A method for degrading multiple FQs in water based on LaCaCuFeO perovskite

Abstract

The present invention discloses a method for degrading multiple FQs in water based on LaCaCuFeO perovskite, belonging to the field of water treatment technology. The present invention adds LaCaCuFeO perovskite and persulfate to the water body, and simultaneously and efficiently degrades multiple FQs in the composite water body in a short period of time. The catalyst in this system can be applied to the degradation of higher concentrations of FQs, has a relatively good degradation effect in a relatively wide pH range, and has a high recycling rate and high catalyst stability and reusability. This system has good high salt resistance and can effectively degrade FQs at higher chloride ion and sulfate ion concentrations, and carbonate and bicarbonate ions have little effect on the system. Moreover, it can be used in a high-concentration phosphate environment and has good application prospects.

Description

Technical Field

[0001] The invention relates to a method for degrading multiple FQs in water based on LaCaCuFeO perovskite, belonging to the technical field of water treatment. Background Art

[0002] Fluoroquinolone antibiotics (FQs) are a class of macromolecular organic compounds containing fluorine atoms. They are widely used in the pharmaceutical industry due to their strong antimicrobial activity. FQs are chemically stable and have long half-lives. However, their potent antimicrobial activity can affect microbial resistance genes, making them difficult to degrade by microorganisms, making them persistent emerging pollutants in water. Contact with humans can cause numerous adverse reactions, such as allergies, dizziness, and neurotoxicity. Recent studies have shown that FQs are detected in both surface and groundwater, and even low concentrations pose a high ecological risk. FQ degradation methods primarily include physical, chemical, and biological methods. Current research on the degradation of fluoroquinolone pollutants primarily focuses on single pollutants. However, in real water bodies, multiple pollutants are often present. Catalytic systems suitable for single pollutants have limited catalytic degradation capabilities in mixed pollutant systems, making it difficult to simultaneously degrade multiple FQs in water. Therefore, there is an urgent need for a system that can efficiently degrade mixed fluoroquinolone pollutants in water.

[0003] Advanced oxidation technology is a chemical oxidation technology that uses highly oxidizing free radicals to effectively decompose organic pollutants in the water environment and even completely convert them into harmless inorganic substances. After persulfate activation, it can produce a large amount of SO 4. - , has a high redox potential (2.5-3.1V) and has a strong redox ability. In addition to the free radical reaction pathway (sulfate radical and hydroxyl radical), there are also some non-free radical reaction pathways in the persulfate system, such as superoxide radical (O2 ·- ), singlet oxygen ( 1 O2) and electron transfer pathways, this system of coexistence of free radicals and non-free radicals is beneficial for treating refractory organic matter in complex water bodies.

[0004] Wastewater discharged from industrial processes such as chemical and pharmaceutical production often contains large amounts of sodium, chloride, and sulfate ions. These ions in high-salt organic wastewater can combine with free radicals in advanced oxidation processes to generate weaker free radicals, which inhibit the degradation efficiency of the system. Therefore, it is of practical significance to provide a technical means for removing FQs that can also be adapted to high-salt environments. Summary of the Invention

[0005] Technical issues:

[0006] In response to the above-mentioned issues regarding ordinary wastewater and the inability of ordinary advanced oxidation technologies to treat water bodies containing a variety of difficult-to-degrade organic substances such as FQs under high-salt conditions, the present invention provides a method for simultaneously degrading multiple FQs in complex water bodies and can efficiently degrade FQs in a high-salt environment.

[0007] Technical solution:

[0008] The present invention provides a method for degrading multiple FQs in water. The method comprises adding LaCaCuFeO perovskite and persulfate into the water body for degradation treatment.

[0009] In one embodiment of the present invention, the FQs are ofloxacin (OFX) and ciprofloxacin (CIP) coexisting.

[0010] The present invention provides a method for degrading multiple FQs in high-salinity wastewater. The method comprises adding LaCaCuFeO perovskite and persulfate to the high-salinity wastewater for degradation treatment. The high-salinity wastewater generally refers to wastewater with a mass fraction of total dissolved solids greater than 3.5%.

[0011] The present invention also provides a method for simultaneously degrading ofloxacin (OFX) and ciprofloxacin (CIP) in water. The method comprises adding LaCaCuFeO perovskite and persulfate into the water body for degradation treatment.

[0012] In one embodiment of the present invention, the high salt system includes any one or more of the following cations: Na + , K + and any one or more of the following anions: Cl - 、HCO3 - 、CO3 2- 、H2PO4 - 、SO4 2- .

[0013] In one embodiment of the present invention, the dosage of LaCaCuFeO perovskite relative to water is 0.1-0.5 g / L; further, 0.2-0.25 g / L is optional.

[0014] In one embodiment of the present invention, the dosage of LaCaCuFeO perovskite relative to the high salt system is 0.1-0.5 g / L; further optionally 0.2-0.25 g / L.

[0015] In one embodiment of the present invention, the persulfate is sodium peroxodisulfate and / or potassium peroxodisulfate; preferably sodium peroxodisulfate.

[0016] In one embodiment of the present invention, the dosage of peroxodisulfate relative to water or high-salt wastewater is 2-6 mmol / L, and specifically 4 mmol / L.

[0017] In one embodiment of the present invention, the degradation treatment is to adjust the pH to 3-11, more preferably 5-11, and most preferably 7-8.

[0018] In one embodiment of the present invention, the experimental concentration of the target pollutant FQs is 5-20 ppm. Considering the possible concentration and degradation rate of BPA in actual sewage treatment plants, the optimal FQs concentration is preferably 10 ppm.

[0019] In one embodiment of the present invention, the LaCaCuFeO perovskite is prepared by a sol-gel method with EDTA chelation:

[0020] Soluble copper salt, soluble iron salt, soluble lanthanum salt, soluble calcium salt, EDTA and citric acid are dispersed and dissolved in water and mixed to obtain a mixed system; then the pH is adjusted to neutral, heated to produce a gel, and then the gel is dried, ground, and then calcined.

[0021] In one embodiment of the present invention, the soluble copper salt may be copper nitrate or its hydrate, copper sulfate or its hydrate, copper chloride or its hydrate; specifically, copper nitrate trihydrate may be selected.

[0022] In one embodiment of the present invention, the soluble iron salt may be ferric nitrate or its hydrate, ferric sulfate or its hydrate, ferric chloride or its hydrate; specifically, ferric nitrate nonahydrate.

[0023] In one embodiment of the present invention, the soluble lanthanum salt may be lanthanum nitrate or a hydrate thereof; specifically, lanthanum nitrate hexahydrate may be selected.

[0024] In one embodiment of the present invention, the soluble calcium salt may be calcium chloride, calcium nitrate or a hydrate thereof; specifically, calcium chloride dihydrate may be selected.

[0025] In one embodiment of the present invention, in the mixed system, the molar ratio of lanthanum salt, calcium salt, copper salt and iron salt is 9:1:5:5.

[0026] In one embodiment of the present invention, the amount of EDTA added to the mixed system is 0.1-0.5 mol / L, and specifically 0.15 mol / L.

[0027] In one embodiment of the present invention, the amount of citric acid added to the mixed system is 0.2-0.8 mol / L, and specifically 0.3 mol / L.

[0028] In one embodiment of the present invention, the temperature for heating to gel is 80-100°C, specifically 90°C; and the drying temperature for gel is 240°C.

[0029] In one embodiment of the present invention, the calcination is performed by preheating at 450° C. for 2 hours, and then continuing to heat up to 700° C. and calcining for 6 hours.

[0030] Beneficial effects:

[0031] (1) The present invention proposes to prepare LCCFO perovskite by calcium ion doping modified copper iron perovskite, which can activate PDS and effectively degrade various FQs in water bodies.

[0032] (2) The LCCFO perovskite prepared in the present invention can tolerate high salt and degrade FQs under high salt conditions in a short time, and the degradation rate increases in a high concentration phosphate environment.

[0033] (3) The LCCFO perovskite structure is stable, and the metal dissolution amount can reach the A-level standard of the "Water Quality Control Project for Sewage Discharge into Urban Sewers". After repeating four times, it can still achieve a degradation effect of more than 70% on the CIP in the system and more than 93% on the OFX in the system, which is highly efficient and environmentally friendly.

[0034] (4) This reaction system can achieve a degradation effect of more than 73% on CIP in the system and more than 85% on OFX in the system within the pH range of 5 to 11, and is suitable for removing some organic pollutants in actual water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing the effect of FQs concentration on the degradation effect of the system in Example 1 (Figure a is CIP; Figure b is OFX).

[0036] Figure 2 This is a diagram showing the effect of pH on the degradation effect of the system in Example 2 (Figure a is CIP; Figure b is OFX).

[0037] Figure 3 Graph showing the effect of different salts on the degradation effect of the system in Example 3 (Figure a is CIP; Figure b is OFX).

[0038] Figure 4 This is the degradation rate diagram of the LCCFO perovskite recycling in Example 4 (Figure a is CIP; Figure b is OFX).

[0039] Figure 5 This is a comparison of the FQs removal results of the perovskite materials obtained under different copper-iron ratios and calcium ion doping conditions in Comparative Example 1 (Figure a is CIP; Figure b is OFX).

[0040] Figure 6 This is a comparison of the FQs removal results of the perovskite materials obtained under different alkaline earth metal doping conditions in Comparative Example 2 (Figure a is CIP; Figure b is OFX).

[0041] Figure 7 This is the XRD pattern of the catalyst LCCFO perovskite obtained in Example 1.

[0042] Figure 8 The catalyst obtained in Example 1 . SEM image of LCCFO perovskite. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited to these examples.

[0044] The degradation rate of FQs involved in the present invention = the concentration of FQs after degradation C t / Initial FQs concentration C0*100%.

[0045] The Cu 2+ 、Fe 2+ The dissolution amount refers to the content of free Cu and Fe ions in the system.

[0046] Example 1 LCCFO perovskite degradation of FQs

[0047] LCCFO perovskite is prepared by EDTA chelated gel sol method, the specific steps are as follows:

[0048] (1) Preparation of LCCFO perovskite by EDTA chelated gel sol method: weigh a certain amount of copper nitrate trihydrate, iron nitrate nonahydrate, lanthanum nitrate hexahydrate, and calcium chloride dihydrate, add appropriate amount of deionized water to dissolve; EDTA and citric acid are dissolved in deionized water respectively and then mixed; metal salt solution is added dropwise to the above mixed solution, and the pH is adjusted to about 7 with ammonia water;

[0049] (2) The homogeneous mixture was transferred to a water bath at 90°C and stirred to evaporate until a gel was formed; the gel was then placed in an oven at 240°C for 5 h to obtain a fluffy intermediate product;

[0050] (3) The intermediate product was ground and calcined in a muffle furnace. The temperature was programmed to 450°C for preheating for 2 hours, and then continued to rise to 700°C for calcination for 6 hours. The obtained product was washed alternately with ethanol and deionized water, and dried in an oven overnight to obtain La. 0.9 Ca 0.1 Cu 0.5 Fe 0.5 O3 perovskite, referred to as LCCFO perovskite. The XRD pattern and SEM image of the obtained LCCFO perovskite are as follows Figure 7 、 8 shown.

[0051] In a typical system (LCCFO perovskite 0.25g / L, PDS concentration of 4mM, pH 7), FQs solutions (CIP and OFX coexist) of different concentrations (5, 10, 15, 20ppm) were added and magnetic stirring was applied. Samples were taken at regular time intervals, and the reaction was quenched by adding an equal amount of ethanol solution and filtered. The concentration of FQs in the solution was measured by high-performance liquid chromatography. The degradation rate of FQs in the above system is shown in Table 1. Figure 1 .

[0052] Table 1 Degradation rate of different FQs concentration systems (%)

[0053] FQs concentration (ppm) 5 10 15 20 CIP 78 77 63 66 OFX 100 100 100 98

[0054] From Table 1 and Figure 1 The results show that as the FQs concentration in the composite solution increased from 5 ppm to 20 ppm, the CIP degradation rate decreased from 78% to 66% after 2 hours, and the OFX degradation rate decreased from 100% to 98%. The increase in FQs concentration had little effect on OFX, with 98% degradation achieved even at 20 ppm after 2 hours. This demonstrates that the LCCFO perovskite-activated PDS FQs degradation system is suitable for a wide range of pollutant concentrations.

[0055] Example 2 Effect of different initial pH of the system on degradation ability

[0056] In a typical system (LCCFO perovskite 0.25g / L, PDS concentration of 4mM, FQs concentration of 10ppm), the pH of the initial solution of the system was changed to 3, 4, 7, 8, 9, and 11, and magnetic stirring was added. Samples were taken at certain time intervals, and an equal amount of ethanol solution was added to quench the reaction and filtered. The concentration of FQs in the solution was detected by high-performance liquid chromatography. The post-reaction solution was filtered and recovered for testing, and the metal ion concentration in the solution was detected by atomic absorption spectrophotometry. The degradation rate of FQs in the above system is shown in Table 2. Figure 2 .

[0057] Table 2 Degradation rate of different FQs concentration systems (%)

[0058] Initial pH of the system 3 4 7 8 9 11 CIP 80 75 78 74 66 73 OFX 100 100 100 100 90 85

[0059] Note: Degradation rate = (C t / C0)*100%(C t : FQs concentration in the system at time t; C0: initial FQs concentration)

[0060] From Table 2 and Figure 2The results showed that the system is applicable in a wide pH range. The degradation rate is significantly accelerated under acidic conditions, and the degradation ability is slightly inhibited under alkaline conditions. However, for OFX, relatively excellent degradation effects can be achieved in all pH ranges. Even at a pH of 11, the system can achieve 85% degradation after 2 hours. For CIP, the degradation rate is slightly inhibited under alkaline conditions, but 73% degradation can still be completed. This shows that the LCCFO perovskite-activated PDS degradation FQs system is suitable for a relatively wide range of water pH conditions.

[0061] In order to explore the appropriate pH of the system, the metal ion concentration in the system after the reaction was detected. The metal ion concentration after the reaction at different system pH values ​​is shown in Table 3:

[0062] Table 3 Metal ion concentrations in the solution after reaction

[0063] Initial pH of the solution 3 4 7 8 9 11 <![CDATA[Cu 2+ (ppm)]]> 8.12 5.82 1.98 0.46 0.15 0.07 <![CDATA[Fe 2+ (ppm)]]> 0.27 0.25 0.26 0.21 0.23 0.29

[0064] As can be seen from Table 3, LCCFO perovskite can activate PDS to degrade FQs under a wide range of water pH conditions, and Cu 2+ 、Fe 2+ The amount of ion dissolution decreases with the increase of pH, and can reach the Class A standard of "Water Quality Control Project for Sewage Discharge into Urban Sewers" in neutral and alkaline conditions. The catalyst has a good degradation effect in the pH range of 7-11.

[0065] Example 3 Degradation of FQs in a high salt system

[0066] In a typical system (LCCFO perovskite 0.25g / L, PDS concentration of 4mM, FQs concentration of 10ppm, pH 7), NaCl (50, 150g / L), Na2SO4 (50, 100g / L), Na2CO3 (10g / L), NaHCO3 (10g / L), and KH2PO4 (50g / L) were added, respectively, and magnetic stirring was applied. Samples were taken at regular time intervals, and the reaction was quenched by adding an equal amount of ethanol solution and filtered. The concentration of FQs in the solution was measured by high-performance liquid chromatography. The degradation rate of FQs in the above system is shown in Table 4. Figure 3 .

[0067] Table 4 FQs degradation rate under different high salt environments (%)

[0068]

[0069] Note: Degradation rate = (C t / C0)*100%(C t : FQs concentration in the system at time t; C0: initial FQs concentration)

[0070] From Table 4 and Figure 3 The results showed that this system can adapt to higher salt concentration environment. - 、SO4 2- 、CO3 2- It showed a slight inhibitory effect on the system, but in all high-salt systems, OFX in the composite solution could achieve a degradation effect of more than 84% in 2 hours, and CIP could also achieve a degradation effect of more than 74%. - (50g / L), HCO 3- (10 g / L) showed a promoting effect on the system, indicating that this system has good high salt tolerance and can achieve effective degradation of FQs in a variety of high salt environments.

[0071] Example 4: Testing the Recycling Capacity of LCCFO Perovskite

[0072] In a typical system (LCCFO perovskite 0.25g / L, PDS concentration 4mM, FQs concentration 10ppm, pH 7) with magnetic stirring. Samples were taken at regular time intervals, and an equal amount of ethanol solution was added to quench the reaction and filtered. The concentration of FQs in the solution was measured by high-performance liquid chromatography. The catalyst was recovered after the reaction and washed alternately with ethanol and deionized water and dried. The above experiment was repeated four times using the recovered catalyst. The degradation rate of the cyclic test system is shown in Table 5. Figure 4 .

[0073] Table 5 Cyclic test degradation rate (%)

[0074] Number of cycles 1st 2nd 3rd 4th CIP 100 100 100 93 OFX 77 73 71 70

[0075] Note: Degradation rate = (C t / C0)*100%(C t : FQs concentration in the system at time t; C0: initial FQs concentration)

[0076] From Table 5 and Figure 4 The results show that after four cycles of LCCFO perovskite, the OFX degradation rate in the system can still be maintained at over 93% for 2 hours, and the CIP degradation rate in the system can still be maintained at over 70%. This shows that calcium ion doping not only significantly improves catalyst activity but also maintains a certain stability, making this reaction system conducive to recycling.

[0077] Comparative Example 1 Comparison of the degradation ability and stability of various modified copper-iron perovskites on the system

[0078] The modified perovskite was prepared by EDTA chelated gel sol method:

[0079] (1) Weigh a certain amount of copper nitrate trihydrate, iron nitrate nonahydrate, and lanthanum nitrate hexahydrate, and dissolve them in appropriate amount of deionized water; weigh a certain amount of EDTA and dissolve it in ammonia water; weigh a certain amount of citric acid and dissolve it in deionized water;

[0080] (2) Pour the EDTA aqueous solution into the citric acid solution, add the above mixed metal salt solution dropwise, and adjust the pH to about 7 with ammonia water;

[0081] (3) The uniform mixture was transferred to a water bath at 90°C and stirred to evaporate until a gel was formed; the gel was then placed in an oven at 240°C for 5 hours to obtain a fluffy intermediate product; the intermediate product was ground and calcined in a muffle furnace, with the temperature programmed to 450°C for preheating for 2 hours, and then continued to heat to 700°C for calcination for 6 hours. The obtained product was washed alternately with ethanol and deionized water, and dried in an oven overnight to obtain LaCu x Fe 1-x O3 perovskite (x = 0.1, 0.25, 0.5, 0.9), abbreviated as LCFO-1:9, LCFO-1:3, LCFO-1:1, LCFO-9:1.

[0082] In a typical system (catalyst 0.25 g / L, PDS concentration 4 mM, FQs concentration 10 ppm, pH 7), equal amounts of various modified copper-iron perovskites were added and magnetic stirring was applied. Samples were taken at regular intervals, the reaction was quenched by adding equal amounts of ethanol solution, and the solution was filtered. The FQs concentration in the solution was measured by high-performance liquid chromatography. The FQs degradation rates in the above systems are shown in Table 6. Figure 5 To investigate the stability of the catalyst, the post-reaction solution was filtered and recovered for testing. The metal ion concentration in the solution was measured using an atomic absorption spectrophotometer. The metal ion concentrations in the post-reaction solution of the above system are shown in Table 7.

[0083] From Table 6 and Figure 5 The results show that under the same experimental conditions, after 2 hours, LCFO-1:9 can degrade 69% of CIP and LCFO-9:1 perovskite can degrade 73% of CIP, but the degradation rate of OFX by these two perovskites is significantly weaker than that of LCCFO. LCFO-1:3 and LCFO-1:1 perovskites can both degrade OFX by 100%, but the degradation rates of CIP are 62% and 46% respectively, neither of which can simultaneously meet the requirements for efficient degradation of CIP and OFX in the composite solution. The prepared LCCFO-activated PDS can effectively degrade 81% of CIP and 100% of OFX at the same time. As can be seen from Table 7, compared with other modified perovskites, LCCFO maintains high activity while also meeting the Class A standard of the "Water Quality Control Project for Wastewater Discharge into Urban Sewers" for metal ion dissolution. It is efficient and environmentally friendly and is expected to be suitable for advanced oxidation reactions in composite water bodies.

[0084] Table 6 FQs degradation rate of different perovskite systems (%)

[0085] Catalyst system LCCFO LCFO-1:9 LCFO-1:3 LCFO-1:1 LCFO-9:1 CIP 81 69 62 46 73 OFX 100 82 100 100 81

[0086] Note: Degradation rate = (C t / C0)*100%(C t : FQs concentration in the system at time t; C0: initial FQs concentration).

[0087] Table 7 Metal ion concentrations after reaction in different perovskite systems

[0088] Catalyst system LCCFO LCFO-1:9 LCFO-1:3 LCFO-1:1 LCFO-9:1 <![CDATA[Cu 2+ (ppm)]]> 1.67 0.18 0.7 1.52 1.87 <![CDATA[Fe 2+ (ppm)]]> 0.22 0.2 0.2 0.19 0.21

[0089] Comparative Example 2 Comparison of the degradation ability of different alkaline earth metal doped perovskites on the system

[0090] Alkaline earth modified perovskite was also prepared by EDTA chelated gel sol method, using strontium chloride hexahydrate to replace calcium ions. The obtained perovskite is recorded as La 0.9 Sr 0.1 Cu 0.5 Fe 0.5 O3, referred to as LSCFO perovskite. In a typical system (catalyst 0.25g / L, PDS concentration 4mM, FQs concentration 10ppm, pH 7), equal amounts of alkaline earth metal-modified copper iron perovskite were added and magnetic stirring was applied. Samples were taken at regular time intervals, the reaction was quenched by adding equal amounts of ethanol solution, and the solution was filtered. The concentration of FQs in the solution was measured by high-performance liquid chromatography. The FQs degradation rate in the above system is shown in Table 8. Figure 6 .

[0091] Table 8 FQs degradation rate of different alkaline earth metal perovskite systems (%)

[0092] Catalyst system LCCFO LSCFO CIP 84 56 OFX 100 88

[0093] Note: Degradation rate = (C t / C0)*100%(C t : FQs concentration in the system at time t; C0: initial FQs concentration)

[0094] From Table 8 and Figure 6 The results show that after 2 h of reaction, LSCFO can only degrade 56% of CIP and 88% of OFX in the system, while LCCFO can degrade 84% of CIP and 100% of OFX. The degradation performance of LCCFO perovskite for FQs in the composite system is significantly better than that of LSCFO.

Claims

1. A method for degrading fluoroquinolone antibiotics in high-salt wastewater, characterized in that: LaCaCuFeO perovskite and persulfate are added to high-salinity wastewater for degradation treatment; the high-salinity wastewater is wastewater with a total dissolved solids mass fraction greater than 3.5%; the fluoroquinolone antibiotics are ofloxacin and ciprofloxacin; High-salt wastewater includes any one or more of the following cations: Na + , K + ; and any one or more of the following anions: Cl - 、HCO3 - 、CO3 2- 、H2PO4 - 、SO4 2- ; The dosage of LaCaCuFeO perovskite relative to water or high-salt wastewater is 0.2-0.25 g / L; The persulfate is selected from sodium persulfate, potassium persulfate, or a combination of the two; The LaCaCuFeO perovskite is prepared by a sol-gel method with EDTA chelation: A soluble copper salt, a soluble iron salt, a soluble lanthanum salt, a soluble calcium salt, EDTA, and citric acid are dispersed and dissolved in water and mixed to obtain a mixed system. The pH is then adjusted to neutral, the mixture is heated to produce a gel, and the gel is dried, ground, and subsequently calcined. The metal molar ratio in the mixed system is La:Ca:Cu:Fe=9:1:5:

5.

2. The method according to claim 1, characterized in that The soluble copper salt is selected from copper nitrate or its hydrate, copper sulfate or its hydrate, copper chloride or its hydrate; the soluble iron salt is selected from iron nitrate or its hydrate, iron sulfate or its hydrate, iron chloride or its hydrate; the soluble lanthanum salt is selected from lanthanum nitrate or its hydrate; the soluble calcium salt is selected from calcium chloride, calcium nitrate or its hydrate.

3. The method according to claim 1, characterized in that Heat to a gel temperature of 80-100°C.

4. The method according to any one of claims 1 to 3, characterized in that The calcination is performed by preheating at 450° C. for 2 h, and then continuing to heat up to 700° C. and calcining for 6 h.

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