Green synthesis of iron nanoparticles and their application as a Fenton-like catalyst for the degradation of aqueous cationic and anionic dyes
TL;DR: In this article, green tea leaves (GT-Fe NPs) were used as a Fenton-like catalyst for decolorization of aqueous solutions containing methylene blue (MB) and methyl orange (MO) dyes.
About: This article is published in Chemical Engineering Journal.The article was published on 2011-08-01 and is currently open access. It has received 659 citations till now. The article focuses on the topics: Iron oxide & Aqueous solution.
Summary (2 min read)
Jump to: [1. Introduction] – [2.1. Preparation of GT-Fe NPs] – [2.4. Characterization of GT-Fe NPs] – [3.1. Characterization of GT-Fe NPs] – [3.2.1. Fenton-like mechanism and pH effect] – [3.2.3. Kinetic experiments] – [3.2.4. Effect of dye concentration] – [3.3. Comparison of GT-Fe NPs with BH-Fe NPs] and [4. Conclusions]
1. Introduction
- Iron nanoparticles were readily synthesized using green tea leaf extracts (GT-Fe NPs).
- Green tea is known to contain polyphenols that act both as a reducing agent and a capping agent.
- The main objective of the current study is to test the applicability of GT-Fe NPs as a Fenton catalyst in the removal of cationic (methylene blue) and anionic (methyl orange) model dyes.
- Another objective of the study is to compare the extent of degradation of GT-Fe NPs with that of nZVI produced by borohydride reduction (BH-Fe NPs).
- At room temperature it appears as a solid, odorless, dark green powder, which yields a blue solution when dissolved in water.
2.1. Preparation of GT-Fe NPs
- The synthesis of iron nanoparticles using green tea extracts was described previously [17, 18] .
- The green tea extract was prepared by heating 60.0 g L −1 green tea (Alwald Brand) until boiling.
- After settling for 1.0 h, the extract was vacuum-filtered.
- Following this, 1.0 M NaOH solution was added until the pH was 6.0 and the formation of GT-Fe NPs was marked by the appearance of intense black precipitate.
- The iron particles were then separated first by evaporating water from the iron solution on a hot plate (Freed Electric), and then by drying it overnight in a fume hood.
2.4. Characterization of GT-Fe NPs
- For XPS, samples were analyzed under high vacuum using a Thermo Fisher Scientific Escascope X-ray photoelectron spectrometer equipped with a dual anode (Mg/Al) source and a concentric hemispherical electron energy analyzer.
- Data acquisition and manipulation were carried out using Pisces (Dayta Systems, UK) software.
- Charge referencing was carried out against adventitious hydrocarbon (C 1s = 284.8 eV binding energy).
- Nanoparticle samples were sonicated in analytical grade methanol for 30 s and mounted on 200 mesh holey carbon coated copper grids.
3.1. Characterization of GT-Fe NPs
- The same elements appearing in the EDX spectrum are also observed using XPS spectra.
- Auger electron peaks are observed for Na and O in addition to their photoelectron peaks.
- These signals are thought to arise primarily from the C atoms in the polyphenol groups attached to GT-Fe NPs, with the duplet indicating two types of C with different chemical environments.
- These peaks are attributed to the polyphenols presumably present at the surface of iron nanoparticles.
3.2.1. Fenton-like mechanism and pH effect
- Eqs. (i) and (ii) show that ferrous ions initiate the reaction leading to production of hydroxyl radicals, which then attack the organic pollutants leading to their degradation.
- Iron oxides, iron oxohydroxide, and zero valent iron can be used as a source of ferrous ions in a Fenton-like process.
- In the case of azo dyes, the cleavage of the azo bond (-N N-) in the chromophore of the dye leads to decolorization of the dye solution [20] .
- The surface area and surface activity of the Fenton catalyst are crucial.
- Doubtlessly, the nanosize of the GT-Fe material greatly enhances its activity as a catalyst.
3.2.3. Kinetic experiments
- Eqs. ( 3) and ( 4) were employed to describe the data corresponding to the pre-equilibrium stage (up to 120 min) for both dyes.
- The results of the linear regression analysis were used to calculate the rate constants for each case.
- At a given liquid concentration of a solute, for a fixed rate constant, the variation of the rate is more pronounced in the case of second order kinetics compared with first order.
- For a given rate order (first or second), the response of the rate at a given concentration will depend on the value of the rate constant.
- In both cases, the larger rate constant of MB reflects its faster removal kinetics.
3.2.4. Effect of dye concentration
- To further assess the efficiency of GT-Fe NPs as a catalyst, blank experiments were performed without the addition of the material to the peroxide containing reaction mixture.
- The results showed less than 3% removal of the dye even in the most dilute solution.
3.3. Comparison of GT-Fe NPs with BH-Fe NPs
- Nevertheless, the reported results must not undermine the effectiveness of BH-Fe NPs in dye removal.
- Preliminary data of their ongoing experiments suggest that BH-Fe NPs would be much more effective than GT-Fe NPs when used directly (not as a Fenton-like catalyst; without H 2 O 2 ) to catalyze dye degradation/sorption.
4. Conclusions
- As a Fenton-like catalyst, GT-Fe NPs demonstrated impressive removal capabilities towards both of MB and MO, in terms of the extent of removal and the kinetics.
- Compared with BH-Fe NPs, GT-Fe NPs showed higher dye removal percentages and faster kinetics when used as a Fenton-like catalyst.
Did you find this useful? Give us your feedback
Figures (12)
Table 1 Rate constants obtained from linear regression analysis of the data of dye removal. 
Fig. 7. Linear plots of the kinetic data: (a) first order plot for MB, (b) secon 
Table 2 The percentage removal of MB and MO at different initial concentrations when GT-Fe NPs are used as a Fenton-like catalyst. Cl stands for the equilibrium liquid concentration. 
Fig. 8. (a) SEM image, and (b) EDX spectrum of BH-Fe NPs. 
Fig. 3. A typical XRD pattern of GT-Fe NPs. 
Fig. 2. (a and b) TEM images, and (c) EDX spectrum, of GT-Fe NPs. 
Table 3 Kinetic and equilibrium data corresponding to removal of MB when borohydride-reduced Fe (BH-Fe NPs) is used as a Fenton-like catalyst. 
Table 4 Kinetic and equilibrium data corresponding to removal of MO when borohydride-reduced Fe (BH-Fe NPs) is used as a Fenton-like catalyst. 
Fig. 9. XRD pattern of BH-Fe NPs. 
Fig. 4. XPS spectra of GT-Fe NPs. The insets sh 
Fig. 5. FTIR bands corresponding to: (a) polyphenols, (b) MB, and (c) MO. The 
Fig. 6. Variation of dye concentration with time: (a) MB, and (b) MO. The inset
Citations
More filters
TL;DR: This review systematically introduces the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years.
Abstract: Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.
1,549 citations
TL;DR: This review, which examines 'greener' routes to nanoparticles of zerovalent metals, metal oxides, and salts with an emphasis on recent developments, discusses the key materials used in the field: silver, gold, iron, metal alloys, oxides and salts.
778 citations
TL;DR: In this article, the potential developments in nanotechnology with respect to wastewater treatment are reviewed and discussed utilization of various classes of nano-materials for wastewater treatment processes, including activated carbon, carbon nanotubes, grapheme, manganese oxide, zinc oxide, titanium oxide, magnesium oxide and ferric oxides.
479 citations
Cites background from "Green synthesis of iron nanoparticl..."
...It is reported that the heterogeneous MFe2O4 is extensively used as catalyst due to its high chemical and thermal stability (Kurian and Nair, 2015) Magnetically separable nano-particles of iron oxide can be used as Fenton catalysts for removal of several types of pollutants (Shahwan et al., 2011; Sun and Lemley, 2011)....
[...]
TL;DR: In this article, a comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions, as well as the operational factors that govern the adsorption of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity.
Abstract: Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity. Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency. Herein, this comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions. The operational factors affecting the photodegradation of either cationic or anionic dye molecules, as well as the charge-carrier properties of the photocatalyst, are also fully explored. By further analyzing past works to clarify key active species for photodegradation reactions and optimal conditions, this review provides helpful guidelines that can be applied to foster the development of efficient photodegradation systems.
464 citations
Cites background from "Green synthesis of iron nanoparticl..."
...performed photodegradatio of methyl blue and methyl orange [13], a d f und that the pH of solution and steric structure were highly related to photocatalytic fficiency....
[...]
...performed photodegradation of methyl blue and methyl orange [13], and found that the pH of solution and steric structure were highly related to photocatalytic efficiency....
[...]
...This phenomenon was studied for other dye molecules, including the AR14/TiO2 [3] and other systems [13,14,68,69]....
[...]
...During the photodegradation reaction, a redshift or blueshift can be sometimes seen in the characteristic absorption of dye molecules, possibly caused by the aggregation of organic dyes [13,30]....
[...]
TL;DR: An environmentally benign and unexploited method for the synthesis of silver nanocatalysts using Trigonella foenum-graecum seeds, which is a potential source of phytochemicals is reported.
389 citations
References
More filters
Book•
01 Jan 1963
TL;DR: In this paper, a sequence of procedures for identifying an unknown organic liquid using mass, NMR, IR, and UV spectroscopy is presented, along with specific examples of unknowns and their spectra.
Abstract: Presents a sequence of procedures for identifying an unknown organic liquid using mass, NMR, IR, and UV spectroscopy, along with specific examples of unknowns and their spectra,
11,753 citations
TL;DR: This work presents a systematic characterization of the iron nanoparticles prepared with the method of ferric iron reduction by sodium borohydride and results may foster better understanding, facilitate information exchange, and contribute to further research and development of Iron nanoparticles for environmental and other applications.
871 citations
TL;DR: In this article, simulated dye wastewater, separately prepared with disperse, reactive, direct, acid and basic dyes, were decolorized with a hydrogen peroxide-ferrous ion system, known as Fenton's reagent.
668 citations
TL;DR: Iron and silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous sorghum extracts as both the reducing and capping agent.
Abstract: Iron and silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous sorghum extracts as both the reducing and capping agent. Silver ions were rapidly reduced by the aqueous sorghum bran extracts, leading to the formation of highly crystalline silver nanoparticles with an average diameter of 10 nm. The diffraction peaks were indexed to the face-centered cubic (fcc) phase of silver. The absorption spectra of colloidal silver nanoparticles showed a surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. Amorphous iron nanoparticles with an average diameter of 50 nm were formed instantaneously under ambient conditions. The reactivity of iron nanoparticles was tested by the H2O2-catalyzed degradation of bromothymol blue as a model organic contaminant.
565 citations