Expanded graphite catalyst for degrading chemical pharmaceutical wastewater and preparation method thereof

Abstract

The application relates to the technical field of wastewater treatment, and discloses an expanded graphite catalyst for degrading chemical pharmaceutical wastewater and a preparation method. In the application, 2,2'-diamino-N-(hydroxypropyl trimethyl ammonium chloride) diethylamine is used to carry out an amidation reaction with carboxyl groups on the surface of oxidized expanded graphite, so as to bond and introduce active functional groups such as amino groups, quaternary ammonium salts and hydroxyl groups on the surface of the expanded graphite; then, through high-temperature hydrothermal reaction, zinc oxide particles are uniformly generated in the expanded graphite, and the expanded graphite catalyst is obtained. The active groups such as the hydroxyl groups of the expanded graphite catalyst form hydrogen bonds and other interactions with tetracycline hydrochloride, so that the adsorption and removal rate of the tetracycline hydrochloride is improved. The zinc oxide particles are uniformly grown in the expanded graphite matrix and are not prone to agglomeration, and a large number of photocatalytic active sites are exposed, so that the expanded graphite catalyst has better photocatalytic degradation performance on the tetracycline hydrochloride.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of wastewater treatment, in particular to an expanded graphite catalyst for degrading chemical pharmaceutical wastewater and a preparation method. BACKGROUND

[0002] In recent years, the chemical pharmaceutical industry in China has developed very rapidly, and a large amount of pharmaceutical industrial wastewater, mainly including phenols, chlorinated hydrocarbons, antibiotics and other pollutants, is generated. The pollutants are difficult to degrade and cause serious pollution. Effective treatment of the pharmaceutical wastewater is directly related to environmental protection and the benefits and survival of pharmaceutical enterprises. At present, the methods for treating the pharmaceutical wastewater include adsorption, membrane separation, photocatalytic degradation and ozone catalytic oxidation.

[0003] Expanded graphite has a large specific surface area, stable chemical properties and is cheap and easy to obtain, and is widely applied in adsorption materials, catalyst carriers and wastewater treatment. However, the adsorption performance of the expanded graphite is poor. The expanded graphite can be modified by using silane coupling agents, diethylene triamine and cetyltrimethylammonium bromide to improve the adsorption performance of the expanded graphite. However, the adsorption effect is limited due to the single functional group. Zinc oxide is a photocatalyst with excellent performance and has good photocatalytic degradation performance on tetracycline and phenols. The catalyst obtained by loading zinc oxide on expanded graphite has good photocatalytic performance. However, the dispersion of zinc oxide in the expanded graphite carrier is poor, which is not conducive to improving the photocatalytic degradation effect. SUMMARY

[0004] The application solves the problem of poor adsorption and degradation performance of the expanded graphite photocatalyst on tetracycline and other pollutants.

[0005] The technical scheme of the application is a preparation method of an expanded graphite catalyst:

[0006] (1) expanded graphite is added into a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, ultrasonic dispersion is carried out, the product is filtered, water-washed and dried to obtain oxidized expanded graphite.

[0007] (2) 2,3-epoxypropyltrimethylammonium chloride and 1,7-bis-BOC-1,4,7-triazepane are added into ethanol, reaction is carried out, ethanol is removed by rotary evaporation, the crude product is added into dichloromethane, hydrogen chloride ethyl acetate solution is added, reaction is carried out, saturated sodium carbonate solution is added, oscillation extraction is carried out, the organic phase is rotary evaporated, the product is added into an ethanol aqueous solution, and recrystallization purification is carried out to obtain 2,2'-diamino-N-(hydroxypropyltrimethylammonium chloride) diethylamine. The preparation reaction formula is as follows:

[0008] .

[0009] (3) adding the oxidized expanded graphite into N,N-dimethylformamide, ultrasonic dispersion, then adding 2,2'-diamino-N-(hydroxypropyltrimethylammonium) diethylamine, heating and stirring reaction, filtering, washing the product with water and ethanol, drying to obtain the modified expanded graphite.

[0010] (4) adding the modified expanded graphite and zinc compound into the aqueous ethanol solution, stirring, then pouring the solution into a hydrothermal reaction kettle, reacting, filtering, washing the product with water and ethanol, drying to obtain the expanded graphite catalyst.

[0011] Further, the volume ratio of concentrated sulfuric acid and concentrated nitric acid in (1) is 3:1.

[0012] Further, the ultrasonic dispersion time in (1) is 4-6h.

[0013] Further, the molar ratio of 2,3-epoxypropyltrimethylammonium chloride and 1,7-bis-BOC-1,4,7-triazacycloheptane in (2) is (1-1.2):1.

[0014] Further, the temperature of the first reaction in (2) is 30-50℃, and the reaction time is 18-24h.

[0015] Further, the temperature of the second reaction in (2) is 15-25℃, and the reaction time is 6-10h.

[0016] Further, the temperature of the reaction in (3) is 120-140℃, and the reaction time is 6-18h.

[0017] Further, the mass ratio of the oxidized expanded graphite and 2,2'-diamino-N-(hydroxypropyltrimethylammonium) diethylamine in (3) is 1:(5-20).

[0018] Further, the temperature of the reaction in (4) is 160-180℃, and the reaction time is 12-18h.

[0019] Further, the mass ratio of the modified expanded graphite and zinc compound in (4) is 1:(0.2-0.6).

[0020] Further, the zinc compound in (4) is zinc chloride, zinc acetate, zinc sulfate or zinc nitrate.

[0021] Further, the expanded graphite catalyst is applied to degrade chemical pharmaceutical wastewater.

[0022] Further, the expanded graphite catalyst can be combined with heterogeneous ozone O3 catalytic oxidation to degrade pollutants in pharmaceutical wastewater.

[0023] The application has the beneficial technical effects that: one amino group of 2,2'-diamino-N-(hydroxypropyl trimethyl ammonium chloride) diethylamine is subjected to amidation reaction with carboxyl on the surface of the oxidized expanded graphite at high temperature, so that active functional groups such as amino groups, quaternary ammonium salts and hydroxyl groups are bonded and introduced on the surface of the expanded graphite, the amino groups and the hydroxyl groups have adsorption coordination effects on zinc ions, the zinc ions are uniformly adsorbed in the expanded graphite matrix, then high-temperature hydrothermal reaction is performed, zinc oxide particles are uniformly generated in the expanded graphite, and the expanded graphite catalyst is obtained.

[0024] The expanded graphite catalyst of the application contains hydrophilic amino groups, hydroxyl groups and quaternary ammonium salt groups, the hydrophilicity of the catalyst is improved, the water dispersibility is excellent, more adsorption sites are provided, the adsorption performance of the catalyst on tetracycline hydrochloride is improved, and the active groups such as the amino groups, the hydroxyl groups and the quaternary ammonium salt groups form hydrogen bonds and other interactions with the tetracycline hydrochloride, so that the adsorption and removal rates of the catalyst on the tetracycline hydrochloride are further improved.

[0025] The zinc oxide particles of the application are uniformly grown in the expanded graphite matrix and are not prone to agglomeration, a large number of photocatalytic active sites are exposed, the photocatalytic degradation performance of the catalyst on the tetracycline hydrochloride is better, and the catalyst has good practical application in the treatment of pharmaceutical wastewater.

[0026] The expanded graphite catalyst of the application can also be combined with heterogeneous ozone O3 catalytic oxidation to efficiently realize degradation of pollutants in the pharmaceutical wastewater. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0028] Embodiment 1:

[0029] (1) 2 g of expanded graphite is added into a mixed acid solution of 180 mL of concentrated sulfuric acid (mass fraction 98%) and 60 mL of concentrated nitric acid (mass fraction 68%), ultrasonic dispersion is performed in an ultrasonic dispersion instrument for 6 h, the product is filtered and washed with water, and drying is performed to obtain oxidized expanded graphite.

[0030] (2) 60 mmol of 2,3-epoxypropyltrimethylammonium chloride, 60 mmol of 1,7-bis-BOC-1,4,7-triazheptane were added into 200 mL of ethanol, heated to 50°C, stirred for 18 h, rotary evaporation was performed to remove ethanol, the crude product was added into 200 mL of dichloromethane, 200 mL of hydrogen chloride ethyl acetate solution with a concentration of 3.5 mol / L was added, stirred for 10 h at 15°C, saturated sodium carbonate solution was added, oscillation extraction was performed, the organic phase was rotary evaporated, the product was added into an ethanol aqueous solution, recrystallization purification was performed, and 2,2'-diamino-N-(hydroxypropyltrimethylammonium chloride) diethylamine was obtained.

[0031] (3) 2 g of oxidized expanded graphite was added into 100 mL of N,N-dimethylformamide, ultrasonic dispersion was performed for 20 min, then 10 g of 2,2'-diamino-N-(hydroxypropyltrimethylammonium chloride) diethylamine was added, heated to 120°C, stirred and condensed to reflux for 18 h, filtration was performed, the product was washed with water and ethanol, and drying was performed, and modified expanded graphite was obtained.

[0032] (4) 5 g of modified expanded graphite, 1 g of zinc acetate were added into 120 mL of an ethanol aqueous solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reaction was performed at 180°C for 12 h, after filtration, the product was washed with water and ethanol, and drying was performed, and an expanded graphite catalyst was obtained.

[0033] Example 2:

[0034] (1) 2 g of expanded graphite was added into a mixed acid solution of 240 mL of concentrated sulfuric acid (mass fraction 98%) and 80 mL of concentrated nitric acid (mass fraction 68%), ultrasonic dispersion was performed in an ultrasonic disperser for 4 h, filtration was performed, the product was washed with water, and drying was performed, and oxidized expanded graphite was obtained.

[0035] (2) 72 mmol of 2,3-epoxypropyltrimethylammonium chloride, 60 mmol of 1,7-bis-BOC-1,4,7-triazheptane were added into 250 mL of ethanol, heated to 30°C, stirred for 24 h, rotary evaporation was performed to remove ethanol, the crude product was added into 250 mL of dichloromethane, 300 mL of hydrogen chloride ethyl acetate solution with a concentration of 2 mol / L was added, stirred for 6 h at 25°C, saturated sodium carbonate solution was added, oscillation extraction was performed, the organic phase was rotary evaporated, the product was added into an ethanol aqueous solution, recrystallization purification was performed, and 2,2'-diamino-N-(hydroxypropyltrimethylammonium chloride) diethylamine was obtained.

[0036] (3) 2 g of oxidized expanded graphite was added to 150 mL of N,N- dimethylformamide, ultrasonic dispersion for 20 min, then 20 g of 2,2'-diamino-N- (hydroxypropyltrimethylammonium) diethylamine was added, heated to 140°C, stirred and condensed reflux reaction for 6 h, filtered, the product was washed with water and ethanol, and dried to obtain modified expanded graphite.

[0037] (4) 5 g of modified expanded graphite, 1.5 g of zinc acetate was added to 150 mL of aqueous ethanol solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 160°C for 18 h, after filtration, the product was washed with water and ethanol, and dried to obtain an expanded graphite catalyst.

[0038] Example 3:

[0039] (1) 2 g of oxidized expanded graphite (prepared by Example 1) was added to 200 mL of N,N-dimethylformamide, ultrasonic dispersion for 20 min, then 30 g of 2,2'-diamino-N- (hydroxypropyltrimethylammonium) diethylamine (prepared by Example 1) was added, heated to 130°C, stirred and condensed reflux reaction for 12 h, filtered, the product was washed with water and ethanol, and dried to obtain modified expanded graphite.

[0040] (2) 5 g of modified expanded graphite, 2.2 g of zinc sulfate was added to 200 mL of aqueous ethanol solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 170°C for 12 h, after filtration, the product was washed with water and ethanol, and dried to obtain an expanded graphite catalyst.

[0041] Example 4:

[0042] (1) 2 g of oxidized expanded graphite (prepared by Example 1) was added to 200 mL of N,N-dimethylformamide, ultrasonic dispersion for 30 min, then 40 g of 2,2'-diamino-N- (hydroxypropyltrimethylammonium) diethylamine (prepared by Example 1) was added, heated to 140°C, stirred and condensed reflux reaction for 12 h, filtered, the product was washed with water and ethanol, and dried to obtain modified expanded graphite.

[0043] (2) 5 g of modified expanded graphite, 3 g of zinc chloride was added to 200 mL of aqueous ethanol solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 180°C for 12 h, after filtration, the product was washed with water and ethanol, and dried to obtain an expanded graphite catalyst.

[0044] Comparative Example 1, the difference between this comparative example and Example 1 is that oxidized expanded graphite is used instead of modified expanded graphite.

[0045] (1) 5 g of oxidized expanded graphite, 1 g of zinc acetate were added to 120 mL of an ethanol aqueous solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 180°C for 12 h, after filtration, the product was washed with water and ethanol, dried to obtain an expanded graphite catalyst.

[0046] Comparative Example 2, the difference between this comparative example and Example 1 is that diethylenetriamine is used instead of 2,2'-diamino-N-(hydroxypropyltrimethylammonium) diethylamine.

[0047] (1) 2 g of oxidized expanded graphite was added to 100 mL of N,N-dimethylformamide, ultrasonic dispersion for 20 min, then 10 g of diethylenetriamine was added, heated to 120°C, stirred and condensed refluxed for 18 h, filtered, the product was washed with water and ethanol, dried to obtain modified expanded graphite.

[0048] (2) 5 g of modified expanded graphite, 1 g of zinc acetate were added to 120 mL of an ethanol aqueous solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 180°C for 12 h, after filtration, the product was washed with water and ethanol, dried to obtain an expanded graphite catalyst.

[0049] Comparative Example 3, the difference between this comparative example and Example 1 is that 2,3-epoxypropyltrimethylammonium chloride is used instead of 2,2'-diamino-N-(hydroxypropyltrimethylammonium) diethylamine.

[0050] (1) 2 g of oxidized expanded graphite was added to 100 mL of N,N-dimethylformamide, ultrasonic dispersion for 20 min, then 10 g of 2,3-epoxypropyltrimethylammonium chloride was added, heated to 120°C, stirred and condensed refluxed for 18 h, filtered, the product was washed with water and ethanol, dried to obtain modified expanded graphite.

[0051] (2) 5 g of modified expanded graphite, 1 g of zinc acetate were added to 120 mL of an ethanol aqueous solution, after stirring, the solution was poured into a hydrothermal reaction kettle, reacted at 180°C for 12 h, after filtration, the product was washed with water and ethanol, dried to obtain an expanded graphite catalyst.

[0052] 100 mg of tetracycline hydrochloride was added to 1 L of distilled water, 1.5 g of expanded graphite catalyst was added, stirred and adsorbed in the dark, the concentration of tetracycline hydrochloride in the supernatant was determined at different adsorption times by ultraviolet-visible spectrophotometry, and the adsorption rate was calculated.

[0053] Table 1 adsorption rate test

[0054]

[0055] To 1 L distilled water, 100 mg of tetracycline hydrochloride was added, 1.5 g of expanded graphite catalyst was added, and adsorption was carried out under irradiation of a 200 W xenon lamp and stirring, the concentration of tetracycline hydrochloride in the supernatant was determined at different adsorption times by a UV-visible spectrophotometer, and the degradation rate was calculated.

[0056] Table 2 adsorption rate test

[0057]

[0058] Through testing, compared with Comparative Example 1, each of the examples utilizes one amino group of 2,2'-diamino-N-(hydroxypropyltrimethylammonium) diethylamine to react with carboxyl groups on the surface of oxidized expanded graphite at high temperature to form an amide, thereby introducing active functional groups such as amino groups, quaternary ammonium salts, and hydroxyl groups onto the surface of the expanded graphite, the amino groups and the hydroxyl groups have adsorption coordination effects on zinc ions, thereby uniformly adsorbing the zinc ions in the expanded graphite matrix, then hydrothermal reaction at high temperature, and uniformly generating zinc oxide particles in the expanded graphite, to obtain an expanded graphite catalyst. The expanded graphite contains hydrophilic amino groups, hydroxyl groups, and quaternary ammonium salt groups, thereby improving the hydrophilicity of the expanded graphite catalyst, the water dispersibility is excellent, there are more adsorption sites, which is conducive to improving the adsorption performance of the expanded graphite catalyst on tetracycline hydrochloride, and the active groups such as the amino groups, the hydroxyl groups, and the quaternary ammonium salts form hydrogen bonds and other interactions with tetracycline hydrochloride, thereby further improving the adsorption and removal rate of tetracycline hydrochloride. Furthermore, the zinc oxide particles are uniformly grown in the expanded graphite matrix, are not prone to agglomeration, and expose a large number of photocatalytic active sites, thereby having better photocatalytic degradation performance on tetracycline hydrochloride.

[0059] Comparative Example 2 utilizes diethylenetriamine to modify the surface of expanded graphite, the modified expanded graphite does not contain active groups such as hydroxyl groups and quaternary ammonium salts, the hydrophilicity and the water dispersibility of the expanded graphite are not good, and the adsorption performance on tetracycline hydrochloride is low, and the expanded graphite is difficult to uniformly adsorb zinc ions in the expanded graphite matrix, cannot uniformly generate zinc oxide particles in the expanded graphite, and the zinc oxide particles are prone to agglomeration, which is not conducive to improving the photocatalytic degradation performance of the expanded graphite catalyst.

[0060] Comparative Example 3 utilizes the epoxy groups of 2,3-epoxypropyltrimethylammonium chloride to react with carboxyl groups on the surface of oxidized expanded graphite, the modified expanded graphite does not contain active groups such as amino groups, the hydrophilicity and the water dispersibility of the expanded graphite are not good, and the adsorption performance on tetracycline hydrochloride is low, and the expanded graphite is difficult to uniformly adsorb zinc ions in the expanded graphite matrix, cannot uniformly generate zinc oxide particles in the expanded graphite, and the zinc oxide particles are prone to agglomeration, which leads to poor photocatalytic degradation performance of the expanded graphite catalyst.

[0061] The above merely preferred embodiments of the present application are not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an expanded graphite catalyst for degrading chemical pharmaceutical wastewater, characterized by, The preparation method comprises the following steps: (1) adding oxidized expanded graphite into N, N-dimethylformamide, ultrasonic dispersion, then adding 2, 2'-diamino-N-(2-hydroxypropyl trimethyl ammonium chloride) diethylamine, heating and stirring reaction, filtering, washing the product, drying to obtain modified expanded graphite; (2) adding modified expanded graphite and zinc compound into ethanol aqueous solution, stirring, then pouring the solution into a hydrothermal reaction kettle, carrying out reaction, filtering, washing the product, drying to obtain expanded graphite catalyst; The preparation method of the 2, 2'-diamino-N-(2-hydroxypropyl trimethyl ammonium chloride) diethylamine comprises the following steps: adding 2, 3-epoxypropyl trimethyl ammonium chloride and 1, 7-bis-BOC-1, 4, 7-triazepane into ethanol in a molar ratio of (1-1.2):1, heating to 30-50℃, stirring for 18-24h, removing ethanol by rotary evaporation, adding the crude product into dichloromethane, adding hydrogen chloride ethyl acetate solution, stirring at 15-25℃ for 6-10h, extracting, recrystallizing and purifying the product to obtain 2, 2'-diamino-N-(2-hydroxypropyl trimethyl ammonium chloride) diethylamine.

2. The method of claim 1, wherein the method is characterized by, The reaction temperature in the step (1) is 120-140℃, and the reaction time is 6-18h.

3. The method of claim 1, wherein the method is characterized by, The mass ratio of the oxidized expanded graphite and the 2, 2'-diamino-N-(2-hydroxypropyl trimethyl ammonium chloride) diethylamine in the step (1) is 1:(5-20).

4. The method of claim 3, wherein the method is characterized by, The preparation method of the oxidized expanded graphite comprises the following steps: adding expanded graphite into a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, ultrasonic dispersion for 4-6h, filtering, washing the product, drying to obtain oxidized expanded graphite.

5. The method for preparing the expanded graphite catalyst according to claim 1, characterized in that, The reaction temperature in the step (2) is 160-180℃, and the reaction time is 12-18h.

6. The method for preparing the expanded graphite catalyst according to claim 1, characterized in that, The mass ratio of the modified expanded graphite and the zinc compound in the step (2) is 1:(0.2-0.6).

7. The method of claim 6, wherein the method is characterized by, The zinc compound is zinc chloride, zinc acetate, zinc sulfate or zinc nitrate.

8. An expanded graphite catalyst obtained by the preparation method according to any one of claims 1-7.

9. Application of the expanded graphite catalyst according to claim 8 in degrading chemical pharmaceutical wastewater.

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