Synthesis of silver nanoparticles/porphyrin/reduced graphene oxide hydrogel as dye adsorbent for wastewater treatment

Abstract Facile and versatile strategies for the preparation of reduced graphene oxide hydrogel (rGH) are of great interest due to its various applications in pollution adsorption, catalysis, gas sensors and tissue engineering. In this study, the preparation of a novel self-assembled reduced graphene oxide hydrogel modified with silver nanoparticles (AgNPs) and various porphyrin complexes using the green hydrothermal approach were reported. The AgNPs were successfully decorated on the reduced graphene sheets via electrostatic interactions. On the other hand, the interaction of porphyrin complex with the Ag/rGH is via esterification and π-π interactions. Based on thermogravimetric analysis and BET analysis, the intercalation of porphyrin complex improved the thermal stability and specific surface area (SSA) of the modified hydrogels. Further characterizations of the modified hydrogel were accomplished using Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR), scanning electron microscope-energy dispersive spectroscopy (SEM/EDS), and UV–Vis spectrophotometry. The adsorption capacity of the modified hydrogels increased with the integration of AgNPs and porphyrin complexes due to the increase of the number of adsorption sites. The Ag/TPP/rGH exhibited the highest adsorption capacity (130.37 mg/g) towards the cationic dye, methylene blue (MB) which is attributed to the additional binding sites from the available unoccupied aromatic structures of the TPP. All prepared hydrogels kinetic reaction conformed to the pseudo second-order model with good stability for removing MB with efficiency above 90%.