View of GREEN SYNTHESIS OF IRON NANOPARTICLES AND THEIR ENVIRONMENT APPLICATIONS IN DEGRADATION OF COLORANTS

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Vol.04,Special Issue 04, ²^nd Conference (ICIRSTM) April 2019, Available Online: www.ajeee.co.in/index.php/AJEEE

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GREEN SYNTHESIS OF IRON NANOPARTICLES AND THEIR ENVIRONMENT APPLICATIONS IN DEGRADATION OF COLORANTS

Dr. Vijay Devra¹, Ajay Rathore²

Department of Chemistry: J.D.B. Govt. Girls College, Kota (Raj)^1,2

Abstract:- Iron nanoparticles are recently gaining great interest in environmental remediation circles. Iron nanoparticles (FeNPs) were synthesized by extract of Azadirachta Indica (Neem) leaves. The synthesized particles were characterized by U.V. Visible spectrophotometric and Fourier transforms infrared spectrophotometric technique. The results indicates the highest peak of absorption spectra were obtained at 268 nm wavelength and FT-IR peak at 594 cm^-1confirms the formation of zero valent iron nanoparticles. The obtained nanoparticles were then applied as catalyst in degradation of methyl orange (MO) in presence of peroxodisulphate (PDS) as catalyst. The related experiments investigated the removal kinetics and the effect of concentrations of reactants.

The loading experiment indicates almost complete removal of dye from water.

Keywords:- Green synthesis, Iron nanoparticles, Oxidant, catalyst, Azo dye 1. INTRODUCTION

The environmental impact of colorants is a concern over the last few decades. Industries such as textile, leather, paper, plastic and pharmaceutical produce a great amount of waste water contaminated with dyes in the world [1][2]. Among all synthetic dyes, Azo dyes are the largest and most important class of dye for industrial application [3]. The presence of dyes not only highly colors the effluent even at low concentration; it also causes environmental problems due to their toxic and carcinogenic characteristics [4]. Azo dyes are difficultly degraded by conventional treatment methods because of their complex structure and stability. The different treatment methods such as adsorption and flocculation are not efficient because they generate solid waste; this creating another environmental problem requires further treatment [5].

Among various treatment methods, advance oxidation processes (AOR) are considered as one of the most effective methods to degrade Azo dyes, which involves the generation of powerful oxidizing species such as sulfate radicals (SO4-) that attack the dye molecule [6], and degrade into harmless products. The field of Nano catalysis has undergone an explosive growth during few decades both in homogenous and heterogeneous catalysis [7]. Since nanoparticles have a large surface to volume ratio compound to bulk materials, they are wildly applied as catalyst [8].Metal nanoparticles with high specific catalytic activity are well known in modern synthesis organic chemistry during the recent years [9]. Amongst them Nano scale iron particles have gaining attention in environmental remediation and water treatment due to its large specific surface area and high reaction activity [10].

The physiochemical properties of iron nanoparticles and its reductive capacity enhance its application in the rapid degradation of many organic pollutants [11]. Chemical methods reports successfully were applied in synthesis of iron nanoparticles. However drawbacks include chemical substance such as NaBH4, organic solvents, stabilizing and dispersing agents being harmful and expensive. Therefore the development of biocompatible, nontoxic and ecofriendly method for synthesis of iron nanoparticles (FeNPs).

The green synthesis of nanoparticles has nanotechnology potential applying plant extract as reducing as well capping agents. It is superior to physical and chemical methods because of its simple, cast effective and reproducibility [12].

Presently there are only a few studies were reported the synthesis of iron nanoparticles (FeNPs) using plant extracts [13][14].FeNPs were synthesized using extracts of green tea leaves and then applied as use as Fenton like catalyst for degradation of methylene blue and methyl orange dyes [15]. The results reveal fast degradation of dyes with the kinetic data of methylene blue following second order whereas methyl orange were fitted first order degradation rate. However, no reports has documented the synthesized conditions impacting on formation FeNPs using Neem leaf extracts and its reactivity on degradation of methyl orange.

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Here, we have developed a ecofriendly and convenient green route for synthesis of FeNPs from Ferric chloride using leaf extract of Indian medicinal plane namely Azadirachta indica (Neem). Azadirachtaindica belongs to meliaceae family and found in India and in nearly subcontinents. Azadirachta indica contain flavonoids, protein, terpenoids, polyphenols etc., these biomolecules act as reducing as well as capping agents to minimize the coagulation of nanoparticles. The synthesized FeNPs were characterized by U.V.Visible spectrophotometer and Fourier transforms infrared (FT-IR) spectroscopy. A textile Azo dye, methyl orange was chosen as the model compound because it is widely used dye and resistant to degradation by conventional methods [16]. Finally, the degradation pathway of methyl orange in presence of FeNPs was proposed.

2. EXPERIMENTAL 2.1 Material

Ferric chloride, peroxodisulphate were obtained from E. merck. A fresh solution of peroxodisulphate was prepared before initiate the experiments. Methyl orange and other reagents were of analytical grade. Azadirachta indica (Neem) leaves were collected from Kota (Raj.) in India. Fresh and healthy 30 gm leaves with 150 ml water stirred on magnetic stirrer at 80ᵒC for 20 min. The prepared extract was filtered twice through what man paper and stored at 4ᵒC temperature for future use. Deionized water was used throughout the study.

2.2 Synthesis Process

The one step synthesis process for iron nanoparticles initiates with ferric chloride (1x10^-

3mol lit^-1) in deionized water, 20% neem leaf extract drop wise added to the aqueous solution of ferric chloride while vigorously stirring at 60ᵒC in oil bath. With the passage of time the color of dispersion gradually changes from bright yellow to brown finally brownish black with a number of intermediate stages. The appearance of brown black followed by dark black brown indicated the formation of fine nano scales iron nanoparticles from leaf extract assisted reduction. The resulting dispersion was centrifuged for 15 minutes and supernatant was placed under 4ᵒC temp for 21 days.

2.3 Instrumentation

U.V. Visible spectroscopy from a double beam spectroscopy (U.V. 3000⁺LAB INDIA) was used for preliminary estimation of iron nanoparticles and further formation of FeNPs and presence of functional group of biomolecules in leaf extract identified by (ALPHA-T Bruker, Germany) FTIR spectrophotometer using KBR pellet technique.

2.4 Kinetic Measurements

The other reactants and desired concentration of methyl orange placed Stoppard Erlenmeyer flask at 30ᵒCtemperature and degradation of methyl orange was initiated by mixing a known concentration of PDS solution. The rate of degradation was studied by decrease in intensity at the characteristic peak of methyl orange at 465 nm wavelength in regular time interval by U.V. Visible spectrophotometer attached with Peltier accuracy (temperature controlled). A plot of log (C/C o) versus time was obtained linear, indicates pseudo first order kinetics.

3. RESULTS AND DISCUSSION

3.1 Characterization Of Iron Nanoparticles

The recent several studies have shown that optical properties of metal nanoparticles depend upon the geometry and size, thus the optical response of metal nanoparticles can be control shape and size of metal nanoparticle [17]. Optical spectroscopy can be used as primary tool for investigation of metal nanoparticles, during the synthesis of FeNPs in aqueous solution.

The yellow dispersion gradually turned to brown and finally changes into brownish black solution, which indicates formation of iron nanoparticles.

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Figure-A: Color change during Fe NPs synthesis process.

The absorption spectra of dispersion was obtained maximum at 250 nm wavelength.(Fig- B)This can be confidently described to surface Plasmon resonance of (SPR) of FeNPs [18].

Figure-B: U.V visible spectra of synthesized Fe NPS

The stability of nanoparticles dispersion is key factor in their application. In this study, Neem leaf extract used both reducing and capping agent without any other special capping agent. The presence of active components in neem leaves extract such as terpenoids, flavonoids and polyphenols are responsible for reduction of iron nanoparticles as well as stabilization of FeNPs was confirmed by FT-IR spectra of synthesized FeNPs.(Fig.-C)

Figure-C: FT-IR spectra of synthesized FeNPs.

0 2 4 6 8 10 12

200 220 240 260 280 300 320

absorbance

wavelength

3393.36 2922.10 2395.02 1627.07 1383.72 1076.00 594.65 491.44480.36467.90435.48423.92

500 1000

1500 2000

2500 3000

3500

Wavenumber cm-1

020406080100

Transmittance [%]

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The I.R spectra of synthesized FeNPs shows major peak at 3000 cm^-1 (O-H stretching) and 1627 cm^-1 (C=O stretching) of carbonyl functional group of alcohol, ether, acids and esters and 594 cm^-1 is attributed to zero valent iron as reported in literature[19].

3.2. Effect of Experimental condition 3.2.1 Peroxodisulphate dependence-

PDS play a important role as source of sulfate radicals in the FeNPs /PDS system to evaluate the effect of PDS concentration on degradation of methyl orange was studied at different concentration of PDS from 1x 10^-4 or 1x 10^-3 mol dm^-3 at 30ᵒC temperature, constant concentration of methyl orange 5x10^-5mol dm^-3, [Fe NPs] = 1x10^-8mol dm^-3 and PH

=6.5. The rate of dye degradation increases with increase the initial concentration of PDS, as a result of large amount of sulfate radicals being produced at a higher PDS concentration.

As increase in PDS concentration to 5x10^-4mol dm^-3 did not improve the degradation efficiency and further probably due to the fact that excess PDS would react to the side reaction between persulfate ion S2O8-2 and sulfate radical [SO4 -] [20].Which would consume more PDS, hence remains percentage of PDS decrease with increase of PDS concentration.

(Table no-1)

S2O8-2 + SO4 -→ S2O8 - +SO4-2

3.2.2. Dye Dependence

The initial concentration of methyl orange varying from1.0x 10^-5to 1.0x 10^-4mol dm^-3 at 30ᵒC temperature and other reactant concentration were constant. The results indicates degradation rate was increases with increasing concentration of methyl orange in FeNPs/

PDS system and after the certain concentration of dye 5x10^-3mol dm^-3, the degradation rate was decreased. It may be at constant concentration of PDS, the availability of SO4-radicals not sufficient to degrade dye molecule at higher concentration [21].

3.2.3 Effect of P^H

Since P^H is an important factor influencing FeNPs and then the efficiency of Fe NPs/PDS the effect of initial P^Hranging from 3.0 to 9.0 on degradation rate of methyl orange in FeNPs/PDS system are presented in figure-D

Figure-D: The effect of P^H on degradation of methyl orange at 30ᵒC and fixed concentration [PDS]=5x10^-4mol L^-1, [MO]= 5x10^-5mol L^-1, [Fe NPs] = 1x10^-8mol L^-1.

The observed reaction rate constant of methyl orange (Kobs) at P^H 3.0 to 9.0 were determined, the values Kobs experienced a decrease with increasing initial P^H from 3.0 to 9.0, which was associated with at lower P^H greater SO4°- generation rate. Interestingly, the Kobsat P^H 9.0, is greater than at P^H 7.0, which may be ascribed to the generation of OH following by equation under alkaline conditions.

SO4°-+^-OH → OH + SO4-2

As P^H increased (eg> 8.5) the conversion of SO4 - to OH become increasingly important but the precondition was the generation of enough SO4-2[22].

3.2.4. Effect OF Iron Nanoparticles

The catalytic activity of synthesized FeNPs was evaluated in oxidative degradation of methyl orange by PDS with verifying concentration from 0.2x10^-8 to 2.0 x 10^-8 mol dm^-3 at fixed

0 1 2 3 4 5 6 7 8

0 2 4 6 8 10

104 Kobs

P^H

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concentration of other reactants. The rate of degradation of methyl orange increases with increasing concentration of FeNPs. Increasing concentration of FeNPs would correspond to higher available Fe^oconcentration, improved the decomposition of PDS to generate sulfate radicals. In order to show the catalytic activity, a graph plotted between different concentration of FeNPs and rate constants at different three temperatures(Fig-E).The plot gives straight line indicating direct depending of degradation rate on FeNPs concentration.

The value of activation energy 19.92KJ mol^-1 in FeNPs/PDS system shows that the rate of degradation of methyl orange is fast reaction.

Figure-E: Effect on Fe-NPs on degradation of methyl orange at three different temperature at fixed [PDS]=5x10^-4mol L^-1, [MO]= 5x10^-5mol L^-1, PH=3.0.

Figure-F: Plot between log Kobs and 1/T.

4. CONCLUSION

The present study reports highly stable FeNPs synthesized by the Azadirachta indica (Neem) leaf extract as an efficient, ecofriendly and cost effective reducing and capping agent. The green synthesized FeNPs were applied as catalyst for oxidative degradation of methyl orange in aqueous solution. The FeNPs exhibited good efficiency for activation of PDS to generate sulfate radicals for degrading methyl orange molecule into harmless products. Increasing PDS concentration and catalyst concentration the degradation rate of methyl orange was also increases. The results suggested that Fe NPs have a strong potential for fast dye degradation technology.

Table No-1- Effect of variation of [PDS][M.O], [FeNPs] and P^H an oxidative degradation of methyl orange at 30ᵒC

S.No. 10⁴ [PDS]

mol dm^-3 10⁵[M.O]

mol dm^-3 10⁸[Fe-NPs]

mol dm^-3 P^H 10⁴Kobs (sec^-1)

1 1.0 5.0 1.0 3.0 1.20

2 2.5 5.0 1.0 3.0 3.80

3 5.0 5.0 1.0 3.0 7.60

4 7.5 5.0 1.0 3.0 7.00

5 10.0 5.0 1.0 3.0 6.60

6 5.0 1.0 1.0 3.0 3.30

7 5.0 2.5 1.0 3.0 6.60

0 2 4 6 8 10 12 14 16

0 1 2 3

104 Kobs

10⁸(Fe NPs) mol dm^-3

25ᵒC 30ᵒC 35ᵒC

4.8 4.82 4.84 4.86 4.88 4.9 4.92 4.94 4.96

0.0032 0.00325 0.0033 0.00335 0.0034

log 10

4

K

obs

1/T

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8 5.0 5.0 1.0 3.0 7.60

9 5.0 7.5 1.0 3.0 7.10

10 5.0 5.0 1.0 3.0 6.00

11 5.0 5.0 0.0 3.0 1.30

12 5.0 5.0 0.20 3.0 2.60

13 5.0 5.0 0.50 3.0 4.50

14 5.0 5.0 0.75 3.0 6.00

15 5.0 5.0 1.00 3.0 7.60

16 5.0 5.0 1.50 3.0 10.40

17 5.0 5.0 3.00 3.0 13.60

18 5.0 5.0 1.0 3.0 7.60

19 5.0 5.0 1.0 4.0 7.10

20 5.0 5.0 1.0 5.0 6.50

21 5.0 5.0 1.0 6.0 6.01

22 5.0 5.0 1.0 7.0 5.60

23 5.0 5.0 1.0 9.0 6.40

5. ACKNOWLEDGEMENTS

This work was supported by Department of science of technology sponsored FIST Laboratory of our institution for experimental work.

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