Solar-Light-Driven Photodegradation of Paracetamol Using Green-Synthesized TiO₂ Nanoparticles from Eucalyptus globulus Leaf Extract
Rasha Waleed Al-Khateeb*
| Raghad N. Mohammed | Abeer I. Alwared | Noor A. Mohammed
© 2026 The authors. This article is published by IIETA and is licensed under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/).
OPEN ACCESS
In this study, Eucalyptus globulus leaf extract was utilized to fabricate TiO2 nanoparticles (denoted as E-TiO2) by using a green synthesis method. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) techniques were used to confirm the formation, particle size, and shape of the synthesized E-TiO2 particles. In the presence of sunlight, the efficacy of E-TiO2 nanoparticles was examined for their photocatalytic decomposition of paracetamol (PC) residues from aqueous solutions at different operating conditions, including pH (3, 5, 7, and 11), initial PC dosage (10, 25, and 100) mg/L, E-TiO2 dosage (20, 40, and 100) mg/L, concentration of H2O2 (150, 250, 400, and 600) mg/L. At the best operating conditions of pH 7, E-TiO₂ dosage 40 mg/L, PC dosage 10 mg/L, and H₂O₂ concentration 250 mg/L, respectively, the proposed E-TiO2 demonstrated high efficiency in the treatment of PC contaminated water 94.13% while commercial TiO2 achieved only 78.23% at the same degradation time (120 min). Additionally, a first-order kinetics model with R2 ˃ 98% was followed by the reaction. The findings demonstrated that E-TiO2 nanocomposite exhibits commendable efficiency in the degradation of PC, with its relatively straightforward synthesis rendering it an appropriate nanoparticle for the removal of pharmaceutical residues, alongside remarkable reusability and stability, evidenced by the negligible loss in photocatalytic activity over multiple cycles.
green synthesis, eucalyptus leaf, TiO2, paracetamol, solar light
Pharmaceuticals are extensively used in fishing, medicine, animal husbandry, and other areas, which has resulted in their constant presence in the environment and possible threats to human health and the ecology. A proportion ranging from approximately 11% to 85% of pharmaceutical compounds is excreted without undergoing metabolic transformation. Even though pharmaceutical chemicals are only found in small amounts in home wastewater, they are mostly between ng L−1 to μg L−1, their chemically stable and physiologically resistant characteristics make their total removal from wastewater treatment systems difficult [1, 2]. The issue is made worse by the COVID-19 pandemic, which the World Health Organization states has caused 5 million deaths and nearly 250 million confirmed cases. Despite the widespread use of medications, especially for symptom relief, controlling COVID-19 remains a significant global issue. Paracetamol (PC) (4-hydroxyacetanilide, 4-acetamidephenol, acetaminophen, or Tylenol) is one such drug used to lower fever and ease COVID-19-related muscle soreness. However, the extensive usage of drugs like acetaminophen contaminates the environment and jeopardizes the biosphere [3, 4]. PC was detected in wastewater treatment facility effluents at amounts as high as 6 μg/L. Due to the growing population and their modern lifestyles, paracetamol concentrations in water and wastewater may increase. The manufacturing of paracetamol has expanded dramatically worldwide as a result of the sharp rise in usage [5]. Different treatment technologies are improved for the elimination of pharmaceuticals, encompassing photocatalysis, electrochemical treatment processes, adsorption, membrane filtration, biological treatment, and disinfection, which is under investigation [6]. However, biological treatment methods often take longer than chemical ones and are ineffective for very persistent pollutants [7, 8]. Thus, due to their high operational cost and low removal efficiency, they are not widely applied. Therefore, Antibiotics' capacity to inhibit bacteria has been improved by the use of advanced oxidation processes (AOPs), which also increased the biodegradability and elimination rate of the antibiotics [9]. In general, advanced oxidation processes (AOPs) degrade pollutants by generating highly reactive species, such as hydroxyl radicals (•OH), sulfate radical (SO4), and superoxide radical (O2•-), which react with pollutants at near diffusion-controlled rates [10]. Among various AOPs, photocatalytic degradation of toxicants has become one of the most promising approaches in green chemistry [11]. Among the many types of catalysts, TiO2 NPs have been used because it has a high surface area, uniform pore size, and highly reactive surface atoms. In aqueous photocatalytic systems, TiO₂ nanoparticles function as catalyst supports. The interaction of water molecules adsorbed on their surfaces significantly affects the surface reaction pathways [12]. The nanoparticles biosynthesis is a green synthetic process, which involves employing reducing agents, that are biologically sourced, i.e. plants and microorganisms. Such an approach is characterized by various important merits such as the safety of the environment, low cost, biocompatibility, renewability, and non-toxicity [13]. To this end, numerous scholars have utilized diverse plant extracts, such as leaves of Zizyphus spina-christi [14], a blend of extracts of Piper betel, Ocimum tenuiflorum, Moringa oleifera, and Coriandrum sativum to synthesize nano-TiO2 [15], and grape leaves [16]. The conversion of bio-based waste into valuable products offers substantial potential for advancing global economic development while simultaneously addressing waste management challenges [17, 18]. There are various benefits of using plant extracts to create nanomaterials: (i) Plant material is easily accessible; (ii) Operational safety; (iii) Minimal running expenses; (iv) The biomolecules present in the extracts' capacity to function as stabilizing, capping, and reducing agents; (v) Removing complex bacterial, fungal, and yeast maintenance; (vi) Quick synthesis methods; (vii) Using eco-friendly procedures; (viii) Creating nanoparticles that are more stable; (ix) The potential for improved control over the nanoparticles' size and shape; (x) Large-scale suitability [19]. Eucalyptus trees are quite widespread throughout China, which can be explained by their high viability, low cost of cultivation, and the abundance of polyphenolic compounds; the utilization of the material of the eucalyptus leaves produces a significant environmental impact with the reduction of waste and the creation of added value when preparing titanium nanoparticles [20]. Many previous studies utilized eucalyptus leaf extract for the synthesis of TiO2 nanoparticles, such as Balaji et al. [12] employed the resulting TiO2 as a catalyst in one-pot, three-component A3 coupling reactions; Torres-Limiñana et al. [21] used them in bacteria inhibition; Uwaya et al. [22] assessed the interaction between efavirenz and TiO2 NPs employed as an analytical nano-vehicle. Our study is concerned with the synthesis of TiO2 NPs prepared from the eucalyptus leaf extract, and testing the ability to degrade PC from aqueous solution by a heterogeneous photocatalyst, investigating the characteristics of the TiO2 NPs via Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Brunauer–Emmett–Teller Surface Area Analysis (BET), and evaluating the PC elimination percentage under various experimental conditions.
2.1 Materials
The chemical materials used in this study are: powdered paracetamol (PC, 99%), and their chemical structures and specifications are provided in Figure 1 and Table 1, respectively. The precursor, Titanium Tetra-Isopropoxide (TTIP), consisted of 95% anatase and 5% rutile phases. Isopropanol and hydrogen peroxide (H₂O₂, 50 w/w%). These materials, requiring no further purification, were obtained from Merck. The pH of the aqueous solutions was adjusted to the desired values using hydrochloric acid or sodium hydroxide.
Figure 1. Paracetamol chemical structure [23]
Table 1. Main properties of paracetamol [24]
|
Parameters |
Character/Value |
|
Molecular formula |
C8H9NO2 |
|
Molar mass |
151.163 g/mol |
|
Water solubility at 25℃ (g/L) |
13.85 |
|
Dissociation constant (pKa) |
9.4 |
2.2 Methods
2.2.1 Leaves extract preparation
Fresh leaves were collected from eucalyptus trees located in Baghdad, Iraq, first washed twice or thrice with tap water then distilled water and dried at ambient temperature during a week in a chamber devoid of dust in a parallel protocol, powdered and 10 g of the fine powder was put in boiling water of 100 mL and left to extract after 15 min to get an aqueous extract. The aqueous extract was filtered, centrifuged at 5000 rpm, and the supernatant was refrigerated at 4℃ to prevent contamination by microbes [12].
2.2.2 Green synthesis of E-TiO2 NPs
E-TiO2 NPs were prepared by dropwise adding 50 mL of eucalyptus leaves extract to a solution of (3 mL of TTIP + 50 mL of ethanol), which was added dropwise in the ratio of 1:1 (v/v). The mixture was stirred constantly for two to three hours until a brownish-yellow precipitate formed, then after the mixture was centrifuged at 10,000 rpm for 15 min and cleaned with ethanol twice times in order to get rid of any remaining contaminants. The brownish-yellow precipitate was thoroughly pulverized with an agate mortar and pestle, dried for 2 hours at 80℃ in a hot air oven, and then calcinated at 500℃ for 3 hours [12].
2.2.3 Procedure and analysis
Batch solar photocatalytic decomposition experiments were performed in a Pyrex mode reactor under natural sunlight (Figure 2). A mirror positioned at the bottom of the Pyrex enhanced irradiation by reflecting additional solar light onto the reaction mixture. On successive sunny days in June and July of 2025, the solutions were exposed to direct solar radiation from 12 a.m. to 3 p.m. SPM-1116SD was used to measure the amount of solar radiation that reached the reactor. Batch solar photocatalytic decomposition experiments were performed in a Pyrex mode reactor under natural sunlight (Figure 2). A mirror positioned at the bottom of the Pyrex enhanced irradiation by reflecting additional solar light onto the reaction mixture. On successive sunny days in June and July of 2025, the solutions were exposed to direct solar radiation from 12 a.m. to 3 p.m. SPM-1116SD was used to measure the amount of solar radiation that reached the reactor.
Figure 2. Schematic of the solar photo-oxidation process
Figure 3. Standard curve of paracetamol
PC solutions with concentrations of 10, 25, and 100 g/L were prepared, and the pH was adjusted using 1 M HCl or NaOH. E-TiO₂ nanoparticles were added at concentrations of 20, 40, or 100 mg/L. The suspensions were magnetically stirred (MSH-300N, BOECO, Hamburg, Germany) at 200 rpm for 120 minutes. An initial dark period of 30 minutes allowed adsorption equilibrium between PC and the E-TiO₂ surface. Subsequently, H₂O₂ (150, 250, 400, or 600 mg/L) was introduced, and the reaction mixture was exposed to sunlight to initiate photocatalysis. Aliquots of 10 mL were collected at predetermined intervals. The catalyst was separated by centrifugation at 2000-5000 rpm for 15 minutes, and the supernatants were analyzed using a Perkin–Elmer 55 OSE UV–Vis spectrophotometer at 243 nm, where the standard curve was examined at 5, 10, 25, 50, 100, and 150 mg/L, as indicated in Figure 3. The degradation percentage efficiency of PC was determined by using Eq. (1):
$PC \, elimination \, percentage=\frac{C_o-C_e}{C_o} \times 100$ (1)
where, Co and Ce are the initial and final concentrations of PC (mg/L), respectively.
3.1 E-TiO₂ NPs characterization
3.1.1 X-ray Diffraction analysis
The crystalline structure of the synthesized metallic nanoparticles was investigated using XRD, following the methodology of Huang et al. [25]. E-TiO₂ nanoparticles were examined with a SMART Bruker D8 Advance diffractometer using Cu Kα radiation ($\lambda=1.54 \,Å$). Diffraction patterns were recorded over a 2θ range of 10–80° to assess both the phase composition and crystallinity of the nanoparticles. The obtained diffraction pattern was compared with the standard JCPDS file No. 21-1272 [12], which confirmed that the indexed hkl reflections—25° (101), 38° (112), 48° (200), 55° (211), and 63° (204)—correspond to the anatase polymorph. As illustrated in Figure 4, the E-TiO₂ nanoparticles exhibit a tetragonal crystal lattice. The average crystal size for E-TiO2 was 40.123nm, while that for commercial TiO2 was 25 nm, determined using Scherrer’s equation (Eq. (2)).
$D=\frac{K \lambda}{\beta \cos \theta}$ (2)
where, $D$ is crystallite size, $\beta$ is the full width at half maximum (FWHM) of diffraction peak to the corresponding crystallographic plane of anatase, $\theta$ is the angle of the XRD peak, $K$ represents Scherrer constant (0.94), $\lambda$ is defined as a wavelength of X-ray radiation $(0.15418 \,Å)$[14].
Figure 4. X-ray Diffraction (XRD) pattern for E-TiO2
3.1.2 Scanning and electron microscopy
The adsorbent's surface morphology before and after the adsorption was examined using SEM analysis. Figure 5(a) illustrates the SEM image of the E-TiO2 NPs before treatment, while Figure 5(b) represents the surface morphology after the degradation of the PC. And the findings of Figure 5(a) demonstrated the morphology of the E- TiO2 before treatment with a relatively uniform, but irregular, surface, characterized by spherical irregular aggregates [26]. The availability of microscopic pores and numerous cavities was also a further sign of the suitability of E-TiO2 NPs to be used in photocatalytic applications [27]. Figure 5(b) shows that the morphological changes on E-TiO2 that occurred during PC adsorption were pronounced. When the pore surfaces became filled with the antibiotic particles, it was possible to observe changes in the catalyst surface, which became less rough and smoother, and some formerly separated aggregates became mixed. The main factor, which might have led to the high antibiotic uptake, is possibly the obvious pores of the catalyst, since adsorption is performed on the active surface groups present on the pore.
(a) Before PC degradation
(b) After PC degradation
Figure 5. Scanning Electron Microscopy (SEM) analysis for E-TiO2
3.1.3 Fourier Transform Infrared Spectroscopy analysis
FTIR analysis is a powerful method for identifying functional groups present on nanoparticle surfaces; thus, it was employed to characterize the E-TiO₂ samples before (black spectrum) and after (red spectrum) use in removing PC from aqueous solutions. As illustrated in Figure 6 (black spectrum), the absorption bands appearing between 500 and 800 cm⁻¹ correspond to Ti–O stretching vibrations, confirming the formation of TiO₂ nanoparticles. The band at 2843.52 cm⁻¹ is assigned to C–H stretching of aldehyde groups, whereas the peak at 1643.61 cm⁻¹ arises from the H–O–H bending vibration of adsorbed water and/or the C=O stretching vibration of residual organic species originating from the plant extract used during synthesis, accompanied by CH₃ stretching at 2921.63 cm⁻¹. In addition, the broad absorption associated with –OH stretching and bending appears at 3423.99 cm⁻¹, and the Ti–O–Ti stretching mode is detected at 1395.28 cm⁻¹ [15]. Following PC degradation (red spectrum in Figure 6), noticeable changes in peak intensities were observed, indicating adsorption or chemical interaction between the active surface groups of the catalyst and PC molecules or adsorption [28, 29].
Figure 6. Fourier Transform Infrared Spectroscopy (FTIR) analysis for E-TiO2
3.1.4 Surface area and porosity analysis
The adsorption and desorption isotherms of nitrogen molecules is used to determine the specific surface area and pore size distribution of E-TiO2 NPs [30]. The synthetic E-TiO2 NPs have a BET specific surface area of 345.25 m2/gm. Compared to commercially available chemically produced TiO2 NPs (< 100 m2/g), a higher surface area provides a larger number of accessible active sites, enhancing the adsorption of pollutant molecules and facilitating their close contact with photogenerated charge carriers. Consequently, this promotes more efficient photocatalytic degradation by increasing the probability of interfacial redox reactions and reducing mass-transfer limitations. The enhanced surface area, therefore, plays a critical role in the superior photocatalytic performance observed for the synthesized TiO₂ compared with commercial counterparts. This discussion has been added to the revised manuscript. The results obtained are relatively better [28].
E-TiO2 nanoparticles have an average pore diameter of 3.7869 nm and a total pore volume of 0.2883 cm3/gm.
3.2 Photocatalytic activity of E-TiO2
3.2.1 pH
The impact of pH on the photodegradation process of a solution containing 10 mg/L of PC, 40 mg/L of E-TiO2, and 250 mg/L of H2O2 was investigated in a stir photoreactor at discrete values of pH (3, 5, 7, and 11). The results shown in Figure 7 show that the rate at which the contaminant is degraded is greatly affected by pH during photocatalysis. This figure shows that the maximum elimination of PC is at pH 7, then after that, the rate of degradation increases steadily with the increasing of pH value. It is explained by the fact that this increases the production of hydroxide ions; at high pH levels, more hydroxide ions will be located on the E-TiO2 surface and can be easily oxidized, increasing the percentage of PC residue elimination [31]. On the other hand, Figure 7 also presents that the removal of PC is lessened at the highest pH levels, and this is mainly due to the intensified surface ionization of E-TiO2. Here, the study of the point of zero charge (pHpzc) is essential in the process of establishing the pH at which the surface of the catalyst is uncharged overall. That is, the catalyst surface is negatively charged at pH values greater than pHpzc and positively charged at lower pHs [32]. As can be seen by Eqs. (3) and (4), the surface of the photocatalyst can be protonated and deprotonated in the presence of acidic and alkaline conditions, respectively.
$\mathrm{pH}<\mathrm{pH}_{\mathrm{pzc}} \quad \mathrm{TiOH}+\mathrm{H}+\rightarrow \mathrm{TiOH}_2^{+}$ (3)
$\mathrm{pH}>\mathrm{pH}_{\mathrm{pzc}} \quad \mathrm{TiOH}+\mathrm{OH}-\rightarrow \mathrm{TiO}-+\mathrm{H}_2 \mathrm{O}$ (4)
The point of zero charge (Pzc) of E-TiO₂, which has been extensively studied, was approximately 7.5.
Figure 7. Impact of pH on the PC elimination
In acidic solutions, the E-TiO₂ surface carries a positive charge, whereas in alkaline environments it becomes negatively charged. Electrostatic attraction between paracetamol and E-TiO₂ increases with increasing pH [29], since paracetamol also acquires a negative charge when the pH exceeds 7. Consequently, the degradation efficiency of paracetamol declines at pH values above this level [30].
3.2.2 Initial PC concentration
To assess the impact of PC concentration, the PC loads of 10, 25, and 100 mg/L were tested at constant levels of other variables (pH value of 7, E-TiO2 of 40 mg/L, and H2O2 of 250 mg/L, and 150 min irradiation time). The results are depicted in Figure 8, which demonstrates that the removal efficiency declined as the initial PC concentration increased (94.13, 71, and 57)%, respectively. The two processes explaining the reduction can be the following: First, the rate of free radical generation does not depend on the dose of catalyst, thus when the PC load is increased, the fraction rate of removal is decreased [33]. Second, at high concentrations of PC, additional molecules adsorb onto the catalyst surface, thus blocking active sites and preventing photon propagation to the deeper parts of the nanoparticle [34]. Also, the figure shows that increasing the contact time (120 to 150 minutes) results in a slight increase in degradation with additional increasing contact time, but the results are insignificant, which may be attributed to the limited supply of PC and H2O2. These results are in line with the findings of research [35].
Figure 8. Impact of PC dosage on the photocatalytic system's elimination
3.2.3 H2O2 concentration
Figure 9 shows the effects of various concentrations of H₂O₂ (150–600 mg/L) on the degradation rate of 10 mg/L of PC in aqueous solution were examined under constant conditions of E-TiO₂ dosage (40 mg/L), pH (7), and irradiation time (120 min). According to the findings, the degradation efficiency of PC decreased from 94.13% to 58.3% as the H₂O₂ concentration increased from 250 to 600 mg/L. Therefore, the ideal H2O2 concentration for photo-oxidation was 250 mg/L. Low H₂O₂ concentrations enhance the rate of photocatalysis, whereas higher concentrations inhibit it. At low H₂O₂ concentrations, photolysis generates hydroxyl radicals, as shown in Eq. (5). Since H₂O₂ is a more effective electron scavenger than O₂, it helps minimize electron–hole recombination. However, at high concentrations, H₂O₂ reacts with E-TiO₂ to generate HO₂• radicals (Eq. (7)), which have a lower oxidative potential than OH• [36].
$\mathrm{H}_2 \mathrm{O}_2+h v \rightarrow 2^{.} \mathrm{OH}^{.} $ (5)
$\mathrm{H}_2 \mathrm{O}_2+e-\rightarrow \mathrm{^{.} OH}+\mathrm{OH}^{-}$ (6)
$\mathrm{OH}+\mathrm{H}_2 \mathrm{O}_2 \rightarrow \mathrm{H}_2 \mathrm{O}+\mathrm{HO}_2$ (7)
Figure 9. Impact of H2O2 dosage on PC degradation by photocatalytic system
3.2.4 Type and concentration of catalyst
The amount of catalyst is also essential for the photocatalytic elimination of PC. Experiments where the E-TiO₂ dose was varied between 20 and 100 mg L⁻¹ as shown in Figure 10 shows that the rate of degradation is high at the concentration of 40 mg L-1 (94.13%) and decreases with a higher concentration of the catalyst. The light penetration, as opposed to the availability of surface active-sites, can explain this trend in that as the catalyst load increases, so does the total active surface area, but the nanoparticles aggregation increases, and the light scattering, thereby reducing the effective irradiation of the suspension [37]. All these observations are in agreement with the activation steps of E-TiO2 to the sun radiation [38].
Figure 10. Impact of E-TiO2 concentration on PC elimination
$\mathrm{E}-\mathrm{TiO}_2+h v \rightarrow e^{-}+h^{+}$ (8)
$e^{-}+O_2 \rightarrow O_2 \cdot-$ (9)
where, $h^{+}$and $e^{-}$ are potent agents of oxidation and reduction, respectively. The following is an expression for the oxidative and reductive reaction steps:
Oxidative reaction:
$h^{+}+ organic \rightarrow \mathrm{CO}_2$ (10)
$h^{+}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{OH}+\mathrm{H}$ (11)
Reductive reaction:
$\mathrm{OH}+ organic \rightarrow \mathrm{CO}_2$ (12)
Figure 11. Influence of TiO2-type catalyst on PC degradatio
To determine the efficiency of E-TiO2 synthesis, an experiment was conducted using commercial TiO2 under optimal operating conditions. The percentage elimination of the PC drug residue is higher when E-TiO2 is used than when commercial TiO2 is used; at 40 mg/L of E-TiO2 and TiO2, the removal efficiency showed an increment ratio of more than 19.8%, as indicated in Figure 11.
3.3. Recyclability of E-TiO2 NPs
Figure 12. The reusability of E-TiO2 nanoparticles for the degradation of PC
A 180-minute experimental series was performed at a pH value of 7 using 40 mg/L of E-TiO₂, 10 mg/L of paracetamol, and 250 mg/L of H₂O₂ to evaluate the performance of the reused photocatalyst. The corresponding results are presented in Figure 12. Across five uses conducted over four successive recycling cycles, the catalyst achieved efficiencies of 94.13%, 90.5%, 84.23%, 79.6%, and 64.2%, respectively. The gradual decline in degradation efficiency can be linked to the partial catalyst loss during filtration [39]. With repeated reuse, previously active surface regions become unavailable for paracetamol adsorption and photon absorption, thereby diminishing photocatalytic activity [40]. Overall, the observed performance confirms the reusability of the E-TiO₂ nanoparticles.
3.4 Total organic carbon
The complete decomposition of organic materials to H2O and CO2 is known as mineralization. Therefore, the goal of any photocatalytic process should be to achieve a thorough mineralization. Monitoring the treated samples' total organic carbon (TOC) readings can reveal the extent of mineralization. TOC is considered the most relevant for the determination of organic pollution [41]. The TOC values of PC after photocatalytic treatment with E-TiO2 samples are given in Figure 13. It is clearly shown that a reduction in the concentration of TOC occurs as a function of time. Also, this figure shows that the use of hydrogen peroxide increases the total organic carbon decomposition by providing a greater number of hydroxyl radicals [42]. TOC is thought to be the most significant variable in determining organic contamination.
Figure 13. The mineralization process of PC using E-TiO2 NPs
3.5 Photo degradation kinetics
Understanding the photodegradation process and reaction rate, which rely on the dynamic interaction of PC and the nanocomposite surface, requires kinetic modelling. The pseudo-first-order kinetics model (Eq. (13)) was used in this study.
$\ln \frac{C}{C_o}=K_{o b s} \cdot t$ (13)
where, Kobs (1/min) represents the reaction rate constant for pseudo-first-order, Co and C (mg/L) are the initial and final concentrations of PC at irradiation time t, respectively (min). The kinetics results are obtained by plotting $In \frac{C}{C_o}$ as a function of t ranging between 0 and 150 min, as seen in Figure 14, and tabulated in Table 2.
The outcome demonstrates that increasing the concentration of PC at the beginning reduces the constant of degradation rate (Kobs) and higher R2 values (more than 98%), which demonstrates the photodegradation over E-TiO2, followed by this model, which was consistent with the investigational findings cited in section 3.2.2.
Table 2. The parameters of the reaction rate for PC elimination in the photocatalyst
|
PC Dosage (mg/L) |
Percentage of Removal % at 150 min |
First-Order |
|
|
R2 |
Kobs (min-1) |
||
|
10 |
98.03 |
0.9833 |
0.0244 |
|
25 |
86.23 |
0.9955 |
0.0118 |
|
50 |
65.32 |
0993 |
0.0057 |
|
100 |
54 |
0.9955 |
0.0044 |
Figure 14. pseudo-first-order kinetics model for PC degradation at various beginning concentrations
In this research, titanium oxide nanoparticles were successfully prepared using Eucalyptus globulus leaves (denoted as E-TiO2) extract, characterized, and then used to remove PC residual in aqueous solution by using a batch mode reactor. Characteristic analysis proved the heterogeneous texture, rough surface, and absence of any secondary phases or impurity peaks. The efficacy of E- TiO2 was measured in a batch reactor under the sunlight with the following parameters (pH, PC concentration, time of irradiation, concentration of E-TiO2, and H2O2). And the maximum removal efficiency reached 94.13% at an optimum condition of pH 7, PC 10 mg/L, E-TiO₂ of 40 mg/L, and H2O2 of 250 mg/L, and irradiation time of 120 min, while only 78.23% of PC was removed by using commercial TiO2 at the same operation conditions. The findings also show that the rate constant of the pseudo-first order model for first-order degradation is decreased with increasing the initial PC concentration, and the high values of R2 of the degradation curves under different PC loads prove that the photodegradation follows a pseudo-first order model. As a result, this cheap catalyst has a significant photocatalytic activity, which makes it possible to consider it a green photocatalyst that is able to remove the pollutant under sunlight.
The authors are grateful for the financial and scientific support from the University of Baghdad.
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