Ferrate composite coagulant and preparation method thereof

Abstract

The invention discloses a ferrate composite coagulant and a preparation method thereof, and the ferrate composite coagulant comprises the following components in percentage by mass: 5%-70% of ferrate, 5%-30% of ferric trichloride, 2%-20% of periodate, 5%-40% of beta-cyclodextrin and 1%-10% of alkaline auxiliary materials. The preparation method comprises the following steps: adding beta-cyclodextrin into a KOH solution, heating, adding ferrate, and carrying out primary inclusion to obtain an intermediate product; adding ferric trichloride, periodate and auxiliary materials into the intermediate product, and then adding into a heated saturated aqueous solution of beta-cyclodextrin for secondary inclusion. Periodate is adopted as a stabilizer, so that the ion concentration of decomposition reaction products such as K < + > can be increased, the decomposition reaction of ferrate is inhibited, and the stability of the solution is improved. The composite coagulant can be stably stored at normal temperature, is slowly and stably released in an aqueous solution, can keep high strength for a long time, and has good flocculation performance in water treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of water coagulation and clarification, and particularly relates to a ferrate composite coagulant and a preparation method thereof. Background Art

[0002] In winter in the northern regions of China, the seawater temperature is relatively low. When using conventional coagulation clarification or air flotation processes, the chemical dosage is large, the process flow is relatively complex, and the treatment effect is not ideal. Merely increasing the dosage of the coagulant cannot effectively improve the effluent quality to meet the requirements of the subsequent system inlet. Moreover, conventional coagulants cannot simultaneously remove suspended substances such as algae, organic matter, and colloids in the raw seawater, and additional bactericides need to be added.

[0003] Ferrate is a multifunctional green environmental protection water treatment agent in drinking water and wastewater treatment. Due to its high-efficiency oxidation, coagulation, disinfection, and sterilization capabilities, and the fact that it does not produce toxic and harmful substances, it has received extensive attention in the water treatment field. Because ferrate is greatly affected by pH value, temperature, and impurities in water, it has strong instability and is prone to decomposition and deterioration during storage, resulting in a low content of its active ingredients; after being prepared into an aqueous solution, due to the relatively fast reaction rate, the rapid failure of the reagent will occur, affecting the effect of the coagulation clarification reaction process, and it cannot fully play its role in the water treatment process, thus being restricted in application.

[0004] The chemical instability of ferrate is the core bottleneck restricting its large-scale promotion. Therefore, it is necessary to provide a ferrate composite coagulant that can be stably stored at room temperature and has good flocculation performance in water treatment. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a ferrate composite coagulant and a preparation method thereof, which can improve the storage stability of ferrate at room temperature. The ferrate composite coagulant can be stably stored at room temperature, slowly and stably release in an aqueous solution, can maintain a high strength for a long time, and has good flocculation performance in water treatment.

[0006] To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0007] A ferrate composite coagulant, by mass percentage, comprises 5% - 70% of ferrate, 5% - 30% of ferric chloride, 2% - 20% of periodate, 5% - 40% of β-cyclodextrin, and 1% - 10% of alkaline auxiliary materials.

[0008] Further, the ferrate is potassium ferrate or sodium ferrate.

[0009] Further, the periodate is sodium periodate or potassium periodate.

[0010] Further, the alkaline auxiliary material is calcium hydroxide or sodium hydroxide.

[0011] A preparation method of a ferrate composite coagulant includes the following steps:

[0012] 1) Add β-cyclodextrin into an aqueous KOH solution, heat until β-cyclodextrin is dissolved, then add ferrate for primary inclusion, cool, and dry to obtain an intermediate product;

[0013] 2) Add ferric chloride, periodate, and an alkaline auxiliary material to the intermediate product, mix evenly, and then add the mixture to a heated saturated aqueous solution of β-cyclodextrin for secondary inclusion, and dry to obtain the ferrate composite coagulant.

[0014] Further, the pH value of the aqueous KOH solution is 9 - 12.

[0015] Further, the heating temperature is 40°C - 50°C.

[0016] Further, the time for primary inclusion is 20 min - 60 min.

[0017] Further, drying is carried out under vacuum, the drying temperature is 40°C - 45°C, and the time is 4 h - 6 h.

[0018] Further, the mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1 - 1:1.5.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] A ferrate composite coagulant of the present invention is composed of ferrate (5% - 70%), ferric chloride (5% - 30%), periodate (2% - 20%), β-cyclodextrin (5% - 40%), and auxiliary material (1% - 10%). β-cyclodextrin can form a stable inclusion layer on the surface of ferrate to prevent ferrate from reacting with moisture and reducing components in the air; at the same time, it slowly releases the active components, reduces their reaction rate in the aqueous solution, can maintain effective dissolution for a long time, and improves their utilization efficiency in the coagulation process. Using periodate as a stabilizer can increase the ion concentration of reaction products such as K + and inhibit the decomposition reaction of ferrate, thereby improving the stability of the solution.

[0021] A kind of ferrate composite coagulant of the present invention is prepared by the double inclusion method of saturated alkali solution-saturated aqueous solution method. Since ferrate is more stable under alkaline conditions, β-cyclodextrin is dissolved in saturated alkali solution during the first inclusion, which can improve the recovery rate of ferrate. After the inclusion process is completed, by cooling and lowering the temperature, the inclusion compound of ferrate and β-cyclodextrin can precipitate, and the un-included ferrate and sodium hydroxide can be removed by washing and filtration. In addition, adding alkaline auxiliary materials to the coagulant can maintain the initial pH value of the solution to be alkaline and improve the coagulation reaction effect. Using this composite coagulant for the pretreatment of low-temperature and low-turbidity seawater can efficiently remove pollutants such as suspended solids, colloids, oils and algae in seawater simultaneously. The Fe 3+ hydrolysis products of ferrate produce a flocculation effect, making itself destabilized and removed by sedimentation. Moreover, ferrate has strong oxidizing properties, and after being compounded with ferric chloride, etc., obvious treatment effects can be achieved under the condition of lower dosage. Specific embodiments

[0022] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below through specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0023] A kind of ferrate composite coagulant of the present invention, calculated by mass percentage, the main components include ferrate (5% - 70%), ferric chloride (5% - 30%), periodate (2% - 20%), β-cyclodextrin (5% - 40%) and auxiliary materials (1% - 10%).

[0024] The ferrate composite coagulant is prepared by the saturated alkali solution-saturated aqueous solution method, and the specific preparation method is as follows:

[0025] Add β-cyclodextrin to the KOH aqueous solution with a pH value of 9 - 12, heat it to 40°C - 50°C, after β-cyclodextrin is fully dissolved, add ferrate at 40°C - 50°C, and use stirring or ultrasonic mixing to uniformly disperse ferrate for 20 min - 40 min, that is, perform the first inclusion. Then cool down, wash and filter, and vacuum dry in a vacuum drying oven at 40°C - 45°C for 4 h - 6 h to obtain an intermediate product.

[0026] A certain proportion of ferric chloride, periodate, and auxiliary materials are added to the intermediate product, mixed and ground evenly, and then added to a saturated aqueous solution of β-cyclodextrin at 40°C to 60°C. Stirring or ultrasonic mixing is used to make it evenly dispersed for 20 min to 60 min, then secondary inclusion is carried out, followed by cooling, washing with water, and vacuum drying in a vacuum drying oven at 40°C to 45°C for 4 h to 6 h. Finally, it is ground to obtain a ferrate composite coagulant for standby.

[0027] Among them, the ferrate can be a soluble salt such as potassium ferrate or sodium ferrate.

[0028] The periodate is a soluble salt such as sodium periodate or potassium periodate.

[0029] The auxiliary materials include alkaline substances such as calcium hydroxide or sodium hydroxide.

[0030] The following are specific examples.

[0031] Example 1

[0032] 1) The first inclusion process (saturated alkali solution method): The pH of the KOH aqueous solution is 10, and the mass ratio of β-cyclodextrin to ferrate (potassium ferrate) is 8:1. β-cyclodextrin is added to the KOH aqueous solution with a pH of 10, heated to 40°C, and after β-cyclodextrin is dissolved, ferrate (potassium ferrate) is added. An ultrasonic mixer is used to make the ferrate evenly dispersed, and the mixing time is 20 min. After complete cooling, vacuum drying in a vacuum drying oven at 40°C for 6 h, and grinding, an intermediate product is formed.

[0033] 2) The second inclusion process (saturated aqueous solution method): In this step, the mass ratio of β-cyclodextrin to the intermediate product is 8:1. Ferric chloride, periodate (sodium periodate), and auxiliary materials (sodium hydroxide) are added to the intermediate product, mixed and ground evenly, and then added to a saturated aqueous solution of β-cyclodextrin at 50°C. An ultrasonic mixer is used to make the ferrate evenly dispersed, and the mixing time is 45 min. After complete cooling and drying in a vacuum drying oven at 45°C for 5 h, it is ground to make a ferrate composite coagulant. In the ferrate composite coagulant, the mass percentage of ferrate is 40%, the mass percentage of ferric chloride is 20%, the mass percentage of periodate is 10%, the mass percentage of β-cyclodextrin is 20%, and the mass percentage of auxiliary materials is 10%.

[0034] Example 2

[0035] The difference between this example and Example 1 is that the pH of the KOH aqueous solution in the first inclusion process is 12, and other conditions and processes are exactly the same as those in Example 1.

[0036] Example 3

[0037] The difference between this example and Example 2 is that the mass ratio of β-cyclodextrin to ferrate in the first inclusion process is 10:1, and other conditions and processes are exactly the same as those in Example 2.

[0038] Example 4

[0039] The difference between this example and Example 3 is that the water bath heating temperature of β-cyclodextrin in the first inclusion process is 40°C, and other conditions and processes are exactly the same as those in Example 3.

[0040] Example 5

[0041] The difference between this example and Example 4 is that the mixing time of β-cyclodextrin and ferrate in the first inclusion process is 30 min, and other conditions and processes are exactly the same as those in Example 4.

[0042] Example 6

[0043] The difference between this example and Example 4 is that the mass ratio of β-cyclodextrin to ferrate in the second inclusion process is 10:1, and other conditions and processes are exactly the same as those in Example 4.

[0044] Example 7

[0045] The difference between this example and Example 6 is that the water bath heating temperature of β-cyclodextrin in the second inclusion process is 60°C, and other conditions and processes are exactly the same as those in Example 6.

[0046] Example 8

[0047] The difference between this example and Example 7 is that the mixing time of β-cyclodextrin and ferrate in the second inclusion process is 60 min, and other conditions and processes are exactly the same as those in Example 7.

[0048] Example 9

[0049] 1) Add β-cyclodextrin to a KOH aqueous solution with a pH of 9, heat to 40°C, and after β-cyclodextrin is fully dissolved, add ferrate (sodium ferrate) at 40°C. Use stirring or ultrasonic mixing to uniformly disperse ferrate (sodium ferrate) for 20 min, that is, perform the first inclusion. Then cool down, wash and filter with water, and vacuum dry in a vacuum drying oven at 40°C for 6 h to obtain an intermediate product.

[0050] 2) Add a certain proportion of ferric chloride, periodate (potassium periodate), and auxiliary material (calcium hydroxide) to the intermediate product, mix and grind evenly, then add it to a saturated aqueous solution of β-cyclodextrin at 40 °C, and use stirring or ultrasonic mixing to make it evenly dispersed for 50 min, that is, perform secondary inclusion. Cool, wash with water, vacuum dry in a vacuum drying oven at 40 °C for 6 h, and finally grind to obtain a ferrate composite coagulant. Among them, the mass percentage of ferrate is 5%, the mass percentage of ferric chloride is 30%, the mass percentage of periodate is 20%, the mass percentage of β-cyclodextrin is 40%, and the mass percentage of auxiliary material is 5%.

[0051] The mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1.5.

[0052] Example 10

[0053] 1) Add β-cyclodextrin to a KOH aqueous solution with a pH value of 10, heat to 50 °C, and after β-cyclodextrin is fully dissolved, add ferrate (potassium ferrate) at 50 °C, and use stirring or ultrasonic mixing to make ferrate (potassium ferrate) evenly dispersed for 40 min, that is, perform primary inclusion. Then cool down, wash with water and filter, and vacuum dry in a vacuum drying oven at 45 °C for 4 h to obtain an intermediate product.

[0054] 2) Add a certain proportion of ferric chloride, periodate (potassium periodate), and auxiliary material (calcium hydroxide) to the intermediate product, mix and grind evenly, then add it to a saturated aqueous solution of β-cyclodextrin at 50 °C, and use stirring or ultrasonic mixing to make it evenly dispersed for 40 min, that is, perform secondary inclusion. Cool, wash with water, vacuum dry in a vacuum drying oven at 45 °C for 4 h, and finally grind to obtain a ferrate composite coagulant. Among them, the mass percentage of ferrate is 70%, the mass percentage of ferric chloride is 13%, the mass percentage of periodate is 2%, the mass percentage of β-cyclodextrin is 5%, and the mass percentage of auxiliary material is 10%.

[0055] The mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1.

[0056] Example 11

[0057] 1) Add β-cyclodextrin to a KOH aqueous solution with a pH value of 11, heat to 45 °C, and after β-cyclodextrin is fully dissolved, add ferrate (potassium ferrate) at 45 °C, and use stirring or ultrasonic mixing to make ferrate (potassium ferrate) evenly dispersed for 30 min, that is, perform primary inclusion. Then cool down, wash with water and filter, and vacuum dry in a vacuum drying oven at 42 °C for 5 h to obtain an intermediate product.

[0058] 2) Add a certain proportion of ferric chloride, periodate (sodium periodate), and auxiliary materials (sodium hydroxide) to the intermediate product, mix and grind evenly, then add it to a saturated aqueous solution of β-cyclodextrin at 60 °C, and use stirring or ultrasonic mixing to disperse it evenly for 60 min, that is, perform secondary inclusion. Cool, wash with water, vacuum dry in a vacuum drying oven at 43 °C for 5 h, and finally grind to obtain a ferrate composite coagulant. Among them, the mass percentage of ferrate is 64%, the mass percentage of ferric chloride is 5%, the mass percentage of periodate is 10%, the mass percentage of β-cyclodextrin is 20%, and the mass percentage of auxiliary materials is 1%.

[0059] The mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1.2.

[0060] Example 12

[0061] 1) Add β-cyclodextrin to a KOH aqueous solution with a pH value of 12, heat to 50 °C, and after β-cyclodextrin is fully dissolved, add ferrate (sodium ferrate) at 50 °C, and use stirring or ultrasonic mixing to disperse ferrate (sodium ferrate) evenly. Vacuum dry at 45 °C for 4 h to obtain an intermediate product.

[0062] 2) Add a certain proportion of ferric chloride, periodate (sodium periodate) salt, and auxiliary materials (sodium hydroxide) to the intermediate product, mix and grind evenly, then add it to a saturated aqueous solution of β-cyclodextrin at 45 °C, and use stirring or ultrasonic mixing to disperse it evenly for 20 min, that is, perform secondary inclusion. Cool, wash with water, vacuum dry in a vacuum drying oven at 40 °C for 5 h, and finally grind to obtain a ferrate composite coagulant. Among them, the mass percentage of ferrate is 27%, the mass percentage of ferric chloride is 20%, the mass percentage of periodate is 15%, the mass percentage of β-cyclodextrin is 30%, and the mass percentage of auxiliary materials is 8%.

[0063] The mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1.4.

[0064] Active component detection:

[0065] Perform active component detection on the ferrate composite coagulant prepared in the above examples. The specific steps are as follows:

[0066] Take a certain amount of the prepared ferrate composite coagulant and put it into a beaker containing 25 ml of a KOH aqueous solution with a concentration of 6 mol / L. When the composite ferrate no longer dissolves under ultrasonic treatment, absorb the supernatant and measure the absorbance at 505 nm. Calculate the total dissolution mass concentration of the active ingredients in the composite potassium ferrate material according to the absorbance, and calculate the recovery rate of the active components. The results are shown in Table 1.

[0067] The results show that the ferrate composite coagulant prepared in Examples 1 - 12 of the present invention has a relatively high recovery rate of active components, and the recovery rate of active components is in the range of 74% - 93%.

[0068] Detection of release rate:

[0069] At room temperature (20 °C), the ferrate composite coagulant prepared in the above examples was dissolved in water for the detection of the 30 - minute release rate, including:

[0070] Take 0.1 g of the ferrate composite coagulant prepared in Examples 1 - 12, add it to 200 mL of water. After 30 minutes, dissolve the medicament in 200 mL of KOH aqueous solution with a concentration of 6 mol / L, and measure the content of the active component of ferrate in the remaining substance at a wavelength of 510 nm by an ultraviolet spectrophotometer, and take the average value. The results are shown in Table 1 for details.

[0071] The results show that the ferrate composite coagulant prepared in Examples 1 - 8 of the present invention has a release rate of more than 90% in 30 minutes, and the average release rate is 95%, which meets the coagulation time in a conventional coagulation sedimentation tank (considering the medicament configuration and transportation time).

[0072] Stability detection:

[0073] The ferrate composite coagulant prepared in Examples 1 - 12 above was subjected to stability detection, including:

[0074] The ferrate composite coagulants of Examples 1 - 12 were exposed to air at 25 °C, and then the content of the active ferrate component in the ferrate composite coagulant was measured after 30 days. Take three portions of the ferrate composite coagulant with the same mass and place them under the same environmental conditions. After 30 days, dissolve the medicament in 200 mL of KOH aqueous solution with a concentration of 6 mol / L, and measure the content of the active component of ferrate in the remaining substance at a wavelength of 510 nm by an ultraviolet spectrophotometer, and calculate the percentage of the remaining active substance. The results are shown in Table 1 for details.

[0075] The results show that the ferrate composite coagulant prepared in Examples 1 - 12 of the present invention has good stability at room temperature, and the percentage of the remaining active substance after 30 days is in the range of 80% - 85%.

[0076] Table 1 Performance test results of ferrate composite coagulants prepared under different conditions

[0077]

[0078]

[0079] Test on the coagulation and clarification effect of ferrate prepared in Examples 1 - 8 of the present invention on low - temperature and low - turbidity water:

[0080] The water used in the coagulation and clarification beaker test is the seawater in Jiaozhou Bay, Shandong Province. In winter, the seawater temperature is between - 7°C and 5°C, and the turbidity of the original seawater is below 1 NTU, with an average value of 0.62 NTU, belonging to typical low - temperature and low - turbidity water. The ferrate composite coagulant prepared by this method is used to conduct a coagulation and clarification beaker experiment on the original seawater with a six - joint electric stirring device.

[0081] Add 1000 mL of test water (control the water temperature at 0°C through an ice - water bath) to the beaker; place the beaker under the six - joint stirrer, and add 0.5 mg / L, 1 mg / L, 2 mg / L, and 5 mg / L of the ferrate composite coagulant prepared in Example 8 respectively. Stir rapidly at a high speed (250 r / min) for 2 min to fully mix the reagent with the colloidal particles in the wastewater; then stir at a medium speed (150 r / min) for 2 min to start forming fine flocculent alum flowers; finally, stir slowly at a low speed (60 r / min) for 5 min to further form larger flocs. After the stirring is completed, let it stand for 30 min, take samples at 2 cm below the water surface, and measure the turbidity, COD, and TOC of the effluent. See Table 2 below.

[0082] According to the results in Table 2, it can be seen that the ferrate prepared in the examples of the present invention has a good coagulation and clarification effect on low - temperature and low - turbidity water and can effectively remove suspended solids and organic substances such as colloids in water. When the dosage of the reagent is 0.5 mg / L, the turbidity removal rate is 64.52%, the COD removal rate is 48.51%, and the TOC removal rate is 39.47%; when the dosage is increased to 5 mg / L, the turbidity removal rate is 80.65%, the COD removal rate is 65.11%, and the TOC removal rate is 60.90%. It can be seen that with the increase of the dosage, the removal effect on pollutants is further improved.

[0083] Table 2 Seawater quality before and after the coagulation experiment

[0084]

[0085] The present invention is prepared by the double - inclusion method of saturated alkali solution - saturated aqueous solution method and has a high recovery rate. β - cyclodextrin can form a stable inclusion layer on the surface of ferrate, preventing ferrate from reacting with moisture and reducing components in the air; at the same time, it slowly releases the active components, reduces its reaction rate in aqueous solution, can maintain effective dissolution for a long time, and improves its utilization efficiency in the coagulation process.

[0086] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

[0087] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A ferrate composite coagulant, characterized in that, By mass percentage, it includes 5% - 70% of ferrate, 5% - 30% of ferric chloride, 2% - 20% of periodate, 5% - 40% of β-cyclodextrin, and 1% - 10% of alkaline auxiliary materials.

2. The ferrate composite coagulant according to claim 1, wherein The ferrate is potassium ferrate or sodium ferrate.

3. The ferrate composite coagulant according to claim 1, characterized in that, The periodate is sodium periodate or potassium periodate.

4. The ferrate composite coagulant according to claim 1, characterized in that, The alkaline auxiliary material is calcium hydroxide or sodium hydroxide.

5. A preparation method of a ferrate composite coagulant according to any one of claims 1-4, characterized in that, It includes the following steps: 1) Add β-cyclodextrin into the KOH aqueous solution. After heating until β-cyclodextrin is dissolved, add ferrate for the first inclusion, cool, and dry to obtain an intermediate product. 2) Add ferric chloride, periodate, and alkaline auxiliary materials to the intermediate product, mix evenly, and then add it to the heated saturated aqueous solution of β-cyclodextrin for the second inclusion, and dry to obtain the ferrate composite coagulant.

6. The preparation method of the ferrate composite coagulant according to claim 5, characterized in that The pH value of the KOH aqueous solution is 9 - 12.

7. The preparation method of the ferrate composite coagulant according to claim 5, characterized in that, The heating temperature is 40°C - 50°C.

8. The preparation method of the ferrate composite coagulant according to claim 5, characterized in that, The time for the first inclusion and the second inclusion is 20 min - 60 min.

9. The preparation method of the ferrate composite coagulant according to claim 5, characterized in that, Drying is carried out under vacuum, the drying temperature is 40°C - 45°C, and the time is 4 h - 6 h.

10. The preparation method of the ferrate composite coagulant according to claim 5, characterized in that, The mass ratio of β-cyclodextrin in step 1) to β-cyclodextrin in step 2) is 1:1 - 1:1.5.

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