Method for removing heavy metals by acidizing bleaching earth

Abstract

The invention provides a method for removing heavy metals by acidizing bleaching earth. The heavy metals in the bleaching earth are removed by using a heavy metal adsorbent. Firstly, acrylate reacts with diethanol amine to generate an esterification product, then the esterification product reacts with trimethylolpropane to form a hydroxyl-terminated hyperbranched polymer, and then the hydroxyl-terminated hyperbranched polymer reacts with isocyanate acrylate to introduce double bonds to obtain hyperbranched acrylate. Meanwhile, sodium alginate reacts with 4-chlorophenylboronic acid to obtain boric acid modified sodium alginate, then the boric acid modified sodium alginate reacts with tannic acid to introduce a large amount of hydroxyl groups, and finally the boric acid modified sodium alginate reacts with 3-aminopropanol vinyl ether to introduce double bonds, so that the sodium alginate compound containing double bonds is prepared. And copolymerizing the two monomers with acrylic acid, N-(2-aminoethyl) acrylamide and 2-acrylamido-2-methylpropanesulfonic acid to obtain the adsorbent with a three-dimensional network structure and multiple functional groups. Through the treatment, the heavy metal content of the bleaching earth is obviously reduced, no foreign impurities exist, and the functions of high decolorization rate and strong adsorbability are reserved.

Description

Technical Field

[0001] This invention relates to the field of heavy metal removal technology, specifically to a method for removing heavy metals by acidification treatment with bleaching clay. Background Technology

[0002] Bleaching clay is a type of natural adsorbent earthy substance made primarily from attapulgite clay or bentonite. After treatment with inorganic acids, it can form activated clay with even better adsorption properties. Due to its high decolorization rate and strong adsorption capacity, it is widely used in the refining of animal and vegetable oils, petrochemicals, and environmental protection, and is also a commonly used functional raw material in the cosmetics industry. In cosmetic formulations, its porous structure and surface activity effectively adsorb excess oil, dirt, and impurities from the skin surface. It can also improve the smoothness and formula stability of products such as cleansing creams, cleansing masks, and oil-control powders, providing crucial support for the product's user experience. However, natural bleaching clay is easily affected by surrounding minerals during its geological formation process, or impurities may be introduced during mining, transportation, or preliminary processing due to improper protection, resulting in a common presence of heavy metals such as lead, chromium, and copper. Even activated clay prepared through acid treatment may still pose risks due to incomplete removal of heavy metal residues from the raw material base. If these heavy metals come into long-term contact with human skin through cosmetics, they may not only cause local inflammatory reactions such as redness, swelling, and itching, but may also gradually accumulate in the human body through skin penetration, causing potential damage to the nervous and endocrine systems and seriously threatening the health and safety of consumers. Therefore, the efficient removal of heavy metals from bleaching clay has become a core requirement to ensure its safety as a raw material in cosmetics and other application fields.

[0003] Currently, various technical solutions have been developed in the industry for the removal of heavy metals from bleaching clay. Among them, chemical precipitation involves adding agents such as hydroxides and sulfides to the bleaching clay treatment system containing heavy metals, causing heavy metal ions to be converted into insoluble salts and precipitated for separation. This was a widely used basic treatment method in the early days. Adsorption utilizes the adsorption properties of materials such as activated carbon, zeolite, and modified clay to physically retain heavy metal ions in bleaching clay. Due to its simple operation and ease of achieving deep treatment, it is commonly used in small and medium-scale treatment scenarios. Ion exchange utilizes the ion exchange capacity of cation exchange resins or chelating resins to replace and adsorb heavy metal ions onto the resin, achieving precise removal of heavy metals. In some scenarios, heavy metals can also be recovered. In addition, biological treatment uses the metabolic activities or cell structures of microorganisms to adsorb and transform heavy metals. Due to its environmentally friendly and low-cost characteristics, it has been gradually applied in recent years to the treatment of bleaching clay with low concentrations of heavy metal pollution.

[0004] However, existing technologies still have significant drawbacks when applied to the removal of heavy metals from bleaching soil. While chemical precipitation is low-cost, it easily generates large amounts of heavy metal-containing sludge, making subsequent treatment difficult. Furthermore, residual chemicals may introduce new impurities, negatively impacting the adsorption performance and purity of the bleaching soil itself. Traditional adsorption methods use materials such as activated carbon with limited adsorption capacity and poor selectivity for different heavy metal ions. Once saturated, these materials require frequent replacement or regeneration, increasing treatment costs and potentially causing secondary pollution due to incomplete regeneration. Ion exchange methods rely on expensive core resin materials, which are susceptible to contamination from other organic impurities and suspended solids in the bleaching soil, shortening resin lifespan and making it difficult to meet the efficiency and cost requirements of large-scale industrial production. Biological treatment, while environmentally friendly, is significantly affected by environmental conditions such as temperature and pH, has a long treatment cycle, and is ineffective in treating bleaching soil with high concentrations of heavy metals, failing to meet the stringent requirements for heavy metal removal efficiency and stability in cosmetic raw materials.

[0005] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0006] Based on this, the present invention provides a method for removing heavy metals from bleaching clay through acidification treatment, using a heavy metal adsorbent to remove heavy metals from the bleaching clay. The present invention first reacts acrylate with diethanolamine to generate an esterified product, then reacts with trimethylolpropane to form a terminal hydroxyl hyperbranched polymer, subsequently reacting with isocyanate acrylate to introduce double bonds, yielding hyperbranched acrylate. Simultaneously, sodium alginate reacts with 4-chlorophenylboronic acid to obtain boric acid-modified sodium alginate, then reacts with tannic acid to introduce a large number of hydroxyl groups, and finally reacts with 3-aminopropanol vinyl ether to introduce double bonds, preparing a sodium alginate complex containing double bonds. These two compounds are then copolymerized with acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid to obtain an adsorbent with a three-dimensional network structure and multiple functional groups. After treatment, the heavy metal content of the bleaching clay is significantly reduced, and no foreign impurities are introduced, while retaining high decolorization rate and strong adsorption properties.

[0007] One object of the present invention is to provide a method for removing heavy metals by acidification treatment of bleaching clay, comprising the following steps: S1. Under inert gas protection, acrylate and diethanolamine are heated to react and obtain product A; trimethylolpropane and catalyst 1 are added to product A and heated to react, then isocyanate acrylate, polymerization inhibitor and catalyst 2 are added and heated to react to obtain hyperbranched acrylate. Under S2 and inert gas protection, sodium alginate was mixed with 4-chlorophenylboronic acid and potassium carbonate and heated to obtain intermediate 1; intermediate 1 was mixed with tannic acid and heated to obtain intermediate 2; intermediate 2 was mixed with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and hydroxysuccinimide (NHS), and 3-aminopropanol vinyl ether was added and reacted under low temperature conditions to obtain sodium alginate complex containing double bonds; S3. The hyperbranched acrylate, sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid are mixed together, an initiator is added, and the mixture is heated to react and obtain a heavy metal adsorbent. S4. The bleaching clay and acid solution are mixed, heated and stirred for acidification treatment to obtain a crude product; the crude product is dispersed in water, the heavy metal adsorbent is added, and the mixture is stirred for adsorption to obtain bleaching clay with heavy metals removed.

[0008] Further, in step S1, the mass ratio of acrylate to diethanolamine is 1:(1-3); the mass ratio of product A, trimethylolpropane, and isocyanate acrylate is 1:(0.1-0.5):(1-3).

[0009] Further, in step S1, the heating reaction temperature of acrylate and diethanolamine is 40-60℃; the heating reaction temperature of product A and trimethylolpropane is 110-130℃; and the heating reaction temperature after adding isocyanate acrylate is 40-70℃.

[0010] Further, in step S2, the mass ratio of sodium alginate to 4-chlorophenylboronic acid is 10:(2-4); the mass ratio of intermediate 1 to tannic acid is 1:(0.1-0.4); and the mass ratio of intermediate 2 to 3-aminopropanol vinyl ether is 1:(0.2-0.5).

[0011] Furthermore, in step S2, the heating reaction temperature of sodium alginate with 4-chlorophenylboronic acid is 90-110℃; the heating reaction temperature of intermediate 1 and tannic acid is 40-60℃; and the reaction temperature of intermediate 2 and 3-aminopropanol vinyl ether is 5-15℃.

[0012] Further, in step S3, the mass ratio of the hyperbranched acrylate, the sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid is 1:(2-6):(1-5):(2-4):(1-2).

[0013] Furthermore, in step S3, the heating temperature is 60-80℃.

[0014] Further, in step S4, the acid in the acid solution is selected from one or more of sulfuric acid, citric acid, and acetic acid.

[0015] Furthermore, in step S4, the heating temperature is 90-110°C.

[0016] The present invention has the following beneficial effects: This invention provides a method for removing heavy metals from bleaching clay through acidification treatment. The method utilizes a heavy metal adsorbent to remove heavy metals from the bleaching clay. First, acrylate and diethanolamine are used as starting materials. An esterification product is generated via Michael addition reaction. This product is then reacted with trimethylolpropane to form a terminally hydroxyl hyperbranched polymer. Further reaction with isocyanate acrylate introduces double bonds, forming a hyperbranched acrylate. Its highly branched structure provides abundant reaction sites for subsequent reactions. Simultaneously, hydroxyl groups in sodium alginate react with chlorine atoms in 4-chlorophenylboronic acid to generate boric acid-modified sodium alginate. Boric acid then reacts with hydroxyl groups to generate tannic acid-based sodium alginate, introducing a large number of hydroxyl groups to enhance the adsorption capacity of the adsorbent. Finally, a double bond is introduced through reaction with 3-aminopropanol vinyl ether, yielding a sodium alginate complex containing double bonds. Finally, a heavy metal adsorbent with a three-dimensional network structure and multiple functional groups was prepared by copolymerizing hyperbranched acrylate, sodium alginate complex containing double bonds with acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

[0017] The adsorption of heavy metals in bleaching soil by this heavy metal adsorbent relies on the synergistic effect of multiple mechanisms, specifically manifested in the following three aspects: First, the abundant carboxyl and amino groups on the adsorbent surface, as well as the phenolic hydroxyl groups provided by tannic acid, can react with Pb in the bleaching soil. 2+ Cr(VI), Cu 2+ The adsorbent forms stable five- or six-membered ring chelates with heavy metal ions, which are then firmly bound to the adsorbent surface through chemical chelation. This process exhibits strong selectivity and stability, effectively capturing heavy metal ions in the system. Secondly, the sulfonic acid groups in the adsorbent molecules have strong ionization properties, dissociating into H+ in aqueous solution. +This adsorbent can undergo ion exchange reactions with free or weakly bound heavy metal cations in bleaching soil, rapidly transferring and immobilizing heavy metal ions and increasing the adsorption rate. Furthermore, the hyperbranched three-dimensional structure of the adsorbent enables high-density integration and spatial enrichment of functional adsorption groups such as carboxyl, amino, and sulfonic acid groups. This not only significantly increases the number of effective binding sites but also enhances their accessibility due to its unique topology, thereby significantly improving the capture capacity and adsorption efficiency for heavy metal ions. This structure also creates a spatial encapsulation effect on already bound heavy metal ions, enhancing binding stability, effectively inhibiting desorption, and ensuring the durability and reliability of the adsorption effect. After treatment with this adsorbent, the heavy metal content in bleaching soil is significantly reduced, and the adsorbent itself does not introduce foreign impurities, maintaining the original high decolorization rate and strong adsorption performance of the bleaching soil, fully meeting its stringent safety requirements in cosmetics, animal and vegetable oil refining, and other fields. Detailed Implementation

[0018] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0019] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0020] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0021] The present invention uses the following raw materials: Sodium alginate: brand name S100128, purchased from Aladdin Reagent.

[0022] Bleaching clay: Activated white clay, model SL1060, purchased from Leping Clean Bleaching Clay Co., Ltd.

[0023] All water used in this invention is deionized water.

[0024] In this invention, "parts" refers to parts by mass.

[0025] Preparation Example The preparation method of heavy metal adsorbent includes the following steps: S1. Under nitrogen protection, using methanol as solvent, 91.2 g of methyl acrylate and 105 g of diethanolamine were mixed and stirred at 25°C for 1 h. Then, the temperature was increased to 45°C and the mixture was stirred for 4.5 h. The methanol and excess methyl acrylate were removed by rotary evaporation to obtain product A. 30 g of N,N-dimethylformamide was used as solvent, and 114.6 g of product A and 26.8 g of trimethylolpropane were mixed. 0.8 g of p-toluenesulfonic acid was added, and the mixture was stirred at 110°C for 3.5 h. During the reaction, the generated methanol was removed using a water separator to ensure the reaction proceeded. After the reaction was completed, 217.9 g of ethyl isocyanate acrylate was added, followed by 1.8 g of p-hydroxyanisole and 0.4 g of dibutyltin dilaurate. The reaction was carried out at 50°C. The NCO content was monitored using the di-n-butylamine method. When the NCO content reached the theoretical value, the reaction was stopped. The solvent was removed by vacuum distillation to obtain hyperbranched acrylate. S2-1. Under nitrogen protection, take 500 mL of a mixed solution of DMSO and H2O (DMSO and H2O volume ratio of 1:1) as solvent, add 100 g of sodium alginate and 5 g of potassium carbonate, mix well, then add 500 mL of 4-chlorophenylboronic acid solution (obtained by dissolving 20 g of 4-chlorophenylboronic acid in 500 mL of DMSO), react at 100℃ for 12 h, cool to room temperature, adjust pH to 7 with hydrochloric acid (concentration 10 wt%), then add 500 mL of anhydrous ethanol, stir well, let stand for 30 min to precipitate, centrifuge and dry to obtain intermediate 1; S2-2. Add 60 g of intermediate 1 and 15 g of tannic acid to 400 mL of deionized water, stir well, add 10 mL of 0.1 M phosphate buffer (pH 5.0), and react at 40 °C for 8 h. Remove the generated water using a water separator during the reaction. After the reaction is complete, add 0.1 M NaOH solution to adjust the pH to neutral, then add 500 mL of anhydrous ethanol to precipitate, stir well, let stand for 30 min, precipitate, centrifuge to collect the precipitate, and vacuum dry at 50 °C for 6 h to obtain intermediate 2. S2-3. Take 2 g of the intermediate 2 and add it to 200 mL of hydrochloric acid (pH 4) and stir to dissolve it to obtain a solution of intermediate 2. Then, dissolve 0.96 g of EDC·HCl and 0.58 g of NHS in 5 mL of deionized water and add them to the solution of intermediate 2. Stir at 15 °C for 30 min, then add 0.58 mL of 3-aminopropanol vinyl ether and continue stirring for 5 h. After the reaction is completed, precipitate with ethanol, filter, wash the precipitate with ethanol and diethyl ether three times each, and dry to obtain a sodium alginate complex containing double bonds. S3. Using N,N-dimethylformamide as a solvent, the hyperbranched acrylate, sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid were blended (the mass ratio of hyperbranched acrylate, sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid was 1:2:2:3:2), and initiator BPO (1 wt% of total reactants) was added. The mixture was reacted at 80°C for 10 h. After removing the solvent, a heavy metal adsorbent was obtained.

[0026] Example 1 A method for removing heavy metals by acidification of bleaching clay includes the following steps: Take 50 g of 200-mesh bleaching clay, add 150 mL of 3 M sulfuric acid aqueous solution, stir at 100℃ for 5 h, filter, wash, dry and pulverize to obtain crude product; take 100 g of the crude product and add 5 g of heavy metal adsorbent to 500 mL of deionized water, stir and adsorb for 7 days, then filter, wash and dry to obtain bleaching clay with heavy metals removed.

[0027] Example 2 A method for removing heavy metals by acidification of bleaching clay includes the following steps: Take 50 g of 200-mesh bleaching clay, add 150 mL of 1 M sulfuric acid aqueous solution, stir at 110℃ for 5 h, filter, wash, dry and pulverize to obtain crude product; take 100 g of the crude product and add 5 g of heavy metal adsorbent to 500 mL of deionized water, stir and adsorb for 7 days, then filter, wash and dry to obtain bleaching clay with heavy metals removed.

[0028] Example 3 A method for removing heavy metals by acidification of bleaching clay includes the following steps: Take 50 g of 200-mesh bleaching clay, add 150 mL of 5 M sulfuric acid aqueous solution, stir at 90℃ for 5 h, filter, wash, dry and pulverize to obtain crude product; take 100 g of the crude product and add 500 mL of deionized water, add 5 g of heavy metal adsorbent, stir and adsorb for 7 days, then filter, wash and dry to obtain bleaching clay with heavy metals removed.

[0029] Comparative Example 1 A method for removing heavy metals by acidification treatment of bleaching clay; the difference between Comparative Example 1 and Example 1 lies in the different heavy metal adsorbents used. The preparation method of the heavy metal adsorbent in Comparative Example 1 differs from that in the Preparation Example in that step S1 is omitted, and in step S3, the hyperbranched acrylate is replaced with methyl acrylate by mass. The other steps and amounts are the same as in the Preparation Example.

[0030] Comparative Example 2 A method for removing heavy metals by acidification treatment of bleaching clay; the difference between Comparative Example 2 and Example 1 is that the heavy metal adsorbent used is different. The preparation method of the heavy metal adsorbent in Comparative Example 2 differs from that in the Preparation Example in that intermediate 1 is not prepared in step S2, and intermediate 1 is replaced by sodium alginate in equal mass in subsequent reactions. Other steps and amounts are the same as in the Preparation Example.

[0031] Test case The adsorption performance of Examples 1-3 and Comparative Examples 1-2 was tested.

[0032] Test method: Take 1 g of sample (bleaching clay, crude product, or heavy metal-removed bleaching clay (hereinafter referred to as "product")) and place it in a 50 mL polytetrafluoroethylene crucible. Moisten the sample with a small amount of water. Add 15 mL of concentrated nitric acid and heat (controlling the temperature T = 100-120℃), maintaining a gentle boil. Stop heating when the sample becomes a viscous paste. Take 2.5 mL of concentrated nitric acid and 10 mL of perchloric acid, mix them, and add them to the crucible. Continue heating (T = 150-170℃) until the liquid is nearly dry. Add 4.0 mL of perchloric acid and 8.0 mL of hydrofluoric acid to the crucible sequentially and continue heating for digestion until all the liquid has evaporated. (During heating, the crucible needs to be shaken continuously every 10 minutes). The inner wall of the crucible was cleaned with 5 wt% dilute nitric acid, the residue was dissolved by gentle heating, and after cooling, it was filtered. The filtrate was transferred to a 50 mL volumetric flask and diluted to volume with 5 wt% dilute nitric acid. The contents of heavy metal ions Pb, Cr(VI), and Cu in the digestion solution were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the heavy metal removal rate was calculated.

[0033] The calculation formula is as follows; Removal rate (%) = (H0-H1) / H0×100; In the formula: H0 is the heavy metal content of the sample (bleaching clay) before treatment, and H1 is the heavy metal content of the sample (crude product and finished product) after treatment.

[0034] The test results are shown in Table 1: Table 1 Performance Test Results The test results above show that the present invention can effectively improve the adsorption of heavy metals by the heavy metal adsorbent and improve the treatment effect of the heavy metal adsorbent on heavy metals in bleaching soil.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for removing heavy metals by acidification treatment of bleaching clay, characterized in that, Includes the following steps: S1. Under inert gas protection, acrylate and diethanolamine are heated to react and obtain product A; trimethylolpropane and catalyst 1 are added to product A and heated to react, then isocyanate acrylate, polymerization inhibitor and catalyst 2 are added and heated to react to obtain hyperbranched acrylate. Under S2 and inert gas protection, sodium alginate was mixed with 4-chlorophenylboronic acid and potassium carbonate, and heated to obtain intermediate 1; intermediate 1 was mixed with tannic acid and heated to obtain intermediate 2; intermediate 2 was mixed with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and hydroxysuccinimide, and 3-aminopropanol vinyl ether was added, and reacted under low temperature conditions to obtain sodium alginate complex containing double bonds; S3. The hyperbranched acrylate, sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid are mixed together, an initiator is added, and the mixture is heated to react and obtain a heavy metal adsorbent. S4. The bleaching clay and acid solution are mixed, heated and stirred for acidification treatment to obtain a crude product; the crude product is dispersed in water, the heavy metal adsorbent is added, and the mixture is stirred for adsorption to obtain bleaching clay with heavy metals removed.

2. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S1, the mass ratio of acrylate to diethanolamine is 1:(1-3); the mass ratio of product A, trimethylolpropane, and isocyanate acrylate is 1:(0.1-0.5):(1-3).

3. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S1, the heating reaction temperature of acrylate and diethanolamine is 40-60℃; the heating reaction temperature of product A and trimethylolpropane is 110-130℃; and the heating reaction temperature after adding isocyanate acrylate is 40-70℃.

4. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S2, the mass ratio of sodium alginate to 4-chlorophenylboronic acid is 10:(2-4); the mass ratio of intermediate 1 to tannic acid is 1:(0.1-0.4); and the mass ratio of intermediate 2 to 3-aminopropanol vinyl ether is 1:(0.2-0.5).

5. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S2, the heating reaction temperature of sodium alginate with 4-chlorophenylboronic acid is 90-110℃; the heating reaction temperature of intermediate 1 and tannic acid is 40-60℃; and the reaction temperature of intermediate 2 and 3-aminopropanol vinyl ether is 5-15℃.

6. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S3, the mass ratio of the hyperbranched acrylate, the sodium alginate complex containing double bonds, acrylic acid, N-(2-aminoethyl)acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid is 1:(2-6):(1-5):(2-4):(1-2).

7. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S3, the heating temperature is 60-80℃.

8. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S4, the acid in the acid solution is selected from one or more of sulfuric acid, citric acid, and acetic acid.

9. The method for removing heavy metals by acidification treatment of bleaching clay according to claim 1, characterized in that, In step S4, the heating temperature is 90-110℃.

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