Potassium modified TiO2 and application thereof in thallium-containing wastewater treatment

Abstract

The invention belongs to the technical field of thallium-containing wastewater treatment, and discloses potassium modified TiO2 and application thereof in thallium-containing wastewater treatment. Titanium sulfate is used as a titanium source, the potassium modified TiO2 is obtained through a potassium hydroxide precipitation method, the adsorption capacity of the potassium modified TiO2 reaches 990mg / g, the highest removal rate of the potassium modified TiO2 to Tl (I) reaches 99.2% or above under the condition that the pH value is 4-12, and the concentration of the Tl (I) can be effectively reduced to 0.1 microgram / L or below. The invention provides a modified titanium dioxide material with high adsorption capacity for treatment of thallium-containing wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of thallium-containing sewage treatment and relates to a potassium-modified TiO 2 And its application in the treatment of thallium-containing wastewater. Background Art

[0002] Thallium is a colorless, odorless, toxic heavy metal element. It exists in trace amounts in sulfide ores such as iron and zinc. Its natural distribution in environmental media such as water, soil, mineral rocks, organisms and the human body is relatively low. However, with the smelting of thallium and the manufacture of thallium materials, waste gas, waste water and waste residue containing thallium enter the environment, causing thallium pollution. Long-term exposure to thallium can cause symptoms including poisoning, spasms of blood vessels and muscles, skin inflammation and renal dysfunction. Thallium can enter the human body through drinking water, food and breathing and accumulate. It is mutagenic, carcinogenic and teratogenic, and can cause a variety of diseases such as esophageal cancer, liver cancer and colorectal cancer.

[0003] At present, the treatment of thallium-containing wastewater mainly includes chemical precipitation, adsorption, ion exchange and membrane separation. Among them, the adsorption method mainly removes thallium ions from wastewater through the selective adsorption of thallium ions by adsorbents. It has the advantages of high efficiency, low cost, simple operation and small amount of toxic sludge. The adsorption method mainly treats thallium pollution through physical adsorption and chemical adsorption. Physical adsorption is to adsorb thallium pollutants in water by the intermolecular force of porous adsorption materials, and chemical adsorption is to form adsorption chemical bonds through electron transfer between thallium ions in water and the surface of the material to adsorb and remove thallium pollutants in water.

[0004] Commonly used adsorbents include activated carbon, zeolite, titanium dioxide, etc. Titanium dioxide, commonly known as titanium dioxide, has shown 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 needs of efficient removal of thallium ions, resulting in poor treatment effects. Therefore, providing a modified titanium dioxide with a higher adsorption capacity is of great significance for the treatment of thallium-containing wastewater. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a potassium-modified TiO 2 The present invention uses titanium sulfate as a titanium source and obtains the potassium-modified TiO 2 , potassium-modified TiO 2 The adsorption capacity of the potassium-modified TiO 2Under the condition of pH=4-12, the highest removal rate of Tl(I) reaches more than 99.2%, and the concentration of Tl(I) can be effectively reduced to below 0.1μg / L. The present invention 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 invention, on the one hand, the present invention provides potassium-modified TiO 2 Application of potassium-modified TiO in the treatment of thallium-containing wastewater 2 The dosage is 0.1-1 g / L; preferably, the potassium-modified TiO 2 The dosage is 0.2g / L.

[0007] Furthermore, the present invention uses titanium sulfate as a titanium source and modifies TiO 2 The potassium-modified TiO 2 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. Potassium hydroxide is added dropwise to the titanium sulfate solution to a pH of 7.0-9.0. The solution is washed with water and dried at 45°C for 12 hours to obtain the potassium-modified TiO 2 .

[0008] Furthermore, the potassium-modified TiO 2 Applicable to thallium-containing wastewater with a pH value of 4.0 to 12.0.

[0009] Specifically, the present invention compares the thallium removal effects of different materials under different solution initial pH conditions and finds that when the pH value ranges from 2 to 9 and the pH is 11, the potassium-modified TiO 2 With TiO 2 There is a significant difference in the Tl(I) removal capacity between TiO2 and BC. 2 The overall performance was higher in removing Tl(I) and the effluent Tl(I) concentration was lower, which confirmed that the addition of TiO 2 Benefits of potassium modification. When pH ≥ 4, potassium modified TiO 2 The concentration of Tl(I) after adsorption was kept below 0.1 μg / L, while TiO 2 and BC adsorbents are difficult to reach this standard. 2 Combining potassium modification has the advantage of significantly improving the thallium removal effect.

[0010] Furthermore, the potassium-modified TiO 2 Removal of Tl(I) from thallium-containing wastewater via inner sphere surface complexation, ion exchange and electrostatic adsorption.

[0011] Specifically, the present invention analyzes potassium-modified TiO 2The removal mechanism of Tl(I) was found to involve the first process of Tl(I) and the interaction between Tl(I) and TiO 2 The second process is concentrated in the K-rich + TiO 2 The surface, through ion exchange, forms -OK structure, which is due to Tl + and K + The ionic radii are similar, so an ion exchange reaction will occur, resulting in K + By Tl + The third process occurs under alkaline conditions, TiO 2 Mainly TiO - This state is conducive to Tl + The electrostatic adsorption of ions on the surface of the composite material neutralizes the electronegativity of the material and forms Ti-O-Tl.

[0012] On the other hand, the present invention claims a potassium-modified TiO 2 Using titanium sulfate as the titanium source, TiO was modified by potassium hydroxide precipitation method. 2 The potassium-modified TiO 2 , specifically including the following steps:

[0013] At room temperature, 500 mL of 0.1 mol / LTi(SO 4 ) 2 Place in a 1000mL beaker, continue stirring under a magnetic stirrer, and slowly add 0.1-1.2mol / L KOH until the pH is maintained at 7.0-9.0, then stop stirring to obtain TiO 2 The suspension was centrifuged and washed twice with ultrapure water, then dried at 45 °C for 12 h, and ground to obtain potassium-modified TiO 2 Material.

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

[0015] (1) Potassium-modified TiO 2 The material has a good removal effect on Tl(I), especially under the condition of pH 4-12, the thallium removal rate reaches more than 99.2%, and can effectively reduce the concentration of Tl(I) to below 0.1μg / L, meeting the requirements of China's "Sanitary Standards for Drinking Water" (GB 5749-2022). 2The maximum adsorption capacity of the material in removing high-concentration Tl(I) solution is 990.41 mg / g, which is significantly better than other materials of the same type.

[0016] (2) Potassium-modified TiO 2 The material has a strong adaptability to the interference of coexisting ions. Potassium-modified TiO 2 The thallium removal performance of the material is affected by the Na + , K + and Mg 2+ The effect of the presence of lower concentrations of Na + Enhanced potassium-modified TiO 2 The ability to remove thallium. + In comparison, Mg 2+ The interference level of potassium-modified TiO 2 Under the condition of 1-100 mM coexisting ions, the removal effect of Tl(I) is still higher than 90%.

[0017] (3) Potassium-modified TiO 2 The material removes Tl(I) from thallium-containing wastewater through inner sphere surface complexation, ion exchange and electrostatic adsorption. The first process of its removal mechanism involves the interaction of Tl(I) with the TiO 2 The second process is concentrated in the K-rich + TiO 2 The surface, through ion exchange, forms -OK structure, which is due to Tl + and K + The ionic radii are similar, so an ion exchange reaction will occur, resulting in K + By Tl + The third process occurs under alkaline conditions, TiO 2 It mainly exists in the form of TiO-, which is beneficial to Tl + The electrostatic adsorption of ions on the surface of the composite material neutralizes the electronegativity of the material and forms Ti-O-Tl. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Potassium-modified TiO 2 The removal rate of Tl(I) in Tl(I) solutions with different initial pH values.

[0019] Figure 2 Potassium-modified TiO 2 Results of endpoint pH in Tl(I) solutions with different initial pH.

[0020] Figure 3 Potassium-modified TiO 2 and TiO 2 Results of the effluent concentration of Tl(I) in Tl(I) solutions with different initial pH.

[0021] Figure 4 Potassium-modified TiO 2 isoelectric point diagram.

[0022] Figure 5 Effect of different constant pH values ​​on potassium-modified TiO 2 Influence diagram of thallium removal effect.

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

[0024] Figure 7 For different potassium-modified TiO 2 The effect of dosage on Tl(I) removal rate is shown in the figure.

[0025] Figure 8 Effect of different initial concentrations of Tl(I) on potassium-modified TiO 2 Influence diagram of thallium removal effect.

[0026] Fig. 9 Effect of different cation concentrations on potassium-modified TiO 2 Influence diagram of thallium removal effect.

[0027] Fig.10 Potassium-modified TiO 2 Adsorption kinetic model for Tl(I).

[0028] Fig.11 Potassium-modified TiO 2 Adsorption isotherms for Tl(I).

[0029] Fig.12 Potassium-modified TiO 2 Mechanistic analysis diagram for removal of Tl(I).

[0030] Fig.13 Potassium-modified TiO 2 Adsorption-desorption cycle diagram for Tl(I).

[0031] Fig.14 Potassium-modified TiO 2 Thallium removal effect diagram for thallium-contaminated river water with different initial pH values.

[0032] Fig.15 Different addition amounts of potassium modified TiO 2 Diagram of the thallium removal effect on thallium-contaminated river water. DETAILED DESCRIPTION

[0033] The technical scheme of the present invention is now described in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0034] Example 1

[0035] This example provides potassium-modified TiO 2 Preparation and application in Tl(I) removal.

[0036] At room temperature, 500 mL 0.1 mol / L Ti(SO 4 ) 2 Place in a 1000 mL beaker, stir continuously under a magnetic stirrer, and slowly add 0.1 mol / L KOH until the pH is maintained at 7.0. Stop stirring to obtain TiO 2 The suspension was centrifuged and washed twice with ultrapure water, then dried at 45 °C for 12 h, and ground to obtain potassium-modified TiO 2 Material.

[0037] The thallium removal experiment was carried out on a constant temperature air bath shaker. The reaction temperature was controlled at room temperature (25°C) and the shaking speed was 250 r / min. 2 The material was added to a solution with an initial Tl(I) concentration of 2μg / L, the material dosage was 0.1g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40mL, the reaction time was 2h, and the pH change was recorded after the reaction. Then 10mL of the supernatant was filtered through a 0.22μm 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 and nitric acid with a concentration of 0.1M or 1M. The actual thallium concentration in the effluent was measured to be 0.09μg / L.

[0038] Example 2

[0039] This example provides potassium-modified TiO 2 Preparation and application in Tl(I) removal.

[0040] At room temperature, 500 mL 0.1 mol / L Ti(SO 4 ) 2 Place in a 1000 mL beaker, continue stirring under a magnetic stirrer, and slowly add 0.8 mol / L KOH until the pH is maintained at 8.0. Stop stirring to obtain TiO 2 The suspension was centrifuged and washed twice with ultrapure water, then dried at 45 °C for 12 h, and ground to obtain potassium-modified TiO2 Material.

[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) and the shaking speed was 250 r / min. 2 The material was added to a solution with an initial Tl(I) concentration of 2μg / L, the material dosage was 0.1g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40mL, the reaction time was 2h, and the pH change was recorded after the reaction. Then 10mL of the supernatant was filtered through a 0.22μm 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 and nitric acid with a concentration of 0.1M or 1M. The actual thallium concentration in the effluent was measured to be 0.04μg / L.

[0042] Example 3

[0043] This example provides potassium-modified TiO 2 Preparation and application in Tl(I) removal.

[0044] At room temperature, 500 mL 0.1 mol / L Ti(SO 4 ) 2 Place in a 1000 mL beaker, stir continuously under a magnetic stirrer, and slowly add 1.2 mol / L KOH until the pH is maintained at 9.0. Stop stirring to obtain TiO 2 The suspension was centrifuged and washed twice with ultrapure water, then dried at 45 °C for 12 h, and ground to obtain potassium-modified TiO 2 Material.

[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) and the shaking speed was 250 r / min. 2 The material was added to a solution with an initial Tl(I) concentration of 2μg / L, the material dosage was 0.1g / L, the initial pH value of the Tl(I) solution was 10, the reaction system was 40mL, the reaction time was 2h, and the pH change was recorded after the reaction. Then 10mL of the supernatant was filtered through a 0.22μm 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 and nitric acid with a concentration of 0.1M or 1M. The actual thallium concentration in the effluent was measured to be 0.05μg / L.

[0046] Example 4

[0047] This example provides potassium-modified TiO 2 Single factor test applied in thallium removal.

[0048] The thallium removal experiment was carried out on a constant temperature air bath shaker. The reaction temperature was controlled at room temperature (25°C) and the shaking speed was 250 r / min. 2 The 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, the reaction time was 2 h, and the pH change was recorded after the reaction. Then 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, and 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.

[0049] The removal rate (R, %) of Tl(I) by adsorbent is calculated by R = (C 0 -C e )×100 / C 0 Calculate. In the formula, C 0 is the initial concentration of Tl(I), μg / L; C e is the equilibrium concentration of Tl(I), μg / L.

[0050] The adsorption capacity of the adsorbent (q e , μg / g) by q e =(C 0 -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 potassium-modified TiO 2 Effect of Thallium Removal

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

[0053] Depend on Figure 1 It can be seen that at pH = 2, potassium modified TiO 2 The materials showed poor Tl(I) removal efficiency. As the initial pH ≥ 4, the potassium-modified TiO 2 The Tl(I) removal rate of the material showed a continuous improvement. When the pH value was 4-12, the removal efficiency was high, reaching more than 99.2%. Figure 2It can be seen that in the range of initial pH value of 2 to 3, the end point pH value has no significant change, and under other initial pH conditions, the end point pH value has a significant increase. This phenomenon is consistent with the corresponding removal efficiency trend, because the alkaline condition helps to increase the hydroxyl group on the adsorbent surface, resulting in Tl + Complexation occurs with the hydroxyl groups on the surface of the material, thereby increasing the material's resistance to Tl + The binding affinity.

[0054] 2. Thallium removal effects of different materials under different solution initial pH conditions

[0055] The pH of Tl(I) solution was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, respectively, and potassium-modified TiO 2 、TiO 2 The thallium removal effects of different materials were compared by reacting with biochar (BC). The effluent concentration of Tl(I) of different materials under different solution initial pH conditions is shown in Figure 3 shown.

[0056] Depend on Figure 3 It can be seen that when the pH value range is 2-9 and pH is 11, potassium-modified TiO 2 With TiO 2 There is a significant difference in the Tl(I) removal capacity between TiO2 and BC. 2 The overall performance was higher in removing Tl(I) and the effluent Tl(I) concentration was lower, which confirmed that the addition of TiO 2 Benefits of potassium modification. When pH ≥ 4, potassium modified TiO 2 The concentration of Tl(I) after adsorption was kept below 0.1 μg / L, while TiO 2 and BC adsorbents are difficult to reach this standard. 2 Combining potassium modification has the advantage of significantly improving the thallium removal effect.

[0057] 3. Effect of Tl(I) solutions with different constant pH values ​​on potassium-modified TiO 2 Effect of Thallium Removal

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

[0059] Depend on Figure 4 It can be seen that potassium-modified TiO 2 Isoelectric pH IEP When the pH value is higher than 2.4, the surface of the material is negatively charged, which enhances the + The electrostatic attraction of , therefore, the removal rate of Tl (I) is on the rise. Figure 5 It can be seen that in the reaction system with a constant pH value, when the pH value of the Tl(I) solution is maintained at 2, the potassium-modified TiO 2 The removal rate of Tl(I) was only 12.0±3.9%; when the pH value rose to 4, the removal rate increased slightly to 52.5±1.9%; when the pH value was ≥6, the removal efficiency increased significantly, and the removal efficiency was the highest at pH=10, reaching 97.3±0.5%, and the Tl(I) effluent concentration was only 0.06±0.009μg / L. Figure 6 It can be seen that the change in Tl(I) removal rate caused by pH change may be related to the type and valence state of the elements affected by ORP value. When pH < 4, Tl(I) solution is mainly composed of Tl + The ionic state exists, which leads to the reaction with a large amount of H + Compete for adsorption sites. At the same time, potassium modified TiO 2 TiO 2 TiOH 2 + The state exists, showing electrostatic repulsion (Formula 1), resulting in a decrease in the removal rate of Tl(I). When pH>4, TiO - The content of Tl increases (Formula 2), making it easier to adsorb Tl + , which leads to a gradual increase in the removal rate of Tl(I). Also, as the solution becomes alkaline, the removal of H + The competition of potassium-modified TiO 2 The increased number of negatively charged hydroxyl functional groups on the surface resulted in a removal efficiency of more than 90% at pH ≥ 6. Therefore, electrostatic adsorption and surface complexation mechanisms play a significant role in the potassium-modified TiO 2 It plays an important role in the removal of Tl(I).

[0060] ≡TiOH+H + →≡TiOH 2 + Formula 1;

[0061] ≡TiOH+OH - →≡TiO - +H 2 O formula 2.

[0062] 4. Potassium modified TiO 2 Effect of dosage on Tl(I) removal rate

[0063] Potassium modified TiO 2 The dosages were 0.05, 0.1, 0.2, 0.5, and 1 g / L, respectively. 2 Effect of dosage on Tl(I) removal rate Figure 7 As shown. Figure 7 It can be seen that potassium-modified TiO 2 The dosage of TiO2 was positively correlated with the removal rate of Tl(I). At a low adsorbent dosage of 0.05 g / L, the removal rate was 94.3 ± 0.2%, and the Tl(I) effluent concentration was 0.12 ± 0.004 μg / L, which may be due to the small amount of adsorbent material and the limited effective adsorption sites on the surface combined with Tl(I). When the dosage was increased to 0.1 g / L, the removal rate was significantly increased to 97.1 ± 0.4%, thereby reducing the Tl(I) effluent concentration to 0.06 ± 0.002 μg / L. The effect was even more significant when the adsorbent material dosage was 1 g / L, Tl(I) was almost completely removed, and the effluent concentration further dropped to 0.007 ± 0.0007 μg / L. It can be seen that potassium-modified TiO2 2 High efficiency in deep removal of trace amounts of Tl(I).

[0064] 5. Effect of initial concentration of Tl(I) on potassium-modified TiO 2 Effect of Thallium Removal

[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 concentrations of Tl(I) on the potassium-modified TiO 2 The effect of thallium removal is as follows: Figure 8 And as shown in Table 1.

[0066] Table 1: Effect of different initial concentrations of Tl(I) on potassium-modified TiO 2 Effect of adsorption capacity

[0067] Tl(I) initial concentration / (μg / L) Tl(I) adsorption capacity / (μg / 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] Depend on Figure 8 As shown in Table 1, with the increase of the initial concentration of Tl(I) in the solution, the potassium-modified TiO 2The effluent concentration showed an increasing trend. Although the removal rate decreased with the increase of the initial concentration, the overall effluent concentration was always kept below 25 μg / L. When the initial concentration of Tl(I) increased from 8.4 μg / L to 17.8 μg / L, the adsorption capacity increased significantly, from 58.4±0.5 μg / g to 113.7±2.8 μg / g. When the initial concentration of Tl(I) was 49.65 μg / L, the effluent Tl(I) concentration was 21.1±0.7 μg / L, the adsorption capacity reached 285.5±7.4 μg / g, and the removal rate was 57.5±1.5%. This experimental result shows that although the adsorption sites on the surface of the material are limited and the Tl(I) removal rate is relatively low when the initial concentration of Tl(I) is high, the adsorption capacity data show that the adsorbent material still has potential applicability when it comes to water samples with high Tl(I) pollution levels, and effective removal can be achieved by adjusting the material dosage or increasing the reaction time.

[0069] 6. Effect of cation interference on potassium-modified TiO 2 Effect of Thallium Removal

[0070] Set KNO separately 3 、NaNO 3 MgSO 4 The concentrations of 1, 10, 50, and 100 mM were used to investigate the effects of coexisting cations in the solution on the potassium-modified TiO 2 Effect of removing Tl(I) Fig. 9 ).

[0071] Depend on Fig. 9 It can be seen that when the concentration of interfering cations in the solution is low (1mM), the removal rate of Tl(I) does not change significantly. However, as the concentration of interfering cations in the solution is higher than 1mM, K + and Mg 2+ In potassium-modified TiO 2 Except Tl + The K + or Mg 2+ The higher the concentration of Tl + The lower the removal rate. + The removal efficiency was 98.6±0.05%, while when K + Mg 2+ When the concentration reached 100 mM, the removal rates decreased to 94.7 ± 0.2% and 91.2 ± 0.6%, respectively. This may be due to the fact that K + with Tl + The atomic radius of the MgO2 is similar, and they compete for adsorption sites, resulting in a decrease in removal efficiency. 2+ Ions are also higher than monovalent Tl +ions have a stronger competitive side effect. However, the presence of Na + When Tl + The effect on removal rate is the opposite, Na + The presence of potassium promotes the 2 In addition to Tl + Effect, when Na + When the concentration was 1 mM, the removal rate increased to 99.2 ± 0.3%. + As the concentration increases, its promoting effect slowly decreases. + When the concentration was 100 mM, the removal efficiency was 98.3 ± 0.4%, which was 0.3% lower than that of the blank control group. 2+ >K + >Na + Therefore, in the application of this adsorption material, Mg should be removed by alkaline precipitation or other methods in the pre-treatment step. 2+ Interference to achieve better Tl(I) removal effect.

[0072] Example 5

[0073] This example provides potassium-modified TiO 2 Adsorption kinetics, adsorption isotherms and mechanism analysis for Tl(I) removal.

[0074] 1. Potassium modified TiO 2 Adsorption kinetics and adsorption isotherms

[0075] Kinetic experiment: The volume of Tl(I) solution was 250 mL, the reaction time was 8 h, and 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 follows: Fig.10 The adsorption kinetic parameters are shown in Table 2.

[0076] The calculation formula of the pseudo-first-order kinetic model is:

[0077]

[0078] The calculation formula of the pseudo-second-order kinetic model is:

[0079]

[0080] In the formula, q e is the equilibrium adsorption capacity of the sample by the adsorbent, μg / g; q t is the adsorption amount of the sample by the adsorbent at time t, μg / g; t is the time, min; K 1 / (min -1 ), K 2 / (g / μg·min) are the pseudo-first-order kinetic constant and 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 isotherm models were used to fit the adsorption process. The adsorption isotherms are shown in Figure 2. Fig.11 The adsorption isotherm parameters are shown in Table 3.

[0082]

[0083]

[0084]

[0085] In the formula, q e and Q max are the equilibrium adsorption capacity and the maximum adsorption capacity, mg / g; C e is the equilibrium concentration of the adsorbate, mg / L; K L represents the Langmuir isotherm adsorption constant; K F and n represent the Freundlich adsorption isotherm constant; R is the universal gas constant, which is 8.314 J / mol·K; T represents the Kelvin temperature; b and K T Substitute for the Temkin constant, where the b value is related to the heat of adsorption.

[0086] Table 2: Potassium-modified TiO 2 Adsorption kinetic parameters of Tl(I)

[0087]

[0088] Table 3: Potassium-modified TiO 2 In addition to the adsorption isotherm parameters of Tl(I)

[0089]

[0090] Depend on Fig.10It can be seen that within the first 1 minute of the adsorption reaction, due to the high Tl(I) concentration gradient and a large number of active sites on the material surface, the adsorption amount of Tl(I) rapidly increased to 9.37±0.6μg / g. As time went on, due to the decrease in the Tl(I) concentration gradient and the reduction in the binding sites on the adsorbent, the adsorption amount continued to remain at a high level without significant changes, and the adsorption rate gradually slowed down, eventually reaching equilibrium in about 2 hours, with an equilibrium adsorption capacity of 19.53±1.2μg / g. As shown in Table 2, the R values ​​of the pseudo-first-order kinetic and pseudo-second-order kinetic models were 2 The values ​​are 0.934 and 0.936, respectively, indicating that both adsorption kinetic models can fit the adsorption process well, but the pseudo-second-order kinetic model is more suitable for representing the adsorption of potassium-modified TiO 2 The adsorption process of Tl(I) indicates that potassium-modified TiO 2 The adsorption mechanism of Tl(I) is mainly chemical adsorption.

[0091] Depend on Fig.11 It can be seen that at a lower initial Tl(I) concentration, the adsorption capacity increases rapidly with the increase of Tl(I) concentration. However, when the initial Tl(I) concentration is close to 200 mg / L, the growth rate of the adsorption capacity decreases significantly, which may be due to the limited binding sites on the adsorbent, but the potassium-modified TiO 2 The adsorption capacity of Tl(I) was greatly improved. When the initial concentration of Tl(I) was 1.12 mg / L, the adsorption capacity was 11.11±1.2 mg / g. Then, when the initial concentration of Tl(I) increased to 1045.45 mg / L, the adsorption capacity increased to 990.41±11.7 mg / g. As shown in Table 3, the R values ​​of the Langmuir, Freundlich and Temkin isotherm models are 2 The values ​​are 0.947, 0.985 and 0.898, respectively, indicating that the Freundlich model is most suitable for describing the potassium-modified TiO 2 The adsorption behavior of the adsorption process is more consistent with multilayer chemical adsorption and is a rapid adsorption process.

[0092] 2. Potassium modified TiO 2 Mechanism analysis of Tl(I) removal

[0093] According to the above experimental results, potassium-modified TiO 2 The mechanism of Tl(I) removal by adsorption materials can be divided into three main processes, such as Fig.12 The first process of its removal mechanism involves the interaction of Tl(I) with TiO 2 The second process is concentrated in the K-rich+ TiO 2 The surface, through ion exchange, forms -OK structure, which is due to Tl + and K + The ionic radii are similar, so an ion exchange reaction will occur, resulting in K + By Tl + The third process occurs under alkaline conditions, TiO 2 It mainly exists in the form of TiO-, which is beneficial to Tl + The electrostatic adsorption of ions on the surface of the composite material neutralizes the electronegativity of the material and forms Ti-O-Tl (Formula 4). A comprehensive analysis of the reaction mechanism clarifies the potassium-modified TiO 2 The material has multiple adsorption interactions that effectively remove 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 potassium-modified TiO 2 The recycling performance of materials.

[0099] The initial concentration of Tl(I) solution was 20 mg / L, and 5 adsorption-desorption cycles were set. Each adsorption or desorption time was 2 h. 0.1 M HNO 3 The adsorbent was desorbed to modify the TiO 2 The material's reusability is evaluated, and the evaluation results are as follows: Fig.13 shown.

[0100] Depend on Fig.13 It can be seen that using 0.1M HNO 3 The adsorbed material was desorbed by the solution. After five regeneration cycles, the removal efficiency of Tl(I) decreased from the initial 99.6±0.13% to 77.9±2.1%. This may be because the acid treatment during the regeneration process caused the potassium-modified TiO 2The chemical properties of the material surface changed, resulting in a decrease in the adsorption rate. However, in the first four cycles, the removal rate remained above 90%. This result shows that potassium-modified TiO 2 The adsorption performance can be kept stable for up to four cycles. In addition, the desorption efficiency shows an upward trend, increasing from 70.1±5.6% to 96.4±5.6% in five cycles. This observation indicates that HNO 3 The solution can be used as potassium-modified TiO 2 It has excellent applicability as a desorbent for Tl(I), and potassium-modified TiO 2 The material can be used as a regenerative adsorbent within a limited number of cycles and has certain application prospects.

[0101] Example 6

[0102] This example provides potassium-modified TiO 2 Application of materials in wastewater treatment.

[0103] The thallium-contaminated river water in a mining area in southwest China was used as the test object, and its water quality was referenced to the water quality parameters listed in the study of Liu et al. (Liu, Y., Huang, L., Xiong, Z., Zhang, W., Li, H., Liu, Y., Zheng, 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 TiO 2 (0.1 g / L) was used to investigate the removal effect of Tl(I) in thallium-contaminated river water under different initial pH conditions. The results are as follows Fig.14 Controlled potassium-modified TiO 2 The dosage was 0.05, 0.1, 0.2, 0.5, 1 g / L to treat the same volume of thallium-contaminated river water. The results are as follows: Fig.15 shown.

[0104] Depend on Fig.14 It can be seen that when potassium is used to modify TiO 2 When remediating thallium-contaminated river water, the initial pH value of 10 is the best. Therefore, potassium-modified TiO 2 In the actual treatment of wastewater, it is necessary to consider adjusting the pH value to between 8 and 10 to improve the treatment effect of wastewater. Fig.15 It can be seen that due to the presence of competitive impurity ions in the actual wastewater matrix, especially interfering cations such as Ca 2+ etc., compete with Tl(I) for adsorption sites, resulting in a lower removal rate than that in the experiment. 2 Increasing the dosage to 0.2 g / L can reduce the effluent Tl(I) concentration to below 0.1 μg / L, thus ensuring that it meets the prescribed water discharge standards.

[0105] As described above, the basic principle, main features and advantages of the present invention are well described. The above embodiments and descriptions are only descriptions of the preferred embodiments of the present invention, and the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the protection scope determined by the present invention.

Claims

1. Application of potassium-modified TiO2 in the treatment of thallium-containing wastewater, characterized in that: The dosage of the potassium-modified TiO2 is 0.1-1 g / L; The potassium-modified TiO2 is obtained by a potassium hydroxide precipitation method.

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

3. The use according to claim 1, characterized in that: The potassium-modified TiO2 uses titanium sulfate as a titanium source, and the concentration of the 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. Potassium hydroxide is added dropwise to the titanium sulfate solution at a pH of 7.0-9.

0. The potassium-modified TiO2 is obtained after washing with water and drying.

4. The use according to claim 3, characterized in that: The drying temperature is 45° C. and the drying time is 12 h.

5. The use according to claim 1, characterized in that: The potassium-modified TiO2 is applied to thallium-containing wastewater with a pH value of 4.0 to 12.

0.

6. The use according to claim 1, characterized in that: The potassium-modified TiO2 removes Tl from thallium-containing wastewater through inner sphere surface complexation, ion exchange and electrostatic adsorption. + .

7. The use according to claim 1, characterized in that: The potassium-modified TiO2 removes Tl from the thallium-containing wastewater. + The concentration dropped to below 0.1 μg / L.

8. A potassium-modified TiO2, characterized in that: The potassium-modified TiO2 is obtained by using titanium sulfate as a titanium source through a potassium hydroxide precipitation method; The concentration of potassium hydroxide in the potassium hydroxide precipitation method is 0.1-1.2 mol / L. Potassium hydroxide is added dropwise to the titanium sulfate solution at a pH of 7.0-9.

0. The potassium-modified TiO2 is obtained after washing with water and drying.

9. The potassium-modified TiO2 according to claim 8, characterized in that The drying temperature is 45° C. and the drying time is 12 h.

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