Iron-based MOF modified denitrification filler, preparation and application thereof

Abstract

The present application belongs to the technical field of wastewater treatment, and particularly relates to an iron-based MOF modified denitrification filler as well as preparation and application thereof. The present application connects sulfur autotrophic denitrification filler with chitosan modified iron-based MOF material. A large number of active functional groups of chitosan itself are conducive to chemical reaction, and can also serve as a carbon source to provide raw materials for denitrification. In combination with sulfur autotrophic denitrification filler itself with sulfur, the autotrophic / heterotrophic denitrification coupling process is applicable. In addition, the network framework of the MOF material wraps the filler inside, which can enhance the strength of the filler and also strengthen the slow-release performance of the filler. The present application adds excellent physicochemical properties of the iron-based MOF material to the sulfur autotrophic denitrification filler, so that the performance of the sulfur autotrophic denitrification filler is greatly improved in all aspects, the startup speed and running stability of the coupling process are effectively improved, and the performance of the sulfur autotrophic denitrification is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to an iron-based MOF modified denitrification filler as well as preparation and application thereof. BACKGROUND

[0002] Heterotrophic denitrification and sulfur autotrophic denitrification are currently popular research directions in the field of water treatment denitrification, and the two are complementary in principle and have similar living environments, so coupling the two can achieve an ideal denitrification effect. However, the coupling of the two is not simply mixed, but needs to be cultured and debugged for a long time to ensure stable operation. Therefore, the denitrification filler plays a crucial role in the start-up and operation of the coupling process.

[0003] Chinese patent CN 111285462A discloses a collaborative denitrification composite suspended filler, which contains elemental sulfur, calcium carbonate and coal powder, realizes the coupling of heterotrophic denitrification and sulfur autotrophic denitrification, solves the problem of excessively high or low pH in traditional denitrification technology, and reduces the generation of secondary pollution, but the highest total nitrogen removal rate is only above 80%. SUMMARY

[0004] The application aims to provide an iron-based MOF modified denitrification filler as well as preparation and application thereof. The total nitrogen removal rate of the iron-based MOF modified denitrification filler provided by the application is above 95%.

[0005] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0006] The application provides an iron-based MOF modified denitrification filler, which comprises a base unit and a modified unit covering the base unit.

[0007] The modified unit is a chitosan-modified iron-based MOF material.

[0008] The base unit is a sulfur autotrophic denitrification filler, and the sulfur autotrophic denitrification filler contains sulfur.

[0009] The modified unit and the base unit are connected by an ester bond obtained by the reaction of carboxyl in the modified unit and hydroxyl in the base unit.

[0010] Preferably, the mass ratio of the modified unit to the base unit is 1:2-4.

[0011] The molar ratio of chitosan to the iron-based MOF material in the modified unit is 2.8-6:1.

[0012] Preferably, the BET specific surface area of the iron-based MOF modified denitrification filler is 300-330m 2 / g, and the pore volume is 0.15-0.20 cm 3 / g.

[0013] Preferably, the sulfur autotrophic denitrification filler comprises one or more of sulfur, polyvinyl alcohol and siderite.

[0014] Preferably, the organic ligand in the chitosan-modified iron-based MOF material comprises one or more of carboxyl and amino.

[0015] The application also provides a preparation method of the iron-based MOF modified denitrification filler described in the above scheme, comprising the following steps:

[0016] (1) mixing iron salt, organic ligand compound and chitosan to perform dehydration condensation reaction to obtain a chitosan-modified iron-based MOF material;

[0017] (2) mixing the chitosan-modified iron-based MOF material with sulfur autotrophic denitrification filler and phase transfer catalyst to perform dehydration condensation reaction to obtain an iron-based MOF modified denitrification filler.

[0018] Preferably, in step (1), the molar ratio of iron element in the iron salt to the organic ligand compound is 4.9-6.5:1.

[0019] The molar ratio of the chitosan to the organic ligand compound is 1-2:1.

[0020] Preferably, in step (2), the mass ratio of the chitosan-modified iron-based MOF material to the sulfur autotrophic denitrification filler is 1:2-4.

[0021] The molar ratio of the phase transfer catalyst to the chitosan-modified iron-based MOF material is 1:30-50.

[0022] Preferably, in step (2), the dehydration condensation reaction is performed at a temperature of 90-100℃ for 2-3h.

[0023] The application also provides an application of the iron-based MOF modified denitrification filler described in the above scheme or the iron-based MOF modified denitrification filler obtained by the preparation method described in the above scheme in wastewater treatment.

[0024] The application provides an iron-based MOF modified denitrification filler.

[0025] In addition, the iron-based MOF material has a similar structure to the zeolite, is rich in raw materials and low in price, has a higher porosity and specific surface area than the zeolite, and has a more excellent effect than the traditional filler with the added zeolite in terms of microbial film growth; meanwhile, the iron-based MOF material has an adsorption effect on some toxic and harmful substances in water, and the Fenton-like effect of Fe ions can be used for the degradation of organic matter, thereby expanding the applicability of the sulfur autotrophic denitrification filler in wastewater treatment.

[0026] The application further provides a preparation method of the iron-based MOF modified denitrification filler.

[0027] The application further provides an application of the iron-based MOF modified denitrification filler or the iron-based MOF modified denitrification filler prepared by the preparation method in wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0029] Figure 1 The denitrification efficiency diagram of the iron-based MOF modified denitrification filler prepared in Embodiment 1 of the present application;

[0030] Figure 2 The denitrification efficiency diagram of the control denitrification filler not modified by chitosan in Application Example 1;

[0031] Figure 3 The methyl orange adsorption efficiency diagram of the iron-based MOF modified denitrification filler prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0032] The present application provides an iron-based MOF modified denitrification filler, comprising a base unit and a modified unit covering the base unit;

[0033] The modified unit is a chitosan modified iron-based MOF material;

[0034] The base unit is a sulfur autotrophic denitrification filler; the sulfur autotrophic denitrification filler contains sulfur;

[0035] The modified unit and the base unit are connected by an ester bond obtained by the reaction of carboxyl in the modified unit and hydroxyl in the base unit.

[0036] In the present application, the mass ratio of the modified unit to the base unit is preferably 1:2-4, more preferably 1:2.5-3.5, and further preferably 1:2.8-3.2; the molar ratio of chitosan to iron-based MOF material in the modified unit is preferably 2.8-6:1, more preferably 2.8-4:1, and further preferably 2.8:1.

[0037] In the present application, the BET specific surface area of the iron-based MOF modified denitrification filler is preferably 300-330m 2 / g, more preferably 310-320m 2 / g, and further preferably 313-317m 2 / g; the pore volume is preferably 0.15-0.20m 3 / g, more preferably 0.16-0.19m 3 / g, and further preferably 0.17-0.18m 3 / g.

[0038] In the present application, the sulfur autotrophic denitrification filler preferably comprises one or more of sulfur, polyvinyl alcohol and siderite.

[0039] In the present application, the organic ligand in the chitosan-modified iron-based MOF material preferably comprises one or more of carboxyl and amino.

[0040] In the present application, the iron-based MOF modified denitrification filler preferably carries a fixed solid sulfur source. The iron-based MOF modified denitrification filler provided by the present application can carry a fixed solid sulfur source, so that low-cost sulfur powder can be used for sulfur autotrophic denitrification, avoiding the problem of loss of sulfur source with effluent caused by crushing of solid sulfur powder, and enabling slow provision of sulfur source for sulfur autotrophic bacteria, and also avoiding the problem of reduction of mass transfer efficiency caused by covering of microorganisms by the solid sulfur source; at the same time, iron element has a promoting effect on cell growth, is an important component of cytochrome in biological oxidation enzyme system, and Fe 2+ can play the role of electron transfer and coenzyme activator, so as to not only exert the advantages of MOF material such as large specific surface area, high porosity, uniform pores and high active sites, but also help to improve microbial activity through the Fe element contained in the material, thereby improving the total nitrogen removal rate.

[0041] The present application also provides a preparation method of the iron-based MOF modified denitrification filler described in the above scheme, comprising the following steps:

[0042] (1) mixing iron salt, organic ligand compound and chitosan (denoted as first mixing) to perform dehydration condensation reaction, to obtain chitosan-modified iron-based MOF material;

[0043] (2) mixing the chitosan-modified iron-based MOF material with sulfur autotrophic denitrification filler and phase transfer catalyst (denoted as second mixing) to perform dehydration condensation reaction, to obtain iron-based MOF modified denitrification filler.

[0044] In the present application, the iron salt is preferably FeCl3·6H2O, FeCl3, Fe2(SO4)3·5H2O, Fe2(SO4)3, Fe(NO3)3 or Fe(NO3)3·9H2O.

[0045] In the present application, the organic ligand compound is preferably terephthalic acid.

[0046] In the present application, the molar ratio of iron element in the iron salt to the organic ligand compound is preferably 4.9-6.5:1, more preferably 5.3-6.1:1, and further preferably 5.5-5.7:1.

[0047] In the present application, the molar ratio of the chitosan and the organic ligand compound is preferably 1-2:1, more preferably 1.2-1.8:1, and further preferably 1.3-1.5:1.

[0048] In the present application, the first mixing is preferably: pre-mixing (denoted as first pre-mixing) the iron salt, the organic ligand compound and the amide solvent (denoted as first amide solvent) to obtain a solution A, and pre-mixing (denoted as second pre-mixing) the chitosan and the amide solvent (denoted as second amide solvent) to obtain a solution B, and then pouring the solution B into the solution A and mixing (denoted as first A mixing).

[0049] In the present application, the volume-mass ratio of the first amide solvent to the iron salt is preferably (35-40) mL:1 g, and more preferably 40 mL:1 g; the first amide solvent is preferably DMF; the volume-mass ratio of the second amide solvent to the chitosan is preferably (15-20) mL:1 g, and more preferably 20 mL:1 g; and the second amide solvent is preferably DMF.

[0050] In the present application, the first pre-mixing is preferably first ultrasonic and stirring; the frequency of the first ultrasonic is preferably 42 kHz, and the time is preferably 5-10 min, and more preferably 10 min; the second pre-mixing is preferably second ultrasonic and stirring; the frequency of the second ultrasonic is preferably 42 kHz, and the time is preferably 10-20 min, and more preferably 20 min; the pouring of the solution B into the solution A is preferably carried out under ultrasonic condition; and the first A mixing is preferably third ultrasonic; and the time of the third ultrasonic is preferably 30-60 min, and more preferably 30 min.

[0051] In the present application, the temperature of the dehydration condensation reaction is preferably 120-130℃, more preferably 122-128℃, and further preferably 124-126℃, and the holding time is preferably 15-20 h, more preferably 17-19 h, and further preferably 18 h; and the dehydration condensation reaction is preferably carried out in a reaction kettle.

[0052] In the present application, the reaction product obtained after the dehydration condensation reaction is preferably subjected to post-treatment; and the post-treatment is preferably: cooling the reaction product, and then sequentially washing and centrifuging, filtering the supernatant, and drying.

[0053] In the present application, the washing preferably comprises DMF washing, alcohol washing and water washing, which are sequentially carried out; the alcohol used in the alcohol washing is preferably one or both of ethanol and methanol; the water used in the water washing is preferably deionized water; and the number of times of the DMF washing, the alcohol washing and the water washing is independently preferably 3-5 times, and more preferably 4-5 times.

[0054] In the present application, the centrifugal speed is preferably 8000-12000 rpm, more preferably 8000 rpm; the centrifugal times are preferably 3-5 times, more preferably 3 times.

[0055] In the present application, the filtration is preferably suction filtration; the drying is preferably oven drying; the drying device is preferably an oven; the drying temperature is preferably 50-60 DEG C, more preferably 60 DEG C, and the holding time is preferably more than 8 h, more preferably 8-12 h.

[0056] After obtaining the chitosan-modified iron-based MOF material, the present application mixes (denoted as the third mixing) the chitosan-modified iron-based MOF material with the sulfur autotrophic denitrification filler and a phase transfer catalyst to perform a dehydration condensation reaction, thereby obtaining an iron-based MOF modified denitrification filler.

[0057] In the present application, the preparation method of the sulfur autotrophic denitrification filler is preferably: heating and mixing sulfur, polyvinyl alcohol, siderite powder, a sulfur modifier and a toughening agent, and then granulating.

[0058] In the present application, the sulfur modifier is preferably a mixture of dicyclopentadiene and cyclopentadiene or dicyclopentadiene; the mass ratio of dicyclopentadiene to cyclopentadiene is preferably 2:0-3, more preferably 2:0-2, and further preferably 2:0-1; and the toughening agent is preferably liquid polysulfide rubber.

[0059] In the present application, the mass ratio of sulfur to polyvinyl alcohol is preferably 60-70:5-10, more preferably 62-68:6-9, and further preferably 64-66:7-8.

[0060] In the present application, the mass ratio of sulfur to siderite powder is preferably 60-70:10-20, more preferably 62-68:12-18, and further preferably 64-66:14-16.

[0061] In the present application, the mass ratio of the sulfur modifier to sulfur is preferably 1:20-25, more preferably 1:21-24, and further preferably 1:22-23.

[0062] In the present application, the mass ratio of the toughening agent to sulfur is preferably 1-5:100, more preferably 2-4:100, and further preferably 3:100.

[0063] In the present application, the temperature of the heating and mixing is preferably 130-160 DEG C, more preferably 140-160 DEG C, and further preferably 150-160 DEG C.

[0064] In the present application, the heating mixing is preferably that the sulfur and polyvinyl alcohol premix (denoted as the third premix) are heated to a molten state, and the obtained molten liquid and siderite powder premix (denoted as the fourth premix); the obtained premix liquid, sulfur modifier and toughening agent are mixed (denoted as the Bth mixing).

[0065] In the present application, the fourth premix is preferably stirring; and the Bth mixing is preferably stirring.

[0066] In the present application, the particle size of the granulation is preferably 2-10 mm, more preferably 3-8 mm, and further preferably 4-6 mm; and the granulation device is preferably a granulator.

[0067] In the present application, the phase transfer catalyst is preferably a mixture of tetrabutylammonium bromide and tetrabutylammonium chloride or tetrabutylammonium bromide.

[0068] In the present application, the mass ratio of the chitosan-modified iron-based MOF material and the sulfur autotrophic denitrification filler is preferably 1:2-4, more preferably 1:2.5-3.5, and further preferably 1:2.7-3.0.

[0069] In the present application, the molar ratio of the phase transfer catalyst and the chitosan-modified iron-based MOF material is preferably 1:30-50, more preferably 1:35-45, and further preferably 1:38-41.

[0070] In the present application, the third mixing is preferably that the dried iron-based MOF material, the sulfur autotrophic denitrification filler, the phase transfer catalyst and the good solvent are mixed.

[0071] In the present application, the drying temperature is preferably 100-110°C, more preferably 105°C, the vacuum degree is preferably ≤100 Pa, more preferably ≤50 Pa, and the holding time is preferably 3-6 h, more preferably 5 h; and the good solvent is preferably N-methyl-2-pyrrolidone (NMP).

[0072] In the present application, the temperature of the dehydration condensation reaction is preferably 90-100°C, more preferably 92-98°C, and further preferably 94-96°C, and the holding time is preferably 2-3 h, more preferably 2.5 h; and the dehydration condensation reaction is preferably carried out under stirring.

[0073] In the present application, the dehydration condensation reaction is preferably followed by drying; the drying is preferably constant-temperature drying; and the temperature of the constant-temperature drying is preferably 100-110°C, more preferably 105°C.

[0074] The present application also provides an application of the iron-based MOF modified denitrification filler in wastewater treatment.

[0075] The iron-based MOF modified denitrification filler provided by the application can achieve excellent denitrification effect in deep denitrification of wastewater, especially for nitrogen-containing wastewater with certain chroma, and has high practical utilization value.

[0076] In order to further illustrate the application, the scheme of the application is described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the application.

[0077] Example 1

[0078] 3.4 g of FeCl3·6H2O and 1 g of terephthalic acid were weighed into 130 mL of DMF solvent, ultrasonically treated for 10 min, and uniformly stirred to obtain an A solution;

[0079] 1 g of chitosan was weighed into 20 mL of DMF solvent, ultrasonically treated for 10 min, and uniformly stirred to obtain a B solution;

[0080] The B solution was slowly poured into the A solution while ultrasonically treating, and ultrasonically treated for 30 min to fully mix; the obtained solution was transferred into a reaction kettle and continuously reacted at 120℃ for 20 h, and then cooled, centrifugally washed with DMF, ethanol and deionized water for 3 times respectively, and then suction filtered, and the obtained solid was dried in a 60℃ oven overnight to obtain a chitosan modified iron-based MOF material;

[0081] 70 g of sulfur and 10 g of polyvinyl alcohol were mixed and heated to 160℃ to be in a molten state, then 20 g of siderite powder was poured into the obtained molten liquid for stirring, 3.5 g of dicyclopentadiene and 3.5 g of liquid polysulfide rubber were continuously added and uniformly stirred, and then a granulator was used for granulation to obtain a sulfur autotrophic denitrification filler;

[0082] 5 g of the chitosan modified iron-based MOF material was dried at 105℃ under vacuum for 5 h, and then reacted with 15 g of the sulfur autotrophic denitrification filler in a medium N-methyl-2-pyrrolidone, a phase transfer catalyst tetrabutylammonium bromide was added, and stirring reaction was carried out at 90℃ for 3 h, and then the obtained solid was taken out and dried at 105℃ to obtain an iron-based MOF modified denitrification filler.

[0083] Example 2

[0084] 3.4 g of FeCl3·6H2O and 1 g of terephthalic acid were weighed into 120 mL of DMF solvent, ultrasonically treated for 10 min, and uniformly stirred to obtain an A solution;

[0085] 0.8 g of chitosan was weighed into 20 mL of DMF solvent, ultrasonically treated for 10 min, and uniformly stirred to obtain a B solution;

[0086] While ultrasonic, slowly pour the B solution into the A solution, and continue to ultrasonic for 30 min to fully mix; transfer the obtained solution to a reaction kettle and continuously react at 120℃ for 20 h, take out and cool, then centrifugal wash with DMF, ethanol and deionized water for 3 times respectively, then perform suction filtration, and dry the obtained solid in an oven at 60℃ overnight to obtain a chitosan modified iron-based MOF material;

[0087] Take 60 g of sulfur and 10 g of polyvinyl alcohol, heat to 160℃ to a molten state, then pour 20 g of siderite powder into the molten liquid and stir, continue to add 2.5 g of dicyclopentadiene and 3 g of liquid polysulfide rubber and stir uniformly, then use a granulator to granulate to obtain a sulfur autotrophic denitrification filler;

[0088] Take 5 g of chitosan modified iron-based MOF material dried at 105℃ under vacuum for 5 h, and react with 15 g of sulfur autotrophic denitrification filler in medium N-methyl-2-pyrrolidone, add phase transfer catalyst tetrabutylammonium bromide, stir and react at 90℃ for 3 h, then take out the obtained solid and dry at 105℃ to obtain an iron-based MOF modified denitrification filler.

[0089] Example 3

[0090] Take 3.4 g of FeCl3·6H2O and 1 g of terephthalic acid, add 120 mL of DMF solvent, ultrasonic for 10 min, and stir uniformly to obtain an A solution;

[0091] Take 0.7 g of chitosan, add 20 mL of DMF solvent, ultrasonic for 10 min, and stir uniformly to obtain a B solution;

[0092] While ultrasonic, slowly pour the B solution into the A solution, and continue to ultrasonic for 30 min to fully mix; transfer the obtained solution to a reaction kettle and continuously react at 120℃ for 20 h, take out and cool, then centrifugal wash with DMF, ethanol and deionized water for 3 times respectively, then perform suction filtration, and dry the obtained solid in an oven at 60℃ overnight to obtain a chitosan modified iron-based MOF material;

[0093] Take 60 g of sulfur and 5 g of polyvinyl alcohol, heat to 160℃ to a molten state, then pour 10 g of siderite powder into the molten liquid and stir, continue to add 2.5 g of dicyclopentadiene and 2.5 g of liquid polysulfide rubber and stir uniformly, then use a granulator to granulate to obtain a sulfur autotrophic denitrification filler;

[0094] 5 g of chitosan modified iron-based MOF material was dried under vacuum at 105℃ for 5 h, and then reacted with 15 g of sulfur autotrophic denitrification filler in medium N-methyl-2-pyrrolidone, and a phase transfer catalyst tetrabutylammonium bromide was added, and the reaction was stirred at 90℃ for 3 h, and then the obtained solid was taken out and dried at 105℃ to obtain the iron-based MOF modified denitrification filler.

[0095] Example 4

[0096] The preparation method of this example is the same as that of Example 1, the only difference being that the iron salt is FeCl3.

[0097] Example 5

[0098] The preparation method of this example is the same as that of Example 1, the only difference being that the iron salt is Fe2(SO4)3·5H2O.

[0099] Example 6

[0100] The preparation method of this example is the same as that of Example 1, the only difference being that the iron salt is Fe(NO3)3.

[0101] Application Example 1

[0102] The iron-based MOF modified denitrification filler prepared in Example 1 and the filler without introducing chitosan (without introducing chitosan but introducing iron-based MOF) were used for anaerobic ammonia oxidation and sulfur autotrophic denitrification culture, and were filled into a fixed bed biological column reactor, and were inoculated with sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria to carry out biofilm formation; after the biofilm formation was completed, a peristaltic pump was used to introduce simulated nitrogen-containing wastewater into the reactor, and the simulated nitrogen-containing wastewater was prepared from sodium nitrate, ammonium sulfate and tap water, and the nitrate nitrogen concentration in the simulated nitrogen-containing wastewater was 50 mg / L, and the ammonia nitrogen concentration was 40 mg / L.

[0103] The effective volume of the reactor was 6 L, and the whole reaction process was divided into three stages, which were respectively recorded as stages I, II and III, and each stage was operated for 16 days, and the hydraulic retention time was 8 h, 8 h and 4 h respectively, wherein the load of the reactor was increased by increasing the concentration of the simulated wastewater and reducing the hydraulic retention time in stages II and III respectively, and finally stable operation was achieved. The reactor corresponding to the iron-based MOF modified denitrification filler prepared in Example 1 of the application was R1, and the reactor corresponding to the filler without introducing chitosan was R2. The application carried out nitrogen concentration monitoring of the influent (inf) and effluent (eff) for 50 days, and the results are shown in Figure 1 and Figure 2 .

[0104] According to Figure 1 and Figure 2It can be seen that the total nitrogen removal rate of the reactor R1 is up to 96.99%, and finally the total nitrogen removal rate is stable at more than 95% under the condition that the HRT is 4h; while the total nitrogen removal rate of the reactor R2 is slightly higher than that of R1 under the condition that the final HRT is 4h, but the effect in the start-up stage of the early stage of the reaction is much worse than that of the reactor R1, and the packing in R1 has a higher specific surface area due to the introduction of chitosan during preparation, which creates a better environment for the metabolism of microorganisms. After testing, the growth rate of the specific surface area of the iron-based MOF modified denitrification packing with chitosan introduced is more than 300% compared with the packing without chitosan introduced. Considering comprehensively, the iron-based MOF modified denitrification packing with chitosan introduced has higher cost performance.

[0105] Application Example 2

[0106] The iron-based MOF modified denitrification packing prepared in Example 1 is subjected to dye adsorption experiment, and is compared with the packing without chitosan introduced (without chitosan introduced but with iron-based MOF introduced) (control group). The simulated dye wastewater is mainly prepared by methyl orange (MO) and tap water, the concentration of methyl orange in the simulated dye wastewater is 30mg / L, three groups of parallel experiments are established and the average value is calculated. 5mg of the prepared packing is weighed in a centrifuge tube, 10mL of methyl orange solution is added, and a clear solution is obtained by filtering after sampling every 5min with a syringe. The absorbance value is measured at 465nm by ultraviolet spectrophotometry, and the concentration of methyl orange in the current solution and the adsorption capacity of the packing for methyl orange are calculated. The adsorption capacity of the packing for methyl orange is as shown in Figure 3 .

[0107] According to Figure 3 It can be seen that the adsorption capacity of the iron-based MOF modified denitrification packing prepared in Example 1 for methyl orange is 97.63-108.34mg / g, and the average value is 103.78mg / L. Compared with the packing without chitosan introduced, the adsorption capacity is increased by 1.3-1.4 times.

[0108] From the above examples, it can be seen that the iron-based MOF modified denitrification packing provided by the present application can achieve excellent denitrification effect in deep denitrification of sewage, especially in nitrogen-containing wastewater with colority, and the total nitrogen removal rate is more than 95%.

[0109] Although the above examples have made a detailed description of the present application, it is only a part of the examples of the present application, not all the examples, and other examples can be obtained under the premise of no creativity according to the present examples, which all belong to the protection scope of the present application.

Claims

1. An iron-based MOF modified denitrification packing material, comprising a matrix unit and a modified unit coating the matrix unit; The modified unit is a chitosan-modified iron-based MOF material; The matrix unit is a sulfur autotrophic denitrification packing; the sulfur autotrophic denitrification packing contains sulfur; The modified unit and the matrix unit are connected by an ester bond obtained by the reaction of the carboxyl group in the modified unit and the hydroxyl group in the matrix unit; The mass ratio of the modified unit to the matrix unit is 1:2~4; The molar ratio of chitosan to iron-based MOF material in the modified unit is 2.8~6:1; The iron-based MOF-modified denitrification packing has a BET specific surface area of ​​300-330 m². 2 / g, pore volume 0.15~0.20cm³ 3 / g; The sulfur autotrophic denitrification filler includes sulfur, polyvinyl alcohol and siderite.

2. The iron-based MOF modified denitrification packing material according to claim 1, characterized in that, The organic ligands in the chitosan-modified iron-based MOF material include carboxyl and amino groups.

3. The preparation method of the iron-based MOF modified denitrification packing material according to claim 1 or 2, comprising the following steps: (1) Iron salt, organic ligand compound and chitosan were mixed and subjected to dehydration condensation reaction to obtain chitosan modified iron-based MOF material; (2) The chitosan-modified iron-based MOF material is mixed with sulfur autotrophic denitrification packing and phase transfer catalyst to carry out dehydration condensation reaction to obtain iron-based MOF modified denitrification packing.

4. The preparation method according to claim 3, characterized in that, In step (1), the molar ratio of iron to organic ligand compound in the iron salt is 4.9~6.5:1; The molar ratio of chitosan to organic ligand compound is 1~2:

1.

5. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the chitosan-modified iron-based MOF material to the sulfur autotrophic denitrification filler is 1:2~4; The molar ratio of the phase transfer catalyst to the chitosan-modified iron-based MOF material is 1:30~50.

6. The preparation method according to claim 3 or 5, characterized in that, In step (2), the temperature of the dehydration condensation reaction is 90~100℃ and the holding time is 2~3h.

7. The application of the iron-based MOF modified denitrification packing material according to claim 1 or 2, or the iron-based MOF modified denitrification packing material obtained by the preparation method according to any one of claims 3 to 6, in wastewater treatment.

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