Method for degrading pollutants by friction catalytic activation of persulfate

Abstract

The invention discloses a method for degrading pollutants by activating persulfate through friction catalysis, and belongs to the technical field of environmental catalysis and pollutant treatment. The method comprises the following steps that a rotating disc is added into a container containing sewage containing pollutants to be treated, persulfate is added, friction pairs are formed between the rotating disc and the bottom of the container, the persulfate is activated through the catalytic action generated by friction between the friction pairs, active oxygen is generated to degrade the pollutants, and the active oxygen comprises singlet oxygen. According to the invention, the technical obstacle that the persulfate cannot be efficiently activated by the existing catalytic means is overcome, a new implementation form is provided for a key path for converting mechanical energy into chemical activity, the technical bottlenecks that the traditional friction catalytic system is limited in activation capability and weak in degradation capability under the condition of no oxidant are broken through, and the method has a good industrial application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of environmental catalysis and pollutant treatment, and in particular to a method for degrading pollutants by friction catalytically activating persulfate. Background Art

[0002] With the acceleration of industrialization, a large number of refractory organic pollutants (such as antibiotics, dyes, and pesticides) are discharged into the environment, posing a serious threat to ecosystems and human health. Persulfate is a green oxidant with strong oxidizing power and simple operation. It has been widely used in advanced oxidation technologies. Its activation can produce a variety of highly reactive reactive oxygen species (ROS), including sulfate radicals (SO4· - ), hydroxyl radical (·OH - ) and superoxide radicals (·O2 - ), with excellent oxidative degradation performance.

[0003] Common persulfate activation methods include transition metal catalysis (such as Fe, Co, and Mn), thermal catalysis, photocatalysis, electrocatalysis, sonocatalysis, and carbon material catalysis. Metal toxicity, energy costs, and material lifespan remain key obstacles to the industrialization of metal catalysts. Field-assisted methods such as light and electricity require excessive energy consumption and complex equipment, limiting their application in resource-constrained areas or practical engineering applications. Furthermore, these technologies all suffer from insufficient persulfate activation rates.

[0004] Most existing persulfate activation methods rely on a large amount of external energy input, such as heat energy, light energy, electrical energy or metal ion synergistic catalysis. These methods have the problems of high energy consumption, complex equipment, material toxicity or harsh operating conditions, and limited recyclability, which limit their widespread application in practical engineering. In recent years, the introduction of friction catalysis technology has provided a new development direction for environmental catalysis. As a technology that uses mechanical energy for energy conversion, friction easily produces a large number of free electrons. These electrons are usually used to generate superoxide radicals with weaker oxidizing ability or are compounded. For example, in the Chinese invention patent with publication number CN109850983A, the inventor team provides a pollutant control method based on semiconductor powder friction catalysis. This method utilizes the friction catalytic effect of semiconductor powder. Through friction, the semiconductor obtains energy to generate electron-hole pairs, thereby degrading the pollutants in the solution. No light irradiation is required in the process, which overcomes the various shortcomings of photocatalytic materials in the process of pollutant treatment and can be used to control pollutants in a wider environment. Furthermore, existing methods for activating persulfate to degrade pollutants utilize electron-hole pairs, primarily based on the interaction between persulfate and carriers generated during semiconductor photocatalysis, achieving efficient degradation of pollutants through free radical or non-radical pathways. Therefore, if persulfate, which also accepts electrons to activate it, could be successfully introduced into the reaction system, energy efficiency could be greatly improved.

[0005] To date, the technical obstacles to achieving the above effects are that there have been no successful reports on the tribocatalytic activation of persulfate due to the inability to generate an effective electron transfer pathway and the failure of the friction interface to form an effective energy band structure. There is also no systematic material design, catalytic mechanism explanation and practical application plan. Specifically, the traditional simple mechanical stirring or friction method is difficult to effectively stimulate the decomposition of persulfate to generate sulfate radicals or hydroxyl radicals, resulting in low degradation efficiency and poor mineralization rate. Simple tribocatalysis is difficult to degrade pollutants such as dyes, antibiotics, and phenols due to its low efficiency and weak mineralization ability. The actual organic matter is simply decolorized and no real mineralization is achieved, resulting in a low removal rate. In addition, the traditional activation of persulfate to degrade pollutants still relies on extremely acidic conditions, with a narrow pH range of application, making it difficult to apply in practice. At this stage, there is an urgent need to develop a more effective activation scheme. The tribocatalytic activation of persulfate can form a combination with efficient triboelectron transfer, which is expected to become an extremely efficient catalytic combination.

[0006] In summary, a low-energy, green and sustainable pollution control technology based on friction catalytic activation of persulfate is provided, which has important scientific research value and broad application prospects. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the present invention provides a method for degrading pollutants by tribocatalytic activation of persulfate, which is highly efficient, simple, easy to operate, and widely applicable, comprising the following steps: A rotating disc and persulfate are added to a container containing wastewater to be treated, and the rotating disc and the bottom of the container form a friction pair; The friction between the friction pairs generates a catalytic effect to activate the persulfate, generating active oxygen to degrade the pollutants, and the active oxygen includes singlet oxygen.

[0008] Preferably, the pH of the sewage is 3-11.

[0009] Preferably, the concentration of pollutants in the sewage is ≤200 mg / L; the solid-liquid ratio of the persulfate to the sewage is 5-10:30 mg / mL.

[0010] Preferably, the persulfate includes peroxymonosulfate (PMS) and / or peroxydisulfate (PDS).

[0011] Preferably, the material of the turntable includes polytetrafluoroethylene (PTFE) or polyvinyl chloride (PVC), and the material of the bottom of the container includes one of polytetrafluoroethylene, titanium, and cobalt tetroxide.

[0012] Preferably, the method further comprises adding a semiconductor material to the wastewater containing the pollutants to be treated, activating the persulfate through friction between the semiconductor material and the turntable and the bottom of the container, generating free radicals and active oxygen to degrade the pollutants, wherein the active oxygen includes singlet oxygen.

[0013] Further preferably, the semiconductor material is in powder form and includes at least one of stannous oxide, titanium dioxide, and iron sulfide.

[0014] Further preferably, the solid-liquid ratio of the semiconductor material to the sewage is 30:30~300 mg / mL.

[0015] Preferably, during the friction, the rotation speed of the turntable is 100-800 rpm.

[0016] Preferably, the degradation is carried out at room temperature in the dark, and the degradation treatment time is 0.5 to 4 hours.

[0017] Based on the above technical solutions, the design concept and principle of the present invention are as follows: Existing technologies, such as photothermal catalytic activation of persulfate, require a continuous light source (e.g., a xenon lamp), are inefficient, and have demanding conditions. Precious metals (e.g., Ag, NPs) or single-atom catalysts are complex to prepare and have high costs for scale-up. When using semiconductor powders alone for tribocatalytic pollutant treatment, the treatment effect falls short of practical requirements. To address this, the present invention utilizes the tribocatalytic effect. By designing a suitable friction pair, friction-generated free electrons promote the activation of persulfate to produce a variety of free radicals (including sulfate radicals, hydroxyl radicals, and superoxide radicals), as well as non-radical pathways to generate singlet oxygen. This allows for broad-spectrum degradation of pollutants in a variety of aqueous solutions (e.g., dyes, antibiotics, phenols, etc.) and achieves true mineralization.

[0018] The present invention targets different application requirements and includes two solutions with or without semiconductor materials. Among them, for the low-cost green powder-free catalyst solution, a turntable and a bottom of suitable material are added to the aqueous solution containing the pollutants to be treated to form a friction pair. The turntable or the bottom material has friction catalytic properties, which activate an appropriate amount of persulfate to produce singlet oxygen to degrade the pollutants. Since singlet oxygen has extremely strong selectivity and is milder than hydroxyl radicals, it has less impact on life in the water body, and this solution is more green and environmentally friendly. For the high-efficiency catalyst solution, a semiconductor material with a suitable energy band structure and surface polarity and an appropriate amount of persulfate are added to the aqueous solution containing the pollutants to be treated. Under a suitable turntable, the friction between the semiconductor powder and the turntable surface and the bottom of the container can activate the persulfate, generate a large amount of free radicals and singlet oxygen, and degrade the pollutants in the solution.

[0019] In this design, a rotating disk is used to press the bottom under magnetic attraction or pressure to form a friction pair, greatly increasing effective friction. For extremely efficient catalysts (such as stannous oxide), significant activation occurs at speeds greater than 100 rpm. Furthermore, different combinations in the reaction can produce distinct effects. For example, when an N-type semiconductor like titanium dioxide contacts a titanium metal bottom, due to its different work function, it can rapidly transfer electrons, reducing electron-hole pair recombination. This leads to rapid decomposition of chromogenic groups such as dyes (typically within seconds at concentrations below 100 mg / L). Typically, due to the selectivity of sulfate groups, this produces a large number of difficult-to-degrade byproducts, preventing effective reduction of total organic carbon (TOC) content in the water and even producing more harmful organic matter. However, when a Teflon bottom is used in the present invention, its extremely negative charge can accumulate a large number of free electrons, resulting in an extremely high local free radical concentration. Although color removal is slow, the mineralization rate of organic matter is high. Similarly, different oxidants can be selected for wastewater with different pH values. Sulfate radicals will hydrolyze under neutral and alkaline conditions. PMS (such as potassium persulfate) produces hydroxyl radicals and sulfate radicals at the same time when activated. It is more suitable for treating wastewater with a pH between 3 and 11. PDS (such as sodium persulfate) produces a large amount of sulfate radicals, which is more efficient and less costly when treating highly acidic wastewater.

[0020] The present invention can achieve high efficiency degradation by controlling the amount of persulfate to within 2 times the molar amount of the pollutant. It should be noted that too high a concentration will not improve efficiency. When the concentration is too high, it will cause free radicals to react with each other (such as the coupling reaction SO4· - +SO4· - =S2O8 2- , and at the same time, it combines with pollutants to produce a large amount of by-products, which will deteriorate the reaction.

[0021] Compared to existing technologies, the present invention requires only mild mechanical energy to generate friction in the system by rotating the turntable, which converts mechanical energy into persulfate activation, achieving efficient and low-cost organic degradation. Furthermore, the system boasts a rich set of free radical degradation pathways and non-radical linear oxygen degradation pathways, successfully overcoming the limitations of conventional tribocatalysis. It can easily treat difficult-to-degrade organic compounds (such as phenol and antibiotics) across a wide range of pH values ​​and achieve extremely rapid degradation of organic pollutants such as dyes. This overcomes the limitations of many existing persulfate activation technologies and effectively degrades wastewater at various pH values ​​in the absence of light, an external electric field, or high temperatures. The present invention features low energy consumption, simple equipment, and relies on a simple stirring turntable to achieve the catalytic process. The oxidant (persulfate) used is significantly lower than in other reported studies, making it suitable for practical engineering applications in low-resource scenarios. By selecting pH-insensitive materials and rationally designing the friction interface structure, contact material combination, and force application pattern, directional electron migration and localized energy enrichment during the friction process are achieved, successfully activating persulfate molecules.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a method for tribocatalytically activating persulfate to degrade pollutants, overcoming the technical obstacle of existing catalytic means being unable to activate persulfate, providing a new implementation form for the key path of converting mechanical energy into chemical activity, breaking through the technical bottlenecks of limited activation ability of traditional catalytic systems and weak degradation ability under oxidant-free conditions, and having good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the degradation effect of titanium dioxide powder on rhodamine B by friction catalysis (adding a magnetic turntable) and simple stirring (adding a magnet) in the presence and absence of PMS; Figure 2 Schematic diagram of the change of organic matter content with stirring time when phenol is degraded by stannous oxide powder through friction catalysis (with PMS and without PMS); Figure 3 The degradation of phenol by titanium dioxide powder through tribocatalysis (with and without PMS) was compared by electron paramagnetic resonance detection after 30 min of reaction. DETAILED DESCRIPTION

[0024] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0025] In the following examples or comparative examples, potassium persulfate was used as PMS and sodium persulfate was used as PDS.

[0026] Example 1 This embodiment provides a method for tribocatalytic activation of persulfate to degrade pollutants, the steps of which are as follows: 30 mg of commercially available semiconductor material titanium dioxide nanopowder (Shanghai McLean Company, 20 nm powder) was added to 30 mL of methyl orange solution (concentration of 50 mg / L, pH close to neutral) in a 50 mL beaker; a magnetic turntable with a Teflon surface and a Teflon gasket at the bottom was added to the beaker, 10 mg of PMS was added, and magnetic stirring was performed at a speed of 400 rpm. During the process, the mixture was shielded from light and kept at a constant temperature of 25°C. The stirring treatment was carried out for 0.5 h, during which the change in methyl orange concentration was monitored by TOC.

[0027] Example 2 This embodiment provides a method for tribocatalytic activation of persulfate to degrade pollutants, the steps of which are as follows: 30 mg of commercially available stannous oxide powder was added to 30 mL of phenol solution (concentration of 20 mg / L, slightly acidic, pH ≈ 6) in a 50 mL beaker; a magnetic turntable with a Teflon surface and a Teflon gasket at the bottom was added to the beaker, 10 mg of PMS was added, and magnetic stirring was performed at a speed of 400 rpm. During the process, the mixture was shielded from light and kept at a constant temperature of 25°C. The stirring treatment was carried out for 2 hours, during which the change in phenol concentration was monitored by TOC.

[0028] Example 3 This embodiment provides a method for tribocatalytic activation of persulfate to degrade pollutants, the steps of which are as follows: 30 mg of commercially available pyrite (iron sulfide, Shanghai McLean Company) micron powder was added to 30 mL of rhodamine B solution (concentration of 50 mg / L, pH close to neutral) in a 50 mL beaker; a magnetic turntable with a Teflon surface and a Teflon gasket at the bottom was added to the beaker, 5 mg of PDS was added, and magnetic stirring was performed at a speed of 400 rpm. During the process, the mixture was shielded from light and kept at a constant temperature of 25°C. The stirring treatment was carried out for 2 h. During this period, the change in rhodamine B concentration was monitored by TOC. After 1 h of stirring, the degradation rate of rhodamine B reached more than 97%.

[0029] Example 4 This embodiment provides a method for tribocatalytic activation of persulfate to degrade pollutants, the steps of which are as follows: 10 mg of PMS and 30 mL of a rhodamine B solution (50 mg / L, near-neutral pH) were added to a 50 mL beaker with a Ti metal gasket attached to the bottom. A Teflon-surfaced magnetic turntable was placed in the beaker and magnetically stirred at 400 rpm. The mixture was shielded from light and maintained at a constant temperature of 25°C. The change in rhodamine B concentration was measured by TOC analysis. After 4 hours of stirring, the degradation rate of rhodamine B reached over 92%.

[0030] Comparative Example 1 The method of this comparative example is basically the same as that of Example 1, the only difference being the friction form. In this comparative example, a magnet is added to the beaker.

[0031] Comparative Example 2 The method of this comparative example is basically the same as that of Example 1, except that PMS is not added.

[0032] Comparative Example 3 The method of this comparative example is basically the same as that of Example 2, except that PMS is not added.

[0033] Test Example 1 Based on the design concept of the present invention, this method can promote the activation of persulfate to produce various free radicals and non-radical pathways to generate singlet oxygen, enabling broad-spectrum degradation of pollutants in various aqueous solutions and achieving true mineralization. Because tribocatalysis in existing dyes simply removes chromophores, resulting in decolorization of the chromogenic groups, this test uses TOC organic carbon content instead of UV-visible absorption spectroscopy to determine effective organic matter removal.

[0034] The degradation effects of Example 1, Comparative Examples 1 and 2 on Rhodamine B are as follows: Figure 1 As shown. Figure 1 As can be seen, after 0.5 h of treatment, Example 1 achieved a methyl orange degradation rate exceeding 95% as measured by TOC, while the solution containing only magnetic particles showed no organic matter degradation. Comparative Example 2 achieved better results than Comparative Example 1, but far less than Example 1. The above changes in organic matter content over degradation time demonstrate that this method successfully removes organic matter from water in a short period of time, significantly improving upon traditional tribocatalysis.

[0035] Test Example 2 This test example compares the degradation effect of SnO commercial powder on phenol by friction catalysis (with PMS and without PMS) in Example 2 and Comparative Example 3. The organic matter content changes with stirring time as shown in Figure 2. Figure 2 As shown by Figure 2 The results show that the technology of the present invention, when utilizing semiconductor materials, can efficiently mineralize pollutants that cannot be treated by tribocatalysis.

[0036] Test Example 3 This test example uses Example 1 and Comparative Example 2 as the objects to study the degradation pathway of phenol by commercial titanium dioxide powder through tribocatalysis (with and without PMS). The active substance content after 30 minutes of reaction was detected by electron paramagnetic resonance and compared. The results are as follows: Figure 3 As shown. Figure 3 The results show that under the same external conditions, the new system with the addition of PMS produces more abundant free radicals, which contributes to the efficient degradation of pollutants. This method system has a rich free radical degradation pathway and non-free radical linear oxygen degradation pathway, breaking through the limitations of conventional tribocatalysis.

[0037] In summary, the present invention only requires mild mechanical energy to rotate the turntable and generate friction in the system. By converting mechanical energy to activate persulfate, efficient and low-cost organic degradation can be achieved. In addition, the system has a wealth of free radical degradation routes and non-free radical linear oxygen degradation routes, which successfully breaks through the limitations of conventional friction catalysis. It can easily handle organic matter that is difficult to degrade under a wide range of pH values, and achieves extremely fast degradation of organic pollution such as dyes, overcoming the limitations of many existing activated persulfate technologies. In the absence of light, external electric field, and high temperature, it can effectively degrade sewage at various pH values. The present invention has low working energy consumption and simple equipment. It relies on a simple stirring turntable to realize the catalytic process, and the oxidant used is much lower than other reports, making it suitable for actual engineering low-resource scenarios. By selecting materials that are insensitive to pH values, rationally designing the friction interface structure, contact material combination, and force application mode, directional electron migration and local energy enrichment during the friction process are achieved, thereby successfully activating persulfate molecules. The present invention provides a new implementation form for the key path of converting mechanical energy into chemical activity, breaking through the technical bottlenecks of limited activation ability of traditional friction catalytic systems and weak degradation ability under oxidant-free conditions, and has good industrial application prospects.

[0038] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for degrading pollutants by tribocatalytic activation of persulfate, characterized in that: The steps include: A rotating disc and persulfate are added to a container containing wastewater to be treated, and the rotating disc and the bottom of the container form a friction pair; The friction between the friction pairs generates a catalytic effect to activate the persulfate, generating active oxygen to degrade the pollutants, and the active oxygen includes singlet oxygen.

2. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The pH of the sewage is 3-11.

3. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The concentration of pollutants in the sewage is ≤200 mg / L; the solid-liquid ratio of the persulfate to the sewage is 5~10:30 mg / mL.

4. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The persulfate includes peroxymonosulfate and / or peroxydisulfate.

5. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The material of the turntable includes polytetrafluoroethylene or polyvinyl chloride, and the material of the bottom of the container includes one of polytetrafluoroethylene, titanium, and cobalt tetroxide.

6. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The method also includes adding semiconductor materials to the sewage containing the pollutants to be treated, activating persulfate through friction between the semiconductor materials and the turntable and the bottom of the container, generating free radicals and active oxygen to degrade the pollutants, wherein the active oxygen includes singlet oxygen.

7. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 6, characterized in that: The semiconductor material is in powder form and includes at least one of stannous oxide, titanium dioxide, and iron sulfide.

8. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 6, characterized in that: The solid-liquid ratio of the semiconductor material to the sewage is 30:30~300 mg / mL.

9. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: During the friction, the rotation speed of the turntable is 100-800 rpm.

10. The method for degrading pollutants by tribocatalytic activation of persulfate according to claim 1, characterized in that: The degradation is carried out at room temperature and in the dark, and the degradation treatment time is 0.5 to 4 hours.

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