A method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate

Abstract

The present invention discloses a method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate, belonging to the technical field of sewage treatment. The steps of the above method are as follows: (1) Dissolve ferrate in buffer A to obtain a Fe(VI) solution; (2) Add the Fe(VI) solution and silver oxide into buffer B containing phenolic compounds for a degradation reaction; (3) After the reaction is completed, add a quenching agent to terminate the reaction to obtain a reaction solution, adjust the pH value of the reaction solution to precipitate silver oxide in the reaction solution, and obtain recyclable silver oxide after centrifugation. In order to solve the technical problems that in the existing oxidation solution system of single ferrate, the oxidant is prone to rapid self-decomposition, resulting in high utilization rate and low pollutant degradation rate, the present invention increases the oxidizing property and stability of the system by adding silver oxide outside the ferrate pollutant degradation system to achieve efficient degradation of pollutants, and at the same time realizes the recycling of silver oxide through pH adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate. Background Art

[0002] Phenolic pollutants are the most common organic pollutants in industrial wastewater from various industries, such as petrochemical, coke oven, coal mine, oil refining, pharmaceutical, and textile industries, and their contents vary from 0.1 to 1600 mg / L. Phenolic compounds have been detected in lakes, surface water, and the effluent of sewage treatment plants. These phenols are soluble in water and have stable structures. They can enter the human body through skin contact, drinking water, and food intake. They have endocrine-disrupting properties, genotoxicity, neurotoxicity, can damage active metabolites in cells, resulting in mutagenicity and carcinogenicity, etc., causing great harm to human health and the ecological environment. Among them, bisphenol B (2,2-bis(4-hydroxyphenyl)butane, BPB) has been developed and widely used in the manufacture of epoxy resins, tin coatings, and dental composites. With the increase in its use, BPB has been frequently detected in environmental samples such as sewage, sludge, and human urine, and has even been observed in human dietary exposures, thus becoming an emerging phenolic pollutant. As a model compound, the degradation process of BPB can represent the removal of a series of phenols and is typical.

[0003] Ferrate (Fe(VI)), as a new type of green oxidant, has received extensive attention due to its high oxidation ability and excellent chemical properties. Fe(VI) can remove organic pollutants (aliphatic sulfur, amino acids, organic nitrogen compounds, phenols) and inorganic pollutants (cyanides, ammonia, hydroxylamine, hydrogen sulfide, etc.) in the water environment, and at the same time has the functions of flocculation, sterilization, and removal of suspended / colloidal materials. It has been reported that Fe(VI) shows great potential in oxidizing antibiotics, estrogens, and other organic pollutants. However, due to the easy and rapid self-decomposition of Fe(VI) in aqueous solution and poor degradation rate at low doses, its low utilization efficiency remains one of its biggest disadvantages. Summary of the Invention

[0004] Object of the Invention: To solve the technical problems existing in the prior art, the present invention aims to provide a method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate with high oxidant utilization rate and high degradation efficiency.

[0005] Technical Solution: The method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate according to the present invention includes the following steps:

[0006] (1) Dissolve ferrate in buffer solution A to obtain a Fe(VI) solution;

[0007] (2) Add an Fe(VI) solution and silver oxide to buffer B containing phenolic compounds for a degradation reaction.

[0008] Further, in step (1), the ferrate is potassium ferrate or sodium ferrate, preferably potassium ferrate.

[0009] Further, in step (1), the pH of buffer A is 9.0 - 11.0, preferably 9.0; buffer A is obtained by compounding a borax buffer and a phosphate buffer, wherein the concentration of the borax buffer is 0.1 - 2.0 mmol / L and the concentration of the phosphate buffer is 0.5 - 11.0 mmol / L; the phosphate is dipotassium hydrogen phosphate. Dissolving the ferrate in buffer A can inhibit the self-decomposition of K2FeO4 to prevent attenuation of the oxidant activity.

[0010] Further, in step (2), the concentration of the phenolic compound in buffer B is 10 - 100 μmol / L.

[0011] Further, in step (2), the pH value of buffer B is 7 - 10; buffer B is a boric acid buffer, and the concentration of the boric acid buffer is 10 - 20 mmol / L, preferably 10 mmol / L; the boric acid buffer is prepared by mixing a boric acid solution and a sodium tetraborate solution.

[0012] Further, in step (2), the concentration of silver oxide in buffer B is 0.5 - 3.0 mmol / L, preferably 2.0 mmol / L; the concentration of the ferrate in the Fe(VI) solution is 1 - 100 times the concentration of the phenolic compound in buffer B.

[0013] Further, in step (2), the conditions of the degradation reaction are: the reaction temperature is 20 - 30 °C and the reaction time is 10 - 100 s.

[0014] Further, the steps also include: (3) After the reaction, add a quenching agent to terminate the reaction to obtain a reaction solution, adjust the pH value of the reaction solution to precipitate silver oxide in the reaction solution, and obtain recyclable silver oxide after centrifugation.

[0015] Further, the quenching agent is Na2S2O3 and methanol; the pH value of the reaction solution is 9.5 - 12.0.

[0016] Further, the phenolic compounds include bisphenolic compounds, benzophenone compounds, and chlorophenolic compounds.

[0017] Principle of the invention: In the prior art, under a single oxidation system of ferrate, the oxidant has the drawback of rapid self-decomposition, resulting in low utilization rate of the oxidant and insufficient oxidation ability of low-dose ferrate. Silver oxide (Ag2O) is the most common and thermodynamically most stable form of silver. When Ag2O exists in a solution, Ag2O reacts with Fe(VI) to generate silver peroxide (AgO) with stronger oxidation ability, which can rapidly oxidize pollutants and improve the removal rate. During this process, AgO itself is reduced to Ag2O by the pollutants, and finally Ag2O plays a role in catalyzing the degradation of Fe(VI). The AgO formed by silver oxide in a strong oxidation system not only has strong oxidizing properties but also has special bactericidal properties, and can be used as a multifunctional active substance to efficiently strengthen the treatment of wastewater containing pollutants. Therefore, the Fe(VI)-Ag2O system in the present invention is an efficient and green method for removing phenolic pollutants. Ag2O can effectively improve the utilization rate of Fe(VI), and at the same time has excellent recycling performance and good bactericidal effect, and provides a new strategy for treating other organic pollutants such as antibiotics and estrogens, inorganic pollutants such as cyanides, ammonia, hydroxylamine, and hydrogen sulfide, and sterilization.

[0018] In addition, the active species AgO generated by the silver oxide-ferrate system has bactericidal efficacy, and ferrate is currently also applied to disinfection treatment. Therefore, the nano silver oxide-ferrate system also has the potential function of sterilization and disinfection.

[0019] Advantageous effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0020] (1) In the method for efficiently degrading phenolic compounds by nano silver oxide catalyzing ferrate of the present invention, while the Ag2O nanoparticles synergistically degrade phenolic pollutants with Fe(VI), they also have good recyclability, solving the problem that ordinary reducing activators are difficult to recover.

[0021] (2) In the method for efficiently degrading phenolic compounds by nano silver oxide catalyzing ferrate of the present invention, a new active oxidant AgO is generated during the activation process. In-situ electrochemical analysis and identification of active substances confirm that Fe(VI) can oxidize Ag2O to generate AgO with a higher electrode potential to oxidize pollutants, thereby promoting the degradation of pollutants. At the same time, AgO is reduced back to Ag2O, and the oxidation performance is improved compared with the single Fe(VI) system.

[0022] (3) In the method for efficiently degrading environmental pollutants by nano silver oxide catalyzing ferrate of the present invention, Ag2O has excellent bactericidal effect, providing an additional advantage for wastewater treatment. Description of the drawings

[0023] Figure 1It is a bar chart of the utilization rate of Fe(VI) (i.e., the reaction stoichiometric efficiency) in the Fe(VI) single system in Comparative Example 1 and the Fe(VI)-Ag2O system in Example 1 of the present invention;

[0024] Figure 2 It is a kinetic curve of the degradation of BPB by the Fe(VI)-Ag2O system at different Ag2O concentrations in Example 2 of the present invention;

[0025] Figure 3 It is a kinetic curve of the degradation of BPB by the Fe(VI)-Ag2O system at different pH values in Example 3 of the present invention;

[0026] Figure 4 It is a kinetic curve of the degradation of BPB by the Fe(VI)-Ag2O system with the nano-Ag2O material recycled 5 times in Example 5 of the present invention. Detailed implementation mode

[0027] Next, the present invention will be further described in conjunction with specific examples and drawings.

[0028] Example 1: The method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate according to the present invention includes the following steps:

[0029] (1) At room temperature, 0.1059 g of K2FeO4 powder is dissolved in 4 mL of 1.0 mmol·L -1 borax / 5.0 mmol·L -1 potassium hydrogen phosphate buffer solution (pH = 9.0) to prepare an Fe(VI) solution. This process can inhibit the self-decomposition of K2FeO4 to prevent the attenuation of the oxidant activity;

[0030] (2) Quickly take 100 μL of the prepared Fe(VI) solution and add it to 40 mL of 20 mmol·L -1 containing 10.0 μmol·L - 1 BPB and 2.0 mmol·L -1 Ag2O boric acid buffer solution (BBS). The boric acid buffer solution is prepared by mixing 20 mmol·L -1 boric acid solution and 5 mmol·L -1 sodium tetraborate solution in a ratio of 7:3. Continuously stir magnetically and carry out the degradation reaction at 20 °C, maintaining the pH value at 8.0;

[0031] (3) At reaction times of 0 s, 10 s, 20 s, 30 s, 60 s, 180 s, and 300 s respectively, transfer 1.0 mL of the solution in step (2) to a pre-added 0.1 mL of Na2S2O3 (0.2 mol·L -1In a centrifuge tube containing

[0032] (4) After centrifuging the sample to remove solid particles, transfer it to a brown HPLC vial for analysis.

[0033] All tests were carried out in triplicate. The K2FeO4 powder and Ag2O nanoparticles used were both commercially purchased products.

[0034] Comparative Example 1: The difference from Example 1 is that: Ag2O is not added in step (2).

[0035] The analysis results of the Fe(VI)-Ag2O system used in Example 1 and the Fe(VI) alone system used in Comparative Example 1 are shown in Table 1. It can be seen from Table 1 that the degradation efficiency of the Fe(VI)-Ag2O system for BPB in Example 1 can reach 98.6%, which is significantly better than the degradation efficiency of only 69.1% of the Fe(VI) alone system for BPB in Comparative Example 1, and the second-order reaction kinetic rate constant value of the Fe(VI)-Ag2O system is 370.21 mol -1 s -1 , relative to the rate constant of the Fe(VI) alone system (41.72 mol -1 s -1 ) is increased by about 9 times.

[0036] Table 1 Comparison of the degradation effects of the Fe(VI)-Ag2O system in Example 1 and the Fe(VI) alone system in Comparative Example 1 after reacting for 300 s

[0037]

[0038] In addition, to compare the utilization rates of Fe(VI) in the two reaction systems, the present invention calculated the reaction stoichiometric efficiency (RSE) of the Fe(VI)-Ag2O system and the Fe(VI) alone system, that is, the ratio of the degraded concentration of the organic matter to the consumed Fe(VI) concentration within a certain period of time. The specific test results are as Figure 1 shown. It can be seen from the figure that the Fe(VI)-Ag2O system is higher than the Fe(VI) system, which indicates that the addition of Ag2O increases the utilization rate of Fe(VI) by 2-3 times and promotes the removal of BPB in the Fe(VI)-Ag2O system.

[0039] Example 2: The difference from Example 1 is that: in step (2), the concentration of Ag2O is 0.1 mmol·L -1 .

[0040] Example 3: The difference from Example 1 is that in step (2), the concentration of Ag2O is 0.5 mmol·L -1 .

[0041] Example 4: The difference from Example 1 is that in step (2), the concentration of Ag2O is 1.0 mmol·L -1 .

[0042] In Example 2, the concentration of nano-Ag2O is 0.1 mmol·L -1 , the concentration of Fe(VI) is 100 μmol·L -1 , and the degradation efficiency of BPB is 78.2%. In addition, in Example 3 and Example 4, the concentrations of Ag2O nanoparticles are set to 0.5 mmol·L -1 and 1.0 mmol·L -1 respectively. Examples 1-4 and Comparative Example 1 compared the influence of catalyst concentration on catalytic performance, and the degradation curve is as shown in Figure 2 . It can be seen from the figure that as the dosage of Ag2O increases from 0 mmol·L -1 to 1 mmol·L -1 , the degradation efficiency of BPB increases from 69.2% to 98.6%. The increase in the concentration of Ag2O enhances the oxidation of BPB by Fe(VI). The preferred dosages of Ag2O are 1 mmol·L -1 and 2 mmol·L -1 . The specific degradation performance comparison data of the Fe(VI)-Ag2O system under different dosages of nano-silver oxide are listed in Table 2.

[0043] Table 2 Degradation performance of Fe(VI)-Ag2O system under different dosages of nano-silver oxide

[0044]

[0045] Example 5: The difference from Example 3 is that in step (2), the pH is maintained at 7.0.

[0046] Example 6: The difference from Example 3 is that in step (2), the pH is maintained at 9.0.

[0047] Example 7: The difference from Example 3 is that in step (2), the pH is maintained at 10.0.

[0048] In Example 5, the pH is 7.0, and a relatively low concentration of Ag2O (0.5 mmol·L -1), A lower catalyst dosage is more conducive to comparing the effect of pH on the degradation performance of the Fe(VI)-Ag2O system. When pH = 7.0, the degradation rate of BPB is about 80%. In addition, keeping other conditions unchanged, the pH is set to 8.0, 9.0, and 10.0 respectively, and the degradation rate of BPB fluctuates within the range of 80% - 90%. The degradation efficiencies of the Fe(VI)-Ag2O system at different pH values involved in this example are listed in Table 3, and the specific degradation curve is as shown in Figure 3 shown. As can be seen from Figure 3 , in neutral and alkaline conditions (pH = 7.0 - 10.0), the Fe(VI)-Ag2O oxidation system has excellent degradation efficiency, effectively improving the defect that the oxidation activity of ferrate almost disappears under alkaline conditions.

[0049] Table 3 Degradation performance of Fe(VI)-Ag2O system under different pH conditions

[0050]

[0051] Example 8: The same as Example 1, replace the pollutant BPB with benzophenone-1 of the same concentration, and keep the other conditions unchanged. The degradation efficiency of the Fe(VI)-Ag2O system can reach 93.1% within 5 minutes of reaction time. In addition, under the same reaction conditions, the Fe(VI)-Ag2O system is used to treat a large number of pollutants as target pollutants, including bisphenols, benzophenones, chlorophenols and other phenolic pollutants. As shown in Table 4, good degradation effects can be achieved.

[0052] Table 4 Degradation performance of Fe(VI)-Ag2O system on different phenolic pollutants

[0053]

[0054]

[0055] Example 9: Recycle the nano-Ag2O material and compare the degradation effects. The steps are as follows:

[0056] (1) At room temperature, dissolve 0.1059 g of K2FeO4 powder in 4 mL of 1.0 mol·L -1 borax / 5.0 mol·L -1 dipotassium hydrogen phosphate buffer solution (pH = 9.0) to prepare an Fe(VI) solution;

[0057] (2) Quickly take 100 μL of the prepared Fe(VI) solution and add it to 40 mL of 20 mmol·L containing 10.0 μmol·L -1 BPB and 2.0 mmol·L - 1 Ag2O-1 In boric acid buffer solution (BBS), continuous magnetic stirring was carried out, and the degradation reaction was carried out at 20 °C while maintaining the pH value at 8.0;

[0058] (3) At reaction times of 0 s, 10 s, 20 s, 30 s, 60 s, 180 s, and 300 s respectively, 1.0 mL of the solution in step (2) was pipetted into a centrifuge tube pre-added with 0.1 mL of Na2S2O3 (0.2 mol·L -1 ), and 0.3 mL of methanol to quench the reaction and simultaneously desorb the organic matter captured on the solid particles;

[0059] (4) After the sample was centrifuged to remove solid particles, it was transferred to a brown HPLC vial for analysis;

[0060] (5) After the reaction ended, the pH of the solution was adjusted to 9.5 - 12.0 to promote the rapid precipitation of Ag2O from the solution, and the regenerated Ag2O was obtained by centrifugation for recycling;

[0061] (6) Using the nano-Ag2O recovered in step (5) as the catalytic material, steps (1)-(5) were repeated, and the nano-Ag2O material was recycled five times in total.

[0062] Figure 4 is the curve of the change of BPB degradation with time for the nano-Ag2O material in the Fe(VI)-Ag2O system after 5 cycles. It can be seen from Figure 4 that after 5 cycle experiments, the degradation efficiency of BPB remained basically unchanged, all greater than 99%, indicating that the nano-Ag2O material has good reusability.

[0063] Comparative Example 2: The difference from Example 1 is that in step (2), copper oxide was used to replace silver oxide.

[0064] Comparative Example 3: The difference from Example 1 is that in step (2), manganese dioxide was used to replace silver oxide.

[0065] Comparative Example 4: The difference from Example 1 is that in step (2), iron tetroxide was used to replace silver oxide.

[0066] Comparative Example 5: The difference from Example 1 is that in step (2), silver oxide was used to replace silver oxide. The data of the effects of using different transition metal oxides to activate Fe(VI) to degrade BPB in Comparative Examples 2 - 5 are shown in Table 5.

[0067] Table 5 Comparison table of the effects of common transition metal oxides activating Fe(VI) to degrade BPB

[0068]

[0069] Reaction conditions: metal oxide concentration = 2 mmol·L -1 , [Fe(VI)] = 30 μmol·L -1 , [BPB] = 10 μmol·L -1 , temperature = 20 °C.

[0070] As can be seen from Table 5, the Ag2O material has a unique catalytic effect on Fe(VI), which is due to the formation of active AgO species, while other common transition metal oxides have no significant effect.

Claims

1. A method for efficiently degrading phenolic compounds by using silver oxide to catalyze ferrate, which is characterized in that It includes the following steps: (1) Dissolve ferrate in buffer A to obtain a Fe(VI) solution; (2) Add the Fe(VI) solution and silver oxide into buffer B containing phenolic compounds for a degradation reaction.

2. The method according to claim 1, wherein In step (1), the ferrate is potassium ferrate or sodium ferrate.

3. The method according to claim 1, wherein In step (1), the pH of buffer A is 9.0 - 11.0; buffer A is prepared by compounding borax buffer and phosphate buffer, wherein the concentration of borax buffer is 0.1 - 2.0 mmol / L, and the concentration of phosphate buffer is 0.5 - 11.0 mmol / L.

4. The method according to claim 1, characterized in that In step (2), the concentration of phenolic compounds in buffer B is 10 - 100 μmol / L.

5. The method according to claim 1, characterized in that In step (2), the pH value of buffer B is 7 - 10; buffer B is boric acid buffer, and the concentration of boric acid buffer is 10 - 20 mmol / L.

6. The method according to claim 1, wherein In step (2), the concentration of silver oxide in buffer B is 0.5 - 3.0 mmol / L; the concentration of ferrate in the Fe(VI) solution is 1 - 100 times the concentration of phenolic compounds in buffer B.

7. The method according to claim 1, characterized in that, In step (2), the conditions for the degradation reaction are: the reaction temperature is 20 - 30 °C, and the reaction time is 10 - 100 s.

8. The method according to claim 1, characterized in that, The said steps further include: (3) After the reaction ends, add a quenching agent to terminate the reaction to obtain a reaction solution, adjust the pH value of the reaction solution to precipitate silver oxide in the reaction solution, and obtain recyclable silver oxide after centrifugation.

9. The method according to claim 8, wherein The pH value of the reaction solution is 9.5 - 12.

0.

10. The method according to claim 1, characterized in that, The phenolic compounds include bisphenolic compounds, benzophenone compounds, and chlorophenolic compounds.

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