Heavy-metal capturing agent, and preparation method therefor and use thereof

Abstract

The present disclosure belongs to the technical field of water treatment. Provided are a heavy-metal capturing agent, and a preparation method therefor and the use thereof. In the present disclosure, calcium sulfate hemihydrate crystal whiskers are first prepared from phosphogypsum; a silylamino group is grafted onto a hydroxyl group of the calcium sulfate hemihydrate crystal whiskers by means of primary modification; double bonds are then introduced by means of secondary modification; and a sulfydryl compound is then grafted by means of a sulfydryl-alkenyl click chemical reaction, thereby obtaining a heavy-metal capturing agent. The heavy-metal capturing agent contains a hydroxyl group, an amino group and a sulfydryl group at the same time, and therefore the heavy-metal capturing agent can adsorb heavy metals in heavy-metal wastewater by means of physical and chemical adsorption effects, so as to achieve the purpose of removing the heavy metals.

Description

A heavy metal scavenger and its preparation method and application Technical Field

[0001] The present disclosure relates to the field of water treatment technology, and in particular to a heavy metal scavenger and a preparation method and application thereof. Background Art

[0002] Phosphogypsum is a by-product of the wet-process phosphoric acid production process, with approximately 4-5 tons of phosphogypsum produced for every ton of phosphoric acid produced. The main environmental hazards are the highly acidic phosphides and fluorides. my country's "three phosphorus" (phosphate rock, phosphorus chemical industry, and phosphogypsum depots) are densely distributed in the middle and upper reaches of the Yangtze River, and many phosphogypsum depots are distributed along the river, which is an important reason for the excessive total phosphorus in the Yangtze River basin. According to data from the China Phosphate and Compound Fertilizer Industry Association, 77 million tons of phosphogypsum were produced in 2022, and 38.8 million tons of phosphogypsum were comprehensively utilized in 2022. Although this has reached 50%, nearly 50% of the phosphogypsum is still unused.

[0003] The main challenges with phosphogypsum resource utilization include complex impurities, large storage volumes, low added value, immature and unstable technology, and so on. In major markets for phosphogypsum comprehensive utilization, products are highly homogeneous, competitive, and low in added value, making market development challenging. Furthermore, as phosphogypsum is a byproduct of the chemical industry, there is still some misunderstanding and distrust of this product. Regarding storage, phosphogypsum depots are designed for a limited lifespan, and high inventories of phosphogypsum have led to corrosion in some storage areas, resulting in varying degrees of pollution to groundwater, rivers, and soil. The production of gypsum comprehensive utilization products requires significant investment, resulting in low operating rates, and the vast majority operating at a loss. Consequently, there is a significant conflict between the quality and quantity of phosphogypsum comprehensive utilization.

[0004] Currently, phosphogypsum-based resource utilization products are primarily used in construction, agriculture, and the chemical industry. Building materials account for the vast majority of phosphogypsum consumption, and mature processes exist to convert phosphogypsum into gypsum powder that meets the standards for "Construction Gypsum." However, due to the real estate market, cost competition, and limited transportation, the market for construction gypsum is currently saturated. Therefore, there is a need to actively explore other technologies and methods for phosphogypsum consumption.

[0005] The main component of phosphogypsum is calcium sulfate, which can be produced into hemihydrate calcium sulfate whiskers through impurity removal, roasting, and atmospheric pressure acidification. Hemihydrate calcium sulfate whiskers are used as water treatment agents. On the one hand, hemihydrate calcium sulfate whiskers are easily soluble in water, which increases the calcium ion concentration in the water and introduces new impurities. On the other hand, the pores between calcium sulfate whiskers are large and their affinity with heavy metal ions is poor, which limits their application in water treatment.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a heavy metal scavenger and its preparation method and application. The heavy metal scavenger is used in water treatment to remove nickel, cobalt and manganese heavy metal ions in water.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions: First, a method for preparing a heavy metal scavenger is provided, comprising the following steps:

[0009] Preparation of calcium sulfate hemihydrate whiskers: treating phosphogypsum with hydrochloric acid and then aging to obtain calcium sulfate hemihydrate whiskers;

[0010] Preparing a primary modified product: uniformly mixing calcium sulfate hemihydrate whiskers and a first alcohol solvent, adjusting the pH of the solution to 2-5 to obtain a first solution; uniformly mixing γ-aminopropyltriethoxysilane and a second alcohol solvent, adjusting the pH of the solution to 2-5 to obtain a second solution; and dropwise adding the first solution to the second solution for reaction to obtain a primary modified product;

[0011] preparing a secondary modified product; after uniformly mixing maleimide and a polar solvent, adjusting the pH of the solution to 7-7.5 to obtain a third solution; adding the primary modified product to the third solution for reaction to obtain a secondary modified product;

[0012] Preparation of heavy metal scavenger: uniformly dispersing a mixture of a secondary modified substance, a photoinitiator, a thiol compound, and a tertiary alcohol solvent, and performing a photocuring reaction to obtain a heavy metal scavenger;

[0013] Wherein, the thiol compound is at least one of trimethylolpropane-3-mercaptopropionate, ethyl 3-mercaptopropionate, and 3-mercapto-1-propanol; and the mass ratio of the secondary modified product to the thiol modified product is (1:0.65)-(1:0.85).

[0014] In one embodiment, the mass ratio of the secondary modified product to the mercapto modified product is (1:0.7)-(1:0.85).

[0015] In one embodiment, the mass ratio of the calcium sulfate hemihydrate whiskers to γ-aminopropyltriethoxysilane is (0.75:1)-(1.1:1).

[0016] In one embodiment, the mass ratio of the maleimide to the primary modified product is (0.6:1)-(1.2:1).

[0017] In one embodiment, the mass ratio of the secondary modified product to the photoinitiator is (50:1)-(60:1).

[0018] In one embodiment, the pH of the first solution and the second solution are each independently selected from 2.5-5.

[0019] In one embodiment, the specific surface area of ​​the calcium sulfate hemihydrate whiskers is 40-130 m 2 / g, aspect ratio is 80-110.

[0020] In one embodiment, in the preparation of the primary modified product, the reaction temperature is 20-40° C., and the reaction time is 0.5-3 h.

[0021] In one embodiment, in the preparation of the secondary modified product, the reaction time is 10-12 hours.

[0022] In one embodiment, in the preparation of the heavy metal scavenger, ultrasonic oscillation is used for dispersion, and the ultrasonic oscillation time is 10-30 minutes.

[0023] In one embodiment, the solid-liquid ratio of the phosphogypsum and hydrochloric acid is 0.1-0.2 g / mL; and / or the treatment temperature is 110-130° C., and the treatment time is 10-30 min; and / or the mass fraction of the hydrochloric acid is 21%-98%; and / or the aging time is 5-8 h.

[0024] In one embodiment, the alcohol solvent is at least one of ethanol, methanol, propanol, and n-butanol.

[0025] In one embodiment, the polar solvent is at least one of dimethyl sulfoxide, N,N'-dimethylformamide, and N,N'-dimethylacetamide.

[0026] In one embodiment, the photoinitiator is benzoin and its derivatives.

[0027] In a second aspect, a heavy metal scavenger is provided, wherein the heavy metal scavenger is prepared by the above-mentioned preparation method of the heavy metal scavenger.

[0028] In one embodiment, the grafting rate of the thiol compound in the heavy metal scavenger is 19-55%.

[0029] In a third aspect, the invention provides the use of the heavy metal scavenger in water treatment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the present disclosure, phosphogypsum is first prepared into hemihydrate calcium sulfate whiskers, which have a needle-like structure. A silane amino group is grafted onto the hydroxyl group of the hemihydrate calcium sulfate whiskers through a primary modification to introduce an amino group; a double bond is then introduced through a secondary modification, and then a thiol compound is grafted using a thiol-alkenyl click chemistry reaction to introduce a thiol group; a heavy metal scavenger is obtained, which contains hydroxyl, amino and thiol groups at the same time. The amino group can form a chelate with some heavy metals. On the one hand, the thiol group can reduce the hydrophobicity of the heavy metal scavenger, and on the other hand, the thiol group can form a chelate with heavy metal ions; in addition, after the hemihydrate calcium sulfate whiskers are modified three times, the porosity of the hemihydrate calcium sulfate whiskers is reduced. The above multiple aspects work together to enable the heavy metal scavenger to adsorb heavy metals in heavy metal wastewater through physical and chemical adsorption, thereby achieving the purpose of removing heavy metals.

[0032] (2) The heavy metal scavenger obtained after modification of phosphogypsum is applied to the treatment of heavy metal wastewater, which provides new ideas for the resource utilization of phosphogypsum and achieves waste treatment with waste, responds to the policy call of "zero-waste city" and achieves energy conservation, emission reduction, low carbon and environmental protection. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present disclosure, the present disclosure will be further described below in conjunction with specific embodiments and comparative examples. Its purpose is to understand the content of the present disclosure in detail, rather than to limit the present disclosure. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of the present disclosure are all commonly used ordinary reagents and instruments.

[0034] To achieve the above objectives, the present invention adopts the following technical solutions: First, a method for preparing a heavy metal scavenger is provided, comprising the following steps:

[0035] Preparation of calcium sulfate hemihydrate whiskers: treating phosphogypsum with hydrochloric acid and then aging to obtain calcium sulfate hemihydrate whiskers;

[0036] Preparing a primary modified product: uniformly mixing calcium sulfate hemihydrate whiskers and a first alcohol solvent, adjusting the pH of the solution to 2-5 to obtain a first solution; uniformly mixing γ-aminopropyltriethoxysilane and a second alcohol solvent, adjusting the pH of the solution to 2-5 to obtain a second solution; and dropwise adding the first solution to the second solution for reaction to obtain a primary modified product;

[0037] preparing a secondary modified product; after uniformly mixing maleimide and a polar solvent, adjusting the pH of the solution to 8-9 to obtain a third solution; adding the primary modified product to the third solution for reaction to obtain a secondary modified product;

[0038] Preparation of heavy metal scavenger: uniformly dispersing a mixture of a secondary modified substance, a photoinitiator, a thiol compound, and a tertiary alcohol solvent, and performing a photocuring reaction to obtain a heavy metal scavenger;

[0039] Wherein, the thiol compound is at least one of trimethylolpropane-3-mercaptopropionate, ethyl 3-mercaptopropionate, and 3-mercapto-1-propanol; and the mass ratio of the secondary modified product to the thiol modified product is (1:0.65)-(1:0.85).

[0040] In the present disclosure, phosphogypsum is first prepared into calcium sulfate hemihydrate whiskers, which have a needle-shaped structure. Silane amino groups are grafted onto the hydroxyl groups of the calcium sulfate hemihydrate whiskers through a primary modification to introduce amino groups. A double bond is then introduced through a secondary modification. Subsequently, a thiol compound is grafted onto the thiol-alkenyl click chemistry reaction to introduce thiol groups. A heavy metal scavenger is obtained, which contains hydroxyl groups, amino groups, and thiol groups. The amino groups can form chelates with some heavy metals. On the one hand, the thiol groups can reduce the hydrophobicity of the heavy metal scavenger, and on the other hand, the thiol groups can form chelates with heavy metal ions. In addition, after the three modifications of the calcium sulfate hemihydrate whiskers, the porosity of the calcium sulfate hemihydrate whiskers is reduced. The above multiple aspects work together to enable the heavy metal scavenger to adsorb heavy metals in heavy metal wastewater through physical and chemical adsorption, thereby achieving the purpose of removing heavy metals.

[0041] In the present disclosure, the mass ratio of the secondary modifier to the thiol modifier is (1:0.65)-(1:0.85), for example, it can be 1:0.65, 1:0.68, 1:0.70, 1:0.72, 1:0.75, 1:0.77, 1:0.80, 1:0.83, 1:0.85 or a range consisting of any two thereof, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; ... The mass ratio of the secondary modifier and the thiol modifier affects the grafting rate of the heavy metal scavenger. When the mass ratio of the secondary modifier and the thiol modifier is less than 1:0.65, it will affect the reaction conversion rate. When the mass ratio of the secondary modifier and the thiol modifier is greater than 1:0.85, it will affect the hydrophobicity. The inventors found that when the mass ratio of the secondary modifier and the thiol modifier is (1:0.65)-(1:0.85), heavy metal scavengers with different grafting rates of thiol compounds can be obtained, thereby improving the effect of the heavy metal scavenger in removing heavy metals.

[0042] In the present disclosure, the mass ratio of the calcium sulfate hemihydrate whiskers to γ-aminopropyltriethoxysilane (KH550) is 0.75:1-1.1:1, for example, it can be 0.75:1, 0.78:1, 0.80:1, 0.85:1, 0.90:1, 0.95:1, 1.00:1, 1.05:1, 1.1:1 or a range consisting of any two thereof, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; when the mass ratio of the calcium sulfate hemihydrate whiskers to γ-aminopropyltriethoxysilane is less than 0.75:1, the coupling effect of the coupling agent will be affected; when the mass ratio of the calcium sulfate hemihydrate whiskers to γ-aminopropyltriethoxysilane is greater than 1.1:1, the degree of modification will be affected.

[0043] In the present disclosure, the mass ratio of the maleimide to the primary modified product is 0.6:1-1.2:1, for example, it can be 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1 or a range consisting of any two thereof, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; the mass ratio of maleimide to the primary modified product is 0.6:1-1.2:1, for example, it can be 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1 or a range consisting of any two thereof, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; The reaction of maleimide and the primary modifier must be carried out under slightly neutral conditions. If maleimide and the primary modifier are under slightly alkaline conditions, the maleimide will be hydrolyzed, resulting in the secondary modifier being unable to react with the thiol compound. Under slightly neutral conditions, the mass ratio of maleimide to the primary modifier is another factor affecting the secondary modification. If the mass ratio of maleimide to the primary modifier is greater than 1.2:1 or less than 0.6:1, the modification effect of maleimide will be reduced, and thus the removal rate of heavy metals by the heavy metal scavenger will decrease.

[0044] In the present disclosure, the mass ratio of the secondary modifier to the photoinitiator is 50:1-60:1, for example, it can be 50:1, 51:1, 52:1, 53:1, 54:1, 55:1, 56:1, 57:1, 58:1, 59:1, 60:1 or a range consisting of any two of them, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In the process of preparing heavy metal scavengers, the amount of secondary modifier, photoinitiator, and thiol compound is a factor affecting the grafting rate of the thiol compound. The present invention obtains heavy metal scavengers with different grafting rates by adjusting the amount of secondary modifier, photoinitiator, and thiol compound.

[0046] In the present disclosure, the pH of the first solution and the second solution are each independently selected from 2.5-5, for example, it can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 4.0, 4.5, 5.0 or a range consisting of any two thereof, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Calcium sulfate hemihydrate whiskers and γ-aminopropyltriethoxysilane can only react under acidic conditions. If the pH of the first solution and the second solution is alkaline, the calcium sulfate hemihydrate whiskers and γ-aminopropyltriethoxysilane cannot react. The inventors found that when the pH of the first solution and the second solution is the same and within the pH range of 2.5-3.5, the calcium sulfate hemihydrate whiskers and γ-aminopropyltriethoxysilane can fully react, providing a good foundation for subsequent secondary modification.

[0048] In the present disclosure, the specific surface area of ​​the calcium sulfate hemihydrate whiskers is 40-130m 2 / g, and the aspect ratio is 80-110; for example, the specific surface area of ​​hemihydrate calcium sulfate whiskers can be 40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g, 60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g、80m 2 / g、85m 2 / g、90m 2 / g、95m 2 / g、100m 2 / g、105m 2 / g、110m 2 / g, 115m 2 / g, 120m 2 / g、125m 2 / g, 130m 2 / g, but not limited thereto; the aspect ratio of the calcium sulfate hemihydrate whiskers can be 80, 82, 84, 85, 87, 89, 90, 91, 93, 95, 96, 98, 100, 102, 104, 106, 108, 110, but not limited thereto.

[0049] The specific surface area and aspect ratio of calcium sulfate hemihydrate whiskers will affect the removal effect of heavy metals by heavy metal scavengers. The inventors found that the specific surface area of ​​calcium sulfate hemihydrate whiskers is 40-130m 2 / g, and an aspect ratio of 80-110, which can increase the effect of heavy metal capture agents in removing heavy metals.

[0050] In the present disclosure, in the preparation of the primary modified product, the reaction temperature is 20-40°C, and the reaction time is 0.5-3h; specifically, the reaction temperature can be 20°C, 23°C, 25°C, 28°C, 30°C, 32°C, 35°C, 37°C, 40°C, but not limited thereto; the reaction time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, but not limited thereto.

[0051] In the present disclosure, in the preparation of the secondary modified product, the reaction time is 10-12 hours; within the above reaction time range, a secondary modified product with good secondary modification effect can be obtained.

[0052] In the present disclosure, the specific steps for preparing the heavy metal scavenger are as follows:

[0053] The photoinitiator and the mercapto compound are added to the third alcohol solvent, ultrasonically vibrated for 3-5 minutes, and then the secondary modifier is added and ultrasonically vibrated for 10-15 minutes; the obtained solution is subjected to a photocuring reaction, and the reaction product is dried, washed, and filtered to obtain a heavy metal scavenger.

[0054] Firstly subjecting the photoinitiator and the thiol compound to ultrasonic oscillation and then adding the secondary modifier to ultrasonic oscillation can avoid the secondary modifier or the thiol compound from agglomerating and affecting the progress of the photocuring reaction.

[0055] In the present disclosure, the solid-liquid ratio of the phosphogypsum and hydrochloric acid is 0.1-0.2 g / mL; and / or the treatment temperature is 110-130°C and the treatment time is 10-30 min; and / or the mass fraction of the hydrochloric acid is 21%-98%; and / or the aging time is 5-8 h; by adjusting the solid-liquid ratio of the phosphogypsum and hydrochloric acid, the treatment temperature, time, the mass fraction of the hydrochloric acid and the aging time, a specific surface area of ​​40-120 m 2 / g, hemihydrate calcium sulfate whiskers with an aspect ratio of 80-100.

[0056] In addition, in the present disclosure, before treating the phosphogypsum with hydrochloric acid, the phosphogypsum may be pretreated, and the pretreatment steps include water washing or flotation, which can remove soluble impurities and organic matter in the phosphogypsum.

[0057] In the present disclosure, the first alcohol solvent, the second alcohol solvent, and the third alcohol solvent are each independently selected from at least one of ethanol, methanol, propanol, and n-butanol. During the preparation of the first solution, calcium sulfate hemihydrate whiskers are readily soluble in water, and therefore, the first alcohol solvent is selected to be an anhydrous alcohol solvent, such as anhydrous ethanol or anhydrous methanol. During the preparation of the second solution, the aqueous solution of the second alcohol solvent can promote the reaction between γ-aminopropyltriethoxysilane and calcium sulfate hemihydrate whiskers. The inventors have found that when the volume ratio of the second alcohol solvent to water is 2-4, the reaction between the silane γ-aminopropyltriethoxysilane and the calcium sulfate hemihydrate whiskers can be effectively enhanced.

[0058] In the present disclosure, the polar solvent is at least one of dimethyl sulfoxide, N,N'-dimethylformamide, and N,N'-dimethylacetamide.

[0059] In the present disclosure, the photoinitiator is benzoin and its derivatives, such as benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether. In the present disclosure, benzoin dimethyl ether (BDK) is selected as the photoinitiator.

[0060] In a second aspect, a heavy metal scavenger is provided, wherein the heavy metal scavenger is prepared by the above-mentioned preparation method of the heavy metal scavenger.

[0061] In the present disclosure, the grafting rate of the thiol compound in the heavy metal capture agent is 19%-55%. For example, the grafting rate of the thiol compound in the heavy metal capture agent can be but is not limited to 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%. The inventors found that when the grafting rate of the thiol compound in the heavy metal scavenger is less than 19% or greater than 55%, the effect of the heavy metal scavenger in removing heavy metals will decrease. When the grafting rate of the thiol compound in the heavy metal scavenger is 25-40%, the removal rate of the heavy metal scavenger for heavy metals can be improved.

[0062] In a third aspect, the invention provides the use of the heavy metal scavenger in water treatment.

[0063] The heavy metal scavenger disclosed in the present invention can remove heavy metals such as nickel, cobalt, and manganese in wastewater, thereby expanding the application scope of phosphogypsum in water treatment.

[0064] Example 1

[0065] This embodiment provides a method for preparing a heavy metal scavenger, comprising the following steps:

[0066] Preparation of calcium sulfate hemihydrate whiskers:

[0067] 500 g of phosphogypsum was slurried, the black oil film was scraped off with a laboratory simulated scraper, and then the slurry was put into a laboratory simulated three-stage countercurrent washing device for impurity removal. After impurity removal, the sample was filtered and dried to obtain phosphogypsum that met the "Building Gypsum" standard, which is the pretreated phosphogypsum;

[0068] 21% hydrochloric acid and 98% hydrochloric acid were placed in a water bath at a volume ratio of 20:1 and stirred evenly. After heating to 120°C, 10g of pretreated phosphogypsum was added and reacted for 15 minutes. The obtained product was filtered while hot. After the filtrate was aged for 6 hours, the obtained product was washed, filtered and dried to obtain hemihydrate calcium sulfate whiskers. The specific surface area of ​​the hemihydrate calcium sulfate whiskers was 60m 2 / g, and the aspect ratio is 90.

[0069] Preparation of a modified product:

[0070] 2 g of calcium sulfate hemihydrate whiskers were added to 200 mL of anhydrous ethanol, and then stirred at 200 rpm for 50 min to dissolve, and dilute sulfuric acid was added to adjust the pH of the solution to 3 to obtain a first solution;

[0071] 2.5 g of KH550 was added to 50 mL of ethanol-water solution, and the solution was stirred at 200 rpm for 20 min to dissolve. Then, dilute sulfuric acid was added to adjust the pH of the solution to 3 to obtain a second solution, wherein the volume ratio of ethanol to water in the ethanol-water solution was 2:1;

[0072] Under the conditions of a rotation speed of 200 rpm and a temperature of 30° C., the second solution was added dropwise to the first solution and reacted for 1 hour. The obtained product was dried to obtain a primary modified product.

[0073] Preparation of a secondary modified product: Add 2 g of maleimide to N,N'-dimethylformamide, stir and dissolve, then add 2% by mass of sodium hydroxide solution to adjust the pH of the solution to 7.2 to obtain a third solution; add 2 g of the primary modified product to the third solution, react at room temperature for 11 hours, and dry the obtained product to obtain a secondary modified product.

[0074] Preparation of a heavy metal scavenger: 0.04 g of BDK was added to 50 mL of methanol solution and stirred uniformly. 1.5 g of trimethylolpropane-3-mercaptopropionate was then added and ultrasonically vibrated for 5 minutes. Then, 2 g of the secondary modifier was added and ultrasonically vibrated for 15 minutes. The resulting solution was smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product was washed with ethanol solution and filtered. The filter material obtained was the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger was 53%.

[0075] Example 2

[0076] This embodiment provides a method for preparing a heavy metal scavenger, comprising the following steps:

[0077] Preparation of calcium sulfate hemihydrate whiskers:

[0078] 500 g of phosphogypsum was slurried, the black oil film was scraped off with a laboratory simulated scraper, and then the slurry was put into a laboratory simulated three-stage countercurrent washing device for impurity removal. After impurity removal, the sample was filtered and dried to obtain phosphogypsum that met the "Building Gypsum" standard, which is the pretreated phosphogypsum;

[0079] 21% hydrochloric acid and 98% hydrochloric acid were placed in a water bath at a volume ratio of 20:1 and stirred evenly. After heating to 120°C, 10g of pretreated phosphogypsum was added and reacted for 15 minutes. The obtained product was filtered while hot. After the filtrate was aged for 6 hours, the obtained product was washed, filtered and dried to obtain hemihydrate calcium sulfate whiskers. The specific surface area of ​​the hemihydrate calcium sulfate whiskers was 60m 2 / g, and the aspect ratio is 90.

[0080] Preparation of a modified product:

[0081] 2 g of calcium sulfate hemihydrate whiskers were added to 200 mL of anhydrous ethanol, and then stirred at 200 rpm for 50 min to dissolve, and dilute sulfuric acid was added to adjust the pH of the solution to 3 to obtain a first solution;

[0082] 1.8 g of KH550 was added to 50 mL of ethanol-water solution and stirred at 200 rpm for 20 min to dissolve. Dilute sulfuric acid was then added to adjust the pH of the solution to 3 to obtain a second solution, wherein the volume ratio of ethanol to water in the ethanol-water solution was 2:1;

[0083] Under the conditions of a rotation speed of 200 rpm and a temperature of 30° C., the second solution was added dropwise to the first solution and reacted for 1 hour. The obtained product was dried to obtain a primary modified product.

[0084] Preparation of a secondary modified product: 1.6 g of maleimide was added to N,N'-dimethylformamide, stirred and dissolved, and then a 2% by mass sodium hydroxide solution was added to adjust the pH of the solution to 7.5 to obtain a third solution; 2 g of the primary modified product was added to the third solution, and the mixture was reacted at room temperature for 11 h. After the obtained product was dried, a secondary modified product was obtained.

[0085] Preparation of a heavy metal scavenger: 0.04 g of BDK was added to 50 mL of methanol solution and stirred uniformly. 1.7 g of ethyl 3-mercaptopropionate was then added and ultrasonically vibrated for 5 minutes. Then, 2 g of the secondary modifier was added and ultrasonically vibrated for 15 minutes. The resulting solution was smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product was washed with ethanol solution and filtered. The filter material obtained was the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger was 31%.

[0086] Example 3

[0087] This embodiment provides a method for preparing a heavy metal scavenger, comprising the following steps:

[0088] Preparation of calcium sulfate hemihydrate whiskers:

[0089] 500 g of phosphogypsum was slurried, the black oil film was scraped off with a laboratory simulated scraper, and then the slurry was put into a laboratory simulated three-stage countercurrent washing device for impurity removal. After impurity removal, the sample was filtered and dried to obtain phosphogypsum that met the "Building Gypsum" standard, which is the pretreated phosphogypsum;

[0090] 21% hydrochloric acid and 98% hydrochloric acid were placed in a water bath at a volume ratio of 20:1 and stirred evenly. After heating to 120°C, 10g of pretreated phosphogypsum was added and reacted for 15 minutes. The obtained product was filtered while hot. After the filtrate was aged for 6 hours, the obtained product was washed, filtered and dried to obtain hemihydrate calcium sulfate whiskers. The specific surface area of ​​the hemihydrate calcium sulfate whiskers was 60m 2 / g, and the aspect ratio is 90.

[0091] Preparation of a modified product:

[0092] 2 g of calcium sulfate hemihydrate whiskers were added to 200 mL of anhydrous ethanol, and then stirred at 200 rpm for 50 min to dissolve, and dilute sulfuric acid was added to adjust the pH of the solution to 3 to obtain a first solution;

[0093] 2.6 g of KH550 was added to 50 mL of ethanol-water solution, stirred at 200 rpm for 20 min to dissolve, and then dilute sulfuric acid was added to adjust the pH of the solution to 3 to obtain a second solution, wherein the volume ratio of ethanol to water in the ethanol-water solution was 2:1;

[0094] Under the conditions of a rotation speed of 200 rpm and a temperature of 30° C., the second solution was added dropwise to the first solution and reacted for 1 hour. The obtained product was dried to obtain a primary modified product.

[0095] Preparation of a secondary modified product: 1.2 g of maleimide was added to N,N'-dimethylformamide, stirred and dissolved, and then a 2% by mass sodium hydroxide solution was added to adjust the pH of the solution to 7 to obtain a third solution; 2 g of the primary modified product was added to the third solution, and the mixture was reacted at room temperature for 11 hours. After the obtained product was dried, a secondary modified product was obtained.

[0096] Preparation of a heavy metal scavenger: 0.04 g of BDK was added to 50 mL of methanol solution, stirred evenly, and then 1.3 g of 3-mercapto-1-propanol was added. The mixture was ultrasonically vibrated for 5 minutes, and then 2 g of the secondary modifier was added. The mixture was ultrasonically vibrated for 15 minutes. The resulting solution was smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product was washed with ethanol solution and filtered. The filter material obtained was the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger was 19%.

[0097] Example 4

[0098] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the steps for preparing the heavy metal catalyst are different. The steps for preparing the heavy metal catalyst in this embodiment are as follows: 0.04 g of BDK is added to 50 mL of methanol solution, stirred evenly, 1.6 g of trimethylolpropane-3-mercaptopropionate is added, ultrasonically vibrated for 5 minutes, and then 2 g of a secondary modifier is added, ultrasonically vibrated for 15 minutes, the resulting solution is smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product is washed with an ethanol solution and filtered, and the resulting filter material is the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger is 40%.

[0099] Example 5

[0100] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the steps for preparing the heavy metal catalyst are different. The steps for preparing the heavy metal catalyst in this embodiment are as follows: 0.04 g of BDK is added to 50 mL of methanol solution, stirred evenly, 1.7 g of trimethylolpropane-3-mercaptopropionate is added, ultrasonically oscillated for 5 minutes, then 2 g of a secondary modifier is added, ultrasonically oscillated for 15 minutes, the resulting solution is smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product is washed with an ethanol solution and filtered, and the resulting filter material is the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger is 31%.

[0101] Example 6

[0102] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the steps for preparing the heavy metal catalyst are different. The steps for preparing the heavy metal catalyst in this embodiment are as follows: 0.04 g of BDK is added to 50 mL of methanol solution, stirred evenly, 1.4 g of trimethylolpropane-3-mercaptopropionate is added, ultrasonically oscillated for 5 minutes, then 2 g of a secondary modifier is added, ultrasonically oscillated for 15 minutes, the resulting solution is smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product is washed with an ethanol solution and filtered, and the resulting filter material is the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger is 19%.

[0103] Example 7

[0104] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the steps for preparing the heavy metal catalyst are different. The steps for preparing the heavy metal catalyst in this embodiment are as follows: 0.04 g of BDK is added to 50 mL of methanol solution, stirred evenly, 1.35 g of trimethylolpropane-3-mercaptopropionate is added, ultrasonically oscillated for 5 minutes, then 2 g of a secondary modifier is added, ultrasonically oscillated for 15 minutes, the resulting solution is smeared on a watch glass, irradiated with ultraviolet light for 5 minutes, and then dried. The resulting product is washed with an ethanol solution and filtered, and the resulting filter material is the heavy metal scavenger; the grafting rate of the thiol compound in the heavy metal scavenger is 15%.

[0105] Example 8

[0106] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH of the first solution and the second solution are different. In this embodiment, the pH of the first solution is 3.5, and the pH of the second solution is 3.5.

[0107] Example 9

[0108] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH of the first solution and the second solution are different. In this embodiment, the pH of the first solution is 2.5, and the pH of the second solution is 2.5.

[0109] Example 10

[0110] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH values ​​of the first solution and the second solution are different. In this embodiment, the pH value of the first solution is 5, and the pH value of the second solution is 5.

[0111] Example 11

[0112] This embodiment provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH of the first solution and the second solution are different. In this embodiment, the pH of the first solution is 2, and the pH of the second solution is 2.

[0113] Example 12

[0114] This embodiment provides a method for preparing a heavy metal scavenger. The only difference between this embodiment and embodiment 1 is that the aging time in the preparation of calcium sulfate hemihydrate whiskers is different. The aging time in this embodiment is 5 hours, and the specific surface area of ​​the calcium sulfate hemihydrate whiskers is 40m 2 / g, and the aspect ratio is 80.

[0115] Example 13

[0116] This embodiment provides a method for preparing a heavy metal scavenger. The only difference between this embodiment and embodiment 1 is that the aging time in the preparation of calcium sulfate hemihydrate whiskers is different. The aging time in this embodiment is 5 hours, and the specific surface area of ​​the calcium sulfate hemihydrate whiskers is 120m 2 / g, and the aspect ratio is 100.

[0117] Example 14

[0118] This embodiment provides a method for preparing a heavy metal scavenger. The only difference between this embodiment and embodiment 1 is that the aging time in the preparation of calcium sulfate hemihydrate whiskers is different. The aging time in this embodiment is 5 hours, and the specific surface area of ​​the calcium sulfate hemihydrate whiskers is 130m 2 / g, and the aspect ratio is 110.

[0119] Comparative Example 1

[0120] This comparative example provides a preparation method of a heavy metal scavenger, which differs from Example 1 only in that 3-mercaptopropionic acid is used instead of trimethylolpropane-3-mercaptopropionate, and the grafting rate of the mercapto compound in the obtained heavy metal scavenger is 31%.

[0121] Comparative Example 2

[0122] This comparative example provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is used instead of KH550.

[0123] Comparative Example 3

[0124] This comparative example provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH of the third solution is 10.

[0125] Comparative Example 4

[0126] This comparative example provides a method for preparing a heavy metal scavenger, which differs from Example 1 only in that the pH values ​​of the first solution and the second solution are different. In this comparative example, the pH value of the first solution is 6, and the pH value of the second solution is 6.

[0127] Effect Example 1

[0128] This effect example tests the removal effects of the primary modified product, secondary modified product and heavy metal scavenger obtained in Example 1 on heavy metals under different pH conditions.

[0129] The test method is as follows:

[0130] (1) Take 500 mL of ternary lithium battery precursor mother liquor wastewater, adjust the pH of the wastewater to 5, wherein nickel is 120 mg / L, cobalt is 30 mg / L, and manganese is 5 mg / L, add 1 g of the primary modifier, secondary modifier and heavy metal scavenger obtained in Example 1 respectively, react for 2 h, add 2 ml of flocculant, react for 30 min, test the nickel, cobalt and manganese contents in the wastewater, and calculate the removal rates of nickel, cobalt and manganese.

[0131] (2) Take 500 mL of ternary lithium battery precursor mother liquor wastewater, adjust the pH of the wastewater to 7, wherein nickel is 120 mg / L, cobalt is 30 mg / L, and manganese is 5 mg / L, add 1 g of the primary modifier, secondary modifier and heavy metal scavenger obtained in Example 1 respectively, react for 2 h, add 2 ml of flocculant, react for 30 min, test the nickel, cobalt and manganese contents in the wastewater, and calculate the removal rates of nickel, cobalt and manganese.

[0132] (3) Take 500 mL of ternary lithium battery precursor mother liquor wastewater, adjust the pH of the wastewater to 9, wherein nickel is 120 mg / L, cobalt is 30 mg / L, and manganese is 5 mg / L, add 1 g of the primary modifier, secondary modifier and heavy metal scavenger obtained in Example 1 respectively, react for 2 h, add 2 ml of flocculant, react for 30 min, test the nickel, cobalt and manganese contents in the wastewater, and calculate the removal rates of nickel, cobalt and manganese.

[0133] The test results are shown in Table 1-3.

[0134] Table 1 Removal rates of nickel, cobalt and manganese by different modifiers at pH = 5

[0135] Table 2 Removal rates of nickel, cobalt and manganese by different modifiers at pH = 7

[0136] Table 3 Removal rates of nickel, cobalt and manganese by different modifiers at pH = 9

[0137] It can be seen from Tables 1-3 that under acidic conditions, the heavy metal scavenger treats wastewater, wherein the nickel removal rate is 20.83%, the cobalt removal rate is 30%, and the manganese removal rate is 28%; under neutral conditions, the heavy metal scavenger treats wastewater, wherein the nickel removal rate is 87.5%, the cobalt removal rate is 56.67%, and the manganese removal rate is 86%; under alkaline conditions, the heavy metal scavenger treats wastewater, wherein the nickel removal rate is 94%, the cobalt removal rate is 71.33%, and the manganese removal rate is 98%; it can be seen that the heavy metal scavenger disclosed in the present invention has good removal effects on nickel, cobalt, and manganese under neutral and alkaline conditions (pH = 7-9).

[0138] Effect Example 2

[0139] This effect example tests the heavy metal removal effects of the heavy metal scavengers obtained in Examples 1-14 and Comparative Examples 1-4.

[0140] The test method is as follows: 500 mL of ternary lithium battery precursor mother liquor wastewater was taken and the pH of the wastewater was adjusted to 9. The nickel content was 120 mg / L, the cobalt content was 30 mg / L, and the manganese content was 5 mg / L. 1 g of the primary and secondary modified products obtained in Example 1 and a heavy metal scavenger were added, respectively. The reaction was allowed to proceed for 2 hours. 2 ml of flocculant was added and the reaction was continued for 30 minutes. The nickel, cobalt, and manganese contents in the wastewater were tested, and the nickel, cobalt, and manganese removal rates were calculated. The test results are shown in Table 4.

[0141] Table 4

[0142] As can be seen from Table 4, the heavy metal scavenger disclosed herein has a good removal effect on nickel, cobalt and manganese.

[0143] Comparing Example 1 with Examples 4-7, it can be seen that when the grafting rate of the thiol compound in the heavy metal scavenger is 19-55%, the removal rate of the heavy metal scavenger for nickel is 62%-94%, the removal rate for cobalt is 48%-71%, and the removal rate for manganese is 76%-98%.

[0144] By comparing Example 1 with Examples 8-11, it can be seen that when the pH of the first solution and the second solution are independently 2.5-5, the heavy metal scavenger has a nickel removal rate of 84%-94%, a cobalt removal rate of 67%-71%, and a manganese removal rate of 88%-98%.

[0145] Comparing Example 1 with Examples 12-14, it can be seen that when the specific surface area of ​​calcium sulfate hemihydrate whiskers is 60-130 m 2 / g, and when the aspect ratio is 80-110, the heavy metal capture agent has a nickel removal rate of 91%-97%, a cobalt removal rate of 65%-76%, and a manganese removal rate of 87%-98%.

[0146] By comparing Example 1 with Comparative Examples 1-4, it can be seen that only the heavy metal scavenger prepared by selecting the raw materials and parameters disclosed in the present invention has a good removal effect on nickel, cobalt and manganese.

[0147] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present disclosure rather than to limit the scope of protection of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present disclosure may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present disclosure.

Claims

1. A method for preparing a heavy metal scavenger, It is characterized in that The following steps are involved: Preparation of calcium sulfate hemihydrate whiskers: treating phosphogypsum with hydrochloric acid and then aging to obtain calcium sulfate hemihydrate whiskers; Preparing a primary modified product: mixing the calcium sulfate hemihydrate whiskers and the first alcohol solvent evenly, and adjusting the pH of the solution to 2-5 to obtain a first solution; After γ-aminopropyltriethoxysilane and the second alcohol solvent are uniformly mixed, the pH of the solution is adjusted to 2-5 to obtain a second solution; the first solution is added dropwise to the second solution to react to obtain a primary modified product; preparing a secondary modified product; After the maleimide and the polar solvent are uniformly mixed, the pH of the solution is adjusted to 8-9 to obtain a third solution; the primary modified product is added to the third solution for reaction to obtain a secondary modified product; Preparation of heavy metal scavenger: after uniformly dispersing a mixture of a secondary modified substance, a photoinitiator, a thiol compound, and a third alcohol solvent, performing a photocuring reaction to obtain a heavy metal scavenger; Wherein, the thiol compound is at least one of trimethylolpropane-3-mercaptopropionate, 3-mercaptopropionic acid ethyl ester, and 3-mercapto-1-propanol; the mass ratio of the secondary modified product to the thiol modified product is (1:0.65)-(1:0.85).

2. The preparation method according to claim 1, It is characterized in that The mass ratio of the secondary modified product to the mercapto modified product is (1:0.7)-(1:0.85).

3. The preparation method according to claim 1, It is characterized in that The mass ratio of the calcium sulfate hemihydrate whiskers to γ-aminopropyltriethoxysilane is (0.75:1)-(1.1:1).

4. The preparation method according to claim 1, It is characterized in that The mass ratio of the maleimide to the primary modified product is (0.6:1)-(1.2:1).

5. The preparation method according to claim 1, It is characterized in that The mass ratio of the secondary modified product to the photoinitiator is (50:1)-(60:1).

6. The preparation method according to claim 1, It is characterized in that The pH of the first solution and the second solution are each independently selected from 2.5-5.

7. The preparation method according to claim 1, It is characterized in that The specific surface area of ​​the calcium sulfate hemihydrate whisker is 40-130 m 2 / g, aspect ratio is 80-110.

8. The preparation method according to claim 1, It is characterized in that In the preparation of the primary modified product, the reaction temperature is 20-40° C. and the reaction time is 0.5-3 h.

9. The preparation method according to claim 1, It is characterized in that In the preparation of the secondary modified product, the reaction time is 10-12 hours.

10. The preparation method according to claim 1, It is characterized in that In the preparation of the heavy metal capture agent, ultrasonic oscillation is used for dispersion, and the time of ultrasonic oscillation is 10-20 minutes.

11. The preparation method according to claim 1, It is characterized in that The solid-to-liquid ratio of the phosphogypsum and hydrochloric acid is 0.1-0.2 g / mL; and / or the treatment temperature is 110-130° C. and the treatment time is 10-30 min; and / or the mass fraction of the hydrochloric acid is 21%-98%; and / or the aging time is 5-8 h.

12. The preparation method according to claim 1, It is characterized in that The first alcohol solvent, the second alcohol solvent and the third alcohol solvent are each independently selected from at least one of ethanol, methanol, propanol and n-butanol.

13. The preparation method according to claim 1, It is characterized in that The polar solvent is at least one of dimethyl sulfoxide, N,N'-dimethylformamide and N,N'-dimethylacetamide.

14. The preparation method according to claim 1, It is characterized in that The photoinitiator is benzoin and its derivatives.

15. A heavy metal capture agent, It is characterized in that The heavy metal scavenger is prepared by the preparation method of the heavy metal scavenger according to any one of claims 1 to 14.

16. The heavy metal scavenger according to claim 15, It is characterized in that The grafting rate of the mercapto compound in the heavy metal capture agent is 19-55%.

17. The heavy metal scavenger according to claim 16, It is characterized in that The grafting rate of the mercapto compound in the heavy metal capture agent is 25-40%.

18. Use of the heavy metal scavenger according to claims 15 to 17 in water treatment.

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