Sulfur autotrophic denitrification filter material for water treatment as well as preparation method and application of sulfur autotrophic denitrification filter material

Abstract

The invention relates to the technical field of water treatment, in particular to a sulfur autotrophic denitrification filter material for water treatment as well as a preparation method and application thereof.The sulfur autotrophic denitrification filter material is prepared by compounding pyrite, siderite and sulfur as a sulfur source, selecting a biological raw material starch as a binder and taking an environment-friendly material halloysite nanotube as an adsorbent. Mixing with sodium silicate, silica fume and deionized water, and granulating to obtain the unfired sulfur autotrophic denitrification filter material. The preparation method comprises the following steps: coprecipitating nano FeS and ascorbic acid on a halloysite nanotube, and grafting carboxyl-containing composite branched chitosan to obtain a modified halloysite nanotube; wherein the carboxyl-containing composite branched chitosan is prepared by the following steps: preparing aldehyde chitosan from sodium periodate, reacting the aldehyde chitosan with chitosan to obtain self-branched chitosan, and grafting a multi-carboxyl conjugated microporous polymer; corn starch is used as a raw material, carboxyl-containing composite branched chitosan, itaconic acid and silica sol are used as grafting monomers, and the biomass binder is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and particularly relates to a sulfur autotrophic denitrification filter material for water treatment and a preparation method and application thereof. BACKGROUND

[0002] With the rapid advancement of industrialization and urbanization, the pollution problems of nitrogen and phosphorus in water bodies are increasingly serious, thereby leading to a series of environmental problems. Traditional biological denitrification processes are mainly heterotrophic denitrification, which mostly needs to add extra organic carbon sources, thereby increasing the operation cost and possibly causing secondary pollution risks. Compared with traditional heterotrophic denitrification, sulfur autotrophic denitrification has the advantages of no need of external organic carbon source, low sludge yield and low operation cost. Therefore, the development of an economic and environmental autotrophic denitrification filter material has become a research hotspot in the field of water treatment.

[0003] However, the practical application of the existing sulfur autotrophic denitrification filter material still faces the following challenges: most of the filter materials mainly use sulfur as the main material, and the components are mostly single, which leads to limited denitrification efficiency; some filter materials need to be sintered at high temperature, which has a high cost; most of the sulfur autotrophic denitrification filter materials are difficult to simultaneously meet the multifunctional requirements in complex working conditions such as denitrification, phosphorus removal, pH buffering and durability. SUMMARY

[0004] The present application aims to provide a sulfur autotrophic denitrification filter material for water treatment and a preparation method and application thereof, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present application provides the following technical scheme:

[0006] A preparation method of a sulfur autotrophic denitrification filter material for water treatment, comprising the following steps:

[0007] S1: crushing, mixing and sieving sulfur, pyrite powder and siderite powder to obtain a mixed sulfur-containing powder;

[0008] S2: mixing, stirring, granulating, aging and curing the mixed sulfur-containing powder, composite starch, modified halloysite nanotubes, sodium silicate, silica ash and deionized water to obtain a sulfur autotrophic denitrification filter material for water treatment.

[0009] Further, in the preparation of the mixed sulfur-containing powder, the mass ratio of sulfur, pyrite powder and siderite powder is 7:2:1, and the particle size of the mixed sulfur-containing powder is 100 mesh.

[0010] Further, the working conditions for curing are as follows: humidity is 88%, temperature is 20-25 DEG C, and time is 7d.

[0011] Further, the working conditions for aging are as follows: temperature is 18-25 DEG C, and time is 22-24h.

[0012] Further, the raw material composition of the filter material is 24-33 parts of mixed sulfur-containing powder, 15-25 parts of composite starch, 8-11 parts of modified halloysite nanotube, 1-4 parts of sodium silicate, 3-7 parts of silica fume and 10-23 parts of deionized water.

[0013] Further, the preparation of the modified halloysite nanotube comprises the following steps:

[0014] 1) Under a nitrogen atmosphere, mix the halloysite nanotube and sodium sulfide solution, stir for 1-2 h, add the mixture of ascorbic acid and deionized water, add ferrous sulfate, ultrasonic treatment for 8-10 min, filter, wash, freeze-dry to obtain pretreated halloysite nanotube;

[0015] 2) Mix 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxy succinimide, deionized water and carboxyl-containing composite branched chitosan, add the pretreated halloysite nanotube, heat to 75-80℃ for 4-5 h to obtain the modified halloysite nanotube.

[0016] Further, the preparation of the composite starch comprises the following steps:

[0017] Mix the starch, carboxyl-containing composite branched chitosan and hydrochloric acid solution, water bath stir at 55-60℃ for 1-2 h, adjust the pH to 3.9-4.1, heat to 68-70℃, add ammonium persulfate, add the mixture of sodium dodecyl sulfate, deionized water and itaconic acid, heat for 1-2 h, add ammonium persulfate, heat for 1-2 h, add silica sol and polyvinyl alcohol solution, heat to 80-85℃ for 20-40 min, discharge to obtain the composite starch.

[0018] Further, the mass ratio of the starch, carboxyl-containing composite branched chitosan, itaconic acid and silica sol is 35:5:1.1:1.5.

[0019] Further, the preparation of the carboxyl-containing composite branched chitosan comprises the following steps:

[0020] (1) Under a nitrogen atmosphere, mix 1,3,5-triethynylbenzene, 2,5-dibromoterephthalic acid, bis(triphenylphosphine)palladium dichloride, cuprous iodide and triphenylphosphine, sequentially add toluene and triethylamine, stir, heat to 88-90℃ oil bath for 23-24 h, cool to 18-25℃, sequentially wash with chloroform, methanol and deionized water, filter and dry to obtain the polycarboxyl conjugated microporous polymer;

[0021] (2) under the protection of nitrogen, the chitosan, sodium periodate solution is mixed, avoid light, at 28-28 DEG C oscillation 1-2h, add ethylene glycol solution, stand 20-30min, filter, add acetone, precipitate, suction filtration, wash, dry, obtain aldehyde group chitosan;Chitosan, acetic acid solution is mixed, add aldehyde group chitosan, mix and stir 1-2h, add sodium borohydride, continue to stir 3-4h, dialysis 46-48h, obtain branched chitosan;

[0022] (3) 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide, potassium phosphate buffer solution is mixed, stirring in ice water bath 8-10min, add polycarboxyl conjugated microporous polymer, ultrasonic dispersion 5-8min, stirring in ice water bath 20-30min, add potassium phosphate buffer solution, branched chitosan, oscillation 11-12h, suction filtration, wash, dry, obtain the composite branched chitosan containing carboxyl.

[0023] A kind of water treatment with sulfur autotrophic denitrification filter material is applied to the denitrification and phosphorus removal purification process in water treatment.

[0024] Compared with the prior art, the beneficial effects of the present application are:

[0025] The present application provides a kind of water treatment with sulfur autotrophic denitrification filter material and its preparation method and application, by optimizing the component ratio of filter material and process design, prepare green environmental protection, recyclable, with high efficient denitrification and phosphorus removal and heavy metal adsorption force high strength baking-free sulfur autotrophic denitrification filter material, when used in water treatment, can effectively improve water pollution, improve purification efficiency.

[0026] In order to meet the requirements of green production, the pyrite, siderite and sulfur in the present application are used as sulfur source, the biological raw material starch is used as binder, and the halloysite nanotube is used as adsorbent, which is mixed with sodium silicate, silica ash and deionized water to prepare the baking-free sulfur autotrophic denitrification filter material, by optimizing the component ratio, the structural stability of the sulfur autotrophic denitrification filter material is improved, which can realize high efficient denitrification and phosphorus removal without additional carbon source, and has strong adsorption capacity for pollutants in water.

[0027] In order to improve the uniformity of halloysite nanotube dispersion in sulfur autotrophic denitrification filter material, the nanometer FeS and ascorbic acid are co-precipitated on halloysite nanotube to prepare pretreated halloysite nanotube with multiple hydroxyl groups, and then the composite branched chitosan containing carboxyl groups is grafted, which greatly improves the adsorption and purification of halloysite nanotube; the introduction of nanometer FeS further plays a synergistic effect with the mixed sulfur-containing powder, thereby buffering the pH of the system, reducing the inhibition effect of sulfate accumulation on microorganisms, and improving the denitrification efficiency and stability.

[0028] The complex branched chitosan containing carboxyl groups is prepared by using sodium periodate to prepare aldehyde group chitosan, and then reacting with chitosan to obtain self-branched chitosan, which is only based on chitosan segments without introducing other artificial synthetic blocks, so that the performance is improved while the excellent biological safety is maintained, in order to improve the stability of branched chitosan, the conjugated microporous polymer with multiple carboxyl groups is grafted on the surface of the branched chitosan, the conjugated microporous polymer has a unique conjugated structure, a high specific surface area, a skeleton structure and good chemical stability, so that the complex branched chitosan has good metal ion storage capacity, and at the same time as a biological membrane carrier, it is beneficial for microorganisms to adhere to the surface of the sulfur autotrophic denitrification filter material, and when the sulfur autotrophic denitrification is carried out, the contact area between the water body and the microorganisms is increased, so that the denitrification and phosphorus removal efficiency of the sulfur autotrophic denitrification filter material is greatly improved.

[0029] In the present application, starch is selected as a binder and a plant carbon source, in order to improve the bonding strength and water resistance of starch, corn starch is used as a raw material, and the complex branched chitosan containing carboxyl groups, itaconic acid and silica sol are used as grafting monomers to obtain a biomass binder, which has a complex effect on mixed sulfur-containing powder, modified halloysite nanotube, sodium silicate and silica ash, improves the bonding strength between filter material raw materials, reduces the amount of sediment, and uses the conjugated microporous polymer with multiple carboxyl groups in the complex branched chitosan as a skeleton to greatly improve the mechanical strength and carbon release stability of the filter material, as a microbial carrier, increases the contact area between the water body to be treated and the microorganisms, and improves the adsorption and denitrification and phosphorus removal efficiency of the filter material. DETAILED DESCRIPTION

[0030] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0031] It should be noted that if the present application involves directional indications such as up, down, left, right, front, back in the embodiments, the directional indications are only used to explain the relative position relationship, movement condition and the like between the components in a certain specific posture, and if the specific posture changes, the directional indications also change accordingly. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that the technical solutions can be realized by those skilled in the art, and when the combination of the technical solutions contradicts each other or cannot be realized, it should be considered that the combination of the technical solutions does not exist and is not within the protection scope of the present application.

[0032] The technical solutions of the present application will be further described in detail below in combination with specific embodiments. It should be understood that the following embodiments are only used to explain the present application, and are not used to limit the present application.

[0033] Embodiment 1: A preparation method of a sulfur autotrophic denitrification filter material for water treatment, comprising the following steps:

[0034] S1: crushing, mixing, and sieving sulfur, pyrite powder, and siderite powder to obtain a mixed sulfur-containing powder;

[0035] In the preparation of the mixed sulfur-containing powder, the mass ratio of sulfur, pyrite powder, and siderite powder is 7:2:1, and the particle size of the mixed sulfur-containing powder is 100 mesh;

[0036] S2: mixing and stirring the mixed sulfur-containing powder, composite starch, modified halloysite nanotubes, sodium silicate, silica fume, and deionized water, granulating, aging, curing, and obtaining a sulfur autotrophic denitrification filter material for water treatment;

[0037] The working conditions for curing are: humidity of 88%, temperature of 20℃, and time of 7d;

[0038] The working conditions for aging are: temperature of 18℃, and time of 22h;

[0039] The raw material composition of the filter material is: 24 parts of mixed sulfur-containing powder, 15 parts of composite starch, 8 parts of modified halloysite nanotubes, 1 part of sodium silicate, 3 parts of silica fume, and 10 parts of deionized water, by mass fraction;

[0040] The preparation of the modified halloysite nanotubes comprises the following steps:

[0041] 1) Under a nitrogen atmosphere, mix 4g of halloysite nanotubes and 100mL of 2mol / L sodium sulfide solution, stir for 1h, add a mixture of 0.6g of ascorbic acid and 500mL of deionized water, add 200mL of 1mol / L ferrous sulfate solution, ultrasonic treatment for 8min, filter, and freeze-dry to obtain pretreated halloysite nanotubes;

[0042] 2) Mix 2g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, 1g of N-hydroxysuccinimide, 120mL of deionized water, and 4.2g of composite branched chitosan containing carboxyl groups, add 9.3g of pretreated halloysite nanotubes, heat to 70℃ for 5h to obtain modified halloysite nanotubes;

[0043] The preparation of the composite starch comprises the following steps:

[0044] Mix 35 g of starch, 5 g of complex branched chitosan containing carboxyl, 55 mL of 1 mol / L hydrochloric acid solution, stir in a 55℃ water bath for 2 h, adjust the pH to 3.9, heat to 68℃, add 0.3 g of ammonium persulfate, add a mixture of 0.6 g of sodium dodecyl sulfate, 15 mL of deionized water, 1.1 g of itaconic acid, and heat for 1 h, add 0.2 g of ammonium persulfate and heat for 1 h, add 1.5 g of silica sol, 20 mL of 10% polyvinyl alcohol solution, heat to 80℃ for 40 min, discharge, and obtain a complex starch;

[0045] The preparation of the complex branched chitosan containing carboxyl includes the following steps:

[0046] (1) Under a nitrogen atmosphere, mix 3 mmol of 1,3,5-triethynylbenzene, 4.5 mmol of 2,5-dibromoterephthalic acid, 158 mg of bis(triphenylphosphine)palladium dichloride, 42.8 mg of cuprous iodide, and 590 mg of triphenylphosphine, and then sequentially add 78 mL of toluene and 98 mL of triethylamine, stir, heat to 88℃ in an oil bath for 24 h, cool to 18℃, and then sequentially wash with chloroform, methanol, and deionized water, filter, and dry to obtain a polycarboxyl conjugated microporous polymer;

[0047] (2) Under nitrogen protection, mix 3 g of chitosan with 150 mL of 0.3 mol / L sodium periodate solution, avoid light, and oscillate at 28℃ for 2 h, add 20 mL of 0.1 mol / L ethylene glycol solution, stand for 20 min, filter, add 100 mL of acetone, precipitate, suction filter, wash, and dry to obtain aldehyde chitosan; mix 0.6 g of chitosan with 50 mL of 1% acetic acid solution, add 0.3 g of aldehyde chitosan, mix and stir for 1 h, add 0.5 g of sodium borohydride, continue to stir for 3 h, and dialyze for 46 h to obtain branched chitosan;

[0048] (3) Mix 0.32 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 0.24 g of N-hydroxysuccinimide, and 20 mL of pH 7 potassium phosphate buffer in an ice water bath, stir for 8 min, add 0.1 g of polycarboxyl conjugated microporous polymer, ultrasonic dispersion for 5 min, stir in an ice water bath for 20 min, add 20 mL of pH 7 potassium phosphate buffer and 0.2 g of branched chitosan, seal, oscillate at 25℃ for 11 h, suction filter, wash, and dry to obtain complex branched chitosan containing carboxyl.

[0049] Example 2: A preparation method of a sulfur autotrophic denitrification filter material for water treatment, including the following steps:

[0050] S1: Crush sulfur, pyrite powder, and siderite powder, mix, sieve, and obtain a mixed sulfur-containing powder;

[0051] In the preparation of the mixed sulfur-containing powder, the mass ratio of sulfur, pyrite powder and siderite powder is 7:2:1, and the particle size of the mixed sulfur-containing powder is 100 mesh.

[0052] S2: Mix sulfur-containing powder, composite starch, modified halloysite nanotubes, sodium silicate, silica fume, and deionized water, granulate, age, and cure to obtain a sulfur-autotrophic denitrification filter media for water treatment.

[0053] The aging conditions are: temperature 20℃, time 23h;

[0054] The working conditions for maintenance are: humidity 88%, temperature 23℃, and time 7 days;

[0055] The raw material composition of the filter media by mass is as follows: 27 parts of mixed sulfur-containing powder, 20 parts of composite starch, 9 parts of modified halloysite nanotubes, 3 parts of sodium silicate, 5 parts of silica fume, and 18 parts of deionized water.

[0056] The preparation of the modified halloysite nanotubes includes the following steps:

[0057] 1) Under a nitrogen atmosphere, 4g halloysite nanotubes and 100mL of 2mol / L sodium sulfide solution were mixed and stirred for 1.5h. A mixture of 0.6g ascorbic acid and 500mL of deionized water was added, along with 200mL of 1mol / L ferrous sulfate solution. The mixture was sonicated for 9min, filtered, and freeze-dried to obtain pretreated halloysite nanotubes.

[0058] 2) Mix 2g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1g of N-hydroxysuccinimide, 120mL of deionized water, and 4.2g of carboxyl-containing composite branched chitosan. Add 9.3g of pretreated halloysite nanotubes and heat to 75℃ for 4.5h to obtain modified halloysite nanotubes.

[0059] The preparation of the composite starch includes the following steps:

[0060] Mix 35g starch, 5g carboxyl-containing composite branched chitosan, and 55mL 1mol / L hydrochloric acid solution. Stir in a water bath at 58℃ for 1.5h, adjust the pH to 4, raise the temperature to 69℃, add 0.3g ammonium persulfate, add a mixture of 0.6g sodium dodecyl sulfate, 15mL deionized water, and 1.1g itaconic acid, keep warm for 1.5h, add 0.2g ammonium persulfate, keep warm for 1.5h, add 1.5g silica sol and 20mL 10% polyvinyl alcohol solution, raise the temperature to 83℃ and keep warm for 30min, then discharge to obtain composite starch.

[0061] The preparation of the carboxyl-containing composite branched chitosan includes the following steps:

[0062] (1) Under a nitrogen atmosphere, 3 mmol of 1,3,5-triethynylbenzene, 4.5 mmol of 2,5-dibromoterephthalic acid, 158 mg of bis(triphenylphosphine)palladium dichloride, 42.8 mg of cuprous iodide and 590 mg of triphenylphosphine were mixed, and 78 mL of toluene and 98 mL of triethylamine were added in sequence. The mixture was stirred, heated to 89 °C and kept in an oil bath for 23.5 h, cooled to 20 °C, and washed, filtered and dried with chloroform, methanol and deionized water in sequence to obtain a polycarboxyl conjugated microporous polymer.

[0063] (2) Under nitrogen protection, 3g of chitosan and 150mL of 0.3mol / L sodium periodate solution were mixed, protected from light, and shaken at 30℃ for 1.5h. 20mL of 0.1mol / L ethylene glycol solution was added, and the mixture was allowed to stand for 25min. After filtration, 100mL of acetone was added, and the mixture was precipitated, filtered, washed, and dried to obtain aldehyde-modified chitosan. 0.6g of chitosan and 50mL of 1% acetic acid solution were mixed, and 0.3g of aldehyde-modified chitosan was added. The mixture was stirred for 1.5h, and 0.5g of sodium borohydride acetate was added. The mixture was stirred for another 3.5h and dialyzed for 47h to obtain branched chitosan.

[0064] (3) Mix 0.32g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 0.24g of N-hydroxysuccinimide, and 20mL of potassium phosphate buffer at pH 7. Stir in an ice-water bath for 9min. Add 0.1g of a polycarboxyl conjugated microporous polymer and sonicate for 7min. Stir in an ice-water bath for 25min. Add 20mL of potassium phosphate buffer at pH 7 and 0.2g of branched chitosan. Seal and shake at 25℃ for 11.5h. Filter, wash, and dry to obtain a composite branched chitosan containing carboxyl groups.

[0065] Example 3: A method for preparing a sulfur-autotrophic denitrification filter media for water treatment, comprising the following steps:

[0066] S1: Crush sulfur, pyrite powder, and siderite powder, mix them, and sieve them to obtain a mixed sulfur-containing powder.

[0067] In the preparation of the mixed sulfur-containing powder, the mass ratio of sulfur, pyrite powder and siderite powder is 7:2:1, and the particle size of the mixed sulfur-containing powder is 100 mesh.

[0068] S2: Mix sulfur-containing powder, composite starch, modified halloysite nanotubes, sodium silicate, silica fume, and deionized water, granulate, age, and cure to obtain a sulfur-autotrophic denitrification filter media for water treatment.

[0069] The aging conditions are: temperature 20℃, time 24h;

[0070] The working conditions for maintenance are: humidity 88%, temperature 25℃, and time 7 days;

[0071] The raw material composition of the filter media by mass is as follows: 33 parts of mixed sulfur-containing powder, 25 parts of composite starch, 11 parts of modified halloysite nanotubes, 4 parts of sodium silicate, 7 parts of silica fume, and 23 parts of deionized water.

[0072] The preparation of the modified halloysite nanotubes includes the following steps:

[0073] 1) Under a nitrogen atmosphere, 4g halloysite nanotubes and 100mL of 2mol / L sodium sulfide solution were mixed and stirred for 1-2h. A mixture of 0.6g ascorbic acid and 500mL of deionized water was added, along with 200mL of 1mol / L ferrous sulfate solution. The mixture was sonicated for 8-10min, filtered, and freeze-dried to obtain pretreated halloysite nanotubes.

[0074] 2) Mix 2g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1g of N-hydroxysuccinimide, 120mL of deionized water, and 4.2g of carboxyl-containing composite branched chitosan. Add 9.3g of pretreated halloysite nanotubes and heat to 70-80℃ for 4-5h to obtain modified halloysite nanotubes.

[0075] The preparation of the composite starch includes the following steps:

[0076] Mix 35g starch, 5g carboxyl-containing composite branched chitosan, and 55mL 1mol / L hydrochloric acid solution. Stir in a water bath at 55-60℃ for 1-2 hours, adjust the pH to 3.9-4.1, raise the temperature to 68-70℃, add 0.3g ammonium persulfate, add a mixture of 0.6g sodium dodecyl sulfate, 15mL deionized water, and 1.1g itaconic acid, keep warm for 1-2 hours, add 0.2g ammonium persulfate, keep warm for 1-2 hours, add 1.5g silica sol and 20mL 10% polyvinyl alcohol solution, raise the temperature to 80-85℃ and keep warm for 20-40 minutes, then discharge to obtain composite starch.

[0077] The preparation of the carboxyl-containing composite branched chitosan includes the following steps:

[0078] (1) Under a nitrogen atmosphere, 3 mmol of 1,3,5-triethynylbenzene, 4.5 mmol of 2,5-dibromoterephthalic acid, 158 mg of bis(triphenylphosphine)palladium dichloride, 42.8 mg of cuprous iodide and 590 mg of triphenylphosphine were mixed, and 78 mL of toluene and 98 mL of triethylamine were added in sequence. The mixture was stirred and heated to 88-90 °C and kept in an oil bath for 23-24 h. The mixture was then cooled to 18-25 °C and washed, filtered and dried with chloroform, methanol and deionized water in sequence to obtain a polycarboxyl conjugated microporous polymer.

[0079] (2) Under nitrogen protection, mix 3g of chitosan and 150mL of 0.3mol / L sodium periodate solution, protect from light, shake at 28-32℃ for 1-2h, add 20mL of 0.1mol / L ethylene glycol solution, let stand for 20-30min, filter, add 100mL of acetone, precipitate, filter, wash, and dry to obtain aldehyde-modified chitosan; mix 0.6g of chitosan and 50mL of 1% acetic acid solution, add 0.3g of aldehyde-modified chitosan, mix and stir for 1-2h, add 0.5g of sodium borohydride acetate, continue stirring for 3-4h, dialyze for 46-48h to obtain branched chitosan;

[0080] (3) Mix 0.32g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 0.24g of N-hydroxysuccinimide, and 20mL of potassium phosphate buffer at pH 7. Stir in an ice-water bath for 8-10min. Add 0.1g of polycarboxyl conjugated microporous polymer and sonicate for 5-8min. Stir in an ice-water bath for 20-30min. Add 20mL of potassium phosphate buffer at pH 7 and 0.2g of branched chitosan. Seal and shake at 25℃ for 11-12h. Filter, wash, and dry to obtain a composite branched chitosan containing carboxyl groups.

[0081] Comparative Example 1: Using Example 1 as the control group, the modified halloysite nanotubes were replaced with halloysite nanotubes, while other processes were normal.

[0082] Comparative Example 2: Using Example 1 as the control group, corn starch was used to replace the compound starch, while other processes were normal.

[0083] Comparative Example 3: Using Example 1 as the control group, no carboxyl-containing composite branched chitosan was prepared, and other processes were normal.

[0084] Source of raw materials used (for illustrative purposes only):

[0085] Pyrite powder (by mass fraction, main elemental composition: iron 50.31%, sulfur 39.45%, oxygen 7.21%, silicon 1.02%, zinc 0.59%, aluminum 0.54%, magnesium 0.51%, potassium 0.09%); Siderite powder (main chemical component is FeCO3): commercially available; Silica fume A00918: Wuhan Jiyesheng Chemical Co., Ltd.; Silica sol (30%): Jiangmen Huihe Yongsheng Nanotechnology Co., Ltd.; Sulfur S106611, Halloysite nanotubes H431905, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride D303121, N-hydroxysuccinimide H109330, corn starch S116030, persulfate Ammonium, itaconic acid I106140, polyvinyl alcohol P139542, 1,3,5-triethynylbenzene T162680, 2,5-dibromoterephthalic acid D138185, bis(triphenylphosphine)palladium dichloride D196276, triphenylphosphine T104475, sodium borohydride acetate S106573, potassium phosphate buffer at pH 7 P406801, ascorbic acid A103533, ferrous sulfate F116338, chitosan C105802: Aladdin reagent; sodium silicate, sodium sulfide, hydrochloric acid, toluene, triethylamine, chloroform, methanol, sodium periodate, ethylene glycol, acetone, acetic acid, sodium dodecyl sulfate, cuprous iodide, analytical grade, commercially available.

[0086] Performance testing: The filter media prepared in the examples and comparative examples were tested:

[0087] The filter media was filled into the reactor, with a bulk density of 0.8 g / cm³. 3 A peristaltic pump was used to stabilize the influent, with a hRT of 9.6 h, simulating wastewater influent. The influent concentration was configured as follows: nitrate nitrogen concentration of 130 mg / L and total phosphorus concentration of 5 mg / L. The system was run continuously for 5 days to test the removal rates of nitrate nitrogen and total phosphorus in the wastewater. The filter media was then subjected to a 6-cycle experiment with wastewater, with one cycle lasting 1 day. The adsorption capacity for chromium ions was then tested using 80 mL of a 80 mg / L filter media. 6+ The test solution was used as wastewater; the removal rate was (X0-X1) / X0×100%; (X0 is the concentration of nitrate nitrogen, total phosphorus, and metal ions in the initial wastewater, and X1 is the concentration of nitrate nitrogen, total phosphorus, and metal ions in the treated wastewater); the results are shown in Table 1.

[0088] Table 1

[0089]

[0090] This invention provides a sulfur autotrophic denitrification filter media for water treatment, its preparation method, and its application. By optimizing the composition ratio and process design of the filter media, a high-strength, non-burning sulfur autotrophic denitrification filter media that is green, environmentally friendly, recyclable, and has high efficiency in nitrogen and phosphorus removal and heavy metal adsorption is prepared. When used in water treatment, it can effectively improve water pollution and increase purification efficiency.

[0091] Comparing Example 1 with Comparative Examples 1 and 3, it can be seen that in order to improve the uniformity of halloysite nanotube dispersion in sulfur autotrophic denitrification filter media, pretreated halloysite nanotubes with multiple hydroxyl groups were prepared by co-precipitating nano-FeS and ascorbic acid on halloysite nanotubes, and then grafting carboxyl-containing composite branched chitosan, which significantly improved the adsorption and purification performance of halloysite nanotubes. The introduction of nano-FeS further achieved an iron-sulfur synergistic effect with the mixed sulfur-containing powder, thereby buffering the pH of the system, reducing the effect of sulfate accumulation on microbial inhibition, and improving denitrification efficiency and stability.

[0092] The carboxyl-containing composite branched chitosan is prepared by using sodium periodate to prepare aldehyde-modified chitosan, which is then reacted with chitosan to obtain self-branched chitosan. Based solely on chitosan segments without introducing other artificially synthesized blocks, it maintains excellent biocompatibility while improving performance. To enhance the stability of branched chitosan, its surface hydroxyl groups are grafted with conjugated microporous polymers containing multiple carboxyl groups. Utilizing the unique conjugated structure, high specific surface area, skeletal structure, and good chemical stability of the conjugated microporous polymers, the composite branched chitosan possesses excellent metal ion storage capacity. Simultaneously, as a biofilm carrier, it facilitates the attachment of microorganisms to the surface of the sulfur autotrophic denitrification filter media. During sulfur autotrophic denitrification, it synergistically increases the contact area between the water and microorganisms, thereby significantly improving the nitrogen and phosphorus removal efficiency of the sulfur autotrophic denitrification filter media.

[0093] Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that in this invention, starch is selected as a binder and plant carbon source. To improve the bonding strength and water resistance of starch, corn starch is used as raw material, and carboxyl-containing composite branched chitosan, itaconic acid, and silica sol are used as grafting monomers to obtain a biomass binder. This binder has a composite effect on the mixed sulfur-containing powder, modified halloysite nanotubes, sodium silicate, and silica fume, improving the bonding strength between filter media materials and reducing the amount of sediment. The multi-carboxyl conjugated microporous polymer in the carboxyl-containing composite branched chitosan is used as a framework to significantly improve the mechanical strength and carbon release stability of the filter media. As a microbial carrier, it increases the contact area between the water to be treated and the microorganisms, improving the adsorption and nitrogen and phosphorus removal efficiency of the filter media.

[0094] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention's specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a sulfur-autotrophic denitrification filter media for water treatment, characterized in that, Includes the following steps: S1: Crush sulfur, pyrite powder, and siderite powder, mix them, and sieve them to obtain a mixed sulfur-containing powder. S2: Mix sulfur-containing powder, composite starch, modified halloysite nanotubes, sodium silicate, silica fume, and deionized water, granulate, age, and cure to obtain a sulfur-autotrophic denitrification filter media for water treatment.

2. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 1, characterized in that, In the preparation of the mixed sulfur-containing powder, the mass ratio of sulfur, pyrite powder and siderite powder is 7:2:1, and the particle size of the mixed sulfur-containing powder is 100 mesh.

3. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 1, characterized in that, The working conditions for maintenance are: humidity 88%, temperature 20-25℃, and time 7 days.

4. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 1, characterized in that, The raw material composition of the filter media by mass is as follows: 24-33 parts of mixed sulfur-containing powder, 15-25 parts of composite starch, 8-11 parts of modified halloysite nanotubes, 1-4 parts of sodium silicate, 3-7 parts of silica fume, and 10-23 parts of deionized water.

5. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 1, characterized in that, The preparation of the modified halloysite nanotubes includes the following steps: 1) Under a nitrogen atmosphere, halloysite nanotubes and sodium sulfide solution were mixed and stirred for 1-2 hours. A mixture of ascorbic acid and deionized water was added, followed by ferrous sulfate. The mixture was ultrasonically treated for 8-10 minutes, filtered, washed, and freeze-dried to obtain pretreated halloysite nanotubes. 2) Mix 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, deionized water, and carboxyl-containing composite branched chitosan, add pretreated halloysite nanotubes, heat to 75-80℃ and keep warm for 4-5 hours to obtain modified halloysite nanotubes.

6. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 1, characterized in that, The preparation of the composite starch includes the following steps: Starch, carboxyl-containing composite branched chitosan, and hydrochloric acid solution are mixed and stirred in a water bath at 55-60℃ for 1-2 hours. The pH is adjusted to 3.9-4.1, and the temperature is raised to 68-70℃. Ammonium persulfate, sodium dodecyl sulfate, deionized water, and itaconic acid are added and kept at this temperature for 1-2 hours. Ammonium persulfate is added again and kept at this temperature for 1-2 hours. Silica sol and polyvinyl alcohol solution are added, and the temperature is raised to 80-85℃ and kept at this temperature for 20-40 minutes. The product is then discharged to obtain composite starch.

7. The method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 6, characterized in that, The mass ratio of starch, carboxyl-containing composite branched chitosan, itaconic acid, and silica sol is 35:5:1.1:1.

5.

8. A method for preparing a sulfur-autotrophic denitrification filter media for water treatment according to claim 5 or 6, characterized in that, The preparation of the carboxyl-containing composite branched chitosan includes the following steps: (1) Under a nitrogen atmosphere, 1,3,5-triethynylbenzene, 2,5-dibromoterephthalic acid, bis(triphenylphosphine)palladium dichloride, cuprous iodide and triphenylphosphine were mixed, and toluene and triethylamine were added in sequence. The mixture was stirred, heated to 88-90℃ and kept in an oil bath for 23-24 hours, and then cooled to 18-25℃. The mixture was washed in sequence with chloroform, methanol and deionized water, filtered and dried to obtain a polycarboxyl conjugated microporous polymer. (2) Under nitrogen protection, chitosan and sodium periodate solution are mixed, protected from light, and shaken at 28-32℃ for 1-2 hours. Ethylene glycol solution is added, and the mixture is allowed to stand for 20-30 minutes. After filtration, acetone is added, and the mixture is precipitated, filtered, washed, and dried to obtain aldehyde-modified chitosan. Chitosan and acetic acid solution are mixed, aldehyde-modified chitosan is added, and the mixture is stirred for 1-2 hours. Sodium borohydride acetate is added, and the mixture is stirred for another 3-4 hours. The mixture is then dialyzed for 46-48 hours to obtain branched chitosan. (3) Mix 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and potassium phosphate buffer, stir in an ice-water bath for 8-10 min, add the polycarboxyl conjugated microporous polymer, sonicate for 5-8 min, stir in an ice-water bath for 20-30 min, add potassium phosphate buffer and branched chitosan, shake for 11-12 h, filter, wash and dry to obtain carboxyl-containing composite branched chitosan.

9. A sulfur-autotrophic denitrification filter media for water treatment, characterized in that, Prepared by the preparation method according to any one of claims 1-7.

10. The application of the sulfur-autotrophic denitrification filter media for water treatment according to claim 9, characterized in that, It is used in the denitrification and phosphorus removal purification process in water treatment.

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