Ionic polyacrylamide hydrogel improved by graphene oxide for efficient adsorption of methylene blue

The ionic polyacrylamide/graphene oxide (PAM/GO) hydrogel as an excellent methylene blue (MB) adsorbent was prepared by an improved one-step radical polymerization method using graphene oxide, acrylamide, and polar second monomers. The hydrogel was characterized by Fourier transform infrared spectroscopy, Raman spectra, X-ray diffraction, scanning electron microscopy, and 13C nuclear magnetic resonance spectrum. The effects of pH, contact time, initial concentration of MB, and temperature on the adsorption capacity for MB of the prepared hydrogel were investigated. The Langmuir isotherm was a suitable model for describing the adsorption process. The adsorption system fitted with the pseudo-second-order kinetic model in the adsorption process. Compared with the ionic PAM/GO, the anionic PAM/GO significantly improved the adsorption capacity for MB with an increase from 128.23 to 255.48 mg g−1 at 20 °C.