Xiulan Weng

Green synthesis of iron nanoparticles by various tea extracts: comparative study of the reactivity.

Iron nanoparticles (Fe NPs) are often synthesized using sodium borohydride with aggregation, which is a high cost process and environmentally toxic. To address these issues, Fe NPs were synthesized using green methods based on tea extracts, including green, oolong and black teas. The best method for degrading malachite green (MG) was Fe NPs synthesized by green tea extracts because it contains a high concentration of caffeine/polyphenols which act as both reducing and capping agents in the synthesis of Fe NPs. These characteristics were confirmed by a scanning electron microscope (SEM), UV-visible (UV-vis) and specific surface area (BET). To understand the formation of Fe NPs using various tea extracts, the synthesized Fe NPs were characterized by SEM, X-ray energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). What emerged were different sizes and concentrations of Fe NPs being synthesized by tea extracts, leading to various degradations of MG. Furthermore, kinetics for the degradation of MG using these Fe NPs fitted well to the pseudo first-order reaction kinetics model with more than 20 kJ/mol activation energy, suggesting a chemically diffusion-controlled reaction. The degradation mechanism using these Fe NPs included adsorption of MG to Fe NPs, oxidation of iron, and cleaving the bond that was connected to the benzene ring.

Synthesis of iron-based nanoparticles using oolong tea extract for the degradation of malachite green

Iron-based nanoparticles (OT-FeNP) were synthesized using oolong tea extracts. Their morphology, structure and size were confirmed by scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV-visible (UV-vis) and Fourier Transform Infrared spectroscopy (FTIR). Formation of FeNP results in mostly spherical particles with diameters ranging from 40 to 50 nm. Degradation of malachite green (MG) using OT-FeNP demonstrated that kinetics fitted well to the pseudo first-order reaction by removing 75.5% of MG (50 mg/L). This indicated that OT-FeNP has the potential to serve as a green nanomaterial for environmental remediation.

Enhancement of catalytic degradation of amoxicillin in aqueous solution using clay supported bimetallic Fe/Ni nanoparticles.

Despite bimetallic Fe/Ni nanoparticles have been extensively used to remediate groundwater, they have not been used for the catalytic degradation of amoxicillin (AMX). In this study, bentonite-supported bimetallic Fe/Ni (B-Fe/Ni) nanoparticles were used to degrade AMX in aqueous solution. More than 94% of AMX was removed using B-Fe/Ni, while only 84% was removed by Fe/Ni at an initial concentration of 60 mg L(-1) within 60 min due to bentonite serving as the support mechanism, leading to a decrease in aggregation of Fe/Ni nanoparticles, which was confirmed by scanning electron microscopy (SEM). The formation of iron oxides in the B-Fe/Ni after reaction with AMX was confirmed by X-ray diffraction (XRD). The main factors controlling the degradation of AMX such as the initial pH of the solution, dosage of B-Fe/Ni, initial AMX concentration, and the reaction temperature were discussed. The possible degradation mechanism was proposed, which was based on the analysis of degraded products by liquid chromatography-mass spectrometry (LC-MS).

Reactivity of iron-based nanoparticles by green synthesis under various atmospheres and their removal mechanism of methylene blue

In this study, iron-based nanoparticles (Fe NPs) were synthesized using tea extracts under various atmospheres (N2, O2 and air) to understand how atmospheres impact on the reactivity of Fe NPs, where Fe NPs were used for the degradation of methylene blue (MB). SEM and FTIR confirmed the morphology and change in size of iron-based nanoparticles before and after reaction with MB, indicating that different Fe composition, morphology and size were obtained under various atmospheres resulting in different reactivity of Fe NPs. In addition, various parameters impacting on removing MB by Fe NPs synthesized under various atmospheres show that the solution pH significantly affects the reactivity of Fe NPs. Furthermore, the data fitted well to the pseudo-second-order adsorption and pseudo-first-order reduction models, confirming that the removal of MB was based on both adsorption and reduction. Langmuir and Freundlich isotherms demonstrate that the removal of MB by Fe NPs synthesized under various atmospheres was different due to their composition, morphology and size. Finally, the degraded products such as benzothiazole were identified by gas chromatography-mass spectrometry (GC-MS) after the degradation of MB, and finally a feasible removal pathway is proposed.

Simultaneous removal of amoxicillin, ampicillin and penicillin by clay supported Fe/Ni bimetallic nanoparticles

This study examined functional bentonite-supported nanoscale Fe/Ni (B-Fe/Ni) for the simultaneous removal of β-lactam antibiotics such as amoxicillin (AMX), ampicillin (AMP) and penicillin (PEN). The results show only 94.6% of AMX, 80.6% of AMP and 53.7% of PEN were removed in the mixed antibiotic solution, while 97.5% of AMX, 85.1% of AMP and 74.5% of PEN were removed in individual antibiotic solution. The decreased removal in a mixed antibiotic solution was attributed to competition between antibiotics for: firstly, active sites of iron oxide for the adsorption; and secondly, accepted electrons for the degradation in passivation of the nZVI surface. These were confirmed by various characterization techniques. Kinetics studies of mixed antibiotics using B-Fe/Ni confirmed that adsorption and degradation occurred simultaneously as removing of antibiotics in the presence of particles. Furthermore, the stability and durability of B-Fe/Ni applied to remove β-lactam antibiotics was demonstrated. Finally, B-Fe/Ni was used to reduce the concentration of mixed antibiotics from pharmaceutical wastewater, which indicated B-Fe/Ni is a promising material for antibiotics wastewater treatment.

Green reduction of graphene oxide using eucalyptus leaf extract and its application to remove dye

Reduction of graphene oxide (RGO) utilizing green methods such as plants has attracted much attention due to its efficiency, eco-friendly features and low cost. However, the key components in plant extracts and their bioreduction functions concerning GO are still not well understood. In this study, the GO was reduced by Eucalyptus leaf (EL) extract. The optimal conditions for bioreduction were at volume ratio of leaf extract (10 g L-1) and GO (0.5 g L-1) solution of 1:4 for 8 h at 80 °C. The RGO was characterized with Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). Results confirmed the oxygen-containing groups in GO were efficiently removed, formation of capping layer on the surface of RGO, and good dispersion of RGO in aqueous solution. Furthermore, biomolecules were identified by Gas Chromatography-Mass Spectrometer (GC-MS), where eucalyptols, aldehydes, terpineols, alcohols, amides and ethers of Eucalyptus leaf extract may act as reducing and capping agents for the formation of RGO. Finally, the methyl blue (MB) adsorption on EL-RGO, activated carbon, graphite powder and commercial graphene were investigated separately. The order of the maximum adsorption capacity of different adsorbents emerged as: EL-RGO > commercial graphene > activated carbon > graphite powder.

Mechanism for removing 2,4-dichlorophenol via adsorption and Fenton-like oxidation using iron-based nanoparticles

In this paper, iron-based nanoparticles (Fe NPs) synthesized by Euphorbia cochinchensis leaf extract were used to remove 2,4-dichlorophenol (2,4-DCP). The possible mechanism for removing the adsorption and heterogeneous Fenton-like oxidation of 2,4-DCP was investigated. Various parameters affecting removal efficiency were tested, and the results showed that more than 83.5% of 2,4-DCP was removed with the addition of 10 mM H2O2 and the initial concentration of 2,4-DCP of 30 mg/L at pH 6.26 under 303 K. To understand the suggested removal mechanism, SEM and FTIR were used to characterize the surface change of Fe NPs before and after the adsorption and oxidation. This process confirmed that the removal of 2,4-DCP by Fe NPs was based on pre-adsorption and Fenton-like oxidation. Furthermore, GC-MS served to identify the intermediate and final products of 2,4-DCP to understand the possible pathway. Finally, Fe NPs were used in the treatment of wastewater and the removal efficiency of 2,4-DCP reached as high as 67.5%. Subsequently, a potentially efficient option for in situ organic pollutants remediation was demonstrated.