Design and tuning of monodisperse microporous ternary hydrogels of GO-MgFe2O4-Gelatin for removing divalent metal ions: Doping optimization and insights into adsorption mechanism

Abstract

The current work proposes the synthesis of a scalable gelatin hydrogel doped with graphene oxide (GO) and magnesium ferrite (MF) through direct compounding and drip emulsification procedures. The composite hydrogel is studied in static conditions to investigate its applicability in large-scale continuous flow systems. The cross-section of the hydrogel showed how nanofillers were uniformly dispersed inside the polymer matrix. The process of crosslinking improved the pH resistance of the hydrogel through a Schiff base formation. The composite's point of zero charge (pHzpc) is estimated as 6.7. The ternary composite hydrogel exhibited 97 % and 91 % uptake efficiency for Ni(II) and Cd(II) respectively at static conditions. The effective removal of Ni (II) and Cd (II) ions is due to the synergistic involvement of GO, MF, and Gelatin (Gel). XPS findings reveal that Ni (II) and Cd (II) were present as oxides and hydroxides on the GMG5 surfaces. A combination of physical and chemical interactions such as surface complexation, ion exchange, electrostatic interactions, and dipole-dipole interactions catered to the improved uptake of metal ions. The hydrogel rendered stable adsorption-desorption characteristics up to three regeneration cycles with 0.1 M CH3COOH as a desorbing agent. The initial desorption efficiency was 75% for Ni (II) and 56% for Cd (II).