Synthesis of modified gum tragacanth/graphene oxide composite hydrogel for heavy metal ions removal and preparation of silver nanocomposite for antibacterial activity.

New composite hydrogels were synthesized based on gum tragacanth (GT) carbohydrate and graphene oxide (GO). GT was sulfonic acid-functionalized and cross-linked by using 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and N,N'-methylenebisacrylamide (MBA) monomers and ceric ammonium nitrate (CAN) as an initiator. The prepared hydrogels were characterized by Fourier transform infrared spectrum (FT-IR), field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Adsorption process for removal of heavy metal ions has followed the pseudo-first-order kinetic model and fitted well with the Langmuir model. The maximum adsorption capacity (Qm ) was 142.50, 112.50 and 132.12mgg-1 for Pb(II), Cd(II), and Ag(I), respectively. The removal percentage decreased slightly after several adsorption/desorption cycles. The adsorbed Ag(I) ions in hydrogel were transformed to Ag0 nanoparticles (with a narrow distribution and mean size of 13.0nm) by using Achillea millefolium flower extract. The antibacterial performance of the Ag0 nanocomposite hydrogel was also investigated.