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TiO2 photocatalyst
Journal of Colloid and Interface Science xxx (xxxx) xxx
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UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst Zhao Wang a,⇑, Varsha Srivastava a, Shaobin Wang b, Hongqi Sun c, Senthil K. Thangaraj d, Janne Jänis d, Mika Sillanpää a a
Department of Green Chemistry, LUT University, Sammonkatu 12, FI-50130 Mikkeli, Finland School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia School of Engineering, Edith Cowan University, Perth, WA 6027, Australia d Department of Chemistry, University of Eastern Finland, Yliopistokatu 7, 80130 Joensuu, Finland b c
g r a p h i c a l a b s t r a c t
a r t i c l e
i n f o
Article history: Received 19 August 2019 Revised 18 November 2019 Accepted 23 November 2019 Available online xxxx Keywords: Nd-doped Carbamazepine Photocatalytic UVC Sb2O3/TiO2
a b s t r a c t The photocatalytic degradation of carbamazepine (CBZ) in ultra-pure water was investigated by using neodymium (Nd)-doped antimony trioxide (Sb2O3)/titanium dioxide (TiO2) photocatalyst under the UVC irradiations of 254 nm wavelength. The hydrothermal method was used for the fabrication catalyst samples with different ratios of Nd (0%–2%) dopant, and characterised by X-ray diffraction pattern (XRD) to investigate the crystallinity. Scanning electron microscopy (SEM) provided the surface morphologies, Bruanuer-Emmer-Teller (BET) analysis gave the textural properties, and UV–Vis diffuse reflectance absorption spectroscopy (DRS) was used for the investigation of the optical properties of synthesized catalysts. TEM images of Sb2O3 showed a nanorod-like structure while, in the Nd-doped Sb2O3/TiO2, a small dot-like structure was observed along with the nanorods. The surface area and band gap of 1% Nd-doped Sb2O3/TiO2 were found to be 9.56 m2 g1 and 3.0 eV respectively. It was observed that the CBZ cannot be degraded in the absence of catalyst under UV light, while photocatalyst 1% Nd-doped Sb2O3/TiO2 at 0.5 g/ L of catalyst dose showed the best photocatalytic activity towards CBZ degradation. The main degradation products were identified with high-resolution mass spectrometry. Moreover, the degradation of CBZ followed pseudo first-order kinetics and the rate constant was 0.017 min1. Quenching tests by the addition
⇑ Corresponding author. E-mail address: [email protected] (Z. Wang). https://doi.org/10.1016/j.jcis.2019.11.094 0021-9797/Ó 2019 Elsevier Inc. All rights reserved.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
of methanol from 100 to 500 mM were carried out to determine the major reactive oxygen species, which showed that OH radicals was involved in the CBZ degradation. Active species-trapping experiments revealed that ∙O 2 is also responsible for the degradation of CBZ. Ó 2019 Elsevier Inc. All rights reserved.
1. Introduction Nowadays the trend of pharmaceutical drugs consumption goes increasing, hence these chemicals have been detected in water bodies. Traditional water treatment technologies are not efficient for the complete removal of pharmaceutical drugs from wastewater and, due to inappropriate disposal, these chemicals have been found in natural water bodies [1–3]. One of the pharmaceuticals, carbamazepine (5H-dibenzo [b,f] azepine-5-carboxamide) has attracted attention as it was detected in the surface water, tap water, and in wastewater at a significant concentration. Carbamazepine (CBZ) has been widely used for trigeminal neuralgia, seizure disorders, and other psychiatric disease treatment. It is known that 1.014 tonnes of CBZ are produced every year, and it is now the most common pharmaceutical pollutant found in water bodies. The concentration of CBZ was detected to be 610 ngL1 in groundwater and 18 ngL1 in drinking water [4–6]. Moreover, for aquatic life, CBZ is also a toxic pharmaceutical. For example, algae, invertebrates, bacteria, and fish can be severely influenced by CBZ in water, so the development of an effective elimination method for CBZ is crucial for wastewater treatment. Not only the CBZ, but other organic pollutants also co-exist in wastewater. To improve the capacity of the adsorption of TiO2, molecularly imprinted polymers can be used with the combination of TiO2 to eliminate the different types of organic pollutants [7]. CBZ and other pharmaceutical drugs contaminants can be removed by an advanced oxidation process (AOP) [8]. AOP is an effective method with the possibility of mineralisation of contaminants and degradation of pollutants [9–12]. AOPs can generate reactive radicals, for example, hydroxyl radicals (OH), which are a strong oxidative species and can degrade the organic pollutants into carbon dioxide (CO2) and water (H2O) [13]. The AOPs have been developed in recent years for the remediation of organic pollutants. Among them, heterogeneous photocatalysis has been considered as a promising method for the elimination of a variety of organic contaminants [14–17]. Sb2O3 has been widely used as a coupling component in the development of photocatalyst due to its low cost, reproducibility and long-term stability. Liu et al. [18] reported that Sb2O3 coupled with TiO2 can transfer the valence band (VB) holes in the TiO2 surface and localise the conduction band (CB) electrons on the surface of Sb2O3. TiO2 is the most efficient and popular semiconductor photocatalyst due to its stability and low cost [19–22]. One of the methods of enhancing the activity of TiO2 is non-metal doping. Nitrogen is a significant non-metal dopant because of its lower ionisation and high stability. N-doped TiO2 response under the visible light was explored by some researchers [23,24]. The band gap also can be decreased by adding other non-metals such as C, P, and S. The valence and conduction bands from the electronic disorder are changed by the variety of lattice parameters and by creating trapping states [25–27]. Bokare et al. found that Nd-doped TiO2 showed effective photocatalytic activity under UV and solar light irradiations [28]. Various efforts are being made by many researchers to understand the fundamental mechanisms for enhancing the efficiency of TiO2. Various dopant have been added with TiO2 for enhancement of catalytic activity. However, neodymium (Nd) doped Sb2O3/TiO2 for CBZ degradation has not been well explored.
The aims of the present study are the synthesis of Neodymium (Nd) doped Sb2O3/TiO2 at different ratios of Nd by a hydrothermal method and the investigation of their photocatalytic performances towards CBZ degradation under UVC light irradiation. The reaction parameters such as the pH of CBZ solution, initial concentration, and catalyst dose were optimised for the photocatalytic degradation of CBZ. 2. Materials and methods 2.1. Chemicals Titanium (IV) butoxide, titanium (IV) isopropoxide, antimony (III) chloride, triethanolamine, carbamazepine (CBZ) and neodymium oxide were purchased from Sigma-Aldrich. The deionised water from a Milli-Q water purification system was used for the preparation experiment solution. Sodium hydroxide, potassium hydroxide, and ammonia solution were used for the pH adjustment. 2.2. Synthesis of Nd-doped Sb2O3/TiO2 photocatalyst Nd-doped (0%–2%) Sb2O3/TiO2 catalysts were prepared using a facile hydrothermal method as reported in the literature by Liu et al. and Bokare et al. [18,28]. For the synthesis of catalyst, the solution A was made by antimony trichloride (SbCl3) which was dissolved in 40 mL methanol. TiO2 was synthesised by the sol– gel method according to the literature [29]. The TiO2 was dissolved in 40 mL deionized water and named as solution B. For Solution C, neodymium oxide was firstly dissolved in nitric acid, and a certain amount of Nd dopant was achieved using neodymium nitratenitric acid solution dissolved in a mixture of 10:1 with ethanol and water. All three solutions A, B and C were mixed and the pH value at 8–9 was adjusted by the addition of ammonia solution. The mixture solution was transferred in the autoclave and kept at 120 °C for 12 h. When the synthesised Nd-doped Sb2O3/TiO2 catalyst was cooled down to room temperature, the deionised water was used for washing of the synthesized catalysts and dried at 50 °C for 4 h. 2.3. Characterisation of catalysts The synthesised Nd-doped Sb2O3/TiO2 catalysts were characterised by different techniques. The crystalline phases of the catalysts were investigated from the X-ray diffraction patterns (XRD) measured with a step size of 0.02° and a scan speed of 2°/min over a 2h range of 5–100° by a PANalytical X-ray Diffractometer. The surface area and porosity of the synthesised catalysts were analysed from N₂ adsorption-desorption isotherm at 77 K using a Micromeritics Tristar II plus a BET surface area analyser. The band gap of catalysts was determined by the UV–Vis diffuse reflectance spectroscopy (Lambda 950 spectrophotometer). The surface morphology of catalysts was investigated by a Scanning Electron Microscope (HITACHI, S-4800) and the particle diameter of the catalysts was measured through the transmission electron microscopy (TEM-Hitachi 7700).
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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2.4. Photodegradation experiments A 50 mL quartz beaker was used for photocatalytic experiments under the UVC irradiation. A certain concentration of CBZ solution with the catalyst was taken into the reactor and for proper dispersion of catalyst in CBZ solution, a magnetic stirrer at the 500 rpm rotational speed was used. Before UVC irradiation, catalyst adsorption-desorption reactions were carried out in the dark for 2 h stirring in a magnetic stirrer. The samples were withdrawn periodically using 0.2 mm regeneration cellulose (RC) membrane for catalyst filter and stored in the vials for HPLC analysis. Catalyst adsorption-desorption reactions were carried out in the dark for 2 h, stirring in a magnetic stirrer. 2.5. Analytical methods A high-performance liquid chromatography (HPLC) system (SHIMADZUÒ) was used for the measurement of the carbamazepine concentration in the treated samples. A C18 HPLC column (PhenomenexÒ 5 mm, 150 mm 4.6 mm) with a UV detector at a wavelength of 285 nm was used in this study. The acetonitrile and water were used as buffer solution for the mobile phase. The ratio between acetonitrile and water was 60:40. The mineralisation degrees of CBZ were tested by a total organic carbon (TOC) analyser (Shimadzu TOC-V CPH/CPN and ASI-V Autosampler). Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer (Bruker Daltonics, Bremen, Germany) was used for the determination of the degradation products of CBZ. The FT-ICR running in the positive-ion mode. 10 mL sample was prepared with 1v-% acetic acid in methanol (10:20, v/v). The instrument control and data acquisition have used the software of Bruker ftms Control 2.1. Bruker Data Analysis 4.4 was used for analysis of the mass spectra. 3. Results and discussion 3.1. Catalyst characterisation XRD patterns of Sb2O3 and Sb2O3/TiO2 catalysts with different molar ratios of Nd doping are shown in Fig. 1. The existence of both anatase and rutile phase of TiO2 can be seen in synthesised catalysts. The characteristic peaks were compared with the reference (ICSD #98-001-5409) and (ICSD #98-007-4532) for anatase and rutile with the characteristic peaks 29.55° and 32.50°, respectively.
* TiO # Sb O ¤ Nd *# * 2
2
#
0.5% Nd-doped Sb 2 O 3 /TiO 2
* *
¤
¤ 1% Nd-doped Sb 2 O 3 /TiO 2
Intensity (a.u.)
#
* ¤
¤ 1.5% Nd-doped Sb2 O 3/TiO 2
#
*
*
¤
¤
¤
¤
#
2% Nd-doped Sb 2 O 3 /TiO 2
* *
Sb 2 O 3
#
0
20
Sb2O3 peaks were confirmed with the reference (ICSD #98-0031102). Peaks at 58.58° and 64.61° (ICSD#98-064-5585) are corresponding to Nd3+ dopant. The FT-IR spectra of 0%2% Nd-doped Sb2O3/TiO2 and synthesised Sb2O3 are shown in Fig. 2. The peak 3400 cm1 is due to the adsorbed water molecules, but it was not present in pure Sb2O3. The peak at 1632 cm1 can be attributed to the surface hydroxyl group [30]. The range from 500 to 800 cm1 can be attributed to the Ti-O and Sb-O stretching modes [31,32]. SEM and TEM images of Sb2O3/TiO2 with different ratios of Nd doping and pure Sb2O3 are shown in Fig. 3. The SEM images showed that the particles have agglomerated as flower-like structures when a high Nd doping level was used. In addition, a rodshaped structure can be seen in the pure Sb2O3, which is also proved by Deng et al. [33]. Based on the image of the synthesised Sb2O3, it can be speculated that the dot parts in Nd-doped Sb2O3/ TiO2 are the Nd-doped TiO2. The reflectance spectra of Nd-doped Sb2O3/TiO2 photocatalysts are illustrated in Fig. 4. For all different ratios of Nd-doped Sb2O3/TiO2, the band gap was calculated to be 3.0 eV. It was observed that for the sample without Nd doping, band gap energy is slightly higher (3.05 eV) than in other Nd-doped catalysts. For synthesised Sb2O3, The band gap is 3.3 eV. The lower band gap can enhance the activity of catalysts [34]. Table 1 shows the band gap energies, porosity and specific surface areas of synthesised Nd-doped Sb2O3/TiO2 catalysts. The BET adsorption-desorption isotherm plots for Nd-doped Sb2O3/TiO2 are shown in Fig. 5. From 0.5% Nd-doped Sb2O3/TiO2 to 2% Nddoped Sb2O3/TiO2, the BET surface areas increased from 3.78 to 12.14 m2 g1 respectively. However, the BET surface area is not the only factor to affect the photocatalytic ability of catalysts [35]. 3.2. Kinetics study of CBZ photocatalytic degradation The kinetics study of the photocatalytic degradation of CBZ was investigated by varying the reaction time, solution pH and catalyst dose. The degradation kinetics of CBZ over Nd (0%–2%)-doped Sb2O3/TiO2 were analysed by the following pseudo-first order kinetic model.
ln
C0 Ct
¼ kt
ð1Þ
where C0 is the initial concentration of CBZ and Ct is the CBZ concentration after treatment. t refer to the treatment time and k is the constant of reaction rate (min1).
0% Nd-doped Sb2O 3 /TiO 2
3
*
3
40
60
80
100
2Theta (degree) Fig. 1. The XRD patterns of the prepared Nd-doped Sb2O3/TiO2 as comparison to pure Sb2O3.
3.2.1. Effect of initial pH In photocatalytic water treatment, one of the significant factor is the pH value of the solution, as the isoelectric point of the photocatalysts can be affected by pH. The catalysts can change the surface charge, which may affect the interaction between water contaminants and catalysts surfaces. Moreover, Aghabeygi and Khademi-shamami [36] reported that the electron hole may change the rate of recombination for the catalyst surface by vary pH value of the solution. To investigate the effect of pH on the photocatalytic degradation of CBZ under UVC irradiation, pH values of CBZ solution were adjusted to 3, 5, 7, 9 and 11 for the photocatalytic experiment. All experiments were conducted the CBZ solution with 20 ppm concentration, 1 g/L dose of catalysts and irradiation time is 120 min. As shown in Fig. 6, at different pH conditions, the degradation efficiency of synthesised catalysts did not respond similarly. Overall, different catalysts gave good performances in degradation of CBZ at pH 7 and pH 9. The most efficient catalyst is 1% Nd-doped Sb2O3/TiO2 with 66.9% degradation efficiency at pH 9. This result
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
Transmittance (%)
4
3400
1632
0% Nd doped Sb 2 O 3 /TiO
0.5% Nd doped Sb 2 O 3 /TiO 1% Nd doped Sb 2 O 3 /TiO
4000
3500
1.5% Nd doped Sb 2 O 3 /TiO
2
2
2
3000
2% Nd doped Sb 2 O 3 /TiO
800
2
2
Sb 2 O 3
2500
2000
1500
1000
500
-1
Wavenumber (cm ) Fig. 2. FTIR spectra of 0%–2% Nd-doped Sb2O3/TiO2 and Sb2O3.
Fig. 3. Images of SEM (a,b,c,d,e,f) and images of TEM (g,h,i,j,k,l) of the various Nd-doped Sb2O3/TiO2.
was in good agreement with the a reported study by Bokare et al., which showed that 1% Nd-doped TiO2 can enhance the efficiency of the catalyst [28].
The higher density of hydroxyl ions can appear under the alkaline conditions, which facilitate the generation of more hydroxyl radicals. The catalyst stability was investigated by measuring the
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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catalyst dose, the experiments were conducted with constant parameters (pH 9, 20 ppm CBZ solution, 1% Nd-doped Sb2O3/TiO2 catalyst, and irradiation time of 120 min). Fig. 10 shows the degradation rate and adsorption removal of CBZ by the synthesised catalysts. It can be clearly seen that the optimum value for catalyst loading is 0.5 g/L, but adsorption removal is not the best at this catalyst dose. With higher catalysts loading, the degradation rate was not satisfied. Adsorption removal is increased by increasing the catalyst dose. The optimum degradation rate is 88.2% with 0.5 g/L catalyst dose and the adsorption removal is 6.78% with 2 g/L catalyst dose. By membrane bioreactor (MBR) treatment, 68 ± 10%, removal of for the CBZ can be achieved but needs near-anoxic conditions [38]. The Photo-Fenton process is also a better choice for CBZ degradation, but the pH value condition is somewhat strict [39].
Fig. 4. The derived plots from Kubelka-Munk function for catalysts synthesised.
concentration of leached metal ion after 120 min UV irradiation at different pH values (Fig. 7). The metal ion centration was measured by Inductively coupled plasma- optical emission spectroscopy (ICP-OES Agilent 5110). It was observed that, from pH 3 to pH 11, Nd ions were not found in solutions. However, leaching of Ti and Sb ions was observed at a high pH value (pH 11). It was noticed that with 0% Nd-doped Sb2O3/TiO2 at pH 11, Ti ion leaching is the highest among all catalysts, while Sb ion leaching is the lowest. Sb ion leaching increased with the increase in the pH of CBZ solutions. The total organic carbon (TOC) was used for measuring the mineralisation of the treated CBZ samples after 2 h of treatment at different pH values. As shown in Fig. 8, not all the selected catalysts showed significant degradation of CBZ. It can be speculated that, with CBZ degradation treatment, some intermediates were produced under the photodegradation, so cannot be mineralised [37]. And another possibility is due to the low specific surface area of the catalyst, the photocatalysts were saturated. Another significant factor for catalysis is the recyclability of the catalysts for industrial applications. To make sure that the catalysts can be used in large scale, the catalysts were reused and tested for stability. After 120 min of irradiation, each catalyst was washed with deionized water and centrifuged. The catalysts were reused for the second round to degrade the 20 ppm CBZ solution. The best degradation rate of recycled catalyst showed a slight decrease (4%) compared to the first time on 1% Nd-doped Sb2O3/TiO2 (Fig. 9). 3.2.2. Catalysts dose loading study Catalyst loading is one of the important factors for photocatalytic reaction rate. Due to the light screening effect by the excess catalyst, the photodegradation rate starts to decrease when the catalyst dose is beyond optimum loading. To understand the optimum
Fig. 5. BET adsorption-desorption isotherm plot for synthesised catalysts.
Fig. 6. The degradation performance of CBZ by Sb2O3/TiO2 with different ratios of Nd doping and different initial pH. (Initial concentration = 20 ppm, Dose of catalysts = 1 g/L, UVC treatment time = 120 min).
Table 1 Band gap energies and structural parameters of the catalysts. Catalysts
Bandgap energy (eV)
BET surface area (m2 g1)
Pore volume (cm3 g1)
Pore size (Å)
0% Nd-doped Sb2O3/TiO2 0.5% Nd-doped Sb2O3/TiO2 1% Nd-doped Sb2O3/TiO2 1.5% Nd-doped Sb2O3/TiO2 2% Nd-doped Sb2O3/TiO2 Sb2O3
3.05 3.0 3.0 3.0 3.0 3.3
14.5 3.8 9.6 10.7 12.1 4.6
0.03 0.02 0.02 0.02 0.02 0.01
88.3 227.5 86.1 83.6 87.0 75.1
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
6
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx 50 0% Nd doped Sb2O3/TiO2
5
Sb
0.5% Nd doped Sb2O3/TiO2 1% Nd doped Sb2O3/TiO2
40
Metal Leaching (mg/L)
6
Meatal Leaching (mg/L)
Ti
0% Nd doped Sb2O3/TiO2 0.5% Nd doped Sb2O3/TiO2 1% Nd doped Sb2O3/TiO2 1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2
4
3
2
1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2 Sb2O3
30
20
10
1
0
pH 3
pH 5
pH 7
pH 9
0
pH 11
pH 3
pH 5
pH 7
(a)
pH 9
pH 11
(b)
Fig. 7. The catalysts metal ion leaching during the degradation of CBZ at different pH value: Ti leaching (a) and Sb leaching (b).
Fig. 8. Mineralisation degree for the photocatalytic degradation of CBZ on Sb2O3/ TiO2 with different ratios of Nd doping (Initial concentration = 20 ppm, Dose of catalysts = 1 g/L, UVC treatment time = 120 min). 0% Nd doped Sb2O3/TiO2 0.5% Nd doped Sb2O3/TiO2
Fig. 10. Degradation rate of CBZ by 1% Nd-doped Sb2O3/TiO2.
1% Nd doped Sb2O3/TiO2
70
1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2 Sb2O3
3,0
20ppm 15ppm 10ppm 5ppm
50
2,5 40
Ln (C0/Ct)
Degradation rate %
60
30 20
2,0
1,5
1,0
10
0,5
0 1st
2nd
Cycle number Fig. 9. Stabilisation degree on the photocatalytic degradation of CBZ by Nd doped catalyst (initial concentration = 20 ppm, 1 g/L of catalysts dose, UVC treatment time = 120 min).
0,0 0
15
30
45
60
75
90
105
120
Time (min) Fig. 11. Degradation kinetic modelling of CBZ by 1% Nd-doped Sb2O3/TiO2 at different initial concentrations of CBZ.
3.2.3. Effect of initial CBZ concentration The experiments for CBZ concentration effects were conducted at different initial concentrations at a constant pH value, catalyst dose and irradiation time. The photodegradation of CBZ by 1%
Nd-doped Sb2O3/TiO2 at a different initial concentration of CBZ from 5 to 20 ppm was conducted under UVC irradiations at pH 9 and a catalyst dose of 0.5 g/L. The maximum degradation and
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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experimental data. With 5 ppm of CBZ solution, the degradation rate constant was 0.049 min1. With the previous study, the degradation rate constant by using TiO2 for dye was reported to be 0.059 min1 [15]. Hydroxyl radicals (OH, 1.9–2.7 V) and sulphate radical (SO 4, 2.5–3.1 V) are common reactive species in AOPs. Methanol was used for the further confirmation of the effects of radical scavengers. The reaction rate constants by methanol for HO and SO 4 are 9.7 108 and 3.2 106 min1, respectively [40,41]. As shown in Fig. 12, the CBZ degradation was conducted in 20 ppm CBZ solution with 0.5 g/L and 1% Nd-doped Sb2O3/TiO2 catalysts at pH 9 for 120 min irradiation. Liang et al. reported that both HO and SO 4 are present at pH 9 [42], but HO is the predominant radical at high pH value. These were in good agreement with electron paramagnetic resonance (EPR) results by Dogliotti et al. and Normal et al. according to which, at a high pH value (>8.5), the SO 4 usually converts into HO [43,44]. Moreover, the degradation of CBZ was inhibited greatly by the addition of excess methanol, which revealed that the major reactive oxygen species is OH radicals for CBZ degradation. Fig. 13 shows EPR spectroscopic analysis to determine the radicals produced by 1% Nd-doped Sb2O3/TiO2. The presence of hydroxyl radicals was confirmed by DMPO-OH adduct. By adding the 2,2,6,6-tetramethylpiperidine (TEMP) trapping agent, three distinct peaks were indexed. The TEMP-1O2 adduct shows the peaks of intensity are 1:1:1 in EPR spectra. This is also proved by previous reports for singlet oxygen [34]. EPR analysis showed the presence of OH and 1O2 radicals in 1% Nd-doped Sb2O3/TiO2 catalyst.
removal were obtained at a 5 ppm initial concentration. This was also proved by Aghabeygi et al. [36]. The effect of concentration of CBZ ‘plot of –ln(C0/Ct) vs time (min) is shown in Fig. 11. Table 2 present the kinetic parameters of different initial concentrations of CBZ degradation by 1% Nd-doped Sb2O3/TiO2. The rate constant of CBZ was decreased, when the concentration of CBZ was increasead. A good relationship was found between the model and
Table 2 Kinetic parameters by adding 1% Nd-doped Sb2O3/TiO2 for CBZ degradation in different initial concentration. Initial concentration, ppm
5
10
15
20
k (min1) R2
0.049 0.89
0.031 0.93
0.023 0.92
0.017 0.90
1,0 0,9
CBZ (C/C0)
0,8
CBZ CBZ+100mM Methanol CBZ+500mM Methanol
0,7 0,6
4. Degradation products of CBZ
0,5
ESI FT-ICR MS analysis was performed to identify the main photocatalytic degradation products of CBC through accurate mass measurements. Because of the dominant photochemically reactive species, OH and 1O2 radicals are responsible for the CBZ degradation. Only two CBZ degradation products viz. 2-phenylindolizine (C14H11N, exact mass: 193.0891 Da) and acridine-9-carbaldehyde (C14H9NO, exact mass: 207.0684 Da) were identified (Fig. 14). Both degradation products have been detected in previous studies [3,45].
0,4 0,3 0
20
40
60
80
100
120
Time (min) Fig. 12. Radical scavengers on CBZ degradation (20 ppm of CBZ concentration, 0.5 g/L catalyst dose, 120 min UVC irradiation).
# TEMP- 1 O
#
#
+ DMPO-OH
+
.
+
325
330
1% Nd doped Sb 2 O 3 /TiO 2
#
2
+
1% Nd doped Sb 2 O 3 /TiO 2
+
335
340
345
350
Magnetic field (mT) Fig. 13. EPR spectra of catalyst obtained with TEMP and DMPO spin-tapping reagent.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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Fig. 14. Possible degradation pathways of the photocatalytic degradation of CBZ by 1% Nd-doped Sb2O3/TiO2.
5. Conclusions
References
Different Nd-doped Sb2O3/TiO2 catalysts were synthesised hydrothermally for the photocatalytic degradation of CBZ. The synthesized Nd doped catalyst showed enhanced catalytic activity towards the CBZ degradation in comparison to catalyt samples without Nd doping. The structural properties were affected by the molar ratio of Nd doped Sb2O3/TiO2. Synthesised Sb2O3 showed nanorods type morphology, while in the Nd-doped Sb2O3/TiO2 showed the dots for Nd-doped TiO2. An increased surface area was recorded when the Nd ratio was increased in Sb2O3/TiO2. Nd doping decreased the band gap energy of catalyst, which enhanced the catalytic activity of catalyst to some extent. Further, the metal leaching test suggested that synthesised catalysts are highly stable in neutral pH. The alkaline range gave better degradation performance of CBZ. It was observed that 1% Nd-doped Sb2O3/TiO2 enhanced the degradation of CBZ in the aqueous solution. The result of kinetic experiment was well fitted in the equation of pseudo first order kinetic model. The quenching tests demonstrated that the major reactive oxygen species are OH radicals for CBZ degradation. The ability of generation of reactive species during the degradation process makes the synthesised catalyst very efficient and gave a significant degradation of CBZ. The EPR analysis further indicated the involvement of 1O2 and ∙OH radicals for CBZ photocatalytic degradation. Only two by-products were detected in treated CBZ solutions. The catalyst with 1% Nd doped Sb2O3/TiO2 can be efficiently used for the degradation of CBZ.
[1] B. Strenn, M. Clara, O. Gans, N. Kreuzinger, Carbamazepine, diclofenac, ibuprofen and bezafibrate - investigations on the behaviour of selected pharmaceuticals during wastewater treatment, Water Sci. Technol. 50 (2004) 269–276. [2] C. Tixier, H.P. Singer, S. Oellers, S.R. Müller, Occurrence and fate of carbamazepine, clofibric acid, diclofenac, ibuprofen, ketoprofen, and naproxen in surface waters, Environ. Sci. Technol. 37 (2003) 1061–1068, https://doi.org/10.1021/es025834r. [3] C. Martínez, M. Canlel, M.I. Fernández, J.A. Santaballa, J. Faria, Kinetics and mechanism of aqueous degradation of carbamazepine by heterogeneous photocatalysis using nanocrystalline TiO2, ZnO and multi-walled carbon nanotubes–anatase composites, Appl. Catal. B 102 (2011) 563–571, https:// doi.org/10.1016/j.apcatb.2010.12.039. [4] T. Heberer, Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: a review of recent research data, Toxicol. Lett. 131 (2002) 5–17, https://doi.org/10.1016/S0378-4274(02)00041-3. [5] T.A. Ternes, Occurrence of drugs in German sewage treatment plants and rivers1Dedicated to Professor Dr. Klaus Haberer on the occasion of his 70th birthday.1, Water Research. 32 3245–3260 (1998), https://doi.org/10.1016/ S0043-1354(98)00099-2. [6] S.D. Kim, J. Cho, I.S. Kim, B.J. Vanderford, S.A. Snyder, Occurrence and removal of pharmaceuticals and endocrine disruptors in South Korean surface, drinking, and waste waters, Water Res. 41 (2007) 1013–1021, https://doi. org/10.1016/j.watres.2006.06.034. [7] L. Sun, J. Guan, Q. Xu, X. Yang, J. Wang, X. Hu, Synthesis and applications of molecularly imprinted polymers modified TiO2 nanomaterials: a review, Polymers 10 (2018) 1248, https://doi.org/10.3390/polym10111248. [8] M. Sillanpää, M.C. Ncibi, A. Matilainen, Advanced oxidation processes for the removal of natural organic matter from drinking water sources: A comprehensive review, J. Environ. Manage. 208 (2018) 56–76, https://doi. org/10.1016/j.jenvman.2017.12.009. [9] Z. Wang, A. Deb, V. Srivastava, S. Iftekhar, I. Ambat, M. Sillanpää, Investigation of textural properties and photocatalytic activity of PbO/TiO2 and Sb2O3/TiO2 towards the photocatalytic degradation Benzophenone-3 UV filter 115763, Sep. Purif. Technol. 228 (2019), https://doi.org/10.1016/j.seppur.2019.115763. [10] I. Levchuk, C. Guillard, F. Dappozze, S. Parola, D. Leonard, M. Sillanpää, Photocatalytic activity of TiO2 films immobilized on aluminum foam by atomic layer deposition technique, J. Photochem. Photobiol., A 328 (2016) 16–23, https://doi.org/10.1016/j.jphotochem.2016.03.034. [11] Y. Zhai, Y. Dai, J. Guo, L. Zhou, M. Chen, H. Yang, L. Peng, Novel biochar@CoFe2O4/Ag3PO4 photocatalysts for highly efficient degradation of bisphenol a under visible-light irradiation, J. Colloid Interface Sci. 560 (2020) 111–121, https://doi.org/10.1016/j.jcis.2019.08.065. [12] A. Yuan, H. Lei, Z. Wang, X. Dong, Improved photocatalytic performance for selective oxidation of amines to imines on graphitic carbon nitride/bismuth tungstate heterojunctions, J. Colloid Interface Sci. 560 (2020) 40–49, https:// doi.org/10.1016/j.jcis.2019.10.060. [13] Z. Wang, G. Nguyen Song Thuy Thuy, V. Srivastava, I. Ambat, M. Sillanpää, Photocatalytic degradation of an artificial sweetener (Acesulfame-K) from synthetic wastewater under UV-LED controlled illumination, Process Saf. Environ. Prot. 123 (2019) 206–214, https://doi.org/10.1016/j. psep.2019.01.018.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements The authors are grateful to Biocenter Kuopio/Biocenter Finland for providing the FT-ICR MS instrument facility. Financial support from the European Regional Development Fund (grant A70135) is gratefully acknowledged.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx [14] M. Abid, S. Bouattour, A.M. Ferraria, D.S. Conceição, A.P. Carapeto, L.F. Vieira Ferreira, A.M. Botelhodo Rego, M.M. Chehimi, M. Rei Vilar, S. Boufi, Facile functionalization of cotton with nanostructured silver/titania for visible-light plasmonic photocatalysis, J. Colloid Interface Sci. 507 (2017) 83–94, https:// doi.org/10.1016/j.jcis.2017.07.109. [15] F. Mousli, A. Chaouchi, S. Hocine, A. Lamouri, M. Rei Vilar, A. Kadri, M.M. Chehimi, Diazonium-modified TiO2/polyaniline core/shell nanoparticles. Structural characterization, interfacial aspects and photocatalytic performances, Appl. Surf. Sci. 465 (2019) 1078–1095, https://doi.org/ 10.1016/j.apsusc.2018.09.252. [16] C.-C. Nguyen, N.-N. Vu, T.-O. Do, Efficient hollow double-shell photocatalysts for the degradation of organic pollutants under visible light and in darkness, J. Mater. Chem. A 4 (2016) 4413–4419, https://doi.org/10.1039/C5TA09016D. [17] F. Mousli, A. Chaouchi, M. Jouini, F. Maurel, A. Kadri, M.M. Chehimi, Polyaniline-grafted RuO2-TiO2 heterostructure for the catalysed degradation of methyl orange in darkness, Catalysts 9 (2019) 578, https://doi.org/ 10.3390/catal9070578. [18] D.-N. Liu, G.-H. He, L. Zhu, W.-Y. Zhou, Y.-H. Xu, Enhancement of photocatalytic activity of TiO2 nanoparticles by coupling Sb2O3, Appl. Surf. Sci. 258 (2012) 8055–8060, https://doi.org/10.1016/j.apsusc.2012.04.171. [19] A. Rey, P. García-Muñoz, M.D. Hernández-Alonso, E. Mena, S. García-Rodríguez, F.J. Beltrán, WO3–TiO2 based catalysts for the simulated solar radiation assisted photocatalytic ozonation of emerging contaminants in a municipal wastewater treatment plant effluent, Appl. Catal. B 154–155 (2014) 274–284, https://doi.org/10.1016/j.apcatb.2014.02.035. [20] V.J. Pereira, H.S. Weinberg, K.G. Linden, P.C. Singer, UV degradation kinetics and modeling of pharmaceutical compounds in laboratory grade and surface water via direct and indirect photolysis at 254 nm, Environ. Sci. Technol. 41 (2007) 1682–1688, https://doi.org/10.1021/es061491b. [21] J. Schneider, M. Matsuoka, M. Takeuchi, J. Zhang, Y. Horiuchi, M. Anpo, D.W. Bahnemann, Understanding TiO2 photocatalysis: mechanisms and materials, Chem. Rev. 114 (2014) 9919–9986, https://doi.org/10.1021/cr5001892. [22] K. Qi, R. Selvaraj, T. Al Fahdi, S. Al-Kindy, Y. Kim, G.-C. Wang, C.-W. Tai, M. Sillanpää, Enhanced photocatalytic activity of anatase-TiO2 nanoparticles by fullerene modification: A theoretical and experimental study, Appl. Surf. Sci. 387 (2016) 750–758, https://doi.org/10.1016/j.apsusc.2016.06.134. [23] H. Sun, Y. Bai, W. Jin, N. Xu, Visible-light-driven TiO2 catalysts doped with lowconcentration nitrogen species, Sol. Energy Mater. Sol. Cells 92 (2008) 76–83, https://doi.org/10.1016/j.solmat.2007.09.003. [24] R. Asahi, T. Morikawa, T. Ohwaki, K. Aoki, Y. Taga, Visible-light photocatalysis in nitrogen-doped titanium oxides, Science 293 (2001) 269–271, https://doi. org/10.1126/science.1061051. [25] T. Ohno, T. Mitsui, M. Matsumura, Photocatalytic activity of S-doped TiO2 photocatalyst under visible light, Chem. Lett. 32 (2003) 364–365, https://doi. org/10.1246/cl.2003.364. [26] M. Shen, Z. Wu, H. Huang, Y. Du, Z. Zou, P. Yang, Carbon-doped anatase TiO2 obtained from TiC for photocatalysis under visible light irradiation, Mater. Lett. 60 (2006) 693–697, https://doi.org/10.1016/j.matlet.2005.09.068. [27] K. Yang, Y. Dai, B. Huang, Understanding photocatalytic activity of S- and Pdoped TiO2 under visible light from first-principles, J. Phys. Chem. C 111 (2007) 18985–18994, https://doi.org/10.1021/jp0756350. [28] A. Bokare, M. Pai, A.A. Athawale, Surface modified Nd doped TiO2 nanoparticles as photocatalysts in UV and solar light irradiation, Sol. Energy 91 (2013) 111– 119, https://doi.org/10.1016/j.solener.2013.02.005. [29] S. Lee, I.-S. Cho, J.H. Lee, D.H. Kim, D.W. Kim, J.Y. Kim, H. Shin, J.-K. Lee, H.S. Jung, N.-G. Park, K. Kim, M.J. Ko, K.S. Hong, Two-step SolGel method-based TiO2 nanoparticles with uniform morphology and size for efficient photoenergy conversion devices, Chem. Mater. 22 (2010) 1958–1965, https://doi. org/10.1021/cm902842k.
9
[30] T. Lopez, J. Manjarrez, D. Rembao, E. Vinogradova, A. Moreno, R.D. Gonzalez, An implantable sol–gel derived titania–silica carrier system for the controlled release of anticonvulsants, Mater. Lett. 60 (2006) 2903–2908, https://doi.org/ 10.1016/j.matlet.2006.02.017. [31] C. Kang, L. Jing, T. Guo, H. Cui, J. Zhou, H. Fu, Mesoporous SiO2-modified nanocrystalline TiO2 with high anatase thermal stability and large surface area as efficient photocatalyst, J. Phys. Chem. C. 113 (2009) 1006–1013, https://doi. org/10.1021/jp807552u. [32] F. Yang, X. Zhang, X. Wu, F. Tian, F. Gan, Preparation of highly dispersed antimony-doped tin oxide nanopowders by azeotropic drying with isoamyl acetate, Trans. Nonferrous Met. Soc. China 17 (2007) 626–632, https://doi.org/ 10.1016/S1003-6326(07)60146-0. [33] Z. Deng, D. Chen, F. Tang, X. Meng, J. Ren, L. Zhang, Orientated attachment assisted self-assembly of Sb2O3 nanorods and nanowires: end-to-end versus side-by-side, J. Phys. Chem. C 111 (2007) 5325–5330, https://doi.org/10.1021/ jp068545o. [34] B. Gao, Z. Safaei, I. Babu, S. Iftekhar, E. Iakovleva, V. Srivastava, B. Doshi, S.B. Hammouda, S. Kalliola, M. Sillanpää, Modification of ZnIn2S4 by anthraquinone-2-sulfonate doped polypyrrole as acceptor-donor system for enhanced photocatalytic degradation of tetracycline, J. Photochem. Photobiol., A 348 (2017) 150–160, https://doi.org/10.1016/j.jphotochem.2017.08.037. [35] B. Gao, L. Liu, J. Liu, F. Yang, Photocatalytic degradation of 2,4,6tribromophenol over Fe-doped ZnIn2S4: Stable activity and enhanced debromination, Appl. Catal. B 129 (2013) 89–97, https://doi.org/10.1016/j. apcatb.2012.09.007. [36] S. Aghabeygi, M. Khademi-Shamami, ZnO/ZrO2 nanocomposite: Sonosynthesis, characterization and its application for wastewater treatment, Ultrason. Sonochem. 41 (2018) 458–465, https://doi.org/10.1016/ j.ultsonch.2017.09.020. [37] S.B. Hammouda, F. Zhao, Z. Safaei, I. Babu, D.L. Ramasamy, M. Sillanpää, Reactivity of novel Ceria-Perovskite composites CeO2- LaMO3 (MCu, Fe) in the catalytic wet peroxidative oxidation of the new emergent pollutant ‘Bisphenol F’: Characterization, kinetic and mechanism studies, Appl. Catal. B 218 (2017) 119–136, https://doi.org/10.1016/j.apcatb.2017.06.047. [38] F.I. Hai, X. Li, W.E. Price, L.D. Nghiem, Removal of carbamazepine and sulfamethoxazole by MBR under anoxic and aerobic conditions, Bioresour. Technol. 102 (2011) 10386–10390, https://doi.org/10.1016/j.biortech.2011.09.019. [39] M.M. Ahmed, S. Chiron, Solar photo-Fenton like using persulphate for carbamazepine removal from domestic wastewater, Water Res. 48 (2014) 229–236, https://doi.org/10.1016/j.watres.2013.09.033. [40] H. Eibenberger, S. Steenken, P. O’Neill, D. Schulte-Frohlinde, Pulse radiolysis and electron spin resonance studies concerning the reaction of SO.-4 with alcohols and ethers in aqueous solution 82, J. Phys. Chem. (1978) 749–750, https://doi.org/10.1021/j100495a028. [41] G.V. Buxton, C.L. Greenstock, W.P. Helman, A.B. Ross, Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (OH/O in aqueous solution, J. Phys. Chem. Ref. Data 17 (1988) 513– 886, https://doi.org/10.1063/1.555805. [42] C. Liang, H.-W. Su, Identification of sulfate and hydroxyl radicals in thermally activated persulfate, Ind. Eng. Chem. Res. 48 (2009) 5558–5562, https://doi. org/10.1021/ie9002848. [43] L. Dogliotti, E. Hayon, Flash photolysis of per[oxydi]sulfate ions in aqueous solutions. The sulfate and ozonide radical anions, J. Phys. Chem. 71 (1967) 2511–2516, https://doi.org/10.1021/j100867a019. [44] J. Chem. Soc., B: (1970) 1087, https://doi.org/10.1039/j29700001087. [45] Z. Wang, V. Srivastava, S. Iftekhar, I. Ambat, M. Sillanpää, Fabrication of Sb2O3/ PbO photocatalyst for the UV/PMS assisted degradation of carbamazepine from synthetic wastewater, Chem. Eng. J. 354 (2018) 663–671, https://doi.org/ 10.1016/j.cej.2018.08.068.
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UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst Zhao Wang a,⇑, Varsha Srivastava a, Shaobin Wang b, Hongqi Sun c, Senthil K. Thangaraj d, Janne Jänis d, Mika Sillanpää a a
Department of Green Chemistry, LUT University, Sammonkatu 12, FI-50130 Mikkeli, Finland School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia School of Engineering, Edith Cowan University, Perth, WA 6027, Australia d Department of Chemistry, University of Eastern Finland, Yliopistokatu 7, 80130 Joensuu, Finland b c
g r a p h i c a l a b s t r a c t
a r t i c l e
i n f o
Article history: Received 19 August 2019 Revised 18 November 2019 Accepted 23 November 2019 Available online xxxx Keywords: Nd-doped Carbamazepine Photocatalytic UVC Sb2O3/TiO2
a b s t r a c t The photocatalytic degradation of carbamazepine (CBZ) in ultra-pure water was investigated by using neodymium (Nd)-doped antimony trioxide (Sb2O3)/titanium dioxide (TiO2) photocatalyst under the UVC irradiations of 254 nm wavelength. The hydrothermal method was used for the fabrication catalyst samples with different ratios of Nd (0%–2%) dopant, and characterised by X-ray diffraction pattern (XRD) to investigate the crystallinity. Scanning electron microscopy (SEM) provided the surface morphologies, Bruanuer-Emmer-Teller (BET) analysis gave the textural properties, and UV–Vis diffuse reflectance absorption spectroscopy (DRS) was used for the investigation of the optical properties of synthesized catalysts. TEM images of Sb2O3 showed a nanorod-like structure while, in the Nd-doped Sb2O3/TiO2, a small dot-like structure was observed along with the nanorods. The surface area and band gap of 1% Nd-doped Sb2O3/TiO2 were found to be 9.56 m2 g1 and 3.0 eV respectively. It was observed that the CBZ cannot be degraded in the absence of catalyst under UV light, while photocatalyst 1% Nd-doped Sb2O3/TiO2 at 0.5 g/ L of catalyst dose showed the best photocatalytic activity towards CBZ degradation. The main degradation products were identified with high-resolution mass spectrometry. Moreover, the degradation of CBZ followed pseudo first-order kinetics and the rate constant was 0.017 min1. Quenching tests by the addition
⇑ Corresponding author. E-mail address: [email protected] (Z. Wang). https://doi.org/10.1016/j.jcis.2019.11.094 0021-9797/Ó 2019 Elsevier Inc. All rights reserved.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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of methanol from 100 to 500 mM were carried out to determine the major reactive oxygen species, which showed that OH radicals was involved in the CBZ degradation. Active species-trapping experiments revealed that ∙O 2 is also responsible for the degradation of CBZ. Ó 2019 Elsevier Inc. All rights reserved.
1. Introduction Nowadays the trend of pharmaceutical drugs consumption goes increasing, hence these chemicals have been detected in water bodies. Traditional water treatment technologies are not efficient for the complete removal of pharmaceutical drugs from wastewater and, due to inappropriate disposal, these chemicals have been found in natural water bodies [1–3]. One of the pharmaceuticals, carbamazepine (5H-dibenzo [b,f] azepine-5-carboxamide) has attracted attention as it was detected in the surface water, tap water, and in wastewater at a significant concentration. Carbamazepine (CBZ) has been widely used for trigeminal neuralgia, seizure disorders, and other psychiatric disease treatment. It is known that 1.014 tonnes of CBZ are produced every year, and it is now the most common pharmaceutical pollutant found in water bodies. The concentration of CBZ was detected to be 610 ngL1 in groundwater and 18 ngL1 in drinking water [4–6]. Moreover, for aquatic life, CBZ is also a toxic pharmaceutical. For example, algae, invertebrates, bacteria, and fish can be severely influenced by CBZ in water, so the development of an effective elimination method for CBZ is crucial for wastewater treatment. Not only the CBZ, but other organic pollutants also co-exist in wastewater. To improve the capacity of the adsorption of TiO2, molecularly imprinted polymers can be used with the combination of TiO2 to eliminate the different types of organic pollutants [7]. CBZ and other pharmaceutical drugs contaminants can be removed by an advanced oxidation process (AOP) [8]. AOP is an effective method with the possibility of mineralisation of contaminants and degradation of pollutants [9–12]. AOPs can generate reactive radicals, for example, hydroxyl radicals (OH), which are a strong oxidative species and can degrade the organic pollutants into carbon dioxide (CO2) and water (H2O) [13]. The AOPs have been developed in recent years for the remediation of organic pollutants. Among them, heterogeneous photocatalysis has been considered as a promising method for the elimination of a variety of organic contaminants [14–17]. Sb2O3 has been widely used as a coupling component in the development of photocatalyst due to its low cost, reproducibility and long-term stability. Liu et al. [18] reported that Sb2O3 coupled with TiO2 can transfer the valence band (VB) holes in the TiO2 surface and localise the conduction band (CB) electrons on the surface of Sb2O3. TiO2 is the most efficient and popular semiconductor photocatalyst due to its stability and low cost [19–22]. One of the methods of enhancing the activity of TiO2 is non-metal doping. Nitrogen is a significant non-metal dopant because of its lower ionisation and high stability. N-doped TiO2 response under the visible light was explored by some researchers [23,24]. The band gap also can be decreased by adding other non-metals such as C, P, and S. The valence and conduction bands from the electronic disorder are changed by the variety of lattice parameters and by creating trapping states [25–27]. Bokare et al. found that Nd-doped TiO2 showed effective photocatalytic activity under UV and solar light irradiations [28]. Various efforts are being made by many researchers to understand the fundamental mechanisms for enhancing the efficiency of TiO2. Various dopant have been added with TiO2 for enhancement of catalytic activity. However, neodymium (Nd) doped Sb2O3/TiO2 for CBZ degradation has not been well explored.
The aims of the present study are the synthesis of Neodymium (Nd) doped Sb2O3/TiO2 at different ratios of Nd by a hydrothermal method and the investigation of their photocatalytic performances towards CBZ degradation under UVC light irradiation. The reaction parameters such as the pH of CBZ solution, initial concentration, and catalyst dose were optimised for the photocatalytic degradation of CBZ. 2. Materials and methods 2.1. Chemicals Titanium (IV) butoxide, titanium (IV) isopropoxide, antimony (III) chloride, triethanolamine, carbamazepine (CBZ) and neodymium oxide were purchased from Sigma-Aldrich. The deionised water from a Milli-Q water purification system was used for the preparation experiment solution. Sodium hydroxide, potassium hydroxide, and ammonia solution were used for the pH adjustment. 2.2. Synthesis of Nd-doped Sb2O3/TiO2 photocatalyst Nd-doped (0%–2%) Sb2O3/TiO2 catalysts were prepared using a facile hydrothermal method as reported in the literature by Liu et al. and Bokare et al. [18,28]. For the synthesis of catalyst, the solution A was made by antimony trichloride (SbCl3) which was dissolved in 40 mL methanol. TiO2 was synthesised by the sol– gel method according to the literature [29]. The TiO2 was dissolved in 40 mL deionized water and named as solution B. For Solution C, neodymium oxide was firstly dissolved in nitric acid, and a certain amount of Nd dopant was achieved using neodymium nitratenitric acid solution dissolved in a mixture of 10:1 with ethanol and water. All three solutions A, B and C were mixed and the pH value at 8–9 was adjusted by the addition of ammonia solution. The mixture solution was transferred in the autoclave and kept at 120 °C for 12 h. When the synthesised Nd-doped Sb2O3/TiO2 catalyst was cooled down to room temperature, the deionised water was used for washing of the synthesized catalysts and dried at 50 °C for 4 h. 2.3. Characterisation of catalysts The synthesised Nd-doped Sb2O3/TiO2 catalysts were characterised by different techniques. The crystalline phases of the catalysts were investigated from the X-ray diffraction patterns (XRD) measured with a step size of 0.02° and a scan speed of 2°/min over a 2h range of 5–100° by a PANalytical X-ray Diffractometer. The surface area and porosity of the synthesised catalysts were analysed from N₂ adsorption-desorption isotherm at 77 K using a Micromeritics Tristar II plus a BET surface area analyser. The band gap of catalysts was determined by the UV–Vis diffuse reflectance spectroscopy (Lambda 950 spectrophotometer). The surface morphology of catalysts was investigated by a Scanning Electron Microscope (HITACHI, S-4800) and the particle diameter of the catalysts was measured through the transmission electron microscopy (TEM-Hitachi 7700).
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
2.4. Photodegradation experiments A 50 mL quartz beaker was used for photocatalytic experiments under the UVC irradiation. A certain concentration of CBZ solution with the catalyst was taken into the reactor and for proper dispersion of catalyst in CBZ solution, a magnetic stirrer at the 500 rpm rotational speed was used. Before UVC irradiation, catalyst adsorption-desorption reactions were carried out in the dark for 2 h stirring in a magnetic stirrer. The samples were withdrawn periodically using 0.2 mm regeneration cellulose (RC) membrane for catalyst filter and stored in the vials for HPLC analysis. Catalyst adsorption-desorption reactions were carried out in the dark for 2 h, stirring in a magnetic stirrer. 2.5. Analytical methods A high-performance liquid chromatography (HPLC) system (SHIMADZUÒ) was used for the measurement of the carbamazepine concentration in the treated samples. A C18 HPLC column (PhenomenexÒ 5 mm, 150 mm 4.6 mm) with a UV detector at a wavelength of 285 nm was used in this study. The acetonitrile and water were used as buffer solution for the mobile phase. The ratio between acetonitrile and water was 60:40. The mineralisation degrees of CBZ were tested by a total organic carbon (TOC) analyser (Shimadzu TOC-V CPH/CPN and ASI-V Autosampler). Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer (Bruker Daltonics, Bremen, Germany) was used for the determination of the degradation products of CBZ. The FT-ICR running in the positive-ion mode. 10 mL sample was prepared with 1v-% acetic acid in methanol (10:20, v/v). The instrument control and data acquisition have used the software of Bruker ftms Control 2.1. Bruker Data Analysis 4.4 was used for analysis of the mass spectra. 3. Results and discussion 3.1. Catalyst characterisation XRD patterns of Sb2O3 and Sb2O3/TiO2 catalysts with different molar ratios of Nd doping are shown in Fig. 1. The existence of both anatase and rutile phase of TiO2 can be seen in synthesised catalysts. The characteristic peaks were compared with the reference (ICSD #98-001-5409) and (ICSD #98-007-4532) for anatase and rutile with the characteristic peaks 29.55° and 32.50°, respectively.
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0
20
Sb2O3 peaks were confirmed with the reference (ICSD #98-0031102). Peaks at 58.58° and 64.61° (ICSD#98-064-5585) are corresponding to Nd3+ dopant. The FT-IR spectra of 0%2% Nd-doped Sb2O3/TiO2 and synthesised Sb2O3 are shown in Fig. 2. The peak 3400 cm1 is due to the adsorbed water molecules, but it was not present in pure Sb2O3. The peak at 1632 cm1 can be attributed to the surface hydroxyl group [30]. The range from 500 to 800 cm1 can be attributed to the Ti-O and Sb-O stretching modes [31,32]. SEM and TEM images of Sb2O3/TiO2 with different ratios of Nd doping and pure Sb2O3 are shown in Fig. 3. The SEM images showed that the particles have agglomerated as flower-like structures when a high Nd doping level was used. In addition, a rodshaped structure can be seen in the pure Sb2O3, which is also proved by Deng et al. [33]. Based on the image of the synthesised Sb2O3, it can be speculated that the dot parts in Nd-doped Sb2O3/ TiO2 are the Nd-doped TiO2. The reflectance spectra of Nd-doped Sb2O3/TiO2 photocatalysts are illustrated in Fig. 4. For all different ratios of Nd-doped Sb2O3/TiO2, the band gap was calculated to be 3.0 eV. It was observed that for the sample without Nd doping, band gap energy is slightly higher (3.05 eV) than in other Nd-doped catalysts. For synthesised Sb2O3, The band gap is 3.3 eV. The lower band gap can enhance the activity of catalysts [34]. Table 1 shows the band gap energies, porosity and specific surface areas of synthesised Nd-doped Sb2O3/TiO2 catalysts. The BET adsorption-desorption isotherm plots for Nd-doped Sb2O3/TiO2 are shown in Fig. 5. From 0.5% Nd-doped Sb2O3/TiO2 to 2% Nddoped Sb2O3/TiO2, the BET surface areas increased from 3.78 to 12.14 m2 g1 respectively. However, the BET surface area is not the only factor to affect the photocatalytic ability of catalysts [35]. 3.2. Kinetics study of CBZ photocatalytic degradation The kinetics study of the photocatalytic degradation of CBZ was investigated by varying the reaction time, solution pH and catalyst dose. The degradation kinetics of CBZ over Nd (0%–2%)-doped Sb2O3/TiO2 were analysed by the following pseudo-first order kinetic model.
ln
C0 Ct
¼ kt
ð1Þ
where C0 is the initial concentration of CBZ and Ct is the CBZ concentration after treatment. t refer to the treatment time and k is the constant of reaction rate (min1).
0% Nd-doped Sb2O 3 /TiO 2
3
*
3
40
60
80
100
2Theta (degree) Fig. 1. The XRD patterns of the prepared Nd-doped Sb2O3/TiO2 as comparison to pure Sb2O3.
3.2.1. Effect of initial pH In photocatalytic water treatment, one of the significant factor is the pH value of the solution, as the isoelectric point of the photocatalysts can be affected by pH. The catalysts can change the surface charge, which may affect the interaction between water contaminants and catalysts surfaces. Moreover, Aghabeygi and Khademi-shamami [36] reported that the electron hole may change the rate of recombination for the catalyst surface by vary pH value of the solution. To investigate the effect of pH on the photocatalytic degradation of CBZ under UVC irradiation, pH values of CBZ solution were adjusted to 3, 5, 7, 9 and 11 for the photocatalytic experiment. All experiments were conducted the CBZ solution with 20 ppm concentration, 1 g/L dose of catalysts and irradiation time is 120 min. As shown in Fig. 6, at different pH conditions, the degradation efficiency of synthesised catalysts did not respond similarly. Overall, different catalysts gave good performances in degradation of CBZ at pH 7 and pH 9. The most efficient catalyst is 1% Nd-doped Sb2O3/TiO2 with 66.9% degradation efficiency at pH 9. This result
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
Transmittance (%)
4
3400
1632
0% Nd doped Sb 2 O 3 /TiO
0.5% Nd doped Sb 2 O 3 /TiO 1% Nd doped Sb 2 O 3 /TiO
4000
3500
1.5% Nd doped Sb 2 O 3 /TiO
2
2
2
3000
2% Nd doped Sb 2 O 3 /TiO
800
2
2
Sb 2 O 3
2500
2000
1500
1000
500
-1
Wavenumber (cm ) Fig. 2. FTIR spectra of 0%–2% Nd-doped Sb2O3/TiO2 and Sb2O3.
Fig. 3. Images of SEM (a,b,c,d,e,f) and images of TEM (g,h,i,j,k,l) of the various Nd-doped Sb2O3/TiO2.
was in good agreement with the a reported study by Bokare et al., which showed that 1% Nd-doped TiO2 can enhance the efficiency of the catalyst [28].
The higher density of hydroxyl ions can appear under the alkaline conditions, which facilitate the generation of more hydroxyl radicals. The catalyst stability was investigated by measuring the
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catalyst dose, the experiments were conducted with constant parameters (pH 9, 20 ppm CBZ solution, 1% Nd-doped Sb2O3/TiO2 catalyst, and irradiation time of 120 min). Fig. 10 shows the degradation rate and adsorption removal of CBZ by the synthesised catalysts. It can be clearly seen that the optimum value for catalyst loading is 0.5 g/L, but adsorption removal is not the best at this catalyst dose. With higher catalysts loading, the degradation rate was not satisfied. Adsorption removal is increased by increasing the catalyst dose. The optimum degradation rate is 88.2% with 0.5 g/L catalyst dose and the adsorption removal is 6.78% with 2 g/L catalyst dose. By membrane bioreactor (MBR) treatment, 68 ± 10%, removal of for the CBZ can be achieved but needs near-anoxic conditions [38]. The Photo-Fenton process is also a better choice for CBZ degradation, but the pH value condition is somewhat strict [39].
Fig. 4. The derived plots from Kubelka-Munk function for catalysts synthesised.
concentration of leached metal ion after 120 min UV irradiation at different pH values (Fig. 7). The metal ion centration was measured by Inductively coupled plasma- optical emission spectroscopy (ICP-OES Agilent 5110). It was observed that, from pH 3 to pH 11, Nd ions were not found in solutions. However, leaching of Ti and Sb ions was observed at a high pH value (pH 11). It was noticed that with 0% Nd-doped Sb2O3/TiO2 at pH 11, Ti ion leaching is the highest among all catalysts, while Sb ion leaching is the lowest. Sb ion leaching increased with the increase in the pH of CBZ solutions. The total organic carbon (TOC) was used for measuring the mineralisation of the treated CBZ samples after 2 h of treatment at different pH values. As shown in Fig. 8, not all the selected catalysts showed significant degradation of CBZ. It can be speculated that, with CBZ degradation treatment, some intermediates were produced under the photodegradation, so cannot be mineralised [37]. And another possibility is due to the low specific surface area of the catalyst, the photocatalysts were saturated. Another significant factor for catalysis is the recyclability of the catalysts for industrial applications. To make sure that the catalysts can be used in large scale, the catalysts were reused and tested for stability. After 120 min of irradiation, each catalyst was washed with deionized water and centrifuged. The catalysts were reused for the second round to degrade the 20 ppm CBZ solution. The best degradation rate of recycled catalyst showed a slight decrease (4%) compared to the first time on 1% Nd-doped Sb2O3/TiO2 (Fig. 9). 3.2.2. Catalysts dose loading study Catalyst loading is one of the important factors for photocatalytic reaction rate. Due to the light screening effect by the excess catalyst, the photodegradation rate starts to decrease when the catalyst dose is beyond optimum loading. To understand the optimum
Fig. 5. BET adsorption-desorption isotherm plot for synthesised catalysts.
Fig. 6. The degradation performance of CBZ by Sb2O3/TiO2 with different ratios of Nd doping and different initial pH. (Initial concentration = 20 ppm, Dose of catalysts = 1 g/L, UVC treatment time = 120 min).
Table 1 Band gap energies and structural parameters of the catalysts. Catalysts
Bandgap energy (eV)
BET surface area (m2 g1)
Pore volume (cm3 g1)
Pore size (Å)
0% Nd-doped Sb2O3/TiO2 0.5% Nd-doped Sb2O3/TiO2 1% Nd-doped Sb2O3/TiO2 1.5% Nd-doped Sb2O3/TiO2 2% Nd-doped Sb2O3/TiO2 Sb2O3
3.05 3.0 3.0 3.0 3.0 3.3
14.5 3.8 9.6 10.7 12.1 4.6
0.03 0.02 0.02 0.02 0.02 0.01
88.3 227.5 86.1 83.6 87.0 75.1
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx 50 0% Nd doped Sb2O3/TiO2
5
Sb
0.5% Nd doped Sb2O3/TiO2 1% Nd doped Sb2O3/TiO2
40
Metal Leaching (mg/L)
6
Meatal Leaching (mg/L)
Ti
0% Nd doped Sb2O3/TiO2 0.5% Nd doped Sb2O3/TiO2 1% Nd doped Sb2O3/TiO2 1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2
4
3
2
1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2 Sb2O3
30
20
10
1
0
pH 3
pH 5
pH 7
pH 9
0
pH 11
pH 3
pH 5
pH 7
(a)
pH 9
pH 11
(b)
Fig. 7. The catalysts metal ion leaching during the degradation of CBZ at different pH value: Ti leaching (a) and Sb leaching (b).
Fig. 8. Mineralisation degree for the photocatalytic degradation of CBZ on Sb2O3/ TiO2 with different ratios of Nd doping (Initial concentration = 20 ppm, Dose of catalysts = 1 g/L, UVC treatment time = 120 min). 0% Nd doped Sb2O3/TiO2 0.5% Nd doped Sb2O3/TiO2
Fig. 10. Degradation rate of CBZ by 1% Nd-doped Sb2O3/TiO2.
1% Nd doped Sb2O3/TiO2
70
1.5% Nd doped Sb2O3/TiO2 2% Nd doped Sb2O3/TiO2 Sb2O3
3,0
20ppm 15ppm 10ppm 5ppm
50
2,5 40
Ln (C0/Ct)
Degradation rate %
60
30 20
2,0
1,5
1,0
10
0,5
0 1st
2nd
Cycle number Fig. 9. Stabilisation degree on the photocatalytic degradation of CBZ by Nd doped catalyst (initial concentration = 20 ppm, 1 g/L of catalysts dose, UVC treatment time = 120 min).
0,0 0
15
30
45
60
75
90
105
120
Time (min) Fig. 11. Degradation kinetic modelling of CBZ by 1% Nd-doped Sb2O3/TiO2 at different initial concentrations of CBZ.
3.2.3. Effect of initial CBZ concentration The experiments for CBZ concentration effects were conducted at different initial concentrations at a constant pH value, catalyst dose and irradiation time. The photodegradation of CBZ by 1%
Nd-doped Sb2O3/TiO2 at a different initial concentration of CBZ from 5 to 20 ppm was conducted under UVC irradiations at pH 9 and a catalyst dose of 0.5 g/L. The maximum degradation and
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
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Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
experimental data. With 5 ppm of CBZ solution, the degradation rate constant was 0.049 min1. With the previous study, the degradation rate constant by using TiO2 for dye was reported to be 0.059 min1 [15]. Hydroxyl radicals (OH, 1.9–2.7 V) and sulphate radical (SO 4, 2.5–3.1 V) are common reactive species in AOPs. Methanol was used for the further confirmation of the effects of radical scavengers. The reaction rate constants by methanol for HO and SO 4 are 9.7 108 and 3.2 106 min1, respectively [40,41]. As shown in Fig. 12, the CBZ degradation was conducted in 20 ppm CBZ solution with 0.5 g/L and 1% Nd-doped Sb2O3/TiO2 catalysts at pH 9 for 120 min irradiation. Liang et al. reported that both HO and SO 4 are present at pH 9 [42], but HO is the predominant radical at high pH value. These were in good agreement with electron paramagnetic resonance (EPR) results by Dogliotti et al. and Normal et al. according to which, at a high pH value (>8.5), the SO 4 usually converts into HO [43,44]. Moreover, the degradation of CBZ was inhibited greatly by the addition of excess methanol, which revealed that the major reactive oxygen species is OH radicals for CBZ degradation. Fig. 13 shows EPR spectroscopic analysis to determine the radicals produced by 1% Nd-doped Sb2O3/TiO2. The presence of hydroxyl radicals was confirmed by DMPO-OH adduct. By adding the 2,2,6,6-tetramethylpiperidine (TEMP) trapping agent, three distinct peaks were indexed. The TEMP-1O2 adduct shows the peaks of intensity are 1:1:1 in EPR spectra. This is also proved by previous reports for singlet oxygen [34]. EPR analysis showed the presence of OH and 1O2 radicals in 1% Nd-doped Sb2O3/TiO2 catalyst.
removal were obtained at a 5 ppm initial concentration. This was also proved by Aghabeygi et al. [36]. The effect of concentration of CBZ ‘plot of –ln(C0/Ct) vs time (min) is shown in Fig. 11. Table 2 present the kinetic parameters of different initial concentrations of CBZ degradation by 1% Nd-doped Sb2O3/TiO2. The rate constant of CBZ was decreased, when the concentration of CBZ was increasead. A good relationship was found between the model and
Table 2 Kinetic parameters by adding 1% Nd-doped Sb2O3/TiO2 for CBZ degradation in different initial concentration. Initial concentration, ppm
5
10
15
20
k (min1) R2
0.049 0.89
0.031 0.93
0.023 0.92
0.017 0.90
1,0 0,9
CBZ (C/C0)
0,8
CBZ CBZ+100mM Methanol CBZ+500mM Methanol
0,7 0,6
4. Degradation products of CBZ
0,5
ESI FT-ICR MS analysis was performed to identify the main photocatalytic degradation products of CBC through accurate mass measurements. Because of the dominant photochemically reactive species, OH and 1O2 radicals are responsible for the CBZ degradation. Only two CBZ degradation products viz. 2-phenylindolizine (C14H11N, exact mass: 193.0891 Da) and acridine-9-carbaldehyde (C14H9NO, exact mass: 207.0684 Da) were identified (Fig. 14). Both degradation products have been detected in previous studies [3,45].
0,4 0,3 0
20
40
60
80
100
120
Time (min) Fig. 12. Radical scavengers on CBZ degradation (20 ppm of CBZ concentration, 0.5 g/L catalyst dose, 120 min UVC irradiation).
# TEMP- 1 O
#
#
+ DMPO-OH
+
.
+
325
330
1% Nd doped Sb 2 O 3 /TiO 2
#
2
+
1% Nd doped Sb 2 O 3 /TiO 2
+
335
340
345
350
Magnetic field (mT) Fig. 13. EPR spectra of catalyst obtained with TEMP and DMPO spin-tapping reagent.
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Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx
Fig. 14. Possible degradation pathways of the photocatalytic degradation of CBZ by 1% Nd-doped Sb2O3/TiO2.
5. Conclusions
References
Different Nd-doped Sb2O3/TiO2 catalysts were synthesised hydrothermally for the photocatalytic degradation of CBZ. The synthesized Nd doped catalyst showed enhanced catalytic activity towards the CBZ degradation in comparison to catalyt samples without Nd doping. The structural properties were affected by the molar ratio of Nd doped Sb2O3/TiO2. Synthesised Sb2O3 showed nanorods type morphology, while in the Nd-doped Sb2O3/TiO2 showed the dots for Nd-doped TiO2. An increased surface area was recorded when the Nd ratio was increased in Sb2O3/TiO2. Nd doping decreased the band gap energy of catalyst, which enhanced the catalytic activity of catalyst to some extent. Further, the metal leaching test suggested that synthesised catalysts are highly stable in neutral pH. The alkaline range gave better degradation performance of CBZ. It was observed that 1% Nd-doped Sb2O3/TiO2 enhanced the degradation of CBZ in the aqueous solution. The result of kinetic experiment was well fitted in the equation of pseudo first order kinetic model. The quenching tests demonstrated that the major reactive oxygen species are OH radicals for CBZ degradation. The ability of generation of reactive species during the degradation process makes the synthesised catalyst very efficient and gave a significant degradation of CBZ. The EPR analysis further indicated the involvement of 1O2 and ∙OH radicals for CBZ photocatalytic degradation. Only two by-products were detected in treated CBZ solutions. The catalyst with 1% Nd doped Sb2O3/TiO2 can be efficiently used for the degradation of CBZ.
[1] B. Strenn, M. Clara, O. Gans, N. Kreuzinger, Carbamazepine, diclofenac, ibuprofen and bezafibrate - investigations on the behaviour of selected pharmaceuticals during wastewater treatment, Water Sci. Technol. 50 (2004) 269–276. [2] C. Tixier, H.P. Singer, S. Oellers, S.R. Müller, Occurrence and fate of carbamazepine, clofibric acid, diclofenac, ibuprofen, ketoprofen, and naproxen in surface waters, Environ. Sci. Technol. 37 (2003) 1061–1068, https://doi.org/10.1021/es025834r. [3] C. Martínez, M. Canlel, M.I. Fernández, J.A. Santaballa, J. Faria, Kinetics and mechanism of aqueous degradation of carbamazepine by heterogeneous photocatalysis using nanocrystalline TiO2, ZnO and multi-walled carbon nanotubes–anatase composites, Appl. Catal. B 102 (2011) 563–571, https:// doi.org/10.1016/j.apcatb.2010.12.039. [4] T. Heberer, Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: a review of recent research data, Toxicol. Lett. 131 (2002) 5–17, https://doi.org/10.1016/S0378-4274(02)00041-3. [5] T.A. Ternes, Occurrence of drugs in German sewage treatment plants and rivers1Dedicated to Professor Dr. Klaus Haberer on the occasion of his 70th birthday.1, Water Research. 32 3245–3260 (1998), https://doi.org/10.1016/ S0043-1354(98)00099-2. [6] S.D. Kim, J. Cho, I.S. Kim, B.J. Vanderford, S.A. Snyder, Occurrence and removal of pharmaceuticals and endocrine disruptors in South Korean surface, drinking, and waste waters, Water Res. 41 (2007) 1013–1021, https://doi. org/10.1016/j.watres.2006.06.034. [7] L. Sun, J. Guan, Q. Xu, X. Yang, J. Wang, X. Hu, Synthesis and applications of molecularly imprinted polymers modified TiO2 nanomaterials: a review, Polymers 10 (2018) 1248, https://doi.org/10.3390/polym10111248. [8] M. Sillanpää, M.C. Ncibi, A. Matilainen, Advanced oxidation processes for the removal of natural organic matter from drinking water sources: A comprehensive review, J. Environ. Manage. 208 (2018) 56–76, https://doi. org/10.1016/j.jenvman.2017.12.009. [9] Z. Wang, A. Deb, V. Srivastava, S. Iftekhar, I. Ambat, M. Sillanpää, Investigation of textural properties and photocatalytic activity of PbO/TiO2 and Sb2O3/TiO2 towards the photocatalytic degradation Benzophenone-3 UV filter 115763, Sep. Purif. Technol. 228 (2019), https://doi.org/10.1016/j.seppur.2019.115763. [10] I. Levchuk, C. Guillard, F. Dappozze, S. Parola, D. Leonard, M. Sillanpää, Photocatalytic activity of TiO2 films immobilized on aluminum foam by atomic layer deposition technique, J. Photochem. Photobiol., A 328 (2016) 16–23, https://doi.org/10.1016/j.jphotochem.2016.03.034. [11] Y. Zhai, Y. Dai, J. Guo, L. Zhou, M. Chen, H. Yang, L. Peng, Novel biochar@CoFe2O4/Ag3PO4 photocatalysts for highly efficient degradation of bisphenol a under visible-light irradiation, J. Colloid Interface Sci. 560 (2020) 111–121, https://doi.org/10.1016/j.jcis.2019.08.065. [12] A. Yuan, H. Lei, Z. Wang, X. Dong, Improved photocatalytic performance for selective oxidation of amines to imines on graphitic carbon nitride/bismuth tungstate heterojunctions, J. Colloid Interface Sci. 560 (2020) 40–49, https:// doi.org/10.1016/j.jcis.2019.10.060. [13] Z. Wang, G. Nguyen Song Thuy Thuy, V. Srivastava, I. Ambat, M. Sillanpää, Photocatalytic degradation of an artificial sweetener (Acesulfame-K) from synthetic wastewater under UV-LED controlled illumination, Process Saf. Environ. Prot. 123 (2019) 206–214, https://doi.org/10.1016/j. psep.2019.01.018.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements The authors are grateful to Biocenter Kuopio/Biocenter Finland for providing the FT-ICR MS instrument facility. Financial support from the European Regional Development Fund (grant A70135) is gratefully acknowledged.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094
Z. Wang et al. / Journal of Colloid and Interface Science xxx (xxxx) xxx [14] M. Abid, S. Bouattour, A.M. Ferraria, D.S. Conceição, A.P. Carapeto, L.F. Vieira Ferreira, A.M. Botelhodo Rego, M.M. Chehimi, M. Rei Vilar, S. Boufi, Facile functionalization of cotton with nanostructured silver/titania for visible-light plasmonic photocatalysis, J. Colloid Interface Sci. 507 (2017) 83–94, https:// doi.org/10.1016/j.jcis.2017.07.109. [15] F. Mousli, A. Chaouchi, S. Hocine, A. Lamouri, M. Rei Vilar, A. Kadri, M.M. Chehimi, Diazonium-modified TiO2/polyaniline core/shell nanoparticles. Structural characterization, interfacial aspects and photocatalytic performances, Appl. Surf. Sci. 465 (2019) 1078–1095, https://doi.org/ 10.1016/j.apsusc.2018.09.252. [16] C.-C. Nguyen, N.-N. Vu, T.-O. Do, Efficient hollow double-shell photocatalysts for the degradation of organic pollutants under visible light and in darkness, J. Mater. Chem. A 4 (2016) 4413–4419, https://doi.org/10.1039/C5TA09016D. [17] F. Mousli, A. Chaouchi, M. Jouini, F. Maurel, A. Kadri, M.M. Chehimi, Polyaniline-grafted RuO2-TiO2 heterostructure for the catalysed degradation of methyl orange in darkness, Catalysts 9 (2019) 578, https://doi.org/ 10.3390/catal9070578. [18] D.-N. Liu, G.-H. He, L. Zhu, W.-Y. Zhou, Y.-H. Xu, Enhancement of photocatalytic activity of TiO2 nanoparticles by coupling Sb2O3, Appl. Surf. Sci. 258 (2012) 8055–8060, https://doi.org/10.1016/j.apsusc.2012.04.171. [19] A. Rey, P. García-Muñoz, M.D. Hernández-Alonso, E. Mena, S. García-Rodríguez, F.J. Beltrán, WO3–TiO2 based catalysts for the simulated solar radiation assisted photocatalytic ozonation of emerging contaminants in a municipal wastewater treatment plant effluent, Appl. Catal. B 154–155 (2014) 274–284, https://doi.org/10.1016/j.apcatb.2014.02.035. [20] V.J. Pereira, H.S. Weinberg, K.G. Linden, P.C. Singer, UV degradation kinetics and modeling of pharmaceutical compounds in laboratory grade and surface water via direct and indirect photolysis at 254 nm, Environ. Sci. Technol. 41 (2007) 1682–1688, https://doi.org/10.1021/es061491b. [21] J. Schneider, M. Matsuoka, M. Takeuchi, J. Zhang, Y. Horiuchi, M. Anpo, D.W. Bahnemann, Understanding TiO2 photocatalysis: mechanisms and materials, Chem. Rev. 114 (2014) 9919–9986, https://doi.org/10.1021/cr5001892. [22] K. Qi, R. Selvaraj, T. Al Fahdi, S. Al-Kindy, Y. Kim, G.-C. Wang, C.-W. Tai, M. Sillanpää, Enhanced photocatalytic activity of anatase-TiO2 nanoparticles by fullerene modification: A theoretical and experimental study, Appl. Surf. Sci. 387 (2016) 750–758, https://doi.org/10.1016/j.apsusc.2016.06.134. [23] H. Sun, Y. Bai, W. Jin, N. Xu, Visible-light-driven TiO2 catalysts doped with lowconcentration nitrogen species, Sol. Energy Mater. Sol. Cells 92 (2008) 76–83, https://doi.org/10.1016/j.solmat.2007.09.003. [24] R. Asahi, T. Morikawa, T. Ohwaki, K. Aoki, Y. Taga, Visible-light photocatalysis in nitrogen-doped titanium oxides, Science 293 (2001) 269–271, https://doi. org/10.1126/science.1061051. [25] T. Ohno, T. Mitsui, M. Matsumura, Photocatalytic activity of S-doped TiO2 photocatalyst under visible light, Chem. Lett. 32 (2003) 364–365, https://doi. org/10.1246/cl.2003.364. [26] M. Shen, Z. Wu, H. Huang, Y. Du, Z. Zou, P. Yang, Carbon-doped anatase TiO2 obtained from TiC for photocatalysis under visible light irradiation, Mater. Lett. 60 (2006) 693–697, https://doi.org/10.1016/j.matlet.2005.09.068. [27] K. Yang, Y. Dai, B. Huang, Understanding photocatalytic activity of S- and Pdoped TiO2 under visible light from first-principles, J. Phys. Chem. C 111 (2007) 18985–18994, https://doi.org/10.1021/jp0756350. [28] A. Bokare, M. Pai, A.A. Athawale, Surface modified Nd doped TiO2 nanoparticles as photocatalysts in UV and solar light irradiation, Sol. Energy 91 (2013) 111– 119, https://doi.org/10.1016/j.solener.2013.02.005. [29] S. Lee, I.-S. Cho, J.H. Lee, D.H. Kim, D.W. Kim, J.Y. Kim, H. Shin, J.-K. Lee, H.S. Jung, N.-G. Park, K. Kim, M.J. Ko, K.S. Hong, Two-step SolGel method-based TiO2 nanoparticles with uniform morphology and size for efficient photoenergy conversion devices, Chem. Mater. 22 (2010) 1958–1965, https://doi. org/10.1021/cm902842k.
9
[30] T. Lopez, J. Manjarrez, D. Rembao, E. Vinogradova, A. Moreno, R.D. Gonzalez, An implantable sol–gel derived titania–silica carrier system for the controlled release of anticonvulsants, Mater. Lett. 60 (2006) 2903–2908, https://doi.org/ 10.1016/j.matlet.2006.02.017. [31] C. Kang, L. Jing, T. Guo, H. Cui, J. Zhou, H. Fu, Mesoporous SiO2-modified nanocrystalline TiO2 with high anatase thermal stability and large surface area as efficient photocatalyst, J. Phys. Chem. C. 113 (2009) 1006–1013, https://doi. org/10.1021/jp807552u. [32] F. Yang, X. Zhang, X. Wu, F. Tian, F. Gan, Preparation of highly dispersed antimony-doped tin oxide nanopowders by azeotropic drying with isoamyl acetate, Trans. Nonferrous Met. Soc. China 17 (2007) 626–632, https://doi.org/ 10.1016/S1003-6326(07)60146-0. [33] Z. Deng, D. Chen, F. Tang, X. Meng, J. Ren, L. Zhang, Orientated attachment assisted self-assembly of Sb2O3 nanorods and nanowires: end-to-end versus side-by-side, J. Phys. Chem. C 111 (2007) 5325–5330, https://doi.org/10.1021/ jp068545o. [34] B. Gao, Z. Safaei, I. Babu, S. Iftekhar, E. Iakovleva, V. Srivastava, B. Doshi, S.B. Hammouda, S. Kalliola, M. Sillanpää, Modification of ZnIn2S4 by anthraquinone-2-sulfonate doped polypyrrole as acceptor-donor system for enhanced photocatalytic degradation of tetracycline, J. Photochem. Photobiol., A 348 (2017) 150–160, https://doi.org/10.1016/j.jphotochem.2017.08.037. [35] B. Gao, L. Liu, J. Liu, F. Yang, Photocatalytic degradation of 2,4,6tribromophenol over Fe-doped ZnIn2S4: Stable activity and enhanced debromination, Appl. Catal. B 129 (2013) 89–97, https://doi.org/10.1016/j. apcatb.2012.09.007. [36] S. Aghabeygi, M. Khademi-Shamami, ZnO/ZrO2 nanocomposite: Sonosynthesis, characterization and its application for wastewater treatment, Ultrason. Sonochem. 41 (2018) 458–465, https://doi.org/10.1016/ j.ultsonch.2017.09.020. [37] S.B. Hammouda, F. Zhao, Z. Safaei, I. Babu, D.L. Ramasamy, M. Sillanpää, Reactivity of novel Ceria-Perovskite composites CeO2- LaMO3 (MCu, Fe) in the catalytic wet peroxidative oxidation of the new emergent pollutant ‘Bisphenol F’: Characterization, kinetic and mechanism studies, Appl. Catal. B 218 (2017) 119–136, https://doi.org/10.1016/j.apcatb.2017.06.047. [38] F.I. Hai, X. Li, W.E. Price, L.D. Nghiem, Removal of carbamazepine and sulfamethoxazole by MBR under anoxic and aerobic conditions, Bioresour. Technol. 102 (2011) 10386–10390, https://doi.org/10.1016/j.biortech.2011.09.019. [39] M.M. Ahmed, S. Chiron, Solar photo-Fenton like using persulphate for carbamazepine removal from domestic wastewater, Water Res. 48 (2014) 229–236, https://doi.org/10.1016/j.watres.2013.09.033. [40] H. Eibenberger, S. Steenken, P. O’Neill, D. Schulte-Frohlinde, Pulse radiolysis and electron spin resonance studies concerning the reaction of SO.-4 with alcohols and ethers in aqueous solution 82, J. Phys. Chem. (1978) 749–750, https://doi.org/10.1021/j100495a028. [41] G.V. Buxton, C.L. Greenstock, W.P. Helman, A.B. Ross, Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (OH/O in aqueous solution, J. Phys. Chem. Ref. Data 17 (1988) 513– 886, https://doi.org/10.1063/1.555805. [42] C. Liang, H.-W. Su, Identification of sulfate and hydroxyl radicals in thermally activated persulfate, Ind. Eng. Chem. Res. 48 (2009) 5558–5562, https://doi. org/10.1021/ie9002848. [43] L. Dogliotti, E. Hayon, Flash photolysis of per[oxydi]sulfate ions in aqueous solutions. The sulfate and ozonide radical anions, J. Phys. Chem. 71 (1967) 2511–2516, https://doi.org/10.1021/j100867a019. [44] J. Chem. Soc., B: (1970) 1087, https://doi.org/10.1039/j29700001087. [45] Z. Wang, V. Srivastava, S. Iftekhar, I. Ambat, M. Sillanpää, Fabrication of Sb2O3/ PbO photocatalyst for the UV/PMS assisted degradation of carbamazepine from synthetic wastewater, Chem. Eng. J. 354 (2018) 663–671, https://doi.org/ 10.1016/j.cej.2018.08.068.
Please cite this article as: Z. Wang, V. Srivastava, S. Wang et al., UVC-assisted photocatalytic degradation of carbamazepine by Nd-doped Sb2O3/TiO2 photocatalyst, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2019.11.094