RESEARCH PAPER

 

Improved photocatalytic degradation of methylene blue by novel hexagonal ZnO particles

 

 

Zehra Yiğit Avdan^{I, II}; Ilknur Demirtaş^I; Ender Suvaci^{III, IV}

^IDepartment of Environmental Engineering, Eskişehir Technical University, Eskişehir, Türkiye
^IIEnvironmental Research Centre (ÇEVMER), Eskişehir Technical University, 26555 Eskişehir, Türkiye
^IIIDepartment of Materials Science and Engineering, Eskişehir Technical University, Eskişehir, Türkiye
^IVEntekno Materials Corp., Eskişehir, Türkiye

Correspondence

 

 

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ABSTRACT

Recently, the use of nanoparticles as photocatalysts has gained great importance. However, nanoparticles exhibit some drawbacks for this application and there is a need for new particle technologies to mitigate these drawbacks. A novel particle technology called MicNo based on ZnO has been designed and manufactured, which exhibits the advantages and properties of both micron and nano size. Although performance of MicNo-ZnO has been tested in various applications, it has not been tested as a photocatalyst in any photocatalytic degradation process. In this study, novel designed ZnO was used as a catalyst for methylene blue (MB) degradation in the presence of UV irradiation. The MicNo-ZnO particles were characterized by structural and morphological properties by XRD, BET and SEM analyses. The effects of catalyst amount, pH, temperature and initial concentration on the degradation process were investigated. In addition, a reusability study was carried out with 4 cycles under optimum conditions. The MicNo-ZnO particles showed excellent photocatalytic activity with a degradation rate of 96% for methylene blue in 180 min. The pseudo-first-order rate constant for the photocatalytic degradation of MB by MicNo-ZnO was as high as 0.0236 min^-1, confirming that MicNo-ZnO particles can be effectively utilized as an alternative catalyst material.

Keywords: methylene blue, MicNo-ZnO, photocatalyst, photocatalytic degradation, wastewater treatment

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INTRODUCTION

Water is one of the most crucial substances for the sustainability of life. Expeditious development of economy and industry, the rapid rise in population and increasing living standards result in increased water demand. On the other hand, underground and surface water sources have been polluted rapidly as a result of irresponsible industrial and agricultural activities (Bagheri and Chaibakhsh, 2021; Gupta and Suhas, 2009; Hasanpour and Hatami, 2020; Sawyer et al., 2003). Water pollution is one of the biggest problems faced globally today. Pollution is increasing every year, and poses a significant threat to environmental and public health (Hasanpour and Hatami, 2020; Natarajan et al., 2018). Dyes are among the most important pollutants and cause comparatively greater environmental pollution than many other water pollutants. Dyes are widely utilized in many industries such as textile, rubber, paper, leather, plastic, cosmetics, pigment production, printing, food and beverage, photoelectrochemical cell, chemical, and petrochemical (Bensalah et al., 2009; Dawood et al., 2014; Forgacs et al., 2004; Gupta and Suhas, 2009; Hasanpour and Hatami, 2020; Natarajan et al., 2018; Sokolowska-Gajda et al., 1996; Welderfael et al., 2016; Wróbel et al. 2001; Wu, 2007; Ozudogru et al., 2022). More than 100 000 types of commercial dyes are consumed annually by these industries (Gupta and Suhas, 2009; Hasanpour and Hatami, 2020). It is estimated that 70 000 to 1 000 000 tons of commercial paints are produced annually and about 10-15% of the used dyes are released to the environment as wastes (Dizge et al., 2008; Dotto et al., 2012; Gupta et al., 2013; Gupta and Suhas, 2009; Hasanpour and Hatami, 2020; McMullan et al., 2001). Wastewater from industries that use dyes creates serious environmental problem, such as contamination with organic pollutants, when discharged directly to the receiving environment without any treatment. One of the most significant problems of dyes is their toxicity to humans, aquatic animals and plants. In addition, dyes are bioaccumulated in nature (Işik and Sponza, 2004; Rani et al., 2021; Wong and Yuen, 1996). Dyes are chemically and photolytically stable in natural environments, so they are resistant to biological degradation (Gupta et al., 2013; Işik and Sponza, 2004; Wong and Yuen, 1996). Dyes that cause turbidity in the receiving environment inhibit the penetration of sunlight. Subsequently, photosynthesis is diminished and the dissolved oxygen level declines in the water. Therefore, the ecological health of the water body is impaired. It is known that dye compounds are reduced in aquatic sediments and spread to the natural environment by producing carcinogenic aromatic substances (Cirik et al., 2013). Wastewater containing dyes can cause important problems affecting aquatic organisms (fish, algae, bacteria, etc.) and humans, as well as aesthetic problems, and hence it must be treated prior to discharge to the receiving environment (Cirik et al., 2013; Forgacs et al., 2004; Gupta et al., 2013; Hasanpour and Hatami, 2020; Wu, 2007).

Physical (membrane filtration, coagulation, adsorption, ion-exchange, irradiation), chemical (photocatalysis, electrochemical routes, ozonation, Fenton's Reagent), and biological (anaerobic degradation, aerobic degradation) treatment methods are used for the removal of organic matter from water/wastewater (Gupta and Suhas, 2009; Gusain et al., 2019; Song et al., 2015). Among these methods, adsorption and photocatalysis have been widely used as effective methods for dye removal. Although adsorption is one of the most widely used methods, this method has limitations due to long desorption times and potential of generating secondary organic pollutants (Guo et al., 2021).

On the other hand, photocatalytic degradation is one of the most effective methods used for the complete degradation of dyes in wastewater (Hasanpour and Hatami, 2020). In the photocatalytic process, various materials such as ZnO (Al-Zahrani et al., 2020; Becker et al., 2011; Lam et al., 2012; Mao et al., 2019; Yashni et al., 2021; Zheng et al., 2019); CdS (Li et al., 2017; Yang et al., 2019), Fe₂O₃ (Kusior et al., 2019), WO₃ (El-Yazeed and Ahmed, 2019; Singh et al., 2018), TiO₂ (Al-Mamun et al., 2019; Al-Zahrani et al., 2020; Tichapondwa et al., 2020; Torane et al., 2020; Wong and Yuen, 1996), SnO₂ (Manikandan et al., 2018), Ni-doped ZnO nanocatalysts (Ahmad et al., 2022), Fe-doped ZnS photocatalysts (Shakoor et al., 2024), and Sr-based nanomaterials (Bashir et al. 2023) are used as a photocatalyst in the degradation of organic environmental pollutants like dyes. The ideal catalyst to be used in water treatment should be photoactive under visible and/or UV light, biologically and chemically inert, stable, cost effective and non-toxic. Recently, utilization of nanoparticles as photocatalysts has gained enormous popularity. Furthermore, numerous studies have been conducted utilizing nanoparticles for the purpose of purifying and reclaiming a wide range of contaminants (Ansari Moghaddam et al., 2023; Bazrafshan et al., 2023; Bazrafshan et al., 2021; Ghamkhari et al., 2020; Mohammadi et al., 2021). Metal or metal oxide nanoparticles are one of the compounds that have been widely investigated in this regard. Although there has been a significant amount of research on the application of metal-based nanoparticles for wastewater treatment, a substantial component of these materials is produced from hazardous metals and can exhibit intrinsic toxicity. Therefore, it is crucial to meticulously select secure and dependable metal-based nanoparticles for efficiently eliminating pollutants in wastewater treatment procedures (Bashir et al., 2023).

At nano scale, the specific surface area of powders increases and both chemical and physical, as well as, impacting optical and biological behaviours change or are enhanced, with the possibility of the material gaining additional properties. On the other hand, there are disadvantages of powders at nanoscale due to the fact that they are very small particles. Nano particles have very high surface energy because of their very small particle size, and therefore tend to agglomerate. Due to this agglomeration, the structure becomes micron sized. Also, in agglomerating; nano-sized particles come together in a random arrangement; because of this randomness, the surface area of the structure decreases. These factors make nano-sized particles difficult to use in many applications including photocatalyic degradation. In addition, when becoming a micron-sized structure due to agglomeration, the properties that were present when the particles were nano sized, disappear. Another problem specific to the photocatalytic degradation process is related to the difficulty of filtration or recovery of the photocatalyst powders during and after the photocatalytic water treatment process due to their very small particle size. During the filtration of powders, efficient separation of the solution and the catalyst particles is critical to achieve effective purification or treatment of the water. Accordingly, there is a need for development of new particle technologies which will overcome uncontrolled agglomeration, as well as the filtration and recovery problems associated with nanoparticles, while still maintaining their advantages.

Recently, Suvaci and co-workers (2009) designed and manufactured a novel particle technology, called MicNo, based on ZnO. MicNo-ZnO particles are micron-sized platelets which are composed of fine primary particles. MicNo-ZnO particles exhibit the advantages and properties of both micron and nano size. In previous studies, it has been shown that MicNo-ZnO is much less phytotoxic (Nazikcan, 2015) and much more biocompatible (Genç et al., 2018) than simply ZnO nanoparticles. Although the performance of MicNo-ZnO has been tested in various applications, such as lithium battery cathode material (Dermenci et al., 2020), conductive fillers as antistatic/ESD additives (Sengun et al., 2020), and antimicrobial agents (Demirel et al., 2018), it has not been tested as a photocatalyst in any photocatalytic degradation process.

The intentionally manufactured, micron-sized, controlled agglomerated platelet morphology of MicNo-ZnO has the potential to eliminate the uncontrolled agglomeration problem and its micron size enables easier filtration and recovery of the MicNo-ZnO particles from the solution. Consequently, the research objective of this study was to investigate the water purification performance of the novel designed micron-sized ZnO platelets with nano infrastructure, in the presence of methylene blue under UV irradiation, and hence evaluate its usability for dye removal processes.

 

MATERIALS AND METHODS

Materials and reagents

In this study, methylene blue (MB), sodium hydroxide (NaOH), and hydrochloric acid (HCl) were used. The sodium hydroxide (NaOH, 97%) and hydrochloric acid (HCl, 37%) were supplied by Merck; MB dye was provided by ChemBio Laboratory Research (Product code: CB2702, 100 g). MB is commercial grade and was used without further purification. 0.1 M HCl and 0.1 M NaOH were prepared for adjusting the pH. MB solutions were prepared from 100 mg/L stock solutions.

The chemical and structural properties of MB dye are detailed in Table 1.

Instrumentation

All solutions were prepared with deionized water (Millipore Milli-Q Direct 8 Water Purification System). A pH meter (Thermo Orion Star A321 Portable pH Meter) was used for measuring the pH values of solutions. A precision balance (OHAUS Adventurer-Pro) was used for the preparation of the solutions. The samples were filtered using a 0.45 μm membrane filter. A UV-visible spectrophotometer (Hach Lange DR5000) with a 1 cm quartz cell was used for wavelength scanning of the MB solution and determining the absorbance values of the samples.

Catalyst particles and their characterization

MicNo-ZnO particles, used in this study, were provided by Entekno Materials, Inc. The particles were characterized by an x-ray diffractometer (XRD) and a scanning electron microscope (SEM) to determine crystal phase, and size and morphology of the particles, respectively. In addition, specific surface area of the particles was measured by a BET analyser. Prior to the BET analyses, the powder samples were degassed at 120°C for 18h. Furthermore, particle size distribution of the particles was determined by the laser light scattering method. Aqueous suspensions of the particles were treated by an ultrasonic tip for 3 min before the analyses.

Photocatalytic degradation of methylene blue

The photocatalytic experiments (Fig. 1) were performed on a WTW TR-1 Heidolph UNIMAX 2010 shaker. 15 W UV-C lamp was used as the light source. The shaker and UV-C lamp were placed in an aluminium foil-covered cabinet to eliminate the influence of external light. There is also a unit to adjust the temperature in the cabinet, which was kept constant. A UV-C lamp does not affect the temperature of the reactor.

 

 

Photocatalytic degradation (Fig. 2) is used to purify water by breaking down organic pollutants into inorganic acids such as CO₂, H₂O, and HCl. This method is based on the use of a combination of ultraviolet light and semiconductors to break down organic pollutants in water. A photocatalytic system consists of semiconductor particles suspended in the liquid phase and a light source that is used to illuminate this suspension. A semiconductor has a valence band (VB) filled with electrons and a conductivity band (CB) containing empty energy levels. A spherical semiconductor particle is shown in Fig. 2. When the hv energy of the light used is greater than the energy difference (E_g) between the valence band and the conductivity band of the semiconductor, the semiconductor particle interacts with the photon (hv) to excite an electron in the valence band to the conductivity band, leaving a positive gap (h+_VB) inside the particle. The electron/space enables the formation of e^-_CB(electron)/h+ _VB (hole) pairs (Eq. 1) These formed electron/space pairs cause redox reactions to start on the semiconductor surface. The pairs of spaces form hydroxyl radicals (OH*) by absorbing OH^- or H₂O molecules, and electrons react with oxygen to form anionic superoxide radicals (O₂^-*) (Eqs 2-3). These radicals oxidize the adsorbed organic molecules. Organic intermediate products are re-oxidized by molecular oxygen and/or OH* radicals, producing carbon dioxide and water (Eq. 4). These radicals then form molecular oxygen and hydrogen peroxide. Thus, photo-stimulated semiconductor photocatalyst enables both oxidation and reduction to occur at the surface (Al-Mamun et al., 2019; Lam et al., 2012; Natarajan et al., 2018; Shakoor et al., 2024).

In this study, photocatalytic MB degradation experiments were conducted under 270 min of UV light irradiation at 200 r/min stirring speed, different catalyst dosages, pH, temperatures and initial MB concentrations. The photocatalytic MB degradation rate was calculated using Eq. 5. C₀ is the initial concentration of MB, and C_t is the concentration after irradiation time t; A_o represents the initial absorbance. A_t describes the change in absorbance of the MB at the characteristic absorption wavelength 664 nm (Bel Hadjltaief et al., 2018; Bhatia et al., 2016; El-Yazeed and Ahmed, 2019; Güy et al., 2016; Natarajan et al., 2018).

MicNo-ZnO was collected under optimum conditions to examine the post-reaction reusability of the catalyst. Two methods were used for reusability experiments. First, after the catalyst was air-dried, it was kept under UV light for 3 h. In the second method, the catalyst was washed with distilled water a few times and dried at 110°C for 12 h (Bel Hadjltaief et al., 2018). Photocatalytic experiments were carried out with MicNo-ZnO collected by these two methods, and the removal efficiencies were investigated.

Kinetic study

The photodegradation reactions of many organic compounds using various nanoparticles follows the Langmuir Hinshelwood (L-H) kinetics model (Hasanpour and Hatami, 2020; Li et al., 2018; Li et al., 2016). The kinetic study for MicNo-ZnO nanoparticles (photocatalyst) for photodegradation of MB was thus done using the Langmuir-Hinshelwood kinetic model. Since the organic pollutant concentration C₀ is very low, the Langmuir Hinshelwood (L-H) kinetics model can be simplified to an obvious pseudo-first-order kinetic equation (Eq. 6) (Chowdhury et al., 2018; Hasanpour and Hatami, 2020; Konstantinou and Albanis, 2004; Trandafilovic et al., 2017). Methylene blue photocatalytic degradation kinetics were investigated using the pseudo-first-order rate law equation which can be expressed as:

where: k is the rate constant, C₀ is the initial concentration at time t = 0, and C_t is the concentration at any time t during the reaction. According to pseudo-first-order kinetics, the reaction constant (k) is calculated by plotting ln (C_t/C₀) versus the reaction time (t). In general, the pseudo-first-order kinetics model is convenient for the overall concentration range for low concentrations. Various studies have shown that the rate of photocatalytic activity was well assessed by fitting the experimental data to this kinetic model (Hasanpour and Hatami, 2020; Kim et al., 2013; Lu et al., 2018; Najafidoust et al., 2019; Vaiano et al., 2014; Wang, 2007; Xiao et al., 2007). The resulting linear relationship demonstrates that the photodegradation of organic pollutants is well described by the Langmuir-Hinshelwood (L-H) kinetic model.

 

RESULTS AND DISCUSSION

Preliminary experimental studies

Wavelength scanning for MB was performed, and a standard calibration curve was prepared. According to the wavelength scanning results (Fig. 3), readings were made at 664 nm peak wavelength.

The mixture of MB and catalyst (MicNo-ZnO) was stirred in the dark for 15 min to ensure adsorption-desorption equilibrium before UV light irradiation. Subsequently, samples were collected at intervals of 10 min for the first 30 min, then at 30 min intervals, and filtered through a 0.45 μm membrane filter. Readings were done on a UV-visible spectrophotometer. Also, control experiments were carried out, as shown in Fig. 4. The MB concentration appears to be stable under a UV lamp without the catalyst. Addition of MicNo-ZnO achieves the removal of 10.27% of the MB in the dark environment, and is almost constant. Under visible light, 32.61% removal was achieved in the 120^th minute and the removal efficiency curve follows a wave pattern.

 

 

This can be attributed to the fact that the adsorption-desorption of MB on MicNo-ZnO occurs at certain intervals. Under the UV lamp with catalyst, MB removal reached 91.13% in the 150^th minute and 96.04% in the 180^th minute.

Studies were carried out at three different positions on the shaker to determine whether the UV lamp, located 10.5 cm above the mixing device, would give the same effect at every point of the shaker. The study was carried out by placing beakers in the middle (90°), right (41.4°) and left (41.4°) rows of the shaker according to the angle of the UV lamp. It is concluded that the UV effect perpendicular to the beakers is higher than the effect for the other two rows (Fig. 5). Although 96.04% removal for MB was achieved in the 180^th minute in the vertical position, in the other two rows a removal of 72.29-79.33% was achieved in the 270^th minute. It was thus decided to perform the studies under a UV lamp at a vertical distance of 10.5 cm. In the 180^th minute 96.04% removal was achieved and the removal efficiency in the 270^th minute approached almost 100%. Therefore, the photocatalytic degradation studies were conducted for 270 min.

Catalyst characterization

Figure 6 shows the XRD pattern of the catalyst particles. The peaks in the XRD pattern confirm that the catalyst particles are single-phase ZnO with a hexagonal wurtzite-type crystal structure. It should be also noted that the peaks demonstrate a broadening effect which suggests that the primary particles of the catalyst are nano-sized.

 

 

Figures 7 and 8 show the SEM image and EDX result, respectively, for the catalyst particles. The particles exhibit a polygonic (mostly hexagonal) morphology with a 2-10 μm particle size. The laser scattering analyses also showed that the catalyst particle size distribution lies in the 2-10 μm range with a mean value of approx. 5 μm. It can be observed in the SEM micrographs that the particles are thin enough to be transparent, such that the particles beneath them are also visible. All these results indicate that the catalyst particles are micron-sized platelets, composed of chemically bonded nano-sized particles. The BET analyses showed that the catalyst particles exhibit a specific surface area of 20-30 m²/g.

 

 

 

 

Figure 9 shows the uncontrolled aggregated particles and MicNo-ZnO particles, formed via controlled aggregation of the same number of particles as in the uncontrolled case. MicNo-ZnO's novel morphology enables one to achieve improved surface coverage and greater surface reactivity which is desired for effective photocatalytic degradation processes.

 

 

Effect of various processing parameters on the photocatalytic degradation of MB

Catalyst dosage, pH, temperature and initial concentration parameters were evaluated for photocatalytic degradation of MB.

Effect of catalyst dosage

The amount of catalyst is one of the main parameters determining the dye degradation rate. Figure 10 shows that when the amount of catalyst in the reactor increases from 0.1 g/L to 0.25 g/L, removal efficiency also increases. Generally, the increase in the active site on the catalyst surface with increasing dosage increases the dye degradation rate (Bel Hadjltaief et al., 2018). It is seen that the removal efficiencies are almost the same when using 0.5 g/L and 1 g/L catalyst. Since the increased amount of catalyst increases the turbidity of the suspension and thereby decreases UV light penetration with the increased scattering effect, the removal efficiency decreases (Bel Hadjltaief et al., 2018). The photocatalytic degradation rate with the active region formed when 0.25 g/L was added approached the removal efficiency (~97-98%) when 0.5 g/L and 1 g/L were added.

Effect of pH

Since the pH range of wastewater differs, pH is one of the other main parameters to be considered for dye degradation in the presence of a catalyst. In photocatalytic dye degradation, the initial pH may result in a different activity for each dye and catalyst (Hasanpour and Hatami, 2020). In Fig. 11, the effect of initial pH on photocatalytic degradation of 10 mg/L MB using 0.25 g/L MicNo-ZnO is shown. The MB solution has an initial pH of about 6. In this study, pH values of 4, 6, 8, and 10 were studied. There is no sharp change in MB degradation over time at pH values of 6, 8 and 10 (Fig. 11). There is a minimal increase in removal at pH 10 compared to pH 6 and 8. This may be related to the pH zero-charge point (pH_pzc) value of MicNo-ZnO being 8.5. Above the pH_pzc value, the net surface charge of MicNo-ZnO becomes negative, indicating that better results can be obtained for MB with a cationic character. At pH 4, the removal efficiencies until the 90^th minute are approximately the same as for other pH values, while a decrease is observed after the 120^th minute.

Effect of temperature

The effect of photocatalytic degradation of MB solution with catalyst on temperature was investigated and the results shown in Fig. 12 were obtained. Very close removal efficiencies were obtained at 20°C and room temperature (25°C). Increasing the reactor temperature to 40°C will reduce the removal efficiency a little and cause additional energy consumption in the system. Therefore, it was concluded that the room temperature was optimum for the studies.

Effect of initial MB concentration

The photocatalytic activity of MicNo-ZnO was determined at different initial concentrations of MB with 0.25 g/L catalyst. The lowest concentration tested, at 10 mg/L MB, degraded the fastest (Fig. 13: 91.13% at 150 min, 96.04% at 180 min, 96.44% at 210 min, 97.86% at 240 min, 98.42% at 270 min). An increase in initial MB concentration resulted in lower degradation and lower removal/efficiency.

The photocatalytic degradation achieved is inversely proportional to the initial concentration. The likely cause is that more and more dye molecules are adsorbed to the catalyst surface when the initial concentration increases. Therefore, since there are only a few active sites for the adsorption of hydroxyl ions and hydroxyl radicals, the formation of hydroxyl radicals will be reduced.

Furthermore, as the concentration of a dye solution increases, photons are captured before they reach the catalyst surface; hence the absorption of photons by the catalyst decreases and, as a result, the percentage degradation decreases (Bel Hadjltaief et al., 2018; Tichapondwa et al., 2020).

Reusability of catalyst

Reusability of catalyst materials is an important and decisive factor for sustainable and practical applications (Bel Hadjltaief et al., 2018; El-Yazeed and Ahmed, 2019; Najafidoust et al., 2019). In this study, reusability was investigated under optimum conditions in consecutive periods with two methods specified in the title "Photocatalytic degradation of methylene blue" (Bel Hadjltaief et al., 2018) MicNo-ZnO efficiency was investigated for up to 4 cycles (Fig. 14). The methods were performed again after each cycle. It was concluded that Method 1 (air-dried, kept under UV light for 3 h) is better for this catalyst to recondition the surface activity. With this method, a decrease in degradation of 26% occurred in the second cycle, which indicates that the catalyst's efficiency tends to decrease slowly from the second cycle onward.

 

 

Kinetic study

Kinetic models for photocatalytic degradation of MB with MicNo-ZnO catalyst were investigated using the optimum parameters (pH = 6, C₀ = 10 mg/L, [catalyst], = 0.25 g/L, T = room temperature). As shown in Fig. 15, the curve is linear and reveals that the kinetic data for photocatalytic degradation of MB fit the pseudo-first-order reaction kinetic model. Rate constants for dye degradation (k) and regression coefficients (R²) were calculated from a pseudo-first-order linear fit to be 0.0177 min^-1 and 0.9718, respectively. Table 2 shows the pseudo-first-order kinetic coefficients obtained with photocatalytic dye removal with different catalysts in this and previous studies.

When 0.25 g/L of MicNo-ZnO was used in the experiment, the k value was obtained as 0.0177 min^-1. If the amount of MicNo-ZnO is increased to 1 g/L, the k value becomes 0.0236 min^-1 (R² = 0.9541). Although the surface area of the catalyst in our study is quite low compared to the photocatalysts used in other studies (Ahmed et al., 2013; Bel Hadjltaief et al., 2018; Dassanayake et al., 2018), it has a similar k value when approximately the same amount of catalyst (0.8-1 g/L) is used. The reason for deciding not to increase the amount of MicNo-ZnO used as photocatalyst in this study was the difficulty of recovery processes in the slurry system.

 

CONCLUSIONS

Wastewater containing dyes creates a severe environmental problem when directly discharged to the receiving environment without any treatment. The objective of this study was to test novel designed MicNo-ZnO particles for the first time as photocatalysts to remove methylene blue from water.

Results ofthe photocatalytic experiments showed that the optimum dose for 10 mg/L MB was 0.25 g/L MicNo-ZnO, achieving a removal efficiency of 96% at the 180^th minute. The pseudo-first-order rate constants for the photocatalytic degradation of MB by MicNo-ZnO were found to be as high as 0.0236 min^-1 and the kinetic study confirmed that the photocatalytic degradation of MB follows the kinetics of the pseudo-first-order model. These results show that MicNo-ZnO is a suitable candidate for effective photocatalytic dye degradation of methylene blue and possibly other dyes.

 

ACKNOWLEDGEMENTS

This work was supported by the Eskisehir Technical University Scientific Research Projects Commission (Project Number: 19ADP044). The authors would like to thank Entekno Materials Co. for providing MicNo-ZnO powder samples.

 

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

 

AUTHOR CONTRIBUTIONS

ZYA: writing - original draft, writing - review and editing, conceptualization, methodology, supervision, resources. ID: conceptualization, methodology, writing - review and editing, visualization. ES: writing - review & editing, conceptualization, methodology, supervision, resources.

 

ORCIDS

Zehra Yiğit Avdan: https://orcid.org/0000-0001-7445-3393

Ilknur Demirtaş: https://orcid.org/0000-0002-5264-4559

Ender Suvaci: https://orcid.org/0000-0002-2635-4822

 

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Correspondence:
Zehra Yiğit Avdan
Email: zyigit@eskisehir.edu.tr

Received: 6 September 2022
Accepted: 8 October 2024