A novel green synthesis of zero valent iron nanoparticles (nZVI) using walnut green skin: characterisation, catalytic degradation and toxicity studies

In the present study, green synthesised nanoparticles were used to activate persulphate and used for the oxidation of metronidazole (MTZ). In the process of green synthesis, the walnut green skin was used for the synthesis of zero-valent iron (nZVI) particles. These nanoparticles' FESEM images revealed that they were spherical-shaped nanoparticles with a diameter ranging from 18 to 72 nm. Also, the FTIR spectra indicated the functional groups of polyphenols on the surfaces of the nZVI nanoparticles. Moreover, the XRD pattern illustrated that the synthesised particles possessed a high crystalline quality structure. According to the results, under the optimum conditions, the removal efficiency of the process in degradation of MTZ was 90.3%. LC-MS chromatography showed 7 by-products with reduced toxicity in the reactor outputs. It was found that the green synthesised nZVI had a good effect on the activation of the PS and the PS/nZVI process had a high ability in degradation of MTZ from aqueous solutions.