Catalysis of SO2 to SO3 by Ocimum Sanctum Mediated Potassium Vanadate (KV2O5) Nanocuboids

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Journal of Chemistry and Chemical Sciences, Vol.7(4), 297-306, April 2017 (An International Research Journal), www.chemistry-journal.org

ISSN 2229-760X (Print) ISSN 2319-7625 (Online)

Catalysis of SO2 to SO3 by Ocimum Sanctum Mediated Potassium Vanadate (KV2O5) Nanocuboids

Arvind Singh K. Heer*, Sajid M. Mansoori, Nikita K.Chamria and Satish R. Ingale

Department of Chemistry, Mithibai College, Ville Parle (West), Mumbai-400056, Maharashtra, INDIA.

email: [email protected]

(Received on: March 31, Accepted: April 4, 2017)

ABSTRACT

Eco friendly and cost effective methods of green mediated synthesis of nanoparticles are the present research in the limb of nanotechnology. The present work leads to the synthesis of potassium-deficient (KV2O5) nanocuboid from 0.008 moles of Ammonium Meta-Vanadate and 0.002 mole of Potassium Oxalate added to aqueous leaf extract of Ocimum Sanctum which acts as reducing as well as capping agent. The characteristics of Potassium Vanadate nanoparticles were studied by using UV-VIS spectroscopy, XRD, FTIR, SEM and EDS. Ultraviolet scanning spectroscopy was used to detect the distinct absorption spectrum of KV2O5

nanoparticles. The peak value observed at 345 nm. The EDS spectrum of the KV2O5

nanoparticles confirmed the presence of elemental Potassium and Vanadium and pentavalent Vanadium was also determined by EDS in its oxide form. The size of synthesized nanocuboid lies between 50-200 nm. The catalytic activity of prepared nanoparticles was studied for the oxidation of SO2 to SO3.

Keywords: KV2O5 Nanocuboids, UV-VIS spectroscopy, XRD, FTIR, SEM and EDS and Catalysis.

INTRODUCTION

Nanotechnology is an up-and-coming and hasty mounting field of science which is

being exploited in an extensive spectrum of disciplines such as electronics, energy, environment and health sectors. Nanoscience has revolutionized these fields in achieving the processes and products that are hardly possible to evolve through conservative systems.

Nanotechnology is the creation and consumption of functional materials devices and systems with novel properties and functions that are achieved through the control and

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Arvind Singh K. Heer, et al., J. Chem. & Cheml. Sci. Vol.7(4), 297-306 (2017)

reformation of matter at the atomic, molecular and macromolecular levels. Nanotechnology has animatedly developed as a research for the synthesis of structure of particles with facet smaller than 100nm.

Nanotechnology is always surrounded by the fact that the particles at nanoscale behave very differently than they do in their original form. Green nanotechnology has been described as the development of clean technologies, to minimize potential environmental and human health risks associated with the manufacture and use of nanotechnology products and to encourage replacement of existing products with new nano-products that are more environmentally friendly throughout their lifecycle1-4. Green synthesis of nanoparticle depends on plant source and the organic compound in the crude leaf extract. It has no harmful particles to help in building better products. In the midst of the assorted biosynthetic approaches the use of plant extracts is easily available, safe to handle and cost effective. An economic novel alternative choice for chemical and physical methods of nanoparticles synthesis is green method5. KV2O5 nanoparticles are presently under intensive study for applications in the field of optical devices, sensors, catalysis, biotechnology, chemical and biological sensors and as catalyst6.

Vanadium compounds (pentoxide and certain vanadates) are used as catalyst in the oxidation of SO2 to SO3; ethanol to acetaldehyde; in the synthesis of phthalic and maleic anhydrides; in the manufacture of polyamides (nylon); sugar to oxalic acid, and anthracene to anthraquinone. It is also used for the manufacture of yellow glass; inhibiting UV light transmission in glass; depolarizer; as developer in photography; and as mordant in dyeing and printing fabrics and in manufacture of aniline black in form of ammonium vanadate.

The catalytic oxidation of SO2 to SO3 and alcohols to aldehydes is focus of interest in both industrial and fundamental catalysis. In spite of the economic significance of such reactions, only a few papers have reported on the selective oxidation of SO2. In the present paper we report on the selective oxidation of SO2 on potassium promoted V2O5.

Sulphur dioxide (SO2) is one of a group of highly reactive gases known as “oxides of sulphur”. SO2 is linked with a number of adverse effects on the respiratory system and other environmental issues. It is an important industrial emission gas which causes several difficulties in the environment like acid rain7. Sulphur dioxide is a ubiquitous component of fuel combustion exhausts and one of the first air pollutants to be regulated all over world. Several approaches have been adopted to reduce SO2 content in the environment8. One of the most difficult environmental problems facing industry is how to economically control SO2

emissions. Conversion of H2SO4 from SO2, which could be a great impact on reducing pollution. Production of Sulphuric acid is one of the best choices considering it’s economical

values and utilities9. This paper addresses the different processes to control SO2 and to use SO2

in most economic and productive way to reduce SO2 effect in environment. A review of various treatment methods has been provided and a brief description of each process has been included and their technical applicability is also compared10,11. The process of Sulphur dioxide removal from various Sulphur operations and production of Sulphuric acid from this SO2 is studied in this paper.

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EXPERIMENTAL

Materials and Methods

Leaves of Ocimum Sanctum were collected in the month of Oct. 2016 from Mumbai region. They were surface cleaned with running tap water to remove debris and other contaminated organic contents, followed by double distilled water, air dried at room temperature and finely grinded to powder. The different qualitative chemical tests were performed for establishing profile of given extract for its chemical composition.

Qualitative phytochemical analysis was done using the standard procedures from 12-14 and 23. The qualitative examination of the aqueous extracts of the leaf sample of Ocimum Sanctum showed the presence of phytochemical constituents such as Alkaloid, Carbohydrate, Glycoside, Flavonoid, Terpenoid, Tannins and Steroid.

TABLE.1 Phytochemical constituents of Ocimum Sanctumaqueous leaf extract

Phyto-constituents Reagents Results Carbohydrates Molisch’s, Benedict’s +,+ Flavonoids Alkaline Reagent, Shinoda’s +,+ Alkaloids Mayer’s, Wagner’s +,+ Tannin Lead acetate, Ferry chloride, Wagner’s -, +, + Steroids Liebermann Burchard’s + Terpenoids Thionyl chloride + Saponin Gelatin - Glycosides Legal’s, Borntrager’s +, + Reducing Sugar Fehling solutions - Fixed oils Spot test -

+ Presence; – Absence *all tests have been performed in triplicate.

Preparation of Ocimum Sanctum extract

About 10 gm of finely grinded leaves powder were kept in a beaker containing 100 ml double distilled water and boiled for 30 min. After cooling at room temperature, it was centrifuged at 6000 rpm for 10 minutes and filtered. The filtrate was stored at 4°C for further experiments. The filtrate was used as reducing and stabilizing agent

Synthesis of KV2O5 nanocuboids using Ocimum Sanctum The obtain leaf extract was heat stirred in erlenmeyer flask till it attains the

temperature of 60oC. After the solution attains the temperature of 60oC, 0.008 moles of Ammonium Meta-Vanadate and 0.002 moles of Potassium Oxalate was added to the above solution. Then stirring was continued for 1hr at 80oC-90oC. After 1hr of heat stirring the solution turns in to a thick black paste which was washed with first double distilled water and then with ethanol for complete isolation of plant matter. Then the obtained black paste was


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oven dried for 2hrs at 110oC. After completion of drying process the black paste turns into dark blue powder which was grinded in mortar pestle for 1hr and sintered in horizontal furnace for 24hr at 510oC. The dark blue powder now turns into dark brown shinny KV2O5

nanoparticles which were subjected to further characterisation.

Characterisation

UV-Vis spectral analysis was done by using UV-Visible spectrophotometer (UV- 1100, India). UV-Visible absorption spectrophotometer with a resolution of 5 nm between 200 and 600 nm was used. One millilitre of the sample was pipetted into a test tube and subsequently analysed at room temperature. FTIR spectra of were recorded on Perkin Elmer Spectrum 2 FTIR Spectrophotometer. The particle size and surface morphology was analysed using Scanning electron microscopy (SEM), operated at an accelerated voltage of 200 kV. Elemental composition of the present sample was analyzed with energy dispersive analysis of X-ray (EDS) spectroscopy. X-ray diffraction (XRD) patterns of the synthesized KV2O5 NPs were collected on PANalytical Empyrean 300TT X-ray diffractometer with Cu K(λ=1.542Å)

radiation.

Catalysis of SO2

SO2 gas was prepared by heating 1mole of Sodium Dihydrogen Phosphate with 4moles of Concentrated Sulphuric acid15. The SO2 gas was first collected in 100ml Hydrogen Peroxide(H2O2) and the resultant solution was titrated against 0.001N NaOH for determination of total amount of SO2 gas evolved with above reaction. NaH2PO2 + 4H2SO4 SO2 + H5PO4 + 3H+ + Na+ +2SO 2-+ 2H2O SO2 + H2O2 H2SO4

Then the prepared SO2 gas was collected in a beakers containing 100ml Distilled water with the varying content of prepared KV2O5 nanoparticles. This experiment was performed with blank (without KV2O5 NPs), 0.09, 0.18, 0.27, 0.36, 0.45, 0.54, 0.63, 0.72, 0.81, 0.90 and mmoles of KV2O5 nanoparticles.

The resultant solution after delivering SO2 gas to beaker containing Distilled water and KV2O5nanoparticles was titrated against 0.001N NaOH, for determination of amount of H2SO4 formed.

H2O + SO2 KV2O5 H2SO4 +O

RESULTS AND DISCUSSIONS

Synthesis of KV2O5 nanocuboid

The mechanism of formation of KV2O5 nanocuboids probably proceeds through the following reactions.


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K2C2O4 + 4NH4VO3 + Aqueous extract of OcimumSanctum leaves 2KV2O5 (1) -O

K2C2O4 2K+ +2CO2 (2)

4NH4VO3 (2VO3)2 + NH4 (3)

2VO3 -O V2O5 (4)

2K+ + 2V2O5 2KV2O5 (5)

Reaction (1) represents the general reaction for formation of KV2O5 nanocuboids, in this reaction the plant extract acts as reducing as well as capping agent between K+ ions and V2O5 where in reaction (4) the plant extract reduces the 2VO3 to V2O5 and helps in dopping potassium in the lattice of V2O5. The Vanadium Ions (V+6) reacts with solvated electrons and undergo reduction to generate V+5 species. However the V+5 ions are highly stable, so to dope K+ ions in V2O5, Sintering at high temperature of 510oC was required for the formation of KV2O5 nanocuboids.

XRD Analysis

The phase identification of the KV2O5 nanoparticles was carried out by X-ray diffraction method. X-ray powder diffraction measurement was carried out by using PANalytical Empyrean 300TT X-ray powder diffractometer with long fine focus Cu anode operated at 40 KV and 30 mA in Bragg-Brentano geometry.

Figure1. XRD analysis of Potassium Vanadate Nanoparticles, Figure 2.XRD analysis of Potassium Vanadate Nanoparticles and Plant matter

The powder XRD data were obtained in the 2 range from 10° to 80° in step-scan mode with 2 step of 0.02°. The X-ray diffractometer was calibrated by means of external silicon standard, SRM 640a. The diffraction pattern indicated that the sample is the KV2O5

nanoparticles. The Bragg reflections at 2=16.372, 28.433, 31.362 and 33.090 can be indexed to the (020), (121), (002) and (040) orientation confirms the presence of KV2O5 nanoparticle in orthorhombic crystal system.The conversion of Potassium oxalate and Ammonium Meta-


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Vanadate to KV2O5 nanoparticle was greater than ninety percent and smaller peaks contributed to Ocimum Sanctum extract impurity. The XRD pattern of the mixture is shown in the Figure.2 and XRD pattern of the Potassium Vanadate nanoparticle is shown in Figure 1.

FTIR Analysis

A small amount of the glass powder was mixed and ground with a relatively large quantity of KBr which is transparent to IR radiation. Discs for measurement of IR absorption spectra were formed by pressing the mixture at a pressure of 10-15 tons for few minutes under vacuum. The infrared absorption spectra of the heat treated and as quenched samples were determined by using Perkin Elmer Spectrum 2 FT- Infrared Spectrometer in the range of 400 to 4000 cm−1. As s hown in figure 2.

Figure 2. FTIR spectra of Potassium Vanadate Nanoparticles

The earlier reports17 show flavonoids and terpenoids were present in the Ocimum Sanctum leaf. The spectrum reveals that carbonyl group (C-O, 1636 cm-1) was involved in the reduction of V6+ to V5+. Hence, it may be conclude that flavonoids and terpenoids were responsible for reduction and efficient stabilization. The peaks at 1026 cm-1 and 570 cm-1

confirms the formations of VR-SO3 and Metal-Ligand(V-O) bond.

UV-Visible Spectroscopy Analysis

The UV- Visible Spectrum of Ocimum Sanctum leaves extract (fig. 3a) shows the a well-defined absorption at 420nm which indicates the presence of reducing agents such as flavonoids and terpenoids which has already been confirmed by phytochemical analysis (Table. 1) and in the SPR band at 345 nm in the spectrum of prepared nanoparticles (fig. 3b) shows the presences metal-metal bond formation16. The direct band gap calculated from diffused reflectance spectra is 3.59 eV, which is higher for nano Potassium vanadate than that for bulk Potassium vanadate20. The increment of the values of optical band gap arises due to improvement in the crystallinity of during annealing treatment21,22.


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Figure3a. UV-Visible spectra of Ocimum Sanctum leaves extract

Figure3b. UV-Visible spectra of Potassium Vanadate nanoparticles SEM and EDS Analysis Scanning electron microscopy (SEM) has been used to identify the size, shape and morphology of nanoparticles. It reveals that the KV2O5 nanoparticles are well dispersed and predominantly cuboidal in shape, while some of the nanoparticles were found to be having structures of irregular shape as shown in fig. 4(a, b, c and d). The nanoparticles are homogenous and cuboidal shape which conforms to the SPR band in UV- Visible spectrum. The Energy Dispersive X-ray Spectroscopy (EDS) spectrum of the synthesised KV2O5 nanoparticles fig. 5 shows strong potassium signal along with vanadium and weak peaks of oxygen and oxides analysis by EDS confirms the formation of pentavalent Vanadium(V2O5) and Potassium Ions(K+) i.e KV2O5.

(a) (b)

420nm

0

0.5

1

1.5

2

0 200 400 600 800A

bso

rban

ceWavelength (nm)

345nm

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0.5

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1.5

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0 200 400 600

Ab

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(c) (d) Figure4.(a, b and c) SEM images for prepared Potassium Vanadate nanoparticles

Figure5. EDS spectra of prepared Potassium Vanadate nanoparticles Catalysis of SO2

The previous articles [18,19] has discussed different methods of SO2 emission control and a way to produce Sulphuric acid (H2SO4) from industrial SO2 emission and the oxidation of sulphur dioxide to sulphur trioxide over supported Vanadia catalysts. In this paper we have tried to introduce a very cost effective and safe method for conversion of SO2 to Sulphuric acid using the prepared KV2O5 nanoparticles as catalyst and distilled water. The varying amount of catalyst was placed in 100 cm3 of distilled water and SO2(g) was passed in this water containing catalyst. It was observed that when the SO2(g) was passed in water containing catalyst the color of water turns light yellow which indicates the formation of Sulphuric acid and the color gets denser with the increase in amount of catalyst and when the SO2(g) was passed in water without catalyst the color of water does not change. The total amount of SO2 gas evolved was determined by the reaction of H2O2 and SO2 as shown in esperimental section, it was found that the total amount SO2 (g) evolved was 21.4375 moles.


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Table 2. Catalysis of SO2

Amount of Catalyst dispersed in distilled water (in mmoles) Percentage of SO2 converted to H2SO4 0 0%

0.09 11.6% 0.18 23.6% 0.27 36.14% 0.36 52.25% 0.45 60% 0.54 70.21% 0.63 82.85% 0.72 84.92% 0.81 85.21% 0.90 92.28% 1.8 92.28%

*all tests have been performed in triplicate. According to the results of following experiments, when 0.09 mmoles of KV2O5 nanoparticle (catalyst) was placed in distilled water it converts 11.6% of SO2(g) to Sulphuric acid and the conversion rate increases with the increase in amount of catalyst. But it was found that after a certain amount of 0.63 mmoles the rate of conversion decreases, even on adding the prepared catalyst in excess. Maximum of 92.28% of SO2 (g) can be converted to Sulphuric acid by this technique. CONCLUSION Compared to other costlier techniques of SO2 emission control this has been found to be an cost effective and easy technique to control the dispersion of SO2 (g) in environment and it not only controls the emission of SO2(g) in environment but also gives a very useful by-product in the form of H2SO4, which is used in many industrial processes. The synthesis of KV2O5 nanoparticles by plant extract have found to be safe and effective method, as there was no evolution of harmful fumes and yield of nanoparticle obtained by this method is greater compared to other preparative techniques. ACKNOWLEDGEMENT We wish to express our sincere gratitude to Mithibai College and Chemistry Department, to give us chance to do research work, Head of the Chemistry Department, Mrs.Rajeshwari Mirji, for providing all facilities to work in Laboratory, Earth Science Department, IIT Bombay, for XRD analysis and ICON Analytical Laboratory, Worli, Mumbai for SEM and EDS analysis. Special thanks to Tanmay Shukla and Dr.Rajiv Pandit.


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Catalysis of SO2 to SO3 by Ocimum Sanctum Mediated Potassium Vanadate (KV2O5) Nanocuboids

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