SnO2–SrO based nanocomposites and their photocatalytic activity for the treatment of organic pollutants

Accepted Manuscript SnO2-SrO based nanocomposites and their photocatalytic activity for the treatment of organic pollutants Saima Sultana, Rafiuddin, Mohammad Zain Khan, Khalid Umar, Arham S. Ahmed, Mohammad Shahadat PII:

S0022-2860(15)30057-0

DOI:

10.1016/j.molstruc.2015.06.032

Reference:

MOLSTR 21584

To appear in:

Journal of Molecular Structure

Received Date: 16 February 2015 Revised Date:

17 May 2015

Accepted Date: 9 June 2015

Please cite this article as: S. Sultana, Rafiuddin, M.Z. Khan, K. Umar, A.S. Ahmed, M. Shahadat, SnO2SrO based nanocomposites and their photocatalytic activity for the treatment of organic pollutants, Journal of Molecular Structure (2015), doi: 10.1016/j.molstruc.2015.06.032. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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SnO2-SrO based nanocomposites and their photocatalytic activity for the treatment of organic pollutants

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Saima Sultanaa, Rafiuddina, Mohammad Zain Khana, Khalid Umarb, Arham S. Ahmedc, Mohammad Shahadat*d a Department of Chemistry, bDepartment of Civil Engineering, c Department of Physics, Aligarh Muslim University, Aligarh 202 002, India d School of Distance Education, Universiti Sains Malaysia (USM) 11800, Penang, Malaysia

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Abstract

The present paper reports development of SnO2-SrO based nanocomposites using facile

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hydrothermal and sol-gel method. Nanocomposites were characterized on the basis of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Studies (EDS), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR), Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) techniques. The

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materials were explored for the photocatalytic activity degrading the treatment of organic pollutants viz- azo-dye, pesticide and drug. In addition, a comparative study was performed in term of particle size using hydrothermal and sol-gel route. It was observed that hydrothermal

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route showed an improved particle size, which affects the photocatalytic activity, porosity and crystalline nature of the nanocomposite. Further, kinetic and thermodynamic parameters were

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also calculated for the photodegradation experiments. It was found that the rate of photodegradation reaction followed the pseudo-first order kinetics and the highest rate was observed for azo-dye while it was lowest for the drug. A negative values of the Gibbs free energy (∆G) show that the photodegradation proceeds with a net decrease in free energy of the system. The results of photodegradation of dye, pesticide and drug indicate that nanocomposites of SnO2SrO can be effectively applied for the treatment of organic pollutants. 1

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Keywords: Nanocomposite materials, sol-gel, hydrothermal, X-ray diffraction, photocatalytic activity

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Corresponding author; [email protected]

1. Introduction

Natural water resources are being continuously contaminated by anthropogenic activities. Effluent from textile mills, pesticide industries and pharmaceutical manufacturing units is being

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regularly disposed off to the rivers, lakes and sea, thereby polluting our pristine sources of water

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[1]. These toxic xenobiotics may cause serious disorders in human beings and aquatic life and they are equally harmful to the plant kingdom as well. Thus, globally it becomes a very important issue to control discharges of organic pollutants to the natural waters [2]. However, the current technologies are still far away for large scale applications due to their low efficiency,

[3-6].

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high cost, intensive energy requirement, shorter lifetime and/or possibility of secondary pollution

Recently, a number of studies have concentrated on the degradation of toxic organic compounds in wastewater via photocatalysis of various semiconductors [7-13]. TiO2 in anatase

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phase has been most widely studied due to its superior photocatalytic activity, chemical stability

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and cost effectiveness [14, 15]. Moreover, several other transition metal oxides are also believed to possess amazing photocatalytic activities which enable their application for the decomposition and destruction of organic pollutants thereby resulting complete decontamination of water [16]. It was investigated that their properties can be improved by using transition metal oxides in the nano range owing to their large surface to volume ratio [17-19]. SnO2 (band gap energy Eg= 3.64 eV) is most widely used material for gas sensitivity, lithium recharge batteries and electronic devices [20-21]. It receives special attention due to its low cost and environmental friendly 2

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nature [22]. Furthermore, SnO2 nanoparticles (NPs) and its derivatives with other transition metal oxides are also believed to possess excellent photocatalytic activity under UV irradiation and can be used for degrading xenobiotic pollutants [23, 24]. These nanocomposites can be

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synthesized using various methods such as sol-gel [25-28], chemical vapor deposition [29], thermal evaporation [30] and hydrothermal synthesis [27]. It was found that SrO2 being less reactive but thermally more stable, didn’t receive much attention. In order to improve

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applicability in term of thermal stability, SrO2 doped SnO2 nanocomposites were synthesized. The present paper deals with the synthesis of SnO2 doped SrO nanocomposits by

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hydrothermal and sol-gel techniques and their characterization using XRD, SEM, EDX, TEM, FTIR, TGA and DSC analyses. The paper further involves the comparison of the particle size, nature and photocatalytic activity for the degradation of widely distributed organic pollutants viz- azo-dye, pesticide and drug.

2.1. Reagents and solutions

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2. Materials and Methods

All the chemicals were of analytical grade and procured from SRL chemicals, New Delhi,

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(India). The azo-dye was taken from the Department of Textile Engineering, Indian Institute of Technology, Delhi (India).

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2.2. Synthesis of SnO2-SrO nanocomposites (NCs) 2.2.1 Sol-gel route method

Nanocomposites of SnO2-SrO were prepared using sol-gel and hydrothermal methods. It is generally observed that for the preparation of these materials, sol-gel route is found to be relatively easy and low cost technique [32]. In a typical sol-gel synthesis, 1.0 g each of SnCl2.2H2O and SrOCl2.2H2O was dissolved in 100 mL ethanol to get a clear solution which is 3

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followed by drop wise addition of suitable amounts of double distilled water under constant stirring to establish hydrolysis [33]. The pH of the resulting solution was adjusted to 4 using dilute HCl. Then, the mixed solution was stirred for 2 h and aged for 12 h. Finally, the obtained

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white colloid was filtered and rinsed repeatedly with distilled water and ethanol to remove any excess reagent. The gels were heated in an oven at 120oC. The dried materials were heated at the rate of 5oC min−1 to the calcination temperature (400oC) for 2 h, and then allowed to cool

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naturally. The heat treatment, causes the transformation of Sn (II) to Sn (IV). So the final product

2.2.2 Hydrothermal Method

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is in the form of the SnO2-SrO nanostructure. The materials were sieved and kept in a desiccator.

Hydrothermal route is often used when high purity and crystallinity is desired. Hydrothermal synthesis of SnO2-SrO nanocomposites was carried out by dissolving salts of SnCl2.2H2O, SrOCl2.2H2O (0.5 g each) and Na2SO4 (1.0 g) in 40 mL distilled water. To acidify the solid

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solution mixture, 1 mL HNO3 (4 M) solution was used. The mixture was transferred to a Teflonlined stainless steel autoclave and placed in an oven at 180oC for two days. After completion of the reaction, the autoclave was removed from the oven and kept at room temperature (25±2ºC).

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The obtained solid product was separated from the liquid phase via centrifugation and washed with distilled water and pure ethanol. Finally, the products were dried in vacuum desiccators at

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room temperature overnight for characterization. 2.3 UV Photoreactor set-up

The photoreactor consisted of the reaction vessel, immersion well and UV lamp. The lamp was placed in an immersion tube, which was immersed in the sample contained in the reaction vessel to be irradiated with UV radiations. The reaction temperature was controlled by an outer cooling water jacket. The intensity of the UV lamp was 1.50 mW/cm2 and the capacity of the 4

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photoreactor was 200 mL. In order to maintain the required oxygen level and material transfer, air was bubbled through the reactor at the rate of 50-60 mL/s. Suspension of the as-prepared nanocomposites along with the solution of the toxic organic substrate is poured into the outer

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chamber of the photoreactor and continuously stirred with the help of magnetic stirrer during the course of experiments. The initial concentrations of substrates were determined at zero time. Thereafter, the content of the reactor were irradiated with UV light and degradation studies were

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carried out. 2.4. Instruments

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The crystal structure and particle size of the nanocomposites were determined by the powder X-ray diffraction (XRD) technique (Phillips PW1729, CuKα). The samples were sprinkled on a pre-greased glass slide and diffractograms were recorded between the angles 20° and 80°. The morphology and surface characterization of the materials were done with the help of scanning

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electron microscopy (SEM, Joel JSM-6360) and transmission electron microscope (TEM, Philips CM200) techniques. The TEM images provide useful information about the average particle size of the nanomaterials to further strengthen the XRD results. In order to verify the elemental

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composition of the composite material, energy dispersive x-ray technique coupled with the scanning electron microscope was employed. Thermal gravimetric analysis and the differential

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scanning calorimetric analysis were done by the Perkin–Elmer TGA/DSC analyzer in order to study the thermal stability and various thermal reactions (endothermic or exothermic arrest). The samples were heated in the temperature range of 25-800 ºC for TGA and 50-400 ºC for DSC at the rate of 10⁰C/min using alumina powder as a reference. The functional group characterization was done by using the ‘Interspec 2020-Spectrolab UK, FTIR spectrometer in the far IR range extending from 25-700 cm-1 with KBr. 5

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2.5 Photodegradation experiment The photocatalytic activity of SnO2-SrO nanocomposite was examined in a UV photoreactor using organic pollutants (azo-dye, pesticide and drug) and the residual concentrations were

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determined by UV-visible spectrophotometer. The UV spectra of the aqueous solution of pure azo-dye, pesticide as well as drug were first scanned to confirm the wavelength maxima. Calibration curves were prepared for the respective substrates in the concentration range 0-2 mM

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and used for estimating the residual concentrations of the substrate during UV irradiation. Initial concentration of Acid Red 88 (0.35 mM), pesticide (Metalaxyl (1.0 mM)) and drug (Tinidazole

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(0.75 mM) was fed to the reactor with an outer water jacket to control the reaction temperature. The UV source was placed in the innermost chamber while the substrate solution was continuously stirred in the outer chamber and cooling water was circulated into the middle one. 3. Results and Discussion

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3.1 X-ray diffraction analysis

XRD spectra of SnO2-SrO nanocomposites prepared by sol-gel and hydrothermal route are shown in Fig. 1. It can be seen that both the nanocomposites exhibit well defined peaks which

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shows the crystalline nature of SnO2-SrO. Crystallite size of nanocomposite was calculated using

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Debye-Scherrer formula given by:

where β is full width at half maximum (FWHM), θ is the angle of diffraction, λ is the wavelength of X-rays used and 0.9 is a shape dependent factor. Crystallite size calculated for SnO2-SrO nanocomposites prepared by sol-gel and hydrothermal route was 37 and 16 nm, respectively. Most of the peaks (2θ = 25.2°, 36.4°, 44.13°) with corresponding crystal planes of 6

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(1 1 0), (2 0 0), (2 1 0) match well with the XRD spectra of pure SnO2 (JCPDS file no. 41-1445) [34]. Other peaks (2θ = 37.5°, 41.3°, 47.7°, 52.3º) are associated with the SrO NPs and matched well with the standard pattern (JCPDS file no. 6-520) [35]. The sharp and strong peaks exhibit

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the crystalline nature and phase purity of the composites. The crystalline nature of nanocomposites is related to the type of metal-oxygen framework which is a function of various parameters such as reaction time, temperature, method of synthesis etc [36]. Moreover, the

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crystallinity and crystallite size is affected by the calcinations temperatures as well. 3.2 Surface characterization and elemental composition by SEM/EDX

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SEM images show fine nanostructures of the materials with a little bit aggregation of the particles which may be ascribed to high surface energy (Fig. 2a). Due to the fine particle size, the surface to volume ratio is very high. Thus, SnO2-SrO nanomaterials are supposed to have high photocatalytic activity. SEM images of SnO2-SrO nanocomposites exhibit wire like morphology.

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The length of these wire-like nanostructures may be several microns; however the radial dimensions are not more than 100 nm. These nanowire are crooked and dispersed, without particular orientation (Fig. 2b). Aggregation of wires was also not observed, but they were in

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dispersed form. Materials prepared through hydrothermal route shows finer particle size than solgel route. The most important advantage of hydrothermal synthesis is to bring down the

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diameters of SnO2 nanoparticles.

EDX provides valuable information about the chemical composition of the materials (Fig. 2a’ and b’). It generates spectra based on the fact that each and every element has a unique atomic structure that responds to X-ray with a unique sense [37]. EDX images show the materials were made up of Sn, Sr and O along with a very low percentage of Na-atom (Fig. 2b’) which was used in the form of Na2SO4 during hydrothermal synthesis. The EDX images show strong 7

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X-ray emission arising due to its interaction with SnO2-SrO nanocomposites. The images confirmed a high percentage of target elements (i.e. Sn, Sr and O) in the samples, thereby confirming the high purity and efficient mixing of the samples.

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3.3 TEM analysis

For further investigation and confirmation of the particle size of SnO2-SrO, TEM analysis was employed. The wire-like nanostructures visible in SEM images are not visible in the TEM

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images (Fig. 3). However, the nanostructures are found to be quite smooth and uniform wherein the dark colored SnO2 NPs are enclosing the light colored SrO NPs. The nanoparticles are much

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smaller than the magnified area of 100 nm under the transmission electron micrographs which again confirmed that the particle size of the as-prepared nanocomposites was below 100 nm. It was also found that the materials prepared by hydrothermal method appear to be even smaller in size than materials prepared by sol-gel route.

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3.4 FTIR analysis

The functional group characterization was done by scanning the prepared materials in the far IR range (700-30 cm-1). It is a low energy region and almost adjacent to the microwave region.

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The molecules absorb in this region owing to rotational transitions only. In the present case, the prepared nanomaterials being completely inorganic in nature (without any organic moiety) are

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expected to absorb below 700 cm-1 in the far IR region (Fig. 4). Numerous peaks corresponding to Sn, Sr and oxide linkage are observed in the spectra. The Sn-O-Sn stretching is observed at around 450 cm-1 while in both spectra a the sharp peak at around 620 cm-1 is the characteristic antisymmetric Sn-O-Sn stretching of the surface bridging oxide due to the condensation of adjacent surface hydroxyl groups [38-39]. The other band observed at around 430 cm-1 corresponds to asymmetric vibration frequency of Sr-O bond. Various sharp bands at 300 cm−1, 8

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250 cm−1 and 200 cm-1 are due to the stretching vibrations of Sr-O bonds [39-40]. The frequencies becomes even stronger at high temperature resulting in to Sr-O-Sr molecular framework [36]. Although, both the spectra are quite similar to each other, few peaks are very

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intense and sharp in the case of materials prepared by hydrothermal method due to higher purity, better crystallinity and fine particle size. 3.5 TGA and DSC analysis

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The formation of SRO doped SnO2 nanocomposite was also supported by thermal analysis. The TGA and DSC curves are presented in Fig. 5. As it can be seen in the TGA thermograms in

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Fig 5a, the pure samples show major weight loss at around 300 ºC and the loss continues gradually upto the end. Contrarily, the nanocomposites show considerable stability against the weight loss as evidenced on the respective TGA curves. In the beginning, upto 100 ºC, the loss is consistent with all samples as it may be due to loss of the solvent adsorbed on the samples. After

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100 ºC, all samples show a little inconsistency according to their thermal capacity. The sharp decrease in weight around 270 ºC indicates that the samples undergo major changes along with decomposition at this temperature. However, it is less evident in the composites justifying their

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greater stability.

The results are consistent with those observed in the DSC thermograms. Pure samples show

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an endothermic peak at and around 100 ºC indicating the loss of the adsorbed solvent. The prominent endothermic peaks at and around 275 ºC in the nanocomposites indicate that there is a massive structural transition at this temperature which initiates the thermal decomposition and weight loss. This result is consistent with that observed in the TGA curves. The endothermic peaks in the DSC are more prominent and sharp in case of SnO2-SrO nanocomposites prepared by sol-gel. The plots of SnO2 doped with SrO shows a small additional 9

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peak corresponding to SrO. The plots 1 and 2 give sharp peaks, showing appreciable crystallinity and high purity of the samples. The composite samples do not show any appreciable effect on the

oxide composite [41-43]. 3.6 Photocatalytic activity for the treatment of organic pollutants

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temperature of the phase transition. This behavior has been observed frequently in the ionic salt

The photocatalytic degradation depends upon the light-harvesting efficiency, the efficiency

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of the reaction of the photogenerated electron/hole, and the reaction of photogenerated electron/holes with substrate molecules. The actual reaction occurs when semiconductor

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nanocrystals illuminated with light (of energy not less than the band gap) and produce electron/hole pairs, i.e. holes in the valence band and electrons in the conduction band. A fraction of these charge carriers reaches the crystal surface and react with water and oxygen to generate hydroxyl (•OH) and hydroperoxyl radicals (•OOH) which then initiate the degradation

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of the substrate [44]. The photocatalytic degradation is a fast and very effective method of degrading toxic and complex organic pollutants [45]. The decrease in substrate concentration (C/C0) was plotted against time (min) as shown in Fig. 6.

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It was found that SnO2-SrO nanocomposites synthesized using hydrothermal method show superior photocatalytic activity because of their smaller size. The photocatalytic activity was

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improved due to the reduction in particle size of the materials which increases the surface to volume ratio. The photodegradation follows the pseudo-first order kinetics. This improvement in photocatalytic activity was further explained by the fact that photogenerated holes in SnO2 might get trapped within the SrO nanoparticles increasing charge separation and in turn suppressing the recombination of electron and holes thereby increasing the photocatalytic activity [46]. A

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comparison between properties of nanocomposites synthesized by different method, i.e. sol-gel and hydrothermal is shown in Table 1. 3.7 Kinetic studies

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The choice of substrate has a profound effect on the kinetics and thermodynamics of photodegradation as appeared from the Table 2. The photocatalytic activity of as-prepared nanomaterials were tested against three different substrates viz. Acid Red 88 ‘AR’ (azo-dye),

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Metalaxyl ‘ML’ (pesticide) and Tinidazole ‘TN’ (drug) and the two key parameters (kinetic as well as thermodynamic) i.e. rate constant (k) and change in Gibbs free energy (∆G) are presented

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in Table-2. The negative sign of the pseudo-first order rate constant (k) shows the declining trend of plots thereby confirming removal of toxic substrate. However, the magnitude of different values of the k shows the degradation rate of the dye was highest followed by pesticide and drug. Additionally, ∆G values show a decrease net free energy of the system during photodegradation

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thereby favouring the reaction under the conditions of study. This thermodynamic parameter (∆G) is also related to the chemical potential (µ) of the system which is defined as the change in free energy of the system with respect to composition. Therefore, the as-prepared nanomaterials,

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can be used for any of the three substrates, however best suits for dye (in the cleavage of azo bond i.e. N=N). Nonetheless, SnO2-SrO based nanocomposites have significant potential to

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remove mixture of toxic organic pollutants present in wastewater before it is disposed off to conserve the purity of natural water resources. 4. Conclusion

The nanocomposites of SnO2-SrO prepared by hydrothermal route have finer particle size than the composites synthesized by sol-gel method; however the thermal stability is more or less same. The hydrothermal method of synthesis is found to be better in terms of purity, crystallinity 11

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and size whilst sol-gel method is relatively simple and low cost. It is also observed that the method of synthesis of nanomaterials and the choice of substrate has a profound effect on photocatalytic activity. Among the three different organic substrates, the photodegradation was

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highest in case of azo-dye followed by pesticide and then drug. The kinetic and thermodynamic parameters support better degradation by the nanocomposites prepared by hydrothermal route. Thus, the hydrothermal method of synthesis offers higher purity, better crystallinity and higher

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degradation rate.

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5. Acknowledgement

Authors are thankful to the Department of Textile Engineering, Indian Institute of technology for providing pure azo-dye. SS is thankful to CSIR, New Delhi for providing financial support to

6. References

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this project.

[1] S.V. Awate, K. Suzuki, Enhanced adsorption capacity and photo-catalytic oxidative activity of dyes in aqueous medium by hydrothermally treated titania pillared clay,

EP

Adsorption 7 (2001) 319-32.

AC C

[2] E. Dvininova, M. Ignata, P. Barvinschib, M.A. Smithersc, E. Popovicia, New SnO2/MgAl-layered double hydroxide composites as photocatalysts for cationic dyes bleaching, J. Hazard. Mater. 177 (2010) 150-158.

[3] S. Sultana, Rafiuddin, M.Z. Khan, K. Umar, M. Muneer, Electrical, Thermal, Photocatalytic and Antibacterial Studies of Metallic oxide nanocomposite doped Polyaniline, J. Mat. Sci. Technol. 29 (2013) 795–800.

12

ACCEPTED MANUSCRIPT

[4] P. Pichat, H. Khalaf, D. Tabet, M. Houari, M. Saidi, Ti-montmorillonite as photocatalyst to remove 4-chlorophenol in water and methanol in air, Environ. Chem. Lett. 2 (2005) 191-194.

II: hybrid methods, Adv. Environ. Res. 8 (2004) 553-597.

RI PT

[5] P.R. Gogate, A.B. Pandit, A review of imperative technologies for wastewater treatment

[6] S. Sultana, Rafiuddin, M.Z. Khan, M. Shahadat, Development of ZnO and ZrO2

http://dx.doi.org/10.1016/j.jece.2015.02.024

SC

nanoparticles: Their Photocatalytic and Bactericidal Activity, J. Environ. Chemical Eng.

M AN U

[7] S.J. Doh, C. Kim, S.G. Lee, S.J. Lee, H. Kim, Development of photocatalytic TiO2 nanofibers by electrospinning and its application to degradation of dye pollutants, J. Hazard. Mater. 154 (2008) 118-127.

[8] H. Park, W. Choi, Photoelectrochemical investigation on electron transfer mediating

TE D

behaviors of polyoxometalate in UV-illuminated suspensions of TiO2 and Pt/TiO2, J. Phys. Chem. B 107 (2003) 3885-3890.

[9] H.G. Kim, D.W. Hwang, J.S. Lee, An undoped, single-phase oxide photocatalyst

EP

working under visible light, J. Am. Chem. Soc. 126 (2004) 8912-8913. [10] Md. Shahadat, R. Bushra, M. R Khan, M. Rafatullah, T.T. Tow, A comparative study

AC C

for the synthesis and characterization of polyaniline based nanocomposite materials,

RSC Adv. 4 (2014) 20686-20692.

[11] R. Bushra, Md. Shahadat, S.A. Nabi, A.S. Raeissi, M. Oves, K. Umar, M. Muneer, A. Ahmad, Synthesis, characterization, antimicrobial activity and applications of composite adsorbent for the analysis of organic and inorganic pollutants, J. Hazard. Mater. 264 (2014) 481-489. 13

ACCEPTED MANUSCRIPT

[12] Md. Shahadat, S.A. Nabi, R. Bushra, A.S. Raeissi, K. Umar, M.O. Ansari, Synthesis, characterization, photolytic degradation, electrical conductivity and applications of nanocomposite adsorbent for the treatment of pollutants, RSC Advances, 2 (2012)

RI PT

7207-7220.

[13] S.A. Nabi, Md. Shahadat, R. Bushra, M. Oves, F. Ahmed, Synthesis and Characterization of PolyanilineZr(IV)sulphosalicylate composite and its applications (1)

SC

electrical conductivity, (2) and antimicrobial activity studies, Chem. Eng. J., 173 (2011) 706-714.

M AN U

[14] W. Xi, S.U. Geissen, Effect of pH, charge separation and oxygen concentration in photoelectrocatalytic systems: active chlorine production and chlorate formation, Water Res. 35 (2001) 1256-1262.

[15] Md. Shahadat, T.T. Teng, M. Rafatullah, M. Arshad, Titanium-based nanocomposite

TE D

materials: A review of recent advances and perspectives, Colloids and Surfaces B: Biointerfaces 126 (2015) 121-137

[16] M. Bizarro, M.A. Tapia-Rodriguez, M.L. Ojeda, J.C. Alonso and A. Ortiz,

EP

Photocatalytic activity enhancement of TiO2 films by micro and nano-structured surface modification, App. Surf. Sci. 255 (2009) 6274-6278.

AC C

[17] S. Sultana, Rafiuddin, M.Z. Khan, K. Umar, Synthesis and characterization of copper ferrite nanoparticles doped polyaniline, J. Alloys Compds. 535 (2012) 44-49.

[18] T.L. Thompson, Jr. J.T. Yates, Surface science studies of the photoactivation of TiO2-new photochemical processes, Chem. Rev. 106 (2006) 4428-4453.

[19] Chen, S.S. Mao, Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications, Chem. Rev. 107 (2007) 2891-2959. 14

ACCEPTED MANUSCRIPT

[20] M. Law, H. Kind, B. Messer, F. Kim, P. Yang, Photochemical Sensing of NO2 with SnO2 Nanoribbon Nanosensors at Room Temperatur, Angew. Chem. Int. Ed. 41 (2002) 2405-2408.

RI PT

[21] Y. Idota, T. Kubota, A. Matsufuji, Y. Maekawa, T. Miyasaka, Tin based amorphous oxide: A high capacity lithium ion storage material, Science 276 (1997) 1395-1397. [22] Z.A. Hu, Y.L. Xie, Y.X. Wang, L.P. Mo, Y.Y. Yang, Z.Y. Zhang, Polyaniline/SnO<

SC

sub> 2 nanocomposite for supercapacitor applications, Mat. Chem. Phys. 114 (2009) 990-995.

M AN U

[23] H. Xia, H. Zhuang, T. Zhang, D. Xiao, Visible-light-activated nanocomposite photocatalyst of Fe2O3/SnO2, Mater. Lett. 62 (2008) 1126-1128. [24] C. Wang, B.Q. Xu, X. Wang, J. Zhao, Preparation and photocatalytic activity of ZnO/TiO2/SnO2 mixture, J. Sol State Chem. 178 (2005) 3500-3506.

Their

TE D

[25] S Sultana, M.Z. Khan, Md. Shahadat, Development of ZnO and ZrO 2 nanoparticles: photocatalytic

and

bactericidal

activity,

J.

Environ.

Chem.

Eng.

doi:10.1016/j.jece.2015.02.024

EP

[26] S.A. Nabi, A.S. Raeissi, Md. Shahadat, R. Bushra, A.M. Khan, Synthesis and characterization of novel cation exchange adsorbent for the treatment of real samples for

AC C

metal ions, Chem.Eng. J. 200 (2012) 426-432

[27] SA Nabi, R Bushra, M Shahadat, Application of Zr (IV) tungstate for removal of metal ions from aqueous solutions, Toxic. Envir. Chem. 94 (3), 468-481

[28] F Pourfayaz, A Khodadadi, Y Mortazavi, SS Mohajerzadeh, CeO< sub> 2 doped SnO< sub> 2 sensor selective to ethanol in presence of CO, LPG and CH< sub> 4, Sensors Actuators B 108 (2005) 172-176. 15

ACCEPTED MANUSCRIPT

[29] Y. Liu, E. Koep, M. Liu, A highly sensitive and fast-responding SnO2 sensor fabricated by combustion chemical vapor deposition, Chem. Mater. 17 (2005) 3997.

Nanotubes, J. Phys. Chem. B 106 (2002) 1274-1279.

RI PT

[30] Z.R. Dai, J.L. Gole, J.D. Stout, Z.L. Wang, Tin Oxide Nanowires, Nanoribbons, and

[31] S. Fujihara, T. Maeda, H. Ohgi, E. Hosono, H. Imai, S. Kim, Hydrothermal Routes To Prepare Nanocrystalline Mesoporous SnO2Having High Thermal Stability, Langmuir 20

SC

(2004) 6476-6481.

[32] H.J. Jeon, S.C. Yi, S.G. Oh, Preparation and antibacterial effects of Ag–SiO2 thin films

[33] Z.A.

Hu,

Y.L.

Xie,

M AN U

by sol–gel method, Biomaterials, 24 (2003) 4921-4928. Y.X.

Wang,

L.P.

Mo,

Y.Y.

Yang,

Z.Y.

Zhang,

Polyaniline/SnO2 nanocomposite for supercapacitor applications, Mat. Chem. Phys., 114 (2009) 990-995.

TE D

[34] Joint Committee on Powder Diffraction Standards, Powder Diffraction File No. JCPDS41-1445) (ICSD data).

[35] Joint Committee on Powder Diffraction Standards, Powder Diffraction File No. JCPDS-

EP

6-520).

[36] T. Athar, Synthesis and Characterization of Strontium Oxide Nanoparticles via Wet

AC C

Process, Materials Focus, 2 (2013) 450–453.

[37] J. Goldstein, (2003). Scanning Electron Microscopy and X-Ray Microanalysis. Springer, ISBN 978-0-306-47292-3. Retrieved 30 Aug 2014.

[38] A.S. Ahmed, M.M. Shafeeq, M.L. Singla, M. Chaman, S. Tabassum, Temperature dependent structural and optical properties of tin oxide nanoparticles, J. Phys. Chem. Solids, 73 (2012) 943-947. 16

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[39] Inorganic IR spectra Sadtler Research Lab, Philadelphia, PA (1965); New York (1976) [40] K. Nakamoto, Infrared and raman spectra of inorganic and coordination compounds, 5th edn., Wiley-Interscience, New York (1997).

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[41] S. Sultana, Rafiuddin, Electrical properties of V2O5-doped TlI, Radiation Effects and Defects in Solids: Incorporating Plasma Science and Plasma Technology, 164 (2009) 771-778.

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[42] G.V. Lavrova, V.G. Ponomareva, E.B. Burgina, Proton conductivity and structural dynamics in Cs5H3(SO4)4/SiO2composites, Solid State Ionics, 176 (2005) 767-771.

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[43] N.F. Uvarov, P. Vanek, Yu.I. Yuzyuk, V. Zelenzy, V. Studnika, B.B. Bocknonov, V.E. Dutepov, J. Peptzept, Properties of rubidium nitrate in ion-conducting RbNO3Al2O3nanocomposites, Solid State Ionics 90 (1996) 201-207. [44] G. Bandekar, N.S. Rajurkar, I.S. Mulla, U.P. Mulik, D.P. Amalnerkar, P.V. Adhyapak,

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Synthesis, characterization and photocatalytic activity of PVP stabilized ZnO and modified ZnO nanostructures, Appl. Nanosci., 4 (2014) 199-208. [45] C. Fernandez, M.S. Larrechi, P. M. Callao, An analytical overview of processes for

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removing organic dyes from wastewater effluents, Trends Anal. Chem., 29 (2010) 1202-1211.

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[46] A.A. Firooz, A.R. Mahjoub, A.A. Khodadadi, World Academy of Science, Engineering and Technology 52 (2011) 138-140.

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Figure captions: Fig. 1. X-ray diffraction pattern of SnO2-SrO nanomaterials by two different routes (hkl values for corresponding peaks are given in blue color for SnO2 and brown color for SrO NPs)

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Fig. 2. SEM images of SnO2-SrO nanocomposites along with EDX spectra for elemental composition (a, a’) SnO2-SrO nanocomposite prepared by sol-gel route; (b, b’) SnO2-SrO nanocomposites prepared by hydrothermal route Fig. 3. TEM images of SnO2-SrO nanocomposites prepared by sol-gel and hydrothermal route. Fig. 4. FTIR spectra of the as-prepared SnO2-SrO nanocomposites

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Fig. 5. Thermal analysis of the as-prepared materials (a) TGA (1- SnO2-SrO sol-gel; 2- SnO2SrO Hyd; 3- SnO2 sol-gel; 4- SnO2 Hyd); (b) DSC (1- SnO2-SrO sol-gel; 2- SnO2- SrO Hyd)

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Fig. 6. Photocatalytic activity of nanomaterials (a) SnO2-SrO sol-gel; (b) SnO2-SrO Hyd, for the degradation of dye, drug and pesticide

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Table 1: Comparison of various properties of the nanomaterials prepared by two different methods. Properties

Sol-gel approach

1. 2.

Particle size (nm) Phase

37 Rutile

3.

Surface morphology

Fine structures with more vacant spaces

4. 5. 6.

Porosity Thermal stability Photocatalytic activity

High Very high Low

Hydrothermal approach 16 Rutile Very fine structures with less vacant spaces Low High High

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Table 2: Effect of types of substrates on kinetics and thermodynamics parameters (k and ∆G).

SnO2 sol-gel SnO2-SrO sol-gel SnO2 Hydrothermal SnO2-SrO Hydrothermal

AR-88 (dye) k1 (S-1)

∆G1 (kJm 1 )

-1.60 -2.30

-16.1 -15.2

-2.30 -3.00

ML (pesticide)

-

TN (drug) k3 (S-1)

∆G3 (kJm1 )

-16.6 -15.5

-1.00 -1.30

-17.2 -16.6

-1.90

-15.6

-1.50

-16.2

-2.40

-15.0

-1.60

-16.1

k2 (S-1)

∆G2 (kJm 1 )

-1.30 -2.00

-15.2 -14.5

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Nanocomposite materials

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The negative sign in slope (k) represents that the concentrations are decreasing and plots show a decreasing trend.

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Synthesis of SnO2-SrO based nanocomposites using two different methods
Comparison of the particle size, nature and photocatalytic activity

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Characterization on the basis of XRD, SEM, TEM and TGA analyses

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Potential application for the photochemical degradation of environment pollutants