# Photo-Oxidation of Organic Dye by Fe2O3 Nanoparticles: Catalyst, Electron Acceptor, and Polyurethane Membrane (PU-Fe2O3) Effects

Authors: Bachir Yaou Balarabe; Maman Nasser Illiassou Oumarou; Abdoul Salam Koroney; Irédon Adjama; Abdoul Razak Ibrahim Baraze
Journal: Journal of Nanotechnology
 (2023)

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## Abstract

The textile industry’s discharges have long been regarded as severe water pollution. The photocatalytic degradation of dyes using semiconductors is one of the crucial methods. The present study efficiently used the mechanical method to synthesize Iron oxide Nanoparticles. XRD, FT-IR, UV-Vis DRS, and Raman analyses were performed to analyze the structural and optical. From the data provided by XRD and Raman data, we believed that the as-synthesized Iron oxide was pure hematite (α-Fe2O3) with a hexagonal structure. Additionally, the EDS results show that the synthesized material is pure. By adjusting specific parameters, including the dye concentration, the catalyst dosage, the pH, and the oxidizing agent such as H2O2 and K2S2O8, the degradation of eosin yellowish using Fe2O3 as a photocatalyst has been discussed. Additionally, the kinetics of eosin yellowish degradation has been studied. A study was also conducted using Fe2O3 nanoparticles attached to polyurethane polymer (PU) to investigate its photocatalytic activity on methylene blue, methyl orange, and indigo carmine. In 30 minutes, nearly 90% of the dyes had degraded. The total organic carbon (TOC) analysis confirmed this result.


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## Body

## 1. Introduction

The fast growth of the social economy and industrialization results in hundreds of new pollutants being released into the environment, causing massive damage [1]. Dye is used in many sectors, such as dyeing, printing, beauty care products, medications, calfskin, printing ink, and fluorescent color. Most Dyes are natural carcinogens, and their release into the environment as wastewater is a significant source of visual contamination, eutrophication, and disruption of aquatic life [2]. Eosin yellow, also known as 2-(2,4,5,6-Tetrabromo-6-oxido-3-oxido-3H xanthenes-9-yl) benzoate disodium salt, is an anionic dye. According to toxicological writings on eosin yellow, the dye can cause severe skin and eye irritation. When it comes into contact with the skin, it causes irritation, redness, and inconvenience. When consumed, it has various adverse effects, most notably on vital organs such as the liver and kidneys. The retinal ganglion cell, found on the retina’s internal surface, can be permanently damaged when eosin yellowish comes into direct contact with the eye. Additionally, it destroys DNA in the digestive systems of living things, causing various human disorders [3–7]. Numerous improvements in wastewater treatment have been made over the decade, including electrochemical treatment, oxidation, ozonation, and photochemical treatment. A standard method for degrading harmful substances has been photocatalytic degradation driven by semiconductors. In essence, photodegradation begins with the formation of electron/hole pairs in the semiconductor as a result of light absorption with energy comparable to or more potent than the bandgap [8]. TiO2 and ZnO are two of the few semiconductors used in photocatalysis. They both have high photosensitivity, especially in the UV range, suggesting that they can effectively drive the oxidation and reduction processes. Despite their exceptional qualities, the semiconductors, as mentioned above, have significant disadvantages, such as fast charge transporter recombination and large bandgap [8, 9]. A new era of materials responding to a wide range of wavelengths has overcome these limitations. The solution can ideally be the solution for the photocatalytic activity of a material with a suitable crystal structure, surface area, size distribution, porosity, ideal bandgap, and magnetic property. Iron oxides, including Fe3O4 (magnetite), α-Fe2O3, β-Fe2O3, ϒ-Fe2O3, FeO, and spinel ferrites (MFe2O4), relatively cheap and stable, have earned much interest in the field of photocatalysis are one of them [10, 11]. Additionally, it is well known that magnetic iron oxides can be used as an efficient visible-light semiconductor photocatalyst due to their low bandgap, high conductivity, and high catalytic activity in the visible light region [12, 13]. For example, α-Fe2O3 nanoparticles could altogether remove an aqueous solution of Rose Bengal within a short time [14]. Liu et al. used chemical solutions to prepare a porous Fe2O3, and the degradation efficiency was approx. 86.4% for the degradation of rhodamine B [15]. According to Deng et al., the electrospinning synthesized α-Fe2O3 nanowires could remove 85% of a highly concentrated solution of rhodamine B [16]. Several methods/techniques have recently been used to synthesize Iron Oxide nanoparticles, among them surfactant-assisted hydrothermal, microemulsion, and many other ways [8, 17–19]. Developing a reusable catalyst for treating dye-contaminatedstill-water bodies under visible light would also be very attractive [20–22]. By immobilizing nanomaterials on porous solid substrates, it is possible to improve their recyclability and efficiency [22]. According to Zhang et al., PVDF/GO/ZnO composite membranes have been shown to degrade methylene blue in water [23]. There are several membrane substrates available; however, polyurethane (PU) is one of the most promising materials because it is simple to process, versatile, and easily functionalized [24]. Per our survey, mechanical techniques such as grinding are among the most advantageous methods because of their simple procedure and low chemical consumption. In this study, α-Fe2O3 nanoparticles reported elsewhere were used to remove eosin yellow under visible light irradiation. Additionally, Fe2O3 nanoparticles attached to polyurethane polymer (PU) were investigated for their photocatalytic activity on methylene blue, methyl orange, and indigo carmine.


## 2. Experimental

### 2.1. Materials

All materials and solvents were obtained from commercial sources (Sisco Research Laboratories Pvt. Ltd., India, Sigma Aldrich, and Abhishek Enterprise Pvt. Ltd.) and used unchanged. Nonahydrate iron nitrate (extra pure, 99%), ammonium bicarbonate (extra pure AR, 99%), hydrogen peroxide (30%), sodium persulphate (extra pure, 99%), polyurethane foam, eosin yellowish, methylene blue, methyl orange and indigo carmine (dye content, ∼99%). All measurements were performed with milli-Q water and spectroscopic-grade solvents. The optical properties measurements were carried out using a JASCO V.670 spectrophotometer for PL spectra, JASCO FT/4700 spectrophotometer for FT-IR spectra, and JASCO UV/VIS/NIR Spectrometer for UV-vis DRS analysis. The SEM images and EDS spectra were captured by using a field emission gun, a Nano Nova Scanning Electron Microscope (FEG-SEM) 450 with EDAX (FESEM) with an accelerating voltage ranging from 20V to 30 kV. Renishaw InVia Raman Spectroscopy was used to record Raman spectra. The X-ray diffraction pattern was measured using an X-ray diffractometer (GNR APD 2000 PRO) with a Cu-K light source. For the analysis of total organic carbon in treated dye solutions, OI Analytical Aurora model 1030, TOC instrument, was used.


### 2.2. Synthesis of Fe2O3 Nanoparticles

Fe2O3 nanoparticles were synthesized by grinding 2 g of iron nitrate with 1 g of Ammonium Bicarbonate route [25]. The reddish residue was washed several times with ethanol, followed by distilled water. The nanoparticles were collected, dried in a hot air oven at 100°C, and then calcined for 2 hours at 300°C. PU-Fe2O3 was synthesized by mixing 40 ml of polyurethane foam and 200 mg of Fe2O3 nanoparticles in accordance with the procedure shown in Figure 1.Figure 1
Synthesis of Fe2O3 nanoparticles and PU-Fe2O3 membrane.


### 2.3. Characterization

#### 2.3.1. UV-Vis DRS Analysis

Using a JASCO V-670 spectrophotometer, the absorbance spectra of the as-prepared Fe2O3 nanoparticles were measured using UV-Vis diffused reflectance spectroscopy. The absorbance spectra from DRS measurements are shown in Figure 2(a), with maximum absorbance at 503 nm. The absorption edge of the nanoparticles synthesized demonstrates that the composites can be excited in the visible region. The spectra of the catalyst revealed a high absorbance with a direct bandgap of 1.5 eV (Figure 2(b)).Figure 2
(a) UV-Vis diffuse reflectance spectra, (b) direct bandgap, (c) Fourier transform infrared analysis (FT-IR), and (d) photoluminescence spectra of Fe2O3 nanoparticles.
(a)(b)(c)(d)Fourier-transform infrared (FT-IR) spectroscopy was used to examine the detailed chemical interaction and quality of the as-prepared Fe2O3 nanoparticles. Figure 2(c) illustrates several well-defined absorption bands in the FTIR spectra. The absorption band at 3220.5 cm−1 is caused by the O-H stretching vibration of the H2O molecule. The absorption band at 2275.5 cm−1 can be attributed to the triple bond between carbon and nitrogen (C≡N). The peaks at 1650.7 cm−1 and 995.0 cm−1 could be attributed to the organic solvent’s alkenes (>C=C<) and C−O−C− vibrations. The signal at 809.9 cm−1 is most likely assigned to Fe−O stretching mode.To confirm the separation of photogenerated electrons and holes of the catalysts, the photoluminescence emission spectra of pureα-Fe2O3 were measured. The intensity of PL emission is well understood to be proportional to the rate of recombination of excited electron-hole pairs. Lower intensity indicates that more excited electrons are transferred or trapped, while higher intensity suggests that recombination occurs faster [26, 27]. At 250 nm excitation wavelength, α-Fe2O3 nanoparticles exhibit a narrow emission peak with a maximum of 688 nm (see Figure 2(d)). Rufus et al. achieved the same result when synthesizing α-Fe2O3 nanoparticles for antibacterial and nanofluid applications [28].The X-ray diffraction (XRD) technique was used to assess the crystal structure, phase, and purity of as-synthesized material. Figure3(a) illustrates all of the diffraction peaks in the XRD pattern of as-synthesized material peaks corresponding to (012), (104), (110), (113), (124), (116), (214), (300), and (208) lines in the XRD pattern are well matched with JCPDS file no 33-0664, indicating that the crystal system is pure hematite (α-Fe2O3). Furthermore, the diffraction pattern clearly shows that the XRD peaks are intense and broad, meaning that good crystalline and small-sizeα-Fe2O3 materials are formed. Scherer’s formula (equation (1)) was used to calculate the size of crystallites in synthesized materials.(1)d=0.9λβcosθB,where λ is the X-ray wavelength (1.54056), θ is the Bragg diffraction angle, and β is the line width at half the maximum of the most dominating peak. Using the above equation, the average crystallite size of the materials is 15.27 nm. The percent porosity of the iron nanoparticles was calculated using the following equation [29, 30]:(2)percentage porosity=1×100%.Figure 3
(a) XRD pattern, (b) Raman spectra, and (c) EDS pattern of synthesizedα-Fe2O3 nanoparticles.
(a)(b)(c)db and dx represent the X-ray density and bulk density, respectively. The percent porosity of iron oxide nanoparticles is 37.03%.Raman spectroscopy measurements were used to analyze the chemical composition of the nanoparticle after synthesis. The Raman spectrum of a heavy metal oxide, such as Fe2O3, generally consists of four distinct features, which are as follows: Raman modes with low wavenumber (30–70 cm−1), heavy metal ion vibrations (70–160 cm−1), intermediate bridged anion modes (300–600 cm−1), and nonbridging anion modes (>600 cm−1) [31, 32]. The third and last categories are present in our sample. Figure 3(b) depicts the spectrum obtained from iron oxide nanoparticles in this study. Peaks at 221 cm−1, 287 cm−1, 405, 493 cm−1, 608 cm−1, and 1326 cm−1 correspond to α-Fe2O3. A peak at 659 cm−1 indicates the presence of a trace amount of Fe3O4. These Raman peaks are identical to those reported by a researcher [33]. According to the quantitative analysis by the EDS graph, the material has a relatively high concentration of iron and oxygen. There were no other impurities found (Figure 3(c)).The surface morphologies of the prepared samples were studied using a scanning electron microscope. Figure4 shows an SEM image of a Fe2O3 nanoparticle. The image confirms the uniformity of the phase formation as well as the particle size. The nanoparticles are all spherical, ranging from 30 nm to 100 nm, with an average particle size of 66.84 nm.Figure 4
FESEM image (inset) nanoparticles size.


### 2.4. Photocatalytic Activity Measurements

The photocatalytic performance of Fe2O3 nanoparticles in a photocatalytic reactor with visible lamp irradiation (High-pressure Mercury lamp, 125 watts) at room temperature was investigated. The photocatalytic reaction occurred in 500 ml closed flasks containing 200 ml of an aqueous solution of EY dye at a specific concentration of Fe2O3 nanoparticles. Before irradiation, the suspension was magnetically stirred in the dark for 15 minutes to achieve an adsorption-desorption equilibrium. At regular intervals, 1 mL aliquots from the flask were taken and mixed with 1 ml of deionized water, and the absorbance was measured with a spectrophotometer (Figure 5). The degradation efficiency of the photocatalyst can be expressed as follows:(3)degradation efficiency%=C0-CtC0∗100%.Figure 5
Photocatalytic reactor setup, (a) before treatment, (b) during treatment, and (c) after treatment of eosin yellowish dye.
(a)(b)(c)C0 represents the dye concentration at adsorption equilibrium, and Ct represents the residual pollutant concentration at different illumination intervals [34–36]. Except for the effect of time exposure and the effect of the light source, which is 100 and 75 ppm for dye solution and catalyst quantity, respectively, the catalyst dose of 75 ppm and EY dye concentration of 75 ppm were chosen for the entire study.


#### 2.4.1. Effect of the Light Source

To achieve a high degradation rate, the choice of a light source is an imperative parameter. For 100 ppm dye and 75 ppm iron nanoparticles, degradation occurs almost completely under visible light after 35 minutes of exposure; however, when exposed to visible light, it is reduced by half (Figure6). This confirms the bandgap of the material obtained at 1.5 eV, which corresponds to the visible and near-infrared spectrums. According to Saquib and Muneer, independent of the parameters that contribute to degradation, the light source plays a crucial role in degradation [37].Figure 6
Eosin yellowish degradation studies the effect of light exposure: (a) visible light and (b) UV light.
(a)(b)


#### 2.4.2. Effect of Dye Concentration

Trials with 25, 50, 75, and 100 ppm were performed to explore the influence of dye concentration. The dye concentration and catalyst were both set to 75 ppm. It was found that as the dye solution concentration increased, the photocatalytic degradation rate decreased gradually (Figure7(a)). This could be due to more dye molecules being adsorbed on the outer layer of Fe2O3. As a result, this represses the activity of the particles, diminishing the receptive OH• and O2•2 free radicals attacking the dye molecules and photodegradation achievement. Increasing the initial dye concentration increases the chance of interactions between dye atoms and oxidizing species. Furthermore, due to the high dye concentration, a large amount of visible radiation may be consumed by dye molecules, reducing the amount of radiation penetrating the semiconductor. Finally, as the concentration of • OH and O2•− radicals decreases so does the effectiveness of the photocatalyst degradation response [38, 39].Figure 7
(a) Effect of dye concentration, (b) effect of catalyst dosage, (c) effect of temperature, and (d) effect of pH on eosin yellowish removable after 15 min exposure time.
(a)(b)(c)(d)


#### 2.4.3. Effect of Catalyst Dosage

In the presence of visible light, the effect of Fe2O3 dosage on color removal was investigated, as shown in Figure 7(b). Similarly, increasing the particle amount speeded up photodegradation. The maximum removal rate was obtained at 100 ppm Fe2O3. Following that, the rate declined to 150 ppm. This demonstrates that the catalyst dosage is an important variable affecting the photocatalytic dye’s removal. The reduction occurred by increased suspension opacity caused by an abundance of Fe2O3 particles. The main reason is that light penetration is reduced by increasing the amount of photocatalyst. Furthermore, exceeding the ideal photocatalyst concentration could cause nanoparticle coagulation, resulting in less surface area and, thus, less photon retention, slowing the rate of photocatalyst degradation [38, 40–42].


#### 2.4.4. Effect of Temperature

The solubility and mobility of dye molecules increase as the temperature rises, allowing them to interact more effectively with the active sites on the adsorbents’ surfaces. The dissolved oxygen in the solution decreases when the temperature rises, which prevents the nanoparticles from oxidizing. A dye molecule’s penetration is also enhanced by temperature, which affects activation energy and swelling within the adsorbent structure [43]. Eosin yellowish degradation was observed at 45°C (Figure 7(c)). Other researchers have found a similar effect of temperature on dye decolorization. Increasing the dye solution temperature from 30 to 50°C results in maximum degradation of the dye [43, 44].


#### 2.4.5. Effect of pH

The pH of the solution is one of the essential regulating parameters in dye degradation. The pH effect can be described using the catalyst’s point of zero charge. Synthetic Fe-oxides typically have a point of zero charge (PZC) between pH 7 and 9. When the pH falls below pHpzc, the catalyst surface becomes positively charged, favoring electrostatic interactions with anionic dyes. When the pH of cationic dye exceeds pHpzc, electrostatic interaction is observed [45]. This study assessed the effect of pH on the degradation of EY dye by Fe2O3 at 2, 6, 9, and 12 after 15 minutes (Figure 7(d)). The findings revealed that the efficiency of EY degradation is greater at pH 6 (10% greater than pH 12). It has been discovered. However, those hydroxyl radicals are formed due to the interaction of OH- and h+, essential oxidizing species at lower pH levels.In contrast, hydroxyl radicals predominate at neutral or higher pH levels. High pH values generally prevent the retention of anionic dyes with a negative charge available on the photocatalyst’s outer layer. As a result, it is strongly recommended that pH remain a pioneer in photocatalytic dye degradation [46–48].


#### 2.4.6. Effect of Time

For 35 minutes, the effect of time exposure was studied for 100 ppm dye solution and 75 ppm nanoparticles. The absorbance peak was gradually reduced by increasing the time, as shown in Figure8(a). After 35 minutes, the degradation of eosin reached nearly 100%. The following equation estimates the pseudofirst-order kinetics and kinetic rate constant:(4)-lnC0Ct=kt.Figure 8
(a) Eosin yellowish degradation at different interval times and (b) the corresponding kinetic linear simulation curves (ln(C0/Ct) vs. time).
(a)(b)The curve is nearly linear curve fitting. The linear logarithm plot versus irradiation time indicates that the photodegradation reaction approximates first-order kinetics with a rate constant (K) = 0.08 min−1. Based on these “k” values, it can be confirmed that Fe2O3 has excellent photocatalytic activity (Figure 8(b)).


#### 2.4.7. Effect of Hydrogen Peroxide

According to photocatalytic degradation studies, H2O2 concentration is a critical variable that can significantly impact color removable. Adding H2O2 as an oxidant alongside visible light and Fe2O3 increased productivity significantly. When a light source with a frequency similar to hydrogen peroxide is absorbed, H2O2 produces •OH radicals (equations (5), (6). In the photooxidation cycle, a conjugation of Fe2O3 and H2O2 is required to achieve high efficiency in a short enlightenment period. The combination of light irradiation, H2O2, and Fe2O3 demonstrated the most excellent photodegradation rate (Figure 9(a)). •OH radicals produced on the catalyst’s outer layer and those produced by the interaction of light and H2O2 oxidize dye molecules (equations (5), (6). As a result, experiments were conducted with differing volumes of H2O2 (30%) ranging from 0.5 to 8 ml at 75 ppm dye solution and 75 ppm catalyst. As shown in Figure 8(a), the initial rate of dye degradation increases significantly by ∼90% without H2O2 and ∼100% with H2O2. This aspect clearly explains the impact of H2O2 as an electron acceptor, as seen in equation (7), and may be due to a delay in the electron-hole recombination process following the generation of • OH by H2O2 on the consumption of an electron from the conduction band [49–55].(5)H2O⟶12H2+•OH(6)H2O2⟶2•OH(7)Fe2O3e−+H2O2⟶OH•+OH−Figure 9
(a) Effect of hydrogen peroxide and (b) effect of potassium persulphate on eosin yellowish removable after 10 min exposure time.
(a)(b)


#### 2.4.8. Effect of Potassium Persulphate

The persulphate ion improves the efficiencies of EY photodegradation significantly. Figure9(b) illustrates the influence of sodium persulphate at concentrations ranging from 25 to 300 ppm. As the amount of K2S2O8 increases, so does the rate of degradation of eosin. After 15 minutes of visible light irradiation, the 200 and 300 ppm K2S2O8 were 100% removable. Because sodium persulphate acts as an electron trap, the reactive radical intermediate SO4•− is formed (equation (8)). The sulfate radical anion is a strong oxidizing agent that removes electrons from neutral molecules such as water and produces the hydroxyl radical (equation (9)).(8)Fe2O3e−+S2O82-⟶SO4•−+SO42-(9)SO4•−+H2O⟶OH•+SO42−+H+Conversely, persulphate acts as an oxidant and an electron scavenger, preventing (e−/h+) recombination at the semiconductor surface. As a result, the faster photodegradation rate in the presence of persulphate ion is attributed to the formation of reactive sulfate radical anion, which generates a highly oxidative hydroxyl radical capable of removing the color molecules [11, 41, 56].


#### 2.4.9. PU-Fe2O3Membrane-Based Photocatalysis for Dye Degradation

As a part of this study, we have successfully degraded methylene blue (MB), methyl orange (MO), and indigo carmine (IC) using square cut-upPU-Fe2O3, as we described above. As a result of the first cycle of treatment with MB, the percentage of degradation was 89.23% (Figure 10(a)), while the percentage of degradation for the second cycle of treatment with MO was 91.23% (Figure 10(b)), and for the third cycle of treatment with IC was 83.51% (Figure 10(c)). Additionally, after 150 minutes of treatment under visible light, PU-Fe2O3 was able to remove 66% of carbon from MB, 70% from MO, and 79% from IC after 150 minutes of treatment under visible light (Figure 10(d)). Immobilizing iron nanoparticles on the polyurethane surface does not affect the catalytic performance of iron nanoparticles, but this material has the advantage of being reusable multiple times without difficulty.Figure 10
(a) MB, (b) MO, (c) IC degradation by PU-Fe2O3 membrane after, (d) organic carbon removable after 150 min (TOC data).
(a)(b)(c)(d)


## 2.1. Materials

All materials and solvents were obtained from commercial sources (Sisco Research Laboratories Pvt. Ltd., India, Sigma Aldrich, and Abhishek Enterprise Pvt. Ltd.) and used unchanged. Nonahydrate iron nitrate (extra pure, 99%), ammonium bicarbonate (extra pure AR, 99%), hydrogen peroxide (30%), sodium persulphate (extra pure, 99%), polyurethane foam, eosin yellowish, methylene blue, methyl orange and indigo carmine (dye content, ∼99%). All measurements were performed with milli-Q water and spectroscopic-grade solvents. The optical properties measurements were carried out using a JASCO V.670 spectrophotometer for PL spectra, JASCO FT/4700 spectrophotometer for FT-IR spectra, and JASCO UV/VIS/NIR Spectrometer for UV-vis DRS analysis. The SEM images and EDS spectra were captured by using a field emission gun, a Nano Nova Scanning Electron Microscope (FEG-SEM) 450 with EDAX (FESEM) with an accelerating voltage ranging from 20V to 30 kV. Renishaw InVia Raman Spectroscopy was used to record Raman spectra. The X-ray diffraction pattern was measured using an X-ray diffractometer (GNR APD 2000 PRO) with a Cu-K light source. For the analysis of total organic carbon in treated dye solutions, OI Analytical Aurora model 1030, TOC instrument, was used.


## 2.2. Synthesis of Fe2O3 Nanoparticles

Fe2O3 nanoparticles were synthesized by grinding 2 g of iron nitrate with 1 g of Ammonium Bicarbonate route [25]. The reddish residue was washed several times with ethanol, followed by distilled water. The nanoparticles were collected, dried in a hot air oven at 100°C, and then calcined for 2 hours at 300°C. PU-Fe2O3 was synthesized by mixing 40 ml of polyurethane foam and 200 mg of Fe2O3 nanoparticles in accordance with the procedure shown in Figure 1.Figure 1
Synthesis of Fe2O3 nanoparticles and PU-Fe2O3 membrane.


## 2.3. Characterization

### 2.3.1. UV-Vis DRS Analysis

Using a JASCO V-670 spectrophotometer, the absorbance spectra of the as-prepared Fe2O3 nanoparticles were measured using UV-Vis diffused reflectance spectroscopy. The absorbance spectra from DRS measurements are shown in Figure 2(a), with maximum absorbance at 503 nm. The absorption edge of the nanoparticles synthesized demonstrates that the composites can be excited in the visible region. The spectra of the catalyst revealed a high absorbance with a direct bandgap of 1.5 eV (Figure 2(b)).Figure 2
(a) UV-Vis diffuse reflectance spectra, (b) direct bandgap, (c) Fourier transform infrared analysis (FT-IR), and (d) photoluminescence spectra of Fe2O3 nanoparticles.
(a)(b)(c)(d)Fourier-transform infrared (FT-IR) spectroscopy was used to examine the detailed chemical interaction and quality of the as-prepared Fe2O3 nanoparticles. Figure 2(c) illustrates several well-defined absorption bands in the FTIR spectra. The absorption band at 3220.5 cm−1 is caused by the O-H stretching vibration of the H2O molecule. The absorption band at 2275.5 cm−1 can be attributed to the triple bond between carbon and nitrogen (C≡N). The peaks at 1650.7 cm−1 and 995.0 cm−1 could be attributed to the organic solvent’s alkenes (>C=C<) and C−O−C− vibrations. The signal at 809.9 cm−1 is most likely assigned to Fe−O stretching mode.To confirm the separation of photogenerated electrons and holes of the catalysts, the photoluminescence emission spectra of pureα-Fe2O3 were measured. The intensity of PL emission is well understood to be proportional to the rate of recombination of excited electron-hole pairs. Lower intensity indicates that more excited electrons are transferred or trapped, while higher intensity suggests that recombination occurs faster [26, 27]. At 250 nm excitation wavelength, α-Fe2O3 nanoparticles exhibit a narrow emission peak with a maximum of 688 nm (see Figure 2(d)). Rufus et al. achieved the same result when synthesizing α-Fe2O3 nanoparticles for antibacterial and nanofluid applications [28].The X-ray diffraction (XRD) technique was used to assess the crystal structure, phase, and purity of as-synthesized material. Figure3(a) illustrates all of the diffraction peaks in the XRD pattern of as-synthesized material peaks corresponding to (012), (104), (110), (113), (124), (116), (214), (300), and (208) lines in the XRD pattern are well matched with JCPDS file no 33-0664, indicating that the crystal system is pure hematite (α-Fe2O3). Furthermore, the diffraction pattern clearly shows that the XRD peaks are intense and broad, meaning that good crystalline and small-sizeα-Fe2O3 materials are formed. Scherer’s formula (equation (1)) was used to calculate the size of crystallites in synthesized materials.(1)d=0.9λβcosθB,where λ is the X-ray wavelength (1.54056), θ is the Bragg diffraction angle, and β is the line width at half the maximum of the most dominating peak. Using the above equation, the average crystallite size of the materials is 15.27 nm. The percent porosity of the iron nanoparticles was calculated using the following equation [29, 30]:(2)percentage porosity=1×100%.Figure 3
(a) XRD pattern, (b) Raman spectra, and (c) EDS pattern of synthesizedα-Fe2O3 nanoparticles.
(a)(b)(c)db and dx represent the X-ray density and bulk density, respectively. The percent porosity of iron oxide nanoparticles is 37.03%.Raman spectroscopy measurements were used to analyze the chemical composition of the nanoparticle after synthesis. The Raman spectrum of a heavy metal oxide, such as Fe2O3, generally consists of four distinct features, which are as follows: Raman modes with low wavenumber (30–70 cm−1), heavy metal ion vibrations (70–160 cm−1), intermediate bridged anion modes (300–600 cm−1), and nonbridging anion modes (>600 cm−1) [31, 32]. The third and last categories are present in our sample. Figure 3(b) depicts the spectrum obtained from iron oxide nanoparticles in this study. Peaks at 221 cm−1, 287 cm−1, 405, 493 cm−1, 608 cm−1, and 1326 cm−1 correspond to α-Fe2O3. A peak at 659 cm−1 indicates the presence of a trace amount of Fe3O4. These Raman peaks are identical to those reported by a researcher [33]. According to the quantitative analysis by the EDS graph, the material has a relatively high concentration of iron and oxygen. There were no other impurities found (Figure 3(c)).The surface morphologies of the prepared samples were studied using a scanning electron microscope. Figure4 shows an SEM image of a Fe2O3 nanoparticle. The image confirms the uniformity of the phase formation as well as the particle size. The nanoparticles are all spherical, ranging from 30 nm to 100 nm, with an average particle size of 66.84 nm.Figure 4
FESEM image (inset) nanoparticles size.


## 2.3.1. UV-Vis DRS Analysis

Using a JASCO V-670 spectrophotometer, the absorbance spectra of the as-prepared Fe2O3 nanoparticles were measured using UV-Vis diffused reflectance spectroscopy. The absorbance spectra from DRS measurements are shown in Figure 2(a), with maximum absorbance at 503 nm. The absorption edge of the nanoparticles synthesized demonstrates that the composites can be excited in the visible region. The spectra of the catalyst revealed a high absorbance with a direct bandgap of 1.5 eV (Figure 2(b)).Figure 2
(a) UV-Vis diffuse reflectance spectra, (b) direct bandgap, (c) Fourier transform infrared analysis (FT-IR), and (d) photoluminescence spectra of Fe2O3 nanoparticles.
(a)(b)(c)(d)Fourier-transform infrared (FT-IR) spectroscopy was used to examine the detailed chemical interaction and quality of the as-prepared Fe2O3 nanoparticles. Figure 2(c) illustrates several well-defined absorption bands in the FTIR spectra. The absorption band at 3220.5 cm−1 is caused by the O-H stretching vibration of the H2O molecule. The absorption band at 2275.5 cm−1 can be attributed to the triple bond between carbon and nitrogen (C≡N). The peaks at 1650.7 cm−1 and 995.0 cm−1 could be attributed to the organic solvent’s alkenes (>C=C<) and C−O−C− vibrations. The signal at 809.9 cm−1 is most likely assigned to Fe−O stretching mode.To confirm the separation of photogenerated electrons and holes of the catalysts, the photoluminescence emission spectra of pureα-Fe2O3 were measured. The intensity of PL emission is well understood to be proportional to the rate of recombination of excited electron-hole pairs. Lower intensity indicates that more excited electrons are transferred or trapped, while higher intensity suggests that recombination occurs faster [26, 27]. At 250 nm excitation wavelength, α-Fe2O3 nanoparticles exhibit a narrow emission peak with a maximum of 688 nm (see Figure 2(d)). Rufus et al. achieved the same result when synthesizing α-Fe2O3 nanoparticles for antibacterial and nanofluid applications [28].The X-ray diffraction (XRD) technique was used to assess the crystal structure, phase, and purity of as-synthesized material. Figure3(a) illustrates all of the diffraction peaks in the XRD pattern of as-synthesized material peaks corresponding to (012), (104), (110), (113), (124), (116), (214), (300), and (208) lines in the XRD pattern are well matched with JCPDS file no 33-0664, indicating that the crystal system is pure hematite (α-Fe2O3). Furthermore, the diffraction pattern clearly shows that the XRD peaks are intense and broad, meaning that good crystalline and small-sizeα-Fe2O3 materials are formed. Scherer’s formula (equation (1)) was used to calculate the size of crystallites in synthesized materials.(1)d=0.9λβcosθB,where λ is the X-ray wavelength (1.54056), θ is the Bragg diffraction angle, and β is the line width at half the maximum of the most dominating peak. Using the above equation, the average crystallite size of the materials is 15.27 nm. The percent porosity of the iron nanoparticles was calculated using the following equation [29, 30]:(2)percentage porosity=1×100%.Figure 3
(a) XRD pattern, (b) Raman spectra, and (c) EDS pattern of synthesizedα-Fe2O3 nanoparticles.
(a)(b)(c)db and dx represent the X-ray density and bulk density, respectively. The percent porosity of iron oxide nanoparticles is 37.03%.Raman spectroscopy measurements were used to analyze the chemical composition of the nanoparticle after synthesis. The Raman spectrum of a heavy metal oxide, such as Fe2O3, generally consists of four distinct features, which are as follows: Raman modes with low wavenumber (30–70 cm−1), heavy metal ion vibrations (70–160 cm−1), intermediate bridged anion modes (300–600 cm−1), and nonbridging anion modes (>600 cm−1) [31, 32]. The third and last categories are present in our sample. Figure 3(b) depicts the spectrum obtained from iron oxide nanoparticles in this study. Peaks at 221 cm−1, 287 cm−1, 405, 493 cm−1, 608 cm−1, and 1326 cm−1 correspond to α-Fe2O3. A peak at 659 cm−1 indicates the presence of a trace amount of Fe3O4. These Raman peaks are identical to those reported by a researcher [33]. According to the quantitative analysis by the EDS graph, the material has a relatively high concentration of iron and oxygen. There were no other impurities found (Figure 3(c)).The surface morphologies of the prepared samples were studied using a scanning electron microscope. Figure4 shows an SEM image of a Fe2O3 nanoparticle. The image confirms the uniformity of the phase formation as well as the particle size. The nanoparticles are all spherical, ranging from 30 nm to 100 nm, with an average particle size of 66.84 nm.Figure 4
FESEM image (inset) nanoparticles size.


## 2.4. Photocatalytic Activity Measurements

The photocatalytic performance of Fe2O3 nanoparticles in a photocatalytic reactor with visible lamp irradiation (High-pressure Mercury lamp, 125 watts) at room temperature was investigated. The photocatalytic reaction occurred in 500 ml closed flasks containing 200 ml of an aqueous solution of EY dye at a specific concentration of Fe2O3 nanoparticles. Before irradiation, the suspension was magnetically stirred in the dark for 15 minutes to achieve an adsorption-desorption equilibrium. At regular intervals, 1 mL aliquots from the flask were taken and mixed with 1 ml of deionized water, and the absorbance was measured with a spectrophotometer (Figure 5). The degradation efficiency of the photocatalyst can be expressed as follows:(3)degradation efficiency%=C0-CtC0∗100%.Figure 5
Photocatalytic reactor setup, (a) before treatment, (b) during treatment, and (c) after treatment of eosin yellowish dye.
(a)(b)(c)C0 represents the dye concentration at adsorption equilibrium, and Ct represents the residual pollutant concentration at different illumination intervals [34–36]. Except for the effect of time exposure and the effect of the light source, which is 100 and 75 ppm for dye solution and catalyst quantity, respectively, the catalyst dose of 75 ppm and EY dye concentration of 75 ppm were chosen for the entire study.


### 2.4.1. Effect of the Light Source

To achieve a high degradation rate, the choice of a light source is an imperative parameter. For 100 ppm dye and 75 ppm iron nanoparticles, degradation occurs almost completely under visible light after 35 minutes of exposure; however, when exposed to visible light, it is reduced by half (Figure6). This confirms the bandgap of the material obtained at 1.5 eV, which corresponds to the visible and near-infrared spectrums. According to Saquib and Muneer, independent of the parameters that contribute to degradation, the light source plays a crucial role in degradation [37].Figure 6
Eosin yellowish degradation studies the effect of light exposure: (a) visible light and (b) UV light.
(a)(b)


### 2.4.2. Effect of Dye Concentration

Trials with 25, 50, 75, and 100 ppm were performed to explore the influence of dye concentration. The dye concentration and catalyst were both set to 75 ppm. It was found that as the dye solution concentration increased, the photocatalytic degradation rate decreased gradually (Figure7(a)). This could be due to more dye molecules being adsorbed on the outer layer of Fe2O3. As a result, this represses the activity of the particles, diminishing the receptive OH• and O2•2 free radicals attacking the dye molecules and photodegradation achievement. Increasing the initial dye concentration increases the chance of interactions between dye atoms and oxidizing species. Furthermore, due to the high dye concentration, a large amount of visible radiation may be consumed by dye molecules, reducing the amount of radiation penetrating the semiconductor. Finally, as the concentration of • OH and O2•− radicals decreases so does the effectiveness of the photocatalyst degradation response [38, 39].Figure 7
(a) Effect of dye concentration, (b) effect of catalyst dosage, (c) effect of temperature, and (d) effect of pH on eosin yellowish removable after 15 min exposure time.
(a)(b)(c)(d)


### 2.4.3. Effect of Catalyst Dosage

In the presence of visible light, the effect of Fe2O3 dosage on color removal was investigated, as shown in Figure 7(b). Similarly, increasing the particle amount speeded up photodegradation. The maximum removal rate was obtained at 100 ppm Fe2O3. Following that, the rate declined to 150 ppm. This demonstrates that the catalyst dosage is an important variable affecting the photocatalytic dye’s removal. The reduction occurred by increased suspension opacity caused by an abundance of Fe2O3 particles. The main reason is that light penetration is reduced by increasing the amount of photocatalyst. Furthermore, exceeding the ideal photocatalyst concentration could cause nanoparticle coagulation, resulting in less surface area and, thus, less photon retention, slowing the rate of photocatalyst degradation [38, 40–42].


### 2.4.4. Effect of Temperature

The solubility and mobility of dye molecules increase as the temperature rises, allowing them to interact more effectively with the active sites on the adsorbents’ surfaces. The dissolved oxygen in the solution decreases when the temperature rises, which prevents the nanoparticles from oxidizing. A dye molecule’s penetration is also enhanced by temperature, which affects activation energy and swelling within the adsorbent structure [43]. Eosin yellowish degradation was observed at 45°C (Figure 7(c)). Other researchers have found a similar effect of temperature on dye decolorization. Increasing the dye solution temperature from 30 to 50°C results in maximum degradation of the dye [43, 44].


### 2.4.5. Effect of pH

The pH of the solution is one of the essential regulating parameters in dye degradation. The pH effect can be described using the catalyst’s point of zero charge. Synthetic Fe-oxides typically have a point of zero charge (PZC) between pH 7 and 9. When the pH falls below pHpzc, the catalyst surface becomes positively charged, favoring electrostatic interactions with anionic dyes. When the pH of cationic dye exceeds pHpzc, electrostatic interaction is observed [45]. This study assessed the effect of pH on the degradation of EY dye by Fe2O3 at 2, 6, 9, and 12 after 15 minutes (Figure 7(d)). The findings revealed that the efficiency of EY degradation is greater at pH 6 (10% greater than pH 12). It has been discovered. However, those hydroxyl radicals are formed due to the interaction of OH- and h+, essential oxidizing species at lower pH levels.In contrast, hydroxyl radicals predominate at neutral or higher pH levels. High pH values generally prevent the retention of anionic dyes with a negative charge available on the photocatalyst’s outer layer. As a result, it is strongly recommended that pH remain a pioneer in photocatalytic dye degradation [46–48].


### 2.4.6. Effect of Time

For 35 minutes, the effect of time exposure was studied for 100 ppm dye solution and 75 ppm nanoparticles. The absorbance peak was gradually reduced by increasing the time, as shown in Figure8(a). After 35 minutes, the degradation of eosin reached nearly 100%. The following equation estimates the pseudofirst-order kinetics and kinetic rate constant:(4)-lnC0Ct=kt.Figure 8
(a) Eosin yellowish degradation at different interval times and (b) the corresponding kinetic linear simulation curves (ln(C0/Ct) vs. time).
(a)(b)The curve is nearly linear curve fitting. The linear logarithm plot versus irradiation time indicates that the photodegradation reaction approximates first-order kinetics with a rate constant (K) = 0.08 min−1. Based on these “k” values, it can be confirmed that Fe2O3 has excellent photocatalytic activity (Figure 8(b)).


### 2.4.7. Effect of Hydrogen Peroxide

According to photocatalytic degradation studies, H2O2 concentration is a critical variable that can significantly impact color removable. Adding H2O2 as an oxidant alongside visible light and Fe2O3 increased productivity significantly. When a light source with a frequency similar to hydrogen peroxide is absorbed, H2O2 produces •OH radicals (equations (5), (6). In the photooxidation cycle, a conjugation of Fe2O3 and H2O2 is required to achieve high efficiency in a short enlightenment period. The combination of light irradiation, H2O2, and Fe2O3 demonstrated the most excellent photodegradation rate (Figure 9(a)). •OH radicals produced on the catalyst’s outer layer and those produced by the interaction of light and H2O2 oxidize dye molecules (equations (5), (6). As a result, experiments were conducted with differing volumes of H2O2 (30%) ranging from 0.5 to 8 ml at 75 ppm dye solution and 75 ppm catalyst. As shown in Figure 8(a), the initial rate of dye degradation increases significantly by ∼90% without H2O2 and ∼100% with H2O2. This aspect clearly explains the impact of H2O2 as an electron acceptor, as seen in equation (7), and may be due to a delay in the electron-hole recombination process following the generation of • OH by H2O2 on the consumption of an electron from the conduction band [49–55].(5)H2O⟶12H2+•OH(6)H2O2⟶2•OH(7)Fe2O3e−+H2O2⟶OH•+OH−Figure 9
(a) Effect of hydrogen peroxide and (b) effect of potassium persulphate on eosin yellowish removable after 10 min exposure time.
(a)(b)


### 2.4.8. Effect of Potassium Persulphate

The persulphate ion improves the efficiencies of EY photodegradation significantly. Figure9(b) illustrates the influence of sodium persulphate at concentrations ranging from 25 to 300 ppm. As the amount of K2S2O8 increases, so does the rate of degradation of eosin. After 15 minutes of visible light irradiation, the 200 and 300 ppm K2S2O8 were 100% removable. Because sodium persulphate acts as an electron trap, the reactive radical intermediate SO4•− is formed (equation (8)). The sulfate radical anion is a strong oxidizing agent that removes electrons from neutral molecules such as water and produces the hydroxyl radical (equation (9)).(8)Fe2O3e−+S2O82-⟶SO4•−+SO42-(9)SO4•−+H2O⟶OH•+SO42−+H+Conversely, persulphate acts as an oxidant and an electron scavenger, preventing (e−/h+) recombination at the semiconductor surface. As a result, the faster photodegradation rate in the presence of persulphate ion is attributed to the formation of reactive sulfate radical anion, which generates a highly oxidative hydroxyl radical capable of removing the color molecules [11, 41, 56].


### 2.4.9. PU-Fe2O3Membrane-Based Photocatalysis for Dye Degradation

As a part of this study, we have successfully degraded methylene blue (MB), methyl orange (MO), and indigo carmine (IC) using square cut-upPU-Fe2O3, as we described above. As a result of the first cycle of treatment with MB, the percentage of degradation was 89.23% (Figure 10(a)), while the percentage of degradation for the second cycle of treatment with MO was 91.23% (Figure 10(b)), and for the third cycle of treatment with IC was 83.51% (Figure 10(c)). Additionally, after 150 minutes of treatment under visible light, PU-Fe2O3 was able to remove 66% of carbon from MB, 70% from MO, and 79% from IC after 150 minutes of treatment under visible light (Figure 10(d)). Immobilizing iron nanoparticles on the polyurethane surface does not affect the catalytic performance of iron nanoparticles, but this material has the advantage of being reusable multiple times without difficulty.Figure 10
(a) MB, (b) MO, (c) IC degradation by PU-Fe2O3 membrane after, (d) organic carbon removable after 150 min (TOC data).
(a)(b)(c)(d)


## 2.4.1. Effect of the Light Source

To achieve a high degradation rate, the choice of a light source is an imperative parameter. For 100 ppm dye and 75 ppm iron nanoparticles, degradation occurs almost completely under visible light after 35 minutes of exposure; however, when exposed to visible light, it is reduced by half (Figure6). This confirms the bandgap of the material obtained at 1.5 eV, which corresponds to the visible and near-infrared spectrums. According to Saquib and Muneer, independent of the parameters that contribute to degradation, the light source plays a crucial role in degradation [37].Figure 6
Eosin yellowish degradation studies the effect of light exposure: (a) visible light and (b) UV light.
(a)(b)


## 2.4.2. Effect of Dye Concentration

Trials with 25, 50, 75, and 100 ppm were performed to explore the influence of dye concentration. The dye concentration and catalyst were both set to 75 ppm. It was found that as the dye solution concentration increased, the photocatalytic degradation rate decreased gradually (Figure7(a)). This could be due to more dye molecules being adsorbed on the outer layer of Fe2O3. As a result, this represses the activity of the particles, diminishing the receptive OH• and O2•2 free radicals attacking the dye molecules and photodegradation achievement. Increasing the initial dye concentration increases the chance of interactions between dye atoms and oxidizing species. Furthermore, due to the high dye concentration, a large amount of visible radiation may be consumed by dye molecules, reducing the amount of radiation penetrating the semiconductor. Finally, as the concentration of • OH and O2•− radicals decreases so does the effectiveness of the photocatalyst degradation response [38, 39].Figure 7
(a) Effect of dye concentration, (b) effect of catalyst dosage, (c) effect of temperature, and (d) effect of pH on eosin yellowish removable after 15 min exposure time.
(a)(b)(c)(d)


## 2.4.3. Effect of Catalyst Dosage

In the presence of visible light, the effect of Fe2O3 dosage on color removal was investigated, as shown in Figure 7(b). Similarly, increasing the particle amount speeded up photodegradation. The maximum removal rate was obtained at 100 ppm Fe2O3. Following that, the rate declined to 150 ppm. This demonstrates that the catalyst dosage is an important variable affecting the photocatalytic dye’s removal. The reduction occurred by increased suspension opacity caused by an abundance of Fe2O3 particles. The main reason is that light penetration is reduced by increasing the amount of photocatalyst. Furthermore, exceeding the ideal photocatalyst concentration could cause nanoparticle coagulation, resulting in less surface area and, thus, less photon retention, slowing the rate of photocatalyst degradation [38, 40–42].


## 2.4.4. Effect of Temperature

The solubility and mobility of dye molecules increase as the temperature rises, allowing them to interact more effectively with the active sites on the adsorbents’ surfaces. The dissolved oxygen in the solution decreases when the temperature rises, which prevents the nanoparticles from oxidizing. A dye molecule’s penetration is also enhanced by temperature, which affects activation energy and swelling within the adsorbent structure [43]. Eosin yellowish degradation was observed at 45°C (Figure 7(c)). Other researchers have found a similar effect of temperature on dye decolorization. Increasing the dye solution temperature from 30 to 50°C results in maximum degradation of the dye [43, 44].


## 2.4.5. Effect of pH

The pH of the solution is one of the essential regulating parameters in dye degradation. The pH effect can be described using the catalyst’s point of zero charge. Synthetic Fe-oxides typically have a point of zero charge (PZC) between pH 7 and 9. When the pH falls below pHpzc, the catalyst surface becomes positively charged, favoring electrostatic interactions with anionic dyes. When the pH of cationic dye exceeds pHpzc, electrostatic interaction is observed [45]. This study assessed the effect of pH on the degradation of EY dye by Fe2O3 at 2, 6, 9, and 12 after 15 minutes (Figure 7(d)). The findings revealed that the efficiency of EY degradation is greater at pH 6 (10% greater than pH 12). It has been discovered. However, those hydroxyl radicals are formed due to the interaction of OH- and h+, essential oxidizing species at lower pH levels.In contrast, hydroxyl radicals predominate at neutral or higher pH levels. High pH values generally prevent the retention of anionic dyes with a negative charge available on the photocatalyst’s outer layer. As a result, it is strongly recommended that pH remain a pioneer in photocatalytic dye degradation [46–48].


## 2.4.6. Effect of Time

For 35 minutes, the effect of time exposure was studied for 100 ppm dye solution and 75 ppm nanoparticles. The absorbance peak was gradually reduced by increasing the time, as shown in Figure8(a). After 35 minutes, the degradation of eosin reached nearly 100%. The following equation estimates the pseudofirst-order kinetics and kinetic rate constant:(4)-lnC0Ct=kt.Figure 8
(a) Eosin yellowish degradation at different interval times and (b) the corresponding kinetic linear simulation curves (ln(C0/Ct) vs. time).
(a)(b)The curve is nearly linear curve fitting. The linear logarithm plot versus irradiation time indicates that the photodegradation reaction approximates first-order kinetics with a rate constant (K) = 0.08 min−1. Based on these “k” values, it can be confirmed that Fe2O3 has excellent photocatalytic activity (Figure 8(b)).


## 2.4.7. Effect of Hydrogen Peroxide

According to photocatalytic degradation studies, H2O2 concentration is a critical variable that can significantly impact color removable. Adding H2O2 as an oxidant alongside visible light and Fe2O3 increased productivity significantly. When a light source with a frequency similar to hydrogen peroxide is absorbed, H2O2 produces •OH radicals (equations (5), (6). In the photooxidation cycle, a conjugation of Fe2O3 and H2O2 is required to achieve high efficiency in a short enlightenment period. The combination of light irradiation, H2O2, and Fe2O3 demonstrated the most excellent photodegradation rate (Figure 9(a)). •OH radicals produced on the catalyst’s outer layer and those produced by the interaction of light and H2O2 oxidize dye molecules (equations (5), (6). As a result, experiments were conducted with differing volumes of H2O2 (30%) ranging from 0.5 to 8 ml at 75 ppm dye solution and 75 ppm catalyst. As shown in Figure 8(a), the initial rate of dye degradation increases significantly by ∼90% without H2O2 and ∼100% with H2O2. This aspect clearly explains the impact of H2O2 as an electron acceptor, as seen in equation (7), and may be due to a delay in the electron-hole recombination process following the generation of • OH by H2O2 on the consumption of an electron from the conduction band [49–55].(5)H2O⟶12H2+•OH(6)H2O2⟶2•OH(7)Fe2O3e−+H2O2⟶OH•+OH−Figure 9
(a) Effect of hydrogen peroxide and (b) effect of potassium persulphate on eosin yellowish removable after 10 min exposure time.
(a)(b)


## 2.4.8. Effect of Potassium Persulphate

The persulphate ion improves the efficiencies of EY photodegradation significantly. Figure9(b) illustrates the influence of sodium persulphate at concentrations ranging from 25 to 300 ppm. As the amount of K2S2O8 increases, so does the rate of degradation of eosin. After 15 minutes of visible light irradiation, the 200 and 300 ppm K2S2O8 were 100% removable. Because sodium persulphate acts as an electron trap, the reactive radical intermediate SO4•− is formed (equation (8)). The sulfate radical anion is a strong oxidizing agent that removes electrons from neutral molecules such as water and produces the hydroxyl radical (equation (9)).(8)Fe2O3e−+S2O82-⟶SO4•−+SO42-(9)SO4•−+H2O⟶OH•+SO42−+H+Conversely, persulphate acts as an oxidant and an electron scavenger, preventing (e−/h+) recombination at the semiconductor surface. As a result, the faster photodegradation rate in the presence of persulphate ion is attributed to the formation of reactive sulfate radical anion, which generates a highly oxidative hydroxyl radical capable of removing the color molecules [11, 41, 56].


## 2.4.9. PU-Fe2O3Membrane-Based Photocatalysis for Dye Degradation

As a part of this study, we have successfully degraded methylene blue (MB), methyl orange (MO), and indigo carmine (IC) using square cut-upPU-Fe2O3, as we described above. As a result of the first cycle of treatment with MB, the percentage of degradation was 89.23% (Figure 10(a)), while the percentage of degradation for the second cycle of treatment with MO was 91.23% (Figure 10(b)), and for the third cycle of treatment with IC was 83.51% (Figure 10(c)). Additionally, after 150 minutes of treatment under visible light, PU-Fe2O3 was able to remove 66% of carbon from MB, 70% from MO, and 79% from IC after 150 minutes of treatment under visible light (Figure 10(d)). Immobilizing iron nanoparticles on the polyurethane surface does not affect the catalytic performance of iron nanoparticles, but this material has the advantage of being reusable multiple times without difficulty.Figure 10
(a) MB, (b) MO, (c) IC degradation by PU-Fe2O3 membrane after, (d) organic carbon removable after 150 min (TOC data).
(a)(b)(c)(d)


## 3. Conclusion

According to the findings of this study, the initial dye concentration, catalyst dosage, pH, and exposure time all influenced the rate of degradation of eosin yellowish. For effective removal (95%) of 75 ppm eosin yellowish, 75 ppm Fe2O3 nanoparticles, and pH 6, a 15-minute exposure time is required. Furthermore, only 0.5 ml H2O2 (30% concentration) is required to increase eosin yellowish photocatalytic degradation. When K2S2O8 was used, the same observation was made. Additionally, the reaction followed pseudofirst-order kinetics in terms of dye photo-removability. Also, the subsequent degradation of methylene blue, methyl orange, and indigo carmine with the PU-Fe2O3 membrane is almost as efficient as when the nanoparticles are used alone. As a result, the material can be readily degraded without any difficulties in removing and reusing it. Furthermore, an analysis of the total organic carbon (TOC) of the aforementioned dyes confirms the conclusions above.



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*Source: 1292762-2023-02-17.xml*