A Facile Synthesis, Characterization, and Photocatalytic Activity of Magnesium Ferrite Nanoparticles via the Solution Combustion Method

Hindawi Journal of Chemistry Volume 2019, Article ID 3428681, 8 pages https://doi.org/10.1155/2019/3428681 Research Article A Facile Synthesis, Characterization, and Photocatalytic Activity of Magnesium Ferrite Nanoparticles via the Solution Combustion Method Loan T. T. Nguyen ,1 Lan T. H. Nguyen,1 Nhuong Chu Manh,1 Dung Nguyen Quoc,1 Hai Nguyen Quang,2 Hang T. T. Nguyen,3 Duy Chinh Nguyen ,4 and Long Giang Bach4,5 1 Faculty of Chemistry, Thai Nguyen University of Education, Thai Nguyen University, Thai Nguyen, Vietnam Faculty of Physics, Thai Nguyen University of Education, Thai Nguyen University, Thai Nguyen, Vietnam 3 Thai Nguyen University of Technology, Thai Nguyen University, Thai Nguyen, Vietnam 4 NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 5 Faculty of Chemical Engineering and Food Technology, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam 2 Correspondence should be addressed to Loan T. T. Nguyen; Received 27 November 2018; Revised 23 January 2019; Accepted 3 March 2019; Published 25 March 2019 Academic Editor: Darren Sun Copyright © 2019 Loan T. T. Nguyen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this study, we adopted the solution combustion method to synthesize magnesium ferrite (MgFe2O4) using urea as the fuel. Various techniques including TGA, XRD, SEM, TEM, FTIR, UV-Vis DRS, and EDS were employed to characterize the synthesized MgFe2O4 nanoparticles. The XRD analysis revealed that single-phase MgFe2O4 was formed at a calcination temperature of at 500–600°C for 3 hours in the absence of an intermediate phase. TEM analysis also revealed the formation of monodisperse magnesium ferrite nanoparticles, averaged at 30 nm in size. The photocatalytic activity of the synthesized MgFe2O4 nanoparticles against methylene blue dye under visible light was investigated, showing the efficiency of 89.73% after 240 minutes of light irradiation with the presence of H2O2. 1. Introduction Ferrite nanoparticles, MFe2O4 where M is any divalent metal ions such as Mg, Mn, Ni, Co, Fe, Cu, etc, find wide applications in several fields [1]. Depending on the area of application, ferrite nanoparticles need to exhibit distinct characteristics. For example, in order to be suitable as an absorbent for decontamination of wastewater, ferrites should have exceptional chemical reactivity, adsorption capacity, and most importantly, reasonable Ms value, which is critical for magnetic recovery of the adsorbent from the aqueous solution [2]. The choice of synthesis method should also be considered when it comes to exploring the mechanism of formation of ferrite properties. To be specific, the distribution of metallic ions among crystallographic lattice sites, which defines the characteristics of the materials, largely depends on the synthesis method. This effectively makes the method selection crucial when it comes to adapting the materials to the needs of application [1, 3, 4]. Usually, the maximum band gap energy of ferrites is approximately 2 eV, allowing the materials to effectively absorb visible light [5]. Furthermore, advantageous magnetic properties also offer ferrites useful applications [6]. Both forms of ferrites, in individual photocatalysts or in combination with others, are accentuated in literature for being separable and reusable from the reaction mixture [5, 7]. One of the typical uses of ferrites is as visible light photocatalysts for the degradation of pollutants in water and wastewater [7–10]. This capability of ferrite catalysts is 2 possible due to effective utilization of light energy, which in turn allows formation of e− /h+ pairs on the photocatalytic surface. The e− /h+ pairs, owing to their susceptibility to oxidation and reduction, play an important role in formation of reactive oxygen species, such as • OH and O2 •− , consequently promoting the decomposition of pollutants. Previous studies also suggested the addition of oxidants such as H2O2 into the reaction to create a Fenton-type system [6, 8, 11, 12] aiding the degradation through formation of hydroxyl radicals. Among magnetic ferrites, magnesium ferrite (MgFe2O4) is a typical inverse spinel, where Fe3+ ions are located in the tetrahedral (A) and octahedral (B) sites and Mg2+ ions are located in octahedral sites only [13]. The application of magnesium ferrite is diverse ranging from that in highdensity recording media [14] to that in the fields of heterogeneous catalysis [7, 15–17], adsorption [18–20], anode material [21], cancer cure [22], and sensors [23]. In addition, the material is also a soft magnetic n-type semiconducting materials with a narrow band gap (1.9 eV) [24]. Methods devised for preparation of magnesium ferrite nanocrystallites included the coprecipitation method [19, 25–28], sol-gel method [20, 29], combustion method [30, 31], hydrothermal method [32], thermal decomposition method [33], and solvothermal method [34]. Among the methods used to synthesize ferrite nanoparticles, the solution combustion synthesis is favored for its simplicity, short reaction time, and low annealing temperature [35]. These advantages have made resulting ferrites to have fine particle size, reduced impurities, and improved physical properties [36]. In the combustion reaction, the fuels play the role of forming complexes with metal cations [35]. Frequently used fuels in previous studies included glycine, urea, citric acid, and EDTA (ethylene diammin tetraacetic acid). In this work, MgFe2O4 nanoparticles are prepared by the solution combustion method with urea as fuel. The structural, chemical composition, thermal, morphology, and photocatalytic activity of MgFe2O4 nanoparticles are investigated. 2. Materials and Method 2.1. Materials. All chemicals including magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), iron nitrate nonahydrate (Fe(NO3)3·9H2O), urea (CH4N2O), and methylene blue (C16H18ClN3S) were obtained from Merck and used as received. 2.2. Preparation of MgFe2O4 Nanoparticles. The combustion preparation of MgFe2O4 with urea fuel in this study is described as follows. First, urea was dissolved in water, followed by an appropriate amount of magnesium nitrate hexahydrate and iron nitrate nonahydrate following the mole ratio for Mg(II)/Fe(III) of 1 : 2 under vigorous stirring to form a mixed solution. Afterwards, the mixed solution was further stirred for 4 hours until gel was formed. The gel was then dried in an oven at 80°C for 10 hours. Finally, the precipitate was calcined at 500–800°C for 3 hours with a heating rate of 5°C·min−1 [37]. Journal of Chemistry 2.3. Characterizations. The gel precursor was studied for its thermal decomposition behavior through thermogravimetry (TG) and differential thermal analysis (DTA) on a Labsys Evo S60/58988 instrument (Setaram, France) in the temperature range of (...truncated)