A facile one-step approach to functionalized graphene oxide-based hydrogels used as effective adsorbents toward anionic dyes

Herein, we used a facile method mainly through self-assemble, hydrogen bonding and electrostatic interaction to synthesize poly(diallyldimethylammonium chloride)/graphene oxide (PDDA/GO) hydrogels, which can be easily used as adsorbents to eliminate anionic dyes. The as-prepared PDDA/GO hydrogels were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. In order to research the adsorption kinetics for the removal of anion dyes from water pollution, we further investigated that the effect of concentration, temperature, pH, ionic strength or cycle number on the removal process. The results indicated that due to the strong π-π stacking and anion-cation interaction, there were high removal efficiencies for both ponceau S (PS) and trypan blue (TB). The equilibrium time of adsorption is 30 min and 120 min for PS and TB, respectively, at which the solution could be decolorized to nearly colorless. Meanwhile, the adsorption process was more according with the pseudo-second-order model than the pseudo-first-order model. The hydrogels exhibited high removal efficiency for those two anionic dyes after four repeated adsorption and desorption treatments. It was demonstrated that PDDA/GO hydrogels would have great potential as a freestanding and reusable adsorbent for the practical application in water purification.