Potassium modified titanium dioxide and its application in treatment of wastewater containing thallium

Abstract

The application belongs to the technical field of thallium-containing wastewater treatment, and discloses a potassium-modified TiO2 and application of the potassium-modified TiO2 in thallium-containing wastewater treatment. The potassium-modified TiO2 is obtained by using titanium sulfate as a titanium source and a potassium hydroxide precipitation method, and the adsorption capacity of the potassium-modified TiO2 reaches 990 mg / g. The potassium-modified TiO2 can remove Tl(I) by more than 99.2% under the condition of pH 4-12, and can effectively reduce the concentration of Tl(I) to below 0.1 μg / L. The application provides a modified titanium dioxide material with high adsorption capacity for the treatment of thallium-containing wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thallium-containing wastewater treatment and relates to a potassium-modified TiO2 and application of the potassium-modified TiO2 in thallium-containing wastewater treatment. BACKGROUND

[0002] Thallium is a colorless, odorless and toxic heavy metal element that exists in trace amounts in sulfide minerals such as iron and zinc. The natural distribution of thallium in environmental media such as water, soil, mineral rocks, organisms and human bodies is relatively low. However, with the smelting of thallium and the manufacturing of thallium materials, thallium-containing waste gas, wastewater and residue enter the environment, causing thallium pollution. Long-term exposure of the human body to thallium can cause symptoms such as poisoning, blood vessel and muscle spasm, skin inflammation and kidney dysfunction. Thallium can enter the human body through drinking water, food and breathing and accumulate, and has mutagenicity, carcinogenicity and teratogenicity, leading to various diseases such as esophageal cancer, liver cancer and colorectal cancer.

[0003] Currently, the treatment of thallium-containing wastewater mainly includes chemical precipitation, adsorption, ion exchange and membrane separation methods. Among them, the adsorption method mainly removes thallium ions from wastewater through the selective adsorption of adsorbents, and has the advantages of high efficiency, low cost, simple operation and generation of a small amount of toxic sludge. The treatment of thallium pollution by adsorption mainly includes physical adsorption and chemical adsorption. Physical adsorption is the adsorption of thallium pollutants in water by the intermolecular forces of porous adsorbent materials, and chemical adsorption is the adsorption and removal of thallium pollutants in water by electron transfer between thallium ions in water and the surface of the material to form an adsorption chemical bond.

[0004] Common adsorbents include activated carbon, zeolite and titanium dioxide. Titanium dioxide, commonly known as titanium white powder, has good application prospects in the treatment of thallium-containing wastewater. Titanium dioxide has a certain adsorption capacity for thallium ions. However, in some treatment environments, the adsorption capacity of titanium dioxide may not meet the demand for efficient removal of thallium ions, resulting in poor treatment effect. Therefore, it is of great significance to provide a modified titanium dioxide with high adsorption capacity for the treatment of thallium-containing wastewater. SUMMARY

[0005] To solve the above technical problems, the application provides a potassium-modified TiO2 and application of the potassium-modified TiO2 in thallium-containing wastewater treatment. The potassium-modified TiO2 is obtained by a potassium hydroxide precipitation method using titanium sulfate as a titanium source. The adsorption capacity of the potassium-modified TiO2 reaches 990 mg / g. The highest removal rate of Tl(I) of the potassium-modified TiO2 under the condition of pH = 4-12 is above 99.2%, and the concentration of Tl(I) can be effectively reduced to below 0.1 μg / L. The application provides a modified titanium dioxide material with high adsorption capacity for the treatment of thallium-containing wastewater.

[0006] To achieve the technical purpose of the present application, in one aspect, the present application provides application of potassium-modified TiO2 in thallium-containing wastewater treatment, wherein the dosage of the potassium-modified TiO2 is 0.1-1 g / L; preferably, the dosage of the potassium-modified TiO2 is 0.2 g / L.

[0007] Further, the present application obtains the potassium-modified TiO2 by modifying TiO2 with potassium hydroxide precipitation method, wherein the concentration of titanium sulfate is 0.1 mol / L, the concentration of potassium hydroxide in the potassium hydroxide precipitation method is 0.1-1.2 mol / L, the pH of the solution is 7.0-9.0 after the potassium hydroxide is added dropwise to the titanium sulfate solution, and the potassium-modified TiO2 is obtained after water washing and drying at 45℃ for 12 h.

[0008] Further, the present application applies the potassium-modified TiO2 to thallium-containing wastewater with pH of 4.0-12.0.

[0009] Specifically, the present application finds that there is a significant difference in Tl(I) removal ability between the potassium-modified TiO2 and TiO2 and BC when the pH value is in the range of 2-9 and pH is 11 by comparing the Tl(I) removal effects of different materials under different initial pH conditions of the solution. The potassium-modified TiO2 as a whole shows higher Tl(I) removal ability, so that the Tl(I) concentration of the effluent is lower, which confirms the benefits of potassium modification of TiO2. When pH is greater than or equal to 4, the Tl(I) concentration after adsorption of the potassium-modified TiO2 is maintained below 0.1 μg / L, while the Tl(I) concentration after adsorption of TiO2 and BC adsorbents is difficult to reach this standard. It is shown that the potassium-modified TiO2 has the advantage of significantly improving the Tl(I) removal effect.

[0010] Further, the present application removes Tl(I) in thallium-containing wastewater by inner-sphere surface complexation, ion exchange and electrostatic adsorption of the potassium-modified TiO2.

[0011] Specifically, the present application finds that the first process of the removal mechanism of the potassium-modified TiO2 involves inner-sphere surface complexation of Tl(I) and -OH groups on the surface of TiO2, and this interaction leads to the formation of -OTl on the surface of the adsorbent material. The second process focuses on the K + -rich TiO2 surface, and -OK structure is formed through ion exchange, which is due to the similar ionic radii of Tl + and K + , so that ion exchange reaction occurs, leading to replacement of K + by Tl + , thereby forming -OTl complex. The third process occurs under alkaline conditions, and TiO2 mainly exists in the form of TiO - , which is beneficial to Tl +The static adsorption of ions on the surface of the composite material, the adsorption neutralizes the electronegativity of the material, and forms Ti-O-Tl.

[0012] In another aspect, the present application claims a potassium-modified TiO2, which is prepared by a potassium hydroxide precipitation method using titanium sulfate as a titanium source, and specifically comprises the following steps:

[0013] At room temperature, 500 mL of 0.1 mol / L Ti(SO4)2 is placed in a 1000 mL beaker, continuously stirred under a magnetic stirrer, and 0.1-1.2 mol / L KOH is slowly added dropwise until the pH is maintained at 7.0-9.0, the stirring is stopped, and a TiO2 suspension is obtained. The suspension is centrifuged and washed twice with ultrapure water, then dried at 45°C for 12 h, and ground to obtain a potassium-modified TiO2 material.

[0014] Compared with the prior art, the technical solution provided by the present application at least has the following beneficial effects or advantages:

[0015] (1) The potassium-modified TiO2 material has a better removal effect on Tl(I), especially at a pH of 4-12, the thallium removal rate reaches more than 99.2%, and the Tl(I) concentration can be effectively reduced to below 0.1 μg / L, meeting the requirements of the "Drinking Water Health Standards" (GB 5749-2022) of China. The maximum adsorption capacity of the potassium-modified TiO2 material in removing high-concentration Tl(I) solution reaches 990.41 mg / g, which is significantly better than other materials of the same type.

[0016] (2) The potassium-modified TiO2 material has a strong adaptability to coexisting ion interference, and the thallium removal performance of the potassium-modified TiO2 material is affected by Na + , K + and Mg 2+ , and the presence of a low concentration of Na + enhances the thallium removal capacity of the potassium-modified TiO2. Compared with K + , Mg 2+ has a higher degree of interference, but the potassium-modified TiO2 still has a Tl(I) removal effect of more than 90% under the interference of 1-100 mM coexisting ions.

[0017] (3) The potassium-modified TiO2 material removes Tl(I) in thallium-containing wastewater through inner-sphere surface complexation, ion exchange and static adsorption. The first process of the removal mechanism involves the inner-sphere surface complexation of Tl(I) with -OH groups on the surface of TiO2, and this interaction leads to the formation of -OTl on the surface of the adsorption material. The second process focuses on the K +TiO2 surface, forming -OK structure by ion exchange, because Tl + and K + have similar ionic radius, so ion exchange reaction occurs, resulting in K + being replaced by Tl + , thus forming -OTl complex. The third process occurs under alkaline conditions, TiO2 mainly exists in the form of TiO-, which is conducive to the electrostatic adsorption of Tl + ions on the surface of the composite material, which neutralizes the electronegativity of the material and forms Ti-O-Tl. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is the removal rate of Tl(I) by potassium-modified TiO2 in Tl(I) solution with different initial pH values.

[0019] Figure 2 The figure is the end point pH of potassium-modified TiO2 in Tl(I) solution with different initial pH values.

[0020] Figure 3 The figure is the effluent concentration of Tl(I) by potassium-modified TiO2 and TiO2 in Tl(I) solution with different initial pH values.

[0021] Figure 4 The figure is the isoelectric point of potassium-modified TiO2.

[0022] Figure 5 The figure is the effect of different constant pH values on the removal of thallium by potassium-modified TiO2.

[0023] Figure 6 The figure is the stability field of the reaction system under different constant pH conditions.

[0024] Figure 7 The figure is the effect of different potassium-modified TiO2 dosages on the removal rate of Tl(I) and.

[0025] Figure 8 The figure is the effect of different initial concentrations of Tl(I) on the removal of thallium by potassium-modified TiO2.

[0026] Figure 9 The figure is the effect of different concentrations of cations on the removal of thallium by potassium-modified TiO2.

[0027] Figure 10 The figure is the adsorption kinetics model of Tl(I) by potassium-modified TiO2.

[0028] Figure 11 The figure is the adsorption isotherm of Tl(I) by potassium-modified TiO2.

[0029] Figure 12 The mechanism analysis diagram of potassium-modified TiO2 for removing Tl(I).

[0030] Figure 13 The adsorption-desorption cycle diagram of potassium-modified TiO2 for Tl(I).

[0031] Figure 14 The effect diagram of potassium-modified TiO2 for removing thallium from river water with different initial pH values.

[0032] Figure 15 The effect diagram of potassium-modified TiO2 with different potassium addition amounts for removing thallium from river water. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described in combination with examples, but the present application is not limited to the following examples. The experimental methods and detection methods described in the following examples are all conventional methods unless otherwise specified; and the reagents and materials described are all commercially available unless otherwise specified.

[0034] Example 1

[0035] This example provides the preparation of potassium-modified TiO2 and its application in removing Tl(I).

[0036] Under normal temperature conditions, 500 mL of 0.1 mol / L Ti(SO4)2 was placed in a 1000 mL beaker, continuously stirred under a magnetic stirrer, and 0.1 mol / L KOH was slowly added dropwise until the pH was maintained at 7.0, the stirring was stopped, and a TiO2 suspension was obtained. The suspension was centrifuged and washed twice with ultrapure water, then dried at 45℃ for 12 h, ground, and potassium-modified TiO2 material was obtained.

[0037] The thallium removal experiment was carried out on a constant-temperature air bath shaker, the reaction temperature was controlled at normal temperature (25℃), the shaking speed was 250 r / min, the potassium-modified TiO2 material was added to a solution with an initial Tl(I) concentration of 2 μg / L, the material addition amount was 0.1 g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40 mL, the reaction time was 2 h, after the reaction was completed, the pH change was recorded, then 10 mL of supernatant was filtered through a 0.22 μm pore size filter membrane and 2% nitric acid (v / v) was added for preservation, and the Tl(I) concentration in the solution was determined. The pH of the Tl(I) solution was adjusted using sodium hydroxide with a concentration of 0.1 M or 1 M and nitric acid. The actual effluent thallium concentration was measured to be 0.09 μg / L.

[0038] Example 2

[0039] This example provides the preparation of potassium-modified TiO2 and its application in removing Tl(I).

[0040] The 500 mL 0.1 mol / L Ti(SO4)2 was placed in a 1000 mL beaker under constant stirring with a magnetic stirrer, while 1.2 mol / L KOH was slowly added until the pH was maintained at 9.0, and the stirring was stopped to obtain a TiO2 suspension. The suspension was centrifuged and washed twice with ultrapure water, and then dried at 45°C for 12 h. After grinding, the potassium-modified TiO2 material was obtained.

[0041] The thallium removal experiment was carried out on a constant-temperature air bath shaker, the reaction temperature was controlled at room temperature (25°C), the shaking speed was 250 r / min, the potassium-modified TiO2 material was added to a solution with an initial Tl(I) concentration of 2 μg / L, the material dosage was 0.1 g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40 mL, and the reaction time was 2 h. After the reaction, the pH change was recorded, and then 10 mL of supernatant was filtered through a 0.22 μm pore size filter membrane and added with 2% nitric acid (v / v) for preservation. The Tl(I) concentration in the solution was determined. The pH of the Tl(I) solution was adjusted using 0.1 M or 1 M sodium hydroxide and nitric acid. The actual effluent thallium concentration was measured to be 0.05 μg / L.

[0042] Example 3

[0043] This example provides the preparation of potassium-modified TiO2 and its application in Tl(I) removal.

[0044] The 500 mL 0.1 mol / L Ti(SO4)2 was placed in a 1000 mL beaker under constant stirring with a magnetic stirrer, while 1.2 mol / L KOH was slowly added until the pH was maintained at 9.0, and the stirring was stopped to obtain a TiO2 suspension. The suspension was centrifuged and washed twice with ultrapure water, and then dried at 45°C for 12 h. After grinding, the potassium-modified TiO2 material was obtained.

[0045] The thallium removal experiment was carried out on a constant-temperature air bath shaker, the reaction temperature was controlled at room temperature (25°C), the shaking speed was 250 r / min, the potassium-modified TiO2 material was added to a solution with an initial Tl(I) concentration of 2 μg / L, the material dosage was 0.1 g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40 mL, and the reaction time was 2 h. After the reaction, the pH change was recorded, and then 10 mL of supernatant was filtered through a 0.22 μm pore size filter membrane and added with 2% nitric acid (v / v) for preservation. The Tl(I) concentration in the solution was determined. The pH of the Tl(I) solution was adjusted using 0.1 M or 1 M sodium hydroxide and nitric acid. The actual effluent thallium concentration was measured to be 0.05 μg / L.

[0046] Example 4

[0047] This embodiment provides a single-factor experiment on the application of potassium-modified TiO2 in thallium removal.

[0048] The thallium removal experiment was conducted on a constant-temperature air bath shaker. The reaction temperature was controlled at room temperature (25℃), and the shaking speed was 250 r / min. Potassium-modified TiO2 material was added to a solution with an initial Tl(I) concentration of 2 μg / L. The material addition amount was 0.1 g / L, the initial pH of the Tl(I) solution was 10, the reaction system volume was 40 mL, and the reaction time was 2 h. After the reaction, the pH change was recorded. Subsequently, 10 mL of the supernatant was filtered through a 0.22 μm pore size filter membrane and 2% nitric acid (v / v) was added for preservation. The Tl(I) concentration in the solution was measured. The pH of the Tl(I) solution was adjusted using 0.1 M or 1 M sodium hydroxide and nitric acid.

[0049] The removal rate (R, %) of Tl(I) by the adsorbent is expressed as R = (C0 - C10) / (C ... e The initial concentration of Tl(I) is calculated as (100 / C0). In the formula, C0 is the initial concentration of Tl(I), in μg / L; C... e The equilibrium concentration of Tl(I) is μg / L.

[0050] Adsorption capacity of adsorbent (q) e (μg / g) via q e =(C0-C e V / m calculation. In the formula, V is the total volume of the solution, L; m is the amount of adsorbent added, g.

[0051] 1. Effect of initial solution pH on the thallium removal efficiency of potassium-modified TiO2

[0052] The pH of the Tl(I) solution was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, respectively, and potassium-modified TiO2 was added. The removal rate of Tl(I) by potassium-modified TiO2 in Tl(I) solutions with different initial pH values ​​is shown in the following figures. Figure 1 As shown, the final pH results of potassium-modified TiO2 solutions with different initial pH Tl(I) are as follows: Figure 2 As shown.

[0053] Depend on Figure 1 It can be seen that at pH=2, the potassium-modified TiO2 material exhibits a poor Tl(I) removal rate. As the initial pH ≥4, the Tl(I) removal rate of the potassium-modified TiO2 material continuously increases, reaching a high removal efficiency of over 99.2% at pH values ​​between 4 and 12. Figure 2 It can be seen that within the initial pH range of 2–3, the final pH value shows no significant change; however, under other initial pH conditions, the final pH value shows a significant increase. This phenomenon is consistent with the corresponding removal efficiency trend, because alkaline conditions promote the increase of hydroxyl groups on the adsorbent surface, leading to increased Tl.+ It complexes with the hydroxyl groups on the material surface, thereby improving the material's resistance to Tl. + The combination of affinity.

[0054] 2. Thallium removal efficiency of different materials under different initial pH conditions of solutions

[0055] The pH of the Tl(I) solution was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, respectively. Potassium-modified TiO2, TiO2, and biochar (BC) were then added to the solutions, and the thallium removal efficiency of the different materials was compared. The effluent concentration of Tl(I) under different initial pH conditions was as follows: Figure 3 As shown.

[0056] Depend on Figure 3 It was found that there were significant differences in Tl(I) removal capacity between potassium-modified TiO2 and TiO2 and BC adsorbents when the pH range was 2–9 and at pH 11. Potassium-modified TiO2 generally exhibited a higher Tl(I) removal capacity, resulting in a lower Tl(I) concentration in the effluent, which confirms the benefits of potassium modification of TiO2. When pH ≥ 4, the Tl(I) concentration after adsorption by potassium-modified TiO2 remained below 0.1 μg / L, while TiO2 and BC adsorbents struggled to achieve this standard. This indicates that the combination of TiO2 and potassium modification has a significant advantage in improving thallium removal efficiency.

[0057] 3. Effect of Tl(I) solutions with different constant pH values ​​on the thallium removal efficiency of potassium-modified TiO2

[0058] The pH of the Tl(I) solution was adjusted using 0.1M or 1M sodium hydroxide and nitric acid, and the pH of the Tl(I) solution was kept constant at 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, respectively. The isoelectric point of potassium-modified TiO2 was calculated. Figure 4 The effect of different constant pH values ​​on the thallium removal efficiency of potassium-modified TiO2 is as follows: Figure 5 As shown, the stability field diagrams of the reaction system under different constant pH conditions are as follows: Figure 6 As shown.

[0059] Depend on Figure 4 It can be seen that the isoelectric point pH of potassium-modified TiO2 is... IEP The pH value is 2.4. When the pH value is higher than 2.4, the material surface becomes negatively charged, which enhances its resistance to Tl. + Due to electrostatic attraction, the removal rate of Tl(I) shows an increasing trend. Figure 5It can be seen that in a reaction system with a constant pH, when the pH of the Tl(I) solution is maintained at 2, the removal rate of Tl(I) by potassium-modified TiO2 is only 12.0±3.9%; when the pH rises to 4, the removal rate increases slightly to 52.5±1.9%; when pH ≥ 6, the removal efficiency increases significantly, and the highest removal efficiency is achieved at pH = 10, reaching 97.3±0.5%, with an effluent Tl(I) concentration of only 0.06±0.009 μg / L. Figure 6 It can be seen that the change in Tl(I) removal rate caused by pH changes may be related to the types and valence states of elements affected by ORP. When pH < 4, the Tl(I) solution mainly reacts with Tl. + The ionic state of [the substance] leads to its interaction with a large amount of H+ in the acidic solution. + Competing for adsorption sites. Simultaneously, TiO2 in potassium-modified TiO2 uses TiOH2 as its adsorption site. + The presence of this state exhibits electrostatic repulsion (Equation 1), leading to a decrease in the removal rate of Tl(I). When pH > 4, TiO2... - The increased content of Tl (Equation 2) makes it easier for Tl to be adsorbed. + This leads to a gradual increase in the removal rate of Tl(I). Also, as the solution becomes alkaline, the removal of H+... + With reduced competition, the number of negatively charged hydroxyl functional groups on the surface of potassium-modified TiO2 increases, resulting in a removal rate exceeding 90% at pH ≥ 6. Therefore, electrostatic adsorption and surface complexation mechanisms play important roles in the removal of Tl(I) by potassium-modified TiO2.

[0060] ≡TiOH+H + →≡TiOH2+ Equation 1;

[0061] ≡TiOH+OH - →≡TiO - +H2O Formula 2.

[0062] 4. Effect of potassium-modified TiO2 dosage on Tl(I) removal rate

[0063] The dosages of potassium-modified TiO2 were 0.05, 0.1, 0.2, 0.5, and 1 g / L. The effects of different potassium-modified TiO2 dosages on the Tl(I) removal rate are as follows: Figure 7 As shown. By Figure 7It can be seen that the dosage of potassium-modified TiO2 is positively correlated with the removal rate of Tl(I). At a low adsorbent dosage of 0.05 g / L, the removal rate is 94.3 ± 0.2%, and the effluent concentration of Tl(I) is 0.12 ± 0.004 μg / L, which may be due to the limited number of effective adsorption sites on the surface of the adsorbent material at a low dosage. When the dosage is increased to 0.1 g / L, the removal rate increases significantly to 97.1 ± 0.4%, thereby reducing the effluent concentration of Tl(I) to 0.06 ± 0.002 μg / L. The effect is more significant when the dosage of adsorbent material is 1 g / L, as Tl(I) is almost completely removed, and the effluent concentration is further reduced to 0.007 ± 0.0007 μg / L, indicating the high efficiency of potassium-modified TiO2 in the deep removal of trace Tl(I).

[0064] 5. Effect of initial Tl(I) concentration on the removal of Tl(I) by potassium-modified TiO2

[0065] The initial concentrations of Tl(I) were 3.85, 8.44, 17.88, 26.75, 36.33, and 49.65 μg / L, respectively. The effects of different initial Tl(I) concentrations on the removal of Tl(I) by potassium-modified TiO2 are shown in Figure 8 and Table 1.

[0066] Table 1: Effect of different initial Tl(I) concentrations on the adsorption capacity of potassium-modified TiO2

[0067] Tl(I) initial concentration / (pg / L) Tl(I) adsorption capacity / (pg / g) 3.85 26.6±0.5 8.43 58.4±0.5 17.88 113.7±2.8 26.75 158.2±2.9 36.33 214.5±3.9 49.65 285.5±7.4

[0068] From Figure 8 and Table 1, it can be seen that as the initial concentration of Tl(I) in the solution increases, the effluent concentration of potassium-modified TiO2 tends to increase. Although the removal rate decreases as the initial concentration increases, the overall effluent concentration remains below 25 μg / L. When the initial concentration of Tl(I) increases from 8.4 μg / L to 17.8 μg / L, the adsorption capacity significantly increases from 58.4 ± 0.5 μg / g to 113.7 ± 2.8 μg / g. When the initial concentration of Tl(I) is 49.65 μg / L, the effluent concentration of Tl(I) is 21.1 ± 0.7 μg / L, and the adsorption capacity reaches 285.5 ± 7.4 μg / g, with a removal rate of 57.5 ± 1.5%. This experimental result indicates that although the adsorption sites on the surface of the material are limited, and the removal rate of Tl(I) is relatively low at high initial concentrations of Tl(I), the adsorbent material still has potential applicability in water samples with high Tl(I) pollution levels, and effective removal can be achieved by adjusting the dosage of the material or increasing the reaction time.

[0069] 6. Effect of cation interference on the removal of Tl(I) by potassium-modified TiO2

[0070] The concentrations of KNO3, NaNO3, and MgSO4 were set to 1, 10, 50, and 100 mM, respectively, to investigate the effect of coexisting cations in the solution on the removal of Tl(I) by potassium-modified TiO2. Figure 9 ).

[0071] As can be seen from Figure 9 , when the concentration of interfering cations in the solution was low (1 mM), the removal rate of Tl(I) did not change significantly. However, when the concentration of interfering cations in the solution was higher than 1 mM, K + and Mg 2+ exhibited a significant inhibitory effect on the removal of Tl + by potassium-modified TiO2. The higher the concentration of K + or Mg 2+ in the solution, the lower the removal rate of Tl + . The removal rate of Tl + in the blank control group was 98.6 ± 0.05%, while when the concentrations of K + and Mg 2+ reached 100 mM, the removal rates decreased to 94.7 ± 0.2% and 91.2 ± 0.6%, respectively. This may be because K + and Tl + have similar atomic radii, and compete for adsorption sites, resulting in a decrease in the removal rate. In addition, the multivalent Mg 2+ ions also have a stronger competitive side effect than the monovalent Tl + ions. However, the presence of Na + in the solution had the opposite effect on the removal rate of Tl + , and the presence of Na + promoted the removal of Tl + by potassium-modified TiO2. When the concentration of Na + was 1 mM, the removal rate increased to 99.2 ± 0.3%. As the concentration of Na + increased, the promoting effect decreased slowly, and when the concentration of Na + was 100 mM, the removal rate was 98.3 ± 0.4%, which was 0.3% lower than that of the blank control group. Therefore, the degree of interference exhibited by the three cations was Mg 2+ > K + > Na + . Therefore, in the application of this adsorbent material, Mg 2+ interference should be removed in the pretreatment step using methods such as alkaline settling to achieve a better effect of removing Tl(I).

[0072] Example 5

[0073] This example provides an analysis of the adsorption kinetics, adsorption isotherm, and mechanism of the removal of Tl(I) by potassium-modified TiO2.

[0074] 1. Adsorption kinetics and adsorption isotherm of potassium-modified TiO2

[0075] Kinetic experiment: The volume of Tl(I) solution was 250 mL, the reaction time was 8 h, and the samples were taken at different reaction times (0, 0.5, 1, 5, 10, 30, 60, 120, 240, 360, 480 min), the adsorption kinetic model was as shown in Figure 10 , and the adsorption kinetic parameters were as shown in Table 2.

[0076] The calculation formula of the pseudo-first-order kinetic model was as follows:

[0077]

[0078] The calculation formula of the pseudo-second-order kinetic model was as follows:

[0079]

[0080] In the formula, q e was the equilibrium adsorption capacity of the adsorbent to the sample, μg / g; q t was the adsorption capacity of the adsorbent to the sample at t time, μg / g; t was time, min; K1 / (min -1 ), and K2 / (g / μg·min) were the pseudo-first-order kinetic constant and the pseudo-second-order kinetic constant, respectively.

[0081] Isothermal adsorption experiment: The initial Tl(I) concentration gradient of the solution was set to 1, 5, 10, 20, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900 mg / L, the reaction time was 2 h, and the experiment was carried out at room temperature 298.15 K. The Langmuir, Freundlich and Temkin isothermal models were used to fit the adsorption process, the adsorption isotherm was as shown in Figure 11 , and the adsorption isotherm parameters were as shown in Table 3.

[0082]

[0083]

[0084]

[0085] In the formula, q e and Q max were the equilibrium adsorption capacity and the maximum adsorption capacity, mg / g; C e was the equilibrium concentration of the adsorbate, mg / L; K L represented the Langmuir isothermal adsorption constant; and K Fand n represents the Freundlich adsorption isotherm constant; R is the universal gas constant with a value of 8.314 J / mol-K; T represents the temperature in Kelvin; b and K T Temkin constant, where the value of b is related to the heat of adsorption.

[0086] Table 2: Adsorption kinetic parameters of potassium-modified TiO2 for Tl(I) removal

[0087]

[0088] Table 3: Adsorption isotherm parameters of potassium-modified TiO2 for Tl(I) removal

[0089]

[0090] From Figure 10 it can be seen that the adsorption capacity of Tl(I) rapidly increased to 9.37 ± 0.6 μg / g within the first 1 min of the adsorption reaction due to the high Tl(I) concentration gradient and a large number of active sites on the surface of the material. As time increased, the adsorption capacity remained at a high level without significant change due to the decreasing Tl(I) concentration gradient and the decreasing number of binding sites on the adsorbent, and the adsorption rate gradually became slow, eventually reaching an equilibrium state around 2 h, with an equilibrium adsorption capacity of 19.53 ± 1.2 μg / g. From Table 2, it can be seen that the R 2 values of the pseudo-first-order kinetic and pseudo-second-order kinetic models were 0.934 and 0.936, respectively, indicating that both adsorption kinetic models could well fit the adsorption process, but the pseudo-second-order kinetic model was more suitable for representing the adsorption process of Tl(I) by potassium-modified TiO2, which indicated that the mechanism of Tl(I) adsorption by potassium-modified TiO2 was mainly chemical adsorption.

[0091] From Figure 11 it can be seen that at a low initial Tl(I) concentration, the adsorption capacity rapidly increased with the increase in Tl(I) concentration. However, when the initial Tl(I) concentration approached 200 mg / L, the growth rate of the adsorption capacity significantly decreased, which might be due to the limited number of binding sites on the adsorbent, but the adsorption capacity of Tl(I) by potassium-modified TiO2 was greatly improved, reaching 11.11 ± 1.2 mg / g when the initial Tl(I) concentration was 1.12 mg / L, and then increasing to 990.41 ± 11.7 mg / g when the initial Tl(I) concentration increased to 1045.45 mg / L. From Table 3, it can be seen that the R 2The values of 0.947, 0.985 and 0.898, respectively, show that the Freundlich model is the most suitable to describe the adsorption behavior of the potassium-modified TiO2, and the adsorption process is more in line with the multilayer chemical adsorption, and is a rapid adsorption process.

[0092] 2. Mechanism analysis of potassium-modified TiO2 for removing Tl(I)

[0093] According to the above experimental results, the mechanism of the potassium-modified TiO2 adsorption material for removing Tl(I) can be divided into three main processes, as shown in Figure 12 The first process of the removal mechanism involves the complexation of Tl(I) with the inner-sphere surface of the -OH groups located on the surface of TiO2, and this interaction leads to the formation of -OTl on the surface of the adsorption material. The second process focuses on the TiO2 surface rich in K + , and forms the -OK structure through ion exchange, because the ionic radii of Tl + and K + are similar, so ion exchange reaction occurs, resulting in K + being replaced by Tl + , thereby forming the -OTl complex. The third process occurs under alkaline conditions, and TiO2 mainly exists in the form of TiO-, which is conducive to the electrostatic adsorption of Tl + ions on the surface of the composite material, and this adsorption neutralizes the electronegativity of the material, forming Ti-O-Tl (Formula 4). The comprehensive analysis of the reaction mechanism illustrates that the potassium-modified TiO2 material has multiple aspects of adsorption interaction for effectively removing Tl(I).

[0094] pH < 9: ≡TiOH + Tl + → ≡TiOHTl + Formula 3;

[0095] pH = 10: ≡TiO - + Tl + → ≡TiOTl Formula 4;

[0096] pH > 10: ≡TiO - + ≡TlOH → TiOTlOH - Formula 5.

[0097] Example 4

[0098] This example evaluates the cyclic regeneration performance of the potassium-modified TiO2 material.

[0099] The concentration of the initial Tl(I) solution is 20 mg / L, and 5 adsorption-desorption cycles are set, with each adsorption or desorption time being 2 h. The adsorbent is desorbed using 0.1 M HNO3, and the repeated use performance of the potassium-modified TiO2 material is evaluated, and the evaluation results are as follows Figure 13As shown.

[0100] Depend on Figure 13 It was found that after five regeneration cycles of desorption treatment with 0.1M HNO3 solution, the removal rate of Tl(I) decreased from 99.6±0.13% initially to 77.9±2.1%. This may be because the acid treatment during regeneration alters the chemical properties of the potassium-modified TiO2 material surface, leading to a decrease in adsorption rate. However, the removal rate remained above 90% throughout the first four cycles. This result indicates that potassium-modified TiO2 can maintain stable adsorption performance over up to four cycles. Furthermore, the desorption efficiency showed an upward trend, increasing from 70.1±5.6% to 96.4±5.6% over the five cycles. This observation suggests that HNO3 solution can serve as an excellent desorbent for Tl(I) by potassium-modified TiO2, and that potassium-modified TiO2 material can be used as a regenerable adsorbent within a limited number of cycles, demonstrating promising application prospects.

[0101] Example 6

[0102] This embodiment provides the application of potassium-modified TiO2 materials in wastewater treatment.

[0103] Using thallium-contaminated river water from a mining area in southwest China as the test object, the water quality parameters were referenced from those listed in the study by Liu et al. (Liu,Y.,Huang,L.,Xiong,Z.,Zhang,W.,Li,H.,Liu,Y.,Zhang,G.,2023.Highly effective removal of thallium(I) by nanostructured titanium pyrophosphate from acidic wastewater.Journal of Environmental Chemical Engineering 11(6),111417). The initial pH of the thallium-contaminated river water was adjusted to 2, 4, 6, 8, 10, and 12, respectively, and the same mass of potassium-modified TiO2 (0.1 g / L) was added. The removal effect of Tl(I) in the thallium-contaminated river water under different initial pH conditions was investigated. The results are as follows: Figure 14 As shown in the figure. The dosage of potassium-modified TiO2 was controlled at 0.05, 0.1, 0.2, 0.5, and 1 g / L to treat the same volume of thallium-contaminated river water. The results are as follows. Figure 15 As shown.

[0104] Depend on Figure 14It is known that the effect is the best when the initial pH value is 10 in the application of potassium-modified TiO2 to repair the river water polluted by thallium. Therefore, it is necessary to consider adjusting the pH value to 8-10 in the actual treatment of wastewater by potassium-modified TiO2, so as to improve the treatment effect of wastewater. Figure 15 It is known that due to the existence of competitive impurity ions in the actual wastewater matrix, especially the cations with interference effect, such as Ca 2+ and the like, which compete with Tl(I) for adsorption sites, resulting in a lower removal rate than in the experiment. Increasing the dosage of potassium-modified TiO2 to 0.2 g / L can reduce the Tl(I) concentration in the effluent to below 0.1 μg / L, thereby ensuring that the water discharge standard is met.

[0105] As described above, the basic principles, main features and advantages of the present application are better described. The above examples and descriptions only describe the preferred embodiments of the present application, and the present application is not limited by the above examples. Various changes and improvements to the technical solutions of the present application made by those skilled in the art without departing from the spirit and scope of the present application shall fall within the scope of protection of the present application.

Claims

1. The application of potassium-modified TiO2 in the treatment of thallium-containing wastewater, characterized in that, The dosage of potassium-modified TiO2 is 0.1~1 g / L; The method for preparing potassium-modified TiO2 consists of the following steps: At room temperature, 500 mL of 0.1 mol / L Ti(SO4)2 was placed in a 1000 mL beaker and stirred continuously with a magnetic stirrer while slowly adding 0.1~1.2 mol / L KOH dropwise until the pH was maintained at 7.0~9.

0. Stirring was then stopped to obtain a TiO2 suspension. The TiO2 suspension was centrifuged and washed twice with ultrapure water, then dried at 45℃ for 12 h. After grinding, the potassium-modified TiO2 was obtained. The potassium-modified TiO2 is used to treat thallium-containing wastewater with a pH of 4.0~12.0; The potassium-modified TiO2 removes thallium from thallium-containing wastewater through complexation on the inner sphere surface, ion exchange, and electrostatic adsorption. + .

2. The application according to claim 1, characterized in that, The dosage of potassium-modified TiO2 is 0.2 g / L.

3. The application according to claim 1, characterized in that, The potassium-modified TiO2 will remove Tl from the thallium-containing wastewater. + The concentration was reduced to below 0.1 µg / L.

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