جستجوی مقالات مرتبط با کلیدواژه "green chemistry" در نشریات گروه "محیط زیست"

Rice husk is an agricultural by-product material comprising about 22% of the weight of rice. Even though some of this husk is converted into end products such as feedstock and adsorbent most is burnt openly, causing environmental and health problems especially in poor and developing countries. Therefore, it is very important to find pathways to fully utilize the rice husk.

In this study, the fabrication and characterization of ZSM-12 zeolite using rice husk ash as an alternative cheap silica source, and synthesis and characterization of magnesium oxide nanoparticles in ZSM-12 matrix by solid state reaction and ion exchange methods is reported. Disk diffusion method and MIC were used to evaluate the antimicrobial activity of nanoparticles on gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) strains of bacteria compared to standard commercial antibiotic disks.

Synthesized samples were evaluated using X-ray diffraction, scanning electron microscopy, energy dispersive X-Ray spectroscopy and transmission electron microscopy. XRD results revealed diffraction peaks for each of the two compounds in the MgO/ZSM-12 nanocomposite.

Transmission electron microscopy image of nanocomposite indicated that nanoparticles size of MgO is ~ 35 nm. Nanocomposite exhibited antibacterial activity with minimal inhibitory concentration of 96 µg/mL against E. coli and S. aureus.

 Nowadays, the use of green synthesis methods without the use of chemicals to produce biocompatible nanoparticles with specific properties has been widely considered. One of the most important methods of green synthesis is the production of metallic nanoparticles using organisms. Exploiting various plant materials for green synthesis of nanoparticles is a green technology because it does not involve any harmful chemicals. One of the techniques of the green synthesis method is the use of plant extracts, which reduces metal salts to metal ions by using reductive compounds in them. In recent years, coated magnetic nanoparticles have found new and widespread applications in industry and medicine due to their unique properties. Modifying the surface of these nanoparticles by plant extract enhances their efficiency in absorbing hazardous dyes and mineral pollutants. They also have antibacterial and anti-inflammatory activities.

 In order to synthesize the nanoparticles, iron chloride and nickel nitrate salts were mixed with the extract of Terminalia chebula and subjected to severe stirring. The immediate change of color from brown to black at this stage indicated the revival of metal ions to metal salts. The sample was then dried and powdered with mortar. Structure and morphology of synthesized nanoparticles were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM).

 The purpose of this research was to synthesize and develop a novel method for the preparation of super-magnetic nanoparticles using environmental and green chemistry methods. For this purpose, T. chebula was used as a medicinal plant in the preparation of iron-nickel magnetic nanoparticles for the first time. The FTIR method confirmed the surface modification of magnetic nanoparticles using T. chebula extract and SEM determined the morphology and approximate size of uncoated and bio operative magnetic nanoparticles. The results also showed that the nanoparticles were nearly spherical with approximately 26.67 nm average diameter. The X-ray diffraction pattern showed the crystalline nature, high purity, and cube-centered structure of the uncoated and bioactive magnetic nanoparticles.

 The proposed method in this study makes it possible to synthesize green binary magnetic nanoparticles using the extract of T. chebula. Not using hydrothermal and sedimentary methods in nanoparticle fabrication as well as preparation of a plant extract in the aquatic environment were important advantages of this study. According to this method, phenolic antioxidant compounds in the plant extract simultaneously reduced metal ions and chelating agents and also the synthesis of metal nanoparticles, which also have antibacterial properties.