A high-efficiency thallium adsorbent for water treatment and a preparation method thereof

Abstract

The application discloses a kind of high-efficiency thallium-removing adsorbents for water treatment and preparation method thereof, it is related to water treatment technical field, high-efficiency thallium-removing adsorbents include alginate-based hydrogel microspheres and the prussian blue compound particle loaded thereon, wherein the prussian blue compound particle is selected from at least one of the following: nano prussian blue particle;High-entropy prussian blue analogue particle.The high-efficiency thallium-removing adsorbents provided by the application have higher saturated adsorption capacity compared with conventional prussian blue powder;And can be in the structure of complete acidic environment of pH 1~5, adsorption capacity is basically attenuated low, solve the existing prussian blue material in acidic smelting wastewater easy failure problem;And adsorption equilibrium time is shorter, applicable to industrial continuous processing;Using alginate-based hydrogel microspheres form, can be separated quickly by simple filtration or sedimentation, avoid the loss of powder adsorbent and secondary pollution risk.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to a highly efficient thallium removal adsorbent for water treatment and its preparation method. Background Technology

[0002] Thallium (Tl) is an extremely toxic heavy metal element; the lethal dose for adults is only 10-15 mg / kg. Its toxicity primarily stems from Tl. + Ions and K + The high similarity of ions in ionic radius and hydration properties leads to Tl + It can enter cells through potassium ion channels, interfere with the sodium-potassium pump function, and cause damage to multiple organs, including the nervous system and digestive system.

[0003] Existing thallium removal technologies mainly include chemical precipitation, ion exchange, membrane separation, and adsorption. Among these, adsorption has attracted much attention due to its simplicity and low cost. Commonly used adsorbents include activated carbon, zeolite, manganese oxide, biochar, titanium dioxide, and Prussian blue (PB). Prussian blue, in particular, exhibits excellent thallium removal properties due to its unique Fe-CN framework structure and open lattice channels. + It exhibits extremely high selective adsorption capacity, and can efficiently capture Tl even in environments with high concentrations of coexisting cations. + It has become one of the most promising materials for thallium removal.

[0004] However, traditional Prussian blue is mostly in powder form, which makes it easy to agglomerate and difficult to separate when used in water, making recycling difficult and causing secondary pollution. Furthermore, it has poor stability in acidic wastewater (pH 1~5), and is prone to partial dissolution or Fe / CN framework collapse, resulting in decreased adsorption capacity or material loss. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a highly efficient thallium removal adsorbent for water treatment and its preparation method. The specific technical solution is as follows: A highly efficient thallium removal adsorbent for water treatment comprises alginate-based hydrogel microspheres and Prussian blue compound particles loaded thereon, wherein the Prussian blue compound particles are selected from at least one of the following: a) Nano-Prussian blue particles; b) High-entropy Prussian blue analogue particles.

[0006] Preferably, the nano-Prussian blue particles are obtained by reacting a first solution and a second solution, wherein the volume ratio of the first solution and the second solution is 1:(1~2); wherein the first solution contains an iron source and a chelating agent, and the second solution contains a ferrocyanide source.

[0007] Preferably: In the first solution, the iron source is ferric chloride or its hydrate, the chelating agent is citric acid or its hydrate, and the molar ratio of the iron source to the chelating agent is 1:(2~4). In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

[0008] Preferably, the high-entropy Prussian blue analog particles are obtained by reacting a third solution with a second solution, wherein the volume ratio of the third solution to the second solution is 1:(0.5~2); wherein the third solution contains a transition metal source and a chelating agent, and the second solution contains a ferrocyanide source.

[0009] Preferably: In the third solution, the transition metal source is a chloride, nitrate, sulfate, or hydrate of a transition metal, and the transition metal is at least five of Fe, Mn, Co, Ni, Cu, and Zn. The molar ratio of any two transition metals is (0.8~1.2):1, and the total concentration of the transition metal source is 0.01~0.1 mol / L. The chelating agent is citric acid or its hydrate, and the molar ratio of the transition metal source to the chelating agent is 1:(1~4). In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

[0010] The present invention also provides a preparation method for preparing a highly efficient thallium removal adsorbent for water treatment as described in any one of the above claims, the preparation method comprising the following steps: S1. Preparation of Prussian blue-like compound particles; S2. Prepare an aqueous solution of alginate, and add the Prussian blue compound particles to the aqueous solution of alginate, stir and disperse evenly to obtain a composite dispersion; S3. The composite dispersion is added dropwise to an aqueous crosslinking agent solution, and crosslinking and solidification are carried out to form alginate-based hydrogel microspheres, which are then washed and dried to obtain the final product.

[0011] Preferably, the Prussian blue compound particles are nano-Prussian blue particles, which are prepared by the following steps: S01. Dissolve ferric chloride hexahydrate and citric acid monohydrate in water at a molar ratio of 1:(2~4) and stir until homogeneous to obtain the first solution; S02. Dissolve potassium ferrocyanide in water and stir until homogeneous to obtain a second solution with a concentration of 0.001~0.003 mol / L; S03. A portion of the first solution is added to the reaction vessel beforehand, and then the remaining first solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring to carry out the reaction; S04. After the addition is complete, react for 1 to 3 hours under stirring conditions of 50~70℃ and 1000~1500 rpm; S05. After the reaction is complete, the precipitate is obtained by centrifugation and dried to obtain the final product.

[0012] Preferably, the Prussian blue compound particles are high-entropy Prussian blue analog particles, which are prepared by the following steps: S001. Dissolve a transition metal salt in water, wherein the transition metal salt is a chloride of Fe, Mn, Co, Ni, or Cu, and stir until homogeneous to obtain a transition metal salt solution with a concentration of 0.01~0.1 mol / L; S002. Add citric acid monohydrate to the transition metal salt solution, the amount added being 1 to 4 times the molar amount of the transition metal salt, and stir until homogeneous to obtain a third solution; S003. A portion of the third solution is added to the reaction vessel beforehand, and then the remaining third solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring conditions to carry out the reaction; S004. After the addition is complete, continue the reaction for 1 to 4 hours under stirring conditions of 20~60℃ and 800~1200 rpm; S005. After the reaction is complete, the precipitate is obtained by centrifugation, and then washed and dried to obtain the final product.

[0013] Preferably: In step S03, the amount of the first solution added beforehand is 2.5% to 100% of its total volume; And / or in step S003, the amount of the third solution added in advance is 5% to 100% of its total volume.

[0014] Preferably: In step S2, the alginate aqueous solution is a sodium alginate aqueous solution with a mass concentration of 1% to 5%, and the mass ratio of the Prussian blue compound particles to the alginate is (0.5 to 2): 2. In step S3 and / or step S4, the crosslinking agent aqueous solution is a calcium chloride solution with a mass concentration of 1% to 5%, the crosslinking curing time is 1 to 3 hours, and the drying method is freeze drying.

[0015] The high-efficiency thallium removal adsorbent for water treatment provided by this invention has the following beneficial effects: 1. Its saturated adsorption capacity is much higher than that of conventional Prussian blue powder; 2. The structure remains intact in an acidic environment with pH 1~5, and the adsorption capacity basically decreases with low decay, which solves the problem of easy failure of existing Prussian blue materials in acidic smelting wastewater; 3. Short adsorption equilibrium time, suitable for continuous industrial processing; 4. The alginate-based hydrogel microspheres can be quickly separated through simple filtration or sedimentation, avoiding the loss of powdered adsorbent and the risk of secondary pollution. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0017] Figure 1 The synthesis flow chart of the high-efficiency thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention; Figure 2 The images shown are scanning electron microscope images of the high-efficiency thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention before and after adsorption. Figure 3 This is a saturated adsorption capacity diagram of the high-efficiency thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention; Figure 4 This is a diagram showing the time required for the highly efficient thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention to reach saturation adsorption. Figure 5 This is a graph showing the effect of pH in the aquatic environment on the adsorption of the high-efficiency thallium removal adsorbent for water treatment provided in Example 1 of the present invention. Figure 6 This is an optimization diagram of the dosage of a high-efficiency thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention; Figure 7 The effect of coexisting cations on the high-efficiency thallium removal adsorbent for water treatment provided in Example 1 of the present invention is shown in the figure. Figure 8 A graph showing the effect of coexisting organic matter on the high-efficiency thallium removal adsorbent for water treatment provided in Example 1 of the present invention; Figure 9 This is a diagram showing the effect of the high-efficiency thallium removal adsorbent for water treatment provided in Embodiment 1 of the present invention on the adsorption of other heavy metals. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0019] This embodiment provides a highly efficient thallium removal adsorbent for water treatment, comprising alginate-based hydrogel microspheres and Prussian blue compound particles loaded thereon, wherein the Prussian blue compound particles are selected from at least one of the following: a) Nano-Prussian blue particles.

[0020] b) High-entropy Prussian blue analogue particles.

[0021] Among them, nano-Prussian blue particles (PB) possess classic Fe... 2+ [Fe 3+ [CN]6] Framework structure, open lattice channels (aperture approximately 3.2 Å) for Tl + It exhibits extremely high affinity. (Tl) + (Hydrated ionic radius 1.47 Å) and K + Similar to (1.33 Å), it can be selectively captured through ion exchange and lattice intercalation mechanisms. Nanoparticle size (<300 nm) significantly increases the specific surface area, improving adsorption site utilization and diffusion rate.

[0022] High-entropy Prussian blue analogue particles (HE-PBA) introduce at least five transition metals (Fe, Mn, Co, Ni, Cu, Zn, etc.), resulting in high configurational entropy. This leads to lattice distortion, coexistence of multiple valence states, and optimization of the channel microenvironment, further enhancing the resistance to Tl. + It improves selectivity and adsorption capacity while enhancing structural stability under acidic conditions.

[0023] Alginate (usually sodium alginate) can be processed via Ca... 2+ Cross-linking forms a three-dimensional porous network structure, rich in carboxyl groups (-COO). - The presence of hydroxyl groups (-OH) provides additional electrostatic adsorption and complexation sites. Microsphere morphology (typically hundreds of micrometers to several millimeters in diameter) solves the separation challenges of powdered PB, facilitating filtration or sedimentation recovery and avoiding secondary pollution. The porous structure is beneficial for Tl... + It rapidly diffuses to the internal active sites while protecting the loaded Prussian blue particles from mechanical abrasion and acid corrosion.

[0024] Prussian blue particles provide highly selective lattice trapping; alginate supports provide auxiliary adsorption and structural support; the combination of the two forms a "functional core-protective shell" system, achieving a synergistic improvement in capacity, rate, stability, and separation performance. When nano-PB and high-entropy PBA are simultaneously loaded, a further synergistic effect can be generated: nano-PB provides high-capacity sites, while high-entropy PBA provides anti-interference and potential photoresponse sites.

[0025] The particle size of nano-Prussian blue particles is preferably less than 300 nm. The smaller the particle size, the larger the specific surface area and the more adsorption sites are exposed. However, excessive nano-sizing should be avoided to prevent agglomeration or decreased stability.

[0026] Specifically, the high-efficiency thallium removal adsorbent of this embodiment uses sodium alginate hydrogel as a carrier and loads nano-Prussian blue particles as the adsorption functional component. This adsorbent combines the selective adsorption characteristics of Prussian blue for the heavy metal thallium with the advantages of the porous structure and abundant polyhydroxy sites of the hydrogel material, thereby achieving high-capacity adsorption of thallium and making it suitable for the specific removal of the heavy metal thallium from wastewater.

[0027] When adding a high-efficiency thallium removal adsorbent to thallium-containing wastewater, the dosage is 1~3 g / L, preferably 2 g / L. When the dosage of the high-efficiency thallium removal adsorbent is 2 g / L, the removal rate of heavy metal thallium in industrial wastewater is ≥70%, and the adsorption equilibrium time is ≤50 min.

[0028] Even when wastewater contains coexisting cations such as potassium, calcium, sodium, and magnesium, or coexisting organic matter such as fulvic acid, humic acid, and EDTA, highly efficient thallium adsorbents can still achieve selective adsorption of the target heavy metals.

[0029] Advantageously, the high-efficiency thallium removal adsorbent of the present invention (PBNPs / SA adsorbent) is a sodium alginate hydrogel microsphere loaded with nano-Prussian blue particles. Nano-Prussian blue particles exhibit excellent selective adsorption of thallium. Sodium alginate (SA), as a natural anionic polymer derived from brown algae, contains a large number of highly active carboxyl functional groups (-COOH) and hydroxyl functional groups (-OH) in its molecular framework. It not only possesses good biocompatibility, biodegradability, and renewability, but is also an excellent cationic heavy metal adsorbent. This embodiment of the high-efficiency thallium removal adsorbent combines the selective adsorption characteristics of Prussian blue for thallium with the advantages of the porous structure and abundant polyhydroxyl sites of the hydrogel material, thereby achieving high-capacity adsorption of thallium. The saturated adsorption capacity for thallium can stably reach 350~760 mg / g, and the adsorption process is rapid, reaching adsorption equilibrium within 50 minutes.

[0030] The PBNPs / SA adsorbent of this embodiment overcomes the problems of secondary pollution and difficulty in separation and recovery when traditional powder adsorbents are used in water. It has good stability under acidic conditions, maintains its morphology, and does not cause additional environmental risks. In addition, after 5 cycles of use, the removal rate of thallium can still be maintained at more than 70%.

[0031] In this embodiment, the PBNPs / SA adsorbent maintains a removal rate of over 75% within an acidic range of 0.1 g / L and pH 1–5, while conventional adsorbents typically perform well only under alkaline conditions. Therefore, this embodiment fills the gap in adsorbent materials for the efficient removal of the heavy metal thallium under acidic environments.

[0032] The PBNPs / SA adsorbent in this embodiment not only has a very good treatment effect on the heavy metal thallium, but also shows good removal ability for mercury, lead and zinc ions.

[0033] The PBNPs / SA adsorbent provided in this embodiment still exhibits excellent thallium removal efficiency in actual industrial wastewater treatment.

[0034] Furthermore, nano-Prussian blue particles are obtained by reacting a first solution and a second solution, with a volume ratio of 1:(1~2); wherein the first solution contains an iron source and a chelating agent, and the second solution contains a ferrocyanide source.

[0035] Furthermore: In the first solution, the iron source is ferric chloride or its hydrate, and the chelating agent is citric acid or its hydrate. The molar ratio of the iron source to the chelating agent is 1:(2~4).

[0036] In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

[0037] Furthermore, high-entropy Prussian blue analog particles are obtained by reacting a third solution with a second solution, the volume ratio of which is 1:(0.5~2); wherein the third solution contains a transition metal source and a chelating agent, and the second solution contains a ferrocyanide source.

[0038] Furthermore: In the third solution, the transition metal source is a chloride, nitrate, sulfate or hydrate of a transition metal, and the transition metal is at least five of the following: Fe, Mn, Co, Ni, Cu and Zn. The molar ratio of any two transition metals is (0.8~1.2):1, the total concentration of the transition metal source is 0.01~0.1 mol / L, the chelating agent is citric acid or its hydrate, and the molar ratio of the transition metal source to the chelating agent is 1:(1~4).

[0039] In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

[0040] Specifically, high-entropy Prussian blue analogue (HE-PBA) is a multimetallic Prussian blue analogue whose crystal structure is based on the Fe of classic Prussian blue. 2+ [Fe 3+ The framework [(CN)6] is used, but by introducing at least five transition metals (Fe, Mn, Co, Ni, Cu, Zn, etc.) to replace some of the Fe sites, a solid solution structure with high configurational entropy is formed.

[0041] The third solution (a multi-metal precursor) contains at least five transition metal sources and chelating agents. The chelating agents complex with multiple metal ions, mitigating the differences in reactivity between different metal ions and preventing preferential nucleation of a single metal, leading to uniform multi-metal co-precipitation. The synergistic introduction of multiple metals generates lattice distortion, defect modulation, and multi-valence coexistence, optimizing the lattice channel size and charge distribution, thus enhancing its reactivity with Tl. + Its affinity has been further enhanced.

[0042] The second solution (cyanide complex source) provides [Fe(CN)6]. 4- The ions co-precipitate with the metal ions in the third solution to form the HE-PBA framework structure.

[0043] This embodiment also provides a preparation method for preparing a high-efficiency thallium removal adsorbent for water treatment as described in any one of the above embodiments. The preparation method includes the following steps: S1. Preparation of Prussian blue-like compound particles.

[0044] S2. Prepare an aqueous solution of alginate, and add Prussian blue compound particles to the aqueous solution of alginate, stir and disperse evenly to obtain a composite dispersion.

[0045] S3. The composite dispersion is added dropwise to the crosslinking agent aqueous solution, and crosslinking and solidification are carried out to form alginate-based hydrogel microspheres, which are then washed and dried to obtain the final product.

[0046] Furthermore, the Prussian blue compound particles are nano-sized Prussian blue particles, which are prepared through the following steps: S01. Dissolve ferric chloride hexahydrate and citric acid monohydrate in water at a molar ratio of 1:(2~4) and stir until homogeneous to obtain the first solution.

[0047] S02. Dissolve potassium ferrocyanide in water and stir until homogeneous to obtain a second solution with a concentration of 0.001~0.003 mol / L.

[0048] S03. A portion of the first solution is added to the reaction vessel beforehand, and then the remaining first solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring conditions to carry out the reaction.

[0049] S04. After the addition is complete, react for 1 to 3 hours under stirring conditions of 50~70℃ and 1000~1500 rpm.

[0050] S05. After the reaction is complete, the precipitate is obtained by centrifugation and dried to obtain the final product.

[0051] The drying method can be oven drying at 60℃, vacuum drying, freeze drying, or spray drying. Freeze drying is preferred as it best preserves the porous structure and dispersibility of the particles.

[0052] Furthermore, the Prussian blue-like compound particles are high-entropy Prussian blue analog particles, which are prepared through the following steps: S001. Dissolve a transition metal salt in water, wherein the transition metal salt is a chloride of Fe, Mn, Co, Ni, or Cu, and stir until homogeneous to obtain a transition metal salt solution with a concentration of 0.01~0.1 mol / L.

[0053] S002. Add citric acid monohydrate to the transition metal salt solution, the amount added being 1 to 4 times the molar amount of the transition metal salt, and stir until homogeneous to obtain the third solution.

[0054] S003. A portion of the third solution is added to the reaction vessel beforehand, and then the remaining third solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring conditions to carry out the reaction.

[0055] S004. After the addition is complete, continue the reaction for 1 to 4 hours under stirring conditions of 20~60℃ and 800~1200 rpm.

[0056] S005. After the reaction is complete, the precipitate is obtained by centrifugation, and then washed and dried to obtain the final product.

[0057] The drying method can be vacuum drying at 50~70℃, freeze drying, or low-temperature oven drying. Vacuum drying or freeze drying is preferred to avoid changes in the valence state of the metal or an increase in lattice defects in the high-entropy structure caused by high temperature.

[0058] Furthermore: In step S03, the amount of the first solution added beforehand is 2.5% to 100% of its total volume.

[0059] And / or in step S003, the amount of the third solution added beforehand is 5% to 100% of its total volume.

[0060] In this embodiment, when the Prussian blue compound particles include both nano-Prussian blue particles and high-entropy Prussian blue analog particles, a simple physical mixing method is preferred, which is to add both types of particles to an alginate aqueous solution, stir and disperse them evenly, and then drop them into the solution to form the final product.

[0061] In addition, the following load methods can also be used: In-situ generation method: First, nano-Prussian blue particles are loaded into an alginate solution to form microspheres. Then, the microspheres are immersed in a precursor solution of high-entropy Prussian blue analog particles to synthesize the second type of particles in situ within the pores of the microspheres.

[0062] Stepwise loading method: First, microspheres loaded with high-entropy PBA are prepared, and then nano-Prussian blue particles are loaded by impregnation or secondary drop-addition.

[0063] Core-shell or gradient loading methods: forming a core (one type of particle)-shell (another type of particle) structure through multi-layer drop-addition or template method, or forming a concentration gradient distribution along the radial direction of the microsphere.

[0064] The above methods can be flexibly selected according to the actual water quality (whether light response, resistance to organic interference, etc. are required) to further optimize the synergistic adsorption performance.

[0065] Furthermore: In step S2, the alginate aqueous solution is a sodium alginate aqueous solution with a mass concentration of 1% to 5%, and the mass ratio of Prussian blue compound particles to alginate is (0.5 to 2): 2.

[0066] In step S3 and / or step S4, the crosslinking agent aqueous solution is a calcium chloride solution with a mass concentration of 1% to 5%, the crosslinking curing time is 1 to 3 hours, and the drying method is freeze drying.

[0067] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Example 1

[0068] The preparation process in this embodiment is as follows: Figure 1 As shown, it includes the following steps: Step 1: Synthesis of nano-Prussian blue particles: 0.2703 g of FeCl3·6H2O was ultrasonically dispersed in 20 mL of pure water. After uniform dispersion, 0.6307 g of citric acid monohydrate (CA) was added to the FeCl3 aqueous solution and magnetically stirred at room temperature for 30 min to obtain Fe... 3+ -CA solution. Weigh 0.4224g K4[Fe(CN)6]·3H2O and ultrasonically disperse it in 20mL of pure water to obtain a K4[Fe(CN)6] solution. Add 2mL of Fe 3+ -Add the CA solution to a 250 mL three-necked flask beforehand, then add 18 mL of Fe 3+ -CA solution and 20 mL of K4[Fe(CN)6]·3H2O were fixed on a dual-channel microfluidic syringe pump. Under conditions of a 60℃ water bath and mechanical stirring at 1200 rpm, both solutions were simultaneously added dropwise to a three-necked flask at a rate of 30–50 mL / h. After the addition was complete, the reaction was continued for 2 h under the same conditions of 60℃ and 1200 rpm. After the reaction was complete, the water bath was turned off, and the three-necked flask was allowed to slowly cool to room temperature. After the reaction was complete, the mixture was centrifuged at 8000 rpm for 5 min until the supernatant was clear or no yellow solution appeared. The resulting precipitate was dried at 60℃ for 12 h, and then ground through an 80-mesh sieve.

[0069] Step 2, Preparation of sodium alginate hydrogel material: Prepare a 2wt% solution by weighing 2g of sodium alginate and dissolving it in 100ml of deionized water. Stir magnetically at 60℃ for 3h until it is fully dissolved and dispersed, and finally obtain a clear, viscous, bubble-free homogeneous solution. Then prepare a 2wt% calcium chloride solution by weighing 2g of calcium chloride solid powder and dissolving it in 100ml of deionized water.

[0070] Step 3: Preparation of sodium alginate Prussian blue adsorbent: Take 1g of synthesized nano Prussian blue powder and dissolve it in the uniformly dispersed sodium alginate hydrogel. Stir magnetically for 3h to ensure that it is fully dispersed and uniformly loaded to obtain PNBPs / SA solution.

[0071] Step 4: After drawing the PNBPs / SA solution into a syringe and fixing it to the syringe pump, place a calcium chloride solution 20 cm directly below the syringe. Add the solution dropwise at a steady rate of 0.2–2 ml / min to induce cross-linking. After addition, allow the hydrogel microspheres to cross-link in the calcium chloride solution for 2 hours, then wash the surface with deionized water until no calcium chloride residue remains. Freeze-dry for 12 hours to obtain the highly efficient thallium removal adsorbent.

[0072] Please see Figures 2-9 : Figure 2 The images show scanning electron microscopy (SEM) images and energy scattering spectra of the PBNPs / SA adsorbent prepared in this embodiment before and after adsorption of the heavy metal thallium. Figure a shows the blank sodium alginate hydrogel without PBNPs loading, demonstrating the excellent pore structure of the blank SA. Figure b shows the highly efficient thallium removal adsorbent loaded with PBNPs, clearly showing the uniform loading of cubic PBNPs on the SA. Figures c-g show the elemental spectra of the material before adsorption, and h-m show the elemental spectra of the material after adsorption. Comparing the images before and after adsorption, it can be seen that thallium is clearly present after adsorption, indicating that the adsorbent has an adsorption effect on the heavy metal thallium.

[0073] Figure 3 The figure shows the saturated adsorption capacity of the PBNPs / SA prepared in this embodiment. The maximum saturated adsorption capacity of this adsorbent for the heavy metal thallium can reach 754.18 mg / g, and the adsorption process is more in line with the Langmuir adsorption model. In the figure, the value a represents the saturated adsorption capacity of the adsorbent, and the value b represents the equilibrium constant of the adsorption.

[0074] Figure 4The figure shows the time required for the PBNPs / SA adsorbent prepared in this embodiment to reach saturation adsorption capacity for different initial thallium concentrations (10, 20, 50 mg / L). The adsorbent undergoes rapid adsorption within the first 30 minutes, and the adsorption gradually stabilizes after 50 minutes. The figure shows that this adsorption process more closely resembles a pseudo-second-order kinetic adsorption process, indicating that chemisorption is the main rate-limiting step in the thallium ion adsorption of PBNPs / SA.

[0075] Figure 5 The effect of pH in the aquatic environment on the adsorption of PBNPs / SA adsorbent prepared in this embodiment was investigated. Under low pH (1~5) conditions, the adsorbent had a higher adsorption capacity. This was because the high pH (7~12) environment destroyed the stable pore structure of the adsorbent and caused PBNPs to fall off the SA, thus reducing the adsorption effect of the adsorbent.

[0076] Figure 6 To optimize the dosage of the PBNPs / SA adsorbent prepared in this embodiment, the highest adsorption capacity was found at a dosage of 0.1 g / L. Selecting this dosage can save production costs and achieve the best adsorption effect.

[0077] Figure 7 To investigate the effect of cations in the aquatic environment on the adsorption process of the PBNPs / SA adsorbent prepared in this embodiment, the metal partition coefficient is commonly used to describe the selectivity of the adsorbent for thallium. The smaller the metal partition coefficient Kd, the stronger the inhibitory effect of the metal cation on adsorption. The effects of potassium, calcium, sodium, and magnesium ions on the adsorption of thallium vary under different concentrations, but the inhibitory effect on adsorption increases with increasing concentration of these cations. Figure 7 It can be seen that the Kd value is the smallest for high concentrations of potassium ions. This is because potassium ions have a similar hydration radius to thallium ions (1.33 Å for potassium ions and 1.47 Å for thallium ions), and their inhibition during adsorption is more obvious.

[0078] Figure 8 To investigate the influence of coexisting organic matter in the aquatic environment on the adsorption process of the PBNPs / SA adsorbent prepared in this embodiment, the metal partition coefficient of EDTA was significantly lower than that of the other two substances. This is because EDTA readily forms a stable complex with thallium ions, thus exhibiting a stronger inhibitory effect on adsorption. In contrast, fulvic acid and humic acid, as large molecular organic compounds, may encapsulate or cover the active adsorption sites of sodium alginate when they coexist with sodium alginate, forming steric hindrance and preventing heavy metal thallium ions from approaching the adsorption sites of sodium alginate, thereby inhibiting the adsorption process.

[0079] Figure 9The effect of the PBNPs / SA adsorbent prepared in this embodiment on the adsorption of other heavy metals shows that the adsorbent not only has a specific adsorption capacity for thallium ions, but also exhibits good removal effects on other heavy metal ions such as mercury and zinc under different environmental conditions. Example 2

[0080] The only difference between this embodiment and Embodiment 1 is that the mass of PBNPs added to the sodium alginate hydrogel in step three is 0.5g.

[0081] Tests showed that the high-efficiency thallium adsorbent in this embodiment has an adsorption capacity of 368.7 mg / g for the heavy metal thallium. Compared with most adsorbent materials, whose adsorption capacity is only 0~200 mg / g, the adsorbent material prepared in this example has achieved a strong adsorption effect. Example 3

[0082] The only difference between this embodiment and Embodiment 1 is that the mass of PBNPs added to the sodium alginate hydrogel in step three is 2g.

[0083] Tests showed that the high-efficiency thallium adsorbent in this embodiment has an adsorption capacity of 497.5 mg / g for the heavy metal thallium, demonstrating a strong adsorption effect. Example 4

[0084] The difference between this embodiment and Embodiment 1 is that in step three, 0.5 g each of nano-Prussian blue particles and high-entropy Prussian blue analog particles are added simultaneously, with the total loading still being 1 g, and a simple physical mixing method is used for compounding.

[0085] Step 1: Synthesis of nano-Prussian blue particles: Same as Step 1 in Example 1.

[0086] Step 2: Synthesis of high-entropy Prussian blue analogue particles: Weigh 0.0495 g of FeCl2·4H2O, 0.0495 g of MnCl2·4H2O, 0.0595 g of CoCl2·6H2O, 0.0593 g of NiCl2·6H2O, and 0.0426 g of CuCl2·2H2O, and ultrasonically disperse them in 50 mL of pure water. Add 0.525 g of citric acid monohydrate and stir magnetically at room temperature for 30 min to obtain the third solution. Weigh 0.2112 g of K4[Fe(CN)6]·3H2O and dissolve it in 50 mL of pure water to obtain the second solution. Add 10 mL of the third solution to a 250 mL three-necked flask beforehand. Fix the remaining third solution and the second solution in a double-channel syringe pump and add them dropwise at a rate of 40 mL / h while stirring at 1000 rpm at 25 °C. After the addition is complete, continue stirring for 3 h. The precipitate was separated by centrifugation at 8000 rpm for 5 min, washed three times with deionized water, and dried under vacuum at 60℃ for 12 h to obtain high-entropy Prussian blue analog particles.

[0087] Step 3: Preparation of sodium alginate composite adsorbent: Take 0.5 g of nano-Prussian blue particles and 0.5 g of high-entropy Prussian blue analog particles and add them simultaneously to 100 mL of 2 wt% sodium alginate aqueous solution. Stir magnetically for 3 h to disperse evenly and obtain composite dispersion.

[0088] Step 4: Same as Step 4 in Example 1, with a syringe pump flow rate of 0.2~2 mL / min, a dropping height of 20 cm, cross-linking for 2 h, washing with deionized water, and freeze-drying for 12 h to obtain a highly efficient thallium removal adsorbent.

[0089] Tests showed that the adsorbent in this embodiment could adsorb 868.3 mg / g of the heavy metal thallium, with an adsorption equilibrium time of about 40 min. After 5 cycles, the removal rate remained above 82%, which is a significant improvement in both capacity and rate compared to Example 1.

[0090] Comparative Example 1 This comparative example uses conventional Prussian blue powder as a control.

[0091] Preparation process: 0.5406 g of FeCl3·6H2O was dissolved in 40 mL of pure water to obtain solution A, and 0.8448 g of K4[Fe(CN)6]·3H2O was dissolved in 40 mL of pure water to obtain solution B. Solutions A and B were rapidly mixed at room temperature and magnetically stirred for 2 h. After the reaction was complete, the precipitate was separated by centrifugation at 8000 rpm for 5 min, washed three times with deionized water, dried in an oven at 60℃ for 12 h, and ground through an 80-mesh sieve to obtain Prussian blue powder.

[0092] Adsorption performance test: 1 g of Prussian blue powder was used for thallium removal adsorption experiment (dosage 2 g / L, initial Tl concentration 50 mg / L, pH 4).

[0093] Tests showed that the conventional Prussian blue powder in this comparative example had an adsorption capacity of 185.6 mg / g for the heavy metal thallium, an adsorption equilibrium time of over 120 min, and partial dissolution under acidic conditions of pH 3-4. After two cycles of use, the removal rate dropped to below 50%, indicating significant problems of agglomeration, difficulty in separation, and secondary pollution. The adsorption performance was far lower than that of the embodiments described in this example.

[0094] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A highly efficient thallium removal adsorbent for water treatment, characterized in that, The invention comprises alginate-based hydrogel microspheres and Prussian blue-like compound particles loaded thereon, wherein the Prussian blue-like compound particles are selected from at least one of the following: a) Nano-Prussian blue particles; b) High-entropy Prussian blue analogue particles.

2. The high-efficiency thallium removal adsorbent for water treatment according to claim 1, characterized in that, The nano-Prussian blue particles are obtained by reacting a first solution and a second solution, wherein the volume ratio of the first solution and the second solution is 1:(1~2); wherein the first solution contains an iron source and a chelating agent, and the second solution contains a ferrocyanide source.

3. The high-efficiency thallium removal adsorbent for water treatment according to claim 2, characterized in that: In the first solution, the iron source is ferric chloride or its hydrate, the chelating agent is citric acid or its hydrate, and the molar ratio of the iron source to the chelating agent is 1:(2~4). In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

4. The high-efficiency thallium removal adsorbent for water treatment according to claim 1, characterized in that, The high-entropy Prussian blue analog particles are obtained by reacting a third solution with a second solution, wherein the volume ratio of the third solution to the second solution is 1:(0.5~2); wherein the third solution contains a transition metal source and a chelating agent, and the second solution contains a ferrocyanide source.

5. The high-efficiency thallium removal adsorbent for water treatment according to claim 4, characterized in that: In the third solution, the transition metal source is a chloride, nitrate, sulfate, or hydrate of a transition metal, and the transition metal is at least five of Fe, Mn, Co, Ni, Cu, and Zn. The molar ratio of any two transition metals is (0.8~1.2):1, and the total concentration of the transition metal source is 0.01~0.1 mol / L. The chelating agent is citric acid or its hydrate, and the molar ratio of the transition metal source to the chelating agent is 1:(1~4). In the second solution, the ferrocyanide source is potassium ferrocyanide, with a concentration of 0.001~0.003 mol / L.

6. A preparation method, characterized in that, The preparation method for the high-efficiency thallium removal adsorbent for water treatment as described in any one of claims 1 to 5 comprises the following steps: S1. Preparation of Prussian blue-like compound particles; S2. Prepare an aqueous solution of alginate, and add the Prussian blue compound particles to the aqueous solution of alginate, stir and disperse evenly to obtain a composite dispersion; S3. The composite dispersion is added dropwise to an aqueous crosslinking agent solution, and crosslinking and solidification are carried out to form alginate-based hydrogel microspheres, which are then washed and dried to obtain the final product.

7. The preparation method according to claim 6, characterized in that, The Prussian blue compound particles are nano-Prussian blue particles, which are prepared through the following steps: S01. Dissolve ferric chloride hexahydrate and citric acid monohydrate in water at a molar ratio of 1:(2~4) and stir until homogeneous to obtain the first solution; S02. Dissolve potassium ferrocyanide in water and stir until homogeneous to obtain a second solution with a concentration of 0.001~0.003 mol / L; S03. A portion of the first solution is added to the reaction vessel beforehand, and then the remaining first solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring to carry out the reaction; S04. After the addition is complete, react for 1 to 3 hours under stirring conditions of 50~70℃ and 1000~1500 rpm; S05. After the reaction is complete, the precipitate is obtained by centrifugation and dried to obtain the final product.

8. The preparation method according to claim 7, characterized in that, The Prussian blue-like compound particles are high-entropy Prussian blue analog particles, which are prepared through the following steps: S001. Dissolve a transition metal salt in water, wherein the transition metal salt is a chloride of Fe, Mn, Co, Ni, or Cu, and stir until homogeneous to obtain a transition metal salt solution with a concentration of 0.01~0.1 mol / L; S002. Add citric acid monohydrate to the transition metal salt solution, the amount added being 1 to 4 times the molar amount of the transition metal salt, and stir until homogeneous to obtain a third solution; S003. A portion of the third solution is added to the reaction vessel beforehand, and then the remaining third solution and the second solution are simultaneously added dropwise to the reaction vessel under stirring conditions to carry out the reaction; S004. After the addition is complete, continue the reaction for 1 to 4 hours under stirring conditions of 20~60℃ and 800~1200 rpm; S005. After the reaction is complete, the precipitate is obtained by centrifugation, and then washed and dried to obtain the final product.

9. The preparation method according to claim 8, characterized in that: In step S03, the amount of the first solution added beforehand is 2.5% to 100% of its total volume; And / or in step S003, the amount of the third solution added in advance is 5% to 100% of its total volume.

10. The preparation method according to any one of claims 6 to 9, characterized in that: In step S2, the alginate aqueous solution is a sodium alginate aqueous solution with a mass concentration of 1% to 5%, and the mass ratio of the Prussian blue compound particles to the alginate is (0.5 to 2):

2. In step S3 and / or step S4, the crosslinking agent aqueous solution is a calcium chloride solution with a mass concentration of 1% to 5%, the crosslinking curing time is 1 to 3 hours, and the drying method is freeze drying.

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