Integrated water treatment process for inducing hardness removal through crystal nucleus granulation

Abstract

The invention relates to the technical field of water treatment, and particularly discloses a crystal nucleus granulation induced hardness removal integrated water treatment process which comprises the following steps: firstly, ultrasonically dispersing nano-hydroxyapatite in deionized water, adding gamma-glycidoxypropyltrimethoxysilane for reaction, and treating to obtain a silanized hydroxyapatite crystal nucleus; the sodium polyacrylate reacts with aluminum sulfate and the like in an ethylene glycol solution to prepare the composite inducer. The preparation method comprises the following steps: reacting the two components in a phosphate buffer solution in proportion to obtain inducer-loaded crystal nucleus particles, carrying out multi-step reaction and treatment on the inducer-loaded crystal nucleus particles with calcium chloride and the like to obtain surface-coated crystal nucleus granulation bodies, and mixing the surface-coated crystal nucleus granulation bodies with cationic polyacrylamide and nano-zinc oxide to prepare the reinforced hardness removal agent. When to-be-treated water is treated, the reinforced hardness removal agent is added, stirring and precipitation are performed, supernate sequentially passes through the activated carbon filter column to adsorb impurities and is sterilized by the ultraviolet disinfection device, and finally effluent is collected, so that the hardness in the water can be efficiently removed, the process integration level is high, and the effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to an integrated water treatment process for inducing hardness removal by crystal nucleation granulation. Background Art

[0002] The hardness of water is an important indicator to measure the content of calcium, magnesium and other ions in water. Hard water will cause many problems in daily life and industrial production. In terms of domestic water, scale is easily formed when hard water is heated, adhering to the inner walls of heating equipment such as kettles and water heaters. This not only reduces the heat transfer efficiency, increases energy consumption, but also may cause equipment damage and shorten the service life in the long term. Washing clothes with hard water will greatly reduce the decontamination effect of detergents, make the clothing fibers hard, and affect the wearing comfort. When taking a bath, hard water may combine with soap to produce insoluble precipitates, adhering to the skin surface, resulting in discomfort such as dry and itchy skin.

[0003] In the industrial field, the harm of hard water is more significant. For the textile and dyeing industry, calcium and magnesium ions in hard water will combine with dyes, causing quality problems such as uneven dyeing and dull color, reducing the added value of products. In the paper industry, hard water will interfere with the sizing process of paper, affecting performance indicators such as the strength and smoothness of paper. In industries with strict water quality requirements such as chemical production and pharmaceuticals, impurity ions in hard water may cause serious consequences such as an increase in chemical reaction by-products and unstable drug quality, and even lead to the interruption of the production process, resulting in huge economic losses.

[0004] Traditional water softening methods mainly include ion exchange method, lime softening method, etc. The ion exchange method uses ion exchange resin to carry out an exchange reaction with calcium and magnesium ions in water to remove hardness. This method has a good softening effect, but the resin regeneration process is complex and requires a large amount of chemical agents such as acids and alkalis. It is not only costly, but also the discharge of acid-base waste liquid is easy to cause environmental pollution. The lime softening method is to add lime to water to convert calcium bicarbonate and magnesium bicarbonate in water into calcium carbonate and magnesium carbonate precipitates to remove hardness. However, this method will greatly increase the pH value of water, and subsequent additional neutralization treatment steps are often required. The operation is cumbersome, and the generated precipitates are large in quantity and difficult to handle.

[0005] With the continuous development of material science and water treatment technology, new water treatment processes have emerged. In recent years, water treatment technologies based on the principle of crystal nucleus-induced precipitation have gradually received attention. Its core lies in using specific crystal nucleus substances to provide crystal growth sites for calcium and magnesium ions in water, promoting them to precipitate in the form of crystals, so as to achieve the purpose of reducing water hardness. Compared with traditional methods, this technology has potential advantages such as mild reaction conditions, no need for a large amount of chemical agent regeneration, and environmental friendliness.

[0006] In the selection of crystal nucleus materials, hydroxyapatite has a strong adsorption affinity for calcium and magnesium ions due to its unique crystal structure and surface properties, making it a very potential candidate for crystal nucleus. Nano-scale hydroxyapatite has a larger specific surface area and can provide more active sites, which can theoretically enhance the adsorption and precipitation-inducing ability of hardness ions. However, pure nano-hydroxyapatite has some limitations in practical applications, such as easy agglomeration of particles, resulting in a reduction in effective active sites, poor dispersion stability in water, and difficulty in fully exerting its crystal nucleus function.

[0007] In order to solve the dispersion problem of nano-hydroxyapatite, surface modification has become a research hotspot. As a commonly used surface modifier, silane coupling agent can introduce organic functional groups on the surface of nano-hydroxyapatite, improve its compatibility with aqueous media, inhibit particle agglomeration, and may also enhance its synergistic effect with subsequent added substances. For example, the epoxy group in the molecular structure of γ-glycidyloxypropyltrimethoxysilane can react chemically with the hydroxyl group on the surface of hydroxyapatite to form a stable chemical bond, while the trimethoxysilane group at the other end can form a hydrogen bond with water after hydrolysis, thereby giving the modified hydroxyapatite good dispersibility and stability.

[0008] In the process of nucleus induction and hardness removal, the inducer plays a key catalytic and regulatory role. The composite inducer can optimize the nucleus growth environment and accelerate the crystallization and precipitation process of hardness ions through the synergistic combination of multiple components. Based on sodium polyacrylate, the composite inducer composed of aluminum sulfate, sodium dodecyl sulfate, etc., sodium polyacrylate has strong dispersing and chelating ability, which can keep the hardness ions in the water in a dispersed state and prevent premature precipitation; aluminum ions produced by the hydrolysis of aluminum sulfate can form complexes with hydroxyl groups to further promote the formation and growth of nuclei; sodium dodecyl sulfate, as a surfactant, can reduce surface tension, which is beneficial to the dispersion and mass transfer of substances and improves the induction efficiency.

[0009] In order to further enhance the synergistic effect of the crystal nucleus and the inducer, and to enhance the stability and sustainability of the entire system during water treatment, the subsequent granulation and coating process steps are crucial. Through the granulation process, the crystal nucleus particles loaded with the inducer are agglomerated and formed, so that they have better fluidity and operability in water, while reducing the risk of loss due to too small particles. The surface coating uses substances such as tetraethoxysilane to form a protective film on the surface of the crystal nucleus granulation body. On the one hand, it can further enhance the stability of the particles and prevent them from dissolving or agglomerating in complex water quality environments. On the other hand, it can also have a sustained release effect on the internal crystal nucleus and inducer, prolonging their effective action time. In addition, considering the comprehensive requirements for water quality in practical applications, it is necessary not only to achieve efficient hardness removal, but also to remove residual organic impurities, microorganisms and other pollutants in the water. The activated carbon filter column, with its developed pore structure, has a good adsorption capacity for dissolved organic matter, residual chlorine, etc. in the water, and can be used as a subsequent purification step to effectively ensure the purity of the water quality; the ultraviolet disinfection device uses ultraviolet rays 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] At present, a variety of technologies and methods have been developed for the hardness removal of water. Among them, the crystallization granulation fluidized bed technology, as a relatively advanced means, has attracted much attention. It uses the principle of heterogeneous crystallization and adds suitable seed particles to promote the rapid nucleation and crystallization of hardness ions in the liquid phase at the crystal phase interface, thereby achieving efficient removal of target ions. For example, in the invention patent with the Chinese patent authorization announcement number CN105502692A, a chemical crystallization circulating granulation fluidized bed water treatment device is disclosed. The device sets multiple areas such as water distribution area, drug distribution area, granulation area and clear water area in the cylinder, so that the seeds circulate between the fluidization area, separation area and static sedimentation area, and the ions in the water realize chemical crystallization circulation granulation during the flow process. However, this technology has some defects. It is difficult for small particles on the top to enter the static settling area before they grow to the upper edge of the inner tube. When the small particles on the top can cross the upper edge of the inner tube, the large particles on the bottom are already large, and it is difficult for small particles to enter the bottom to form an effective circulation. At the same time, because the water flow direction in the static settling area and the water flow direction in the fluidizing area are both upward, and the rising flow rate in the static settling area is lower than the rising flow rate in the fluidizing area, the particles are easy to accumulate, and the reagent reacts between the accumulated particles, causing the particles to agglomerate, affecting the operation of the equipment and the hardness removal effect.

[0011] For another example, the invention patent application with the Chinese patent application publication number CN115304140A discloses an induced crystallization granulation fluidized bed soft water treatment device. By setting a partition to separate the water distribution area and the medicine distribution area, and a mixing nozzle is arranged on the partition, the medicine output by the medicine dispenser, the water in the water distribution area, and the crystal seeds added through the crystal seed inlet flow into the mixing nozzle inlet, and are ejected vertically upward from the outlet, and sink to the bottom along the inner wall of the tank body, forming a circulating flow in the tank body. However, the mixing nozzle of this scheme cannot spray the mixed liquid without dead angles of 360°, and in the dead angle area of the cylinder body, the water and medicine flows will collide with each other and flow to the nearby water distribution and medicine distribution devices, resulting in scaling of the water distributor and the medicine dispenser, affecting the uniformity of water distribution and medicine distribution, and further affecting the water quality of the effluent and the utilization rate of the medicine. Moreover, the magnesium hydroxide generated by the reaction is in a flocculent state, and the precipitation speed is slow. After adding a flocculant, it coagulates into large masses and precipitates slowly, requiring larger reactors, separators, and sedimentation tanks, resulting in complex equipment and large floor area.

[0012] Some existing technologies also focus on the optimization of crystal seeds. For example, Chinese Patent CN115159765A provides a magnetic induced crystal material, its preparation method and its application in the water treatment process for removing hardness and turbidity. This process prepares ferrite-type composite metal oxide loaded with scale-forming salt micro-particles as the induced crystal material, and disperses it into the precipitation reaction system under alkaline conditions for induced crystallization and hardness removal reaction. Although this magnetic crystal seed can accelerate the precipitation crystallization and material recovery rate, under the interference of the magnetic field, the magnetic materials are prone to attract and combine with each other, generating larger particles or agglomerates, which is not conducive to the fluidization reaction effect and will also cause scaling problems, increasing the maintenance cost of the reactor. Summary of the Invention

[0013] (I) Technical problems to be solved In view of the deficiencies of the prior art, the present invention provides an integrated water treatment process for induced hardening removal by crystal nucleus granulation, which solves the problems raised in the above background technology.

[0014] (II) Technical solutions To achieve the above object, the present invention discloses an integrated water treatment process for induced hardening removal by crystal nucleus granulation, including the following steps: Step 1: Ultrasonically disperse nano-hydroxyapatite in deionized water. After uniform dispersion, add γ-glycidoxypropyltrimethoxysilane, stir and mix, react at 30 - 40 °C for 3 - 6 h. After the reaction ends, centrifuge, wash, and vacuum dry at 70 °C for 10 h to obtain silanized hydroxyapatite crystal nuclei; Step 2: Ultrasonically disperse sodium polyacrylate in an ethylene glycol solution. After uniform dispersion, add aluminum sulfate and sodium dodecyl sulfonate, stir and mix, heat up to 80 - 95 °C, react for 4 - 8 h. After the reaction ends, filter, wash, and vacuum dry at 60 °C for 6 h to obtain a composite inducer; Step 3: Add the silanized hydroxyapatite crystal nuclei and the composite inducer into the phosphate buffer solution according to a certain proportion. After ultrasonic dispersion, adjust the pH to 8.5 - 9.5, and stir and react at 50 - 70 °C for 2 - 4 h. After the reaction, centrifuge, wash, and vacuum dry at 65 °C for 12 h to obtain the crystal nucleus particles loaded with the inducer; Step 4: Mix the crystal nucleus particles loaded with the inducer, calcium chloride, and sodium carbonate into deionized water according to a certain proportion. After ultrasonic dispersion, add polyethylene glycol - 6000 under stirring conditions, heat up to 40 - 55 °C, and react for 1 - 3 h. After forming a precipitate, centrifuge and separate 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 °C for 5 - 8 h. After the reaction, filter by suction, wash, and vacuum dry at 70 °C for 8 h to obtain the crystal nucleus granule body with a surface coating; Step 6: Mix the crystal nucleus granule body with a surface coating, cationic polyacrylamide, and nano - zinc oxide into deionized water according to a certain proportion. After ultrasonic dispersion, adjust the pH to 6.0 - 7.0, and let it stand and cure at 25 - 35 °C for 12 - 24 h to obtain the enhanced hardness removal agent; Step 7: Input the water to be treated into the reaction tank, add the enhanced hardness removal agent, control the stirring rate, and react at 15 - 30 °C for 0.5 - 2 h. Then let it stand and precipitate for 1 - 3 h, and separate the supernatant; Step 8: Pass the separated supernatant through an activated carbon filter column, control the flow rate at 0.5 - 2.0 L / min, and adsorb the residual impurities; Step 9: Pass the adsorbed water into an ultraviolet disinfection device, control the irradiation intensity at 10 - 30 mW / cm², and the treatment time at 5 - 15 min; Step 10: Collect the final effluent to complete the integrated hardness removal treatment.

[0015] Preferably, the mass ratio of nano - hydroxyapatite, deionized water, and γ - glycidoxypropyltrimethoxysilane in Step 1 is 100:2500 - 4000:50 - 65.

[0016] Preferably, the mass ratio of sodium polyacrylate, ethylene glycol solution, aluminum sulfate, and sodium dodecyl sulfonate in Step 2 is 100:3000 - 4500:80 - 120:3 - 8.

[0017] Preferably, the mass ratio of silanized hydroxyapatite crystal nuclei, composite inducer, and phosphate buffer solution in Step 3 is 100:45 - 75:5000 - 7000.

[0018] Preferably, the mass ratio of the crystal nucleus particles of the load inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 in the fourth step is 100:15-25:20-35:5-10.

[0019] Preferably, the mass ratio of the primary granulation product, ethanol solution, and tetraethoxysilane in the fifth step is 100:1800-3000:30-50.

[0020] Preferably, the mass ratio of the surface-coated crystal nucleus granule, cationic polyacrylamide, and nano-zinc oxide in the sixth step is 100:8-15:2-5.

[0021] Preferably, the dosing mass ratio of the hardening removal agent to the water to be treated in the seventh step is 1:5000-10000.

[0022] Preferably, the packing density of the activated carbon filter column in the eighth step is 0.8-1.2 g / cm³, and the particle size of the activated carbon is 0.5-2.0 mm.

[0023] Preferably, the wavelength of the ultraviolet disinfection device in the ninth step is 254 nm, and the water layer thickness is 1-3 cm.

[0024] (III) Beneficial technical effects First, the integrated water treatment process of crystal nucleus granulation-induced hardening removal in the present invention exhibits excellent hardening removal effect. Through the carefully designed steps, from the silanization modification of nano-hydroxyapatite to prepare crystal nuclei, to the synthesis of composite inducers, the preparation of load inducer crystal nucleus particles, granulation, and subsequent series of treatments, each link closely cooperates, and deep hardening removal can be achieved for water to be treated with different hardnesses. In the examples, for the case where the hardness of the water to be treated is as high as 450 mg / L (calculated as calcium carbonate), after being treated by this process, the final effluent hardness can be reduced to below 15 mg / L, meeting the high-quality water use requirements, greatly expanding the range of treatable water sources. Whether it is surface water or groundwater with high hardness in domestic drinking water sources, or the pre-treatment of process water sensitive to hardness in industrial production, it can effectively ensure that the subsequent water use links are not troubled by hard water.

[0025] Second, using a silane coupling agent to modify nano-hydroxyapatite, such as γ-glycidoxypropyltrimethoxysilane, the epoxy group in the molecular structure chemically bonds with the hydroxyl groups on the surface of hydroxyapatite, and the trimethoxysilyl group hydrolyzes to form hydrogen bonds with water, effectively inhibiting particle aggregation, endowing it with good dispersibility and stability, enabling the crystal nuclei to maintain high activity in water for a long time, providing sufficient and stable sites for subsequent induced precipitation, and significantly improving the adsorption and induction ability for calcium and magnesium ions compared with unmodified nano-hydroxyapatite, strengthening the hardening removal efficiency from the root cause.

[0026] The prepared composite inducer has sodium polyacrylate as the main body, which has both dispersion and chelation effects, enabling the hardness ions to be evenly dispersed and avoiding 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 the surface tension to assist mass transfer. The multi-components work together to create an ideal growth microenvironment for crystal nuclei, accelerating the crystallization and precipitation of hardness ions, and further optimizing the effect of crystal nucleus-induced hardness removal.

[0027] Thirdly, the granulation process agglomerates and forms the crystal nucleus particles loaded with the inducer, which not only improves their fluidity and operability in water, facilitating the dosing and mixing in water treatment facilities of different scales, but also reduces the problem of easy loss due to the small size of the particles, ensuring that the active ingredients can fully play their roles and guaranteeing the sustainability of the treatment effect.

[0028] In the surface coating step, tetraethoxysilane is used to form a protective film on the surface of the crystal nucleus granule, enhancing the stability of the particles in complex water quality (such as containing organic matter, microorganisms, acid-base fluctuations, etc.), preventing dissolution or agglomeration, and at the same time realizing the slow release of the internal crystal nucleus and inducer, prolonging their action time in water, reducing the need for frequent dosing of chemicals, and reducing the operation cost and the intensity of manual management.

[0029] Fourthly, compared with the traditional ion exchange method, this process does not require a large amount of acids and alkalis for resin regeneration, avoiding soil and water pollution caused by the discharge of acid-base waste liquid, reducing the environmental protection pressure, and at the same time reducing the costs of chemical reagent procurement, storage and waste liquid treatment. Compared with the lime softening method, it will not significantly increase the pH value of water, does not require additional complex neutralization steps, reduces the consumption of chemical reagents and the generation amount of precipitates, reduces the difficulty and cost of subsequent sludge treatment, conforms to the environmental protection concept of sustainable development, and has significant advantages in water resource protection and ecological maintenance.

[0030] Fifthly, as a key subsequent purification step, the activated carbon filter column, with a packed density of 0.8 - 1.2 g / cm³ and a developed pore structure of activated carbon with a particle size of 0.5 - 2.0 mm, can efficiently adsorb impurities such as dissolved organic matter and residual chlorine in water, further purify the water quality on the basis of hardness removal, remove odors and colors, and improve the sensory quality of water, meeting the requirements of fields with high water quality purity requirements such as domestic drinking and food processing.

[0031] The ultraviolet disinfection device uses ultraviolet light with a wavelength of 254 nm and, at a water layer thickness of 1 - 3 cm, precisely destroys the DNA structure of microorganisms, inactivates pathogens such as bacteria and viruses, ensures the microbial safety of the effluent, eliminates the risk of water-borne diseases, and comprehensively guarantees that the treated water quality meets the high-standard comprehensive requirements, and can be directly applied to various scenarios with strict water quality requirements. Specific implementation mode

[0032] For the convenience of understanding the present invention, the present invention will be described more comprehensively below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0033] Example 1: Step 1: Preparation of silanized hydroxyapatite crystal nuclei Accurately weigh 100 g of nano-hydroxyapatite, slowly add it to 2500 g of deionized water, place it in an ultrasonic disperser, and ultrasonically disperse it for 30 min at a power of 400 W to ensure uniform dispersion of the nano-hydroxyapatite.

[0034] Add 50 g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirring device, and continuously stir and mix for 3 h under the conditions of 30 °C and a stirring rate of 300 rpm.

[0035] After the reaction is completed, transfer the mixture to a high-speed centrifuge, centrifuge at a speed of 8000 rpm for 15 min, and discard the supernatant. The precipitate is washed 3 times with anhydrous ethanol, with each washing amount being 500 mL. Subsequently, place the washed precipitate in a vacuum drying oven and vacuum dry it for 10 h under the conditions of 70 °C and a vacuum degree of -0.09 MPa to obtain silanized hydroxyapatite crystal nuclei.

[0036] Step 2: Preparation of a composite inducer Weigh 100 g of sodium polyacrylate and add it to 3000 g of ethylene glycol solution. Similarly, use an ultrasonic disperser to ultrasonically disperse it for 40 min at a power of 350 W until it is uniformly dispersed.

[0037] Then add 80 g of aluminum sulfate and 3 g of sodium dodecyl sulfonate to it, transfer the mixture to a four-necked flask equipped with a condensing reflux device and a magnetic stirrer, heat it up to 80 °C, and react for 4 h under the condition of a stirring rate of 400 rpm.

[0038] After the reaction is completed, filter it while it is hot with a Buchner funnel. The filter cake is washed 4 times with deionized water, 600 mL each time, and then placed in a vacuum drying oven and dried for 6 h under the conditions of 60 °C and a vacuum degree of -0.08 MPa to obtain a composite inducer.

[0039] Step 3: Preparation of crystal nucleus particles loaded with an inducer Accurately weigh the silylated hydroxyapatite crystal nuclei, composite inducer, and phosphate buffer solution (pH = 7.0) according to the mass ratio of 100:45:5000. First, add the silylated hydroxyapatite crystal nuclei and the composite inducer to the phosphate buffer solution, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 min at 500 W.

[0040] After that, adjust the pH of the mixed solution to 8.5 with 1 mol / L sodium hydroxide solution, transfer it to a constant temperature water bath, and stir and react for 2 h at 50 °C and a stirring rate of 350 rpm.

[0041] After the reaction is completed, centrifuge at 9000 rpm for 20 min, wash the precipitate 3 times with deionized water, 400 mL each time, and then vacuum dry at 65 °C and a vacuum degree of -0.09 MPa for 12 h to obtain the crystal nucleus particles loaded with the inducer.

[0042] Step Four: Prepare the primary granulation product Weigh the crystal nucleus particles loaded with the inducer, calcium chloride, sodium carbonate, and polyethylene glycol - 6000 according to the mass ratio of 100:15:20:5. Add the crystal nucleus particles loaded with the inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water, ultrasonically disperse them evenly (ultrasonic power 450 W, time 25 min), then add polyethylene glycol - 6000 under the condition of a stirring rate of 400 rpm, and raise the temperature to 40 °C.

[0043] Maintain this temperature and stirring state and react for 1 h. After the precipitate is formed, centrifuge and separate at 10000 rpm for 10 min, discard the supernatant, and obtain the primary granulation product.

[0044] Step Five: Prepare the surface-coated crystal nucleus granule Take 100 g of the primary granulation product and disperse it in 1800 g of ethanol solution, add 30 g of tetraethoxysilane, transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser tube, and stir and mix at 60 °C and a stirring rate of 300 rpm for 5 h.

[0045] After the reaction is completed, filter with a suction filtration device, wash the filter cake 3 times with absolute ethanol, 500 mL each time, and then dry it in a vacuum drying oven at 70 °C and a vacuum degree of -0.09 MPa for 8 h to obtain the surface-coated crystal nucleus granule.

[0046] Step Six: Prepare the enhanced hardness removal agent Weigh the surface-coated crystal nucleus granule, cationic polyacrylamide, and nano-zinc oxide according to the mass ratio of 100:8:2. Mix them in an appropriate amount of deionized water. After ultrasonic dispersion (ultrasonic power 550W, time 15min), adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0047] After the adjustment, place the mixed solution in a constant temperature incubator and let it stand and age at 25°C for 12h to obtain the hardening removal enhancer.

[0048] Step Seven: Treat the water to be treated Measure 5000L of the water to be treated (hardness is 300mg / L in terms of calcium carbonate) and input it into the reaction tank. Add 1kg of the hardening removal enhancer to it, turn on the stirring device, control the stirring rate at 200rpm, react at 15°C for 0.5h, then stop stirring and let it stand and precipitate for 1h.

[0049] After the precipitation, separate the supernatant by the siphon principle.

[0050] Step Eight: Filter the residual impurities Pass the separated supernatant through an activated carbon filter column (packing density 0.8g / cm³, activated carbon particle size 0.5mm) at a flow rate of 0.5L / min to adsorb the residual impurities.

[0051] Step Nine: Ultraviolet disinfection Pass the adsorbed water into an ultraviolet disinfection device with a wavelength of 254nm, control the irradiation intensity at 10mW / cm², the water layer thickness at 1cm, and the treatment time at 5min.

[0052] Step Ten: Collect the final effluent. After testing, the hardness of the final effluent is reduced to below 30mg / L, meeting the hardness requirements of general domestic water, and the integrated hardening removal treatment is completed.

[0053] Example 2: Step One: Prepare silanized hydroxyapatite crystal nucleus Weigh 100g of nano-hydroxyapatite and add it to 3000g of deionized water, and perform ultrasonic dispersion (power 450W, 35min). Add 55g of γ-glycidoxypropyltrimethoxysilane and react at 35°C and a stirring rate of 320rpm for 4h.

[0054] Subsequent centrifugation (8500rpm, 18min), washing (anhydrous ethanol, 3 times, 550mL each time), and vacuum drying (70°C, vacuum degree -0.09MPa, 10h) operations are the same as in Example 1 to obtain the silanized hydroxyapatite crystal nucleus.

[0055] Step Two: Prepare the composite inducer Disperse 100 g of sodium polyacrylate in 3500 g of ethylene glycol solution (ultrasonic power 380 W, 45 min), add 100 g of aluminum sulfate and 5 g of sodium dodecyl sulfate, heat up to 85 °C, and react for 6 h at a stirring rate of 420 rpm.

[0056] The steps of filtration, washing (deionized water, 4 times, 650 mL each time), and drying (60 °C, vacuum degree -0.08 MPa, 6 h) are the same as those in Example 1 to obtain a composite inducer. Step Three: Prepare nucleating particles loaded with the inducer Weigh the raw materials according to the mass ratio of 100:60:6000, ultrasonically disperse (power 520 W, 25 min), then adjust the pH to 9.0 (using 1 mol / L sodium hydroxide solution), and react at 60 °C and a stirring rate of 380 rpm for 3 h.

[0057] Centrifuge (9500 rpm, 22 min), wash (deionized water, 3 times, 450 mL each time), and dry (65 °C, vacuum degree -0.09 MPa, 12 h) as in Example 1 to obtain nucleating particles loaded with the inducer.

[0058] Step Four: Prepare the primary granulation product Weigh each component according to the mass ratio of 100:20:25:8, ultrasonically disperse (power 480 W, 30 min), then heat up to 45 °C, add polyethylene glycol - 6000, and react at a stirring rate of 420 rpm for 2 h, and centrifuge (10000 rpm, 12 min) to obtain the primary granulation product.

[0059] Step Five: Prepare the surface-coated nucleating granule Take 100 g of the primary granulation product, mix it with 2200 g of ethanol solution and 40 g of tetraethoxysilane, and react at 65 °C and a stirring rate of 320 rpm for 6 h.

[0060] Carry out suction filtration, washing (absolute ethanol, 3 times, 550 mL each time), and drying (70 °C, vacuum degree -0.09 MPa, 8 h) as in Example 1 to obtain the surface-coated nucleating granule.

[0061] Step Six: Prepare the enhanced hardness remover Weigh the raw materials according to the mass ratio of 100:12:3, ultrasonically disperse (power 580 W, 20 min), then adjust the pH to 6.5 (using 0.1 mol / L hydrochloric acid solution), and let it stand and cure at 30 °C for 18 h to obtain the enhanced hardness remover.

[0062] Step Seven: Treat the water to be treated Take 7500 L of water to be treated (hardness is 350 mg / L in terms of calcium carbonate), add 1.5 kg of enhanced hardening removal agent, with a stirring rate of 250 rpm, react for 1 h at 18 °C, let it stand for sedimentation for 2 h, and siphon to separate the supernatant.

[0063] Step Eight: Filter residual impurities The supernatant passes 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.

[0064] Step Nine: Ultraviolet disinfection Pass it into an ultraviolet disinfection device (wavelength 254 nm, irradiation intensity 20 mW / cm², water layer thickness 2 cm), and the treatment time is 10 min.

[0065] Step Ten: Collect the final effluent. After detection, the hardness of the final effluent is reduced to below 25 mg / L, and the integrated hardening removal treatment is completed.

[0066] Example 3: Step One: Prepare silanized hydroxyapatite crystal nuclei Take 100 g of nano-hydroxyapatite and ultrasonically disperse it in 3500 g of deionized water (power 500 W, 40 min), add 60 g of γ - glycidoxypropyltrimethoxysilane, and react at 38 °C and a stirring rate of 350 rpm for 5 h.

[0067] After centrifugation (9000 rpm, 20 min), washing (anhydrous ethanol, 3 times, 600 mL each time), and vacuum drying (70 °C, vacuum degree -0.09 MPa, 10 h), silanized hydroxyapatite crystal nuclei are obtained.

[0068] Step Two: Prepare a composite inducer Ultrasonically disperse 100 g of sodium polyacrylate in 4000 g of ethylene glycol solution (power 400 W, 50 min), add 110 g of aluminum sulfate and 6 g of sodium dodecyl sulfonate, heat up to 90 °C, and react at a stirring rate of 450 rpm for 7 h.

[0069] After filtration, washing (deionized water, 4 times, 700 mL each time), and drying (60 °C, vacuum degree -0.08 MPa, 6 h), a composite inducer is obtained.

[0070] Step Three: Prepare crystal nucleus particles loaded with an inducer Weigh according to a mass ratio of 100:70:6500, ultrasonically disperse (power 550 W, 30 min), adjust the pH to 9.2 (1 mol / L sodium hydroxide), and react at 65 °C and a stirring rate of 400 rpm for 3.5 h.

[0071] Centrifuge (10000 rpm, 25 min), wash (deionized water, 3 times, 500 mL each time), and dry (65 °C, vacuum degree -0.09 MPa, 12 h) to obtain the crystal nucleus particles loaded with the inducer.

[0072] Step Four: Prepare the primary granulation product Weigh according to the mass ratio of 100:22:30:9, perform ultrasonic dispersion (power 500 W, 35 min), raise the temperature to 50 °C and add polyethylene glycol - 6000, and react for 2.5 h at a stirring rate of 450 rpm. Centrifuge (11000 rpm, 15 min) to obtain the primary granulation product.

[0073] Step Five: Prepare the surface-coated crystal nucleus granule Mix 100 g of the primary granulation product with 2500 g of ethanol solution and 45 g of tetraethoxysilane, and react at 68 °C and a stirring rate of 350 rpm for 7 h.

[0074] Perform suction filtration, wash (anhydrous ethanol, 3 times, 600 mL each time), and dry (70 °C, vacuum degree -0.09 MPa, 8 h) to obtain the surface-coated crystal nucleus granule.

[0075] Step Six: Prepare the enhanced hardness removal agent Weigh according to the mass ratio of 100:14:4, perform ultrasonic dispersion (power 600 W, 25 min), adjust the pH to 6.8 (0.1 mol / L hydrochloric acid), and let it stand and ripen at 32 °C for 20 h to obtain the enhanced hardness removal agent.

[0076] Step Seven: Treat the water to be treated Take 10000 L of the water to be treated (hardness is 400 mg / L in terms of calcium carbonate), add 2 kg of the enhanced hardness removal agent, stir at a rate of 300 rpm, react at 22 °C for 1.5 h, let it stand and precipitate for 2.5 h, and siphon to separate the supernatant.

[0077] Step Eight: Filter the residual impurities The supernatant passes 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.

[0078] Step Nine: Ultraviolet disinfection Pass it into an ultraviolet disinfection device (wavelength 254 nm, irradiation intensity 25 mW / cm², water layer thickness 2.5 cm), and the treatment time is 12 min.

[0079] Step Ten: Collect the final effluent, and after detection, the hardness of the final effluent is reduced to below 20 mg / L, completing the integrated hardness removal treatment.

[0080] Example 4: Step 1: Preparation of silanized hydroxyapatite crystal nuclei Weigh 100 g of nano-hydroxyapatite and put it into 4000 g of deionized water. Ultrasonically disperse (power 550 W, 45 min), add 65 g of γ-glycidoxypropyltrimethoxysilane, and react at 40 °C with a stirring rate of 380 rpm for 6 h.

[0081] Centrifuge (9500 rpm, 22 min), wash (anhydrous ethanol, 3 times, 650 mL each time), and vacuum dry (70 °C, vacuum degree -0.09 MPa, 10 h) to obtain silanized hydroxyapatite crystal nuclei.

[0082] Step 2: Preparation of composite inducer Take 100 g of sodium polyacrylate and add it to 4500 g of ethylene glycol solution. Ultrasonically disperse (power 420 W, 55 min), add 120 g of aluminum sulfate and 8 g of sodium dodecyl sulfonate, heat up to 95 °C, and react at a stirring rate of 480 rpm for 8 h.

[0083] Filter, wash (deionized water, 4 times, 750 mL each time), and dry (60 °C, vacuum degree -0.08 MPa, 6 h) to obtain the composite inducer.

[0084] Step 3: Preparation of crystal nucleus particles loaded with inducer Weigh according to a mass ratio of 100:75:7000, ultrasonically disperse (power 580 W, 35 min), adjust the pH to 9.5 (1 mol / L sodium hydroxide), and react at 70 °C with a stirring rate of 420 rpm for 4 h.

[0085] Centrifuge (10500 rpm, 28 min), wash (deionized water, 3 times, 550 mL each time), and dry (65 °C, vacuum degree -0.09 MPa, 12 h) to obtain crystal nucleus particles loaded with inducer.

[0086] Step 4: Preparation of primary granulation product Weigh according to a mass ratio of 100:25:35:10, ultrasonically disperse (power 520 W, 40 min), heat up to 55 °C and add polyethylene glycol-6000, and react at a stirring rate of 480 rpm for 3 h. Centrifuge (12000 rpm, 18 min) to obtain the primary granulation product.

[0087] Step 5: Preparation of surface-coated crystal nucleus granule Mix 100 g of the primary granulation product with 3000 g of ethanol solution and 50 g of tetraethoxysilane, and react at 75 °C with a stirring rate of 380 rpm for 8 h.

[0088] Perform suction filtration, washing (with absolute ethanol, 3 times, 700 mL each time), and drying (at 70 °C, vacuum degree -0.09 MPa, 8 h) to obtain the surface-coated crystal nucleus granule.

[0089] Step Six: Prepare the hardness removal enhancer Weigh according to the mass ratio of 100:15:5, perform ultrasonic dispersion (power 620 W, 30 min), adjust the pH to 7.0 (with 0.1 mol / L hydrochloric acid), and let it stand and ripen at 35 °C for 24 h to obtain the hardness removal enhancer.

[0090] Step Seven: Treat the water to be treated Take 12000 L of the water to be treated (hardness is 450 mg / L in terms of calcium carbonate), add 2.4 kg of the hardness removal enhancer, stir at a rate of 350 rpm, react at 25 °C for 2 h, let it stand and precipitate for 3 h, and siphon to separate the supernatant.

[0091] Step Eight: Filter the residual impurities The supernatant passes 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.

[0092] Step Nine: Ultraviolet disinfection Pass it into an ultraviolet disinfection device (wavelength 254 nm, irradiation intensity 30 mW / cm², water layer thickness 3 cm), and the treatment time is 15 min.

[0093] Step Ten: Collect the final effluent. After detection, the hardness of the final effluent is reduced to below 15 mg / L, and the integrated hardness removal treatment is completed.

[0094] Comparative Example 1: Omit the silanization modification step. Step One: Prepare hydroxyapatite crystal nuclei (not silanized) Weigh 100 g of nano-hydroxyapatite and add it to 2500 g of deionized water, perform ultrasonic dispersion (power 400 W, 30 min) to obtain a hydroxyapatite dispersion solution for standby.

[0095] Step Two: Prepare the composite inducer Perform the same operation as in Step Two of Example 1, that is, weigh 100 g of sodium polyacrylate, add it to 3000 g of ethylene glycol solution, perform ultrasonic dispersion (power 350 W, 40 min) until it is uniformly dispersed, then add 80 g of aluminum sulfate and 3 g of sodium dodecyl sulfonate to it, transfer the mixed solution to a four-necked flask equipped with a condensing reflux device and a magnetic stirrer, heat up to 80 °C, and react for 4 h under the condition of a stirring rate of 400 rpm.

[0096] After the reaction is completed, filter while it is hot with a Buchner funnel. Wash the filter cake 4 times with deionized water, 600 mL each time, and then place it in a vacuum drying oven. Dry it at 60 °C and a vacuum degree of -0.08 MPa for 6 h to obtain the composite inducer.

[0097] Step 3: Prepare the crystal nucleus particles loaded with the inducer Directly add the prepared hydroxyapatite dispersion and the composite inducer into the phosphate buffer solution (5000 g, pH = 7.0) according to a mass ratio of 100:45 (assuming 100 g of nano-hydroxyapatite in the hydroxyapatite dispersion). After ultrasonic dispersion (power 500 W, 20 min), adjust the pH of the mixed solution to 8.5 with 1 mol / L sodium hydroxide solution, transfer it to a constant temperature water bath, and stir and react at 50 °C and a stirring rate of 350 rpm for 2 h.

[0098] After the reaction ends, centrifuge at 9000 rpm for 20 min. Wash the precipitate 3 times with deionized water, 400 mL each time, and then vacuum dry at 65 °C and a vacuum degree of -0.09 MPa for 12 h to obtain the crystal nucleus particles loaded with the inducer.

[0099] Step 4: Prepare the primary granulation product Weigh the crystal nucleus particles loaded with the inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to a mass ratio of 100:15:20:5. Add the crystal nucleus particles loaded with the inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water, and disperse them evenly by ultrasonic wave (ultrasonic power 450 W, 25 min). Then add polyethylene glycol-6000 under the condition of a stirring rate of 400 rpm and raise the temperature to 40 °C.

[0100] Maintain this temperature and stirring state and react for 1 h. After the precipitate is formed, centrifuge and separate at 10000 rpm for 10 min, and discard the supernatant to obtain the primary granulation product.

[0101] Step 5: Prepare the surface-coated crystal nucleus granule Take 100 g of the primary granulation product and disperse it in 1800 g of ethanol solution. Add 30 g of tetraethoxysilane, transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser tube, and stir and mix at 60 °C and a stirring rate of 300 rpm for 5 h.

[0102] After the reaction ends, filter with a suction filtration device. Wash the filter cake 3 times with anhydrous ethanol, 500 mL each time, and then place it in a vacuum drying oven at 70 °C and a vacuum degree of -0.09 MPa to dry for 8 h to obtain the surface-coated crystal nucleus granule.

[0103] Step 6: Preparation of the enhanced hardness remover Weigh the surface-coated crystal nucleus granule, cationic polyacrylamide, and nano-zinc oxide according to the mass ratio of 100:8:2. Mix them in an appropriate amount of deionized water. After ultrasonic dispersion (ultrasonic power 550W, 15 min), adjust the pH to 6.0 with 0.1 mol / L hydrochloric acid solution.

[0104] After the adjustment, place the mixed solution in a constant temperature incubator and let it stand and age at 25 °C for 12 h to obtain the enhanced hardness remover.

[0105] Step 7: Treatment of the water to be treated Measure 5000 L of the water to be treated (hardness is 300 mg / L in terms of calcium carbonate) and input it into the reaction tank. Add 1 kg of the enhanced hardness remover to it. Turn on the stirring device, control the stirring rate at 200 rpm, react at 15 °C for 0.5 h, then stop stirring and let it stand and precipitate for 1 h.

[0106] After the precipitation, separate the supernatant by the principle of siphon.

[0107] Step 8: Filtration of residual impurities Pass the separated supernatant through an activated carbon filter column (packing density is 0.8 g / cm³, activated carbon particle size is 0.5 mm) at a flow rate of 0.5 L / min to adsorb the residual impurities.

[0108] Step 9: Ultraviolet disinfection Pass the adsorbed water into an ultraviolet disinfection device with a wavelength of 254 nm, control the irradiation intensity at 10 mW / cm², the water layer thickness at 1 cm, and the treatment time at 5 min.

[0109] Step 10: Collect the final effluent. After detection, the hardness of the final effluent is 80 mg / L. Compared with Example 1, the hardness removal effect has decreased significantly, indicating that the silanization modification plays an important role in improving the performance of the crystal nucleus.

[0110] Comparative Example 2: Changing the composite inducer formula Step 1: Preparation of silanized hydroxyapatite crystal nucleus Perform the same operation as in Step 1 of Example 1, that is, accurately weigh 100 g of nano-hydroxyapatite, slowly add it to 2500 g of deionized water, place it in an ultrasonic disperser, and disperse it ultrasonically at a power of 400 W for 30 min to ensure the uniform dispersion of nano-hydroxyapatite.

[0111] Add 50 g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirring device, and continuously stir and mix at 30 °C and a stirring rate of 300 rpm for 3 h.

[0112] After the reaction was completed, the mixture was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 15 min. The supernatant was discarded. The precipitate was washed three times with absolute ethanol, with 500 mL of ethanol used each time. Subsequently, the washed precipitate was placed in a vacuum drying oven and vacuum-dried at 70 °C under a vacuum of -0.09 MPa for 10 h to obtain silanized hydroxyapatite crystal nuclei.

[0113] Step 2: Preparation of a composite inducer (changing the formula) Weigh 100 g of sodium polyacrylate and add it to 3000 g of ethylene glycol solution. Ultrasonically disperse (power 350 W, 40 min) until evenly dispersed.

[0114] Then add 50 g of aluminum sulfate and 1 g of sodium dodecyl sulfate (the amounts of aluminum sulfate and sodium dodecyl sulfate are reduced compared to Example 1) to it. Transfer the mixture to a four-necked flask equipped with a condensing reflux device and a magnetic stirrer, heat it to 80 °C, and react for 4 h under a stirring rate of 400 rpm.

[0115] After the reaction is completed, filter it while it is hot with a Buchner funnel. Wash the filter cake four times with deionized water, 600 mL each time, and then place it in a vacuum drying oven and dry it at 60 °C under a vacuum of -0.08 MPa for 6 h to obtain the composite inducer.

[0116] Step 3: Preparation of crystal nucleus particles loaded with an inducer Accurately weigh silanized hydroxyapatite crystal nuclei, the composite inducer, and phosphate buffer solution (pH = 7.0) according to a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite crystal nuclei and the composite inducer to the phosphate buffer solution, place it in an ultrasonic cleaner, and ultrasonically disperse it at 500 W for 20 min.

[0117] Then adjust the pH of the mixture to 8.5 with 1 mol / L sodium hydroxide solution, transfer it to a constant-temperature water bath, and stir and react at 50 °C under a stirring rate of 350 rpm for 2 h.

[0118] After the reaction is completed, centrifuge it at 9000 rpm for 20 min. Wash the precipitate three times with deionized water, 400 mL each time, and then vacuum-dry it at 65 °C under a vacuum of -0.09 MPa for 12 h to obtain crystal nucleus particles loaded with an inducer.

[0119] Step 4: Preparation of primary granulation products Weigh the nucleating particles loaded with the inducer, calcium chloride, sodium carbonate, and polyethylene glycol - 6000 according to the mass ratio of 100:15:20:5. Add the nucleating particles loaded with the inducer, calcium chloride, and sodium carbonate to an appropriate amount of deionized water, and disperse them evenly by ultrasonic wave (ultrasonic power 450W, 25min). Then add polyethylene glycol - 6000 under the condition of a stirring rate of 400rpm, and raise the temperature to 40°C.

[0120] Maintain this temperature and stirring state for reaction for 1h. After the precipitate is formed, centrifuge at 10000rpm for 10min, discard the supernatant, and obtain the primary granulation product.

[0121] Step Five: Prepare the surface - coated nucleating granule Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane, transfer it to a three - necked flask equipped with a mechanical stirrer and a condenser, and stir and mix at 60°C and a stirring rate of 300rpm for 5h.

[0122] After the reaction is completed, filter it with a suction filtration device. Wash the filter cake with anhydrous ethanol 3 times, 500mL each time, and then place it in a vacuum drying oven at 70°C and a vacuum degree of - 0.09MPa for drying for 8h to obtain the surface - coated nucleating granule.

[0123] Step Six: Prepare the enhanced hardness - removing agent Weigh the surface - coated nucleating granule, cationic polyacrylamide, and nano - zinc oxide according to the mass ratio of 100:8:2. Mix them in an appropriate amount of deionized water, disperse them by ultrasonic wave (ultrasonic power 550W, 15min), and then adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0124] After the adjustment, place the mixed solution in a constant - temperature incubator and let it stand and ripen at 25°C for 12h to obtain the enhanced hardness - removing agent.

[0125] Step Seven: Treat the water to be treated Measure 5000L of the water to be treated (the hardness is 300mg / L in terms of calcium carbonate) and input it into the reaction tank. Add 1kg of the enhanced hardness - removing agent to it, turn on the stirring device, control the stirring rate to 200rpm, react at 15°C for 0.5h, then stop stirring and let it stand for precipitation for 1h.

[0126] After the precipitation is completed, separate the supernatant by the principle of siphon.

[0127] Step Eight: Filter the residual impurities The separated supernatant is passed through an activated carbon filter column at a flow rate of 0.5 L / min (the packing density is 0.8 g / cm³, and the activated carbon particle size is 0.5 mm) to adsorb residual impurities.

[0128] Step Nine: Ultraviolet disinfection The adsorbed water is passed into an ultraviolet disinfection device with a wavelength of 254 nm, controlling the irradiation intensity to be 10 mW / cm², the water layer thickness to be 1 cm, and the treatment time to be 5 min.

[0129] Step Ten: Collect the final effluent. After detection, the hardness of the final effluent is 60 mg / L, which is higher than that in Example 1, indicating that the reasonable formulation of the composite inducer has a significant effect on the hardness removal effect.

[0130] Comparative Example 3: Omit the surface coating step. Step One: Prepare silanized hydroxyapatite nuclei Perform the operation in Step One of Example 1, that is, accurately weigh 100 g of nano-hydroxyapatite, slowly add it to 2500 g of deionized water, place it in an ultrasonic disperser, and ultrasonically disperse it at a power of 400 W for 30 min to ensure uniform dispersion of the nano-hydroxyapatite.

[0131] Add 50 g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirring device, and continuously stir and mix for 3 h under the conditions of 30 °C and a stirring rate of 300 rpm.

[0132] After the reaction is completed, transfer the mixed solution to a high-speed centrifuge, centrifuge at a speed of 8000 rpm for 15 min, and discard the supernatant. The precipitate is washed 3 times with anhydrous ethanol, with each washing amount being 500 mL. Subsequently, place the finally washed precipitate in a vacuum drying oven and vacuum dry it at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite nuclei.

[0133] Step Two: Prepare the composite inducer Perform the operation in Step Two of Example 1, that is, weigh 100 g of sodium polyacrylate, add it to 3000 g of ethylene glycol solution, and ultrasonically disperse it (power 350 W, 40 min) until it is uniformly dispersed.

[0134] Then add 80 g of aluminum sulfate and 3 g of sodium dodecyl sulfonate to it, transfer the mixed solution to a four-necked flask equipped with a condensing reflux device and a magnetic stirrer, heat it to 80 °C, and react for 4 h under the condition of a stirring rate of 400 rpm.

[0135] After the reaction was completed, filtration was carried out while it was hot using a Buchner funnel. The filter cake was washed 4 times with deionized water, 600 mL each time, and then placed in a vacuum drying oven and dried at 60 °C and a vacuum degree of -0.08 MPa for 6 h to obtain the composite inducer.

[0136] Step 3: Preparation of nucleating particles loaded with the inducer The same operation as in Step 3 of Example 1 was carried out, that is, the silylated hydroxyapatite nuclei, the composite inducer, and phosphate buffer solution (pH = 7.0) were accurately weighed according to the mass ratio of 100:45:5000. First, the silylated hydroxyapatite nuclei and the composite inducer were added to the phosphate buffer solution, and the mixture was placed in an ultrasonic cleaner and ultrasonically dispersed at 500 W for 20 min.

[0137] After that, the pH of the mixed solution was adjusted to 8.5 with 1 mol / L sodium hydroxide solution, and the mixture was transferred to a constant temperature water bath and stirred and reacted at 50 °C and a stirring rate of 350 rpm for 2 h.

[0138] After the reaction ended, centrifugation was carried out at 9000 rpm for 20 min. The precipitate was washed 3 times with deionized water, 400 mL each time, and then vacuum dried at 65 °C and a vacuum degree of -0.09 MPa for 12 h to obtain the nucleating particles loaded with the inducer.

[0139] Step 4: Preparation of the primary granulation product The same operation as in Step 4 of Example 1 was carried out, that is, the nucleating particles loaded with the inducer, calcium chloride, sodium carbonate, and polyethylene glycol - 6000 were weighed according to the mass ratio of 100:15:20:5. The nucleating particles loaded with the inducer, calcium chloride, and sodium carbonate were added to an appropriate amount of deionized water and ultrasonically dispersed evenly (ultrasonic power 450 W, 25 min). Subsequently, polyethylene glycol - 6000 was added under the condition of a stirring rate of 400 rpm, and the temperature was raised to 40 °C.

[0140] Maintain this temperature and stirring state and react for 1 h. After the precipitate was formed, centrifugal separation was carried out at 10000 rpm for 10 min, and the supernatant was discarded to obtain the primary granulation product.

[0141] Step 5: Directly use the primary granulation product for subsequent steps (omitting surface coating) The primary granulation product was used as the nucleating granule body with surface coating. The primary granulation product, cationic polyacrylamide, and nano - zinc oxide were weighed according to the mass ratio of 100:8:2. They were mixed into an appropriate amount of deionized water, ultrasonically dispersed (ultrasonic power 550 W, 15 min), and then the pH was adjusted to 6.0 with 0.1 mol / L hydrochloric acid solution.

[0142] After adjustment, place the mixed solution in a constant temperature incubator and let it stand and ripen at 25°C for 12 hours to obtain the enhanced hardness removal agent.

[0143] Step Six: Treat the water to be treated Measure 5000 L of the water to be treated (with a hardness of 300 mg / L in terms of calcium carbonate) and input it into the reaction tank. Add 1 kg of the enhanced hardness removal agent to it, turn on the stirring device, control the stirring rate at 200 rpm, react at 15°C for 0.5 h, then stop stirring and let it stand and precipitate for 1 h.

[0144] After precipitation, separate the supernatant by the principle of siphon.

[0145] Step Seven: Filter the residual impurities Pass the separated supernatant 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 the residual impurities.

[0146] Step Eight: UV disinfection Pass the adsorbed water into a UV disinfection device with a wavelength of 254 nm, control the irradiation intensity at 10 mW / cm², the water layer thickness at 1 cm, and the treatment time at 5 min.

[0147] Step Nine: Collect the final effluent. After detection, the hardness of the final effluent is 70 mg / L. Compared with Example 1, after omitting the surface coating step, the effluent hardness increases, indicating that the surface coating promotes the stability of the crystal nucleus granule and the hardness removal effect.

[0148] Comparative Example 4: Change the reaction temperature and time. Step One: Prepare silanized hydroxyapatite crystal nuclei Accurately weigh 100 g of nano-hydroxyapatite, slowly add it to 2500 g of deionized water, place it in an ultrasonic disperser, and disperse it ultrasonically at a power of 400 W for 30 min to ensure the uniform dispersion of nano-hydroxyapatite.

[0149] Add 50 g of γ-glycidoxypropyltrimethoxysilane to the above dispersion, transfer it to a three-necked flask equipped with a mechanical stirring device, and continuously stir and mix at 25°C (lower than the normal range) and a stirring rate of 300 rpm for 2 h (lower than the normal range).

[0150] After the reaction is completed, transfer the mixture to a high-speed centrifuge and centrifuge at 8000 rpm for 15 min. Discard the supernatant. Wash the precipitate three times with absolute ethanol, with 500 mL used for each wash. Subsequently, place the washed precipitate in a vacuum drying oven and vacuum dry it at 70 °C and a vacuum degree of -0.09 MPa for 10 h to obtain silanized hydroxyapatite crystal nuclei.

[0151] Step 2: Prepare a composite inducer Weigh 100 g of sodium polyacrylate and add it to 3000 g of ethylene glycol solution. Ultrasonically disperse (power 350 W, 40 min) until evenly dispersed.

[0152] Then add 80 g of aluminum sulfate and 3 g of sodium dodecyl sulfonate to it. Transfer the mixture to a four-necked flask equipped with a condensing reflux device and a magnetic stirrer, heat it up to 75 °C (lower than the normal range), and react for 3 h (lower than the normal range) under the condition of a stirring rate of 400 rpm.

[0153] After the reaction is completed, filter it while it is hot with a Buchner funnel. Wash the filter cake four times with deionized water, 600 mL each time, and then put it into a vacuum drying oven and dry it at 60 °C and a vacuum degree of -0.08 MPa for 6 h to obtain a composite inducer.

[0154] Step 3: Prepare crystal nucleus particles loaded with an inducer Accurately weigh silanized hydroxyapatite crystal nuclei, a composite inducer, and phosphate buffer solution (pH = 7.0) according to a mass ratio of 100:45:5000. First, add the silanized hydroxyapatite crystal nuclei and the composite inducer to the phosphate buffer solution, place it in an ultrasonic cleaner, and ultrasonically disperse it at 500 W for 20 min.

[0155] Then adjust the pH of the mixture to 8.5 with 1 mol / L sodium hydroxide solution, transfer it to a constant temperature water bath, and stir and react at 45 °C (lower than the normal range) and a stirring rate of 350 rpm for 1.5 h (lower than the normal range).

[0156] After the reaction is completed, centrifuge at 9000 rpm for 20 min. Wash the precipitate three times with deionized water, 400 mL each time, and then vacuum dry it at 65 °C and a vacuum degree of -0.09 MPa for 12 h to obtain crystal nucleus particles loaded with an inducer.

[0157] Step 4: Prepare primary granulation products Weigh the crystal nucleus particles loaded with the inducer, calcium chloride, sodium carbonate, and polyethylene glycol-6000 according to the mass ratio of 100:15:20:5. Add the crystal nucleus particles loaded with the inducer, calcium chloride, and sodium carbonate into an appropriate amount of deionized water, and disperse them evenly by ultrasonic wave (ultrasonic power 450W, 25min). Subsequently, under the condition of a stirring rate of 400rpm, add polyethylene glycol-6000 and raise the temperature to 35°C (lower than the normal range).

[0158] Maintain this temperature and stirring state for reaction for 0.5h (lower than the normal range). After the precipitate is formed, centrifuge at 10000rpm for 10min, discard the supernatant, and obtain the primary granulation product.

[0159] Step Five: Prepare the surface-coated crystal nucleus granule Take 100g of the primary granulation product and disperse it in 1800g of ethanol solution. Add 30g of tetraethoxysilane, transfer it to a three-necked flask equipped with a mechanical stirrer and a condenser, and stir and mix at 55°C (lower than the normal range) and a stirring rate of 300rpm for 4h (lower than the normal range).

[0160] After the reaction is completed, filter with a suction filtration device. Wash the filter cake with anhydrous ethanol 3 times, 500mL each time, and then place it in a vacuum drying oven at 70°C and a vacuum degree of -0.09MPa for drying for 8h to obtain the surface-coated crystal nucleus granule.

[0161] Step Six: Prepare the enhanced hardness removal agent Weigh the surface-coated crystal nucleus granule, cationic polyacrylamide, and nano-zinc oxide according to the mass ratio of 100:8:2. Mix them into an appropriate amount of deionized water, disperse them by ultrasonic wave (ultrasonic power 550W, 15min), and then adjust the pH to 6.0 with 0.1mol / L hydrochloric acid solution.

[0162] After the adjustment, place the mixed solution in a constant temperature incubator and let it stand and ripen at 20°C (lower than the normal range) for 10h (lower than the normal range) to obtain the enhanced hardness removal agent.

[0163] Step Seven: Treat the water to be treated Measure 5000L of the water to be treated (the hardness is 300mg / L in terms of calcium carbonate) and input it into the reaction tank. Add 1kg of the enhanced hardness removal agent to it, turn on the stirring device, control the stirring rate to be 200rpm, react at 15°C for 0.5h, then stop stirring and let it stand and precipitate for 1h.

[0164] After the precipitation is completed, separate the supernatant by the principle of siphonage.

[0165] Step Eight: Filter the residual impurities The separated supernatant was passed through an activated carbon filter column at a flow rate of 0.5 L / min (the activated carbon had a packing density of 0.8 g / cm³ and a particle size of 0.5 mm) to adsorb residual impurities.

[0166] Step Nine: Ultraviolet disinfection The adsorbed water was passed into an ultraviolet disinfection device with a wavelength of 254 nm, controlling the irradiation intensity at 10 mW / cm², the water layer thickness at 1 cm, and the treatment time at 5 min.

[0167] Step Ten: Collect the final effluent. After testing, the hardness of the final effluent was 90 mg / L. Compared with Example 1, after changing the reaction temperature and time of the key steps, the hardness removal effect was greatly reduced, indicating that appropriate reaction conditions are crucial for the process performance.

[0168] To more intuitively demonstrate the advantages of the process of the present invention, the key parameters and the hardness of the final effluent of Examples 1 - 4 and Comparative Examples 1 - 4 were sorted into the following table: Table 1: Comparison of process steps and conditions

[0169] Table 2: Comparison of water treatment volume, chemical agent dosage, and water quality

[0170] It can be clearly seen from the table that: in Examples 1 - 4, as the hardness of the water to be treated increased, by reasonably adjusting the process parameters of each step, such as the raw material addition ratio, reaction temperature, time, etc., the hardness of the final effluent could be stably controlled at a low level to meet the hardness removal requirements under different water quality conditions. Comparing with Comparative Example 1, after omitting the silanization modification step, the hardness of the final effluent increased significantly to 80 mg / L, indicating that silanization modification can significantly improve the performance of the crystal nuclei, enhance their synergistic effect with other substances, and thus improve the hardness removal effect. After changing the composite inducer formula in Comparative Example 2, the effluent hardness increased to 60 mg / L, indicating that the specific formula of the composite inducer plays a key role in inducing the growth of crystal nuclei and promoting the hardness removal reaction, and an inappropriate formula will weaken the overall process performance. After omitting the surface coating step in Comparative Example 3, the hardness of the final effluent was 70 mg / L, reflecting that surface coating helps to improve the stability of the crystal nucleus granulates, reduce their agglomeration or dissolution in the subsequent treatment process, and thus ensure the hardness removal effect. In Comparative Example 4, changing the reaction temperature and time made the hardness of the final effluent reach 90 mg / L, highlighting the necessity of strictly following the appropriate reaction conditions to ensure the effective operation of the process and achieve efficient hardness removal.

[0171] In addition, to further explore the influence degree of each factor on the hardness removal effect, a one-way analysis of variance was also carried out, and the results are shown in the following table: Table 3: Variance analysis table of the effects of various factors on hardness removal

[0172] According to the results of variance analysis, it can be seen that the silanization modification and reaction conditions have a highly significant impact on the hardness removal effect. This means that small changes in these two factors may cause large fluctuations in the hardness of the final effluent, and strict control is required in actual process operations. The composite inducer formula and surface coating also have a significant impact on the hardness removal effect. Although the degree is slightly less than the former two, it cannot be ignored either. Their reasonable optimization can further improve the hardness removal performance of the process.

[0173] In summary, the integrated water treatment process for induced hardness removal by crystal nucleation granulation of the present invention, through the fine design and coordinated cooperation of each step, including specific raw material pretreatment, crystal nucleus preparation, inducer synthesis, granulation, coating, and subsequent treatment links, can efficiently remove the hardness in water, and the indispensability of each key step and factor is verified through experimental comparison, providing a reliable and innovative solution for actual water treatment projects.

[0174] The above examples show that low-temperature grinding, inert gas protection, double-layer coating, and specific drying conditions can significantly improve the enzyme activity retention rate and product stability. The deviation of any process parameter in the comparative example results in a decrease in key quality indicators, verifying the necessity and synergistic effect of the process parameters of the present invention.

[0175] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood 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 application of the present invention shall still fall within the scope covered by the patent of the present invention.

Claims

1. An integrated water treatment process for crystal nucleation granulation and induction hardness removal, characterized in that: The steps include: Step 1, ultrasonically dispersing nano-hydroxyapatite in deionized water, adding γ-glycidyloxypropyltrimethoxysilane after uniform dispersion, stirring and mixing, reacting at 30-40° C. for 3-6 hours, centrifuging after the reaction, washing, and vacuum drying at 70° C. for 10 hours to obtain silanized hydroxyapatite crystal nuclei; Step 2, ultrasonically disperse sodium polyacrylate into ethylene glycol solution, after uniform dispersion, add aluminum sulfate and sodium dodecyl sulfate, stir and mix, heat to 80-95°C, react for 4-8h, filter after the reaction, wash, and vacuum dry at 60°C for 6h to obtain a composite inducer; Step 3: Add the silanized hydroxyapatite crystal core and the composite inducer to a phosphate buffer in proportion, and after ultrasonic dispersion, adjust the pH to 8.5-9.5, and stir the reaction at 50-70°C for 2-4 hours. After the reaction is completed, centrifuge, wash, and vacuum dry at 65°C for 12 hours to obtain crystal core particles loaded with the inducer; Step 4: Mix the inducing agent-loaded crystal core particles with calcium chloride and sodium carbonate in deionized water in proportion, disperse them uniformly by ultrasonication, add polyethylene glycol-6000 under stirring conditions, heat to 40-55° C., react for 1-3 hours, generate a precipitate, and then centrifuge to obtain a primary granulation product; Step 5, dispersing the primary granulation product into an ethanol solution, adding tetraethoxysilane, stirring and mixing, reacting at 60-75° C. for 5-8 hours, and after the reaction is completed, filtering, washing, and vacuum drying at 70° C. for 8 hours to obtain a surface-coated crystal core granulation body; Step 6: Mix the surface-coated crystal core granules, cationic polyacrylamide and nano zinc oxide in deionized water in proportion, and after ultrasonic dispersion, adjust the pH to 6.0-7.0, and stand and mature at 25-35° C. for 12-24 hours to obtain a reinforced de-hardening agent; Step 7: Input the water to be treated into the reaction tank, add the enhanced de-hardening agent, control the stirring rate, react at 15-30°C for 0.5-2h, then let it stand for 1-3h, and separate the supernatant; Step 8: Pass the separated supernatant through an activated carbon filter column at a flow rate of 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 10-30mW / cm², and the treatment time to 5-15min; Step 10: Collect the final effluent and complete the integrated hardness removal treatment.

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

3. The integrated water treatment process for crystal nucleation granulation and induced hardness removal according to claim 1 is characterized in that: In the step 2, the mass ratio of sodium polyacrylate, ethylene glycol solution, aluminum sulfate and sodium dodecyl sulfate is 100:3000-4500:80-120:3-8.

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

5. The integrated water treatment process for crystal nucleation granulation and induction hardness removal according to claim 1 is characterized in that: In the step 4, the mass ratio of the inducing agent-loaded crystal core particles, calcium chloride, sodium carbonate, and polyethylene glycol-6000 is 100:15-25:20-35:5-10.

6. The integrated water treatment process for crystal nucleation granulation and induced hardness removal according to claim 1, characterized in that: In the step 5, the mass ratio of the primary granulation product, the ethanol solution and tetraethoxysilane is 100:1800-3000:30-50.

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

8. The integrated water treatment process of crystal nucleation granulation and induced hardness removal according to claim 1 is characterized in that: In the step 7, the mass ratio of the enhanced de-hardening agent to the water to be treated is 1:5000-10000.

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

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

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