Enhanced reactivity of bimetallic Fe/Cu-organic composite (Fe/Cu-OC) using biosynthesis with tea extract for As(V) removal

Biosynthesis strategies are promising methods for the sustainable preparation of nanoparticles because they are less toxic to living organisms and the environment. However, there are still several knowledge gaps concerning the exact mechanisms involved in the biosynthesis of bimetallic composites when used for the removal of arsenic species. Thus, this work focused on the biosynthesis mechanism involved in the formation of a Fe/Cu bimetallic bio-composite (Fe/Cu-OC), and determination of the specific biomolecules in tea extract involved in biosynthesis, and identification of the reactive sites involved in the removal of As(V). FTIR , XPS, GC-MS, and LC-MS analysis of the main components of the tea extract proved that the surface of Fe/Cu-OC contained many different functional groups, including -OH, Fe/Cu-O, and O C-OH, which were mainly associated with theanine and caffeine complexes. SEM and TEM analyses indicated that Fe/Cu-OC had both crystalline and amorphous features with an average particle size of 366 ± 10 nm. A 97 % removal efficiency for As(V) was obtained by Fe/Cu-OC, suggesting that the surface contained numerous reactive sites, including unsaturated Fe and Cu complexes, as well as saturated benzene rings. Moreover, DFT calculations indicated that the Gibbs free energy changes for the preparation of Fe/Cu-OC were < 0, suggesting that in the composites biosynthesis was a thermodynamically favored spontaneous reaction. A biosynthetic mechanism for the formation of Fe/Cu-OC was proposed, involving a series of spontaneous coordination, redox, and organic adsorption reactions.