Method for degrading perfluorooctanoic acid in water through cooperation of titanium-loaded molecular sieve and persulfate

Abstract

The invention discloses a method for degrading perfluorooctanoic acid in water through cooperation of a titanium-loaded molecular sieve and persulfate, and belongs to the field of environmental pollution treatment. The method comprises the following steps: firstly, preparing a titanium-loaded molecular sieve by using ZSM-5 and USY type molecular sieves as matrix materials and titanocene dichloride as a titanium source through an ion exchange method; then, the titanium-loaded molecular sieve and persulfate are combined to degrade the perfluorooctanoic acid. The titanium-loaded molecular sieve is simple in synthesis method, low in cost, good in stability and good in environmental compatibility. Experimental results show that the titanium-loaded molecular sieve has excellent degradation efficiency on perfluorooctanoic acid in cooperation with persulfate, the degradation rate is close to 100%, and the defluorination rate is gt; the defluorination rate can be up to 54.51%.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental pollution control, and specifically relates to a method for degrading perfluorooctanoic acid in water using a titanium-supported molecular sieve catalyst in collaboration with persulfate. Background Art

[0002] Perfluorooctanoic acid (PFOA) is a typical representative of perfluoro / polyfluoroalkyl compounds (PFAS). With its unique hydrophobic and oleophobic properties, it is widely used in industrial and civilian fields such as non-stick cookware coatings, textile waterproofing, electronic component surface modification, and firefighting foam preparations. However, the extremely strong CF covalent bond (bond energy of about 460 kJ / mol) in the PFOA molecule gives it extremely high chemical stability, making it difficult to degrade through natural pathways such as hydrolysis, photolysis, or biological metabolism, thereby remaining in the environment for a long time. What is more serious is that PFOA can be amplified step by step in the ecological chain through bioaccumulation, and eventually accumulates in human blood, liver and other tissues, and is significantly related to toxic effects such as increased cancer incidence, immune system suppression, and abnormal reproductive development (Steenland K, et.al. Environmental health perspectives, 2010, 118 (8): 1100-1108.). At present, PFOA has been widely detected in extreme environments such as global drinking water sources, farmland soils, and even Arctic glaciers. Due to its persistence, bioaccumulation and toxicity, it was officially included in Annex A (List of Elimination Substances) of the Stockholm Convention on Persistent Organic Pollutants in 2019.

[0003] The current degradation technologies for PFOA mainly include physical adsorption, chemical oxidation, thermal degradation and photocatalysis, but they are limited by the inherent defects of a single technology and face severe challenges in practical application. For example, although the physical adsorption method can quickly enrich PFOA, it only realizes the phase transfer of pollutants and fails to break through the dual bottlenecks of low adsorbent regeneration efficiency and insufficient pollutant mineralization rate; the use of O3 and persulfate chemical oxidants alone has limited degradation efficiency; although the thermal degradation method decomposes thoroughly, it consumes a lot of energy and easily produces toxic gases such as hydrogen fluoride (HF), and the tail gas treatment is complicated; photocatalytic degradation currently still has the limitations of low light energy utilization and dependence on ultraviolet light (CN 112371143A). It can be seen that a single technical route is difficult to take into account degradation efficiency, economy and environmental safety. Therefore, the development of integrated technology with multi-technology coupling has become an important direction to break through the existing technical barriers.

[0004] CN107416943A can achieve a defluorination rate of up to 56.21% through the synergistic effect of SiO2-phosphotungstic acid and UVC ultraviolet light, but the system has the defects of too high phosphotungstic acid loading rate (10% to 50%) and relying on high-energy UVC light sources. CN117550673A increases the PFOA degradation rate to nearly 100% through the trivalent iron modified zeolite molecular sieve-persulfate-simulated sunlight combined technology. However, under the optimal conditions (the dosage of trivalent iron modified zeolite molecular sieve is 0.5g L -1 , sodium persulfate concentration is 0.2mM, initial PFOA concentration is 0.024mM, and light exposure is 12h) and its defluorination rate is only 29.6%, indicating that the mineralization process is not yet perfect. CN117123208A uses mSiO2@CeO2 composite catalyst to achieve a 30% degradation rate of PFOA under ultraviolet light, but does not disclose key defluorination rate data. Therefore, the efficiency of the existing combination of multiple technologies to degrade PFOA is still not satisfactory. Summary of the invention

[0005] Based on the problem of low defluorination rate in the prior art, the present invention provides a method for efficiently degrading PFOA in water by using titanium-supported molecular sieves in cooperation with persulfate. The method utilizes adsorption-oxidation to degrade PFOA, with high degradation efficiency and thorough degradation.

[0006] The method provided by the present invention for degrading PFOA in water by using titanium-loaded molecular sieve in cooperation with persulfate comprises the following steps:

[0007] Step 1: putting the matrix molecular sieve into a dichlorotitacenene aqueous solution, stirring, filtering, washing and drying to obtain a titanium-loaded molecular sieve;

[0008] Step 2: Add the titanium-loaded molecular sieve and persulfate to an aqueous solution containing PFOA, and degrade the solution under heating conditions of 60 to 150° C. for 12 to 48 hours.

[0009] Furthermore, in step 1, the base molecular sieve of the titanium-loaded molecular sieve is preferably a ZSM-5 molecular sieve or a USY molecular sieve, and the titanium element loading rate is 0.1% to 2%.

[0010] Furthermore, in step 1, the concentration of the titanocene dichloride aqueous solution is preferably 0.002 to 0.02 mol / L.

[0011] Furthermore, in step 1, the stirring time is preferably 24 to 96 hours.

[0012] Furthermore, in step 2, the concentration of PFOA in the PFOA-containing aqueous solution is preferably 1 to 5 g / L.

[0013] Furthermore, in step 2, the feed mass ratio of the titanium-loaded molecular sieve to PFOA is preferably 0.5-10:0.5-10:1.

[0014] Furthermore, in step 2, the persulfate is preferably sodium persulfate and potassium persulfate, and the mass ratio of the persulfate to PFOA is 1 to 60:1.

[0015] Furthermore, in step 2, the degradation temperature is preferably 80-100° C., and the reaction time is 15-30 h.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. The present invention uses commercial molecular sieve as the matrix material, uses stable, cheap and easily available dichlorodipentadienyl titanocene as the titanium source, and synthesizes the titanium-loaded molecular sieve by ion exchange method. All raw materials are low in cost, the synthesis method is simple, easy to operate, highly safe, and has low requirements on equipment. In addition, the titanium-loaded molecular sieve has stable properties.

[0018] 2. The present invention uses titanium-loaded molecular sieve and persulfate to synergistically degrade PFOA in water, which has the advantages of high degradation efficiency and thorough degradation. The degradation rate is close to 100%, and the defluorination rate can reach up to 54.51%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the full XPS spectrum of the titanium-loaded molecular sieve Ti-Z5 prepared in Example 1.

[0020] Figure 2 This is a scanning electron microscope image of the titanium-loaded molecular sieve Ti-Z5 prepared in Example 1.

[0021] Figure 3 It is an XRD comparison diagram of the titanium-loaded molecular sieve Ti-Z5 prepared in Example 1 and the matrix molecular sieve ZSM-5.

[0022] Figure 4 This is a N2 adsorption-desorption diagram of the titanium-loaded molecular sieve Ti-Z5 prepared in Example 1.

[0023] Figure 5 This is the full XPS spectrum of the titanium-loaded molecular sieve Ti-A prepared in Example 2.

[0024] Figure 6 This is a scanning electron microscope image of the titanium-loaded molecular sieve Ti-A prepared in Example 2.

[0025] Figure 7 This is an XRD comparison diagram of the titanium-loaded molecular sieve Ti-A prepared in Example 2 and the matrix molecular sieve USY.

[0026] Figure 8 This is a N2 adsorption-desorption diagram of the titanium-loaded molecular sieve Ti-A prepared in Example 2. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with embodiments and drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1

[0029] Step 1: Add 20 g ZSM-5 molecular sieve to 160 mL 0.01 mol / L dichlorotitanocene aqueous solution, stir at room temperature for 72 h, centrifuge, filter, wash the solid with ultrapure water and dry at 100 ° C for 72 h to obtain titanium-loaded molecular sieve Ti-Z5, in which the titanium loading rate is 0.4%. Figure 1 The titanium element signal can be seen, indicating that Ti-Z5 was successfully synthesized. Figure 2 It can be seen that it is in the shape of a flattened hexagonal prism, which is consistent with the morphology of the ZSM-5 molecular sieve, indicating that the structure of the ZSM-5 molecular sieve has not changed significantly during the titanium loading process. Figure 3 It can be seen that the main peaks of ZSM-5 molecular sieve have not changed at all, indicating that the structure of ZSM-5 molecular sieve has not changed significantly during the titanium loading process. Figure 4 It can be seen that Ti-Z5 is a microporous material, and its S BET 333.301m 2 g -1 , pore size is 0.1592cc g -1 .

[0030] Step 2: 6 mL of 3.45 g / L PFOA aqueous solution, 0.59524 g of sodium persulfate, and 0.1 g of titanium-loaded molecular sieve Ti-Z5 were added to a round-bottom flask in sequence, and reacted at 80°C for 24 hours to degrade PFOA. The results showed that the PFOA degradation rate was nearly 100%, and the defluorination rate was 54.51%.

[0031] The degradation effect of this embodiment is compared with the degradation effect of not adding titanium-loaded molecular sieve Ti-Z5 or replacing titanium-loaded molecular sieve Ti-Z5 with ZSM-5 molecular sieve (other conditions are the same as those in step 2 above). As can be seen from Table 1, the introduction of the catalyst improves the defluorination rate of the reaction, and the degradation effect of the catalyst after titanium loading on PFOA is greatly improved, which proves the importance of loading titanium on ZSM-5 molecular sieve.

[0032] Table 1

[0033]

[0034] Example 2

[0035] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.05952 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 35.17%.

[0036] Example 3

[0037] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.1190 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 41.17%.

[0038] Example 4

[0039] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.2381 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 42.13%.

[0040] Example 5

[0041] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.9524 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 39.48%.

[0042] Example 6

[0043] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 1.1905 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 35.51%.

[0044] Example 7

[0045] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.59524 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 120° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 30.43%.

[0046] Example 8

[0047] Step 1 of this embodiment is the same as step 1 of embodiment 1, and titanium-supported molecular sieve Ti-Z5 is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.59524 g of sodium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-Z5 are added to a round-bottom flask in sequence, and reacted at 80° C. for 12 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 31.19%.

[0048] Example 9

[0049] Step 1: Add 20 g of USY molecular sieve to 160 mL of 0.01 mol / L dichlorotitacenes aqueous solution, stir at room temperature for 72 h, centrifuge, filter, wash the solid with ultrapure water and dry at 100 ° C for 72 h to obtain titanium-loaded molecular sieve Ti-A, in which the loading rate of titanium element is 0.4%. Figure 5 The titanium element signal can be seen, indicating that the Ti-A synthesis was successful. Figure 6 It shows that it is consistent with the morphology of USY molecular sieve, indicating that the structure of USY molecular sieve has not changed significantly during the titanium loading process. Figure 7 It can be seen that the main peaks of USY molecular sieve have not changed, indicating that the structure of USY molecular sieve has not changed significantly during the titanium loading process. Figure 8 It can be seen that Ti-A is a microporous material, and its S BET 725.633m 2 g -1 , pore size is 0.3406cc g -1 .

[0050] Step 2: 6 mL of 0.05 3.45 g / L PFOA aqueous solution, 0.2703 g of potassium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-A were added to a round-bottom flask in sequence, and reacted at 80 ° C for 24 hours to degrade PFOA. The results showed that the PFOA degradation rate was nearly 100%, and the defluorination rate was 53.70%.

[0051] Example 10

[0052] Step 1 of this embodiment is the same as step 1 of embodiment 9, and titanium-supported molecular sieve Ti-A is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.2703 g of potassium persulfate, and 0.15 g of titanium-supported molecular sieve Ti-A are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 48.56%.

[0053] Embodiment 11

[0054] Step 1 of this embodiment is the same as step 1 of embodiment 9, and titanium-supported molecular sieve Ti-A is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.1352 g of potassium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-A are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 39.11%.

[0055] Example 12

[0056] Step 1 of this embodiment is the same as step 1 of embodiment 9, and titanium-supported molecular sieve Ti-A is obtained. In step 2 of this embodiment, 6 mL of 3.45 g / L PFOA aqueous solution, 0.6758 g of potassium persulfate, and 0.1 g of titanium-supported molecular sieve Ti-A are added to a round-bottom flask in sequence, and reacted at 80° C. for 24 hours to degrade PFOA. The results show that the PFOA degradation rate is nearly 100%, and the defluorination rate is 35.74%.

Claims

1. A method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate, characterized in that The steps include: Step 1: putting the matrix molecular sieve into a dichlorotitacenene aqueous solution, stirring, filtering, washing and drying to obtain a titanium-loaded molecular sieve; Step 2: Add the titanium-loaded molecular sieve and persulfate to an aqueous solution containing perfluorooctanoic acid, and degrade them under heating conditions of 60 to 150° C. for 12 to 48 hours.

2. The method for degrading perfluorooctanoic acid in water using titanium-loaded molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 1, the matrix molecular sieve is ZSM-5 molecular sieve or USY molecular sieve.

3. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 1, the loading rate of titanium element in the titanium-loaded molecular sieve is 0.1% to 2%.

4. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 1, the concentration of the titanocene dichloride aqueous solution is 0.002-0.02 mol / L.

5. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 1, the stirring time is 24 to 96 hours.

6. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 2, the concentration of perfluorooctanoic acid in the aqueous solution containing perfluorooctanoic acid is 1 to 5 g / L.

7. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 2, the mass ratio of the titanium-loaded molecular sieve to perfluorooctanoic acid is 0.5 to 10:

1.

8. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 2, the persulfate is sodium persulfate or potassium persulfate.

9. The method for degrading perfluorooctanoic acid in water using titanium-supported molecular sieve in cooperation with persulfate according to claim 1 or 8, characterized in that: In step 2, the mass ratio of the persulfate to perfluorooctanoic acid is 1 to 60:

1.

10. The method for degrading perfluorooctanoic acid in water by using titanium-supported molecular sieve in cooperation with persulfate according to claim 1, characterized in that: In step 2, the degradation temperature is 80-100° C. and the time is 15-30 hours.

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