An integrated water treatment process for hardness removal induced by crystal nucleation and granulation

Abstract

This invention relates to the field of water treatment technology, specifically disclosing an integrated water treatment process for hardness removal induced by crystal nucleation granulation. First, nano-hydroxyapatite is ultrasonically dispersed in deionized water, and then reacted and treated with γ-glycidyl etheroxypropyltrimethoxysilane to obtain silanized hydroxyapatite crystal nuclei. Sodium polyacrylate is reacted with aluminum sulfate and other substances in ethylene glycol solution to prepare a composite inducer. The two react in a phosphate buffer solution in a specific ratio to obtain crystal nuclei particles loaded with the inducer. After multiple reactions and treatments with calcium chloride and other substances, surface-coated crystal nuclei granules are obtained. These are then mixed with cationic polyacrylamide and nano-zinc oxide to prepare a strengthened hardness removal agent. When treating water, the strengthened hardness removal agent is added, and after stirring and sedimentation, the supernatant is sequentially passed through an activated carbon filter to adsorb impurities and then sterilized with an ultraviolet disinfection device. Finally, the effluent is collected, which can efficiently remove hardness from water, with high process integration and excellent results.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to an integrated water treatment process for hardness removal induced by crystal nucleation granulation. Background Technology

[0002] Water hardness is an important indicator of the content of calcium, magnesium, and other ions in water. Hard water can cause numerous problems in daily life and industrial production. In terms of domestic water use, hard water easily forms scale when heated, which adheres to the inner walls of heating equipment such as kettles and water heaters. This not only reduces heat transfer efficiency and increases energy consumption, but long-term accumulation can also damage the equipment and shorten its lifespan. Washing clothes with hard water significantly reduces the cleaning effectiveness of detergents, and makes clothing fibers stiff, affecting wearing comfort. During bathing, hard water may combine with soap to produce insoluble precipitates that adhere to the skin surface, causing dryness, itching, and other discomfort.

[0003] In the industrial sector, the hazards of hard water are even more pronounced. In the textile printing and dyeing industry, calcium and magnesium ions in hard water can combine with dyes, causing uneven dyeing, dull colors, and other quality problems, reducing the added value of products. In the papermaking industry, hard water can interfere with the sizing process, affecting the paper's strength, smoothness, and other performance indicators. In industries with stringent water quality requirements, such as chemical production and pharmaceuticals, impurities in hard water can lead to increased chemical reaction byproducts, unstable drug quality, and other serious consequences, even causing production process interruptions and resulting in huge economic losses.

[0004] Traditional water softening methods mainly include ion exchange and lime softening. Ion exchange utilizes ion exchange resins to react with calcium and magnesium ions in the water, thereby removing hardness. This method has a good softening effect, but the resin regeneration process is complex and requires large amounts of acid and alkali chemicals, resulting in high costs and environmental pollution from the discharge of acid and alkali wastewater. Lime softening involves adding lime to the water, causing calcium bicarbonate and magnesium bicarbonate to precipitate as calcium carbonate and magnesium carbonate, thus removing hardness. However, this method significantly increases the pH value of the water, often requiring additional neutralization steps, making the operation cumbersome and generating large amounts of precipitate that are difficult to treat.

[0005] With the continuous development of materials science and water treatment technology, new water treatment processes have emerged. In recent years, water treatment technology based on the principle of nucleus-induced precipitation has gradually attracted attention. Its core lies in utilizing specific nucleus materials to provide crystal growth sites for calcium and magnesium ions in the water, causing them to precipitate in crystalline form, thereby reducing water hardness. Compared with traditional methods, this technology has potential advantages such as mild reaction conditions, no need for large amounts of chemical regeneration, and environmental friendliness.

[0006] In the selection of nucleation materials, hydroxyapatite, due to its unique crystal structure and surface properties, exhibits a strong adsorption affinity for calcium and magnesium ions, making it a highly promising candidate material. Nanoscale hydroxyapatite possesses a larger specific surface area, providing more active sites and theoretically enhancing its adsorption and precipitation-inducing ability for hardness ions. However, pure nano-hydroxyapatite has some limitations in practical applications, such as easy particle agglomeration, leading to a reduction in effective active sites, poor dispersion stability in water, and difficulty in fully utilizing its nucleation function.

[0007] To address the dispersion problem of nano-hydroxyapatite, surface modification has become a research hotspot. Silane coupling agents, as commonly used surface modifiers, can introduce organic functional groups onto the surface of nano-hydroxyapatite, improving its compatibility with aqueous media, inhibiting particle aggregation, and potentially enhancing its synergistic effect with subsequent additives. For example, γ-glycidoxypropyltrimethoxysilane, whose epoxy groups in its molecular structure can chemically react with the hydroxyl groups on the surface of hydroxyapatite to form stable chemical bonds, while the trimethoxysilane group at the other end can form hydrogen bonds with water after hydrolysis, thus endowing the modified hydroxyapatite with good dispersibility and stability.

[0008] In the process of nucleus-induced hardness removal, the inducer plays a crucial catalytic and regulatory role. Composite inducers, through the synergistic effect of multiple components, can optimize the nucleus growth environment and accelerate the crystallization and precipitation process of hardness ions. A composite inducer based on sodium polyacrylate, with the addition of aluminum sulfate, sodium dodecyl sulfonate, etc., utilizes the strong dispersing and chelating abilities of sodium polyacrylate to maintain the dispersion of hardness ions in water and prevent premature precipitation. Aluminum ions generated from the hydrolysis of aluminum sulfate can form complexes with hydroxyl groups, further promoting the formation and growth of nuclei. Sodium dodecyl sulfonate, as a surfactant, can reduce surface tension, which is beneficial for the dispersion and mass transfer of substances, thus improving the induction efficiency.

[0009] To further enhance the synergistic effect of crystal nuclei and inducers, and to strengthen the stability and sustainability of the entire system during water treatment, subsequent granulation and coating processes are crucial. Granulation agglomerates the inducer-loaded crystal nuclei, improving their flowability and maneuverability in water while reducing the risk of loss due to small particle size. Surface coating utilizes substances such as tetraethoxysilane to form a protective film on the surface of the granulated crystal nuclei. This further enhances particle stability, preventing dissolution or agglomeration in complex water conditions, and also provides a slow-release effect on the internal crystal nuclei and inducers, extending their effective action time. Furthermore, considering the comprehensive water quality requirements in practical applications, it is necessary not only to achieve efficient hardness removal but also to remove residual organic impurities, microorganisms, and other pollutants from the water. Activated carbon filter columns, with their well-developed pore structure, have a good adsorption capacity for dissolved organic matter and residual chlorine in water, and can be used as a subsequent purification step to effectively ensure the purity of water quality; ultraviolet disinfection devices use ultraviolet light of a specific wavelength (such as 254nm) to destroy the DNA structure of microorganisms, thereby inactivating pathogens such as bacteria and viruses in the water and ensuring the microbial safety of the effluent.

[0010] Currently, various technologies and methods have been developed for water hardness removal. Among them, crystallization granulation fluidized bed technology, as a relatively advanced method, has attracted much attention. It utilizes the principle of heterogeneous crystallization, by adding suitable seed crystals, to promote the rapid nucleation and crystallization of hardness ions in the liquid phase at the crystal interface, thereby achieving efficient removal of target ions. For example, Chinese patent authorization announcement number CN105502692A discloses a chemical crystallization circulating granulation fluidized bed water treatment device. This device sets up multiple zones within the cylinder, including a water distribution zone, a chemical distribution zone, a granulation zone, and a clear water zone, allowing seed crystals to circulate between the fluidization zone, separation zone, and settling zone, achieving chemical crystallization granulation of ions in the water during the flow process. However, this technology has some drawbacks. The small particles at the top have difficulty entering the settling zone before they reach the upper edge of the inner cylinder. By the time the small particles at the top can cross the upper edge of the inner cylinder, the large particles at the bottom are already quite large, making it difficult for the small particles to enter the bottom and form an effective circulation. At the same time, since the water flow direction in both the settling zone and the fluidization zone is upward, and the upward flow velocity in the settling zone is lower than that in the fluidization zone, the particles tend to accumulate. The reagent reacts between the accumulated particles, causing the particles to clump together, which affects the operation of the equipment and the hardening removal effect.

[0011] For example, Chinese patent application publication number CN115304140A discloses an induced crystallization granulation fluidized bed softening water treatment device. It separates the water distribution zone and the chemical distribution zone by setting a baffle, and installs a mixing nozzle on the baffle. This allows the chemical output from the distributor, the water in the water distribution zone, and the seeds added at the seed crystal addition port to flow into the mixing nozzle inlet and be sprayed vertically upwards from the outlet, settling along the inner wall of the tank to the bottom, forming a circulating flow within the tank. However, the mixing nozzle in this design cannot achieve 360° spraying of the mixed liquid without dead angles. In the dead corners of the cylinder, water and chemical flows may mix and flow towards nearby water and chemical distribution devices, causing scaling on the distributor and chemical distributor, affecting the uniformity of water and chemical distribution, and consequently affecting the effluent water quality and chemical utilization rate. Furthermore, the magnesium hydroxide generated in the reaction is flocculent and settles slowly. After adding flocculants, it coagulates into large clumps and slowly settles, requiring a larger reactor, separator, and sedimentation tank, resulting in complex equipment and a large footprint.

[0012] Some existing technologies focus on optimizing seed crystals. For example, Chinese patent CN115159765A provides a magnetic seed crystal material, its preparation method, and its application in hardness removal and turbidity reduction water treatment processes. This process uses ferrate-type composite metal oxide-loaded micron-sized scale-causing salt particles as seed crystal materials, which are dispersed into the precipitation reaction system under alkaline conditions to induce crystallization and hardness removal. Although this magnetic seed crystal can accelerate precipitation crystallization and material recovery rates, under magnetic field interference, the magnetic materials are prone to attracting and binding each other, producing larger particles or agglomerates, which is detrimental to the fluidization reaction effect and can also cause scaling problems, increasing reactor maintenance costs. Summary of the Invention

[0013] (a) Technical problems to be solved

[0014] To address the shortcomings of existing technologies, this invention provides an integrated water treatment process for hardening induced by crystal nucleation granulation, which solves the problems mentioned in the background section.

[0015] (II) Technical Solution

[0016] To achieve the above objectives, this invention discloses an integrated water treatment process for hardness removal induced by crystal nucleation granulation, comprising the following steps:

[0017] Step 1: Disperse nano-hydroxyapatite in deionized water by ultrasonication. After uniform dispersion, add γ-glycidyl etheroxypropyltrimethoxysilane, stir and mix, and react at 30-40℃ for 3-6 hours. After the reaction is completed, centrifuge, wash, and vacuum dry at 70℃ for 10 hours to obtain silanized hydroxyapatite crystal nuclei.

[0018] Step 2: Disperse sodium polyacrylate in ethylene glycol solution by ultrasonication. After uniform dispersion, add aluminum sulfate and sodium dodecyl sulfonate, stir and mix, heat to 80-95℃, react for 4-8 hours. After the reaction is completed, filter, wash, and vacuum dry at 60℃ for 6 hours to obtain composite inducer.

[0019] Step 3: Add silanized hydroxyapatite nuclei and composite inducer to phosphate buffer in a certain proportion, disperse by ultrasonication, adjust pH to 8.5-9.5, stir and react at 50-70℃ for 2-4 hours. After the reaction is completed, centrifuge, wash, and vacuum dry at 65℃ for 12 hours to obtain nuclei loaded with inducer.

[0020] Step 4: Mix the crystal nuclei particles loaded with the inducer with calcium chloride and sodium carbonate in deionized water in a certain proportion. After ultrasonic dispersion, add polyethylene glycol-6000 under stirring, heat to 40-55℃, react for 1-3 hours, and centrifuge to separate the precipitate to obtain the primary granulation product.

[0021] Step 5: Disperse the primary granulation product into an ethanol solution, add tetraethoxysilane, stir and mix, and react at 60-75℃ for 5-8 hours. After the reaction is completed, filter, wash, and vacuum dry at 70℃ for 8 hours to obtain surface-coated nucleus granules.

[0022] Step 6: Mix the surface-coated crystal nuclei with cationic polyacrylamide and nano zinc oxide in deionized water in a certain proportion, disperse by ultrasonication, adjust the pH to 6.0-7.0, and let it stand at 25-35℃ for 12-24 hours to obtain the enhanced hardening agent.

[0023] Step 7: Input the water to be treated into the reaction tank, add the hardening agent, control the stirring rate, react at 15-30℃ for 0.5-2 hours, then let it stand to settle for 1-3 hours, and separate the supernatant.

[0024] Step 8: Pass the separated supernatant through an activated carbon filter column, controlling the flow rate at 0.5-2.0 L / min, to adsorb residual impurities;

[0025] Step 9: Pass the adsorbed water into the ultraviolet disinfection device, control the irradiation intensity to be 10-30mW / cm², and the treatment time to be 5-15min.

[0026] Step 10: Collect the final effluent to complete the integrated hardness removal treatment.

[0027] Preferably, in step one, the mass ratio of nano-hydroxyapatite, deionized water, and γ-glycidyl etheroxypropyltrimethoxysilane is 100:2500-4000:50-65.

[0028] Preferably, in step two, the mass ratio of sodium polyacrylate, ethylene glycol solution, aluminum sulfate, and sodium dodecyl sulfonate is 100:3000-4500:80-120:3-8.

[0029] Preferably, in step three, the mass ratio of silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer is 100:45-75:5000-7000.

[0030] Preferably, in step four, the mass ratio of the nucleus particles loaded with the inducing agent, calcium chloride, sodium carbonate, and polyethylene glycol-6000 is 100:15-25:20-35:5-10.

[0031] Preferably, in step five, the mass ratio of the primary granulation product, the ethanol solution, and the tetraethoxysilane is 100:1800-3000:30-50.

[0032] Preferably, in step six, the mass ratio of the surface-coated crystal nucleus granules, cationic polyacrylamide, and nano zinc oxide is 100:8-15:2-5.

[0033] Preferably, in step seven, the mass ratio of the hardening agent to the water to be treated is 1:5000-10000.

[0034] Preferably, in step eight, the filling density of the activated carbon filter column is 0.8-1.2 g / cm³, and the particle size of the activated carbon is 0.5-2.0 mm.

[0035] Preferably, in step nine, the wavelength of the ultraviolet disinfection device is 254nm, and the water layer thickness is 1-3cm.

[0036] (iii) Beneficial technical effects

[0037] Firstly, the integrated water treatment process for hardness removal induced by nucleation granulation of this invention exhibits excellent hardness removal effect. Through carefully designed steps, from the preparation of nuclei by silanization modification of nano-hydroxyapatite, to the synthesis of composite inducers, the preparation of nuclei particles loaded with inducers, granulation, and a series of subsequent treatments, each step works in close coordination, achieving deep hardness removal for water of varying hardness. In the embodiments, when the hardness of the water to be treated is as high as 450 mg / L (calculated as calcium carbonate), after treatment by this process, the hardness of the final effluent can be reduced to below 15 mg / L, meeting the requirements for high-quality water and greatly expanding the range of treatable water sources. Whether it is surface water or groundwater with high hardness in drinking water sources, or pretreatment of process water that is sensitive to hardness in industrial production, it can effectively ensure that subsequent water use is not affected by hard water.

[0038] Secondly, nano-hydroxyapatite is modified using silane coupling agents, such as γ-glycidoxypropyltrimethoxysilane. The epoxy groups in the molecular structure are chemically bonded to the hydroxyl groups on the surface of hydroxyapatite. After hydrolysis, the trimethoxysilane groups form hydrogen bonds with water, effectively inhibiting particle aggregation and giving it good dispersibility and stability. This allows the crystal nuclei to maintain high activity in water for a long time, providing sufficient and stable sites for subsequent induced precipitation. Compared with unmodified nano-hydroxyapatite, it significantly improves the adsorption and induction capacity for calcium and magnesium ions, thereby strengthening the hardening efficiency from the root.

[0039] The prepared composite inducer is mainly composed of sodium polyacrylate, which also has a dispersing and chelating effect, so that the hardness ions are evenly dispersed and avoid premature precipitation and agglomeration. The aluminum ions generated by the hydrolysis of aluminum sulfate synergistically promote the formation and growth of crystal nuclei. Sodium dodecyl sulfonate reduces surface tension and helps mass transfer. The multi-component synergistically creates an ideal growth microenvironment for crystal nuclei, accelerates the crystallization and precipitation of hardness ions, and further optimizes the crystal nucleus-induced hardness removal effect.

[0040] Third, the granulation process agglomerates the crystal nuclei loaded with inducers, which not only improves their fluidity and operability in water, making it convenient for addition and mixing in water treatment facilities of different scales, but also reduces the problem of easy loss due to small particles, ensuring that the effective ingredients can play a full role and guaranteeing the continuity of treatment effect.

[0041] The surface coating process uses tetraethoxysilane to form a protective film on the surface of the crystal nucleus granules, which enhances the stability of the particles in complex water conditions (such as those containing organic matter, microorganisms, and acid-base fluctuations), prevents dissolution or aggregation, and at the same time enables the slow release of internal crystal nuclei and inducers, prolonging their action time in water, reducing the need for frequent addition of chemicals, and lowering operating costs and manual management intensity.

[0042] Fourth, compared to traditional ion exchange methods, this process does not require large amounts of acid and alkali for resin regeneration, avoiding soil and water pollution caused by acid and alkali wastewater discharge, reducing environmental pressure, and simultaneously reducing the costs of chemical reagent procurement, storage, and wastewater treatment. Compared to lime softening, it does not significantly increase the pH value of the water, eliminates the need for additional complex neutralization steps, reduces chemical reagent consumption and precipitate generation, and lowers the difficulty and cost of subsequent sludge treatment. This aligns with the environmental protection concept of sustainable development and offers significant advantages in water resource protection and ecological maintenance.

[0043] Fifth, activated carbon filter columns, as a key step in subsequent purification, utilize the well-developed pore structure of activated carbon with a packing density of 0.8 - 1.2 g / cm³ and a particle size of 0.5 - 2.0 mm to efficiently adsorb dissolved organic matter, residual chlorine, and other impurities in the water. On the basis of hardness removal, they further purify the water quality, remove odors and colors, and improve the sensory quality of the water, meeting the needs of drinking water, food processing, and other fields with high requirements for water purity.

[0044] The ultraviolet disinfection device uses 254nm wavelength ultraviolet light to precisely destroy the DNA structure of microorganisms in a water layer of 1-3cm thickness, inactivating pathogens such as bacteria and viruses, ensuring the safety of microorganisms in the effluent, eliminating the risk of waterborne diseases, and comprehensively ensuring that the treated water quality meets high standards. It can be directly applied to a variety of scenarios with stringent water quality requirements. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0046] Example 1: Step 1: Preparation of silanized hydroxyapatite nuclei

[0047] Accurately weigh 100g of nano hydroxyapatite and slowly add it to 2500g of deionized water. Place the mixture in an ultrasonic disperser and ultrasonically disperse it for 30 minutes at 400W power to ensure uniform dispersion of the nano hydroxyapatite.

[0048] Add 50g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirrer, and stir and mix continuously for 3h at 30°C and a stirring speed of 300rpm.

[0049] After the reaction was completed, the mixture was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min, and the supernatant was discarded. The precipitate was washed three times with anhydrous ethanol, 500 mL each time. The washed precipitate was then placed in a vacuum drying oven and vacuum dried at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite nuclei.

[0050] Step 2: Preparation of composite inducer

[0051] Weigh 100g of sodium polyacrylate and add it to 3000g of ethylene glycol solution. Use an ultrasonic disperser to ultrasonically disperse the solution at 350W for 40 minutes until it is uniformly dispersed.

[0052] Next, add 80g of aluminum sulfate and 3g of sodium dodecyl sulfonate, transfer the mixture to a four-necked flask equipped with a reflux condenser and a magnetic stirrer, heat to 80°C, and react for 4 hours at a stirring rate of 400 rpm.

[0053] After the reaction was complete, the mixture was filtered while hot using a Buchner funnel. The filter cake was washed four times with 600 mL of deionized water each time, and then placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.08 MPa for 6 hours to obtain the composite inducer.

[0054] Step 3: Preparation of nuclei for loading inducing agents

[0055] Accurately weigh the silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer (pH = 7.0) at a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite nuclei and composite inducer to the phosphate buffer, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 minutes at 500W.

[0056] The pH of the mixture was then adjusted to 8.5 with 1 mol / L sodium hydroxide solution, and the mixture was transferred to a constant temperature water bath and stirred at 50°C and 350 rpm for 2 hours.

[0057] After the reaction was completed, the mixture was centrifuged at 9000 rpm for 20 min. The precipitate was washed three times with 400 mL of deionized water each time, and then dried under vacuum at 65 °C and -0.09 MPa for 12 h to obtain crystal nuclei loaded with the inducing agent.

[0058] Step 4: Preparation of primary granulation product

[0059] Weigh the nucleus particles of the loading inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to a mass ratio of 100:15:20:5. Add the nucleus particles of the loading inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water and ultrasonically disperse them evenly (ultrasonic power 450W, time 25min). Then, add polyethylene glycol-6000 while stirring at a speed of 400rpm and heat to 40℃.

[0060] Maintain the temperature and stirring for 1 hour. After the precipitate is formed, centrifuge at 10,000 rpm for 10 minutes, discard the supernatant, and obtain the primary granulation product.

[0061] Step 5: Preparation of surface-coated nucleus granules

[0062] Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane and transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser. Stir and mix at 60℃ and a stirring speed of 300rpm for 5h.

[0063] After the reaction was completed, the mixture was filtered using a vacuum filtration device. The filter cake was washed three times with 500 mL of anhydrous ethanol each time, and then dried in a vacuum drying oven at 70℃ and a vacuum degree of -0.09 MPa for 8 hours to obtain surface-coated nucleus granules.

[0064] Step Six: Preparation of Strengthening Hardening Agent

[0065] Weigh the surface-coated crystal nuclei, cationic polyacrylamide, and nano zinc oxide in a mass ratio of 100:8:2, mix them in an appropriate amount of deionized water, and then ultrasonically disperse them (ultrasonic power 550W, time 15min). Adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0066] After adjustment, place the mixture in a constant temperature incubator and let it stand at 25°C for 12 hours to obtain the hardening agent.

[0067] Step 7: Treat the water to be treated

[0068] Measure 5000L of water to be treated (hardness is 300mg / L based on calcium carbonate) and input it into the reaction tank. Add 1kg of hardening agent to the tank, turn on the stirring device, control the stirring speed at 200rpm, react at 15℃ for 0.5h, then stop stirring and let it stand for 1h to settle.

[0069] After sedimentation, the supernatant is separated using the siphon principle.

[0070] Step 8: Filter out residual impurities

[0071] The separated supernatant was passed through an activated carbon filter column (packing density of 0.8 g / cm³, activated carbon particle size of 0.5 mm) at a flow rate of 0.5 L / min to adsorb residual impurities.

[0072] Step Nine: Ultraviolet Disinfection

[0073] The adsorbed water was passed through a UV disinfection device with a wavelength of 254nm, the irradiation intensity was controlled at 10mW / cm², the water layer thickness was 1cm, and the treatment time was 5min.

[0074] Step 10: Collect the final effluent. After testing, the hardness of the final effluent is reduced to below 30 mg / L, which meets the hardness requirements for general domestic water, thus completing the integrated hardness removal treatment.

[0075] Example 2: Step 1: Preparation of silanized hydroxyapatite nuclei

[0076] Weigh 100g of nano-hydroxyapatite and add it to 3000g of deionized water, then ultrasonically disperse it (450W, 35min). Add 55g of γ-glycidoxypropyltrimethoxysilane and react at 35℃ and 320rpm for 4h.

[0077] Subsequent centrifugation (8500 rpm, 18 min), washing (anhydrous ethanol, 3 times, 550 mL each time), and vacuum drying (70 °C, vacuum degree -0.09 MPa, 10 h) were performed in the same manner as in Example 1 to obtain silanized hydroxyapatite crystal nuclei.

[0078] Step 2: Preparation of composite inducer

[0079] Disperse 100g of sodium polyacrylate in 3500g of ethylene glycol solution (ultrasonic power 380W, 45min), add 100g of aluminum sulfate and 5g of sodium dodecyl sulfonate, heat to 85℃, and react for 6h at a stirring rate of 420rpm.

[0080] The filtration, washing (with deionized water, 4 times, 650 mL each time), and drying (60°C, vacuum -0.08 MPa, 6 h) steps were the same as in Example 1 to obtain the composite inducer. Step 3: Preparation of crystal nuclei loaded with the inducer.

[0081] Weigh the raw materials at a mass ratio of 100:60:6000, disperse them ultrasonically (520W, 25min), adjust the pH to 9.0 (using 1mol / L sodium hydroxide solution), and react at 60℃ and a stirring speed of 380rpm for 3h.

[0082] The centrifugation (9500 rpm, 22 min), washing (deionized water, 3 times, 450 mL each time), and drying (65 °C, vacuum degree -0.09 MPa, 12 h) were performed as in Example 1 to obtain crystal nuclei loaded with the inducer.

[0083] Step 4: Preparation of primary granulation product

[0084] Weigh each component according to a mass ratio of 100:20:25:8, disperse ultrasonically (480W, 30min), heat to 45℃, add polyethylene glycol-6000 and react at a stirring rate of 420rpm for 2h, centrifuge (10000rpm, 12min) to obtain the primary granulation product.

[0085] Step 5: Preparation of surface-coated nucleus granules

[0086] Take 100g of the primary granulation product and mix it with 2200g of ethanol solution and 40g of tetraethoxysilane. React at 65℃ and 320rpm for 6h.

[0087] The same procedures as in Example 1 were followed for filtration, washing (3 times with anhydrous ethanol, 550 mL each time), and drying (70°C, vacuum degree -0.09 MPa, 8 h) to obtain surface-coated nucleus granules.

[0088] Step Six: Preparation of Strengthening Hardening Agent

[0089] Weigh the raw materials at a mass ratio of 100:12:3, disperse them ultrasonically (580W, 20min), adjust the pH to 6.5 (using 0.1mol / L hydrochloric acid solution), and let them stand and mature at 30℃ for 18h to obtain the hardening agent.

[0090] Step 7: Treat the water to be treated

[0091] Take 7500L of water to be treated (hardness is 350mg / L based on calcium carbonate), add 1.5kg of hardening agent, stir at 250rpm, react at 18℃ for 1h, let stand to precipitate for 2h, and siphon the supernatant.

[0092] Step 8: Filter out residual impurities

[0093] The supernatant was passed through an activated carbon filter column (packing density 1.0 g / cm³, activated carbon particle size 1.0 mm) at a flow rate of 1.0 L / min.

[0094] Step Nine: Ultraviolet Disinfection

[0095] The ultraviolet disinfection device (wavelength 254nm, irradiation intensity 20mW / cm², water layer thickness 2cm) was introduced, and the treatment time was 10min.

[0096] Step 10: Collect the final effluent. The hardness of the final effluent is found to be reduced to below 25 mg / L, completing the integrated hardness removal treatment.

[0097] Example 3: Step 1: Preparation of silanized hydroxyapatite nuclei

[0098] Take 100g of nano-hydroxyapatite and 3500g of deionized water and ultrasonically disperse (power 500W, 40min). Add 60g of γ-glycidyl etheroxypropyltrimethoxysilane and react at 38℃ and stirring speed 350rpm for 5h.

[0099] The silanized hydroxyapatite nuclei were obtained by centrifugation (9000 rpm, 20 min), washing (3 times with anhydrous ethanol, 600 mL each time), and vacuum drying (70 °C, vacuum degree -0.09 MPa, 10 h).

[0100] Step 2: Preparation of composite inducer

[0101] 100g of sodium polyacrylate was ultrasonically dispersed in 4000g of ethylene glycol solution (400W, 50min), 110g of aluminum sulfate and 6g of sodium dodecyl sulfonate were added, the temperature was raised to 90℃, and the reaction was carried out at a stirring rate of 450rpm for 7h.

[0102] The composite inducer was obtained by filtration, washing (with deionized water, 4 times, 700 mL each time), and drying (60℃, vacuum degree -0.08MPa, 6h).

[0103] Step 3: Preparation of nuclei for loading inducing agents

[0104] Weigh the ingredients in a mass ratio of 100:70:6500, disperse them ultrasonically (550W, 30min), adjust the pH to 9.2 (1mol / L sodium hydroxide), and react at 65℃ and 400rpm for 3.5h.

[0105] Centrifugation (10000 rpm, 25 min), washing (deionized water, 3 times, 500 mL each time), and drying (65℃, vacuum degree -0.09 MPa, 12 h) yielded crystal nuclei loaded with the inducing agent.

[0106] Step 4: Preparation of primary granulation product

[0107] Weigh the product according to a mass ratio of 100:22:30:9, disperse it ultrasonically (500W, 35min), heat it to 50℃, add polyethylene glycol-6000, react it at a stirring speed of 450rpm for 2.5h, and centrifuge it (11000rpm, 15min) to obtain the primary granulated product.

[0108] Step 5: Preparation of surface-coated nucleus granules

[0109] 100g of primary granulation product was mixed with 2500g of ethanol solution and 45g of tetraethoxysilane, and reacted at 68℃ and a stirring rate of 350rpm for 7h.

[0110] The surface-coated nucleus granules were obtained by filtration, washing (3 times with anhydrous ethanol, 600 mL each time), and drying (70℃, vacuum degree -0.09MPa, 8h).

[0111] Step Six: Preparation of Strengthening Hardening Agent

[0112] Weigh the sample according to a mass ratio of 100:14:4, disperse it ultrasonically (600W, 25min), adjust the pH to 6.8 (0.1mol / L hydrochloric acid), and let it stand at 32℃ for 20h to obtain the hardening agent.

[0113] Step 7: Treat the water to be treated

[0114] Take 10,000 L of water to be treated (hardness is 400 mg / L based on calcium carbonate), add 2 kg of hardening agent, stir at 300 rpm, react at 22℃ for 1.5 h, let stand to precipitate for 2.5 h, and siphon the supernatant.

[0115] Step 8: Filter out residual impurities

[0116] The supernatant was passed through an activated carbon filter column (packing density 1.1 g / cm³, activated carbon particle size 1.5 mm) at a flow rate of 1.5 L / min.

[0117] Step Nine: Ultraviolet Disinfection

[0118] The ultraviolet disinfection device (wavelength 254nm, irradiation intensity 25mW / cm², water layer thickness 2.5cm) was introduced, and the treatment time was 12min.

[0119] Step 10: Collect the final effluent. If the hardness of the final effluent is found to be below 20 mg / L, the integrated hardness removal treatment is complete.

[0120] Example 4: Step 1: Preparation of silanized hydroxyapatite nuclei

[0121] Weigh 100g of nano-hydroxyapatite and place it in 4000g of deionized water. Disperse the mixture by ultrasonication (550W, 45min). Add 65g of γ-glycidyl etheroxypropyltrimethoxysilane and react at 40℃ and 380rpm for 6h.

[0122] Centrifugation (9500 rpm, 22 min), washing (anhydrous ethanol, 3 times, 650 mL each time), and vacuum drying (70℃, vacuum degree -0.09 MPa, 10 h) yielded silanized hydroxyapatite crystal nuclei.

[0123] Step 2: Preparation of composite inducer

[0124] Take 100g of sodium polyacrylate and add it to 4500g of ethylene glycol solution for ultrasonic dispersion (power 420W, 55min). Add 120g of aluminum sulfate and 8g of sodium dodecyl sulfonate. Heat to 95℃ and react at a stirring rate of 480rpm for 8h.

[0125] The composite inducer was obtained by filtration, washing (with deionized water, 4 times, 750 mL each time), and drying (60℃, vacuum degree -0.08MPa, 6h).

[0126] Step 3: Preparation of nuclei for loading inducing agents

[0127] Weigh the ingredients according to a mass ratio of 100:75:7000, disperse them ultrasonically (580W, 35min), adjust the pH to 9.5 (1mol / L sodium hydroxide), and react at 70℃ and a stirring speed of 420rpm for 4h.

[0128] Centrifugation (10500 rpm, 28 min), washing (deionized water, 3 times, 550 mL each time), and drying (65℃, vacuum degree -0.09 MPa, 12 h) yielded crystal nuclei loaded with the inducing agent.

[0129] Step 4: Preparation of primary granulation product

[0130] Weigh the product according to a mass ratio of 100:25:35:10, disperse it ultrasonically (520W, 40min), heat it to 55℃, add polyethylene glycol-6000, react it at a stirring speed of 480rpm for 3h, and centrifuge it (12000rpm, 18min) to obtain the primary granulated product.

[0131] Step 5: Preparation of surface-coated nucleus granules

[0132] 100g of primary granulation product was mixed with 3000g of ethanol solution and 50g of tetraethoxysilane, and reacted at 75℃ and a stirring rate of 380rpm for 8h.

[0133] The surface-coated crystalline nuclei were obtained by filtration, washing (with anhydrous ethanol, 3 times, 700 mL each time), and drying (70℃, vacuum degree -0.09MPa, 8h).

[0134] Step Six: Preparation of Strengthening Hardening Agent

[0135] Weigh the sample according to a mass ratio of 100:15:5, disperse it ultrasonically (620W, 30min), adjust the pH to 7.0 (0.1mol / L hydrochloric acid), and let it stand at 35℃ for 24h to obtain the hardening agent.

[0136] Step 7: Treat the water to be treated

[0137] Take 12000L of water to be treated (hardness is 450mg / L based on calcium carbonate), add 2.4kg of hardening agent, stir at 350rpm, react at 25℃ for 2h, let stand to precipitate for 3h, and siphon the supernatant.

[0138] Step 8: Filter out residual impurities

[0139] The supernatant was passed through an activated carbon filter column (packing density 1.2 g / cm³, activated carbon particle size 2.0 mm) at a flow rate of 2.0 L / min.

[0140] Step Nine: Ultraviolet Disinfection

[0141] The ultraviolet disinfection device (wavelength 254nm, irradiation intensity 30mW / cm², water layer thickness 3cm) was introduced, and the treatment time was 15min.

[0142] Step 10: Collect the final effluent. The hardness of the final effluent is found to be reduced to below 15 mg / L, completing the integrated hardness removal treatment.

[0143] Comparative Example 1: Silanization modification step omitted. Step 1: Preparation of hydroxyapatite nuclei (without silanization).

[0144] Weigh 100g of nano hydroxyapatite and add it to 2500g of deionized water. Disperse the mixture by ultrasonication (400W, 30min) to obtain a hydroxyapatite dispersion for later use.

[0145] Step 2: Preparation of composite inducer

[0146] The same procedure as step two in Example 1 was followed, namely, weighing 100g of sodium polyacrylate and adding it to 3000g of ethylene glycol solution, ultrasonically dispersing it (power 350W, 40min) until it was uniformly dispersed, then adding 80g of aluminum sulfate and 3g of sodium dodecyl sulfonate, transferring the mixture to a four-necked flask equipped with a reflux condenser and a magnetic stirrer, heating it to 80°C, and reacting it for 4h at a stirring rate of 400rpm.

[0147] After the reaction was complete, the mixture was filtered while hot using a Buchner funnel. The filter cake was washed four times with 600 mL of deionized water each time, and then placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.08 MPa for 6 hours to obtain the composite inducer.

[0148] Step 3: Preparation of nuclei for loading inducing agents

[0149] The prepared hydroxyapatite dispersion and the composite inducer were added directly to phosphate buffer (5000g, pH = 7.0) at a mass ratio of 100:45 (assuming that the nano hydroxyapatite in the hydroxyapatite dispersion is 100g). After ultrasonic dispersion (500W, 20min), the pH of the mixture was adjusted to 8.5 with 1mol / L sodium hydroxide solution. The mixture was then transferred to a constant temperature water bath and stirred at 50℃ and 350rpm for 2h.

[0150] After the reaction was completed, the mixture was centrifuged at 9000 rpm for 20 min. The precipitate was washed three times with 400 mL of deionized water each time, and then dried under vacuum at 65 °C and -0.09 MPa for 12 h to obtain crystal nuclei loaded with the inducing agent.

[0151] Step 4: Preparation of primary granulation product

[0152] Weigh the nucleus particles of the loading inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to a mass ratio of 100:15:20:5. Add the nucleus particles of the loading inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water and ultrasonically disperse them evenly (ultrasonic power 450W, 25min). Then, add polyethylene glycol-6000 while stirring at 400rpm and heat to 40℃.

[0153] Maintain the temperature and stirring for 1 hour. After the precipitate is formed, centrifuge at 10,000 rpm for 10 minutes, discard the supernatant, and obtain the primary granulation product.

[0154] Step 5: Preparation of surface-coated nucleus granules

[0155] Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane and transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser. Stir and mix at 60℃ and a stirring speed of 300rpm for 5h.

[0156] After the reaction was completed, the mixture was filtered using a vacuum filtration device. The filter cake was washed three times with 500 mL of anhydrous ethanol each time, and then dried in a vacuum drying oven at 70℃ and a vacuum degree of -0.09 MPa for 8 hours to obtain surface-coated nucleus granules.

[0157] Step Six: Preparation of Strengthening Hardening Agent

[0158] Weigh the surface-coated crystal nuclei, cationic polyacrylamide, and nano zinc oxide in a mass ratio of 100:8:2, mix them in an appropriate amount of deionized water, and then ultrasonically disperse them (ultrasonic power 550W, 15min). Adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0159] After adjustment, place the mixture in a constant temperature incubator and let it stand at 25°C for 12 hours to obtain the hardening agent.

[0160] Step 7: Treat the water to be treated

[0161] Measure 5000L of water to be treated (hardness is 300mg / L based on calcium carbonate) and input it into the reaction tank. Add 1kg of hardening agent to the tank, turn on the stirring device, control the stirring speed at 200rpm, react at 15℃ for 0.5h, then stop stirring and let it stand for 1h to settle.

[0162] After sedimentation, the supernatant is separated using the siphon principle.

[0163] Step 8: Filter out residual impurities

[0164] The separated supernatant was passed through an activated carbon filter column (packing density of 0.8 g / cm³, activated carbon particle size of 0.5 mm) at a flow rate of 0.5 L / min to adsorb residual impurities.

[0165] Step Nine: Ultraviolet Disinfection

[0166] The adsorbed water was passed through a UV disinfection device with a wavelength of 254nm, the irradiation intensity was controlled at 10mW / cm², the water layer thickness was 1cm, and the treatment time was 5min.

[0167] Step 10: Collect the final effluent. The hardness of the final effluent was 80 mg / L. Compared with Example 1, the hardness removal effect was significantly reduced, indicating that silanization modification plays an important role in improving the performance of crystal nuclei.

[0168] Comparative Example 2: Changing the Composite Inducer Formulation Step 1: Preparation of Silanized Hydroxyapatite Crystal Nuclei

[0169] The same procedure as in step one of Example 1 is followed, namely, accurately weighing 100g of nano hydroxyapatite, slowly adding it to 2500g of deionized water, placing it in an ultrasonic disperser, and ultrasonically dispersing it at 400W power for 30 minutes to ensure uniform dispersion of the nano hydroxyapatite.

[0170] Add 50g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirrer, and stir and mix continuously for 3h at 30°C and a stirring speed of 300rpm.

[0171] After the reaction was completed, the mixture was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min, and the supernatant was discarded. The precipitate was washed three times with anhydrous ethanol, 500 mL each time. The washed precipitate was then placed in a vacuum drying oven and vacuum dried at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite nuclei.

[0172] Step 2: Preparation of composite inducers (by modifying the formulation)

[0173] Weigh 100g of sodium polyacrylate and add it to 3000g of ethylene glycol solution. Disperse the solution by ultrasonication (350W, 40min) until it is evenly dispersed.

[0174] Next, 50g of aluminum sulfate and 1g of sodium dodecyl sulfonate were added (the amount of aluminum sulfate and sodium dodecyl sulfonate was reduced compared to Example 1). The mixture was then transferred to a four-necked flask equipped with a reflux condenser and a magnetic stirrer. The temperature was raised to 80°C, and the mixture was reacted for 4 hours at a stirring rate of 400 rpm.

[0175] After the reaction was complete, the mixture was filtered while hot using a Buchner funnel. The filter cake was washed four times with 600 mL of deionized water each time, and then placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.08 MPa for 6 hours to obtain the composite inducer.

[0176] Step 3: Preparation of nuclei for loading inducing agents

[0177] Accurately weigh the silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer (pH = 7.0) at a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite nuclei and composite inducer to the phosphate buffer, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 minutes at 500W.

[0178] The pH of the mixture was then adjusted to 8.5 with 1 mol / L sodium hydroxide solution, and the mixture was transferred to a constant temperature water bath and stirred at 50°C and 350 rpm for 2 hours.

[0179] After the reaction was completed, the mixture was centrifuged at 9000 rpm for 20 min. The precipitate was washed three times with 400 mL of deionized water each time, and then dried under vacuum at 65 °C and -0.09 MPa for 12 h to obtain crystal nuclei loaded with the inducing agent.

[0180] Step 4: Preparation of primary granulation product

[0181] Weigh the nucleus particles of the loading inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to a mass ratio of 100:15:20:5. Add the nucleus particles of the loading inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water and ultrasonically disperse them evenly (ultrasonic power 450W, 25min). Then, add polyethylene glycol-6000 while stirring at 400rpm and heat to 40℃.

[0182] Maintain the temperature and stirring for 1 hour. After the precipitate is formed, centrifuge at 10,000 rpm for 10 minutes, discard the supernatant, and obtain the primary granulation product.

[0183] Step 5: Preparation of surface-coated nucleus granules

[0184] Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane and transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser. Stir and mix at 60℃ and a stirring speed of 300rpm for 5h.

[0185] After the reaction was completed, the mixture was filtered using a vacuum filtration device. The filter cake was washed three times with 500 mL of anhydrous ethanol each time, and then dried in a vacuum drying oven at 70℃ and a vacuum degree of -0.09 MPa for 8 hours to obtain surface-coated nucleus granules.

[0186] Step Six: Preparation of Strengthening Hardening Agent

[0187] Weigh the surface-coated crystal nuclei, cationic polyacrylamide, and nano zinc oxide in a mass ratio of 100:8:2, mix them in an appropriate amount of deionized water, and then ultrasonically disperse them (ultrasonic power 550W, 15min). Adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0188] After adjustment, place the mixture in a constant temperature incubator and let it stand at 25°C for 12 hours to obtain the hardening agent.

[0189] Step 7: Treat the water to be treated

[0190] Measure 5000L of water to be treated (hardness is 300mg / L based on calcium carbonate) and input it into the reaction tank. Add 1kg of hardening agent to the tank, turn on the stirring device, control the stirring speed at 200rpm, react at 15℃ for 0.5h, then stop stirring and let it stand for 1h to settle.

[0191] After sedimentation, the supernatant is separated using the siphon principle.

[0192] Step 8: Filter out residual impurities

[0193] The separated supernatant was passed through an activated carbon filter column (packing density of 0.8 g / cm³, activated carbon particle size of 0.5 mm) at a flow rate of 0.5 L / min to adsorb residual impurities.

[0194] Step Nine: Ultraviolet Disinfection

[0195] The adsorbed water was passed through a UV disinfection device with a wavelength of 254nm, the irradiation intensity was controlled at 10mW / cm², the water layer thickness was 1cm, and the treatment time was 5min.

[0196] Step 10: Collect the final effluent. The hardness of the final effluent was 60 mg / L, which was higher than that in Example 1, indicating that the reasonable formulation of the composite inducer has a significant impact on the hardness removal effect.

[0197] Comparative Example 3: Omitting the surface coating step Step 1: Preparation of silanized hydroxyapatite nuclei

[0198] The same procedure as in step one of Example 1 is followed, namely, accurately weighing 100g of nano hydroxyapatite, slowly adding it to 2500g of deionized water, placing it in an ultrasonic disperser, and ultrasonically dispersing it at 400W power for 30 minutes to ensure uniform dispersion of the nano hydroxyapatite.

[0199] Add 50g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirrer, and stir and mix continuously for 3h at 30°C and a stirring speed of 300rpm.

[0200] After the reaction was completed, the mixture was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min, and the supernatant was discarded. The precipitate was washed three times with anhydrous ethanol, 500 mL each time. The washed precipitate was then placed in a vacuum drying oven and vacuum dried at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite nuclei.

[0201] Step 2: Preparation of composite inducer

[0202] The same procedure as step two in Example 1 is followed, i.e., 100g of sodium polyacrylate is weighed and added to 3000g of ethylene glycol solution, and ultrasonically dispersed (power 350W, 40min) until uniformly dispersed.

[0203] Next, add 80g of aluminum sulfate and 3g of sodium dodecyl sulfonate, transfer the mixture to a four-necked flask equipped with a reflux condenser and a magnetic stirrer, heat to 80°C, and react for 4 hours at a stirring rate of 400 rpm.

[0204] After the reaction was complete, the mixture was filtered while hot using a Buchner funnel. The filter cake was washed four times with 600 mL of deionized water each time, and then placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.08 MPa for 6 hours to obtain the composite inducer.

[0205] Step 3: Preparation of nuclei for loading inducing agents

[0206] Follow the same procedure as step three in Example 1, that is, accurately weigh the silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer (pH = 7.0) at a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite nuclei and composite inducer to the phosphate buffer, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 minutes at 500W.

[0207] The pH of the mixture was then adjusted to 8.5 with 1 mol / L sodium hydroxide solution, and the mixture was transferred to a constant temperature water bath and stirred at 50°C and 350 rpm for 2 hours.

[0208] After the reaction was completed, the mixture was centrifuged at 9000 rpm for 20 min. The precipitate was washed three times with 400 mL of deionized water each time, and then dried under vacuum at 65 °C and -0.09 MPa for 12 h to obtain crystal nuclei loaded with the inducing agent.

[0209] Step 4: Preparation of primary granulation product

[0210] The procedure is the same as step four in Example 1, i.e., weigh the nucleus particles of the loading inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 in a mass ratio of 100:15:20:5. Add the nucleus particles of the loading inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water, and ultrasonically disperse them evenly (ultrasonic power 450W, 25min). Then, add polyethylene glycol-6000 while stirring at 400rpm and heat to 40°C.

[0211] Maintain the temperature and stirring for 1 hour. After the precipitate is formed, centrifuge at 10,000 rpm for 10 minutes, discard the supernatant, and obtain the primary granulation product.

[0212] Step 5: Directly use the primary granulation product in subsequent steps (omitting surface coating).

[0213] The primary granulation product was used as a surface-coated nucleus granule. The primary granulation product, cationic polyacrylamide, and nano zinc oxide were weighed in a mass ratio of 100:8:2. They were mixed into an appropriate amount of deionized water, ultrasonically dispersed (ultrasonic power 550W, 15min), and then the pH was adjusted to 6.0 with 0.1mol / L hydrochloric acid solution.

[0214] After adjustment, place the mixture in a constant temperature incubator and let it stand at 25°C for 12 hours to obtain the hardening agent.

[0215] Step Six: Treat the water to be treated

[0216] Measure 5000L of water to be treated (hardness is 300mg / L based on calcium carbonate) and input it into the reaction tank. Add 1kg of hardening agent to the tank, turn on the stirring device, control the stirring speed at 200rpm, react at 15℃ for 0.5h, then stop stirring and let it stand for 1h to settle.

[0217] After sedimentation, the supernatant is separated using the siphon principle.

[0218] Step 7: Filter out residual impurities

[0219] The separated supernatant was passed through an activated carbon filter column (packing density of 0.8 g / cm³, activated carbon particle size of 0.5 mm) at a flow rate of 0.5 L / min to adsorb residual impurities.

[0220] Step 8: Ultraviolet disinfection

[0221] The adsorbed water was passed through a UV disinfection device with a wavelength of 254nm, the irradiation intensity was controlled at 10mW / cm², the water layer thickness was 1cm, and the treatment time was 5min.

[0222] Step 9: Collect the final effluent. The hardness of the final effluent was 70 mg / L. Compared with Example 1, the hardness of the effluent increased after omitting the surface coating step, indicating that the surface coating has a promoting effect on the stability of the crystal nuclei and the hardness removal effect.

[0223] Comparative Example 4: Changing the reaction temperature and time. Step 1: Preparation of silanized hydroxyapatite nuclei.

[0224] Accurately weigh 100g of nano hydroxyapatite and slowly add it to 2500g of deionized water. Place the mixture in an ultrasonic disperser and ultrasonically disperse it for 30 minutes at 400W power to ensure uniform dispersion of the nano hydroxyapatite.

[0225] Add 50g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirrer, and continue stirring and mixing for 2 hours (below the normal range) at 25°C (below the normal range) and a stirring speed of 300 rpm.

[0226] After the reaction was completed, the mixture was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min, and the supernatant was discarded. The precipitate was washed three times with anhydrous ethanol, 500 mL each time. The washed precipitate was then placed in a vacuum drying oven and vacuum dried at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite nuclei.

[0227] Step 2: Preparation of composite inducer

[0228] Weigh 100g of sodium polyacrylate and add it to 3000g of ethylene glycol solution. Disperse the solution by ultrasonication (350W, 40min) until it is evenly dispersed.

[0229] Next, add 80g of aluminum sulfate and 3g of sodium dodecyl sulfonate, transfer the mixture to a four-necked flask equipped with a reflux condenser and a magnetic stirrer, heat to 75°C (below the normal range), and react for 3 hours at a stirring speed of 400 rpm (below the normal range).

[0230] After the reaction was complete, the mixture was filtered while hot using a Buchner funnel. The filter cake was washed four times with 600 mL of deionized water each time, and then placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.08 MPa for 6 hours to obtain the composite inducer.

[0231] Step 3: Preparation of nuclei for loading inducing agents

[0232] Accurately weigh the silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer (pH = 7.0) at a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite nuclei and composite inducer to the phosphate buffer, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 minutes at 500W.

[0233] The pH of the mixture was then adjusted to 8.5 with 1 mol / L sodium hydroxide solution, and transferred to a constant temperature water bath. The mixture was stirred at 45°C (below the normal range) and a stirring rate of 350 rpm for 1.5 h (below the normal range).

[0234] After the reaction was completed, the mixture was centrifuged at 9000 rpm for 20 min. The precipitate was washed three times with 400 mL of deionized water each time, and then dried under vacuum at 65 °C and -0.09 MPa for 12 h to obtain crystal nuclei loaded with the inducing agent.

[0235] Step 4: Preparation of primary granulation product

[0236] Weigh the nucleus particles of the loading inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to a mass ratio of 100:15:20:5. Add the nucleus particles of the loading inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water and ultrasonically disperse them evenly (ultrasonic power 450W, 25min). Then, under the condition of stirring speed 400rpm, add polyethylene glycol-6000 and heat to 35℃ (below the normal range).

[0237] Maintain the reaction at this temperature and with stirring for 0.5 h (below the normal range). After the precipitate is formed, centrifuge at 10,000 rpm for 10 min, discard the supernatant, and obtain the primary granulation product.

[0238] Step 5: Preparation of surface-coated nucleus granules

[0239] Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane and transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser. Stir and mix at 55℃ (below the normal range) and a stirring speed of 300rpm for 4h (below the normal range).

[0240] After the reaction was completed, the mixture was filtered using a vacuum filtration device. The filter cake was washed three times with 500 mL of anhydrous ethanol each time, and then dried in a vacuum drying oven at 70℃ and a vacuum degree of -0.09 MPa for 8 hours to obtain surface-coated nucleus granules.

[0241] Step Six: Preparation of Strengthening Hardening Agent

[0242] Weigh the surface-coated crystal nuclei, cationic polyacrylamide, and nano zinc oxide in a mass ratio of 100:8:2, mix them until an appropriate amount of water is removed, and then ultrasonically disperse them (ultrasonic power 550W, 15min). Adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0243] After adjustment, place the mixture in a constant temperature incubator and let it stand at 20℃ (below the normal range) for 10 hours (below the normal range) to obtain the hardening agent.

[0244] Step 7: Treat the water to be treated

[0245] Measure 5000L of water to be treated (hardness is 300mg / L based on calcium carbonate) and input it into the reaction tank. Add 1kg of hardening agent to the tank, turn on the stirring device, control the stirring speed at 200rpm, react at 15℃ for 0.5h, then stop stirring and let it stand for 1h to settle.

[0246] After sedimentation, the supernatant is separated using the siphon principle.

[0247] Step 8: Filter out residual impurities

[0248] The separated supernatant was passed through an activated carbon filter column (with a packing density of 0.8 g / cm³ and an activated carbon particle size of 0.5 mm) at a flow rate of 0.5 L / min to adsorb residual impurities.

[0249] Step Nine: Ultraviolet Disinfection

[0250] The adsorbed water was passed through a UV disinfection device with a wavelength of 254nm, the irradiation intensity was controlled at 10mW / cm², the water layer thickness was 1cm, and the treatment time was 5min.

[0251] Step 10: Collect the final effluent. The hardness of the final effluent was 90 mg / L. Compared with Example 1, the hardness removal effect was greatly reduced after changing the reaction temperature and time of the key steps, indicating that suitable reaction conditions are crucial to process performance.

[0252] To more intuitively demonstrate the advantages of the process of this invention, the key parameters and final effluent hardness of Examples 1-4 and Comparative Examples 1-4 are summarized in the following table:

[0253] Table 1: Comparison of Process Steps and Conditions

[0254]

[0255] Table 2: Comparison of treated water volume, chemical dosage, and water quality

[0256]

[0257] As can be clearly seen from the table: In Examples 1-4, as the hardness of the water to be treated increases, by reasonably adjusting the process parameters of each step, such as the raw material addition ratio, reaction temperature, and time, the final effluent hardness can be stably controlled at a low level, meeting the hardness removal requirements under different water quality conditions. Compared with Comparative Example 1, after omitting the silanization modification step, the final effluent hardness increased significantly to 80 mg / L, indicating that silanization modification can significantly improve the performance of crystal nuclei and enhance their synergistic effect with other substances, thereby improving the hardness removal effect. In Comparative Example 2, after changing the composite inducer formulation, the effluent hardness increased to 60 mg / L, indicating that the specific formulation of the composite inducer plays a key role in inducing crystal nucleus growth and promoting the hardness removal reaction; an inappropriate formulation will weaken the overall process performance. In Comparative Example 3, omitting the surface coating step, the final effluent hardness was 70 mg / L, reflecting that surface coating helps improve the stability of the crystal nucleus granules, reduces their agglomeration or dissolution in subsequent treatment processes, and thus ensures the hardness removal effect. Comparative Example 4 showed that by changing the reaction temperature and time, the final effluent hardness reached 90 mg / L, highlighting the necessity of strictly adhering to appropriate reaction conditions to ensure effective process operation and achieve efficient hardness removal.

[0258] In addition, to further explore the influence of each factor on the hardening effect, a one-way ANOVA was conducted, and the results are shown in the table below:

[0259] Table 3: Analysis of Variance Table of Each Factor on Hardening Effect

[0260]

[0261] Analysis of variance results show that silanization modification and reaction conditions have a highly significant impact on hardness removal efficiency. This means that even small changes in these two factors can cause significant fluctuations in the final effluent hardness, requiring strict control in actual process operation. The formulation of the composite inducer and surface coating also have a significant impact on hardness removal efficiency, although slightly less than the former two, but still considerable. Reasonable optimization of these factors can further improve the hardness removal performance of the process.

[0262] In summary, the integrated water treatment process for hardness removal induced by crystal nucleation granulation of the present invention, through the meticulous design and synergistic cooperation of each step, including specific raw material pretreatment, crystal nucleus preparation, inducer synthesis, granulation, coating, and subsequent treatment, can efficiently remove hardness from water. Furthermore, experimental comparisons have verified the indispensability of each key step and factor, providing a reliable and innovative solution for practical water treatment engineering.

[0263] The above examples demonstrate that employing low-temperature pulverization, inert gas protection, double-layer coating, and specific drying conditions can significantly improve enzyme activity retention and product stability. Deviations from any process parameter in the comparative examples resulted in a decrease in key quality indicators, verifying the necessity and synergistic effect of the process parameters in this invention.

[0264] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. An integrated water treatment process for hardness removal induced by crystal nucleation and granulation, characterized in that, Includes the following steps: Step 1: Disperse nano-hydroxyapatite in deionized water by ultrasonication. After uniform dispersion, add γ-glycidyl etheroxypropyltrimethoxysilane, stir and mix, and react at 30-40℃ for 3-6 hours. After the reaction is completed, centrifuge, wash, and vacuum dry at 70℃ for 10 hours to obtain silanized hydroxyapatite crystal nuclei. Step 2: Disperse sodium polyacrylate in ethylene glycol solution by ultrasonication. After uniform dispersion, add aluminum sulfate and sodium dodecyl sulfonate, stir and mix, heat to 80-95℃, react for 4-8 hours. After the reaction is completed, filter, wash, and vacuum dry at 60℃ for 6 hours to obtain composite inducer. Step 3: Add silanized hydroxyapatite nuclei and composite inducer to phosphate buffer in a certain proportion, disperse by ultrasonication, adjust pH to 8.5-9.5, stir and react at 50-70℃ for 2-4 hours. After the reaction is completed, centrifuge, wash, and vacuum dry at 65℃ for 12 hours to obtain nuclei loaded with inducer. Step 4: Mix the crystal nuclei particles loaded with the inducer with calcium chloride and sodium carbonate in deionized water in a certain proportion. After ultrasonic dispersion, add polyethylene glycol-6000 under stirring, heat to 40-55℃, react for 1-3 hours, and centrifuge to separate the precipitate to obtain the primary granulation product. Step 5: Disperse the primary granulation product into an ethanol solution, add tetraethoxysilane, stir and mix, and react at 60-75℃ for 5-8 hours. After the reaction is completed, filter, wash, and vacuum dry at 70℃ for 8 hours to obtain surface-coated nucleus granules. Step 6: Mix the surface-coated crystal nuclei with cationic polyacrylamide and nano zinc oxide in deionized water in a certain proportion, disperse by ultrasonication, adjust the pH to 6.0-7.0, and let it stand at 25-35℃ for 12-24 hours to obtain the enhanced hardening agent. Step 7: Input the water to be treated into the reaction tank, add the hardening agent, control the stirring rate, react at 15-30℃ for 0.5-2 hours, then let it stand to settle for 1-3 hours, and separate the supernatant. Step 8: Pass the separated supernatant through an activated carbon filter column, controlling the flow rate at 0.5-2.0 L / min, to adsorb residual impurities; Step 9: Pass the adsorbed water into the ultraviolet disinfection device, control the irradiation intensity to be 10-30mW / cm², and the treatment time to be 5-15min. Step 10: Collect the final effluent to complete the integrated hardness removal treatment.

2. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step one, the mass ratio of nano-hydroxyapatite, deionized water, and γ-glycidyl etheroxypropyltrimethoxysilane is 100:2500-4000:50-65.

3. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step two, the mass ratio of sodium polyacrylate, ethylene glycol solution, aluminum sulfate, and sodium dodecyl sulfonate is 100:3000-4500:80-120:3-8.

4. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step three, the mass ratio of silanized hydroxyapatite nuclei, composite inducer, and phosphate buffer is 100:45-75:5000-7000.

5. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step four, the mass ratio of the nucleus particles loaded with the inducing agent, calcium chloride, sodium carbonate, and polyethylene glycol-6000 is 100:15-25:20-35:5-10.

6. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step five, the mass ratio of the primary granulation product, ethanol solution, and tetraethoxysilane is 100:1800-3000:30-50.

7. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step six, the mass ratio of the surface-coated nucleus granules, cationic polyacrylamide, and nano zinc oxide is 100:8-15:2-5.

8. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step seven, the mass ratio of the hardening agent to the water to be treated is 1:5000-10000.

9. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step eight, the packing density of the activated carbon filter column is 0.8-1.2 g / cm³, and the particle size of the activated carbon is 0.5-2.0 mm.

10. The integrated water treatment process for hardness removal induced by crystal nucleation granulation according to claim 1, characterized in that, In step nine, the wavelength of the ultraviolet disinfection device is 254nm, and the thickness of the water layer is 1-3cm.

Images