A one step synthesis of hybrid Fe/Ni-rGO using green tea extract for the removal of mixed contaminants

Abstract

The use of biomass for the synthesis of value-added products, such as functional nanomaterial for the removal of contaminants, is a challenge. In this study, hybrid bimetallic Fe/Ni nanoparticles and reduced graphene supported bimetallic Fe/Ni nanoparticles (Fe/Ni-rGO) were prepared via a one-step green synthesis using green tea extract, and thereafter evaluated for the simultaneous removal of rifampicin (RIF) and Pb(II) from aqueous solution. The efficiencies of Pb(II) and RIF removal by Fe/Ni-rGO were 87.5 and 96.8%, respectively. The removal performance of the hybrid Fe/Ni-rGO was better than either nFe/Ni, rGO, or Fe-rGO. Detailed characterization and analyses of Fe/Ni-rGO indicated that both Fe and Ni nanoparticles were evenly distributed over the surface of rGO and that aggregation of Fe, Ni nanoparticles, and stacking of rGO in the hybrid were decreased. Furthermore, while LC-TOF-MS analysis showed that RIF was degraded into small-molecule fragments, XPS showed that Pb(II) was not reduced to Pb0. The major conditions impacting removal efficiency, adsorption kinetics, and fit to adsorption isotherm models were examined to better understand the removal mechanism. While the adsorption of both contaminants fit well a pseudo-second-order kinetic model, the adsorption of RIF fit the Freundlich isotherm model best, while the adsorption of Pb(II) fit the Langmuir isotherm model best. Thus, the removal mechanism of both contaminants firstly being chemical adsorbed onto the surface, while nFe/Ni continues to participate in the catalytic reduction of RIF. Moreover, Fe/Ni-rGO could be reused and performed well for wastewater treatment, thus suitable as a practical resource recycling technology.