Preparation method of activated carbon loaded multi-metal catalyzed nano zero-valent iron deep denitrification material

Abstract

The invention discloses a preparation method of an activated carbon loaded multi-metal catalytic nano zero-valent iron deep denitrification material. The method is characterized by comprising the following steps: selection and pretreatment of activated carbon, selection and pretreatment of zero-valent iron nanoparticles, selection and pretreatment of catalytic metal nanoparticles, preparation of the multi-metal catalytic carbon-supported nano zero-valent iron material and the like. The method solves the problems that the existing microbial denitrification technology is greatly influenced by environmental factors such as temperature and water quality, stable and ultralow emission of total nitrogen is difficult to realize, and the traditional nano zero-valent iron technology is agglomerated in particles and low in nitrogen selectivity, has better effluent indexes, does not need extra chemicals, does not increase the sewage denitrification energy consumption, and is suitable for industrial production. The material can be used as a main filler for deep denitrification of sewage.

Description

Technical Field

[0001] The present invention belongs to the field of advanced sewage denitrification in the field of energy conservation and environmental protection, and particularly relates to a preparation method of an activated carbon supported multi-metal catalytic nano zero-valent iron advanced denitrification material. Background Art

[0002] At present, nitrogen in sewage is mainly removed by microbial denitrification technology, which can basically ensure the up-to-standard discharge of total nitrogen and ammonia nitrogen indexes of sewage. However, the microbial treatment technology is affected by microbial activity, temperature change, influent total nitrogen load, etc., and there is a risk of exceeding the standard. Moreover, it is difficult for the microbial denitrification process to further reduce the total nitrogen (such as from 15 mg / L to 3 mg / L). The increasingly strict energy conservation and carbon reduction policies and sewage discharge standards put forward higher requirements for the total nitrogen effluent index and energy consumption index.

[0003] As a current research hotspot and frontier in denitrification, zero-valent iron denitrification technology can be an important supplement to microbial denitrification technology and is not affected by microbial activity, temperature and external stress. However, it has disadvantages such as low denitrification efficiency and low nitrogen selectivity. Due to its nano effect, nano zero-valent iron denitrification technology significantly enhances its denitrification efficiency of reducing nitrate nitrogen to ammonia nitrogen. However, the use of single nano zero-valent iron will have the phenomenon of "agglomeration", resulting in the gradual inactivation of its denitrification and nitrogen removal efficiency and the generation of passivation phenomenon. Loading nano zero-valent iron onto the surface of activated carbon solves the problem of "agglomeration" and maintains the reduction activity of nano zero-valent iron, and its denitrification efficiency is also significantly improved. However, the proportion of nitrate nitrogen reduced to nitrogen gas is still relatively low, that is, the nitrogen selectivity is poor.

[0004] The activated carbon supported multi-metal catalytic nano zero-valent iron material not only solves the problem of "agglomeration" of zero-valent iron particles, but also due to the catalytic effect of appropriate amounts of transition metals such as nano Cu, the nitrogen selectivity of this type of material will be greatly improved, so that the advanced and efficient removal of total nitrogen in sewage can be achieved. The present invention is based on this and optimizes the selection of catalytic metals and the addition amount, and performs high-temperature annealing treatment on the optimized material, so that the metal particles inside the material undergo lattice rearrangement, improving the nitrogen selectivity and also increasing its adhesion performance between the pores and lamellae of the activated carbon. If the effluent after sewage biological denitrification treatment needs to further remove total nitrogen to achieve ultra-low discharge of total nitrogen, this material is a better choice. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of an activated carbon supported multi-metal catalytic nano zero-valent iron advanced denitrification material. The material obtained by this method can be used as the main filler for advanced sewage denitrification, overcomes the defects that the microbial denitrification technology is easily affected by temperature, water quality, etc., and has better effluent indexes, does not require additional use of chemicals, and does not increase the energy consumption of sewage denitrification.

[0006] The technical solution of the present invention is: a method for preparing an activated carbon-supported multi-metal catalyzed nano zero-valent iron deep denitrification material, comprising the following steps:

[0007] A: Selection and pretreatment of activated carbon;

[0008] A1: Activated carbon is made from fruit shells, the microstructure is flake or amorphous, and the size is between 100nm-800nm;

[0009] A2: Weigh 0.6 g of the activated carbon described in step A1 and add it to 30 ml of a 65% concentrated nitric acid solution, stir and mix thoroughly to obtain a mixture No. 0, pour the mixture No. 0 into a 100 ml high-pressure reactor, and perform a hydrothermal shock reaction at 142±2°C for 20 hours;

[0010] A3: The mixed solution treated in step A2 is vacuum filtered and washed with ultrapure water for 3-5 times until the pH value of the filtrate remains above 6.8, and the filtered activated carbon is vacuum freeze-dried to obtain an activated carbon carrier material;

[0011] B: Selection and pretreatment of zero-valent iron nanoparticles;

[0012] B1: Select nano zero-valent iron particles below 100nm, with an iron content of >99.9% excluding oxygen;

[0013] B2: Weigh 0.12 g of the nano zero-valent iron particles described in step B1 and quickly add them into 15 ml of acetone solution, stir and mix thoroughly, and treat the mixture No. 0 with 100-300 W ultrasonic vibration in a nitrogen atmosphere for 4-6 hours to obtain a mixture No. 1;

[0014] C: Selection and pretreatment of catalytic metal nanoparticles;

[0015] Select catalytic metal particles below 100 nm, weigh 0.06 g Cu nanoparticles, 0.003 g Mo nanoparticles, 0.006 g Pd nanoparticles, 0.0006 g Co nanoparticles, and 0.012 g Ni nanoparticles, respectively, add them to 15 ml acetone solution, stir and mix thoroughly, and treat the mixture with 100-300 W ultrasonic oscillation for 4-6 hours to obtain mixture No. 2;

[0016] D: Preparation of multi-metal catalytic carbon-supported nano-zero-valent iron materials;

[0017] D1: Weigh 0.6 g of the activated carbon carrier material obtained in step A3, mix it with the mixture No. 1 obtained in step B2 and the mixture No. 2 obtained in step C to obtain a mixture No. 3, and treat the mixture No. 3 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that various nano-metal particles are fully attached to the activated carbon sheets and activated carbon pores;

[0018] D2: The mixture No. 3 treated in step D1 is dried under anaerobic conditions and annealed at 420-500℃ for 10h to further recrystallize the various metal particles in the material. After annealing, it is washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported multi-metal catalytic nano zero-valent iron deep denitrification material, i.e., multi-metal / Fe 0 @AC Materials;

[0019] D3: Weigh 0.6 g of the activated carbon carrier material obtained in step A3 and mix it with the mixture No. 1 obtained in step B2 to obtain a mixture No. 4, and treat the mixture No. 4 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that the nano zero-valent iron particles are fully attached to the activated carbon sheets and activated carbon pores;

[0020] D4: The No. 3 mixture after the treatment in step D3 is dried under anaerobic conditions and annealed at 420-500°C for 10 hours. After annealing, it is washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported nano zero-valent iron denitrification material, namely Fe 0 @AC.

[0021] Furthermore, in the above-mentioned method for preparing activated carbon-loaded multi-metal catalytic nano zero-valent iron deep denitrification material, the activated carbon in step A1 is made of coconut shell.

[0022] The present invention aims to solve the problems of low denitrification efficiency, low nitrogen selectivity, easy agglomeration, etc. in current zero-valent iron denitrification technology, nano zero-valent iron denitrification technology, etc., by preparing activated carbon carrier materials, nano zero-valent iron materials, and ultrasonic impregnation treatment, and filtering to obtain activated carbon-loaded multi-metal catalytic nano zero-valent iron denitrification materials, which solves the problem of "agglomeration" of zero-valent iron particles, greatly improves nitrogen selectivity, and achieves deep and efficient removal of total nitrogen in sewage, meeting the increasingly stringent energy-saving and carbon-reduction policies and sewage discharge standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the present invention;

[0024] Figure 2 For multi-metal / Fe 0 @TEM image of AC material;

[0025] Figure 3 For multi-metal / Fe 0 @Mapping distribution of various metal elements in AC materials;

[0026] Figure 4 For multi-metal / Fe 0Mass percentage of various metal elements in @AC material;

[0027] Figure 5 For multi-metal / Fe 0 XRD pattern of @AC material after being placed in air at room temperature for 3 weeks;

[0028] Figure 6 For Fe 0 @AC material and multi-metal / Fe 0 Change of nitrate nitrogen in @AC material for deep denitrification;

[0029] Figure 7 For Fe 0 @AC material and multi-metal / Fe 0 Change of ammonia nitrogen in @AC material for deep denitrification. Detailed implementation method

[0030] Example 1: A preparation method of an activated carbon supported multi-metal catalytic nano zero-valent iron deep denitrification material, comprising the following steps:

[0031] A: Selection and pretreatment of activated carbon;

[0032] A1: The activated carbon selected is fruit shell activated carbon, with a microscopic structure of flaky or amorphous, and the size is between 100nm and 800nm;

[0033] A2: Weigh 0.6g of the activated carbon described in step A1 and add it to 30ml of a concentrated nitric acid solution with a mass concentration of 65%, stir well to mix evenly to obtain a No. 0 mixture, pour the No. 0 mixture into a high-pressure reaction kettle with a volume of 100ml, and carry out hydrothermal oscillation reaction at 142±2°C for 20h;

[0034] A3: Vacuum filter the mixed solution treated in step A2, and wash it 3-5 times with ultrapure water until the pH value of the filtrate remains above 6.8. Freeze-dry the filtered activated carbon under vacuum to obtain an activated carbon carrier material;

[0035] B: Selection and pretreatment of zero-valent iron nanoparticles;

[0036] B1: Select nano zero-valent iron particles with a size below 100nm, and the iron content without oxygen > 99.9%;

[0037] B2: Weigh 0.12g of the nano zero-valent iron particles described in step B1 and quickly add them to 15ml of acetone solution, stir well to mix evenly, and subject the No. 0 mixture to ultrasonic oscillation treatment at 100-300W in a nitrogen atmosphere for 4-6h to obtain a No. 1 mixture;

[0038] C: Selection and pretreatment of catalytic metal nanoparticles;

[0039] Select catalytic metal particles below 100 nm, weigh 0.06 g Cu nanoparticles, 0.003 g Mo nanoparticles, 0.006 g Pd nanoparticles, 0.0006 g Co nanoparticles, and 0.012 g Ni nanoparticles, respectively, add them to 15 ml acetone solution, stir and mix thoroughly, and treat the mixture with 100-300 W ultrasonic oscillation for 4-6 hours to obtain mixture No. 2;

[0040] D: Preparation of multi-metal catalytic carbon-supported nano-zero-valent iron materials;

[0041] D1: Weigh 0.6 g of the activated carbon carrier material obtained in step A3, mix it with the mixture No. 1 obtained in step B2 and the mixture No. 2 obtained in step C to obtain a mixture No. 3, and treat the mixture No. 3 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that various nano-metal particles are fully attached to the activated carbon sheets and activated carbon pores;

[0042] D2: The mixture No. 3 treated in step D1 is dried under anaerobic conditions and annealed at 420-500℃ for 10h to further recrystallize the various metal particles in the material. After annealing, it is washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported multi-metal catalytic nano zero-valent iron deep denitrification material, i.e., multi-metal / Fe 0 @AC Materials;

[0043] The prepared multi-metal / Fe0@AC material was characterized by electron microscopy, and it can be observed that Figure 2 The large particles are shown to be flaky activated carbon. Figure 3 The small particles with different particle sizes are various metal particles supported by activated carbon. Figure 4 It shows that among the metals actually contained in the prepared material, Fe 0 The percentage content is 63.7%, followed by catalytic metal Cu, which accounts for 33.25%.

[0044] D3: Weigh 0.6 g of the activated carbon carrier material obtained in step A3 and mix it with the mixture No. 1 obtained in step B2 to obtain a mixture No. 4, and treat the mixture No. 4 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that the nano zero-valent iron particles are fully attached to the activated carbon sheets and activated carbon pores;

[0045] D4: The No. 3 mixture after the treatment in step D3 is dried under anaerobic conditions and annealed at 420-500°C for 10 hours. After annealing, it is washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported nano zero-valent iron denitrification material, namely Fe 0 @AC.

[0046] Experimental verification:

[0047] Prepare 400 ml of a solution with a nitrate nitrogen concentration of 15 mg / L as artificial simulated wastewater, and add 0.2 g of Fe 0 @AC material and 0.2 g of multi-metal / Fe 0 @AC material. After rapid mixing by magnetic stirring, take a sample, which is the initial water sample. The reaction temperature is kept constant at 25 °C by a water bath, and the pH value is 7.2 - 7.4. Subsequently, carry out the denitrification reaction continuously for 8 h, and take samples at irregular intervals to measure the nitrate nitrogen and ammonia nitrogen concentrations in the solution. The results are as Figure 6 and Figure 7 .

[0048] It can be seen from the test results that in the Fe 0 @AC material group, 10 mg / L of nitrate nitrogen was reduced after 8 h of reaction, and finally 6.22 mg / L of ammonia nitrogen was produced. Therefore, only 3.78 mg / L of nitrate nitrogen was reduced to nitrogen gas, that is, the nitrogen selectivity was only 37.8% (no nitrite nitrogen was detected by testing). While in the multi-metal / Fe 0 @AC material group, 12.96 mg / L of nitrate nitrogen was reduced after 8 h of reaction, and finally only 0.93 mg / L of ammonia nitrogen was produced. Therefore, finally 12.03 mg / L of nitrate nitrogen was reduced to nitrogen gas, that is, the nitrogen selectivity reached 92.8%. Therefore, the multi-metal / Fe 0 @AC material group has a higher denitrification efficiency and a higher nitrogen selectivity than the Fe 0 @AC material group, and can truly achieve deep denitrification of sewage. In addition, the multi-metal / Fe 0 @AC material after annealing treatment was placed in normal temperature air for three weeks, Figure 5 and its XRD pattern showed that the characteristic peaks of Fe 0 were still significant. Therefore, the zero-valent iron would not be oxidized due to long-term storage, resulting in the failure of its denitrification performance.

[0049] Example 2: On the basis of Example 1, coconut shell was selected as the activated carbon in step A1, and the same technical effects as in Example 1 were obtained.

Claims

1. A method for preparing an activated carbon-supported multi-metal catalyzed nano zero-valent iron deep denitrification material, characterized in that: The following steps are involved: A: Selection and pretreatment of activated carbon; A1: Activated carbon is made from fruit shells, with a flaky or amorphous microstructure and a size between 100nm and 800nm. A2: Weigh 0.6 g of the activated carbon described in step A1 and add it to 30 ml of a 65% concentrated nitric acid solution, stir and mix thoroughly to obtain a mixture No. 0, pour the mixture No. 0 into a 100 ml high-pressure reactor, and perform a hydrothermal shock reaction at 142±2°C for 20 hours; A3: The mixed solution treated in step A2 is vacuum filtered and washed with ultrapure water for 3-5 times until the pH value of the filtrate remains above 6.8, and the filtered activated carbon is vacuum freeze-dried to obtain an activated carbon carrier material; B: Selection and pretreatment of zero-valent iron nanoparticles; B1: Select nano zero-valent iron particles with a size of less than 100 nm, and the iron content excluding oxygen is > 99.9%; B2: Weigh 0.12 g of the nano zero-valent iron particles described in step B1 and quickly add them into 15 ml of acetone solution, stir and mix thoroughly, and treat the mixture No. 0 with 100-300 W ultrasonic vibration in a nitrogen atmosphere for 4-6 hours to obtain a mixture No. 1; C: Selection and pretreatment of catalytic metal nanoparticles; Select catalytic metal particles below 100 nm, weigh 0.06 g Cu nanoparticles, 0.003 g Mo nanoparticles, 0.006 g Pd nanoparticles, 0.0006 g Co nanoparticles, and 0.012 g Ni nanoparticles, respectively, add them to 15 ml acetone solution, stir and mix thoroughly, and treat the mixture with 100-300 W ultrasonic oscillation for 4-6 hours to obtain mixture No. 2; D: Preparation of multi-metal catalytic carbon-supported nano-zero-valent iron materials; D1: Weigh 0.6 g of the activated carbon carrier material obtained in step A3, mix it with the mixture No. 1 obtained in step B2 and the mixture No. 2 obtained in step C to obtain a mixture No. 3, and treat the mixture No. 3 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that various nano-metal particles are fully attached to the activated carbon sheets and activated carbon pores; D2: The mixture No. 3 treated in step D1 is dried under anaerobic conditions and annealed at 420-500℃ for 10h to further recrystallize the various metal particles in the material. After annealing, it is washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported multi-metal catalytic nano zero-valent iron deep denitrification material, i.e., multi-metal / Fe 0 @AC Materials; D3: Weigh 0.6 g of the activated carbon carrier material obtained in step A3 and mix it with the mixture No. 1 obtained in step B2 to obtain a mixture No. 4, and treat the mixture No. 4 by an ultrasonic impregnation process at 300-500 W for 10-12 h, so that the nano zero-valent iron particles are fully attached to the activated carbon sheets and activated carbon pores; D4: The No. 4 mixture treated in step D3 was dried under anaerobic conditions and annealed at 420-500°C for 10 hours. After annealing, it was washed with ultrapure water for 3 times and filtered to obtain the activated carbon-supported nano zero-valent iron denitrification material, namely Fe 0 @AC.

2. The method for preparing an activated carbon-supported multi-metal catalyzed nano zero-valent iron deep denitrification material according to claim 1, characterized in that: The activated carbon in step A1 is made of coconut shell.

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