Simultaneous removal of Pb(II) and Cr(III) by magnetite nanoparticles using various synthesis conditions

This study concerns the removal of Pb(II) and Cr(III) using magnetite nanoparticles synthesized by co-precipitation methods with (NCM) or without (CM) nitrogen gas passing through. Removal of Pb(II) significantly decreased from 80.56 to 41.41% when Cr(III) was co-presented, while decrease of Cr(III) was negligible when Pb(II) was present, falling from 42.37 to 38.48%. The characterizations indicated that the removal mechanism occurred through adsorption rather than chemical redox reaction. A co-adsorption mechanism is based on Pb(II) involved surface complexation, while Cr(III) was firstly adsorbed onto magnetite, followed by a partially substitution of Cr(III) for Fe(III) in $Cr-Fe_3O_4$ through ion exchanges.