A g-C3N4 / FeCu-LDH composite material, its preparation method and application

Abstract

This invention belongs to the field of composite material technology, and relates to a g-C3N4 / FeCu-LDH composite material, its preparation method, and its application. The preparation method includes: 1) synthesizing g-C3N4 from urea; 2) dispersing Fe(NO3)3·9H2O and Cu(NO3)3·3H2O in water to obtain solution A; dispersing NaOH in water to obtain solution B; dispersing NaNO3 and formamide in water to obtain solution C; simultaneously adding solutions A and B to solution C, stirring and washing under a N2 atmosphere to obtain FeCu-LDH; 3) mixing g-C3N4 and ethanol, then adding FeCu-LDH, ultrasonicating, stirring in a water bath, and grinding to obtain the composite material. Using the composite material prepared by this invention as a catalyst, it can generate active substances under photo-assisted conditions, which synergistically interact with the free radicals generated by activated oxidants, effectively improving the removal of pollutants.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and relates to a g-C3N4 / FeCu-LDH composite material, its preparation method and application. Background Technology

[0002] Over the past few decades, antibiotics, especially tetracyclines, have been used in aquaculture and for medical treatment in humans and animals. However, the long half-life and poor metabolism of tetracyclines have caused harm to ecosystems and human health.

[0003] Tetracyclines (TCs), broad-spectrum antibiotics, mainly include tetracycline, oxytetracycline, chlortetracycline, demeclocycline, doxycycline, and minocycline, and are widely used in the medical, animal husbandry, and aquaculture industries. The large-scale entry of antibiotics and their intermediates into the environment leads to the selection of resistant strains and antibiotic resistance among microbial populations, and even causes carcinogenicity, teratogenicity, and mutagenicity, interfering with physiological functions and seriously threatening human health and the ecological environment. Therefore, advanced oxidation technology based on the in-situ generation of highly reactive free radicals from strongly reactive substances can remove TCs simply, effectively, and economically. Through catalytic activation by enhancers such as H2O2 and persulfate, more reactive hydroxyl radicals (·OH) and superoxide radicals (·O2) are generated. - ) and sulfate free radicals (SO4) ·- These strong oxidizing free radicals degrade TCs into CO2, H2O and other inorganic salts, ultimately achieving the harmless disposal of TCs.

[0004] Compared with other oxidation technologies, advanced oxidation technologies have the following advantages: First, they have a fast catalytic reaction rate; second, they are non-selective, and highly reactive free radicals such as ·OH can degrade almost all organic pollutants; third, they operate under mild catalytic conditions, typically requiring low temperature, pressure, or strong acid or strong alkaline media; fourth, they can rapidly generate a series of chain reactions, and ·OH itself has a strong electron affinity (569.3 kJ), which can induce the dehydrogenation of saturated hydrocarbons to generate free radicals R·, promoting the self-oxidation of organic matter; fifth, they can be used in combination with multiple technologies, such as biological and physical methods, which can significantly reduce the concentration of organic pollution or the retention of intermediates; sixth, they are easy to assemble and manage, and simple to operate. g-C3N4 is a graphite-like layered polymer semiconductor, with layers consisting of sp atoms of C and N atoms. 2The large π-bond conjugated system composed of orbital hybridization, with the interlayer connected by van der Waals forces to form a blocky structure, has great application prospects in the field of photocatalysis due to its suitable band gap (2.7 eV), unique electronic band structure, excellent physical and chemical stability, green and simple synthesis process, and easy functionalization. It can be used in advanced oxidation technologies, but pure graphitic carbon nitride has the following disadvantages: (1) the band gap of pure graphitic carbon nitride is insufficient to respond to visible light; (2) the recombination rate of photogenerated carriers separated by pure graphitic carbon nitride under visible light is too high; (3) pure graphitic carbon nitride is easily decomposed by its own photogenerated holes, resulting in weak activity and poor cycle stability. Summary of the Invention

[0005] To address the technical problems of low activity and poor stability of existing catalysts, this invention provides a g-C3N4 / FeCu-LDH composite material, its preparation method, and its application. Under light assistance, the catalyst itself generates active substances, which, together with the free radicals generated by the simultaneously activated oxidant, effectively improve the removal of pollutants.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a g-C3N4 / FeCu-LDH composite material includes the following steps:

[0008] 1) Synthesis of g-C3N4

[0009] Urea was synthesized into thin-layer g-C3N4 using a two-step calcination method:

[0010] 2) FeCu-LDH Synthesis

[0011] 2.1) Disperse Fe(NO3)3·9H2O and Cu(NO3)3·3H2O in water to obtain solution A; the ratio of Fe(NO3)3·9H2O, Cu(NO3)3·3H2O and water is 0.0001~0.0005mol: 0.0002~0.001mol: 10~50ml;

[0012] 2.2) Disperse NaOH in water to obtain solution B; the ratio of NaOH to water is 0.001-0.005 mol: 10-50 ml;

[0013] 2.3) Disperse NaNO3 and formamide in water to obtain solution C; the ratio of NaNO3, formamide and water is 0.0003-0.0005 mol: 10-11.5 mL: 300-355 mL;

[0014] 2.4) Add solutions A and B to solution C simultaneously, stir under N2 atmosphere, and wash to obtain FeCu-LDH;

[0015] 3) Synthesis of g-C3N4 / FeCu-LDH

[0016] 3.1) Disperse g-C3N4 in ethanol and sonicate to obtain g-C3N4 turbidity;

[0017] 3.2) Weigh FeCu-LDH and add it to g-C3N4 turbidity, then sonicate to obtain a dispersion;

[0018] 3.3) Under water bath conditions, the dispersion was stirred and the ethanol was evaporated. The product was then ground to obtain the g-C3N4 / FeCu-LDH composite material.

[0019] The mass ratio of g-C3N4, ethanol and FeCu-LDH is 0.01-0.05g: 10-30ml: 0.0025-0.025g.

[0020] Further specifying that in step 2.4), the washing process uses an alternating washing method of distilled water and ethanol.

[0021] Further specifying, in steps 3.1) and 3.2), the stirring conditions are: time 30 min, power 490W~500W.

[0022] Further specifying, in step 3.3), the water bath conditions are: temperature 70℃~80℃, time 3h~5h.

[0023] Further specifying, step 1) specifically includes:

[0024] 1.1) Urea is calcined once, cooled to room temperature, and then ground to obtain a solid.

[0025] 1.2) g-C3N4 is obtained by calcining the solid twice.

[0026] Further specifying, the conditions for both the first and second calcination are: temperature 500℃~520℃, time 2h~3h.

[0027] Further specified, both the primary and secondary calcinations employ gradient heating at a rate of 5°C / min.

[0028] The g-C3N4 / FeCu-LDH composite material prepared by the aforementioned preparation method.

[0029] The application of the aforementioned g-C3N4 / FeCu-LDH composite material as a catalyst in the degradation of antibiotic wastewater.

[0030] The beneficial effects of this invention are:

[0031] 1. The preparation method of the present invention first uses thermal polycondensation and wet chemical method to synthesize g-C3N4 and FeCu-LDH respectively, and then further synthesizes g-C3N4 / FeCu-LDH composite catalyst. Its low recombination rate of photogenerated electrons and holes is conducive to the separation and migration of electrons and holes and further redox reactions to generate active substances, thereby improving photocatalytic performance.

[0032] 2. The g-C3N4 / FeCu-LDH prepared by this invention has a wider light response range and is more easily excited to generate photogenerated carriers than pure g-C3N4. Under light assistance, it can generate active substances, which work synergistically with the free radicals generated by the activated oxidant to effectively improve the removal of pollutants.

[0033] 3. This invention reduces the cost of catalysts by loading copper and iron into a pure g-C3N4 framework and replacing the precious metals in existing catalysts with copper and iron.

[0034] 4. The g-C3N4 / FeCu-LDH catalyst prepared in this invention exhibits good catalytic activity. In wastewater treated with persulfate (PMS) to degrade tetracycline (TC), TC was removed to 85% without LED illumination, and to 99% under illumination. This demonstrates that copper and iron ions can activate PMS to produce SO4. ·- The catalyst directly disrupts the chemical structure of TC, achieving photocatalytic degradation. Furthermore, the presence of coexisting anions in the actual aquatic environment significantly affects TC removal efficiency. The influence of anions on TC degradation was also investigated, with the catalyst maintaining a photocatalytic removal rate of 87–99% for most anions. Attached Figure Description

[0035] Figure 1 XRD patterns of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH catalysts;

[0036] Figure 2 SEM images of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH;

[0037] Figure 3 UV-Vis DRS and Eg spectra of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts with different mass ratios;

[0038] Figure 4 PL spectra of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts with different mass ratios;

[0039] Figure 5 The IT and EIS diagrams are for g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH catalysts.

[0040] Figure 6 Degradation and first-order kinetics of TC by g-C3N4 / FeCu-LDH composites in different systems and with different mass ratios were simulated. (ac) Degradation and first-order kinetics of TC in different systems; (df) Degradation and first-order kinetics of TC by g-C3N4 / FeCu-LDH composites with different mass ratios; Conditions: [catalyst] = 100 mg / L, [PMS] = 0.5 mM, pH = 5 and TC = 20 ppm;

[0041] Figure 7 XRD and FTIR spectra of the g-C3N4 / FeCu-LDH catalyst for cyclic degradation experiments, quencher experiments, and the catalytic degradation experiment; (a) cyclic degradation experiment; (b) quencher experiment; (c, d) XRD and FTIR spectra of the g-C3N4 / FeCu-LDH catalyst; conditions: [catalyst] = 100 mg / L, [PMS] = 0.5 mM, pH = 5 and TC = 20 ppm;

[0042] Figure 8 Anion interference experiment; conditions: [catalyst] = 100 mg / L, [PMS] = 0.5 mM, pH = 5 and TC = 20 ppm. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] A method for preparing a g-C3N4 / FeCu-LDH composite material includes the following steps.

[0045] 1) Synthesis of g-C3N4

[0046] This step involves synthesizing thin-layer g-C3N4 from urea using a two-step calcination method, specifically including:

[0047] 1.1) Urea is calcined once, cooled to room temperature, and then ground to obtain a solid.

[0048] 1.2) g-C3N4 is obtained by calcining the solid twice.

[0049] The conditions for both primary and secondary calcination were: temperature 500℃~520℃, time 2h~3h.

[0050] Both the primary and secondary calcinations employed gradient heating at a rate of 5°C / min.

[0051] 2) FeCu-LDH Synthesis

[0052] 2.1) Disperse Fe(NO3)3·9H2O and Cu(NO3)3·3H2O in water to obtain solution A; the ratio of Fe(NO3)3·9H2O, Cu(NO3)3·3H2O and water is 0.0001~0.0005mol: 0.0002~0.001mol: 10~50ml.

[0053] 2.2) Disperse NaOH in water to obtain solution B; the ratio of NaOH to water is 0.001-0.005 mol: 10-50 ml.

[0054] 2.3) Disperse NaNO3 and formamide in water to obtain solution C; the ratio of NaNO3, formamide and water is 0.0003~0.0005mol: 10~11.5mL: 300~355mL.

[0055] 2.4) Add solutions A and B to solution C simultaneously, stir under N2 atmosphere, and wash to obtain FeCu-LDH.

[0056] In step 2.4), the washing process uses an alternating washing method with distilled water and ethanol.

[0057] 3) Synthesis of g-C3N4 / FeCu-LDH

[0058] 3.1) Disperse g-C3N4 in ethanol and sonicate to obtain g-C3N4 turbidity;

[0059] 3.2) Weigh FeCu-LDH and add it to g-C3N4 turbidity, then sonicate to obtain a dispersion;

[0060] 3.3) Under water bath conditions, the dispersion was stirred and the ethanol was evaporated. The product was then ground to obtain the g-C3N4 / FeCu-LDH composite material.

[0061] The mass ratio of g-C3N4, ethanol and FeCu-LDH is 0.01-0.05g: 10-30ml: 0.0025-0.025g.

[0062] In both step 3.1) and step 3.2), the stirring conditions are: time 30 min, power 490-500 W.

[0063] In step 3.3), the water bath conditions are: temperature 70℃~80℃, time 3~5h.

[0064] The application of the g-C3N4 / FeCu-LDH composite material prepared in this invention as a catalyst in the degradation of antibiotic wastewater.

[0065] The preparation and performance of the catalyst of the present invention will be explained in detail below with several specific examples.

[0066] It should be noted that, unless otherwise specified, the operations used in the following embodiments are all conventional operations in the art. The pharmaceutical reagents used in the following embodiments were all purchased from the market.

[0067] Example 1

[0068] (1) Thin-layer g-C3N4 was synthesized by a two-step calcination method.

[0069] 10g of urea was placed in an alumina crucible and then in the center of a muffle furnace. The furnace was heated at 520℃ for 2 hours at a speed of 5℃ / min. After cooling to ambient temperature, the urea was removed and ground evenly to obtain a light yellow solid. Then, the solid was placed back into the alumina crucible and heated in a muffle furnace at 520℃ for 4 hours at a speed of 5℃ / min to obtain a light white solid, labeled as g-C3N4.

[0070] (2) Synthesis of FeCu-LDH

[0071] 0.0005 mol Fe(NO3)3·9H2O and 0.001 mol Cu(NO3)3·3H2O were dispersed in 50 mL of distilled water and labeled as solution A.

[0072] 0.005 mol NaOH was dispersed in 50 mL of distilled water and labeled as solution B.

[0073] 0.0005 mol NaNO3 and 11.5 mL formamide were dispersed in 355 mL distilled water and labeled as solution C.

[0074] Solution A and solution B were simultaneously added to solution C, and the mixture was stirred for 1 hour at room temperature under a N2 atmosphere. The resulting colloidal dispersion was then washed three times alternately with distilled water and ethanol.

[0075] (3) Synthesis of g-C3N4 / FeCu-LDH catalyst

[0076] First, 0.05 g of g-C3N4 was dispersed in 30 mL of ethanol and sonicated for 30 min (500 W) to obtain a milky white g-C3N4 turbidity.

[0077] Then, weigh 0.0005g FeCu-LDH and add it to g-C3N4 turbidity, and continue sonication for 30min to obtain a uniform dispersion.

[0078] Finally, the dispersion was placed in a water bath at 70°C and stirred for 4 hours until the ethanol evaporated to dryness. After grinding, the catalyst was obtained and denoted as 1% g-C3N4 / FeCu-LDH catalyst, where 1% represents the mass ratio of FeCu-LDH to g-C3N4.

[0079] Example 2

[0080] (1) Synthesis of g-C3N4: Same as in Example 1;

[0081] (2) Synthesis of FeCu-LDH: Same as in Example 1;

[0082] (3) Synthesis of 5% g-C3N4 / FeCu-LDH catalyst

[0083] First, 0.05 g of g-C3N4 was dispersed in 30 mL of ethanol and sonicated for 30 min (500 W) to obtain a milky white turbid liquid.

[0084] Then, 0.0025g of FeCu-LDH was weighed and added to g-C3N4 turbidity, and sonicated for another 30 minutes to obtain a uniform dispersion.

[0085] Finally, the dispersion was placed in a water bath at 70°C and stirred for 5 hours until the ethanol evaporated to dryness. After grinding, the catalyst was obtained and designated as 5% g-C3N4 / FeCu-LDH catalyst, where 5% represents the mass ratio of FeCu-LDH to g-C3N4.

[0086] Example 3

[0087] (1) Synthesis of g-C3N4: Same as in Example 1;

[0088] (2) Synthesis of FeCu-LDH: Same as in Example 1;

[0089] (3) Synthesis of 30% g-C3N4 / FeCu-LDH catalyst

[0090] First, 0.05 g of g-C3N4 was dispersed in 30 mL of ethanol and sonicated for 30 min (500 W) to obtain a milky white turbid liquid.

[0091] Then, 0.015g of FeCu-LDH was weighed and added to g-C3N4 turbidity, and sonicated for another 30 minutes to obtain a uniform dispersion.

[0092] Finally, the dispersion was placed in a water bath at 80°C and stirred for 4 hours until the ethanol evaporated to dryness. After grinding, the catalyst was obtained and designated as 30% g-C3N4 / FeCu-LDH catalyst, where 30% represents the mass ratio of FeCu-LDH to g-C3N4.

[0093] Under LED light irradiation for 30 minutes, the degradation rate of TC by 30% g-C3N4 / FeCu-LDH / PMS reached 99%. Compared with pure g-C3N4 / PMS (62%), the 30% g-C3N4 / FeCu-LDH / PMS composite catalyst has the strongest photocatalytic activity.

[0094] Example 4

[0095] (1) Synthesis of g-C3N4: Same as in Example 1;

[0096] (2) Synthesis of FeCu-LDH: Same as in Example 1;

[0097] (3) Synthesis of 50% g-C3N4 / FeCu-LDH catalyst

[0098] First, 0.05 g of g-C3N4 was dispersed in 30 mL of ethanol and sonicated for 30 min (500 W) to obtain a milky white turbid liquid.

[0099] Then, 0.025g of FeCu-LDH was weighed and added to g-C3N4 turbidity, and sonicated for another 30 minutes to obtain a uniform dispersion.

[0100] Finally, the dispersion was placed in a water bath at 80°C and stirred for 3 hours until the ethanol evaporated to dryness. After grinding, the catalyst was obtained and designated as 50% g-C3N4 / FeCu-LDH catalyst, where 50% represents the mass ratio of FeCu-LDH to g-C3N4.

[0101] The prepared composite material was subjected to the following verification tests to demonstrate its catalytic performance.

[0102] Verification 1: X-ray diffraction (XRD)

[0103] Samples: g-C3N4, FeCu-LDH, and 30% g-C3N4 / FeCu-LDH prepared in each step of Example 3*

[0104] XRD patterns of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH were obtained using X-ray diffraction, thus verifying the crystal structures of the catalysts. The XRD patterns are shown below. Figure 1 As shown.

[0105] like Figure 1It can be seen that pure g-C3N4 exhibits two typical characteristic diffraction peaks. The peaks at 2θ, at 12.4° and 27.4°, belong to the in-plane stacked heptaazine units (100) and the π-π interlayer stacking (002) of g-C3N4, respectively. Peaks 003, 006, 009, and 110 are characteristic diffraction peaks of FeCu-LDH. Furthermore, since the integration of g-C3N4 and FeCu-LDH is prepared through physical mixing, no other new characteristic peaks appeared. Moreover, the characteristic diffraction peaks of g-C3N4 / FeCu-LDH at 2θ are consistent with those of g-C3N4 and FeCu-LDH, indicating that we have successfully prepared the g-C3N4 / FeCu-LDH catalyst.

[0106] Verification 2: Scanning electron microscopy (SEM)

[0107] Samples: g-C3N4, FeCu-LDH, and 30% g-C3N4 / FeCu-LDH prepared in each step of Example 3.

[0108] SEM images of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH were obtained using scanning electron microscopy. The results are as follows: Figure 2 As shown, where, Figure 2 (a) is a SEM image of g-C3N4; (b) is a SEM image of FeCu-LDH; (c) and (d) are SEM images of g-C3N4 / FeCu-LDH, respectively.

[0109] See Figure 2 It is evident that g-C3N4, a thin-layered sheet-like structure obtained by calcining urea twice at high temperatures, can effectively promote the attraction between urea and organic pollutants through certain forces (such as electrostatic interactions and hydrogen bonds), causing organic pollutants to adhere to the surface of the thin-layered sheet-like structure. FeCu-LDH is composed of numerous nanosheets with uneven surfaces. The g-C3N4 / FeCu-LDH catalyst shows that g-C3N4 and FeCu-LDH are integrated together by electrostatic interactions. This indicates the successful preparation of the g-C3N4 / FeCu-LDH catalyst.

[0110] Verification 3: UV-Vis DRS

[0111] Samples: g-C3N4 and 30% FeCu-LDH prepared in each step of Example 3, and g-C3N4 / FeCu-LDH with different mass ratios prepared in Examples 1 to 4.

[0112] Using a UV-Vis DSR instrument (model TU-1901), baseline scanning was performed on BaSO4 to subtract the influence of blank values. The scanning wavelength range was 200–800 nm with 2 nm intervals, and the UV-Vis DRS and Eg spectra of g-C3N4, FeCu-LDH, and catalysts with different mass ratios of g-C3N4 / FeCu-LDH were obtained. The results are as follows: Figure 3 As shown, Figure 3 (a) UV-Vis DRS of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts with different mass ratios; Figure 3 (b) shows the Eg spectra of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts with different mass ratios.

[0113] Figure 3 As shown in (a), UV-vis DRS measurements indicate that the absorption edge of pure g-C3N4 is approximately at a wavelength of 450 nm. With increasing FeCu-LDH content, the absorption edge gradually red-shifts, suggesting that the introduction of FeCu-LDH enhances the light capture capacity of pure g-C3N4. (Based on Tauc plots (αhv)) 1 / 2 =A(hv-Eg) calculates the band gap energy. Where hv is the photon energy (h is Planck's constant, v is the light frequency), Eg is the apparent band gap, A is a constant, and α is the absorption coefficient.

[0114] like Figure 3 (b) It can be seen that the band gap values ​​of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH are 2.80eV, 1.88eV and 2.76eV, respectively. Compared with pure g-C3N4, g-C3N4 / FeCu-LDH has a wider optical response range and is more easily excited to generate photogenerated carriers than g-C3N4.

[0115] Verification of photoluminescence emission spectra (PL) of 4 cells

[0116] Samples: g-C3N4, FeCu-LDH, and 30% g-C3N4 / FeCu-LDH prepared in each step of Example 3.

[0117] PL spectra of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH were obtained using X-ray diffraction to verify the separation efficiency of photogenerated electrons and holes on the g-C3N4, g-C3N4 / FeCu-LDH, and FeCu-LDH catalysts; the results are as follows. Figure 4 As shown.

[0118] Depend on Figure 4It can be seen that the emission peak intensity of g-C3N4 at a wavelength of 460 nm is much higher than that of g-C3N4 / FeCu-LDH and FeCu-LDH catalysts. In addition, g-C3N4 / FeCu-LDH has the lowest emission peak, which proves that its recombination rate of photogenerated electrons and holes is low, which is conducive to the separation and migration of electrons and holes and further redox reactions to generate active substances, thereby improving photocatalytic performance.

[0119] Validation of transient photocurrent (IT) and electrochemical impedance spectroscopy (EIS) measurements.

[0120] Samples: g-C3N4, FeCu-LDH, and 30% g-C3N4 / FeCu-LDH prepared in each step of Example 3.

[0121] The photoresponse performance of g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH catalysts was investigated using IT and EIS tests. The IT and EIS plots of the g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH catalysts were obtained, and the results are shown below. Figure 5 As shown, Figure 5 (a) is the IT diagram of g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts; Figure 5 (b) shows the EIS diagrams of the g-C3N4, FeCu-LDH and g-C3N4 / FeCu-LDH catalysts.

[0122] Depend on Figure 5 (a) It can be seen that the photocurrent density of g-C3N4 / FeCu-LDH is higher than that of g-C3N4 and FeCu-LDH, indicating that the g-C3N4 / FeCu-LDH catalyst generates photocurrent when photoexcited. - and h + Effective separation or diffusion can be achieved. Furthermore, according to... Figure 5 (b) It can be seen that compared with g-C3N4 and FeCu-LDH, g-C3N4 / FeCu-LDH has the smallest radius of curvature, i.e., the smallest resistance. This indicates that g-C3N4 / FeCu-LDH has the fastest electron transport rate, i.e., photogenerated electrons. - and h + The recombination rate is the lowest. FeCu-LDH and g-C3N4 have better integration and enhance photocatalytic activity.

[0123] Verification 6: Photocatalytic Performance Analysis

[0124] 1. Degradation and first-order kinetics of TC in different systems

[0125] Samples: g-C3N4, FeCu-LDH, and 30% g-C3N4 / FeCu-LDH prepared in each step of Example 3.

[0126] Figure 6 (ac) test process.

[0127] The experimental group setup is as follows.

[0128] Blank test (Black) - no catalyst, no PMS, and no light irradiation were added to the wastewater.

[0129] Group 1: PMS was added to the wastewater and light was applied.

[0130] Group 2: Add g-C3N4, PMS and light irradiation to wastewater.

[0131] Group 3: Add FeCu-LDH, PMS and light irradiation to wastewater.

[0132] Group 4: Wastewater with g-C3N4 / FeCu-LDH, PMS, and no light irradiation.

[0133] Group 5: Add g-C3N4 / FeCu-LDH, PMS, and light irradiation to the wastewater.

[0134] Group 6: Add g-C3N4-Cu to the wastewater, do not add PMS, and irradiate with light.

[0135] Experimental conditions: Catalyst dosage = 100 mg / L, [PMS] dosage = 0.5 mM, initial pH of wastewater degradation = 5, tetracycline wastewater TC concentration = 20 ppm. Experiments were conducted according to the corresponding catalyst types and dosages for the above groups. Wastewater degradation lasted 30 minutes. The tetracycline concentration (C) in the wastewater was measured every 5 minutes from 0 to 30 minutes. The C / C ratio was calculated to determine the degradation rate over time curve and to perform a first-order kinetic simulation. (See [link to relevant documentation]). Figure 6 (a) Figure 6 (b) and Figure 6 As shown in (c).

[0136] See also Figure 6 As shown in (ac), under blank conditions, the TC concentration remained almost unchanged, and its structure remained intact after stirring for 1 hour. Under LED light irradiation, the TC removal rate was 52% after the addition of PMS. In the g-C3N4 / FeCu-LDH system, without the addition of PMS, the TC removal rate was 30%. Most of the TC was adsorbed on the surface of the sheet-like catalyst, and a small amount of TC was degraded by a small number of free radicals generated by photocatalytic activation.

[0137] The degradation rates of TC by g-C3N4 / PMS, FeCu-LDH / PMS, and g-C3N4 / FeCu-LDH / PMS were 62%, 85%, and 99%, respectively. Compared with the pure g-C3N4 / PMS system, the g-C3N4 / FeCu-LDH / PMS composite catalyst exhibits strong photocatalytic activity. Furthermore, even without LED light irradiation, g-C3N4 / FeCu-LDH / PMS could remove up to 85% of TC, indicating that copper and iron ions can also activate PMS to produce SO4. ·- This directly disrupts the chemical structure of TC. To further understand the degradation rate of TC, the following formula was used for first-order kinetic simulation:

[0138] -ln(C / C0)=kt

[0139] Where k represents the first-order rate constant (min) -1 ); t represents the reaction time; C0 and C represent the initial and final concentrations of TC degradation at time t, respectively. The removal rates of PMS, g-C3N4, FeCu-LDH, and g-C3N4 / FeCu-LDH catalysts were 0.01855 min. -1 0.02481min -1 0.04291min -1 0.11539min -1 This is because during the photocatalytic process, the electrons on the conduction band of the g-C3N4 / FeCu-LDH composite material... - or price band retention h + They react with dissolved oxygen (O2) or H2O respectively to generate ·O2 - ·OH, simultaneously activating PMS to produce SO4. ·- ·OH, both of which synergistically degrade TC. Among them, the g-C3N4 / FeCu-LDH composite material exhibits excellent photocatalytic performance.

[0140] 2. Degradation of TC and first-order kinetic simulation of g-C3N4 / FeCu-LDH composites with different mass ratios.

[0141] A simple physical mixing method was used to load FeCu-LDH onto thin-layer g-C3N4 with different mass ratios. Specifically, the mass ratios of FeCu-LDH to g-C3N4 were 0%, 1%, 5%, 10%, 30%, and 50%, respectively.

[0142] Experimental conditions: Catalyst dosage = 100 mg / L, [PMS] dosage = 0.5 mM, initial pH of wastewater degradation = 5, tetracycline wastewater TC concentration = 20 ppm. Experiments were conducted according to the corresponding catalyst types and dosages for the above groups. Wastewater degradation lasted 30 minutes. Within 0–30 minutes, the tetracycline concentration (C) in the wastewater was measured every 5 minutes. The C / C ratio was calculated, and the degradation rate trend over time and first-order kinetic simulation were obtained. (See [link to relevant documentation]). Figure 6 (d) Figure 6 (e) and Figure 6 As shown in (f).

[0143] like Figure 6 As shown in (df), the photocatalytic activation performance for PMS degradation increases with increasing FeCu-LDH loading. Furthermore, according to first-order kinetic simulations, the degradation performance of 30% g-C3N4 / FeCu-LDH (k = 0.11539 min) is significantly improved. -1 The degradation rate of TC is g-C3N4 (k = 0.02481 min). -1 4.6 times that of ).

[0144] Verification 7

[0145] (1) Stability test

[0146] Four cycles of TC degradation experiments were conducted on the g-C3N4 / FeCu-LDH catalyst.

[0147] Sample: g-C3N4 / FeCu-LDH prepared in Example 3

[0148] Experimental conditions: Catalyst dosage = 100 mg / L, [PMS] dosage = 0.5 mM, initial pH of wastewater degradation = 5, tetracycline wastewater TC concentration = 20 ppm. Wastewater was degraded for 30 min. Within the 0–30 min period, the tetracycline concentration (C) in the wastewater was measured every 5 min, the C / C ratio was calculated, and the degradation rate over time was observed. The catalyst was then recovered, and the degradation of tetracycline wastewater with a concentration of 20 ppm was repeated using the same method for a total of four cycles. Results are as follows: Figure 7 As shown, where, Figure 7 (a) Cyclic degradation experiment; Figure 7 (b) Quenching agent experiment; Figure 7 (c) and Figure 7 (d) are the XRD and FTIR spectra of the g-C3N4 / FeCu-LDH catalyst, respectively.

[0149] Depend on Figure 7(a) It can be seen that the degradation rates of TC sequentially were 99%, 98%, 98%, and 89%, respectively. However, the degradation rate of TC decreased slightly after the fourth cycle, which may be due to a small portion of the intermediates of TC being destroyed adsorbed on the catalyst surface after multiple cycles, or a very small amount of iron or copper ions escaping from the catalyst surface. However, after four consecutive cycles, the degradation rate can still reach over 89%. The results show that the g-C3N4 / FeCu-LDH catalyst has good stability and reproducibility in photocatalysis.

[0150] (2) Quenching agent experiment

[0151] Quenching agent experiments were conducted on the g-C3N4 / FeCu-LDH catalyst.

[0152] Sample: 30% g-C3N4 / FeCu-LDH prepared in Example 3

[0153] Experimental conditions: Triethanolamine (TEOA), tert-butanol (TBA), p-benzoquinone (BQ), and L-histidine were used to fill holes (h) + ), ·OH, ·O 2- and 1 O2 active substance quencher. Catalyst addition amount = 100 mg / L, quencher dosage = 0.5 mM, initial pH of wastewater degradation = 5, tetracycline wastewater TC concentration = 20 ppm. The 30% g-C3N4 / FeCu-LDH prepared in Example 3 was tested to degrade wastewater for 30 min. The tetracycline concentration C in the wastewater was measured every 5 min within the 0–30 min period. The C / C ratio was calculated, and the degradation rate trend over time was obtained. The results are as follows: Figure 7 As shown in (b).

[0154] Depend on Figure 7 (b) It is shown that the addition of TEOA, TBA, EtOH, BQ, and L-histidine resulted in TC degradation rates of 37%, 66%, 60%, 32%, and 74%, respectively. The quenching results indicate that all active substances, including SO4, were degraded. ·- ,·OH,·O2 - h + and 1 O2 and other substances participate in the degradation process of TC.

[0155] In addition, we examined the catalyst structure after multiple cycles. Figure 7 (c) and Figure 7 As shown in (d), XRD and FT-IR indicate that the crystal structure and chemical structure of the catalyst have not changed significantly, further supporting the stability of the g-C3N4 / FeCu-LDH catalyst.

[0156] Experiment to verify the interference of 8 anions

[0157] Anion interference experiments were conducted on the g-C3N4 / FeCu-LDH catalyst.

[0158] Sample: 30% g-C3N4 / FeCu-LDH prepared in Example 3

[0159] Experimental conditions: Under optimal experimental conditions, the effects of anions such as nitrate (NO3) on the g-C3N4 / FeCu-LDH system were investigated. - ), sulfate (SO4) 2- ), chloride (Cl - ) and bicarbonate (HCO3) - ), carbonates (CO3) 2- ), phosphate (HPO4) 2- The effect of catalyst addition on TC degradation. Catalyst addition amount = 100 mg / L, anion dosage = 0.5 mM, initial pH of wastewater degradation = 5, TC concentration in tetracycline wastewater = 20 ppm.

[0160] The 30% g-C3N4 / FeCu-LDH prepared in Example 3 was tested to degrade wastewater for 30 minutes. The tetracycline concentration (C) in the wastewater was measured every 5 minutes from 0 to 30 minutes, and the C / C ratio was calculated. The degradation rate over time was also determined. The results are as follows: Figure 8 As shown.

[0161] like Figure 8 The results show that the photocatalytic removal rate of most anions remains at 87-99%, indicating that the catalyst prepared in this invention has a good anti-interference ability against anions.

[0162] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a g-C3N4 / FeCu-LDH composite material in assisting the photocatalytic degradation of tetracycline wastewater by persulfate, characterized in that, The preparation method of g-C3N4 / FeCu-LDH composite material includes the following steps: 1) Synthesis of g-C3N4 Urea was synthesized into thin-layer g-C3N4 using a two-step calcination method: Step 1) specifically includes: 1.1) Urea is calcined once, cooled to room temperature, and then ground to obtain a solid. 1.2) The solid was calcined twice to obtain g-C3N4; The conditions for both the first and second calcination are: temperature 500℃~520℃, time 2h~3h; 2) FeCu-LDH Synthesis 2.1) Disperse Fe(NO3)3•9H2O and Cu(NO3)3•3H2O in water to obtain solution A; the ratio of Fe(NO3)3•9H2O, Cu(NO3)3•3H2O and water is 0.0001~0.0005mol: 0.0002~0.001mol: 10~50ml; 2.2) Disperse NaOH in water to obtain solution B; the ratio of NaOH to water is 0.001~0.005 mol: 10~50 ml; 2.3) Disperse NaNO3 and formamide in water to obtain solution C; the ratio of NaNO3, formamide and water is 0.0003~0.0005 mol: 10~11.5 mL: 300~355 mL; 2.4) Add solutions A and B to solution C simultaneously, stir under N2 atmosphere, and wash to obtain FeCu-LDH; 3) Synthesis of g-C3N4 / FeCu-LDH 3.1) Disperse g-C3N4 in ethanol and sonicate to obtain g-C3N4 turbidity; 3.2) Weigh FeCu-LDH and add it to g-C3N4 turbidity, then sonicate to obtain a dispersion; 3.3) Under water bath conditions, the dispersion was stirred and the ethanol was evaporated. The product was then ground to obtain the g-C3N4 / FeCu-LDH composite material. The mass ratio of g-C3N4, ethanol, and FeCu-LDH is 0.05g:30ml:0.015g.

2. The application of the g-C3N4 / FeCu-LDH composite material according to claim 1 in the photocatalytic degradation of tetracycline wastewater by persulfate, characterized in that, In step 2.4), the washing process uses an alternating washing method with distilled water and ethanol.

3. The application of the g-C3N4 / FeCu-LDH composite material according to claim 1 in the photocatalytic degradation of tetracycline wastewater by persulfate, characterized in that, In both steps 3.1) and 3.2), the ultrasound conditions are: time 30 min, power 490W~500W.

4. The application of the g-C3N4 / FeCu-LDH composite material according to claim 1 in assisting the photocatalytic degradation of tetracycline wastewater by persulfate, characterized in that, In step 3.3), the water bath conditions are: temperature 70℃~80℃, time 3h~5h.

5. The application of the g-C3N4 / FeCu-LDH composite material according to claim 1 in assisting the photocatalytic degradation of tetracycline wastewater by persulfate, characterized in that, Both the primary and secondary calcinations employ gradient heating at a rate of 5°C / min.

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