Selective adsorption thallium removal agent and preparation method thereof

Abstract

The invention provides a selective adsorption thallium removal agent and a preparation method thereof, and belongs to the technical field of adsorption materials. The thallium removal agent provided by the invention comprises bentonite and Prussian blue loaded on the bentonite, the mass of the Prussian blue accounts for 10-30% of the mass of the bentonite, the crystal space after the bentonite absorbs water and expands is fully utilized, and Prussian blue nanoparticles are uniformly dispersed between layers and on the surface of the bentonite, so that the thallium removal agent is prepared. The adsorption sites of Prussian blue and bentonite are fully exerted, and the adsorbability of thallium ions in wastewater is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption materials, and particularly relates to a selective thallium adsorbent and a preparation method thereof. Background Art

[0002] Thallium is a typical highly toxic heavy metal element, and in aqueous solutions, it usually exists in the form of monovalent state (Tl+). The limit value of thallium in industrial wastewater is 5 μg / L, and the maximum contaminant level of thallium in drinking water is 0.1 μg / L. In view of the high toxicity of thallium and its strict emission limit standards, it is necessary to adsorb and remove thallium ions in wastewater.

[0003] Bentonite is a natural clay material mainly composed of montmorillonite, and its basic structure consists of two layers of silica tetrahedron flakes and one layer of aluminum (magnesium) oxygen octahedron flakes, forming a 2:1 type layered silicate. This unique crystal structure endows bentonite with characteristics such as lattice substitution, water absorption and swelling, and ion exchange, making it have a certain adsorption capacity for thallium ions in wastewater. However, pure bentonite as an adsorbent has problems such as low adsorption capacity and easy desorption, and it is difficult to directly meet the actual application requirements.

[0004] Therefore, it is necessary to provide a selective thallium adsorbent and a preparation method thereof to solve the problems raised in the above background art. Summary of the Invention

[0005] The present invention provides a selective thallium adsorbent and a preparation method thereof. The thallium adsorbent is prepared by loading Prussian blue on bentonite. This method makes full use of the crystal space after the water absorption and swelling of bentonite, uniformly disperses Prussian blue nanoparticles between and on the surface of bentonite layers, gives play to the adsorption sites of Prussian blue and bentonite, greatly improves the adsorption performance for thallium ions in aqueous solutions, and can effectively solve at least one technical problem involved in the background art.

[0006] In order to solve the above technical problems, the present invention is implemented as follows:

[0007] A selective thallium adsorbent includes bentonite and Prussian blue loaded on the bentonite, and the mass ratio of Prussian blue is 10 - 30% of the mass of bentonite.

[0008] As a preferred improvement, the bentonite is sodium-based bentonite.

[0009] As a preferred improvement, the selective thallium adsorbent further includes polyvinylpyrrolidone, and the doping amount is 1 - 1.2% of the mass of bentonite.

[0010] As a preferred improvement, the adsorption capacity of the selective thallium adsorbent for thallium ions is 50 - 60 mg / g.

[0011] As a preferred improvement, the selective thallium adsorbent is used to remove thallium ions from wastewater.

[0012] As a preferred improvement, the dosage of the selective thallium adsorbent in wastewater is 0.5 - 1 g / L.

[0013] A preparation method of the selective thallium adsorbent as described above includes the following steps:

[0014] Step S1: Disperse bentonite in deionized water to obtain a bentonite slurry, and gradually add nitric acid dropwise to the bentonite slurry. After stirring evenly, an acidified bentonite slurry is obtained;

[0015] Step S2: Based on the reaction of potassium ferrocyanide and ferric chloride to generate Prussian blue, calculate the masses of potassium ferrocyanide and ferric chloride required to meet the Prussian blue proportion requirement. Take the corresponding masses of potassium ferrocyanide and ferric chloride and dissolve them in deionized water to obtain a potassium ferrocyanide solution and a ferric chloride solution. Then, successively add the potassium ferrocyanide solution and the ferric chloride solution dropwise to the acidified bentonite slurry. After the addition is completed, stir evenly to obtain a mixed slurry;

[0016] Step S3: Centrifuge the mixed slurry. The centrifuged product is washed twice with deionized water and ethanol respectively, then the product is placed in an oven at 65 °C and dried for 24 h, and finally ground to obtain the selective thallium adsorbent.

[0017] As a preferred improvement, Step S1 specifically includes the following steps:

[0018] Take 500 g of deionized water and place it in a 1 L beaker. Stir at a speed of 300 - 500 r / min. During the stirring process, add 10 g of bentonite to the beaker in small batches with a spoon. Stir for 2 h to obtain a bentonite slurry. Gradually add nitric acid with pH = 2 dropwise to the bentonite slurry and stir for 1 h to obtain an acidified bentonite slurry. Among them, the addition amount of nitric acid is determined according to the mass of bentonite, and the addition amount of nitric acid corresponding to each gram of bentonite is 10 - 15 ml.

[0019] As a preferred improvement, in Step S2, after adding the potassium ferrocyanide solution and before adding the ferric chloride solution, the following steps are further included:

[0020] Add polyvinylpyrrolidone to the acidified slurry. The dosage of polyvinylpyrrolidone is 1 - 1.2% of the mass of bentonite.

[0021] As a preferred improvement, in Step S3, the centrifugation process is carried out by a centrifuge. The speed of the centrifuge is 5000 r / min, and the centrifugation time is 10 min.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) Compared with the defects of easy agglomeration of adsorption sites and poor mechanical stability of traditional thallium removal agents, the present invention utilizes the large specific surface area and water absorption and swelling characteristics of bentonite to uniformly disperse Prussian blue particles on the surface and interlayer of bentonite, so that the adsorption performance of the selective adsorption thallium removal agent for thallium ions is greatly improved compared with both bentonite and Prussian blue;

[0024] (2) Compared with traditional thallium removal agents, in the coexistence of multiple heavy metals / acids / alkalis / salts and other ions, the adsorption sites are easily occupied by other ions, resulting in a decrease in the adsorption performance for thallium ions. In the selective adsorption thallium removal agent of the present invention, Prussian blue is loaded on bentonite. The cavity of Prussian blue is close to the hydration size of thallium ions, and it has a high selective adsorption for thallium ions;

[0025] (3) The preparation process of the present invention is simple, the reaction conditions are mild, with low energy consumption and high yield. The obtained selective adsorption thallium removal agent can be sealed in a sealed bag, which is convenient for storage. The bentonite used in the present invention is a natural component in nature, with low price, wide source, no environmental pollution, etc. The selected reagents are low in price and non-toxic. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings, where:

[0027] Figure 1 It represents the competitive adsorption test result diagram of thallium ions and other ions;

[0028] Figure 2 It represents the schematic diagram of the adsorption and filtration device provided by the present invention;

[0029] Figure 3 It represents the adsorption capacity comparison diagram of bentonite, Prussian blue, CPB - Bent and PPB - Bent for thallium ions in aqueous solution;

[0030] Figure 4 It represents the adsorption capacity comparison diagram of the thallium removal agent samples in Examples 1 - 3 and Comparative Examples 1 - 2 for thallium ions in aqueous solution;

[0031] Figure 5 It represents the adsorption rate comparison diagram of the thallium removal agent samples in Examples 1 - 3 and Comparative Examples 1 - 2 for thallium ions in aqueous solution;

[0032] Figure 6 It represents the X - ray diffraction patterns of the thallium removal agent samples in Examples 1 - 3 and Comparative Examples 1 - 2;

[0033] Figure 7 Indicate the Fourier infrared spectrogram of the thallium removal agent samples of Examples 1-3 and Comparative Examples 1-2. Detailed implementation manners

[0034] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] This implementation manner provides a selective adsorption thallium removal agent, including bentonite and Prussian blue loaded on the bentonite, and the mass ratio of Prussian blue to the mass of bentonite is 10-30%.

[0036] Bentonite (Bent) is a natural clay material mainly composed of montmorillonite. Its basic structure consists of two layers of silica tetrahedron flakes and one layer of aluminum (magnesium) oxygen octahedron flakes, forming a 2:1 type layered silicate. This unique crystal structure endows it with the ability to adsorb thallium ions in aqueous solutions. The adsorption of thallium ions in aqueous solutions by bentonite is mainly based on ion exchange and electrostatic interactions.

[0037] Prussian blue (Fe4[Fe(CN)6]3, PB) is a microporous inorganic material with strong coordination ability, belonging to the cubic crystal system, and the lattice constant is about There are mainly two types of voids in the lattice. The smaller tetrahedral voids are composed of Fe(CN)6 4- units, with a diameter of about The larger octahedral voids are located at the center of the cubic unit cell, with a diameter of about The hydrated ionic radius of thallium ions (Tl + ) is about Close to the octahedral voids of Prussian blue, it can occupy the sites in the lattice through ion exchange. For other heavy metals, due to the mismatch between the hydrated ionic radius and the voids of Prussian blue, Prussian blue shows a selective adsorption ability for thallium ions (Tl + ). In the presence of multiple heavy metal ions, even if the concentration of other heavy metal ions is dozens to hundreds of times higher, Prussian blue still preferentially adsorbs thallium ions.

[0038] As Figure 1 shown, set up an ion competitive adsorption test to respectively test Zn 2+ , Cd 2+ , Cu 2+ , Pb 2+ , K + , Na +And the mixture of all the above ions and Tl + The competitive adsorption effect in 20% PB-Bent, where the concentration of Tl + is set to 1 mg / L, and the concentrations of other ions are 100 mg / L. It can be seen from Figure 1 that under the condition of a huge concentration difference, Tl + still maintains a high removal rate, indicating that PB-Bent has a good selective adsorption effect on thallium ions.

[0039] The present invention adopts the method of loading Prussian blue on bentonite. While retaining the adsorption capacity of bentonite and Prussian blue for thallium ions, it makes full use of the crystal space after the water absorption and swelling of bentonite to uniformly disperse Prussian blue nanoparticles between and on the surface of bentonite layers, giving full play to the adsorption sites of Prussian blue and bentonite, and greatly improving the adsorption performance of thallium ions in aqueous solution. On the one hand, it solves the agglomeration phenomenon of Prussian blue, and on the other hand, it uses the cyanide group in Prussian blue to react with thallium ions to solve the problem of easy desorption of bentonite adsorption.

[0040] Preferably, the bentonite is selected as sodium-based bentonite, and its montmorillonite content is above 90%, which is higher than that of other types of bentonite, and can effectively increase the interaction between bentonite and Prussian blue.

[0041] Preferably, polyvinylpyrrolidone (PVP) is also added to the selective adsorption thallium removal agent, and the dosage is 1-1.2% of the mass of bentonite. Polyvinylpyrrolidone (PVP) can in-situ limit the growth of Prussian blue, form highly dispersed Prussian blue nanoparticles, and control the size of Prussian blue microtubes, so that Prussian blue can be uniformly dispersed on bentonite, increasing the contact opportunity between Prussian blue and thallium ions and improving the removal effect of thallium ions.

[0042] The adsorption capacity of the selective adsorption thallium removal agent provided by the present invention for thallium ions is 50-60 mg / g, which is about 250-300% higher than the adsorption capacity of pure bentonite for thallium ions of about 20 mg / g, and about 142-171% higher than the adsorption capacity of pure Prussian blue for thallium ions of about 35 mg / g.

[0043] The selective adsorption thallium removal agent is used to remove thallium ions in wastewater, and the dosage of the selective adsorption thallium removal agent in wastewater is 0.5-1 g / L.

[0044] The adsorption reaction of the thallium removal agent occurs rapidly within the first 30 min, and the adsorption equilibrium can be reached in about 3 h. The dosage of the thallium removal agent in wastewater is 0.5-1 g / L.

[0045] Such as Figure 2As shown in the figure, to more clearly illustrate the content of this embodiment, this embodiment also provides an adsorption and filtration device, including a filter tank 1 and a water distribution tank 2 installed above the filter tank 1. A water inlet pipe 7 is installed on one side of the water distribution tank 2. Wastewater enters from the water inlet pipe 7. After being temporarily stored and distributed by the water distribution tank 2, it is discharged from below the water distribution tank 2.

[0046] Two layers of ceramsite permeable stone layers 4 are arranged at intervals below the water distribution tank 2. The two layers of ceramsite permeable stone layers 5 divide the space below the water distribution tank 2 into an upper transition zone 3, a reaction zone 6, and a lower transition zone 13. Among them, the reaction zone 6 is located between the two layers of ceramsite permeable stone layers 4, the upper transition zone 3 is located above the reaction zone 6, and the lower transition zone 13 is located below the reaction zone 6. The upper and lower sides of the ceramsite permeable stone layer 4 are wrapped by a filter screen plate 5.

[0047] An adsorbent feeding port 8 is arranged in the upper region of the reaction zone 6 for adding a selective thallium-removing adsorbent into the reaction zone 6. An adsorbent reaction discharge port 9 and an air flushing pipe 10 are arranged in the lower region. The adsorbent reaction discharge port 9 is used to discharge the selective thallium-removing adsorbent that has completed the reaction in the reaction zone 6. The air flushing pipe 10 is used to convey pressurized gas to the reaction zone 6 to assist the selective thallium-removing adsorbent to be discharged from the adsorbent reaction discharge port 9.

[0048] A bottom water collection device 12 is arranged in the lower transition zone 13 for collecting the water body after adsorption. An outlet pipe 11 is installed on the bottom water collection device 12 for randomly sampling and inspecting the water body after adsorption to see if it meets the discharge standards (industrial wastewater < 5 μg / L, drinking water < 0.1 μg / L).

[0049] Valves 14 are arranged on the water inlet pipe 7, the adsorbent feeding port 8, the adsorbent reaction discharge port 9, and the air flushing pipe 10 for controlling the conduction and truncation of the corresponding pipelines.

[0050] The wastewater containing thallium ions is input from the water inlet pipe 7 and is first preliminarily filtered by the upper ceramsite permeable stone layer 4 in the upper transition zone 3, and then enters the reaction zone 6; the selective thallium-removing adsorbent is mixed with clean water and is added into the reaction zone 6 from the feeding port 8 through a pumping device, and fully contacts the wastewater containing thallium ions in the reaction zone 6 to adsorb the thallium ions in the wastewater; after the adsorption reaction ends, the wastewater enters the lower transition zone 13 through the lower ceramsite permeable stone layer 4 and is collected by the bottom water collection device 12.

[0051] Bentonite is an expansive soil. When the water collection speed of the bottom water collection device 12 significantly decreases, it indicates that the content of the selective thallium-removing adsorbent in the reaction zone 6 is too high and causes blockage, and cleaning is required. At this time, the valve on the water inlet pipe 7 is closed to stop water inlet, and then pressurized gas is input through the air flushing pipe 10, and under the action of pressure, the selective thallium-removing adsorbent is discharged from the adsorbent reaction discharge port 9.

[0052] The ceramsite permeable stone is made from shale, fired at 1100 - 1300 °C in a rotary kiln for about 20 minutes, naturally cooled after being taken out of the furnace, and pressed into the required size by a pressing machine.

[0053] The mesh diameter of the filter screen plate is 3 - 5 mm; the filter screen plate is made of stainless steel.

[0054] This embodiment also provides a preparation method of a selective adsorption thallium removal agent, which includes the following steps:

[0055] Step S1: Disperse bentonite in deionized water to obtain a bentonite slurry, and gradually add nitric acid dropwise to the bentonite slurry, and stir evenly to obtain an acidified bentonite slurry;

[0056] Step S2: Based on the reaction of potassium ferrocyanide and ferric chloride to generate Prussian blue, calculate the masses of potassium ferrocyanide and ferric chloride required to meet the Prussian blue proportion requirement, dissolve the corresponding masses of potassium ferrocyanide and ferric chloride in deionized water to obtain a potassium ferrocyanide solution and a ferric chloride solution, and then successively add the potassium ferrocyanide solution and the ferric chloride solution dropwise to the acidified bentonite slurry, and stir evenly after the addition is completed to obtain a mixed slurry;

[0057] Step S3: Centrifuge the mixed slurry, wash the centrifuged product 2 times each with deionized water and ethanol, then place the product in an oven at 65 °C and dry for 24 h, and finally grind to obtain the selective adsorption thallium removal agent.

[0058] Step S1 specifically includes the following steps:

[0059] Take 500 g of deionized water and place it in a 1 L beaker, stir at a speed of 300 - 500 r / min, and during the stirring process, add 10 g of bentonite to the beaker in small batches with a spoon, stir for 2 h to obtain a bentonite slurry, gradually add nitric acid with pH = 2 dropwise to the bentonite slurry, and stir for 1 h to obtain an acidified bentonite slurry. Among them, the addition amount of nitric acid is determined according to the mass of bentonite, and the addition amount of nitric acid corresponding to each gram of bentonite is 10 - 15 ml.

[0060] The surface of bentonite is negatively charged, and Fe(CN)6 4- ions in Prussian blue (Fe4[Fe(CN)6]3) are also negatively charged. If the Prussian blue solution is directly combined with bentonite, due to the same electric charge, the direct loading effect of Prussian blue on bentonite is not good. Therefore, in this application, the bentonite is acidified, and the use of H + changes the electronegativity of the bentonite surface, which is beneficial to the subsequent adsorption of Prussian blue; in addition, the addition of the nitric acid solution can also dredge the pores of the bentonite, increase the specific surface area of the bentonite, and further increase the Prussian blue loading sites.

[0061] Through research, it is found that under acidic conditions, when Prussian blue is directly added to bentonite, Prussian blue is easily separated from bentonite, resulting in poor loading effect of Prussian blue. The reason is that this method belongs to the physical mixing of Prussian blue and bentonite, and the two are only bonded together by physical attraction (similar to electrostatic attraction) (only existing on the surface of bentonite). Under acidic conditions, especially under strong acidic conditions, the concentration of H + is very high, which will react with the surface of bentonite, causing the Prussian blue attached to the surface of bentonite to fall off. Once Prussian blue is peeled off, it is easy to agglomerate, so the adsorption effect is reduced. To solve this problem, in the present invention, potassium ferrocyanide is first mixed with bentonite, and then ferric chloride is added. Prussian blue is generated by the reaction of potassium ferrocyanide and ferric chloride. The generation process of Prussian blue belongs to chemical preparation, and ions react through redox reactions, enabling the liquid phase to directly compound on the surface of bentonite, generating a structure similar to a chemical bond. This structure exists between the layers and on the surface of bentonite, resisting the competitive adsorption of H + so strongly that Prussian blue is not easily detached from the surface of bentonite. As shown in Figure 3 , both C20%PB - Bent and P20%PB - Bent represent bentonite selective adsorption thallium removal agents loaded with 20% Prussian blue. However, C represents the synthesis of Prussian blue using potassium ferricyanide solution and ferric chloride solution provided by the present invention; P represents the direct addition of Prussian blue. It can be seen from Figure 3 that under stronger acidic conditions, the adsorption capacity of P20%PB - Bent is weaker, basically the same as that of single Prussian blue; while C20%PB - Bent still maintains a strong adsorption capacity.

[0062] Potassium ferrocyanide solution and ferric chloride solution generate Prussian blue through the following reaction:

[0063] 4FeCl3 + 3K4[Fe(CN)6] = Fe4[Fe(CN)6]3↓ + 12KCl.

[0064] In step S2, after the addition of potassium ferrocyanide solution and before the addition of ferric chloride solution, the following steps are further included: adding polyvinylpyrrolidone to the acidified mud, and the dosage of polyvinylpyrrolidone is 1 - 1.2% of the mass of bentonite.

[0065] In step S3, the centrifugation process is carried out by a centrifuge. The rotation speed of the centrifuge is 5000r / min, and the centrifugation time is 10min.

[0066] Example 1

[0067] This example provides a preparation method of a selective adsorption thallium removal agent. The selective adsorption thallium removal agent is bentonite loaded with Prussian blue with a mass ratio of 10%. The preparation method includes the following steps:

[0068] Take 500 g of deionized water in a 1 L beaker, with a stirring speed of 300 - 500 r / min. Add 10 g of bentonite dried at 105 °C for 24 h and passed through a 200-mesh sieve into the beaker in small portions and multiple batches using a medicine spoon, stir for 2 h, and after stirring evenly, place it in an ultrasonic cleaning tank and ultrasonicate for 10 min;

[0069] Dropwise add 100 ml of nitric acid with pH = 2 into the bentonite slurry, stir for 1 h to obtain an acidified bentonite slurry;

[0070] Dissolve 1.473 g of potassium ferrocyanide in 150 g of deionized water to obtain a potassium ferrocyanide solution. Use a separatory funnel to dropwise add the potassium ferrocyanide solution into the acidified bentonite slurry and stir well for 2 - 3 h;

[0071] Add polyvinylpyrrolidone to the acidified slurry, and the dosage of polyvinylpyrrolidone is 1% of the mass of bentonite;

[0072] Dissolve 0.754 g of ferric chloride in 150 g of deionized water to obtain a ferric chloride solution. Use a separatory funnel to dropwise add the ferric chloride solution into the acidified bentonite slurry containing potassium ferrocyanide and stir well for 2 - 3 h;

[0073] After the stirring ends, centrifuge at 5000 r / min for 10 min. Wash the centrifuged product twice with deionized water and ethanol respectively to obtain a preliminary product;

[0074] Place the product in an oven and dry at 65 °C for 24 h, and grind to obtain a thallium-selective adsorbent with 10% Prussian blue loaded on bentonite (10% PB - Bent).

[0075] Example 2

[0076] This example provides a preparation method of a thallium remover. The thallium-selective adsorbent is bentonite loaded with 20% by mass of Prussian blue. The preparation method includes the following steps:

[0077] Take 500 g of deionized water in a 1 L beaker, with a stirring speed of 300 - 500 r / min. Add 10 g of bentonite dried at 105 °C for 24 h and passed through a 200-mesh sieve into the beaker in small portions using a medicine spoon and add in multiple batches, stir for 2 h to make the bentonite slurry evenly distributed;

[0078] Dropwise add 120 ml of nitric acid with pH = 2 into the bentonite slurry and stir for 1 h; obtain an acidified bentonite slurry;

[0079] Dissolve 2.946 g of potassium ferrocyanide in 150 g of deionized water, and use a separatory funnel to dropwise add it into the acidified bentonite slurry and stir well for 2 - 3 h;

[0080] Polyvinylpyrrolidone was added to the acidified mud, and the dosage of polyvinylpyrrolidone was 1.1% of the mass of bentonite;

[0081] 1.508 g of ferric chloride solution was dissolved in 150 g of deionized water, and it was added dropwise to the bentonite mud containing potassium ferrocyanide through a separatory funnel, and stirred thoroughly for 2 - 3 h;

[0082] After the stirring ended, it was centrifuged at 5000 r / min for 10 min with a centrifuge. The centrifuged product was washed twice each with deionized water and ethanol to obtain a preliminary product;

[0083] The product was placed in an oven and dried at 65 °C for 24 h, and then ground to obtain a thallium - selective adsorbent of bentonite loaded with 20% Prussian blue (20% PB - Bent).

[0084] Example 3

[0085] This example provides a preparation method of a thallium - removing agent. The thallium - selective adsorbent is bentonite loaded with 30% Prussian blue by mass ratio, and the preparation method includes the following steps:

[0086] 500 g of deionized water was taken in a 1 L beaker, and the stirring speed was 300 - 500 r / min. 10 g of bentonite dried at 105 °C for 24 h and passed through a 200 - mesh sieve was added to the beaker in small batches with a medicine spoon and stirred for 2 h to make the bentonite mud evenly distributed;

[0087] 150 ml of nitric acid with pH = 2 was added dropwise to the bentonite mud and stirred for 1 h to obtain an acidified bentonite mud;

[0088] 4.419 g of potassium ferrocyanide was dissolved in 150 g of deionized water, and it was added dropwise to the acidified bentonite mud through a separatory funnel and stirred thoroughly for 2 - 3 h;

[0089] Polyvinylpyrrolidone was added to the acidified mud, and the dosage of polyvinylpyrrolidone was 1.2% of the mass of bentonite;

[0090] 2.263 g of ferric chloride solution was dissolved in 150 g of deionized water, and it was added dropwise to the bentonite mud containing potassium ferrocyanide through a separatory funnel and stirred thoroughly for 2 - 3 h;

[0091] After the stirring ended, it was centrifuged at 5000 r / min for 10 min with a centrifuge. The centrifuged product was washed twice each with deionized water and ethanol to obtain a preliminary product;

[0092] The product was placed in an oven and dried at 65 °C for 24 h, and then ground to obtain a thallium - selective adsorbent of bentonite loaded with 30% Prussian blue (30% PB - Bent).

[0093] To verify the performance of the thallium removal agent provided by the present invention, a comparative experiment was set up. Single bentonite was used as Comparative Example 1, and single Prussian blue was used as Comparative Example 2. The samples of Examples 1-2 and Comparative Examples 1-2 were subjected to the following comparative experiments:

[0094] (1) Thallium ion equilibrium adsorption capacity test

[0095] Measure the equilibrium adsorption capacity of different adsorbents. The study of the adsorption equilibrium concentration can provide the mutual relationship between the concentration of the adsorbate in the solution and the adsorbed mass on the surface of the adsorbent at liquid-solid equilibrium. The equilibrium adsorption capacity (qe) is an index to measure the adsorption degree of a certain adsorbent for the adsorbate in the solution and is often used to judge the adsorption performance of the adsorbent. The value of qe can be calculated using the following formula:

[0096]

[0097] In the formula, q e is the equilibrium adsorption capacity of the adsorbent, C0 is the concentration of thallium ions in the solution, C e is the concentration of thallium ions at adsorption equilibrium in the solution, V is the volume of the solution, and m is the mass of the adsorbent.

[0098] The adsorption test process is as follows:

[0099] Weigh 0.0651 g of thallium nitrate solid into a 100 ml beaker, dissolve the thallium nitrate solid by ultrasonic treatment with deionized water, and then make a constant volume with a 500 ml volumetric flask to obtain a 100 mg / L thallium nitrate solution. Take 50 ml of the thallium nitrate solution into a centrifuge tube, and then add 0.05 g of bentonite, Prussian blue, 10% PB-Bent, 20% PB-Bent, and 30% PB-Bent to the thallium nitrate. After covering the lid, shake well. Place the centrifuge tube in a water bath constant temperature oscillator, set the temperature to 25 °C and the amplitude to 125 rpm, and react for 24 h. After the reaction reaches equilibrium, centrifuge at a speed of 5000 rpm for 10 min, take the supernatant and dilute it 3000 times in 3 times according to 10×10×30. Add 2% dilute nitric acid during the dilution process, and finally measure the remaining thallium ion concentration using inductively coupled plasma mass spectrometry (ICP-MS). The experiment was repeated three times, and error bars were added.

[0100] Figure 4The equilibrium adsorption capacities of different adsorbents are shown. The results indicate that bentonite loaded with Prussian blue exhibits excellent adsorption performance in terms of adsorption capacity, and its adsorption capacity for thallium ions is much greater than that of bentonite and Prussian blue. The adsorption capacity of pure bentonite is approximately 20 mg / g, and that of Prussian blue is approximately 37 mg / g. After the composite modification of the two, the adsorption capacity of 10% PB-Bent increases to about 51 mg / g, and the adsorption capacities of 20% PB-Bent and 30% PB-Bent increase to about 60 mg / g. This shows that the spatial structure of bentonite effectively avoids the aggregation of Prussian blue particles, enabling the active adsorption sites to fully contact with thallium ions. The adsorption capacities of 20% PB-Bent and 30% PB-Bent are close to each other, indicating that the optimal loading amount of Prussian blue loaded on bentonite is 20% of its mass, and more Prussian blue cannot provide more effective loading sites after its formation on bentonite.

[0101] (2) Thallium ion removal rate test

[0102] Take 50 ml of 100 mg / L thallium nitrate solution in a centrifuge tube, and then add 0.1 g of bentonite, Prussian blue, 10% PB-Bent, 20% PB-Bent, and 30% PB-Bent into the thallium nitrate. Cap the tube and shake well. Place the centrifuge tube in a water bath thermostatic oscillator, set the temperature to 25 °C and the amplitude to 125 rpm, and react for 24 h. After the reaction reaches equilibrium, centrifuge at 5000 rpm for 10 min, take the supernatant and dilute it 3000 times in three steps of 10×10×30. Add 2% dilute nitric acid during the dilution process, and finally measure the remaining thallium ion concentration using inductively coupled plasma mass spectrometry (ICP-MS). The experiment was repeated three times, and error bars were added.

[0103] Figure 5 It shows that the thallium removal agent of bentonite loaded with Prussian blue synthesized in the present invention has excellent adsorption performance for thallium ions. In a 100 mg / L high-concentration thallium ion solution, the removal rate of 20% PB-Bent for thallium ions is as high as 99.62%, demonstrating the potential for efficient adsorption treatment of thallium pollution.

[0104] (3) Characterization of different adsorbents

[0105] Figure 6X-ray diffraction patterns of bentonite (Bent), Prussian blue (PB), 10% Bent, 20PB-Bent, and 30% PB-Bent. It can be seen from the figure that the characteristic peak d001 of bentonite is 1.23 nm, while the characteristic peak d001 of 10% Bent, 20PB-Bent, and 30% PB-Bent is 1.46 nm, indicating that the interlayer spacing of bentonite increases after loading Prussian blue. It is possible that some Prussian blue nanoparticles enter the interlayer of bentonite, increasing the interlayer spacing of bentonite. Prussian blue shows corresponding characteristic peaks at 2θ = 17.51°, 24.84°, and 35.35°. 10% Bent, 20PB-Bent, and 30% PB-Bent also show corresponding characteristic peaks at 17.51°, 24.84°, and 35.35°. Moreover, with the increase of the Prussian blue content, the diffraction intensity increases, while pure bentonite does not show corresponding characteristic peaks. Figure 6 It indicates that Prussian blue is successfully loaded on the surface and interlayer of bentonite.

[0106] Figure 7 Fourier transform infrared spectra of bentonite (Bent), Prussian blue (PB), 10% Bent, 20PB-Bent, and 30% PB-Bent. Both bentonite loaded with Prussian blue and pure Prussian blue show a vibration absorption peak of -C≡N- at 2073 cm-1, and with the increase of the Prussian blue content, the diffraction intensity of the absorption peak increases. Prussian blue shows an absorption peak of Fe(II)-C≡N-Fe(III) at 497 cm-1, while the Fe(II)-C≡N-Fe(III) absorption peaks of 10% Bent, 20PB-Bent, and 30% PB-Bent are all shifted to 469 cm -1 . The Fourier transform infrared spectra prove that Prussian blue is successfully loaded on the surface of bentonite. Although the Fe(II)-C≡N-Fe(III) of bentonite loaded with Prussian blue is shifted, this is a normal phenomenon during the preparation and synthesis process.

[0107] Figure 6 and Figure 7 The results show that Prussian blue is successfully loaded on the surface or interlayer of bentonite, but mainly on the surface.

[0108] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention, and all belong to the protection scope of the present invention.

Claims

1. A selective adsorption thallium removal agent, characterized in that, It includes bentonite and Prussian blue loaded on the bentonite, and the mass ratio of Prussian blue is 10 - 30% of the mass of bentonite.

2. The selective thallium adsorbent according to claim 1, wherein The bentonite is sodium-based bentonite.

3. The selective thallium adsorbent according to claim 1, wherein The selective thallium-removing adsorbent also includes polyvinylpyrrolidone, and the dosage is 1 - 1.2% of the mass of bentonite.

4. The selective thallium adsorbent according to claim 1, wherein, The adsorption capacity of the selective thallium-removing adsorbent for thallium ions is 50 - 60 mg / g.

5. The selective thallium-removing adsorbent according to claim 1, wherein The selective thallium-removing adsorbent is used to remove thallium ions in wastewater.

6. The selective thallium-removing adsorbent according to claim 5, wherein The dosage of the selective thallium-removing adsorbent in wastewater is 0.5 - 1 g / L.

7. A preparation method of the selective adsorption thallium removal agent according to any one of claims 1-6, characterized in that, It includes the following steps: Step S1: Disperse the bentonite in deionized water to obtain a bentonite slurry, and add nitric acid dropwise to the bentonite slurry. After stirring evenly, an acidified bentonite slurry is obtained; Step S2: Based on the reaction of potassium ferrocyanide and ferric chloride to form Prussian blue, calculate the masses of potassium ferrocyanide and ferric chloride required to meet the Prussian blue proportion requirement. Take the corresponding masses of potassium ferrocyanide and ferric chloride and dissolve them in deionized water to obtain a potassium ferrocyanide solution and a ferric chloride solution. Then, dropwise add the potassium ferrocyanide solution and the ferric chloride solution to the acidified bentonite slurry in sequence. After the addition is completed, stir evenly to obtain a mixed slurry; Step S3: Centrifuge the mixed slurry. The centrifuged product is washed twice with deionized water and ethanol respectively, and then the product is placed in an oven at 65°C and dried for 24 h. Finally, it is ground to obtain the selective thallium-removing adsorbent.

8. The preparation method of the selective adsorption thallium removal agent according to claim 7, characterized in that, Step S1 specifically includes the following steps: Take 500 g of deionized water and place it in a 1 L beaker. Stir at a speed of 300 - 500 r / min. During the stirring process, add 10 g of bentonite to the beaker in small batches with a medicine spoon. Stir for 2 h to obtain a bentonite slurry. Add nitric acid with a pH of 2 dropwise to the bentonite slurry and stir for 1 h to obtain an acidified bentonite slurry. Among them, the addition amount of nitric acid is determined according to the mass of bentonite, and the addition amount of nitric acid corresponding to each gram of bentonite is 10 - 15 ml.

9. The preparation method of the selective adsorption thallium removal agent according to claim 7, characterized in that, In Step S2, after adding the potassium ferrocyanide solution and before adding the ferric chloride solution, the following steps are also included: Add polyvinylpyrrolidone to the acidified slurry, and the dosage of polyvinylpyrrolidone is 1 - 1.2% of the mass of bentonite.

10. The preparation method of the selective adsorption thallium removal agent according to claim 7, characterized in that, In Step S3, the centrifugation process is carried out by a centrifuge. The rotation speed of the centrifuge is 5000 r / min, and the centrifugation time is 10 min.

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