Green synthesis of ion-imprinted macroporous composite magnetic hydrogels for selective removal of nickel (II) from wastewater

Abstract Ion imprinted composite hydrogel need to be prepared to improve selectivity and efficiency for treating wastewater containing Ni(II). In this paper, Ni(II) imprinted composite hydrogel (CoFe2O4/Bentonite@ polyvinyl alcohol, abbr. IIP-BCFPVAs) was prepared in a environmental friendly way. The polyvinyl alcohol (PVA) was the main non-toxic component of the composite material, and citric acid(CA) was chosen as cross-linking reagent to enhance the stability of the ion imprinted holes. IIP-BCFPVAs was characterized by SEM, EDS, FTIR, XRD, VSM, BET and XPS. The adsorption effects of pH, reaction time and initial concentration of solution were studied. The selective coefficient K of Ni(II)/Mg(II), Ni(II)/Zn(II) and Ni(II)/Cu(II) were 1.646, 2.453, and 1.973, respectively, indicating that IIP-BCFPVAs showed good selective performance on separation of Ni(II). Adsorption kinetics conforms to pseudo-second-order kinetics and Langmuir model. Refering to XPS, Ni(II) was complexed by hydroxyl groups (-OH). IIP-BCFPVAs is a green and selective adsorbent for removing Ni(II) from wastewater.