Green Synthesis of Iron Oxide Nanoparticles by RS Lichen Extract and its Application in Removing Heavy Metals of Lead and Cadmium.

The present study was carried out with the aim of green synthesis of iron oxide nanoparticles by a distilled extract of SR (Ramalina sinensis), a local species of Fandoghlu forest in Ardabil. Among effective compounds in the extract of this local plant to remove lead and cadmium toxic metals are carbohydrates and phenolic compounds and the green synthesis of Fe3O4 nanoparticles was accomplished in a 1 h period at 70 degrees Celsius, with gradual addition of ammonia to the distiled extract obtained from plant. Synthesized iron oxide nanoparticles have been confirmed by various techniques such as ultra-violet spectrophotometry, XRD, FT-IR, SEM, and EDAX elemental analysis. In the spectrum obtained from the UV-spectrophotometer, the peak appearing at 310 ± 5 nm indicates the electron transfer of oxygen to the synthesized iron from the SR lichen. The XRD spectrum also showed the characteristics of Ɵ2 Theta=30.55, 36, and 43.35, which confirmed with iron oxide nanoparticles. The uniform spherical nature of iron oxide nanoparticles (III) in size from 20 to 40 nm were visible using SEM images. The obtained peak at 514 cm-1 in the infrared spectrum showed the formation of a new bond between iron and oxygen. The thermodynamic studies and adsorption investigation showed that lead was followed by the Langmuir adsorption model (R2 = 0.999) and cadmium was followed by Freundlich absorption model (R2 = 0.986) and the process of removing is spontaneous and exothermic. The data obtained from kinetic studies of removing lead and cadmium from aqueous solutions were fitted in a second-order kinetic model with an appropriate correlation coefficient of 0.99. The ability to remove lead and cadmium by magnetic nanoparticles of iron oxide was respectively 82% and 77% for initial concentration of 50 mg/l and pH in the range of 5-4.