A treatment process for high-concentration sulfate wastewater

Abstract

This invention discloses a treatment process for high-concentration sulfate wastewater, belonging to the field of wastewater purification technology. The invention first provides a multifunctional composite ion sieve, the raw materials of which include magnetic core microspheres, calcium aluminate precursor components, heavy metal chelating agents, scale inhibitors, antioxidants, antibacterial agents, host-guest recognition agents, polysaccharide compounds, polyacrylic acid compounds, crosslinking agents, and initiators. The ion sieve is prepared through steps including magnetic core preparation, calcium aluminate precursor functional layer deposition, small molecule modification layer loading, and pH-responsive outer shell coating. In use, the ion sieve is added to wastewater and stirred for adsorption. After adsorption saturation, solid-liquid separation is achieved through magnetic separation, and the material is regenerated and recycled sequentially using desorption and reconstruction solutions.

Description

Technical Field

[0001] This invention relates to the field of wastewater purification technology, specifically to a treatment process for high-concentration sulfate wastewater. Background Technology

[0002] High-concentration sulfate wastewater is widely generated in industries such as mining, metallurgy, chemicals, printing and dyeing, and pharmaceuticals, with sulfate concentrations typically reaching thousands or even tens of thousands of milligrams per liter. If this wastewater is discharged directly without proper treatment, it will not only increase water mineralization and damage soil structure, but may also be converted into hydrogen sulfide by sulfate-reducing bacteria under anaerobic conditions, producing foul odors and exacerbating the corrosion of metal pipelines. With increasingly stringent environmental standards, higher requirements are being placed on the synergistic removal of sulfate and its associated heavy metals and organic pollutants.

[0003] Currently, the main technologies for treating high-concentration sulfate wastewater can be categorized into precipitation, ion exchange, membrane separation, and biological methods. Chemical precipitation generates calcium sulfate precipitate by adding calcium sources such as lime, but it suffers from drawbacks such as high sludge production, incomplete sulfate removal, and susceptibility to scaling and clogging. Ion exchange, while achieving deep sulfate removal, suffers from resin contamination by suspended solids and organic matter in the wastewater, requiring frequent regeneration and incurring high costs. Membrane separation technologies such as reverse osmosis and nanofiltration can efficiently retain sulfate, but they have stringent requirements for influent water quality, high energy consumption, and the resulting high-salt concentrate requires further treatment. Biological methods utilize sulfate-reducing bacteria to convert sulfate into sulfides; while relatively low-cost, they have long reaction cycles, are sensitive to temperature and pH, and the generated hydrogen sulfide poses a risk of secondary pollution. Each of these single technologies often struggles to simultaneously address the comprehensive requirements of sulfate removal, simultaneous heavy metal stabilization, pollution resistance, and long-term operational stability.

[0004] In recent years, composite functional materials have received widespread attention in the field of water treatment. By integrating functions such as adsorption, ion exchange, chelation, and magnetic separation into a single material system, it is expected to achieve synergistic removal and convenient recovery of multiple pollutants. However, existing composite materials generally suffer from problems such as rapid loss of active components, insufficient selective adsorption capacity, susceptibility to interference from high ionic strength, and poor regeneration and recycling performance when dealing with high sulfate environments. Especially under complex water quality conditions containing coexisting ions such as calcium and magnesium, inorganic salt deposition easily occurs on the material surface, leading to blockage of adsorption sites and a significant reduction in service life. In addition, the preparation processes of some composite materials are complex and involve toxic solvents, making it difficult to achieve large-scale production and engineering applications. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a treatment process for high-concentration sulfate wastewater. It aims to efficiently remove sulfate ions and heavy metals from high-concentration sulfate wastewater, while achieving easy separation and regeneration of materials.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater, the raw material comprising the following components in parts by weight: 15 to 25 parts by weight of magnetic core microspheres; 30 to 45 parts by weight of calcium aluminate precursor component; 2 to 4 parts by weight of heavy metal chelating agent; 2 to 3 parts by weight of scale inhibitor; Antioxidant 1.5 to 3 parts by weight; 0.5 to 1 part by weight of antibacterial agent; 2 to 4 parts by weight of the subject-object identification agent; 2 to 6 parts by weight of polysaccharide compounds; 3 to 10 parts by weight of polyacrylic acid compounds; Crosslinking agent, 0.1 to 0.5 parts by weight; Initiator 0.05 to 0.2 parts by weight.

[0007] Furthermore, the magnetic core microspheres are selected from one or more of the following: iron oxide microspheres with a silica shell, cobalt ferrite microspheres with a silica shell, and nickel ferrite microspheres with a silica shell. The calcium aluminate precursor component is generated by the reaction of an aluminum source and a calcium source, wherein the aluminum source is selected from one or more of sodium aluminate and potassium aluminate; and the calcium source is selected from one or more of calcium hydroxide, calcium oxide and calcium nitrate. The heavy metal chelating agent is selected from one or more of sodium dithiocarbamate, sodium dimethyl dithiocarbamate, and sodium diethyl dithiocarbamate. The scale inhibitor is selected from one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and hydroxyethylidene diphosphonic acid; The antioxidant is selected from one or more of reduced glutathione, levocysteine ​​and ascorbic acid; The antibacterial agent is selected from one or more of 2,4,4-trichloro-2-hydroxydiphenyl ether, methylisothiazolinone, and chlorhexidine; The host-guest identification agent is selected from one or more of sodium calix tetraaryl sulfonate, p-tert-butylcalix tetraaryl, and p-sulfonylcalix hexaaryl; The polysaccharide compound is selected from one or more of carboxymethyl chitosan, sodium alginate, and sodium hyaluronate; The polyacrylic acid compound is selected from one or more of polyacrylic acid with a molecular weight of 5,000, polymethacrylic acid with a molecular weight of 5,000, and polymaleic acid with a molecular weight of 5,000. The crosslinking agent is selected from one or more of N,N-methylenebisacrylamide, glutaraldehyde, and epichlorohydrin; The initiator is selected from one or more of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

[0008] Furthermore, the preparation method of the multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater includes the following steps: Step 1: Preparation of the magnetic core: 10 parts by mass of ferric chloride hexahydrate, 6 parts by mass of anhydrous sodium acetate, and 2 parts by mass of polyethylene glycol tetrahydrate were dissolved in 80 parts by mass of ethylene glycol. After magnetic stirring for 30 minutes, the mixture was transferred to a polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 200 degrees Celsius for 10 hours. After cooling to room temperature, the mixture was magnetically separated, washed with ethanol, and vacuum dried at 60 degrees Celsius for 6 hours to obtain internal microspheres. The obtained internal microspheres were dispersed in a mixture of 100 parts by mass of ethanol and water, and 4 parts by mass of tetraethyl orthosilicate and 2 parts by mass of 25% ammonia were added. The mixture was stirred at 25 degrees Celsius for 8 hours, and after magnetic separation, washing with water, and drying, magnetic core microspheres were obtained. The second step is the deposition of the calcium aluminate precursor functional layer: 15 to 25 parts by mass of the magnetic core microspheres obtained in the first step are ultrasonically dispersed in an aqueous solution containing sodium aluminate or potassium aluminate, heated to 40 degrees Celsius, and an aqueous solution containing a calcium source is added dropwise until the pH of the system is 12.0 to 12.5. The mixture is stirred at 60 degrees Celsius for 3 hours to deposit the calcium aluminate precursor, and then magnetically separated and washed until neutral. The third step is the loading of the small molecule modified layer: 2 to 4 parts by weight of heavy metal chelating agent, 2 to 3 parts by weight of scale inhibitor, 1.5 to 3 parts by weight of antioxidant, 0.5 to 1 part by weight of antibacterial agent pre-dissolved in 5 parts by weight of acetone, and 2 to 4 parts by weight of host-guest recognition agent are dissolved together in 50 parts by weight of phosphate buffer with a pH of 7.4; the microspheres obtained in the second step are added to this solution, and adsorbed by shaking at 4 degrees Celsius in the dark for 12 hours, followed by magnetic separation and drying with cold air; The fourth step is acid-base responsive outer shell coating: The microspheres from the third step are dispersed in 100 parts by mass of a mixed solution containing 2 to 6 parts by mass of polysaccharide compounds and 3 to 10 parts by mass of polyacrylic acid compounds. 0.1 to 0.5 parts by mass of crosslinking agent and 0.05 to 0.2 parts by mass of initiator are added. After nitrogen deoxygenation for 30 minutes, a free radical crosslinking reaction is carried out at 50 degrees Celsius for 2 hours. After magnetic separation, water washing, and freeze drying at -40 degrees Celsius for 12 hours, a multifunctional composite ion sieve for use in the treatment process of high-concentration sulfate wastewater is obtained.

[0009] Furthermore, in the second step of depositing the calcium aluminate precursor functional layer, the aqueous solution containing sodium aluminate is prepared by 3.5 parts by mass of sodium aluminate and 146.5 parts by mass of pure water, and the aqueous solution containing the calcium source is prepared by 15 parts by mass of calcium hydroxide and 100 parts by mass of pure water. The dropwise addition operation makes the pH of the system reach 12.0.

[0010] Furthermore, in the third step of loading the small molecule modification layer, the heavy metal chelating agent used is sodium dimethyl dithiocarbamate in an amount of 3 parts by mass, the scale inhibitor used is ethylenediaminetetramethylenephosphonic acid in an amount of 2.5 parts by mass, the antioxidant used is cysteine ​​in an amount of 2 parts by mass, the antibacterial agent used is methylisothiazolinone in an amount of 0.8 parts by mass, and the host-guest recognition agent used is p-tert-butylcalix tetraaromatic hydrocarbon in an amount of 3 parts by mass.

[0011] Furthermore, in the fourth step of acid-base response outer shell coating, the polysaccharide compound used is sodium hyaluronate in an amount of 6 parts by mass, the polyacrylic acid compound used is polymaleic acid in an amount of 10 parts by mass with a molecular weight of 5,000, the crosslinking agent used is epichlorohydrin in an amount of 0.5 parts by mass, and the initiator used is azobisisobutyronitrile in an amount of 0.2 parts by mass.

[0012] Furthermore, in the first step of magnetic core preparation, the ethanol-water mixture is prepared by mixing 80 parts by mass of ethanol and 20 parts by mass of water, and the internal microspheres are washed with ethanol 3 times.

[0013] A treatment process for high-concentration sulfate wastewater utilizes the multifunctional composite ion sieve described above, and the specific operating steps include: The multifunctional composite ion sieve is added to the wastewater at a ratio of 2 to 8 parts by weight per 1000 parts by weight of wastewater, and the mixture is stirred and adsorbed for 0.5 to 3 hours. A vacuum pump is used to provide a gauge pressure of -0.02 to -0.07 MPa to draw the adsorption-treated wastewater into a temporary storage tank. The pH is adjusted to 6 to 9 in the temporary storage tank. A buffer tank is set between the temporary storage tank and the negative pressure system. After the ion sieve adsorption is saturated, solid-liquid separation is performed by an external magnetic field of not less than 0.3 Tesla, and the material is regenerated and recycled in sequence using desorption liquid and reconstruction liquid.

[0014] Furthermore, the adsorption treatment time was 0.5 hours, and the pH was adjusted to 6.

[0015] Furthermore, after the ion sieve adsorption becomes saturated, an external magnetic field of 0.3 Tesla to 0.5 Tesla is applied for solid-liquid separation. First, an desorption solution prepared with 0.73 parts by mass of hydrogen chloride, 1.46 parts by mass of ethylenediaminetetraacetic acid, and 100 parts by mass of pure water is used for acid washing and desorption, followed by washing with pure water until neutral. Then, the desorbed ion sieve is dispersed in an aluminum source aqueous solution prepared with 3.5 parts by mass of sodium aluminate and 146.5 parts by mass of pure water, and a calcium source aqueous solution prepared with 15 parts by mass of calcium hydroxide and 100 parts by mass of pure water is added dropwise to bring the pH of the system to 12.0 to 12.5. The system is stirred at 60 degrees Celsius for 1 to 2 hours to reconstruct the active layer of the calcium aluminate precursor.

[0016] This invention achieves efficient synergistic removal of sulfate and heavy metals by constructing a multi-layered core-shell composite ion sieve. A magnetic core endows the material with the ability to rapidly separate and recover under an external magnetic field; the calcium aluminate precursor layer reacts with sulfate in wastewater to form a sulfate-containing solid phase, thereby achieving sulfate fixation and removal; the heavy metal chelating agent in the small molecule modification layer captures heavy metal ions in wastewater through coordination, while the scale inhibitor inhibits the deposition of inorganic salts such as calcium and magnesium on the material surface; antioxidants and antibacterial agents synergistically maintain the chemical stability and resistance to biofouling in complex wastewater environments; the host-guest recognition agent selectively enriches specific pollutants using a cavity structure; the outermost pH-responsive shell layer is cross-linked from polysaccharide compounds and polyacrylic acid compounds, maintaining a dense structure under neutral conditions to prevent the loss of active components. In the regeneration stage, sulfate and associated metals on the material surface and in the pores are first removed by an acidic desorption solution, and then the calcium aluminate precursor active layer is restored through an alkaline reconstruction step using aluminum and calcium sources. This mechanism enables the ion sieve to integrate multiple functions such as adsorption precipitation, chelation, molecular recognition, magnetic separation, and reconfigurable regeneration in a single material system, achieving deep purification of high-concentration sulfate wastewater and material recycling.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By integrating multiple mechanisms such as calcium aluminate fixation of sulfate, heavy metal chelation, host-guest recognition, and acid-base response mass transfer, the shortcomings of single technologies in simultaneously and efficiently removing sulfate and heavy metals are overcome, and the synergistic treatment capability of complex pollutants is significantly improved.

[0018] 2. By using a composite modification of scale inhibitors, antioxidants and antibacterial agents, problems such as inorganic scaling, oxidation failure of active components and microbial adhesion in high-salt environments are effectively suppressed, thus extending the continuous operating life of the material under harsh water quality conditions.

[0019] 3. By utilizing a magnetic core, rapid magnetic separation and recovery are achieved after adsorption saturation. Combined with the regeneration path of "acidic desorption-alkaline reconstruction", the adsorption sites can be restored and the material can be recycled, reducing the difficulty of process operation and the amount of solid waste generated. Detailed Implementation

[0020] The following will provide a clear and complete description of the technical solutions of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Example 1

[0021] A treatment process for high-concentration sulfate wastewater: 1. Preparation of multifunctional composite ion sieves: 1.1 parts by weight of raw material components: 20 parts by weight of magnetic core microspheres; 38 parts by weight of calcium aluminate precursor components; 3 parts by weight of sodium dimethyl dithiocarbamate; 2.5 parts by weight of ethylenediaminetetramethylenephosphonic acid; 2 parts by weight of L-cysteine; 0.8 parts by weight of methylisothiazolinone; 3 parts by mass of p-tert-butylcalix tetraaromatic hydrocarbon; 6 parts by weight of sodium hyaluronate; 10 parts by mass of polymaleic acid with a molecular weight of 5,000; 0.5 parts by weight of epichlorohydrin; 0.2 parts by weight of azobisisobutyronitrile.

[0022] Among them, the magnetic core microspheres are iron oxide microspheres with a silica shell on the surface; the calcium aluminate precursor component is generated by the reaction of sodium aluminate and calcium hydroxide.

[0023] 1.2 Preparation method: Step 1, magnetic core fabrication: 10 parts by mass of ferric chloride hexahydrate, 6 parts by mass of anhydrous sodium acetate, and 2 parts by mass of polyethylene glycol tetrahydrate were dissolved in 80 parts by mass of ethylene glycol. After magnetic stirring for 30 minutes, the mixture was transferred to a polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 200°C for 10 hours. After cooling to room temperature, magnetic separation was performed using a magnetic field. The mixture was washed three times with ethanol and dried in a vacuum drying oven at 60°C for 6 hours to obtain internal iron oxide microspheres. The obtained internal microspheres were dispersed in 100 parts by mass of an ethanol-water mixture prepared by mixing 80 parts by mass of ethanol and 20 parts by mass of water. 4 parts by mass of tetraethyl orthosilicate and 2 parts by mass of 25% ammonia water were added. The mixture was stirred at a constant temperature of 25°C for 8 hours. After magnetic separation, washing with deionized water until neutral, and drying, iron oxide magnetic core microspheres with a silica shell were obtained.

[0024] Step 2: Deposition of the calcium aluminate precursor functional layer: Twenty parts by mass of the magnetic core microspheres obtained in the first step were ultrasonically dispersed in an aqueous solution of sodium aluminate prepared from 3.5 parts by mass of sodium aluminate and 146.5 parts by mass of pure water. The system was heated to 40 degrees Celsius, and an aqueous solution of calcium source prepared from 15 parts by mass of calcium hydroxide and 100 parts by mass of pure water was slowly added dropwise until the pH of the system reached 12.0. Then the system was heated to 60 degrees Celsius and stirred at a constant temperature for 3 hours to allow the calcium aluminate precursor to be fully deposited on the surface of the magnetic core microspheres. After magnetic separation, the system was washed with deionized water until it was neutral and set aside for later use.

[0025] Step 3: Loading of small molecule modified layers: Three parts by mass of sodium dimethyl dithiocarbamate, 2.5 parts by mass of ethylenediaminetetramethylenephosphonic acid, 2 parts by mass of L-cysteine, 0.8 parts by mass of methylisothiazolinone pre-dissolved in 5 parts by mass of acetone, and 3 parts by mass of p-tert-butylcalix tetraaromatic hydrocarbon were dissolved together in 50 parts by mass of phosphate buffer with a pH of 7.4. The mixture was stirred thoroughly until all components were completely dissolved. The microspheres with calcium aluminate precursor layer obtained in the second step were added to the mixed solution and placed in a light-protected environment at 4 degrees Celsius for 12 hours for adsorption by shaking. After magnetic separation, the surface of the microspheres was dried with cold air and set aside for later use.

[0026] Step 4: Acid-base responsive outer shell coating: The microspheres with the small molecule modified layer obtained in the third step were dispersed in 100 parts by mass of pure water. 6 parts by mass of sodium hyaluronate and 10 parts by mass of polymaleic acid with a molecular weight of 5,000 were added and stirred until completely dissolved to form a mixed solution. Subsequently, 0.5 parts by mass of epichlorohydrin and 0.2 parts by mass of azobisisobutyronitrile were added to the mixed solution. Nitrogen gas was continuously purged into the system for 30 minutes to remove oxygen. After completion, the system was heated to 50 degrees Celsius and subjected to a free radical cross-linking reaction for 2 hours. After the reaction, the microspheres were obtained by magnetic separation, washed with deionized water until neutral, and then freeze-dried in a freeze dryer at -40 degrees Celsius for 12 hours to obtain the multifunctional composite ion sieve.

[0027] 2. A specific treatment process for high-concentration sulfate wastewater: 2.1 Wastewater quality treatment: In this embodiment, the wastewater being treated is high-concentration sulfate wastewater from open-pit mining and tailings dam leachate. The various ion and water quality indicators are shown in Table 1 (unit: mg / L, pH dimensionless): Table 1 2.2 Process flow: Step 1: The raw water is pretreated using a grid + quartz sand filter to remove suspended solids such as silt and tailings debris with a particle size >50μm. After pretreatment, the SS is reduced to ≤30mg / L. Step 2: Add 5 parts by weight of multifunctional composite ion sieve to every 1000 parts by weight of pretreated wastewater; add to a mechanically stirred reactor, stir at a stirring rate of 150 r / min, and stir and adsorb at room temperature (25℃) for 0.5 hours; Step 3: The vacuum pump provides a stable negative pressure of -0.05MPa to draw the adsorbed wastewater into the temporary storage tank; sodium hydroxide solution (10% by mass) is added to adjust the pH of the wastewater to 6.0; Step 4: Apply an external magnetic field of 0.4 Tesla. The wastewater flows through the magnetic separation zone at a flow rate of 0.5 m / s. The saturated ion sieve is completely magnetically trapped, achieving a solid-liquid separation efficiency of 100% and a separation time of ≤1 minute. Step 5: First, prepare an desorption solution by mixing 0.73 parts hydrogen chloride, 1.46 parts ethylenediaminetetraacetic acid, and 100 parts pure water (prepare fresh before use); add the magnetically separated ion sieve to the regeneration vessel, add the desorption solution at a solid-liquid ratio of 1:10, and stir for 1 hour at 30℃ and 100 rpm; wash with pure water until neutral, then add the ion sieve to an aluminum source aqueous solution prepared by mixing 3.5 parts sodium aluminate and 146.5 parts pure water, and slowly add a calcium source aqueous solution prepared by mixing 15 parts calcium hydroxide and 100 parts pure water to bring the pH of the system to 12.0~12.5, and stir for 1 hour at 60℃ and 100 rpm; finally, wash with pure water until the pH of the washing solution is 6.5~7.0, and set aside.

[0028] Step 6: The multifunctional composite ion sieve after desorption and reconstruction is directly reused for the next batch of mine sulfate wastewater treatment, with the same amount added in the cycle as the first time. Example 2

[0029] A treatment process for high-concentration sulfate wastewater is described, referring to the preparation method and treatment process of Example 1, except that sodium dimethyl dithiocarbamate is replaced with sodium diethyl dithiocarbamate, and the rest remains the same as in Example 1. Example 3

[0030] A treatment process for high-concentration sulfate wastewater is described, referring to the preparation method and treatment process of Example 1, except that the p-tert-butylcalix tetraaromatic hydrocarbon is replaced with p-sulfonylcalix hexaaromatic hydrocarbon, while the rest remains the same as in Example 1.

[0031] Comparative Example 1 A treatment process for high-concentration sulfate wastewater, referring to the preparation method and treatment process of Example 1, except that sodium dimethyl dithiocarbamate is not added, and the rest remains the same as in Example 1.

[0032] Comparative Example 2 A treatment process for high-concentration sulfate wastewater, referring to the preparation method and treatment process of Example 1, except that ethylenediaminetetramethylenephosphonic acid is not added, and the rest remains the same as in Example 1.

[0033] Comparative Example 3 A treatment process for high-concentration sulfate wastewater, referring to the preparation method and treatment process of Example 1, except that p-tert-butylcalix tetraaromatic hydrocarbon is not added, and the rest remains the same as in Example 1.

[0034] Comparative Example 4 A treatment process for high-concentration sulfate wastewater is described, referring to the preparation method and treatment process of Example 1, except that sodium dimethyl dithiocarbamate is replaced with disodium ethylenediaminetetraacetate, while the rest remains the same as in Example 1.

[0035] Comparative Example 5 A treatment process for high-concentration sulfate wastewater is described, referring to the preparation method and treatment process of Example 1, except that sodium dimethyl dithiocarbamate is replaced with trisodium citrate, and the rest remains the same as in Example 1.

[0036] Performance testing: 1. Sulfate removal rate test: After adsorption, the supernatant was collected, filtered through a 0.45 μm filter membrane, and the sulfate concentration C1 in the effluent was detected by ion chromatography. The sulfate concentration C0 in the raw water was recorded. The sulfate removal rate η(SO4) was calculated. 2-= (C0-C1) / C0×100%, and the data is shown in Table 2.

[0037] 2. Heavy metal ion removal efficiency test: Using the supernatant after the above adsorption, the total Fe and Mn in the raw water and effluent were detected by ICP-MS. 2+ The removal rate was calculated, and the data are shown in Table 2.

[0038] 3. Regeneration cycle performance test: Repeated adsorption-magnetic separation-acidic desorption-alkaline reconstruction cycle operation 20 times, detect sulfate removal rate, calculate performance retention rate, removal rate retention rate after n cycles = sulfate removal rate after n cycles / initial sulfate removal rate × 100%, the data are shown in Table 2.

[0039] Table 2 In the examples, the group using the complete multifunctional composite ion sieve formulation showed the best overall performance in sulfate removal, heavy metal ion capture, and long-term cycle stability. While the absence of heavy metal chelating agents significantly weakened the heavy metal removal capacity, it had a smaller impact on sulfate removal. The absence of scale inhibitors led to a significant decrease in sulfate removal efficiency and cycle life. The absence of host-guest recognition agents or the use of ordinary chelating agents as substitutes resulted in a moderate decrease in removal rate and stability. This demonstrates that the synergistic effect of each functional component is irreplaceable for achieving efficient and synergistic removal of sulfate and heavy metals and long-term stable operation of the material.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multifunctional composite ion sieve for use in the treatment process of high-concentration sulfate wastewater, characterized in that, The raw materials include the following components in parts by weight: 15 to 25 parts by weight of magnetic core microspheres; 30 to 45 parts by weight of calcium aluminate precursor component; 2 to 4 parts by weight of heavy metal chelating agent; 2 to 3 parts by weight of scale inhibitor; Antioxidant 1.5 to 3 parts by weight; 0.5 to 1 part by weight of antibacterial agent; 2 to 4 parts by weight of the subject-object identification agent; 2 to 6 parts by weight of polysaccharide compounds; 3 to 10 parts by weight of polyacrylic acid compounds; Crosslinking agent, 0.1 to 0.5 parts by weight; Initiator 0.05 to 0.2 parts by weight.

2. The multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater according to claim 1, characterized in that, The magnetic core microspheres are selected from one or more of the following: iron oxide microspheres with a silica shell, cobalt ferrite microspheres with a silica shell, and nickel ferrite microspheres with a silica shell. The calcium aluminate precursor component is generated by the reaction of an aluminum source and a calcium source, wherein the aluminum source is selected from one or more of sodium aluminate and potassium aluminate; and the calcium source is selected from one or more of calcium hydroxide, calcium oxide and calcium nitrate. The heavy metal chelating agent is selected from one or more of sodium dithiocarbamate, sodium dimethyl dithiocarbamate, and sodium diethyl dithiocarbamate. The scale inhibitor is selected from one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and hydroxyethylidene diphosphonic acid; The antioxidant is selected from one or more of reduced glutathione, levocysteine ​​and ascorbic acid; The antibacterial agent is selected from one or more of 2,4,4-trichloro-2-hydroxydiphenyl ether, methylisothiazolinone, and chlorhexidine; The host-guest identification agent is selected from one or more of sodium calix tetraaryl sulfonate, p-tert-butylcalix tetraaryl, and p-sulfonylcalix hexaaryl; The polysaccharide compound is selected from one or more of carboxymethyl chitosan, sodium alginate, and sodium hyaluronate; The polyacrylic acid compound is selected from one or more of polyacrylic acid with a molecular weight of 5,000, polymethacrylic acid with a molecular weight of 5,000, and polymaleic acid with a molecular weight of 5,000. The crosslinking agent is selected from one or more of N,N-methylenebisacrylamide, glutaraldehyde, and epichlorohydrin; The initiator is selected from one or more of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

3. A method for preparing a multifunctional composite ion sieve for use in a treatment process of high-concentration sulfate wastewater as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: Preparation of the magnetic core: 10 parts by mass of ferric chloride hexahydrate, 6 parts by mass of anhydrous sodium acetate, and 2 parts by mass of polyethylene glycol tetrahydrate were dissolved in 80 parts by mass of ethylene glycol. After magnetic stirring for 30 minutes, the mixture was transferred to a polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 200 degrees Celsius for 10 hours. After cooling to room temperature, the mixture was magnetically separated, washed with ethanol, and vacuum dried at 60 degrees Celsius for 6 hours to obtain internal microspheres. The obtained internal microspheres were dispersed in a mixture of 100 parts by mass of ethanol and water, and 4 parts by mass of tetraethyl orthosilicate and 2 parts by mass of 25% ammonia were added. The mixture was stirred at 25 degrees Celsius for 8 hours, and after magnetic separation, washing with water, and drying, magnetic core microspheres were obtained. The second step is the deposition of the calcium aluminate precursor functional layer: 15 to 25 parts by mass of the magnetic core microspheres obtained in the first step are ultrasonically dispersed in an aqueous solution containing sodium aluminate or potassium aluminate, heated to 40 degrees Celsius, and an aqueous solution containing a calcium source is added dropwise until the pH of the system is 12.0 to 12.

5. The mixture is stirred at 60 degrees Celsius for 3 hours to deposit the calcium aluminate precursor, and then magnetically separated and washed until neutral. The third step is the loading of the small molecule modified layer: 2 to 4 parts by weight of heavy metal chelating agent, 2 to 3 parts by weight of scale inhibitor, 1.5 to 3 parts by weight of antioxidant, 0.5 to 1 part by weight of antibacterial agent pre-dissolved in 5 parts by weight of acetone, and 2 to 4 parts by weight of host-guest recognition agent are dissolved together in 50 parts by weight of phosphate buffer with a pH of 7.4; the microspheres obtained in the second step are added to this solution, and adsorbed by shaking at 4 degrees Celsius in the dark for 12 hours, followed by magnetic separation and drying with cold air; The fourth step is acid-base responsive outer shell coating: The microspheres from the third step are dispersed in 100 parts by mass of a mixed solution containing 2 to 6 parts by mass of polysaccharide compounds and 3 to 10 parts by mass of polyacrylic acid compounds. 0.1 to 0.5 parts by mass of crosslinking agent and 0.05 to 0.2 parts by mass of initiator are added. After nitrogen deoxygenation for 30 minutes, a free radical crosslinking reaction is carried out at 50 degrees Celsius for 2 hours. After magnetic separation, water washing, and freeze drying at -40 degrees Celsius for 12 hours, a multifunctional composite ion sieve for use in the treatment process of high-concentration sulfate wastewater is obtained.

4. The method for preparing the multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater according to claim 3, characterized in that, In the second step of calcium aluminate precursor functional layer deposition, the aqueous solution containing sodium aluminate was prepared by 3.5 parts by mass of sodium aluminate and 146.5 parts by mass of pure water, and the aqueous solution containing calcium source was prepared by 15 parts by mass of calcium hydroxide and 100 parts by mass of pure water. The dropwise addition operation was used to make the pH of the system reach 12.

0.

5. The method for preparing the multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater according to claim 3, characterized in that, In the third step of loading the small molecule modification layer, the heavy metal chelating agent used is sodium dimethyl dithiocarbamate in a weight of 3 parts by mass, the scale inhibitor used is ethylenediaminetetramethylenephosphonic acid in a weight of 2.5 parts by mass, the antioxidant used is cysteine ​​in a weight of 2 parts by mass, the antibacterial agent used is methylisothiazolinone in a weight of 0.8 parts by mass, and the host-guest recognition agent used is p-tert-butylcalix tetraaromatic hydrocarbon in a weight of 3 parts by mass.

6. The method for preparing the multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater according to claim 3, characterized in that, In the fourth step of acid-base response outer shell coating, the polysaccharide compound used is sodium hyaluronate in a weight of 6 parts by mass, the polyacrylic acid compound used is polymaleic acid in a weight of 10 parts by mass and a molecular weight of 5,000, the crosslinking agent used is epichlorohydrin in a weight of 0.5 parts by mass, and the initiator used is azobisisobutyronitrile in a weight of 0.2 parts by mass.

7. The method for preparing the multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater according to claim 3, characterized in that, In the first step of magnetic core preparation, the ethanol-water mixture is prepared by mixing 80 parts by mass of ethanol and 20 parts by mass of water, and the internal microspheres are washed with ethanol 3 times.

8. A treatment process for high-concentration sulfate wastewater, characterized in that, The multifunctional composite ion sieve used in the treatment process of high-concentration sulfate wastewater as described in any one of claims 1 to 2 is employed, and the specific operating steps include: The multifunctional composite ion sieve is added to the wastewater at a ratio of 2 to 8 parts by weight per 1000 parts by weight of wastewater, and the mixture is stirred and adsorbed for 0.5 to 3 hours. A vacuum pump is used to provide a gauge pressure of -0.02 to -0.07 MPa to draw the adsorption-treated wastewater into a temporary storage tank. The pH is adjusted to 6 to 9 in the temporary storage tank. A buffer tank is set between the temporary storage tank and the negative pressure system. After the ion sieve adsorption is saturated, solid-liquid separation is performed by an external magnetic field of not less than 0.3 Tesla, and the material is regenerated and recycled in sequence using desorption liquid and reconstruction liquid.

9. The treatment process for high-concentration sulfate wastewater according to claim 8, characterized in that, The adsorption treatment time was 0.5 hours, and the pH was adjusted to 6.

10. The treatment process for high-concentration sulfate wastewater according to claim 8, characterized in that, After the ion sieve adsorption becomes saturated, an external magnetic field of 0.3 to 0.5 Tesla is applied for solid-liquid separation. First, acid washing and desorption are performed using an desorption solution prepared with 0.73 parts by mass of hydrogen chloride, 1.46 parts by mass of ethylenediaminetetraacetic acid, and 100 parts by mass of pure water. Then, the desorbed ion sieve is dispersed in an aluminum source aqueous solution prepared with 3.5 parts by mass of sodium aluminate and 146.5 parts by mass of pure water. A calcium source aqueous solution prepared with 15 parts by mass of calcium hydroxide and 100 parts by mass of pure water is added dropwise to bring the pH of the system to 12.0 to 12.

5. The system is stirred at 60 degrees Celsius for 1 to 2 hours to reconstruct the active layer of the calcium aluminate precursor.

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