Highly active nanoscale zero-valent iron (nZVI)-Fe3O4 nanocomposites for the removal of chromium(VI) from aqueous solutions

► Fe0-Fe3O4 nanocomposites were synthesized and used for Cr(VI) removal. ► The synthesized nanocomposites were observed by SEM, HRTEM, XRD, and XPS. ► Effects of mass composition, pH, and initial Cr(VI) concentration were investigated. ► Kinetics and adsorption isotherms of such system were firstly described. ► Reaction mechanism has been deeply discussed and clearly presented in the figures.