A new insight on the adsorption mechanism of amino-functionalized nano-Fe3O4 magnetic polymers in Cu(II), Cr(VI) co-existing water system

A series of NH2-functionalized nano-magnetic polymer adsorbents (NH2-NMPs) coupled with different multi-amino groups, i.e., ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), named as EDA-NMPs, DETA-NMPs, TETA-NMPs and TEPA-NMPs have been prepared and used for the investigation of the adsorption mechanism of Cu(II) and Cr(VI) co-existing water system. Three approaches, e.g. by adsorbing Cu(II). Cr(VI) from water simultaneously, or adsorbing Cr(VI) followed by adsorbing Cu(II), and vice versa, were applied for the adsorption mechanism investigation. The results showed that the adsorption of Cu(II) or/and Cr(VI) on NH2-NMPs was competitive as well as cooperative. The adsorption mechanisms of Cu(II),Cr(VI) co-existing system could be related with coordination interactions, electrostatic attraction, and ion exchange. New adsorbents can be obtained via adsorption of Cu(II) or Cr(VI) by NH2-NMPs, named as Cu-NH2-NMPs, i.e., Cu-EDA-NMPs, Cu-DETA-NMPs, Cu-TETA-NMPs, Cu-TEPA-NMPs; and Cr-NH2-NMPs, i.e., Cr-EDA-NMPs, Cr-DETA-NMPs, Cr-TETA-NMPs, Cr-TEPA-NMPs, respectively. Cu-NH2-NMPs and Cr-NH2-NMPs can be reused for the adsorption of Cr(VI) or Cu(II), with high selectivity, broad pH applicable range and comparable adsorption properties with NH2-NMPs themselves. (C) 2011 Elsevier B.V. All rights reserved.