Green synthesis of iron nanoparticle by tea extract (polyphenols) and its selective removal of cationic dyes

The traditional synthesis of iron nanoparticles has the problems of high cost and secondary pollution. There is an urgent need for an economic, effective and environment-friendly method to solve this key issue. Here, the iron nanoparticles were prepared by a novel biosynthesis based on extracted tea polyphenols. Five kinds of tea were tested by microwave method, and the optimum extraction conditions were determined by orthogonal experiment L-9(3(4)). The obtained materials were characterized by XRD, SEM, FTIR, XPS, Zeta potential and UV-Vis. The iron nanoparticle has a regular spherical or ellipsoidal shape with a particle size of about 75-100 nm. It was noted that it shows good selective removal for cationic dyes (malachite green (MG), rhodamine B (RB) and methylene blue (MB)). Kinetic experiment of iron nanoparticle on cationic dyes was in accordance with the pseudo first order kinetic model. Further, the possible removal mechanism was proposed, which mainly involves the process of adsorption and reduction. Mostly, its removal capacity of Malachite green reaches as high as 190.3 mg/g.