Adsorbent material for removing contaminants and method for making same

Abstract

The present application relates to the technical field of environmental protection adsorption material, and discloses an adsorption material for removing pollutants and a preparation method thereof, the adsorption material is a titanium-iron-silicon composite adsorption material, which is prepared by cross-linking and solidifying total metal ions, silicon elements and gluconate under non-calcination conditions at a molar ratio of 1:(0.3-0.5):(0.08-0.12), wherein the molar ratio of titanium to iron is 1:(0.8-1.5). During preparation, the titanium-iron precursor is oxidized, mixed with silicate and gluconate to obtain an acidic sol; a first alkaline reagent is added for pre-aging and rheological torque is monitored; when the torque reaches a trigger threshold, process ice is thrown in and a second alkaline reagent is injected, the latent heat of ice phase change is used to collide with the acid-base neutralization exothermic, the cross-linking temperature is controlled below 15 DEG C, and finally the product is obtained through washing and low-temperature drying. The present application inhibits local overheating and hard agglomeration of the reaction system, retains the amorphous porous skeleton and active adsorption sites, and improves the adsorption performance of the material.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly adsorption materials technology, specifically to an adsorption material for removing pollutants and its preparation method. Background Technology

[0002] Polymetallic silicate materials have attracted attention in the field of water pollutant removal due to their abundant surface-active groups and porous structure. Currently, the preparation of multi-component composite adsorbent materials containing titanium, iron, silicon, etc., mainly employs liquid-phase chemical precipitation or sol-gel methods. The core step of these methods is to inject an alkaline reagent into an acidic metal precursor solution, promoting the hydrolysis and condensation reactions of dissolved metal ions, thereby cross-linking to form a solid-phase gel network.

[0003] During the liquid-phase gelation reaction stage, the acid-base neutralization process releases a large amount of heat instantaneously. Due to the hysteresis of heat transfer within the reactor, conventional external jacketed cooling devices are insufficient to effectively eliminate the instantaneously generated localized high-temperature zones within the system. This uncontrolled localized temperature rise alters the thermodynamic metastable state of the colloidal particles, driving the primary particles to rapidly shrink and harden, and inducing a transformation of the material into a more stable, dense crystalline phase, leading to the collapse of the original porous framework.

[0004] Meanwhile, due to localized overheating, effective adsorption sites such as terminal hydroxyl groups within the gel network are prone to premature condensation and dehydration. Conventional processes often involve high-temperature calcination after liquid-phase molding to obtain a stable material morphology, which further exacerbates pore shrinkage and leads to the carbonization and decomposition of organic modified components within the system. These thermal control challenges in the preparation process result in a denser solid-phase microstructure in the final product, significantly reducing the number of effective surface active sites and limiting the material's actual adsorption capacity for pollutants. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an adsorbent material for removing pollutants and its preparation method. The technical problem it solves is that in the existing liquid-phase reaction preparation of polymetallic silicate composite adsorbent materials, the acid-base neutralization stage is highly exothermic and the system temperature is difficult to control, which leads to local overheating of the material and subsequent hard agglomeration or uncontrollable crystallization, resulting in densification of the solid phase microstructure of the material and a decrease in effective adsorption sites.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides an adsorbent material for removing pollutants, employing the following technical solution:

[0008] An adsorbent material for removing pollutants, wherein the adsorbent material is a titanium-iron-silicon composite adsorbent material, prepared by chemical liquid-phase crosslinking and curing of raw materials containing the following relative molar ratios under non-calcination conditions:

[0009] Total metal ions: silicon: gluconate = 1:(0.3-0.5):(0.08-0.12);

[0010] The total metal ions are the sum of titanium ions and iron ions, and the molar ratio of titanium ions to iron ions is 1:(0.8-1.5).

[0011] By employing the above technical solution, titanium ions and iron ions undergo co-hydrolysis in the liquid phase. During this process, silicon elements, in the form of silicic acid, interpenetrate between the titanium-iron polynuclear hydroxyl complexes, thereby forming a porous cross-linked structure. The gluconate ions in the formulation system participate in the coordination of metal ions through polyhydroxyl and carboxyl groups. This process introduces a certain steric hindrance effect, limiting the excessive densification of the framework structure.

[0012] The cross-linking of the components in the above specific molar ratio under non-calcination conditions helps to retain effective terminal hydroxyl groups and other active groups in the material structure, thus obtaining an amorphous composite material with high adsorption capacity for pollutants.

[0013] Preferably, the raw materials include titanium oxysulfate, ferrous sulfate, sodium silicate, and sodium gluconate.

[0014] By employing the above technical solution, the sulfate system can provide suitable free acidity, maintaining the dissolved state of metal ions in the initial stage of the reaction. Simultaneously, since sodium gluconate and sodium silicate are miscible in the aqueous phase, their mixture can form a homogeneous blend, which is beneficial for subsequent cross-linking reactions to proceed in a homogeneous system.

[0015] Secondly, the present invention provides a method for preparing an adsorbent material for removing pollutants, employing the following technical solution:

[0016] A method for preparing an adsorbent material for removing pollutants includes the following steps:

[0017] An aqueous solution of an acidic metal precursor containing titanium ions and ferrous ions is prepared. An oxidant is slowly added dropwise to the aqueous solution of the acidic metal precursor. After the ferrous ions are oxidized, an oxidized precursor is obtained.

[0018] A silicate containing silicon and a compound containing gluconate are dissolved in water to form a blend.

[0019] The blend solution is injected into the oxidized precursor and mixed evenly to obtain a homogeneous acidic sol.

[0020] A first alkaline reagent was slowly added to the homogeneous acidic sol for pre-aging, and the rheological torque change of the system was monitored in real time.

[0021] When the system torque rises to the preset crosslinking trigger threshold, process ice is added to the system, and a second alkaline reagent is injected to control the overall pH of the system to jump to an alkaline environment for crosslinking aging. The process ice absorbs latent heat during phase change and offsets the heat released by acid-base neutralization.

[0022] The aged material is subjected to solid-liquid separation and washing, and then dried and pulverized at low temperature to obtain the titanium-iron-silicon composite adsorbent material.

[0023] By adopting the above technical solutions, the core reaction principle and mechanism of this invention are mainly reflected in three aspects: precursor conversion, sol formation, and low-temperature crosslinking.

[0024] Specifically, under acidic conditions, strong oxidizing agents such as hydrogen peroxide oxidize ferrous ions in the system to ferric ions. The main redox reaction is: 2Fe2+ + Fe2+ + Fe3+ + Fe2+. 2+ +H₂O₂ + 2H₂ + →2Fe 3+ +2H2O. Since the precipitation pH ranges of ferric ions and tetravalent titanium ions are closer in the subsequent alkalization stage, this provides a material basis for achieving uniform co-precipitation cross-linking in the later stage.

[0025] When silicates are added to a strongly acidic system, they often transform into silica oligomers, accompanied by partial coordination reactions between gluconate ions and oxidized metal ions. By controlling the mixing of the system in a strongly acidic environment, the hydrolysis and precipitation pathway of metal ions can be effectively blocked, thereby forming a stable, transparent, homogeneous acidic sol.

[0026] As a weakly alkaline first reagent is slowly added dropwise, the pH of the system gradually rises, which usually promotes the hydrolysis of metal ions to produce polynuclear hydroxyl complexes. During this process, the rheological torque data of the liquid phase system directly reflects the degree of cross-linking polymerization of colloidal particles. By using real-time torque monitoring, the critical state of network growth within the sol can be quantitatively identified.

[0027] During the crosslinking stage, the injection of a strong base into the liquid phase leads to a vigorous exothermic acid-base neutralization reaction, the main reaction being: H + +OH - →H2O. If process ice fragments are introduced at the moment of torque triggering, the fragments undergo phase change melting and absorb latent heat. This endothermic physical process and the neutralization exothermic chemical reaction can be relatively synchronized in terms of time and spatial distribution. Through the enthalpy counterbalancing mechanism, the system temperature is forcibly constrained within a low-temperature range, effectively mitigating the crystal phase transformation and particle shrinkage and agglomeration caused by high temperatures. Simultaneously, the pH jump drives the silicic acid and titanium iron hydroxyl polymer to undergo a strong instantaneous condensation crosslinking reaction, forming a porous gel framework. Finally, a low-temperature drying process removes the free moisture in the pores, solidifying and preserving the porous structure formed in the above crosslinking stage.

[0028] Preferably, the specific process for preparing the oxidized precursor includes:

[0029] The initial temperature of the system was controlled at 25-30℃. Hydrogen peroxide was slowly added dropwise to the aqueous solution of the acidic metal precursor containing free sulfuric acid, and the temperature rise of the system during the dropwise process was controlled to be less than or equal to 5℃.

[0030] The system potential is monitored online using an oxidation-reduction potential meter. When the oxidation-reduction potential value suddenly jumps and stabilizes in the range of 450-500mV, the addition of hydrogen peroxide is stopped, and stirring is continued for 15-20 minutes. The oxidation reaction can be confirmed to be basically completed by sampling and detecting the residual ferrous ion content.

[0031] By employing the above technical solutions, the system temperature rise is controlled at a low level, which helps to reduce the ineffective high-temperature spontaneous decomposition reaction of hydrogen peroxide. The abrupt change in redox potential usually indicates that ferrous ions in the system have essentially converted to ferric ions. Using online potential feedback monitoring instead of quantitative addition can, to some extent, reduce the interference of excessive residual oxidant on subsequent colloidal growth.

[0032] Preferably, during the preparation of the homogeneous acidic sol, the injection rate and multi-point feeding method of the blend solution are controlled, the overall pH of the reaction system is maintained between 1.0 and 1.5 during the mixing stage, and the mixing time is 20 to 30 minutes.

[0033] By adopting the above technical solution, the multi-point feeding method disperses the local concentration concentration zone at the moment of fluid entry. Maintaining the pH between 1.0 and 1.5 is beneficial to maintaining the dissolved state of silica and metal ions, preventing the precipitation of titanium or iron ions as hydroxides due to localized instantaneous high alkalinity, and thus promoting uniform mixing of all components at the molecular scale.

[0034] Preferably, the pre-aging process parameters are controlled as follows:

[0035] The first alkaline reagent is ammonia water, and the dropping rate of the ammonia water is controlled at 0.3 to 0.5 pH / min. The dropping of the ammonia water is stopped when the pH of the system rises to 2.5 to 3.5.

[0036] Maintain the system temperature at 30-35℃ and continue stirring for aging. Record the torque of the stirring motor when the ammonia water is stopped being added, and record it as the initial torque reference value.

[0037] The crosslinking trigger threshold is 1.15 to 1.18 times the initial torque reference value.

[0038] By employing the above technical solution, ammonia, as a weak alkaline solution, can control the gradual increase of the system's pH. Combined with a temperature of 30–35°C, this provides a suitable polymerization kinetic rate. When the torque rises to 1.15 to 1.18 times the initial torque reference value, a primary metal-silicon-oxygen network with a specific degree of polymerization is usually formed in the liquid phase system. Choosing this point as the rheological trigger for subsequent cold-induced crosslinking has a positive effect on improving the skeleton's connectivity.

[0039] Preferably, the specific process of crosslinking aging includes:

[0040] An aqueous solution of the acidic metal precursor with a liquid phase free sulfuric acid mass fraction of 10% to 15% was obtained;

[0041] The process-made crushed ice of the specified mass is prepared in advance based on the free acidity and final pH enthalpy parameters within the system.

[0042] When the torque reaches the crosslinking trigger threshold, the process ice crushing is introduced in one go.

[0043] Within 45 to 60 seconds after the process ice is added, a second alkaline reagent is injected, and the overall pH of the system is controlled to jump and stabilize between 8.0 and 8.5 within 3 to 5 minutes. The second alkaline reagent is a sodium hydroxide aqueous solution with a mass fraction of 25% to 30%.

[0044] The maximum temperature of the system during the entire cross-linking aging process is controlled to be below or equal to 15°C, and then the stirring speed is reduced to continue aging for 30 to 45 minutes.

[0045] By employing the above technical solution, the enthalpy of the reaction is calculated based on the initial free sulfuric acid content and target pH of the system, and corresponding mass of process crushed ice is pre-prepared to achieve a relative balance in heat balance. A high-concentration sodium hydroxide aqueous solution is injected within 45–60 seconds after the crushed ice is added to create an instantaneously high-alkalinity environment, promoting spatial coupling and solidification of the primary polymer network. The maximum temperature is controlled to be below or equal to 15°C throughout the process, effectively maintaining the amorphous mesostatic structure and reducing the risk of hydrothermal aging and collapse of the framework due to heating.

[0046] Preferably, the low-temperature drying process includes:

[0047] The dehydrated and washed solid material is placed at a constant temperature of 95-105℃ and dried for 4-6 hours.

[0048] By adopting the above technical solution, the temperature conditions of 95-105℃ not only meet the physical requirements for evaporation and removal of internal capillary water, but also avoid the surface hydroxyl condensation dehydration reaction and the internal gluconate carbonization decomposition reaction that may be caused by excessively high temperatures.

[0049] This invention provides an adsorbent material for removing pollutants and a method for preparing the same. It has the following beneficial effects:

[0050] 1. This invention solves the problem of localized overheating in the multi-metal liquid-phase polymerization process by combining rheological torque monitoring with the endothermic phase transition characteristics of crushed ice. By introducing pre-made crushed ice at the torque trigger threshold and simultaneously injecting a strong alkali, the latent heat absorbed by the melting crushed ice directly offsets the intense chemical exothermic reaction generated by acid-base neutralization, thus confining the system temperature to 15°C or below throughout the crosslinking process. This in-situ enthalpy balance mechanism effectively mitigates the hard agglomeration and shrinkage of colloidal particles due to heating, reduces the risk of the system transforming into a stable crystalline phase, and better solidifies and preserves the amorphous porous network structure inside the material.

[0051] 2. This invention employs a specific molar ratio of inorganic metal components and organic gluconate formulation, and prepares the composite material under non-calcination conditions, thereby increasing the density of effective adsorption sites on the surface of the composite material. Silicate oligomers are intercalated within the titanium-iron polynuclear hydroxyl complex, and the steric hindrance generated by the gluconate ligands inhibits the excessive densification growth of the inorganic framework. Simultaneously, by avoiding the traditional high-temperature calcination process, the active groups such as terminal hydroxyl groups formed during the reaction stage are spared from thermal condensation and dehydration, resulting in amorphous materials exhibiting high adsorption capacity for target pollutants.

[0052] 3. This invention ensures uniform composite composition of multiple components at the molecular scale by precisely controlling the local pH of the precursor oxidation state and the homogeneous mixing stage. Ferrous ions are oxidized to ferric ions in advance, making the precipitation pH range of iron and titanium more consistent. Subsequently, a silicon and gluconate blend is injected into a strongly acidic substrate with a pH maintained between 1.0 and 1.5 using a multi-point feeding method. This maintains the stable dissolved state of each core component and avoids premature precipitation of single-phase titanium or iron hydroxides caused by localized instantaneous high alkalinity, providing a material basis for the subsequent construction of a uniformly distributed titanium-iron-silicon composite framework. Attached Figure Description

[0053] Figure 1 Fourier transform infrared spectra of pure sodium gluconate standard in Test Example 1, pre-lyophilized powder of Example 1, pre-lyophilized powder of Comparative Example 1 (blank group), and pre-lyophilized powder of Comparative Example 3 are compared.

[0054] Figure 2 The figures show the X-ray photoelectron spectra of the powder materials in each test group in Test Example 3, with high-resolution O 1s energy spectra and peak fitting comparisons. Figure (a) shows the test results of the powder material in Example 1, and Figure (b) shows the test results of the powder material in Comparative Example 6. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0057] Titanium oxysulfate, CAS number 13825-74-6, analytical grade.

[0058] Ferrous sulfate heptahydrate, CAS number 7782-63-0, analytical grade.

[0059] Sodium silicate, CAS number 1344-09-8, industrial grade, modulus 3.0.

[0060] Sodium gluconate, CAS number 527-07-1, mass fraction greater than or equal to 98%.

[0061] Hydrogen peroxide, CAS number 7722-84-1, mass fraction 30%.

[0062] Ammonia water, analytical grade, with a mass fraction of 15% or 20%.

[0063] Sodium hydroxide, analytical grade, is prepared as an aqueous solution with a mass fraction of 25% or 30% for use.

[0064] Lead nitrate, analytical grade.

[0065] Nitric acid, analytical grade, prepared as a 0.1 mol / L solution;

[0066] Potassium bromide, spectrally pure;

[0067] Deionized water has a resistivity of not less than 18.2 MΩ·cm, which meets the laboratory grade I water standard.

[0068] Preparation Examples 1-3:

[0069] Preparation Example 1:

[0070] This preparation example provides a method for preparing a blend of a mesoscopic framework and a kinetic buffer, comprising the following steps:

[0071] At 25°C, a sodium silicate aqueous solution containing 0.4 mol silicon and 0.1 mol sodium gluconate were measured and added together to 200 mL of deionized water. Mechanical stirring was started and the stirring speed was controlled at 250 rpm. Stirring was continued for 15 minutes until the solution was completely dissolved and a colorless and transparent homogeneous aqueous solution was formed, thus obtaining a blend solution for matching the treatment of 1 mol of total metal ions.

[0072] Preparation Example 2:

[0073] This preparation example provides a method for preparing a blend of a mesoscopic framework and a kinetic buffer, comprising the following steps:

[0074] At 20°C, a sodium silicate aqueous solution containing 0.3 mol silicon and 0.08 mol sodium gluconate were measured and added together to 200 mL of deionized water. Mechanical stirring was started and the stirring speed was controlled at 200 rpm. Stirring was continued for 20 minutes until the solution was completely dissolved and a colorless and transparent homogeneous aqueous solution was formed, thus obtaining a blend solution for matching the treatment of 1 mol of total metal ions.

[0075] Preparation Example 3:

[0076] This preparation example provides a method for preparing a blend of a mesoscopic framework and a kinetic buffer, comprising the following steps:

[0077] At 25°C, a sodium silicate aqueous solution containing 0.5 mol silicon and 0.12 mol sodium gluconate were measured and added together to 200 mL of deionized water. Mechanical stirring was started and the stirring speed was controlled at 300 rpm. Stirring was continued for 15 minutes until the solution was completely dissolved and a colorless and transparent homogeneous aqueous solution was formed, thus obtaining a blend solution for matching the treatment of 1 mol of total metal ions.

[0078] Examples 1-4:

[0079] Example 1:

[0080] This embodiment provides a method for preparing a titanium-iron-silicon composite adsorbent material, including the following steps:

[0081] Prepare 1 L of an aqueous solution containing titanium oxysulfate and ferrous sulfate, with a titanium ion to ferrous ion molar ratio of 1:1, a total metal ion concentration of 1.0 mol / L, and a free sulfuric acid mass fraction of 12% in the liquid phase. The amount of process crushed ice added is estimated based on the heat of acid-base neutralization, the change in sensible heat of the system, the latent heat of melting of the ice, and the sensible heat of heating after melting. The amount is determined with the constraint that the highest temperature of the system during the strong alkali injection stage does not exceed 15℃. Thus, 250 g of process crushed ice with a particle size of approximately 3 mm to 10 mm is prepared in advance.

[0082] The aqueous solution of the metal precursor was pumped into an industrial stirred reactor equipped with a torque meter, an online redox potential monitor (using Ag / AgCl as the reference electrode), and a multi-point submersible feed pipe. The initial temperature was controlled at 28°C, and stirring was started at a speed of 130 rpm. (Note: In the following examples, the redox potential was measured using the Ag / AgCl electrode as the reference electrode).

[0083] Slowly add 30% hydrogen peroxide to the reactor, controlling the temperature rise of the system to not exceed 5°C. Observe the oxidation-reduction potential value. When the value jumps suddenly and stabilizes at 480mV, stop adding hydrogen peroxide and continue stirring for 15 minutes.

[0084] Then, while maintaining the stirring speed, the blend obtained in Preparation Example 1 was injected into the reactor in a jet manner through the submerged multi-point distribution feed pipe. By controlling the injection rate of the blend and the submerged multi-point distribution feed method, the pH detected at different sampling points in the reactor was not higher than 2.0, and the overall pH was stabilized at 1.2. After mixing for 25 minutes, a homogeneous acidic sol was obtained.

[0085] Turn on the ammonia dosing pump and add 20% ammonia solution at a rate of 0.4 pH / min. Stop adding the solution when the pH of the system rises to 3.0. Maintain the reactor temperature at 32°C, adjust the speed to 110 rpm and continue aging. Record the initial torque reference value T0 of the stirring motor at this time.

[0086] The torque change is monitored in real time. When the torque value rises to 1.16T0, 250g of pre-prepared process ice is immediately added into the reactor.

[0087] Within 50 seconds of adding ice, a high-pressure pump is started to pump in a 30% sodium hydroxide aqueous solution at a high flow rate. The amount added is controlled by feedback from an online pH meter. Within 4 minutes, the overall pH of the system jumps and stabilizes at 8.2. The highest temperature of the system throughout the process does not exceed 14°C.

[0088] The stirring speed was then reduced to 70 rpm at 14°C, and the mixture was aged for 40 minutes. The aged suspension was then pumped into a plate and frame filter press, with the feed pressure controlled at 0.7 MPa. After dehydration, the filter cake was washed with deionized water until the pH of the filtrate reached 7.2.

[0089] The obtained filter cake was transferred to a forced-air drying oven and dried at 100°C for 5 hours. It was then mechanically pulverized and passed through an 80-mesh sieve to obtain the titanium-iron-silicon composite adsorbent material.

[0090] Example 2:

[0091] This embodiment provides a method for preparing a titanium-iron-silicon composite adsorbent material, including the following steps:

[0092] Prepare 1L of aqueous solution containing titanium oxysulfate and ferrous sulfate as a metal precursor, wherein the molar ratio of titanium ions to ferrous ions is 1:0.8, the total metal ion concentration is 1.0mol / L, the mass fraction of free sulfuric acid in the liquid phase is 15%, and 320g of process crushed ice is prepared in advance based on the mass fraction of free sulfuric acid and the enthalpy balance of final pH.

[0093] The aqueous solution of the metal precursor was pumped into a stirred reactor equipped with a torque meter, an online redox potential monitor, and a submerged multi-point feed pipe. The initial temperature was controlled at 25°C, and the stirring speed was 150 rpm. 30% hydrogen peroxide was slowly added dropwise to the reactor, controlling the temperature rise to no more than 5°C. When the redox potential stabilized at 450 mV, the addition of hydrogen peroxide was stopped, and stirring continued for 15 minutes.

[0094] The blend obtained in Preparation Example 3 was injected into the reactor through a submerged multi-point feed pipe, and the overall pH was controlled to be stable at 1.0. After mixing for 30 minutes, a homogeneous acidic sol was obtained.

[0095] Add 20% ammonia solution at a rate of 0.3 pH / min until the pH of the system reaches 2.5, then stop adding the solution. Maintain the reactor temperature at 35°C and adjust the rotation speed to 120 rpm for continuous aging. Record the initial torque reference value T0.

[0096] When the torque value rises to 1.15T0, immediately add 320g of process crushed ice. Within 45 seconds of adding the ice, pump in a 30% sodium hydroxide aqueous solution, raising the pH of the system to 8.0 within 3 minutes. The maximum temperature of the system throughout the entire process does not exceed 15℃.

[0097] The speed was reduced to 80 rpm at 15℃ and aged for 30 minutes. The suspension was dehydrated by a plate and frame filter press (feed pressure 0.8 MPa), washed until the pH of the filtrate was 7.0, and the filter cake was dried at 105℃ for 4 hours, pulverized and passed through a 100-mesh sieve to obtain titanium-iron-silicon composite adsorbent material.

[0098] Example 3:

[0099] This embodiment provides a method for preparing a titanium-iron-silicon composite adsorbent material, including the following steps:

[0100] Prepare 1L of aqueous solution containing titanium oxysulfate and ferrous sulfate as a metal precursor, wherein the molar ratio of titanium ions to ferrous ions is 1:1.5, the total metal ion concentration is 1.0mol / L, the mass fraction of free sulfuric acid in the liquid phase is 10%, and 180g of process crushed ice is prepared in advance based on the mass fraction of free sulfuric acid and the enthalpy balance of final pH.

[0101] The aqueous solution of the metal precursor was pumped into a stirred reactor equipped with a torque meter, an online redox potential monitor, and a submerged multi-point feed pipe. The initial temperature was controlled at 30°C, and the stirring speed was 120 rpm. Hydrogen peroxide with a mass fraction of 30% was added dropwise, and the temperature rise was controlled to not exceed 5°C. When the redox potential stabilized at 500 mV, the addition of hydrogen peroxide was stopped, and stirring continued for 20 minutes.

[0102] The blend obtained in Preparation Example 2 was injected into the reactor through a distributed feed pipe, and the overall pH was kept stable at 1.5. The mixture was mixed for 20 minutes. Ammonia solution with a mass fraction of 15% was added dropwise at a rate of 0.5 pH / min until the pH of the system rose to 3.5. The addition was then stopped, and the reactor temperature was maintained at 30°C. The rotation speed was adjusted to 100 rpm for continuous aging, and the initial torque reference value T0 was recorded.

[0103] When the torque value rises to 1.18T0, immediately add 180g of process crushed ice. Within 60 seconds of adding the ice, pump in a 25% sodium hydroxide aqueous solution, raising the pH of the system to 8.5 within 5 minutes. The maximum temperature throughout the process does not exceed 12℃.

[0104] The rotation speed was reduced to 60 rpm at 12℃ and aged for 45 minutes. The suspension was dehydrated by plate and frame filter press (pressure 0.6 MPa), washed until the pH of the filtrate was 7.5, dried at 95℃ for 6 hours, and pulverized through a 60-mesh sieve to obtain the titanium-iron-silicon composite adsorbent material.

[0105] Example 4:

[0106] This embodiment provides a method for preparing a titanium-iron-silicon composite adsorbent material, including the following steps:

[0107] Prepare 1L of aqueous solution containing titanium oxysulfate and ferrous sulfate as a metal precursor, wherein the molar ratio of titanium ions to ferrous ions is 1:1.2, the total metal ion concentration is 1.0mol / L, the mass fraction of free sulfuric acid in the liquid phase is 13%, and 270g of process crushed ice is prepared in advance based on the mass fraction of free sulfuric acid and the enthalpy balance of final pH.

[0108] The aqueous solution of the metal precursor was pumped into a stirred reactor equipped with a torque meter, an online redox potential monitor, and a submerged multi-point feed pipe. The initial temperature was controlled at 26°C, and the stirring speed was 140 rpm. Hydrogen peroxide with a mass fraction of 30% was added dropwise, and the temperature rise was not more than 5°C. The addition was stopped when the redox potential stabilized at 470 mV, and the mixture was stirred for 15 minutes.

[0109] The blend obtained in Preparation Example 1 was injected into the reactor through a distribution tube, and the pH was kept stable at 1.3. The mixture was mixed for 25 minutes. Ammonia solution with a mass fraction of 20% was added dropwise at a rate of 0.4 pH / min until the pH rose to 3.2. The reactor temperature was maintained at 33°C, and the rotation speed was adjusted to 110 rpm for aging. The initial torque reference value T0 was recorded.

[0110] When the torque value rises to 1.17T0, 270g of crushed ice is added. Within 50 seconds of adding the ice, a 30% sodium hydroxide aqueous solution is pumped in, raising the pH to 8.3 within 4 minutes, with the maximum temperature not exceeding 13℃. It is then aged at 13℃ and 70rpm for 40 minutes. After pressure filtration and dehydration (0.7MPa), washing until the pH reaches 7.2, drying at 100℃ for 5 hours, and pulverizing through an 80-mesh sieve, the titanium-iron-silicon composite adsorbent material is obtained.

[0111] Comparative Examples 1-6:

[0112] Comparative Example 1:

[0113] Compared with Example 1, the difference is that sodium gluconate is not added when preparing the blend, and only sodium silicate containing the corresponding molar amount of silicon is dissolved in deionized water and injected into the reaction vessel. All other aspects are the same.

[0114] Comparative Example 2:

[0115] Compared with Example 1, the difference is that when the torque value rises to 1.16T0, the pre-prepared process crushed ice is not added, and the high-pressure pump is started directly to pump sodium hydroxide aqueous solution into the reactor under the current reactor temperature for alkalization. All other aspects are the same.

[0116] Comparative Example 3:

[0117] Compared with Example 1, the difference is that the feeding and reaction sequence are changed. At the initial set temperature, the blend obtained in Example 1 is first injected into the aqueous solution of the metal precursor for mixing, and then hydrogen peroxide is added dropwise to the reactor for oxidation. All other aspects are the same.

[0118] Comparative Example 4:

[0119] Compared with Example 2, the difference is that: instead of calculating the enthalpy balance based on the mass fraction of free sulfuric acid, 250g of process crushed ice of the same mass as in Example 1 was blindly added. Since the amount of ice was insufficient to offset the neutralization exothermic reaction caused by the high acidity, everything else was the same.

[0120] Comparative Example 5:

[0121] Compared with Example 1, the difference is that after adding ammonia water until the pH of the system rises to 3.0, the real-time monitoring and feedback triggering of the stirring motor torque is not performed. Instead, after aging for a fixed time of 2 hours, process crushed ice is added and sodium hydroxide aqueous solution is pumped in. All other aspects are the same.

[0122] Comparative Example 6:

[0123] Compared with Example 1, the difference is that the material dried at 100°C is further transferred into a muffle furnace and calcined at 450°C for 4 hours, and then mechanically crushed and sieved. The rest are the same.

[0124] Test Examples 1-5:

[0125] Test Example 1:

[0126] The homogeneous acidic sol obtained after mixing for 25 minutes in Example 1, and the acidic sol formed after hydrogen peroxide addition in Comparative Example 3 were extracted as intermediate samples to be tested. Simultaneously, pure sodium gluconate standard was prepared as a control. To eliminate interference from inorganic silicates in the system on specific absorption peaks, the inorganic acidic sol after mixing in Comparative Example 1 was extracted simultaneously as a blank control sample.

[0127] Three sol samples were rapidly frozen in liquid nitrogen to solidify, and then transferred to a vacuum freeze dryer. The cold trap temperature was controlled at -60°C and the vacuum system pressure was below 10 Pa. The samples were dried continuously for 48 hours to obtain powdered pre-lyophilized powder of Example 1, pre-lyophilized powder of Comparative Example 3, and pre-lyophilized powder of Comparative Example 1 (blank group).

[0128] 1.2 mg of pure sodium gluconate standard, pre-lyophilized powder of Example 1, pre-lyophilized powder of Comparative Example 3 and pre-lyophilized powder of Comparative Example 1 (blank group) were weighed and added to 110 mg of dried spectroscopically pure potassium bromide powder. They were ground evenly in an agate mortar and pressed into transparent sheets under a pressure of 15 MPa.

[0129] Transmission spectra of the compressed samples were acquired using a Fourier transform infrared spectrometer at room temperature, with a scanning range of 4000 cm⁻¹. -1 Up to 400cm -1 The resolution is 4cm. -1 The scan was performed 32 times to obtain the relative transmittance data for the corresponding wavenumber.

[0130] Table 1. Transmittance data of key infrared characteristic peaks of pure standard products and pre-lyophilized powders of each test group.

[0131] Test object Hydroxyl stretching vibration peak position and transmittance Position of carboxyl antisymmetric stretching vibration peak and transmittance Peak position and transmittance of the overlapping region of carbon-oxygen bond / silicon-oxygen bond stretching vibrations Pure sodium gluconate standard <![CDATA[3354cm -1 (21.34%)]]> <![CDATA[1612cm -1 (15.67%)]]> <![CDATA[1085cm -1 (12.89%)]]> Example 1: Pre-lyophilized powder <![CDATA[3348cm -1 (26.51%)]]> <![CDATA[1608cm -1 (22.43%)]]> <![CDATA[1081cm -1 (18.27%)]]> Comparative Example 3 Pre-lyophilized Powder <![CDATA[3361cm -1 (78.42%)]]> <![CDATA[1618cm -1 (85.19%)]]> <![CDATA[1092cm -1 (48.36%)]]> Comparative Example 1: Pre-lyophilized powder (blank group) <![CDATA[3345cm -1 (46.72%)]]> <![CDATA[1625cm -1 (68.35%)]]> <![CDATA[1095cm -1 (42.15%)]]>

[0132] Summary: Combining the transmittance data in Table 1 with... Figure 1The Fourier transform infrared spectrum curves show that pure sodium gluconate standard ( Figure 1 (Black solid line) at 3354cm -1 1612cm -1 and 1085cm -1 Characteristic absorptions are observed at these locations, with the peak positions primarily corresponding to the stretching vibrations of the polyhydroxyl group, the antisymmetric stretching vibration of the carboxyl group, and the stretching vibrations of the carbon-oxygen bond. Example 1: Pre-lyophilized powder ( Figure 1 The transmittance of the blue solid line (in the corresponding bands) was 26.51%, 22.43%, and 18.27%, respectively. The overall peak distribution was similar to that of the standard, indicating that the relevant functional groups of sodium gluconate molecules were well preserved in the reaction system of Example 1.

[0133] Considering 1080cm -1 The vicinity represents the overlapping region of the stretching vibrations of carbon-oxygen and silicon-oxygen bonds, and is used as an auxiliary reference. Comparative Example 1 pre-lyophilized powder (inorganic blank group, solid green line) at 3345 cm⁻¹ -1 and 1095cm -1 The presence of absorption in the vicinity (transmittance 46.72% and 42.15%) indicates that the metal hydroxyl groups, adsorbed water, and silicon-oxygen framework within the system contribute to the background of the hydroxyl groups and the overlapping region; however, its absorption at 1625 cm⁻¹ is relatively low. -1 The absorption in the nearby carboxylate characteristic wavenumber range is weak (transmittance 68.35%), and the overall peak shape differs significantly from that of Example 1. Therefore, it can be inferred that the relevant characteristic absorption in Example 1 is not solely due to the inorganic background, but rather includes an effective signal from the gluconate functional group. In contrast, the pre-lyophilized powder of Comparative Example 3 ( Figure 1 The absorption intensity of the red solid line in the above bands is significantly reduced (transmittance is 78.42%, 85.19% and 48.36% respectively), indicating that the characteristic absorption of its hydroxyl and carboxyl regions has been attenuated to a certain extent.

[0134] From a mechanistic perspective, the differences in the aforementioned spectral characteristics may be related to the influence of different oxidation sequences on the stability of organic ligands. Comparative Example 3, which introduced sodium gluconate followed by hydrogen peroxide, showed that the ferrous ions present in the system readily induced an oxidation process similar to the Fenton reaction upon contact with hydrogen peroxide. The oxidizing species generated in this process may non-selectively oxidize the gluconate ion, leading to damage to its polyhydroxy and carboxylic acid groups. This inference is consistent with... Figure 1The decrease in absorption intensity shown by the solid red line is consistent with this phenomenon. In Example 1, oxidation was first performed in a purely inorganic state, and the conversion state of ferrous ions was monitored using the redox potential jump. The mixture containing sodium gluconate was added only after the system stabilized and the input of the oxidant was stopped. This sequence of operations kept the concentration of free reactive species that could potentially trigger organic degradation at a low level, helping to maintain the structural stability of the gluconate molecule. This is consistent with... Figure 1 The characteristic absorption preserved by the solid blue line in the middle indicates that the process conditions help the organic ligands maintain their chemical activity in the system, thereby providing the necessary material conditions for the subsequent formation of transient complexes with metal ions and the regulation of hydrolysis kinetics.

[0135] Test Example 2:

[0136] The distributed control system log files of Example 1, Comparative Example 2 and Comparative Example 4 during the preparation process were selected as the data extraction source.

[0137] The starting time for data recording is determined when ammonia water is added and the system enters the aging stage for each batch.

[0138] The time, stirring motor torque, and temperature parameters inside the reactor were extracted for each test group during the aging stage and the subsequent high-pressure pump injection of sodium hydroxide aqueous solution. The extracted torque parameters were divided by the initial baseline value recorded by each system and then normalized.

[0139] Non-equidistant characteristic time point data from the conventional aging range, torque threshold trigger range, and ice addition and strong alkali injection range were screened and compiled into a comparison record table.

[0140] Table 2. Torque and Temperature Evolution Data for Each Test Group's Reaction System

[0141] Record time (min) Example 1: Relative Torque Example 1 Temperature (°C) Comparative Example 2: Relative Torque Comparative Example 2 Temperature (°C) Comparative Example 4: Relative Torque Comparative Example 4 Temperature (°C) 0.0 1.00 32.1 1.00 32.0 1.00 35.1 8.2 1.05 31.8 1.06 31.9 1.04 34.8 10.3 1.16 32.2 1.16 32.1 1.15 35.2 11.5 1.34 8.4 1.89 64.3 1.62 18.2 14.1 1.41 13.6 2.15 72.5 1.76 36.7

[0142] Summary: According to the data in Table 2, within the range of 0 to 10.3 minutes, the relative torques of Example 1, Comparative Example 2, and Comparative Example 4 all showed a slow upward trend, reaching 1.16, 1.16, and 1.15 respectively at 10.3 minutes. This numerical range roughly corresponds to the preset feeding trigger conditions. During the alkali addition and mixing stage from 11.5 minutes to 14.1 minutes, the system temperature of Comparative Example 2, due to the lack of added crushed ice for cooling, significantly increased from 32.1℃ to 72.5℃, and the relative torque also increased accordingly, reaching a maximum of 2.15. Although Comparative Example 4 used a fixed amount of 250g of crushed ice, this fixed addition may not have completely offset the neutralization exothermic reaction corresponding to the relatively high (15%) free sulfuric acid mass fraction in the precursor. As a result, the system still experienced a certain temperature rise during the strong alkali injection stage, reaching 36.7℃, and the final relative torque reached 1.76. In Example 1, by introducing process ice that matches the calculated amount of free acidity in the system at the trigger point, the system temperature drops to 8.4°C in the initial stage of strong alkali injection, and then maintains a maximum of about 13.6°C. The relative torque of the system shows a gradual increase and eventually stabilizes at around 1.41.

[0143] From a process control perspective, Example 1 utilizes real-time torque signal changes to aid in determining the crosslinking state of the system and introduces process ice fragments that match the neutralization heat of the system for temperature intervention. Utilizing the latent heat absorbed during the phase transition of the ice fragments to buffer the large amount of heat released during strong alkali neutralization helps maintain the dehydration condensation reaction of silicic acid monomers and oligomeric siloxanes within a relatively low and controlled temperature range. This temperature control strategy may be beneficial for regulating the polymerization rate of inorganic components, making it more time-matched with the crosslinking reaction at the titanium-iron interface, thereby providing favorable process conditions for forming a uniform three-dimensional network framework.

[0144] Test Example 3:

[0145] The final powder material obtained in Example 1 and the final powder material obtained in Comparative Example 6 after calcination at 450°C were used as test objects.

[0146] The powder materials from Example 1 and Comparative Example 6 were uniformly coated onto double-sided conductive carbon adhesive and fixed on the sample stage. They were then pushed into the ultra-high vacuum analysis chamber of the X-ray photoelectron spectroscopy instrument, with the system background vacuum set below 5 × 10⁻⁶. -9 mbar.

[0147] Monochromatic aluminum Kα rays (energy 1486.6 eV) were used as the excitation source. The working voltage was set to 15 kV and the emission current to 10 mA. The test sample was subjected to full-spectrum scanning and O 1s high-resolution scanning. The pass energy of the high-resolution scan was set to 30 eV and the step size was set to 0.05 eV.

[0148] Photoelectron spectroscopy data for each test group were recorded, and the obtained spectral binding energies were charge-calibrated using the C 1s peak (binding energy 284.8 eV) of contaminated carbon. The calibrated O 1s high-resolution spectra were subtracted from the Shirley background, and peak fitting was performed using a Gaussian-Lorentz mixture function to calculate the relative peak area ratios of the lattice oxygen component and the surface hydroxyl component.

[0149] Table 3. Peak fitting data of O 1s high-resolution energy spectrum for each test group.

[0150] Example 1 529.83 eV (42.36%) 531.57 eV (48.51%) 533.12 eV (9.13%) Comparative Example 6 530.08 eV (81.42%) 531.76 eV (14.19%) 533.28 eV (4.39%)

[0151] Summary: Combining the data in Table 3 with... Figure 2 The peak fitting curves show that the distribution of chemical states on the material surface differs significantly under different curing methods. Figure 2 In Example 1 shown in (a), the calculated area percentage of the red dashed line representing surface hydroxyl groups (M-OH) (binding energy 531.57 eV) is 48.51%, which is close to the content level of the blue dashed line representing lattice oxygen (MO) (binding energy 529.83 eV, area percentage 42.36%); meanwhile, the green dotted line representing adsorbed water (H2O) also maintains a certain area percentage (9.13%). In comparison, Figure 2 (b) The high-resolution energy spectrum distribution of Comparative Example 6 shows a significant change: the area of ​​the blue dashed line representing lattice oxygen increases to 81.42%, while the area of ​​the red dotted line representing surface hydroxyl groups decreases to 14.19%, and the proportion of adsorbed water represented by the green dotted line also decreases to 4.39%.

[0152] The changes in the above-mentioned spectral morphology (i.e. Figure 2 The decrease in the proportion of red characteristic peaks and the increase in the proportion of blue characteristic peaks suggest that the curing process conditions may affect the density of active sites on the material surface. Conventional inorganic composite adsorbent materials usually employ high-temperature calcination to promote framework curing. During the 450°C high-temperature heat treatment of Comparative Example 6, adjacent terminal hydroxyl groups on the material surface and within the pores are prone to dehydration condensation reactions, leading to the dehydration of some hydroxyl groups and their transformation into lattice oxygen (MOM) bridging structures with relatively low ligand exchange activity. This may result in a reduction in the number of sites directly involved in heavy metal complexation. In contrast, Example 1 uses a chemical liquid-phase curing approach, combined with temperature control and rheological state monitoring, to promote cross-linking between the oligomeric siloxane network and the titanium-iron interface during the wet reaction stage, thus eliminating the need for a high-temperature calcination process. This relatively mild molding condition helps retain a higher proportion of terminal hydroxyl groups on the material surface (e.g., Figure 2(As shown by the red dotted line in (a)). The presence of more hydroxyl groups not only helps to provide potential chemical sites for the coordination complexation reaction of heavy metal ions, but may also maintain a certain amount of adsorbed water (green dotted line) through hydrogen bonding, thereby providing a suitable hydration microenvironment for the diffusion of heavy metal ions to the material surface. This provides favorable conditions for improving the overall adsorption performance of the material.

[0153] Test Example 4:

[0154] The original suspensions from Examples 1 to 4, Comparative Example 1, and Comparative Example 5 that had undergone aging treatment but had not yet undergone pressure filtration and dewatering were selected as test subjects, and 10 liters of suspension were measured for each group. The solid content of the original suspensions in each test group was controlled within the range of 3 wt% to 5 wt%.

[0155] The measured suspensions were transferred into storage tanks equipped with low-speed paddle mixers, and the mixing speed was maintained at 60 rpm to maintain the uniform suspension of solid particles.

[0156] Start the high-pressure diaphragm pump and pump the suspension into the test plate and frame filter press with an effective filtration area of ​​0.1 square meters. Set the feed pressure to a constant 0.6 MPa through the pressure regulating valve.

[0157] Place a graduated measuring cylinder at the filtrate outlet of the filter press, and start timing from the first drop of filtrate flowing out, recording the cumulative filtrate volume at multiple discrete time points within the interval of 0 minutes to 20 minutes.

[0158] After 20 minutes of pressure filtration, the feed was stopped, the filter press plates and frames were removed, and the wet filter cake on the surface of the filter cloth was scraped off and weighed initially. The wet filter cake was then placed in a 105°C forced-air drying oven for constant-temperature drying until the difference between two consecutive weighings was less than 0.1 grams. The dry constant weight was recorded, and the moisture content of the filter cake was calculated from the difference between the wet and dry weights. The constant-pressure filtration test for each suspension was performed in triplicate, and the average results were recorded in Table 4.

[0159] Table 4. Data on the constant pressure dehydration performance of suspensions and the moisture content of filter cake for each test group.

[0160] Test object Cumulative permeate volume (L) over 5 minutes Cumulative permeate volume (L) over 15 minutes Cumulative permeate volume (L) over 20 minutes Final filter cake moisture content (%) Example 1 4.86 8.24 9.05 65.18 Example 2 4.62 8.07 8.92 66.43 Example 3 4.98 8.41 9.27 64.02 Example 4 4.75 8.16 9.03 65.75 Comparative Example 1 0.82 1.15 1.22 87.94 Comparative Example 5 1.95 2.68 2.87 81.36

[0161] Summary: According to the data in Table 4, Examples 1 to 4 exhibited high solid-liquid separation rates under a constant pressure filtration condition of 0.6 MPa. The cumulative permeate volume of the four examples showed a stable upward trend within the test range, with the cumulative permeate volume at the end of 20 minutes ranging from 8.92 L to 9.27 L, corresponding to a filter cake moisture content maintained between 64.02% and 66.43%. In contrast, Comparative Example 1 had a permeate volume of 0.82 L in the first 5 minutes of pressure filtration, with a significantly slower rate of permeate growth thereafter, reaching a cumulative permeate volume of 1.22 L after 20 minutes, and a final filter cake moisture content of 87.94%. Comparative Example 5 also exhibited a relatively low permeate rate, with a cumulative permeate volume of 2.87 L after 20 minutes and a filter cake moisture content of 81.36%.

[0162] Differences in macroscopic dehydration performance may be related to the rheological state and spatial framework network configuration of the microscopic suspended particles. In the example system, gluconate containing polyhydroxy structures was introduced during the acidic hydrolysis stage. This component may have played a steric hindrance role, helping to reduce excessive aggregation of silicic acid monomers. Under subsequent conditions combining torque monitoring to assist in determining the crosslinking state and the introduction of process ice crushing, the pH increase of the system was completed in a controlled, relatively low-temperature environment. These process conditions helped to regulate the hydrolysis rate of high-valence metal ions, making it relatively matched with the dehydration and polycondensation process of silicic acid on a time scale, thereby facilitating the interpenetration of the siloxane framework between metal hydroxy oxides and improving the overall rigidity of the framework. Effective crosslinking at the microscopic level may lead to a reduction in the surface energy of primary particles, macroscopically manifesting as a sand-like physical morphology of the composite particles. During the pressure filtration stage, these particles with a certain structural rigidity stack each other, more easily retaining pore channels within the filter cake layer, thus facilitating liquid phase penetration and achieving a high permeability.

[0163] In contrast, Comparative Example 1, lacking an organic isolating ligand, may have caused silicates to react too rapidly in certain areas during the acid-base neutralization phase, potentially leading to the formation of an inorganic hydrogel structure. This type of gel structure exhibits weak resistance to deformation and a degree of viscosity, making it prone to physical deformation on the filter media surface, thus obstructing filtration channels and causing water retention. While Comparative Example 5 shares a similar component base, its fixed-time aging mode and lack of monitoring of the system's rheological state may have resulted in a mismatch between its actual operation and the appropriate crosslinking stage of the oligomeric siloxane components. Time deviations in the aging stage could lead to unintended aggregation of colloidal particles, failing to establish a three-dimensional support framework with sufficient mechanical strength. The insufficiently crosslinked flexible gel network or flocculent structure within the system is prone to compaction deformation during constant-pressure filtration, which could also narrow the internal liquid channels of the filter cake and increase the final water content.

[0164] Test Example 5:

[0165] The final product powders obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were collected as test subjects and placed in a vacuum dryer for later use.

[0166] Analytical grade lead nitrate was used to prepare Pb solutions with initial concentrations of 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L. 2+ The simulated wastewater was treated with 0.1 mol / L nitric acid and sodium hydroxide solutions to uniformly adjust the pH to 5.0. No significant Pb was observed in the blank control system under the same pH and shaking conditions. 2+ Precipitation or concentration loss.

[0167] Accurately weigh 0.05g of powder sample from each test group and add it to 50mL of Pb solution of different concentrations. 2+ The conical flask was used to simulate wastewater. The flask was placed in a constant-temperature shaker, set at 25°C, and shaken continuously at 150 r / min for 24 hours to allow the adsorption reaction to reach equilibrium.

[0168] After equilibration, the suspension was filtered through a 0.22 μm microporous membrane, and the residual Pb in the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). 2+ Concentration. The equilibrium adsorption capacity was calculated by the concentration difference before and after adsorption, and the theoretical maximum saturation adsorption capacity was calculated by nonlinear fitting of the data using the Langmuir isotherm adsorption model.

[0169] Take another batch of powder samples and prepare a suspension with a solid content of 5 g / L in deionized water at 25℃, and stir thoroughly. Quickly transfer 100 mL of the suspension into a stoppered standard graduated cylinder and place it on a horizontal platform to stand.

[0170] Starting from the moment of settling, the scale height of the solid-liquid interface between the clear liquid layer and the suspension layer in the graduated cylinder is recorded at different time points. The initial settling rate in the first 5 minutes is calculated by the ratio of the interface drop height to the corresponding time.

[0171] Each of the above performance tests was performed in parallel three times. The theoretical maximum saturated adsorption capacity is expressed as mean ± standard deviation, and the Langmuir model fitting coefficient, initial sedimentation rate, and final sedimentation volume percentage after 60 minutes are expressed as mean values.

[0172] Table 5. Isothermal adsorption and sedimentation separation performance data of samples in each test group

[0173] Test object Theoretical maximum saturated adsorption capacity (mg / g) <![CDATA[Fitting coefficient of Langmuir model (R 2 )]]> Initial settling rate at the solid-liquid interface (cm / min) Percentage of final settlement volume after 60 minutes (%) Example 1 308.42±5.14 0.9961 4.86 18.4 Example 2 296.75±6.21 0.9943 4.62 20.1 Example 3 312.18±4.85 0.9972 5.03 17.5 Example 4 301.56±5.52 0.9958 4.75 19.2 Comparative Example 1 154.21±8.63 0.9634 1.18 68.3 Comparative Example 2 203.44±7.41 0.9821 2.54 42.6 Comparative Example 3 218.63±8.05 0.9885 2.91 38.7 Comparative Example 4 247.19±6.88 0.9912 3.42 31.4 Comparative Example 5 176.85±7.56 0.9746 1.45 55.8 Comparative Example 6 78.36±4.12 0.9511 4.12 25.6

[0174] In summary, based on the data in Table 5, the theoretical maximum saturated adsorption capacity of Examples 1 to 4 ranged from 296.75 mg / g to 312.18 mg / g, the initial sedimentation rate at the solid-liquid interface ranged from 4.62 cm / min to 5.03 cm / min, and the final sedimentation volume percentage remained below 20.1% after 60 minutes, exhibiting good overall adsorption performance and solid-liquid separation efficiency. In contrast, the adsorption capacities of Comparative Examples 1 and 5 decreased to 154.21 mg / g and 176.85 mg / g, respectively, and their sedimentation performance showed varying degrees of weakening, with initial sedimentation rates decreasing to 1.18 cm / min and 1.45 cm / min, respectively, while the final sedimentation volume percentage remained at a relatively high level. The adsorption and sedimentation performance of Comparative Example 3 was between that of Examples 1 and Comparative Example 1. Although Comparative Example 6 maintained an initial sedimentation rate of 4.12 cm / min, its theoretical maximum adsorption capacity significantly decreased to 78.36 mg / g.

[0175] From a materials chemistry perspective, the aforementioned differences in macroscopic separation performance and adsorption capacity may be closely related to the cross-linking state of the microstructure and the distribution of surface active sites. The gluconate ions containing polyhydroxy structures introduced into the example system may have played a steric hindrance role, helping to regulate the hydrolysis rate of metal ions.

[0176] By combining thermodynamic intervention with rheological state (torque) monitoring, the process conditions may facilitate the interpenetration and cross-linking of silicon-oxygen chains with metal precursors at the mesoscale, thereby forming a three-dimensional network structure with a certain degree of rigidity. This relatively low-temperature curing process, which does not require high-temperature calcination, helps the composite particles form a more compact physical structure, thus exhibiting faster gravity settling characteristics on a macroscopic scale.

[0177] Meanwhile, these mild conditions are conducive to retaining a larger proportion of terminal hydroxyl groups (e.g., Ti-OH, Fe-OH) on the material surface. These hydroxyl groups may serve as potential chemically active sites for Pb. 2+ The inner-layer complexation reaction provides a reasonable mechanism to support the high adsorption capacity of the material.

[0178] In contrast, comparative examples 1, lacking an organic ligand as a spatial isolation medium, and comparative example 5, possibly limited by a fixed-time aging mode, failed to achieve a suitable cross-linking rheological state. Both could lead to the silicic acid component tending to self-polymerize, resulting in an inorganic hydrogel structure with high water content. This relatively loose hydrogel structure, with a density close to that of water, often exhibits a slow sedimentation rate. Furthermore, the microporous morphology within the gel may increase the mass transfer resistance of heavy metal ions diffusing into the material, making it difficult to effectively utilize some potential adsorption sites, thus resulting in a relatively low adsorption capacity.

[0179] Comparative Example 3 may have induced a strong oxidation process similar to the Fenton reaction during the introduction of the oxidant. This process may have caused some damage to the molecular configuration of the organic ligands, leading to the unexpected aggregation of some metal ions. This may have reduced the uniformity of the mesoscopic cross-linked network, and thus affected the sedimentation and adsorption performance to some extent.

[0180] For Comparative Example 6, although the high-temperature heat treatment process helps to densify the particles and maintain a certain sedimentation rate, during this thermally driven process, a large number of active terminal hydroxyl groups on the material surface are prone to dehydration condensation reactions, transforming into lattice oxygen structures with relatively weak coordination activity. The decrease in the density of effective chemical complexation sites on the surface is usually the main reason for the significant decline in the saturated adsorption capacity of this group of materials.

Claims

1. An adsorbent material for removing pollutants, characterized in that, The adsorbent material is a titanium-iron-silicon composite adsorbent material, prepared by chemical liquid-phase crosslinking and curing of raw materials containing the following relative molar ratios under non-calcination conditions: Total metal ions: silicon: gluconate = 1:(0.3-0.5):(0.08-0.12); The total metal ions are the sum of titanium ions and iron ions, and the molar ratio of titanium ions to iron ions is 1:(0.8-1.5).

2. The adsorbent material according to claim 1, characterized in that, The raw materials include titanium oxysulfate, ferrous sulfate, sodium silicate, and sodium gluconate.

3. A method for preparing an adsorbent material for removing pollutants as described in any one of claims 1-2, characterized in that, Includes the following steps: An aqueous solution of an acidic metal precursor containing titanium ions and ferrous ions is prepared. An oxidant is slowly added dropwise to the aqueous solution of the acidic metal precursor. After the ferrous ions are oxidized, an oxidized precursor is obtained. A silicate containing silicon and a compound containing gluconate are dissolved in water to form a blend. The blend solution is injected into the oxidized precursor and mixed evenly to obtain a homogeneous acidic sol. A first alkaline reagent was slowly added to the homogeneous acidic sol for pre-aging, and the rheological torque change of the system was monitored in real time. When the system torque rises to the preset crosslinking trigger threshold, process ice is added to the system, and a second alkaline reagent is injected to control the overall pH of the system to jump to an alkaline environment for crosslinking aging. The process ice absorbs latent heat during phase change and offsets the heat released by acid-base neutralization. The aged material is subjected to solid-liquid separation and washing, and then dried and pulverized at low temperature to obtain the titanium-iron-silicon composite adsorbent material.

4. The preparation method according to claim 3, characterized in that, The specific process for preparing the oxidized precursor includes: The initial temperature of the system was controlled at 25-30℃. Hydrogen peroxide was slowly added dropwise to the aqueous solution of the acidic metal precursor containing free sulfuric acid, and the temperature rise of the system during the dropwise process was controlled to be less than or equal to 5℃. The system potential is monitored online using an oxidation-reduction potential meter. When the oxidation-reduction potential value suddenly jumps and stabilizes in the range of 450-500mV, the addition of hydrogen peroxide is stopped, and stirring is continued for 15-20 minutes. The oxidation reaction can be confirmed to be basically completed by sampling and detecting the residual ferrous ion content.

5. The preparation method according to claim 3, characterized in that, In the process of preparing the homogeneous acidic sol, the injection rate and multi-point feeding method of the blend solution are controlled, the overall pH of the reaction system is maintained between 1.0 and 1.5 during the mixing stage, and the mixing time is 20 to 30 minutes.

6. The preparation method according to claim 3, characterized in that, The pre-aging process parameters are controlled as follows: The first alkaline reagent is ammonia water, and the dropping rate of the ammonia water is controlled at 0.3 to 0.5 pH / min. The dropping of the ammonia water is stopped when the pH of the system rises to 2.5 to 3.

5. Maintain the system temperature at 30-35℃ and continue stirring for aging. Record the torque of the stirring motor when the addition of ammonia water stops, and record it as the initial torque reference value.

7. The preparation method according to claim 6, characterized in that, The crosslinking trigger threshold is 1.15 to 1.18 times the initial torque reference value.

8. The preparation method according to claim 3, characterized in that, The specific process of cross-linking aging includes: An aqueous solution of the acidic metal precursor with a liquid phase free sulfuric acid mass fraction of 10% to 15% was obtained; The process-made crushed ice of the specified mass is prepared in advance based on the free acidity and final pH enthalpy parameters within the system. When the torque reaches the crosslinking trigger threshold, the process ice crushing is introduced in one go. Within 45 to 60 seconds after the crushed ice is added, a second alkaline reagent is injected, and the overall pH of the system is controlled to jump and stabilize between 8.0 and 8.5 within 3 to 5 minutes. The maximum temperature of the system during the entire cross-linking aging process is controlled to be below or equal to 15°C, and then the stirring speed is reduced to continue aging for 30 to 45 minutes.

9. The preparation method according to claim 3, characterized in that, The low-temperature drying process includes: The dehydrated and washed solid material is placed at a constant temperature of 95-105℃ and dried for 4-6 hours.

10. The preparation method according to claim 8, characterized in that, The second alkaline reagent is a sodium hydroxide aqueous solution with a mass fraction of 25% to 30%.

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