Seed crystal for recovering silicon ions in wastewater, preparation method and core crystal granulation process

Abstract

The present disclosure relates to the technical field of wastewater treatment, and particularly relates to a crystal seed for recovering silicon ions in wastewater, a preparation method and a core crystal granulation process. The preparation method is simple, convenient and low in cost, pure raw materials are used, no other pollutants are brought in, and the method is beneficial to industrial production. The crystal seed prepared by the present disclosure can strengthen the recovery of silicon ions in practical application, make the silicon ions in the water body tend to adhere to the crystal seed and grow, improve the utilization rate of the crystal seed, increase the removal rate of the silicon ions, achieve the purpose of reducing cost and increasing efficiency in the silicon-containing wastewater treatment process, and is beneficial to industrial production and application.

Description

Technical Field

[0001] This disclosure relates to the field of wastewater treatment technology, and in particular to a seed crystal for recovering silicon ions from wastewater, its preparation method, and its nucleation granulation process. Background Technology

[0002] Silicon-containing wastewater refers to wastewater containing a high concentration of silicon ions, typically generated during the production processes of industries such as semiconductors, solar cells, electronic components, and glass. This wastewater poses the following hazards: 1) Environmental pollution: Direct discharge of silicon-containing wastewater into rivers, lakes, and other water bodies can cause the water to become opaque and turbid, and in severe cases, can damage the aquatic ecosystem; 2) Threat to human health: Silicon is a harmful substance, and long-term exposure to silicon-containing wastewater may affect the function of organs such as the nervous system, liver, and kidneys.

[0003] Currently, the main treatment methods for this type of wastewater are: (1) Chemical treatment method, which mainly uses chemical reactions to convert silicon substances in silicon-containing wastewater into silicates or silica gels that are easy to precipitate, filter and remove; (2) Biological treatment method, which mainly uses the action of biological activators to convert silicon substances in wastewater into ammonia nitrogen, nitrate nitrogen and other substances, and uses microorganisms to remove pollutants such as organic matter; (3) Membrane separation method, which mainly uses reverse osmosis membranes, ultrafiltration membranes and other methods to retain silicon substances in wastewater on the membrane, so that the wastewater has no or low silicon content after treatment; (4) Electrochemical treatment method, which mainly uses electrochemical reactions to convert silicon substances in silicon-containing wastewater into substances that are easy to precipitate or remove, and can also remove other pollutants.

[0004] However, the aforementioned wastewater treatment methods all suffer from high costs, and the resulting solid waste is generally difficult to recycle, leading to resource waste. Some methods may also generate secondary pollution during wastewater treatment.

[0005] In conclusion, how to provide a treatment method that is low-cost, effective in removing silicon, and enables the recycling of the resulting solid materials is an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a seed crystal for recovering silicon ions from wastewater, a preparation method, and a nucleation granulation process. The seed crystal prepared by this disclosure, when applied to the nucleation granulation process, can efficiently remove silicon from wastewater, improve the wastewater reuse rate, and simultaneously produce dense granules, avoiding the generation of large amounts of hazardous sludge and effectively reducing treatment costs.

[0007] In a first aspect, this disclosure provides a method for preparing seed crystals for recovering silicon ions from wastewater, the method comprising the following steps:

[0008] A silicon source, alkali, and solvent are mixed and reacted to form a precipitate.

[0009] The resulting precipitate was subjected to aging treatment, solid-liquid separation and drying in sequence to obtain seed crystals for recovering silicon ions from wastewater;

[0010] The molar ratio of the silicon source to the alkali is (1-2):(1-2).

[0011] The molar ratio of silicon source to alkali can be selected as 1:1, 1.5:2, 1.2:1, 2:1.5, 2:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] A suitable silicon source to alkali ratio helps improve the quality and ability of seed crystals. If too little silicon source is added, there will be too few silicon ion sites on the surface of the seed crystals, reducing the crystallization rate; if too little alkali is added, a sufficient number of seed crystals will not be generated, resulting in waste of reagents.

[0013] The following are preferred technical solutions of this disclosure, but are not intended to limit the technical solutions provided by this disclosure. The technical objectives and beneficial effects of this disclosure can be better achieved through the following technical solutions.

[0014] As a preferred technical solution of this disclosure, the silicon source includes sodium silicate and / or tetraethyl orthosilicate.

[0015] Preferably, the alkali includes ammonia and / or sodium hydroxide.

[0016] Preferably, the solvent includes water.

[0017] As a preferred technical solution of this disclosure, the mixing operation includes: mixing the silicon source and the alkali with a solvent respectively to obtain a silicon source solution and a first alkali solution; and then adding the silicon source solution to the first alkali solution.

[0018] Preferably, the silicon source solution is added to the first alkaline solution at a rate of 1-3 mL / s, such as 1 mL / s, 1.5 mL / s, 12 mL / s, 2.5 mL / s, or 3 mL / s, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] Preferably, the concentration of the silicon source solution is 1-5 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the concentration of the first alkaline solution is 2-10 mol / L, such as 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, stirring is performed during the mixing process.

[0022] Preferably, the stirring speed is 200-500 r / min, such as 200 r / min, 300 r / min, 400 r / min or 500 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of this disclosure, the reaction temperature is 30-80℃, such as 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the reaction time is 1-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the aging treatment includes: allowing the obtained precipitate to stand in the reaction system for 1-24 hours, such as 1 hour, 2 hours, 5 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, or 24 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] Preferably, the aging treatment temperature is 0-20°C higher than the reaction temperature, for example, 0°C, 5°C, 10°C, 15°C or 20°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] As a preferred technical solution of this disclosure, the drying temperature is 80-120℃, such as 80℃, 90℃, 100℃, 110℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the drying time is 1-2 hours, such as 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Secondly, this disclosure provides a seed crystal for recovering silicon ions from wastewater, the seed crystal being prepared using the preparation method described in the first aspect.

[0030] Thirdly, this disclosure provides a nucleus crystal granulation process for recovering silicon ions from wastewater, using seed crystals prepared by the preparation method described in the first aspect or seed crystals described in the second aspect;

[0031] The nucleus crystal granulation process includes:

[0032] The seed crystals, silicon-containing wastewater, and precipitant are mixed;

[0033] The silicon-containing wastewater reacts with the precipitant to generate a silicon-containing precipitate, which crystallizes in an orderly manner on the surface of the seed crystal to form granules.

[0034] As a preferred technical solution of this disclosure, the nucleus crystal granulation process is carried out in a nucleus crystal granulation reactor, which includes an outer cylinder and an inner cylinder;

[0035] The inner cylinder is suspended within the outer cylinder and is vertically connected.

[0036] The lower side wall of the outer cylinder is independently equipped with a wastewater inlet pipe and a precipitant inlet pipe, and the height of both is lower than the bottom of the inner cylinder; the top of the outer cylinder is equipped with a toothed overflow weir and a water outlet pipe; the bottom of the outer cylinder is equipped with a granulation material discharge pipe.

[0037] As a preferred technical solution of this disclosure, the nucleus crystal granulation process includes the following steps:

[0038] (1) Fill the inner cylinder of the nucleogranulation reactor with the seed crystals;

[0039] (2) Silicon-containing wastewater and precipitant are introduced into the nuclear crystal granulation reactor to make the seed crystals fluidized. The silicon ions in the silicon-containing wastewater react with the precipitant to generate silicon-containing precipitate and crystallize in an orderly manner on the surface of the seed crystals to form granules. The resulting granules are discharged from the bottom of the nuclear crystal granulation reactor, and the regenerated water obtained after nuclear crystal granulation treatment is discharged from the top of the nuclear crystal granulation reactor.

[0040] Preferably, the filling height of the seed crystals in the nucleation granulation reactor in step (1) is 5-50% of the height of the inner cylinder, such as 5%, 10%, 20%, 30%, 40% or 50%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] As a preferred technical solution of this disclosure, the silica-containing wastewater in step (2) is first adjusted to pH 8.5-10.5 before being introduced into the nucleation granulation reactor, such as 8.5, 9, 9.5, 10 or 10.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the pH of the silicon-containing wastewater is adjusted using an acid solution or a second alkaline solution.

[0043] Preferably, the acid solution includes hydrochloric acid and / or sulfuric acid.

[0044] Preferably, the second alkaline solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0045] Preferably, the concentrations of the acid solution and the second alkaline solution are each independently 1-3 mol / L, such as 1 mol / L, 2 mol / L or 3 mol / L, but are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] Preferably, the precipitant in step (2) is introduced in the form of a solution, and the precipitant includes one or more of sodium chlorate, sodium aluminate, calcium chloride, magnesium chloride or magnesium sulfate, such as a combination of sodium chlorate and sodium aluminate, a combination of magnesium chloride and magnesium sulfate, etc.

[0047] As a preferred technical solution of this disclosure, in the nucleus crystal granulation process, the number of nucleus crystal granulation reactors is not less than two, and multiple nucleus crystal granulation reactors are connected in series. The regenerated water discharged from the previous stage nucleus crystal granulation reactor is used as the feed wastewater for the next stage nucleus crystal granulation reactor.

[0048] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0049] (1) The method for preparing seed crystals for recovering silicon ions from wastewater provided in this disclosure is simple, convenient, and low in cost. The raw materials used are pure and there are no other pollutants introduced, which is conducive to industrial production.

[0050] (2) The seed crystals prepared in this disclosure can enhance silicon ion recovery in practical applications, causing silicon ions in water to adhere to the seed crystals and grow, thereby increasing the utilization rate of the seed crystals and improving the removal rate of silicon ions, which is beneficial to industrial production and application. Attached Figure Description

[0051] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0052] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1This is a SEM image of the granules obtained in the nucleus granulation process described in Embodiment 1 of this disclosure. Detailed Implementation

[0054] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0055] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0056] The nucleogranulation reactor used in the following embodiments and comparative examples of this disclosure includes an outer cylinder and an inner cylinder;

[0057] The inner cylinder is suspended within the outer cylinder and is vertically connected.

[0058] The lower side wall of the outer cylinder is independently equipped with a wastewater inlet pipe and a precipitant inlet pipe, and the height of both is lower than the bottom of the inner cylinder; the top of the outer cylinder is equipped with a toothed overflow weir and a water outlet pipe; the bottom of the outer cylinder is equipped with a granulation material discharge pipe.

[0059] Example 1

[0060] This embodiment provides a method for preparing seed crystals for recovering silicon ions from wastewater and a nucleation granulation process. The preparation method includes the following steps:

[0061] Prepare a 1 mol / L sodium silicate solution and a 2 mol / L sodium hydroxide solution;

[0062] At 30°C, the above sodium silicate solution was added to the sodium hydroxide solution at a dropping rate of 1 mL / s, while stirring at a speed of 200 r / min. The reaction was carried out for 3 hours, and the final molar ratio of sodium silicate to sodium hydroxide was controlled to be 1:1.2. A precipitate was formed after the reaction.

[0063] The resulting precipitate was aged at 30°C for 12 hours, then washed with deionized water, and dried at 100°C for 1 hour to obtain seed crystals for recovering silicon ions from wastewater.

[0064] The seed crystals prepared in this embodiment are subjected to a nucleation granulation process, including:

[0065] (1) Fill the inner cylinder of the nucleation granulation reactor with the seed crystals used to recover silicon ions from the wastewater, and fill the inner cylinder to a height of 5% of the height of the inner cylinder;

[0066] (2) Wastewater with a silicon ion concentration of 100 mg / L and a pH of 9 is introduced from the bottom of the nuclear crystal granulation reactor at a flow rate of 2000 L / h. At the same time, a sodium aluminate solution with a concentration of 600 mg / L is introduced from the bottom of the nuclear crystal granulation reactor at a flow rate of 60 L / h, so that the seed crystals are in a fluidized state.

[0067] Silicon ions in silicon-containing wastewater react with sodium aluminate to form silicon-containing precipitate, which crystallizes in an orderly manner on the surface of the seed crystal to form granules. The resulting granules are discharged from the bottom of the nucleation granulation reactor, and the regenerated water obtained after nucleation granulation treatment is discharged from the top of the nucleation granulation reactor.

[0068] The SEM image of the obtained granules is shown below. Figure 1 As shown.

[0069] Example 2

[0070] This embodiment provides a method for preparing seed crystals for recovering silicon ions from wastewater and a nucleation granulation process. The preparation method includes the following steps:

[0071] Prepare a 5 mol / L sodium silicate solution and a 10 mol / L sodium hydroxide solution;

[0072] At 50°C, the above sodium silicate solution was added to the sodium hydroxide solution at a dropping rate of 2 mL / s, while stirring at a speed of 500 r / min. The reaction was carried out for 1 hour, and the final molar ratio of sodium silicate to sodium hydroxide was controlled to be 1.5:2. A precipitate was formed after the reaction.

[0073] The resulting precipitate was aged at 52°C for 24 hours, then washed with deionized water, and dried at 80°C for 2 hours to obtain seed crystals for recovering silicon ions from wastewater.

[0074] The seed crystals prepared in this embodiment are subjected to a nucleation granulation process, including:

[0075] (1) Fill the inner cylinder of the nucleation granulation reactor with the seed crystals used to recover silicon ions from the wastewater, and fill the inner cylinder to a height of 30% of the height of the inner cylinder.

[0076] (2) Wastewater with a silicon ion concentration of 150 mg / L and a pH of 9.1 is introduced from the bottom of the nuclear crystal granulation reactor at a flow rate of 2000 L / h. At the same time, magnesium sulfate solution with a concentration of 600 mg / L is introduced from the bottom of the nuclear crystal granulation reactor at a flow rate of 60 L / h, so that the seed crystals are in a fluidized state.

[0077] Silicon ions in silicon-containing wastewater react with magnesium sulfate to form silicon-containing precipitates, which then crystallize in an orderly manner on the surface of the seed crystals to form granules. The resulting granules are discharged from the bottom of the nuclear crystal granulation reactor, and the reclaimed water obtained after nuclear crystal granulation treatment is discharged from the top of the nuclear crystal granulation reactor.

[0078] Example 3

[0079] This embodiment provides a method for preparing seed crystals for recovering silicon ions from wastewater and a nucleation granulation process. The preparation method includes the following steps:

[0080] Prepare a 3 mol / L sodium silicate solution and a 7 mol / L sodium hydroxide solution;

[0081] At 80°C, the above sodium silicate solution was added to the sodium hydroxide solution at a dropping rate of 2.5 mL / s, while stirring at a speed of 300 r / min. The reaction was carried out for 5 h, and the final molar ratio of sodium silicate to sodium hydroxide was controlled to be 1.8:2. A precipitate was formed after the reaction.

[0082] The resulting precipitate was aged at 80°C for 16 hours, then washed with deionized water, and dried at 120°C for 1.5 hours to obtain seed crystals for recovering silicon ions from wastewater.

[0083] The seed crystals prepared in this embodiment are used for a nucleation crystal granulation process, wherein the nucleation crystal granulation device includes a primary nucleation crystal granulation reactor and a secondary nucleation crystal granulation reactor arranged in series.

[0084] The nucleus crystal granulation process includes:

[0085] (1) The seed crystals used to recover silicon ions from wastewater are filled into the inner cylinders of the primary and secondary nucleation granulation reactors respectively, and the filling height is 50% of the height of the inner cylinder.

[0086] (2) Wastewater with a silicon ion concentration of 300 mg / L and a pH of 9.1 is introduced from the bottom of the first-stage nucleation granulation reactor at a flow rate of 3000 L / h. At the same time, magnesium sulfate solution with a concentration of 600 mg / L is introduced from the bottom of the nucleation granulation reactor at a flow rate of 60 L / h, so that the seed crystals are in a fluidized state.

[0087] Silicon ions in silicon-containing wastewater react with magnesium sulfate to form silicon-containing precipitates, which crystallize orderly on the surface of the seed crystals to form primary granules. The primary granules are discharged from the bottom of the primary nucleation granulation reactor. The primary reclaimed water obtained after nucleation granulation treatment flows out from the top of the primary nucleation granulation reactor and enters the secondary nucleation granulation reactor.

[0088] (3) At the same time as the primary reclaimed water enters the secondary nucleation granulation reactor, a magnesium chloride solution with a concentration of 500 mg / L is introduced from the bottom of the secondary nucleation granulation reactor at a flow rate of 60 L / h, so that the seed crystals are fluidized. The silicon ions in the primary reclaimed water react with magnesium chloride to generate silicon-containing precipitates and crystallize in an orderly manner on the surface of the seed crystals to form secondary granules. The resulting secondary granules are discharged from the bottom of the secondary nucleation granulation reactor, and the secondary reclaimed water obtained after nucleation granulation treatment flows out from the top of the secondary nucleation granulation reactor.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing seed crystals for recovering silicon ions from wastewater and a nucleation granulation process. The preparation method is the same as that in Example 1, except that the final molar ratio of sodium silicate to sodium hydroxide is controlled to be 1:3.

[0091] The nucleus crystal granulation process is the same as that in Example 1, except that the seed crystals prepared in Example 1 are replaced with the seed crystals of this comparative example.

[0092] Comparative Example 2

[0093] This comparative example provides a method for preparing seed crystals for recovering silicon ions from wastewater and a nucleation granulation process. The preparation method is the same as that in Example 1, except that the final molar ratio of sodium silicate to sodium hydroxide is controlled to be 3:1.

[0094] The nucleus crystal granulation process is the same as that in Example 1, except that the seed crystals prepared in Example 1 are replaced with the seed crystals of this comparative example.

[0095] Comparative Example 3

[0096] This comparative example provides a seed crystal for recovering silicon ions from wastewater, wherein the seed crystal is quartz sand.

[0097] The nucleus crystal granulation process is the same as that in Example 1, except that the seed crystals prepared in Example 1 are replaced with the seed crystals of this comparative example.

[0098] After running for 120 hours, the pH, silicon ion concentration, and turbidity of the reclaimed water after the nucleogranulation process in Examples 1-3 and Comparative Examples 1-3 were measured, and the silicon ion removal rate was calculated. The results are shown in Table 1.

[0099] Table 1

[0100]

[0101] As shown in Table 1, compared with existing commercial seed crystals, the seed crystals prepared by the method disclosed in this invention achieve a silicon ion removal rate of over 90% and a turbidity of less than 8.9 NTU in practical applications, effectively improving the silicon ion recovery rate and achieving the goal of reducing costs and increasing efficiency in silicon-containing wastewater treatment processes.

[0102] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0103] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nucleogranulation process for recovering silicon ions from wastewater, characterized in that, The process uses the following steps to prepare seed crystals to recover silicon ions from wastewater: mixing a silicon source, an alkali, and a solvent and reacting them to generate a precipitate; the silicon source includes sodium silicate and / or tetraethyl orthosilicate; the alkali includes ammonia and / or sodium hydroxide; the mixing operation includes: mixing the silicon source and the alkali with the solvent respectively to obtain a silicon source solution and a first alkali solution; then adding the silicon source solution to the first alkali solution; The resulting precipitate was subjected to aging treatment, solid-liquid separation and drying in sequence to obtain seed crystals for recovering silicon ions from wastewater; The molar ratio of the silicon source to the alkali is (1-2):(1-2); The nucleus crystal granulation process includes: The seed crystals, silicon-containing wastewater, and precipitant are mixed; The silicon-containing wastewater reacts with the precipitant to generate a silicon-containing precipitate, which crystallizes in an orderly manner on the surface of the seed crystal to form granules. The nucleus crystal granulation process is carried out in a nucleus crystal granulation reactor, which includes an outer cylinder and an inner cylinder. The inner cylinder is suspended within the outer cylinder and is vertically connected. The lower side wall of the outer cylinder is independently equipped with a wastewater inlet pipe and a precipitant inlet pipe, and the height of both is lower than the bottom of the inner cylinder; the top of the outer cylinder is equipped with a toothed overflow weir and a water outlet pipe; the bottom of the outer cylinder is equipped with a granulation body discharge pipe. The nucleus crystal granulation process includes the following steps: (1) Fill the inner cylinder of the nucleogranulation reactor with the seed crystals; (2) Silicon-containing wastewater and precipitant are introduced into the nuclear crystal granulation reactor to make the seed crystals fluidized. The silicon ions in the silicon-containing wastewater react with the precipitant to generate silicon-containing precipitate and crystallize in an orderly manner on the surface of the seed crystals to form granules. The resulting granules are discharged from the bottom of the nuclear crystal granulation reactor, and the regenerated water obtained after nuclear crystal granulation treatment is discharged from the top of the nuclear crystal granulation reactor. In step (2), the precipitant is introduced in the form of a solution, and the precipitant includes one or more of sodium chlorate, sodium aluminate, calcium chloride, magnesium chloride or magnesium sulfate.

2. The nucleus crystal granulation process according to claim 1, characterized in that, In step (1), the seed crystals are filled to a height of 5-50% of the height of the inner cylinder in the nucleation granulation reactor. In step (2), the pH of the silicon-containing wastewater is adjusted to 8.5-10.5 before it is introduced into the nucleation granulation reactor; The pH of the silicon-containing wastewater is adjusted using an acid solution or a second alkaline solution; The acid solution includes hydrochloric acid and / or sulfuric acid; The second alkaline solution includes sodium hydroxide solution and / or potassium hydroxide solution; The concentrations of the acid solution and the second alkaline solution are each independently 1-3 mol / L.

3. The nucleus crystal granulation process according to claim 1 or 2, characterized in that, In the nucleus crystal granulation process, the number of nucleus crystal granulation reactors is not less than two, and multiple nucleus crystal granulation reactors are connected in series. The regenerated water discharged from the previous stage nucleus crystal granulation reactor is used as the feed wastewater for the next stage nucleus crystal granulation reactor.

4. The nucleus crystal granulation process according to claim 1 or 2, characterized in that, The solvent includes water.

5. The nucleus crystal granulation process according to claim 1 or 2, characterized in that, The silicon source solution is added to the first alkaline solution at a rate of 1-3 mL / s; The concentration of the silicon source solution is 1-5 mol / L; The concentration of the first alkaline solution is 2-10 mol / L; Stirring is performed during the mixing process; The stirring speed is 200-500 r / min.

6. The nucleus crystal granulation process according to claim 1 or 2, characterized in that, The reaction temperature is 30-80℃; The reaction time is 1-5 hours; The aging process includes: allowing the resulting precipitate to stand in the reaction system for 1-24 hours; The aging treatment temperature is 0-20°C higher than the reaction temperature.

7. The nucleus crystal granulation process according to claim 1 or 2, characterized in that, The drying temperature is 80-120℃; The drying time is 1-2 hours.

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