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Article

Investigating the Performance and Stability of Fe3O4/Bi2MoO6/g-C3N4 Magnetic Photocatalysts for the Photodegradation of Sulfonamide Antibiotics under Visible Light Irradiation

by
Ke Li
1,2,
Miaomiao Chen
1,
Lei Chen
1,*,
Wencong Xue
1,
Wenbo Pan
1 and
Yanchao Han
2
1
Key Laboratory of Song Liao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun 130118, China
2
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
*
Author to whom correspondence should be addressed.
Processes 2023, 11(6), 1749; https://doi.org/10.3390/pr11061749
Submission received: 4 May 2023 / Revised: 4 June 2023 / Accepted: 6 June 2023 / Published: 8 June 2023
(This article belongs to the Special Issue Novel Materials/Technologies for the Adsorption and Removal of Antibiotics from Aqueous Solution)
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Abstract

:
In this study, an Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst was synthesized for the visible-light-driven photocatalytic degradation of sulfonamide antibiotics, specifically sulfamerazine (SM1). Characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), UV-vis diffuse reflectance spectra (UV-vis), and the use of a vibrating sample magnetometer (VSM), were employed to analyze the fabricated samples. The composite exhibited efficient visible-light absorption and charge separation, with optimal photocatalytic performance achieved at a pH value of 9.0. The study reveals the importance of solution pH in the degradation process and the potential applicability of the composite for efficient magnetic separation and recycling in photocatalytic processes. The Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst demonstrated exceptional stability and recyclability, maintaining a high degradation efficiency of over 87% after five consecutive cycles. An XRD analysis conducted after the cycling tests confirmed that the composite’s composition and chemical structure remained unchanged, further supporting its chemical stability. This investigation offers valuable insights into the photocatalytic degradation of sulfonamide antibiotics using magnetic composite photocatalysts and highlights the potential of the Fe3O4/Bi2MoO6/g-C3N4 composite for practical applications in environmental remediation.

1. Introduction

The presence of emerging contaminants, such as pharmaceuticals and personal care products (PPCPs), in the aquatic environment has raised increasing concern in recent years owing to their potential impact on ecosystems and human health [1,2,3,4,5]. As PPCPs, sulfonamide antibiotics have been extensively employed in both human and veterinary medicine worldwide [6,7,8]. Nevertheless, their improper disposal into wastewater systems results in their accumulation in aquatic ecosystems, leading to significant environmental and public health concerns [9,10,11]. Traditional techniques, such as membrane filtration [12], biodegradation [13], and adsorption [14], have been employed to address this issue. However, these conventional methods face challenges in effectively eradicating sulfonamide antibiotics from wastewater due to their high stability and resistance to biological treatment [15,16]. Therefore, there is an urgent need to develop innovative and efficient approaches to removing them.
Photocatalysis, as a promising advanced oxidation process (AOP), has emerged as a promising approach for the degradation of organic pollutants owing to its environmentally friendly nature, high level of efficiency, and potential for utilizing solar energy [17,18,19]. Among the numerous photocatalytic materials, graphitic carbon nitride (g-C3N4 or g-CN) has emerged as a metal-free, non-toxic, and environmentally friendly photocatalyst with a suitable bandgap for visible light absorption [20,21]. Despite its potential, the photocatalytic effectiveness of g-CN is hindered by several drawbacks: it suffers from a high rate of charge carrier recombination, a limited absorption spectrum in the visible light range, and lackluster electrical conductivity [22,23]. To overcome these limitations, various strategies have been explored, including heterojunction construction, metal or non-metal doping, defect engineering, and morphological control [24,25,26,27,28,29]. Heterostructure photocatalysts have the potential to reduce electron–hole recombination and bolster light absorption [30,31]. Therefore, the construction of a heterojunction between g-C3N4 and other semiconductors with well-matched band structures using a Z-scheme mechanism can significantly enhance the separation efficiencies of photogenerated charge carriers [32,33,34].
In recent years, bismuth-based semiconductors have garnered considerable attention owing to their remarkable visible light absorption capabilities and distinct electronic properties. Among these semiconductors, bismuth molybdate (Bi2MoO6) has emerged as a highly promising photocatalyst due to its exceptional photocatalytic performance, non-toxic nature, and chemical stability [35,36]. Bi2MoO6, with its unique layered structure and strong oxidizing potential, demonstrates advantageous properties that contribute to its effectiveness as a photocatalyst [37]. The Bi2MoO6 crystal structure comprises alternating MoO4 and Bi2O2 layers, resulting in a highly polarized lattice that promotes the generation of an internal electric field. This field serves to suppress the recombination of photogenerated charge carriers, thereby boosting the photocatalytic activity of the material [38]. The integration of graphitic carbon nitride (g-CN) with Bi2MoO6 forms a heterojunction that can substantially enhance charge carrier separation, leading to an improvement in the photocatalytic performance of the composite material [38,39]. The coupling of g-CN and Bi2MoO6 also facilitates the construction of Z-scheme systems, which have proven to be highly effective for various water remediation applications [40,41]. This heterojunction not only benefits from the synergistic effects of g-CN’s appealing electronic structure and responsiveness to visible light but also capitalizes on Bi2MoO6’s excellent photocatalytic properties and chemical stability [40,42]. Addressing the challenge of conveniently and economically retrieving catalysts from a substantial volume of water without resulting in loss or clumping is paramount. Conventional retrieval methods, such as filtration and centrifugation, despite their effectiveness, are deemed time-consuming and costly and are thus not optimal for large-scale industrial implementations. The employment of nano-magnetite (Fe3O4), known for its superior superparamagnetic characteristics, has been explored to solve these retrieval issues by enabling the magnetic recovery of nanocomposites [43,44]. Fe3O4 nanoparticles offer the benefits of enhancing photocatalytic performance due to their exceptional electrical conductivity, high surface-to-volume ratios, and notable optical and chemical attributes [45,46]. Additionally, Fe3O4 facilitates charge separation when integrated with other nanocomposites as it traps photogenerated electrons with its Fe3+ ions, thus further boosting the efficiency of the photocatalytic process [47].
In this study, we present the synthesis and application of a magnetic Fe3O4/Bi2MoO6/g-C3N4 composite photocatalyst for the efficient degradation of SM under visible light irradiation. The composite was characterized using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), UV-vis diffuse reflectance spectra (UV-vis) and the use of a vibrating sample magnetometer (VSM). The photocatalytic performance of the Fe3O4/Bi2MoO6/g-C3N4 composite was evaluated for the degradation of sulfamerazine (SM1). Furthermore, the stability and reusability of the composite photocatalyst were assessed through cyclic degradation experiments. This research contributes to the ongoing efforts to develop highly efficient and environmentally friendly photocatalysts for the removal of sulfonamide antibiotics from contaminated water sources.

2. Materials and Methods

2.1. Materials

The chemicals used in this study, including urea, Bi(NO3)3·5H2O, sodium molybdate (Na2HPO4·12H2O), and sodium hydroxide (NaOH), were sourced from Tianjin Xintong Fine Chemicals Company Limited, Tianjin, China. SM1 and Iron(III) chloride hexahydrate (FeCl3·6H2O) were acquired from Shanghai McLean Biochemical Technology Co., Ltd., Shanghai, China, while polyethylene glycol (PEG) was obtained from Merck Chemical Technology (Shanghai, China) Co., Ltd. All reagents employed in this study were of analytical grade and were used without further purification. Deionized water was used for the preparation of all solutions.

2.2. Preparation of Photocatalyst

2.2.1. Synthesis of g-C3N4

The g-C3N4 samples were synthesized according to the literature [48]. Briefly, 10 g of urea was heated at 550 °C for 4 h in a covered crucible, resulting in a yellow-colored powder. After cooling, the powder was washed with deionized water and ethanol, dried at 60 °C for 12 h, and calcined at 500 °C for 330 min. The final product was identified as g-C3N4.

2.2.2. Synthesis of Bi2MoO6

Bi2MoO6 was synthesized using a hydrothermal process. Initially, 0.97 g of Bi(NO3)3·5H2O and 0.242 g of Na2MoO4·12H2O were dissolved in 38 mL of deionized water, followed by stirring with a magnetic stirrer for 1 h and 30 min of ultrasonication to ensure homogeneous dispersion. The pH of the mixture was adjusted to 6 using a 2.0 mol/L NaOH solution, and the solution was stirred for another hour to achieve a uniform suspension. The mixture was subsequently transferred to a hydrothermal reaction vessel and heated at 160 °C for 12 h. Upon the completion of the hydrothermal reaction, the yellow solid was collected by filtration, washed alternatively with ethanol and deionized water several times, and then dried at 60 °C for 24 h.

2.2.3. Synthesis of Fe3O4

Magnetic Fe3O4 nanoparticles were synthesized using a solvothermal method. Initially, 40 mL of ethylene glycol was mixed with 1.35 g of FeCl3·6H2O, and the solution was stirred until a clear yellow color was achieved. Subsequently, 3.6 g of anhydrous sodium acetate and 1.0 g of polyethylene glycol were added, and the mixture was stirred for 30 min. The resulting solution was transferred to a 100 mL hydrothermal reaction kettle and heated at 200 °C in a convection-drying oven for 8 h. After cooling the kettle to room temperature, the black Fe3O4 precipitated particles were collected, washed alternately with anhydrous ethanol and deionized water three times, and dried in a convection-drying oven at 60 °C for 24 h to obtain the magnetic Fe3O4 nanoparticles.

2.2.4. Synthesis of Fe3O4/Bi2MoO6/g-C3N4

The Bi2MoO6/g-C3N4 composite was prepared using a wet-impregnation method. Briefly, 0.3 g of g-C3N4 was dispersed in methanol, combined with Bi2MoO6, and sonicated for 1h. The composite was collected, washed, and dried at 60 °C for 24 h. The Fe3O4 was first dispersed in a mixture of deionized water and anhydrous ethanol by ultrasonication. The prepared Bi2MoO6/g-C3N4 was added and mixed for 2 h, followed by further ultrasonication. The mixture was transferred to a hydrothermal reaction kettle and heated at 180 °C for 8 h. The resulting black solution was washed with anhydrous ethanol and deionized water and dried at 60 °C for 24 h to obtain the Fe3O4/Bi2MoO6/g-C3N4 composite. The ratio of Bi2MoO6 to g-C3N4 is 1:32, and the ratio of Fe3O4 to the Bi2MoO6/g-C3N4 is 1:8.

2.3. Characterization

An XRD analysis was conducted utilizing a Rigaku Ultima IV diffractometer with Cu Kα radiation, scanning the 2θ range between 10 and 90°. SEM images were acquired using a FEI Quanta-PEG 450 microscope. The XPS measurements were carried out using a Thermo VG ESCALAB-250 under A1Kα (1486.6 eV) radiation. PL measurements were performed with an F-98 system (Shanghai, China), and FT-IR spectroscopy was carried out using a PerkinElmer Spectrum Two spectrometer. UV-vis spectroscopy measurements were obtained using a TU-1901 spectrophotometer (Beijing, China), covering a wavelength range of 200–800 nm. The magnetic properties were determined using a VSM (Lake Shore).

2.4. Photocatalytic Experiments

The photocatalytic degradation of SM1 by the Fe3O4/Bi2MoO6/g-C3N4 samples was examined under irradiation using a 500 W xenon lamp equipped with a 420 nm cut-off filter. An SM1 solution (3 mg/L) was prepared, to which 800 mg of the synthesized photocatalysts was added, followed by dilution to a final volume of 50 mL. To establish an adsorption/desorption equilibrium between SM1 and the photocatalysts, the suspensions were magnetically stirred in the dark for 30 min before irradiation commenced. At regular intervals, 1.5 mL aliquots of the suspension were extracted and filtered through a 0.22 μm filter (Millipore) to determine the residual SM1 concentration. The concentration of SM1 was quantified via HPLC (Agilent Technologies 1200-Series). To assess the stability and reusability of the photocatalyst, cyclic experiments of SM1 photodegradation were conducted. The catalyst stability was determined after many reaction cycles in which the catalysts were collected magnetically and washed with deionized water before the next cycle.

3. Results and Discussion

3.1. Characterization

The results of the XRD analysis of the g-C3N4, Bi2MoO, Fe3O4 and Fe3O4/Bi2MoO6/g-C3N4 prepared in this study are depicted in Figure 1. The XRD patterns of g-C3N4 exhibit well-defined diffraction peaks at 2θ values of approximately 13.0° and 27.4°. The diffraction peak located near 13.0° corresponds to the (100) plane of g-C3N4, while the peak observed around 27.4° is attributed to the (002) plane of g-C3N4. These peak positions are in good agreement with the characteristic XRD patterns of g-C3N4 (JCPDS 87-1526) [49]. For the Bi2MoO6 sample, distinct characteristic peaks are observed at 2θ values of 27.361°, 31.705°, 32.562°, 45.481°, 53.905°, 56.441°, and 66.429°. These peaks correspond to the (131), (200), (151), (202), (331), (262), and (004) planes of the orthorhombic Bi2MoO6 phase, as referenced in the standard card (JCPDS 76-2388) [50]. In the case of the Fe3O4 sample, well-defined characteristic peaks are observed at 2θ values of 30.206°, 35.501°, 43.190°, 53.717°, 57.221°, and 62.738°. These peaks correspond to the (220), (311), (400), (422), (511), and (440) planes of Fe3O4, as indicated in the standard card (JCPDS 19-0629) [51]. The Fe3O4/Bi2MoO6/g-C3N4 diffraction pattern clearly reveals the presence of the g-C3N4 (002) plane, the Bi2MoO6 (131), (200), (151), and (202) planes, and the Fe3O4 (220), (311), (400), (422), (511), and (440) planes. Moreover, the diffraction peaks of Bi2MoO6 and Fe3O4 remain unshifted, suggesting that the loading of Bi2MoO6 and Fe3O4 onto the g-C3N4 surface does not modify their respective crystal structures. The diffraction pattern is devoid of any additional impurity peaks, implying that the reaction did not produce new impurities and that the synthesized magnetic photocatalyst composite exhibits a high level of purity. Furthermore, the intensities of the Fe3O4 diffraction peaks in the Fe3O4/Bi2MoO6/g-C3N4 sample are marginally lower compared to those of the pure Fe3O4 diffraction peaks, indicating the presence of interactions between Fe3O4 and the Bi2MoO6/g-C3N4 composite.
As depicted in Figure 2a, the g-C3N4 synthesized using the thermal oxidation exfoliation method with urea as a precursor resulted in a profusion of irregularly stacked lamellar structures. These layered architectures play a critical role in facilitating shorter electron transfer pathways, thereby promoting the efficient migration of photogenerated charge carriers. Moreover, the enhanced specific surface area and pore volume offer a greater number of active sites for photocatalytic reactions, which could lead to improved photocatalytic performance. Figure 2b illustrates the Bi2MoO6 synthesized via the hydrothermal method. The sample exhibits a stacked, block-like morphology with an estimated block size ranging from approximately 200 to 400 nm. Notably, the presence of significant agglomeration within the sample is observed, which could impact the photocatalytic efficiency due to the increased surface area for reactions to occur on. In Figure 2c, Fe3O4 nanospheres are presented, which have been synthesized using the solvothermal technique. These nanospheres display favorable dispersibility, which can be attributed to their relatively small dimensions. This characteristic may contribute to a more uniform distribution of active sites and improved accessibility for reactants, leading to enhanced photocatalytic performance. Figure 2d demonstrates that the Fe3O4 nanospheres are well-dispersed across the surface of the Bi2MoO6/g-C3N4 composite. The integration of Fe3O4 into the composite not only enables rapid photocatalyst recovery due to its magnetic properties but also contributes to improved electron migration rates owing to its exceptional electronic conductivity. Furthermore, the presence of Fe3O4 may reduce the recombination of photogenerated electron–hole pairs, thereby increasing the photocatalytic efficiency of the composite material. Overall, the enhanced material properties and morphological characteristics of the Fe3O4/Bi2MoO6/g-C3N4 composite are expected to result in good photocatalytic performance.
As illustrated in Figure 3, the Fe3O4/Bi2MoO6/g-C3N4 composites with varying ratios display pronounced absorption peaks in the regions of 810 cm−1, 1200–1700 cm−1, and 3200–3400 cm−1, which are in line with the absorption peaks observed for the pure g-C3N4. The distinct absorption peak situated around 810 cm−1 can be attributed to the bending vibrations associated with the 3-s-triazine ring [52]. The multiple absorption peaks that emerge between 1200 and 1700 cm−1 are likely a result of stretching vibrations pertaining to C-N and C=N heterocyclic rings [53]. Furthermore, the broad absorption peak in the range of 3200–3400 cm−1 may arise due to the stretching vibrations of the NH and NH2 functional groups or the O-H stretching vibrations present in H2O molecules [54]. These observations suggest that the g-C3N4 structure remains intact during the composite formation process, corroborating the findings from the XRD characterization. Significant variations in the FT-IR spectrum of Bi2MoO6 are mainly observed between 400 and 900 cm−1. The absorption peaks detected between 732 and 841 cm−1 primarily stem from the stretching vibrations of Mo-O bonds. In contrast, the absorption peaks between 450 and 565 cm−1 result from the stretching and deformation vibrations related to Bi-O bonds [55]. The absorption peak near 3400 cm−1, which is induced by O-H vibrations, coincides with the corresponding peak for g-C3N4. The Fe3O4/Bi2MoO6/g-C3N4 composite reveals a characteristic Fe-O stretching vibration of Fe3O4 around 589 cm−1 [56]. This observation suggests an enhancement in the absorption peak of surface-adsorbed O-H groups and an increase in the density of hydroxyl on the Fe3O4/Bi2MoO6/g-C3N4 composite surface. Consequently, these factors contribute to the improvement of the adsorption performance for the photocatalyst. This evidence implies that the photocatalyst formation is not a mere aggregation of components; instead, it involves interactions mediated by intermolecular forces.
To further verify the chemical compositions of the magnetic composite photocatalysts and investigate the interplay between the -C3N4 nanosheets, Bi2MoO6, and Fe3O4 nanospheres, XPS was utilized to analyze their chemical compositions, chemical bonds, and chemical binding states. Figure 4 presents the XPS survey spectra for g-C3N4, Bi2MoO6, the Fe3O4 nanospheres, and the Fe3O4/Bi2MoO6/g-C3N4 composite. The g-C3N4 nanosheets are primarily composed of carbon and nitrogen elements, with oxygen originating from oxygen-containing compounds adsorbed on the sample surface. Bi2MoO6 consists of carbon, oxygen, bismuth, and molybdenum elements. In contrast, Fe3O4 is formed from carbon, oxygen, and iron elements. The Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst encompasses carbon, nitrogen, oxygen, bismuth, molybdenum, and iron elements, signifying the presence of all three constituents: g-C3N4 nanosheets, Bi2MoO6, and Fe3O4 nanospheres. This finding corroborates the results obtained from the FT-IR characterization.
Figure 5 presents the XPS spectra for C 1s, N 1s, O 1s, Bi 4f, Mo 3d, and Fe 2p. Each sample’s binding energy is calibrated using the C 1s standard binding energy (284.8 eV). In Figure 5a, the C 1s spectra of the Fe3O4/Bi2MoO6/g-C3N4 sample exhibit characteristic peaks at 284.8 eV, 286.3 eV, and 288.3 eV, corresponding to the C-C, C-O, and N=C-N chemical bonds [57,58],. Figure 5b displays the N 1s spectra with three distinct peaks at 398.8 eV (C–N–C), 400.1 eV (N-(C)3), and 401.2 eV (N–H groups) [59], with no significant alterations compared to the g-C3N4 sample. In Figure 5c, the O 1s spectra of the Fe3O4/Bi2MoO6/g-C3N4 sample present three characteristic peaks at 529.6 eV (OL), 532.0 eV (C-O), and 533.6 eV (C=O) [60]. The intensity at 532.3 eV reduces to 532.0 eV, while the intensity at 533.6 eV remains constant. This change suggests interactions between g-C3N4 and the other components (Fe3O4 and Bi2MoO6) in the composite, causing a shift in the binding energy of the oxygen atoms associated with the C-O bond. Figure 5d,e depict the Bi 4f and Mo 3d high-resolution spectra for the Bi2MoO6 and Fe3O4/Bi2MoO6/g-C3N4 samples, revealing slight decreases in peak intensities, indicating consistent binding energies and the occurrence of chemical bonding or strong electrostatic interactions between the photocatalysts [61]. In Figure 5f, the Fe 2p spectra of the Fe3O4 sample exhibit two characteristic peaks at 710.3 eV and 723.4 eV, corresponding to Fe 2p3/2 and Fe 2p1/2 orbitals of Fe+ [62]. The Fe3O4/Bi2MoO6/g-C3N4 sample shows reduced peak intensities at 709.6 eV and 722.8 eV, confirming the successful interaction and combination of Fe3O4, Bi2MoO6, and g-C3N4 in the photocatalyst.
The use of PL emission spectra is a widely adopted technique for evaluating the efficiency of photogenerated electron–hole pair separation in various materials. As depicted in Figure 6, the fluorescence intensities can be arranged in descending order as follows: g-C3N4 > Fe3O4 > Bi2MoO6 > Fe3O4/Bi2MoO6/g-C3N4. The observed fluorescence intensities for the Fe3O4/Bi2MoO6/g-C3N4 composites are lower than those of their individual constituents, g-C3N4, Fe3O4, and Bi2MoO6. This finding implies that the formation of composite photocatalysts leads to a significant reduction in the recombination rate of the photogenerated electron–hole pairs. Additionally, the spectral data suggest that Fe3O4 inherently possesses favorable electronic conductivity, which facilitates the migration of photogenerated charge carriers. Consequently, the improved charge separation and migration contribute to the enhanced photocatalytic performance of the composite materials.
The photocatalytic activity of a material is predominantly influenced by its capacity to absorb and exploit incident light. In order to investigate the optical absorption characteristics of the magnetic composite photocatalyst Fe3O4/Bi2MoO6/g-C3N4, UV-vis diffuse reflectance spectroscopy was employed. As depicted in Figure 7, all samples exhibit a degree of light absorption capacity within the ultraviolet range, as well as a discernable response within the visible light range. This behavior is primarily governed by the samples’ bandgap width. The as-synthesized g-C3N4 demonstrates an absorption edge at approximately 438 nm, while the Bi2MoO6 sample exhibits an absorption edge at approximately 460 nm. According to the prior literature [63], the primary absorption wavelength of Fe3O4 resides within the ultraviolet light region. Upon the incorporation of Fe3O4, the absorption edge for the Fe3O4/Bi2MoO6/g-C3N4 composite is observed at approximately 710 nm, which further expands the response range within the visible light domain. According to the Kubelka–Munk function, the bandgaps of the g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4 are 2.96 eV, 3.03 eV, 1.16 eV, and 2.80 eV, respectively. The bandgap energy of a material is closely associated with its absorption properties and therefore its photocatalytic performance. When the aforementioned materials are combined to form Fe3O4/Bi2MoO6/g-C3N4, the composite material presents a bandgap of 2.80 eV, slightly smaller than those of g-C3N4 and Bi2MoO6 yet significantly larger than the bandgap of Fe3O4. This composite behavior results in an enhanced absorption of light, especially in the visible region, as is evident from the absorption edge observed at approximately 710 nm. The results highlight the synergistic effect of the three components in which Fe3O4 effectively extends the light absorption to the visible range, while the wide bandgap materials (g-C3N4 and Bi2MoO6) contribute to the overall photocatalytic performance under UV light. Consequently, the composite photocatalyst exhibits an enhanced capability to generate active species under identical illumination conditions, which ultimately leads to its improved photocatalytic performance.
As depicted in Figure 8, the magnetic hysteresis loops for Fe3O4 and Fe3O4/Bi2MoO6/g-C3N4 are illustrated. Employing the solvothermal method, the synthesized Fe3O4 nanospheres possess dimensions exceeding the critical size threshold for superparamagnetism, thereby conferring ferromagnetic characteristics to the Fe3O4/Bi2MoO6/g-C3N4 composite material. The saturation magnetization and coercivity values for the Fe3O4 are determined to be 74.32 emu/g and 50.74 Oe, respectively. In contrast, the Fe3O4/Bi2MoO6/g-C3N4 composite exhibits a saturation magnetization of 7.24 emu/g and a coercivity of 5.49 Oe. Owing to the relatively smaller proportion of Fe3O4 in the magnetic composite photocatalyst, the magnetization strength decreases in comparison to that of the pristine Fe3O4 nanoparticles. Nevertheless, the Fe3O4/Bi2MoO6/g-C3N4 composite demonstrates favorable ferromagnetic and magnetic recovery properties, indicating its potential applicability for efficient magnetic separation and recycling in photocatalytic processes. This finding emphasizes the necessity of optimizing the compositions of magnetic composite photocatalysts to achieve a balance between desirable magnetic properties and overall photocatalytic performance.

3.2. Photocatalyst Performance Analysis

Due to the inherent stability of SM1, its degradation under visible light without a photocatalyst presents a significant challenge. Following 120 min of visible light irradiation, the photocatalysts in the dark condition demonstrated a minimal removal efficiency for SM1 at less than 5%. This observation suggests that the adsorption by the photocatalysts can be largely disregarded in the overall process. To investigate the influence of solution pH on the degradation of SM1 under visible light using Fe3O4/Bi2MoO6/g-C3N4, photocatalytic experiments were conducted with initial pH values adjusted to 5.0, 6.0, 7.0, 8.0, and 9.0. Figure 9a demonstrates that when the initial pH of the sulfonamide antibiotic solution ranged from 5.0 to 8.0, no significant changes were observed in the photodegradation efficiency of SM1. However, at a pH of 9.0, the photodegradation efficiency of SM1 markedly increased. At pH values of 5.0, 6.0, 7.0, 8.0, and 9.0, the degradation efficiencies of SM1 by Fe3O4/Bi2MoO6/g-C3N4 within 120 min were 63.23%, 74.22%, 73.68%, 81.91%, and 95.58%, respectively. As depicted in Figure 9b, the degradation kinetic constants at pH values of 5.0, 6.0, 7.0, 8.0, and 9.0 were 0.00839, 0.01082, 0.01032, 0.01358, and 0.02574 min− 1, respectively. Within the pH range of 5.0 to 8.0, the observed stability could be attributed to the different species of SM1 present at various pH values having similar reactivities with the generated OH· radicals. However, a significant increase in degradation efficiency at a pH of 9.0 suggests that the interaction between the generated OH· radicals and the dominant anionic species of SM1 at this pH value may result in a more effective degradation process. Moreover, the increased concentrations of OH- ions (or the availability of H2O molecules) at higher pH values could contribute to the enhanced generation of active species, leading to improvements in the photodegradation performance.
The photochemical stability of a photocatalyst is a critical factor in determining its suitability for practical applications. To evaluate the stability of the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst, five consecutive photocatalytic degradation cycles of SM1 were performed under identical experimental conditions. As shown in Figure 10a, the solution pH was adjusted to 9. The visible light degradation rate of SM1 was monitored within a 120 min time frame. In the five degradation cycles, the degradation rates were 95.58%, 93.70%, 91.77%, 89.82%, and 87.86%, respectively. With the increasing number of recovery cycles of the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst, the degradation rate of SM1 decreased slightly. However, the rate tended to stabilize as the number of recovery cycles increased. After five cycles, the degradation rate remained above 87%, indicating no significant decrease in performance. This demonstrates that the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst retains its effective photocatalytic degradation capabilities and recyclability after multiple cycles, confirming its stable photocatalytic performance. Following the five consecutive cycles, the catalyst sample was filtered, dried, and analyzed using XRD. Figure 10b reveals no apparent changes in the composition or chemical structure of the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst, providing evidence of its chemical stability.
It is worth noting that the consistent photocatalytic performance can be attributed to several factors, including the robustness of the composite material, effective charge separation and transfer, and the resistance to photocorrosion. The incorporation of Fe3O4 in the composite not only enhances the magnetic properties but also contributes to the stability of the material by improving electron conductivity. In future studies, a more comprehensive investigation could be performed to examine the possible degradation of the catalyst’s surface and structural alterations and potential changes in the active sites after extended usage. Such assessments would further contribute to our understanding of the catalyst’s long-term stability and its potential for practical applications in environmental remediation.

4. Conclusions

In summary, this study presents a comprehensive investigation into the synthesis, characterization, and application of a Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst for the visible-light-driven photocatalytic degradation of sulfonamide antibiotics, with a particular focus on SM1. The findings highlight the importance of solution pH in the degradation process, which influences not only the speciation of sulfonamides, transitioning between cationic, molecular, and anionic forms, but also the generation of reactive species such as hydroxyl radicals that are crucial for effective degradation. Through a series of carefully designed experiments, the study revealed that optimal photocatalytic performance was achieved at a pH value of 9.0. Moreover, the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite photocatalyst exhibited exceptional stability and recyclability, maintaining a high degradation efficiency of over 87% after five consecutive cycles. An XRD analysis conducted after the cycling tests confirmed that the composite’s composition and chemical structure remained unchanged, further supporting its chemical stability. This comprehensive investigation not only contributes valuable insights into the photocatalytic degradation of sulfonamide antibiotics using magnetic composite photocatalysts but also underscores the potential of the Fe3O4/Bi2MoO6/g-C3N4 magnetic composite for practical applications in environmental remediation. To further advance this research and its potential impact, future studies could explore the long-term stability and performance of the catalyst under a broader range of operational conditions. Additionally, in-depth investigations into potential degradation pathways and mechanisms could provide a deeper understanding of the catalyst’s applicability and its effectiveness in addressing complex water pollution challenges. Overall, the findings of this study pave the way for the development of more efficient and sustainable strategies for water treatment and pollution control.

Author Contributions

Conceptualization, K.L., M.C. and L.C.; methodology, W.X., W.P. and Y.H.; software M.C. and W.X.; investigation, M.C. and W.X.; resources, K.L. and L.C.; data curation, K.L.; writing—original draft preparation, K.L., M.C. and W.X.; writing—review and editing, K.L. and L.C.; visualization, Y.H.; supervision, K.L. and L.C.; funding acquisition, K.L. and L.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Natural Science Foundation of China (51878316) and the Science and Technology Research Planning Project of Jilin Provincial Department of Education (JJKH20220297KJ).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

All authors thank the editor and anonymous reviewers for their constructive comments and suggestions to improve the quality of this paper.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Liu, J.-L.; Wong, M.-H. Pharmaceuticals and personal care products (PPCPs): A review on environmental contamination in China. Environ. Int. 2013, 59, 208–224. [Google Scholar] [CrossRef]
  2. Dey, S.; Bano, F.; Malik, A. Pharmaceuticals and personal care product (PPCP) contamination—A global discharge inventory. In Pharmaceuticals and Personal Care Products: Waste Management and Treatment Technology; Elsevier: Amsterdam, The Netherlands, 2019; pp. 1–26. [Google Scholar]
  3. Yang, L.; Wang, T.; Zhou, Y.; Shi, B.; Bi, R.; Meng, J. Contamination, source and potential risks of pharmaceuticals and personal products (PPCPs) in Baiyangdian Basin, an intensive human intervention area, China. Sci. Total Environ. 2021, 760, 144080. [Google Scholar] [CrossRef] [PubMed]
  4. Wang, C.; Lu, Y.; Sun, B.; Zhang, M.; Wang, R.; Li, X.; Mao, R.; Cao, Z.; Song, S. Contamination, transport, and ecological risks of pharmaceuticals and personal care products in a large irrigation region. Sci. Total Environ. 2022, 851, 158179. [Google Scholar] [CrossRef] [PubMed]
  5. Rienzie, R.; Ramanayaka, S.; Adassooriya, N.M. Nanotechnology applications for the removal of environmental contaminants from pharmaceuticals and personal care products. In Pharmaceuticals and Personal Care Products: Waste Management and Treatment Technology; Elsevier: Amsterdam, The Netherlands, 2019; pp. 279–296. [Google Scholar]
  6. Li, N.; Wang, Y.; Li, W.; Li, H.; Yang, L.; Wang, J.; Mahdy, H.A.; Mehany, A.B.; Jaiash, D.A.; Santali, E.Y. Screening of some sulfonamide and sulfonylurea derivatives as anti-Alzheimer’s agents targeting BACE1 and PPARγ. J. Chem. 2020, 2020, 1–19. [Google Scholar] [CrossRef]
  7. Navia, M.A. A chicken in every pot, thanks to sulfonamide drugs. Science 2000, 288, 2132–2133. [Google Scholar] [CrossRef]
  8. Ovung, A.; Bhattacharyya, J. Sulfonamide drugs: Structure, antibacterial property, toxicity, and biophysical interactions. Biophys. Rev. 2021, 13, 259–272. [Google Scholar] [CrossRef]
  9. Tai, Y.; Tam, N.F.-Y.; Ruan, W.; Yang, Y.; Yang, Y.; Tao, R.; Zhang, J. Specific metabolism related to sulfonamide tolerance and uptake in wetland plants. Chemosphere 2019, 227, 496–504. [Google Scholar] [CrossRef]
  10. Leal, C.S.; Mesquita, D.P.; Amaral, A.L.; Amaral, A.M.; Ferreira, E.C. Environmental impact and biological removal processes of pharmaceutically active compounds: The particular case of sulfonamides, anticonvulsants and steroid estrogens. Crit. Rev. Environ. Sci. Technol. 2020, 50, 698–742. [Google Scholar] [CrossRef] [Green Version]
  11. Baran, W.; Adamek, E.; Ziemiańska, J.; Sobczak, A. Effects of the presence of sulfonamides in the environment and their influence on human health. J. Hazard. Mater. 2011, 196, 1–15. [Google Scholar] [CrossRef]
  12. Lee, J.-C.; Jang, J.K.; Kim, H.-W. Sulfonamide degradation and metabolite characterization in submerged membrane photobioreactors for livestock excreta treatment. Chemosphere 2020, 261, 127604. [Google Scholar] [CrossRef]
  13. Yang, C.-W.; Hsiao, W.-C.; Chang, B.-V. Biodegradation of sulfonamide antibiotics in sludge. Chemosphere 2016, 150, 559–565. [Google Scholar] [CrossRef] [PubMed]
  14. Luo, B.; Huang, G.; Yao, Y.; An, C.; Zhang, P.; Zhao, K. Investigation into the influencing factors and adsorption characteristics in the removal of sulfonamide antibiotics by carbonaceous materials. J. Clean. Prod. 2021, 319, 128692. [Google Scholar] [CrossRef]
  15. Larsson, D.J.; de Pedro, C.; Paxeus, N. Effluent from drug manufactures contains extremely high levels of pharmaceuticals. J. Hazard. Mater. 2007, 148, 751–755. [Google Scholar] [CrossRef] [PubMed]
  16. Xu, J.; Xu, Y.; Wang, H.M.; Guo, C.S.; Qiu, H.Y.; He, Y.; Zhang, Y.; Li, X.C.; Meng, W. Occurrence of antibiotics and antibiotic resistance genes in a sewage treatment plant and its effluent-receiving river. Chemosphere 2015, 119, 1379–1385. [Google Scholar] [CrossRef]
  17. Zhang, Z.; Zada, A.; Cui, N.; Liu, N.; Liu, M.; Yang, Y.; Jiang, D.; Jiang, J.; Liu, S. Synthesis of ag loaded ZnO/BiOCl with high photocatalytic performance for the removal of antibiotic pollutants. Crystals 2021, 11, 981. [Google Scholar] [CrossRef]
  18. González-Poggini, S.; Rosenkranz, A.; Colet-Lagrille, M. Two-dimensional nanomaterials for the removal of pharmaceuticals from wastewater: A critical review. Processes 2021, 9, 2160. [Google Scholar] [CrossRef]
  19. Gan, W.; Fu, X.C.; Guo, J.; Zhang, M.; Li, D.D.; Ding, C.S.; Lu, Y.Q.; Wang, P.; Sun, Z.Q. Ag nanoparticles decorated 2D/2D TiO2/g-C3N4 heterojunction for efficient removal of tetracycline hydrochloride: Synthesis, degradation pathways, and mechanism. Appl. Surf. Sci. 2022, 606, 154837. [Google Scholar] [CrossRef]
  20. Mahmood, A.; Irfan, A.; Wang, J.L. Molecular level understanding of the chalcogen atom effect on chalcogen-based polymers through electrostatic potential, non-covalent interactions, excited state behaviour, and radial distribution function. Polym. Chem. 2022, 13, 5993–6001. [Google Scholar] [CrossRef]
  21. Mahmood, A.; Khan, S.U.D.; Rehman, F.U. Assessing the quantum mechanical level of theory for prediction of UV/Visible absorption spectra of some aminoazobenzene dyes. J. Saudi Chem. Soc. 2015, 19, 436–441. [Google Scholar] [CrossRef] [Green Version]
  22. Liu, J.Y.; Fang, W.J.; Wei, Z.D.; Qin, Z.; Jiang, Z.; Shangguan, W.F. Efficient photocatalytic hydrogen evolution on N-deficient g-C3N4 achieved by a molten salt post-treatment approach. Appl. Catal. B-Environ. 2018, 238, 465–470. [Google Scholar] [CrossRef]
  23. Yang, X.L.; Qian, F.F.; Zou, G.J.; Li, M.L.; Lu, J.R.; Li, Y.M.; Bao, M.T. Facile fabrication of acidified g-C3N4/g-C3N4 hybrids with enhanced photocatalysis performance under visible light irradiation. Appl. Catal. B-Environ. 2016, 193, 22–35. [Google Scholar] [CrossRef]
  24. Li, J.Q.; Qi, Y.; Mei, Y.Q.; Ma, S.C.; Li, Q.; Xin, B.F.; Yao, T.J.; Wu, J. Construction of phosphorus-doped carbon nitride/phosphorus and sulfur co-doped carbon nitride isotype heterojunction and their enhanced photoactivity. J. Colloid. Interf. Sci. 2020, 566, 495–504. [Google Scholar] [CrossRef] [PubMed]
  25. Li, K.; Chen, M.; Chen, L.; Zhao, S.; Xue, W.; Han, Z.; Han, Y. Synthesis of g-C3N4 Derived from Different Precursors for Photodegradation of Sulfamethazine under Visible Light. Processes 2023, 11, 528. [Google Scholar] [CrossRef]
  26. Dong, H.; Guo, X.T.; Yang, C.; Ouyang, Z.Z. Synthesis of g-C3N4 by different precursors under burning explosion effect and its photocatalytic degradation for tylosin. Appl. Catal. B-Environ. 2018, 230, 65–76. [Google Scholar] [CrossRef]
  27. Mou, Z.G.; Chen, T.; Tao, Y.; Gao, Y.; Sun, J.H.; Lei, W.I. Fabrication of g-C3N4/N,Fe co-doped CQDs composites: In situ decoration of g-C3N4 with N-CQDs and Fe and efficient visible-light photocatalytic degradation of tetracycline. J. Phys. D Appl. Phys. 2022, 55, 5. [Google Scholar] [CrossRef]
  28. Yang, C.; Xue, Z.; Qin, J.; Sawangphruk, M.; Zhang, X.; Liu, R. Heterogeneous structural defects to prompt charge shuttle in g-C3N4 plane for boosting visible-light photocatalytic activity. Appl. Catal. B Environ. 2019, 259, 118094. [Google Scholar] [CrossRef]
  29. Xia, X.; Xu, B.G.; Zhang, H.Y.; Ji, K.; Ji, X.S.; Wang, D.; Yang, P. NiCoP/g-C3N4 Schottky heterojunctions towards efficient photocatalytic NO oxidation. J. Alloys Compd. 2022, 928, 167207. [Google Scholar] [CrossRef]
  30. Yin, X.L.; Liu, J.; Jiang, W.J.; Zhang, X.; Hu, J.S.; Wan, L.J. Urchin-like Au@CdS/WO3 micro/nano heterostructure as a visible-light driven photocatalyst for efficient hydrogen generation. Chem. Commun. 2015, 51, 13842–13845. [Google Scholar] [CrossRef]
  31. Zhu, Y.F.; Liu, Y.F.; Ai, Q.; Gao, G.H.; Yuan, L.; Fang, Q.Y.; Tian, X.Y.; Zhang, X.; Egap, E.; Ajayan, P.M.; et al. In Situ Synthesis of Lead-Free Halide Perovskite-COF Nanocomposites as Photocatalysts for Photoinduced Polymerization in Both Organic and Aqueous Phases. ACS Mater. Lett. 2022, 4, 464–471. [Google Scholar] [CrossRef]
  32. Kang, J.; Jin, C.; Li, Z.; Wang, M.; Chen, Z.; Wang, Y. Dual Z-scheme MoS2/g-C3N4/Bi24O31Cl10 ternary heterojunction photocatalysts for enhanced visible-light photodegradation of antibiotic. J. Alloys Compd. 2020, 825, 153975. [Google Scholar] [CrossRef]
  33. Li, J.; Zhang, M.; Li, X.; Li, Q.; Yang, J. Effect of the calcination temperature on the visible light photocatalytic activity of direct contact Z-scheme g-C3N4-TiO2 heterojunction. Appl. Catal. B Environ. 2017, 212, 106–114. [Google Scholar] [CrossRef]
  34. Zhang, J.; Fu, J.; Wang, Z.; Cheng, B.; Dai, K.; Ho, W. Direct Z-scheme porous g-C3N4/BiOI heterojunction for enhanced visible-light photocatalytic activity. J. Alloys Compd. 2018, 766, 841–850. [Google Scholar] [CrossRef]
  35. Vattikuti, S.V.P.; Police, A.K.R.; Shim, J.; Byon, C. In situ fabrication of the Bi2O3-V2O5 hybrid embedded with graphitic carbon nitride nanosheets: Oxygen vacancies mediated enhanced visible-light-driven photocatalytic degradation of organic pollutants and hydrogen evolution. Appl. Surf. Sci. 2018, 447, 740–756. [Google Scholar] [CrossRef]
  36. Du, F.Y.; Lai, Z.; Tang, H.Y.; Wang, H.Y.; Zhao, C.X. Construction of dual Z-scheme Bi2WO6/g-C3N4/black phosphorus quantum dots composites for effective bisphenol A degradation. J. Environ. Sci. 2023, 124, 617–629. [Google Scholar] [CrossRef]
  37. Bi, J.; Wu, L.; Li, J.; Li, Z.; Wang, X.; Fu, X. Simple solvothermal routes to synthesize nanocrystalline Bi2MoO6 photocatalysts with different morphologies. Acta Mater. 2007, 55, 4699–4705. [Google Scholar] [CrossRef]
  38. Yu, H.; Jiang, L.; Wang, H.; Huang, B.; Yuan, X.; Huang, J.; Zhang, J.; Zeng, G. Modulation of Bi2MoO6-based materials for photocatalytic water splitting and environmental application: A critical review. Small 2019, 15, 1901008. [Google Scholar] [CrossRef]
  39. Di, G.; Zhu, Z.; Zhang, H.; Qiu, Y.; Yin, D.; Crittenden, J. Simultaneous sulfamethazine oxidation and bromate reduction by Pd-mediated Z-scheme Bi2MoO6/g-C3N4 photocatalysts: Synergetic mechanism and degradative pathway. Chem. Eng. J. 2020, 401, 126061. [Google Scholar] [CrossRef]
  40. Opoku, F.; Govender, K.K.; van Sittert, C.G.C.E.; Govender, P.P. Insights into the photocatalytic mechanism of mediator-free direct Z-scheme g-C3N4/Bi2MoO6 (010) and g-C3N4/Bi2WO6 (010) heterostructures: A hybrid density functional theory study. Appl. Surf. Sci. 2018, 427, 487–498. [Google Scholar] [CrossRef]
  41. Wu, H.; Meng, F.; Liu, X.; Yu, B. Carbon nanotubes as electronic mediators combined with Bi2MoO6 and g-C3N4 to form Z-scheme heterojunctions to enhance visible light photocatalysis. Nanotechnology 2021, 33, 115203. [Google Scholar] [CrossRef]
  42. Zhong, K.D.; Feng, J.W.; Gao, H.B.; Zhang, Y.M.; Lai, K.R. Fabrication of BiVO4@g-C3N4(100) heterojunction with enhanced photocatalytic visible-light-driven activity. J. Solid State Chem. 2019, 274, 142–151. [Google Scholar] [CrossRef]
  43. Beketova, D.; Motola, M.; Sopha, H.; Michalicka, J.; Cicmancova, V.; Dvorak, F.; Hromadko, L.; Frumarova, B.; Stoica, M.; Macak, J.M. One-step decoration of TiO2 nanotubes with Fe3O4 nanoparticles: Synthesis and photocatalytic and magnetic properties. ACS Appl. Nano Mater. 2020, 3, 1553–1563. [Google Scholar] [CrossRef]
  44. Stefan, M.; Leostean, C.; Pana, O.; Toloman, D.; Popa, A.; Perhaita, I.; Senilă, M.; Marincas, O.; Barbu-Tudoran, L. Magnetic recoverable Fe3O4-TiO2: Eu composite nanoparticles with enhanced photocatalytic activity. Appl. Surf. Sci. 2016, 390, 248–259. [Google Scholar] [CrossRef]
  45. Elshypany, R.; Selim, H.; Zakaria, K.; Moustafa, A.H.; Sadeek, S.A.; Sharaa, S.; Raynaud, P.; Nada, A.A. Elaboration of Fe3O4/ZnO nanocomposite with highly performance photocatalytic activity for degradation methylene blue under visible light irradiation. Environ. Technol. Innov. 2021, 23, 101710. [Google Scholar] [CrossRef]
  46. Blaney, L. Magnetite (Fe3O4): Properties, Synthesis, and Applications; Lehigh University Lehigh Preserve: Bethlehem, PA, USA, 2007; Volume 15, p. 5. [Google Scholar]
  47. Hussain, S.; Alam, M.M.; Imran, M.; Ali, M.A.; Ahamad, T.; Haidyrah, A.S.; Alotaibi, S.M.R.; Shariq, M. A facile low-cost scheme for highly photoactive Fe3O4-MWCNTs nanocomposite material for degradation of methylene blue. Alex. Eng. J. 2022, 61, 9107–9117. [Google Scholar] [CrossRef]
  48. Niu, P.; Zhang, L.; Liu, G.; Cheng, H.M. Graphene-like carbon nitride nanosheets for improved photocatalytic activities. Adv. Funct. Mater. 2012, 22, 4763–4770. [Google Scholar] [CrossRef]
  49. Jiang, M.; Zou, Y.; Xu, F.; Sun, L.; Hu, Z.; Yu, S.; Zhang, J.; Xiang, C. Synthesis of g-C3N4/Fe3O4/MoS2 composites for efficient hydrogen evolution reaction. J. Alloys Compd. 2022, 906, 164265. [Google Scholar] [CrossRef]
  50. Li, S.; Shen, X.; Liu, J.; Zhang, L. Synthesis of Ta3N5/Bi2 MoO6 core–shell fiber-shaped heterojunctions as efficient and easily recyclable photocatalysts. Environ. Sci. Nano 2017, 4, 1155–1167. [Google Scholar] [CrossRef]
  51. Irianti, F.; Sutanto, H.; Priyono, P.; Wibowo, A.; Syahida, A.; Alkian, I. Characterization structure of Fe3O4@ PEG-4000 nanoparticles synthesized by co-precipitation method. J. Phys. Conf. Ser. 1943, 1943, 012014. [Google Scholar] [CrossRef]
  52. Zhang, H.; Zhao, L.X.; Geng, F.L.; Guo, L.H.; Wan, B.; Yang, Y. Carbon dots decorated graphitic carbon nitride as an efficient metal-free photocatalyst for phenol degradation. Appl. Catal. B-Environ. 2016, 180, 656–662. [Google Scholar] [CrossRef]
  53. Bavani, T.; Madhavan, J.; Preeyanghaa, M.; Neppolian, B.; Murugesan, S. Construction of direct Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst with enhanced visible light activity towards the degradation of methylene blue. Environ. Sci. Pollut. Res. 2022, 30, 10179–10190. [Google Scholar] [CrossRef]
  54. Preeyanghaa, M.; Dhileepan, M.D.; Madhavan, J.; Neppolian, B. Revealing the charge transfer mechanism in magnetically recyclable ternary g-C3N4/BiOBr/Fe3O4 nanocomposite for efficient photocatalytic degradation of tetracycline antibiotics. Chemosphere 2022, 303, 135070. [Google Scholar] [CrossRef] [PubMed]
  55. Iordanova, R.; Dimitriev, Y.; Dimitrov, V.; Kassabov, S.; Klissurski, D. Glass formation and structure in the system MoO3–Bi2O3–Fe2O3. J. Non-Cryst. Solids 1998, 231, 227–233. [Google Scholar] [CrossRef]
  56. Fialips, C.-I.; Huo, D.; Yan, L.; Wu, J.; Stucki, J.W. Effect of Fe oxidation state on the IR spectra of Garfield nontronite. Am. Mineral. 2002, 87, 630–641. [Google Scholar] [CrossRef]
  57. Yang, N.; Li, G.; Wang, W.; Yang, X.; Zhang, W. Photophysical and enhanced daylight photocatalytic properties of N-doped TiO2/g-C3N4 composites. J. Phys. Chem. Solids 2011, 72, 1319–1324. [Google Scholar] [CrossRef]
  58. Zhang, G.; Wu, Z.; Liu, H.; Ji, Q.; Qu, J.; Li, J. Photoactuation healing of α-FeOOH@ g-C3N4 catalyst for efficient and stable activation of persulfate. Small 2017, 13, 1702225. [Google Scholar] [CrossRef] [PubMed]
  59. Dong, F.; Zhao, Z.; Xiong, T.; Ni, Z.; Zhang, W.; Sun, Y.; Ho, W.-K. In situ construction of g-C3N4/g-C3N4 metal-free heterojunction for enhanced visible-light photocatalysis. ACS Appl. Mater. Inter. 2013, 5, 11392–11401. [Google Scholar] [CrossRef] [PubMed]
  60. Cui, Z.; Yang, H.; Zhao, X. Enhanced photocatalytic performance of g-C3N4/Bi4Ti3O12 heterojunction nanocomposites. Mater. Sci. Eng. B 2018, 229, 160–172. [Google Scholar] [CrossRef]
  61. Habibi-Yangjeh, A.; Mousavi, M.; Nakata, K. Boosting visible-light photocatalytic performance of g-C3N4/Fe3O4 anchored with CoMoO4 nanoparticles: Novel magnetically recoverable photocatalysts. J. Photochem. Photobiol. A Chem. 2019, 368, 120–136. [Google Scholar] [CrossRef]
  62. Amer, M.; Matsuda, A.; Kawamura, G.; El-Shater, R.; Meaz, T.; Fakhry, F. Characterization and structural and magnetic studies of as-synthesized Fe2+ CrxFe (2−x) O4 nanoparticles. J. Magn. Magn. Mater. 2017, 439, 373–383. [Google Scholar] [CrossRef]
  63. Tang, J.; Myers, M.; Bosnick, K.A.; Brus, L.E. Magnetite Fe3O4 nanocrystals: Spectroscopic observation of aqueous oxidation kinetics. J. Phys. Chem. B 2003, 107, 7501–7506. [Google Scholar] [CrossRef]
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Figure 1. XRD patterns of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
Figure 1. XRD patterns of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
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Figure 2. SEM images of (a) g-C3N4, (b) Bi2MoO6 (c) Fe3O4, and (d) Fe3O4/Bi2MoO6/g-C3N4.
Figure 2. SEM images of (a) g-C3N4, (b) Bi2MoO6 (c) Fe3O4, and (d) Fe3O4/Bi2MoO6/g-C3N4.
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Figure 3. FT-IR spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
Figure 3. FT-IR spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
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Figure 4. XPS survey spectra of (a) g-C3N4, (b) Bi2MoO6, (c) Fe3O4, and (d) Fe3O4/Bi2MoO6/g-C3N4.
Figure 4. XPS survey spectra of (a) g-C3N4, (b) Bi2MoO6, (c) Fe3O4, and (d) Fe3O4/Bi2MoO6/g-C3N4.
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Figure 5. XPS spectra of Fe3O4/Bi2MoO6/g-C3N4 in (a) C 1s, (b) N 1s, (c) O 1s, (d) Bi 4f, (e) Mo 3d, and (f) Fe 2p.
Figure 5. XPS spectra of Fe3O4/Bi2MoO6/g-C3N4 in (a) C 1s, (b) N 1s, (c) O 1s, (d) Bi 4f, (e) Mo 3d, and (f) Fe 2p.
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Figure 6. PL spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
Figure 6. PL spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
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Figure 7. UV–Vis DRS spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
Figure 7. UV–Vis DRS spectra of g-C3N4, Bi2MoO6, Fe3O4, and Fe3O4/Bi2MoO6/g-C3N4.
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Figure 8. VSM spectra of Fe3O4 and Fe3O4/Bi2MoO6/g-C3N4.
Figure 8. VSM spectra of Fe3O4 and Fe3O4/Bi2MoO6/g-C3N4.
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Figure 9. (a) Photocatalytic efficiencies of Fe3O4/Bi2MoO6/g-C3N4 with different pH for SM1 under visible light irradiation. (b) Plots of ln(C0/Ct) versus irradiation time for SM1.
Figure 9. (a) Photocatalytic efficiencies of Fe3O4/Bi2MoO6/g-C3N4 with different pH for SM1 under visible light irradiation. (b) Plots of ln(C0/Ct) versus irradiation time for SM1.
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Figure 10. (a) Stability and reusability test; (b) XRD pattern of Fe3O4/Bi2MoO6/g-C3N4 of after reaction.
Figure 10. (a) Stability and reusability test; (b) XRD pattern of Fe3O4/Bi2MoO6/g-C3N4 of after reaction.
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Li, K.; Chen, M.; Chen, L.; Xue, W.; Pan, W.; Han, Y. Investigating the Performance and Stability of Fe3O4/Bi2MoO6/g-C3N4 Magnetic Photocatalysts for the Photodegradation of Sulfonamide Antibiotics under Visible Light Irradiation. Processes 2023, 11, 1749. https://doi.org/10.3390/pr11061749

AMA Style

Li K, Chen M, Chen L, Xue W, Pan W, Han Y. Investigating the Performance and Stability of Fe3O4/Bi2MoO6/g-C3N4 Magnetic Photocatalysts for the Photodegradation of Sulfonamide Antibiotics under Visible Light Irradiation. Processes. 2023; 11(6):1749. https://doi.org/10.3390/pr11061749

Chicago/Turabian Style

Li, Ke, Miaomiao Chen, Lei Chen, Wencong Xue, Wenbo Pan, and Yanchao Han. 2023. "Investigating the Performance and Stability of Fe3O4/Bi2MoO6/g-C3N4 Magnetic Photocatalysts for the Photodegradation of Sulfonamide Antibiotics under Visible Light Irradiation" Processes 11, no. 6: 1749. https://doi.org/10.3390/pr11061749

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