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Article

Polymer-Based Immobilized FePMo12O40@PVP Composite Materials for Photocatalytic RhB Degradation

by
Zijing Wang
*,
Yuze Tang
,
Limei Ai
,
Minghui Liu
and
Yurong Wang
College of Biomedical and Chemical Engineering, Liaoning Institute of Science and Technology, Benxi 117004, China
*
Author to whom correspondence should be addressed.
Inorganics 2024, 12(6), 144; https://doi.org/10.3390/inorganics12060144
Submission received: 20 April 2024 / Revised: 16 May 2024 / Accepted: 20 May 2024 / Published: 22 May 2024
(This article belongs to the Special Issue Photoelectrochemical and Photocatalytic Properties of Nano-Semiconductor Materials)
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Abstract

:
FePMo12O40@PVP composite materials were synthesized with the regulation of polyvinylpyrrolidone (PVP) to control the structure. The samples were characterized by FT-IR, XRD, XPS, SEM, TEM and UV-Vis DRS. The composite retains the Keggin-type polyoxometalates structure, exhibiting a high specific surface area that enhances photon capture efficiency. Analysis of UV-Vis DRS absorption band edge and band gap indicated that the composite was responsive to visible light. Photocatalytic degradation of Rhodamine B (RhB) by FePMo12O40@PVP was investigated under commonly used LED light source, demonstrating excellent photocatalytic performance as 2.5 g-FePMo12O40@PVP (0.015 g) can remove 83% of RhB (10 mg/L) in 40 min. The FePMo12O40@PVP composite material demonstrated sustained moderate degradation efficiency even after undergoing three cycles of repeated use. The non-covalent interaction and strong interfacial coupling between PVP and FePMo12O40 promoted the transfer of h+, and e−, ∙O2−, ·OH, and h+ served as the primary active species in this photocatalytic system. This environmentally friendly material has the potential to significantly reduce energy consumption and offers valuable insights for the future treatment of dye wastewater.

1. Introduction

Organic pollutants are a primary contributor to water pollution due to their high toxicity, strong accumulation, and resistance to degradation. Photocatalysis technology has been widely employed for the degradation of organic pollutants in water, offering advantages such as energy efficiency, environmental friendliness, and cost-effectiveness [1,2,3,4,5]. The key factor in photocatalysis technology lies in the choice of photocatalyst. Currently, commonly used semiconductor photocatalysts for degrading organic pollutants include TiO2 [6,7,8], CdS [9,10,11,12], ZnO [13,14,15,16], and Bi2O3 [17,18,19,20], among others. However, the electrons and holes in this kind of photocatalyst are easy to recombine, resulting in low photocatalytic performance. Polyoxometalates (POMs) are clusters of anionic metal oxides formed through the coordination of pre-transition metals/transition metals with oxygen atoms in high oxidation states. In a 2001 review by Anastasia Hiskia et al., it was noted that polyacids possess the capability for photoinduced HOMO→LUMO electron transition (metal-metal charge transfer), similar to classical semiconductors such as WO3 and TiO2, thereby facilitating the generation of reactive oxygen species (·OH and ·O2−) through photocatalysis [21]. Therefore, polyacids can be regarded as semiconductor-like photocatalysis. In recent years, the remarkable reactivity of POMs has distinguished them in the field of photocatalytic applications [22,23,24]. However, using only POMs as a photocatalyst presents certain drawbacks, including low visible light catalytic activity, limited specific surface area, poor stability during catalytic reactions, susceptibility to dissolution in polar solvents, and challenges in recovery and reuse. Therefore, it is crucial to modify POMs to enhance the photocatalytic degradation of organic pollutants. To achieve this objective, composite materials based on POMs are often modified by combining them with semiconductor oxides [25,26,27,28], molecular sieves [29,30,31,32], ion exchange resins [33], metal-organic frameworks (MOFs) [34,35,36,37,38], etc.
The organic polymer material PVP, known for its excellent biocompatibility and minimal environmental impact, is widely utilized as a carrier to support photocatalysts. The combination of photocatalysts with PVP results in the formation of nanocomposite materials, leading to a significant enhancement in photocatalytic performance. For instance, the BiOBr-PVP flower-like microsphere structure composite has demonstrated efficient degradation of 2,4-dichlorophenol [39], ofloxacin (OFL)/norfloxacin (NOR) [40], Cr (VI) [41], Rhodamine B (RhB), and diclofenac [42]. Zhiguo Zhang et al. [43] demonstrated that the ultra-fine PVP-BiO2−x nanomaterial, with a particle size distribution ranging from 5 to 10 nm, exhibited enhanced absorption capacity in the visible light spectrum. In comparison to BiO2−x, PVP-BiO2−x displayed improved photocatalytic properties for Rhodamine B and methyl orange under visible light irradiation. Additionally, Na Zhao et al. [44] synthesized PVP-capped CdS nanopopcorns with adjustable size and structure, which effectively degraded Rhodamine B in water under visible light irradiation while achieving a H2 yield of 3.52 mmol·h−1·g−1 with excellent cyclability. SP. Keerthana et al. [45] utilized a novel hydrothermal technique to prepare PVP assisted Mn-CdS nanorod-like material, which exhibits significant efficacy in degrading methylene blue dye and holds promising potential for application in wastewater treatment. Saba Abdolalian et al. [46] synthesized Zn-polyvinylpyrrolidone (ZnO-PVP) modified ZnO nanoparticles. Compared to pristine ZnO, ZnO-PVP demonstrates enhanced photocatalytic degradation efficiency for COD (from 63% to 83%) and phosphate (from 68% to 87%).
Polyoxometalates (POMs) combined with PVP-modified composites have garnered significant attention due to their exceptional properties in the realm of photochromic materials. However, there has been limited investigation into the performance of POMs-PVP composites in the field of photocatalysis. In this study, we present a composite prepared from polyoxometalate FePMo12O40 and PVP, utilizing Rhodamine B as the pollutant template to validate its photocatalytic properties. In order to enhance suitability for practical degradation applications, the commonly utilized LED light source in daily life was chosen for irradiation. Compared with xenon lamp sources commonly used in photocatalytic experiments, LED light is more energy efficient and avoids significant temperature changes in the reaction system. It was observed that the FePMo12O40@PVP composite materials exhibited significantly enhanced photocatalytic performance and achieved reusability.

2. Results and Discussion

2.1. FT-IR Analysis

Figure 1 shows the FT-IR spectra of FePMo12O40 (Figure 1a), 1.5 g-FePMo12O40@PVP (Figure 1b), 2 g-FePMo12O40@PVP (Figure 1c), 2.5 g-FePMo12O40@PVP (Figure 1d), and 3 g-FePMo12O40@PVP (Figure 1e). The IR spectrum of FePMo12O40 (Figure 1a) shows the signal at 1066 cm−1 ν(P-Oa), 962 cm−1 ν(M-Od), 865 cm−1 ν(M-Ob-M), and 794 cm−1 ν(M-Oc-M). Four characteristic peaks of FePMo12O40 still exist in the FePMo12O40@PVP composite materials with a few wavelengths shifts (Figure 1b–e). The results illustrate that the Keggin skeleton structure was not damaged, and a powerful interfacial interaction existed between FePMo12O40 and PVP. Additionally, the characteristic absorption peaks of PVP (~2953 cm−1, ~2890 cm−1 ν(C-H); ~1660 cm−1 ν(C=O)) are retained in Figure 1b–e. Detailed IR spectra absorption peaks of FePMo12O40 and FePMo12O40@PVP composite materials are presented in Table 1.

2.2. XRD Analysis

The X-ray diffraction patterns of the FePMo12O40 and 2.5 g-FePMo12O40@PVP samples are depicted in Figure 2, revealing their respective crystalline and amorphous states. The XRD pattern of FePMo12O40 exhibited characteristic diffraction peaks within the range of 2θ = 10~40°, consistent with literature values [47]. The curve in Figure 2b appears smooth, suggesting uniform dispersion of FePMo12O40 within the PVP network and an amorphous state. Additionally, other FePMo12O40@PVP composite materials also exhibited amorphous characteristics, as evidenced by their XRD patterns shown in Figure S2.

2.3. XPS Analysis

In the XPS measurement (Figure 3a), the peaks observed at 284.80 eV, 530.83 eV, 398.75 eV, 719.03 eV, 133.16, and 232.31 eV corresponded to C1s, O1s, N1s, Fe2p1, P2p, and Mo3d, respectively. These results indicate the successful loading of FePMo12O40 on PVP and further determines its valence state for the main elements. Figure 3b presents a high-resolution spectrum of C1s, which reveals three characteristic peaks corresponding to C-C (284.50 eV), C-N (285.57 eV), and C=O (287.17 eV). Figure 3c illustrates the O1s spectrum displaying three distinct peaks corresponding to C=O (532.52 eV), Mo-O (531.20 eV) and Mo=O (530.38 eV). The valence state of Mo is reflected in the Mo3d spectrum (Figure 3d). During hydrothermal synthesis, electron transfer from the polymer to FePMo12O40 occurs via hydrogen bonding, leading to partial reduction of Mo6+ to Mo5+. The fitting peaks of Mo spin splitting energy levels correspond to Mo3d3/2 and Mo3d5/2, with binding energy values for the double peak of Mo6+ at 232.42 eV and 235.56 eV and for Mo5+ at 231.23 eV and 234.46 eV.

2.4. SEM and TEM

The morphology and microstructure of the PVP-modified FePMo12O40 materials were characterized using SEM and TEM. Figure 4a,b depict the SEM images of the 2.5 g-FePMo12O40@PVP composite material, revealing a planar stacked structure with a high specific surface area that enhances photon capture by diffracting and reflecting light. The structural features of the 2.5 g-FePMo12O40@PVP were further confirmed through TEM analysis, as shown in Figure 4c,d, demonstrating good correspondence with the SEM images.

2.5. UV-Vis DRS Analysis

The UV-Vis DRS absorption spectra of FePMo12O40 and 2.5 g-FePMo12O40@PVP in the wavelength range of 200–800 nm are depicted in Figure 5a. The O-M characteristic absorption of FePMo12O40 occurred at 420 nm, while the absorption peak of 2.5 g-FePMo12O40@PVP at 330 nm was blue shifted compared with FePMo12O40, attributed to electron transition from the valence band to the conduction band. However, our study demonstrates that the prepared 2.5 g-FePMo12O40@PVP composite exhibits a higher absorption intensity, indicative of enhanced light-collecting behavior. The UV-VIS absorption band edge analysis reveals that the introduction of PVP caused a redshift in the absorption edge of FePMo12O40@PVP composite photocatalyst to 560 nm, compared to pure FePMo12O40 (535 nm), indicating an expanded utilization range of visible light. The band gap of the material was determined using the Tauc plot formula, and it was observed that the addition of PVP maintained the original narrow band gap of the photocatalyst, with a measured value of 2.38 eV for FePMo12O40 modified by PVP, similar to that of unmodified FePMo12O40 (2.32 eV) as shown in Figure 5b.

2.6. Photocatalytic Performance Analysis

In order to evaluate the photocatalytic performance of FePMo12O40@PVP series composites, 100 mL 10 mg/L Rhodamine B (RhB) solution was selected as the target pollutant for photocatalytic degradation under LED light irradiation, as shown in Figure 6a. Then, 0.01 g photocatalyst was reacted with RhB under dark condition for 30 min, during which the FePMo12O40@PVP series samples exhibited noticeable adsorption properties. Subsequently, the solution was subjected to LED light for photodegradation. The final degradation rates of Rhodamine B by the catalysts were observed as follows: 1.5 g-FePMo12O40@PVP—53% after 80 min irradiation, 2 g-FePMo12O40@PVP—75% after 80 min irradiation, 2.5 g-FePMo12O40@PVP—78% after 50 min irradiation, and 3 g-FePMo12O40@PVP—70% after 90 min irradiation. It was evident that 2.5 g-FePMo12O40@PVP exhibited the most favorable catalytic effect. The increase in FePMo12O40 content enhanced the photocatalytic efficiency, while a decrease in the PVP ratio weakened the composite effect with polyoxometalates, thereby negatively impacting the catalytic performance. Pure FePMo12O40 also demonstrated some adsorption capability towards RhB solution, possibly due to coordination of RhB to Fe3+. However, it did not exhibit catalytic activity after LED light irradiation, possibly due to the limited spectral range of the LED light source and the energy loss near 480 nm in white LEDs. The results of controlled experiments are depicted in Figure S3. It was observed that Rhodamine B did not exhibit any degradation in the absence of a catalyst. However, when 0.01 g of PVP was introduced as a catalyst, the degradation rate remained negligible under both light and dark conditions. Furthermore, it was found that RhB could not be adsorbed by PVP reagent alone. PVP was combined with FePMo12O40 at a high temperature to form a surface area favorable for adsorption. Pseudo-first-order reaction kinetics were employed for data fitting. As depicted in Figure 6b, the maximum degradation rate constant for the catalytic reaction of 2.5g-FePMo12O40@PVP was determined to be 0.027 min−1, further confirming its superior photodegradation performance. The rate constant (k) values and corresponding determination coefficients (R2) for each FePMo12O40@PVP composite are presented in Table 2.
Using 2.5 g-FePMo12O40@PVP as catalyst, the degradation efficiency of RhB in composites under various conditions was assessed by altering the catalyst dosage (0.005 g, 0.01 g, 0.015 g, and 0.02 g), the initial concentration of RhB (10 mg/L, 15 mg/L, 20 mg/L, and 25 mg/L), and the initial solution pH value (3–11). As depicted in Figure 7a, an increase in catalyst dosage from 0.005 g to 0.015 g resulted in a significant improvement in degradation efficiency (83% within 40 min). The higher amount of catalyst provided more active sites for the reaction and enhanced adsorption of RhB molecules, thereby improving photodegradation efficiency. However, when the catalyst dosage was further increased to 0.02 g, only a slight enhancement in photocatalytic activity was observed (86% within 40 min). Therefore, for further study on optimal photolysis efficiency, a catalyst dosage of 0.015 g was deemed appropriate (Figure 7b). The higher concentration of RhB dye leads to a reduction in photon transmission path and light transmittance, consequently decreasing the available free radical active groups [48]. Photodegradation efficiency decreased as the concentration of RhB solution increased to 10, 15, 20, and 25 mg/L. For instance, compared to an 83% degradation rate within 40 min at a concentration of 10mg/L, a longer reaction time (80–100 min) was required at concentrations of 15–25mg/L to achieve similar degradation effects. Under the condition of a catalyst dosage of 0.015 g and a RhB solution concentration of 10mg/L, the impact on degradation efficiency was assessed by varying the pH value. As depicted in Figure 7c, favorable adsorption of RhB molecules occurred under acidic conditions (pH = 3 and 5), with no significant difference in the reaction time and final degradation rate compared to neutral conditions (pH = 7). In alkaline solutions (pH = 9 and 11), there was a notable reduction in removal efficiency. pH plays a crucial role in modulating the surface charge of catalysts and organic dyes, thereby influencing the rate of photocatalytic degradation [49]. The negatively charged group of Rhodamine B is attracted to the positively charged catalyst surface in an acidic environment, facilitating the adsorption of Rhodamine B by the catalyst. When the solution contains a high concentration of H+, the photoexcited electrons are induced to migrate towards the surface of the positively charged catalyst, leading to increased generation of photooxidants and enhanced catalytic activity [50]. In an alkaline environment, a significant concentration of OH− ions is present in the solution, resulting in the surface of the catalyst acquiring a negative charge. However, the negatively charged catalyst has the ability to adsorb photogenerated holes, leading to a reduction in the density of ∙OH in the solution and subsequently decreasing the activity of the catalyst [51]. These findings suggest that adjusting the solution pH for RhB is unnecessary. Three consecutive cycles of RhB photodegradation were conducted using 2.5 g-FePMo12O40@PVP catalyst to assess its reusability. Following the photocatalytic experiment, the catalyst was isolated through pumping and filtration, washed with deionized water and anhydrous ethanol, centrifuged, and then dried at 80 °C for 12 h before being utilized in the subsequent cycle. As depicted in Figure 7d, the degradation efficiencies of the first, second, and third cycles were determined to be 83%, 80%, and 77% respectively. These results indicate that despite a decreasing trend in degradation efficiency over the three cycles, the catalyst still exhibited favorable stability and recyclability.

2.7. Possible Mechanism of Photocatalytic Degradation

The active species involved in the 2.5 g-FePMo12O40@PVP photocatalytic degradation of RhB were identified through free radical trapping experiments. 4-hydroxy-tempo, isopropyl alcohol (IPA), and triethanolamine (TEOA) were utilized as trapping agents for ∙O2−, ·OH, and h+, respectively. Figure 8 demonstrates that the addition of IPA, TEMPO, and TEOA during the photocatalytic process led to a decrease in the degradation efficiency of 2.5g-FePMo12O40@PVP on RhB, indicating that ∙O2−, ·OH, and h+ serve as the primary active species in this photocatalytic system. The possible catalytic mechanism is shown in Figure 9. Under illumination, electrons transition from the valence band (VB) to the conduction band (CB) within the FePMo12O40 photocatalyst, resulting in the formation of a photogenerated electron-hole (e−/h+) pair. The presence of hydrogen bonding between polyoxometalates and organic polymers has been reported in several articles discussing photochromic film materials containing polyoxometalates [52,53]. This non-covalent interaction phenomenon has also existed in semiconductor photocatalysts and materials synthesized through PVP hydrothermal/solvothermal methods [43]. Following the modification of FePMo12O40 with PVP, non-covalent interactions and strong interface coupling between PVP and FePMo12O40 may facilitate the transfer of h+ and e−. Electrons (e−) are transferred outward through PVP to generate reactive oxygen species (ROS). The hole (h+) reacts with H2O to produce the hydroxyl radical ∙OH. The resulting ∙O2− and ∙OH actively participate in the redox reaction and effectively degrade RhB.

3. Materials and Methods

3.1. Reagents and Instruments

The preparation of FePMo12O40 followed the method previously described in [47]. Rhodamine B, PVP (MW 50,000) and KBr were analytical grade and ordered from HEOWNS chemical reagent (Tianjin, China). Isopropyl alcohol (IPA) and triethanolamine (TEOA) were analytical grade and ordered from DAMAO chemical reagent (Tianjin, China). 4-hydroxy-tempo was analytical grade and ordered from Innochem (Beijing, China). Deionized water was used throughout the experiments.
Infrared spectra were detected by WQF-510A FT/IR spectrometer (Beifen-Ruili, Beijing, China) using a KBr pellet. XRD was detected by Shimadzu XRD-6100 (Shimadzu, Kyoto, Japan) using the graphite monochromatized Cu Kα radiation (λ = 1.5406 Å) in a 2θ range from 10° to 80° at a scanning rate of 5º/min. X-ray photoelectron spectroscopy was detected by Thermofisher ESCALAB Xi+ (Thermo Fisher Scientific, Waltham, MA, USA). SEM images were detected by HITACHI SU8010, EDS:X-maxN HORIBA (HITACHI, Toyko, Japan). The samples for SEM analysis were prepared by dispersing powdered nanoparticles on a carbon tape and then sputter coating a very thin layer of gold. TEM images were detected by FEI, tecnai F20 EDS:Oxford X-MAX (FEI Company, Hillsbor, OR, USA). The sample for TEM measurement was prepared by dropping a highly diluted dispersion of 2.5 g-FePMo12O40@PVP nanoparticles on copper grid of mesh 100UV–Vis diffuse reflectance spectra and were detected by a Shimadzu 3600-plus UV-vis spectrophotometer (Shimadzu, Kyoto, Japan). UV-vis absorption of the RhB solution was detected by a Beijing Persee Specord T6 UV-vis spectrophotometer (Beijing Persee General Instrument Co., Ltd., Beijing, China). Light irradiation used a 20 W 220 V JT-9006 LED lamp (YongXing, Guangzhou, China).

3.2. Catalyst Preparation

First, 1 g PVP was dissolved in 50 mL ethyl alcohol. Then, 1.5 g FePMo12O40 was added into the solution and stirred for 30 min. The solution was transferred to a polytetrafluoroethylene hydrothermal reactor and heated at 160 °C for 12 h. After cooling, the solution was filtered and washed with deionized water, and the solid was dried to obtain 1.5 g-FePMo12@PVP. The same method was used to prepare 2 g-FePMo12O40@PVP, 2.5 g-FePMo12O40@PVP and 3 g-FePMo12O40@PVP.

3.3. Photocatalytic Degradation of Rhodamine B Dye

The photocatalytic degradation studies of Rhodamine B (RhB) dye were conducted at room temperature. The photocatalyst was introduced into a 100 mL RhB solution, and the resulting mixture was magnetically stirred for 30 min in a dark environment to achieve adsorption-desorption equilibrium. Subsequently, the respective batches of dye-photocatalyst suspensions were exposed to LED light with an intensity of 20 W (220 V) at a distance of 30 cm. At intervals during the experiment, 2 mL of the reaction solution was extracted and subsequently filtered using a 0.22 μm polyether sulfone filter membrane. Dilute HCl and NaOH were used to adjust the pH of the dye solution. RhB solution with gradient concentration were used to determine the absorbance at λ = 554 nm by UV-VIS spectrophotometer. By fitting the curve of concentration and absorbance change according to Lamberbier’s law, the equation obtained was Abs = 0.0363C-0.0014. The percentage degradation of RhB dye was calculated using Equation (1). Here, C0 and C are the initial and final concentrations of RhB, respectively:
D e g r a d a t i o n % = 1 − C C 0 × 100
In the free radical capture experiment, isopropyl alcohol (IPA: 0.5 mL), 4-hydroxy-tempo (TEMPO: 0.02 g) and triethanolamine (0.2 mL) were, respectively, used as the trapping agent of ·OH, h+, and ∙O2− active species; a certain amount of different trapping agents was added to the reaction system before light, and the other steps were consistent with the photocatalytic degradation experiment.

4. Conclusions

A series of FePMo12O40@PVP composites with varying mass ratios were successfully synthesized, and their photocatalytic performance in RhB degradation was investigated. Polyoxomethoate FePMo12O40 modified by PVP maintained the keggin structure and formed an amorphous phase catalyst with high specific surface area, which could enhance photon capture. Additionally, the photocatalyst retained the original narrow band gap of FePMo12O40, enabling its utilization in the visible light spectrum. It is suggested that PVP may interact with FePMo12O40 through non-covalent interaction and strong interface coupling to facilitate the transfer of h+ and e−. By optimizing the experimental conditions, the optimal process parameters for treating Rhodamine B simulated wastewater with FePMo12O40@PVP composite material were determined: the catalyst dosage of 2.5 g-FePMo12O40@PVP was 0.015 g, the concentration of Rhodamine B was 10 mg/L in 100 mL solution, pH was maintained at 7, and the reaction time under LED light conditions was set to 40 min, resulting in a final removal rate of 83%. Furthermore, after three cycles of recycling, the degradation rate of the composite remained at medium degradation rate, demonstrating its commendable stability. The possible mechanism of photocatalytic degradation was also discussed. In summary, the synthesized FePMo12O40@PVP composite exhibited a favorable degradation effect on RhB under energy-efficient LED light irradiation. In comparison to the pure polyoxometalate FePMo12O40 catalyst, it demonstrated enhanced efficiency and recyclability in removing RhB, making it an ideal candidate material for photocatalytic wastewater treatment.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/inorganics12060144/s1, Figure S1: The detail IR spectra of FePMo12O40 and FePMo12O40@PVP composite materials; Figure S2: XRD of (a) 1.5 g-FePMo12O40@PVP; (b) 2 g-FePMo12O40@PVP; (c) 2.5 g-FePMo12O40@PVP; (d) 3 g-FePMo12O40@PVP; Figure S3: Blank controlled experiment of photocatalyzed Rhodamine B.

Author Contributions

Conceptualization, Z.W. and M.L.; methodology, Z.W. and L.A.; validation, Y.T. and Y.W.; formal analysis, M.L. and L.A.; investigation, Y.T.; data curation, Z.W. and Y.W.; writing—original draft preparation, Z.W., M.L. and Y.T.; writing—review and editing, Z.W., M.L. and Y.T. All authors have read and agreed to the published version of the manuscript.

Funding

The study was financially supported by the Doctoral Start-up Foundation of Liaoning Province (No. 2021-BS-250, No. 2021-BS-251) and Pharmaceutical Cleaner Production & Industrialization Innovation Team Foundation (No. XKT202304).

Data Availability Statement

Data are contained within the article and Supplementary Material.

Conflicts of Interest

The authors declare no conflicts of interest.

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Inorganics 12 00144 g001
Figure 1. FT-IR spectra of (a) FePMo12O40; (b) 1.5 g-FePMo12O40@PVP; (c) 2 g-FePMo12O40@PVP; (d) 2.5 g-FePMo12O40@PVP; and (e) 3 g-FePMo12O40@PVP.
Figure 1. FT-IR spectra of (a) FePMo12O40; (b) 1.5 g-FePMo12O40@PVP; (c) 2 g-FePMo12O40@PVP; (d) 2.5 g-FePMo12O40@PVP; and (e) 3 g-FePMo12O40@PVP.
Inorganics 12 00144 g001
Inorganics 12 00144 g002
Figure 2. XRD of (a) FePMo12O40; (b) 2.5 g-FePMo12O40@PVP.
Figure 2. XRD of (a) FePMo12O40; (b) 2.5 g-FePMo12O40@PVP.
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Inorganics 12 00144 g003
Figure 3. XPS spectra (a) full spectrum; (b) C1s; (c) O1s; (d) Mo3d energy level of 2.5 g-FePMo12O40@PVP.
Figure 3. XPS spectra (a) full spectrum; (b) C1s; (c) O1s; (d) Mo3d energy level of 2.5 g-FePMo12O40@PVP.
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Inorganics 12 00144 g004
Figure 4. (a,b) SEM images of 2.5 g-FePMo12O40@PVP; (c,d) TEM images of 2.5 g-FePMo12O40@PVP.
Figure 4. (a,b) SEM images of 2.5 g-FePMo12O40@PVP; (c,d) TEM images of 2.5 g-FePMo12O40@PVP.
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Inorganics 12 00144 g005
Figure 5. (a) UV–Vis diffuse reflectance spectra of FePMo12O40 and 2.5 g-FePMo12O40@PVP; (b) Tauc plot for FePMo12O40 and 2.5 g-FePMo12O40@PVP.
Figure 5. (a) UV–Vis diffuse reflectance spectra of FePMo12O40 and 2.5 g-FePMo12O40@PVP; (b) Tauc plot for FePMo12O40 and 2.5 g-FePMo12O40@PVP.
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Inorganics 12 00144 g006
Figure 6. Photodegradation curves of RhB under LED light (a) and its pseudo-first-order kinetics (b).
Figure 6. Photodegradation curves of RhB under LED light (a) and its pseudo-first-order kinetics (b).
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Inorganics 12 00144 g007
Figure 7. Effects of (a) catalyst dosage (b) RhB concentration, (c) pH on degradation efficiency; (d) cycling experiments of photocatalytic degradation of RhB over 2.5 g-FePMo12O40@PVP.
Figure 7. Effects of (a) catalyst dosage (b) RhB concentration, (c) pH on degradation efficiency; (d) cycling experiments of photocatalytic degradation of RhB over 2.5 g-FePMo12O40@PVP.
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Inorganics 12 00144 g008
Figure 8. The photocatalytic degradation activity of 2.5 g-FePMo12O40@PVP for RhB under different trapping agents.
Figure 8. The photocatalytic degradation activity of 2.5 g-FePMo12O40@PVP for RhB under different trapping agents.
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Inorganics 12 00144 g009
Figure 9. Possible degradation mechanism of 2.5 g-FePMo12O40@PVP.
Figure 9. Possible degradation mechanism of 2.5 g-FePMo12O40@PVP.
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Table 1. The detail IR spectra of the FePMo12O40 and FePMo12O40@PVP composite materials.
Table 1. The detail IR spectra of the FePMo12O40 and FePMo12O40@PVP composite materials.
ν(P-Oa)ν(M-Od)ν(M-Ob-M) ν (M-OC-M)
FePMo12O401066962865794
1.5 g-FePMo12O40@PVP1062958883806
2 g-FePMo12O40@PVP1060954881804
2.5 g-FePMo12O40@PVP1062956883811
3 g-FePMo12O40@PVP1060956881809
Table 2. The values of k and R2 for FePMo12O40@PVP composite materials.
Table 2. The values of k and R2 for FePMo12O40@PVP composite materials.
K (min−1)R2
1.5 g-FePMo12O40@PVP0.0110.990
2 g-FePMo12O40@PVP0.0170.989
2.5 g-FePMo12O40@PVP0.0270.990
3 g-FePMo12O40@PVP0.0130.990
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Wang, Z.; Tang, Y.; Ai, L.; Liu, M.; Wang, Y. Polymer-Based Immobilized FePMo12O40@PVP Composite Materials for Photocatalytic RhB Degradation. Inorganics 2024, 12, 144. https://doi.org/10.3390/inorganics12060144

AMA Style

Wang Z, Tang Y, Ai L, Liu M, Wang Y. Polymer-Based Immobilized FePMo12O40@PVP Composite Materials for Photocatalytic RhB Degradation. Inorganics. 2024; 12(6):144. https://doi.org/10.3390/inorganics12060144

Chicago/Turabian Style

Wang, Zijing, Yuze Tang, Limei Ai, Minghui Liu, and Yurong Wang. 2024. "Polymer-Based Immobilized FePMo12O40@PVP Composite Materials for Photocatalytic RhB Degradation" Inorganics 12, no. 6: 144. https://doi.org/10.3390/inorganics12060144

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