In situ green synthesis of MnFe₂O₄@EP@Ag nanocomposites using Epilobium parviflorum green tea extract: An efficient magnetically recyclable catalyst for the reduction of hazardous organic dyes

Abstract

The present paper introduces a plant-mediated green synthesis of highly stable MnFe 2 O 4 @EP@Ag magnetically recyclable nanocomposites (MRNCs) using Epilobium parviflorum (EP) tea extract as a coating material on MnFe 2 O 4 nanoparticles (NPs) for the Ag immobilization. Fourier transform infrared spectroscopy-attenuated total reflectance (ATR-FTIR) studies confirmed the presence of the polyphenolics in EP extract, including tannic, gallic, and other derivatives, which can enhance the complexation properties with silver ions on MnFe 2 O 4 NPs. Thus, the capacity and the surface properties of the resulting nanosorbent (MnFe 2 O 4 @EP) can also improve their ability to form magnetic nanocatalyts without using any additional chemicals, toxic or extra-reducing agents. The transmission electron microscopy (TEM) verified the successful coating of EP extract on MnFe 2 O 4 core as a 5 nm shell. X-ray diffraction (XRD) patterns and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM-EDX) confirmed the presence of both MnFe 2 O 4 and crystalline silver nanoparticles in the core-shell structure of the MnFe 2 O 4 @EP@Ag MRNCs. The obtained MnFe 2 O 4 @EP@Ag MRNCs displayed high efficiency and catalytic activity for the reduction of various azo dyes like methyl orange (MO), methyl red (MR), congo red (CR), alizarin yellow (AY), nitro aromatic compound, 4-Nitrophenol (4 NP), and a common tracer, rhodamine B (RhB). Results displayed that the MnFe 2 O 4 @EP@Ag MRNCs revealed higher catalytic activity with the normalized rate constant (k nor ) of 350.47 s −1 g −1 for RhB reduction. Furthermore, they were highly efficient in the reduction of other azo dyes and nitro compound in the order of MO (85.51 s −1 g −1 ) > CR (70.09 s −1 g −1 ) > 4 NP (62.15 s −1 g −1 ) > AY (54.67 s −1 g −1 ) > MR (46.73 s −1 g −1 ). In addition, the MnFe 2 O 4 @EP@Ag MRNCs exhibited an excellent unchanged recovery efficiency even after several cycles; therefore, they can be good potential candidates for the treatment of organic pollutants in wastewater and a wide range of applications in heterogeneous catalysis.

Reductant free green synthesis of magnetically recyclable MnFe2O4@SiO2-Ag core- shell nanocatalyst for the direct reduction of organic dye pollutants

“…Moreover, The EDS analysis of MnFe2O4@SiO2-Ag clearly displayed signals from Ag, Mn, Fe and Si atoms (Figure 2d). In this point, our previous study confirms that AgNPs are formed as a result of the in situ upon oxidation of active phenolic functional groups and derivatives in the EP extract by Ag + ions at neutral pH [25]. The resulting AgNPs were observed in spherical in shape with 15 nm of average particle size in TEM analysis (Figure 2e, f).…”

Design and Development of Gold-Loaded and Boron-Attached Multicore Manganese Ferrite Nanoparticles as a Potential Agent in Biomedical Applications

“…In the blue spectrum related to MnFe 2 O 4 nanoparticles, the broadband at 3600–3000 cm –1 is attributed −to OH stretching vibration due to absorbed water molecules and the peaks at 1650 and 597 cm –1 belong to the C=O stretching of the residual PVP molecules and metal–O (Mn–O or Fe–O) bond vibrations of MnFe 2 O 4 nanoparticles, respectively. 58 The other spectrum of MnFe 2 O 4 @PDA nanoparticles indicates the new peaks at 1606 and 1510 cm –1 , which belong to C=C stretching vibrations of a benzene ring and N–H bending vibrations, respectively, verifying the presence of PDA with MnFe 2 O 4 nanoparticles. 20 The confirmation and determination of the PDA coating were performed by TGA, as shown in Figure 1 c. While MnFe 2 O 4 nanoparticles showed a total weight loss of 10.3% due to absorbed water (2.3%) on the surface from 25 to 150 °C and residual PVP molecules (8%) from 150 to 1000 °C, MnFe 2 O 4 @PDA nanoparticles had 3 and 42.6% weight losses between the same temperatures.…”

Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment

“…There are various techniques for the synthesis of magnetic materials: co-precipitation of Fe ions in alkaline solutions [71,72], thermal decomposition of iron precursors in organic solutions [73][74][75], hydrothermal [76,77], solvothermal [78,79], combustion [80], sol-gel auto combustion [81] and microemulsion methods [82] are some of the techniques that have been reported in literature during the last decade (Table 1). In general, a good synthetic process for nanomaterials results in reproducible, monodispersed nanoparticles with controllable characteristics depending on the desired application.…”

“…In Table 2, recent hybrid magnetic materials containing silver NPs are presented along with their synthesis methods, the particle size(s) and the applications they were tested in. The most common method for Ag integration is the reduction of silver ions in a solution or gaseous medium at high temperatures [72]. In most cases, the integration of Ag NPs is realized as a separate synthesis step: In a typical process [98,112,113], the base catalyst or catalyst composite is mixed with a silver-containing compound (such as AgNO 3 ) in a solution that is usually aqueous.…”