Next Article in Journal
Capturing the Long-Sought Dy@C2v(5)-C80 via Benzyl Radical Stabilization
Next Article in Special Issue
Fabrication of Ternary Nanoparticles for Catalytic Ozonation to Treat Parabens: Mechanisms, Efficiency, and Effects on Ceratophyllum demersum L. and Eker Leiomyoma Tumor-3 Cells
Previous Article in Journal
Explicit Solutions of MHD Flow and Heat Transfer of Casson Fluid over an Exponentially Shrinking Sheet with Suction
Previous Article in Special Issue
Adsorption of Methylene Blue from Aqueous Solution Using Gelatin-Based Carboxylic Acid-Functionalized Carbon Nanotubes@Metal–Organic Framework Composite Beads
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nanomaterials
Volume 12
Issue 19
10.3390/nano12193290
nanomaterials-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Magnetic TiO2/CoFe2O4 Photocatalysts for Degradation of Organic Dyes and Pharmaceuticals without Oxidants

by
Islam Ibrahim
1,*,
George V. Belessiotis
2,
Ahmed Mourtada Elseman
3,
Mohamed Mokhtar Mohamed
4,5,
Yatao Ren
6,7,*,
Tarek M. Salama
1 and
Mahmoud Basseem I. Mohamed
1
1
Department of Chemistry, Faculty of Science, Al-Azhar University, Cairo 11884, Egypt
2
Chemical Engineering Department, National Technical University of Athens NTUA, 15780 Athens, Greece
3
Electronic and Magnetic Materials Department, Advanced Materials Institute, Central Metallurgical Research and Development Institute, Cairo 11421, Egypt
4
Egypt-Japan University of Science and Technology, Borg El Arab, Alexandria 21934, Egypt
5
Chemistry Department, Faculty of Science, Benha University, Benha, Egypt
6
Harbin Institute of Technology, School of Energy Science and Engineering, Harbin, China
7
Faculty of Engineering, University of Nottingham, University Park, Nottingham, UK
*
Authors to whom correspondence should be addressed.
Nanomaterials 2022, 12(19), 3290; https://doi.org/10.3390/nano12193290
Submission received: 15 August 2022 / Revised: 11 September 2022 / Accepted: 17 September 2022 / Published: 21 September 2022
(This article belongs to the Special Issue Advanced Nanocomposite Materials for Water and Wastewater Treatment)
Browse Figures
Review Reports Versions Notes

Abstract

:
In the current study, CoFe2O4 and TiO2 nanoparticles were primarily made using the sol-gel method, and subsequently, the hybrid magnetic composites of TiO2 loaded with CoFe2O4 (5–15 percent w/w) were made using a hydrothermal procedure. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) were all used to thoroughly characterize the materials. Additionally, the zero-charge point (ZCP) determination, the examination of the pore structure by nitrogen adsorption, and an evaluation of magnetic properties were performed. Six organic dye pollutants were selected to evaluate the performance of the synthesized nanocomposites toward photocatalytic degradation, including methylene blue (MB), methyl orange (MO), crystal violet (CV), acridine orange (AO), rhodamine B (RhB), and rhodamine 6G (R-6G). Photodegradation of tetracycline (TL), a model pharmaceutical pollutant, was also studied under UV and visible light. The composites exhibited a high degradation performance in all cases without using any oxidants. The photocatalytic degradation of tetracycline revealed that the CoFe2O4/TiO2 (5% w/w) composite exhibited a higher photocatalytic activity than either pure TiO2 or CoFe2O4, and thus attained 75.31% and 50.4% degradation efficiency under UV and visible light, respectively. Trapping experiments were conducted to investigate the photodegradation mechanism, which revealed that holes and super oxide radicals were the most active species in the photodegradation process. Finally, due to the inherent magnetic attributes of the composites, their easy removal from the treated solution via a simple magnet became possible.

Graphical Abstract

1. Introduction

As a result of the use of dyes for coloring by the textile, plastics, and other industries, the amount of organic dye pollution has increased [1]. Industrial dyes are one of the most prominent water pollutants [2]. Some of the most infamous of these organic dye pollutants (ODP) include: (a) Methylene Blue (MB), known for its toxicity, carcinogenic nature, and non-biodegradability [2], (b) Crystal Violet (CV), which can cause issues from permanent eye injuries to respiratory or kidney failure [3], (c) Methyl Orange (MO), an azo dye that is mutagenic and carcinogenic and has a limited biodegradability [4], (d) Acridine Orange (AO), a cell-permeable toxic dye with mutagenic potential [5], (e) Rhodamine B (RhB), a dye which poses a threat for the respiratory tract and skin with carcinogenic and neurotoxic potential [6] and (f) Rhodamine 6G (R-6G), another dye of the rhodamine family, which presents similar dangers [7]. The chemical structures of the selected six ODP are shown in Figure 1. Pharmaceutical ingredients are another major source of pollutants. They are considered a significant threat to humans’ endocrine, reproductive, and cognitive systems [8]. One such pharmaceutical pollutants is the antibiotic Tetracycline (TL), which often finds its way into the environment, and can accumulate in water due to its high hydrophilicity and cause numerous problems in ecosystems and humans [9]. While numerous methods have been developed to deal with ODP, many of these methods require extra processes, since byproducts are frequently present.
Photocatalysis is an affordable green water treatment technology, which has the potential to be very efficient in the decomposition of the ODP [10,11], as the photo-oxidation of dyes, for example, can result in their mineralization into simpler species without toxicity [2]. Especially prevalent is the use of composite photocatalytic materials [12,13]. With a conscious choice of individual materials, a composite can be comprised of components that complement each other, leading to enhanced performance and utility. The most well-known photocatalyst is titanium dioxide (TiO2) [14,15], especially its anatase phase, due to its high stability and outstanding photocatalytic performance under ultraviolet (UV) light. However, it has significant drawbacks regarding its wide band gap, which renders it photocatalytically active only under UV light, and its fast charge pair recombination impairs its photocatalytic performance. Thus, the formation of composites with TiO2 evolved into a common strategy, since it can rectify its weaknesses [1]. The formation of such a photocatalytic heterojunction can enhance factors such as charge separation, thereby enhancing photocatalytic performance [15,16]. Magnetic materials, on the other hand, have several interesting properties [17,18,19], and their combination with TiO2 is promising [20,21], as the added magnetic properties offer increased utility for the composite: In magnetic composites, after the photocatalytic treatment of a solution is completed, the photocatalyst can be easily removed with a simple magnet, which facilitates its re-usability [22,23]. Spinel ferrites are a prominent family of magnetic ferrite materials with an AFe2O4 structure (A = divalent cation), characterized by a high saturation magnetization, among other favorable features [24]. Thus, the combination of TiO2 with a spinel ferrite material appears especially promising. This work presents a complete overview of the TiO2/spinel ferrite nanocomposites with an extensive evaluation of their photocatalytic capabilities against several of the more well-known organic pollutants. It also presents the potential of the nanocomposites for recyclable usage, taking advantage of their magnetic retrieval ability, thereby highlighting the extensive capacities of the TiO2/spinel ferrite nanocomposites.
In this work, a hydrothermal process was employed to synthesize composites comprised of the CoFe2O4-loaded TiO2. To optimize the composite compositions, three weight percentage ratios of CoFe2O4 to TiO2 corresponding to 5, 10, and 15% w/w were synthesized. A complete characterization of the composites against the starting materials was undertaken via XRD, FTIR, Raman, UV–vis DRS, SEM, and HR-TEM. The structure analysis verified the successful formation of the CoFe2O4/TiO2 hybrid nanocomposites. The photocatalytic performances of the hybrid composites were evaluated in the degradation of six different ODP under UV light and the degradation of tetracycline (TL) under UV and visible light.

2. Experimental Methods

2.1. Materials

The materials used in this research work are presented below. From Acros Organics: Absolute ethanol (≥99%), ferric nitrate (≥99%), titanium (IV), n-butoxide (≥99%), benzoquinone, oxalic acid (≥98%), and tetracycline (≥99%). From Sigma-Aldrich: glacial acetic acid (≥98%). From Chem-Lab: cobalt nitrate (≥99%), HCl. From Sigma-Aldrich: Methylene Blue, Methyl Orange, Crystal Violet, Acridine Orange, Rhodamine B, and Rhodamine 6G were purchased.

2.2. Material Preparation

2.2.1. Synthesis of TiO2 Nanoparticles

The sol-gel method was utilized for the preparation of titanium dioxide nanopowder [25,26]. In a typical process, a solution of 10 mL of Ti (IV) n-butoxide and 40 mL absolute ethanol (A) and a solution of 4 mL DI H2O, 2 mL acetic acid, 10 mL absolute ethanol along with HCl (10% wt/wt) for pH adjustment to ~2 (B) were mixed by the dropwise addition of (B) to (A) and stirring (1 h). A yellow translucent gel was formed 3 h after the end of the stirring and after drying overnight at 100 °C; yellow crystallites were formed, which produced a white powder after grinding. Finally, this powder was calcinated (300 °C for 1 h and 450 °C for 2 h), producing our nano-TiO2 sample (T).

2.2.2. Synthesis of CoFe2O4

The cobalt ferrite was also prepared via a sol-gel technique [11]. A total of 1.9 g of oxalic acid (complexing agent) was slowly added to a mixture of cobalt nitrate (0.01 moles) and ferric nitrate (0.02 moles), under stirring (1 h). After evaporation (80 °C under stirring), the samples were dried (110 °C, 24 h) and annealed (1000 °C, 2 h).

2.2.3. Synthesis of CoFe2O4/TiO2 Composites

For the preparation of the final composites, a hydrothermal method was adopted [11]. Samples with three different w/w % concentrations of CoFe2O4 to TiO2 were prepared by varying the initial quantity of CoFe2O4 in the process: 0.05 (5% w/w), 0.1 (10% w/w), and 0.15 (15% w/w) g of CoFe2O4 was ultrasonically treated in 100 mL of deionized water (2 h) before the adding of 0.95, 0.9, and 0.85 g of TiO2, respectively. A total of 10 g of urea was also added as a combustion fuel. After further ultrasonication (1 h), each solution was put in a 300 mL stainless steel autoclave coated with Teflon, where they were heated (200 °C, 12 h) before the natural cooling of the autoclave (room temperature). After washing and drying, we acquired the TC5, TC10, and TC15 samples, each with an index signifying its % w/w of CoFe2O4 (C) and TiO2 (T).

2.3. Characterization of Samples

For the characterization of the prepared photocatalysts, we utilized X-ray diffraction (XRD, D8-ADVANCE), FTIR (Perkin Elmer Spectrum 100 Spectrometer) and micro Raman (Jobin-Yvon LabRam) vibrational spectroscopy, SEM (Jeol JSM 7401F FieldEmission), HR-TEM (high-resolution JEOL JEM-2100 LaB6), UV-Vis (Hitachi U-4100) spectroscopy, Magnetic measurements were performed via a VSM (9600-1 LDJ, Lake Shore, Columbus, OH, USA) instrument. Textural characterization of the samples was carried out by the N2 adsorption-desorption at −196 °C. Prior the measurements, the samples were outgassed at 200 °C for 48 h. The Brunauer–Emmett–Teller (BET) equation was applied to determine the specific surface area (SBET). The BJH method was applied to the desorption branch of the N2 isotherms to obtain the meso-pore volume (Vmeso) and cumulative surface area (SBJH) of the mesopores. A batch technique was utilized for the determination of zero charge point (ZCP) using six beakers, each containing 0.1 M KCl (12.5 mL) with an assumed initial pH value of 4–12 using 0.1 M HCl or KOH [27]. After adding a standard quantity of a photocatalyst to each beaker, stirring for 24 h until the pH was at equilibrium, the sample was removed by filtration. The ZCP values were determined by graphing the final pH of the solution against the initial pH.
A total of 5 mg of the photocatalyst was added to an ODP or TL solution (50 mL, 10 ppm) to evaluate its photocatalytic degradation performance. After stirring for 1 h in dark conditions (adsorption-desorption equilibrium), the solution was illuminated (Osram L BLUE UVA 15 W/78 lamps), and 4-daylight Sylvania,—F15W/53-765-T8 (450–710 nm) lamps in a photoreactor box. The progress of the photocatalytic degradation was evaluated at standard time intervals by measuring the absorption peak of each dye solution through UV-Visible spectroscopy. The characteristic absorption peaks for the six ODP are: MB (664 nm), CV (585 nm), MO (464 nm), AO (490 nm), RhB (553 nm), Rh6G (526 nm), and (357 nm) for the TL solution. Finally, to study the active species responsible for the photocatalytic degradation, scavenger tests were performed by repeating the above process in the presence of a scavenger (for each studied species) in the solution: KI (h+ quencher), BQ (O2− quencher), KBrO3 (e− quencher), and IPA (OH. quencher) [14].

3. Results and Discussion

3.1. Structural Analysis

In terms of a crystal structure analysis, all samples were analyzed with XRD and the resulting patterns are shown in Figure 2. For TiO2, the expected diffraction peaks and the corresponding Miller indices appear at 2θ of 25.8° (101), 36.9° (103), 37.8° (004), 38.5° (112), 48.0° (200), 53.8° (105), 55.0° (211), 62.8° (204), 68.7° (116), and 70.3° (220), verifying the presence of the pure anatase TiO2 (I41/amd (141) space group, JCPDS Card number 21-1272] [28]. For CoFe2O4, the peaks at 2θ of 18.2° (111), 30.0° (220), 35.4° (311), 37.0° (222), 43.0° (400), 53.4° (422), 56.9° (511) and 62.5° (440) correspond to spinel ferrite with a cubic symmetry (Fd-3m (227) space group, and the JCPDS Card no. 22-1086) [24] were depicted. The diffraction patterns for the TC5, TC10, and TC15 hybrid nanocomposites present peaks that correspond to both starting CoFe2O4 and TiO2 materials, signifying the good chemical hybridization of the two oxides. Following the insertion of CoFe2O4, a considerable decrease in the (101) anatase peak intensities was measured, demonstrating a strong interaction between the components constituting the composites, notably the TC10 sample.
Vibrational spectroscopy, via Raman [29,30] and FT-IR measurements [31], was also utilized to study the samples’ constitution and crystallinity. The corresponding analyses are presented in Figure 3.
Concerning Raman spectroscopy, (Figure 3a): For the TiO2 sample, we observed the Raman active modes at 141 cm−1 (Eg), 196 cm−1 (Eg), 394 cm−1 (B1g), 513 cm−1 (A1g + B1g), and, lastly, 640 cm−1 (Eg) [32], verifying the anatase-TiO2 crystallization. For the CoFe2O4 sample, its characteristic bands appear at 175 cm−1 (T2g), 295 cm−1 (Eg), 468 cm−1 (T2g), and 613 cm−1 (T2g) [33]. As for the composite materials, the characteristic peaks of the individual components appear in the final materials, proposing the amalgamation of the two components forming the composites. In the FT-IR spectra (Figure 3b), TiO2 exhibits a broad absorption band (~469–840 cm−1) related to Ti-O-Ti vibration bonds [34], while CoFe2O4 exhibits a peak at ~469 cm−1 (stretching vibration in Fe(III)-O2−) and another peak at ~586 cm−1 (stretching vibration in Co(II)-O2−) [35]. Thus, a broad absorption at ~462–580 cm−1 appears in the final composites. Thus, the proper merging of TiO2 and CoFe2O4 is verified from either type of vibrational spectroscopy analysis.

3.2. Morphological Analysis

SEM and TEM microscopy were employed to assess the morphology of the synthesized samples concerning the starting components (Figure 4). While TiO2 nanoparticles (NPs) appear distinct, there is an agglomeration of CoFe2O4 nanoparticles, since there are magnetic forces between them [21], making CoFe2O4 nanostructures significantly larger than TiO2 NPs (TiO2 NPs are under 20 nm, while CoFe2O4 clusters are over 120 nm in size). The SEM picture of TC10 (Figure 4c), which depicts the final composites, demonstrates how the CoFe2O4 nanostructures’ surfaces have been suitably ornamented with TiO2 NPs. As observed by the TEM picture (Figure 4d), titania has actually been dispersed over the grains of the ferrite material.

3.3. Surface Analysis

N2 adsorption-desorption isotherms and pore-size distribution plots for each sample have been shown in Figure 5 and Figure 6 to determine the samples’ surface area and porosity.
A Type IV isotherm corresponding hysteresis loop is presented by the base-TiO2 sample (Figure 5a), signifying mesoporous materials [36], while there is no hysteresis loop present for CoFe2O4 (Figure 5b), signifying the type III isotherm [37]. The type IV isotherm is also representative of the composite materials (Figure 5c), meaning they are mesoporous. The specific surface values (m2/g) for the samples were: TiO2 (40), CoFe2O4 (3.2), TC5 (39.1), TC10 (38.2), and TC15 (37). There was a slight decrease in the BET surface area value when going from TiO2 to the TiO2/CoFe2O4 composites due to the low value in the case of the ferrite. Pore size distribution reveals no significant differences for the unimodal type of pore presented, either from the mother TiO2 or the composite TC10, with a pore maximized at around 52 Ă compared to the bimodal type of pores depicted for CoFe2O4 at 30 and 40 Ă. This demonstrates how the composites maintain their mesoporosity sequence. Regarding the surface chemistry of the samples, the zero charge point (ZCP) evaluation (Figure 7) took place for samples TiO2 (4.45), CoFe2O4 (6.95) and TCX (x-5,10,15) (4.9) samples. At solution pH > ZCP pH, the photocatalyst can favor the adsorption of positively charged pollutants such as the positively charged MB [38], (with negatively charged contaminants being favored in the opposite case) [39]. Thus, at a higher solution pH (negatively charged surface), there can be increased pollutant adsorption of dyes such as MB [40] onto the TCX surface.

3.4. Optical Analysis

To learn more about the photocatalysts’ optical characteristics, UV-vis spectroscopy was employed (Figure 8). The band gaps for TiO2 (3.1 eV), CoFe2O4 (1.37 eV), TC5 (3.18 eV), TC10 (3.16 eV), TC15 (3.07 eV) were calculated via the Kubelka-Munk equation and the Tauc plots (derived from diffuse reflectance spectra) (Figure 8a). As for the absorption spectra (Figure 8b), the absorption edge for TiO2 is located near 400 nm, as expected [41], while the spinel ferrite absorbs significantly in the visible region [37]. As a result, the composite materials have enhanced absorption in the visible range.

3.5. Magnetization Analysis

The value of saturation magnetization (Ms) is important for a photocatalyst as it signifies its capability for magnetic removal from a treated solution. The magnetization curves of all magnetic samples are presented in Figure 9.
As expected, the composites of magnetic CoFe2O4 and non-magnetic TiO2 have significantly less Ms (emu/g) values than the pure spinel ferrite: CoFe2O4 (87.6), TC5 (3.1), TC10 (8.4), and TC15 (14.2). Furthermore, it comes as no surprise that composites with a greater percentage of magnetic spinel content present higher Ms values. This decrease, however, does not impair the capability of the magnetic composites to be easily removed from a solution through simple magnetic means (e.g., a magnetic bar).

3.6. Photocatalytic Oxidation Activity

3.6.1. Photocatalytic Degradation of ODP under UV Light

Under UV light irradiation, the photocatalytic oxidation performance of the produced materials was evaluated against six organic dyes (Figure 10). The TCX composites exhibit higher dye degradation efficiencies than either starting material in all cases. This efficiency is due to increased charge carrier separation at the TiO2/CoFe2O4 contact, which enhances the electron lifetime for TCX samples [42].

3.6.2. Photocatalytic Degradation of TL under UV and Visible Light

The photocatalytic oxidation of TL over TiO2, CoFe2O4, TC5, TC10, and TC15 was evaluated under UV and visible light illumination (Figure 11a,b). It is obvious that the cobalt ferrite (CF) present in the TC nanocomposite maintains and slightly enhances the photocatalytic activity of titanium dioxide under both UV and visible light. The highest TL photocatalytic oxidation was observed for TC10, which was 75.31% at 180 min under UV illumination and 50.4% at 180 min under visible light illumination. Pure titania and cobalt ferrite, on the other hand, exhibit minor photocatalytic efficiency when compared to TiO2/CoFe2O4 composites. This means that cobalt ferrite is crucial in enhancing the photocatalytic oxidation process. The high photocatalytic oxidation of the TC composites, particularly the TC10 sample, can be attributed to the presence of ferrites nanoparticles, which can improve light absorption and ensure more efficient charge separation.
We performed recyclability experiments to verify the stability and reusability of the TC10 toward the TL photodegradation. Each time, the TC10 catalyst was collected and recovered, and then used in a cyclic batch. This procedure was conducted five times, with the final degradation efficiency recorded each time (Figure 11c). The TL degradation efficiency decreases slightly as the recycling test progresses, from ~75% in the first cycle to 65% in the final. As a result, we may consider this test to be indicative of the TC10 photocatalyst stability and reusability in the TL degradation.
Additionally, the synergistic interaction between TiO2 and CoFe2O4 in TC10 was the optimal compared to the rest of the composites as depicted in XRD, optical, vibrational, and TEM analysis. Trapping experiments with scavengers were carried out under UV light to elucidate the photocatalytic oxidation mechanism for the TL and to detect the reactive species (Figure 12). There was no change in the oxidation process when IPA (hydroxyl radical scavenger), and KBrO3 (electron scavenger) were added. In contrast, BQ (superoxide radical anion scavenger) had a noticeable effect, whereas the KI (hole scavenger) addition resulted in the photocatalytic oxidation reaction being blocked. Thus, holes were the prime motivator, followed by oxygen peroxide radicals as the main active species in the photocatalytic oxidation process (as observed in the graphical abstract).
The dispersion of ferrites over TiO2, keeping the mesoporous nature and good visible light absorption, in addition to the broad-spectrum range of the catalysts, which allowed them to absorb UV and solar radiation without the help of oxidizing agents, were further causes for the improved photocatalytic activities.
For all dyes, significant degradation efficiency is achieved by the TCX samples: MB (over 95%), MO (45%), CV (over 83%), AO (over 91%), RhB (58%), Rh6G (56%), as will be shown in Figure 13. Among TCX samples, judging by overall performance, the best sample is TC10 (10% w/w CoFe2O4). It means that, the addition of CoFe2O4 has a volcano effect: it improves photocatalytic experiments up to an optimum (sample TC10), while a higher or lower amount decreases photocatalytic reactions.

4. Conclusions

In this study, hybrid nanocomposites comprised of CoFe2O4 loaded into TiO2 (5–15% w/w) were synthesized, characterized, and evaluated in the photocatalytic oxidation of six different organic dye pollutants under UV light and meanwhile under UV and visible light in the degradation of tetracycline. Characterization by XRD, FTIR, and Raman spectroscopy verified the fruitful construction of the CoFe2O4/TiO2 hybrid nanocomposites. The optical analysis revealed enhanced light absorption by the CoFe2O4/TiO2 nanocomposites compared to pure TiO2. In terms of oxidation/removal efficiencies under UV and visible light, CoFe2O4/TiO2 (10% w/w) outperformed the other tested hybrid nanocomposites in the tested six organic azo dyes and the antibiotic tetracycline in the absence of any oxidant. The main reason for the observed behavior was the improved photo-charge carrier separation at the interfaces of TiO2/CoFe2O4 nanocomposites, which is necessary for boosting photocatalytic activity. As long as the primary holes of the reactive species are present, the photocatalytic oxidation can be occurred. As a result, the CoFe2O4/TiO2 catalyst substantially increased the oxidative photocatalytic activity. Finally, the CoFe2O4/TiO2 powder is capable of easily being retrieved from the treated solution with a magnetic means as to its magnetic characteristics.

Author Contributions

Conceptualization, I.I.; methodology, I.I. and G.V.B.; validation, A.M.E., M.M.M. and T.M.S.; formal analysis, M.B.I.M. and I.I.; investigation, I.I. and M.M.M.; resources, I.I. and Y.R.; writing—original draft, I.I.; writing—review and editing, G.V.B., Y.R., and T.M.S.; visualization, T.M.S.; supervision, M.M.M. and T.M.S.; project administration, I.I., M.M.M., and T.M.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Ali, I.; Kim, J.-O. Visible-light-assisted photocatalytic activity of bismuth-TiO2 nanotube composites for chromium reduction and dye degradation. Chemosphere 2018, 207, 285–292. [Google Scholar] [CrossRef] [PubMed]
  2. Khan, I.; Saeed, K.; Zekker, I.; Zhang, B.; Hendi, A.H.; Ahmad, A.; Ahmad, S.; Zada, N.; Ahmad, H.; Shah, L.A.; et al. Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation. Water 2022, 14, 242. [Google Scholar] [CrossRef]
  3. Mittal, A.; Mittal, J.; Malviya, A.; Kaur, D.; Gupta, V. Adsorption of hazardous dye crystal violet from wastewater by waste materials. J. Colloid Interface Sci. 2009, 343, 463–473. [Google Scholar] [CrossRef] [PubMed]
  4. Dutta, S.K.; Amin, K.; Ahmed, J.; Elias, M.; Mahiuddin, M. Removal of toxic methyl orange by a cost-free and eco-friendly adsorbent: Mechanism, phytotoxicity, thermodynamics, and kinetics. S. Afr. J. Chem. Eng. 2022, 40, 195–208. [Google Scholar] [CrossRef]
  5. Chandrika, K.; Chaudhary, A.; Mareedu, T.; Sirisha, U.; Vangalapati, M. Adsorptive removal of acridine orange dye by green tea/copper-activated carbon nanoparticles (Gt/Cu-AC np). Mater. Today Proc. 2021, 44, 2283–2289. [Google Scholar] [CrossRef]
  6. Ahmad, M.; Rehman, W.; Khan, M.M.; Qureshi, M.T.; Gul, A.; Haq, S.; Ullah, R.; Rab, A.; Menaa, F. Phytogenic fabrication of ZnO and gold decorated ZnO nanoparticles for photocatalytic degradation of Rhodamine B. J. Environ. Chem. Eng. 2021, 9, 104725. [Google Scholar] [CrossRef]
  7. Pal, U.; Sandoval, A.; Madrid, S.I.U.; Corro, G.; Sharma, V.; Mohanty, P. Mixed titanium, silicon, and aluminum oxide nanostructures as novel adsorbent for removal of rhodamine 6G and methylene blue as cationic dyes from aqueous solution. Chemosphere 2016, 163, 142–152. [Google Scholar] [CrossRef] [PubMed]
  8. Shenoy, S.; Ahmed, S.; Lo, I.M.; Singh, S.; Sridharan, K. Rapid sonochemical synthesis of copper doped ZnO grafted on graphene as a multi-component hierarchically structured visible-light-driven photocatalyst. Mater. Res. Bull. 2021, 140, 111290. [Google Scholar] [CrossRef]
  9. Huyen, N.T.K.; Pham, T.-D.; Cam, N.T.D.; Van Quan, P.; Van Noi, N.; Hanh, N.T.; Tung, M.H.T.; Dao, V.-D. Fabrication of titanium doped BiVO4 as a novel visible light driven photocatalyst for degradation of residual tetracycline pollutant. Ceram. Int. 2021, 47, 34253–34259. [Google Scholar] [CrossRef]
  10. Ibrahim, I.; Belessiotis, G.V.; Arfanis, M.K.; Athanasekou, C.; Philippopoulos, A.I.; Mitsopoulou, C.A.; Romanos, G.E.; Falaras, P. Surfactant Effects on the Synthesis of Redox Bifunctional V2O5 Photocatalysts. Materials 2020, 13, 4665. [Google Scholar] [CrossRef]
  11. Mohamed, M.M.; Ibrahim, I.; Salama, T.M. Rational design of manganese ferrite-graphene hybrid photocatalysts: Efficient water splitting and effective elimination of organic pollutants. Appl. Catal. A Gen. 2016, 524, 182–191. [Google Scholar] [CrossRef]
  12. Belessiotis, G.V.; Kontos, A.G. Plasmonic silver (Ag)-based photocatalysts for H2 production and CO2 conversion: Review, analysis and perspectives. Renew. Energy 2022, 195, 497–515. [Google Scholar] [CrossRef]
  13. Liao, G.; Li, C.; Liu, S.-Y.; Fang, B.; Yang, H. Emerging frontiers of Z-scheme photocatalytic systems. Trends Chem. 2021, 4, 111–127. [Google Scholar] [CrossRef]
  14. Ibrahim, I.; Athanasekou, C.; Manolis, G.; Kaltzoglou, A.; Nasikas, N.K.; Katsaros, F.; Devlin, E.; Kontos, A.G.; Falaras, P. Photocatalysis as an advanced reduction process (ARP): The reduction of 4-nitrophenol using titania nanotubes-ferrite nanocomposites. J. Hazard. Mater. 2018, 372, 37–44. [Google Scholar] [CrossRef]
  15. Ibrahim, I.; Belessiotis, G.V.; Antoniadou, M.; Kaltzoglou, A.; Sakellis, E.; Katsaros, F.; Sygellou, L.; Arfanis, M.K.; Salama, T.M.; Falaras, P. Silver decorated TiO2/g-C3N4 bifunctional nanocomposites for photocatalytic elimination of water pollutants under UV and artificial solar light. Results Eng. 2022, 14, 100470. [Google Scholar] [CrossRef]
  16. Sridharan, K.; Shenoy, S.; Kumar, S.; Terashima, C.; Fujishima, A.; Pitchaimuthu, S. Advanced Two-Dimensional Heterojunction Photocatalysts of Stoichiometric and Non-Stoichiometric Bismuth Oxyhalides with Graphitic Carbon Nitride for Sustainable Energy and Environmental Applications. Catalysts 2021, 11, 426. [Google Scholar] [CrossRef]
  17. Abdel-Khalek, E.; Ibrahim, I.; Salama, T.M.; Elseman, A.M.; Mohamed, M.M. Structural, optical, dielectric and magnetic properties of Bi1−xLaxFeO3 nanoparticles. J. Magn. Magn. Mater. 2018, 465, 309–315. [Google Scholar] [CrossRef]
  18. Abdel-Khalek, E.K.; Ibrahim, I.; Salama, T.M. Dielectric anomaly in the microwave region and exchange bias effect in LaFeO3 nanoparticles at room temperature. Ferroelectrics 2019, 550, 210–219. [Google Scholar] [CrossRef]
  19. Abdel-Khalek, E.K.; Ibrahim, I.; Salama, T.M.; Elseman, A. Study of the optical, dielectric and magnetic properties of the Bi0.75La0.25FeO3 sample. Ferroelectrics 2020, 558, 150–164. [Google Scholar] [CrossRef]
  20. Liu, H.; Zhang, Z.-G.; Wang, X.-X.; Nie, G.-D.; Zhang, J.; Zhang, S.-X.; Cao, N.; Yan, S.-Y.; Long, Y.-Z. Highly flexible Fe2O3/TiO2 composite nanofibers for photocatalysis and utraviolet detection. J. Phys. Chem. Solids 2018, 121, 236–246. [Google Scholar] [CrossRef]
  21. Sohail, M.; Xue, H.; Jiao, Q.; Li, H.; Khan, K.; Wang, S.; Feng, C.; Zhao, Y. Synthesis of well-dispersed TiO2/CNTs@CoFe2O4 nanocomposites and their photocatalytic properties. Mater. Res. Bull. 2018, 101, 83–89. [Google Scholar] [CrossRef]
  22. Wu, P.-F.; Xue, Q.; Wang, T.-Y.; Li, S.-J.; Li, G.-P.; Xue, G.-L. A PW12/Ag functionalized mesoporous silica-coated magnetic Fe3O4 core–shell composite as an efficient and recyclable photocatalyst. Dalton Trans. 2020, 50, 578–586. [Google Scholar] [CrossRef]
  23. Belessiotis, G.V.; Falara, P.P.; Ibrahim, I.; Kontos, A.G. Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment. Materials 2022, 15, 4629. [Google Scholar] [CrossRef]
  24. Ibrahim, I.; Ali, I.O.; Salama, T.M.; Bahgat, A.; Mohamed, M.M. Synthesis of magnetically recyclable spinel ferrite (MFe2O4, M = Zn, Co, Mn) nanocrystals engineered by sol gel-hydrothermal technology: High catalytic performances for nitroarenes reduction. Appl. Catal. B Environ. 2016, 181, 389–402. [Google Scholar] [CrossRef]
  25. Belessiotis, G.V.; Papadokostaki, K.G.; Favvas, E.P.; Efthimiadou, E.K.; Karellas, S. Preparation and investigation of distinct and shape stable paraffin/SiO2 composite PCM nanospheres. Energy Convers. Manag. 2018, 168, 382–394. [Google Scholar] [CrossRef]
  26. Ye, T.; Chen, W.; Xu, H.; Geng, N.; Cai, Y. Preparation of TiO2/graphene composite with appropriate N-doping ratio for humic acid removal. J. Mater. Sci. 2017, 53, 613–625. [Google Scholar] [CrossRef]
  27. Abdelhaleem, A.; Chu, W. Photodegradation of 4-chlorophenoxyacetic acid under visible LED activated N-doped TiO2 and the mechanism of stepwise rate increment of the reused catalyst. J. Hazard. Mater. 2017, 338, 491–501. [Google Scholar] [CrossRef]
  28. Attia, Y.A.; Altalhi, T.A. Low-cost synthesis of titanium dioxide anatase nanoclusters as advanced materials for hydrogen photoproduction. Res. Chem. Intermed. 2017, 43, 4051–4062. [Google Scholar] [CrossRef]
  29. Belessiotis, G.; Arfanis, M.; Kaltzoglou, A.; Likodimos, V.; Raptis, Y.; Falaras, P.; Kontos, A. Temperature effects on the vibrational properties of the Cs2SnX6 ‘defect’ perovskites (X = I, Br, Cl). Mater. Chem. Phys. 2021, 267, 124679. [Google Scholar] [CrossRef]
  30. Belessiotis, G.; Arfanis, M.; Kaltzoglou, A.; Likodimos, V.; Raptis, Y.; Falaras, P.; Kontos, A. Temperature dependence of the vibrational and emission spectra in the 0D vacancy-ordered Cs2SnI6 perovskite. Mater. Today Proc. 2022. [Google Scholar] [CrossRef]
  31. Stathopoulos, N.; Belessiotis, G.; Oikonomou, P.; Papanicolaou, E. Experimental investigation of thermal degradation of phase change materials for medium-temperature thermal energy storage and tightness during cycling inside metal spheres. J. Energy Storage 2020, 31, 101618. [Google Scholar] [CrossRef]
  32. Arabatzis, I.; Antonaraki, S.; Stergiopoulos, T.; Hiskia, A.; Papaconstantinou, E.; Bernard, M.; Falaras, P. Preparation, characterization and photocatalytic activity of nanocrystalline thin film TiO2 catalysts towards 3,5-dichlorophenol degradation. J. Photochem. Photobiol. A Chem. 2002, 149, 237–245. [Google Scholar] [CrossRef]
  33. Bhowmik, R.; Kazhugasalamoorthy, S.; Sinha, A. Role of initial heat treatment of the ferrite component on magnetic properties in the composite of ferrimagnetic Co1.75Fe1.25O4 ferrite and non-magnetic BaTiO3 oxide. J. Magn. Magn. Mater. 2017, 444, 451–466. [Google Scholar] [CrossRef]
  34. Ali, T.; Ahmed, A.; Alam, U.; Uddin, I.; Tripathi, P.; Muneer, M. Enhanced photocatalytic and antibacterial activities of Ag-doped TiO2 nanoparticles under visible light. Mater. Chem. Phys. 2018, 212, 325–335. [Google Scholar] [CrossRef]
  35. Abroushan, E.; Farhadi, S.; Zabardasti, A. Ag3PO4/CoFe2O4 magnetic nanocomposite: Synthesis, characterization and applications in catalytic reduction of nitrophenols and sunlight-assisted photocatalytic degradation of organic dye pollutants. RSC Adv. 2017, 7, 18293–18304. [Google Scholar] [CrossRef]
  36. Hernández-Gordillo, A.; Arroyo, M.; Zanella, R.; Rodríguez-González, V. Photoconversion of 4-nitrophenol in the presence of hydrazine with AgNPs-TiO2 nanoparticles prepared by the sol–gel method. J. Hazard. Mater. 2014, 268, 84–91. [Google Scholar] [CrossRef]
  37. Chen, X.; Zhao, Q.; Li, X.; Wang, D. Enhanced photocatalytic activity of degrading short chain chlorinated paraffins over reduced graphene oxide/CoFe2O4/Ag nanocomposite. J. Colloid Interface Sci. 2016, 479, 89–97. [Google Scholar] [CrossRef]
  38. Gao, Y.; Wong, K.Y.; Ahiabu, A.; Serpe, M.J. Sequential and controlled release of small molecules from poly(N-isopropylacrylamide) microgel-based reservoir devices. J. Mater. Chem. B 2016, 4, 5144–5150. [Google Scholar] [CrossRef]
  39. Shen, X. 10—Molecularly Imprinted Photocatalysts. In Molecularly Imprinted Catalysts; Elsevier: Amsterdam, The Netherlands, 2016; pp. 211–228. [Google Scholar] [CrossRef]
  40. Boumediene, M.; Benaïssa, H.; George, B.; Molina, S.; Merlin, A. Effects of pH and ionic strength on methylene blue removal from synthetic aqueous solutions by sorption onto orange peel and desorption study. J. Mater. Environ. Sci. 2018, 9, 1700–1711. [Google Scholar] [CrossRef]
  41. Chiang, L.-F.; Doong, R.-A. Enhanced photocatalytic degradation of sulfamethoxazole by visible-light-sensitive TiO2 with low Cu addition. Sep. Purif. Technol. 2015, 156, 1003–1010. [Google Scholar] [CrossRef]
  42. Ghosh, B.K.; Moitra, D.; Chandel, M.; Ghosh, N.N. Preparation of TiO2/Cobalt Ferrite/Reduced Graphene Oxide Nanocomposite Based Magnetically Separable Catalyst with Improved Photocatalytic Activity. J. Nanosci. Nanotechnol. 2017, 17, 4694–4703. [Google Scholar] [CrossRef]
Nanomaterials 12 03290 g001 550
Figure 1. The structures of selected ODP.
Figure 1. The structures of selected ODP.
Nanomaterials 12 03290 g001
Nanomaterials 12 03290 g002 550
Figure 2. XRD patterns of the synthesized photocatalysts.
Figure 2. XRD patterns of the synthesized photocatalysts.
Nanomaterials 12 03290 g002
Nanomaterials 12 03290 g003 550
Figure 3. Vibrational spectrograms: (a) Micro-Raman and (b) FT-IR of synthesized photocatalysts.
Figure 3. Vibrational spectrograms: (a) Micro-Raman and (b) FT-IR of synthesized photocatalysts.
Nanomaterials 12 03290 g003
Nanomaterials 12 03290 g004 550
Figure 4. Microscopy-based analyses of the samples with SEM at 100 nm (a–c) and with TEM at 200 nm (d).
Figure 4. Microscopy-based analyses of the samples with SEM at 100 nm (a–c) and with TEM at 200 nm (d).
Nanomaterials 12 03290 g004
Nanomaterials 12 03290 g005 550
Figure 5. N2 adsorption-desorption isotherm plot of TiO2 (a), CoFe2O4 (b) and TC10 (c).
Figure 5. N2 adsorption-desorption isotherm plot of TiO2 (a), CoFe2O4 (b) and TC10 (c).
Nanomaterials 12 03290 g005
Nanomaterials 12 03290 g006 550
Figure 6. Pore size distribution curves of TiO2, CoFe2O4, and TC10.
Figure 6. Pore size distribution curves of TiO2, CoFe2O4, and TC10.
Nanomaterials 12 03290 g006
Nanomaterials 12 03290 g007 550
Figure 7. pHinitial vs. pHfinal curves for ZCP determination.
Figure 7. pHinitial vs. pHfinal curves for ZCP determination.
Nanomaterials 12 03290 g007
Nanomaterials 12 03290 g008 550
Figure 8. Tauc plots of the prepared photocatalysts (a), along with the relevant absorbance spectra (b).
Figure 8. Tauc plots of the prepared photocatalysts (a), along with the relevant absorbance spectra (b).
Nanomaterials 12 03290 g008
Nanomaterials 12 03290 g009 550
Figure 9. Magnetization curves of CoFe2O4 and the TCX composites.
Figure 9. Magnetization curves of CoFe2O4 and the TCX composites.
Nanomaterials 12 03290 g009
Nanomaterials 12 03290 g010 550
Figure 10. Photocatalytic oxidative degradation of (a) Methylene Blue (MB), (b) Methyl Orange (MO), (c) Crystal Violet (CV), (d) Acridine Orange (AO), and (e) Rhodamine B (RhB and (f)) Rhodamine 6G, under UV irradiation by the prepared samples.
Figure 10. Photocatalytic oxidative degradation of (a) Methylene Blue (MB), (b) Methyl Orange (MO), (c) Crystal Violet (CV), (d) Acridine Orange (AO), and (e) Rhodamine B (RhB and (f)) Rhodamine 6G, under UV irradiation by the prepared samples.
Nanomaterials 12 03290 g010
Nanomaterials 12 03290 g011 550
Figure 11. Photocatalytic oxidative degradation of tetracycline under (a) UV, (b) visible light irradiation using the prepared photocatalysts and (c) Reusability tests for the degradation efficiency of TL under UV for 5 subsequent cycles.
Figure 11. Photocatalytic oxidative degradation of tetracycline under (a) UV, (b) visible light irradiation using the prepared photocatalysts and (c) Reusability tests for the degradation efficiency of TL under UV for 5 subsequent cycles.
Nanomaterials 12 03290 g011
Nanomaterials 12 03290 g012 550
Figure 12. Scavengers’ effects on TL oxidation efficiency using the TC10 composite under UV irradiation.
Figure 12. Scavengers’ effects on TL oxidation efficiency using the TC10 composite under UV irradiation.
Nanomaterials 12 03290 g012
Nanomaterials 12 03290 g013 550
Figure 13. Significant degradation efficiency of all dyes and TL.
Figure 13. Significant degradation efficiency of all dyes and TL.
Nanomaterials 12 03290 g013
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Ibrahim, I.; Belessiotis, G.V.; Elseman, A.M.; Mohamed, M.M.; Ren, Y.; Salama, T.M.; Mohamed, M.B.I. Magnetic TiO2/CoFe2O4 Photocatalysts for Degradation of Organic Dyes and Pharmaceuticals without Oxidants. Nanomaterials 2022, 12, 3290. https://doi.org/10.3390/nano12193290

AMA Style

Ibrahim I, Belessiotis GV, Elseman AM, Mohamed MM, Ren Y, Salama TM, Mohamed MBI. Magnetic TiO2/CoFe2O4 Photocatalysts for Degradation of Organic Dyes and Pharmaceuticals without Oxidants. Nanomaterials. 2022; 12(19):3290. https://doi.org/10.3390/nano12193290

Chicago/Turabian Style

Ibrahim, Islam, George V. Belessiotis, Ahmed Mourtada Elseman, Mohamed Mokhtar Mohamed, Yatao Ren, Tarek M. Salama, and Mahmoud Basseem I. Mohamed. 2022. "Magnetic TiO2/CoFe2O4 Photocatalysts for Degradation of Organic Dyes and Pharmaceuticals without Oxidants" Nanomaterials 12, no. 19: 3290. https://doi.org/10.3390/nano12193290

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop