Synthesis of lignin-poly(N-methylaniline)-reduced graphene oxide hydrogel for organic dye and lead ions removal

Lignin is one of the major contents of lignocellulose and can be used as feedstock for adsorbent materials for wastewater treatment. Here, a lignin-poly(N-methylaniline)-graphene oxide (lignin-PNMA-rGO) hydrogel has been prepared by a two-step method, microspheres of lignin-PNMA was synthesis by the polymerization of NMA monomer in the presence of lignin in aqueous solution, and then they were encapsulated by the as-prepared reduced graphene oxide (GO) hydrogel via a reduction induced self-assembly of the GO nanosheets.The scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and UV–Vis studies have been carried out and revealed that the formation of the 3D porous nanocomposite hydrogel with multilevel structures and sufficient active sites. The lignin-PNMA-rGO adsorbent exhibited high adsorption capacity for both organic dye methylene blue (MB, 201.7 mg/g) and Pb2+ ion (753.5 mg/g). The new lignin-based adsorbent is a low-cost, environmentally benign, which is an attractive adsorbent for wastewater treatment.