated with sodium hypochlorite; A catalyst is used during catalytic oxidation, and the mass ratio of the catalyst to sodium hypochlorite is 1:20. The preparation method of the catalyst comprises the following steps: A1. Mix ZSM-5 molecular sieve, melamine, and dimethylformamide (the mass volume ratio of molecular sieve to dimethylformamide is 1 g:15 mL, and the mass ratio of molecular sieve to melamine is 10:1), and calcine at 500°C for 7 hours to obtain a catalyst precursor; A2. Soak the catalyst precursor in 0.05 mol / L sodium hydroxide (the mass volume ratio of the catalyst precursor to the alkali solution is 1 g / mL), wash, and dry. Add the dried catalyst precursor to 0.05 mol / L ammonium nitrate solution (the mass volume ratio of the catalyst precursor to the ammonium nitrate solution is 0.1 g / mL), stir at 500 rpm at 70°C for 28 hours, filter, wash, dry, and calcine at 500°C for 4 hours to obtain H-type molecular sieve; A3. Soak the H-type molecular sieve in a 0.05 mol / L copper chloride solution at 40°C for 20 h (the mass volume ratio of the H-type molecular sieve to the copper chloride solution is 0.05 g / mL), concentrate, dry, and calcine at 500°C for 5 h to obtain a catalyst.

[0031] Example 3 The only difference between this embodiment and embodiment 2 is that the mass ratio of molecular sieve to melamine in this embodiment is 1:1.

[0032] Example 4 The only difference between this embodiment and embodiment 2 is that the mass ratio of molecular sieve to melamine in this embodiment is 10:3.

[0033] Example 5 The only difference between this embodiment and embodiment 2 is that the mass ratio of molecular sieve to melamine in this embodiment is 2:1.

[0034] Example 6 The only difference between this embodiment and embodiment 5 is that the preparation method of the catalyst in this embodiment further includes the following steps: A4. Impregnate an equal volume of the copper ion-exchanged molecular sieve with a mixed solution of ferric chloride, nickel chloride, and manganese chloride (prepared from water, ferric chloride, nickel chloride, and manganese chloride in a mass ratio of 95:2:2:4), dry, and calcine at 650°C for 4 hours to obtain a catalyst.

[0035] Example 7 The only difference between this embodiment and embodiment 5 is that the preparation method of the catalyst in this embodiment further includes the following steps: A4. Impregnate an equal volume of the copper ion-exchanged molecular sieve with a mixed solution of ferric chloride, nickel chloride, and manganese chloride (prepared from water, ferric chloride, nickel chloride, and manganese chloride in a mass ratio of 95:2:2:3), dry, and calcine at 600°C for 4.5 hours to obtain a catalyst.

[0036] Comparative Example 1 The only difference between this comparative example and Example 2 is that the preparation method of the catalyst in this comparative example includes the following steps: ZSM-5 molecular sieve, melamine and dimethylformamide were mixed evenly (the mass volume ratio of molecular sieve to dimethylformamide was 1 g:15 mL, and the mass ratio of molecular sieve to melamine was 10:1), and calcined at 500° C. for 7 h to obtain a catalyst.

[0037] Comparative Example 2 The only difference between this comparative example and Example 2 is that the preparation method of the catalyst in this comparative example includes the following steps: A1. Soak the ZSM-5 molecular sieve in 0.05 mol / L sodium hydroxide (the mass volume ratio of the catalyst precursor to the alkali solution is 1 g / mL), wash, and dry. Add the dried catalyst precursor to 0.05 mol / L ammonium nitrate solution (the mass volume ratio of the catalyst precursor to the ammonium nitrate solution is 0.1 g / mL), stir at 500 rpm at 70°C for 28 hours, filter, wash, dry, and calcine at 500°C for 4 hours to obtain H-type molecular sieve; A2. Soak the H-type molecular sieve in a 0.05 mol / L copper chloride solution at 40°C for 20 h (the mass volume ratio of the H-type molecular sieve to the copper chloride solution is 0.05 g / mL), concentrate, dry, and calcine at 500°C for 5 h to obtain a catalyst.

[0038] Comparative Example 3 The only difference between this comparative example and Example 2 is that the catalyst in this comparative example is ZSM-5 molecular sieve.

[0039] Experimental example The ammonium content of the mother liquors treated with sodium hypochlorite obtained in Examples 1-7 and Comparative Examples 1-3 was determined using the Nessler's reagent spectrophotometric method: A catalyst was added to a concentrated sulfuric acid solution and heated to convert the organic ammonia in the sample into inorganic ammonium. Under alkaline conditions, the inorganic ammonium evaporated as ammonia, which was then absorbed with a boric acid solution and developed with Nessler's reagent. The colored solution was then photometrically measured at a wavelength of 420 nm. The test results are shown in Table 1.

[0040] Table 1 Total ammonium content test results

[0041] As shown in Table 1, by comparing Examples 1 to 5 with Comparative Examples 1 to 3, it is shown that the present invention reduces the total ammonium content of the treated dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors by preparing copper oxide-doped carbon nitride composite molecular sieves.

[0042] Comparing Examples 6 and 7 with Example 5, it is shown that compounding iron oxide, nickel oxide, and manganese dioxide in the molecular sieve after copper ion exchange further reduces the total ammonium content of the treated dichloroisocyanuric acid and trichloroisocyanuric acid mother liquors.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor, characterized in that: The following steps are involved: S1, acidifying the mother liquor of dichloroisocyanuric acid and trichloroisocyanuric acid, vacuum dechlorination, secondary blow-off dechlorination, neutralization, filtration, sedimentation treatment, adding liquid alkali to obtain a pre-treated liquid; S2, adding sodium hypochlorite to the pre-treated liquid, mixing evenly, catalytically oxidizing, and filtering to obtain a mother liquor treated with sodium hypochlorite; The catalytic oxidation is performed using a catalyst; The preparation method of the catalyst comprises the following steps: A1. Mixing molecular sieves, melamine, and dimethylformamide uniformly, concentrating, drying, and calcining to obtain a catalyst precursor; A2. Soaking the catalyst precursor in alkali solution, filtering, washing, drying, and performing H exchange to obtain an H-type molecular sieve; A3. Exchanging the H-type molecular sieve with copper ions to obtain a catalyst.

2. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, wherein: Copper ion exchange was performed using a copper chloride solution; The concentration of the copper chloride solution is 0.05~1 mol / L; The mass volume ratio of the H-type molecular sieve and the copper chloride solution is 0.05-0.2 g / mL.

3. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: The molecular sieve is ZSM-5 molecular sieve; In step A1, the calcination temperature is 500-570° C. and the calcination time is 5-7 hours.

4. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: The alkali solution is a sodium hydroxide solution with a concentration of 0.05-0.1 mol / L; The H exchange process is as follows: adding the dried catalyst precursor into an ammonium salt solution, stirring, filtering, washing, drying, and calcining at 500-650° C. for 3-4 hours.

5. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: The copper ion exchange process is as follows: immersing the H-type molecular sieve in a copper chloride solution for exchange, filtering, washing, drying, and calcining at 500-600° C. for 3-5 hours.

6. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: The method further includes step A4, specifically: impregnating an equal volume of the copper ion-exchanged molecular sieve with a mixed solution of ferric chloride, nickel chloride, and manganese chloride, drying, and calcining to obtain a catalyst.

7. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 6, characterized in that: In the mixed solution of ferric chloride, nickel chloride and manganese chloride, the mass ratio of water, ferric chloride, nickel chloride and manganese chloride is 95:2:2:3-4.

8. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 7, characterized in that: In step A4, the calcination temperature is 600-650° C. and the calcination time is 4-4.5 hours.

9. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: The pH of the pretreatment liquid is 11-12.

10. The method for treating dichloroisocyanuric acid and trichloroisocyanuric acid mother liquor according to claim 1, characterized in that: In step S2, the molar ratio of cyanuric acid to sodium hypochlorite in the pretreatment solution is 1:7-8; The temperature of the catalytic oxidation is 60-80° C., and the time is 2-3 hours.

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