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Article

Facile Preparation of Attapulgite-Supported Ag-AgCl Composite Photocatalysts for Enhanced Degradation of Tetracycline

by
Xiaojie Zhang
1,*,
Huiqin Wang
1,2,* and
Chenlong Yan
2
1
Jiangsu Provincial Key Laboratory of Palygorskite Science and Applied Technology, Huaiyin Institute of Technology, Huai’an 223003, China
2
School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
*
Authors to whom correspondence should be addressed.
Catalysts 2024, 14(7), 464; https://doi.org/10.3390/catal14070464
Submission received: 25 June 2024 / Revised: 17 July 2024 / Accepted: 18 July 2024 / Published: 19 July 2024
(This article belongs to the Special Issue Mineral-Based Composite Catalytic Materials)

Abstract

:
In this study, Ag-AgCl/attapulgite (Ag-AgCl/ATP) composites were synthesized via a direct precipitation method using ATP nanorods as a catalyst supporter. ATP nanorods helped to increase the dispersion of Ag-AgCl particles and broaden the light absorption spectrum, which would also help to increase the active site of the catalyst to promote the degradation of tetracycline (TC). The photocatalytic activity of the Ag-AgCl/ATP composites was evaluated through the degradation of TC, identifying the loading amount of Ag-AgCl, the concentration of TC, and the reaction temperature as critical factors influencing activity. Specifically, the optimal conditions were observed when the loading of Ag-AgCl was 75%, resulting in a photocatalytic degradation efficiency of 77.65%. Furthermore, the highest degradation efficiency (85.01%) was achieved with a TC concentration of 20 mg/L at 20 °C. Radical trapping experiments suggested that the superoxide anion radical (·O2) was the primary active species in the degradation process, although hydroxyl radicals (·OH) and holes (h+) also contributed. Reusability tests confirmed that the Ag-AgCl/ATP composites exhibited excellent stability and could be effectively reused.

1. Introduction

The country’s rapid industrialization has accelerated China’s move to the center of the world stage, but at the same time, environmental pollution has become more and more serious [1,2,3,4]. In real life, antibiotics are widely used and often treat bacterial infections in humans and animals. Most of the antibiotics are excreted in feces and urine in the form of prototypes or metabolites after use, resulting in generally high concentrations of antibiotics remaining in the feces [5,6,7]. It will increase the resistance of bacteria and accelerate the spread of antibiotic-resistant genes, causing different degrees of harm to humans and the ecology. The World Health Organization has listed the problem of antibiotic resistance genes caused by the abuse of antibiotics as one of the major challenges facing human health in this century [8,9,10]. It is urgent to find a new technology to remove antibiotics. Photocatalytic technology is considered to be one of the most effective technologies for degrading and removing antibiotics [11,12,13]. Photocatalytic technology has been studied by many researchers because of its mild reaction conditions, low price and simple operation [14,15,16]. Although photocatalysis technology has been fully developed, it has not played a very wide role in practical application because most semiconductor photocatalysts have low surface energy and are prone to agglomeration, resulting which has low photocatalytic activity [17,18]. Therefore, it is very important to select a suitable photocatalyst for TC degradation.
Ag-AgCl nanoparticles could possess photocatalytic activity that changes with the crystal face structure, which could be prepared to catalyze the degradation of much pollution, printing dyes and acetaldehyde, etc. [19,20,21,22]. However, Ag-AgCl particles are easy to agglomerate, and finding suitable materials that are too dispersive will help to increase the concentration of the active site to achieve efficient TC degradation. Natural one-dimensional nanomaterial attapulgite (Mg5Si8O20(OH)2(OH2)4·4H2O) (ATP) is a kind of water-containing magnesium-rich aluminum silicate clay mineral with a chain layered structure, belonging to the 2:1 type clay mineral, which possesses ultra-high internal and external specific surface area, non-toxic, tasteless, chemical properties stability and other advantages, for instance, high adsorption performance, catalytic, chargeability, and stability [23,24,25,26,27]. However, the utilization trend of some ATP is not high, which undoubtedly causes the waste and loss of mineral resources. Accordingly, many researchers have devoted themselves to the development and research of ATP resources as carriers [28,29,30].
In this paper, ATP was used as the basic material, and a simple experimental method was used to pre-treat it. Ag-AgCl is built into the attapulgite structure to synthesize a series of new composite catalysts. The photocatalytic degradation efficiency of TC was used to evaluate the photodegradation performance of the composite catalyst. At the same time, the optimal special-performance materials were used to conduct recycling experiments to investigate the stability of the materials. ATP possesses a high specific surface area, with attapulgite as the basic material; it can effectively prevent the occurrence of agglomeration and improve the performance of the catalyst. The introduction of Ag-AgCl nanoparticles is deposited on the surface of the photocatalyst, and the photogenerated electrons generated by the light excitation will diffusion from the surface of the catalyst to the surface of the metal. This work provides new ideas for the design and preparation of composite photocatalysts based on ATP. Realizing the effective utilization of attapulgite, especially in water treatment, attapulgite has important theoretical and practical significance.

2. Results

2.1. XRD Analysis

To determine the crystal structure and composition of the synthesized photocatalytic material, Figure 1 presents the X-ray diffraction (XRD) spectra of ATP, silver chloride (AgCl), AgCl/ATP, and Ag-AgCl/ATP composites. The XRD pattern of attapulgite displays prominent peaks at 2θ values of 13.7°, 16.08°, 20.67°, 21.24°, and 27.5°, corresponding respectively to the (200), (220), (301), (121), and (400) crystallographic planes of ATP [31,32]. Notably, the AgCl peaks appear at 2θ = 27.7°, 32.4°, 46.2°, 54.8°, 57.7°, 67.6°, 74.5°, and 76.9°, aligning with the (111), (200), (220), (311), (222), (400), (331), and (420) planes of AgCl (JCPDS:85-1355) [33,34]. Furthermore, peaks at 38.1° and 44.3° confirm the presence of metallic silver (Ag) corresponding to the (111) and (200) planes (JCPDS: 89-3722), indicative of an in-situ reduction of Ag+ ions on the AgCl surface [35]. This reduction process facilitates the conversion of Ag+ to metallic Ag, confirming the successful preparation of the Ag-AgCl/ATP composite photocatalyst.

2.2. Morphology Analysis

To understand and study the morphology of the catalytic materials, we performed SEM and TEM characterizations. Figure 2A is the SEM image of the attapulgite pre-processed with a magnification of 25,000 times. In Figure 2A, it can be seen that the bumpy clay has an acicular or rod-like structure with a random network of rod crystal fibers with a length of about 2 um [36,37]. Figure 2B shows Ag-AgCl, which is granular with a small number of agglomerates and a few fine particles on the surface, which is consistent with the appearance of Ag. Figure 2C is the enlarged SEM images of Ag-AgCl/ATP. From the figure, it can be clearly seen that the attapulgite is loaded with a large number of AgCl particles, and the dispersion is uniform. Attapulgite clay needles or rods can be observed in Figure 2D consistent with scanning. Whereas the spherical shape of AgCl is also shown in Figure 2E, the rod-like structure can be seen interspersed in the spheres in Figure 2F, indicating that the two were successfully composite. Elemental mapping (Figure 3A–F) reveals the distribution of oxygen (O), iron (Fe), chlorine (Cl), silver (Ag), silicon (Si), aluminum (Al), and magnesium (Mg) in the Ag-AgCl/ATP photocatalytic composite, confirming the complex composition of the material.

2.3. FT-IR Analysis

Figure 4 shows the FT-IR spectra of ATP, Ag-AgCl, and Ag-AgCl/ATP. ATP primarily consists of palygorskite, characterized by prominent infrared spectral peaks at 510, 980, 1030, 1460, 1640–1660 and 3450–3600 cm−1. In the mid-wave number region, the peaks at 980 cm−1 and 1030 cm−1 correspond to the stretching vibrations of Si–O–Si bonds within the internal structure of ATP [38,39,40]. The peaks observed at 1460 and 1640 cm−1 are attributed to coordinated water (surface-adsorbed water) and zeolite water (pore channel). In the high-wave number region, the peak at 3540 cm−1 reflects the stretching vibration of coordinated water, while the peak at 3600 cm−1 corresponds to bond stretching in ATP. The FT-IR spectra of Ag-AgCl/ATP composites indicate that the fundamental properties of attapulgite remain unchanged throughout the synthesis process.

2.4. Surface Chemical State Analysis

Figure 5 presents the compositional analysis and surface chemical states of the optimized photocatalyst, 75% Ag-AgCl/ATP, as determined by X-ray photoelectron spectroscopy (XPS). The full spectrum shown in Figure 5A revealed more pronounced and intense peaks at 532.69 eV, 367.81 eV, 198.22 eV, and 102.49 eV, which correspond to the presence of oxygen (O), silver (Ag), chlorine (CI), and silicon (Si), respectively, corroborating the findings from X-ray diffraction (XRD) and elemental mapping analyses. Figure 5B–E detail the XPS spectra for Ag 3d, Cl 2p, Si 2p, and O 1s, respectively. Among them, the composite of Figure 5B shows peaks at 533.64 eV, 532.29 eV, and 531.21 eV, corresponding to the three partial compositions of Si–O–Si, Si–O–H, and Si–O–Mg, respectively. Figure 5D, on the other hand, shows the fitted high-resolution spectrum of AgMN1, which can be divided into two different peaks, Ag and AgCl. Figure 5C illustrates the characteristic peak of Si at 102.84 eV in a two-dimensional orbital profile. After compounding, the binding energy of Si moves in a large direction, showing a blueshift. The binding energies at 199.41 eV and 197.96 eV, shown in Figure 5D, correspond to the Cl 2p3/2 and Cl 2p1/2 states, respectively. It can be seen that the binding energy of Cl in the composite is shifted in a smaller direction than that of Cl in the monomer, showing a redshift. Lastly, the binding energies of 373.91 eV and 367.92 eV in Figure 5E are assigned to Ag 3d3/2 and Ag 3d5/2, indicating the presence of these elements within the composite [41,42,43]. These spectral results provide comprehensive insights into the chemical states at the catalyst surface, further substantiating the successful synthesis of the composite catalyst.

2.5. UV-Vis DRS

Figure 6 depicts the characterization of the prepared composite photocatalytic materials using an ultraviolet–visible diffuse reflectance spectrometer. The spectral data demonstrate that these materials exhibit pronounced absorption peaks within the wavelength range of 200–400 nm. Notably, ATP and AgCl display distinct absorption edges at 420 nm and 440 nm, respectively. When compared with the ultraviolet-visible diffuse reflectance spectrum of ATP, AgCl and Ag-AgCl/ATP show variations; particularly, the spectrum of Ag-AgCl/ATP exhibits a noticeable blue shift. This shift indicates an increase in the light absorption capacity of the catalyst and an increase in its efficiency in the presence of light.

2.6. Photo-Electrochemistry Analysis

To further investigate charge transfer and separation effects, electrochemical tests were conducted. Figure 7a illustrates stable photocurrent density profiles across all samples, with composites exhibiting prominent photocurrent signals compared to bare ATP with AgCl; notably, the 75% loaded sample shows optimal photocurrent intensity. This suggests that AgCl addition effectively enhances hole-electron pair separation [44]. Furthermore, impedance spectra (EIS) of composite samples with varying AgCl proportions alongside pure AgCl and ATP are presented in Figure 7b. Results reveal the smallest arc radius for the 75% Ag-AgCl/ATP electrode, indicating lower interfacial resistance conducive to enhanced electron transport [45]. Linear sweep voltammetry (LSV) curves in Figure 7c demonstrate that 75% Ag-AgCl/ATP exhibits the lowest overpotential at identical current densities, underscoring the catalysts’ synergistic facilitation of photocatalytic degradation processes. In Figure 6b, the band gaps of ATP and AgCl were tested and found to be 3 eV and 3.24 eV, respectively, and the valence bands (VB) of ATP and AgCl were measured in Figure 6c,d using XPS valence band spectroscopy to be 2.56 eV and 2.76 eV, respectively, and through the empirical formula EVB = ECB + Eg, it can be obtained that the conduction bands (CB) for ATP and AgCl were −0.44 eV and −0.48 eV.

3. Photocatalytic Performance

3.1. Photocatalytic Activity

This study investigates the photocatalytic properties of prepared materials using TC as a model pollutant. Figure 8A depicts the photocatalytic efficiencies of various loadings of photocatalytic materials (ATP, 2%Ag-AgCl/ATP, 5%Ag-AgCl/ATP, 10%Ag-AgCl/ATP, 20%Ag-AgCl/ATP, 50%Ag-AgCl/ATP, 75%Ag-AgCl/ATP, 80%Ag-AgCl/ATP and AgCl). Upon exposure to a 300 W xenon lamp for 120 min, the photocatalytic efficiencies of Ag-AgCl/ATP photocatalysts were 35.00%, 20.11%, 37.46%, 44.83%, 64.23%, 77.65%, 71.60%, and 76.10%, respectively. Notably, at 2% AgCl loading, Ag-AgCl/ATP exhibits the lowest photocatalytic efficiency, even lower than pure ATP. As the AgCl loading increases within Ag-AgCl/ATP, the photocatalytic efficiency improves significantly. The peak efficiency is achieved at 75% AgCl loading, after which further increases diminish photocatalytic performance, likely due to surface blockage of attapulgite preventing effective pollutant-catalyst interaction and reducing activity. Figure 8B illustrates the photocatalytic degradation rate curve of the optimized Ag-AgCl/ATP photocatalytic material across different concentrations of TC (10, 20, 30, 50, and 100 mg/L). After 120 min of photocatalytic degradation, the degradation rates for each TC concentration are 81.46%, 85.01%, 79.08%, 68.42%, and 35.18%, respectively. Notably, the highest degradation rate is achieved at a TC concentration of 20 mg/L, followed by 10 mg/L, and then 30 mg/L. The lowest degradation rate is observed at 100 mg/L TC concentration. These results indicate that the optimized Ag-AgCl/ATP photocatalytic material exhibits greater efficiency at lower TC concentrations, with degradation rates declining as TC concentration increases. This underscores the importance of considering pollutant concentrations when applying such photocatalytic materials in practical environmental remediation scenarios.
The initial concentration of TC in this experiment is in the range of 10–100 mg L−1. The experimental results are shown in Figure 8B,C. The photocatalytic degradation efficiency and rate of TC are negatively correlated with the initial concentration of TC. As the concentration of TC in the solution increases, the total amount of TC also increases. Under the condition of loading with the same AgCl catalyst quality, the degradation rate of high-concentration TC decreases slightly compared with other concentrations. High concentrations of TC cannot absorb photons well and cannot effectively separate photogenerated electrons and holes, which will affect the degradation rate.
The rate equation obtained from the Langmuir–Hinshelwood kinetic equation is expressed as the following Equation (1):
Among them, C0 and C represent the initial and degraded concentration of TC at time t, kc is the pseudo-first rate constant, and KCIP is the equilibrium constant for the adsorption of TC by the catalyst. According to the above equation expression, in the presence of Fe-doped AgCl photocatalyst, the pseudo-first-order kinetic equation of photocatalytic degradation is expressed as the following Equation (2):
Where kobs is the quasi-first order kinetic rate constant, and the above formula can be transformed into (3).
According to Equation (3), the linear relationship between ln(C0/C) and time t is shown in Figure 8D. The linear relationship expression between kobs and C0 can be transformed from Equation (1).
It can be seen from Formula (4) that the reciprocal rate (1/kobs) and the initial concentration of TC show a linear relationship. At the same time, the photocatalytic degradation rate of TC, kobs, changes with the initial concentration, as shown in Figure 9A. According to the slope and intercept of the straight line, the equilibrium adsorption constant of TC KTC = 0.135 L mg−1, and the pseudo-second rate constant kc = 0.933 mg L−1 min−1. In Table 1, we also show the effects of different concentrations on the degradation rate.
R a t e = d C d t = k c K C I P C 1 + K C I P C 0
d C d t = k o b s C = k c K C I P 1 + K C I P C 0 C
ln C C 0 = k o b s t
1 k o b s = 1 k c K C I P + C 0 k c
To assess the impact of temperature on the photocatalytic performance of our prepared samples, we conducted experiments on TC solution degradation using the catalysts under different thermal conditions. Figure 9B presents degradation efficiency curves of the optimized Ag-AgCl/ATP photocatalytic material for degrading a 20 mg/L TC solution at temperatures of 20, 30, 40 and 50 °C. Results show that after 120 min of photocatalytic activity, the degradation efficiencies at these temperatures are 85.01%, 70.18%, 67.49%, and 67.97%, respectively. Notably, the highest degradation rate of 85.01% is achieved at 20 °C, indicating superior TC degradation efficiency of the prepared Ag-AgCl/ATP photocatalytic material at lower temperatures. Conversely, efficiency decreases with increasing temperature. Considering that operational environments for these photocatalytic materials typically involve room temperature conditions, the findings highlight the substantial potential for practical applications in TC degradation scenarios.

3.2. Stability

The stability of a material is a crucial metric for assessing its practical applicability. In particular, the stability of photocatalytic materials is indicative of their quality and potential for broader applications. To evaluate the stability of our composite photocatalytic material, we conducted five successive cycles of photocatalytic experiments. As illustrated in Figure 9C, the photocatalytic degradation efficiency after 120 min of photoreaction was recorded at 74.24%, 70.70%, 69.19%, 69.56%, and 69.32% for each cycle, respectively. These results indicate a slight initial decrease in efficiency, which subsequently stabilizes around 69%. This consistent performance demonstrates that the Ag-AgCl/ATP photocatalytic composite material we developed maintains substantial degradation capability after repeated use, thereby confirming its excellent stability and reinforcing its suitability for practical applications in pollutant degradation.

3.3. Capture Experiment

To ascertain the predominant active species involved in the degradation process, this study conducted trapping experiments targeting key reactive species such as holes (h+), hydroxyl radicals (·OH), and superoxide anion radicals (·O2), to elucidate the photocatalytic degradation mechanism of TC (Figure 9D). Triethanolamine, isopropanol (IPA), and p-benzoquinone were utilized as specific scavengers for these active species, respectively. The trapping experiments were integrated into the standard photocatalytic degradation protocol for TC. Specifically, a precise amount of each scavenger was added to the reaction vessel containing the catalyst and 100 mL of TC solution: 0.133 mL of triethanolamine, 0.076 mL of isopropanol, or 0.108 g of p-benzoquinone. Following this, the concentration of TC was monitored by sampling at designated intervals, and the photocatalytic efficiency was quantitatively assessed. This experimental setup was replicated across three separate trials to ensure reproducibility and accuracy in the findings.

3.4. Mechanism Analysis

The role of active species in the photodegradation of TC using an Ag-AgCl/ATP composite photocatalyst was elucidated through a series of trapping experiments. Figure 9D illustrates that the addition of isopropanol, a scavenger for ·OH, has a minimal effect on the degradation rate of TC, indicating a marginal role of ·OH radicals in the degradation process. Conversely, the addition of triethanolamine, a scavenger for h+, significantly impacts the TC degradation rate more than isopropanol, suggesting a predominant role of h+ over ·OH radicals in the TC degradation mechanism. However, the overall influence of both species is limited, leading to the introduction of p-benzoquinone to further probe the degradation kinetics. In Figure 10, the mechanistic pattern of the reaction can be seen. This addition markedly reduces the photocatalytic degradation efficiency of TC compared to the baseline condition without scavengers, confirming that the·O2 is the principal active species in the degradation process. Experimental findings reveal that: (1) the inherent high specific surface area of attapulgite provides numerous active adsorption sites, enhancing the photocatalytic activity of the Ag-AgCl/ATP composite; (2) the presence of silver on the AgCl surface induces plasmon resonance effects upon photolysis, facilitating the generation of active species such as h+ and ·O2, which substantially improve the photocatalytic efficiency of the composite material.

4. Materials and Methods

4.1. Pre-Treatment of the ATP

Initially, ATP was subjected to pre-treatment by dispersing it into an ample volume of deionized water, followed by stirring at a speed of 500 rpm using a magnetic stirrer for 1 h. Subsequently, the mixture was transferred to a filter for filtration. The filtration was rapidly conducted, and the residue was washed thrice. The reagents were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The deionized water used throughout the experiments was obtained from locally purified water. All analytical grade reagents are used directly without further purification.

4.2. Preparation of Ag-AgCl/ATP Materials

Initially, 1 g of pre-treated ATP was added to a 100 mL beaker containing 15 mL of deionized water. The mixture was stirred at a speed of 500 r/min for 30 min to ensure complete dispersion of the ATP in the solution. Subsequently, the AgNO3 solution, previously prepared to the required concentration, was added dropwise to the suspension over 5 min. After the addition, stirring was continued for an additional 30 min. Following this, the required amount of NaCl solution was gradually introduced into the beaker over 5 min, using titration for precise control. Upon completion of the titration, the mixture was stirred at 600 r/min for 60 min. The resultant suspension was then filtered, and the retained solid was washed three times with deionized water and three times with ethanol. The washed solid was dried in a blowing drying oven at 60 °C for 10 h. The resulting AgCl/ATP composite with different loading (2%, 5%, 10%, 20%, 50%, 75% and 80%) was ground into a fine powder and stored in a dark place to prevent photodegradation. For subsequent experiments, the AgCl/ATP was exposed to light for 10 min to prepare the Ag-AgCl/ATP composite.

4.3. Photocatalytic Degradation of Tetracycline

To evaluate the photocatalytic activity of the composites, degradation experiments of TC were conducted under various temperatures and concentrations. The experimental procedure is detailed as follows:
Initially, 25 mg of the catalyst was suspended in 100 mL of a 20 mg/L TC solution to conduct the photocatalytic degradation tests. The mixture was stirred magnetically in the dark for 30 min to establish adsorption-desorption equilibrium. During this period, aliquots of 10 mL were sampled every 10 min using a centrifuge tube, collecting three samples in total. Subsequently, a xenon lamp was activated to initiate the photocatalytic reaction, which was continued under illumination for 60 min. Samples were taken every 20 min, resulting in six additional samples. Including the initial sample, ten samples were analyzed in total. These ten samples were then centrifuged at 6000 r/min for 3 min to separate the supernatants for photometric analysis. The absorbance of each sample was recorded to calculate the photocatalytic degradation efficiency. This procedure was repeated using AgCl/ATP composites with varying loadings to identify the composite with the highest photocatalytic activity. The optimal composite was then used to degrade tetracycline at different temperatures (20, 30, 40 and 50 °C) and concentrations (10, 20, 30, 50, and 100 mg/L). For each condition, the procedure mirrored that of the optimal loading tests, and the temperature was strictly controlled during the reaction. The absorbance values were measured, and the corresponding photocatalytic efficiencies were calculated for each set of experimental conditions. In addition, the stirrer was an H01-1A Intelligent Digital Magnetic Stirrer, while the xenon lamp used a power of 300 W (300 mW cm−2; full spectrum) (Please refer to Supplementary Information for details).

4.4. Stability Test

The recyclability of photocatalysts is critical for the practical application of photocatalytic technologies. To assess whether a photocatalytic material warrants recycling, it is imperative to conduct thorough recycling experiments. These experiments not only evaluate the recyclability of the photocatalyst but also its stability over multiple cycles. The protocol for the recycling experiments mirrors that of the tetracycline photocatalytic degradation tests. Specifically, after each cycle, the nine samples collected are centrifuged to separate the supernatants for photometric analysis to measure their luminosity values. Post-measurement, the supernatants are carefully filtered, and the results are documented. The remaining solution in the centrifuge tubes, along with the sample solution from the degradation container, is recovered. This mixture is then washed and dried to retrieve the catalyst. Subsequently, the recovered catalyst is ground, and its mass is measured. Should there be a shortfall in the catalyst weight, an additional quantity of the original sample is supplemented to match the prescribed mass. This preparation then undergoes another cycle of the tetracycline degradation experiment. This procedure is repeated for a total of five cycles to comprehensively assess the photocatalyst’s performance and stability over repeated use.

5. Conclusions

The direct precipitation method and the oxidation method were used to successfully prepare the Ag-AgCl/ATP composite photocatalytic material. Through photocatalytic degradation experiments under different conditions and detailed analysis of various characteristics of the composite photocatalytic material, we have drawn a series of conclusions: (1) ATP not only enhances the dispersion of Ag-AgCl nanospheres but also ATP aids in the adsorption of TC molecules, thereby synergistically promoting the degradation of TC with Ag-AgCl nanoparticles. (2) Through the test in the photocatalytic degradation of TC solutions of different concentrations, it was found that when the concentration of TC solution is 20 mg/L, the composite photocatalytic material has the highest photocatalytic degradation efficiency of 85.01%. (3) From the photocatalytic degradation test at different temperatures, we found that the photocatalytic composite material has the highest photocatalytic degradation efficiency at a temperature of 20 °C.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal14070464/s1.

Author Contributions

Conceptualization, X.Z. and H.W.; methodology, H.W.; investigation, H.W. and C.Y.; writing-original draft preparation, X.Z.; writing-review and editing, X.Z. and H.W.; supervision, X.Z. and H.W.; project administration, X.Z. and H.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Key Laboratory for Playgorskite Science and Applied Technology of Jiangsu (HPK202006).

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Huong, V.T.; Duc, B.V.; An, N.T.; Anh, T.T.P.; Aminabhavi, T.M.; Vasseghian, Y.; Joo, S.W. 3D-Printed WO3-UiO-66@reduced graphene oxide nanocomposites for photocatalytic degradation of sulfamethoxazole. Chem. Eng. J. 2024, 483, 149277. [Google Scholar] [CrossRef]
  2. Singh, A.; Dhau, J.; Kumar, R.; Badru, R.; Singh, P.; Kumar Mishra, Y.; Kaushik, A. Tailored carbon materials (TCM) for enhancing photocatalytic degradation of polyaromatic hydrocarbons. Prog. Mater. Sci. 2024, 144, 101289. [Google Scholar] [CrossRef]
  3. Chen, C.; Zhang, X.; Liu, E.; Xu, J.; Sun, J.; Shi, H. Biochar decorated Bi4O5Br2/g-C3N4 S-scheme heterojunction with enhanced photocatalytic activity for Norfloxacin degradation. J. Mater. Sci. Technol. 2024, 198, 1–11. [Google Scholar] [CrossRef]
  4. Wang, H.; Wan, Y.; Yin, S.; Xu, M.; Zhao, X.; Liu, X.; Song, X.; Wang, H.; Zhu, C.; Huo, P. Boosting mineralized organic pollutants by using a sulfur-vacancy CdS photocatalyst. Chem. Commun. 2023, 59, 9356–9359. [Google Scholar] [CrossRef] [PubMed]
  5. Yue, Y.; Wu, Q.; Zheng, C.; Sun, Y.; Shah, K.J. Study on the Degradation Effect of Tetracycline Using a Co-Catalyst Loaded on Red Mud. Catalysts 2024, 14, 133. [Google Scholar] [CrossRef]
  6. Wang, H.; Wan, Y.; Li, B.; Ye, J.; Gan, J.; Liu, J.; Liu, X.; Song, X.; Zhou, W.; Li, X.; et al. Rational design of Ce-doped CdS/N-rGO photocatalyst enhanced interfacial charges transfer for high effective degradation of tetracycline. J. Mater. Sci. Technol. 2024, 173, 137–148. [Google Scholar] [CrossRef]
  7. Lee, S.; Devarayapalli, K.C.; Kim, B.; Lim, Y.; Lee, D.S. Fabrication of MXene-derived TiO2/Ti3C2 integrated with a ZnS heterostructure and their synergistic effect on the enhanced photocatalytic degradation of tetracycline. J. Mater. Sci. Technol. 2024, 198, 186–199. [Google Scholar] [CrossRef]
  8. Wang, H.; Li, J.; Wan, Y.; Nazir, A.; Song, X.; Huo, P.; Wang, H. Fabrication of Zn vacancies-tunable ultrathin-g-C3N4@ZnIn2S4/SWNTs composites for enhancing photocatalytic CO2 reduction. Appl. Surf. Sci. 2023, 613, 155989. [Google Scholar] [CrossRef]
  9. Veerakumar, P.; Sangili, A.; Chen, S.-M.; Kumar, R.S.; Arivalagan, G.; Firdhouse, M.J.; Hameed, K.S.; Sivakumar, S. Photocatalytic degradation of phenolic pollutants over palladium-tungsten trioxide nanocomposite. Chem. Eng. J. 2024, 489, 151127. [Google Scholar] [CrossRef]
  10. Cui, Y.; Li, Y.; Liu, Y.; Shang, D.; Liu, Y.; Xie, L.; Zhan, S.; Hu, W. High-efficiency photocatalytic degradation of rhodamine 6G by organic semiconductor tetrathiafulvalene in weak acid-base environment. Chem. Commun. 2022, 58, 4251–4254. [Google Scholar] [CrossRef]
  11. Mergenbayeva, S.; Abitayev, Z.; Batyrbayeva, M.; Vakros, J.; Mantzavinos, D.; Atabaev, T.S.; Poulopoulos, S.G. TiO2/Zeolite Composites for SMX Degradation under UV Irradiation. Catalysts 2024, 14, 147. [Google Scholar] [CrossRef]
  12. Wang, H.; Li, J.; Wan, Y.; Nazir, A.; Song, X.; Huo, P.; Wang, H. Synthesis of AgInS2 QDs-MoS2/GO composite with enhanced interfacial charge separation for efficient photocatalytic degradation of tetracycline and CO2 reduction. J. Alloys Compd. 2023, 954, 170159. [Google Scholar] [CrossRef]
  13. Wang, H.; Liu, Q.; Xu, M.; Yan, C.; Song, X.; Liu, X.; Wang, H.; Zhou, W.; Huo, P. Dual-plasma enhanced 2D/2D/2D g-C3N4/Pd/MoO3-x S-scheme heterojunction for high-selectivity photocatalytic CO2 reduction. Appl. Surf. Sci. 2023, 640, 158420. [Google Scholar] [CrossRef]
  14. Arana Juve, J.-M.; Baami González, X.; Bai, L.; Xie, Z.; Shang, Y.; Saad, A.; Gonzalez-Olmos, R.; Wong, M.S.; Ateia, M.; Wei, Z. Size-selective trapping and photocatalytic degradation of PFOA in Fe-modified zeolite frameworks. Appl. Catal. B Environ. Energy 2024, 349, 123885. [Google Scholar] [CrossRef]
  15. Liu, Y.; Peng, M.; Gao, K.; Fu, R.; Zhang, S.; Xiao, Y.; Guo, J.; Wang, Z.; Wang, H.; Zhao, Y.; et al. Boosting photocatalytic degradation of levofloxacin over plasmonic TiO2-x/TiN heterostructure. Appl. Surf. Sci. 2024, 655, 159516. [Google Scholar] [CrossRef]
  16. Zhang, L.; Chen, Z.; Lu, Y.; Liu, Q.; Kong, L. Oxygen-defected WO3-OVs@Bi2MoO6 S-scheme micro flowers heterojunctions with promoted photocatalytic degradation of tetracycline. Appl. Surf. Sci. 2024, 657, 159654. [Google Scholar] [CrossRef]
  17. Li, N.; Gao, X.; Su, J.; Gao, Y.; Ge, L. Metallic WO2-decorated g-C3N4 nanosheets as noble-metal-free photocatalysts for efficient photocatalysis. Chin. J. Catal. 2023, 47, 161–170. [Google Scholar] [CrossRef]
  18. Sun, H.; Wang, L.; Wang, X.; Dong, Y.; Pei, T. A magnetically recyclable Fe3O4/ZnIn2S4 type-II heterojunction to boost photocatalytic degradation of gemifloxacin. Appl. Surf. Sci. 2024, 656, 159674. [Google Scholar] [CrossRef]
  19. Wang, Z.; Shi, X.M.; Chen, F.Z.; Fan, G.C.; Zhao, W.W. Ag/AgCl-Like Photogating of a COF-on-MOF Heterojunction in Organic Photoelectrochemical Transistor. Adv. Funct. Mater. 2024, 2404497. [Google Scholar] [CrossRef]
  20. Dai, L.; Liu, R.; Hu, L.; Si, C. Simple and green fabrication of AgCl/Ag-cellulose paper with antibacterial and photocatalytic activity. Carbohydr. Polym. 2017, 174, 450–455. [Google Scholar] [CrossRef]
  21. Hu, J.; Chen, F.; Mao, J.; Ni, L.; Lu, J. Direction regulation of interface carrier transfer and enhanced photocatalytic oxygen activation over Z-scheme Bi4V2O11/Ag/AgCl for water purification. J. Colloid Interface Sci. 2023, 641, 695–706. [Google Scholar] [CrossRef]
  22. Zhu, H.; Chen, D.; Li, N.; Xu, Q.; Li, H.; He, J.; Lu, J. Cyclodextrin-functionalized Ag/AgCl foam with enhanced photocatalytic performance for water purification. J. Colloid Interface Sci. 2018, 531, 11–17. [Google Scholar] [CrossRef]
  23. Chen, J.; Lu, X.; Wang, D.; Xiu, P.; Gu, X. Effective depolymerization of alkali lignin using an attapulgite-Ce0.75Zr0.25O2(ATP-CZO)-supported cobalt catalyst in ethanol/isopropanol media. Chin. J. Chem. Eng. 2023, 57, 50–62. [Google Scholar] [CrossRef]
  24. Guan, J.; Wang, H.; Li, J.; Ma, C.; Huo, P. Enhanced photocatalytic reduction of CO2 by fabricating In2O3/CeO2/HATP hybrid multi-junction photocatalyst. J. Taiwan Inst. Chem. Eng. 2019, 99, 93–103. [Google Scholar] [CrossRef]
  25. Fang, Y.; Chen, D. A novel catalyst of Fe-octacarboxylic acid phthalocyanine supported by attapulgite for degradation of Rhodamine B. Mater. Res. Bull. 2010, 45, 1728–1731. [Google Scholar] [CrossRef]
  26. Wu, F.; Li, X.; Zhang, H.; Zuo, S.; Yao, C. Z-Scheme photocatalyst constructed by natural attapulgite and upconversion rare earth materials for desulfurization. Front. Chem. 2018, 6, 477. [Google Scholar] [CrossRef]
  27. Deng, L.; Xie, Y.; Zhang, G. Synthesis of C-Cl-codoped titania/attapulgite composites with enhanced visible-light photocatalytic activity. Chin. J. Catal. 2017, 38, 379–388. [Google Scholar] [CrossRef]
  28. Wang, X.; Mu, B.; An, X.; Wang, A. Insights into the relationship between the color and photocatalytic property of attapulgite/CdS nanocomposites. Appl. Surf. Sci. 2018, 439, 202–212. [Google Scholar] [CrossRef]
  29. Qi, Y.; Zhao, S.; Jiang, X.; Kang, Z.; Gao, S.; Liu, W.; Shen, Y. Visible-Light-Driven BiOBr-TiO2-Attapulgite Photocatalyst with Excellent Photocatalytic Activity for Multiple Xanthates. Catalysts 2023, 13, 1504. [Google Scholar] [CrossRef]
  30. Zeng, J.; Han, C.; Wang, B.; Cao, G.; Yao, C.; Li, X. Construction of plasmonic CuS/attapulgite nanocomposites toward photothermal reforming of biomass for hydrogen production. J. Alloys Compd. 2024, 985, 174038. [Google Scholar] [CrossRef]
  31. Zhu, Z.; Yu, Y.; Dong, H.; Liu, Z.; Li, C.; Huo, P.; Yan, Y. Intercalation effect of attapulgite in g-C3N4 modified with Fe3O4 quantum dots to enhance photocatalytic activity for removing 2-mercaptobenzothiazole under visible light. ACS Sustain. Chem. Eng. 2017, 5, 10614–10623. [Google Scholar] [CrossRef]
  32. Li, X.; He, C.; Zuo, S.; Yan, X.; Dai, D.; Zhang, Y.; Yao, C. Photocatalytic nitrogen fixation over fluoride/attapulgite nanocomposite: Effect of upconversion and fluorine vacancy. Sol. Energy 2019, 191, 251–262. [Google Scholar] [CrossRef]
  33. Kong, X.; Li, L.; Feng, Q.; Liang, Z.; Huang, J.; Wang, X.; Zhang, J.; Li, J. Soft chemical synthesis and visible light photocatalytic performance of Ag@AgCl/H1.07Ti1.73O4 platelike composite with composition controlling. J. Alloys Compd. 2017, 727, 311–317. [Google Scholar] [CrossRef]
  34. Feng, Z.; Yu, J.; Sun, D.; Wang, T. Visible-light-driven photocatalysts Ag/AgCl dispersed on mesoporous Al2O3 with enhanced photocatalytic performance. J. Colloid Interface Sci. 2016, 480, 184–190. [Google Scholar] [CrossRef] [PubMed]
  35. Sun, L.; Yin, S.; Shen, D.; Zhou, Y.; Li, J.; Li, X.; Wang, H.; Huo, P.; Yan, Y. Fabricating acid-sensitive controlled PAA@Ag/AgCl/CN photocatalyst with reversible photocatalytic activity transformation. J. Colloid Interface Sci. 2020, 580, 753–767. [Google Scholar] [CrossRef] [PubMed]
  36. Xu, Y.; Zhang, L.; Yin, M.; Xie, D.; Chen, J.; Yin, J.; Fu, Y.; Zhao, P.; Zhong, H.; Zhao, Y.; et al. Ultrathin g-C3N4 films supported on Attapulgite nanofibers with enhanced photocatalytic performance. Appl. Surf. Sci. 2018, 440, 170–176. [Google Scholar] [CrossRef]
  37. Zhao, S.; Qi, Y.; Lv, H.; Jiang, X.; Wang, W.; Cui, B.; Liu, W.; Shen, Y. Effect of clay mineral support on photocatalytic performance of BiOBr-TiO2 for efficient photodegradation of xanthate. Adv. Powder Technol. 2024, 35, 104431. [Google Scholar] [CrossRef]
  38. Liu, C.; Guo, Y.; Li, S.; Xuan, K.; Guo, Y.; Li, J.; Wang, X.; Li, X.; Zhou, Z. Mesoporous sulfur-doped g-C3N4@attapulgite composite as an advanced photocatalyst for efficiently uranium(VI) recovery from aqueous solutions. J. Environ. Chem. Eng. 2024, 12, 112886. [Google Scholar] [CrossRef]
  39. Tang, X.; Shen, W.; Li, D.; Li, B.; Wang, Y.; Song, X.; Zhu, Z.; Huo, P. Research on cobalt-doping sites in g-C3N4 framework and photocatalytic reduction CO2 mechanism insights. J. Alloys Compd. 2023, 954, 170044. [Google Scholar] [CrossRef]
  40. Cao, G.; Xing, H.; Gui, H.; Yao, C.; Chen, Y.; Chen, Y.; Li, X. Plasmonic quantum dots modulated nano-mineral toward photothermal reduction of CO2 coupled with biomass conversion. Nano Res. 2024, 17, 5061–5072. [Google Scholar] [CrossRef]
  41. Kaushik, V. XPS core level spectra and Auger parameters for some silver compounds. J. Electron. Spectrosc. 1991, 56, 273–277. [Google Scholar] [CrossRef]
  42. Mahmoodi, N.M.; Taghizadeh, A.; Taghizadeh, M.; Abdi, J. In situ deposition of Ag/AgCl on the surface of magnetic metal-organic framework nanocomposite and its application for the visible-light photocatalytic degradation of Rhodamine dye. J. Hazard. Mater. 2019, 378, 120741. [Google Scholar] [CrossRef]
  43. Zeng, Y.; Yin, Q.; Liu, Z.; Dong, H. Attapulgite-interpenetrated g-C3N4/Bi2WO6 quantum-dots Z-scheme heterojunction for 2-mercaptobenzothiazole degradation with mechanism insight. Chem. Eng. J. 2022, 435, 134918. [Google Scholar] [CrossRef]
  44. Bao, Y.; Chen, K. AgCl/Ag/g-C3N4 Hybrid Composites: Preparation, Visible Light-Driven Photocatalytic Activity and Mechanism. Nano-Micro Lett. 2015, 8, 182–192. [Google Scholar] [CrossRef]
  45. Zhang, X.; Wang, P.; Meng, W.; Cui, E.; Zhang, Q.; Wang, Z.; Zheng, Z.; Liu, Y.; Cheng, H.; Dai, Y.; et al. Photococatalytic anticancer performance of naked Ag/AgCl nanoparticles. Chem. Eng. J. 2022, 428, 131265. [Google Scholar] [CrossRef]
Figure 1. XRD patterns of ATP, AgCl, AgCl/ATP and Ag-AgCl/ATP.
Figure 1. XRD patterns of ATP, AgCl, AgCl/ATP and Ag-AgCl/ATP.
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Figure 2. SEM of attapulgite (A), AgCl (B), Ag-AgCl/ATP (C), TEM images of attapulgite (D), AgCl (E), Ag-AgCl/ATP (F).
Figure 2. SEM of attapulgite (A), AgCl (B), Ag-AgCl/ATP (C), TEM images of attapulgite (D), AgCl (E), Ag-AgCl/ATP (F).
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Figure 3. Elemental mapping results of 75%-Ag-AgCl/ATP (AG), Ag (D), O (E), Si (F), Cl (G).
Figure 3. Elemental mapping results of 75%-Ag-AgCl/ATP (AG), Ag (D), O (E), Si (F), Cl (G).
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Figure 4. FT-IR spectra of ATP, Ag-AgCl and Ag-AgCl/ATP photocatalysts.
Figure 4. FT-IR spectra of ATP, Ag-AgCl and Ag-AgCl/ATP photocatalysts.
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Figure 5. (A) XPS spectra of survey scan of 75% Ag-AgCl/ATP; High-resolution XPS spectra of (B) O 1s, (C) Si 2p, (D) AgMN1, (E) Cl 2p.
Figure 5. (A) XPS spectra of survey scan of 75% Ag-AgCl/ATP; High-resolution XPS spectra of (B) O 1s, (C) Si 2p, (D) AgMN1, (E) Cl 2p.
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Figure 6. DRS pattern of Ag-AgCl/ATP, ATP and AgCl (a). Band gap spectra of as-prepared samples (b); VB-XPS of ATP (c) and AgCl (d).
Figure 6. DRS pattern of Ag-AgCl/ATP, ATP and AgCl (a). Band gap spectra of as-prepared samples (b); VB-XPS of ATP (c) and AgCl (d).
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Figure 7. (a) Photocurrent intensity test for all prepared samples; (b) impedance test (EIS); (c) linear sweep voltammetry (LSV).
Figure 7. (a) Photocurrent intensity test for all prepared samples; (b) impedance test (EIS); (c) linear sweep voltammetry (LSV).
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Figure 8. (A) Different loading amounts of Ag-AgCl/ATP; (B) optimal Ag-AgCl/ATP degradation of different concentrations of TC; (C) degradation efficiency of different concentrations of TC; (D) quasi-first kinetic curve, the trend of ln(C0/C) with time under different starting concentrations.
Figure 8. (A) Different loading amounts of Ag-AgCl/ATP; (B) optimal Ag-AgCl/ATP degradation of different concentrations of TC; (C) degradation efficiency of different concentrations of TC; (D) quasi-first kinetic curve, the trend of ln(C0/C) with time under different starting concentrations.
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Figure 9. (A) The linear relationship between the reciprocal of the pseudo-first kinetic rate and the initial concentration of TC; (B) optimal Ag-AgCl/ATP degradation of TC at different temperatures; (C) Ag-AgCl/ATP cycle degradation of TC; (D) Ag-AgCl/ATP photocatalytic degradation of TC capture experiment.
Figure 9. (A) The linear relationship between the reciprocal of the pseudo-first kinetic rate and the initial concentration of TC; (B) optimal Ag-AgCl/ATP degradation of TC at different temperatures; (C) Ag-AgCl/ATP cycle degradation of TC; (D) Ag-AgCl/ATP photocatalytic degradation of TC capture experiment.
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Figure 10. Schematic representation for photocatalytic degradation of TC using Ag-AgCl/ATP composites.
Figure 10. Schematic representation for photocatalytic degradation of TC using Ag-AgCl/ATP composites.
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Table 1. Effect of TC initial concentration on the degradation rate.
Table 1. Effect of TC initial concentration on the degradation rate.
Initial TC (mg L−1)kobs (min−1)1/kobs (min)R2
100.0145768.630.902
200.0146168.450.906
300.0126179.300.943
500.00925108.110.972
1000.00358279.330.960
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Zhang, X.; Wang, H.; Yan, C. Facile Preparation of Attapulgite-Supported Ag-AgCl Composite Photocatalysts for Enhanced Degradation of Tetracycline. Catalysts 2024, 14, 464. https://doi.org/10.3390/catal14070464

AMA Style

Zhang X, Wang H, Yan C. Facile Preparation of Attapulgite-Supported Ag-AgCl Composite Photocatalysts for Enhanced Degradation of Tetracycline. Catalysts. 2024; 14(7):464. https://doi.org/10.3390/catal14070464

Chicago/Turabian Style

Zhang, Xiaojie, Huiqin Wang, and Chenlong Yan. 2024. "Facile Preparation of Attapulgite-Supported Ag-AgCl Composite Photocatalysts for Enhanced Degradation of Tetracycline" Catalysts 14, no. 7: 464. https://doi.org/10.3390/catal14070464

APA Style

Zhang, X., Wang, H., & Yan, C. (2024). Facile Preparation of Attapulgite-Supported Ag-AgCl Composite Photocatalysts for Enhanced Degradation of Tetracycline. Catalysts, 14(7), 464. https://doi.org/10.3390/catal14070464

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