A method for rapidly degrading phenol in phenol-containing wastewater by using iron

Abstract

The application relates to the technical field of wastewater treatment, and discloses a method for rapidly degrading phenol by using iron in phenol-containing wastewater, wherein safe and nontoxic cysteine is selected as a reaction initiator, and meanwhile, reduction and complexation are realized, so that the reaction is rapidly started, and the pH range of a traditional Fenton reaction is widened; Cu 2+ is selected as a reaction intensifier, Fe 3+ / Fe 2+ circulation is accelerated, phenol is rapidly degraded, and the degradation of other organic pollutants is synergistically improved; without preparing and adding complex and high-cost iron-containing activators, a small amount of iron contained in the wastewater is used as a Fe 2+ source, and recycling is formed in the system, so that the pollutant removal speed is greatly improved, and the generation of iron sludge is reduced. The technology has the advantages of being green, efficient, simple to operate and low in cost.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for rapidly degrading phenol using iron in phenol-containing wastewater. Background Technology

[0002] Industries such as chemical engineering, pharmaceuticals, and chemical synthesis generate large amounts of phenol-containing wastewater. Phenolic pollutants are highly toxic, and their untreated discharge into the natural world can seriously harm ecosystems and threaten human health. Therefore, developing efficient and low-cost phenol-containing wastewater treatment technologies is essential. Currently, phenol-containing wastewater treatment technologies mainly fall into three categories: physical, chemical, and biological methods. Among these, chemical oxidation methods offer advantages such as fast treatment rates and high feasibility. The most widely used chemical oxidation treatment method is Fenton oxidation technology based on H2O2. Although H2O2 itself has strong oxidizing properties, it is still difficult to directly oxidize and degrade recalcitrant organic compounds such as phenols. Therefore, an activator is often added to generate highly oxidizing hydroxyl radicals (HO·), which oxidize and degrade phenolic compounds in the water into smaller organic molecules or mineralize them into carbon dioxide and water. The main active ingredient in various activators currently used is generally iron ions or iron-containing compounds, with Fe being the activating agent. 2+ .

[0003] Patent CN113845201B discloses a method for treating phenol-containing wastewater by activating H2O2 with a Si-Fe / γ-Al2O3 activator, achieving relatively good treatment results. This method uses Si as a co-catalyst, Fe as the active component, and γ-Al2O3 as a support to prepare the catalyst. The preparation process requires crushing, high-temperature calcination, and stirring, making it complex, requiring many types of raw materials, and consuming a lot of energy. This significantly increases the difficulty of implementation and operating costs, hindering the widespread adoption of the technology. Patent CN111068641B discloses a method for treating phenol-containing wastewater by activating H2O2 with a bio-activator composed of CeO2, Fe2O3, CuO, MnO2, and precious metals, solving the problem of low COD degradation efficiency in existing activators. However, the preparation of this activator requires drying, calcination at different temperatures, and the addition of precious metals such as Ru, Au, and Pt, also resulting in a complex process and high cost.

[0004] Iron, the fourth most abundant element in the Earth's crust, is widely found in nature and water bodies. Furthermore, iron readily undergoes redox reactions and is widely used in water treatment processes. Utilizing iron in phenol-containing wastewater to treat phenolic compounds has practical application value in reducing costs and increasing efficiency in wastewater treatment. Summary of the Invention

[0005] Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for the rapid degradation of phenol using iron in phenol-containing wastewater. The method utilizes the Fe in the phenol-containing wastewater... 3+ The activated H2O2 reaction can significantly improve the treatment rate of phenol-containing wastewater without the need for additional iron-containing activators.

[0007] Technical solution

[0008] A method for rapidly degrading phenol using iron in phenol-containing wastewater includes the following steps:

[0009] Step (1) Add Fe 3+ Inorganic acid is added to phenol-containing wastewater to adjust its pH; after the wastewater is made acidic, the precipitated Fe(OH)3 in the wastewater dissolves and is released as Fe. 3+ The reaction mechanism is as follows: Fe(OH)3 + 3H+ + =Fe 3+ +3H2O.

[0010] Step (2): Add copper salt and cysteine ​​(Cys) to water, stir to dissolve to obtain a composite solution, then add it dropwise to phenol-containing wastewater and stir evenly; wherein cysteine ​​(Cys) will reduce Fe 3+ Reduced to Fe 2+ Simultaneously, cysteine ​​forms a complex with iron ions, increasing the solubility of iron ions at different pH values; the reaction mechanism is as follows:

[0011] Fe 3+ +Cys→Fe 2+ .

[0012] Fe 2+ +Cys→FeCys (iron ion-cysteine ​​complex).

[0013] Step (3): Add H2O2 aqueous solution dropwise to the phenol-containing wastewater to degrade the pollutants in the wastewater. Fe is generated in the reaction system. 2+ Activation of H2O2 produces HO· free radicals, Fe 2+ Oxidized to Fe 3+ Then, the HO· free radical reacts with phenol to produce hydroquinone (HQ), while cysteine ​​in the reaction system is decomposed; further reaction of Fe in the system 3+ Hydroquinone was reduced to Fe 2+ Simultaneously, hydroquinone radicals (SQ·-) are generated; at the same time, Cu 2+ It can be reduced to Cu by hydroquinone + It generates hydroquinone radicals SQ·-, and the reaction rate k2 is significantly faster than that of Fe. 3+ The reaction rate k1 with hydroquinone.

[0014] Fe 3+ +HQ→Fe 2+ +SQ· - The reaction rate k1 = 4.4 × 10⁻⁶ 2 mol×(L×s) -1 .

[0015] Cu 2+ +HQ→Cu++SQ· - The reaction rate k2 = 5.0 × 10 7 mol×(L×s) -1 .

[0016] Simultaneously, the generated hydroquinone free radicals can also degrade Fe... 3+ Reduced to Fe 2+ It generates p-benzoquinone (BQ), and the reduction rate is faster than that of hydroquinone to Fe. 3+ The reduction reaction rate.

[0017] Fe 3+ +SQ· - →Fe 2+ +BQ; Reaction rate k3 = 4.4 × 10 4 mol×(L×s) -1 .

[0018] After the formation of HO· free radicals in the reaction system, cysteine ​​in the reaction system is decomposed; and Cu 2+ The addition of [a substance] can significantly accelerate the generation rate of hydroquinone free radicals, thereby increasing the Fe [reactivity]. 3+ To Fe 2+ The conversion rate ensures that there is sufficient Fe in the reaction system. 2+ Activated H2O2 produces HO·, a strong oxidizing agent, which oxidizes the wastewater.

[0019] In summary, cysteine ​​plays a crucial role in the initial stage of the reaction by removing Fe from the wastewater before the reaction begins. 3+ Reduced to Fe 2+ The reaction begins; Cu 2+ Its main function is to accelerate the reaction of Fe in the system 3+ / Fe 2+ The cycle serves to enhance the reaction.

[0020] Furthermore, in step (1), Fe in the phenol-containing wastewater 3+ The molar concentration is ≥0.005 mmol / L.

[0021] Furthermore, the inorganic acids in step (1) include hydrochloric acid, nitric acid, and sulfuric acid; the pH of the phenol-containing wastewater is adjusted to 2-5.

[0022] Furthermore, in step (2), the copper salt includes any one or a combination of copper chloride and copper sulfate.

[0023] Furthermore, in step (2), the Cu in the composite solution 2+ The molar concentration of is 0.01–0.05 mmol / L, and the molar concentration of cysteine ​​is 0.01–0.1 mmol / L.

[0024] Furthermore, in step (2), the molar concentration of H2O2 in the phenol-containing wastewater is controlled to be 2-4 mmol / L.

[0025] Furthermore, in step (3), the temperature during degradation is controlled at 15-40℃ and the degradation time is controlled at 1-10 min.

[0026] Technical effect: In this invention, the wastewater is acidified, causing the precipitated Fe(OH)3 in the wastewater to dissolve and release Fe. 3 + Then cysteine ​​(Cys) will... 3+ Reduced to Fe 2+ Simultaneously, cysteine ​​forms a complex with iron ions, increasing the solubility of iron ions at different pH values; H₂O₂ aqueous solution is added dropwise to phenol-containing wastewater to degrade pollutants in the wastewater. Fe generated in the reaction system... 2+ Activation of H2O2 produces HO· free radicals, Fe 2+ Oxidized to Fe 3+ Then, the HO· free radical reacts with phenol to produce hydroquinone (HQ), while cysteine ​​in the reaction system is decomposed; Fe in the reaction system 3+ Hydroquinone was reduced to Fe 2+ Simultaneously, hydroquinone radicals (SQ·-) are generated; at the same time, Cu 2+ It can be reduced to Cu by hydroquinone + The formation of hydroquinone radicals SQ·- is achieved, with the reaction rate k2 significantly faster than that of Fe. 3+ The reaction rate with hydroquinone is k1; simultaneously, the generated hydroquinone radical can also react with Fe. 3+ Reduced to Fe 2+ It generates p-benzoquinone (BQ), and the reduction rate is faster than that of hydroquinone to Fe. 3+ The reduction reaction rate; after the formation of HO· free radicals in the reaction system, cysteine ​​in the reaction system is decomposed; and Cu 2+ The addition of [a substance] can significantly accelerate the generation rate of hydroquinone free radicals, thereby increasing the Fe [reactivity]. 3+ To Fe 2+ The conversion rate ensures that there is sufficient Fe in the reaction system. 2+Activated H₂O₂ produces the highly oxidizing HO·, thus oxidizing the wastewater. In summary, cysteine ​​plays a role in the initial stage of the reaction, acting to remove Fe from the wastewater before the reaction. 3+ Reduced to Fe 2+ The reaction begins; Cu 2+ Its main function is to accelerate the reaction of Fe in the system 3+ / Fe 2+ The cycle serves to enhance the reaction.

[0027] This invention selects safe and non-toxic cysteine ​​as the reaction initiator, which simultaneously acts as a reducing and complexing agent, enabling rapid reaction initiation while broadening the pH range of the traditional Fenton reaction; Cu is selected 2+ As a reaction enhancer, it accelerates the reaction of Fe 3 + / Fe 2+ The recycling process rapidly degrades phenol while synergistically enhancing the degradation of other organic pollutants. It eliminates the need for preparing and adding complex, costly iron-containing activators, utilizing the small amount of iron naturally present in the wastewater as Fe. 2+ The source is identified and recycled within the system, significantly improving the pollutant removal rate and reducing the generation of iron sludge. This technology boasts advantages such as being green, efficient, easy to operate, and low-cost. Attached Figure Description

[0028] Figure 1 The degradation curves of phenol in Example 1 and Comparative Examples 1-3 are shown.

[0029] Figure 2 The degradation curve of phenol in Example 2 is shown.

[0030] Figure 3 The degradation curves of pyridine in Example 2 and Comparative Example 4 are shown. Detailed Implementation

[0031] Degradation simulation experiment of phenol pollutants in phenol wastewater:

[0032] Example 1

[0033] (1) Take 200 mL containing Fe 3+ The wastewater containing phenol was added to a brown glass bottle as simulated wastewater. The concentration of phenol (C0) was determined by ultraviolet spectrophotometry. Hydrochloric acid was added to adjust the pH of the wastewater to 3.

[0034] (2) Add copper sulfate and cysteine ​​to water, stir to dissolve and obtain a composite solution, and control the Cu content in the composite solution. 2+ The molar concentration of α-hydroxyl group was 0.025 mmol / L, and the molar concentration of cysteine ​​was 0.05 mmol / L. The composite solution was added to the simulated wastewater and stirred until homogeneous.

[0035] (3) Add H2O2 aqueous solution dropwise to the simulated wastewater to control the molar concentration of H2O2 in the phenol-containing wastewater to 3 mmol / L, and degrade the pollutants in the phenol-containing wastewater at 25℃. Collect the supernatant at 0.5, 1, 2, 3, 4, 5, 7, and 10 min respectively, and determine the residual concentration C of phenol. t Calculate the remaining concentration of phenol = (C t / C0).

[0036] Comparative Example 1:

[0037] The only difference between Comparative Example 1 and Example 1 is that the combined solution of cysteine ​​and copper sulfate is not added. The remaining steps are the same.

[0038] Comparative Example 2:

[0039] The only difference between Comparative Example 2 and Example 1 is that copper sulfate was added to the composite solution, but cysteine ​​was not added. The remaining steps are the same.

[0040] Comparative Example 3:

[0041] The only difference between Comparative Example 3 and Example 1 is that cysteine ​​was added to the composite solution, but copper sulfate was not added. The remaining steps were the same.

[0042] The residual proportion curves of phenol in Example 1 and Comparative Examples 1-3 are shown below. Figure 1 As shown. In Comparative Example 1, the remaining phenol content in the H2O2 reaction system was 0.934%, and the degradation rate was only 6.6%; in Comparative Example 2, after the addition of Cu... 2+ Formation of Cu 2+ After the / H2O2 reaction system, the remaining phenol content was 0.893, and the degradation rate increased to 10.7%; while in Comparative Example 3, after adding cysteine ​​(Cys) to the reaction system, forming a Cys / H2O2 reaction system, the remaining phenol content was only 0.270, and the degradation rate increased to 73.0%. It can be seen that Cu 2+ The oxidation efficiency of the Cys / H2O2 reaction system was not significantly improved compared to the H2O2 reaction system, while the degradation rate of phenol in the Cys / H2O2 reaction system was greatly improved. This indicates that cysteine ​​can play a role in rapidly initiating the reaction, while Cu... 2+ Can't.

[0043] In Example 1, cysteine ​​and Cu 2+ Simultaneously add the formed Cys / Cu 2+ In the / H2O2 reaction system, phenol degrades rapidly, with the phenol content falling below 0.1% within 10 minutes and a degradation rate exceeding 90%. Compared to the Cys / H2O2 reaction system, the degradation rate and speed of phenol are further improved by approximately 20%, indicating that Cu2+ It serves to enhance the reaction process.

[0044] Degradation simulation experiment of pyridine pollutants in phenol wastewater:

[0045] To verify the synergistic effect of phenol degradation on the degradation of other pollutants in wastewater, the examples used Fe-containing... 3+ Experiments were conducted on wastewater containing phenol and pyridine.

[0046] Example 2

[0047] (1) Take 200ml of wastewater containing iron, phenol and pyridine and add it to a brown glass bottle as simulated wastewater. Use ultraviolet spectrophotometry to determine the concentration C0 of phenol and pyridine. Add hydrochloric acid to adjust the pH of the wastewater to 4.

[0048] (2) Add copper sulfate and cysteine ​​to water, stir to dissolve and obtain a composite solution, and control the Cu content in the composite solution. 2+ The molar concentration of α-hydroxyl group was 0.01 mmol / L, and the molar concentration of cysteine ​​was 0.04 mmol / L. The composite solution was added to the simulated wastewater and stirred until homogeneous.

[0049] (3) An aqueous H2O2 solution was added dropwise to the simulated wastewater to control the molar concentration of H2O2 in the phenol-containing wastewater to 3 mmol / L. The pollutants in the phenol-containing wastewater were degraded at 25℃. The supernatant was collected at different reaction times, and the residual concentrations C of phenol and pyridine were determined by ultraviolet spectrophotometry. t Calculate the remaining mass percentage of pyridine = (C t / C0).

[0050] Comparative Example 4:

[0051] The only difference between Comparative Example 4 and Example 2 is that Comparative Example 4 uses only Fe. 3+ Wastewater containing pyridine and phenol was used as simulated wastewater. The remaining steps were the same.

[0052] The remaining mass of pyridine and its degradation curve in Example 2 are as follows: Figure 2 As shown, the rapid degradation of phenol during the reaction process is evident. After 5 minutes, the residual phenol mass is less than 0.1, and the removal rate reaches over 90%. After 30 minutes, the residual phenol mass is 0.062, and the removal rate is 93.8%.

[0053] The degradation curves of pyridine in Example 2 and Comparative Example 4 are as follows: Figure 3As shown, in the presence of phenol, after 180 min of reaction, the remaining mass of pyridine was only 0.162, and the degradation rate of pyridine reached 83.8%. When phenol was not present in the reaction system, the remaining mass of pyridine was 0.318 after 180 min, and the degradation rate of pyridine was 68.2%. Due to the presence of phenol, the degradation rate of pyridine in the reaction system increased by 15.6%.

[0054] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for rapidly degrading phenol using iron in phenol-containing wastewater, characterized in that: Includes the following steps: Step (1) Add Fe 3+ Inorganic acids are added to phenol-containing wastewater to adjust its pH. Step (2): Add copper salt and cysteine ​​to water, stir to dissolve and obtain a composite solution, then add it dropwise to phenol-containing wastewater and stir evenly; Step (3): Add H2O2 aqueous solution dropwise to the phenol-containing wastewater obtained in step (2) to degrade the pollutants in the phenol-containing wastewater; In step (2), Cu in the composite solution 2+ The molar concentration of is 0.01-0.05 mmol / L, and the molar concentration of cysteine ​​is 0.01-0.1 mmol / L; In step (1), Fe in the phenol-containing wastewater 3+ The molar concentration is ≥0.005 mmol / L.

2. The method for rapidly degrading phenol using iron in phenol-containing wastewater according to claim 1, characterized in that: In step (1), the inorganic acid is hydrochloric acid, nitric acid, or sulfuric acid; the pH of the phenol-containing wastewater is adjusted to 2-5.

3. The method for rapidly degrading phenol using iron in phenol-containing wastewater according to claim 1, characterized in that: The copper salt in step (2) includes any one or a combination of copper chloride and copper sulfate.

4. The method for rapidly degrading phenol using iron in phenol-containing wastewater according to claim 1, characterized in that: In step (3), the molar concentration of H2O2 in the phenol-containing wastewater is controlled to be 2-4 mmol / L.

5. The method for rapidly degrading phenol using iron in phenol-containing wastewater according to claim 1, characterized in that: In step (3), the temperature during degradation is controlled at 15-40℃ and the degradation time is 1-10 min.

Images