Bifunctional modified silica adsorbent and its preparation process and application

Abstract

The application discloses a kind of bifunctional modified silica adsorbents and its preparation process and application, and its adsorbent is nanometer silica, and is obtained by being modified by containing diacetylated mercapto and double carboxyl modified silane, acidolysis, the structure formula of the modified silane containing diacetylated mercapto and double carboxyl is as follows: the mercapto, carboxyl in the bifunctional modified silica adsorbent in alcohol system has strong coordination adsorption effect and high adsorption capacity to lead, nickel, and still has excellent adsorption performance under trace metal concentration, solve the problem that trace metal ion is difficult to remove in alcohol solvent.

Description

Technical Field

[0001] This invention relates to the field of adsorption separation technology, and in particular to a preparation process and application of a bifunctional modified silica adsorbent. Background Technology

[0002] Alcohol solvents, such as methanol, ethanol, and isopropanol, are key basic solvents widely used in industries such as fuels, pharmaceuticals, electronics, and fine chemicals. Their purity directly affects the quality of downstream products, process stability, and the safety of production equipment. Ideally, high-purity alcohol solvents should minimize the introduction of metal ion impurities.

[0003] However, alcohol solvents are highly susceptible to introducing Fe during production, storage, or transportation. 3+ Ni 2+ Pb 2+ Metal ion impurities, even in trace amounts, can cause multifaceted harm. In the fuel ethanol industry, Fe... 3+ and Ni 2+ The presence of Pb catalyzes oxidation reactions, accelerates corrosion of the engine fuel system, leads to decreased combustion efficiency, and creates potential for component failure; in the pharmaceutical industry, Pb... 2+ Plasma may catalyze the decomposition of alcohol solvents or interact with the active pharmaceutical ingredients, thereby affecting the safety and efficacy of the drugs. Especially in the demanding electronics industry, electronic-grade alcohol solvents used for chip cleaning, if containing metal ions, can cause ionic contamination on semiconductor surfaces, leading to circuit leakage, performance degradation, and even product failure. Furthermore, metal ions can also affect the chemical stability of the alcohol solvent itself, accelerating its oxidation and deterioration, and generating undesirable impurities.

[0004] Currently, developing adsorption technologies and materials capable of efficiently and accurately removing specific metal ions from alcohol solvents, especially those exhibiting high adsorption capacity and selectivity even at trace concentrations, has become a key challenge for improving product quality and technological competitiveness in related industries. Existing adsorbents often suffer from low adsorption capacity, poor selectivity, poor dispersibility in alcohol systems, or insufficient adsorption efficiency for trace metals, making it difficult to meet increasingly stringent industry standards. Therefore, developing a novel, highly efficient adsorbent optimized for alcohol systems has significant practical importance and application value. Summary of the Invention

[0005] The purpose of this invention is to provide a bifunctional modified silica adsorbent, its preparation process, and its application. The thiol and carboxyl groups in this bifunctional modified silica adsorbent have strong coordination adsorption effects and high adsorption capacity for lead and nickel in alcohol systems, and also have excellent adsorption performance at trace metal concentrations.

[0006] The first inventive objective of this invention is achieved through the following technical solution: A bifunctional modified silica adsorbent is obtained by modifying nano-silica with a modified silane containing diacetylated mercapto groups and dicarboxyl groups, followed by acid hydrolysis. The structural formula of the modified silane containing diacetylated mercapto groups and dicarboxyl groups is as follows: .

[0007] By adopting the above technical solution, the surface of nano-silica is modified by using a modified silane containing diacetylated mercapto and dicarboxyl groups. The silanoxy group at one end of the modified silane forms a stable covalent bond with the silica surface through hydrolysis and condensation, thereby anchoring the organic chain segment with bifunctional groups onto the inorganic framework. The subsequent acidolysis step is crucial. Its uniqueness lies in the selective cleavage of the CS bond of the acetyl protecting group on the sulfur atom, converting the inert acetylated mercapto group into a free mercapto group (-SH) with high coordination activity, while the carboxyl functional group and silica framework remain stable in this process. Therefore, a strategy of "precursor protection - surface fixation - in-situ activation" is adopted to construct bifunctional synergistic adsorption sites rich in both thiol and carboxyl groups on the surface of nano-silica. This effectively solves the technical problem of easy oxidation and deactivation of highly active thiol groups during the modification process, and achieves the final adsorbent with high adsorption capacity, strong binding force and excellent selectivity for heavy metal ions such as lead and nickel in alcohol solvents, thus solving the problem of difficult removal of trace metal ions in alcohol solvents.

[0008] The second objective of this invention is achieved through the following technical solution: The preparation process of the above-mentioned bifunctional modified silica adsorbent includes the following steps: S1. Take 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent, and first solvent to undergo a condensation reaction. After the reaction is completed, remove the first solvent to obtain a silane coupling agent containing bisamino groups. S2. Take the silane coupling agent containing diamino groups obtained in S1, S-acetyl thiosuccinic anhydride and the first solvent and carry out a ring-opening reaction. After the reaction is completed, remove the first solvent to obtain a modified silane containing diacetylated thiol and dicarboxyl groups. S3. Take nano-silica, the modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and the second solvent for grafting reaction. After the reaction is completed, remove the second solvent, wash and dry to obtain the product. S4. The product obtained in S3 is subjected to acid hydrolysis in hydrochloric acid aqueous solution. After the reaction is completed, the product is filtered, washed, and dried to obtain a dithiol- and dicarboxyl-modified silica adsorbent.

[0009] By employing the above technical solution, starting with the condensation reaction in step S1, tris(2-aminoethyl)amine undergoes nucleophilic substitution with 3-chloropropyltriethoxysilane to generate a silane coupling agent with an extended molecular backbone and terminal diamino groups, providing a key carrier for subsequent functionalization. Then, in step S2, this diamino silane undergoes a ring-opening amidation reaction with S-acetylthiosuccinic anhydride, simultaneously introducing carboxyl groups and protected acetylated thiol groups onto each amino group, thereby efficiently preparing a multifunctional precursor integrating silane coupling sites, carboxyl groups, and protective thiol groups. Step S3 utilizes a silane hydrolysis-condensation reaction... The precursor is covalently grafted onto the silica surface to immobilize the functional groups. In the final step S4, the acetyl protecting group on the thiol group is selectively removed by specific acid hydrolysis, exposing highly active free thiol groups. Through the sequence design of "first constructing a diamino skeleton, then simultaneously introducing bifunctional groups, and finally selectively activating them", especially by adopting the "acetyl protection" strategy, the oxidative deactivation of active thiol groups in the high-temperature grafting step is effectively avoided. This ensures that the surface of the final adsorbent has both high density and high activity of thiol and carboxyl groups, which can efficiently and synergistically adsorb trace amounts of lead and nickel ions in alcohol systems.

[0010] Optionally, the first solvent in S1 is acetonitrile, and the condensing agent is triethylamine.

[0011] By employing the above technical solution, acetonitrile, as a polar aprotic solvent, can effectively dissolve the polar 3-chloropropyltriethoxysilane and tris(2-aminoethyl)amine without undergoing strong solvation with the nucleophile—the amine group. This maximizes the nucleophilic activity of the amine group and promotes its efficient nucleophilic substitution of the chloropropyl group. Triethylamine, as a condensing agent, with its moderate basicity and good steric hindrance, can effectively neutralize the hydrogen chloride generated in the reaction and drive the reaction equilibrium to the right. It can also avoid problems such as unnecessary condensation of silanoxy groups or excessively low reaction rates caused by excessive basicity or excessive steric hindrance (such as the use of DIPEA). The combination of the two synergistically optimizes the solubility, mass transfer, and reactivity of the reactants, achieving efficient and highly selective condensation of the S1 condensation reaction, laying the foundation for the subsequent construction of structurally well-defined bifunctional modified silanes.

[0012] Optionally, the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.5-0.7:4-8, the condensation reaction temperature is 40-60℃, and the condensation reaction time is 10-16h.

[0013] By adopting the above technical solution, the ratio and temperature window ensure that the reactant molecules have the optimal collision frequency and effective reactivity. The amino group of tris(2-aminoethyl)amine can undergo a full and orderly nucleophilic substitution reaction with the chloropropyl group of 3-chloropropyltriethoxysilane. At the same time, an appropriate amount of condensing agent can timely neutralize the hydrohalic acid of the byproduct to maintain the alkalinity of the reaction system and drive the reaction equilibrium to the right. The appropriate amount of solvent ensures the homogeneity and mass transfer efficiency of the reaction system, thereby achieving a high conversion rate of the condensation reaction and a highly selective synthesis of the target product—containing a diaminosilane coupling agent. It effectively inhibits side reactions such as excessive alkylation of secondary amines to generate tertiary amines or quaternary ammonium salts, ensuring the accuracy and purity of the intermediate molecular structure. This lays a controllable molecular foundation for the subsequent construction of high-density bifunctional adsorbents and improves the adsorption capacity and stability of the final adsorbent.

[0014] Optionally, the mass ratio of the diamino silane coupling agent, S-acetyl mercaptosuccinic anhydride, and the first solvent in S2 is 1:1.5-2:12-18; the ring-opening reaction temperature in S2 is 30-50℃, and the ring-opening reaction time is 6-10h.

[0015] By adopting the above technical solution, the dosage ratio ensures that the anhydride functional group is in moderate excess relative to the amino functional group, thereby driving the ring-opening amidation reaction to be more complete. This allows each primary amino group in the diaminosilane coupling agent molecule to react with one molecule of S-acetylthiosuccinic anhydride, thereby simultaneously and quantitatively introducing a carboxyl group and a protected acetylated thiol group at each grafting site. The optimized reaction conditions effectively ensure the high efficiency and high selectivity of functional group transformation, avoid incomplete functionalization due to insufficient anhydride or side reactions that may be caused by excessive reaction, improve the density and grafting regularity of bifunctional groups (thiol and carboxyl groups) on the adsorbent surface, and thus enhance the adsorption capacity of the adsorbent.

[0016] Optionally, the mass ratio of nano-silica in S3, the modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:0.5-2:6-10; the grafting reaction temperature in S3 is 80℃, the reflux temperature of the cyclohexane solvent, and the grafting reaction time is 7-9h.

[0017] By adopting the above technical solution, the material ratio ensures that the modified silane has the optimal concentration in the reaction system, which can achieve high-density grafting coverage on the silica surface and effectively avoid self-condensation side reactions caused by excessive silane. At the same time, the constant reflux temperature provides a continuous and uniform thermodynamic driving force for the complete hydrolysis of silanoxy groups and the efficient condensation with silanol groups on the silica surface. The two synergistically optimize the kinetic process and thermodynamic equilibrium of the interfacial grafting reaction, enabling the modified silane molecules to form a stable monolayer on the silica surface with high orientation and high bonding strength, constructing a uniform, high-density bifunctional surface structure, which affects and improves the adsorption capacity and stability of the final adsorbent for metal ions.

[0018] Optionally, the hydrochloric acid aqueous solution in S4 is a 10wt% hydrochloric acid aqueous solution.

[0019] By adopting the above technical solution, the hydrogen ion activity at this concentration is sufficient to efficiently catalyze the breaking of the chemical bond (S-Ac bond) between sulfur atoms and acetyl groups, thereby specifically and completely converting inert acetylated mercapto groups into highly reactive free mercapto groups (-SH). At the same time, the mild acidic conditions ensure the stability of the silica support framework and the structural integrity of the carboxyl functional groups, balancing reaction efficiency and material stability. This achieves efficient activation of the key adsorption functional group (mercapto group) with minimal structural damage, endowing the adsorbent with superior metal ion adsorption performance.

[0020] Optionally, the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:50-70, the acid hydrolysis reaction time is 2-4 hours, and the acid hydrolysis reaction temperature is 20-30℃.

[0021] By adopting the above technical solution, the sufficient liquid-to-solid ratio ensures full contact and mass transfer efficiency between the acid hydrolysis reagent and the surface of the product particles. The specific mild temperature and time window provide suitable reaction kinetic conditions for the hydrolysis of the acetyl protecting group on the sulfur atom. The combination of these factors precisely controls the process of the deprotection reaction, achieving efficient and complete conversion of acetylated thiol groups into active thiol groups. At the same time, it minimizes side reactions such as dissolution of silica support, degradation of functional groups, or re-dissolution of adsorbed impurities that may be caused by strong acid or long-term reaction. This is the key optimization to ensure that the final adsorbent obtains a high density of active thiol groups and maintains its structural integrity.

[0022] The third inventive objective of this invention is achieved through the following technical solution: The above-mentioned bifunctional modified silica adsorbent is used for the adsorption of lead and nickel ions in methanol, ethanol or isopropanol.

[0023] By adopting the above technical solution, the bifunctional modified silica adsorbent of this application is applied to the adsorption of lead and nickel ions in methanol, ethanol, or isopropanol systems. The free thiol groups (-SH) on the surface of the adsorbent, as soft bases, exhibit a strong specific complexing ability for lead ions, which belong to soft acids, and nickel ions, which are between soft acids and interface acids. The carboxyl groups (-COOH) provide additional adsorption sites through ion exchange and coordination, and produce a synergistic enhancement effect with the thiol groups. The specific structure of the adsorbent is precisely located to achieve a highly efficient matching relationship between the target pollutants (Pb²⁺, Ni²⁺) and the medium environment (alcohol solvents). By making full use of the low polarity and weak solvation effect of alcohol solvents on metal ions, the high selective adsorption performance of the adsorbent's bifunctional groups on the target ions is effectively highlighted and enhanced, thereby solving the technical problem of efficient and deep removal of trace heavy metal ions in alcohol solvents.

[0024] In summary, this application has at least the following beneficial effects: 1. A silane coupling agent containing two amino groups is generated by the condensation reaction of 3-chloropropyltriethoxysilane and tris(2-aminoethyl)amine. The silane coupling agent containing two amino groups is then subjected to a ring-opening reaction with S-acetylmercaptosuccinic anhydride to prepare a modified silane containing two acetylated mercapto groups and two carboxyl groups. The modified silane containing two acetylated mercapto groups and two carboxyl groups is grafted with silica nanoparticles and acid-hydrolyzed to finally obtain silica adsorbents modified with two mercapto groups and two carboxyl groups, respectively. 2. The thiol and carboxyl groups in the bifunctional modified silica adsorbent of the present invention have strong coordination adsorption of lead and nickel ions and high adsorption capacity in alcohol systems, and still have excellent adsorption performance at trace metal concentrations. Attached Figure Description

[0025] Figure 1 The infrared spectrum of the adsorbent in Example 1 is shown. Detailed Implementation

[0026] raw material Nano-silica, a commercially available product, with a particle size of 20nm and a specific surface area of ​​327m². 2 / g, surface hydroxyl density 3.4OH / nm², pore type is mainly mesoporous, and the average pore size of mesopores is 12nm; The 8wt%, 10wt%, and 15wt% hydrochloric acid were prepared by diluting commercially available concentrated hydrochloric acid. 3-Chloropropyltriethoxysilane and 3-mercaptopropyltriethoxysilane are commercially available silane coupling agents; Other raw materials and reagents are commercially available products of analytical grade.

[0027] Example 1 A bifunctional modified silica adsorbent is obtained by first modifying the surface of nano-silica with a modified silane containing diacetylated mercapto groups and dicarboxyl groups, and then acidifying it.

[0028] The structural formula of the modified silane containing diacetylated mercapto groups and dicarboxyl groups is as follows: .

[0029] The specific preparation method is as follows: S1. Add 10g of 3-chloropropyltriethoxysilane, 7g of tris(2-aminoethyl)amine, 6g of condensing agent and 60g of first solvent to the reactor, raise the temperature to 50°C and react for 12 hours. After the reaction is completed, remove the acetonitrile solvent by rotary evaporation to obtain a silane coupling agent containing diamino groups. In this example, the condensing agent is triethylamine and the first solvent is acetonitrile. S2. Add 10g of the silane coupling agent containing diamino groups obtained in S1, 18g of S-acetylmercaptosuccinic anhydride and 160g of the first solvent to the new reactor. Under nitrogen protection, the temperature is raised to 40℃ for reaction and the reaction time is 8h. After the reaction is completed, the first solvent is removed by rotary evaporation to obtain the modified silane containing diacetylated mercapto groups and dicarboxyl groups. S3. Add 10g of nano-silica particles, 10g of the modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and 90g of the second solvent to a new reaction vessel. Heat to 80°C under nitrogen protection and react for 8 hours. After the reaction is completed, remove the second solvent by rotary evaporation, wash, and dry to obtain the product. In this example, the second solvent is cyclohexane. S4. Add 1g of the product obtained from S3 and 60g of 10wt% hydrochloric acid aqueous solution to the reactor, and carry out acid hydrolysis reaction at 25℃ for 3h. After the reaction is completed, filter, wash and dry to obtain dithiol and dicarboxyl modified silica adsorbent.

[0030] The structural formula of the target graft on nano-silica after acid hydrolysis in step S4 is shown below. The siloxane alkyl group on the left side is hydrolyzed and grafted onto the surface of nano-silica. The siloxane alkyl group is retained here for reference: .

[0031] This application also performs infrared spectroscopy on the adsorbent obtained in Example 1 to verify the grafted material on the surface of nano-silica. The obtained infrared spectrum is shown below. Figure 1 As shown, verification confirms the presence of dithiol and dicarboxyl groups.

[0032] Example 2 A bifunctional modified silica adsorbent differs from Example 1 in that the first solvent in S1 is tetrahydrofuran.

[0033] Example 3 A bifunctional modified silica adsorbent, which differs from Example 1 in that the condensing agent in S1 is diisopropylethylamine (DIPEA).

[0034] Example 4 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.4:6.

[0035] Example 5 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.5:6.

[0036] Example 6 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.7:6.

[0037] Example 7 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.9:6.

[0038] Example 8 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.6:3.

[0039] Example 9 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.6:4.

[0040] Example 10 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent and first solvent in S1 is 1:0.7:0.6:8.

[0041] Example 11 A bifunctional modified silica adsorbent differs from Example 1 in that the condensation reaction temperature in S1 is 60°C and the condensation reaction time is 10h.

[0042] Example 11 A bifunctional modified silica adsorbent differs from Example 1 in that the condensation reaction temperature in S1 is 70°C and the condensation reaction time is 10h.

[0043] Example 13 A bifunctional modified silica adsorbent differs from Example 1 in that the condensation reaction temperature in S1 is 40°C and the condensation reaction time is 16h.

[0044] Example 14 A bifunctional modified silica adsorbent differs from Example 1 in that the condensation reaction temperature in S1 is 30°C and the condensation reaction time is 16h.

[0045] Example 15 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:1:16.

[0046] Example 16 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:1.5:16.

[0047] Example 17 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:2:16.

[0048] Example 18 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:1.8:8.

[0049] Example 19 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:1.8:12.

[0050] Example 20 A bifunctional modified silica adsorbent differs from Example 1 in that S2 contains a silane coupling agent with diamino groups, S-acetyl thiosuccinic anhydride, and a first solvent in a mass ratio of 1:1.8:18.

[0051] Example 21 A bifunctional modified silica adsorbent differs from Example 1 in that the ring-opening reaction temperature in S2 is 50°C and the ring-opening reaction time is 6 hours.

[0052] Example 22 A bifunctional modified silica adsorbent differs from Example 1 in that the ring-opening reaction temperature in S2 is 60°C and the ring-opening reaction time is 6 hours.

[0053] Example 23 A bifunctional modified silica adsorbent differs from Example 1 in that the ring-opening reaction temperature in S2 is 30°C and the ring-opening reaction time is 10h.

[0054] Example 24 A bifunctional modified silica adsorbent differs from Example 1 in that the ring-opening reaction temperature in S2 is 25°C and the ring-opening reaction time is 10h.

[0055] Example 25 A bifunctional modified silica adsorbent differs from Example 1 in that the second solvent in S3 is n-hexane.

[0056] Example 26 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:0.3:8.

[0057] Example 27 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:0.5:8.

[0058] Example 28 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:2:8.

[0059] Example 29 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:1.7:4.

[0060] Example 30 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:1.7:6.

[0061] Example 31 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of nano silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:1.7:10.

[0062] Example 32 A bifunctional modified silica adsorbent differs from Example 1 in that the grafting reaction temperature in S3 is 50°C (reflux temperature of cyclohexane solvent), and the grafting reaction time is 8 hours.

[0063] Example 33 A bifunctional modified silica adsorbent differs from Example 1 in that the grafting reaction temperature in S3 is 70°C (reflux temperature of cyclohexane solvent), and the grafting reaction time is 8 hours.

[0064] Example 34 A bifunctional modified silica adsorbent differs from Example 1 in that the grafting reaction temperature in S3 is 80°C (reflux temperature of cyclohexane solvent), and the grafting reaction time is 6 hours.

[0065] Example 35 A bifunctional modified silica adsorbent differs from Example 1 in that the grafting reaction temperature in S3 is 80°C (reflux temperature of cyclohexane solvent), and the grafting reaction time is 7 hours.

[0066] Example 36 A bifunctional modified silica adsorbent differs from Example 1 in that the grafting reaction temperature in S3 is 80°C (the reflux temperature of cyclohexane solvent), and the grafting reaction time is 9 hours.

[0067] Example 37 A bifunctional modified silica adsorbent differs from Example 1 in that the hydrochloric acid aqueous solution in S4 is an 8% hydrochloric acid aqueous solution by mass.

[0068] Example 38 A bifunctional modified silica adsorbent differs from Example 1 in that the hydrochloric acid aqueous solution in S4 is a 15% hydrochloric acid aqueous solution by mass.

[0069] Example 39 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:40, the acid hydrolysis reaction time is 3 hours, and the acid hydrolysis reaction temperature is 25°C.

[0070] Example 40 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:50, the acid hydrolysis reaction time is 3 hours, and the acid hydrolysis reaction temperature is 25°C.

[0071] Example 41 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:70, the acid hydrolysis reaction time is 3 hours, and the acid hydrolysis reaction temperature is 25°C.

[0072] Example 42 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:60, the acid hydrolysis reaction time is 2 hours, and the acid hydrolysis reaction temperature is 30°C.

[0073] Example 43 A bifunctional modified silica adsorbent differs from Example 1 in that the mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:60, the acid hydrolysis reaction time is 4 hours, and the acid hydrolysis reaction temperature is 20°C.

[0074] Comparative Example 1 A silica adsorbent, which is composed of nano-silica particles and is unmodified.

[0075] Comparative Example 2 A modified silica adsorbent, the preparation method of which is as follows: 10g of nano-silica particles, 10g of 3-mercaptopropyltriethoxysilane and 90g of cyclohexane were added to a reaction vessel. The temperature was raised to 80℃ under nitrogen protection and the reaction time was 8h. After the reaction was completed, the cyclohexane was removed by rotary evaporation, and the product was washed and dried to obtain the modified silica adsorbent.

[0076] The adsorbents obtained in Examples 1-43 and Comparative Examples 1-2 were tested. Their adsorption capacity for lead and nickel ions in alcohol solutions was tested.

[0077] The detection method is as follows: 500 mL of methanol was added to beaker 1, 500 mL of ethanol was added to beaker 2, and 500 mL of isopropanol was added to each of beakers 3. The mass of nickel chloride added to beakers 1-3 were 0.171 mg, 0.103 mg, and 0.209 mg, respectively, and the mass of lead chloride added were 0.104 mg, 0.062 mg, and 0.127 mg, respectively, to prepare a mixed alcoholic solution of nickel and lead ions. The concentrations of nickel and lead ions before adsorption were measured using inductively coupled plasma mass spectrometry (ICP-MS). The initial concentrations of nickel and lead ions in beaker 1 were 155 ppb and 155 ppb, respectively; in beaker 2, 93 ppb and 93 ppb, respectively; and in beaker 3, 189 ppb and 189 ppb, respectively.

[0078] Then, the adsorbent to be tested was added to beakers 1-3 for adsorption. The ratio of the mass of the adsorbent to the volume of the alcohol solvent was 1 g: 50 mL. The beakers were then placed in a shaker and shaken at 160 rpm for 1 h at 30 °C. After adsorption, the concentration of nickel ions in the solution was measured by ICP-MS. The results are shown in Table 1.

[0079] Table 1. Detection results of Examples 1-43 and Comparative Examples 1-2

[0080] Table 1. Detection results of Examples 1-43 and Comparative Examples 1-2 (continued)

[0081] Comparing Example 1 and Comparative Examples 1-2, it can be seen that the adsorbent of Comparative Example 2 is nano-silica modified with a silane coupling agent containing thiol groups, and its adsorption effect on metal ions in alcohols is better than that of Comparative Example 1; while the adsorbent of Example 1 is the adsorbent of this application, which is obtained by modifying nano-silica with a modified silane containing diacetylated thiol groups and dicarboxyl groups specifically in this application and then acid hydrolyzing it. The adsorption effect of the adsorbent of Example 1 is significantly improved compared with that of Comparative Example 2.

[0082] The adsorbent of this application utilizes a modified silane containing diacetylated mercapto groups and dicarboxyl groups to perform surface grafting modification on nano-silica. The silanoxy group at one end of the modified silane forms a stable covalent bond with the silica surface through hydrolysis and condensation, thereby anchoring the organic segment with bifunctional groups onto the inorganic framework. The subsequent acid hydrolysis step is crucial, as it selectively breaks the CS bond of the acetyl protecting group on the sulfur atom, converting the inert acetylated mercapto group into a free mercapto group (-SH) with high coordination activity, while the carboxyl functional group and the silica framework remain stable during this process. Thus, by adopting a "precursor protection-surface fixation-in-situ activation" strategy, bifunctional synergistic adsorption sites rich in both mercapto and carboxyl groups are constructed on the surface of nano-silica, effectively solving the technical problem of easy oxidation and deactivation of highly active mercapto groups during modification. This results in the final adsorbent having high adsorption capacity, strong binding force, and excellent selectivity for heavy metal ions such as lead and nickel in alcohol solvents, solving the problem of difficult removal of trace metal ions in alcohol solvents.

[0083] Comparing Examples 1 and 2, it can be seen that the difference between Examples 1 and 2 lies in the first solvent. The concentrations of nickel and lead after adsorption in Example 1 are significantly lower than those in Example 2. This is because the tetrahydrofuran used in Example 2 has a strong solvation effect with the amine group, which reduces the nucleophilic attack ability of the amine group, slows down the condensation reaction rate and reduces the conversion rate. The purity of the silane coupling agent containing diamino groups produced in S1 decreases, and it contains unreacted raw materials and by-reaction products, which affects the purity of the subsequently obtained modified silane coupling agent containing diacetylated mercapto groups and dicarboxyl groups. This leads to a decrease in the grafting density, activity, and uniformity of functionalization modification on the adsorbent surface, and a decrease in the adsorption capacity and stability of metal ions in alcohols.

[0084] Comparing Examples 1 and 3, it can be seen that the difference between Examples 1 and 3 lies in the different condensing agents in S1. The concentrations of nickel and lead after adsorption in Example 1 are significantly lower than those in Example 2. This is because the DIPEA used in Example 2 is too alkaline and has too much steric hindrance. Too much alkalinity may trigger side reactions such as the self-condensation of silanes during the condensation process. Too much steric hindrance makes DIPEA less efficient than triethylamine in neutralizing the hydrogen chloride byproduct of the reaction. Therefore, it affects the purity of the modified silane coupling agent containing diacetylated mercapto groups and dicarboxyl groups, resulting in a decrease in the grafting density, activity, and uniformity of functionalization modification on the adsorbent surface, and a decrease in the adsorption capacity and stability of metal ions in alcohols.

[0085] Therefore, in this application, acetonitrile is preferred as the first solvent and triethylamine is preferred as the condensing agent.

[0086] Comparing Examples 1 and 4-7, the difference lies in the different ratios of condensing agent dosage. The adsorption effects, from best to worst, are Example 1, Example 6, Example 5, Example 7, and Example 4. Comparing Examples 1 and 8-10, the difference lies in the amount of the first solvent used in the S1 condensation reaction. The adsorption effects are ranked from best to worst as follows: Example 1, Example 10, Example 9, and Example 8. Comparing Examples 11-12, it can be seen that the difference lies in the different condensation reaction temperatures in S1. The adsorption effect of Example 11 is similar to that of Example 1, while the adsorption effect of Example 12 shows a significant decrease compared to Example 1. This is because high temperatures easily trigger side reactions, generate byproducts, reduce the purity of intermediates, and have a chain reaction effect on subsequent steps (S2-S4), resulting in a decrease in the grafting density and activity of functional groups on the surface of the adsorbent, and a decrease in adsorption performance.

[0087] Comparing Examples 13-14, it can be seen that the difference lies in the different S1 condensation reaction temperatures. The adsorption effect of Example 13 is similar to that of Example 1, while the adsorption effect of Example 14 shows a significant decrease compared to Example 1. This is because the temperature is too low, and even with a long reaction time, the reaction kinetics are severely limited, resulting in incomplete reaction and low conversion rate. Consequently, the purity of the intermediate is poor, which directly affects the subsequent functionalization effect, significantly reducing the surface functional group density and synergistic adsorption capacity of the adsorbent, and thus decreasing the adsorption performance.

[0088] Therefore, in this application, the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent, and first solvent in S1 is preferably 1:0.7:0.5-0.7:4-8, the condensation reaction temperature is 40-60℃, and the condensation reaction time is 10-16h. This ratio and temperature / time window ensure that the reactant molecules have the optimal collision frequency and effective reactivity. The amino group of tris(2-aminoethyl)amine can undergo a complete and ordered nucleophilic substitution reaction with the chloropropyl group of 3-chloropropyltriethoxysilane, while simultaneously achieving appropriate condensation. The solvent can promptly neutralize the hydrohalic acid of the byproducts to maintain the alkalinity of the reaction system and drive the reaction equilibrium to the right. The appropriate amount of solvent ensures the homogeneity and mass transfer efficiency of the reaction system, thereby achieving a high conversion rate of the condensation reaction and a highly selective synthesis of the target product—containing a diaminosilane coupling agent. It effectively inhibits side reactions such as excessive alkylation of secondary amines to generate tertiary amines or quaternary ammonium salts, ensuring the accuracy and purity of the intermediate molecular structure. This lays a controllable molecular foundation for the subsequent construction of high-density bifunctional adsorbents and improves the adsorption capacity and stability of the final adsorbent.

[0089] Comparing Example 1 and Examples 15-17, the difference lies in the different proportions of acid anhydride in S2. The adsorption effects are ranked from best to worst as Example 1, Example 17, Example 16, and Example 15. Comparing Example 1 and Examples 18-20, the difference lies in the different proportions of acid anhydride in S2. The adsorption effects are ranked from best to worst as Example 1, Example 20, Example 19, and Example 18. Comparing Examples 21 and 22, the difference lies in the ring-opening reaction temperature in S2. The adsorption effect of Example 21 is similar to that of Example 1, while the adsorption effect of Example 22 shows a significant decrease compared to Example 1. Comparing Examples 23 and 24, the difference lies in the ring-opening reaction temperature in S2. The adsorption effect of Example 23 is similar to that of Example 1, while the adsorption effect of Example 24 shows a significant decrease compared to Example 1. Therefore, in this application, the mass ratio of the diamino silane coupling agent, S-acetyl mercaptosuccinic anhydride, and the first solvent in S2 is 1:1.5-2:12-18; the ring-opening reaction temperature in S2 is 30-50℃, and the ring-opening reaction time is 6-10h, which is preferred. The mass ratio ensures that the anhydride functional group is in moderate excess relative to the amino functional group, thereby driving the ring-opening amidation reaction to be more complete. This allows each primary amino group in the diamino silane coupling agent molecule to react with one molecule of S-acetyl mercaptosuccinic anhydride, thereby introducing a carboxyl group and a protected acetylated mercapto group simultaneously and quantitatively at each grafting site. The optimized reaction conditions effectively ensure the high efficiency and high selectivity of functional group conversion, avoid incomplete functionalization due to insufficient anhydride or side reactions that may be caused by excessive reaction, improve the density and grafting regularity of the difunctional groups (mercapto and carboxyl groups) on the adsorbent surface, and thus improve the adsorption capacity of the adsorbent.

[0090] Comparing Example 1 and Example 25, the difference lies in the second solvent in S3. The adsorption effect of Example 1 is better than that of Example 25. Therefore, cyclohexane is selected as the second solvent in this application as it is preferred. Its non-polar properties increase the interfacial energy between the hydrophilic silanol groups on the surface of nano-silica and the hydrophobic organic long chains of modified silane. This drives the hydrophobic ends of the modified silane to adsorb and oriented onto the silica surface through the solvation effect, promoting the hydrolysis of silanol groups and the condensation reaction efficiency with surface silanol groups. Its boiling point matches the reflux temperature (80°C) required by the process, ensuring that the reaction is carried out at a constant and mild temperature. At the same time, its chemical inertness avoids side reactions with the reaction components, providing an optimized non-aqueous reaction environment for the high-density and orderly grafting of silane coupling agents onto the surface of inorganic carriers, influencing and improving the uniformity and stability of the functionalization modification of silica surface.

[0091] Comparing Example 1 and Examples 26-28, the difference lies in the different proportions of silane coupling agent used in S3. The adsorption effects, from best to worst, are Example 1, Example 28, Example 27, and Example 26. Comparing Example 1 and Examples 29-31, the difference lies in the different proportions of solvent used in S3. The adsorption effects, from best to worst, are Example 1, Example 31, Example 30, and Example 29. Comparing Examples 1 and 32-33, the difference lies in the reaction temperature in S3. The adsorption effect of Example 33 is weaker than that of Example 1; the adsorption effect of Example 32 is significantly weaker than that of Examples 33 and 1, which is due to the excessively low reaction temperature and slow reaction speed. Comparing Examples 1 and 34-36, the difference lies in the reaction time in S3, and the adsorption effects, from best to worst, are Example 1, Example 36, Example 35, and Example 34. Therefore, the optimal mass ratio of nano-silica in S3, modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:0.5-2:6-10. The optimal grafting reaction temperature in S3 is 80℃, which is the reflux temperature of the cyclohexane solvent, and the optimal grafting reaction time is 7-9h.

[0092] This material ratio ensures that the modified silane has the optimal concentration in the reaction system, achieving high-density grafting coverage on the silica surface while effectively avoiding self-condensation side reactions caused by excessive silane. At the same time, the constant reflux temperature provides a continuous and uniform thermodynamic driving force for the complete hydrolysis of silanoxy groups and efficient condensation with silanol groups on the silica surface. Both factors synergistically optimize the kinetics and thermodynamic equilibrium of the interfacial grafting reaction, enabling the modified silane molecules to form a stable monolayer on the silica surface with high orientation and high bonding strength. This constructs a uniform, high-density bifunctional surface structure, influencing and improving the adsorption capacity and stability of the final adsorbent for metal ions.

[0093] Comparing Examples 1 and 37-38, the difference lies in the concentration of hydrochloric acid used in S4. The adsorption effect of Example 1 is better than that of Examples 37-38. Therefore, in this application, a 10wt% hydrochloric acid aqueous solution in S4 is preferred. The hydrogen ion activity at this concentration is sufficient to efficiently catalyze the breaking of the chemical bond (S-Ac bond) between sulfur atoms and acetyl groups, thereby specifically and completely converting inert acetylated mercapto groups into highly reactive free mercapto groups (-SH). At the same time, the mild acidic conditions ensure the stability of the silica support framework and the structural integrity of the carboxyl functional groups, balancing the reaction efficiency and material stability. This achieves efficient activation of the key adsorption functional group (mercaptogroup) with minimal structural damage, giving the adsorbent superior metal ion adsorption performance.

[0094] Comparing Examples 1 and 39-41, the difference lies in the different proportions of hydrochloric acid solution used in S4 acid hydrolysis. The adsorption performance, from best to worst, is Example 1, Example 41, Example 40, and Example 39. In conjunction with Examples 1 and 42-43, the difference lies in the reaction temperature and reaction time during acid hydrolysis in S4. Examples 1 and 42-43 are both superior and significantly better than Comparative Example 2. Therefore, in this application, the optimal mass ratio of the product obtained in S3 to the hydrochloric acid aqueous solution in S4 is 1:50-70, the acid hydrolysis reaction time is 2-4 hours, and the acid hydrolysis reaction temperature is 20-30℃. This sufficient liquid-solid ratio ensures sufficient contact and mass transfer efficiency between the acid hydrolysis reagent and the surface of the product particles. The specific mild temperature and time window provides suitable reaction kinetics for the hydrolysis of the acetyl protecting group on the sulfur atom. This combination precisely controls the process of the deprotection reaction, achieving efficient and complete conversion of acetylated thiol groups to active thiol groups. At the same time, it minimizes side reactions such as dissolution of silica support, degradation of functional groups, or re-dissolution of adsorbed impurities that may be caused by strong acid or long-term reaction. This is a key optimization to ensure that the final adsorbent obtains a high active thiol group density and maintains its structural integrity.

[0095] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A bifunctional modified silica adsorbent, characterized in that, The nano-silica is obtained by modification with a silane containing diacetylated mercapto groups and dicarboxyl groups, followed by acid hydrolysis. The structural formula of the modified silane containing diacetylated mercapto groups and dicarboxyl groups is as follows: 。 2. The preparation process of the bifunctional modified silica adsorbent according to claim 1, characterized in that, Includes the following steps: S1. Take 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent, and first solvent to undergo a condensation reaction. After the reaction is completed, remove the first solvent to obtain a silane coupling agent containing bisamino groups. S2. Take the silane coupling agent containing diamino groups obtained in S1, S-acetyl thiosuccinic anhydride and the first solvent and carry out a ring-opening reaction. After the reaction is completed, remove the first solvent to obtain a modified silane containing diacetylated thiol and dicarboxyl groups. S3. Take nano-silica, the modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and the second solvent for grafting reaction. After the reaction is completed, remove the second solvent, wash and dry to obtain the product. S4. The product obtained in S3 is subjected to acid hydrolysis in hydrochloric acid aqueous solution. After the reaction is completed, the product is filtered, washed, and dried to obtain a dithiol- and dicarboxyl-modified silica adsorbent.

3. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, In S1, the first solvent is acetonitrile, and the condensing agent is triethylamine.

4. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, In S1, the mass ratio of 3-chloropropyltriethoxysilane, tris(2-aminoethyl)amine, condensing agent, and first solvent is 1:0.7:0.5-0.7:4-8. The condensation reaction temperature is 40-60℃, and the condensation reaction time is 10-16h.

5. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, The mass ratio of the diamino silane coupling agent, S-acetyl mercaptosuccinic anhydride, and the first solvent in S2 is 1:1.5-2:12-18; the ring-opening reaction temperature in S2 is 30-50℃, and the ring-opening reaction time is 6-10h.

6. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, In S3, the mass ratio of nano-silica, the modified silane containing diacetylated mercapto groups and dicarboxyl groups obtained in S2, and cyclohexane is 1:0.5-2:6-10; the grafting reaction temperature in S3 is 80℃, the reflux temperature of the cyclohexane solvent, and the grafting reaction time is 7-9h.

7. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, The hydrochloric acid solution in S4 is a 10wt% hydrochloric acid solution.

8. The preparation process of a bifunctional modified silica adsorbent according to claim 2, characterized in that, In S4, the mass ratio of the product obtained from S3 to the hydrochloric acid aqueous solution is 1:50-70, the acid hydrolysis reaction time is 2-4 hours, and the acid hydrolysis reaction temperature is 20-30℃.

9. A bifunctional modified silica adsorbent according to claim 1, characterized in that, Applications of adsorption of lead and nickel ions in methanol, ethanol or isopropanol.

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