Next Article in Journal
Probing Polarity and pH Sensitivity of Carbon Dots in Escherichia coli through Time-Resolved Fluorescence Analyses
Next Article in Special Issue
Graphitic Carbon Nitride Nanosheets Decorated with Zinc-Cadmium Sulfide for Type-II Heterojunctions for Photocatalytic Hydrogen Production
Previous Article in Journal
Semi-Empirical Pseudopotential Method for Graphene and Graphene Nanoribbons
Previous Article in Special Issue
High-Crystallinity BiOCl Nanosheets as Efficient Photocatalysts for Norfloxacin Antibiotic Degradation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nanomaterials
Volume 13
Issue 14
10.3390/nano13142067
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

Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe3O4) Nanoparticles

by
Thandi B. Mbuyazi
and
Peter A. Ajibade
*
School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa
*
Author to whom correspondence should be addressed.
Nanomaterials 2023, 13(14), 2067; https://doi.org/10.3390/nano13142067
Submission received: 18 June 2023 / Revised: 5 July 2023 / Accepted: 10 July 2023 / Published: 14 July 2023
(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)
Browse Figures
Versions Notes

Abstract

:
Octylamine (OTA), 1-dodecanethiol (DDT), and tri-n-octylphosphine (TOP) capped magnetite nanoparticles were prepared by co-precipitation method. Powder X-ray diffraction patterns confirmed inverse spinel crystalline phases for the as-prepared iron oxide nanoparticles. Transmission electron microscopic micrographs showed iron oxide nanoparticles with mean particle sizes of 2.1 nm for Fe3O4-OTA, 5.0 nm for Fe3O4-DDT, and 4.4 nm for Fe3O4-TOP. The energy bandgap of the iron oxide nanoparticles ranges from 2.25 eV to 2.76 eV. The iron oxide nanoparticles were used as photocatalysts for the degradation of methylene blue with an efficiency of 55.5%, 58.3%, and 66.7% for Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively, while for methyl orange the degradation efficiencies were 63.8%, 47.7%, and 74.1%, respectively. The results showed that tri-n-octylphosphine capped iron oxide nanoparticles are the most efficient iron oxide nano-photocatalysts for the degradation of both dyes. Scavenger studies show that electrons (e−) and hydroxy radicals (•OH) contribute significantly to the photocatalytic degradation reaction of both methylene blue and methyl orange using Fe3O4-TOP nanoparticles. The influence of the dye solution’s pH on the photocatalytic reaction reveals that a pH of 10 is the optimum for methylene blue degradation, whereas a pH of 2 is best for methyl orange photocatalytic degradation using the as-prepared iron oxide nano-photocatalyst. Recyclability studies revealed that the iron oxide photocatalysts can be recycled three times without losing their photocatalytic activity.

1. Introduction

Water contamination is currently a life-threatening issue and public health emergency that must be addressed promptly to improve global water quality and maintain a healthy ecosystem [1,2]. The excessive discharge of environmental contaminants like organic dyes has become a hinderance to the provision of potable water worldwide [3,4,5]. Organic dyes, with their complex chemical structures with high molecular weights, degrade slowly, are presumably mutagenic and carcinogenic, and have the capacity to block light penetration, hence reducing photosynthetic reactions. As a result, dye-containing effluents disrupt the natural balance of the surface water and significantly impact human health and aquatic ecosystems [6,7,8,9].
Magnetic metal oxide nanoparticles such as ZnO [10,11], CuO [12,13], SnO2 [14], TiO2 [15,16], MgO, and FeO [17,18] have been used as photocatalysts to degrade organic dyes and as adsorbents for removing heavy metal ions. Magnetic photocatalysts combine catalytic characteristics with magnetism, allowing the photocatalyst to be conveniently recovered from the treated solution using an external magnetic field. Magnetic iron oxide nanoparticles, among other forms of nanomaterials, offer unique properties such as abundance, good resistance to corrosion, low toxicity, and chemical and photochemical stability, making them an attractive material for photocatalysis [19,20,21,22]. However, magnetic iron oxide nanoparticles have high surface energies because of their high specific surface-to-volume ratios; therefore, they tend to aggregate to reduce the surface energy, which can change their adsorption ability and magnetic efficiency [23]. Consequently, it is critical to control the particle sizes and distributions of magnetic nanomaterials to prevent agglomeration.
Surfactant selection is of paramount importance in the preparation of magnetic nanoparticles to prevent their aggregation and create narrow particle size distributions with optimal shape and morphology. Numerous studies on the passivation of iron oxide nanoparticles using capping agents have been conducted. Sodipo et al. [24] studied the influence of five different capping agents on the morphology and magnetic properties of magnetite nanoparticles. Sodium citrate was the most effective capping agent, producing nearly spherical nanoparticles with the least agglomeration. Sharma et al. [25] prepared α-Fe2O3 nanoparticles using sodium citrate, polyvinyl pyrrolidone (PVP), and starch as capping agents. The incorporation of capping agents into nanoparticles has been shown to improve their activity and stability as photocatalysts against methylene blue with a maximum efficiency of 98.8% dye removal using PVP-capped α-Fe2O3.
Guidolin et al. [26] prepared Fe3O4 nanoparticles by a sol–gel citrate–nitrate method. The magnetite nanoparticles degraded 93.4% of methylene blue after 210 min when 2250 mg·L−1 of the nanoparticles was used. Rivera et al. [27] investigated the Fenton-like process for methylene blue dye degradation utilizing Fe3O4 nanoparticles prepared by the electrochemical synthesis method. The results showed that complete degradation can be achieved using 2 g·L−1 of Fe3O4 nanoparticles at a concentration of 100 mg/L MB in an acidic medium. Modrogan et al. [28] evaluated the photocatalytic performance of the Fe3O4/PVA composite against methyl orange in the presence of hydrogen peroxide under UV light. Various reaction parameters, such as composite dosage, pH, and the amount of hydrogen peroxide (H2O2), were studied. The results indicated that the level of dye degradation is significantly dependent on the amount of H2O2 in the reaction medium. León-Flores et al. [29] reported the green synthesis of Fe3O4 nanoparticles, using the Coffea arabica L. extract to degrade methyl orange dye under UV light irradiation, and that 80% of the dye was degraded using 10 mg of the nanoparticles in 15 mL of dye solution. Moreover, studies have shown that the morphology and phase composition of iron oxide nanoparticles influences their photocatalytic efficiency [30].
In this study, we report the structural and optical studies of octylamine (OTA), 1-dodecanethiol (DDT), and tri-n-octylphosphine (TOP) capped iron oxide nanoparticles. The as-prepared iron oxide nanoparticles’ potentials as photocatalysts were evaluated for the degradation of methylene blue and methyl orange dyes under visible light irradiation. The photodegradation kinetics, the influence of pH, scavengers, and photostability were also evaluated.

2. Materials and Methods

2.1. Materials

FeCl2·4H2O, Fe2(SO4)3∙H2O, 25% ammonia solution, ethanol, octylamine, 1-dodecanethiol, trioctylphosphine, methylene blue, methyl orange, ethylenediamine tetraacetic acid disodium, ascorbic acid, silver nitrate, isopropanol, hydrochloric acid, and sodium hydroxide were purchased from Merck (Darmstadt, Germany). All the reagents were used as purchased without further purification.

2.2. Synthesis of Iron Oxide Nanoparticles

Iron oxide nanoparticles were prepared using the co-precipitation approach [31]. The experiment was conducted in a nitrogen flow. FeCl2·4H2O (0.2485 g, 0.00125 mol) and Fe2(SO4)3∙H2O (1.0445 g, 0.0025 mol) were dissolved in 100 mL of distilled water and heated to 80 °C. An amount of 15 mL of 25% ammonia solution was added to adjust the pH of the reaction mixture to 11. After 30 min, octylamine (OTA) was introduced, and the temperature was maintained at 80 °C and the reaction was further stirred for 1 h. The nanoparticles were then centrifuged at 3500 rpm and washed several times to remove the excess capping agent and unreacted materials. To evaluate the effect of capping agents, the same procedure was carried out with trioctylphosphine (TOP) and 1-dodecathiol (DDT).

2.3. Characterization

FTIR spectra were recorded using a Cary 630 FTIR spectrometer, and absorption spectra were recorded using a Perkin Elmer lambda 25 UV-Vis spectrophotometer. The dye degradation experiments were conducted using a 70W high-pressure mercury lamp. The morphology of the nanoparticles was determined using a transmission electron microscopy (TEM) image taken with a Japan Electrical Optical Laboratories (JEOL) JEM-1400 electron microscope equipped with Gatan digital microgram software. ImageJ analysis software was used to measure the particle size distribution.

2.4. Adsorption of Methylene Blue (MB) and Methyl Orange (MO) by Iron Oxide Nanoparticles

The batch adsorption efficiency of Fe3O4 nanoparticles was measured using methylene blue (MB) and methyl orange (MO) as model dyes. Typically, 50 mg of Fe3O4 nanoparticles were dispersed in 40 mL of 10 mg/L of dye solution and the mixture was stirred in the dark for 75 min. An aliquot was withdrawn from each flask at 15 min time intervals and was analyzed with a UV-visible spectrometer to determine dye removal. The adsorption capacity, Q (mg/g), of the adsorbent was calculated using Equation (1):
Q = C 0 − C t W V
where C0 is the initial concentration of dye (mg L−1), Ct is the concentration of dye (mg L−1) in solution at a time ‘t’, V is the volume (L) of the dye solution, and W is the mass (g) of the adsorbent used.

2.5. Photocatalytic Experiment

Methylene blue (MB) and methyl orange (MO) dyes were used to investigate the dye degradation performance of iron oxide nanoparticles. In a typical method, a stock solution is prepared by dissolving 10 mg each of MB and MO in 1000 mL of distilled water. A total of 40 mg of iron oxide nanoparticles were dispersed in 40 mL of dye solution, sonicated for 60 min, and stirred in the dark for 60 min. The mixture was then irradiated with visible light and the photocatalytic degradation of the dye was evaluated using 4 mL of each mixed solution every 30 min. A UV-Vis spectrophotometer was used to evaluate the reaction progress by observing the absorbance maxima of the dyes. The degradation efficiency was calculated as:
D = A 0 − A t A 0 × 100
where ‘D’ denotes degradation efficiency (%), A0 refers to dye solution absorbance at ‘t’ zero, and At to dye solution absorbance after time ‘t’.

2.6. Effect of pH

The influence of pH on the degradation efficiency of MB and MO under visible light was examined over a pH range of 2 to 10. The pH of the dye solutions was changed using 0.1 M aqueous HCl and NaOH solutions.

2.7. Radical Scavenger Experiment

To identify the primary reactive species generated during the photocatalytic degradation of MB and MO, scavenging studies were conducted. To do this, isopropanol (IPA), ethylenediamine tetraacetic acid disodium (EDTA-Na2), ascorbic acid (AA), and silver nitrate (SN) were introduced to the reaction mixture to quench •OH, h+, •O2−, and e−, respectively. Then, 40 mg of the photocatalyst and 5 mL of each scavenger (10 mM) were added to 40 mL of dye solution (10 ppm) [32]. The experiment was carried out for 180 min under visible light and the respective absorbance spectra were taken to monitor the reaction progress.

3. Results

3.1. Structural and Morphological Studies of the Iron Oxide Nanoparticles

Powder X-ray diffraction patterns of the as-prepared iron oxide nanoparticles are shown in Figure 1. All diffraction patterns were indexed to the single crystalline inverse spinel structure of magnetite with card No. 19-0629 [33,34]. The 2θ peaks are 21.45°, 35.30°, 41.59°, 50.67°, 63.14°, 67.68°, and 74.55°, corresponding to the (111), (220), (311), (400), (422), (511) and (440) planes of the cubic inverse spinel structure of Fe3O4. The crystal growth orientation preference is toward the (311) plane. The peaks are broad and well-defined which could be due to the small particle sizes and the crystalline nature of the as-prepared iron oxide nanoparticles. No other peaks corresponding to other phases were identified in the XRD patterns, indicating the formation of a pure Fe3O4 phase regardless of the capping agent used to prepare the iron oxide nanoparticles.
TEM micrographs of the as-prepared iron oxide nanoparticles are shown in Figure 2. The TEM image of the OTA-capped iron oxide nanoparticles shows a mixture of square-like, oval, and quasi-spherical particles with an average size of 2.1 nm. The DDT-capped iron oxide nanoparticles also show agglomerated quasi-spherical particles with a mean particle size of 5.0 nm. The iron oxide nanoparticles prepared from TOP are also agglomerated with irregular shaped particles with a mean size of 4.4 nm (Figure S1). The observed agglomeration of the as-prepared nanoparticles may be attributed to the fact that they aggregate to reduce their high surface energy or to the dipole–dipole interactions of magnetic nanoparticles [24,35]. The use of capping agents resulted in more dispersed and well-defined shapes of nanoparticles compared to uncapped nanoparticles (Figure S2). Additionally, the use of different capping agents is observed to influence the as-prepared iron oxide nanoparticle sizes and shapes.
FTIR was used to confirm the interaction of the capping agents with iron oxide nanoparticles (Figure S3). Two weak peaks observed at 3387 and 3283 cm−1 in the OTA-capped iron oxide nanoparticle spectrum are attributed to the asymmetric and symmetric modes of NH2, respectively [36]. The asymmetric and symmetric C—H stretching vibrations of the alkyl chain of OTA are also observed at 2929 and 2833 cm−1. However, in the Fe3O4-OTA nanoparticles spectrum, these peaks are shifted to 2937 and 2905 cm−1. The C—N stretch of OTA appeared at 1477 cm−1, which is shifted to 1469 cm−1 in the Fe3O4-OTA spectrum. This indicates the presence of octylamine on the surface of iron oxide nanoparticles [37]. DDT shows sharp bands at 2913 cm−1 and 2849 cm−1, which are due to the asymmetric and symmetric C—H stretching modes, respectively [38,39]. These bands are blue-shifted by 16 and 8 cm−1, respectively, in the Fe3O4-DDT nanoparticles spectrum. The C—S stretching vibration at 723 cm−1 observed in the DDT spectrum is shifted to 826 cm−1 in the Fe3O4-DDT nanoparticles spectrum. The pure DDT also shows S—H stretching vibrational modes at 2564 cm−1 [40], which is shifted by 3 cm−1 in the Fe3O4-DDT nanoparticles spectrum. TOP exhibits C–P stretching vibrations at 1140 cm−1, while the bands at 2913 cm−1 and 2857 cm−1 are attributed to C—H stretching vibrational modes [41]. The C—H stretching vibrations were observed at 2928 cm−1 and 2856 cm−1 in the Fe3O4-TOP nanoparticles spectrum, while the C—P absorption band was observed at 1139 cm−1. The sharp bands at 552 cm−1 in iron oxide nanoparticles’ spectra are attributed to Fe—O vibration [42].

3.2. Optical Properties

The optical absorption spectra of the as-prepared iron oxide nanoparticles in Figure 3a shows that Fe3O4–OTA, Fe3O4–DDT, and Fe3O4–TOP nanoparticles exhibit absorption peaks at 274, 210, and 209 nm, respectively. The peaks can be attributed to electrons moving from the oxygen atom to the d-metal orbital [43,44]. The optical band gaps estimated from Tauc plots (Figure 3b) were 2.25 eV for Fe3O4–OTA, 2.47 eV for Fe3O4–DDT, and 2.76 eV for Fe3O4–TOP. The band gap energy decreases with increasing capping agent chain length. The variation in absorption band edges and band gap energies may be due to the different morphologies of the nanoparticles. This indicates the modification of the valence band and conduction bands by the quantum confinement effect [45,46].

3.3. Adsorption Studies of Iron Oxide Nanoparticles

Adsorption is a surface phenomenon where pollutants transfer from a liquid phase to the surface of a solid phase via physical forces or chemical interactions [47]. Since photocatalytic degradation of contaminants takes place on the surface of the photocatalyst, the adsorption capacity test is crucial [48]. The Fe3O4 nano-photocatalysts reached equilibrium adsorption capacity for both methylene blue and methyl orange dyes at 45 min (Figure 4). The stability of Fe3O4 nanoparticles after 45 min demonstrates that the adsorption–desorption equilibrium has been attained.

3.4. Photocatalytic Degradation of Methylene Blue and Methyl Orange by Iron Oxide Nanoparticles

The photocatalytic activity of OTA, DDT and TOP-capped iron oxide nanoparticles was evaluated using methylene blue (MB) and methyl orange (MO) dyes as organic pollutants under visible light irradiation. The time-dependent absorption spectra of MB and MO show (Figures S4 and S5) a decrease in characteristic absorption peaks over time. In the absence of iron oxide nanoparticles, the degradation of the dyes was insignificant. However, the dyes degraded significantly in the presence of iron oxide nanoparticles, as indicated by the Ct/C0 plot (Figure S6). The degradation efficiencies of MB by the iron oxide nanoparticles after 180 min irradiation are 55.5%, 58.3% and 66.7% by Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively (Figure 5a). The degradation efficiency is observed to increase with an increase in the chain length of the capping agent. The highest degradation efficiency of methylene blue obtained in this study is slightly higher than that of previous studies using γ–Fe2O3 nanoparticles (38%) [49], hematite iron oxide nanoparticles (51%) [50], and Fe3O4/ZnO nanocomposite (63%) [51]. Degradation efficiencies of 63.8%, 47.7%, and 74.1% were obtained for Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively, against MO dye (Figure 5b). OTA and TOP-capped iron oxide nanoparticles exhibit superior activity against MO compared to Fe3O4-DDT, and this could be due to Fe3O4-DDT’s large band gap. The nanoparticles’ agglomeration impacts their optical properties, which affects their capacity to absorb and disperse the incident radiation as well as their photocatalytic performance [52,53,54]. Therefore, the high photocatalytic degradation efficiency demonstrated by Fe3O4-TOP for both MB and MO dyes could be due to the Fe3O4-TOP nanoparticle morphology and light absorption capacity.
The photocatalytic degradation reaction of MB and MO follows a pseudo-first-order kinetic model as demonstrated by the linear correlation of the graphs of ln(Ct/C0) over irradiation time. Equation (3) was used to calculate the rate constants.
ln C t C 0 = − k t
The rate constants and correlation coefficients (R2) determined from the graphs in Figure S7 are shown in Table 1. The photodegradation rate constants of cationic dye are 4.28 × 10−3 min−1 for Fe3O4-OTA, 5.01 × 10−3 min−1 for Fe3O4-DDT, and 5.57 × 10−3 min−1 for Fe3O4-TOP, while the photodegradation rate constants of anionic dye are 0.00529 min−1 for Fe3O4-OTA, 3.96 × 10−3 min−1 for Fe3O4-DDT, and 7.76 × 10−3 min−1 for Fe3O4-TOP. The degradation rate constant of Fe3O4-DDT is low in the anionic dye but higher in the cationic dye, which is consistent with the degradation efficiency plot. The high correlation coefficient values show that the photodegradation of MB and MO dyes fits the pseudo-first-order kinetic model.

3.5. Effect of Scavengers on the Photocatalytic Degradation of Dyes

A series of scavengers were added to the dye solutions to determine the active species in the photocatalytic degradation of methylene blue and methyl orange dyes by the as-prepared iron oxide nanoparticles. The results were contrasted to dye degradation efficiency obtained using only iron oxide nanoparticles, as shown in Figure 6. Silver nitrate (SN), isopropanol alcohol (IPA), ascorbic acid (AA), and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) were used to detect e−, •OH, •O2−, and h+ scavenging activity [55]. MB dye degradation efficiency by the as-prepared iron oxide nanoparticles decreases from 66.7–55.5% to 10.8–7.2% (SN), 22.9–19.7% (AA), 58.4–43.4% (EDTA), and 13.9–8.1% (IPA). The addition of scavengers also decreased the reaction rate constants as presented in Table 2 (Figure S8). This demonstrates that e− and •OH are the main active species for the degradation of MB for all the as-prepared Fe3O4 nanoparticles. The results are consistent with previous studies using other photocatalysts [56,57]. However, the degradation efficiency of MO by Fe3O4–OTA decreases from 63.8% to 18.5% (SN), 43.7% (AA), 16.7% (EDTA), and 12.9% (IPA), whereas with Fe3O4–DDT the degradation efficiency decreases from 47.7% to 15.3% (SN), 34.7% (AA), 22.4% (EDTA), and 17.5% (IPA). The photocatalytic degradation efficiency of MO by Fe3O4–TOP decreases from 74.1% to 6.4% (SN), 42.7% (AA), 21.5% (EDTA), and 11.3% (IPA). In the presence of an ascorbic acid (AA) scavenger, Fe3O4-TOP exhibited a reaction rate of 1.58 × 10−2 min−1 (Figure S9), which is higher than the dye degradation rate without the scavenger; however, the degradation efficiency percentage remained low. The results indicate that e− and •OH play significant roles in the degradation of MO using Fe3O4–DDT and Fe3O4–TOP, while •OH and h+ are observed to be the main active species with e− acting as the secondary active species for Fe3O4–OTA.

3.6. Effect of pH

Another variable that influences the efficiency of the catalyst charge surface, dye adsorption, and other photocatalytic reaction parameters is pH [58]. Figure 7 shows the results of a study on the photocatalytic degradation of MB and MO at various pH levels between 2 and 10 in the presence of iron oxide nanoparticles. For MB dye, low degradation efficiencies of 10.3–24.5% were obtained at pH 2 and high degradation efficiencies of 72.6% for Fe3O4-OTA, 79.0% for Fe3O4-DDT, and 88.1% for Fe3O4-TOP were obtained at pH 10. The higher degradation efficiency of MB degradation at pH 10 can be attributed to the enhanced adsorption of MB dye molecules on the negatively charged catalyst surface, resulting in a strong interaction between the photocatalyst and the generated radicals, resulting in rapid degradation [35]. In contrast, at pH 2, the existence of additional h+ in the reaction mixture made the catalyst surface more positive, inhibiting dye molecule adsorption due to columbic repulsion interactions, which resulted in a slower rate of radical generation and therefore degradation [59]. In contrast, the degradation efficiency of MO was observed to increase with decreasing pH, and the highest efficiency of 82.1% for Fe3O4-TOP was obtained at pH 2. The pH value has a major influence on the existing forms of methyl orange; in an acidic medium, it is in quinoid form, and it progressively transitioned to an azo structure as the pH of the solution increased [60,61]. In comparison to methyl orange in azo form, the quinoid structure is easier to degrade [62]. Hence, in an acidic medium, methyl orange dye degradation efficiency was higher.

3.7. Photostability Studies

Photostability is a critical property of photocatalysts which makes photocatalysis a cost-effective, practical, and sustainable water treatment method [63]. Hence, recyclability studies were conducted to evaluate the iron oxide nanoparticles’ stability. Figure 8 demonstrates that the photodegradation efficiencies of the MB and MO dyes remained steady until the third cycle, with only a 0.8–11.3% decrease in efficiency over the three cycles. The decrease in photocatalytic degradation efficiency over the three cycles could be ascribed to either the build-up of intermediate products on the particle surface or nanoparticle loss during washing and filtration [64].

4. Conclusions

Iron oxide nanoparticles were prepared by co-precipitation method using three different capping agents to study the effect of capping agents on the morphological, optical, and photocatalytic properties of the as-prepared iron oxide nanoparticles. Powder X-ray diffraction patterns of the as-prepared iron oxide nanoparticles confirmed the cubic inverse spinel structure of Fe3O4. TEM images revealed Fe3O4-OTA nanoparticles are a mixture of square-like, oval, and quasi-spherical particles with an average particle size of 2.1 nm. Fe3O4-DDT nanoparticles were agglomerated quasi-spherical shapes with a mean size of 5.0 nm. The Fe3O4-TOP nanoparticles were also agglomerated and irregularly shaped with particle sizes of 4.4 nm. The results show that the use of different capping agents results in different particle sizes and shapes of the iron oxide nanoparticles. FTIR spectra confirmed the octylamine, 1-dodecanethiol, and tri-n-octylphosphine bond to the surface of the as-prepared iron oxide nanoparticles. Bandgap energies of 2.25, 2.47, and 2.76 eV were obtained for Fe3O4-OTA, Fe3O4-DDT, and Fe3O4-TOP, respectively. The results reveal that the bandgap energy can be tuned using different capping agents due to variations in the morphology of the nanoparticles obtained. The as-prepared iron oxide nanoparticles were used as photocatalysts for the degradation of MB and MO. The results showed that Fe3O4-TOP exhibited high degradation efficiency for the degradation of MB (66.7%) and MO (74.1%). The role of scavengers on the photocatalytic degradation efficiency was also investigated and e− and •OH were found to be the major active species in the photodegradation reaction of MB for all Fe3O4 nanoparticles, respectively, whereas, for MO, •OH and h+ were found to be the major active species when using Fe3O4-OTA. The as-prepared Fe3O4 nano-photocatalysts are photostable and recyclable for the photocatalytic degradation of the organic dyes.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/nano13142067/s1, Figure S1. Size distribution histograms of OTA, DDT and TOP-capped iron oxide nanoparticles. Figure S2. TEM image of uncapped iron oxide nanoparticles. Figure S3. FTIR spectra overlay of octylamine, 1-dodecanethiol and tri-n-octylphosphine capped iron oxide nanoparticles. Figure S4. Absorption spectra of methylene blue (MB) over (a) Fe3O4-OTA, (b) Fe3O4-DDT and (c) Fe3O4-TOP nanoparticles. Figure S5. Absorption spectra of methyl orange (MO) over (a) Fe3O4-OTA, (b) Fe3O4-DDT and (c) Fe3O4-TOP nanoparticles. Figure S6. (a) MB and (b) MO Ct/C0) versus irradiation time plots. Figure S7. Methylene blue (a) and methyl orange (b) photocatalytic degradation kinetics using iron oxide nanoparticles as photocatalysts. Figure S8. Photodegradation kinetics plots of MB by iron oxide nanoparticles in the presence of scavengers. Figure S9. Photodegradation kinetics plots of MO by iron oxide nanoparticles in the presence of scavengers.

Author Contributions

P.A.A.; conceptualization, supervision, writing—review and editing, funding acquisition. T.B.M.; data curation, formal analysis, writing—draft preparation. All authors have read and agreed to the published version of the manuscript.

Funding

The authors acknowledged funding from the National Research Foundation, grant number 129275 and the award of PhD scholarship.

Data Availability Statement

All research data are presented in the paper and the supplementary data.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Bruno, A.; Agostinetto, G.; Fumagalli, S.; Ghisleni, G.; Sandionigi, A. It’s a long way to the tap: Microbiome and DNA-based omics at the core of drinking water quality. Int. J. Environ. Res. Public Health 2022, 19, 7940. [Google Scholar] [CrossRef] [PubMed]
  2. Dagher, L.A.; Hassan, J.; Kharroubi, S.; Jaafar, H.; Kassem, I.I. Nationwide assessment of water quality in rivers across Lebanon by quantifying fecal indicators densities and profiling antibiotic resistance of Escherichia coli. Antibiotics 2021, 10, 883. [Google Scholar] [CrossRef] [PubMed]
  3. Islam, T.; Repon, M.R.; Islam, T.; Sarwar, Z.; Rahman, M.M. Impact of textile dyes on health and ecosystem: A review of structure, causes, and potential solutions. Environ. Sci. Pollut. Res. 2023, 30, 9207–9242. [Google Scholar] [CrossRef]
  4. Al-Tohamy, R.; Ali, S.S.; Li, F.; Okasha, K.M.; Mahmoud, Y.A.G.; Elsamahy, T.; Jiao, H.; Fu, Y.; Sun, J. A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety. Ecotoxicol. Environ. Saf. 2022, 231, 113160. [Google Scholar] [CrossRef]
  5. Elgarahy, A.M.; Elwakeel, K.Z.; Mohammad, S.H.; Elshoubaky, G.A. A critical review of biosorption of dyes, heavy metals and metalloids from wastewater as an efficient and green process. Clean. Eng. Technol. 2021, 4, 100209. [Google Scholar] [CrossRef]
  6. Khan, M.D.; Singh, A.; Khan, M.Z.; Tabraiz, S.; Sheikh, J. Current perspectives, recent advancements, and efficiencies of various dye-containing wastewater treatment technologies. J. Water Process. Eng. 2023, 53, 103579. [Google Scholar] [CrossRef]
  7. Khan, S.; Naushad, M.; Govarthanan, M.; Iqbal, J.; Alfadul, S.M. Emerging contaminants of high concern for the environment: Current trends and future research. Environ. Res. 2022, 207, 112609. [Google Scholar] [CrossRef]
  8. Markandeya; Mohan, D.; Shukla, S.P. Hazardous consequences of textile mill effluents on soil and their remediation approaches. Clean. Eng. Technol. 2022, 7, 100434. [Google Scholar] [CrossRef]
  9. Oladoye, P.O.; Ajiboye, T.O.; Omotola, E.O.; Oyewola, O.J. Methylene blue dye: Toxicity and potential elimination technology from wastewater. Results Eng. 2022, 16, 100678. [Google Scholar] [CrossRef]
  10. Sharma, M.; Poddar, M.; Gupta, Y.; Nigam, S.; Avasthi, D.K.; Adelung, R.; Abolhassani, R.; Fiutowski, J.; Joshi, M.; Mishra, Y.K. Solar light assisted degradation of dyes and adsorption of heavy metal ions from water by CuO–ZnO tetrapodal hybrid nanocomposite. Mater. Today Chem. 2020, 17, 100336. [Google Scholar] [CrossRef]
  11. Smazna, D.; Shree, S.; Polonskyi, O.; Lamaka, S.; Baum, M.; Zheludkevich, M.; Faupel, F.; Adelung, R.; Mishra, Y.K. Mutual interplay of ZnO micro- and nanowires and methylene blue during cyclic photocatalysis process. J. Environ. Chem. Eng. 2019, 7, 103016. [Google Scholar] [CrossRef]
  12. Li, Z.; Liu, D.; Huang, W.; Wei, X.; Huang, W. Biochar supported CuO composites used as an efficient peroxymonosulfate activator for highly saline organic wastewater treatment. Sci. Total Environ. 2020, 721, 137764. [Google Scholar] [CrossRef] [PubMed]
  13. Kiani, R.; Mirzaei, F.; Ghanbari, F.; Feizi, R.; Mehdipour, F. Real textile wastewater treatment by a sulfate radicals-Advanced Oxidation Process: Peroxydisulfate decomposition using copper oxide (CuO) supported onto activated carbon. J. Water Process Eng. 2020, 38, 101623. [Google Scholar] [CrossRef]
  14. Chandra, R.; Singh, V.; Tomar, S.; Nath, M. Multi-core-shell composite SnO2NPs@ZIF-8: Potential antiviral agent and effective photocatalyst for waste-water treatment. Environ. Sci. Pollut. Res. 2019, 26, 23346–23358. [Google Scholar] [CrossRef]
  15. Mousa, H.M.; Alenezi, J.F.; Mohamed, I.M.A.; Yasin, A.S.; Hashem, A.-F.M.; Abdal-hay, A. Synthesis of TiO2@ZnO heterojunction for dye photodegradation and wastewater treatment. J. Alloys Compd. 2021, 886, 161169. [Google Scholar] [CrossRef]
  16. Balakrishnan, A.; Appunni, S.; Chinthala, M.; Vo, D.-V.N. Biopolymer-supported TiO2 as a sustainable photocatalyst for wastewater treatment: A review. Environ. Chem. Lett. 2022, 20, 3071–3098. [Google Scholar] [CrossRef]
  17. Noreen, S.; Khalid, U.; Ibrahim, S.M.; Javed, T.; Ghani, A.; Naz, S.; Iqbal, M. ZnO, MgO and FeO adsorption efficiencies for direct sky Blue dye: Equilibrium, kinetics and thermodynamics studies. J. Mater. Res. Technol. 2020, 9, 5881–5893. [Google Scholar] [CrossRef]
  18. Mohadesi, M.; Gouran, A.; Seifi, K. Removal of ibuprofen from synthetic wastewater using photocatalytic method in the presence of FeO photocatalyst supported on modified Iranian clinoptilolite. Environ. Sci. Pollut. Res. 2022, 29, 34338–34348. [Google Scholar] [CrossRef]
  19. Naseem, T.; Durrani, T. The role of some important metal oxide nanoparticles for wastewater and antibacterial applications: A review. J. Environ. Chem. Ecotoxicol. 2021, 3, 59–75. [Google Scholar] [CrossRef]
  20. Leonel, A.G.; Mansur, A.A.P.; Mansur, H.S. Advanced functional nanostructures based on magnetic iron oxide nanomaterials for water remediation: A review. Water Res. 2021, 190, 116693. [Google Scholar] [CrossRef]
  21. Qumar, U.; Hassan, J.Z.; Bhatti, R.A.; Raza, A.; Nazir, G.; Nabgan, W.; Ikram, M. Photocatalysis vs adsorption by metal oxide nanoparticles. Mater. Sci. Technol. 2022, 131, 122–166. [Google Scholar] [CrossRef]
  22. Jabbar, Z.H.; Esmail Ebrahim, S. Recent advances in nano-semiconductors photocatalysis for degrading organic contaminants and microbial disinfection in wastewater: A comprehensive review. Environ. Nanotechnol. Monit. Manag. 2022, 17, 100666. [Google Scholar] [CrossRef]
  23. You, J.; Wang, L.; Zhao, Y.; Bao, W. A review of amino-functionalized magnetic nanoparticles for water treatment: Features and prospects. J. Clean. Prod. 2021, 281, 124668. [Google Scholar] [CrossRef]
  24. Sodipo, B.K.; Noqta, O.A.; Aziz, A.A.; Katsikini, M.; Pinakidou, F.; Paloura, E.C. Influence of capping agents on fraction of Fe atoms occupying octahedral site and magnetic property of magnetite (Fe3O4) nanoparticles by one-pot co-precipitation method. J. Alloys Compd. 2023, 938, 168558. [Google Scholar] [CrossRef]
  25. Sharma, P.; Kumari, S.; Ghosh, D.; Yadav, V.; Vij, A.; Rawat, P.; Kumar, S.; Sinha, C.; Saini, S.; Sharma, V.; et al. Capping agent-induced variation of physicochemical and biological properties of α-Fe2O3 nanoparticles. Mater. Chem. Phys. 2021, 258, 123899. [Google Scholar] [CrossRef]
  26. Guidolin, T.O.; Possolli, N.M.; Polla, M.B.; Wermuth, T.B.; Franco de Oliveira, T.; Eller, S.; Klegues Montedo, O.R.; Arcaro, S.; Cechinel, M.A.P. Photocatalytic pathway on the degradation of methylene blue from aqueous solutions using magnetite nanoparticles. J. Clean. Prod. 2021, 318, 128556. [Google Scholar] [CrossRef]
  27. Rivera, F.L.; Recio, F.J.; Palomares, F.J.; Sánchez-Marcos, J.; Menéndez, N.; Mazarío, E.; Herrasti, P. Fenton-like degradation enhancement of methylene blue dye with magnetic heating induction. J. Electroanal. Chem. 2020, 879, 114773. [Google Scholar] [CrossRef]
  28. Modrogan, C.; Cǎprǎrescu, S.; Dǎncilǎ, A.M.; Orbuleț, O.D.; Grumezescu, A.M.; Purcar, V.; Radițoiu, V.; Fierascu, R.C. Modified Composite Based on Magnetite and Polyvinyl Alcohol: Synthesis, Characterization, and Degradation Studies of the Methyl Orange Dye from Synthetic Wastewater. Polymers 2021, 13, 3911. [Google Scholar] [CrossRef]
  29. León-Flores, J.; Pérez-Mazariego, J.L.; Marquina, M.; Gómez, R.; Escamilla, R.; Tehuacanero-Cuapa, S.; Reyes-Damián, C.; Arenas-Alatorre, J. Controlled Formation of Hematite—Magnetite Nanoparticles by a Biosynthesis Method and Its Photocatalytic Removal Potential Against Methyl Orange Dye. J. Cluster Sci. 2022, 1–15. [Google Scholar] [CrossRef]
  30. Kusior, A.; Michalec, K.; Jelen, P.; Radecka, M. Shaped Fe2O3 nanoparticles—Synthesis and enhanced photocatalytic degradation towards RhB. Appl. Surf. Sci. 2019, 476, 342–352. [Google Scholar] [CrossRef]
  31. Arévalo, P.; Isasi, J.; Caballero, A.C.; Marco, J.F.; Martín-Hernández, F. Magnetic and structural studies of Fe3O4 nanoparticles synthesized via coprecipitation and dispersed in different surfactants. Ceram. Int. 2017, 43, 10333–10340. [Google Scholar] [CrossRef]
  32. Stanley, R.; Jebasingh, J.A.; Vidyavathy, S.M. Cost-effective and sunlight-driven degradation of anionic and cationic dyes with pure ZnO nanoparticles. Int. J. Environ. Sci. Technol. 2022, 19, 11249–11262. [Google Scholar] [CrossRef]
  33. Elizondo-Villarreal, N.; Verástegui-Domínguez, L.; Rodríguez-Batista, R.; Gándara-Martínez, E.; Alcorta-García, A.; Martínez-Delgado, D.; Rodríguez-Castellanos, E.A.; Vázquez-Rodríguez, F.; Gómez-Rodríguez, C. Green Synthesis of Magnetic Nanoparticles of Iron Oxide Using Aqueous Extracts of Lemon Peel Waste and Its Application in Anti-Corrosive Coatings. Materials 2022, 15, 8328. [Google Scholar] [CrossRef] [PubMed]
  34. Besenhard, M.O.; Panariello, L.; Kiefer, C.; LaGrow, A.P.; Storozhuk, L.; Perton, F.; Begin, S.; Mertz, D.; Thanh, N.T.K.; Gavriilidis, A. Small iron oxide nanoparticles as MRI T1 contrast agent: Scalable inexpensive water-based synthesis using a flow reactor. Nanoscale 2021, 13, 8795–8805. [Google Scholar] [CrossRef]
  35. Kumar, A.P.; Ahmed, F.; Kumar, S.; Anuradha, G.; Harish, K.; Kumar, B.P.; Lee, Y.-I. Synthesis of magnetically recoverable Ru/Fe3O4 nanocomposite for efficient photocatalytic degradation of methylene blue. J. Cluster Sci. 2022, 33, 853–865. [Google Scholar] [CrossRef]
  36. Dhiman, A.; Sharma, A.K.; Bhardwaj, D.; Agrawal, G. Biodegradable dual stimuli responsive alginate based microgels for controlled agrochemicals release and soil remediation. Int. J. Biol. Macromol. 2023, 228, 323–332. [Google Scholar] [CrossRef]
  37. Chen, D.; Ren, X.; Li, T.; Chen, Z.; Cao, Y.; Xu, F. Octylamine-Supporting Interlayer Expanded Molybdenum Diselenide as a High-Power Cathode for Rechargeable Mg Batteries. Energy Environ. Mater. 2022, e12486. [Google Scholar] [CrossRef]
  38. Chen, L.; Li, G. Functions of 1-Dodecanethiol in the Synthesis and Post-Treatment of Copper Sulfide Nanoparticles Relevant to Their Photocatalytic Applications. ACS Appl. Nano Mater. 2018, 1, 4587–4593. [Google Scholar] [CrossRef]
  39. Hu, S.; Chen, Z.; Guo, X. Inhibition Effect of Three-Dimensional (3D) Nanostructures on the Corrosion Resistance of 1-Dodecanethiol Self-Assembled Monolayer on Copper in NaCl Solution. Materials 2018, 11, 1225. [Google Scholar] [CrossRef] [Green Version]
  40. Luo, D.; Luo, Y.; Lu, X.; Shi, M.; Wei, J.; Lu, Z.; Huang, Y.; Ni, Y. Cooperative selective benzyl alcohol oxidation and hydrogen production over Pd6(SC12H25)12 cluster-coupled CdS nanorods: The key role of water in photocatalytic benzyl alcohol splitting. J. Mater. Chem. 2022, 10, 15941–15948. [Google Scholar] [CrossRef]
  41. Ji, Y.; Wang, M.; Yang, Z.; Qiu, H.; Padhiar, M.A.; Zhou, Y.; Wang, H.; Dang, J.; Gaponenko, N.V.; Bhatti, A.S. Trioctylphosphine-Assisted Pre-protection Low-Temperature Solvothermal Synthesis of Highly Stable CsPbBr3/TiO2 Nanocomposites. J. Phys. Chem. Lett. 2021, 12, 3786–3794. [Google Scholar] [CrossRef]
  42. Ananthi, S.; Kavitha, M.; Kumar, E.R.; Balamurugan, A.; Al-Douri, Y.; Alzahrani, H.K.; Keshk, A.A.; Habeebullah, T.M.; Abdel-Hafez, S.H.; El-Metwaly, N.M. Natural tannic acid (green tea) mediated synthesis of ethanol sensor based Fe3O4 nanoparticles: Investigation of structural, morphological, optical properties and colloidal stability for gas sensor application. Sens. Actuators B Chem. 2022, 352, 131071. [Google Scholar] [CrossRef]
  43. Mizuno, S.; Yao, H. On the electronic transitions of α-Fe2O3 hematite nanoparticles with different size and morphology: Analysis by simultaneous deconvolution of UV–vis absorption and MCD spectra. J. Magn. Magn. 2021, 517, 167389. [Google Scholar] [CrossRef]
  44. Kashyap, S.J.; Sankannavar, R.; Madhu, G.M. Iron oxide (Fe2O3) synthesized via solution-combustion technique with varying fuel-to-oxidizer ratio: FT-IR, XRD, optical and dielectric characterization. Mater. Chem. Phys. 2022, 286, 126118. [Google Scholar] [CrossRef]
  45. Andrade Neto, N.F.; Nascimento, L.E.; Correa, M.; Bohn, F.; Bomio, M.R.D.; Motta, F.V. Characterization and photocatalytic application of Ce4+, Co2+, Mn2+ and Ni2+ doped Fe3O4 magnetic nanoparticles obtained by the co-precipitation method. Mater. Chem. Phys. 2020, 242, 122489. [Google Scholar] [CrossRef]
  46. Suman; Chahal, S.; Kumar, A.; Kumar, P. Zn Doped α-Fe2O3: An Efficient Material for UV Driven Photocatalysis and Electrical Conductivity. Crystals 2020, 10, 273. [Google Scholar] [CrossRef] [Green Version]
  47. Adeola, A.O.; Abiodun, B.A.; Adenuga, D.O.; Nomngongo, P.N. Adsorptive and photocatalytic remediation of hazardous organic chemical pollutants in aqueous medium: A review. J. Contam. Hydrol. 2022, 248, 104019. [Google Scholar] [CrossRef]
  48. Pavel, M.; Anastasescu, C.; State, R.-N.; Vasile, A.; Papa, F.; Balint, I. Photocatalytic Degradation of Organic and Inorganic Pollutants to Harmless End Products: Assessment of Practical Application Potential for Water and Air Cleaning. Catalysts 2023, 13, 380. [Google Scholar] [CrossRef]
  49. Rehman, A.; Daud, A.; Warsi, M.F.; Shakir, I.; Agboola, P.O.; Sarwar, M.I.; Zulfiqar, S. Nanostructured maghemite and magnetite and their nanocomposites with graphene oxide for photocatalytic degradation of methylene blue. Mater. Chem. Phys. 2020, 256, 123752. [Google Scholar] [CrossRef]
  50. Shenoy, M.; Sakunthala, A.; Vidhya, B.; Rajesh, S.; Raju, N.; Parthasarathi, S.K.; Sasikumar, M.; Govindan, K.; Tamilarasan, S.; Selvaraju, T.; et al. Visible light sensitive hexagonal boron nitride (hBN) decorated Fe2O3 photocatalyst for the degradation of methylene blue. J. Mater. Sci. Mater. Electron. 2021, 32, 1–18. [Google Scholar] [CrossRef]
  51. Długosz, O.; Szostak, K.; Krupiński, M.; Banach, M. Synthesis of Fe3O4/ZnO nanoparticles and their application for the photodegradation of anionic and cationic dyes. Int. J. Environ. Sci. Technol. 2021, 18, 561–574. [Google Scholar] [CrossRef]
  52. Pellegrino, F.; Pellutiè, L.; Sordello, F.; Minero, C.; Ortel, E.; Hodoroaba, V.-D.; Maurino, V. Influence of agglomeration and aggregation on the photocatalytic activity of TiO2 nanoparticles. Appl. Catal. B 2017, 216, 80–87. [Google Scholar] [CrossRef]
  53. Acosta-Herazo, R.; Mueses, M.Á.; Puma, G.L.; Machuca-Martínez, F. Impact of photocatalyst optical properties on the efficiency of solar photocatalytic reactors rationalized by the concepts of initial rate of photon absorption (IRPA) dimensionless boundary layer of photon absorption and apparent optical thickness. Chem. Eng. J. 2019, 356, 839–849. [Google Scholar] [CrossRef] [Green Version]
  54. Ceballos-Chuc, M.C.; Ramos-Castillo, C.M.; Rodríguez-Pérez, M.; Ruiz-Gómez, M.Á.; Rodríguez-Gattorno, G.; Villanueva-Cab, J. Synergistic Correlation in the Colloidal Properties of TiO2 Nanoparticles and Its Impact on the Photocatalytic Activity. Inorganics 2022, 10, 125. [Google Scholar] [CrossRef]
  55. Jebasingh, R.S.; Stanley, P.K.; Ponmani, P.; Shekinah, M.E.; Vasanthi, J. Excellent Photocatalytic degradation of Methylene Blue, Rhodamine B and Methyl Orange dyes by Ag-ZnO nanocomposite under natural sunlight irradiation. Optik 2021, 231, 166518. [Google Scholar] [CrossRef]
  56. Ma, Z.; Hu, L.; Li, X.; Deng, L.; Fan, G.; He, Y. A novel nano-sized MoS2 decorated Bi2O3 heterojunction with enhanced photocatalytic performance for methylene blue and tetracycline degradation. Ceram. Int. 2019, 45, 15824–15833. [Google Scholar] [CrossRef]
  57. Alshehri, A.A.; Malik, M.A. Biogenic fabrication of ZnO nanoparticles using Trigonella foenum-graecum (Fenugreek) for proficient photocatalytic degradation of methylene blue under UV irradiation. J. Mater. Sci. Mater. Electron. 2019, 30, 16156–16173. [Google Scholar] [CrossRef]
  58. Bibi, S.; Ahmad, A.; Anjum, M.A.R.; Haleem, A.; Siddiq, M.; Shah, S.S.; Kahtani, A.A. Photocatalytic degradation of malachite green and methylene blue over reduced graphene oxide (rGO) based metal oxides (rGO-Fe3O4/TiO2) nanocomposite under UV-visible light irradiation. J. Environ. Chem. Eng. 2021, 9, 105580. [Google Scholar] [CrossRef]
  59. Weldegebrieal, G.K.; Sibhatu, A.K. Photocatalytic activity of biosynthesized α-Fe2O3 nanoparticles for the degradation of methylene blue and methyl orange dyes. Optik 2021, 241, 167226. [Google Scholar] [CrossRef]
  60. Song, S.; Hao, C.; Zhang, X.; Zhang, Q.; Sun, R. Sonocatalytic degradation of methyl orange in aqueous solution using Fe-doped TiO2 nanoparticles under mechanical agitation. Open Chem. 2018, 16, 1283–1296. [Google Scholar] [CrossRef] [Green Version]
  61. Mohamed Isa, E.D.; Che Jusoh, N.W.; Hazan, R.; Shameli, K. Photocatalytic degradation of methyl orange using pullulan-mediated porous zinc oxide microflowers. Environ. Sci. Pollut. Res. 2021, 28, 5774–5785. [Google Scholar] [CrossRef] [PubMed]
  62. Djebli, A.; Boudjemaa, A.; Bendjeffal, H.; Mamine, H.; Metidji, T.; Bekakria, H.; Bouhedja, Y. Photocatalytic degradation of methyl orange using Zn@[Fe(CN)5NO] complex under sunlight irradiation. Inorg. Nano-Met. Chem. 2020, 50, 1115–1122. [Google Scholar] [CrossRef]
  63. Isa, E.D.M.; Shameli, K.; Jusoh, N.W.C.; Hazan, R. Rapid photodecolorization of methyl orange and rhodamine B using zinc oxide nanoparticles mediated by pullulan at different calcination conditions. J. Nanostructure Chem. 2021, 11, 187–202. [Google Scholar] [CrossRef]
  64. Mallikarjunaswamy, C.; Lakshmi Ranganatha, V.; Ramu, R.; Udayabhanu; Nagaraju, G. Facile microwave-assisted green synthesis of ZnO nanoparticles: Application to photodegradation, antibacterial and antioxidant. J. Mater. Sci. Mater. Electron. 2020, 31, 1004–1021. [Google Scholar] [CrossRef]
Nanomaterials 13 02067 g001 550
Figure 1. P-XRD diffraction patterns of OTA, DDT, and TOP-capped Fe3O4 nanoparticles.
Figure 1. P-XRD diffraction patterns of OTA, DDT, and TOP-capped Fe3O4 nanoparticles.
Nanomaterials 13 02067 g001
Nanomaterials 13 02067 g002 550
Figure 2. TEM images of OTA, DDT, and TOP-capped Fe3O4 nanoparticles.
Figure 2. TEM images of OTA, DDT, and TOP-capped Fe3O4 nanoparticles.
Nanomaterials 13 02067 g002
Nanomaterials 13 02067 g003 550
Figure 3. (a) UV-Vis spectra and (b) Tauc plots of iron OTA, DDT and TOP-capped iron oxide nanoparticles.
Figure 3. (a) UV-Vis spectra and (b) Tauc plots of iron OTA, DDT and TOP-capped iron oxide nanoparticles.
Nanomaterials 13 02067 g003
Nanomaterials 13 02067 g004 550
Figure 4. Time profile of (a) methylene blue and (b) methyl orange adsorption.
Figure 4. Time profile of (a) methylene blue and (b) methyl orange adsorption.
Nanomaterials 13 02067 g004
Nanomaterials 13 02067 g005 550
Figure 5. Degradation efficiency curves of (a) MB and (b) MO.
Figure 5. Degradation efficiency curves of (a) MB and (b) MO.
Nanomaterials 13 02067 g005
Nanomaterials 13 02067 g006 550
Figure 6. Effects of scavengers on the photodegradation of (a) MB and (b) MO by iron oxide nanoparticles.
Figure 6. Effects of scavengers on the photodegradation of (a) MB and (b) MO by iron oxide nanoparticles.
Nanomaterials 13 02067 g006
Nanomaterials 13 02067 g007 550
Figure 7. Effect of pH on (a) MB and (b) MO photocatalytic degradation by iron oxide nanoparticles.
Figure 7. Effect of pH on (a) MB and (b) MO photocatalytic degradation by iron oxide nanoparticles.
Nanomaterials 13 02067 g007
Nanomaterials 13 02067 g008 550
Figure 8. The recyclability of iron oxide nano-photocatalysts.
Figure 8. The recyclability of iron oxide nano-photocatalysts.
Nanomaterials 13 02067 g008
Table
Table 1. Photodegradation rate constants and correlation coefficients of MB and MO by iron oxide nanoparticles.
Table 1. Photodegradation rate constants and correlation coefficients of MB and MO by iron oxide nanoparticles.
DyeCatalystDegradation Efficiency (%)Rate Constant (min−1)R2
Methylene blueFe3O4-OTA55.5 4.28 × 10−399.69 × 10−2
Fe3O4-DDT58.35.01 × 10−398.41 × 10−2
Fe3O4-TOP66.75.57 × 10−398.50 × 10−2
Methyl orangeFe3O4-OTA63.8 5.29 × 10−398.89 × 10−2
Fe3O4-DDT47.73.96 × 10−398.97 × 10−2
Fe3O4-TOP74.17.76 × 10−398.95 × 10−2
Table
Table 2. Photodegradation rate constants of MB and MO by iron oxide nanoparticles in the presence of scavengers.
Table 2. Photodegradation rate constants of MB and MO by iron oxide nanoparticles in the presence of scavengers.
DyeCatalystRate Constant (min−1)
SNAAEDTAIPA
Methylene blueFe3O4-OTA6.15 × 10−41.84 × 10−33.18 × 10−38.54 × 10−4
Fe3O4-DDT 1.12 × 10−31.36 × 10−34.68 × 10−36.84 × 10−4
Fe3O4-TOP4.39 × 10−49.08 × 10-44.78 × 10−35.62 × 10−4
Methyl orangeFe3O4-OTA1.26 × 10−33.38 × 10−39.97 × 10−47.66 × 10−4
Fe3O4-DDT9.53 × 10−42.51 × 10−31.42 × 10−31.18 × 10−3
Fe3O4-TOP3.52 × 10−41.58 × 10−21.47 × 10−36.61 × 10−4
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Mbuyazi, T.B.; Ajibade, P.A. Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe3O4) Nanoparticles. Nanomaterials 2023, 13, 2067. https://doi.org/10.3390/nano13142067

AMA Style

Mbuyazi TB, Ajibade PA. Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe3O4) Nanoparticles. Nanomaterials. 2023; 13(14):2067. https://doi.org/10.3390/nano13142067

Chicago/Turabian Style

Mbuyazi, Thandi B., and Peter A. Ajibade. 2023. "Influence of Different Capping Agents on the Structural, Optical, and Photocatalytic Degradation Efficiency of Magnetite (Fe3O4) Nanoparticles" Nanomaterials 13, no. 14: 2067. https://doi.org/10.3390/nano13142067

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