Preparation of polyethyleneimine/graphene oxide membranes and their adsorptions for Pb(II), Cu(II) and Zn(II) in mixed systems

A series of novel polyethyleneimine/graphene oxide (PEI@GO) membranes were prepared and their adsorptions for heavy metal ions in mixed solutions were examined. It was found that they had good sorption performances for Pb(II), Cu(II), and Zn(II) in water. Their adsorptions for Pb(II), Cu(II), and Zn(II) obeyed the first-order kinetic modeling, dominating a physical style. Meanwhile, the fitting of intra-particle diffusion showed that Pb(II) and Cu(II) did not conform to the intra-particle diffusion stage, whereas Zn(II) did. Moreover, it was confirmed that the sorption of PEI@GO membranes for Pb(II), Cu(II), and Zn(II) followed the Langmuir isotherm modeling, and the maximal values could reach 79.6 mg/g for Pb(II), 35.01 mg/g for Cu(II), and 32.27 mg/g for Zn(II), respectively. The calculation of thermodynamic parameters indicated that these adsorptions were spontaneous and endothermic processes. Further, the investigation of PEI@GO membranes for Pb(II), Cu(II), and Zn(II) in ternary mixed systems evidenced that Zn(II) can be preferentially removed via step-by-step mode. In addition, the exploration of sorption mechanism using XPS and FTIR analyses showed that ligand interactions were involved in the adsorptive removal of Pb(II), Cu(II), and Zn(II). This study discloses that PEI@GO membranes are promising adsorbents for the removal of heavy metal ions from water.