Studying the Nanocomposite B/ZnO for Photocatalysis: Facile Control the Morphology via Sol-gel Method and Antibiotic Degradation Investigations

doi:10.21203/rs.3.rs-3901804/v1

Download PDF

Research Article

Studying the Nanocomposite B/ZnO for Photocatalysis: Facile Control the Morphology via Sol-gel Method and Antibiotic Degradation Investigations

https://doi.org/10.21203/rs.3.rs-3901804/v1

This work is licensed under a CC BY 4.0 License

Journal Publication

published 11 Mar, 2024

Read the published version in Journal of Sol-Gel Science and Technology →

You are reading this latest preprint version

In this study, the ZnO and B/ZnO nanocomposites were successfully synthesized by a Sol-gel method. The photocatalytic activity of these materials was evaluated by the removal of antibiotics including tetracycline hydrochloride. After doping with B, the photocatalytic activity of the composite was improved and the optimum content of doped B was 3 wt.%. The effects of synthesis conditions on the morphology, structure and photocatalysis of B/ZnO were investigated. The physical properties of these material samples were analyzed by many different methods. The synthesis conditions significantly influenced the morphology and the photocatalytic performance of the B/ZnO nanocomposite. The optimal synthesis conditions were ethanol as a solvent, a temperature of 60 ℃ and a pH of 8. In 90 min, the TCH removal efficiency of the B/ZnO nanocomposite archived 98.28% with a rate constant of 0.048 min^− 1. In addition, the electrical energy consumption was estimated and the electrical energy per order was only 35.44 W.h.L^− 1.

ZnO

Composite

Tetracycline hydrochloride

Photocatalyst

Energy consumption

B/ZnO nanocomposite was prepared by a Sol-gel method.
The morphology and the photocatalytic performance of the B/ZnO nanocomposite were significantly influenced by the synthesis conditions.
The tetracycline hydrochloride removal efficiency of the B/ZnO nanocomposite archived 98.28 % with a rate constant of 0.048 min^-1 in 90 minutes.
The electrical energy per order was only 35.44 W.h.L^-1.

With industrial development and a growing population, environmental pollution is increasing, leading to high amounts of organic pollutants [1]. Antibiotic contamination in particular is becoming increasingly serious due to its potentially harmful effects on the ecosystem and human health [2–4]. Notably, more than a dozen sulphonamide antibiotics, tetracyclines and fluoroquinolones have been detected in surface and groundwater water [5]. In recent years, various chemical and physical methods have been applied to address this problem, such as physical adsorption, photocatalysis, biodegradation, electrolysis, coagulation, etc [3, 5]. The utilization of solar energy with heterogeneous semiconductor-based photocatalysts has been extensively studied and the potential applications of sunlight for the removal of organic and antibiotic contaminants have been presented. In particular, catalysts based on ZnO and TiO₂ are widely used and applied [6–10] because they are known to be semiconductors with high photocatalytic efficiency for most persistent organic compounds.

Compared to TiO₂, ZnO has a large band gap energy (E_g~3.37 eV) and binding energy (60 meV) [11]. However, its outstanding properties such as low cost, photosensitivity, high redox potential, durability and environmental friendliness bring great benefits in the fields of photocatalysis [12], sensors [13], antimicrobials [14], cosmetics, pharmaceuticals, and energy [15]. Many methods have been used to synthesize ZnO. The most common methods are the hydrothermal method, the sol-gel method, and the precipitation method. Each method produces the corresponding morphology of ZnO in the form of nanoparticles, nanorods, nanoflowers, and nanosheets. Several studies have demonstrated that the size and morphology have a great influence on the catalytic efficiency of ZnO [16, 17].

Because ZnO has a fairly large band gap, it is only effective in the UV light range. Meanwhile, ultraviolet light only accounts for about 5% of solar radiation. In addition, ZnO has a fast recombination of electrons (e⁻) and holes (h⁺). These are the lacks of ZnO for practical applications. Recently, studies have shown that the heterogeneous combination of semiconductors with metallic and non-metallic elements or with graphitic carbon nitride yields outstanding performance due to the reduction in the recombination rate of charge carriers, which is the key to improving the photocatalytic activity of ZnO [18–22]. Heterogeneous contact from combining metallic and non-metallic elements or oxide with pure semiconductors can increase the lifetime of the charge carriers, which improves their disposal possibility.

In our previous study, boron was selected for doping for doping ZnO because of its atomic size and electronic structure [23, 24], but the combination of B with semiconductors is still poorly explored. In 2021, R. E. Núñez-Salas and colleagues prepared B/ZnO using the sol-gel method for photocatalytic inactivation of Escherichia coli. and Enterococcus sp. [25]. The enhancement of the antimicrobial effect of B-ZnO was attributed to the release of Zn²⁺ and the formation of acidic sites promoted by B³⁺ ions in the B-ZnO catalyst. In 2022, Thu Huong Nguyen and colleagues investigated the removal of antibiotics by the B/ZnO nanocomposite prepared via a simple mechanical combustion method [21]. The catalytic activity of ZnO increased when it was combined with B. In 90 min, 90% of tetracycline hydrochloride (TCH) was degraded and the degradation capacity was 24.12 mg/g after 30 min. The effects of reaction conditions such as pH, TCH concentration and catalyst content on the degradation efficiency were also extensively investigated. However, the influence of preparation conditions on the morphology and photocatalytic activity of the B/ZnO composite remains a mystery.

In this study, the B/ZnO nanocomposites were synthesized by the simple sol-gel method. The crucial parameters of the synthesis process including the solvent, reaction temperature, solution pH and B content were varied to adjust the size and morphology of the sample. The catalytic effect of the material is achieved by the decomposition of TCH under visible light. TCH was chosen because it is widely used in humans and animals. It is active against several gram-negative and gram-positive bacteria. In addition, the photocatalytic mechanism of TCH in the B/ZnO catalyst was investigated.

2.1. Materials

Zinc acetate dehydrate (Zn(CH₃COO)₂.2H₂O, 99%), boric acid (H₃BO₃, 99.8%), sodium hydroxide, ethanol, and isopropyl alcohol were purchased from Merck. Tetracycline hydrochloride (C₂₂H₂₄N₂O₈.HCl, 99%) was purchased from Hefei BoMei Biotechnology Co., Ltd, China. All chemicals were used without any purification. Distilled water was used for the preparation of materials and TCH degradation.

2.2. Methods

The material characterization was analyzed using various methods. The morphology of the material samples was observed with a field emission scanning electron microscope (FE-SEM JEOL series 7600F). The samples were characterized by powder X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer (Germany) with Cu K_α radiation (λ = 1.54060 nm). Ultraviolet-visible diffuse reflectance (UV-Vis/DR) spectroscopy was used to investigate the light absorptivity capacity and to determine the band gap energy of the material samples. Fourier transform infrared spectroscopy (FT-IR, Madison, WI, USD) was investigated to determine the changes in the functional groups of the as-synthesized samples.

2.3. Preparation of the materials

Typically, 4.4444 g zinc acetate dehydrates and 0.2822 g boric acid were stirred in 50 mL solvent at room temperature (25$℃$) for 1 h. Then, the 2.0 M NaOH solution was added to the mixture to achieve the desired pH. This mixture was stirred at 60 $℃$ for 3 h to obtain a white gel. This gel was sealed with cling film and incubated overnight, then filtered and washed with distilled water and ethanol. The white precipitate was dried at 80$℃$ for 24 h and ground to a fine powder. Finally, the precipitate was calcined at 500 $℃$ for 4 h to obtain the B/ZnO composites. Samples were stored in sealed bottles before being used for analysis. The ZnO sample was produced using the same procedure as the composite but without boric acid.

To investigate the influence of the reaction parameters on the size and morphology of the materials, we synthesized the following samples: The boron content was investigated at 1, 3, 5, and 7 wt.% and the obtained materials were named B/ZnO-1, B/ZnO-3, B/ZnO-5, and B/ZnO-7, respectively. Ethanol, isopropyl alcohol and water were use as solvents. The obtained samples were designated as B/ZnO-Ethanol, B/ZnO-Isopropyl alcohol and B/ZnO-Water, respectively. The reaction temperature was adjusted to 30, 60 and 75 $℃$. The obtained samples were designated as B/ZnO-30, B/ZnO-60 and B/ZnO-75, respectively. Finally, the pH of the solution was adjusted at 7, 8, 9, 10 and 11. The obtained samples were labelled B/ZnO-pH7, B/ZnO-pH8, B/ZnO-pH9, B/ZnO-pH10 and B/ZnO-pH11, respectively.

2.4. The photocatalytic process

The procedure for evaluating the photocatalytic ability of the material samples was carried out as follows: 50 mg of catalyst was added to a beaker containing 100 mL of TCH 20 mg/L and sonicated for approximately 5 min to disperse the material evenly. This beaker was stirred continuously at 250 rpm for 30 min in dark to establish adsorption/desorption equilibrium. Then this reaction solution was irradiated with a 250 W Hg lamp. After certain time intervals, 3 m Lof suspension was filtered through a filter and the residual concentration of TCH was measured using UV-Vis spectrophotometer (Agilent 8453) at a maximum wavelength of 375 nm. The removal efficiency (Re) and rate constant of TCH were calculated according to equations (1) and (2) respectively [26]:

$$\text{l}\text{n}\frac{{\text{C}}_{\text{o}}}{\text{C}}=\text{k}\text{t}$$

Where: C is the solution concentration at time t; C_o is the initial solution concentration; k is the rate constant; t is the time.

3.1. Comparing ZnO and B/ZnO nanocomposites

The UV-Vis/DR spectrum and Tauc’s plot of ZnO and B/ZnO nanocomposites with different B content are shown in Fig. 1. Although B/ZnO-7 had weaker adsorption compared to other composites and was even weaker than ZnO, all as-synthesized samples showed relatively strong adsorption in the UV region (250–356 nm). In addition, all as-synthesized samples exhibited a significant decrease in adsorption above 400 nm and a steep increase in adsorption at 360–400 nm (Fig. 1(a)). Using the Tauc’s equation, the band gap energies of samples can be calculated [26]:

(αhν)^1/n = A (hν – E_g) (3)

Where, E_g is the band gap energy (eV); α is the absorption coefficient of the material; h is Plank's constant (6.63 × 10^− 34 Js^− 1); ν is the frequency of the light; A is a constant; n is determined by the optical transition type of the semiconductor. The results are shown in Fig. 1(b). The B/ZnO-7 sample had an E_g of 3.17 eV, the other samples had a similar E_g value of 3.15 eV).

The results of studying the photodegradation reaction of TCH are shown in Fig. 1(c-d). The reactions of TCH in ZnO and B/ZnO-1 were similar with a Re of 68.45%. This value drastically increased when the B content increased to 3 wt.%. The Re and rate content of B/ZnO-3 were 92.28% and 0.048 min^− 1, respectively. There was a tendency to reduce the reaction of TCH at higher B contents. The Re value was 82.58% and the rate constant was 0.015 min^− 1 for the B/ZnO-7 sample. For the B/ZnO-5 sample, these were 81.55% and 0.016 min^− 1, respectively. Based on these results, the optimum B doping ratio of 3 wt.% was selected for further investigation.

The morphologies of the ZnO and B/ZnO-3 samples are presented in Fig. 2. The ZnO sample had a clear morphology and an aggregation consisting of many nanoparticles with a size of about 42–79 nm. After doping with B, the size and aggregation state of the nanomaterial significantly changed. The morphology of the B/ZnO-3 composite was relatively rough and its particles were smaller and more compact than those of ZnO, with a size of about 15 nm (Fig. 2(c)). This may be a reason for the enhanced photocatalytic performance of the composite.

The XRD spectra of the ZnO and B/ZnO-3 samples are shown in Fig. 3(a). Both samples had (100), (002), (101), (102), (110), (103), (112), and (201) planes at 2${\theta }$ of 31.78, 34.45, 36.28, 47.60, 56.65, 62.92, 67.99, and 69.19$^\circ$, respectively, with the peak (101) being the strongest, which can be assigned to the hexagonal wurtzite structure of ZnO (JCPDS 36-1451) [26]. This result reveals the crystal structure of ZnO was preserved after doping with B. However, the intensity of the peaks in the B/ZnO composite was lower than that of ZnO. In addition, the peak of B was not observed. This can be explained by the low content and crystallinity of B in the composite. Based on the Scherrer equation, the crystal size of the as-synthesized samples was calculated [11]:

$$\text{D}= \frac{\text{K}{\lambda }}{{\beta }\text{c}\text{o}\text{s}{\theta }} \left(4\right)$$

Where K is a constant that depends on the crystal shape (usually K = 0.9); λ is the X-ray wavelength (1.5406 Å); θ is the Bragg diffraction angle; β is the line width of the sample, which corresponds to half the maximum intensity in radians (FWHM). The crystallite size of the ZnO and B/ZnO samples was 17.68 and 12.11 nm, respectively (Table 1). After doping with B, the crystallite size of the nanomaterial was significantly decreased. The rough surface along with the small crystallite size may be the reason for the enhanced photocatalytic degradation of TCH of the composite.

Table 1

The crystal sizes at different planes and average sizes of ZnO and B/ZnO samples.
Samples	100	002	101	102	110	103	112	$\stackrel{-}{\mathbf{D}}$ (nm)
ZnO	13.44	23.54	22.77	23.09	23.29	21.67	21.93	17.68
B/ZnO	13.44	11.72	13.31	14.92	14.59	13.54	10.78	12.11

The functional groups in the ZnO and B/ZnO-3 samples were characterized by FT-IR analysis. As seen in Fig. 3(b), the stretching vibration of the intermolecular hydrogen bond (O-H), which exists between the absorbed water molecules (H-O-H) was observed at 3417 and 3450 cm^− 1 [27]. The peak at 1252 cm^− 1 in the spectrum of the B/ZnO composite was attributed to the valence vibration of the B-O bond, which was not observed in the spectrum of ZnO [11]. In addition, the oscillations of the O-H bond in ZnO-O-H were observed at 698 and 866 cm^− 1 in the spectrum of ZnO, while they were at 704 and 924 cm^− 1 in the B/ZnO composite [28].

3.2. The influence of synthesis conditions on the morphology and photocatalytic activity of composite

3.2.1. Influence of solvent

The influence of the solvent on the morphology of the B/ZnO nanocomposite is shown in Fig. 4. When the solvent was water, the B/ZnO-Water composite had a non-uniform size of about 57–110 nm, in Fig. 4(a), these nanoparticles were closely arranged and formed spheres, in Fig. 4(b). With ethanol solvent, the B/ZnO-Ethanol had a relatively equal size of about 15 nm, which was smaller and more densely arranged than the samples with other solvents, as shown in Fig. 4(c). The B/ZnO-Isopropyl alcohol also exhibited an aggregate morphology, which possessed many small particles (26–82 nm) (Fig. 4(d)). However, both the B/ZnO-Ethanol and B/ZnO-Isopropyl alcohol composites exhibited a smooth surface, which may be attributed to the high viscosity of alcohol. Although the B signal was not detected, all the samples showed similar crystallinity with corresponding peaks of hexagonal wurtzite ZnO (Fig. 5). It implied that the viscosity of the solvent affects the size and surface but not the crystallinity of the composite.

Figure 6 exhibits that the B/ZnO–ethanol sample had high adsorption and catalytic activity. The Re and rate constant were 98.28% and 0.048 min^− 1, respectively. While the B/ZnO samples synthesized in water and isopropyl alcohol exhibited slower adsorption and reaction, the Re values were 77.22 and 82.09% in 120 min, and the constant rates were 0.016 and 0.019 min^− 1 for the B/ZnO – water and B/ZnO – isopropyl alcohol, respectively. This demonstrated that the smooth surface along with the small particle size could contribute to the enhancement of adsorption and photocatalytic activity of the B/ZnO-ethanol composite.

3.2.2. Influence of synthesis temperature

The experiments were conducted at 30, 60 and 75 $℃$ to explore the influence of temperature. At the synthesis temperature of 30 $℃$, the particles had a uniform size of about 45–63 nm, but there was a large particle with a size of 262 nm, in Fig. 7(a). These particles were arranged closely and clumped together, forming the porous structure in Fig. 7(b). At a high temperature of 60 $℃$, the B/ZnO particles became more uniform with a smaller size of about 15 nm (Fig. 7(c)). When the temperature increased to 75 $℃$, the morphology of B/ZnO changed significantly, showing a flake shape with an uneven size of about 48–158 nm, which was close to each other together, as shown in Fig. 7(e-f). These results indicated that the morphology of the B/ZnO nanocomposite was significantly affected by the synthesis temperature. The synthesis temperature significantly influenced the rate of crystal nucleation. The higher the temperature, the faster the reaction and the easier the crystal nucleation, which led to a disordered arrangement of crystals, which in turn resulted in a significant difference in the size of the composite particles.

The XRD spectra of the as-synthesized B/ZnO samples at different temperatures are shown in Fig. 8. All B/ZnO samples had the diffraction peaks of hexagonal wurtzite structure of ZnO, these peaks were sharp. In addition, no special peaks of B and impurities were found in the as-synthesized samples. As the temperature increased, the intensity of the peaks increased and they became sharper. This showed that the temperature does not only influence the morphology but also the crystallinity of the composite.

The influence of the synthesis temperature on the TCH removal efficiency is presented in Fig. 9. The B/ZnO-60 composite had higher adsorption and photodegradation of TCH than the B/ZnO-30 and B/ZnO-75 samples, with Re values of 72.52, 98.28 and 76.77% and reaction constants were 0.013, 0.048 and 0.012 min^− 1 at 30, 60 and 75 $℃$, respectively. This proved that the crystallinity does not contribute to the reaction efficiency, but the morphology and size of the B/ZnO composite are the decisive factors for the adsorption and photocatalysis efficiency.

3.2.3. Influence of solution pH

The influence of pH on the morphology and structure of the B/ZnO composite was investigated in the range from 7 to 11. Figure 10 shows that the morphology of the B/ZnO sample significantly changed with the pH value. At pH 7, B/ZnO was divided into pieces of about 63–93 nm in size. They were assembled from many nanoparticles and these pieces were tightly arranged into clumps as shown in Fig. 10(b-c). At pH 8, the B/ZnO sample had an equal size and was densely arranged. The size of the B/ZnO particles was about 15 nm (Fig. 10(d)). When the pH increased to 9, the morphology of B/ZnO drastically changed and exhibited both rod- like and sphere-shapes, (Fig. 10(g-i)). The nanospheres were formed from scale fragments with a size of about 20–25 nm and the nanorods and nanospheres were alternately arranged. At pH 10, the rod shape disappeared and a uniform spherical shape with size of 343 nm was observed, as shown in Fig. 10(l-m). At a high pH of 11, the uniform morphology was destroyed. Instead, indeterminate shapes were observed as shown in Fig. 10(n-p). This was also proven in the XRD results. The crystallinity of the B/ZnO-11 sample was slightly reduced compared to the B/ZnO-10 and B/ZnO-9 samples (Fig. 11).

The influence of the synthetic pH conditions on the removal of TCH is shown in Fig. 12. When the pH was increased from 7 to 8, the removal efficiency increased from 91.02 to 98.28% and the rate constant increased from 0.031 to 0.048 min^− 1 but the adsorption abilities of two samples were similar. At pH higher than 8, the adsorption and photodegradation of the B/ZnO composite were drastically decreased. The Re values were 78.68 and 55.03% and the rate constants were 0.021 and 0.01 min^− 1 at pH of 9 and 10, respectively, but the reaction increased with pH at 11. This could be explained by the number of OH⁻ increases with the pH of the solution, leading to an increased ability to generate OH• radicals, which in turn increases the photocatalytic ability of the B/ZnO composite [29]. The above results demonstrated that although a complete morphology of the B/ZnO composite with large and uniform particles was generated at pH 9 and 10, its catalytic activity was still lower than that of the B/ZnO samples at pH 8 with smaller particles.

3.2.4. Photocatalytic mechanism

The valence band energy (E_VB) and the conduction band energy (E_CB) were calculated according to the equation [30]:

E_CB = E_VB – E_g (5)

E_VB = χ – E_c + 0.5E_g (6)

Where E_g is the band gap energy of the material. E_CB and E_VB are the conduction band and valence band edge potential, respectively. E_c is the energy of the free electrons in the hydrogen (4.5 eV). χ is the absolute electronegativity of ZnO (5.95 eV) [31]. The calculated values for E_CB and E_VB were – 0.13 and 3.03 eV, respectively.

Based on the calculated data, the TCH degradation mechanism of the B/ZnO nanocomposite was illustrated in Fig. 13. When a photon energy greater than the band gap energy of the B/ZnO nanocomposite is excited, the electron (e⁻) transfers from the valence band (VB) to the conduction band (CB). At the same time, the holes (h⁺) are created in the VB. These electrons then react with the O₂ molecules in the air to create the radicals (•O₂⁻). These radicals react with H₂O to form the hydroperoxide (H₂O₂) and finally create the hydroxyl radicals (•OH). Similarly, the h⁺ reacts with the hydroxyl anion (OH⁻) in water to form the •OH radicals. All these radicals react with tetracycline hydrochloride to generate intermediate products and finally generate carbon dioxide (CO₂) and water (H₂O), which are friendly products to the environment.

The following reaction:

H₂O → H⁺ + OH⁻ (7)

B/ZnO + hν → B/ZnO (e⁻ + h⁺) (8)

e⁻ + O₂ → •O₂⁻ (9)

•O₂⁻ + H⁺ → HO₂• (10)

HO₂• + HO₂• → H₂O₂ + O₂ (11)

H₂O₂ + hν → 2•OH (12)

h⁺ + OH⁻ → •OH (13)

•OH/•O₂⁻ + TCH → intermediates → CO₂ + H₂O (14)

Since boron is an electron-deficient substance [11], it acts like an electron trap. The boron on the ZnO surface attracts electrons causing the electrons move from the CB region to the B before recombining with the hole in the VB region as presented by the red arrow in Fig. 13. This leads to a shortening of recombination of electrons and holed. Moreover, boron also attracts OH⁻ to the surface of the material, which leads to an increase the generation ability •OH radicals. The increased photocatalytic performance of the ZnO after doping with B could be explained by these things.

3.3. The electrical energy consumption

In the TCH treatment process, electrical energy consumption is an major factor in evaluating the economic efficiency of photocatalysts in industrial applications. Hence, the treatment cost should be estimated and investigated. Electrical energy consumption accounts for a significant part of the treatment cost. The figure-of-merit is the electrical energy per order (E_EO) which is calculated by using the Eq. (15) [32]:

E_EO = $\frac{{\text{P}}_{\text{e}\text{l}}\times \text{t} \times 1000}{\text{V} \times 60 \times \text{l}\text{o}\text{g}\left(\frac{{\text{C}}_{0}}{\text{C}}\right)}$ (15)

Where P_el is the power of the Hg lamp (kW). t is the reaction time (h). V is the volume of the reaction solution (L). C₀ and C are the initial and final TCH concentrations, respectively. The E_EO value of the as-synthesized samples is shown in Table 2.

Table 2

The TCH degradation efficiency and electrical energy consumption values (W.h.L^− 1) of the different samples. Reaction conditions: [TCH] = 20 mg/L, [catalyst] = 0.5 g/L, t = 90 min and 250 W Hg lamp.
Sample	Re (%)	E_EO (WhL^− 1)
ZnO	61.52	150.68
B/ZnO − 1	55.00	160.24
B/ZnO − 3	98.28	35.44
B/ZnO − 5	72.74	110.72
B/ZnO − 7	77.17	97.44
B/ZnO - Ethanol	98.28	35.44
B/ZnO - Water	70.65	117.39
B/ZnO – Isopropyl Alcohol	76.78	98.84
B/ZnO − 30	64.04	140.72
B/ZnO − 60	98.28	35.44
B/ZnO − 75	70.94	116.45
B/ZnO – pH7	91.02	59.70
B/ZnO – pH8	98.28	35.44
B/ZnO – pH9	73.59	108.10
B/ZnO – pH10	47.88	220.84
B/ZnO – pH11	64.57	138.68

After doping with B, the TCH removal increased significantly and the E_EO value decreased. In 90 min, the removal of the ZnO sample achieved only 61.52% and the E_EO value was 150.68 WhL^− 1. After doping with 3 wt.% B into ZnO, the removal significantly increased to 98.28%, but E_EO value decreased to 35.44 WhL^− 1. Thus, doping ZnO with B can improve the catalytic ability of ZnO and significantly saved electrical energy, which led to a decrease in the cost of the treatment process. Besides, the synthesis conditions of the B/ZnO material also affected the E_EO value of the material. For the synthesis solvent, the B/ZnO material synthesized in water had the highest E_EO value (117.39 WhL^− 1). It was 98.84 WhL^− 1 for the B/ZnO– isopropyl alcohol sample. The B/ZnO–ethanol sample consumed the least amount of electrical energy with an E_EO of 35.44 WhL^− 1. For synthesis temperature, the B/ZnO – 60 sample had the lowest E_EO value. The pH also significantly affected the TCH degradation efficiency and the E_EO value. The B/ZnO – pH8 sample had a TCH degradation efficiency of 98.28% and an E_EO value of 35.44 WhL^− 1. The B/ZnO – pH10 sample had the lowest removal efficiency (47.88%) and the highest E_EO value (220.84 WhL^− 1).

The physical properties of the B/ZnO materials were facially controlled by synthesis conditions including solvent, temperature, and solution pH. The ZnO material had an unequal size (42–79 nm). The doping with B led to a decrease in the size of the B/ZnO composite, it had an equal size (~ 15 nm) and was closely arranged, resulting in an increase in TCH removal efficiency. The synthesis conditions have a significantly effect on the morphology of B/ZnO. The viscosity of the solvent had a significantly effect on the size and surface but did not affect the and crystallinity of the composite. Both the B/ZnO-Ethanol and B/ZnO-Isopropyl alcohol composites exhibited a smooth surface. The synthesis temperature had a significantly influence on the rate of crystal nucleation. The higher the temperature, the faster the reaction and the easier the crystal nucleation. This shows that the temperature not only affects the morphology and crystallinity of the composite. At a high temperature of 60 $℃$, the B/ZnO particles became more uniform and had a smaller size of about 15 nm. It was found that although a complete morphology of the B/ZnO composite with large and uniform particles was formed at pH values 9 and 10, its catalytic activity was still lower than that of the B/ZnO samples at pH value of 8 with smaller particles. The optimal conditions for the synthesis of the B/ZnO nanocomposite were ethanol as a solvent, a temperature of 60 $℃$, and a pH of 8. The removal efficiency of the B/ZnO nanocomposite archived 98.28% in 90 min and the rate constant was 0.048 min^− 1. In addition, the electrical energy consumption was estimated and the electrical energy per order only was only 35.44 W.h.L^− 1.

Acknowledgments

This study was funded by the Ministry of Education and Training of Vietnam, under grant number CT2022.04.BKA.01. The work was performed at the Vietnam Germany Catalysis Centre - RoHan Project funded by the German Academic Exchange Service (DAAD, No. 57315854) and the Federal Ministry for Economic Cooperation and Development (BMZ) inside the framework "SDG Bilateral Graduate school programme. Thu Huong Nguyen was funded by the Master, PhD Scholarship Programme of Vingroup Innovation Foundation (VINIF), code VINIF.2023.ThS.061.

Funding: No funding

Author contributions:

All authors contributed to the study's conception and design. Thu Huong Nguyen is the person who came up with the idea and is mainly responsible for this research. Tuan Vu Anh was the person who supported, advised, and reviewed during the study process. Material preparation, data collection, and analysis were performed by Thu Huong Nguyen, Viet Minh Nguyen, Tien Thanh Mai, Thi Phuong Tran, Cam Ly Tran Thi, Cam Vi Dao Thi, Mai Lan Vu Thi, and Thanh Hung Nguyen. The first draft of the manuscript was written by Thu Huong Nguyen and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

L.-J. Bao, K.A. Maruya, S.A. Snyder, E.Y. Zeng, China's water pollution by persistent organic pollutants, Environmental Pollution 163 (2012) 100-108. https://doi.org/https://doi.org/10.1016/j.envpol.2011.12.022.
Q. Chen, S. Wu, Y. Xin, Synthesis of Au–CuS–TiO2 nanobelts photocatalyst for efficient photocatalytic degradation of antibiotic oxytetracycline, 302 (2016) 377-387. https://doi.org/https://doi.org/10.1016/j.cej.2016.05.076.
R. Hao, X. Xiao, X. Zuo, J. Nan, W. Zhang, Efficient adsorption and visible-light photocatalytic degradation of tetracycline hydrochloride using mesoporous BiOI microspheres, J. Hazard. Mater. 209 (2012) 137-145. https://doi.org/https://doi.org/10.1016/j.jhazmat.2012.01.006.
P.T.P. Hoa, S. Managaki, N. Nakada, H. Takada, A. Shimizu, D.H. Anh, P.H. Viet, S. Suzuki, Antibiotic contamination and occurrence of antibiotic-resistant bacteria in aquatic environments of northern Vietnam, Science of The Total Environment 409(15) (2011) 2894-2901. https://doi.org/https://doi.org/10.1016/j.scitotenv.2011.04.030.
C.-Y. Pei, Y.-G. Chen, L. Wang, W. Chen, G.-B. Huang, Step-scheme WO₃/CdIn₂S₄ hybrid system with high visible light activity for tetracycline hydrochloride photodegradation, Appl. Surf. Sci. 535 (2021) 147682. https://doi.org/https://doi.org/10.1016/j.apsusc.2020.147682.
R. Hong, T. Pan, J. Qian, H. Li, Synthesis and surface modification of ZnO nanoparticles, 119(2-3) (2006) 71-81. https://doi.org/https://doi.org/10.1016/j.cej.2006.03.003.
S.-Y. Lee, S.-J. Park, TiO2 photocatalyst for water treatment applications, 19(6) (2013) 1761-1769. https://doi.org/https://doi.org/10.1016/j.jiec.2013.07.012.
X. Liu, R. Ma, L. Zhuang, B. Hu, J. Chen, X. Liu, X. Wang, Recent developments of doped g-C₃N₄ photocatalysts for the degradation of organic pollutants, 51(8) (2021) 751-790. https://doi.org/https://doi.org/10.1080/10643389.2020.1734433.
S. Zhang, H.-S. Chen, K. Matras-Postolek, P. Yang, ZnO nanoflowers with single crystal structure towards enhanced gas sensing and photocatalysis, 17(45) (2015) 30300-30306. https://doi.org/https://doi.org/10.1039/C5CP04860E.
T.H. Nguyen, A.T. Vu, Investigation of enhanced degradation of antibiotic under visible in novel B/ZnO/TiO2 nanocomposite and its electrical energy consumption, Nanotechnology (2023).
T.H. Nguyen, A.-T. Vu, Preparation of B/ZnO Nanocomposite by Simple Mechanical Combustion Method for Removal of Antibiotics in Aqueous Environments, Bulletin of Chemical Reaction Engineering & Catalysis 17(4) (2022) 786-797. https://doi.org/https://doi.org/10.9767/bcrec.17.4.16090.786-797.
T.A.T. Pham, V.A. Tran, V.D. Le, M.V. Nguyen, D.D. Truong, X.T. Do, A.-T. Vu, Facile preparation of ZnO nanoparticles and Ag/ZnO nanocomposite and their photocatalytic activities under visible light, J. Anal. Methods Chem. 2020 (2020) 1-14. https://doi.org/https://doi.org/10.1155/2020/8897667.
A. Tereshchenko, M. Bechelany, R. Viter, V. Khranovskyy, V. Smyntyna, N. Starodub, R. Yakimova, Optical biosensors based on ZnO nanostructures: advantages and perspectives. A review, 229 (2016) 664-677. https://doi.org/https://doi.org/10.1016/j.snb.2016.01.099.
K. Qi, B. Cheng, J. Yu, W. Ho, Review on the improvement of the photocatalytic and antibacterial activities of ZnO, 727 (2017) 792-820. https://doi.org/https://doi.org/10.1016/j.jallcom.2017.08.142.
F. Li, L. Yang, G. Xu, H. Xiaoqiang, X. Yang, X. Wei, Z. Ren, G. Shen, G. Han, Hydrothermal self-assembly of hierarchical flower-like ZnO nanospheres with nanosheets and their application in Li-ion batteries, 577 (2013) 663-668. https://doi.org/https://doi.org/10.1016/j.jallcom.2013.06.147.
V.H. Mac, A.-T. Vu, Controlling the 3D flower-like ZnO via simple precipitation method and its formation mechanism and photocatalytic application, Journal of the Chinese Chemical Society 69(12) (2022) 1997-2005. https://doi.org/https://doi.org/10.1002/jccs.202200437.
T. Vu Anh, T.A.T. Pham, V.H. Mac, T.H. Nguyen, Facile Controlling of the Physical Properties of Zinc Oxide and Its Application to Enhanced Photocatalysis, Journal of Analytical Methods in Chemistry 2021 (2021) 5533734. https://doi.org/10.1155/2021/5533734.
T.A.T. Pham, V.A. Tran, V.D. Le, M.V. Nguyen, D.D. Truong, X.T. Do, A.-T. Vu, Facile Preparation of ZnO Nanoparticles and Ag/ZnO Nanocomposite and Their Photocatalytic Activities under Visible Light, International Journal of Photoenergy 2020 (2020) 8897667. https://doi.org/10.1155/2020/8897667.
T.A. Nguyen Thi, A.-T. Vu, Nanocomposite ZnO/g-C₃N₄for Improved Degradation of Dyes under Visible Light: Facile Preparation, Characterization, and Performance Investigations, Bulletin of Chemical Reaction Engineering & Catalysis 17(2) (2022) 17. https://doi.org/10.9767/bcrec.17.2.13931.403-419.
A.-T. Vu, T.A.T. Pham, X.T. Do, V.A. Tran, V.D. Le, D.D. Truong, T.H. Nguyen, M.V. Nguyen, Preparation of Hierarchical Structure Au/ZnO Composite for Enhanced Photocatalytic Performance: Characterization, Effects of Reaction Parameters, and Oxidizing Agent Investigations, Adsorption Science & Technology 2021 (2021) 5201497. https://doi.org/10.1155/2021/5201497.
T.H. Nguyen, A.-T. Vu, Preparation of B/ZnO Nanocomposite by Simple Mechanical Combustion Method for Removal of Antibiotics in Aqueous Environments, Bulletin of Chemical Reaction Engineering & Catalysis 17(4) (2022) 786-797. https://doi.org/10.9767/bcrec.17.4.16090.786-797.
M. Liu, J. Jiang, H. Tan, B. Chen, J. Ou, H. Wang, J. Sun, L. Liu, F. Wang, J. Gao, C. Liu, F. Peng, Y. Liu, Y. Tu, Light-driven Au–ZnO nanorod motors for enhanced photocatalytic degradation of tetracycline, Nanoscale 14(35) (2022) 12804-12813. https://doi.org/10.1039/D2NR02441A.
H.A. Gatz, D. Koushik, J.K. Rath, W.M.M. Kessels, R.E.I. Schropp, Atomic Layer Deposited ZnO: B As Transparent Conductive Oxide for Increased Short Circuit Current Density in Silicon Heterojunction Solar Cells, Energy Procedia 92 (2016) 624-632. https://doi.org/https://doi.org/10.1016/j.egypro.2016.07.028.
T. Koida, J. Nishinaga, H. Higuchi, A. Kurokawa, M. Iioka, Y. Kamikawa-Shimizu, A. Yamada, H. Shibata, S. Niki, Comparison of ZnO:B and ZnO:Al layers for Cu(In,Ga)Se₂ submodules, Thin Solid Films 614 (2016). https://doi.org/10.1016/j.tsf.2016.03.004.
R.E. Núñez-Salas, J. Rodriguez-Chueca, A. Hernández-Ramírez, E. Rodríguez, M. de Lourdes Maya-Treviño, Evaluation of B-ZnO on photocatalytic inactivation of Escherichia coli and Enterococcus sp, Journal of Environmental Chemical Engineering 9(1) (2021) 104940.
V.H. Mac, A.T. Vu, Controlling the 3D flower‐like ZnO via simple precipitation method and its formation mechanism and photocatalytic application, J. Chin. Chem. Soc. 69(12) (2022) 1997-2005. https://doi.org/https://doi.org/10.1002/jccs.202200437.
A.Z. Ahmed, M.M. Islam, M.M.u. Islam, S.M. Masum, R. Islam, M.A.I. Molla, Fabrication and characterization of B/Sn-doped ZnO nanoparticles via mechanochemical method for photocatalytic degradation of rhodamine B, Inorganic and Nano-Metal Chemistry 51(10) (2020) 1369-1378. https://doi.org/https://doi.org/10.1080/24701556.2020.1835976.
L.T. Mai, L.T. Hoai, V.A. Tuan, Effects of reaction parameters on photodegradation of caffeine over hierarchical flower‐like ZnO nanostructure, 56(5) (2018) 647-653. https://doi.org/https://doi.org/10.1002/vjch.201800064.
T.H. Nguyen, T.A.N. Cong, A.-T. Vu, Synthesis of Carnation-Like ZnO for Photocatalytic Degradation of Antibiotics, Including Tetracycline Hydrochloride, Environmental Engineering Science 40(8) (2023) 329-339. https://doi.org/10.1089/ees.2023.0034.
J. Gao, Y. Zhou, Z. Li, S. Yan, N. Wang, Z. Zou, High-yield synthesis of millimetre-long, semiconducting carbon nitride nanotubes with intense photoluminescence emission and reproducible photoconductivity, 4(12) (2012) 3687-3692. https://doi.org/https://doi.org/10.1039/C2NR30777D.
I. Hegazy, R. Geioushy, S. El-Sheikh, A. Shawky, S. El-Sherbiny, A.-H.T. Kandil, Influence of oxygen vacancies on the performance of ZnO nanoparticles towards CO₂ photoreduction in different aqueous solutions, J. Environ. Chem. Eng. 8(4) (2020) 103887. https://doi.org/https://doi.org/10.1016/j.jece.2020.103887.
N. Modirshahla, M.A. Behnajady, R. Rahbarfam, A. Hassani, Effects of operational parameters on decolorization of CI Acid Red 88 by UV/H₂O₂process: evaluation of electrical energy consumption, CLEAN - Soil Air Water 40(3) (2012) 298-302. https://doi.org/https://doi.org/10.1002/clen.201000574.

No competing interests reported.

Download PDF

Journal Publication

published 11 Mar, 2024

Read the published version in Journal of Sol-Gel Science and Technology →

Editorial decision: Revision requested
01 Feb, 2024
Reviews received at journal
01 Feb, 2024
Reviewers agreed at journal
30 Jan, 2024
Reviewers invited by journal
30 Jan, 2024
Submission checks completed at journal
28 Jan, 2024
Editor assigned by journal
28 Jan, 2024
First submitted to journal
26 Jan, 2024

You are reading this latest preprint version

Studying the Nanocomposite B/ZnO for Photocatalysis: Facile Control the Morphology via Sol-gel Method and Antibiotic Degradation Investigations

Status:

Journal Publication

Version 1

Abstract

Figures

Highlights

1. Introduction

2. Experimental

2.1. Materials

2.2. Methods

2.3. Preparation of the materials

2.4. The photocatalytic process

3. Results and discussion

3.1. Comparing ZnO and B/ZnO nanocomposites

3.2. The influence of synthesis conditions on the morphology and photocatalytic activity of composite

3.2.1. Influence of solvent

3.2.2. Influence of synthesis temperature

3.2.3. Influence of solution pH

3.2.4. Photocatalytic mechanism

3.3. The electrical energy consumption

4. Conclusion

Declarations

References

Additional Declarations

Status:

Journal Publication

Version 1