Waste-acid-free sodium chlorite production process

Abstract

The invention discloses a waste-acid-free sodium chlorite production process in the technical field of green preparation of inorganic chemical materials, and the process adopts a novel multistage pore channel-bifunctional site composite modified material, and the material is prepared through a four-stage gradient process of mesoporous silicon substrate synthesis, metal oxide loading, amino functional group modification and confinement calcination. The catalyst has the functions of catalytic reaction, acid impurity adsorption and solid-liquid separation. Sodium chlorate, methanol and sulfuric acid are used as raw materials, the raw materials are prepared into a solution, the solution reacts with the modified material in a reaction kettle, and the temperature is controlled to be 60-62 DEG C for reaction; cooling to separate solid and liquid after reaction, washing and drying a filter cake, and recovering the material; separating the filtrate through a nanofiltration membrane to obtain a high-purity sodium chlorite solution, evaporating and crystallizing trapped fluid to recover sodium sulfate, concentrating sulfuric acid for recycling, and crystallizing and drying penetrating fluid to obtain sodium chlorite crystals. The process has the advantages of no waste acid discharge, short reaction time, high efficiency, product purity reaching the superior product standard, recyclable materials and environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the technical field of green preparation of inorganic chemical materials, and in particular to a production process of sodium chlorite without waste acid. Background Art

[0002] Sodium chlorite, an important chlorine oxide, is widely used in pulp bleaching, water treatment, and organic synthesis. Traditionally, sodium chlorite is produced through a disproportionation reaction with a reducing agent (such as methanol) under acidic conditions. However, this process consumes large amounts of sulfuric acid to maintain the acidic environment. After the reaction, unreacted sulfuric acid, generated acetic acid, and incompletely converted sodium chlorate remain in the system, requiring alkaline neutralization to remove acidic impurities. This ultimately produces a large amount of waste acid solution containing sodium sulfate and sodium chloride. Treatment of this waste acid solution is costly, and the neutralization process can easily lead to oxidative degradation of the sodium chlorite product, affecting its purity and becoming a key bottleneck in the industry's development.

[0003] To address the waste acid problem in traditional processes, existing technologies attempt to recover waste acid through methods such as membrane separation and extraction. However, membrane separation suffers from high equipment investment and low acid recovery rates, while extraction methods are prone to secondary pollution due to residual organic solvents. Both methods make it difficult to achieve the goal of industrial waste acid-free production. Furthermore, while electrolysis can produce sodium chlorate, it still requires a supporting acid treatment step, which is energy-intensive and does not address the fundamental issue of waste acid emissions. The limitations of these technologies indicate that developing a "waste acid-free" sodium chlorite production process is an urgent need for green upgrading of the industry.

[0004] Based on this background, the present invention proposes a waste-acid-free production process using a novel composite modified material. This material combines catalytic reaction, acid impurity adsorption, and solid-liquid separation capabilities, enabling simultaneous sodium chlorite synthesis and acid recycling within the reaction system, fundamentally eliminating waste acid generation. By optimizing raw material ratios, controlling reaction conditions, and leveraging material properties, the process significantly improves reaction efficiency and product purity while reducing material recycling costs, providing an innovative solution for the green production of sodium chlorite. Summary of the Invention

[0005] The object of the present invention is to provide a sodium chlorite production process without waste acid, which solves the technical problems of low reaction efficiency, poor product purity, large waste acid discharge and non-recyclable materials in the existing traditional process.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: A sodium chlorite production process without waste acid comprises the following steps: S1, grinding and sieving sodium chlorate and mixing it with deionized water to prepare a sodium chlorate solution; mixing methanol with deionized water to prepare a methanol solution; mixing sulfuric acid with deionized water to prepare dilute sulfuric acid; taking the new multi-stage pore-dual functional site composite modified material and adding it to a reaction kettle equipped with a stirrer, a thermometer and a reflux condenser, and sequentially adding the sodium chlorate solution, methanol solution and dilute sulfuric acid, starting stirring and heating; S2, the reaction system is slowly heated to 60-62 ° C, the reaction is kept at a constant temperature, and ClO3 is detected by online HPLC - The end point is determined by the concentration change. When ClO3 - The reaction was stopped when the conversion rate was >98%; S3, after the reaction is completed, the reactor is cooled to 30-32°C, the solid-liquid mixture is separated by a plate and frame filter press, the filter cake is washed with deionized water, and the washing liquid is combined with the filtrate; after the filter cake is dried at 80-82°C, the novel multi-stage pore-dual functional site composite modified material is recovered; S4, passing the filtrate through a nanofiltration membrane; recovering sodium sulfate from the retentate by evaporation and crystallization, and recovering the remaining concentrated sulfuric acid; heating the permeate to 50-52°C, slowly adding sodium chlorite seed crystals under stirring, cooling to 20-22°C for crystallization, filtering, and vacuum drying at 60-62°C.

[0007] In the present invention, the novel multi-level pore-dual functional site composite modified material is an amino-modified manganese dioxide-coated MCM-41 composite material; "amino-modified manganese dioxide-coated MCM-41 composite material" is a composite catalytic material with multi-level pores and dual functional sites. Its name fully and clearly defines the core composition and structure of the material: the MCM-41 molecular sieve with a regular mesoporous channel structure prepared in step A1 is used as the core carrier; in step A2, a layer of manganese dioxide (MnO2) nanofilm is uniformly coated on the inner and outer surfaces of the MCM-41 carrier using atomic layer deposition (ALD) technology, thereby constructing the first functional site (metal oxide active site) and further adjusted the pore properties of the material; then, through step A3, the above-mentioned MCM-41@MnO2 intermediate was surface-modified using the silane coupling agent 3-aminopropyltriethoxysilane, and the amino functional group was successfully grafted, thereby introducing a second functional site (organic amine functional site); the final composite material has an MCM-41 carrier that provides a high specific surface area and diffusion channels, the MnO2 coating layer provides catalytic activity, and the surface-grafted amino groups provide surface modification and synergistic catalytic functions. The three together constitute the complete technical connotation of the composite material, and the name fully reflects its preparation steps and final structure.

[0008] According to the preferred embodiment of the present application, in step S1, the crushed product is passed through an 80-100 mesh sieve; the concentration of the sodium chlorate solution is 200-210 g / L; the concentration of the methanol solution is 150-155 g / L; and the concentration of the dilute sulfuric acid is 50-54 g / L.

[0009] According to the preferred embodiment of the present application, the sodium chlorate is purchased from Jiangsu Tianyuan Metal Products Co., Ltd., with a model of industrial grade and a purity of ≥99%. According to the preferred embodiment of the present application, the methanol is purchased from Shaanxi Yanchang Petroleum (Group) Co., Ltd., with a model of industrial grade and a purity of ≥99.5%. According to the preferred embodiment of the present application, the deionized water is purchased from Shanghai Resin Factory Co., Ltd. (prepared by ion exchange resin), with a model of resistivity ≥18.2 MΩ·cm (25℃). According to the preferred embodiment of the present application, the online HPLC is purchased from Shanghai Wufeng Scientific Instrument Co., Ltd., with a model of LC-100 type high performance liquid chromatograph (with ultraviolet detector, C18 chromatographic column). According to the preferred embodiment of the present application, the plate and frame filter press is purchased from Hangzhou Xingyuan Filtration Technology Co., Ltd., with a model of XAZG100 / 1000-U type plate and frame filter press (filtration area 100 m2, filter cloth aperture ≤10 μm). According to the preferred embodiment of the present application, the nanofiltration membrane is purchased from Times Walton Technology Co., Ltd., with a model of VONTRON NF-90 type nanofiltration membrane element (molecular weight cut-off 1000 Da, operating pressure ≤1.5 MPa). According to the preferred embodiment of the present application, the sodium chlorite crystal seed is purchased from Jiangsu Feixiang Chemical Co., Ltd., with a model of industrial grade and a purity of ≥99% (particle size 0.1-0.3 mm).

[0010] In step S1 of the present invention, after the sodium chlorate is crushed and sieved, its particle size is controlled to 80-100 mesh. This particle size range ensures sufficient contact between the raw materials and water while avoiding excessive solution viscosity caused by overly fine particles. When the sodium chlorate is mixed with deionized water, mechanical stirring (implied in the "mixing" operation) forms a uniform sodium chlorate solution with a concentration controlled at 200-210 g / L. This concentration ensures an adequate supply of reaction raw materials while avoiding solution viscosity caused by excessive concentration, which affects subsequent mass transfer efficiency. The mixing process of methanol and deionized water is similar. Methanol, as a reducing agent, must be fully miscible with water to form a uniform methanol solution (concentration 150-155 g / L). The addition of methanol not only provides a hydrogen source for the disproportionation reaction of the sodium chlorate (participating in the formation of sodium chlorite) but also indirectly promotes the dissociation of sodium chlorate in the solution by reducing the polarity of the system. Sulfuric acid is mixed with deionized water to form dilute sulfuric acid (concentration 50-54 g / L), which provides an acidic environment for the reaction system. + This activates the disproportionation reaction of sodium chlorate while suppressing side reactions (such as oxidative decomposition). The addition of a novel multi-level pore-dual-functional site composite modified material is crucial to this step. The material's multi-level pore structure (microporous-mesoporous) provides a high surface area, enabling rapid dispersion in solution and sufficient contact with reactants. The dual-functional sites (such as MnO2 active sites and amino adsorption sites) pre-condition the subsequent catalytic reaction and acid adsorption. After the material is added, stirring further promotes uniform mixing with the sodium chlorate, methanol, and sulfuric acid solutions, forming a stable dispersion of the "raw material-solvent-catalyst" system, paving the way for the efficient subsequent isothermal reaction.

[0011] According to a preferred embodiment of the present invention, in step S2, the time of the isothermal reaction is 45-50 minutes.

[0012] In step S2 of the present invention, heating the reaction system to 60-62°C is a key parameter that has been optimized. At this temperature, the disproportionation reaction kinetics of sodium chlorate is significantly activated. The increase in temperature reduces the activation energy of the reaction and avoids the formation of byproducts (such as chloric acid) that may be caused by high temperature. The sodium chlorate in the system undergoes a disproportionation reaction with methanol (CH3OH) under acidic conditions. The core reaction pathway is: ClO3 - Accept H + The hydrogen atoms provided by methanol are partially reduced to ClO2 - (target product), partially oxidized to Cl - (However, due to the limitation of methanol reducibility, the side reaction is suppressed.) The modified material plays a dual role in this process: First, the MnO2 active site absorbs ClO3 -Fixed on the surface of the material, forming a local high-concentration reaction micro-area, accelerating the reaction; secondly, the amino functional group adsorbs the H generated by the reaction through electrostatic action + (H + + NH2 - → NH3 + ), avoid H + The acidity caused by accumulation in the solution is too strong (the pH is too low, which will promote the formation of ClO2 - Further oxidized to ClO3 - ). Online HPLC monitoring of ClO3 - The change of concentration is essentially to determine whether the reaction has reached equilibrium by detecting the rate of decrease of the reactant concentration. - When the conversion rate is greater than 98%, it indicates that the reaction is basically completed. Stopping heating at this time can avoid energy waste and excessive decomposition of the product.

[0013] According to a preferred embodiment of the present invention, in step S3, the number of washing with deionized water is 2-3 times; and the filter cake is dried at 80-82° C. for 12-14 hours.

[0014] In step S3 of the present invention, after the reaction is completed, the system temperature drops to 30-32°C. At this time, the viscosity of the solution increases slightly, but the multi-level pore structure of the modified material still maintains high permeability. The core function of the plate and frame filter press is to achieve solid-liquid separation through mechanical pressure: the filter cake is mainly composed of unreacted sodium chlorate, generated sodium chlorite (NaClO2) and adsorbed H + The filter cake is composed of a modified material containing by-products (such as acetic acid); the filtrate is a mixed solution containing NaClO2, unreacted methanol, trace amounts of sulfuric acid, and dissolved NaCl. The filter cake is washed 2-3 times with deionized water to remove residual soluble impurities (such as unreacted methanol and a small amount of sodium sulfate) on the surface. The washings are combined with the filtrate to prevent product loss. The filter cake is dried at 80-82°C for 12-14 hours. This not only restores the material's pore structure through water evaporation (water is removed from the pores during the drying process to prevent pore clogging), but also removes physical water adsorbed on the material's surface, re-exposing the MnO2 active sites and amino functional groups, preparing them for the next reaction cycle. After recycling, the material exhibits minimal loss of catalytic activity and acid adsorption capacity, enabling its reuse.

[0015] According to a preferred embodiment of the present invention, in step S4, the molecular weight cut-off of the nanofiltration membrane is 1000 Da; the concentration of the sodium chlorite seed crystals is 0.5-0.6 g / L; and the crystallization time is 2-4 h.

[0016] In step S4 of the present invention, passing the filtrate through a nanofiltration membrane (molecular weight cutoff 1000 Da) is a key purification step. The pore size of the nanofiltration membrane effectively retains larger molecular weight impurities (such as unreacted sodium chlorate, molecular weight 106.44; sodium sulfate, molecular weight 142.04), while allowing the passage of smaller molecules such as sodium chlorite (molecular weight 90.44), water, and methanol. This process not only removes most inorganic impurities (such as NaCl, which has a small molecular weight of 58.44 but can be selectively retained by adjusting the membrane potential), but also separates organic byproducts (such as acetic acid, molecular weight 60.05), significantly improving the purity of the sodium chlorite in the permeate. Evaporation and crystallization of the retentate to recover sodium sulfate utilizes the solubility difference between sodium sulfate and sodium chloride. At 80°C, the solubility of sodium sulfate is much lower than that of sodium chloride. Evaporation and concentration preferentially precipitate sodium sulfate, which is then filtered and dried to obtain high-purity sodium sulfate for recycling as a byproduct. The remaining concentrated sulfuric acid (concentration restored to 98%) is recycled for the next batch of reactions, achieving zero acid discharge. After the permeate is heated to 50-52°C, sodium chlorite seed crystals (0.5-0.6g / L) are added. This utilizes the surface energy of the seed crystals to lower the solution's nucleation barrier, promoting the rapid formation of sodium chlorite crystals. When the temperature is lowered to 20-22°C, the solution's supersaturation increases, and crystals gradually grow. After filtration, the solution is vacuum-dried at 60-62°C, avoiding high-temperature decomposition of the sodium chlorite (2NaClO2 → NaCl + NaClO3) while also reducing the water evaporation temperature in the vacuum environment, preventing deliquescence of the crystals. This ultimately yields sodium chlorite crystals.

[0017] According to a preferred embodiment of the present invention, the preparation steps of the novel multi-level pore-dual functional site composite modified material include: A1. Add hexadecyltrimethylammonium bromide and deionized water to a three-necked flask and stir magnetically at 40-42°C until completely dissolved. Slowly add aqueous ammonia to adjust the pH to 10-11. Then, add tetraethyl orthosilicate dropwise. Maintain the reaction temperature at 60-62°C and continue stirring. After the reaction is completed, transfer the mixture to a centrifuge tube, collect the precipitate by centrifugation, wash the precipitate with anhydrous ethanol, and finally dry the precipitate in an oven at 100-102°C. Then, transfer the precipitate to a muffle furnace and heat it to 550-560°C to calcine to obtain MCM-41 powder. A2: MCM-41 powder was placed in an ALD reaction chamber and calcined at 300-304°C under an Ar atmosphere. ALD deposition cycles were then performed, with each cycle consisting of: di(ethylcyclopentadienyl)manganese pulse → Ar purge → H2O pulse → Ar purge. The deposited powder was ultrasonically dispersed with anhydrous ethanol, centrifuged, and dried in vacuo at 60-62°C to obtain the MCM-41@MnO2 intermediate. A3, dissolving 3-aminopropyltriethoxysilane in anhydrous toluene, adding MCM-41@MnO2 intermediate powder, and ultrasonically dispersing to form a uniform suspension; transferring the reaction system to a round-bottom flask and refluxing at 110-112°C under nitrogen protection; after completion of the reaction, cooling the mixture to room temperature, collecting the precipitate by suction filtration, washing the precipitate with toluene and anhydrous ethanol, and finally drying the precipitate in a vacuum at 80-82°C to obtain MCM-41@MnO2-NH2 powder; A4, MCM-41@MnO2-NH2 powder was placed in a tube furnace and calcined under a N2 / H2 mixture. The temperature program was as follows: heating to 300-302°C and holding, heating to 400-404°C and holding; after calcination, it was naturally cooled to room temperature in a N2 atmosphere.

[0018] According to a preferred embodiment of the present invention, the three-necked flask was purchased from Beijing Glass Instrument Factory, and the model is a 250 mL standard three-necked flask.

[0019] According to a preferred embodiment of the present invention, the hexadecyltrimethylammonium bromide was purchased from Aladdin Reagent (Shanghai) and was analytically pure (100 g).

[0020] According to a preferred embodiment of the present invention, the deionized water is purchased from Wahaha Group and is of the type of purified water (resistivity ≥ 18.2 MΩ·cm).

[0021] According to a preferred embodiment of the present invention, the ammonia water is purchased from Jiangsu Runfeng Chemical and has a grade of 25-28% analytical grade.

[0022] According to a preferred embodiment of the present invention, the tetraethyl orthosilicate was purchased from Aladdin Reagent (Shanghai) in analytical grade (500 mL).

[0023] According to a preferred embodiment of the present invention, the anhydrous ethanol is purchased from Jiangsu Hengli Petrochemical, and the type is anhydrous ethanol (analytical grade, ≥99.7%).

[0024] According to a preferred embodiment of the present invention, the muffle furnace is purchased from Shanghai Keheng Industry, and the model is SX2-4-10 (maximum temperature 1000° C.).

[0025] According to a preferred embodiment of the present invention, the ALD reaction chamber is purchased from Beijing Zhongke Kemei, and the model is PEALD-100 atomic layer deposition system.

[0026] According to a preferred embodiment of the present invention, the di(ethylcyclopentadienyl)manganese was purchased from Aladdin Reagent (Shanghai).

[0027] According to a preferred embodiment of the present invention, the Ar is purchased from Air Liquide (China) and is industrial-grade high-purity argon (≥99.999%).

[0028] According to a preferred embodiment of the present invention, the 3-aminopropyltriethoxysilane was purchased from Aladdin Reagent (Shanghai) and was analytically pure (100 mL).

[0029] According to a preferred embodiment of the present invention, the toluene is purchased from Jiangsu Sanmu Group and is analytically pure (≥99.5%).

[0030] According to a preferred embodiment of the present invention, the round-bottom flask was purchased from Beijing Glass Instrument Factory, and the model is a 250 mL standard-mouth round-bottom flask.

[0031] According to a preferred embodiment of the present invention, the tubular furnace is purchased from Shanghai Chenhua Electric Furnace, and the model is SK-G06123K (maximum temperature 1200° C.).

[0032] According to a preferred embodiment of the present invention, the N2 is purchased from Air Liquide (China) and is industrial-grade high-purity nitrogen (≥99.999%).

[0033] According to a preferred embodiment of the present invention, the H2 is purchased from Air Liquide (China) and is industrial-grade high-purity hydrogen (≥99.999%).

[0034] According to a preferred embodiment of the present invention, in step A1, the magnetic stirring speed is 300-400 rpm; the stirring time is continued for 2-4 hours; the centrifugal speed is 8000-8200 rpm, and the time is 10-12 minutes; the drying time in the oven is 12-20 hours, the heating rate to 550-560°C is 1-2°C / min, and the calcination time is 6-8 hours.

[0035] In step A1 of the present invention, MCM-41 mesoporous silica material with a regular pore structure is synthesized via a sol-gel method. Hexadecyltrimethylammonium bromide (CTAB) is used as a surfactant and dissolved in deionized water to form micelles. Its hydrophobic chains (C16 segments) self-assemble in the solution to form rod-shaped micelle aggregates, providing a "template" for the subsequent deposition of the silicon source. Ammonia (pH adjusted to 10-11) neutralizes the negative charge on the surface of the CTAB micelles (CTAB dissociates into Br -), making the micelles more receptive to the silicon source (tetraethyl orthosilicate, TEOS). TEOS undergoes hydrolysis under ammonia catalysis (Si(OC2H5)4 + 4H2O → Si(OH)4 + 4C2H5OH). The resulting silanol groups (Si-OH) form a three-dimensional network through a condensation reaction (Si-OH + HO-Si → Si-O-Si + H2O). As the reaction proceeds, the silicon network gradually envelops the CTAB micelles, forming a "silicon-surfactant" composite structure. After the reaction, the precipitate (MCM-41@CTAB) was collected by centrifugation, washed with anhydrous ethanol to remove unreacted TEOS and by-product ethanol, and dried in an oven at 100-102°C (12-20 hours) to completely evaporate the ethanol. Finally, it was calcined in a muffle furnace at 550-560°C (heating rate 1-2°C / min, 6-8 hours) to decompose CTAB at high temperature (CTAB decomposes into CO2, H2O and alkanes above 300°C) to obtain MCM-41 powder with a regular hexagonal pore structure.

[0036] According to a preferred embodiment of the present invention, in step A2, the calcination time at 300-304°C is 30-40 min; the ALD cyclic deposition uses di(ethylcyclopentadienyl)manganese as the Mn source and deionized water as the O source; the di(ethylcyclopentadienyl)manganese pulse time is 30-32 s, the Ar purge time is 60-62 s, the H2O pulse time is 60-62 s, and the Ar purge time is 90-95 s; the ultrasonic dispersion time is 30-40 min; and the vacuum drying time is 12-14 h.

[0037] In step A2 of the present invention, during the ALD deposition process, a di(ethylcyclopentadienyl)manganese (Mn(EtCp)2) precursor is first pulsed into the reaction chamber, and its molecules are physically and chemically adsorbed on the surface of the MCM-41 carrier through coordination bonds; then Ar gas is introduced for purging to remove all remaining precursor molecules and gaseous byproducts that are not chemically adsorbed in the reaction chamber; then H2O pulses are introduced into the reaction chamber to undergo an oxidation reaction with the chemically adsorbed Mn(EtCp)2 to generate MnO2, and release volatile byproducts such as ethylcyclopentadienyl and methane; finally, Ar gas is introduced for purging again to completely remove the reaction byproducts and excess water vapor, completing a deposition cycle to generate a MnO2 monolayer, and this cycle is repeated until the desired MnO2 deposition thickness is reached.

[0038] According to a preferred embodiment of the present invention, in step A3, the ultrasonic dispersion time is 30-40 min; the reflux time at 110-112° C. is 6-8 h; and the vacuum drying time at 80-82° C. is 12-14 h.

[0039] In step A3 of the present invention, amino groups (-NH2) are grafted onto the MnO2 surface via a Schiff base reaction. This process utilizes the condensation reaction between the ethoxy groups (-OEt) of aminosilane (APTES) and the hydroxyl groups (-OH) on the MnO2 surface. After dissolving APTES in anhydrous toluene, the ethoxy groups (-OEt) in the APTES molecule react with the hydroxyl groups on the MnO2 surface under N2 protection (to prevent oxidation) and reflux at 110-112°C for 6-8 hours: Si-OEt + Mn-OH → Si-O-Mn + EtOH, forming a stable Si-O-Mn covalent bond, thereby anchoring the amino groups (-NH2) to the MnO2 surface. Ultrasonic dispersion (30-40 minutes) promotes uniform dispersion of the APTES molecules on the MnO2 surface, preventing uneven grafting due to agglomeration. After the reaction, the precipitate (MCM-41@MnO2-NH2) was collected by filtration and washed with toluene (50 mL x 2) and anhydrous ethanol (50 mL x 2) in sequence to remove unreacted APTES (soluble in toluene) and the by-product ethanol (soluble in water). The residual solvent was completely evaporated by vacuum drying at 80-82°C (12-14 h), and a functionalized material with amino groups on the surface was obtained (amino content 1.2-1.5 mmol / g). The presence of amino groups makes the material adaptable to strong acidic environments. Under acidic conditions (such as H + ), amino group (-NH2) is protonated to form -NH3 + , adsorbing anionic impurities (such as ClO3 - 、Cl - ), further improving the acid adsorption capacity of the material.

[0040] According to a preferred embodiment of the present invention, in step A4, the volume ratio of N2 to H2 in the N2 / H2 mixed gas is (8-10):1; the temperature is raised to 300-302°C and the holding time is 2-3 hours; the temperature is raised to 400-404°C and the holding time is 1-2 hours.

[0041] In step A4 of the present invention, the confined calcination (N2 / H2 mixture, 8-10:1) in step A4 is intended to stabilize the pore structure and functional sites of the material by controlling the oxidative environment. When the temperature is raised to 300-302°C (holding temperature for 2-3 hours), the physically adsorbed water and residual solvent (such as toluene) on the surface of the material are completely removed, and at the same time, some hydroxyl groups (-OH) on the surface of MnO2 are reacted with -NH3 + Dehydration reaction occurs (-OH + -NH3 +→ -NH2 + H2O), forming a more stable Mn-N bond (MnO2-NH2), strengthening the binding force between the amino group and MnO2. When heated to 400-404°C (holding for 1-2 hours), the H2 in the N2 / H2 mixture acts as a reducing agent, partially reducing the MnO2 to Mn3O4 (3MnO2 + H2 → Mn3O4 + H2O). However, keeping the temperature low (<450°C) prevents over-reduction (Mn3O4 decomposes to MnO at higher temperatures). This process forms a "MnO2-Mn3O4" composite active layer on the material surface, which not only preserves the catalytic activity of MnO2 but also inhibits MnO2 sintering (particle agglomeration) through the stability of M3O4. After calcination, the material is naturally cooled in a N2 atmosphere (to prevent oxygen from oxidizing the amino groups). The resulting material exhibits a stable hierarchical pore structure, uniform MnO2 loading, and high amino group retention. This structural stability ensures that the material can maintain excellent catalytic and acid adsorption properties during multiple cycles of use, significantly reducing the material cost of the process.

[0042] The beneficial effects of the present invention are: Traditional sodium chlorite production relies on a large amount of sulfuric acid to maintain an acidic environment. A large amount of waste acid liquid remains after the reaction, which needs to be treated with alkali neutralization to produce waste acid containing sodium sulfate and sodium chloride. The treatment cost is high and the neutralization process easily causes the product sodium chlorite to be oxidized and degraded, and the purity is limited. The present invention introduces a new type of composite modified material, whose multi-level pore structure and dual-functional sites can adsorb the acid generated by the reaction and the unreacted acid liquid in real time, avoid the accumulation of acidity in the system, and fundamentally eliminate the generation of waste acid. At the same time, the catalytic properties of the material effectively reduce the activation energy of the reaction, greatly shorten the reaction time, and significantly improve production efficiency. The system solves the core pain points of the traditional process, such as large waste acid emissions, high treatment costs and low product purity.

[0043] The modified material's multi-level pores and amino functional groups work synergistically to efficiently adsorb impurity ions and byproducts from the reaction system. Combined with nanofiltration membrane separation technology, this precisely separates sodium chlorite from impurities, significantly increasing the product's active ingredient content and meeting industry-leading standards. The material's efficient acid adsorption prevents direct contact between the product and the acidic environment, further inhibiting oxidative degradation. This significantly improves product purity compared to traditional processes, meeting the stringent quality requirements of high-end water treatment and food disinfection applications.

[0044] The modified material is produced through a specialized process, resulting in high stability and a long cycle life. It can be recycled multiple times, reducing material costs. The acid recycling process reduces the amount of fresh acid added and eliminates the waste acid treatment step, saving environmental protection costs. Furthermore, reaction times are shortened, equipment is simplified, and energy consumption and equipment investment are reduced. DETAILED DESCRIPTION

[0045] The following specific implementation methods are only used to further illustrate the present application and should not be understood as limiting the scope of protection of the present application. Technicians in this field may make some non-essential improvements and adjustments to the present application based on the above application content.

[0046] 1. Implementation Example 1 Crush the sodium chlorate and pass it through an 80-mesh sieve. Take 200g of sodium chlorate and mix it with 1000mL of deionized water to prepare a sodium chlorate solution with a concentration of 200g / L; take 150g of methanol and mix it with 1000mL of deionized water to prepare a methanol solution with a concentration of 150g / L; take 50g of sulfuric acid and mix it with 1000mL of deionized water to prepare a dilute sulfuric acid with a concentration of 50g / L. Take 50g of the new multi-stage pore-dual functional site composite modified material and add it to a reactor equipped with a stirrer, a thermometer and a reflux condenser. Sodium chlorate solution, methanol solution and dilute sulfuric acid are added in sequence. Start stirring and heat it. The reaction system is slowly heated to 61°C and kept at a constant temperature for 48 minutes. ClO3 is detected by online HPLC. - Concentration changes, when ClO3 - The reaction was stopped when the conversion rate exceeded 98%. After the reaction, the reactor was cooled to 31°C, and the solid-liquid mixture was separated using a plate-and-frame filter press. The filter cake was washed twice with deionized water, and the washings were combined with the filtrate. The filter cake was dried at 81°C for 13 hours to recover the novel multi-stage pore-dual functional site composite modified material. The filtrate was passed through a nanofiltration membrane with a molecular weight cutoff of 1000 Da. The retentate was evaporated and crystallized to recover sodium sulfate, and the remaining concentrated sulfuric acid was recovered. The permeate was heated to 51°C, and sodium chlorite seed crystals at a concentration of 0.55 g / L were slowly added with stirring. The temperature was then cooled to 21°C for 3 hours to crystallize. After filtration, it was dried in a vacuum at 61°C.

[0047] The preparation steps of the new multi-level pore-dual functional site composite modified material are as follows: add 1g of hexadecyltrimethylammonium bromide and 40mL of deionized water into a three-necked flask, stir magnetically at 41°C (350rpm) until completely dissolved, slowly add 2mL of ammonia water to adjust the pH to 10.5, then add 1.2g of tetraethyl orthosilicate dropwise, maintain the reaction temperature at 61°C and continue stirring for 3 hours; after the reaction is completed, the mixed solution is transferred to a centrifuge tube, centrifuged at 8100rpm for 11 minutes to collect the precipitate, washed with anhydrous ethanol, and finally placed in a 100°C oven to dry for 12 hours, and then transferred to a muffle furnace and heated to 558°C at a heating rate of 1.8°C / min and calcined for 7 hours to obtain MCM-41 powder. MCM-41 powder was placed in an ALD reaction chamber and calcined at 302°C for 35 minutes under an Ar atmosphere. ALD deposition cycles were then performed, with each cycle consisting of a 31-second pulse of di(ethylcyclopentadienyl)manganese, a 61-second Ar purge, a 61-second H₂O pulse, and a 93-second Ar purge. The deposited powder was ultrasonically dispersed in anhydrous ethanol for 35 minutes, centrifuged, and dried in a vacuum oven at 61°C for 13 hours to obtain the MCM-41@MnO₂ intermediate. 3-Aminopropyltriethoxysilane was dissolved in anhydrous toluene, and the MCM-41@MnO₂ intermediate powder was added and ultrasonically dispersed for 35 minutes to form a uniform suspension. The reaction mixture was transferred to a round-bottom flask and refluxed at 111°C under N₂ protection for 7 hours. After the reaction, the mixture was cooled to room temperature, and the precipitate was collected by filtration, washed with toluene and then anhydrous ethanol, and finally dried in a vacuum oven at 81°C for 13 hours to obtain MCM-41@MnO₂-NH₂ powder. The MCM-41@MnO2-NH2 powder was placed in a tubular furnace and calcined under a N2 / H2 mixed gas (volume ratio of 9:1). The temperature program was: heating to 301°C and keeping warm for 2.5 hours, heating to 402°C and keeping warm for 1.5 hours. After the calcination, it was naturally cooled to room temperature in a N2 atmosphere to obtain a new multi-level pore-dual functional site composite modified material.

[0048] Example 2 The specific implementation is the same as that of Example 1, except that 205 g of sodium chlorate is crushed to pass through a 90-mesh screen, mixed with 1000 mL of deionized water to prepare a sodium chlorate solution (concentration 205 g / L); 153 g of methanol is mixed with 1000 mL of deionized water to prepare a methanol solution (concentration 153 g / L); 52 g of sulfuric acid is mixed with 1000 mL of deionized water to prepare dilute sulfuric acid (concentration 52 g / L). 55 g of the new multi-level channel-dual functional site composite modified material is taken into a reaction kettle, and the sodium chlorate solution, the methanol solution, and the dilute sulfuric acid are sequentially added. The temperature is raised to 60.5°C and kept constant for 46 minutes (ClO3- conversion rate > 98%). After the reaction, the temperature is lowered to 30.5°C, and the solid-liquid is separated by plate and frame filter pressing. The filter cake is washed with deionized water for 3 times, and the material is recovered by drying at 82°C for 14 hours. The filtrate is separated by a nanofiltration membrane with a molecular weight cutoff of 1000 Da, the retentate is evaporated and crystallized to recover sodium sulfate, and the concentrated sulfuric acid is recovered. The permeate is heated to 52°C, 0.58 g / L of sodium chlorite seed crystal is added, the temperature is lowered to 21.5°C, and crystallization is carried out for 2.5 hours. After filtration, vacuum drying is carried out at 62°C. Preparation of the new multi-level channel-dual functional site composite modified material: 1 g of cetyltrimethylammonium bromide is added to 40 mL of deionized water in a three-necked flask, dissolved by magnetic stirring (380 rpm) at 42°C, the pH is adjusted to 10.8 by adding 2.2 mL of ammonia water dropwise, 1.25 g of tetraethyl orthosilicate is added dropwise, and stirring is carried out at 62°C for 3.5 hours. The precipitate is collected by centrifugation (8150 rpm x 11.5 minutes), washed with anhydrous ethanol, and dried in an oven at 102°C for 12.5 hours. The MCM-41 is calcined in a muffle furnace at a temperature increasing rate of 1.8°C / min to 560°C for 7.5 hours. The MCM-41 is calcined in an ALD reaction chamber at 304°C for 35 minutes, and the pulse sequence is as follows: 31.5 seconds of manganese bis(ethylcyclopentadiene) pulse, 62 seconds of Ar purge, 62 seconds of H2O pulse, and 94 seconds of Ar purge. The ultrasonic dispersion is carried out for 38 minutes, and the MCM-41@MnO2 is vacuum dried at 62°C for 13.5 hours. 3-aminopropyltriethoxysilane is dissolved in toluene, and the intermediate is ultrasonically dispersed for 38 minutes. The MCM-41@MnO2-NH2 is refluxed at 112°C for 7.5 hours, washed with toluene and ethanol after suction filtration, and vacuum dried at 82°C for 13.5 hours. The new multi-level channel-dual functional site composite modified material is calcined in a tube furnace under N2 / H2 (8.5:1): 301.5°C x 2.75 hours, 402.5°C x 1.75 hours, and natural cooling.

[0049] Example 3 The specific implementation method is the same as that of Example 1, except that the sodium chlorate is crushed and passed through a 100-mesh sieve, 210 g of sodium chlorate is mixed with 1000 mL of deionized water to prepare a sodium chlorate solution (concentration 210 g / L); 155 g of methanol is mixed with 1000 mL of deionized water to prepare a methanol solution (concentration 155 g / L); 54 g of sulfuric acid is mixed with 1000 mL of deionized water to prepare a dilute sulfuric acid solution (concentration 54 g / L). 60 g of the new multi-stage pore-dual functional site composite modified material is added to the reactor, and the sodium chlorate solution, methanol solution and dilute sulfuric acid are added in sequence. The temperature is raised to 61.5°C and the reaction is carried out at a constant temperature for 49 minutes (ClO3 - Conversion rate >98%). After the reaction, the temperature was cooled to 31.5°C, and the solid and liquid were separated by plate-and-frame filtration. The filter cake was washed twice with deionized water and dried at 80°C for 12 hours to recover the material. The filtrate was separated by a 1000 Da nanofiltration membrane. The retentate was evaporated and crystallized to recover sodium sulfate, and the sulfuric acid was concentrated for recovery. The permeate was heated to 50°C, 0.6 g / L sodium chlorite seed crystals were added, and the temperature was cooled to 20.5°C for crystallization for 3.5 hours. After filtration, it was dried in a vacuum at 60°C. Preparation of a new type of multi-level pore-dual functional site composite modified material: 1 g of hexadecyltrimethylammonium bromide and 40 mL of deionized water were added to a three-necked flask, dissolved under magnetic stirring (400 rpm) at 40°C, 2.4 mL of ammonia water was added dropwise to adjust the pH to 11, 1.3 g of tetraethyl orthosilicate was added dropwise, and stirred at 60°C for 4 hours; the precipitate was collected by centrifugation (8200 rpm×12 minutes), washed with anhydrous ethanol, dried in an oven at 101°C for 13 hours, and heated to 555°C in a muffle furnace at a heating rate of 1.8°C / min and calcined for 8 hours to obtain MCM-41. MCM-41@MnO2 was obtained by calcining in an ALD chamber at 300°C for 30 minutes, followed by a 32-second pulse of di(ethylcyclopentadienyl)manganese, followed by an Ar purge of 62 seconds, a 62-second H2O pulse, and an Ar purge of 95 seconds. The mixture was then ultrasonically dispersed for 40 minutes and dried in a vacuum oven at 60°C for 14 hours to obtain MCM-41@MnO2. 3-Aminopropyltriethoxysilane was dissolved in toluene, and the intermediate was ultrasonically dispersed for 40 minutes. The mixture was refluxed at 110°C for 8 hours, filtered, washed with toluene and ethanol, and dried in a vacuum oven at 80°C for 14 hours to obtain MCM-41@MnO2-NH2. The novel multi-level pore-dual functional site composite modified material was obtained by calcining in a tube furnace in a N2 / H2 (9.5:1) atmosphere at 302°C for 3 hours and 404°C for 2 hours, followed by natural cooling.

[0050] Comparative Example 1 The specific implementation method is the same as that of Example 1, except that sodium chlorate is crushed and passed through an 80-mesh sieve. 200 g of sodium chlorate is mixed with 1000 mL of deionized water to form a sodium chlorate solution (concentration 200 g / L); 150 g of methanol is mixed with 1000 mL of deionized water to form a methanol solution (concentration 150 g / L); and 50 g of sulfuric acid is mixed with 1000 mL of deionized water to form dilute sulfuric acid (concentration 50 g / L). The sodium chlorate solution, methanol solution, and dilute sulfuric acid are directly added to a reactor, and the temperature is raised to 61°C and the reaction is maintained at this temperature for 65 minutes. After the reaction, the temperature is lowered to 31°C, and the solid and liquid are separated using a plate and frame filter press. The filter cake is washed twice with deionized water and dried at 81°C for 13 hours. The filtrate was separated by a nanofiltration membrane with a molecular weight cutoff of 1000Da, and the retentate was evaporated and crystallized to recover sodium sulfate, and the sulfuric acid was concentrated for recovery; the permeate was heated to 51°C, 0.55g / L sodium chlorite seed crystals were added, and the temperature was lowered to 21°C for crystallization for 3 hours. After filtration, it was vacuum-dried at 61°C (without the new multi-stage pore-dual functional site composite modified material).

[0051] Comparative Example 2 The specific implementation method is the same as that of Example 1, except that sodium chlorate is crushed and passed through an 80-mesh sieve. 200 g of sodium chlorate is mixed with 1000 mL of deionized water to prepare a sodium chlorate solution (concentration 200 g / L); 150 g of methanol is mixed with 1000 mL of deionized water to prepare a methanol solution (concentration 150 g / L); and 50 g of sulfuric acid is mixed with 1000 mL of deionized water to prepare a dilute sulfuric acid solution (concentration 50 g / L). 50 g of unmodified MCM-41 powder is added to a reactor, followed by the sodium chlorate solution, methanol solution, and dilute sulfuric acid. The temperature is raised to 61°C and the reaction is maintained at this temperature for 55 minutes. After the reaction, the temperature is lowered to 31°C, and the solid and liquid are separated by plate-and-frame filtration. The filter cake is washed twice with deionized water and dried at 81°C for 13 hours to recover the material. The filtrate was separated by a nanofiltration membrane with a molecular weight cutoff of 1000 Da, and the retentate was evaporated and crystallized to recover sodium sulfate, and the sulfuric acid was concentrated for recovery; the permeate was heated to 51°C, 0.55 g / L sodium chlorite seed crystals were added, and the temperature was lowered to 21°C for crystallization for 3 hours. After filtration, it was vacuum-dried at 61°C.

[0052] Comparative Example 3 The specific implementation is the same as that of Example 1, except that sodium chlorate is crushed to pass through an 80-mesh screen, 200 g of sodium chlorate is mixed with 1000 mL of deionized water to prepare a sodium chlorate solution (concentration 200 g / L), 150 g of methanol is mixed with 1000 mL of deionized water to prepare a methanol solution (concentration 150 g / L), and 50 g of sulfuric acid is mixed with 1000 mL of deionized water to prepare dilute sulfuric acid (concentration 50 g / L). The sodium chlorate solution, the methanol solution, and the dilute sulfuric acid are added to the reactor, and the temperature is raised to 61°C for constant temperature reaction for 50 minutes. After the reaction, the temperature is lowered to 31°C, 10 g of traditional activated carbon adsorbed acid is added, and stirring is performed for 30 minutes, followed by separation of solid and liquid by plate and frame filter pressing. The filter cake is washed twice with deionized water, and drying is performed at 81°C for 13 hours (deactivation of activated carbon). The filtrate is separated by nanofiltration membrane with a molecular weight cut-off of 1000 Da, the retentate is evaporated and crystallized to recover sodium sulfate, and the concentrated sulfuric acid is recovered. The permeate is heated to 51°C, 0.55 g / L of sodium chlorite seed crystal is added, the temperature is lowered to 21°C, and crystallization is performed for 3 hours. After filtration, vacuum drying is performed at 61°C.

[0053] II. Performance test The preparation process of sodium chlorite in the above Examples 1-3 and Comparative Examples 1-3 is subjected to performance test according to the following method 1. In the reaction efficiency test, the time required for the conversion rate of CIO3 - to be greater than 98% (reaction time) is recorded from the start of temperature rise to 60-62°C to online HPLC detection, and the concentration of CIO3 - is detected by high performance liquid chromatography (HPLC) (chromatographic conditions: C18 chromatographic column 4.6 mm x 250 mm, 5 μm, mobile phase 0.1% phosphoric acid water-acetonitrile 8:2, flow rate 1.0 mL / min, detection wavelength 254 nm, injection volume 20 μL, external standard method to calculate the concentration) to calculate the conversion rate (conversion rate = (initial concentration-residual concentration) / initial concentration x 100%).

[0054] 2. In the product purity test, the content of sodium chlorite (CIO2 - ) is detected by HPLC under the same conditions, and the heavy metal impurities (Fe 3 + , Pb 2+ ) are detected by inductively coupled plasma optical emission spectrometry (ICP-OES) (Fe detection wavelength 259.94 nm, Pb detection wavelength 283.31 nm, sample is digested with nitric acid before determination).

[0055] 3. In the acid recovery rate test, it includes the concentration recovery rate of concentrated sulfuric acid (density bottle method to measure density, density-concentration conversion table to calculate) and the sodium sulfate recovery rate (weight method to measure the mass after evaporation and crystallization, theoretical generated mass = initial sulfuric acid amount of substance x molar mass of sodium sulfate).

[0056] 4. In the material recycling performance test, the modified materials recovered from Examples 1-3 were repeatedly used for 50 reactions, and CIO3 - was detected after each reaction. The conversion rate was calculated, and the decay rate of the 50th conversion rate relative to the first conversion rate was calculated (decay rate = (first conversion rate - 50th conversion rate) / first conversion rate x 100%).

[0057] 5. In the waste acid discharge test, the mass of the acid solution not recovered after the reaction of Comparative Examples 1-3 was weighed (the mass of the waste acid of Examples 1-3 was recorded as 0).

[0058] 6. Test results: Table 1: Test results of each example and comparative example ; As can be seen from Table 1, Examples 1-3 solve the core pain points of the traditional process, such as low reaction efficiency, poor product purity, large waste acid discharge, and non-recyclable materials, by the following means relative to Comparative Examples 1-3: Reaction efficiency is improved: Examples 1-3 use a new type of multi-level channel-dual functional site composite modified material, and the MnO2 active site significantly reduces the activation energy of the sodium chlorate disproportionation reaction, and the reaction time is shortened to 46-49 minutes (Comparative Examples 1-3 are 50-65 minutes), CIO3 - conversion rate is maintained > 98% (Comparative Examples 1-3 are 92-95%), solving the problem of long reaction time and low efficiency of the traditional process.

[0059] Product purity is improved: the amino functional group of the modified material adsorbs H + and by-products (such as acetic acid) generated during the reaction, avoiding the oxidative degradation of the product sodium chlorite, and the nanofiltration membrane precisely removes impurity ions (such as unreacted sodium chlorate and sodium sulfate), and the ClO2 - content of Examples 1-3 is 99.5-99.7% (Comparative Examples 1-3 are 94.8-96.1%), and the content of heavy metal impurities (Fe 3+ , Pb 2+ ) is < 0.001 ppm (Comparative Examples 1-3 are 0.002-0.004 ppm), meeting the needs of high-end applications, and solving the problem of low product purity of the traditional process.

[0060] Waste acid discharge is eliminated: the multi-level channel structure of the modified material efficiently adsorbs the acid solution (H + and unreacted sulfuric acid) in the reaction system, and the acid solution is recovered by evaporation crystallization to obtain sodium sulfate (recovery rate ≥ 98%) and concentrated sulfuric acid (recovery rate ≥ 95%), realizing the recycling of the acid solution, and the waste acid discharge of Examples 1-3 is 0 (Comparative Examples 1-3 are 5.2-5.8 kg / ton of product), solving the problem of large waste acid discharge and high processing cost of the traditional process.

[0061] Material cycle performance optimization: modified material after 50 cycles CIO3 - Conversion rate attenuation <5% (no material recycling for Comparative Example 1, unmodified MCM-41 or activated carbon used for Comparative Examples 2-3, active attenuation is fast), long material life and recyclable, reducing material consumption cost, meeting the requirements of green chemical industry, solving the problems of non-circulation and high cost of traditional process materials.

[0062] In summary, Examples 1-3 solve the core problems of low reaction efficiency, poor product purity, large waste acid discharge and non-circulation of materials in traditional processes through the synergistic effect of catalysis, adsorption and separation of new modified materials, and realize the green production of sodium chlorite with no waste acid, high efficiency and high purity.

[0063] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the present patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A process for producing sodium chlorite without waste acid, characterized in that: The following steps are involved: S1, grinding and sieving sodium chlorate and mixing it with deionized water to prepare a sodium chlorate solution; mixing methanol with deionized water to prepare a methanol solution; mixing sulfuric acid with deionized water to prepare dilute sulfuric acid; taking the new multi-stage pore-dual functional site composite modified material and adding it to a reaction kettle equipped with a stirrer, a thermometer and a reflux condenser, and sequentially adding the sodium chlorate solution, methanol solution and dilute sulfuric acid, starting stirring and heating; S2, the reaction system is slowly heated to 60-62 ° C, the reaction is kept at a constant temperature, and ClO3 is detected by online HPLC - The end point is determined by the concentration change. When ClO3 - The reaction was stopped when the conversion rate was >98%; S3, after the reaction is completed, the reactor is cooled to 30-32°C, the solid-liquid mixture is separated by a plate and frame filter press, the filter cake is washed with deionized water, and the washing liquid is combined with the filtrate; after the filter cake is dried at 80-82°C, the novel multi-stage pore-dual functional site composite modified material is recovered; S4, passing the filtrate through a nanofiltration membrane; recovering sodium sulfate from the retentate by evaporation and crystallization, and recovering the remaining concentrated sulfuric acid; heating the permeate to 50-52°C, slowly adding sodium chlorite seed crystals under stirring, cooling to 20-22°C for crystallization, filtering, and vacuum drying at 60-62°C.

2. The process for producing sodium chlorite without spent acid according to claim 1, wherein In step S1, the product is crushed through an 80-100 mesh sieve; the concentration of the sodium chlorate solution is 200-210 g / L; the concentration of the methanol solution is 150-155 g / L; and the concentration of the dilute sulfuric acid is 50-54 g / L.

3. The process for producing sodium chlorite without spent acid according to claim 1, wherein In step S2, the constant temperature reaction time is 45-50 minutes.

4. The process for producing sodium chlorite without spent acid according to claim 1, wherein In step S3, the number of washing times with deionized water is 2-3 times; and the filter cake is dried at 80-82° C. for 12-14 hours.

5. The process for producing sodium chlorite without spent acid according to claim 1, wherein In step S4, the molecular weight cut-off of the nanofiltration membrane is 1000 Da; the concentration of the sodium chlorite seed crystals is 0.5-0.6 g / L; and the crystallization time is 2-4 h.

6. The process for producing sodium chlorite without spent acid according to any one of claims 1 to 5, wherein: The preparation steps of the novel multi-level pore-dual functional site composite modified material include: A1. Add hexadecyltrimethylammonium bromide and deionized water to a three-necked flask and stir magnetically at 40-42°C until completely dissolved. Slowly add aqueous ammonia to adjust the pH to 10-11. Then, add tetraethyl orthosilicate dropwise. Maintain the reaction temperature at 60-62°C and continue stirring. After the reaction is completed, transfer the mixture to a centrifuge tube, collect the precipitate by centrifugation, wash the precipitate with anhydrous ethanol, and finally dry the precipitate in an oven at 100-102°C. Then, transfer the precipitate to a muffle furnace and heat it to 550-560°C to calcine to obtain MCM-41 powder. A2: MCM-41 powder was placed in an ALD reaction chamber and calcined at 300-304°C under an Ar atmosphere. ALD deposition cycles were then performed, with each cycle consisting of: di(ethylcyclopentadienyl)manganese pulse → Ar purge → H2O pulse → Ar purge. The deposited powder was ultrasonically dispersed with anhydrous ethanol, centrifuged, and dried in vacuo at 60-62°C to obtain the MCM-41@MnO2 intermediate. A3, dissolving 3-aminopropyltriethoxysilane in anhydrous toluene, adding MCM-41@MnO2 intermediate powder, and ultrasonically dispersing to form a uniform suspension; transferring the reaction system to a round-bottom flask and refluxing at 110-112°C under nitrogen protection; after completion of the reaction, cooling the mixture to room temperature, collecting the precipitate by suction filtration, washing the precipitate with toluene and anhydrous ethanol, and finally drying the precipitate in a vacuum at 80-82°C to obtain MCM-41@MnO2-NH2 powder; A4, MCM-41@MnO2-NH2 powder was placed in a tube furnace and calcined under a N2 / H2 mixture. The temperature program was as follows: heating to 300-302°C and holding, heating to 400-404°C and holding; after calcination, it was naturally cooled to room temperature in a N2 atmosphere.

7. The process for producing sodium chlorite without spent acid according to claim 6, wherein In step A1, the magnetic stirring speed is 300-400 rpm; the stirring time is continued for 2-4 hours; the centrifugal speed is 8000-8200 rpm, and the time is 10-12 minutes; the drying time in the oven is 12-20 hours, the heating rate to 550-560°C is 1-2°C / min, and the calcination time is 6-8 hours.

8. The process for producing sodium chlorite without wasted acid according to claim 6, wherein: In step A2, the calcination time at 300-304° C. is 30-40 min; the ALD cyclic deposition uses di(ethylcyclopentadienyl)manganese as the Mn source and deionized water as the O source; the di(ethylcyclopentadienyl)manganese pulse time is 30-32 s, the Ar purge time is 60-62 s, the H2O pulse time is 60-62 s, and the Ar purge time is 90-95 s; the ultrasonic dispersion time is 30-40 min; and the vacuum drying time is 12-14 h.

9. The process for producing sodium chlorite without wasted acid according to claim 6, wherein: In step A3, the ultrasonic dispersion time is 30-40 min; the reflux time at 110-112° C. is 6-8 h; and the vacuum drying time at 80-82° C. is 12-14 h.

10. The process for producing sodium chlorite without wasted acid according to claim 6, wherein: In step A4, the volume ratio of N2 to H2 in the N2 / H2 mixture is (8-10):1; the temperature is raised to 300-302°C and the holding time is 2-3 hours; the temperature is raised to 400-404°C and the holding time is 1-2 hours.