Sulfur-based water purifying agent based on wastewater denitrification treatment and preparation method thereof

Abstract

The invention discloses a sulfur-based water purifying agent based on wastewater denitrification treatment and a preparation method thereof, belongs to the technical field of water purifying agent preparation, and aims to solve the technical problem that the denitrification performance and the acid and alkali resistance of a sulfur-containing water purifying agent in the prior art need to be further improved. According to the invention, a multi-layer system of'limited release electron supply-selective enrichment-directional transfer 'is constructed; multi-sulfur limited release particles form a-S-S < x >-anchoring layer on a SiO2 / calcium carbonate core shell, so that electron supply is stable, and invalid consumption is reduced; the quaternization network body is provided with fixed cation sites, so that NO3 <-> keeps a relatively high effective concentration on an interface, a mass transfer path is shortened, and NO2 <-> retention is inhibited; the LDH endogenous FeS < x > / Cu < 2-x > S point and a low-resistance channel are subjected to in-situ vulcanization, rapid conversion of electrons and a substrate along a target path is guaranteed, and the three parts correspond to one another and are complementary in function, so that the total nitrogen of effluent is lower and the fluctuation is smaller.

Description

Technical Field

[0001] This invention relates to the field of water purification agent preparation technology, specifically to a sulfur-based water purification agent based on wastewater denitrification treatment and its preparation method. Background Technology

[0002] The autotrophic denitrification of urban and industrial wastewater has long adopted the "sulfur-alkalinity" route. In the early stages, elemental sulfur or sulfur-limestone packing was the main method. Subsequently, practices such as sulfur composite with porous inorganic carriers, particle size distribution and control, surface silanization / functionalization, controlled release of sulfur sources, and online ORP / DO operation management have emerged to improve the continuity of the denitrification process and the stability of the effluent. At the same time, the process started with the addition of alkalinity and carbonate buffers and gradually developed into the introduction of carbonate phases, inorganic shells such as silica or alumina, and layered bimetallic hydroxides into the packing. It is also combined with anion exchange / selective layers, composite buffer formulations, and segmented influent control to adapt to pH fluctuations and long-term operation requirements.

[0003] Currently, sulfur-alkalinity autotrophic denitrification processes are prevalent, but they suffer from mismatches between electron supply and mass transfer, leading to long start-up cycles, limited volumetric loading, and periodic accumulation of NO2⁻. Sulfur source release is difficult to control uniformly, and free sulfur migration and redeposition induce pore blockage and increased pressure drop. Furthermore, the lack of interfacial enrichment and selective transfer of NO3⁻ means that electrons are easily consumed by dissolved oxygen and other bypass pathways, resulting in fluctuating removal efficiency. Additionally, these processes often rely on added alkalinity and a single buffer phase, leading to insufficient interfacial stability under pH disturbances, which can cause over-sulfation or sulfide escape, accompanied by decreased particle strength, increased leachate, and long-term operational fluctuations, making it difficult to achieve both low byproducts and sustained stability.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a sulfur-based water purification agent and its preparation method based on wastewater denitrification treatment, in order to solve the technical problem that the denitrification performance and acid and alkali resistance of sulfur-containing water purification agents in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a sulfur-based water purification agent based on wastewater denitrification treatment, comprising the following raw material components by weight: 36-40 parts of polysulfide limited-release granules, 30-36 g parts of quaternized ammonium network, 8-10 parts of in-situ sulfurized LDH, 30-36 parts of deionized water and 1-2 parts of polyvinyl alcohol.

[0007] The preparation method of the polysulfide limited-release particles includes the following steps:

[0008] A1. Add epoxidized particles and 3wt% sodium bicarbonate aqueous solution to a reaction vessel and stir. After purging with nitrogen for protection and adjusting the pH of the reaction system to 9-10 with saturated ammonia, add sodium thiosulfate to the reaction vessel and control the temperature of the reaction vessel to 25-30℃. Keep the temperature and stir for 2 hours. The thiosulfate particles are then obtained after post-treatment.

[0009] A2. Add the sulfurized particles and deionized water to the reactor and stir. After purging with nitrogen for protection, add sodium sulfide and sulfur dispersion to the reactor in sequence. Raise the temperature of the reactor to 40-50℃ and keep it at this temperature for 2-3 hours. After post-treatment, polysulfide limited-release particles are obtained.

[0010] The reaction principle for preparing polysulfide limited-release particles is as follows:

[0011] Under alkaline conditions, thiosulfate ions undergo nucleophilic ring-opening on the epoxy groups on the surface of epoxidized particles, directionally generating β-hydroxythiosulfate esters and chemically anchoring the sulfur source to the carrier surface, subsequently forming sulfides (S... 2- Under the influence of ), thiosulfate undergoes thiolysis / reduction to transform into surface thiol groups / sulfonates. Ultimately, these active sulfur sites react with dispersed sulfur to undergo anionic polysulfide formation, completing the -SS reaction. x - In-situ growth and cross-linking of covalent chains, the confinement effect of the silicon-oxygen shell, and the covalent fixation of polysulfide chains work together to achieve "slow-release electron donation" and suppress free sulfur precipitation and SO4. 2- The H2S byproduct was used to finally prepare polysulfide-limited-release particles.

[0012] Further, in step A1, the ratio of the epoxidized particles, 3wt% sodium bicarbonate aqueous solution, and sodium thiosulfate is 1g:20mL:0.2-0.3g. The post-treatment includes: after stirring, filtering the reaction solution to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60℃ and vacuum drying it to room temperature to obtain thiolated particles.

[0013] Further, in step A2, the ratio of the sulfurized particles, deionized water, sodium sulfide, and sulfur dispersion is 1g:15mL:0.1-0.2g:0.12-0.15g. The sulfur dispersion is obtained by mixing sulfur and deionized water at a ratio of 3.0-4.0g:10mL. The post-treatment includes: after stirring, waiting for the temperature of the reaction vessel to drop to room temperature, filtering the reaction solution to collect the filter cake, washing it with deionized water until the conductivity is <100μS / cm, and transferring the filter cake to a drying oven at 50℃ for vacuum drying to room temperature to obtain polysulfide-limited release particles.

[0014] Furthermore, the method for preparing epoxidized particles includes the following steps:

[0015] B1. Add heavy calcium carbonate, anhydrous ethanol and deionized water to the reaction vessel and stir. After purging with nitrogen for protection, adjust the pH of the reaction system to 9-10 with saturated ammonia water. Then, add tetraethoxysilane dropwise to the reaction vessel and stir at room temperature for 2-3 hours. After post-treatment, obtain silica-shell particles.

[0016] B2. Add the silica shell particles, anhydrous ethanol, and deionized water to the reactor, purge with nitrogen for protection, adjust the pH of the reaction system to 4.5-5.5 with acetic acid, add 3-epoxypropoxypropyltriethoxysilane to the reactor, raise the temperature of the reactor to 30-35℃, and then process to obtain epoxidized particles.

[0017] The reaction principle for preparing epoxidized particles is as follows:

[0018] First, 3-epoxypropoxypropyltriethoxysilane is hydrolyzed into trifunctional silanol under slightly acidic conditions, releasing ethanol. The generated silanol undergoes heterogeneous condensation with Si-OH on the silicon shell surface to form stable Si-O-Si covalent bonds. At the same time, some molecules undergo intermolecular self-condensation to form a local siloxane network structure, which improves the density and hydrolysis resistance of the layer. Due to the lack of a strong nucleophile and the slightly acidic pH of the system, the side-chain epoxy remains basically unopened, serving as active sites for subsequent nucleophilic ring-opening and the introduction of functional groups, ultimately yielding epoxide particles.

[0019] Further, in step B1, the ratio of heavy calcium carbonate, anhydrous ethanol, deionized water and tetraethoxysilane is 1-2g:15mL:5mL:0.3-0.6g. The post-treatment includes: after stirring, filtering the reaction solution to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60°C to vacuum dry to room temperature to obtain silica shell particles.

[0020] Furthermore, in step B2, the ratio of silica shell particles, anhydrous ethanol, deionized water, and 3-epoxypropoxypropyltriethoxysilane is 1g:12-15mL:3mL:0.2-0.3g. The post-treatment includes: after stirring, waiting for the reaction vessel temperature to drop to room temperature, filtering the reaction solution to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60℃ for vacuum drying to room temperature to obtain epoxidized particles.

[0021] Furthermore, the preparation method of the quaternized network includes the following steps:

[0022] C1. Sulfur, 1,3-diisopropenylbenzene and allyl glycidyl ether were added to a closed reactor and stirred. After nitrogen protection, the reactor was heated to 170-185℃ and sheared for 4 hours. The polysulfide network was then obtained after post-treatment.

[0023] C2. Add the polysulfide network, methanol and deionized water to the reactor and stir. After purging with nitrogen, add 40wt% trimethylamine solution to the reactor. Then heat the reactor to 40-60℃ and stir for 3-5 hours. The quaternized network is then obtained after post-treatment.

[0024] The reaction principle for preparing quaternized network bodies is as follows:

[0025] First, sulfur undergoes ring-opening at high temperatures to generate polysulfide radicals, which then undergo radical addition and cross-linking with 1,3-diisopropenylbenzene / allyl glycidyl ether to form CSS. x -C covalent polysulfide network retains the active sites of the side-chain epoxy. Subsequently, trimethylamine undergoes nucleophilic attack on the carbonormalized ends of the epoxy, generating a β-hydroxy quaternary ammonium salt structure (-CH(OH)-CH2-N). + (CH3)3, the anion is OH-. - (Solvent conjugation) to achieve covalent anchoring and uniform distribution of cation sites. These fixed quaternary ammonium sites can enrich nitrate and improve the hydrophilic / ion transport efficiency at the interface, ultimately preparing a quaternized network.

[0026] Further, in step C1, the ratio of sulfur, 1,3-diisopropenylbenzene and allyl glycidyl ether is 7-8g:2g:1g, and the post-processing includes: after shearing, cooling to room temperature and discharging, mechanically crushing to 0.5-0.8mm particles to obtain polysulfide network body;

[0027] Furthermore, in step C2, the ratio of polysulfide network, methanol, deionized water, and 40wt% trimethylamine aqueous solution is 1g:8-10mL:8mL:0.6-0.8g. The post-treatment includes: after stirring, waiting for the temperature of the reaction vessel to drop to room temperature, filtering the reaction solution to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60℃ for vacuum drying to room temperature to obtain the quaternized network.

[0028] Furthermore, the method for preparing in-situ sulfided LDH includes the following steps:

[0029] D1. Add ferric chloride hexahydrate, copper chloride dihydrate, aluminum chloride hexahydrate and deionized water to a reaction vessel and stir. Adjust the pH of the reaction system to 9-10 at room temperature using a mixed alkali. After stirring for 10-15 min, age for 1 h and then post-process to obtain layered bimetallic hydroxide.

[0030] D2. Add layered bimetallic hydroxide, thiourea and deionized water to the reactor, purge with nitrogen for protection, heat the reactor to 90-95℃, and maintain the temperature for 4-6 hours. Post-processing yields in-situ sulfided LDH.

[0031] The reaction principle for preparing in-situ sulfided LDH is as follows:

[0032] First, under weakly alkaline conditions, Fe 3+ / Cu 2+ / Al 3+ Simultaneous hydrolysis and orderly stacking in the form of layered hydroxides, with positively charged layers and interlayer anions (CO3-) 2- / Cl - (etc.) Electron neutralization, followed by the decomposition of thiourea under mild hydrothermal conditions to release H2S / HS. - Selective in-situ sulfidation of Fe and Cu is preferentially carried out at the layer edges / defect sites to generate nanoscale FeS. x / Cu2- x At point S, accompanied by partial reduction of Fe(III)→Fe(II) and anion exchange, a conductive / selective channel containing active sites of metal sulfides and migratable polysulfide anions is constructed, and in-situ sulfided LDH is finally prepared.

[0033] Further, in step D1, the ratio of ferric chloride hexahydrate, copper chloride dihydrate, aluminum chloride hexahydrate, and deionized water is 5.1-5.4 g: 1.8 g: 2.4 g: 200 mL. The mixed alkali is obtained by mixing sodium hydroxide and sodium carbonate in a ratio of 1 g: 1 g. The post-treatment includes: after stirring, filtering the reaction solution to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60°C and vacuum drying it to room temperature to obtain layered bimetallic hydroxide.

[0034] Further, in step D2, the ratio of the layered bimetallic hydroxide, deionized water, and thiourea is 10g:180-200mL:2-5g. The post-treatment includes: after stirring, waiting for the temperature of the reaction vessel to drop to room temperature, filtering the reaction liquid to collect the filter cake, washing the filter cake 3-5 times with anhydrous ethanol and deionized water, and then transferring the filter cake to a drying oven at 60°C to vacuum dry to room temperature to obtain in-situ sulfided LDH.

[0035] The present invention also discloses a method for preparing a sulfur-based water purification agent based on wastewater denitrification treatment, comprising the following steps: adding polysulfide limited-release particles, quaternized ammonium network, and in-situ sulfurized LDH into a mixing granulator, gradually adding deionized water and polyvinyl alcohol aqueous solution to adjust plasticity, granulating at room temperature into 2-3 mm spherical particles, then transferring the spherical particles to a drying oven at 50°C for vacuum drying to constant weight, and sieving and packaging to obtain the sulfur-based water purification agent.

[0036] The present invention has the following beneficial effects:

[0037] 1. The sulfur-based water purification agent of the present invention constructs a highly efficient denitrification microenvironment through a three-stage synergistic process of "electron donation-enrichment-catalysis," wherein polysulfide-limited-release particles form -SS on the surface of SiO2 / calcium carbonate core-shell. x - A chemical anchoring layer continuously and controllably releases electrons, inhibiting the migration and ineffective consumption of free sulfur and stabilizing the biofilm interface; the quaternized network relies on a covalent polysulfide framework to introduce fixed quaternary ammonium sites, selectively enriching NO3. - Increase local ionic strength and effective concentration, shorten diffusion path, and reduce NO2. - Intermediate retention; in-situ sulfidation of LDH endogenous FeS x / Cu2- x S-site active sites construct low-resistance electron channels and selective reaction sites, promoting NO3- - →NO2 - →The targeted conversion of N2 ultimately provides, and the three work together to reduce electron waste and side reactions, increase volumetric loading and specific rate, and stably achieve low total nitrogen in the effluent and long-term stable operation.

[0038] 2. The stability of the sulfur-based water purifier prepared by this invention under low-temperature conditions is achieved through temperature compensation of the three elements of "electronic potential-concentration difference-channel". Specifically, the polysulfide limited-release particles are chemically anchored -SS x - To provide a slow-release source, maintain a constant electronic chemical potential, and mitigate the rate decay caused by stability reduction; the quaternization network constructs a fixed cation field, continuously enriching NO3. - It also increases the interfacial ionic strength and local concentration gradient, thereby kinetically lowering the apparent activation energy and mitigating the limitations imposed by diffusion dominance at low temperatures; in-situ sulfidation of LDH produces endogenous FeS. x / Cu2- x The S-site forms an "electron relay" and a selective reaction surface, ensuring NO3- - →NO2 - →The N2 pathway is smooth, avoiding feedback inhibition caused by intermediate accumulation. At the same time, the interfacial hydration layer of the core-shell structure and the carbonate buffer maintain suitable ORP and micro-region pH, reducing the impact of low temperature on the deactivation of catalytic sites.

[0039] 3. The acid and alkali resistance of the sulfur-based water purifier of the present invention comes from the synergistic stabilizing effect of each component. Among them, the CaCO3 core of the silica-shell particles in the polysulfide limited-release particles provides a reversible buffer, and the SiO2 shell forms a dense shield, reducing the instantaneous impact of acids and alkalis, and with -SS x - Covalent anchoring ensures continuous electron supply, preventing free sulfur loss due to pH fluctuations; the fixed quaternary ammonium sites in the quaternization network can enrich NO3 under both acidic and alkaline conditions. - Reduces competing ion interference and stabilizes interfacial ionic strength; in-situ sulfidation of LDH with FeS x / Cu2-x S-site active sites and interlayer anion exchange work together to maintain electron channels and selectivity, inhibiting excessive sulfation and sulfide escape. Ultimately, through material synergy, the system achieves a continuous denitrification pathway and NO2 reduction within the pH range of 5.5-9.0. - The intermediates accumulate at a low rate, and the total nitrogen in the effluent remains stable. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In this application, the calcium carbonate used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with the product number C742079; the sulfur used was purchased from Nanjing Chemical Reagent Co., Ltd., with the product number C0990610335.

[0042] Example 1

[0043] This embodiment provides a method for preparing polysulfide limited-release particles, including the following steps:

[0044] Step ①: Preparation of silica-shell particles

[0045] Weigh out 10.0 g of heavy calcium carbonate, 150.0 mL of anhydrous ethanol and 50.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Adjust the pH of the reaction system to 9 with saturated ammonia. Add 3.0 g of tetraethoxysilane dropwise to the reaction vessel and stir at room temperature for 2 hours. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain silica shell particles.

[0046] Step 2: Preparation of epoxidized particles

[0047] Weigh out 10.0g of silica-shell particles, 120.0mL of anhydrous ethanol and 30.0mL of deionized water and add them to the reaction vessel. Purge with nitrogen for protection. Adjust the pH of the reaction system to 4.5 with acetic acid. Add 2.0g of 3-epoxypropoxypropyltriethoxysilane to the reaction vessel. Raise the temperature of the reaction vessel to 30℃. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain epoxidized particles.

[0048] Step ③: Preparation of sulfide particles

[0049] Weigh 10.0g of epoxidized particles and 200.0mL of 3wt% sodium bicarbonate aqueous solution and add them to the reaction vessel. Stir and purge with nitrogen for protection. Adjust the pH of the reaction system to 9 with saturated ammonia water. Add 2.0g of sodium thiosulfate to the reaction vessel and control the temperature of the reaction vessel at 25℃. Keep the vessel at this temperature and stir for 2 hours. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain thiolated particles.

[0050] Step 4: Preparation of polysulfide limited-release particles

[0051] Weigh out 3.0 g of sulfur and mix it with 10.0 mL of deionized water to obtain a sulfur dispersion.

[0052] Weigh 10.0g of sulfurized granules and 150.0mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 1.0g of sodium sulfide and 1.2g of sulfur dispersion to the reaction vessel in sequence. Raise the temperature of the reaction vessel to 40℃ and keep it at this temperature for 2 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake with deionized water until the conductivity is <100μS / cm. Transfer the filter cake to a drying oven at 50℃ and vacuum dry it to room temperature to obtain polysulfide limited-release granules.

[0053] Example 2

[0054] This embodiment provides a method for preparing polysulfide limited-release particles, including the following steps:

[0055] Step ①: Preparation of silica-shell particles

[0056] Weigh out 20.0 g of heavy calcium carbonate, 150.0 mL of anhydrous ethanol and 50.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Adjust the pH of the reaction system to 10 with saturated ammonia. Add 6.0 g of tetraethoxysilane dropwise to the reaction vessel and stir at room temperature for 3 hours. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60°C and vacuum dry it to room temperature to obtain silica shell particles.

[0057] Step 2: Preparation of epoxidized particles

[0058] Weigh out 10.0g of silica-shell particles, 150.0mL of anhydrous ethanol and 30.0mL of deionized water and add them to the reaction vessel. Purge with nitrogen for protection. Adjust the pH of the reaction system to 5.5 with acetic acid. Add 3.0g of 3-epoxypropoxypropyltriethoxysilane to the reaction vessel and raise the temperature of the reaction vessel to 35℃. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain epoxidized particles.

[0059] Step ③: Preparation of sulfide particles

[0060] Weigh 10.0g of epoxidized particles and 200.0mL of 3wt% sodium bicarbonate aqueous solution and add them to the reaction vessel. Stir and purge with nitrogen for protection. Adjust the pH of the reaction system to 10 with saturated ammonia. Add 3.0g of sodium thiosulfate to the reaction vessel and control the temperature of the reaction vessel at 30℃. Keep the vessel at this temperature and stir for 2 hours. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain thiolated particles.

[0061] Step 4: Preparation of polysulfide limited-release particles

[0062] Weigh out 4.0 g of sulfur and mix it with 10.0 mL of deionized water to obtain a sulfur dispersion.

[0063] Weigh 10.0g of sulfide granules and 150.0mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 2.0g of sodium sulfide and 1.5g of sulfur dispersion to the reaction vessel in sequence. Raise the temperature of the reaction vessel to 50℃ and keep it at this temperature for 3 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake with deionized water until the conductivity is <100μS / cm. Transfer the filter cake to a drying oven at 50℃ and vacuum dry it to room temperature to obtain polysulfide limited-release granules.

[0064] Example 3

[0065] This embodiment provides a method for preparing polysulfide limited-release particles, including the following steps:

[0066] Step ①: Preparation of silica-shell particles

[0067] Weigh out 15.0 g of heavy calcium carbonate, 150.0 mL of anhydrous ethanol and 50.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Adjust the pH of the reaction system to 10 with saturated ammonia. Add 4.5 g of tetraethoxysilane dropwise to the reaction vessel and stir at room temperature for 3 h. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake 4 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain silica shell particles.

[0068] Step 2: Preparation of epoxidized particles

[0069] Weigh out 10.0g of silica-shell particles, 135.0mL of anhydrous ethanol and 30.0mL of deionized water and add them to the reaction vessel. Purge with nitrogen for protection. Adjust the pH of the reaction system to 5.0 with acetic acid. Add 2.5g of 3-epoxypropoxypropyltriethoxysilane to the reaction vessel. Raise the temperature of the reaction vessel to 35℃. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain epoxidized particles.

[0070] Step ③: Preparation of sulfide particles

[0071] Weigh 10.0g of epoxidized particles and 200.0mL of 3wt% sodium bicarbonate aqueous solution and add them to the reaction vessel. Stir and purge with nitrogen for protection. Adjust the pH of the reaction system to 10 with saturated ammonia. Add 2.5g of sodium thiosulfate to the reaction vessel and control the temperature of the reaction vessel at 25℃. Keep the vessel at this temperature and stir for 2 hours. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain thiolated particles.

[0072] Step 4: Preparation of polysulfide limited-release particles

[0073] Weigh out 3.6g of sulfur and mix it with 10.0mL of deionized water to obtain a sulfur dispersion.

[0074] Weigh 10.0g of sulfide granules and 150.0mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 1.5g of sodium sulfide and 1.2g of sulfur dispersion to the reaction vessel in sequence. Raise the temperature of the reaction vessel to 45℃ and keep it at this temperature for 3 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake with deionized water until the conductivity is <100μS / cm. Transfer the filter cake to a drying oven at 50℃ and vacuum dry it to room temperature to obtain polysulfide limited-release granules.

[0075] Example 4

[0076] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0077] Step I: Preparation of polysulfide network

[0078] Weigh out 7.0g of sulfur, 2.0g of 1,3-diisopropenylbenzene and 1.0g of allyl glycidyl ether and add them to a sealed reactor and stir. After purging with nitrogen, heat the reactor to 170℃ and shear for 4 hours. After shearing, cool to room temperature and discharge the material. Mechanically crush the material into 0.5mm particles to obtain polysulfide network.

[0079] Step II: Preparation of Quaternized Network

[0080] Weigh 10.0 g of polysulfide network, 80.0 mL of methanol and 80.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 6.0 g of 40 wt% trimethylamine solution to the reaction vessel. Heat the reaction vessel to 40 °C and keep it at that temperature for 3 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain the quaternized ammonium network.

[0081] Example 5

[0082] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0083] Step I: Preparation of polysulfide network

[0084] Weigh out 8.0g of sulfur, 2.0g of 1,3-diisopropenylbenzene and 1.0g of allyl glycidyl ether and add them to a sealed reactor and stir. After purging with nitrogen, heat the reactor to 185℃ and shear for 4 hours. After shearing, cool to room temperature and discharge the material. Mechanically crush the material into 0.8mm particles to obtain polysulfide network.

[0085] Step II: Preparation of Quaternized Network

[0086] Weigh 10.0 g of polysulfide network, 100.0 mL of methanol and 80.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 8.0 g of 40 wt% trimethylamine solution to the reaction vessel. Heat the reaction vessel to 60 °C and keep it at that temperature for 5 h. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain the quaternized ammonium network.

[0087] Example 6

[0088] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0089] Step I: Preparation of polysulfide network

[0090] Weigh out 7.5g of sulfur, 2.0g of 1,3-diisopropenylbenzene and 1.0g of allyl glycidyl ether and add them to a sealed reactor and stir. After purging with nitrogen, heat the reactor to 180℃ and shear for 4 hours. After shearing, cool to room temperature and discharge the material. Mechanically crush the material into 0.6mm particles to obtain polysulfide network.

[0091] Step II: Preparation of Quaternized Network

[0092] Weigh 10.0 g of polysulfide network, 90.0 mL of methanol and 80.0 mL of deionized water and add them to the reaction vessel. Stir and purge with nitrogen. Then add 7.0 g of 40 wt% trimethylamine solution to the reaction vessel. Heat the reaction vessel to 50 °C and keep it at that temperature for 4 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature. Filter the reaction solution and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain the quaternized ammonium network.

[0093] Example 7

[0094] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0095] Step (1): Preparation of layered bimetallic hydroxides

[0096] Weigh out 10.0g of sodium hydroxide and 10.0g of sodium carbonate, mix them to obtain a mixed alkali, and collect it for later use;

[0097] Weigh out 51.0 g of ferric chloride hexahydrate, 18.0 g of copper chloride dihydrate, 24.0 g of aluminum chloride hexahydrate, and 2000.0 mL of deionized water and add them to the reaction vessel. Stir the mixture and adjust the pH of the reaction system to 9 using a mixed alkali at room temperature. After stirring for 10 min, age the mixture for 1 h. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain layered bimetallic hydroxide.

[0098] Step 2: Preparation of in-situ sulfided LDH

[0099] Weigh out 10.0g of layered bimetallic hydroxide, 2.0g of thiourea and 180.0mL of deionized water and add them to the reaction vessel. After purging with nitrogen, heat the reaction vessel to 90℃ and keep it at that temperature for 4 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and deionized water, and then transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain in-situ sulfided LDH.

[0100] Example 8

[0101] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0102] Step (1): Preparation of layered bimetallic hydroxides

[0103] Weigh out 10.0g of sodium hydroxide and 10.0g of sodium carbonate, mix them to obtain a mixed alkali, and collect it for later use;

[0104] Weigh out 54.0 g of ferric chloride hexahydrate, 18.0 g of copper chloride dihydrate, 24.0 g of aluminum chloride hexahydrate, and 2000.0 mL of deionized water and add them to the reaction vessel. Stir the mixture and adjust the pH of the reaction system to 10 using a mixed alkali at room temperature. After stirring for 15 min, age the mixture for 1 h. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain layered bimetallic hydroxide.

[0105] Step 2: Preparation of in-situ sulfided LDH

[0106] Weigh out 10.0g of layered bimetallic hydroxide, 5.0g of thiourea and 200.0mL of deionized water and add them to the reaction vessel. After purging with nitrogen, heat the reaction vessel to 95℃ and keep it at that temperature for 6 hours. After stirring, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and deionized water, and then transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain in-situ sulfided LDH.

[0107] Example 9

[0108] This embodiment provides a method for preparing a quaternized network, including the following steps:

[0109] Step (1): Preparation of layered bimetallic hydroxides

[0110] Weigh out 10.0g of sodium hydroxide and 10.0g of sodium carbonate, mix them to obtain a mixed alkali, and collect it for later use;

[0111] Weigh out 52.0 g of ferric chloride hexahydrate, 18.0 g of copper chloride dihydrate, 24.0 g of aluminum chloride hexahydrate, and 2000.0 mL of deionized water and add them to the reaction vessel. Stir the mixture and adjust the pH of the reaction system to 10 at room temperature using a mixed alkali. After stirring for 12 min, age the mixture for 1 h. After stirring, filter the reaction solution and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and deionized water. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to room temperature to obtain layered bimetallic hydroxide.

[0112] Step 2: Preparation of in-situ sulfided LDH

[0113] Weigh out 10.0g of layered bimetallic hydroxide, 4.0g of thiourea and 200.0mL of deionized water and add them to the reaction vessel. After purging with nitrogen, heat the reaction vessel to 95℃ and keep it at that temperature for 5h. After stirring, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and deionized water, and then transfer the filter cake to a drying oven at 60℃ and vacuum dry it to room temperature to obtain in-situ sulfided LDH.

[0114] Example 10

[0115] This embodiment provides a method for preparing a sulfur-based water purification agent based on wastewater denitrification treatment, including the following steps:

[0116] By weight, 36 parts of the polysulfide limited-release granules prepared in Example 1, 30 parts of the quaternized network prepared in Example 4, and 8 parts of the in-situ sulfurized LDH prepared in Example 7 were weighed and put into a mixing granulator. 30 parts of deionized water and 1 part of polyvinyl alcohol were gradually added to adjust the plasticity. The mixture was then rolled into 2mm spherical particles at room temperature. The spherical particles were then transferred to a drying oven at 50°C and vacuum dried to constant weight. The mixture was then sieved and packaged to obtain the sulfur-based water purification agent.

[0117] Example 11

[0118] This embodiment provides a method for preparing a sulfur-based water purification agent based on wastewater denitrification treatment, including the following steps:

[0119] By weight, 40 parts of the polysulfide limited-release granules prepared in Example 2, 36 parts of the quaternized network prepared in Example 5, and 9 parts of the in-situ sulfurized LDH prepared in Example 8 were weighed and put into a mixing granulator. 32 parts of deionized water and 2 parts of polyvinyl alcohol were gradually added to adjust the plasticity. The mixture was rolled into 3mm spherical particles at room temperature. The spherical particles were then transferred to a drying oven at 50°C and vacuum dried to constant weight. The mixture was then sieved and packaged to obtain the sulfur-based water purification agent.

[0120] Example 12

[0121] This embodiment provides a method for preparing a sulfur-based water purification agent based on wastewater denitrification treatment, including the following steps:

[0122] By weight, 38 parts of the polysulfide limited-release granules prepared in Example 3, 32 parts of the quaternized network prepared in Example 6, and 9 parts of the in-situ sulfurized LDH prepared in Example 9 were weighed and put into a mixing granulator. 32 parts of deionized water and 2 parts of polyvinyl alcohol were gradually added to adjust the plasticity. The granules were rolled into 3mm spherical particles at room temperature. The spherical particles were then transferred to a drying oven at 50°C and vacuum dried to constant weight. The granules were then screened and packaged to obtain the sulfur-based water purification agent.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 12 is that sodium sulfide was not added in step ④ of the preparation process of the polysulfide limited-release particles used.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 12 is that step II was omitted in the preparation process of the quaternized network used.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 12 is that step (2) is omitted in the preparation process of the in-situ sulfurized LDH used.

[0129] Performance testing:

[0130] The total nitrogen discharged from the wastewater treatment plant after purification by the sulfur-based water purification agents prepared in Examples 10-12 and Comparative Examples 1-3 was determined in accordance with the standard GB 18918-2002 "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants".

[0131] The ambient water temperature was lowered to 12℃, and the total nitrogen discharged from the sewage treatment plant after purification by the sulfur-based water purification agents prepared in Examples 10-12 and Comparative Examples 1-3 was measured in accordance with the standard GB 18918-2002 "Pollutant Discharge Standard for Urban Wastewater Treatment Plants". The change rate of total nitrogen at low temperature was calculated.

[0132] The environmental pH was set to 5.5, and the total nitrogen discharged from the wastewater treatment plant after purification by the sulfur-based water purification agents prepared in Examples 10-12 and Comparative Examples 1-3 was measured in accordance with the standard GB 18918-2002 "Pollutant Discharge Standard for Urban Wastewater Treatment Plants". The change rate of acidic total nitrogen was calculated.

[0133] The environmental pH was set to 9.0, and the total nitrogen discharged from the wastewater treatment plant after purification by the sulfur-based water purification agents prepared in Examples 10-12 and Comparative Examples 1-3 was measured in accordance with the standard GB 18918-2002 "Pollutant Discharge Standard for Urban Wastewater Treatment Plants". The change rate of alkaline total nitrogen was calculated, and the specific data are shown in Table 1.

[0134] Table 1 - Performance Test Data for Each Sample

[0135] Project Group Example 10 Example 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Total nitrogen / mg·L -1 > 4.5 4.4 4.4 6.6 5.7 5.4 Low temperature total nitrogen change rate / % 118 116 115 1.36 1.37 1.39 Change rate of total acid nitrogen / % 145 144 142 1.62 1.60 1.55 Change rate of total alkaline nitrogen / % 111 110 108 1.20 1.16 1.17

[0136] Data Analysis:

[0137] A comparative analysis of the data in Table 1 reveals that the total nitrogen content of the wastewater treated with the sulfur-based water purification agent prepared according to this invention is 4.4 mg·L⁻¹. -1 The total nitrogen change rate was 115% at a low temperature of 12℃, 142% under acidic conditions of pH=5.5, and 108% under conditions of pH=9.0. All these data are superior to the comparative example, indicating that:

[0138] Comparative example 1 lost the power of S 2- Initiated polysulfide anions (S x 2- In-situ growth process, surface-SS x - The covalent anchoring layer cannot be formed, and the sulfur source exists in the form of free / physical adsorption, which leads to the electron supply being pulsed and easily consumed by dissolved oxygen and irrelevant acceptors; the interface polarity and hydrophilicity are mismatched, and the contact efficiency between the biofilm and the reaction phase decreases; the migration and redeposition of free sulfur exacerbate pore blockage and increase pressure drop; intermediate states in the reaction pathway are retained, the electron-substrate matching deteriorates, and the overall conversion tends to be discrete and unstable.

[0139] Comparative Example 2 lost the local positive electric field constructed by the fixed quaternary ammonium sites and the selective enrichment effect of nitrate, resulting in a decrease in interfacial ionic strength and effective substrate concentration, and a thickening of the diffusion boundary layer. The epoxy side chain was not converted into a nucleophilic ring-opening cationic structure, resulting in a weakening of intermolecular forces and a decrease in interfacial organization. This led to a mismatch between the time scale of electron supply and substrate arrival, an increase in apparent activation energy, and an easy accumulation of intermediates and bypass consumption in the reaction micro-region, resulting in a simultaneous decline in conversion rate and stability.

[0140] Comparative Example 3 lost FeS x / Cu2- xS-shaped active sites and low-resistance electron channels, layered bimetallic hydroxides only provide static interlayer exchange and lack selective guidance, increasing the interfacial charge transfer resistance; interlayer anion migration no longer cooperates with electron flow, resulting in disordered electron distribution and increased probability of bypass reactions, thereby weakening the continuity of the main reaction path, reducing electron utilization, reducing the ability to suppress by-products, and significantly worsening the system's tolerance to load fluctuations and operating cycles;

[0141] Ultimately, this invention demonstrates that it constructs a multilayer system of "limited-release electron donation-selective enrichment-directional transfer": polysulfide-limited-release particles form -SS on a SiO2 / calcium carbonate core-shell. x - Anchoring layer stabilizes electron supply and reduces ineffective consumption; quaternized network sets fixed cation sites, allowing NO3- to... - Maintaining a high effective concentration at the interface, shortening the mass transfer path, and suppressing NO2 - Retention; In-situ sulfidation of LDH endogenous FeS x / Cu2- x The S-point and low-resistance channel ensure rapid conversion of electrons and substrates along the target path. The three parts complement each other and are functionally complementary, resulting in lower total nitrogen in the effluent and smaller fluctuations, an overall effect that is difficult to achieve with a single material.

[0142] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A sulfur-based water purification agent for wastewater denitrification treatment, characterized in that, The raw material composition includes the following parts by weight: 36-40 parts of polysulfide limited-release particles, 30-36 g parts of quaternized network, 8-10 parts of in-situ vulcanized LDH, 30-36 parts of deionized water and 1-2 parts of polyvinyl alcohol; The preparation method of the polysulfide limited-release particles includes the following steps: A1. Add epoxidized particles and 3wt% sodium bicarbonate aqueous solution to a reaction vessel and stir. After purging with nitrogen for protection and adjusting the pH of the reaction system to 9-10 with saturated ammonia, add sodium thiosulfate to the reaction vessel and control the temperature of the reaction vessel to 25-30℃. Keep the temperature and stir for 2 hours. The thiosulfate particles are then obtained after post-treatment. A2. Add the sulfurized particles and deionized water to the reactor and stir. After purging with nitrogen for protection, add sodium sulfide and sulfur dispersion to the reactor in sequence. Raise the temperature of the reactor to 40-50℃ and keep it at this temperature for 2-3 hours. After post-treatment, polysulfide limited-release particles are obtained.

2. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 1, characterized in that, In step A1, the ratio of the epoxidized particles, 3wt% sodium bicarbonate aqueous solution, and sodium thiosulfate is 1g:20mL:0.2-0.3g; in step A2, the ratio of the thiolated particles, deionized water, sodium sulfide, and sulfur dispersion is 1g:15mL:0.1-0.2g:0.12-0.15g, wherein the sulfur dispersion is obtained by mixing sulfur and deionized water at a ratio of 3.0-4.0g:10mL.

3. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 1, characterized in that, The method for preparing the epoxidized particles includes the following steps: B1. Add heavy calcium carbonate, anhydrous ethanol and deionized water to the reaction vessel and stir. After purging with nitrogen for protection, adjust the pH of the reaction system to 9-10 with saturated ammonia water. Then, add tetraethoxysilane dropwise to the reaction vessel and stir at room temperature for 2-3 hours. After post-treatment, obtain silica-shell particles. B2. Add the silica shell particles, anhydrous ethanol, and deionized water to the reactor, purge with nitrogen for protection, adjust the pH of the reaction system to 4.5-5.5 with acetic acid, add 3-epoxypropoxypropyltriethoxysilane to the reactor, raise the temperature of the reactor to 30-35℃, and then process to obtain epoxidized particles.

4. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 3, characterized in that, In step B1, the ratio of heavy calcium carbonate, anhydrous ethanol, deionized water, and tetraethoxysilane is 1-2g:15mL:5mL:0.3-0.6g; in step B2, the ratio of silica shell particles, anhydrous ethanol, deionized water, and 3-epoxypropoxypropyltriethoxysilane is 1g:12-15mL:3mL:0.2-0.3g.

5. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 1, characterized in that, The method for preparing the quaternized network includes the following steps: C1. Sulfur, 1,3-diisopropenylbenzene and allyl glycidyl ether were added to a closed reactor and stirred. After nitrogen protection, the reactor was heated to 170-185℃ and sheared for 4 hours. The polysulfide network was then obtained after post-treatment. C2. Add the polysulfide network, methanol and deionized water to the reactor and stir. After purging with nitrogen, add 40wt% trimethylamine solution to the reactor. Then heat the reactor to 40-60℃ and stir for 3-5 hours. The quaternized network is then obtained after post-treatment.

6. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 5, characterized in that, In step C1, the ratio of sulfur, 1,3-diisopropenylbenzene and allyl glycidyl ether is 7-8g:2g:1g; in step C2, the ratio of polysulfide network, methanol, deionized water and 40wt% trimethylamine aqueous solution is 1g:8-10mL:8mL:0.6-0.8g.

7. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 1, characterized in that, The method for preparing in-situ sulfided LDH includes the following steps: D1. Add ferric chloride hexahydrate, copper chloride dihydrate, aluminum chloride hexahydrate and deionized water to a reaction vessel and stir. Adjust the pH of the reaction system to 9-10 at room temperature using a mixed alkali. After stirring for 10-15 min, age for 1 h and then post-process to obtain layered bimetallic hydroxide. D2. Add layered bimetallic hydroxide, thiourea and deionized water to the reactor, purge with nitrogen for protection, heat the reactor to 90-95℃, and maintain the temperature for 4-6 hours. Post-processing yields in-situ sulfided LDH.

8. The sulfur-based water purification agent based on wastewater denitrification treatment according to claim 7, characterized in that, In step D1, the ratio of ferric chloride hexahydrate, copper chloride dihydrate, aluminum chloride hexahydrate, and deionized water is 5.1-5.4g:1.8g:2.4g:200mL, wherein the mixed alkali is obtained by mixing sodium hydroxide and sodium carbonate in a ratio of 1g:1g; in step D2, the ratio of the layered bimetallic hydroxide, deionized water, and thiourea is 10g:180-200mL:2-5g.

9. The method for preparing a sulfur-based water purification agent based on wastewater denitrification treatment as described in any one of claims 1-8, characterized in that, The process includes the following steps: adding polysulfide-limited-release granules, quaternized ammonium network, and in-situ sulfurized LDH into a mixing granulator, gradually adding deionized water and polyvinyl alcohol aqueous solution to adjust plasticity, granulating at room temperature into 2-3 mm spherical particles, then transferring the spherical particles to a drying oven at 50°C for vacuum drying to constant weight, and finally sieving and packaging to obtain sulfur-based water purification agent.