Removal of mixed contaminants Cr(VI) and Cu(II) by green synthesized iron based nanoparticles

•Iron-based nanoparticles (Fe NPs) were synthesized by green method.•The functional Fe NPs were observed.•The mixed Cr(VI) and Cu(II) in wastewater were removed by Fe NPs.•The removal mechanism was based on both adsorption and reduction.

In this study, iron based nanoparticles (Fe NPs) synthesized by eucalyptus leaf extracts was used to remove mixed Cr(VI) and Cu(II), where the efficiency was 58.9% and 33.0%, respectively. In contrast, only 20.2% of Cr(VI) and 11.8% of Cu(II) were removed by adsorption using eucalyptus leaf extracts. In addition, the removal mechanism for mixed Cr(VI) and Cu(II) based on both adsorption and reduction by Fe NPs was confirmed by various characterization techniques, including the formations of Fe NPs, iron oxides and capping layer. Furthermore, the kinetics suggested that firstly, their sorption followed the pseudo second-order model well; and secondly, reduction of Cr(VI) and Cu(II) followed the pseudo-first-order model well. Finally, Fe NPs not only removed Cr(VI) and Cu(II), but also Pb(II) and Zn(II) in electroplating wastewater. This provides a new insights into the removal of metal ions using green Fe NPs with a low cost and environmentally friendly remediation strategy.